AROMATIC HYDROCARBONS AS COPONENTS OF AVIATION GASOLINE

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600300558-9
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 12
• Document Creation Date: December 22, 2016
• Document Release Date: September 7, 2011
• Sequence Number: 558
• Publication Date: May 5, 1950
• Content Type: REPORT

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0 CLAS A QO2a IDiIAIl L GONFIDF?TIA1
f CENTRAL INTELLIGENCE AGENCY REPORT[
~p~/ INFORMATION FROM
con FOREIGN DOCUMENTS OR RADIO BROADCASTS CD NO.
COUNTRY USSR DATE OF
INFORMATION 1947
SUBJECT Scientific - Chemistry, Aviation fuels
HOW
PUBLISHED collection of m ogrm
DATE
PUBLISHED 1947
TNIf DOCUMENT CONTAINS INFORMATION Af F[CTIN! TN[ NATIONAL Dt1[NSI
0I TNt YNI}ID fIATIf NITMIM TM[ MtANINf 01 IS ILO N AGI All t0
Y. t. C.. t1 AXO If. Af AM lNO10 ITI TRAXf .. ION OR Tx1 RlY14TI01
KAUTHQNIZKD I If
MIRIIID IT TLA . R[IROOY CT~OX 01 1- IORN If IXO NI IIISD INO?
DATE DIST.J{' May 1950
S~P CEMENT '10
RAP RT NO.
Aromaticheskiye Uglevodorody Neftyanogo proikhozhdeniya, Vol IV, 1947.
A. S. Velikovskiy
S. P. Kachenovskiy
M. B. Vol'f
As a result of research conducted at the Central Institute of Aviation Gaso-
lines and Lubricants (TsIATIM) and the State Red Army Scientific Research Insti-
tute of the Red Army Air Force (GKNII VVSKA) to determine the optimum chemical
composition for aviation fuels, it was determined that aromatic hydrocarbons were
a valuable addition to fuels being used in engines which are repeatedly operated
at overload conditions. It was also possible to draw various theoretical conclu-
sions relevant to the role of aromatic hydrocarbons in the knock-free combustion
of aviation fuels.
La
boratory
and engine pe
rformance tests showe
d that aromatic hyd
roc
arbons
have a high octane rating. Thus benzene, toluene,
and xylene have 10
0-p
lus oc-
tane ratings, but are unsuited for the purpose in
view, as they will not increase
the octane rating of a fuel if added in small q>antities. This can be seen from
the table below:
O
ctane Rating (ac:ordi
ng to engine method
of
testing)
Composition ($)
of mixtures with Component
Gasoline with
Octane Rating
of 70
Component
Isooctane Benzene Toluene
Xylenes
100
0
70 70
70
70
10
73.5 71.5
72
72
8800
20
76 73.5
74.5
74.5
70
30
78.5 76
77
77
50
50
83.5 82
83
83
eorrznrTnr O4N~rI011IA,
FOR OFFICIAL USE ONLY
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CONFIDENTIAL
It was also observed that aromatic hydrocarbons, when pur". or blended with some
other substance, were less sensitive to tetraethyl lead than straight-chain par-
affin hydrocarbons.
It was generally believed that large amounts of aromatic hydrocarbons must
be added to gasoline to improve the latter's performance, but there was never any
doubt as to the effect of these hydrocarbons with respect to increasing the anti-
knock qualities of fuels. Prior to the introduction of ethyl fluid, a mixture of
65 percent aviation benzene and 3~ percent Baku gasoline was used as aviation fuel.
Around 1936 the US Air Force first started using air-cooled engines with high-
pressure fuel injection. It was then held that with the increased operating tem-
peratures, it would not be advisable to use aromatic hydrocarbons which are more
sensitive to temperature changes than paraffin hydrocarbons, and would lose some
of their antiknock qualities with temperature increases. In 1936 the Army method
of testing was adopted in the US, whereby the octane rating was determined accord-
ing to the temperature of the (cylinder) head. The use of Midgley's needle was
discontinued. The temperature of the cooling sleeve of the cylinder was increased
to 160 degrees centigrade, as compared with a temperature of 100 degrees centigrade
under the old engine method of testing. A scale was compiled using as a starting
point that degree of compression under which benzene and a mixture of 88 percent
chemically pure isooctane and 1.2 percent n-heptane produce the same heating of the
(cylinder) head. This temperature is as:,umed to be the standard intensity of
knocking for drawing up the scale and for determining the octane rating of fuels.
Benzene was found to have an octane rating of 88.
In 1936, a special fuel conference was held in Moscow. Much of the discussion
centered around the value of aromatic hydrocarbons as additives to aviation gaso-
lines. But there were many at TsIATIM and GKNII VVSKA who did not believe in the
value of this component. Workers at TsIATIM (Ye I. Zabryanskiy) showed by fuel
tests, according to the Army method, that fuels containing aromatic hydrocarbons
actually had a lower octane rating than that found in the engine performance test.
However, fuels which had a high aromatic hydrocarbon content were more easily mod-
ified by tetraethyl lead under the new procedure than in the engine performance
tests. Therefore it can be concluded that the sensitivity of fuels with a high
aromatic hydrocarbon content to increased temperatures prior to ignition is large-
ly suppressed by tetraethyl lead.
During 1938 and 1939, a series of tests was conducted with various fuels to
evaluate their performance in the M-25A engine. These tests were carried out in
connection with the development of a special antiknock alkylbenzene by TsIATIM
which was brought up to the stage of industrial production in 1936. The tests
themselves were conducted at GKNII VVSKA under the supervision of Army Engineer
Filippenko. Ignition qualities were determined with two matters in mind: (1) the
permissible degree of leanness and (2) the permissible amount of pressure feed.
Prior to the above-mentioned tests, Lhc test motor was operated on D-59, B-70,
B-74, and B-78 gasolines with and without tetraethyl lead to determine the octane
rating of the latter fuels.
The following fuel mixtures were used:
1. Fifty percent isooctane 4- 50 percent B-70 gasoline + 2 milliliters of
ethyl fluid per kilogram
2. Forty percent alkyl benzene}- 60 percent B-70 gasoline + 3 milliliters-
of ethyl fluid per kilogram
3. B-78 gasoline- 4 milliliters of ethyl fluid per kilogram
According to the engine test method all of the fuel mixtures had octane ra-
tings of 96 to 97, but it was found that fuels with varying chemical compositions
behaved differently in a M-25A aircraft engine.
CCNFIll`'''TIAI.
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CONFIDLDTIA1
A mixture of alkylbenzene and straight-run gasoline or B-78 gasoline t4 mil-
liliters per kilogram of ethyl fluid has less tenden.y to produce knocking than
isooctane blends with the same octane rating.
No knocking was observed when the leanness of mixtures of alkylbenzene was
lowered to a rate of r_s+.:.^rr,... ? ttcc of 216 _ grams per horsepower -hour under conditions
of rated power output. -The maximum temperature of the cylinder heads during the
above run remained constant at 222 degrees centigrade.
Infrequent knocking was observed in a run using a mixture of isooctane with
straight-run gasoline at a consumption of 212 grams per horsepower-hour. The max-
imum cylinder head temperature in this case was 230 degrees centigrade.
Tests conducted by raising the amount of pressure feed showed that when 250
grams of fuel were expended per horsepower-hour a mixture of alkylbenzene and gas-
oline gave the best antiknock performance at the highest pressure feed. No knock-
ing was observed until full throttle, i.e., until Pk = 1,119 millimeters of mer-
cury and Nc = 835? Maximum cylinder head temperature at full throttle operation
was 249 degrees centigrade. Knocking started at Pk = 1,110 millimeters of mercury
for a mixture of isooctane and gasoline. Maximum cylinder head temperature reached
was 248 degrees centigrade.
It was necessary to operate at full throttle before knocking was observed with
a mixture of B-78 gasoline containing 4 milliliters of ethyl fluid per kilogram.
(Pk = 1,124 millimeters of mercury and Nc = 813). Maximum cylinder head tempera-
ture was as high as 250 degrees centigrade. It is of interest that where engine
operation was such as to consume fuel at the rate of 280 grams per horse power-hour
no knocking was observed even at full throttle with any of the fuels tested.
Full throttle operation on a mixture of alkylbenzene and gasoline gave 850
horsepower while on a mixture of B-78 gasoline and 4 milliliters per kilogram of
ethyl fluid the maximum horsepower was only 838.
It can therefore be seen that aromatic hydrocarbons can be valuable high-oc-
tane components of aviation gasolines and that they have the characteristics of
performing better at higher pressure feeds, also of developing more power than
isoparaffins. From 1939 to 1940, associates at TsIATIM conducted tests on an M-105
engine and determined that engine performance was far better with fuels containing
large amounts of aromatic hydrocarbons than could be expected merely on the basis
of their octane rating. it was proposed that pyrobenzene could be used as an ad-
ditive to B-78 fuel (at this time it was being used only as an additive to B-70
fuel).
In 1942, a shipment of US aviation gasoline arrived in the USSR, which was
classed B-95 and B-100, to correspond to the octane rating. The B-95 contained
76 percent paraffin hydrocarbons, 20 percent naphthenes, and only 4 percent aro-
matics; while the B-100 contained 90 percent paraffin hydrocarbons, 6 percent
naphthenes, and 3 percent aromatics. Thus both fuels possessed predominantly par-
affin hydrocarbon characteristics (see Table 1). These two fuels were tested in
an aircraft engine which operated under the following conditions: intake pressure
(pressure feed = Pa) 1,288 millimeters of mercury at take-off conditions, 2,150
rpm, compression 6.8, and output 34.3 horsepower per liter of fuel. It was first
established that the engine performed best on a fuel consisting of ordinary B-78
with 4 milliliters of ethyl fluid per kilogram of gasoline. This fuel had a high
naphthene hydrocarbon. content, and with the addition of a given amount of tetra-
ethyl lead would have had an octane rating of around 95. It was therefore be-
lieved that the engine would operate normally on the US fuels.
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B-78 B-95 20% Pyro- 30% Pyro- 20% Xylene 30% Xylene
Gaso- Gaso- Pyro- Xylene benzene+ benzene + Fraction + Fraction +
Constants line line benzene Fraction 80% B-95 70% B-95 80% B-95 B-70
Specific weight dT 0.7280 0.7180 0.8509 0.8317 0.740 0.747 0.731 0.745
Octane rating
(engine method) 94.8 95 89 (*2 82.2 (*3 95.0 94.7 95.0 93.4
Ethyl fluid
(ml/kg) 4.2 4.2 (*l 0 0 4.0 4.0 4.19 4.08
Fractions:
Boiling be-
gins ?c 46.5 49.5 83 136 51 51 66 53
10% boils off
at ?C 68 70.5 85 140 72.5 77 74 75.5
50% boils off
at ?C 92 97 100 146.5 97 109 102.5 106
90% boils off
at ?C 125.5 120 149.5 160 132 149.5 141 147
97% boils off
at ?c 159 150 169 173.5 i64 168.5 168 170
Residue (%) 1.7 1.1 0.9 0.8 1.1 1.3 1.1 1.0
Loss (%) 0.8 1.1 0.9 0.8 1.1 1.3 1.1 1.0
Congelation tem- Less than Less than
perature ?c -60 -60 -20 -- -60 -55 -60 -60
Chemical compo-
sition:
Paraffin hydro-
carbons (%) 39 76 -- -- -- --
Raphthene hydro- 20 30
carbons (%) 58 20 -- -- --
Aromatic hydro-
carbons (%) 3 4 80 70 20 (*1 27 (*4 17 (*4 24.(*4
*1. B-95 contains 3.19 ml ethyl fluid per kilogram (1 ml per kilogram was added besides)
*2. With 4 ml ethyl fluid per kg the octane rating is 94
*3. With 4 ml ethyl fluid per kilogram the octane rating is 87
*4. Date on aromatic hydrocarbon content are established-by computation
u
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~. ~FI?F.Ir 1A1
The fuels were tested by determining engine performance on various fuel mix-
tures with the maximum permissible lean mixtures set by the altitude mixture con-
trol under the following conditions: (1) Take-off conditions at Pa= 1,285 milli-
meters of mercury (2,150 rpm), (2) Nominal at Pa: 1,180 millimeters of mercury
(2,050 and 1,950 rpm).
During these tests the temperature of the water at the exit was maintained at
65 - 75 degrees centigrade. Under operating conditions, the specific expenditure
of fuel at a point where knocking starts should not exceed 300 - 325 grams per
horsepower-hour at take-off conditions, and 285 - 305 grams per horsepower-hour
nominal (at 2,050 rpm). These fuels had a high octane rating, but proved to be in-
adequate for good performance under overload operating conditions. The B-95 fuel
produced very obvious knocking at nominal output where fuel expenditure was Ce = 291
grams per horsepower-hour. It was decided that the octane rating of a fuel is no
criterion for determining the suitability of a fuel for use in a pressure-feed, low-
rpm, large dimensioned engine. However, it was suggested that these US fuels would
give very good performance if doctored with aromatic hydrocarbons.
A series of experiments (supervised by Colonel S. P. Kachenovskiy of the En-
gineers) was conducted to test this theory. Pyrobenzene was added to B-95 and B-100.
Another series of tests was conducted using the "xylene fraction" of pyrobenzene
(this is the pyrobenzene residue after the 125 - 130 degrees centigrade fraction is
distilled). The properties of this fraction are shown in Table 1.
The following mixtures were tested by GKNII VVSKA and TsIATIM during Septem-
ber and October 1942: (1) 80 percent B-95 and 20 percent pyrobenzene, (2) 70 per-
cent B-95 and 30 percent pyrobenzene, (3) 80 percent B-95 and 20 percent xylene
fraction, and (4) 70 percent B-95 and 30 percent xylene fraction. (All mixtures
contained 4 milliliters per kilogram of ethyl fluid.) An analysis of the mixtures
and a group chemical composition of the fractions is shown in Table 1.
The results of the experiments are shown in Table 2. It can be seen that per-
formance was normal with all mixtures notwithstanding the fact that mixtures with
20 percent pyrobenzene and particularly those with 30 percent xylene fraction had
a much lower octane rating than conventional B-95 (xylene fraction with 4 milli-
liters per kilogram of ethyl fluid has an octane rating of 87.)
1). Specific expenditure of fuel during take-off and at nominal output of an
engine operating on a lean mixture until the point of knocking was less with a mix-
ture of 80 percent B;95 and 20 percent xylene fraction than with a mixture of 80
percent B-95 and 20 percent pyrobenzene. This is due to the high qualities of the
aromatic hydrocarbons which are contained in the xylene fractions (xylene fractions
contain all the pyrobenzene hydrocarbons, in addition to benzene; toluene is con-
tainod in minute quantities in pyrobenzene).
2. The relatively lower octane rating (93.4) of a mixture of 70 percent B-95
and 30 percent xylene fraction, as well as the higher specific expenditure of fuel
under lean mixture operation until the start of knocking (in comparison to perfor-
mance with fuel containing 20 percent xylene fraction) it evidence of the poor
antiknock qualities of paraffin and naphthene hydrocarbons which are found in the
xylene fractions.
B-95 fuel henceforth was improved by adding only small amounts of pyrobenzene.
It is also not recommended that more than 20 percent of pyrobenzene be added in
view of the additional circumstance that an amount in excess of this will raise the
congelation point of gasoline above-60 degrees centigrade. The results of these
experiments resulted in a completely new evaluation of aromatic hydrocarbon compo-
nents of aviation fuels. A similar change of opinion has also taken place in the
US and England. Today it is general practice to use aromatic hydrocarbons in gaso-
lines for engines performing under overload conditions, particularly if the princi-
pal constituents of the gasoline are paraffin hydrocarbons.
~E~FfFi~ T1, 1_
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C 1NF1DENT!AL
It may be assured that the antiknock action of aromatic hydrocarbons is two-
fold: (1) oxidation products of aromatics prevent an accumulation of those com-
pounds which result from the oxidation of paraffin hydrocarbons and cause the de-
tonation wave, (2) action consisting in dilution of the paraffin hydrocarbons,
thus reducing the number of collisions between paraffin hydrocarbon molecules or
free radicals and active oxygen.
6-
CONFIDENTIAL
CON FIDF {{1 'IA l
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CONFIDENTIAL
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CONFIDENTIAL
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According to Rice (1), there is a breaking up of hydrocarbons into low molecular
olefins and paraffins as the temperature increases. This occurs over the forma-
tion of radicals. The number of free radicals of straight-chain hydrocarbons
formed in the engine cylinder is larger than the number of those formed from
branched isomers. Rice claims that there is a direct relationship between the n.m-
ber of free radicals which are formed and the tendency of the engine to knock. nn
formation, the lowest hydrocarbons, and possibly free radicals which collide with
the active oxygen, are transformed into that type of oxidized product which in it-
self is the cause of knocking (for example, peroxides in the second stage of com-
bustion).
It is quite evident that ' higher temperatures and partial pressures of ox-
ygen, a greater quantity of low .,,irocarbons will form without preliminary formation
of radicals. These factors will also bi_..g about more intensive oxidation of the
newly formed products. It follows, therefore, that with an increase in the partial
pressure of the oxygen and an increase in the temperature, there will occur knock-
ing during the combustion of hydrocarbons which actually have high knock-resistant
qualities.
Studies to determine the octane rating were conducted under conditions not em-
ploying pressure feed. Consequently, the temperature of the engines was low notwith-
standing the high oxygen pressure in the engines. The results -btained from these
studies could not be used for evaluating the performance of fuels in engines perform-
ing at overload operating conditions. It must be stated that the action of aromatic
hydrocarbons, which would prevent the accumulation of oxidation products causing
knocking, leads to the conclusion that they have the same action as aromatic hydro-
carbons which prevent the oxidation of oils, i.e., that they act as inhibitors of
oxidation. This was shown in studies conducted by N. I. Chernozhukov and S. E.
Kreyn(2).
For the purpose of breaking the chain of oxidation effectively, aromatic hy-
drocarbons must themselves oxidize, but not in the side chains. Oxidation must oc-
cur in the nucleus with the resultant formation of phenols in addition to other ox-
idized compounds. For example, it can be assumed that oxidized aromatic hydrocarbons
react with hydroperoxides in a manner similar to that suggested by Egerton (3) for
the case of metallo-organic antiknock substances which prevent the formation of per-
oxides.
Under rigid oxidation conditions, such as are evident in modern engines oper-
ating at overload, there is an efficient oxidation of the aromatic nucleus, so
that aromatic hydrocarbons are effective antiknock components of aviation fuels.
In engines which do not operate at overload conditions (for example, the engines
which were used to determine the octane rating of fuels), the aromatic hydrocarbons
do not undergo the necessary oxidation and therefore do not serve as effective anti-
oxidizing agents. Instead of breaking the oxidation chain, they merely dilute the
fuel. Under the circumstances, it was necessary to add large amounts of aromatic
hydrocarbons in order that they be effective.
Due to the antioxidant action of aromatic hydrocarbons, it is sufficient to
add them in relatively small quantities (15 percent or so) in order to prevent the
knocking set up by isomeric paraffin hydrocarbons.
LnONFI? 'NTI~
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OONFIDENTIAI.
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ttt~jgjjla
Nevertheless, it must be kept in mind that aromatic hydrocarbons do not inhib-
it oxidation and consequently knocking caused by paraffin 1ydrocarbons in an en-
tirely uniform manner. For the purpose of inhibiting the oxidation of low-octane-
rating hydrocarbons which have a normal or weakly branched structure, it is nec-
essary to use larger amounts of aromatic hydrocarbons than for hydrocarbons having
several side methyl groups. In the former case the aromatic inhibitor has to
break a much larger number of oxidation chains.
It can be seen from Table 3 that the xylene fraction acts with greater effect
in 20 percent amounts than in 30 percent amounts. This can be explained by the fact
that paraffin hydrocarbons with a low octane rating are components of xylene frac-
tions. Moreover, they are weakly branched, thus explaining the relatively low octane
rating of the xylene fraction. Thus the octane rating of 70 percent B-95 and 30
percent xylene fraction mixture is lover than that of a mixture of B-95 with the
same amount of ethyl fluid (93.4 - 95). Engine performance with a mixture contain-
ing 30 percent xylene fraction is poorer than with a mixture containing only 20
percent xylene fraction, due to the fact that in a 30 percent mixture the paraffin
hydrocarbon constituents deteriorate in quality, so that even a large amount of aro-
matic hydrocarbons will not inhibit oxidation and prevent knocking.
The above hac a practical as well as theoretical significance. At present, it
cannot be stated conclusively that there is no necessity for the manufacture of iso-
paraffins. In view of the fact that isoparaffins are most easily protected
against knock-producing decomposition, their presence in fuels is desirable. There-
fore the continued manufacture of hydrocarbons of this type serves a useful purpose.
Separate studies should be conducted to determine the performance of overload
operating engines on naphthene hydrocarbons. From Table 2 it can be seen that the
B-78 gasoline with 4 milliliters of ethyl fluid per kilogram (octane rating 95) did
not produce knock in overload operating conditions. This gasoline is obtained by
straight distillation and contains 60 percent naphthene hydrocarbons, but only 2 -
3 percent of aromatic hydrocarbons. It may be surmised that naphthene hydrocarbons,
under severe oxidation conditions, are partially converted into antioxidizing agents
and thus protect the rest of the naphthene as well as paraffin hydrocarbons from
knock-producing combustion. Both Chernozhukov and Kreyn (2) observed that in the
oxidation process, naphthene hydrocarbons change into aromatic hydrocarbons. Con-
sequently, all prerequisites for the conversion of naphthene hydrocarbons into anti-
oxidizing agents are present.
A most interesting observation was made at GKNII VVSKA (reported 25 December
1942): the addition of isooctane to paraffin hydrocarbon gasolines B-95 and B-100
did not bring about knock-free performance of engines at overload operating con-
ditions. A mixture of 40 percent isooctane with B-70 gasoline (having an octane
rating of 98 with 4 milliliters of ethyl fluid per kilogram and 60 percent naph-
thene hydrocarbon content) resulted in knock-free operation. It follows therefore
that both components -- naphthene gasoline and isooctane -- mutually prevent knock-
ing. Still, naphthene hydrocarbons are less effective antiknock agents than aromatic
hydrocarbons when added to isoparaffins. Thus, the same naphthane gasoline did not
prevent knocking in neohexane fuel and was totally ineffective in preventing knock-
ing in a mixture of isooctane and isopentane (Table 3). Obviously the antiknock
stability of isopentane and neohexane under overload operating conditions is dif-
ferent from that of isooctane, notwithstanding the fact that their octane rating,
when in a 40:60 mixture with B-70 gasoline (with 4 milliliters of ethyl fluid per
kilogram) is the same(95)?
This final problem must be further studied, as it is possible that poor perfor-
mance of fuels containing neohexane and isopentane may be due to defective distribu-
tion of the fuel among the cylinders.
rQNFlU` TL1
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cn~~F~o~~Tia~
Conclusions
1. Aromatic hydrocarbons with low boiling po_nt (benzene, toulene, xylene and
ethyl benzenr) increase the octane rating of gasoline only when added in large quan-
tities, particularly in the presence of tetraethyl lead. These conclusions were
reached on the basis of tests conducted according to the CFR engine method.
2. Under overload operating conditions (with high pressure feed) fuels com-
posed primarily of isoparaffins cause knocking even where the octane rating is high
(95 to 100).
3. The introduction of small quantities of aromatic hydrocarbons into paraffin
high-octane fuels results in a sharp inhibition of knocking in an engine operating
under overload conditions, even through the octane rating of the fuels is not in-
creased.
4. Fuels which are composed of naphthene hydrocarbons, -- for example,
straight run B-78 with up to 60 percent of these hydrocarbons (with 4 milliliters
of ethyl fluid per kilogram), -- burn in an engine c -rating at overload conditions
without knocking, if the fuels have high octane rati.gs.
5. The differences in the performance of fuels rich in paraffins, naphthenes
and aromatic hydrocarbons in present-day engines which operate at overload condi-
tions and in CFR equipment, as well as in other carburetor engines not working at
overload conditions, can be stated as follows:
a. Paraffin hydrocarbons having a branched structure and a high octane
rating do not operate without knocking in an engine operating at overload condi-
tions. This results in high operating temperatures and high partial oxygen pres-
sure. Isoparaffin hydrocarbons can be protected by the addition of small quanti-
ties of aromatic hydrocarbons. A much larger amount of aromatic hydrocarbons is
necessary for knock prevention when normal or weakly branched paraffin hydrocarbons
are used in engines operating at overload conditions.
b. The action of aromatic hydrocarbons is twofold: (1) as a diluent of
hydrocarbons which have a tendency to knock, and (2) by breaking the chain of ox-
idation. This latter effect is not brought about directly by the aromatic hydrocar-
bons, but rather by the products of their oxidation. Under mild oxidation condi-
tions, such as are met i- the Waukesha test (engine method) there is no oxidation of
aromatics. Under severe conditions of oxidation, in these same engines (high temper-
atures, high partial oxygen pressure), the aromatic hydrocarbons oxidize and in this
form easily break the chain of oxidation of paraffin hydrocarbons.
c. Naphthene hydrocarbons in the oxidation process partially change into
aromatic hydrocarbons. Therefore, they can also prevent paraffin hydrocarbons from
causing knock, but not as well as aromatic hydrocarbons.
d. The above-stated facts explain why naphthene gasolines with octane rat-
ings of 88 (with 4 milliliters of ethyl fluid per kilogram) blended with isooctane
will constitute a knockless fuel for engines operating at overload conditions, wile
at the same time a fuel consisting of gasoline containing primarily paraffin hydro-
carbons and having an octane rating of 95 cannot be improved by adding isooctane so
that it will not knock under the same conditions. Low octane naphthene gasoline and
isooctane mutually increase each other's antiknock qualities.
URP,FBD ii, TIA L
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 Sanitized Copy Approved for Release 2011/09/08: CIA-RDP80-00809A000600300558-9 I
CONFIDE TIg
1. F. 0. Rice, Ind Eng Chem Vol XXVI, 259, 1934
2. N. I. Chernozhukov and S. E. Kreyn, "Oxidizability of Petroleum Oils," ONTI,
Azneftizdat, 1936
~. I. Egerton, Just Petr Tech, Vol XIV, 656, 1928
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