PB-240 721
METHODOLOGY FOR ASSIGNMENT OF A
HYDROCARBON PHOTOCHEMICAL REACTI-
VITY INDEX FOR EMISSIONS FROM MOBILE
SOURCES
Francis M. Black, et al
National Environ menial Research Center
Research Triangle Park, North Carolina
March 1975
DISTRIBUTED BY:
National Technical Information Service
U. S. DEPARTMENT OF COMMERCE
-------
TECHNICAL HEPORT DATA
fPleesr rtaJ lutvuctions on the ttvene before Mmpletinrl
r.. _...
1 i\i >'ORT NO.
J7PA-650/2-75r-Q2SL
4. I I It I AND SUUtlH.t
Methodology for Assignment of a Hydrocarbon
Photochemical Reactivity Index for Emissions
from Mobile Sources
'PB 240 721
5. REPORT DATE
March 1975
6. P6KFORMING ORGANIZATION COOt
7. AUTHOR(S)
F. M. Black, L. E. High, and J. E. Sigsby
9. PcMrOHMING ORC- \NIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
National Environmental Research Center
Research Triangle Park, N.C. 27711
8. PERFORMING ORGANIZATION REPORT NO.
1O. PROGRAM ELEMENT NO.
IAAOIO.ROAP No. 26ACV
11.CONTr.ACT/GHANT NO"
2. SPONSORING AGENCY NAME AND ADDRESS
National Environmental Research Center
Chemistry and Physics Laboratory
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. Al'STHACT
An analytical scheme is presented which permits assessment of .the
photochemical significance of light-duty mobile source hydrocarbon emissions.
The scheme incorporates both the mass and atmospheric reactivity of the
hydrocarbon emissions. Analytical procedures supplementary to those de-
fined for light-duly mobile source certification in the Federal Register are
defined. The analytical procedures permit definition of four basic reactivity
classes of hydrocarbons: Class I, nonreactive, including methane^, ethane,
acetylene, prcpane, and benzene; Class !I, reactive, including the C* and
higher paraffins; Class III, reactive, including the aromatics except benzene;
and Class IV, reactive, including the olefins. Procedures for assignment of
a Hydrocarbon Photochemical' Reactivity Index utilizing the reactivity defini-
tion in conjunction with the mass of emissions are described in detail.
NATIONAL TECHNICAL
INFORMATION SERVICE
US O.O.B™,., ,, <:„-,„.,„
d. VA. 2;iS)
KtY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Mobile Sources
Hydrocarbons
Photochemical Reactivity
Indexing Procedures
b.lDENTIFIEHS/OPEN ENDED TERMS
FRluS -I'-..:!:
c. COSATI l-'icid/Ciriiup
..- •*.•* r-f • * j-tp-
.[ TO ti.f-.iJj
. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS ,'Vliijr ReporI/
none
21. NO. OF PAGES
28
20. SECURITY CLASS (This page/
none
22. PRICE
EPA Form 2720-1 (9-73)
-------
EPA-650/2-75-025
REACTIVITY iKDEX
FOR EMISSIONS
SQUSICi;
by
Francis M. Black, Larry E. High, and John E. Sigsby
Chemistry and Physics Laboratory
ROAP No. 26ACV
Program Element No. 1AA010
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
March 1975
-------
EPA REVIEW NOTICE
This report lias been reviewed by I ho National Environmental Research
Center - Research Triangle Park, OHice of Research and Development,
EPA, and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or > ^commendation for use.
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environ-
mental Protection Agency, have'been grouped into series. These broad
categories were established to facilitate further development and applica-
tion of environmental technology. Elimination of traditional grouping war
consciously planned to foster technology transfer and maximum interface
in related fields. These series are:
1. ENVIRONMENTAL HEALTH EFFECTS RESEARCH
2. ENVIRONMENTAL PROTECTION TECHNOLOGY
3. ECOLOGICAL RESEARCH
4. ENVIRONMENTAL MONITORING
5. SOC1OECONOM1C ENVIRONMENTAL STUDIES
6. SCIENTIFIC AND TECHNICAL ASSESSMENT REPORTS
9. MISCELLANEOUS
This report lias br-i n assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY scries. This series describes research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent environmental degradation from point and non-
poinC 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 for sale through the National
Technical Information Service, Springlield. Virginia 22161.
Publication No. EPA-650/2-75-025
-------
CONTENTS
LIST OF FIGURES iv
LIST OF TABLES 1v
ACKNOWLEDGMENTS iv
INTRODUCTION 1
EXPERIMENTAL . . 3
RESULTS AND DISCUSSION 13
CONCLUSIONS 21
REFERENCES 22
TECHNICAL RuPORT DATA AND ABSTRACT 23
111
-------
LIST OF FIGURES
Figure Page
1 Gas Chromatographic System Black Diagram 4
2 Chromatographic Flow Scheme 5
3 System Operation Sequence 7
4 Chromatogram of Calibration Mix 9
5 Valve Programmer 11
6 Exhaust Chromatogram, Catalytic Effect 20
LIST OF TABLES
Table Pa_g_e_
1 Reactivity Classification of Mobile 2
Source Hydrocarbon Emissions
2 Hydrocarbon Reactivity Class Average 15
Carbon Numbers, Fuel
3 Hydrocarbon Reactivity Class Average 16
Carbon Number, Exhaust
4 Photochemical Significance of Hydro- 18
carbon Emissions from Light-Duty
Mobile Sources
ACKNOWLEDGMENTS
We would like to acknowledge and give special recognition to the
Emissions Testing and Characterization Section of the Chemistry and
Physics Laboratory, particularly Dr. R. B>~adow and Mr. F. King, for
their efforts in providing the mobile source exhaust samples utilized
in this work.
-------
METHODOLOGY FOR ASSIGNMENT
OF A HYDROCARBON PHOTOCHEMICAL REACTIVITY INDEX
FOR EMISSIONS FROM MOBILE SOURCES
INTRODUCTION
Air quality criteria for photochemical oxidants have been established
in accordance with Section 107(6) of the Clean Air Act (42 U.S.C.
1857-18571). The current approach to abatement of photochemical oxidants
is based on control of organic emissions. Mobile source certification
procedures dictate control of total hydrocarbon emissions. Many studies
2-5
have been reported that indicate that organic emissions participate in
atmospheric reactions leading to oxidant/ozone formation in varying degrees.
The consensus of these studies indicates that methane, ethane, acetylene,
propane, and benzene, under reasonable hydrocarbon-to-NO ratios, are
^
essentially nonreactive.
Since the standard requiring hydrocarbon emission control is based on
oxidant/ozone formation, procedures for measurement of both mass and reac-
tivity of hydrocarbon emissions are necessary to evaluate adequately the
potential impact on photochemical pollution of prototype hydrocarbon con-
trol systems.
1
-------
Current research practices entail detailed analysis of more than 50
hydrocarbon compounds commonly found in exhaust samples. These are
weighted by reactivity. The chromatographic procedures required for the
analysis of the individual hydrocarbons are cumbersome and beyond the
capabilities of many interested laboratories. It is the inteiit of this
report to suggest less cumbersome procedures that will permit assignment
of a Hydrocarbon Photochemical Reactivity Index for mobile sources.
Hydrocarbon reactivity has been utilized as an index of participation
in atmospheric reactions leading to oxidant/ozone formation. Within the
context of this report, hydrocarbons will be addressed in four be.sic
reactivity classes as set forth in Table 1.
Table 1. REACTIVITY CLASSIFICATION OF MOBILE SOURCE
HYDROCARBON EMISSIONS5
Class
I (nonreactive)
11 (reactive)
III (reactive)
IV (reactive)
Compounds
Methane, ethane,
acetylene, propane,
benzene
C. and higher paraffins
Aromatics less benzene
Olefins
Molar
reactivity rating
1.0
6.5
9.7
14.3
A newly developed gas chromatographic procedure for measurement of
the nonreactive hydrocarbons, Class I, will he discussed in detail. Fur-
ther, the integration of this procedure with previously described sub-
tractive techniques will be discussed for measurement of the three
reactive classes.
-------
EXPERIMENTAL
NONREACTIVE HYDROCARBON MEASUREMENT
A gas chromatographic system has been developed that will permit
quantitative analysis of methane, ethane, acetylene, propane, and benzene.
The system, which includes four packed columns operated in a Perkin-timer
Model 900 gas chroma.tograph (GC) equipped with a flame ionization detector,
is basically illustrated in Figure 1. Multiple columns are required
because of the significantly different physical and chemical character of
the compounds being determined and because of the large variety of poten-
tially interfering compounds found in normal samples. The interfering
compounds include a wide range of other hydrocarbons, oxygenates, sulfur-
and nitrogen-containing organics, and the inorganics 0-, Np, COg, CO, NO,
and NO^. The described column system permits baseline resolution of the
five hydrocarbons defined as nonraactive.
The method involves injection of two sair.ple aliquots: The first on
columns 1 and 2 for methane, ethane, acetylene, and propane analysis; and
the second on columns 3 and 4 for benzene analysis. Both aliquots are
directed to a single detector, with columns 1 and 2 being backflushed to
vent during the period when benzene is eluting from columns 3 and 4. The
second aliquot is injected so as to permit elution of the C, hydrocarbons
of interest prior to eluticn of the benzene.
The details of the system are illustrated in Figure 2. Column 1,
which consists of 96- by 1/8-inch o.d. stainless steel tube packed with
80/100-mesh Poropak 0, is used primarily to resolve methane from air.
Normally, air is considered not to produce a signal of significance in
a flame ionization detector. However, when the detector/signal amplifier
-------
SAMPLE
INLET '
CARRIER
GAS
SAMPLE
VALVE
1
CJ
SAMPLE
LOOP
SAMPLE
LOOP
Q_
VENT
VENT
SAMPLE
VALVE
2
CARRIER
GAS
ANALYTICAL
COLUMNS
1 AND 2
I
t
VENT
VENT
ANALYTICAL
3 AND 4
SIGNAL
PROCESSOR
Figure 1. Gas chromatographic system block diagram.
-------
NOTE:
PRESS. REG.
PRESS. GAUGEO—
NEEDLE
VALVE
FLOW .-
CONTROLLER
SIX-PORT SEIZCOR GAS-SAMPLING VALVES
THREfe- "v SOLENOID VALVES
CHROMATOGRAPHIC ANALYTICAL COLUMNS
RESTRICTER, 0.01 x S-inch CAPILLARY
FID
DETECTOR
VACUUM
50 psig
AIR
7~^\ « r"\ • *
^ O -»» VENT r-O-
VENT
-HO ^
SAMPLE INLET
Figure 2. Chromatographic flow scheme.
-------
is operated with sensitivity appropriate t" methrne levels in samples from
emission-controlled vehicles, the signal resultant from the oxygen in air
is significant and must be resolved from methane. Although the flame
detector rosponds only to hydrogen-carbon compounds, when ths air peak
enters the detector it momentarily changes the ionizatiort characteristics
of the flame and interplays with the background hydrocarbon signal to
yield a positive system response. On the system described, this signal
is equivalent to 0.9 part per million carbon (ppm C). Column 2 consists
of a 48- by 1/8-inch o.d. Teflcr, tube packed with 35/60-mesh Type 58
Silica Gel and is used to resolve the G£ and C, hydrocarbons.
Column 3 consists of a 180- by 1/8-inch o.d. stainless steel tube
packed with 15 percent 1,2,3-tris (2-cyanoethoxy) propane on acid-washed
60/80-mesh firebrick and is used to resolve benzene from the other aro-
Q
matics and from the paraffins/olefins/acetylenes. Column 4 consists of a
24- by 1/8-inch o.d. stainless steel tube packed with 20 percent Hg50. on
30/40-mesh firebrick and is used to resolve benzene from the oxygenated
hydrocarbons. The firebrick columns were prepared utilizing acetone and
water solvents for columns 3 and 4, respectively. The substrates used for
the preparation of columns 3 and 4 were conditioned in a vacuum oven at
110°C for 24 hours prior to column packing.
The stainless steel coVsims are 0.093-inch i.d., and the Teflon col-
umn is 0.0625-inch i.d.; all are operated with a helium carrier at 50
cm /minute.
Figure 3 illustrates the analytical sequence on a time-temperature
plot appropriate tn the system described. The temperature program indi-
cated applies only to columns 1 and 3. Coiumns 2 and 4 are maintained
-------
o
O.
UJ
a:
0.
:g
•vl iu
100
90
80
70
£0
50
30
OVEN TEMPERATURE
f {_
STEP STEP
3 4
I I I I I77!
I/I I
11 12 13 14
.TIME>ini'M
15 16 17 ' ' 26 27
fcTEP
Figure 3. System operation sequence.
-------
isothermal at room temperature (20°C). In the time-zero configuration,
sample valves A and B are ready for loading, columns 1 and 2 are fore-
flushing to the detector, column 3 is foreflushinq to the vent, and column
4 is backflushing to the vent. The analytical sequence includes loading
sample valves A and B with 10-cm ^mple aliquots and the following
steps, as illustrated in Figure 3:
Step 1. Inject sample aliquot A on columns 1 and 2 for C,
• >
C2> and C- analysis and begin 35°C isothermal GC oven
operation.
Step 2. Begin GC oven temperature elevation from 35°C to
100°C at 32°C/minute.
Step 3. Inject sample aliquot b on column 3 for benzene
analysis.
Step 4. Begin 100°C isothermal GC oven operation.
Step 5. Simultaneously switch valves C and J, directing
the flow in columns 1 and 2 to the backflush vent,
and directing the flow in column 3 through column 4
to the detector.
Step 6. Switch valve D directing flow in column 3 to the
backfljsh vent.
Step 7. Reset all valves to time-zero configuration, and
lower GC oven temperature to 35°C.
Figure 4 illustrates the resultant chromatogram.
To facilitate reproducible valve sequencing, a programmer utilizing
three timers (Automatic Timing a>;d Controls, Inc.) has been designed that
permits manual and automatic cycling of the valves. The programmer is
-------
METHANE
AiR
ETHYLEN
i i i i i i i r
ETHANE
ACETYLENE
PROPANE
BENZENE
01 234 5
6789
RETENTION TIME, minutes
F'gure 4. Chromatogram of calibration mix.
10 11 12 13 14
-------
illustrated in Figure 5. Valves A, B, C, D, and J are actuated with high-
pressure air (50 psig) controlled by solenoid valves E, F, G, and H inter-
faced to the programmer. To determine the appropriate valve sequencing,
the programmer is operated in the manual mode. Utilizing a calibration
mix including methane, ethane, ethylene, acetylene, propane, propylene,
and benzene, sample aliquot A is injected on column 1. The GC oven is
maintained at 35°C until after air and methane have eluted. The oven
temperature is then rapidly elevated to 100°C. The rate at which the
temperature is elevated is determined by the C^ and C- hydrocarbon reso-
lution. With the time of Steps 1, 2, and 4 established, Step 5 is deter-
mined by the elutior, of propylene. The time at which sample aliquot B is
•injected is determined by the elution time of benzene from column 3 in
relation to the time of Step 5. This can be observed by manually setting
columns 1 and 2 to backflush through the vent and directing the flow of
columns 3 and 4 to the detector, and then injecting sample aliquot B.
The paraffinic/olefinic/acetylenic compounds will elute 2 to 6 minutes
after injection, and the benzene elutes about 10 minutes after injection.
Step 3 is executed so as to permit elution of propylene, switching the
columns to the detector (Step 5), and establishing baseline prior to
elution of benzene. Step 6 is executed after completion of the benzene
elution, and Step 7 is performed after column 3 has backflushed for a
period equivalent to the period running from injection of aliquot B to the
benzene elution. The three ATC triers are set using the time of Step 3
for timer I, the time of Step 5 for timer II, and the time of Step 6 for
timer III. The programmer can then be utilized in the automatic mode
for reproducible sequencing.
10
-------
SAMPLE
PUMP
TIMER
NOTE:
TIMER: ATC MODEL 325A346 A10PX
SI: DOUBLE POLE, DOUBLE-THROW SWITCH
S2-6: SINGLE POLE, SINGLE-THROW SWITCH
Rl-3: RELAY
SOL: SOLENOID VALVE
L: LIGHT
F: FUSE
Figure 5. Valve programmer.
-------
A Perkin-Elmer Model PEP-1 Data Processor is utilized with the system
to facilitate rapid transposition of peak data to concentration. The
processor is utilized with a calibration mix to compute response factors
for each compound. The response factors are stored with peak retention
data permitting on-line reporting of each sample compound by name and
concentration. System analytical repeatability is +_1.5 percent.
REACTIVE HYDROCARBON MEASUREMENT
As indicated in Table 1, there are three classes of reactive hydro-
carbons of interest: C. and higher paraffins, aromatics except benzene,
and olefins. Three participant components of this definition can be
obtained using the subtractive techniques of Kiosterman: total hydro-
carbon (THC) level, paraffin plus aromatic (PA) level, and paraffin plus
benzene (PB) level. The procedures for obtaining these values are well
described and will not be discussed further. Reactive class values can be
obtained by the following methods: (1) for class II by subtracting the
sum methane + ethane + propane + benzene from (PB); (2) for class III by
subtracting (PB) from (PA); and for class IV by subtracting (PA) +
acetylene from (THC).
Reactive hydrocarbon measurement may be summarized for the ciasses
by the following equations:
Class I = methane + ethane + propane + acetylens + benzene
Class II = (PB) - (benzene + methane + ethane + propane)
Class III = (PA) - (PB)
Class IV - (THC) - (PA + acetylene)
12
-------
RESULTS AND DISCUSSION
Currently defined procedures for certification of light-duty motcr
g
vehicles call for collection of three? exhaust samples: sample 1,
"transient cold start" test-phase emissions; sample 2, "stabilized cold
start" test-phase emissions; and sample 3, "transient hot start" test-
phase emissions. These samples are collected with a Constant Volume
Sampler, which dilutes the auto exhaust with air. Three dilution air
samples are collected coi.current with the exhaust samples. There are
thus six hydrocarbon analyses required per certification run—three
samples and three backgrounds. These values are utilized to calculate
the weighted mass emissions of hydrocarbons in grams per vehicle mile.
The suggested procedure inserts reactivity in this calculation and
results in a Hydrocarbon Photochemical Reactivity Index for the vehicle.
CALCULATIONS
The reactivity rating for each test-phase sample is calculated as
follows:
(% I x r,) + (% II x r9) + (% III x r,) + (% IV x r.) (5)
o - L £ -j t
ht.s.ct ~ 100
where:
R = reactivity rating value calculated for each test phase,
i.e., cold transient, stabilized, and hot transient.
% I, II, III, IV = mass percentage of total hydrocarbon determined
to be in classes I, II, III, and IV, respectively.
13
-------
y i inn exnaust class I hydrocarbons, ppm C
exhaust total hydrocarbons, ppm C
r1 2 3 4 = mass reactivity rating for class I, II, III. and IV
hydrocarbons.
A prerequisite for the determination of class mass reactivity ratings
is definition of the average carbon number of the class emissions. The
average carbon number can t used in conjunction with the molar reactivity
ratings given in Table 1 to determine the mass reactivity ratings.
Detailed hydrocarbon analysis is required to determine the class average
carbon number. The procedures described generate a detailed analysis of
class I, but not of classes II, III, and IV hydrocarbons. Tables 2 and 3
tabulate class average carbon numbers for several fuels and exhaust samples,
respectively, as determined by detailed hydrocarbon analysis.
As can be seen, the average carbon number is dependent on fuel and on
the combustion/control system. The sampling procedures (test cycle) will
also affect the exhaust class average carbon number.
The reactivity ratings utilized by the author will be based on samples
resultant from vehicles operated with the current Federal Test Procedure
(three test phases) and a regular-grade unleaded fuel. The average carbon
numbers utilized to determine the mass reactivity ratings are 5.55, 7.58,
and 2.85 for classes II, III, and IV, respectively. Class I ratings are
determined on a sample-by-sample basis as detailed information is available.
1 average carbon number of test phase
class I hydrocarbons
r _ 6.5, 9.7 , 14.3
2,3,4 5.5 7.58 2.58
r = 1.2, 1.3, 5.0
2,3,4
14
-------
Table 2. HYDROCARBON REACTIVITY CLASS
AVERAGE CARBON NUMBERS, FUEL
Sample
Fuel (1)
API-1.
Premium leaded
1968
Fuel (2)
API -8
Premium unleaded
1968
Fuel (3)
API-10
Regular unleaded
1968
Fuel (4)
Indolene
Regular unleaded
1972
Fuel (5)
Phillip's 66
EPA special
Regular unleaded
1973
Average carbon number,
reactivity class
I
6.00
6. CO
6.00
6.00
6.00
11
6.18
5.78
5.72
6.31
6.68
III
7.43
7.85
7.99
7.49
7.63
IV
6.08
5.59
5.91
4.67
4.87
As specified in the Federal Register, the mass emissions for each
test phase are calculated as follows:
= V mix x density HC x
HC 5oric
If)
where:
Y = mass emissions in grams hydrocarbon per test phase
V mix = total dilute exhaust volume in cubic feet per test
phase corrected to standard conditions (528°R and
760 mm Hg).
15
-------
table 3. HYDROCARBON REACTIVITY CLASS
AVERAGE CARBON NUMBERS, EXHAUST
Sample
1968 vehicle
1969 Federal Test
Procedure
Fuel (1)
1968 vehicle
1969 Federal Te;t
Procedure
Fuel (2)
1968 vehicle
1969 Federal Test
Procedure
Fuel (3)
1972 Chevrolet
1972 Federal Test
Procedure
Fuel (5)
(975 prototype "A"
1972 Federal Test
Procedure
Fuel (5)
1975 prototype "B"
1972 Federal Test
Procedure
Fuel (5)
Test
phase
•
.
I
II
III
I
II
III
I
II
III
Average carbon number,
reactivity class
I
1.58
M.77
1.76
,
1.52
1.44
1.58
1.46
1.04
1.22
1.37
1.02
1.15
II
6.35
5.97
5.88
5.85
5.51
5.79
5.37
5.43
5.14
5.93
5.44
5.49.
Ill
7.55
7.98
8.07
7.40
7.43
7.40
7.57
d.29
7.62
7.39
7.80
7.34
IV
3.16
3.54
3.36
2.72
2.L6
2.66
3.01
2.78
3.54
2.72
2.87
2.80
Density HC = density of hydrocarbons in the exhuast gas
assuming an average carbon-to-hydrogen ratio
of 1:1.85 in grams per cubic foot at 528°R
and 760 mm Hg pressure (16.33 g/ft3).
(Note: Current EPA policy is to express all
measurements in Agency documents in metric
units. When implementing this practice will
16
-------
result in undue difficulty in clarity,
NERC/RTP is providing conversion factors for
the particular nonmetric units used in the
document: cubic foot = 0.02832 cubic meter.)
HC ccnc = hydrocarbon concentration of the dilute exhaust
sample corrected for background, in ppm carbon
equivalent.
The Hydrocarbon Photochemical Reactivity Index combines the reactivity
rating with the mass emission of each test phase and weights the test
phases appropriately.
(0.43 x Yct x Ra) M0.57 x Y / Rht) * (Vs * V (7)
HPRI = _ j ;
APPLICATION
As illustrated in Figure 4, in addiion to the five nonreactive hydro-
carbons, definition of ethylene and propylene is obtained from the chroma-
/
tographic system. Although the analys.is of these compounds is not used in
/
the scheme described, the compounds are relatively abundant in auto exhaust
/
samples and serve as excellent system check peaks. They allow the operator
to ensure that the chromatographic /carrier gas system is stable. They also
/
account for a major portion of the/ difference between the fuel and exhaust
I
olefin average carbon number. /
;
The purpose of the defined'scheme is to permit '.-elating the various
hydrocarbon emission control systems to the photochemical significance of
the hydrocarbons being emitted. To illustrate this application, Federal
certification runs were conducted with a variety of vehicles as indicated
in Table 4. / -
/
/ *
17
-------
Table 4. PHOTOCHEMICAL SIGNIFICANCE OF HYDROCARBON EMISSIONS FROM LIGHT-DUTY MOBILE SOURCES
Vehicle
description
1972 Chevrolet
1975 prototype
"A" with
catalyst
removed
1975 prototype
"A" with
catalyst
in place
1975 prototype
"B" with
catalyst
in place
Test phase
Cold transient
Stabilized
Hot transient
Cold transient
Stabilized
Hot transient
Cold transient
Stabilized
Hot transient
Cold transient
Stabilized
Hot transient
Reactivity class
I
Nonreactive,
percent
23.9
27.4
. 18.3
16.3
24.0
13.9
6.8
40.7
14.4
16.4
38.1
27.0
II
Reactive
paraffins,
percent
32.2
28.9
39.1
39.2
40.3
53.4
54.4
23.6
61.0
38.4
42.0
48.5
III
Reactive
aromatics,
percent
20.6
18.3
21.0
24.3
15.2
16.7
10.0
21.4
8.4
22.9
8.2
11.5
IV
Reactive
olefins.
percent
23.4
25.3
21.6
20.2
20.6
16.0
28.8
14.3
16.2
22.2
11.7
13.0
R
1.98
2.04
1.93
1.91
1.91
1.75
2.27
1.55
1.77
1.99
1.57
1.62
V mix,
ft3
2955
5102
2997
2932
5168
3029
2964
5123
3012
2952
5097
2995
HC cone. ,
ppm C
157.9
52.7
87.9
138.7
27.4
117.3
51.8
8.4
60.6
86.8
9.3
24.8
Y
7.62
4.39
4.79
6.64
2.31
5.80
2.51
0.70
2.98
4.18
0.77
1.21
HPRI
2.76
2.08
0.88
0.79
CO
-------
Prototype "A" gave a 66 percent improvement in mass emissions rela-
tive to the 1972 Chevrolet; prototype "B" showed a 69 percent improvement.
Prototype "A" also gave a 12 percent improvement in the net reactivity
of the emissions, and prototype "B" showed a 16 percent improvement. As
illustrated by the data in Table 4, catalytic emission control systems
yield definite mass improvement but also reactivity improvement. The
degree of mass and reactivity improvement varies between control systems.
The impact of catalytic control systems on individual hydrocarbons,
resultant in the variable reactivity gains, is illustrated in Figure 6.
As evidenced, .the degree of control of the hydrocarbons is variable with
individual hydrocarbons. When the catalytic muffler was placed in the
appropriate position in the exhaust stream, the methane level was reduced
13 percent, whereas the acetylene was reduced 92 percent, the ethylene
74 percent, and the propylene 83 percent.
An additional compound that may be observed on the chromatographic
system when utilized with vehicles without advanced emission control is
propadiene. The compound is baseline-resolved with a retention time of
about 11.9 minutes, eluting after propylehe.
-------
AIR
Ju
AIR
_AJ
7.7 ppm C
METHANE
k j
1975 PROTOTYPE "A"
CATALYST REMOVED
7.7 ppr C
ETHYLENE
16.1 ppii C
ACETYLENE
A 5 J ppm C
I II PROPYLENE
! 1 1 23 ppm C
lOJppmC / \ BENZENE
ETHANE | 1 A
IAJ^ Jl . A
H75 PROTOTYPE "A"
6.7 ppm C CATALYST IN PL/CE
METHANE
12.0 ppm C
ETHYLENE
nino-p l.«ppmC
FT^r °-5ppmC 1-0ppm C BENZENE
ETHANE ftctTYLENE PROPYLENE A,
i JUA /v . y\
i i i i i i i i i i i i
6789
RETENTION TIME, minutes
10 11
13 14
Figure 6. Exnaust chrorr.atogrr.m, catalytic effect.
20
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CONCLUSIONS
The control of hydrocarbon emissions is necessitated by air quality
criteria for photochemical oxidants. In view of the fact that hydro-
carbons do not participate to the same extent in atmospheric reactions
leading to oxidant formation, methods for irieasurement of more than mass
of emissions are necessary to project adequately tho impact of mobile
sources on photochemical pollution.
Hydrocarbon photochemical reactivity can be integrated with mass
measurement methods in varying degrees; total hydrocarbon mass emissions
can be measured with no assessment of atmospheric reactivity. Total hydro-
carbon less metnane levels can be measured, eliminating the most abundant
nonreactive hydrocarbons. Total hydrocarbon less methane, ethane, propane,
acetylene, and benzene levels can be measured, eliminating the essentially
nonreactive hydrocarbons. The emissions can be meured in four hydro-
carbon classes, weighting by class reactivity. The emissions can be
measured in detail, weighting each individual hydrocarbon by its atmos-
pheric reactivity. Methodology permitting assessment in the first four
degrees is available by techniques discussed in thcs paper. Although only
detailed analysis will result in absolute assessment, the procedures
described offer ,.i very good approximation of the hydrocarbon photochemical
reactivity. The technique is weakened only by the need to estimate class
average carbon number. With definition of fuel and vehicle configuration,
this estimation can bo made relatively accurately.
21
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REFERENCES
1. A1r Quality Criteria for Photochemical CxicU.ntr, U.S. DHEK, PHS,
NAPCA, Washington, D.C., AP-63, 1970.
2. Altshuller, A. P. and J. J. Bufalini. Photochemicar Aspects of
Air Pollution: A Review. Environ. Sci. Techno!. 5: 39-63, 1971.
3. Altshuller, A. P., S. L. Kopczynski, D. Wilson, and W. A. Lonneman.
Photochemical Reactivities of N-Butane and Other Paraffinic Hydro-
carbons. J. Air Pell. Cont. Assoc. 19.: 787, 1969.
4. Tuesday, C. S. and W. A. Glasson. Hydrocarbon Reactivity in the
Atmospheric Photooxidation of Nitric Oxide. (Presented at ACS
Meeting, Atlantic City, September 1965.)
5. Dimitriades, B. The Concept of Reactivity and Its Possible Appli-
cation in Control. In: Proceedings of the Solvent Reactivity
Conference. U.S. Environmental Protection Agency, Research Triangle
Park, N.C. EPA-650/3-74-010, November 1974.
6. Klosterman, D. L. and J. E. Sigsby. Application of Subt'ractive
Techniques to the Analysis of Automotive Exhaust. Environ. Sci.
Technol. 1_: 309-314, 1957.
7. Bellar, T. A. and J. £.•Sigsby. Evaluation of Various Silica Gels
it the Gas Chromatographic Analysis of Light Hydrocarbons. Environ.
Set. Technol. Ij 242-246, 1967.
8. Clemans, C. A., P. W. Leach, and A. P. Altshuller. 1,2,3-Tris
(2-cyanoethoxy) Propane as a Stationary Phase in the Gas Chromato-
graphic Analysis of Aromatic Hydrocarbons. Anal. Chem. 35:
1546-1549, 1963.
9.: Title 40 - Protection of the Environment. Part 85, Subpart A,
Emission Regulations for New Gasoline-Fueled Light-duty Vehicles.
Federal Register. 37J221): 24270-24277, November 1972.
22
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