-------
ELECTRON
MULTIPLIER
OUAORUPOLE MASS
FILTER
IONIZER
LN2- COOLED
WALLS
TUNING FORK
CHOPPER
CALIBRATION GAS
EFFUSIVE
SOURCE
6 INCH
DIFFUSION
PUMP
4 INCH
DIFFUSION
PUMP
COLLIMATOR
6 INCH
DIFFUSION
PUMP
SKIMMER
QUARTZ NOZZLE
BURNER
MECHANICAL
VACUUM PUMP
!=<•— PREMIXED GASES
FIGURE 2, MOLECULAR BEAM MASS SPECTROMETER SYSTEM
25
-------
For studying the participate phase the mass spectrometer is removed and
the top flange is replaced by a flange that has a mechanism for mounting elec-
tron microscope grids and moving them in and out of the beam. The grids are
exposed to the beam for a measured time interval with the use of a mechanical
shutter. The particles collected on the grid are analyzed by making electron
micrographs using either shadowing or transmission procedures. Number densi-
ties and size distributions are obtained with the aid of a Zeiss semi-automatic
particle counter. Computation techniques developed by Wersborg will be used
to calculate profiles of average soot particle size, soot particle number
concentration, rates of nucleation, surface growth and coagulation (5).
A schematic of the mass spectrometer instrumentation is shown in Figure 3.
The molecular beam is chopped by the fixed-frequency tuning fork operating
at 220 Hz. The signal from the electron multiplier at any particular mass
has a DC component corresponding to ions originating from the background gas
molecules and an AC component at 220 Hz corresponding to ions originating
from the beam molecules. The signal is amplified with an Extranuclear fast
electrometer preamplifier. The amplified signal is DC coupled to an Extra-
nuclear electrometer to obtain a signal corresponding to the background compo-
nent. A reference signal from the chopper and the AC component of the signal
from the preamplifier are introduced into a Princeton Applied Research HR-8
lock-in amplifier to obtain a signal proportional to the beam component.
Signals corresponding to beam and background components are then displayed
either on a dual-beam storage oscilloscope or a chart recorder.
CALIBRATION
Considerations
Calibration of supersonic molecular beam systems for flame sampling is
not a straight forward task due to the many effects that can influence the
composition of the beam prior to reaching the mass spectrometer ionizer. Shock
formation in front of the skimmer orifice, species condensations, pressure
diffusion in the free jet, Mach number focussing downstream of the skimmer,
scattering of the beam by the background gas in any or all of the chambers,
and effusion of the background gas into the beam are effects that can distort
the beam composition and are discussed extensively in a review article by
Knuth (6). Skimmer interference problems can be avoided by proper design of
external,and internal angles of the skimmer and the selection of the proper
distance between the tip and the supporting wall. Species condensations in
free jet expansion are not believed to be important at flame temperatures and
sub-atmospheric pressures for most flame constituents (6), however little is
known about the behavior of the high molecular weight hydrocarbons and care
must be taken to look for condensation effects in the interpretation of the
data. Pressure diffusion, Mach number focussing and background scattering
and effusion are more difficult effects to avoid altogether and all can be
functions of source conditions. A study of their importance in this system
and techniques for calibration of these effects is now underway. The limited
data indicate that background scattering and effusion are negligible under the
flame conditions presented here. Pressure diffusion and Mach number focus-
sing are lumped together as "mass discrimination" and can be studied in this
26
-------
ELECTRON
MULTIPLIER
SIGNAL
rsi
ELECTROMETER
STORAGE
^ ^
OSCILLOSCOPE
PAR HR-8
LOCK IN
AMPLIFIER
OSCILLOGRAPHIC
RECORDER
MASS
FILTER
IONIZER
REFERENCE SIGNAL
EXTRANUCLEAR
MASS
SPEC.
CONTROLS
TUNING
FORK
CHOPPER
FIGURE 3, SCHEMATIC OF MASS SPECTROMETER INSTRUMENTATION
-------
system with the aid of the effusive source placed in the second stage upstream
of the collimator.
The system for studying mass discrimination is shown schematically in
Figure 4. Mixtures of the major stable species are made by metering through
critical orifice flow meters and mixing dynamically. These mixtures may be
introduced into the mass spectrometer ionizer either as an effusive beam in
which no mass discrimination effects occur or as a supersonic beam (through
the burner and quartz nozzle) in which high molecular weight species are usually
preferentially concentrated relative to low molecular weight species.
To introduce the mixture effusively without mass discrimination, a stain-
less steel sintered disc with a nominal pore size of 0.5 ym is used to leak
into the effusive source in the second stage about 1% of the total gas flow by
the disc. The pressure on the high pressure side of the sintered disc is main-
gained in the range 0.1 to 1 torr. Tubing size and pressures are designed to
give viscous flow (no mass discrimination) everywhere upstream of the sintered
disc and effusive flow through the disc and downstream from it. Under these
conditions the(flow rate of a component through the disc is inversely propor-
tional to the square root of its molecular weight but its density anywhere
downstream of the disc is proportional to its partial pressure upstream. Since
the electron impact ionizer is a density detector, ratios of ion signals are
proportional to the ratios of partial pressures in the gas mixture upstream of
the disc. The effusive source inlet system has been tested with commercially
prepared standard gas mixtures and reproduces the suppliers analysis to within
2% on any component.
By comparing signal ratios in the effusive beam to signal ratios in the sonic
beam the mass discrimination between two species in a mixture can be characterized
by an enrichment factor, ex.,,:
aAB= rE = SX
MB ig i lg t Ag b Ag t
where a.B = enrichment factor of species A relative to species B, dimensionless
I. = beam signal intensity of species A, amperes
ID = beam signal intensity of species B, amperes
S = sonic introduction
E = effusive introduction
X. = mole fraction of species A
Xg = mole fraction of species B
28
-------
MECHANICAL
VACUUM
PUMP
l
STAINLESS
STEEL
SINTERED
DISC
ALUMINA
TRAP
DIFFUSION
PUMP
MKS BARATRON
PRESSURE
TRANSDUCER
T T T T T
CO C02 H2 C2H2 02
EFFUSIVE
SOURCE^
M.S.
STAGE
2ND
STAGE
1ST
STAGE
BURNER
CHAMBER
rvvv
MIXING
VOLUME
1
— — — wr-
J
| CRITICAL
E^ ORIFICE
| FLOW METERS
Ar
FIGURE 4, SCHEMATIC OF GAS INTRODUCTION SYSTEM FOR STUDYING
MASS DISCRIMINATION
29
-------
The effusive source system is also used to obtain relative mass spectro-
meter sensitivity factors for stable species, S.,,:
s .-
AB kB
where k. = sensitivity for species A, amperes/torr
kg = sensitivity for species B, amperes/torr
Mass discrimination effects have been studied most extensivity by Sharma
et al. (7). The enrichment factor may or may not be a function of the source
conditions (flame conditions at the sampling point in this case) depending
upon how the system geometry and source conditions dictate the point of transi-
tion from continuum to free molecular flow. Although the study of these effects
in this system is not complete, preliminary experiments ar room temperature
with a mixture approximating the burned gas composition of the acetylene-
oxygen flames studied here indicate that enrichment factors for the major
species except that for hydrogen are relatively insensitive to source condi-
tions. An increase in source density by a factor of five resulted in a decrease
in aH2,co of 23% and changes in all other enrichment factors of less than 12%.
Further experimental work to assess the effect of gas composition and source
density on the enrichment factors is planned.
. . i
The calibration procedures for mass discrimination in the sonic beam and
for mass spectrometer sensitivities are carried out at room temperature. The
effect of temperature on these two calibration steps must be considered. The
mass spectrometer relative sensitivities in some cases might be functions of
temperature. In conventional (residual gas analyzer) mass spectrometer ion-
izers variation with temperature of absolute ionizer sensitivities for total
ionization have been found to be due only to the effects of temperature on
gas density and the speed of the neutral molecule (which effects ion collection
efficiency), implying that actual total ionization cross-sections are not
temperature sensitive (8). In the type of molecular beam ionizer used here
the neutral beam molecules are directed along the axis and toward the quadru-
poles, therefore the ion collection efficiency might be expected to be high
and less sensitive to translational temperatures perpendicular to the beam
axis. Although total ionization cross-sections are temperature independent,
fragmentation patterns and therefore mass spectrometer sensitivity (when a
specific ion is used to follow concentration changes) is highly dependent upon
the vibrational energies of the molecule-ion (9). As temperature increases
more fragmentation occurs. With current knowledge of vibrational relaxation
processes in supersonic expansions vibrational energies are impossible to
predict and one must if possible avoid the use of high electron energies where
fragmentation, occurs. The appearance potentials of fragment ions, like heats
of reaction, seem to vary but little with temperature (10). So, if fragmenta-
tion does not occur in room temperature calibrations it is 'not likely to
occur in. the case of the flame. However, in spite of these arguments, care
must be taken in the interpretation of the data and simple experiments must
be done to check temperature effects on mass spectrometer sensitivies due to
30
-------
fragmentation effects whereever possible.
The effects of temperature on the mass discrimination enrichment factors
must be assessed using the models designed to handle the prediction of enrich-
ment factors for pressure diffusion and mach number focussing (5,6). Analysis
of these models suggests that these mass discrimination effects depend upon
temperature in only the way in which it effects the source density. Therefore
enrichment factors from room temperature calibrations carried out at a reduced
pressure to reproduce the source density conditions should apply to the higher
pressure and temperature conditions in the flame.
Major Stable Species
In accordance with the considerations discussed above, the calibration
for most major stable species involves the measurement of enrichment factors
and relative mass spectrometer sensitivities. With this calibration information,
ratios of mole fractions in the flame are calculated from ratios of signal
intensities. In the flames studied here 5 mole % argon has been added to the
unburned gases as an aid in following density changes in the flame front.
Since calibration of this system for water is very uncertain the following
relationships are used to calculate mole fractions from ratios of mole frac-
tions in the tail of the flame where diffusion effects are negligible:
an oxygen balance
* XAr + XCO + XC02 + \
"l
T = V + XCO + V + XH90
. 1 f. ~n— c. ~~^-~
and argon balance
njT^Arh = XAr
and from experimental measurements
XH2 XC2H2 X02 XCO XC02
v» Y> ~v ' ~Y ' If
AAr AAr AAr AAr AAr
where nj/np is the ratio of initial number of moles to final number of moles
and (Xn)j refers to the mole fraction of species A in the unburned gas. Carbon
and hydrogen balances can then be used to check the consistency of the data
and calibrations. From the calculated ratio Xu0n in the tail of the flame and
31
-------
experimental !„ ~ ratio it is possible to obtain a calibration factor for
water:
X
H20
where I. = signal intensity of species i, amperes
X. = mole fraction of species i
CM Q . = calibration factor for water relative to argon.
Now with this additional piece of experimental information the oxygen and
argon balances are not needed in the reaction zone where steep gradients
require the use of diffusional terms. The assumption is made that C^O Ar is
constant throughout the flame (i.e. the enrichment factor is not a function
of gas density or composition and mass spectrometer relative sensitivity
factors are not functions of flame position.)
Higher Molecular Height Hydrocarbons
Due to the difficulty of introducing compounds that are liquids of low
vapor pressure and solids at room temperature into the system to obtain mass
spectrometer sensitivities and mass discrimination enrichment factors, all
higher molecular weight hydrocarbon species measurements are made on a
relative basis. To account for any changes in mass spectrometer relative
sensitivities that might occur, the fragmentation pattern at 20 eV electron
energy of perfluorotri butyl ami ne is recorded before and after each experiment.
EXPERIMENTAL PROCEDURE
To check out the experimental technique and procedures several fuel-
rich acetylene-oxygen flames have been investigated. All flames had a cold
gas velocity of 50 cm/sec and burned at a pressure of 20 torr. Five mole
percent argon was added to the unburned gas. Four fuel equivalence ratios
were investigated, <|> = 1.5, <|> = 2.0, = 2.4 (sooting limit) and <|> = 3.0.
Complete profiles were made for <|> = 1.5, 2.0 and 2.4. Two points near the
end of the oxidation zone were sampled in the cj> = 3.0 flame.
The mass spectrometer resolution controls were set to give unit resolu-
tion from 18 to 502 a.m.u. The electron energy was set at a nominal 20eV
which corresponded to an actual electron energy of 17.1eV according to argon
ionization potential measurements. At these conditions, room temperature
32
-------
fragmentation of 02, C02, CO and h^O does not occur. For acetylene peak 25
is less than 1% of peak 26. Mass spectrometer sensitivity and beam enrichment
factor calibrations were made before and after each flame run. Two sweeps
across the mass range 0 - 230 a.m.u. were made at each flame position at a
speed of ^ 1 a.m.u./sec.
RESULTS AND DISCUSSION
Profiles of signal intensities relative to argon for the <|> = 2.4 flame
are shown in Figures 5 and 6. The mole fractions of the major stable species
in the burned gas, as calculated from the procedure described above, are
included in Figure 5.
The experimental points with the most scatter are the hydrogen and water
profiles. The characteristics of quadrupole mass spectrometers make it diffi-
cult to have a high sensitivity for hydrogen and high molecular weight
hydrocarbon species simultaneously. To improve upon this measurement different
tuning conditions can be used for the low molecular weight gases and the high
molecular weight hydrocarbons. The noise in the water signal is due to a
large background peak at 18 a.m.u. The additional cryogenic pumping in the
ionizer region should improve this measurement.
The general features of the profiles are in agreement with the measure-
ments on a similar flame by Homann and colleagues (11,12). About 5.5 mole %
of the acetylene is present in the burned gases. The other hydrocarbons in
the burned gases are mostly polyacetylenes. They increase through the early
part of the oxidation zone and maximize at about 1 cm. Detectable amounts
of polyacetylenes up to CsH2 are still present in the burned gas. Polyacety-
lene formation is preceded in the oxidation zone by vinyl acetylene (C^) and
a C5Hg compound that could be benzene or a straight chain hydrocarbon. These
compounds have concentration maxima that are at least an order of magnitude
lower than the polyactylene of the same carbon number.
The interaction between the major stable species and the hydrocarbon
species throughout the flame is complex and interesting. Oxygen is completely
consumed by about 1.4 cm. At this point CO and H2 have nearly reached their
final values. C02 and H20 molefractions peak near 1 cm and decrease slightly
into the burned gas. Acetylene continues to decrease until about 2.5 cm above
the burner. These basic features can be explained qualitatively by the
following scheme of competing reactions early in the oxidation zone:
33
-------
C2H2/02/Ar P= 20TORR
0.469/0.485/0.05 VQ = 50CM /S
o
e>
cr
<
o
LU
CO Xco = 0.56
LU
(T
LU
=0.055
I 2 3
DISTANCE ABOVE BURNER , CM
FIGURE 5, PROFILES OF SIGNAL INTENSITIES RELATIVE TO ARGON FOR MAJOR STABLE
SPECIES IN AN ACETYLENE-OXYGEN FLAME NEAR THE SOOTING LIMIT.
* = 2,4, P = TORR, V0 = 50 CM/S, 5M% ARGON
34 .
-------
C2H2/02/Ar p= 20 TORR
0.469/0.485/0.05 V0 = 50 CM/S
1234
DISTANCE ABOVE BURNER , CM
FIGURE 6. PROFILES OF SIGNAL INTENSITIES RELATIVE TO ARGON FOR MINOR
SPECIES IN AN ACETYLENE-OXYGEN FLAME NEAR THE SOOTING LIMIT.
* = 2.4, p = 20 TORR. VQ = 50 CM/S, SM% ARGON
35
-------
fast
Reaction leading to polyacetylenes and C02 and f^O are faster than reactions
involving the same radicals leading to CO and H2- This ties up,oxygen in
the form of C02 and H20 and produces super equilibrium amounts of polyacety-
lenes. Near the end of the oxidation zone where the temperature reaches its
maximum, reactions producing OH, CO and H2 from C02 and H20:
H20 + H -> OH + H2
C02 + H -* CO + OH
become important and the oxidation of polyacetylenesbecomes faster than their
production (13). The oxidation rate decreases quickly because of the drop in
OH radical concentration leaving some polyacetylenes in the burned gas (14).
The features of the flame with 4> = 2.0 were essentially the same but
with lower CO, H2, acetylene and polyacetylene concentrations as might be
expected. At $ = 1.5 no acetylene or polyacetylenes were detectable in the
burned gas.
Signals were observed at masses other than those shown in Figures 5 and
6. Table I lists those masses at which positive identifications were not made
or contributions from several species were not sorted out. Masses 15, 16 and
17 peak in the middle of the oxidation zone. The most probable contributor
to peaks 15 and 16 is methane in this fuel rich flame. Masses 29 and 30 are
maximum at the lowest sampling point, 0.17 cm and the contribution of H2CO to
peak 29 has not been determined at these mass spectrometer conditions. Mass
34 appears only at the lowest sampling point. Mass 39 maximizes at 0.62 cm
from the burner. Mass 42, probably corresponding to propylene, maximizes at
0.35 cm. Appearance potential measurements along with measurements at lower
electron energies to prevent contributions from fragmentation of hydrocarbons
must be made to make positive identifications.
36
-------
TABLE I. MASSES AT WHICH SIGNALS WERE OBSERVED BUT POSITIVE
IDENTIFICATIONS WERE NOT MADE, * = 1A, P = 20 TORR, VQ = 5Q CM/S
MASS POSSIBLE CONTRIBUTING SPECIES
14
15
16
17
25
29
30
34
38
39
42
CH2
CH3 ,CI
H4
CH4 (MOST PROBABLE), 0
OH
C2H ,
HCO ,
H2CO,
H202
C3H2
C3H3 -
C3H6
C2H2
H2CO, CI30
C2H6 (UNLIKELY)
C3H3
37
-------
Mass spectra were observed at two points near the end of the oxidation
zone of a sooting flame of fuel equivalence ratio <|> = 3.0. In addition
to the species observed in the 4> = 2.4 flame several higher molecular weight
aromatic hydrocarbons were observed. Their masses, molecular formula and
possible structures are listed in Table II. The sensitivity for higher mole-
cular weight hydrocarbons (100 a.m.u. and above) should be increased by an
order of magnitude when the cryogenic pumping in the ionizer region is added
since the present sensitivity is limited by noise in the beam spectrum caused
by high levels of hydrocarbons in the background.
SUMMARY
A molecular beam mass spectrometer system has been developed for studying
sooting flames. Preliminary measurements suggest that molecular beam mass
discrimination effects may be relatively insensitive to source conditions and
that absolute concentration measurements of major stable species profiles
will be possible.
Profiles of relative signal intensities of several non-sooting and barely
sooting acetylene-oxygen flames have been made. The results are in agreement
with those of previous investigators. Polyacetylenic hydrocarbons up to mass
146 were detected and are the major hydrocarbons present other than the un-
burned fuel. Maxima in the carbon dioxide and water profiles are supportive
of the suggestion that reactions that store oxygen in these species are rapid
compared to reactions that lead to CO formation from the fuel in the early part
of the flame. At the higher temperatures present at the end of the oxidation
zone this oxygen is released in the form of OH that attacks polyacetylene and
unburned fuel.
Under strongly sooting conditions (4> = 3.0) aromatic hydrocarbons have been
detected. The addition of cyrogenic pumping in the ionizer region is expected
to increase the sensitivity for these species by an order of magnitude.
ACKNOWLEDGEMENTS
This work has been done under EPA Grant No. R 803242.
38
-------
TABLE II, ADDITIONAL SPECIES NEAP. THE END OF THE REACTION ZONE
IN A C2H2/02 FLAME, * = 3,0, P = 20 TORR, VQ = 50 CM/S
MASS MOLECULAR POSSIBLE STRUCTURE
FORMULA SPECIES
CH.
3
92 C7H8 TOLUENE
102 C8H6 PHENYLACETYLENE
HC=CH2
104 C8H8 STYRENE (p)
^x.-x^ LJ/••> r*LJ
nVrf = ^rip
118 C9HIO METHYL STYRENE (A
CH3
128 C|0H8 NAPHTHALENE
H
130 C,0H|0 PHENYL BUTADIENE
DIHYDRONAPHTHALENE
42 C|,H|0 METHYL NAPHTHALENE
146 C|2H2 HEXACETYLENE
Q
39
-------
REFERENCES
1. Butze, H.F., and R.C. Ehlers NASA Tech. Mem. NASA JMX-71789. Paper pre-
sented at Western States Section of the Combustion Institute, Palo Alto,
CA. Oct. 20, 1975.
2. Schirmer, R.M. in "Emissions from Continuous Combustion Systems", W.
Cornelius and W.G. Ahnew, ed., p. 189, Plenum Press, N.Y. (1972).
3. Longwell, J.P., "Synthetic Fuels and Combustion" Plenary lecture presented
to Sixteenth Symposium (International) on Combustion, Cambridge, Massa-
chusetts, August, 1976.
4. Biordi, J.C., C.P. Lazzara, and J.F. Papp, Combust. Flame 23, 73 (1974).
5. Wersborg, B.L., J.B. Howard, and G.C. Williams, Fourteenth'International
Symposium on Combustion, p. 929, The Combustion Institute (1973).
6. Knuth, E.L., "Direct Sampling Studies of Combustion Processes" in "Engine
Emissions, Pollutant Formation and Measurement", G.S. Springer and D.J.
Patterson, ed., p. 319, Plenum Press, N.Y. (1973).
7. Sharma, P.K., E.L. Knuth and W.S. Young, J. Chem, Phys. 6£, 4345 (1976).
8. Field, F.H. and O.L. Franklin, "Electron Impact Phenomena and the Proper-
ties of Gaseous Ions," pp. 202-203, Academic Press, N.Y. (1970).
9. Ibid. pp. 203-204.
10. Ibid., p. 81.
11. Homann, K.H. and H.Gg. Wagner, Ben'chte der Bunsengesellschaft 69, 20
(1965).
12. Bonne, U., K.H. Homann, and H. Gg. Wagner, Tenth Symposium (International)
on Combustion, p. 503, The Combustion Institute (1965).
13. Homann, K.H. Combust, and Flame 11, 265 (1967).
14. Bonne, U., H. Gg. Wagner, Berichte der Bunsengesellschaft 69, 35 (1965).
40
-------
APPENDIX C
Soot Concentration Measurements
in Fuels Doped with Nitrogen
and Sulfur Containing Compounds
(Unpublished)
41
-------
SOOT CONCENTRATION MEASUREMENTS IN FUELS DOPED WITH
NITROGEN AND SULFUR CONTAINING COMPOUNDS
by
William J. Kausch.Jr.
Department of Chemical Engineering
Massachusetts Institute of Technology
Cambridge, Massachusetts 02139
September, 1977
42
-------
INTRODUCTION
The purpose of this experimental program was to study the formation of soot
and polycyclic aromatic hydrocarbons (PCAH) in fuels doped with nitrogen and
sulfur containing compounds. The main fuel studied was benzene, but for pur-
poses of comparison a few experiments were also conducted with hexane and methane,
representing (H/C) ratios of 1, 2.3, and 4, respectively. The oxidant used was
oxygen rather than air to allow comparison with other flame studies conducted
with oxygen, and to assure that the origin of any nitrogen contained in poly-
cyclics formed in the inner cone of the flame would have to be the fuel rather
than atmospheric nitrogen.
The use of pure oxygen rather than air led to a benzene flame speed greater
than could be stabilized at convenient gas flows on a one-inch diameter burner,
without resorting to a fuel equivalence ratio () greater than 7. As a flame this
rich was undesirable, methane was added to the fuel in order to lower the flame
speed to an acceptable level. A smaller diameter burner was not substituted
since the water-cooled sampling probe might create too much disturbance in a
smaller flame.
The benzene and hexane studies were conducted with a CH^/CgHx (x = 6 or 14)
ratio of 1.5 and a <(> = 4.5. For all studies the cold gas velocity (v) was kept
constant at 31.8 cm/sec. Soot collected by the probe was trapped in glass wool
packed filters and the PCAH extracted and analyzed by gas chromatography.
APPARATUS AND EXPERIMENTAL DESIGN
The arrangement of the apparatus is shown in Figure 1. The burner used
was a modified Meker burner (see Fig. 2). The four air inlets were replaced
with oxygen feeds, and the fuel inlet was attached to 0.25 inch stainless
steel tube through which the benzene/methane mixture was fed. The fuel mixture
was preheated electrically with heating tape to vaporize the benzene. The
oxygen feeds were also preheated to approximately the same temperature (300-
320°C) to prevent benzene condensation inside the burner.
Temperatures were measured via thermocouples in the lines; CH^ and Q£
flows were monitored by critical orifices, and the benzene flow was measured
before vaporization by passing the liquid through a capillary tube with the
upstream and downstream pressures carefully measured. The liquid flows used
corresponded to Reynolds numbers of between 800-1000 through the capillary
tube. Thus the flow was always laminar and proportional to the pressure drop
through the tube.
43
-------
Exhaust
& soot out
Critical
Orifice
Flowmeter
Ar
liquid fuel tank
exhaust
glass wool packed
filter
Heating
p ape water~collection
ice bath
FIGURE 1. Overall Experimental Arrangements
-------
fuel
Top View
1/8" square
grid
Ventrur i
glass
shield
base to support
glass shield
V
Side View
heating tape
FIGURE 2. Burner Details
-------
EXPERIMENTAL PROCEDURE
A water cooled probe (Figure 3) was used to collect the soot, which was
trapped in a glass wool packed tube. One difference between the present sampling
technique and the one used previously in this laboratory was necessary. The
extremely sooty benzene flame caused some clogging of the probe due to soot
build-up at the tip; consequently the probe was kept out of the flame until all
conditions were ready for the actual sample to be collected. The bypass
filter, which previously collected "extraneous soot" before and after the actual
sampling run,- was totally eliminated.
Four additives were used for the doping procedure. Two compounds (pyrrole
or pyridine); were added to obtain 1% by weight nitrogen in the benzene, and
two other compounds (thiophene or carbon disulfide) were used to obtain 1% sulfur.
One percent of N or S was selected as being representative of the practical
interest for many fuels.
The amount of gas collected through the probe was monitored using a wet
test meter. As usual, the soot was extracted with acetone and methylene chloride
to obtain the yellow-orange colored PCAH. The analysis of these solutions is
achieved with GC, and: as necessary, combined GC/MS techniques. Soot concentrations
were calculated by weighing the soot collected (after extraction of PCAH) and
knowing the amount of gas sampled.
The flame was sampled at different heights above burner (HAB) to obtain
the soot concentration profiles.
RESULTS AND DISCUSSION
Figure 4 is a composite for all four additives to benzene. It is assumed
that the soot concentration is approximately independent of the additive; thus
the composite figure should give a fairly good representation of the actual
soot concentration. The validity of this approximation is based on the
relatively small amounts of additive required to obtain the desired 1% N and
S concentrations, and the similarity of the chemical structure of these com-
pounds to benzene. The 1% concentrations were calculated based on molecular
weights and densities, as follows (using CS_ as an example):
MW CS2 = 76.14
Atomic wt. S in CS = 64.14
MW benzene = 78.11
46
-------
Sample
In
- Water Out
Water In
:^^^
Water Spray
Sample + Water
to Filter
FIGURE 3. Water-Cooled Sampling Probe
-------
100
80
60
C
01
(J
C
o
(J
o
o
CO
4.5
x = CS
(•) = Pyrrole
O = Pyridine
Q= Thiophene
FIGURE 4. Variation of Soot Concentration
with Height Above Burner for Each of
Four Additives in Benzene
20
40 60 80 100
Height Above Burner, mm
120
48
-------
Letting x = wt. fraction (benzene/CS ) ,
76.14 + x(78.11)
=
Solving, x = 81. 1A. This implies that we need 1 g of CS2 per 81.14 g of benzene.
Using densities @ 20°C,
density C^ = 0.8786 g/ml
density CS2 = 1..2632 g/ml
one obtains 1.00 ml of CS0 per 116.67 ml of C,H, .
L a b
This is admittedly the lowest ratio of the four additives, but for the
other three compounds the (C/H) ratio is approximately one, as is that of
benzene. Furthermore the structures are all or mostly aromatic, benzene being
of course totally aromatic (see Table 1) . In all cases the carbon atoms are
in aromatic or at least double-bonded positions. Thus we confidently make, the
aforementioned approximation, and also consider only the €5^5 and CH4 in the
balanced chemical reaction to determine the 4.5 fuel equivalence ratio.
The benzene/oxygen/ uethane flame had a very bright and distinct inner
cone of approximately 70 mm height, thus points shown in Fig. 4 below 70 mm
HAB can be assumed to be similar to a premixed flame, while those above 70 mm
HAB are from the diffusion-like tail of the flame. Concentrations are reported
in ug/cm^ at 20°C and 1 atm. on a water free basis.
The curve in Fig. 4 has been drawn to favor the lower concentration points
(at a given HAB) especially at low HAB. The reason for this is that the small
shell-like diffusion flame which formed around the edges of the burner was
observed to have much more soot than inside the flame (probably due to low
temperatures which prevented soot burnout), and due to the sampling probe
being moved quickly in and out of the flame at the beginning and ending of the
sample collection, the probe was exposed to this soot for a fraction of a
second. This effect is negligible in the upper portions of the flame (> 70 mm)
where there was so much soot that 40-50 mg were usually collected; however, in
the lower portions of the flame ( < 40 mm), this effect might have some small
significance since usually less than 10 mg of soot was collected. The curve
is thus drawn very low at HAB's less than 40 mm, despite some high points in
this region.
Unfortunately, Fig. 4 does not represent the whole story, as some highly
suspect points have been removed. These points are shown in Figs. 5-8, which
represent each of the additives separately. The curves drawn through the. data
ignore the suspected bad points. These curves tend to differ slightly from
the composite graph (Fig. 4), probably due only to an insufficient number of
points.
49
-------
Table 1. Information on Benzene and Additives
Compound
Benzene
Pyridine
Pyrrole
Thiophene
Carbon
Disulfide
Structure
0
0
o
T
H
Q
S-CoS
MW
78.11
79.1
67.04
84.14
76.14
Density
.8786
.9812
.9691
1.0882
1.2632
Volume ratio
ml additive
ml benzene
1% N or S
-
1.00/18.88
1.00/18.81
1.00/49.52
1.00/116.64
C/H ratio
1.0/1.0
1/1
4/5
1/1
1/0
% Aromatic
Atoms
(C,S, or N)
100%
100%
80%
(not N)
80%
(not S)
100%
50
-------
100
80
60
00
3.
<(> = 4.5
C,H/0,/CH
662 4
5H N (Pyridine)
doped
FIGURE 5. Variation of Soot Concentration with
Height Above Burner for Pyridine Additive in
Benzene
20
60 80 100 120
Height Above Burner, mm
140
.51
-------
100
oc
3.
80
60
0
40
<(> = 4.5
C6H6/02/CH4
C^H N (Pyrrole)
doped
20
FIGURE 6. Variation of Soot Concentration with
Height Above Burner for Pyrrole Additive in
Benzene
20 40 60 80 100
Height Above Burner, mm
120
140
52
-------
100
80
t>o
3.
C
a)
o
c
o
o
60
4.5
C,H,/0,/CH;
662 4
C.H,S (Thiophene)
44, ,
doped
20
FIGURE 7. Variation of Soot Concentration with
Height Above Burner for Thiophene Additive in
Benzene
20 40 60 80 100
Height Above Burner, nun
120
53
-------
100
80
00
3.
c
o
cj
60
= 4.5
C,H,/0,/CH.
662 4
CS- doped
FIGURE 8. Variation of Soot Concentration with
Height Above Burner for Carbon Disulfide Additive
in Benzene
20
60 80 100
Height Above Burner, mm
120
54
-------
A circle around a point indicates that it does not appear on the composite.
The reasons why the points are believed to be in error are listed below with
numbers, referring to the numbers in the figures.
(1) Sample was taken at a height greater than 110 mm, where, due to quivering
of the diffusion flame, it was difficult to tell when the probe was in the
flame and when it was not.
(2) A very large amount of soot was collected and some leaked through the
filter during the PCAH extraction.
(3) The probe appeared to clog slightly.
(4) The probe was exposed to the outer diffusion flame shell (discussed above)
for much longer than usual, typically due to the probe slipping during a run.
(5) Much lower than usual gas suction rate through the filter.
(6) Much higher than usual gas suction rate through the filter.
(7) Filter containing soot chipped after completion of sampling. Pieces were
weighed, but a small piece of glass must have been lost.
Two other fuels (methane and hexane) were also tested on this burner at
the same 4> and v. Graphs of data from these two cases are shown in Fig. 9 and
10. The methane/oxygen flame was not doped with any additive, but the hexane/
oxygen/methane flame contained both thiophene and pyrrole (both five member
rings) in proportions such that the final liquid mixture had 1% N and 1% S.
The (CH^/CgH^) ratio was also set at 1.5, the same as for the benzene studies.
Despite the same ()> and v, neither the hexane nor the methane flame exhibited
an inner cone; however the shape of the soot concentration curves are approxi-
matly the same as before. The range of soot concentration curves are approxi-
mately the same as before. The range of soot concentrations with hexane is
l/25th of that for benzene (from 0-100 yg/cm3 to 0-4 yg/cm3) and for methane
it is l/50th (from 0-100 yg/cm3 to 0-2 yg/cm3) .
It was earlier stated that the presence of the additive was negligible
calculating the fuel equivalence ratio. This approximation may become suspect
when one extends it to two additives, as was done with hexane. However, cal-
culations show that the approximation is still very good.
A few samples were also made at a <)> = 4.0, using once again a benzene
and methane mixture as fuel. In order to attain this lower fy with the same v
on our one- inch diameter burner, the ratio (CH^/CfcHfc) unfortunately had to be
increased from 1.5 to 2.0. The resultant flame had an inner cone height of
only 54 mm, rather than 70 as with the (CI^/CgHfc) ratio = 1.5 and = 4.5.
The presence of more methane and less benzene, as well as a lower $ would
lead one to expect lower soot concentrations at a given HAB, yet a comparison
of Figs. 4 and 11 show that this is not the case. This phenomena can perhaps
best be explained by the difference in inner cone heights. If one were to
plot the concentration versus the height, above this inner cone, the resultant
shift to the right of the = 4.0 curve would bring it under the
-------
2.00
1.60
E
u
eo
1.2
o
w .80
.40
20
Pure
= 4.5
FIGURE 9. Variation of Soot Concentration with
Height Above Burner for Pure Methane Fuel with
No Additive
60 80 100
Height Above Burner, mm
120
56
-------
4.0
3.20
<(> = A.5
C6'V°2/CH4
C.H,S (Thiophene) and
4 4
C H N (Pyrrole)
doped
FIGURE 10. Variation of Soot Concentration
with Height Above Burner for Thiophene ar
-------
100
0)
u
c
o
u
o
o
in
80
60
C.H /O./CH.
662 4
4.0
cs_
Q = CHS
4 4
FIGURE 11. Variation of Soot Concentration with Height
Above Burner for Each of Three Additives in Benzene
and a Lower Equivalence Ratio
20
40
60
80 ion
Above liurnor, mm
120
-------
SUMMARY AND CONCLUSIONS
The benzene/methane mixture used to obtain the majority of data in this
report was approximately 25 times more sooty than the hexane/methane mixture
and 50 times more sooty than the pure methane/oxygen flame. The general shape
of the soot concentration profiles are about the same for all fuels, as they
should be since all of the cold gas velocities were the same.
The data for each individual additive is somewhat sketchy, but the compo-
site seems to yield a fairly firm picture of the soot concentration profile.
This is probably due to many sources of error inherent in the techniques used,
necessitating a large number of data points. The single most important source
of error is the deposition of soot at the inlet to the probe, sometimes making
the opening smaller or even clogging it.
The data taken at a $ = 4.0 do not exhibit much, if any, evidence of repro-
ducibility. Apparently many more runs would have been necessary at these condi-
tions to obtain a firm idea concerning the actual location of the concentration
profile. Consequently these results are only included here for the sake of
completeness, not because they convey too much meaning.
59
-------
APPENDIX - DATA TABLE
Notes for Table:
(a) A blank indicates an entry is unchanged from the last listed
value, except in the Error Code Column, where a blank indicates that
the concentration reported is reasonably accurate.
(b) Fuel column indicates fuel in addition to CH^, which was present
in all runs.
(c) All (|> = 4.0 runs have (CH^CeHg) = 2.0, whereas all = 4.5
runs have (CH/CH) =1.5
Run
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Additive HAS
1 % N or S (mm) Fuel
CS0 20.7 4.5 C,H,
i DO
a. 2
15.7
71.05
61.3
C.H_N 80.85
4 5
53.25
26.65
101.6
116.35
111.25 4.0
85.0
95.45
63.65
59.95
33.1
12.5
Soot
(mg)
11.0
2.6
11.2
24.8
59.1
25.3
32.8
4.2
65.95
40.1
25.76
200.7
55.9
89.3
73.3
14.6
2.1
Gas
U)
NA
13.5
15.5
1.05
1.53
0.592
1.59
1.23
0.943
0.943
0.298
2.22
0.732
1.06
1.09
.898
1.14
Cone . Error
(yg/cm3) Code
NA NA
.19
.72
23.76
38.56
42.73
20.7
3.42
68.87
42.57 1,3
86.27
90.19
76.48
84.53
67.28
16.28
1.88
(continued)
60
-------
APPENDIX - DATA TABLE (continued)
Run Additive
No. 1 % N or
18 C5H5N
19
20
21
22
23
24 C.H.S
4 4
25
26
27
28
29
30
31
32
33
34 CS2
35
36
37
38
HAB
S (mm) <(>
11.
31.
71.
109.
89.
136.
148.
116.
88.
63.
37.
17.
45.
89.
110.
91.
88.
112
38.
68.
84.
95 4.5
5
4
3
9
9
7
1
8
9
9
7
2
6
0
95 4.0
2 .4.5
1
0
2
Soot
Fuel (mg)
3
4
56
133
33
102
88
50
60
32
1
0
4
26
51
58
C,H, 38
o o
89
0
20
62
.37
.23
.67
.5
.2
.8
.3
.1
.9
.8
.8
.35
.4
.6
.2
.4
.5
.6
.73
.2
.6
Gas
1
1
0
1
0
1
1
0
1
0
1
0
0
0
0
0
0
0
0
0
0
.153
.18
.846
.585
.737
.339
.172
.758
.58
.876
.15
.547
.903
.383
.492
.547
.410
.986
.355
.465
.657
Cone. Error
(pg/cnH) Code
2
3
66
84
42
76
75
67
38
37
1
0
4
69
103
101
93
90
2
43
95
.92 4
.58
.96
.27
.05 5
.77 1,2
.42 1
.2 1,2,5
.51 2
.5
.55
.639
.85
.47
.95 6,1
,7
.83 4?
.89
.05
.4
.3 6
(continued)
61
-------
APPENDIX - DATA TABLE (continued)
Run
No.
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Additive HAB
1 % N or S (mm) $ Fuel
63.9 4.0
C4H5N 70.0 4.5
86.6
102.1
76.25 4.0
55.5
43.6
C5H5N 49.2 4.5
60.95
14.15
86.5
98.95
None 98.95 CH.
4
83.25
83.25
70.3
54.85
52.6
67.9
39.4
Soot
(rag)
41.2
28.1
46.6
51.7
22.6
25.9
7.1
22.7
23.2
0.93
55.57
44.3
2.38
0.19
1.39
0.62
0.13
0.51
5.89
0.07
Gas
0.542
0.542
0.488
0.484
0.456
0.491
0.573
0.607
0.496
0.685
0.712
0.493
1.367
2.94
1.097
1.59
1.426
13.715
.13.192
21.147
Cone.
(yg/cm )
76.07
51.77
95.6
106.71
41.45
52.85
12.4
37.38
46.65
1.36
78.0
89.88
1.78
0.065
1.266
.3897
0.091
0.037
0.446
0.0033
Error
Code
6
4?
4
7
62
(continued)
-------
APPENDIX - DATA TABLE (continued)
Run Additive HAB
No. 1 % N or S (mm) 4>
59 C.H.S 25.5
4 4
60 and 44.05
61
62
63
64
53.35
71.25
90.25
110.3
Soot
Fuel (mg)
C,H,. 1.01
6 14
1.02
1.68
6.06
6.53
10.45
Gas
U)
12.35
3.81
11.59
5.902
5.048
2.91
Cone . o
(yg/cm )
0.082
0.267
0.145
1.027
1.294
3.592
Error
Code
63
-------
APPENDIX D
Source Identification
of Urban Airborn Polycyclic
Aromatic Hydrocarbons by Gas
Chromatographic Mass Spectrometry
and High Resolution Mass Spectrometry
From: Biomedical Mass Spectrometry,
4, 182 (,1977). Reprinted
with the permission of Heyden
& Son Ltd.
64
-------
Source Identification of Urban Airborne
Poiycydic Aromatic Hydrocarbons by Gas
raphic Mass Specfrometry and High
Resolution Mass Spectrometryt
M. L. Lee, G. P. Prado, J. B. Howard and Ronald A. Hitest
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139. U.S.A.
Poiycydic aromatic hydrocarbons formed during the combustion of three common fuels (coal, wood and
kerosene) were separated and identified by capillary-column gas chromatographic mass spectrometry and were
compared to airborne polycydic aromatic hydrocarbons from Indianapolis, a high coal consuming area, and
Boston, a low coal consuming area. High resolution mass spectral data were utilized in the construction of alkyl
homolog plots for the comparison of alkyl distribution within each sample.
INTRODUCTION
The suspected relationship between atmospheric pollu-
tion and lung cancer is not yet substantiated with good
epidemiological and analytical surveillance data to pro-
vide good quantitative correlations. It seems clear, how-
ever, that a relationship does exist. For example, the
incidence of lung cancer is twice as high among city
dwellers as among rural residents, and it is most common
in cities where general industrial pollution is the
heaviest.1 Polycyclic aromatic hydrocarbons (PAH),
well known constituents of air paniculate matter, have
been credited with being the major class of compounds
responsible for this observed carcinogenic activity.
Many specific PAH have been shown to be carcinogenic
in animals; and, although inferences for man from
experimental studies involving animals must be drawn
with particular caution, there are good reasons to
believe that airborne PAH participate in the induction
of human lung cancej.1
The distribution of PAH in a particular atmospheric
environment, and hence, the carcinogenic potential of
that environment, is largely dependent on the sum of its
sources. PAH are generally produced from combustion
processes utilizing fossil fuels, and their formation is
dependent on various combustion parameters such as
fuel type, temperature and fuel-to-air ratio. Distribu-
tions of PAH in emissions from different combustion
sources differ considerably in type and concentration of
species. Thus, the sum of contributing sources generally
produces an air particulate PAH fraction which is
unique to the area sampled.2'3
It has been determined that approximately 90%
of the PAH emissions in the United States is due to
coal combustion processes, including coal-fired furnaces
and coal-refuse bank burning, and to coke production.4
Most of these processes are concentrated in the mid-
western states. Coal consumption is highest in Ohio and
t Abbreviation: PAH = polycyclic aromatic hydrocarbons.
t To whom correspondence should be addressed.
Pennsylvania with each state consuming more than 60
million tons in 1970." Michigan, Indiana, and Illinois
each used between 26 and 50 million tons." Contrast
these figures with a total of 4.6 million tons consumed by
all of New England during the same period of time.4 It
seems reasonable to expect, therefore, that the PAH
isolated from the combustion products of coal would be
quite well represented in midwestern air particulate
matter. On the other hand, New England airborne PAH
should be similar to the products obtained from the
combustion of fuel oil and gasoline since these are the
major sources of PAH emissions in New England.
The objectives of this study were twofold. First, the
PAH fractions obtained from the combustion of three
common fuels (coal, wood and kerosene) were analyzed
to determine their detailed compositions. Capillary-
column gas chromatography combined with mass spec-
trometry was utilized for separation and identification of
the mixture constituents. Of particular interest was the
identification of the combustion products of coal, which
is the major source of atmospheric PAH. Since the usage
of coal is likely to increase because of the present energy
crisis, information on the PAH distribution in coal com-
bustion products is valuable for future studies concern-
ing the health effects of new modes of energy produc-
tion. Second, the distributions of PAH obtained from
the three different fuels were compared with those of air
particulate matter from a high coal consumption area
(Indiana) and a low coal consumption area (Mas-
sachusetts) by high resolution mass spectrometry to see
if correlations could be made between fuel utilization
and air particulate matter.
EXPERIMENTAL
The apparatus used for burning coal and wood samples
was constructed by placing a stainless steel wire mesh
screen (no asbestos) on a tripod and placing a 16 cmx
10 cm i.d. metal cylinder endwise on the screen. About
ten pieces (approximately 20 g each) of a Pittsburgh
seam bituminous coal or wood chips from a construction
65
-------
grade fir were placed in the chimney (cylinder) and
ignited from underneath with a Bunsen burner. The
burner was removed, and soot samples were collected by
repeatedly lowering a 250 ml Erlenmeyer flask, which
was cooled by a continuous flow of water through the
flask, into the flame for about 30 min, at which time the
fuel was completely consumed. The soot collected on the
glass surface was scraped with a spatula into a small
beaker. Each soot sample (250-400 mg) was then placed
in a Soxhlet apparatus and extracted with 250 ml of
methylene chloride for 18 h. The extract was evaporated
to dryness with a rotary evaporator, dissolved in 50 ml of
cyclohexane and transferrred to a separatory funnel.
The cyclohexane layer was then washed five times with
50 ml of nitromethane. All nitromethane portions were
combined and evaporated to dryness. The residue was
then transferred to a 1 cm i.d. glass column packed with
2 g of silicic acid and eluted with 300 ml of hexane. The
eluate was evaporated to dryness and dissolved in 0.5-
5 ml of methylene chloride prior to gas chromatographic
analysis. This procedure was shown previously to
be effective in separating and purifying the PAH from
the bulk of other organic compounds in the extract.5 It
should be noted that nitrogen-containing polycyclics are
removed by this procedure but sulfur-containing
polycyclics are not.
Kerosene was burned in a specially constructed tur-
bulent diffusion flame burner using an air-assist
atomizer.6 The air-atomizing pressure was 170 KPa
(101bin~2g), the cold gas velocity was 0.96ms~' and
the fuel-air equivalence ratio was 1 (stoichiometry). This
burner and these conditions simulate a poorly main-
tained home-heating furnace. Soot samples were col-
lected from this burner using a novel water-cooled
probe7 at the exhaust of the combustion chamber (50 cm
from the burner nozzle). The collected soot was
extracted with methylene chloride and the extract con-
centrated for gas chromatographic analysis with a rotary
evaporator. All glassware was acid cleaned prior to use,
and all solvents were Nanograde (Mallinckrodt) quality.
Blank runs demonstrated the absence of contamination.
The total yield of PAH in each sample was 2-3% of the
soot extracted.
The PAH samples isolated from air paniculate matter
from Indiana and Massachusetts were utilized in previ-
ous studies and descriptions of each sample work-up
procedure can be found elsewhere.8'9
Gas chromatographic mass spectrometry of each
sample was performed with a Hewlett-Packard
5982Ag.c.m.s. system interfaced to a HP 5933A data
system. A 19 mx 0.26 mm i.d. glass capillary column
coated with SE-52 methyl-phenyl-silicone stationary
phase was used to separate mixtures prior to mass
spectral analysis. The oven temperature was pro-
grammed from 70 °C to 250 °C at 2°Cmin^' during
each chromatographic run. The mass range (from 50 to
350a.m.u.) was continuously scanned every 2.5 s. The
mass spectrometer was operated at 70 eV ionizing
energy.
High resolution mass spectral information was
obtained on each sample by introducing an aliquot of the
methylene chloride extract into a high resolution mass
spectrometer through a direct introduction probe sys-
tem and slowly vaporizing the sample at a continually
increasing temperature while making several exposures
on a photographic plate. The developed plate was read
on a computerized comparator, and the exact masses
were converted to elemental composition. The corre-
sponding intensities were then arranged as tables of
carbon number vs. number of double bonds and rings.
One such table was generated for each exposure and
then a composite table was formed by adding the corre-
sponding entries of each table. This technique has
been described previously.ia" The results from this
high resolution m.s. technique have been validated by a
comparison with quantitative g.c. data obtained on the
Indianapolis air particulate extract. The two methods
give results which are highly correlated (r = 0.93, N = 6)
and thus can be considered self-consistent.
The high resolution m.s. system consists of a DuPont
Instruments 21-110B mass spectrometer and a D. W.
Mann comparator interfaced to an IBM 1802 computer.
The ionizing energy was 70 eV and the resolving power
was about 20 000. This high resolution m.s. system and
its operation are described elsewhere.12
RESULTS AND DISCUSSION
Considerable emphasis has been placed on the necessity
for improved resolution of components in complex PAH
mixtures because of the ongoing interest in exact iden-
tification of potential carcinogens.13'1'? Capillary-
column g.c. has proven to be the most efficient separa-
tion tool presently available for the analysis of PAH, and
its use has provided the means for extremely detailed
studies of PAH mixtures.8-u-15 Figures 1, 2 and 3 show
high resolution gas chromatograms of the PAH fractions
obtained from the three fuels studied here. Table 1 lists
the compounds identified by g.c.m.S: and g.c. retention
data. Several qualitative and semiquantitative observa-
tions result from the comparison of these chromato-
grams: (1) there is a greater relative concentration of
alkylated PAH in the coal combustion products as com-
pared with either wood or kerosene; (2) there is a greater
relative concentration of high molecular weight species
in the wood and kerosene combustion products as com-
pared with coal; (3) the coal soot PAH fraction
contains significant amounts of sulfur-containing
compounds, which are absent in the other combustion
products.
The construction of alkyl homolog plots from high
resolution mass spectral data is an effective way of
representing the distribution of alkylated species within
a PAH mixture.10'11 Figure 4 shows the alkyl homolog
distribution for seven major groups of isomers found in
the coal soot PAH fraction. In agreement with the gas
chromatogram, there tend to be considerable amounts
of alkylated species. The high sensitivity of this tech-
nique shows the presence of alkyl groups containing up
to six carbons for the phenanthrene type series (Z = —
18) and five carbons for the pyrene type series (Z = -
22). The comparison of the Z= -22 series for coal,
wood and kerosene combustion products with air par-
ticulate matter from Indianapolis and Boston is shown in
Fig. 5. There is a remarkable similarity between the
curves for coal-soot PAH and Indianapolis air particu-
lates as well as between the kerosene-soot PAH and
Boston air particulates.
66
-------
70
90
110
130
ISO
170
190
210
230
230
Temp. PC)
Time(min) Q 10 20 30 40 50 60 70 80 90 110
Figure 1. Capillary-column gas chromatogram of the PAH fraction of coal combustion products. Conditions: see text. Key: see Table 1.
Temp.(°C)
Tlme(mln) 0
70
90
110
130
150
170
190
210
230
250
10
20
30
40
50
60
70
80
90
110
Figure 2. Capillary-column gas chromatogram of the PAH fraction of wood combustion products. Conditions: see text. Key: see Table 1.
Early chromatographic peeks with less retention than acenaphthylene have been identified as substituted methoxyphenols and several
other nonpolycyclic compounds.
Figure 6 represents composite alkyl homolog plots
.which were constructed by adding intensities of all par-
ent compounds, all Ci alkylated compounds, all C2
alkylated compounds, etc., for all series represented in
Fig. 4 and plotting the resulting sums. Again, the
similarities observed in Fig. 5 are evident in this compo-
site. The similarity in the results obtained from the
turbulent diffusion flame burner and Boston air particu-
lates is consistent with the fact that fuel oil (which is
chemically similar to kerosene) is Boston's principal
heating and energy producing fuel, while coal burning is
practically nonexistent.
The sulfur-containing polycyclic aromatic species in
the coal combustion products (see Table 1) are identical
to those found in the air particulates from Indianapolis.8
This observation, in addition to the alkyl homolog dis-
tributions, lends support to the belief that the major
contributors to Indianapolis airborne PAH are coal
combustion processes. The relatively low concentration
of high molecular weight compounds in the coal soot
67
-------
70
90
no
130
150
170
190
210
Z30
250
Temp. (°C)
Time (min) 0 10 20 30 40 50 60 70 80 90 110
Figure 3. Capillary-column gas chromatogram of the PAH fraction of kerosene combustion products. Conditions: see text. Key: Table 1.
PAH fraction is not consistent, however, with what has
been observed in the Indianapolis air participates. There
are three possible explanations for this difference. First,
it was found that by altering the combustion conditions
(especially temperature) in the production of carbon
blacks15 the relative proportion of higher molecular
weight to lower molecular weight PAH species could be
either considerably increased or decreased. The same
trends are certainly present in the combustion of coal.
Second, the practice 6 of sampling air paniculate matter
Table 1. PAH identified by g.c.mj.
Peak No. Compound
1 Methylnaphthalene
2 Biphenyl
3 Ethylnaphthalene"
4 Acenaphthylene*
5 Methylbiphenyl
6 Dibenzofuran
7- Propylnaphthalene"
8 Fluorene
9 Methyldibenzofuran
10 C,4He"
11 Methylfluorene
12 Ethyldibenzofuran*
13 Dibenzothiophene
14 Phenanthrene
15 Anthracene
16 Ethylfluorene'
* Could be dimethyl.
b Could be trimethyl or ethylmethyl.
c Could be methylanthracene.
" Could be methylpyrene.
eak No. Compound Peak No.
17 Propyldibenzofuran" 33
18 Methylphenanthrene" 34
19 4H-cyclopentaIde/'lphenanthrene 35
20 Methyl-4W-cyclopenta[der']phenanthrene 36
21 Ethylphenanthrene* 37
22 Fluoranthene 38
23 Benz(e]acenaphthylene 39
24 Benzo[def1dibenzothiophene 40
25 Pyrene 41
26 Ethyl-4H-cyclopenta[derlphenanthrene° 42
27 Methylfluoranthene" 43
28 Benzo|alfluorene 44
29 Benzo[b]fluorene 45
30 Benzo[g/i/)fluoranthene 46
31 C18H,0 (unknown) 47
32 Cyclopentalcdlpyrene 48
Compound
Benz[a|anthracene
Chrysene
Methylchrysene*
Methylcyclopenta(cdjpyrene'
Benzofluoranthene
Benzo(e]pyrene
Benzo[a)pyrene
Perylene
Methylbenzopyrene0
C21H12 (unknown)
C21H12 (unknown)
lndeno[1,2,3-cd]pyrene
Dibenz(a,/i]anthracene
Dibenz[a,c]anthracene
Benzo[g/7/]perylene
Anthanthrene
* Could be methylbenz(a]anthracene.
'Could be methylbenzo[0/i/]fluoranthene.
0 Could be methylbenzofluoranthene.
h Probably cyclopentlbc or fglacenaphthylene, see Ref. 17.
on glass fiber filters followed by drying at slightly ele-
vated temperatures for accurate weight measurements
tends to volatilize many of the lower molecular weight
compounds and enrich the sample in higher molecular
weight species. The third explanation is drawn from
experiments with the turbulent diffusion flame burner in
which there was an enrichment of higher molecular
weight PAH as samples were collected at greater dis-
tances from the burner nozzle. Since the coal- and
wood-soot samples were collected from within the flame
instead of at greater distances, it is possible that these
samples were not as enriched with high molecular weight
species as the exhaust from a typical coal combustor.
The complementary use of high resolution gas
chromatographic mass spectrometry for detailed com-
pound identification and of high resolution mass spec-
50
o
-------
0 14 16 18 20
Corbon number
Rgure 4. Alkyl homolog distribution plots for several PAH series
in coal combustion products. The lines are labeled by the molecu-
lar weight of the unsubstituted species. Example isomers are:
178 (Z=-18)phena'nthrene, 202 (Z=-22)pyrene, 226
(Z= -26)cyclopenta(co1pyrsne, 228 (Z= -24)chrysene, 252
(7=-28)benzo[s]pyrene, 276 (Z=-32)indeno[1,2,3-cd]pyrene
and 278 (Z = -30)dibenzanthracene. The value of Z is derived
from the general formula CnH2n+z.
trometry for alkyl distribution monitoring can greatly
aid in the characterization of airborne PAH and in the
identification of pollution sources. This information is
important for the engineer to design those cleaner com-
bustion processes which will be necessary in the light of
the expected increase in the consumption of coal.
Acknowledgements
The authors thank C. Clampitt and J. Dillon for technical assistance
during this project. This work was supported by Grant No. R803242
from the Environmental Protection Agency.
20
202
~Air pnrticulote (IndionuDolis)
I8 19
Carbon number
20
Rgure 5. Alkyl homolog distribution plots for the pyrene-type
series (Z= -22) in the combustion products of coal, wood and
kerosene, and in air paniculate matter from Indianapolis and
Boston. The abundance of the parent compound in each series
was normalized to 100.
100 -
0 C0 C, C
Number of olkyl sidechoin carbons
Figure 6. Composite alkyl homolog distribution plots (see text)
for PAH in the combustion products of coal, wood and kerosene,
and in air paniculate matter from Indianapolis and Boston. The
abundance of the parent composite in each series was nor-
malized to 100.
REFERENCES
1. Paniculate Polycyclic Organic Matter. National Academy of
Sciences, Washington, D.C. (1972).
2. K. D. Bartle, M. L. Lee and M. Novotny. Int. J. Environ. Anal.
Chem. 3, 349 (1974).
3. J. L. Shultz, A. G. Sharkey and R. A. Friedel, Biomed. Mass
Spectrom. 1, 137(1974).
4. H. S. Stoker, S. L. Seager and R. L. Capener, Energy, p. 163.
Scott Foresman, Glenyiew, Illinois (1975).
5. M. L. Lee. Ph.D. Thesis, Indiana University (1975).
6. J. P. Appleton and J. B. Heywood, Fourteenth International
Symposium on. Combustion, p. 777. The Combustion Insti-
tute, Pittsburgh, Pennsylvania (1973).
7. G. P. Prado, M. L. Lee, R. A. Hites, D. P. Hoult and J. B. Howard,
Sixteenth International Symposium on Combustion.
The Combustion Institute. In press.
8. M. L. Lee, M. Novotny and K. 0. Bartle, Anal. Cham. 48 1566
(1976).
9. A. Hase and R. A. Hites, in Identification and Analysis of
Organic Pollutants in Water, edited by L. H. Keith, p. 205. Ann
Arbor Science, Ann Arbor, Michigan (1976).
10. R. A. Hites and W. G. Biemann. Adv. Chem. 147, 188 (1975).
11. A. Hase and R. A. Hites, Geochim. Cosmochim. Acta 40,1141
(1976).
12. K. Biemann, Application of Computer Techniques in Chemi-
cal Research, pp. 5-19. Institute of Petroleum, London (1972).
13. 0. Hoffmann, W. E. Bondinell and 'i. L. Wynder, Science 183,
215(1974).
14. M. L. Lee, M. Novotny and K. 0. Bartle, Anal. Chem. 48, 405
(1976).
15. M. L. Lee and R. A. Hites, Anal. Chem. 48,1890 (1976).
16. Paniculate Polycyclic Organic Matter. Appendix A. National
Academy of Sciences, Washington, D. C. (1972).
17. B. D. Crittenden and R. Long, Combust. FlameV), 359 (1973).
Received 29 July 1976
69
-------
APPENDIX E
Mixed Charge Exchange-Chemical lonization
Mass Spectrometry of Polycyclic Aromatic
Hydrocarbons
From: Reprinted with permission
from J. Amer. Chem. Soc.,
99, 2008 (1977). Copyright
by the American Chemical
Society.
70
-------
Mixed Charge Exchange-Chemical lonization Mass
Spectrometry of Polycyclic Aromatic Hydrocarbons
The exact structural identification of polycyclic aromatic
hydrocarbons (PAH) and their alkylated derivatives is a dif-
ficult problem, particularly when they are encountered as
complex mixtures. The analytical power of mass spectrometry,
which has had wide application in this Held,1'4 has been limited
because electron impact mass spectra of isomeric PAH are
almost identical. The purpose of this note is to report that
charge exchange-chemical ionization mass spectrometry, using
an argon-methane reagent gas,5 easily differentiates PAH
isomers.
The mass spectra of a series of PAH were measured with a
Hewlett-Packard 5982A gas chromatographic-mass spec-
trometer system by injecting approximately 200 ng of each
compound (dissolved in methylcne chloride) on a 1 80 X 0.32
cm o.d. stainless steel column packed with 3% Dexsil 300 on
80/ 1 00 mesh Chromosorb W. The reagent gas mixture ( 1 0%
methane in argon) served as the carrier gas for the gas chro-
matographic column which was held isothermally at a tem-
perature appropriate to each sample being analyzed. The mass
spectrometer was continuously scanned from 50 to 350 amu
at 81.2 amu/s. The ion source pressure was 0.8 Torr and its
temperature was 1 70 °C. Data were collected and processed
by a HP 5933A data system. Precautions were taken to assure
the absence of water vapor in the ion source, since water is an
excellent proton donor and can greatly increase the abundance
of the protonated molecular ion. In these experiments, there
were no observable traces of water vapor (m/e 18 or 19).
The resulting mass spectra showed considerable differences
in the relative abundances of the molecular (M+) and pro-
tonated molecular (M + \+) ions when different PAH isomers
were analyzed. Table I lists the compounds analyzed in this
stu4y, the resulting ratio of the abundance of the protonated
molecular to molecular ion ((M + 1)/M), and the first ion-
Table I. Abundance Ratios for Selected PAH Obtained by CH4-
Ar Chemical lonization Mass Spectrometry
Abundance
First ionization ratio.
Compound Formula potential (eV)° (M + 1)/M*
Pentacene
Tetracene
Anthanthrene
Perylene
Benzo[a]pyrene
Anthracene
Benz[a]anthracene
Dibenz[a.A]anthra-
cene
Pyrene
Coronene
Benzo[f]pyrene
Acenaphlhene
Chrysene
Fluoranthene
Fluorene
Acenaphthylene
Phenanthrene
Triphenylene
Naphthalene
Benzene
C22H14
CI8H12
C22H,2
C20H12
C2rjH|2
C,4H,0
C18H,2
C22H|4
C,6HIO
C24H12
C20HI2
C12H,0
CI8H,2
C,6H,0
C,3H,0
CI2H8
CI4HIO
C]8H]2
CioH8
C6H6
6.42 (
6.88 (
7.02 (
7.03 (
7.17 (
7.42 (
7.47 (
7.55 (
7.56 (
7.58 (
7.58 (
7.70
7.74
7.76
7.86
8.02
8.02
8.11
8.14
9.29
).32
).45
).38
).32
).73
).82
1.83
J.95
J.73
).66
).82
.00
.26
.57
.66
.34
.59
.73
.68
>.79
ization potential of each compound. It is obvious from this table
that the (M + 1)/M ratio has a high positive correlation with
ionization potential (r = 0.877,/»« 0.01). This trend is con-
sistent with the expectation that as the ionization potential
increases, charge transfer processes will be less effective for
electron extraction while at the same time protonation becomes
more favorable.
This technique should be quite useful for the elucidation of
1.5
M + I
M
1.0
ocoo
° Values were averaged from experimental data found in ref 6-8;
their variability was usually less than ±0.1 eV * The reproducibilily
of these measurements was ±4% over a 3-month period. The ratios
have been corrected for the natural abundance of I3C.
7.0 75 8.0
I. R lev)
Figure I. Plol of the abundance ratio ((M + I )/M) obtained by CH4-Ar
chemical ionization mass spectrometry as a function or ionization potential
(IP) for a series of four tetracyclic polycyclic aromatic hydrocarbons: I.
tetracene; 2. benzja (anthracene: 3. chrysene; 4. Iriphcnylenc
specific isomeric structures of PAH. By using a mixed charge
exchange-chemical ionization reagent gas, such as described
here, different mass spectra can be obtained for most PAH
isomers while conventional mass spectral techniques provide
little differentiation. This fact is demonstrated by the series
of tetracyclic compounds shown in Figure 1. The (M + 1 )/M
ratio of each compound is plotted as a function of its first
ionization potential. It is interesting to note that this abundance
ratio increases from 0.45 to 1.73 as the isomer becomes more
nonlinear, making differentiation quite easy. If a standard
PAH compound were not available, it seems probable that the
mass spectrum of that compound could be predicted from its
ionization potential. The ability to calculate ionization po-
tentials from molecular orbital theory7-8 offers considerable
promise for the future identification of presently unknown
PAH.
Acknowledgments. The authors thank D. P. Beggs (Hew-
lett-Packard, Avondale, Pa.) and G. P. Arsenault (Chemistry
Department, MIT, Cambridge, Mass.) for helpful suggestions
concerning this work. This work was supported by grant
R803242 from the U.S. Environmental Protection Agency.
References and Notes
(1) R. C. Lao. R. S. Thomas. H. O|a. and L. Dubois, Anal. Cham.. 45, 908
(1973).
(2) R. A. Kites and W. G. Blemann, Adv. Chem. Ser., No. 147, 188 (1975).
(3) M. L. Lee. K. D. Bartle. and M. Novotny. Anal. Chem.. 4B, 405 (1976).
(4) M. L. Lee and R. A. Hites. Anal. Chem.. 48, 1890 (1976).
(5) The ability of CH,-Ar mixtures to provide combined CE-CI spectra has been
previously described by D. P. Beggs (Hewlett-Packard Applications Note
No. 176-19). The methane acts as a tow energy proton donor which produces
an Intense protonated molecular ion while the argon participates in charge
exchange reactions to produce a fragmentation pattern normally found In
electron impact mass spectra.
(6) H. Kuroda. nature (London). 201, 1214 (1964).
(7) M. J. S. Dewar. F. R. S. Haselbach. and S. O. Worley. Proc. R See. London.
Ser .A. 315, 431(1970).
(8) M. S. Sung. C. R. Acad. Sci.. Ser. C. 278, 37 (1974).
M. L. Lee, Ronald A. Hites*
Depart mem of Chemical Engineering
Massachusetts Institute of Technology
Cambridge. Massachusetts 02139
Received August 17. 1976
71
-------
APPENDIX F
Charge Exchange - Chemical lonization
of Pplycyclic Aromatic Compounds
72
-------
Carcinogenesis, Vol. 3: Polynuclear Aromatic
Hydrocarbons, edited by P. W. -Jones and
R. I. Freudenthal. Raven Press, New York © 1978.
Charge Exchange-Chemical lonization Mass
Spectrometry of Polycyclic Aromatic Compounds
Ronald A. Hites and George R. Dubay
Massachusetts Institute of Technology, Department of Chemtciil Engineering,
Cambridge, Massachusetts 02139
Certain polycyclic aromatic compounds (PAC) have been of interest
since the early 1800s because of their carcinogenic behavior. Since only
specific PAC isomers are carcinogenic, it is important to have an analytical
tool which can differentiate among these isomeric compounds. Although
GC-MS has had a wide application for the analysis of PAC, one problem
remains: isomeric PAC give identical electron impact mass spectra; thus,
the unambiguous identification of these compounds is sometimes impossible.
We have found that charge exchange-chemical ionization mass spectrometry
can be used to distinguish many isomeric PAC (1). We have established that
spectra of PAC have characteristic ratios of the protonated molecular ion to
the molecular ion when 5% to 10% methane in argon is employed as the
reagent gas. The two most prominent ions in the reagent plasma are C2HB*
and Ar*. The molecule of interest either reacts with the strongly acidic ion,
CoH5+, to give the protonated molecular ion, or it reacts with Ar* ions to
give the molecular ion. The relative rates of these two competing reactions
determine the intensity ratio of the two ions. Variation in ionization potentials
will not significantly affect the rate of protonation by C2H5* ions, but it will
affect the rate of ionization by Ar* ions. Thus, we have found that ionization
potentials are correlated with the ratio of the protonated molecular ion to
the molecular ion (M + 1/M).
A wide variety of PAC have been studied, and the characteristic ratios '
for M 4- 1/M were determined. A partial listing of the PAC investigated is
given in Table 1. (All values have been corrected for the natural abundance
of 13C.) Within any of the subgroups listed, it can be seen that the ionization
potential (IP) of isomeric PAC correlates with the M + 1/M value. Ap-
parently, an increase in the IP causes the rate of ionization by Ar+ to decrease
while the rate of protonation by C^Hs* is unaffected. Thus, there is an in-
crease in the relative rate of protonation as evidenced by an increase in the
ratio of M + 1/M.
Table 1 shows that this technique is applicable to the differentiation of
73
-------
TABLE 1. Some of the pot/cyclic aromatic compounds investigated
Compound
Tetracene
Benzo[a]pyrene
Anthracene
Benz[a]anthracene
Pyrene
Benzo[e]pyrene
Chrysene
Fluoranthene
Phenanthrene
Triphenylene
4-Methylbiphenyl
3-Methylbiphenyl
2-Methylbiphenyl
9-Methylanthracene
2-Methylanthracene
2-Methylphenanthrene
Benz[b]indole
Benz[g]indole
Benzo[b]quinoline
Benzo[f]quinoline
.' Dibenzothiophene
Benzo[l ,2]dibenzothrophene
Formula
CigHi2
C2flHl2
CuHio
CuHt2
CJ^HIQ
C20'"12
Ci8Hi2
ds'MQ
CnHig
CiaH12
Ci3Hi2
CisH,2
Ci3H12
Ci5H,2
Ci&H12
CisHn
C12H9N
CI2H9N
C,3H9N
C,3H9N
C,2H8S
Ci6H,oS
IP(ev)
6.8Bd
7.\7*
7.42''
7.47d
7.S6d
7.56d
7.74d
7.76d
8.02"
8.1 \d
8.15«
8.30«
8.60C
7.36'
7.42'
7.90»
8.1 1*
8.25*
7.88^
8.14-
—
—
M + 1/M"
0.45
0.73
0.82
0.83
0.73
0.82
1.26
1.57
1.59
1.73
—
—
—
—
—
—
—
—
—
—
—
—
M+ 1/M6
—
—
0.70 ± 0.08 c
0.64 ± 0.02
—
—
—
—
1.24 ±0.03
1.79 ± 0.10
2.16 ± 0.10
2.45 ± 0.23
0.62 ± 0.07
0.64 ± 0.03
0.89 ± 0.01
1.03 ± 0.04
1.13 ± 0.07
1.68 ±0.09
2.20 ± 0.06
0.24 ± 0.09
1.25 ±0.08
0 Reagent gai was 10% methane in argon (P-10) from Matheion Gas Products.
6 Reagent gas was 5% methane in argon (P-5) from Matheion Gas Products.
c 90% confidence limits on a minimum of 3 measurements.
d Values are found in ref. 1.
e Determined by photoelectronic spectroscopy, J. P. Maier and D. W. Turner, Faraday Disc.
Chem. Soc., 54:149, 1972.
/ Determined using charge transfer spectra, O. B. Nagy, Tetrahedron, 31:2453, 1975.
* Determined by appearance potentials, P. Nounou, J. Chem. Phyt., 63:994, 1966.
* Calculated values, N. S. Hush, A. S. Cheung, and P. R. Hilton, J. Electron Spec. Rel. Phen.,
7:385, 1975.
1 Calculated values, M. J. S. Dewar, A. J. Hargot, N. Trinajstic, and S. D. Worley, Tetrahedron,
26:4505, 1970.
simple PAC and to some of their methyl derivatives. It is also useful for
some aromatic heterocycles as illustrated by the nitrogen-containing com-
pounds. A difference in the ratios is observed which is dependent on the
basicity of the nitrogen in the ring. Lack of available standards has limited the
investigation of sulfur-containing aromatic heterocycles; the two we have
studied are shown.
In conclusion, it should be noted that this work is in its initial stages. Sub-
stantial work is needed to establish the capabilities and limitations of the
technique. This charge exchange-chemical ionization technique is not ex-
pected to replace electron impact GC-MS; but it should be a useful supple-
mental tool for differentiating isomeric PAC. In addition, by using ionization
potentials calculated from MO theory, it is hoped that this technique can be-
come predictive and be extended to molecules for which no standards are
available.
74
-------
ACKNOWLEDGMENTS
This work has been supported by giants from the U.S. Environmental
Protection Agency (R803242) and the Energy Research and Development
Administration (EE-77-S-02-4267).
REFERENCE
1. Lee, M. L., and Hites, R. A. (1977): Mixed charge exchange—chemical ionization
mass spectrometry of polycyclic aromatic hydrocarbons. A Am. Chem. Soc., 99:
2008.
75
-------
APPENDIX G
Characterization of Sulfur-Containing
Polycyclic Aromatic Compounds in Carbon Blacks
76
-------
Reprinted fnmi ANALYTICAL CHEMISTRY. Vol. IS. \\\ft< ISJHI. Nmcmlvr l:'Ti:
Copyright 197(i hy Ihe American Chemical Society iind reprinted liy permission of the i-npyri^hi owner
Characterization of Sulfur-Containing Polycyclic Aromatic
Compounds in Carbon Blacks
M. L. Lee and Ronald A. Kites'
Department of Chemical Engineering. Massachusetts Institute ol Technology. Cambridge, Mass. 02139
Computerized gas chromatographlc mass spectrometry and
high resolution mass spectrometry have been used to identity
sulfur-containing polycyclics and polycycllc aromatic hydro-
carbons In carbon blacks obtained from sulfur-containing
petroleum feedstocks. Twenty-eight compounds have been
Identified, seven of which are sulfur-containing polycyclics.
Carbon black is a material of considerable commercial im-
portance: More than 1.5 billion pounds per year of domestic
carbon black are used in the manufacture of tires alone (/).
11 is also a material of potentially great environmental concern
because of (a) wide environmental distribution of carbon
black, primarily in automobile tire dust, and (b) the potent
carcinogenicily of a number of compounds adsorbed on carbon
black such as certain polycyclic aromatic hydrocarbons
(PAH). These considerations have led to several studies of the
organic compounds associated with carbon black. For exam-
ple, two recent studies (2, 3) reported the identification of
cyclopenta|rd]pyreneasa major constituent of carbon black
extrncts; in addition, 11 other PAH (2) and several oxygenated
polycyclics (3) were also reported.
This paper reports on the analysis of organic extracts of
several carbon blacks which were manufactured under varying
conditions. Of particular interest is the first reported identi-
fication of sulfur-containing polycyclics in carbon black. In
addition, the detection of high-boiling PAH has been extended
to include compounds of molecular weights up to 376 (C:i»H m).
Capillary column gas chromatography combined with mass
spectrometry (GO/MS) has allowed the positive identification
of'21 compounds and the tentative identification of 10 cithers
(see Figure 1). High-resolution mass spectromelry (HUMS)
of these same samples has verified the elemental composition
of individual compounds, especially for the sulfur polycy-
clics.
EXPERIMENTAL
Samples of four different furnace blacks (seeTahle I) wereobuu'ned
from a commercial source (Cabot Corporation, Boston. Muss). The
aromatic feedstocks used in the production of three of these furnace
blacks were derived from refinery and naphtha-based ethytene type
tnrs. They were over 90% aromatic hydrocarbons, and had a consid-
erable amount of organic sulfur (1.2-3.1%). Appropriate amounts (see
Tahle I) of each furnace black were extracted wit h methylene chloride
for 18 h in a .Soxhlet apparatus. Soxhlet thimbles were extracted wilh
Nanoprade methylene chlnride (Mallinckrodl) for several hours prior
to each sample extraction to remove any organic contaminants in the
thimble or apparatus. The melhylene chloride extracts were then
evaporated to minimal volumes (I-10 ml) by rotary evaporntion under
Figure 1. Compounds identilied in carbon blacks by GC/MS and
HRMS
* Structure is presumed correct but has not been verified by comparison with
authentic compounds. " Exact position of benzo g>oup is not known. c The in-
crease in molecular weight of PAH species also increases the number ol possible
isomers: the lack of authentic compounds in this molecular weight range pre-
vents the elucidation of the exact structures lor these particular GC peaks. The
structures given are examples only; many other isomers are possible. a Detected
only by high resolution mass spectrometry. The structures given are examples
only: many other isomers are possible
77
-------
naphthalene
icenaphthylene
dibenzothiophene
phenonthrene
anthracene
H2,C
4H -cyelopentafdef]-
phenanthrene
tluoranthene
benzfejacenoph-
thylene"
benzo[def] dibenzo-
thiophene0
10
pyrene
benzofaldibenzo-
thiophene
12
benzo[ghj] fluoran-
thene
cyclopenlo[cd]py-
rene
ben z[o_] anthracene
benzoQJf luoran-
thene and benzo[k]
fluoronthene
benzofluoronthene
benzofdejjnaphtho-
benzothiophene0'1"
benzo[e_] pyrene
20
benzo[a]pyrene
22
Indeno[l,2,3-cd]-
pyrene
23
benzo[£M]perylene
24
anthonthrene
30"
7S
-------
10
23*24
TEMP(
I
190
310
370
10
20
30
TIME(MIN) 0
Figure 2. Packed-column gas chromatograms ol the extract of (A) furnace black 1 and (0) furnace black 3 (see Table I). GC conditions: See text.
Key: See Figure 1
chromatographic run. High-temperature gas chromatograms were
run on a HP 5720A gas chromatograph with a 180 cm X 0.32 cm o.d.
stainless steel column packed with 3% Dexsil 300 on 80/100 mush
Chromosorb W which was programmed from 70 to 370 °C at 12 °C/
min with a carrier gas flow rate of 25 ml/min.
High resolution mass spectral information was obtained on each
sample by introducing an aliquot of the methylene chloride extract
into a high-resolution mass spectrometer through a direct introduc-
tion probe system and slowly vaporizing the sample at a continually
increasing temperature while several exposures on a photographic
plate were made. After development, the plate was read on a com-
puterized comparator, and the exact masses were converted to ele-
mental compositions. The HRMS system consists of a DuPont In-
struments 21-110B mass spectrometer and a D.W. Mann comparator
interfaced to an IBM 1802 computer. This system and its operation
have been previously described elsewhere (4). Both mass spectrom-
eters were operated at 70-eV ionizing energy.
RESULTS AND DISCUSSION
Figure 2 compares packed-column gas chromatograms of
extracts from furnace blacks 1 and 3 (see Table I). Peak
numbers refer to compounds listed in Figure 1 which were
identified by gas chromalographic mass spectrometry and
retention data. In all cases where an exact identity is reported,
Table 1. Carbon Black Characteristics
No.
1
9
3
4
Feedstock
Elhylene tar
Refinery tar
Natural gas
Ethylene and
refinery tars
Furnace
temp,
K
1400-1600
1400-1600
1400-1600
1800-2000
Particle
size,
nm
260
75
75
30
Weight of
carbon
black
extracted,
g
8
2
2
34
Yield
of
PAH,
%
0.2
0.1
0.1
0.01
vacuum prior to gas chromatographic analysis. The total yield of PAH
from the tour carbon blacks is given in Table I.
Gas chromatographic mass spectrometry of each sample was per-
formed on a Hewlett-Packard 5982A GC/MS system interfaced to a
H1J 591)3A data system. A 19 m X 0.2fi mm i.d. glass capillary column
coated with SE-52 methylphenylsilicone stationary phase was used
t,o sepnrate mixtures prior to mass spectral analysis. The oven tem-
perature was programmed from 70 to 250 °C at 2 °C/min during each
79
-------
JJ
I lr
,a
TIHF t*C1
70 00 110 130 150 170 190 210 230 250
Tim WIN) 0 10 20 30 40 50 60 70 80 90 110
Figure 3. Glass capillary-column gas chromatogram of the extract of furnace black 1 (see Table I). GC conditions: See text. Key: See Figure 1
the mass spectrum and GC retention time were identical with
those of authentic materials. The gas chromatograms of ex-
tracts from carbon blacks 2 and 4 are very similar to that of
carbon black 3 (Figure 26) and are, therefore, not shown.
These GC/MS data, taken together with the PAH yields
given in Table I, indicate that the amounts and structures of
PAH associated with carbon blacks are quite dependent on
the conditions of carbon black formation. Wallcave et al. (2)
found that of eight carbon blacks examined, cyclopenta [cd] -
pyrene was not detected in three of them and varied consid-
erably in concentration in the others. Of the four furnace
blacks analyzed in this study, the organic composition of
number 1 differed substantially from the other three, which
were qualitatively quite similar to one another. Furnace black
1 was manufactured by a different process than 2 and 3, al-
though furnace temperatures were the same. In addition, the
higher furnace temperature used in the production of number
4 seemed to reduce the total amount of PAH by a factor of ten
as compared to the others, although the qualitative distribu-
tion of PAH was still very similar to 2 and 3. The main dif-
ference in the manufacture of 2 and 3 was the nature of the
feedstock used.
A high-resolution gas chromatogram of the extract of fur-
nace black 1 is shown in Figure 3. Again, numbers refer to
compounds identified and listed in Figure 1. In addition to the
identification of a number of previously unresolved isomers
and trace compounds, four sulfur-containing polycyclic aro-
matic compounds were detected. However, because of the
unavailability of standard compounds, exact identification
of only dibenzothiophene and benzo[a]dibenzothiophene
could be made. On the other hand, proposed structures (see
Figure 1) seem to be reasonable when compared to structures
of PAH identified in the same mixture. For example, although
there are a number of possible structures for CuHsS, the
similarity in the structures of benzo[
-------
APPENDIX H
Cyano-Aromatic Compounds by the Combustion
of Nitrogen Containing Fuels
81
-------
Reprinted from ENVIRONMENT SCIENCE & TECHNOLOGY, Vol. 12, Page 965, August 1978
Copyright is) 1978 by the American Chemical Society and reprinted by permission of the copyright owner
Cyanc-arenes Produced by Combustion of Nitrogen-Containing Fuels
George R. Dubay and Ronald A. Hites*
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge. Mass. 02139
D Cyanonaphthalenes (both isomers) and cyanoacena-
phthylenes (four isomers) were identified in the sixil generated
by the combustion of aromatic hydrocarbon fuels doped with
6-!l()% pyridine. These wore by far the most abundant nitro-
gen-containing organic compounds in this combustion ef-
fluent; mulliring. nitrogen heterocyclic compounds, such as
those commonly observed in airborne particulale matter, were
a minor component. These identifications were made by gas
chromatographic mass spectrometry following a preliminary
separation by alumina column chromatography. The envi-
ronmental significance of these findings is discussed.
Certain organic compounds in scxit cause cancer in man (/).
Determining the structures of these compounds and under-
standing their biological activities have been the subjects of
intense research over the last 50years (2). It is now known that
the major class ol carcinogenic compounds associated with
soot is the polycyclic aromatic1 hydrocarbons (PAH) (,'/). Ni-
trogen-containing aromatic compounds (aza-arenes) are also
associated with soot I'M, and some are known to be carcino-
genic (5). However, because they are much less abundant than
1'AH, these compounds have received proportionately less
attention. In the future, however, it is likely that the envi-
ronmental abundance of a/.a-arcnes will increase as fuels
higher in organic nitrogen content are burned. We have,
therefore, undertaken the identification of the major aza-
arenes produced by the combustion of a model fuel containing
1-6% nitrogen.
Several researchers have developed methods for the analysis
of aza-arenes in atmospheric particulate samples based on
thin-layer, gas, paper, high-pressure liquid, and column
chromatography and on electrophoresis {6-10). All of these
techniques begin with a solvent-solvent extraction utilizing
strong acid to partition the basic aza-arenes away from the
PAH. This procedure obviously discriminates against neutral
aza-arenes that might be present. To avoid this problem, we
have separated the aza-arenes from the bulk of the PAH by
alumina chromatography using gradient elution.
Once the compounds are separated from the PAH, the
identification of the exact molecular structures of aza-arenes
is still very difficult. Almost all assignments made in the lit-
erature are, to some degree, ambiguous. Assignments have
been based on gas chromatographic retention information and
on fluorescence, 1) V, or electron impact mass spectra (6-10).
In these analyses, all the possible isomers of a particular mo-
lecular structure have not been available. Hence, by use ol
these techniques, there is no criterion by which the unavailable
isomers can be ruled out.
To address the problem of determining the precise molec
ular structure of compounds produced by combustion, we hav(
32
-------
developed a method based on charge exchange-chemical
ionization mass spectrometry (CE/CIMS). We have estab-
lished that isomeric PAH and aza-arenes have characteristic
mass spectra when 5 or 10% methane in argon is employed as
the reagent gas for CE/CIMS (11, 12). The two most promi-
nent ions in the reacting plasma are C^Hr/ and Ar+. A mole-
cule reacts either with a strongly acidic C2HS+ ion to give the
protonated molecular ion (M + 1), or it reacts with an Ar+ ion
to give the molecular ion (M). The relative rales of these two
reactions determine the intensity ratio of the two ions. A high,
positive correlation was found between ionization potential
and M + 1/M ratio (//). We have also established that this
relationship holds for some aza-arenes and for some methyl-
ated PAH (12). Aza-arenes that have ionization potentials
differing by more than 0.1 eV can be distinguished using this
method.
The great potential of this technique lies in its predictive
ability. The relationship between ionization potentials and
M + 1/M intensity ratios can be established for all available
isomers. Calculation of ionization potentials from molecular
orbital theory will then allow prediction of the M + 1/M ratio
for unavailable isomers.
Experimental
Combustion Conditions. Soot was obtained in two
ways:
A solution of 32% pyridine in «-xylene (6% fuel nitrogen)
was burned in a wick-fed, alcohol-lamp burner. Soot was
collected on the exterior of a precleaned, water-cooled, filter
flask. The soot was removed by scrubbing the flask with
CH2CI2-soaked glass wool. The soot, glass wool, and associated
CH2C12 were put in a preextracted Soxhlet thimble and ex-
tracted with 200 mL CH2CI2 overnight. The extract volume
was reduced to 1 mL on a rotary evaporator operating at 30
°C and 15 torr. Samples were stored in the dark at 6 °C.
A Meker burner was modified by replacing the air inlets
with oxygen feeds. The fuel inlet was attached to a stainless
steel tube through which a benzene-methane mixture was
passed. The fuel mixture was preheated to vaporize the ben-
zene, and the plumbing was heated (300 °C) to prevent con-
densation. Methane and 02 flows were maintained by critical
orifices, and the benzene flow was measured before vapor-
ization by passing the liquid through a capillary tube in which
the upstream and downstream pressures were carefully
measured. The liquid flows corresponded to Reynold's num-
bers of 800-1000 through the capillary tube. Thus, the flow
was always laminar and proportional to the pressure drop
through the tube. The benzene was doped with sufficient
pyridine (5.3%) to give a fuel containing 1% nitrogen. Fuel
equivalence ratios of 4.0 and 4.5 were used, the CH4/CeH6 ratio
was 1.5, and the cold gas velocity was 31.8 cm/s. Soot was
collected by a water-cooled spray probe (13) and was trapped
in glass wool packed filters. The organic compounds were
extracted first with acetone and then with CH2C12.
Column Chromatography. To eliminate interferences
caused by PAH and to obtain an enrichment of the nitrogen
compounds, the soot extracts were fractionated as follows: The
sample (1 mL) was added to 1 g of neutral alumina (activity
grade 1, ICN Pharmaceuticals) in a 25-mL beaker, and the
CH.jCI'j was allowed to evaporate at room temperature (15
min). This precoated alumina was added to the top of a col-
umn prepared from 5 g of alumina with hexane as the solvent.
Six fractions were then eluted (Table I). These fractions were
then concentrated on a rotary evaporator for analysis.
Instrumentation. A Hewlett-Packard 5730A gas chro-
matograph equipped with dual nitrogen-phosphorus flame
ionization detectors (FID) was used for GC analyses. A
Hewlett-Packard 5982A mass spectrometer interfaced to a
5933A data system was utilized for gas chromatographic mass
spectrometry. Charge exchange-chemical ionization mass
spectrometry was performed with 5% methane in argon
(supplied by Matheson Gas Products). The flow of carrier gas
was 10 mL/min. and the ion source temperature was-195 ± 2
°C. The ratios of the protonated molecular ion to the molec-
ular ion were established by adding all spectra scanned within
a given GC peak.
Results and Discussion
The two different combustion systems gave virtually
identical results; therefore, they will not be distinguished in
the following discussion. As indicated in Table 1, all of the
aza-arenes were collected in fractions 3 and 4. The gas chro-
matogram of fraction 4 was extremely complex. Because this
fraction contained less than a third of the aza-arenes and be-
cause the identities of most of the components in this fraction
corresponded to those reported elsewhere (10), further anal-
yses of this fraction have not been pursued.
Fraction 3 contained most of the aza-arenes; gas chro-
matograms of this fraction are shown in Figure 1. The upper
trace was obtained with a normal FID, and the lower with a
nitrogen specific FID. Comparison of these two traces show
that the nitrogen-FID and the normal FID respond equally
to the early eluting peaks, indicating that nitrogen is present
in all of ihese constituents. The later eluting peaks were de-
tected only by the normal FID, indicating that they are
probably PAH.
The electron impactand CE/CI mass spectra of peaks 1-7
are given in Table II. The spectra of peak 1 were interpreted
as those of either 1- or 2-cyanonaphthalene, and authentic
samples of these two compounds were obtained (K and K
Laboratories). The exact retention time (by coinjection) and
the electron impact and CE/CI mass spectra of 1-cyanona-
phthalene were identical with those of peak I. The identifi-
cation of peak 2 as 2-cyanonaphthalene was proved in a similar
fashion.
Peaks 3-6 all show molecular weights of 177 (Ci:iH7N) (see
Table II). Based on analogy and on the abundant presence of
the parent hydrocarbon, these peaks have been tentatively
identified as the four isomers of cyanoacenaphthylene.
Table I. Fractionatlon of Soot Extracts
acllon Solvent
1 Hexane
2 30% Benzene, 70%
hexane
3 70% Benzene, 30%
hexane
4 Benzene
5 Benzene
6 CH2CI2
Vol
(mL)
30
30
30
30
50
50
Total
% PAH" % Az«-ar«n.a
0
64
12
15
2 7
0 0
0 0
78 22
• Percent of total material in the various fractions as measured from the normal
FID or nitrogen-specific FID responses, respectively.
83
-------
_l
Figure 1. Gas chrornatograms of fraction 3, isolated from organic
compounds produced by combustion of solution of 32% pyridine in
o-xylene
GC conditions: 1.8 m X 6.3 mm o.d. glass column packed with 3% OV-17 on
80/100 mesh Supelcoport. programmed from 100 to 310 °C at 8 °C/min. Upper
trace obtained with normal FID, bottom trace with nitrogen specific FID
These are not available compounds, and proof of their struc-
ture must await their synthesis. Peak 7 has a molecular weight
of 203 (C]SH9N) and probably represents several unresolved
cyanophenanthrene isomers.
Based on the GC data, we estimate that 80% of the aza-
art'nes in fraction 'I are ryanonaphthalencs, cyanoacena-
ptuhylenes, and cyanu|jhenanthrenes. These compounds are
the most abundant class of organic nitrogen compounds in the
effluent from these (lames. Multiring, nitrogen helerocyclic
compounds (such as acridine or phenanthridine) that have
been commonly observed in airborne paniculate matter (10)
are a minor component (<7%) in these effluents.
Cyanonaphthalenes have not been found in comhustion
effluents before. They have, however, been found at trace
levels in cigarette smoke tar (1-1, 15), in petroleum (16), in tar
from the low-temperature pyrolysis of coal (17), and in an-
thracene oil (18). In all of these rases, it is presumed that cy-
anonaphthalenes are formed from the pyrolysis of other ni-
trogen compounds (19). The biological activity of these
compounds is not clear. There have been reports thatcyano-
naphthalenes cause irregular mitoses and chromosomal ab-
errations (14, 20), that they have insecticidal properties (21.
22), and that they are toxic to the eggs of body lice (2.'0. On
the other hand, testing by a quantitative forward mutation
assay using 8-azaguanine resistance in Salmnnclla typ/ii-
murium (24) indicates that these compounds have less than
1% of the activity of henzo[a]pyrcne on a molar basis (2.5).
The environmental significance of our results is twofold.
(a) The relative amount of cyano-arenes being produced by
the combustion of a nitrogen containing fuel is significant (see
Table I), and some of these compounds may be biologically
active. Emission of large amounts of such compounds into the
environment would seem to be undesirable, (b) Although
several cyano-arenes are being produced in flames, it is not
known if they are environmentally persistent. Nitrogen
functional group analyses by KSCA have indicated the pres-
ence of the cyano functionality in certain urban air paniculate
samples (26), but specific cyano-arenes have not been found
in the atmospheric environment. Cyano-arenes may well he
present in air particulates, but because of the analytical lim-
itations outlined above, they have not yet been detected. We
suggest that the quantity (if any) of cyano-arenes in the am-
bient air environment should be measured using techniques
designed for these compounds. Cyano-arenes may be more
prevalent than the multiring, nitrogen heterocyclic com-
pounds studied in the past, and their environmental chemistry
and toxicity may warrant at least equal attention.
Table II. Mass Spectra of
M + 1
M
M- H
M-CN
M-HCN
Others
M
M + H
M + 2
M + CH3
M + C2H5
M + 30
Others
1
m/e
154
153
152
127
126
125
153
154
155
168
182
183
156
i
Int
13
100
7
5
17
4
38
100
15
9
35
6
6
Peaks 1-7 in El (Top)
;
m/e
154
153
152
127
126
125
153
154
155
168
182
183
156
i
Int
13
100
8
5
15
3
40
100
14
9
37
5
3
m/e
178
177
176
151
150
179
175
149
177
178
179
192
206
207
180
208
and CE/CI (Bottom) Modes
Peak
1
Int
15
100
15
9
18
5
6
4
41
100
25
6
34
14
14
6
m/e
178
177
176
151
150
179
175
149
177
178
179
192
206
207
180
208
•
Int
16
100
8
6
15
7
4
6
45
100
18
8
40
8
9
6
m/e
178
177
176
151
150
179
175
149
177
178
179
192
206
207
180
208
5
Inl
18
100
11
4
13
4
7
7
38
100
17
13
45
11
10
3
m/e
178
177
176
151
150
179
175
149
177
178
179
192
206
207
180
208
6
Int
19
100
11
4
18
4
6
3
42
100
16
16
44
11
8
5
7
m/e
204
203
202
177
176
201
175
151
203
204
205
218
232
233
206
234
Inl
22
100
13
6
10
13
7
6
46
100
17
11
41
9
10
5
M + 1/M« 2.63
• Corrected lor 13C.
2.37
2.33
2.10
2.49
2.27
2.01
84
-------
Acknowledgment
The authors thank Jack B. Howard and William J. Kausch,
Jr., for the design and operation of the second burner sys-
tem.
Literature Cited
(1) Pott, P., "Chirugical Observations", p 63. Hawkes. Clarke, and
Collins, London, England, 1775.
(2) National Academy of Sciences, "Particulale Polycyclic Organic
Mailer", Washington, D.C.. 1972.
(3) Hoffmann, D., Wynder, E. L., in "Chemical Carcinogens". C. E.
Searle, Ed., pp 324-65, Amer. Chem. Soc. Monograph 173, Wash-
ington, D.C., 1976.
(4) Sawicki, E.. McPherson, S. P., Stanley, T. W., Meeker, J.. Elbert.
W.C.,lnt.J. Air Water Pnltut , 9,515(1965).
(5) Dipple, A., in "Chemical Carcinogens", C. E. Searle. Ed., pp
245-314, Amer. Chem. Soc. Monograph 173, Washington. D.C.,
1976.
(6) Sawicki, E., Stanley, T. W., McPherson, S., Morgan, M., Taianta,
13,619(1966).
(7) Sawicki, E., Guyer, M., Engel, C. R.. J ChrnmatoRr.. 30. 522
(1967).
(8) Engel, C. R., Sawicki, E., ibid . 31, 109 (1967).
(9) Cautreells, W., van Cauwenberghe, K., Almas. Environ., 10, 447
(1976).
(10) Dong, M. W., Locke, D. C., Hoffmann, D., Environ. Sri. Technal.,
11,612(1977).
(11) Lee, M. L., Hites, R. A., J. Am. Chem. Sot:., 99,2008(1977).
(12) Hites, R. A., Dubay, G. R., in "Carcinogenesis", P. W. Jones, Ed.,
Vol III. pp 85-7, Raven Press, New York, N.Y., 1978.
(13) Prado. C,. P.. Lee. M. I,., Hiles. K. A.. Hmill, D. P., Howard, J.
B.. Sixteenth (Int.) Symp. on Combustion, pp 649-61, Combustion
Institute. Pittsburgh, Pa. 1977.
(141 Izard, C., Moree-Testa, P.. C« .-laid. Sri.. SIT. I). 272, 2581
(1971); (Vii'm. Abstr.. 75,61573j.
(15) Benner. .1.. Keene, C. K., Holt.T. W.. in 4th Tobacco and Health
Workshop Conf. Proc., pp 408-20, Univ. of Kentucky, Lexinglon,
Ky.. 1973. Oicm. Abslr.. 79, 896691).
(16) Hartung. G. K.. Jewell. I). M., Anal. Chem. Ada. 27, 219
(1962).
(17) Andre, J., Duth. P.. Mahieu, J., Grand'Ry, E. H.. Hrennst Chem..
18,369 (19671, Chem. Abslr . B8, 318(i9y.
(18) Prokseh,E..Ocs(crr. Chfm.Zlg.. 67, 105 (1966); Chem. Abslr .
64,19251g.
(191 Patterson..!. M., Haidar, N. K., Smith. Jr., W. T., Chem. Ind.
(London), 1975, p 128.
(201 Bhalla, P. 11. Arnold, K. C.. Sahharwal, 1'. S., J. Hered., 65, 311
(1974).
(21) Swingle. M. C.. Mayer, K. L., (Jahan. J. R.,<7. Econ.'Entomol.,
37,672 (1944); Chem.'Abslr.. .19. 7H4lt>).
(22) Maytr. E. L., Robertson, (I.. Nelson. R. H.. WcxxIward.C. F,. Hur.
r'.ntomol. Plant Quarantine. E-836 (1952); Chem. Abstr., 4f>,
525 la.
(23) Eddy. G. W . Carson, N. B.. J- Kenn. Entnmui. 41, 31 (1948);
Chem.'Abstr.. 42. 5156g.
(24) Skopek.T. R., Liber, H. L., Krolewski,.!. J./Fhilly. W. ('.., /'roc.
:Vo( Acad. .SVi , 75,410(1978).
(25) Kaden. I). A., Thilly, W. (',.. Massachusetts Institute of Tech-
nology. Cambridge, Mass.. private communication. 1977.
(26) Chang. S. C,., Novakov, T., Atrnus. Environ.. 9, 495 (1975).
Reeeil'ed for ret'ieu' November '23. 1977. Accepted February 2-1, /y78.
Wor/i supported 6v the rinuirtmmcntnl Protection Agency (Grant
KHIM2-I2} and the Department of Energy ((.Irani EE-77-S-02-
•1267)
85
-------
TECHNICAL REPORT DATA
(Please read liiur.it'nons on the reverse br/ore completing}
1. REPORT NO.
EPA-800/7-76-167
2.
4. TITLE AND SUBTITLE
Combustion Research on Characterization of Participate
Organic Matter from Flames
6. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
August 157 b
7. AUTHOR(S)
R.A. Kites and J. B. Howard
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Massachusetts Institute of Technology
Department of Chemical Engineering
Cambridge, Massachusetts 02139
10. PROGRAM ELEMENT NO.
EHE624A
11. CONTRACT/GRANT NO.
Grant R803242, Task 1
12. SPONSORING AGENCY NAMF AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPpRT AND PERIOD COVERED
Task Final; 8/74-8/77
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES IERL_RTP project OfflCCF IS John H.
541-2476.
Wasser, Mail Drop 65, 919/
16. ABSTRACT
The report gives results of a study of the formation and emission of soot and
polycyclic aromatic hydrocarbons (PAH) from both laminar flames and a turbulent
continuous-flow combustor. Decreasing the atomizing pressure decreased the amount
of soot and PAH produced in the latter system. Benzene fuel gave more soot and PAH
than did kerosene, and the PAH from benzene were more substituted. Nitrogen- and
sulfur-doped fuels did not alfect total soot production. The distribution of soot and
PAH within the flame was consistent with the concept that certain PAH may serve as
intermediates in soot formation. The PAH formed during combustion of coal, wood.
and kerosene were separated and identified by capillary column gas chromatography
and mass spectrometry. The PAH from coal combustion were found to be similar
to airborne PAH from Indianapolis, a high coal consumption area; those from kero-
sene combustion were similar to airborne PAH from Boston, an area of low coal con-
sumption and high consumption of petroleun derived fuels. Nitrogen containing fuels
primarily produce polycyclic aromatic compounds in which the nitrogen is in a cyano
substituent (approximately 70(7o). This contrasts with the observation that nitrogen
heterocyclic compounds are the major nitrogen containing compounds in airborne
particulate matter.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Pollution
Combustion
Research
Flames
Properties
Organic Compounds
Soot
Aromatic Polycyclic
Hydrocarbons
Benzene
Kerosene
Coal
Wood
Nitrogen
b. IDENTIFIERS/OPEN ENDED TERMS
Pollution Control
Stationary Sources
Particulate
c. COSATi 1-icld/Group
13B
2 IB
14B
07C
2 ID
11L
07B
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
CO
20. SECURITY CLASS i Tliis pane)
Unclassified
22. PRICE
EPA Form 2220-1 (9-?3)
86
-------