United States
Environmental Protection
Agency
Industrial Environmental Research EPA 600 2 78 004w
Laboratory          August 1978
Cincinnati OH 45268
Research and Development
Source  Assessment
Acrylic Acid
Manufacture

State  of the Art


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                RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology  Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

      1.   Environmental  Health Effects Research
      2.   Environmental  Protection Technology
      3.   Ecological Research
      4.   Environmental  Monitoring
      5.   Socioeconomic Environmental Studies
      6.   Scientific and Technical Assessment Reports (STAR)
      7   Interagency Energy-Environment Research and Development
      8.   "Special" Reports
      9.   Miscellaneous Reports

This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                      EPA-600/2-78-004W
                                      August  1978
             SOURCE ASSESSMENT:
          ACRYLIC ACID MANUFACTURE
              State of the Art
                      by

R. W. Serth, D. R. Tierney, and T. W. Hughes
         Monsanto Research Corporation
              Dayton, Ohio 45407
           Contract No. 68-02-1874
              Project Officer

              Ronald J. Turner
    Industrial Pollution Control Division
Industrial Environmental Research Laboratory
           Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
     OFFICE OF RESEARCH AND DEVELOPMENT
    U.S. ENVIRONMENTAL PROTECTION AGENCY
           CINCINNATI, OHIO 45268

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                           DISCLAIMER


This report has been reviewed by the Industrial Environmental
Research Laboratory-Cincinnati, U.S. Environmental Protection
Agency, and approved for publication.  Approval does not signify
that the contents necessarily reflect the views and policies of
the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or
recommendation for use.
                               11

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                            FOREWORD
     When energy and material resources are extracted, processed,
converted, and used, the related pollutional impacts on our
environment and even on our health often require that new arid
increasingly more efficient pollution control methods be used.
The Industrial Environmental Research Laboratory - Cincinnati
(lERL-Ci) assists in developing and demonstrating new and
improved methodologies that will meet these needs both effici-
ently and economically.

     This report contains an assessment of air emissions from the
acrylic acid industry.  This study was conducted to provide a
better understanding of the distribution and characteristics of
emissions from acrylic acid manufacture.  Further information on
this subject may be obtained from the Organic Chemicals and Pro-
ducts Branch, Industrial Pollution Control Divisioh.
                                  David G. Stephan
                                      Director
                    Industrial Environmental Research Laboratory
                                     Cincinnati
                               111

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                             PREFACE
The Industrial Environmental Research Laboratory  (IERL) of the
U.S. Environmental Protection Agency  (EPA) has the responsibil-
ity for insuring that pollution control technology is available
for stationary sources to meet the requirements of the Clean Air
Act, the Federal Water Pollution Control Act, and solid waste
legislation.  If control technology is unavailable, inadequate,
or uneconomical, then financial support is provided for the
development of the needed control techniques for industrial and
extractive process industries.  Approaches considered include:
process modifications, feedstock modifications, add-on control
devices, and complete process substitution.  The scale of |:he
control technology programs ranges from bench- to full-scale
demonstration plants.

IERL has the responsibility for developing control technology
for a large number of operations  (more than 500) in the chemical
and related industries.  As in any technical program, the first
step is to identify the unsolved problems.  Each of the indus-
tries is to be examined in detail to determine if there is
sufficient potential environmental risk to justify the develop-
ment of control technology by IERL.

Monsanto Research Corporation  (MRC) has contracted with EPA to
investigate the environmental impact of various industries that
represent sources of pollutants in accordance with EPA's respon-
sibility, as outlined above.  Dr. Robert C. Binning serves as
MRC Program Manager in this overall program, entitled "Source
Assessment," which includes the investigation of sources in each
of four categories:  combustion, organic materials, inorganic
materials,  and open sources.   Dr.  Dale A.  Denny  of  the  Industrial
Processes Division at Research Triangle Park serves as EPA Pro-
ject Officer for this series.  Reports prepared in this program
are of two types:  Source Assessment Documents, and State-of-
the-Art Reports.

Source Assessment Documents contain data on pollutants from
specific industries.  Such data are gathered from the literature,
government agencies, and cooperating companies.  Sampling and
analysis are also performed by the contractor when the available
information does not adequately characterize the source pollu-
tants.   These documents contain all of the information necessary
for IERL to decide whether a need exists to develop additional
control technology for specific industries.

                               iv

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State-of-the-Art Reports include data on pollutants from spe-
cific industries which are also gathered from the literature,
government agencies and cooperating companies.  However, no
extensive sampling is conducted by the contractor for such
industries.  Results from such studies are published as State-
of-the-Art Reports for potential utility by the government,
industry, and others having specific needs and interests.

This study of acrylic acid plants was undertaken to. provide
information on air emissions.  The study was initiated by IERL-
Research Triangle Park in November 1975.   Mr. Edward J. Wooldridge
served as EPA Project Leader.  The project was transferred later
to the Industrial Pollution Control Division, lERL-Cincinnati
and Mr. Ronald J. Turner served as EPA Project Leader through
completion of the study.
                                v

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                            ABSTRACT


This document reviews the state of the art of air emissions from
acrylic acid manufacture.  The composition, quality, rate, and
environmental effects of emissions are described.

Acrylic acid is a monomer produced in the United States by either
the catalytic vapor-phase oxidation of propylene or the high-
pressure Reppe process which is based on acetylene.  Organic com-
pounds such as acrylic acid and propylene are emitted from
storage tanks, reactor process vents, and recovery and purifica-
tion column vents.  Carbon monoxide and nitrogen oxides are
emitted when waste streams are incinerated.

To assess the severity of emissions from this industry, a repre-
sentative plant was defined based on specific mean values for
various plant parameters.  Source severity was defined as the
ratio of the maximum time-averaged ground level concentration of
a pollutant to the primary ambient air quality standard for
criteria pollutants or to a reduced threshold limit value for
noncriteria pollutants.  At a representative plant, source sever-
ities for hydrocarbons, carbon monoxide,  and nitrogen oxides are
less than 0-7, less than 0.003, and less  than 0.6, respectively.

Controlled emissions from acrylic acid manufacture contribute
less than 0.006%, less than 0.002%, and less than 0.0009%,
respectively, to national emissions of hydrocarbons, carbon
monoxide, and nitrogen oxides from stationary sources.   Very
little increase in emissions from this industry is expected
through 1980.

Hydrocarbon emissions are mainly controlled by the use of thermal
incinerators.  Other control technology used includes nitrogen
blankets in pressurized storage tanks and water-chilled vent
condensers.

This, report was submitted in partial fulfillment of Contract No.
68-0^-1874 by Monsanto Research Corporation under the sponsorship
of the U.S. Environmental Protection Agency.  This report covers
the period December 1975 to December 1977, and work was completed
as of December 1977.
                               VI

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                            CONTENTS
Foreword	iii
Preface	   iv
Abstract	,  .  .  .   vi
Figures	viii
Tables	   ix
Abbreviations and Symbols	,  .  .   xi
Conversion Factors and Metric Prefixes 	 xiii

   1.  Introduction  	  1
   2.  Summary	,  .  .  . ,  2
   3.  Source Description  	  6
            Process description  	  ....  6
            Geographical distribution  	 23
   4.  Emissions	.25
            Selected pollutants  	 25
            Location and description 	 25
            Emission data	30
            Emissions burden	,  ... 30
            Definition of a representative source  ...... 30
            Environmental effects  	 ..... 33
   5.  Control Technology	, . 39
            State of the art	39
            Future considerations  	 41
   6.  Growth and Nature of the Industry	42
            Present technology 	 42
            Emerging technology  	42
            Marketing strengths and weaknesses 	 43

References	T  . . 46
Appendices

   A.  Derivation of source severity equations 	 52
   B.  Calculated emission factors for acrylic acid storage
         tanks	t  T . 65
Glossary
                                                               68
                               VII

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                             FIGURES


Number                                                       Page

  1   SOHIO process for the production of acrylic acid ...   7

  2   Locations of acrylic acid plants	  23'

  3   Incinerator used for the control of organic
        emissions from acrylic acid manufacture  	  40

  4   Production and sales record of acrylic acid  	  45
                              Vlll

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                             TABLES
Number                                                       Page

  1   Controlled Emission Factors and Source
        Severities for a Representative Plant ........   3
  2   Solvents Given in Patent Literature for Acrylic
        Acid Recovery
  3   Acrylic Acid Polymerization Inhibitors Obtained
        from Patent Literature  ............... 19

  4   Summary of Tankage Requirements for a 95,000 Metric
        Ton/Yr Acrylic Acid Plant ........ - ...... 21

  5   Acrylic Acid Plants .................. 24

  6   Compounds Identified in Acrylic Acid Processing
        Streams ....................... 26

  7   Health Effects and Atmospheric Reactivity of
        Selection Compounds in Acrylic Acid Production   ... 27
8
9
«x
10
11
12
Location of Emission Points 	
Acrylic Acid Emission Factors by Compound . .
Controlled Acrylic Acid Emission Factors by
Location 	
Emission Height Data for Acrylic Acid Plants
Contribution of Criteria Pollutants from Aery
	 28
	 31
	 31
• • • * * 3 £»
lie
        Acid Production to National Stationary Source
        Emissions	32

 13   Acrylic Acid Contributions to State Emissions of
        Criteria Pollutants  	 32

 14   Summary of Data for a  Representative Plant	33

 15   Maximum Time-Averaged  Ground Level Concentrations;
        for Compounds Emitted  	 35
                                IX

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                       TABLES  (continued)

Number -                                                      Page

 16   Maximum Time-Averaged Ground Level Concentrations
        for Emission Points	35

 17   Source Severities for Compounds Emitted  	  36

 18   Source Severities for Emission Points  	  36

 19   Affected Population for a Representative Plant   ....  38

 20   Acrylic Acid Consumption	43

 21   Consumption of Acrylic Acid Esters	44

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                   ABBREVIATIONS AND SYMBOLS
a,b,c,d,f   — constants used in dispersion  calculations
C           — diameter factor
Cap         — production capacity
D           •— distance from the source to the near'est
               plant boundary
D'          " tank diameter
e           — 2.72
E           — emission factor
F           — hazard factor
F           — equivalent gasoline working loss

F           — paint factor
H           — emission height
H1          •"- tank outage
K           — turnover factor
L           —- total petrochemical loss
LI          -L- petrochemical loss
L           — t6tal equivalent gasoline loss

L           — equivalent gasoline breathing loss

M           — molecular weight of chemical  stored
N           -— number of turnovers per year
P           —» production rate
AP          — change in pressure
Q           — mass emission rate
S           — source severity
t           — averaging time
t           — short-term averaging time
 o
AT          — average ambient temperature change
TLV         -*- threshold limit value
u           "-*- wind speed
u           — average wind speed
V           -*- tank capacity
W           -*- liquid density of chemical stored
x           •*- downwind dispersion distance  from source
               of emission release
y           -— horizontal distance from centerline of
               dispersion
                               XI

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             ABBREVIATIONS AND SYMBOLS  (continued)

IT           — 3.14
P           — vapor pressure of material stored at bulk
               temperature
Oy          -- standard deviation of horizontal dispersion
crz          -- standard deviation of vertical dispersion
X           -- downwind ground level concentration at
_              reference coordinate x and y
X           -- mean ambient concentration
Xjnax        — maximum ground level concentration
Xmax        — maximum time-averaged ground level concentration
                               xn

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             CONVERSION FACTORS AND METRIC PREFIXES
  To convert from

Degree Celsius  (°C)
Gram/kilogram  (g/kg)
Kilogram  (kg)
Meter (m)
Meter (m)
Meter2 (m2)
Meter3 (m3)
Metric ton

Pascal (Pa)
Pascal (Pa)
Second (s)
             CONVERSION FACTORS

            	To	

            Degree Fahrenheit

            Pound/ton
            Pound-mass (avoirdupois)
            Foot
            Inch
            Mile2
            Foot3
            Ton (short, 2,000 Ib
              mass)
            Inch of water (60°F)
            Pound-force/inch2 (psi)
            Minute
                              Multiply by
                                 1.8 toc + 32

                                        2.000
                                        2.205
                                        3.281
                                  3.937 x 101
                                 3.861 x 10"7
                                  3.531 x 101

                                        1.102
                                 4.019 x 10"3
                                 1.450 x I0~k
                                 1.667 x 10"2
Prefix

Kilo
Milli
Micro
Symbol

  k
  m
  y
     METRIC PREFIXES

Multiplication factor

          103
          10"3
          10~6
       Example
1 km = 1 x 103 meters
1 mm = 1 x 10"3 meter
1 ym = 1 x 10"6 meter
 Standard for Metric Practice.  ANSI/ASTM Designation:
 E 380-76£, IEEE Std 268-1976, American Society  for  Testing  and
 Materials, Philadelphia, Pennsylvania, February 1976.   37 pp.
                               Xlll

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                            SECTION 1

                          INTRODUCTION
Acrylic acid and its derivatives are used in the production of
polymers which include plastic sheet and molding powders; emul-
sion polymers for water-based paints, leather finishing, and
paper coating; and polymers for the sizing, treating, and finish-
ing of textiles.  Acrylates also find use in acrylic fibers
(as comonomers with acrylonitrile), pigment binders, adhesives,
and polishes.

Acrylic acid is produced in this country by two processes:  the
high-pressure Reppe process and the propylene oxidation process.
These two processes and at least three others are being used
throughout the world to produce acrylic acid.

The purpose of this study is to assess the atmospheric emissions
from the production of acrylic acid by the propylene oxidation
process.  The composition, quantity, and rate of emissions are
described.  Data were obtained from appropriate literature
sources and industry communications.

Section 2 of this document summarizes the major findings of this
study.  Section 3 provides a detailed description of the acrylic
acid production process.  Section 4 gives data on emissions and
provides an assessment of the environmental impact of acrylic
acid plants based on source severity and affected population.
Control technology is described in Section 5, and Section 6
relates the growth and nature of the industry.

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                            SECTION 2

                             SUMMARY
Acrylic acid is manufactured by the catalytic vapor-phase oxida-
tion of propylene and by the high-pressure Reppe process.  The
propylene.oxidation process accounts for 93%  (255,000 metric
tons/yra) of the installed capacity.  The high-pressure Reppe
process, based on acetylene, accounts for 7%  (18,000 metric
tons/yr).  There are currently four acrylic acid plants in the
United States; three use the propylene oxidation process and the
other uses the high-pressure Reppe process.  In 1975, these
plants were operating at 40% to 50% of production capacity.
Since no expansion of the Reppe process is anticipated in the
United States, it is not covered in the present study.

Iji those acrylic acid plants using the propylene oxidation proc-
ess, organic compounds are emitted from fugitive sources and from
vents located in the propylene oxidation section, product re-
covery and purification sections, transport loading facility,
and storage tanks.  Depending on the individual plant, part or
all of the vented organics are sent to a thermal incinerator for
disposal.  The incinerator emits carbon monoxide (CO), hydrocar-
bons, and nitrogen oxides (NOV) .
                             A,

A representative plant was defined for the purpose of assessing
the environmental impact of atmospheric emissions from acrylic
acid plants.  The representative plant has a production capacity
of 85,000 metric tons/yr and utilizes the SOHIO technology for
propylene oxidation.  It also uses a thermal incinerator to
control emissions of organic compounds from various vents in the
process.  Emission points and controlled emission factors for the
representative plant are given in Table 1.

In order to quantify the hazard potential of acrylic acid manu-
facture, source severity was defined as the ratio of the maximum
time-averaged ground level concentration, Xmax, of a pollutant
emitted from the representative plant to the hazard level of
exposure F for the pollutant.  The hazard level of exposure was
defined as the primary ambient air quality standard for criteria
al metric ton equals 106 grams; conversion factors and metric
 system prefixes are presented in the prefatory material.

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    TABLE  1.   CONTROLLED  EMISSION  FACTORS  AND  SOURCE
               SEVERITIES  FOR A REPRESENTATIVE  PLANT

Emission point and material emitted
Criteria pollutants:
Hydrocarbons :
Propylene storage tank vents
Heat-transfer circuit vents
Solvent storage tank vents
Intermediate acrylic acid storage
tank vents
Vacuum column steam jets
Acrylic acid storage tank vents
Transport loading facility vents
Incinerator stack
Fugitive emissions
Nitrogen oxides: Incinerator stack
Carbon monoxide: Incinerator stack
Chemical substances:

Acetaldehyde
Acetic acid
Acetone
Acrolein ''
Acrolein dimer
Acrylic acid
Benzene
Diphenyl-diphenyl oxide eutectic
Ethyl acrylate
Formaldehyde
Isopropyl ether
Maleic acid
Phenol
Propane
Propylene
Emission
factor,
g/kg

<0.6b
U
~h
u
~u
D

<0.02
<0.2b
U
~b
U
<0.4
_C
<0.7
<0.7

c
~~c
~c
c
~c
~c
~c
~c
~"c
~c
~c
c
\*
c
~c
~ c

Source
severity

<0
0
0
0

<0
<0
0
0
<0
0
<0
<0


















.7




.05
.2


.3

.6
.002

d
~d
~d
~d
~d
~d
~d
~d
~d
~d
~d
~d
vt
~d
~d
~d


JIncludes  all organic compounds except methane.
^Emissions vented to incinerator.
'Species emitted but not quantified due to lack  of data;
 hence,  emission factors cannot be estimated.
 Not calculated due to lack of data.

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pollutants.9  For noncriteria pollutants, F is a  surrogate  pri-
mary ambient air quality standard defined as a reduced  threshold
limit value  [(TLV)(8/24)(1/100)].  Using Gaussian plume disper-
sion theory, together with the  controlled emission  factors  in
Table 1, source severities were calculated for each emission
point and for each species of emission.  The results are also
presented in Table 1.  Source severities may exceed 0.1 for
nitrogen oxides emitted from the incinerator stack, and for
hydrocarbons emitted from the vacuum column steam jet and the
incinerator stack.

Total emissions from acrylic acid production by propylene oxida-
tion are less than 160 metric tons/yr for hydrocarbons  and less
than 200 metric tons/yr for both carbon monoxide  and nitrogen
oxides.  These emissions represent less than 0.0006%, less than
0.0002%, and less than 0.0009%, respectively, of  total  national
emissions of these compounds from stationary sources.   The above
hydrocarbon emissions represent less than 0.002%  and less than
0.006% of state hydrocarbon emissions in Louisiana and  Texas,
respectively.  The corresponding values for carbon monoxide are
less than 0.0008% in Louisiana  and less than 0.002% in  Texas.
For nitrogen oxides, the values are less than 0.01% in  both
Louisiana and Texas.

The average rmmber of persons exposed to an annual average con-
centration, \, of a pollutant from the representative plant for
which x/F J-s greater than 0.1 was estimated and designated as
the "affected population."  This calculation was made for hydro-
carbons and nitrogen oxides since the upper bounds on source
severity are greater than 0.1 for these compounds.  The affected
populations are less than 600 persons for hydrocarbons  and less
than 1,200 persons for nitrogen oxides.

In addition to the thermal incinerator that controls vented hy-
drocarbons, one plant employs surface condensers  followed by a
chilled-water vent condenser to control hydrocarbon emissions
from vacuum column steam jets.   The control efficiency  of this
system is estimated to be 75% under the worst conditions.   This
plant also employs pressurized nitrogen blankets together with
chilled-water vent condensers to reduce hydrocarbon emissions
from the intermediate acrylic acid storage tanks.  The  control
efficiency of incinerators at acrylic acid plants is estimated
to be greater than 98%.
 There is no primary ambient air quality standard for hydro-
 carbons.  The value of 160 yg/m3 used for hydrocarbons in this
 report is an EPA-recommended guideline for meeting the primary
 ambient air quality standard for oxidants.

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Production of aerylie-acid in the 5-yr period from 1975 through
1980 is expected to increase by 7% annually, or 40% over the
5-yr period.  In 1980, an estimated 140,000 metric tons of
acrylic acid will be produced.  However, incinerators are pres-
ently operating at a fraction of their organic feed capacity
because production is well below existing capacity.  Increased
production will result primarily in the partial substitution of
organic wastes for natural gas as fuel for the incinerators.
Hence, very little increase in emissions from acrylic acid pro-
duction is expected through 1980.

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                            SECTION 3

                       SOURCE DESCRIPTION
PROCESS DESCRIPTION

Currently there are five commercial processes for the production
of acrylic acid via propylene oxidation:  the SOHIO process, the
Rohm & Haas process, the Toyo Soda process, the Mitsubishi Petrol-
eum process, and the Japan Catalytic process.  The processes are
similar, involving the two-stage oxidation of propylene to
acrylic acid followed by recovery and purification of the acid.
The processes differ primarily in the catalysts used and in the
details of the recovery and purification operations.  Of the
three U.S. plants employing propylene oxidation, two are based
on SOHIO technology, while the third uses the Rohm & Haas
process.

A flow diagram for the SOHIO process is presented in Figure 1.
The process itself is described in the following subsections.

Chemistry

Acrolein--
The catalytic vapor-phase oxidation of propylene to acrolein and
the subsequent oxidation of acrolein to acrylic acid can be
represented by the following stoichiometric equations:

            CH2=CH-CH3 + 02 	*• CH2=CH-CHO + H2O             (1)
            propylene  oxygen      acrolein   water

              CH2=CH-CHO + 1/2 02	»> CH2=CH-COOH             (2)

               acrolein    oxygen      acrylic acid

Studies on the catalytic oxidation (oxidative dehydrogenation)
of propylene using bismuth molybdate catalysts have shown that
acrolein is formed by a free-radical mechanism  (1-10).
(1)  Adams, C. R., and T. J. Jennings.  Investigation of the
    Mechanism of Catalytic Oxidation of Propylene to Acrolein and
    Acrylonitrile.  Journal of Catalysis, 2(l):63-68, 1963.

(2)  Adams, C. R., H. H. Voge, C. Z. Morgan, and W. E. Armstrong.

                                                       (continued)
                                6

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                           STEAM
                           _L
                         *
                        WATER
   PREH EATER
            SOLVENT
EXTRACTION      RECOVERY       SOLVENT
 COLUMN       TOWER       STRIPPER
LIGHLENDS
STRIPPER

^_
Jf\



4
i


                                                                                                                   ENVIRONMENTAL EMISSIONS
                                                                                                              -^  PROPYLENE STORAGE TANK VENT GAS
                                                                                                                  HEAT TRANSFER-CIRCUIT VEM5
                                                                                                                  INCINERATOR STACK GAS
                                                                                                                  ACRYLIC ACID STORAGE TANK VENT GAS
                                                                                                                  VACUUM COLUMN STEAM JETS
                                                                                                              9^ TRANSPORT LOADING FACILITY VENT GAS
                                                                                                                 INTERMEDIATE ACRYLIC ACID
                                                                                                                  STORAGE TANK VENT CAS
                                                                                                                  SOLVENT STORAGE TANK VENT GAS
      Figure  1.     SOHIO  process  for  the  production  of  acrylic  acid.

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A free-radical reaction usually involves a combination of or
series of complex reaction steps.  Presently, it is not possible
to give a quantitative mechanistic description of the chemistry
involved in the oxidation of propylene to acrolein  (or acrylic
acid) because the sequence of reaction steps is unknown.  In
addition, several mechanisms may be operating simultaneously.
Therefore, the chemistry of the catalytic oxidation of propylene
must necessarily be limited to a qualitative discussion.

The one conclusion that seems to have been established, and the
one universally accepted mechanism, is that the rate-determining
step involves an initial abstraction of hydrogen from the propy-
lene methyl (a^lylic) group to form a symmetric, labile allyl
intermediate:
 (continued)
     Oxidation of Butylenes and Propylene Over Bismuth Molybdate.
     Journal of Catalysis, 3(4):379-386, 1964.

  (3) Adams, C. R., and T. J. Jennings.  Mechanism Studies of the
     Catalytic Oxidation of Propylene.  Journal of Catalysis,
     3(6):549-558, 1964.

  (4) Keulks, G. W., and M. P. Rosynek.  Mechanistic Studies of
     Propylene Oxidation on Bismuth Molybdate.  Preprints,
     Division Petroleum Chemistry, American Chemical Society,
     14(4):C55-C61, 1969.

  (5) Callahan, J. L., R. K. Grasselli, E. C. Milberger, and
     H. A- Strecker.  Oxidation and Ammoxidation of Propylene
     Over Bismuth Molybdate Catalyst.  Preprints, Division of
     Petroleum Chemistry, American Chemical Society, 14(4):
     C13-C27, 1969.

  (6) Peacock, J. M., A. J. Parker, P. G. Ashmore, and J. A.
     Hockey.  The Oxidation of Propene Over Bismuth Oxide,
     Molybdenum Oxide, and Bismuth Moiybdate Catalysts.  IV.
     The Selective Oxidation of Propene.  Journal of Catalysis,
     15(4) :398-406, 1969.

  (7) Margolis, L. Ya.  On the Mechanism of Catalytic Oxidation
     of Hydrocarbons.  Journal of Catalysis, 21(1):93-101, 1971.

  (8) Keulks, G. W.  The Method of Oxygen Atom Incorporation into
     the Products of Propylene Oxidation Over Bismuth Molybdate.
     Journal of Catalysis, 19(2):232-235, 1970.

  (9) Keulks, G. W., M. P. Rosynek, and C. Daniel.  Bismuth
     Molybdate Catalysts.  Industrial and Engineering Chemistry,
     Product Research and Development, 10(2):138-142, 1971.

 (10) Keulks, G. W., C. Daniel, and J. R. Monnier.  Evidence for
     Surface Initiated Homogeneous Reactions During the
     Catalytic Oxidation of Propylene.  Preprints, Division of
     Petroleum Chemistry, American Chemical Society, 17(1):
     B5-B11, 1972.

                                8

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          CH2=CH-CH3 +  [0]   V   ;>  [CH2	CH	CH2]         (3)

          propylene  oxygen               allyl
                                       intermediate

Since, according to kinetic  studies,  the  interaction  of  hydro-
carbons at the catalyst surface, is the rate-limiting  step,  it
has been postulated that in  the  first step propylene  forms  a IT
complex (through its double  bond) with the catalyst surface (7).
The methyl group is adsorbed, simultaneously, onto a  molecular
oxygen ion (0~2) which abstracts hydrogen to form  an  "allyl-type"
intermediate  (1, 7-9).  This intermediate is bound to the cata-
lyst surface as a ir-ally! complex  (7) .  There is evidence that
the initial removal of a hydrogen atom produces a  "pre-allyl
intermediate," which rapidly isomerizes by means of an electron
shift and then becomes attached  to the catalyst surface  as  a
7r-allyl intermediate complex  (1, 7) .

The sites for propylene reactivity are believed to be "anion
vacancies on the metal atom  in the oxygen boundary layer"  (7).
The bismuth molybdate structure  is composed of layers of bismuth
oxide cations and molybdenum oxide cations connected  by  layers of
molecular oxygen ions.  The  oxygen boundary layers occur on the
molybdenum cation layers creating anion vacancies on  the molyb-
denum atoms (8) .  Molybdenum is  also  known to form TT  and TT-allyl
complexes with olefins.  Consequently, it can be surmised that
when a propylene molecule enters an area  of an anion  vacancy (in
a molybdate), it becomes attached to  the  surface of the  catalyst
by forming a IT bond with the molybdenum.  Concomitantly, the
methyl group would be in the vicinity of  a (negative) molecular
oxygen ion in the oxygen boundary layer,  and it would be adsorbed
because it carries a fractional  electronic positive charge.

Acrolein can be formed from  the  allyl intermediate by parallel
mechanisms that could be operating simultaneously  (10).  One
mechanism that has been proposed (1,  3, 5, 7-10) is that the
initial hydrogen abstraction is  followed  immediately  by  abstrac-
tion of a second hydrogen from either end of the symmetric
intermediate to form the diradical:


         [CH2rT-r^-.CH.-T-r-r-.CH2] +  [0] 	("H) > [CH2=CH-CH]        (4)

               allyl           oxygen        acrolein
             intermediate                    precursor
                                             diradical
a[0] denotes a reactive form of oxygen;  i.e.,  it  could  be  the
 ground state diradical, triplet oxygen,  chemisorbed, or ionic
 oxygen.

-------
The diradical, being highly reactive, would readily  incorporate
oxygen, presumably from the oxide lattice  (6,  8,  10),  to  form
acrolein, which desorbs into the gas phase:


               [CH2=CH-CH] + [0] - > CH2=CH-CHO             (5)
                       •
                 acrolein   oxygen      acrolein
                precursor
                diradical

The overall kinetics for this mechanism are first order in propyl-
ene pressure and zero order in oxygen pressure because the
oxygen in the product comes from the catalyst  (6, 10).  Bismuth,
cobalt, and tin molybdates are three catalysts that  produce
acrolein by this mechanistic pathway.  The activation  energy  is
80 to 130 MJ/kg mole over the temperature range 350°C  to  500°C
(2, 9).  The exothermic heat of reaction is 290 MJ/kg mole  (2).

The oxygen boundary layers are not only the site  of  hydrogen
abstraction; they also serve as the source of  the oxygen  that is
incorporated into the products.  The removal of oxygen from the
boundary layers leaves the surface in a reduced state.  The sur-
face layers are reoxidized to their original valence state by
diffusion of molecular oxygen ions from the catalyst bulk rather
than by gas-phase oxygen  (8) .  The oxygen content of the  cata-
lyst is replenished by oxygen from the gas phase, which becomes
adsorbed on the catalyst surface and then rapidly diffuses
throughout the bulk of the catalyst (8).  These diffusional steps
take place rapidly compared with the reaction steps, so that  no
kinetic dependence on oxygen partial pressure is  observed.

Until recently, the first mechanism was the most  widely accepted
theory of acrolein formation because earlier work had  strongly
suggested that acrolein was produced from metal oxide catalysts,
in general, by this mechanism (1, 3, 10) .  However,  recent
kinetic studies have indicated that a second mechanism may be
operating simultaneously; namely, oxygen is incorporated  before
abstraction of the second hydrogen atom (1, 10) .  In this paral-
lel or second mechanism, the allyl intermediate adds oxygen
before abstraction of the second hydrogen atom to form a  peroxide
or hydroperoxide intermediate which decomposes on the  surface to
produce acrolein:
                        +   02  - >•  [CH2=CH-CH2-O-0- (H) ]   (6)

         allyl           molecular            peroxy or
       intermediate       oxygen             (hydroperoxy)
                                             intermediate
                                    — T-TO •
            [CH2=CH-CH2-0-0-(H) ]    (HO) * CH2=CH-CHO          (7)

                  peroxy or                  acrolein
                 (hydroperoxy)
                 intermediate

                               10

-------
A kinetic dependence on oxygen partial pressure is observed
(first order in oxygen partial pressure and Zero order in propy-
lene pressure) because the oxygen comes from a chemisorbed layer
or from the gas phase rather than from the lattice structure.
These kinetics have been observed over copper and its oxides and
gold, suggesting that acrolein is formed by the second mechanism
in the presence of these catalysts.

The second mechanism more nearly corresponds to accepted theories
of free-radical organic chemistry and free-radical polymerization
(personal communications with J. M. Butler and G. A. Richardson,
Monsanto Research Corp., Dayton, Ohio, 18 August 1977).  Oxygen
is usually incorporated before hydrogen abstraction in these
types of reactions; i.e., the oxygen is incorporated as the
hydroperoxide, which then decomposes.

In addition to the possibility of several simultaneously operat-
ing mechanisms, kinetic studies have indicated that the catalytic
oxidation of olefins may be further complicated by homogeneous
gas-phase reactions.  These surface-initiated homogeneous reac-
tions become important at high propylene-to-oxygen ratios, in
reactors having large postcatalytic volume, or with a catalyst
having a large void fraction (9, 10).

The mechanism and kinetics of the surface-initiated homogeneous
reactions are similar to those in the second mechanism described
above.  The mechanism probably involves the desorption of the
allyl intermediate as an ally radical (7, 10), or the allyl
intermediate adds oxygen before abstraction of the second hydro-
gen atom to form an allyl peroxide intermediate (10).  This
peroxide intermediate or the allyl radical, on desorption into
the gas phase, can react with propylene by a free-radical
mechanism to produce propylene oxide (10):
  L CH 2 » • • • •CH * * * » • CH 2 J

        allyl
      intermediate
                       desorption
                  02
                        [CH2=CH-CH2-0-0(H)
                             peroxy  or
                           ( hy droper oxy )
                           intermediate
                                          •C-CH=CH2
               allyl
              radical
                                                       (8)
[CH2=CH-CH2-0-0(H)

     peroxy or
   (hydroperoxy)
   intermediate
CH2=CH-CH3

propylene
CH2-CH-CH3
  V
propylene
  oxide
                                                               (9)
                               11

-------
The kinetics of this mechanism are typically first order in
oxygen pressure and zero order in propylene pressure.  Copper-
molybdenum, iron-molybdenum, and manganese-molybdenum oxide
catalysts were studied under conditions in which the surface-
initiated homogeneous reaction mechanism should be operative;
i.e., at high propylene-to-oxygen ratios, or in a reactor having
a large postcatalytic volume, or with a catalyst having a large
void fraction.  In each case, propylene oxide was produced, sug-
gesting that the surface-initiated homogeneous reaction mechanism
was operating.  Combinations of the above conditions also yielded
propylene oxide (10).

The surface-initiated homogeneous reactions are independent of
the commonly accepted mechanisms leading to acrolein and, under
the proper conditions of reactor design, catalyst type, and pro-
pylene/oxygen ratio, are probably operating simultaneously.

Acrylic Acid--
The oxidation of acrolein to acrylic acid is usually conducted
over catalysts containing molybdenum or vanadium oxides (see Cat-
alysts, p. 13).  This process appears to be more straightforward
than the oxidation of propylene to acrolein.  Acrylic acid can
be formed by the reaction of acrolein with surface oxygen:

                CH2=CH-CHO + [0] 	*-CH2=CH-COOH             (10)

                 acrolein  surface  acrylic acid
                            oxygen

An alternative, albeit less likely, mechanism may involve an
additional hydrogen abstraction by an oxygen atom or hydroxy
radical, followed by the addition of a hydroxy radical (11):

                     0                    0

              CH2=CH-CH + HO* 	»• CH2=CH-C* + H20           (11)

               acrolein hydroxy     radical   water
                        radical  intermediate

                        0                   O
                        II                   II
                 CH2=CH-C» + HO* 	»CH2=CH-C-OH             (12)

                 radical   hydroxy   acrylic acid
              intermediate radical
(11) Luskin, L. S.  Acrylic Acid, Methacrylic Acid, and the
     Related Esters.  In:  High Polymers, E. C. Leonard, ed.,
     Vol. 24, Part 1.  Wiley-Interscience, New York, New York,
     1970.  pp. 105-203.

                               12

-------
Byproducts —
It has been shown that when propylene is reacted with excess oxy-
gen, virtually all of the side products produced, including car-
bon monoxide and carbon dioxide, result from the further oxidation
of acrolein or its surface species precursors  (9) .  However/ a
pathway becomes available for carbon dioxide formation directly
from propylene in a deficiency  (less than the  stoichiometric
amount required for complete oxidation) of oxygen (9) .

Acetaldehyde, acetic acid, and carbon oxides are the major by-
products formed in the propylene oxidation process.  Other bypro-
ducts which have been reported include maleic  acid, phthalic
acid, formic acid, formaldehyde, propionic acid, propionaldehyde,
acetone, allyl alcohol, ethylene, and hydrogen.  In addition some
high-boiling materials are formed by dimerization, polymeriza-
tion, and condensation reactions of acrylic acid and acrolein;
e.g., poly(acrylic acid/acrolein)  (1-11).  In  commercial pro-
duction of acrylic acid, the formation of byproducts is minimized
by the addition of steam', which improves catalyst selectivity
(see Feed Materials, p. 15).

Catalysts

The catalysts employed in commercial processes for the Oxidation
of propylene to acrolein are complex mixtures  of the oxides of
polyvalent metals.  Cobalt and molybdenum are  usually the pre-
dominant metals, frequently in the form of cobalt molybdate.  In
one example the catalyst consists of cobalt molybdate, iron
oxide, and/or iron molybdate, and an oxide of  tellurium (12) .
The atomic proportions of the metal components of the catalyst
can be represented by the formula
where "a" is a number from 0.01 to 10,  "b" is from 0*5 to 2, "c"
is from 0.5 to 2, and "d" is from 0-01  to 0.1.  A propylene con-
Version of 82% was obtained in the presence of steam with a catal
yst having the specific composition Fe0 f 288coi . 0M°1 . oTeo . o 1 5 •  In
the absence of steam, a conversion of 82% was obtained with a low
iron catalyst having • the composition Fe0 . QJ 2Col . QHol . QTeQ . 01 5 •

In another example, the catalyst composition is expressed by the
general formula

                        Mo Co, Fe Bi ,A O.p
                          a  b  c  d e  f
 (12) Kiff, B. W., and N. R. Cox.  Oxidation of  1,2-Olefins  to
     Oxygenated  Products.  U.S. Patent  3,467,716  (to Union
     Carbide), September 16,  1969.
                                13

-------
where  "a" is equal to 12,  "b" is  7 to 12,  "c"  is  0.3  to  4,  "d"  is
0.4 to 2.5, "e" is 0.1 to  3, and  "f" is 47 to  73  (13).   In  this
formula, "A" represents tin or a  composite system of  tin and  one
or more of the elements aluminum, nickel, tungsten, chromium,
indium, and niobium.  The  maximum conversion of propylene (90.1%)
was obtained with a catalyst having the composition
M0l 2Co i 0Fe ! . 0Bi i . 0Sn0 . 5W0 . 5056 . 5 -
The catalyst in a recent patent is represented by the formula


                          MoaC°bTecXd°e

where "X" represents boron or rhodium  (14).  When "a" is 100,  "b"
is 40 to 200, "c" is 0.1 to 7, "d" is either 5 to 75  (when  "X" is
boron) or 0.1 to 3  (when "X" is rhodium), and "e" is 300 to 900.
The maximum conversion of propylene  (93%) was obtained with a
catalyst having the composition Mo^ Q oCos sTe2 . 6^no . k o®k 72 •
The above catalysts may be used in the form of pellets, or they
may be used with a carrier or support such as silica, alumina,
silicon carbide, alumina-silica, or titania.

In addition to the above catalysts, the SOHIO process reportedly
uses a bismuth phosphomolybdate catalyst for producing acrolein
(15) .  The catalyst composition in one example was Mo =12,
Bi = 2, Mg = 4.5, Fe = 4 , P = 0.5  (16).

Catalysts containing molybdenum and vanadium oxides are typically
used for the oxidation of acrolein to acrylic acid.  For example,
one patented catalyst for this process is characterized by the
formula


                          VaMobWcCrdCue
where "a" is from 14 to 24, "b" is 12, "c" is from 4 to 20, "d"
is from 1 to 10, and "e" is from 0 to 12  (17).   An acrolein con-
version of 97.5% and a one-pass acrylic acid yield of 90.5% were
(13)  Ono, I., and M. Akashi.  Catalyst for the Production of
     Acrolein and Acrylic Acid.  U.S. Patent 3,786,000 (to Rohm
     and Haas), January 15, 1974.
(14)  Levy, L. B.  Catalyst for Oxidation of Olefins.  U.S. Patent
     3,875,078  (to Celanese Corporation), April 1, 1975.

(15)  Propylene Gets the Nod.  Chemical Week, 112(4) :37, 1973.

(16)  Grasselli, R. K.,  et al.   Oxidation of Olefins.  German
     Patent 2,203,710 (to Standard Oil), August 17, 1972.

(17)  Ohara, T., N. M. Ninomiya, I. Yanaqisawa, I. Wada, and
     M. Wada.  Process for the Preparation of Acrylic Acid.  U.S.
     Patent 3,775,474 (to Nippon Shokubai Kagaku Kogyo Co.),
     November 27, 1973.

                               14

-------
obtained with a catalyst having the specific composition
V15Mo12W6-8Cr2>0Cu5>2.

Feed Materials

The feed materials used in the SOHIO process consist of commer-
cial grade  (90% to 95%) propylene, air, and steam.  The principal
impurity is propane, which behaves as an inert  in the reaction.
Small amounts of butane and butylene may also be present in  the
feedstock.  Liquid propylene is vaporized and fed to the first-
stage reactor.  Vaporization is achieved by  circulating  (heated)
cooling water from the quench tower circulation loop.

Reactor feed steam is generated from recycled process water  which
contains organic impurities consisting of reaction products  and
byproducts.  Excess process water is sent from  the steam genera-
tor to a thermal incinerator for disposal.

Process air is passed through a preheater and then fed to the
first-stage reactor.

Feed ratios have not been published for the SOHIO process.
However, the propylene/steam/air fractions for  the Toyo Soda
process are 5/35/60 mole percent  (18).

The purpose of 'the steam introduced with the feed is threefold
(18, 19) :

     • To increase the operating propylene/air  ratio by narrow-
       ing  the explosion range of propylene-air mixture.

     • To facilitate temperature control by removing part of the
       energy liberated by the reaction in the  form of sensible
       heat of the steam.

     • To improve catalyst selectivity by increasing the
       desorption rate of reaction products.

Reaction Section

Propylene is oxidized to acrylic acid in a two-stage, fixed-bed,
tubular reactor system.  Propylene is oxidized  to acrolein in the
first stage.  The effluent from the first reactor is fed to  the
second stage where the acrolein is oxidized to  acrylic acid.  The
reactor system operates at a gage pressure of 103 kPa to 207 kPa
 (18) Nakatani, H.  Toyo's New Aerylate  Process.   Hydrocarbon
     Processing,  48 (5):152-154,  1969.

 (19) Sakuyama, S., T.  Ohara, N.  Shimizu,  and  K.  Kubota.   A New
     Oxidation Process for Acrylic Acid from  Propylene.   Chem-
     tech,  3(6) :350-355, 1973.

                                15

-------
and temperatures between 290°C and 400°C  (20).  The first-stage
reaction is carried out at 290°C to 333°C and the second-stage
reaction at 360°C to 400°C.  Temperature control in both reactors
is maintained by circulating Dowtherm A®  (diphenyl-diphenyl oxide
eutectic) or a similar organic heat-transfer fluid to remove the
heat of reaction.  The energy liberated in the two reactors is
used to produce steam in waste heat boilers.

The yield from the process is 1.1 kg to 1.3 kg acrylic acid per
kilogram 100% propylene feed (18, 19).  The theoretical yield is
1.7 kg acrylic acid per kilogram propylene.

Acrylic Acid Recovery

The effluent from the second-stage reactor is sent to the quench
towep where acrylic acid is condensed and recovered as a 20% to
30% aqueous solution (18, 19).   The off-gas from the quench tower,
consisting primarily of carbon oxides, nitrogen, oxygen, propane,
and unreacted propylene, is sent to the incinerator for disposal.

The aqueous acrylic acid solution is sent to the extraction col-
umn where the acrylic acid is separated from the water by extrac-
tion with an organic solvent.  The extract is fed to the solvent
stripping column, where the solvent is separated from the acrylic
acid by vacuum distillation.  The recovered solvent is taken
overhead, condensed, and recycled to the extraction column.
Crude acrylic acid is obtained as the bottoms product from the
solvent stripping column.

The raffinate from the extraction column is sent to the solvent
recovery tower where the solvent is separated from the water by
distillation at atmospheric pressure.  The recovered solvent is
taken overhead, condensed, and recycled to the extraction column.
The bottoms from the solvent recovery tower, which consist of
water containing organic impurities, are recycled to the steam
generator.a

A large number of solvents can be used in the extraction step.
Solvents described in the patent literature are listed in
Table 2.

Acrylic Acid Purification

The crude acrylic acid from the solvent stripping column is fed
to the light-ends stripping column where the more volatile
 One plant sends this stream to a central wastewater treatment
 facility for disposal.   Another plant employs a wastewater
 treatment facility dedicated solely to the acrylic acid and
 acrylic esters processes.

(20)  Acrylic Acid (SOHIO Process).   Hydrocarbon Processing,
     52(11):95, 1973.

                                16

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           TABLE 2.   SOLVENTS GIVEN  IN PATENT  LITERATURE
                      FOR ACRYLIC ACID RECOVERY


                                            Distribution coefficient
   	Solvent	of acrylic  acid	

   Ethyl acetate                                      2.7
   Ethyl acrylate                                     1.4
   Isopropyl ether                                    1.6
   Ethyl butyl ether                                  1.6
   Methyl isobutyl ketone                              2.9
   Methyl phenyl ketone                               2.2
   Isopropyl acetate                                  2.3
   Ethyl 3-ethoxypropionate                            2.8
   Methyl acrylate                                    2.3
   Methyl ethyl ketone + benzene or toluene             1.2
   N-ethyl-2-hexyl-pyrrolidone                         7.8
   2-Ethylhexanol                                     1.9
   n-Butanol                                         2.9
   Methyl isobutyrate                                  -P
   Ethyl isobutyrate                                   -•
   g-alkyloxy propionate                                -,
   3,3,5-Trimethylcyclohexanone + isophorone              -.
   Butyl acetate + butanol                              -.
   Isophorone                                         -.
   Diisobutyl ketone                                   -.
   Butyl acrylate

   a
    The distribution coefficient is the ratio of the  concentration of
    acrylic acid in a given solvent to the concentration of acrylic
    acid in water when the two phases (solvent and water) are in
    equilibrium.
   b
    Not available.

impurities (chiefly acetic acid and residual  solvent)  are  removed
by vacuum distillation.   The overhead from  the light-ends  strip-
per is  condensed and sent to the solvent recovery tower.   The
bottoms  from the light-ends stripper, which contain the acrylic
acid, are split into two streams.   One stream is sent to the
esterification plant for production of acrylates.   The other
stream  is sent to  the  rectification column where less volatile
impurities (chiefly acrylic polymers and maleic  acid)  are
separated (as  bottoms)  in a vacuum  distillation  step.

The bottom stream  from the rectifier is sent  to  the incinerator
for disposal.   The  overhead product, consisting  of refined
acrylic  acid,  is condensed and sent to a storage tank.  Alterna-
tively,  the refined acrylic acid can be diverted to the esteri-
fication section of the plant for production  of  acrylates.
                                  17

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Refined acrylic acid is pumped from storage tanks to the trans-
port loading facility for shipment in tank cars and/or tank
trucks.

Polymerization Inhibition

Since acrylic acid readily polymerizes, addition of a polymeriza-
tion inhibitor is required at various points in the recovery and
purification sections of the process to prevent fouling of equip-
ment and maintain uninterrupted plant operation.  Hydroquinone
and monoethanolamine are used as polymerization inhibitors in the
SOHIO process.  However, a large number of compounds can be used
for this purpose.  Inhibitor systems obtained from the patent
literature are summarized in Table 3 (21-47).
(21) Recovery of Acrylic Acid.  British Patent 1,293,848 (to
     Toyo Soda Co.), October 25, 1972.

(22) Otsuki, S., K. Hori, and I. Miyanohara.  Polymerization
     Inhibition of Acrylic Acid.  U.S. Patent 3,674,651 (to
     Toyo Soda Co.), July 4, 1972.

(23) Otsuki, S., and I. Miyanohara.  Stabilization of Acrylic
     Acid or Esters Thereof.  U.S. Patent 3,666,794 (to Toyo
     Soda Co.), May 30, 1972.

(24) Stabilization of a,$-Ethylenic Aldehydes.  Netherlands
     Patent Application 65,16553  (Shell International Research),
     June 23, 1966.

(25) Preparation of Esters.  British Patent 1,185,069 (to British
     Titan Products), March 18, 1970.

(26) Alkoxy Phenol Stabilizers.  Netherlands Patent 134846 (to
     ICI), March 15, 1972.

(27) Yamagishi, A., et al.  Method for Inhibiting the Polymeriza-
     tion of Unsaturated Carboxylic Acid Esters.  U.S. Patent
     3,636,086 (to Sumitomo Chemical), January 18, 1972.

(28) Improvements in the Handling of Acrylic Acid.  British
     Patent 958,226 (to Celanese Corporation), May 21, 1964.

(29) Brown, C. J., et al.  Distillation of Acrylic Acid.  British
     Patent 1,265,419  (to BP Chemicals), March 1, 1972.

(30) Hexamethylene Tetramine as Stabilizer for  (Meth) Acrylate
     Esters.  French Patent 2,085,773  (To Japanese Geon),
     December 31, 1971.

(31) Stabilizing Unsaturated Acids.  French Patent 2,100,376  (to
     Japanese Geon), March 17, 1972.

(32) Hartel, H.  Polymerization Inhibitors for Monomeric Vinyl
     Esters, Acrylic Acid Esters, or Styrene.  German Patent
                                                      (Continued)

                               18

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TABLE 3.  ACRYLIC ACID POLYMERIZATION INHIBITORS
          OBTAINED FROM PATENT  LITERATURE  (21-47)
Inhibitor system
Diphenylamine
Hydroquinone
Oxygen
N-methy Idipheny lamine
Hydroquinone
Air
N-c-chlorophenylaniline
Oxygen
N-o-methylphenylaniline
Air
( N , N ' -dipheny 1 -p -pheny lened iamine
Air
Diphenylamine
Benzoquinone
Oxygen
N-methy Idipheny lamine
Benzoquinone
Air
N-o-methylphenylaniline
Benzoquinone
Air
N-o-methylphenylaniline
Benzoquinone
Air
Diphenylamine
Hydroquinone monomethyl ether
Air
Phenothiazine
Cupric dithiocarbamate
4-Alkoxyphenols
Hydroquinone \
Condensed phosphoric acid salts >
Silicic acid salts J
Hydroquinone
Phenol
Oxygen - containing gas
Diphenylamine
Oxygen - containing gas
Hydroquinone monomethyl ether
Phenothiazine
Nitric oxide - containing gas
Hexamethylenetetramine
Phosphorous acid (or oxide) )
Hydroxyl compound such as a cresol >
Phosphoric acid esters, phosphines, or benzaldehyde J
Oximes or hydrazones of p-benzoquinone
2 , 6-Di-t-butyl-p-cresol
Semicarbazone or semicarbazide compounds
Ethylene thiourea
Copper dimethyldithiocarbamate
Copper dialkyldithiocarbamate
Ammonium chloride
Chromium acetate
Phenothiazine
Hydroquinone monomethyl ether)
Benzoquinone /
Oxygen - containing gas J
Protoanemonine
Dialkyl nitroxide
Thiosemicarbazide
Iodine and alkali iodide
N-alkylpyrroles
Phosphates
Concentration
3,000
200
(1.0 vol %)
3,000
200
(5.0 vol %)
3,000
(1.0 vol %)
3,000
(5.0 vol %)
3,000
(5.0 vol %)
500
500
(0.5 vol %)
500
500
(3.0 vol %}
500
500
(3.0 vol %)
500
500
(3.0 vol %)
500
500
(3.0 vol %)
10,000
20 to 50
0.5 to 5.0
10 to 10,000
<50
<200
<2,000
50 to 5,000
(0.02 to 2 vol %)
10 to 200
1 to 550
(0.01 to 0.2 vol %)
10 to 30,000
10 to 50,000
(10-6 to 1.0 mole I)
10 to 50,000
<1.0
2 to 300
500 to 10,000
10 to 50,000
10 to 50,000
<50
1 to 10,000
<50
5 to 5,000
10 to 1,000
1 to 300
50 to 5,000
10 to 1,000
100 to 1,000
                        19

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Process operations such as distillation and quenching involve
both a vapor and a liquid phase.  Thus, inhibitors usually
consist of a volatile and a nonvolatile component.  A typical
(Continued)
     1,233,869 (to Dynamit Nobel), February 7, 1967.

(33) Sato, R., et al.  2,6-Di-tert-p-Cresol as Polymerization
     Inhibitor for Acrylic Acid Derivatives.  German Offen.
     Patent 2,112,053 (to Japanese Geon), October 7, 1971.

(34) Acrylic Esters.  Japanese Patent 42-23404 (to Asahi Chemical
     Industry), November 13, 1967.

(35) Stabilized Vinyl Compounds.  Japanese  Patent 43-201  (to  Toa
     Gosei Chemical Industry), January 6, 1968.

(36) Sudo, M., et al.  Methyl Acrylate.  Japanese Patent 43-10611
     (to Japan Synthetic Chemical Industry), May 4,  1968.

(37) Sudo, M., et al.  Prevention of Polymerization During the
     Preparation of Unsaturated Carboxylates.   Japanese Patent
     43-29926  (to Mitsubishi Rayon), December 23, 1968.

(38) Acrylic or Methacrylic Acids.  Japanese Patent 44-26285  (to
     Mitsui Toatsu Chemicals), November 5, 1969.
(39) Polymerization Inhibition of (Meth) Acrylic Acids.   Japanese
     Patent 45-35285 (to Nippon Kagaku), November 11, 1970.

(40) Kawamura, Y., et al.  Polymerization Inhibitor of Acrylate
     or Methacrylate.  Japanese Patent 46-30173  (to Nitto
     Chemical Industry), September 2, 1971.

(41) Unsaturated Acid Distillation.   Belgian Patent 778,869 (to
     Rohm and Haas), August 2, 1972.

(42) Inhibition of Polymerization of Aqueous Acrylic Acid
     Solution.  Japanese Patent 47-17714  (to Nippon Kayaku),
     September 9, 1972.
(43) Bailey, H. C.  Stabilization of Acrylic Acid.  British
     Patent 1,127,127 (to BP Chemicals), September 11, 1968.

(44) Stabilization of Vinyl Monomer.  Japanese Patent 42-1415  (to
     Toa Gosei Chemical Industry), January 24, 1967.

(45) Stabilization of Methyl Methacrylate and Methyl Acrylate.
     Japanese Patent 42-7765 (to Toyo Rayon),  March 29, 1967.

(46) Girvan, I. J. M.  Stabilization of Acrylic and Methacrylic
     Monomers.  British Patent 1,124,836  (to ICI), August 21,
     1968.

(47) Shima, T., et al.   Stabilization of a,3-Unsaturated
     Aldehydes.  Japanese Patent 46-13009 (to Sumitomo Chemical),
     April 3, 1971.


                               20

-------
example is the hydroquinone-phenol system (21).  Many inhibitors
also require air or  oxygen to effectively suppress the
polymerization reaction (22).

Storage Tanks

Tanks are used to  store quantities of propylene, acrylic acid,
heat-transfer fluid,  polymerization inhibitor and solvents during
processing.  Tank  capacities  range from 1.9 m3 to 930 m3.

The temperature of the  stored liquids is kept between 21°C and
27°C.  A summary of  tankage requirements for a typical acrylic
acid plant is given  in  Table  4.

     TABLE 4.  SUMMARY  OF TANKAGE REQUIREMENTS FOR A 95,000
               METRIC TON/YR  ACRYLIC ACID PLANT9

Tank
No.
1-8
9
10
11
12
13-14
15
16-17
18-19
Material stored
Propylene
Heat- transfer fluid
Polymerization inhibitor
Isopropyl ether
Acrylic acid
Acrylic acid
Acrylic acid
Acrylic acid
Acrylic acid
Capacity,
m3
114
76
15
76
76
216
284
443
920
Turnovers
per year
_b
_c
_c
_c
230
40
30
40
10
Tank height,
m
21.5
6.1
_C
4.6
7.3
11.6
9.7
9.7
9.7

    Data obtained from confidential industry sources.

    Storage tanks are a backup source for normal propylene feed via pipe-
    line.
   C
    Data not available.


Heat-Transfer  Circuits

The SOHIO  process  employs two heat-transfer systems to control
the temperatures in the  two  reactors.  Dowtherm A or a similar
organic heat-transfer fluid  is circulated between the reactor and
the waste  heat boiler.   The  fluid is vaporized in the reactor to
remove the heat of reaction.   The vapor is condensed in thfe waste
heat boiler by heat exchange with boiler feed water to produce
steam.  The condensate is then pumped back to the reactor and
the cycle  is repeated.

Although details of the  heat-transfer circuits used in the SOHIO
process are not available, the general characteristics of organic
                                21

-------
heat-transfer fluid systems are discussed in the literature  (48-
50).  Provision must be made for venting of noncondensables  from
these systems.  Noncondensables which can accumulate include
water, phenol, and benzene  (48).  The latter two compounds are
degradation products of Dowtherm A.

Plant Shutdown, Turnaround, and Startup5

Acrylic acid plants are shut down an average of four times per
year.  Shutdown requires 8 hr and the subsequent start-up opera-
tion requires 12 hr.  In addition, process upset conditions
(tripouts) occur an average of once per month and may last for
several hours to a day, with an average duration of 4 hr.

During process upsets and shutdowns, a mixture of acrylic acid
and solvent is temporarily stored in insulated storage tanks.
Organic vapors may be emitted from these tanks due to working
and breathing losses, especially during filling operations.
These tanks are either vented to the incinerator for emission
control or provided with nitrogen blankets and chilled-water
vent condensers.

Natural gas-fired startup heaters are employed to heat the
reactor cooling medium prior to start-up and to maintain coolant
temperature during tripouts.  Periods of continuous heater oper-
ation range from several hours to several days.  Emissions from
these heaters consist of flue gases from the combustion of
natural gas.

One plant employs two smokeless flares for emission control
during incinerator maintenance shutdowns and during severe proc-
ess upsets.  One flare is used to burn the off-gas from the
quench tower.  The other flare handles the suction vent gases
from the solvent stripper, light ends stripper, and rectifier.

Cleaning and repair of process equipment during periods of proc-
ess shutdown can result in emissions of organic compounds.  One
plant employs a controlled ventilation area for performing these
operations.  The vent gass from this area is fed to the inciner-
ator for disposal.  Solid waste from cleaning and repairing
operations is incinerated in a separate solids incincerator.

 This section is based on data supplied by the operating
 companies.

(48)  Frikken, D. R.,  K. S. Rosenberg, and D.  E. Steinmeyer.
     Understanding Vapor-Phase Heat-Transfer Media.  Chemical
     Engineering,  82 (12):86-90, 1975.

(49)  Conant, A.  R.,  and W. F.  Seifert.   Dowtherm Heat Transfer
     Medium.  Chemical Engineering Progress,  59(5):46-49, 1963.

(50)  Fried, J.  R.   Heat-Transfer Agents for High-Temperature
     Systems.  Chemical Engineering, 80 (12):89-98,  1973.

                               22

-------
Startups, shutdowns, and process upsets can also result in emis-
sions of heat-transfer fluid from the heat-transfer circuits.
These emissions can be controlled by venting the circuits to the
incinerator.

GEOGRAPHICAL DISTRIBUTION

Acrylic acid is currently manufactured by four companies at four
locations in the United States with a combined capacity of 2.7 x
105 metric tons/yr.  The manufacturers, plant locations, plant
capacities, county population densities, and process types are
listed in Table 5.  It can be seen that production is confined
to the Gulf Coast area.  A map showing the locations of these
plants is given in Figure 2.  It should be noted that the present
study covers only the three plants utilizing the propylene
oxidation process.  In addition to the four plants listed in
Table 5, there are currently two plants which produce acrylic
esters, but not acrylic acid.  Dow Chemical Company's plant at
Freeport, Texas, has a capacity of 4,500 metric tons/yr for 2-
hydroxypropyl acrylates (51).  At Deer Park, Texas, the Rohm and
Haas Co., also produces acrylates by a modified Reppe process in
which the ester is obtained directly without acrylic acid as an
intermediate (51, 52).  This unit has a capacity of 1.81 x 105
metric tons/yr of acrylates.  Part of this capacity was placed
on standby status when the propylene oxidation unit came onstream
in 1977  (51) .
(51) Chemical Profile:  Acrylates.  Chemical Marketing Reporter,
     211(17):9, 1977.
(52) Ohara, R.  Production of Acrylic Ester and Its Economics -
     Propylene Oxidation Process.  Chemical Economy & Engineering
     Review, 4(7):24-29, 1972.
                               23

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         TABLE 5.  ACRYLIC ACID PLANTS (51,  52)

Company
Celanese Chemical Co.
Rohm & Haas Co.
Union Carbide Corp.
Dow-Badische Co.
Total
Location
Clear Lake, TX
Deer Park, TX
Hahnville, LA
Freeport , TX

Normal
capacity,
10^ metric
tons/yr
100
90
65
18
273
County
population
density,
persons/km2
386
386
37
29

Process
Propylene oxidation
Propylene oxidation
Propylene oxidation
High-pressure Reppe


 table is also based on information supplied by industry sources.
- BAD ISCHE, FREEPORT, TX
                        *~  '        ^    UNION CARBIDE, HAHNVILLE,LA
                 CELANESE, CLEAR LAKE, TX   \ RQHM & HMS( D£ER pARK> -

     Figure  2.   Locations of  acrylic  acid plants.

                             24

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                           SECTION 4

                           EMISSIONS
SELECTED POLLUTANTS

Compounds which have been identified in process streams in
acrylic acid plants are listed in Table 6.a  Methane and ethane
originate from the natural gas used as supplemental fuel in the
thermal incinerator; propane and propylene are from process feed
materials; ethyl aerylate and isopropyl ether are solvents (see
Table 2).  All other compounds are reaction products of the
oxidation of propylene.  The compounds listed in Table 7 were
selected for study as potential environmental pollutants.
In addition to the above compounds, nitrogen oxides are formed
in the incinerator and emitted with the stack gas.  DOWTHERM A
heat-transfer fluid and its degradation products, phenol and
benzene, are emitted from the vents in the heat-transfer circuits,
A number of other compounds may be emitted depending on the sol-
vent and polymerization inhibitor systems  (see Section 3) em-
ployed in the process.
Atmospheric reactivity and health effects of selected compounds
evident in acrylic acid production are shown in Table 7  (53, 54).
Available threshold limit values  (TLV®) are also shown.

LOCATION AND DESCRIPTION

The locations of emissions from the propylene oxidation process
are given in Table 8.  These locations are pictured in the pro-
cess flow diagram, Figure 1.  In the following description, each
emission point is discussed along with the specific technology
that may be used for its control.
 Based on confidential information supplied by operating
 companies.
(53) TLV® Threshold Limit Values for Chemical Substances and
     Physical Agents in the Workroom Environment with Intended
     Changes for 1976.  American Conference of Governmental
     Industrial Hygienists, Cincinnati, Ohio, 1976.  94 pp.

(54) Sax, N. I.  Dangerous Properties of Industrial Materials,
     Third Edition.  Reinhold Book Corporation, New York,
     New York, 1968.  1258 pp.

                               25

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TABLE 6.  COMPOUNDS IDENTIFIED IN ACRYLIC ACID PROCESSING  STREAMS
              Compound
       Formula
Acetaldehyde
Acetic acid
Acetone
Acrolein
Acrolein dimer
   (3,4-Dihydro-2H-pyran-2-carboxaldehyde)
Acrylic acid
Acrylic dimer
   (2-Carboxylethyl acrylate)
Acrylic polymer

Ethyl acrylate
Formaldehyde
Maleic acid

Propionic acid
Propane
Propylene
Isopropyl ether

Carbon oxides
Methane
Ethane
 CH3CHO
 CH3COOH
 (CH3)2CO
 CH2=CHCHO
    -CHO
 CH2=CHCOOH
 CH 2=CHCOOCH 2CH 2COOH

-/CH2-CH-CH2-CH  V
 \     COOH   COOH/n
 CH2=CHCOOCH2CH3
 ECHO
 HC-COOH
 HC-COOH
 CH3CH2COOH
 CH3CH2CH3
 CH2=CHCH3
    CH3CH3
 CH3CHOCHCH3
 CO, C02
 CH3CH3
                                26

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                   TABLE  7.   HEALTH EFFECTS  AND  ATMOSPHERIC  REACTIVITY OF
                               SELECTED  COMPOUNDS  IN ACRYLIC ACID  PRODUCTION
   Compound
    (53),
 mg/m3
   Atmospheric
   reactivity
             Health effects  (54)
Acetaldehyde

Acetic acid
Acetone

Acrolein
Acrolein dimer
Acrylic acid
Acrylic dimer
Benzene

Ethyl acrylate
Formaldehyde

Isopropyl ether
Maleic acid
Phenol

Propane
Propylene
Carbon monoxide
  180

   25
2,400
    0.25
   80

  100
    3

1,050

   19
Contributes to
  photochemical smog
   55
Toxic effects evident at moderately  chronic  levels.

Caustic irritant at chronic  levels.
No injurious effects reported; possibility of  skin
  irritations.
Extremely toxic.
Unknown.
Similar to acetic acid;  strong irritant.
Unknown.
Recognized carcinogen at chronic  levels;  anemia,
  leukopenia, macrocytosis may result.
Very toxic at acute levels.
A suspected carcinogen;  main toxic effect is
  irritation.
Irritating to skin and mucous membranes.
Irritant; highly toxic.
Prolonged exposure to low concentration results in
  digestive disturbances, nervous disorders  and
  skin eruptions.
Asphyxiant; shows little toxic effect.
Simple asphyxiant; no irritating  effects.
Causes readily reversible effects at chronic levels.
9Blanks indicate no TLV has been established.

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              TABLE 8.  LOCATION OF EMISSION POINTS
   Location    	Emission point	

       A        Propylene storage tank vents
       B        Heat-transfer circuit vents
       C        Solvent storage tank vents
       D        Intermediate acrylic acid storage tank vents
       E        Vacuum column steam jet vent
       F        Acrylic acid storage tank vents
       G        Transport loading facility vents
       H        Incinerator stack
                Fugitive emissions


    Identification letters shown in Figure 1.
    Location unknown.

Propylene Storage Tank Vents

Propylene may be stored in tanks prior to vaporization and oxi-
dation.  In one plant, propylene is produced onsite and held in
bulk storage tanks, which are the source of propylene for the
acrylic acid process.  A venting system releases excess pressure
within these storage tanks by venting propylene to the atmosphere,
Another plant receives process propylene directly via pipeline
from an offsite source.  This plant has a number of backup pro-
pylene storage tanks which are vented to an incinerator.

Heat-Transfer Circuit Vents

Dowtherm A or a similar organic heat-transfer fluid is used in
both acrolein and acrylic acid reactors to maintain proper tem-
peratures.  A venting system prevents the buildup of gaseous
heat-transfer fluid by releasing vapors to the atmosphere.  These
emissions may be controlled by venting them to the incinerator.9

Solvent Storage Tank Vents

Solvents (see Table 2) are stored prior to their use as extrac-
tion agents in the recovery of acrylic acid.  Emissions of
evaporated solvent from the storage tanks may be controlled by
venting them to the incinerator.3
 Retrofitting an existing installation to vent storage tanks,
 heat-transfer circuits, distillation columns, and transport
 loading facilities to an incinerator may not be feasible due to
 economic and safety considerations (personal communication with
 T.  L.  Rapp, Union Carbide Corp., Hahnville, Louisiana, Decem-
 ber 21, 1977).
                               28

-------
Intermediate Acrylic Acid Storage Tank Vents

Intermediate storage tanks are used to temporarily store an
acrylic acid-solvent mixture while process equipment is being
serviced.  Vents on these tanks represent an intermittent source
of organic compound emissions.  Emissions are greatest during the
period of tank filling, which may last from several hours to
several days.  These operations are performed an average of once
per month.  Emissions are controlled in one of two ways:  organic
vapors are vented to the incinerator in the first method; in the
second, a pressurized nitrogen blanket is maintained in the stor-
age tanks to inhibit the formation of organic vapors, and a
chilled water vent condenser is used to remove organics from the
vent gas.

Vacuum Column Steam Jets

Vacuum distillations are required to recover and purify acrylic
acid.  Steam jets, which produce the vacuum, emit acrylic acid
and other organics along with steam.  One plant makes use of a
water-chilled surface condenser to control these emissions.  The
other two plants vent these emissions to the incinerator.

Acrylic Acid Storage Tank Vents

Acrylic acid vapors are emitted from acrylic acid storage tanks
prior to loading and transport.  These emissions may be con-
trolled by venting them to the incinerator.3

Transport Loading Facility Vents

Acrylic acid emissions occur from the loading of acrylic acid
into tank cars.  These emissions are a result of acrylic acid
atomization and evaporation during loading procedures.  Control
of emissions from loading facilities can be accomplished by
venting them to the incinerator.3  However, these emissions are
minimal since most acrylic acid is consumed onsite for produc-
tion of acrylic esters.

Incinerator Stack

Although the incinerator is not required for the oxidation of
propylene to acrylic acid, it is of paramount importance as an
emission control device.  Of the two plants utilizing SOHIO
technology, one vents all waste streams from point sources to
the incinerator, while the other vents all waste streams to the
incinerator except those from intermediate acrylic acid storage
tanks, and transport loading facilities.  The other plant
employing the propylene oxidation process vents all waste
 See footnote on page 28.
                               29

-------
streams to the incinerator except those emanating from two field
storage tanks.  In all cases, greater than 90% of the organic
wastes from the process are controlled by incineration.  Emis-
sions from the incinerator stack consist of carbon monoxide,
nitrogen oxides, and organic compounds resulting from incomplete
combustion of waste organics and auxiliary fuel.

Fugitive Emissions

Fugitive losses of organic compounds result from leaks in process
equipment, from process material spills, and from the repair and
cleaning of process equipment.  Fugitive emissions are generally
controlled through proper plant maintenance and careful loading
procedures.  Acrylic acid plants tend to be tightly controlled
because of the low odor threshold of some of the compounds, such
as acrolein, that are involved in the process.  In addition, much
of the process equipment operates under vacuum, so that leaks
result in air entering the system rather than process chemicals
leaking out.

EMISSION DATA

Emission factors for compounds emitted from the production of
acrylic acid by propylene oxidation are given in Table 9.  The
emission factors for the various sources of emissions are given
in Table 10.  Emission height data for acrylic acid plants are
given in Table 11.  These tables represent composite data sets
based on information supplied by the companies which utilize the
propylene oxidation process.

EMISSIONS BURDEN

The controlled emission factors given in Table 10 were used
together with the plant capacity data in Table 5 to calculate
annual emissions of criteria pollutants from acrylic acid manu-
facture via propylene oxidation.  Nationwide emissions are given
in Table 12, and emissions in the states of Texas and Louisiana
are given in Table 13.

DEFINITION OF A REPRESENTATIVE SOURCE

A representative plant is defined as one utilizing SOHIO tech-
nology for the production of acrylic acid by propylene oxidation.
The use of control technology for the abatement of hydrocarbon
emissions is considered as part of the representative plant.  The
three actual plants that produce acrylic acid by propylene oxida-
tion use incineration to control more than 90% of their process
emissions.  It should be noted that, despite the representative
plant definition, an emission factor, a maximum time-averaged
ground level concentration, and a source severity value for un-
controlled hydrocarbon emissions from acrylic acid production
are given along with the respective values for a representative


                               30

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       TABLE 9.    ACRYLIC ACID EMISSION FACTORS BY COMPOUND
                                       (g/kg)
                       Material emitted
                                                      Emission factor
                                                 Uncontrolled   Controlled
              Criteria pollutants:

                Hydrocarbons
                Carbon monoxide
                Nitrogen oxides

              Chemical substances:
                AcetaIdehyde
                Acetic acid
                Acetone
                Acrolein
                Acrolein dimer
                Acrylic acid
                Benzene
                Diphenyl-diphenyl oxide eutectic
                Ethyl acrylate
                Formaldehyde
                Isopropyl ether
                Maleic acid
                Phenol
                Propane
                Propylene
110c
 NAC
 NA
              Note.
              a
<0.6
<0.7
<0.7
                     Slanks indicate emission factors unknown.
               Data based on information provided by confidential industry
               sources.  Quality of data unknown.

               Includes all organic compounds  except methane.
               Not applicable; emissions result from control device.
TABLE  10.   CONTROLLED  ACRYLIC ACID EMISSION FACTORS  BY LOCATION
                                        (g/kg)
                                                                                     a ,b
Emission point
Propylene storage tank vents
Heat-transfer circuit vents
Solvent storage tank vents
Intermediate acrylic acid
storage tank vents
Vacuum column steam jets
Acrylic acid storage tank
vents
Transport loading facility
vents
Incinerator stack
Fugitive emissions

Carbon
monoxide
NAd
NA
NA

NA
NA

NA

NA
<0.f
Emission factor
Hydrocarbons
_e

_e

<0.02
<0.2


e

<0.4

Nitrogen
oxides
NA
NA
NA

NA
NA

NA

NA
<0.7
              Data based on  information provided by confidential  industry
              sources;  data  quality unknown.

              Emission factors are representative of plants with  control
              technology.

             ""Includes all organic compounds  except methane.

              Not applicable; species not emitted.

             Emissions vented to incinerator.

              Emission factor not known.
                                           31

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               TABLE  11.  EMISSION HEIGHT DATA FOR
                          ACRYLIC  ACID PLANTS3

Emission point
Intermediate acrylic acid storage tank vents
Vacuum column steam jet
Incinerator stack
Height, m
13.7
19.8
25.9

         a
          Data based on information provided by confidential
          industry sources.
TABLE 12.  CONTRIBUTION  OF CRITERIA POLLUTANTS FROM ACRYLIC ACID
           PRODUCTION  TO NATIONAL STATIONARY SOURCE EMISSIONS

Criteria
pollutant
Hydrocarbons
Carbon monoxide
Nitrogen oxides
Total national
emissions,
10 6 metric tons/yr (55)
25
97
22
Emissions from
acrylic acid
manufacture ,
metric tons/yr
<160
<200
<200
Percent of
national
emissions
<0.0006
<0.0002
<0.0009

         TABLE 13.  ACRYLIC ACID CONTRIBUTIONS  TO STATE
                    EMISSIONS OF CRITERIA POLLUTANTS



Criteria
pollutant
Hydrocarbons

Carbon monoxide

Nitrogen oxides




State
Louisiana
Texas
Louisiana
Texas
Louisiana
Texas


State emissions ,
10 metric tons/yr (55)
1,920
2,219
5,634
6,898
423
1,304
Emissions from
acrylic acid
manufacture ,
metric tons/yr
<38
<130
<46
<160
<45
<160
Percent
of
state
emissions
<0.002
<0.006

-------
plant utilizing control technology.  Production capacity, popula-
tion density, emission heights, and emission factors for a repre-
sentative plant are taken from data provided by the operating
companies.  Data for a representative plant are summarized in
Table 14.
      TABLE 14.  SUMMARY OF DATA FOR A  REPRESENTATIVE  PLANT3
                Parameter
     Value for
representative plant
Process
Raw material
Production capacity, metric tons/yr
Population density, persons/km2
Control technology
Emission heights, m:
  Intermediate acrylic acid
    storage tank vents
  Vacuum column steam jet
  Incinerator stack
Emission factors, g/kg:
  Intermediate acrylic acid
    storage tank vents
  Vacuum column steam jet
  Incinerator stack:
    Carbon monoxide
    Hydrocarbons
    Nitrogen oxides
Propylene oxidation
     Propylene
      85 x 103
        297
   Incineration
         13.7
         19.8
         25.9
        <0.02
        <0.2

        <0.7
        <0.4
        <0.7
 Values of the representative plant parameters comprise a com-
 posite data set based on information supplied by the companies
 utilizing the propylene oxidation process.  They do not corres-
 pond exactly to any of the operating plants.

ENVIRONMENTAL EFFECTS

Maximum Ground Level Concentration

The  short-term  (3 min average) maximum ground level concentration,
Xraax, for materials emitted by acrylic acid  production was esti-
mated by Gaussian plume dispersion theory.   Xmax, in grams per
cubic meter, is calculated by the following  equation  (56):
                           X.
                               _   2 Q
                           max
                                  irH2eu
                                                              (13)
 (56) Turner,  D. B.  Workbook  of Atmospheric Dispersion  Estimates.
     Public Health  Service  Publication No. 999-AP-26, U.S.
     Department of  Health,  Education, and Welfare,  Cincinnati,
     Ohio, May 1970.   84  pp.
                                33

-------
where  Q = emission rate, g/s
       H = effective emission height, m
       e = 2.72
       TT = 3.14
       u = average wind speed = 4.5 m/s

Maximum Time-Averaged Ground Level Concentration

The maximum ground level concentration averaged over a given
period of time, Xmax, is calculated from Xmax by the following
equation  (56) :
where  tQ = short-term averaging time  (3 min)

        t = averaging time

The averaging time is 3 hr for hydrocarbons and 24 hr for non-
criteria pollutants.  Since nitrogen oxides have a 1-yr averaging
time, a special equation must be used; it has been derived in
Appendix A.  Table 15 gives X"maj, for compounds emitted from a
representative plant, while Table 16 gives Xmax f°r specific
emission points within a representative plant.  Values in
Table 15 were computed using emission factors from Table 9 and
emission heights for specific compounds given in Table 11.
Values in Table 16 are based on emission factors in Table 10 and
emission heights for individual emission points given in Table 11.

Source Severity

The hazard potential of acrylic acid manufacture can be quanti-
fied by determining a source severity, S, which is defined as the
ratio of the maximum time-averaged ground level concentration to
F, the hazard exposure level for a pollutant.  For criteria pol-
lutants, F is defined as the primary ambient air quality standard
for the particular pollutant. *  For noncriteria pollutants, F is
defined as follows:

                     F E (TLV) (8/24) (0.01)                    (15)

Source severities for compounds emitted from a representative
acrylic acid plant are given in Table 17. _ These values were
obtained by dividing the concentrations, Xmax, in Table 15 by the
appropriate value of F.  Source severities for individual emis-
sion points within a representative plant are given in Table  18.
 There is no primary ambient air quality standard for hydro-
 carbons.  The value of 160 yg/m3 used for hydrocarbons in this
 report is an EPA recommended guideline for meeting the primary
 ambient air quality standard for oxidants.

                               34

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TABLE  15.   MAXIMUM TIME-AVERAGED GROUND  LEVEL
              CONCENTRATIONS  FOR  COMPOUNDS  EMITTED
                         (mg/m3)


                                            "max
   	Material emitted	Uncontrolled   Controlled

   Criteria pollutants:

    Hydrocarbons                        19.           <0.1
    Carbon monoxide                     NA           <0..09
    Nitrogen oxides                     NA           <0.06

   Chemical substances:

    Acetaldehyde
    Acetic acid
    Acetone
    Acrolein
    Acrolein dimer
    Acrylic acid
    Benzene
    Diphenyl-diphenyl oxide eutectic
    Ethyl acrylate
    Formaldehyde
    Isopropyl ether
    Maleic acid
    Phenol
    Propane
    Propylene
   Note.—Blanks indicate x    unknown, see Table 10.
    Includes all organic compounds except methane.
    Not applicable; emissions result from control device.
 TABLE 16.   MAXIMUM TIME-AVERAGED  GROUND  LEVEL
               CONCENTRATIONS  FOR EMISSION POINTS9
                          (mg/m3)

Emission point
Propylene storage tank vents
Heat-transfer circuit vents
Solvent storage tank vents
Intermediate acrylic acid
storage tank vents
Vacuum column steam jet
Acrylic acid storage tank
vents
Incinerator stack
Fugitive emissions
Transport loading facility
vents
Carbon
monoxide
NAC
NA
NA

NA
NA

NA
<0.09
_e
d

Hydrocarbons
d
~d
~d


<0.007
<0.03
H

<0.04
_e
d

Nitrogen
oxides
NA
NA
NA

NA
NA

NA
<0.06
_e
d

 aValues for x    are representative of plants with control
 technology. max
 Includes all organic compounds except methane.

 Not applicable;  species not emitted.

 Emissions vented to incinerator.

 X~    not calculated due to lack of emission data.
                            35

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  TABLE  17.   SOURCE SEVERITIES FOR COMPOUNDS EMITTED


                                            Source severity
     	Material emitted	Uncontrolled   Controlled

     Criteria pollutants:

       Hydrocarbons3                        120.          <0.7
       Carbon monoxide                       NAU          <0.002
       Nitrogen oxides                       NA          <0.6

     Chemical substances:

       Acetaldehyde
       Acetic acid
       Acetone
       Acrolein
       Acrolein dimer
       Acrylic acid
       Benzene
       Diphenyl-diphenyl oxide eutectic
       Ethyl acrylate
       Formaldehyde
       Isopropyl ether
       Maleric acid
       Phenol
       Propane
       Propylene


     Note.—Blanks indicate severity not calculated due to lack of
            emission data.
     alncludes all organic compounds except methane.

      Not applicable; emissions result  from control device.
   TABLE 18.   SOURCE  SEVERITIES FOR EMISSION POINTS3

Emission point
Propylene storage tank vents
Heat-transfer circuit vents
Solvent storage tank vents
Intermediate acrylic acid
storage tank vents
Vacuum column steam jet
Acrylic acid storage tank
vents
Incinerator stack
Fugitive emissions
Transport loading facility
vents
Carbon .
monoxide Hydrocarbons
NA°
NA
NA

NA
NA

NA
<0.002
_d
d

_d
— j
a

<0.05
<0.2
.
-
<0.3
_d
H

Nitrogen
oxides
NA
NA
NA

NA
NA

NA
<0 . 6
_d
A


Source  severities are representative of  plants with control
technology.

Includes  all organic compounds except methane.

Not applicable; species  not emitted.

Source  severity not known or emissions vented to incinerator.
                                36

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These values were derived in a  similar manner  from  the  concen-
trations given in Table 16.

Affected Population

A measure of the population which  is exposed to  a high  contam-
inate concentration due to a representative acrylic acid plant
can be obtained as follows:  The values of x,  downwind  distance
from the source, for which

                                = o.l                         (16)
are determined by iteration.  The value of  X(x),  the annual mean
ground level concentration, is computed from the  equation  (56):


                                                             (17)
                           a ux
                            z

where  Q = emission rate, g/s
       H = effective emission height, m
       x = downwind distance from source, m
       u = average wind speed  (4.5 m/s)
      oz = vertical dispersion coefficient, m

For atmospheric stability class C  (neutral conditions) , az is
given by (57) :

                       az = 0.113 x°-911                     (18)

The affected area is then computed as

                     A = u(x22 - X!2) , km2                   (19)

where xi and x2 are the two roots of Equation 16.

The (capacity-weighted) mean population density, D , is calcu-
lated as follows:

                        E ciDPi
                   D  = l=-~ - , persons/km2                 (20)
where   Cj^ = production capacity of plant i
       Dp^ = county population density for plant i
(57) Eimutis, E. C. , and M. G. Konicek.  Derivations of Continu-
     ous Functions for the Lateral and Vertical Atmospheric Dis-
     persion Coefficients.  Atmospheric Environment, 6(11):
     859-863, 1972.

                               37

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The product (A)»Dp is designated the "affected population."

The area and population affected by a representative acrylic
acid plant were calculated for hydrocarbons and nitrogen oxides
since the upper bounds on source severity for both species
exceed 0.1.  The results are summarized in Table 19.

   TABLE 19.  AFFECTED POPULATION FOR A REPRESENTATIVE PLANT3

           Parameter              Hydrocarbons   Nitrogen oxides

Population density, persons/km2        297               297 ,
Emission height, m                    19.8              25.9
Emission rate, g/s                    <1.6              <1.9
Affected area, km2                    <2.3              <4-7
Affected population, persons          <600            <1,200


 Affected areas and populations are for a source severity of
 0.1 or greater.
                               38

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                            SECTION 5

                       CONTROL TECHNOLOGY3
STATE OF THE ART

Control technology for acrylic acid manufacture is described via
emission points where specific controls are used.  The emission
points concerned are the vacuum column steam jet, intermediate
acrylic acid storage tank, other emission points, and fugitive
emissions.  All control technology discussed is designed for the
control of organic compounds which are emitted during the pro-
duction of acrylic acid.

Vacuum Column Steam Jets

Vacuum-producing steam jets emit organics from the venting of
steam during acrylic acid recovery and refining.  Emissions may
be controlled by utilizing surface condensers which are placed
after each stage of the steam jet, together with a chilled-water
vent condenser.  The surface condensers condense part of the
steam, thereby reducing the volume pf the vent gas.  The chilled-
water condenser then removes organic compounds from the vent gas.
The control efficiency of this system is estimated to be 75%
under the worst conditions.  In a second method of control, steam
and organic vapors from the vacuum jets are vented to a centrally
located incinerator."

Intermediate Acrylic Acid Storage Tanks

The temporary storage of acrylic acid-solvent mixture during pro-
cess upsets results in emissions of organic compounds from load-
ing and breathing losses.  These emissions are controlled by
means of a nitrogen blanket at a gage pressure of 0.5 kPa togeth-
er with a chilled-water vent condenser.  Alternatively, these
tanks may be vented to the incinerator for emission control.13
 Information in this section was provided by confidential
 industry sources.
 See footnote on page 28.

                               39

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Other Emission Points

All three plants that produce acrylic  acid  by  propylene oxidation
make use of incinerators to control more  than  90%  of their total
organic compound emissions.  Emission  points that  are vented to
the incinerator include storage tank vents, reactor  vents, re-
covery and purification process vents,  and  transport loading
facility vents.

Contaminated air and fresh air are mixed  and blown into the in-
cinerator by means of a fan.  Organic  vapors from  process  vents,
wastewater, and waste organics are also injected into the  incin-
erator, along with a sufficient amount of natural  gas to maintain
a stable flame region and adequate operating temperature.   Com-
bustion area temperatures in the range of 760°C to 980°C,  and a
mean residence time of 1 s for contaminants have been reported.8
Following combustion, the hot gases pass  through a waste heat
boiler which produces superheated steam while  reducing the tem-
perature of the stack gases to 260°C.   Figure  3 shows a schematic
of an incinerator used for controlling organic emissions 'from
acrylic acid manufacture.  The control efficiency  of the incin-
erator is estimated to be greater than 98%.
                                                 STACK
        CONTAMINATED
           AIR
        FRESH AIR
                     PROCESS VENTS
                                                    FRESH WATER
       Figure 3.  Incinerator used  for  controlling organic
                  emissions from acrylic  acid manufacture.
 Information provided by confidential  industry  sources,
                                40

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Fugitive Emissions

As mentioned in Section 4, fugitive emissions from acrylic acid plants tend
to be tightly controlled as a result of the low odor threshold of compounds
involved in the process.  One plant employs the following methods for con-
trolling fugitive emissions:

          Mechanical seals are exclusively used as opposed to
          packing glands on pumps.

          Spare pumps are provided at all continuous service
          locations so that a faulty pump can be taken out of
          service immediately for repairs.

          All pumps are mounted above drip pans which drain any
          leaks to a sump which is vented to the incinerator.

          Valves are located inside areas that are diked or
          curbed to prevent escape of leaked material to
          surrounding areas.  These diked areas drain to the
          above sump system which is vented to the incinerator.

Another plant employs a controlled ventilation area for dismantling, repair-
ing, and cleaning process equipment.  This area is vented to the main pro-
cess incinerator.  A separate solid waste incinerator is employed to dispose
of any solid wastes resulting from these operations.

FUTURE CONSIDERATIONS

No additional control technology is expected in the acrylic acid industry.
Incineration is considered an adequate and effective means of control for
emissions from acrylic acid manufacture.  However, if dilute streams of
organics (less than 1,000 ppm) have to be incinerated, operating temperatures
higher than 760°C to 980°C may be required.
                                     41

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                            SECTION 6

                GROWTH AND NATURE OF THE INDUSTRY
PRESENT TECHNOLOGY

Technology for producing acrylic acid is largely based on the
two-stage oxidation of propylene.  This process is employed by
three of the four plants operating in the United States and
accounts for 93% of production capacity.  Two plants utilize
SOHIO technology for propylene oxidation while the third  (Rohm &
Haas) employs technology developed in-house.a  The remaining 7%
of production capacity is held by one plant that uses the high-
pressure Reppe process.  This process employs a nickel compound
as a catalyst for a high-pressure reaction in which acetylene
and carbon manoxide are reacted with water to synthesize acrylic
acid (52).

The Reppe process, conceived in 1939, is the older, more conven-
tional method for acrylic acid production.  The propylene oxida-
tion process, developed around 1960, is considered more economi-
cal due to its low-cost feedstock materials (52).  Union Carbide
established the first commercial plant in the United States for
acrylic acid production by propylene oxidation in 1969 (52).

EMERGING TECHNOLOGY

Since the propylene oxidation process is relatively new,  it still
offers the opportunity for technical improvements.  The low cost
of acrylic acid produced by this process makes it possible to
develop new applications for the acid and its derivatives.  These
new applications include their use as food additives, coagulants,
paper sizing agents, and high molecular weight reforming
agents (52).

The propylene oxidation process is in a considerably advanced
stage.   However, further research and development work on the
     Rohm & Haas process utilizes catalyst technology licensed
 from Japan Catalytic Chemical Industry, as well as certain
 aspects of propylene oxidation technology licensed from
 Toyo Soda Manufacturing Co.

(58) Japan Catalytic Chemical Industry Will Supply Catalyst
     Know-How.  Chemical Week, 112 (19): 33-34, 1973.

                                42

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oxidation and rectification steps, especially with respect to
catalysts, will assume great importance.  The expected result
of this development work is to further decrease the cost of pro-
ducing acrylic acid by propylene oxidation  (52).

MARKETING STRENGTHS AND WEAKNESSES

Approximately 83% of the acrylic acid produced in the United
States is used for the production of acrylic esters, as shown
in Table 20  (59).  The remaining 17% is used for miscellaneous
purposes, which include production of water-soluble resins and
salts, production of specialty acrylates, and use as a comonomer
in acrylic emulsion and solution polymers (59).

            TABLE 20.  ACRYLIC ACID CONSUMPTION (59)


                    End use                  Quantity, %

        Ethyl and methyl acrylate                 52
        n-Butyl and isobutyl acrylate             26
        2-Ethylhexyl and other acrylates           5
        Miscellaneous applications9       •        17

        TOTAL                                    100


         Includes merchant and captively consumed
         acrylic acid for uses other than ester
         intermediates.

The principal end uses of acrylic acid esters are given in
Table 21.  The two largest users of acrylates are acrylic sur-
face coatings, which account for 41% of consumption, and textile
applications, which account for 20% of consumption.  No other
market accounts for more than 10% of acrylic ester consumption
(51).  Thus, the demand for acrylic acid is primarily determined
by the markets for acrylic surface coatings and textile
applications.

Acrylic surface coatings consist of acrylic latex paints, acrylic
lacquers, and acrylic enamels.  The principal market for acrylic
latex paint is in trade sales paints; e.g., interior and exterior
house paints.  Acrylic lacquers and enamels are used primarily
for automobile finishes.  Thus, demand for the latter materials
follows the fluctuations in the automobile industry.  In addi-
tion, acrylic lacquers and enamels contain considerable amounts
of solvents; they are therefore prime candidates for replacement
by water-base or solventless systems as a pollution control
measure.
 (59) Chemical Origins and Markets.  Stanford Research Institute,
     Menlo Park, California, 1977.  118 pp.


                               43

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       TABLE  21.  CONSUMPTION OF ACRYLIC ACID ESTERS  (51)
               	End use	Quantity, %

               Surface coatings           41
               Textiles                   20
               Paper                       5
               Polishes                    4
               Leather                     3
               Adhesives                   4
               Acrylic fibers              4
               Miscellaneous               6
               Exports                    13

               TOTAL                     100
Most acrylates used for textile applications are in the form of
straight acrylic emulsions, although some vinyl acrylics are
also used.   Ethyl acrylate and n-butyl aerylate are the major
acrylate monomers used in these applications, which include
adhesives, backcoatings, fabric finishes, pigment binders, soil
release agents, and thickeners.

Acrylic latex adhesives are used as fabric-to-fabric bonding
agents, flocking adhesives, and binders for nonwoven and imita-
tion (paper) fabric.  Foams and adhesives based on polyurethane
resins are the major competitors with acrylic latex in this area.

Acrylic latexes are used in backcoatings for automotive and furn-
iture upholstery, draperies, and pile fabrics.  Acrylics, as well
as other synthetic latexes and natural resins, such as starch
and gum, are used to improve the feel and body of fabrics.  The
feel and body of the finished fabric can vary from soft to hard
(stiff) depending on the formulation of the acrylic finish applied.

Pigment binders are used in printing and dyeing fabrics.
Binders based on acrylic latexes account for about 50% of this
market, the remainder belonging to styrene-butadiene latexes.

Anticipated growth rates in the principal acrylate markets are
as follows:  7% per year for surface coating and 9% per year
for textiles (51).  Total demand for acrylic acid is expected
to increase at an annual rate of 6% to 8% over the next several
years (51).  Based on the 1975 production of 97,000 metric tons
(51), this rate of growth will result in acrylic acid production
of 130,000 to 143,000 metric tons in 1980.  Overcapacity is
anticipated in the industry for the next several years  (51).
                               44

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Historically, acrylic acid production  increased at  a rate of 12%
to 15% per year in the period  1967  to  1976  (51).  The production
and sales trends of acrylic acid  are shown  graphically in
Figure 4  (60) .  The difference between the  two  curves reflects
captive consumption of the acid.
                          1958  1964   1970   1976
                                 YEAR


  Figure 4.  Production and  sales record of acrylic acid  (60)
(60)  Synthetic Organic Chemicals, U.S. Production and Sales.
     U.S. International Trade Commission  (formerly U.S. Tariff
     Commission), Washington, D.C., 1961-1975.

                               45

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                               47

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                                48

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                                50

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     New York, New York, 1964.  14 pp.

68.   Petrochemical Evaporation Loss from Storage Tanks.  API
     Bulletin 2523, American Petroleum Institute, New York,
     New York, 1969.  14 pp.
                                51

-------
                           APPENDIX A

             DERIVATION OF SOURCE SEVERITY EQUATIONS
SUMMARY OF SEVERITY EQUATIONS

The severity of pollutants may be calculated using the mass
emission rate, Q, the height of the emissions, H, and the thresh-
old limit value, TLV.  The equations summarized in Table A-l are
developed in detail in this appendix.

            TABLE A-l.  POLLUTANT SEVERITY EQUATIONS
                        FOR ELEVATED SOURCES
                Pollutants _ Severity equation


              Particulate            S =  7fLQ
                                           H^-

                                     * -
              Hydrocarbon            S =
              Carbon monoxide        S =
              Other                  S =  5<5 Q
                                         TLV • H2
DERIVATION OF Y    FOR USE WITH U.S. AVERAGE CONDITIONS
               max
The most widely accepted formula for predicting downwind ground
level concentrations from a point source is  (56):
             X =

                               52

-------
where   x = downwind ground level concentration at reference
            coordinate x and y with emission height of H, g/m3
        Q = mass emission rate, g/s
       OTT = 3.14
       ^y = standard deviation of horizontal dispersion, m
        z = standard deviation of vertical dispersion, m
        u = wind speed, m/s
        y = horizontal distance from centerline of dispersion, m
        H = height of emission release, m
        x = downwind dispersion distance from source of emission
            release, m

xmax is assumed to occur when x is much greater than 0 and when
y equals 0.  For a given stability class, standard deviations
of horizontal and vertical dispersion have often been expressed
as a function of downwind distance by power law relationships
as follows  (61) :

                            ay = axb                        (A-2)



                          a  = cxd + f                      (A-3)
                           Z

Values for a, b, c, d, and f are given in Tables A-2 and A-3.
Substituting these general equations into Equation A-l yields :


            x = - r—^ - r- expf" -- ^ -         (A-4)
                                     L  2(cxd +
Assuming that Xmax occurs at x less than 100 m or the stability
class is C, then f equals 0 and Equation A-4 becomes:
                        acirux

For convenience , let :
              [rfial
              |_2c^x'i J
                                 exp                        (fl-5)
                           Q     j T,    -H2
                        = _~— a"^ R  = 	
                          acTru

so that Equation A-5 reduces to:
R - .._.. — "R   2C2
 (61) Martin, D. O., and J. A. Tikvart.  A General Atmospheric
     Diffusion Model for Estimating the Effects on Air Quality
     of One or More Sources.  Presented at the 61st Annual
     Meeting of the Air Pollution Control Association, St. Paul,
     Minnesota, June 23-27, 1968.  18 pp.


                               53

-------
                  TABLE A-2.  VALUES  OF a FOR  THE
                               COMPUTATION OF  a  a  (57)
                        TABLE A-2.
                                VALUES OF a FOR THE
                                COMPUTATION OF a a (57)
Stability class
A
B
C
D
E
F
a
0.3658
0.2751
0.2089
0.1471
0.1046
0.0722
            TABLE A-3.
                           For the equation
 where x = downwind distance
      b = 0.9031 (from
         Reference 62)

VALUES  OF THE CONSTANTS USED TO

ESTIMATE  VERTICAL DISPERSION3  (61)

Usable range, m

>1,000






100 to 1,000





Stability
class Coefficient

A
B
C
D
E
F

A
B
C
D
E
F
C!
0.00024
0.055
0.113
1.26
6.73
18.05
C2
0.0015
0.028
0.113
0.222
0.211
0.086
di
2.094
1.098
0.911
0.516
0.305
0.18
d2
1.941
1.149
0.911
0.725
0.678
0.74
fl
-9.6
2.0
0.0
-13
-34
-48.6
*2
9.27
3.3
0.0
-1.7
-1.3
-0.35
<100





A
B
C
D
E
F
0.192
0.156
0.116
0.079
0.063
0.053
0.936
0.922
0.905
0.881
0.871
0.814
0
0
0
0
0
0

             For the equation
                             az = ex
                                     + f
(62)  Tadmor,  J.,  and Y.  Gur.   Analytical Expressions for the
     Vertical and Lateral  Dispersion Coefficients  in Atmospheric
     Diffusion.   Atmospheric  Environment, 3(6):688-689, 1969.
                                 54

-------
                       X = ARx-(bsHa)  expl-^l                (A-6)
aking the first derivative  of  Equation A-6
                               r   -2dl/       \   b-d i(
                          +  exp BRx    (- b - djx      j     (A-7)
and setting this equal  to  zero  (to  determine the roots which
give the minimum and maximum conditions of x with respect to x)
yields:


                         (exp[BRx-2d])[- 2dBRx-2d - b - d]  (A-8,


Since we define that x  ^ 0 or °° at  Xmax, the following expres-
sion must be equal  to 0:

                        - 2dBDx~2d - d - b = 0              (A-9)
                             K
or
                         (b + d)x2d = - 2dBR               (A-10)
or
                           - 2dBT
                            b + d   2c2(b + d)

or
                                c2(b + d)

or
                        \c2(b + d)/

Thus Equations A-2  and  A-3  become:
                        a   = a /-2-Ji:	                    (A-14)
                        y    \c2(d + b)/
                                55

-------
                 = c
The maximum will be determined for U.S. average conditions of
stability.  According to Gifford  (63), this is when a  = az .

Since b = 0.9031, and upon inspection of Table A-2 under U.S.
average conditions, a  = oz, it can be seen that
0.881 < d < 0.905  (class C stability3).  Thus, it can be assumed
that b is nearly equal to d or:
                            a  =
                             z
                                 /2
and
                                                           (A-17)
Under U.S. average conditions, cr  = oz and a =s c if b =* d and
f = 0 (between class C and D, but closer to belonging in class C) .

Then
                            a  = -                         (A-1
                             Y   /2

Substituting for a  and a  into Equation C-l and letting y = 0 :
                           2 Q
                        = 	
                          TruH2
(A-19)
 The values given in Table A-3 are mean values for stability
 class.   Class C stability describes these coefficients and
 exponents, only within about a factor of two (64) .

(63)  Gifford,  F. A., Jr.   An Outline of Theories of Diffusion in
     the Lower Layers of the Atmosphere.   In:  Meteorology and
     Atomic Energy 1968,  Chapter 3,  D. A. Slade, ed.  Publication
     No.  TID-24190,  U.S.  Atomic Energy Commission Technical
     Information Center,  Oak Ridge,  Tennessee, July 1968.
     p.  113.
(64)  Hydrocarbon Pollutant Systems Study; Volume I,  Stationary
     Sources,  Effects,  and Control.   APTD-1499 (PB 219 073) ,
     U.S.  Environmental Protection Agency, Research Triangle
     Park,  North Carolina, 20 October 1972.  377 pp.
                                56

-------
or


                           Vax  =  -Hr                     (A-20)
                                  ireuH7

For ground level sources  (H = 0),  Xmax  occurs  by  definition  at
the nearest plant boundary or public  access.   Since  this  occurs
when y = Of Equation A-l  becomes:
For U.S. average conditions, u =  4.47 m/s  so that Equation A-20
reduces to:


                        X    - °-0524 Q                     (A-22)
                        Amax       H2

DEVELOPMENT OF SOURCE  SEVERITY EQUATIONS

The general source  severity, S, relationship has been defined  as
follows :


                            s = Jjp*                        (A-23)


where  Xmax = time-averaged maximum ground level concentration
          F = hazard factor

Noncriteria Emissions

The value of Ymax may  be derived  from Xmax, an undefined  "short-
term" concentration.   An approximation for longer term concen-
tration may be made as follows  (56) :

For a 24-hr time period,

                                /t  \°-17
                    Xmax = *max (^)                        (A-24)


or
                              /      -   \0-17
                  —    _      /   3 mm   \                   ra-9^\
                  xmax ~ xmax I 1,440 min 1                   (A  z*>
                           = Y     (0.35)                    (A-26)
                             Amax
                                57

-------
Since the hazard  factor  is  defined and derived from TLV values
as follows:
                        ,  .  (TLV)                            (A-27)
                       F  =  (3.33  x 10~3)  TLV               (A-28)


then the severity  factor, S,  is defined  as:



                     Xmax       (0'35)XTIiax
                 S = -5^1 = - E!^ -              (A-29)

                       F     (3.33 x 10~3)  TLV



                               105 xmax
                          q -       max
                          b -
If a weekly averaging period  is  used,  then:


                    -    -      (   3    V'17
                    xmax   xmax\10,0807


or
and


                      F =




                      F =  (2.38 x  10~3)TLV                  (A-34)


and the severity factor, S, is:




                 S - *max       {0-25)xraax
                 s - J^L = 	!^x	               (A_35)

                       F    (2.38  x  10~3)TLV


or
                               58

-------
which is entirely consistent,  since  the TLV  is being  corrected
for  a different exposure period.

Therefore,  the severity  can be derived from  Xmax directly without
regard  to  averaging time for noncriteria emissions.   Thus, com-
bining  Equations  A-36 and A-22,  for  elevated sources,  gives:
                              S =
  5.5  Q

TLV  •  H'<
                                      (A-37)
 Criteria  Emissions
 For the  criteria  pollutants, established standards may be used
 as F values in Equation A-23.  These are given in Table A-4.
 However,  Equation A-24 must be used to give  the appropriate aver-
 aging period.  These equations are  developed for elevated sources
 using Equation A-22.
               TABLE A-4.
SUMMARY OF NATIONAL AMBIENT
AIR  QUALITY STANDARDS  (65)
Pollutant
Particulate
matter

S0x
A


Carbon
monoxide


Nitrogen
dioxide
Photochemical
oxidants
Hydrocarbons
(nonme thane)
Averaging
time
Annual (geometric
mean)
2 4 -hour b
Annual (arith-
metic mean)
2 4 -hour b
3 -hour b

8 -hour b
l-hourb

Annual (arith-
metic mean)
l-hourb

3 -hour
(6 a.m. to 9 a.m.)
Primary
standards
75 yg/m3

260 ijg/m3
80 yg/m3

365 yg/m3
-

10,000 yg/m3
40,000 Mg/m3

100 yg/m3

160 yg/m3

160 yg/m3d

Secondary
standards
60a Hg/m3

160 yg/m3
60 yg/m3

260C yg/m3
1,300 yg/m3


(Same as
primary)
(Same as
primary)
(Same as
primary)
(Same as
primary)
                The secondary annual standard (60 yg/m3) is a guide for assess-
                ing implementation plans to achieve the 24-hour secondary
                standard.
                Not to be exceeded more than once per year.
               CThe secondary annual standard (260 yg/m3)  is a guide for assess-
                ing implementation plans to achieve the annual standard.
                There is no primary ambient air quality standard for hydro-
                carbons.  The value of 160 yg/m3 used for hydrocarbons in this
                report is an EPA recommended guideline for meeting the primary
                ambient air quality standard for oxidants.
 (65) Code of Federal Regulations,  Title  42  - Public Health,
      Chapter IV - Environmental  Protection  Agency,  Part 410  -
      National Primary and Secondary Ambient Air Quality
      Standards,  April 28, 1971.   16 pp.

                                   59

-------
Carbon Monoxide Severity—
The primary standard for CO is reported  for  a  1-hr  averaging time,
Therefore,

                           t =   60 min


                          t  =  3 min


                                \ 0. 17

                               U                           (A~38)

                                  \  0.17
                               _3                           (A_39)
                        ireuHz \60/


                        	2-2	 (0.6)           (A-40)
                         (3.14)(2.72)(4.5)H2
                 xmax
                      -    =  0.12 x 10-2)Q
                      Amax
                       Severity, S =                        (A-43)
                                      r

Setting F equal to the primary standard for CO, i.e.,  0.04  g/m3,
yields :


                   s = Xmax =  (3.12 x 10~2)Q                (A-44)
                        F          0.04 H2

or

                          S   = ^I^Q                      (A_45)
                           CO     H2


Hydrocarbon Severity —
The primary standard for hydrocarbon is reported  for a 3-hr
averaging time .

                           t = 180 min
                               60

-------
                            t  = 3 min



                               f  3 V"17
                    max ~ xmax \180/                        (A-46)


                        " °-5Xmax                           (A-47)


                        = CO-5) (0.052)  Q                    (A-48)
                               H2
For hydrocarbons, F  -  1.6  x 10"^  g/m3  (as  discussed in
Section 4) , and
                     S  =       =  - -                       (A-50)
                         F      1.6  x IQ-^  H2

or

                         S    =  1^1^
                          HC      H2


Particulate Severity —
The primary standard for particulate is  reported  for  a  24-hr
averaging time.

                              /      \0. 17

                  xmax = Xmax \1,4407                       (A-52)


                       =  (0.052)  Q  (0.35)                   (A-53)

                                H2

                       =  (0.0182) Q
                  Amax       H2


For particulates, F  =  2.6 x ID"4  g/m3, and



                                  0.0182  Q -                (A_55)

                                2.6  x IQ~k  H2
                               61

-------
                            Sp =   -                         (A_56)
                            P    H2

SOX Severity —
The primary standard for SO is reported  for  a  24-hr  averaging
time.                       x
X
Amax
                            =  (0-0182) Q                    (A-57)
                                  H2

The primary standard is  3.65 x  10~4 g/m3,
and


                       xmax      (0.0182)Q
                                                            (A-58)
                        F     3.65 x lO"1* H2

or

                          Sqo  = 52_a                       (A-59)
                           b(J     TTo
                             X    Hz

N0y Severity —
Since NOx has a primary standard with a 1-yr averaging time, the
^max correction equation cannot be used.  As an alternative, the
following equation was selected :
                                                            (A-60)
A difficulty arises, however, because a distance x, from emission
point to receptor, is included; hence, the following rationale  is
used:
The equation
                        ^
                    TT6UH2
is valid for neutral conditions or when a  == a  .  This maximum
occurs when
                            H

and since, under these conditions,

                            a  = ax
                             z
                               62

-------
then the distance, x    , where the maximum concentration occurs is
                    luciX
For class C conditions,



                            a = 0.113



                            b = 0.911


Simplifying Equation  A-60,
                       rr   = 0 11 "i x   0-911
                       °z    U-11J xmax
and



                        u = 4 . 5 m/s



Letting x =  x__w  in Equation A-60,
             In 3.x
-      4
X =	

    xmax
                           _Q_ exJ_ 1 /if!             (A-61)

                           1.911    I  2 Vaz/J
where
                                         1 .098
                        x    = 7.5 H1'098                   (A-63)
                         max



and

                     4 Q    = _ i_Q -             (A_64)


                  x   !'911   (7.5 H1-098)1-911
                   max


Therefore,



                    X -         e,P-
                         0  = O.llSx0-911                    (A-66)
                          z
                                63

-------
  o  = 0.113  (7.5 H1'1)°'
                                                            (A-67)
Therefore,
                           a  =  0.71  H
                           z
- = 0.085 Q
      H2.1
                                         H
                                           (A-68)
                                                            (A-69)
                                       0.71
                     0.085 Q
                              (0.371)
                      H2.1

                 - _ 3.15 x  IP"2 Q
                                           (A-70)

                                           (A-71)
Since the NO  standard is 1.0 x  10~"tf  g/m3,  the  NO  severity
equation is:                                      X
                      NO
           (3.15 x 10~2) Q
            1 x I0~k H2-1
                                                            (A-72)
                                  315  Q
                           NO
                             X     H
                                    2. 1
                                                            (A-73)
                               64

-------
                           APPENDIX B

          CALCULATED EMISSION FACTORS FOR ACRYLIC ACID
                         STORAGE TANKS3


Uncontrolled emission factors for  the acrylic acid  storage  tanks
listed in Table 4 have been determined by calculating the breath-
ing and working  losses of  stored acrylic acid.  These losses
occur due to daily ambient temperature changes and  loading  proce-
dures.  The following equations and calculation procedures  were
developed and reported in  the referenced API Bulletins  (66-68) .

Step 1.  Calculate the equivalent gasoline breathing loss:
    t

                           *
                               1'73  (H'}°<51  (AT}°'5° F C
                                     (H '      Ui)     *C
                        .
     Y   1,000 \14.7 - P/

where  Ly = equivalent gasoline breathing loss, bbl/yr

        P = vapor pressure of material stored at bulk
            temperature, psia

        D = tank diameter, ft

       H" = tank outage, ft

       AT = average ambient temperature change, °F

       Fp = paint factor

        C = diameter factor
 Nonmetric units are used in this appendix because they corres-
 pond to those used in computer calculations.
(66) Evaporation Loss from Fixed Roof Tanks.  API Bulletin 2518,
     American Petroleum Institute, New York, New York, 1962.
     38 pp.
(67) Use of Variable Vapor Space Systems to Reduce Evaporation
     Loss.  API Bulletin 2520, American Petroleum Institute,
     New York, New York, 1964.  14 pp.
(68) Petrochemical Evaporation Loss from Storage Tanks.  API
     Bulletin 2523, American Petroleum Institute, New York,
     New York, 1969.  14 pp.

                               65

-------
Step 2.  Calculate the equivalent gasoline working loss:


                       Fg = 107000  PWKT                    (B'2)

where  F  = equivalent gasoline working loss, bbl/yr

        V = tank capacity, bbl

        N = number of turnovers per year

       K  = turnover factor = 1.0 for N - 36
                            _ 180 + N
                                 6N

Step 3.  Compute total equivalent gasoline loss, L :

                          L  = L  + F                        (B-3)
                           g    y    g

Step 4.  Compute petrochemical losses:

                         L = 0.08(|)Lg                       (B-4)


where  L = total petrochemical loss, bbl/yr
       M = molecular weight of chemical stored
       W = liquid density of chemical stored, Ib/gal

Step 5.  Calculate emission factor in metric units:

                          L! = L(42)(W)                      (B-5)

                               Li
                          E' = ^—                           (B-6)
                               Cap


                           E = |^-                            (B-7)


where   LJ = petrochemical loss, Ib/yr
       Cap = production  capacity, ton/yr
        E1 = emission  factor, Ib/ton
         E = emission  factor, g/kg

The yearly average bulk  temperature of acrylic  acid was given  as
70°F.  Acrylic  acid vapor pressure at  bulk temperature was calcu-
lated at 2.3 psia.  Tank dimensions and number  of turnovers  per
year were obtained through communications with  industry repre-
sentatives (see Table 4).  The average ambient temperature  change,
AT, was estimated at 19°F, which is the national average value.
Diameter factors, C, were determined from a graph given in Ref-
erence 66;  they are between 0.6 and 1.0.  Paint factors, F , were
determined by the outside colors of the tanks.

                               66

-------
Table B-l  lists the input data for  each storage tank and its
calculated emission factor.  The total  emission factor for all
8 tanks  is 1.07 g/kg.  These emission factors represent uncon-
trolled  emissions.  As noted in the main body of the report,
these emissions can be controlled by venting to the incinerator.
In addition,  the emission factors correspond to a plant operating
at 100%  of rated capacity.  Emission factors for tank losses are
non-linear functions of the percent of  capacity at which the plant
is operated.
          TABLE B-l.
INPUT DATA AND EMISSION FACTORS FOR
FIXED-ROOF TANKS  STORING ACRYLIC ACID
                                               Tank number
Input data
Annual production capacity, tons/yr
Average ambient temperature, °F
Average ambient temperature change, °F
Molecular weight of stored material, Ib/lb-mole
Liquid density, Ib/gal
True vapor pressure at bulk temperature, psia
Bulk temperature, °F
Tank diameter, ft
Tank height, ft
Paint factor
Diameter factor
Turnover factor
Number of turnovers per year
Tank capacity, bbl
12
95,000
64
19
72.06
8.76
2.3
70
12
24
1.3
0.6
0.3
230
481
13-14
95,000
64
19
72.06
8.76
2.3
70
16
38
1.3
0.78
0.95
40
1,362
15
95,000
64
19
72.06
8.76
2.3
70
20
32
1.3
0.9
1.0
30
1,786
16-17
95,000
64
19
72.06
8.76
2.3
70
25
32
1.3
0.97
0.95
40
2,786
18-19
95,000
64
19
72.06
8.76
2.3
70
36
32
1.3
1.0
1.0
10
5,786
  Emission factor, g/kg
                0.0415 0.0788 0.0989  0.1751  0.2098
   Tanks are numbered according to those in Table 4.
                                 67

-------
                            GLOSSARY
acrolein:  Simple unsaturated aliphatic aldehyde which is a
     chemical intermediate in the production of acrylic acid.

acrylic esters:  Monomer at high molecular weight used in the
     production of acrylic fibers, emulsions, and resins.

affected population:  Number of nonplant persons exposed to con-
     centrations of airborne materials which are present in
     concentrations greater than a determined hazard potential
     factor.

criteria pollutant:  Emission species for which ambient air
     quality standards have been established.

emission factor:  Weight of material emitted to the atmosphere
     per unit of acrylic acid produced; e.g., g material/kg
     product.

heat-transfer fluid:  High-boiling eutectic capable of transfer-
     ring heat energy over distance.

nitrogen blanket:  Layer of nitrogen gas under pressure which
     lies on the surface of stored volatile organics; designed
     to control hydrocarbon emissions from storage tanks.

noncriteria pollutant:  Emission species for which no ambient air
     quality standards have been established.

polymerization inhibitor:  Substance which prevents the polymeri-
     zation of acrylic acid during its recovery and purification.

propylene:  Unsaturated hydrocarbon and homolog of ethylene C^E&.

source severity:  Ratio of the maximum mean ground level concen-
     tration of emitted species to the hazard factor for the
     species.

stability class:  Factor which characterizes the atmosphere and
     is determined from cloud cover, wind speed, and time of day.
                               68

-------
                              TECHNICAL REPORT DATA
                        (Fleese read instructions on the rrvtnt before completing)
 . REPORT NO.
 EPA-600/2-78-004W
                             3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
 Source Assessment:
Acrylic  Acid Manufacture
State of the Art
6 REPORT DATE
 Aucrust 1978
issuing date
                                                   6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)

 R. W.  Serth, D. R.  Tierney and T. W.  Hughes
                             8. PERFORMING ORGANIZATION REPORT NO.

                                   MRC-DA-784
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Monsanto  Research Corporation
 1515  Nicholas Road
 Dayton,  Ohio  45407
                             10. PROGRAM ELEMENT NO.
                              1AB604
                             11. CbNTRACT/GRANT NO.
                                                    68-02-1874
 12. SPONSORING AGENCY NAME AND ADDRESS
  Industrial Environmental Research  Laborator
  Office of Research  and Development
  U.S.  Environmental  Protection Agency
  Cincinnati, Ohio  45268
                             13. TYPE Of REPORT AND PERIOD COVERED
                              TASK FINAL'] 2/75-1 2/77
                             14. SPONSORING AGENCY CODE
                                EPA/600/12
 15. SUPPLEMENTARY NOTES
  IERL-Ci project  leader for this report is R. J. Turner,  513-684-4481
 16. ABSTRACT
  This  report summarizes data on air  emissions from the  production of
  acrylic acid.  Hydrocarbons, carbon monoxide and nitrogen oxide are
  emitted from various operations.  Hydrocarbon emissions  consist of
  acetaldehyde, acetic acid, acetone  acrolein, acrylic acid,  benzene,
  phenol, propane, propylene and other  materials.  To assess the en-
  vironmental impact  of this industry,  source severity was defined as
  the ratio of the time-averaged maximum ground level concentration
  of  a  pollutant from a representative  plant to the ambient air qual-
  ity standard (for criteria pollutants)  or to a reduced threshold
  limit value  (for noncriteria pollutants).  Source severities were
  not greater than 1.0 for any criteria or noncriteria pollutant.
  Emissions from acrylic acid plants  are not expected to increase in
  the future as plants are installing incinerators on new  plants to
  control emissions.
u.
                            KEY WORDS AND DOCUMENT ANALYSIS
                DESCRIPTORS
 Air  Pollution
 Assessments
 Acrylic Acid
                                        b.lDENTIFIERS/OPEN ENDED TERMS
                  Air Pollution Control
                  Source  Assessment
                                           COS ATI Field/Group
               68D
18. DISTRIBUTION STATEMEN1
 Release  to Public
                  19. SECURITY CLASS (Tht) Report)

                   Unclassified
             U. NO. OF PAGES
                 83
                  20 SECURITY CLASS (Thlspagt)

                   Unclassified
                                                                22. PRICE
EPA Form 2220-1 O-73)
                                     69
                                                            a U.S. GOVERNMENT PRINTING OFFICE; 1978— 657-060/1476

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