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Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978
Deposit Formation from Deoxygenated Hydrocarbons. 3. Effects of Trace Nitrogen and Oxygen Compounds William F. Taylor' and John W. Frankenfeld Exxon Research and Engineering Company, Government Research Laboratories, Linden, New Jersey 07036
The effect on deposit formation rate of the presence of trace amounts of nitrogen and oxygen containing impurities in deoxygenatedJP-5 was investigated. The change in deposit formation rate, following the addition of representative nitrogen and oxygen compounds, was determined over a temperature range of 150-450 O C in fuels with molecular oxygen contents reduced to less than 1 ppm. The addition of nitrogen compounds as pure materials did not increase deposit formation over the temperature range studied. However, certain nitrogen compounds led to sludge formation at temperatures in the range of 20-25 O C . Of the oxygen compounds studied, peroxides as a class were found to be highly deleterious to fuel stability. Some acids, esters, and ketones were moderately deleterious while others had no significant effect on deposit formation. In general, cycloalkyl compounds were less harmful than their aliphatic or aromatic counterparts. Several interactions between trace impurities were discovered which affect deposit formation rates.
Introduction The deposit formation tendencies of jet fuel range hydrocarbons have been the subject of considerable research (Nixon, 1962). Initial work was carried out with air-saturated hydrocarbons in a narrow, near ambient temperature range in order to investigate storage stability characteristics. Subsequent studies were extended to higher temperatures in order to investigate the stability of such fuels when used in high-speed supersonic aircraft (Nixon, 1962; Churchill, 1966). Such studies were carried out mainly with fuels saturated with molecular oxygen via exposure to air although some limited work has been reported with reduced oxygen containing fuels (Nixon and Henderson, 1966; Taylor and Wallace, 1967).This laboratory studied the variables which control the kinetics of the deposit formation process in air-saturated jet fuels at temperatures up to 250 "C at reduced pressures (Taylor, 1968a,b, 1969a,b; Taylor and Wallace, 1967, 1968). Also, studies were carried out using tetralin as a model jet fuel range hydrocarbon (Taylor, 1970a,b, 1972). We are now extending our study of the kinetics of deposit formation to deoxygenated jet fuels (Le., fuels in which the molecular oxygen content has been drastically reduced). The range of conditions investigated was extended to include temperatures up to 649 "C and pressures up to 69 atm. Previously (Taylor, 1974), the effects of deoxygenation on deposit formation in jet fuels were described. With most fuels, removal of molecular oxygen markedly lowered the rate of deposit formation. However, certain poor quality fuels showed less improvement. This surprising result led to a study of the influence of trace impurities on deposit formation in deoxygenated fuels, in order to determine whether such impurities, likely present in poor quality fuels, were negating the beneficial effects of deoxygenation. The effect of sulfur compounds was reported in part 2 of this series (Taylor, 1976).This paper describes the effects of trace impurities which contain one or more atoms of nitrogen or oxygen. Subsequent work will discuss the effects of hydrocarbon types on deposit formation in deoxygenated pure compound systems. Experimental Section Apparatus. A schematic of the Advanced Kinetic Unit used to measure the rate of deposit formation was shown previously (Taylor, 1974). The molecular oxygen content of the fuel to be tested was adjusted in a fuel treatment vessel by sparging 0019-7890/78/1217-0086$01.00/0
the fuel a t atmospheric pressure using helium. The treated fuel was passed through an oxygen sensor cell and delivered to a double piston fuel delivery cylinder. The oxygen sensor cell contained a polarographic sensor and the oxygen content of the total fuel was monitored. Oxygen analyses were also made on selected samples using a thermal conductivity gas chromatographic analyzer. The fuel was delivered to the unit by means of high-pressure nitrogen. The treated fuel was separated from the nitrogen drive gas by use of two individual pistons, separated by a small water layer. The fuel then passed through a heated tubular reactor section consisting of a %-in. o.d., 0.083-in. wall S.S. 304 tube which was contained inside of four individually controlled heaters. Each heater zone was approximately 12 in. long and was controlled by a proportional temperature controller. Unit pressure was controlled by means of a MITY-MITE controller. The rate of deposit formation was measured after a 4-h run. The reactor tube was cut into 16 sections, each 3 in. long, (4 sections per reaction zone) and the tube sections were analyzed for carbonaceous deposits using a modified LECO low carbon analyzer system (Taylor, 1974).The analytical system was calibrated against known standards. The deposit formation rate was obtained by dividing the net carbon production per section by the corresponding inner surface area and expressed as micrograms of carbon per square centimeter per four-hour reaction time. Reagents. The jet fuel employed was JP-5 (MIL-T-5624H) whose properties were previously reported (Fuel A in Table I; Taylor, 1974).This fuel was a highly refined, stable material. It contained 234 ppm of total sulfur and less than 1 ppm of thiol sulfur. The nitrogen content was less than 1 ppm and only traces of peroxides were present. This fuel was obtained additive free from the Baton Rouge Refinery of Exxon Company, U.S.A. The tubing employed in the reactor section of the Advanced Kinetic Unit was 1/4-in.0.d. X 0.083-in. wall stainless steel type 304. Prior to use, the tubing was cleaned inside and out with reagent grade acetone and chloroform and blown dry with nitrogen. Pure organic compounds containing nitrogen and oxygen of the highest quality available were obtained commercially and employed as received. The nitrogen and oxygen compounds were added to the base fuel a t the 100 ppm of N and 0 level. This level was chosen as representative of probable maximums for jet fuels derived from petroleum. 0 1978 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978 87
Table I. The Effect of Individual Nitrogen Compounds on Total Deposit Formation in a Deoxygenated Jet Fuel
Class of added nitrogen compounda
Added compound
Oxygen content, PPm of 0 2
Total depositsb As PPm of carbon based on fuel KLg
Pyrrole
2,5-Dimethylpyrrole 0.3 1310 0.68 Benzo(b)pyrrole (indole) 0.2 1316 0.68 Dibenzopyrrole (carbazole) 0.2 1028 0.54 Pyridine 2,4,6-Trimethylpyridine 0.2 1977 1.02 Benzo(b)pyridine (quinoline) 0.2 1457 0.75 2-Methylquinoline 0.1 1330 0.69 0.2 1441 0.75 Primary amine 2,6-Dimethylaniline 0.3 1228 0.63 Hexylamine N-Methylcyclohexylamine 0.2 1411 0.73 0.1 1049 0.54 Miscellaneous 2-Methylpiperidine Decahydroquinoline 0.2 1380 0.71 Hexanamide 1 1844 0.96 0.4 1485 0.77 Base fuel a All compounds added to the 100 ppm N level. Cumulative deposits produced in 4 h in the Advanced Kinetic Unit. Conditions: 69 atm, zone 1,371 OC; zone 2,427 "C; zone 3,482 O C , zone 4,538 "C.
NO A3DED A M I Y E S
/
/10;0'F
1.20
j90,O"F
1 .30
N O ADDED AbrlINES
8OO'F I 1. 4 0
700'F I
1 .50
1 ,6O
1.70
10OOPK
5 0 110
jl00O"F 120
(900'F
130
,
600'F I
l f 0
I 150
700'F I
1 IbO
110
1003PK
Figure 1. Deoxygenated fuel at 69 atm (0.2 ppm of 0 2 ) : 0 ,with added indole; A, with added 2,5-dimethylpyrrole;m, with added carbazole. All compounds added at 100 ppm of N.
Figure 2. Deoxygenated fuel at 69 atm (0.2 ppm of 0 2 ) : 0 ,with added 2,6-dimethylaniline;,. with added N-methylcyclohexylamine. All compounds added at 100 ppm of N.
Results The source of petroleum is believed .to be the remains of marine animal and vegetable life deposited with sediment in coastal waters (Hodgson, 1971). Bacterial action evolved sulfur, oxygen, and nitrogen as volatile compounds which were never completely eliminated despite the ever increasing pressure of sediment. Hence, crude oil is a mixture of hydrocarbons containing varying quantities of sulfur, nitrogen, and oxygen compounds. The nitrogen content of crude oil ranges from practically zero to a few percent (Ball, 1962). Nitrogen compounds identified in jet fuel range petroleum cuts include pyrroles, indoles, carbazoles, pyridines, quinolines, tetrahydroquinolines, anilines, and amides (Sauer e t al., 1952; Hendrickson, 1959; Nixon and Thorpe, 1962). The most prevalent compound types are pyrroles, indoles, carbazoles, and quinolines. Few reliable analyses of the oxygen content of petroleum products are available. However, oxygenated compounds are more abundant than nitrogenous species and somewhat less abundant than sulfur compounds. Oxygen compounds identified in jet fuel range petroleum fraction are carboxylic acids, phenols, furans, ketones, alcohols, esters, amides, hydroperoxides, and peroxides (Hendrickson, 1959; Nixon and Thorpe, 1962). Representatives of the above classes of nitro-
gen and oxygen compounds were tested in this study a t levels of 100 ppm of N or 100 ppm of 0. In addition, interactive effects, that is, the combined influences of different types of trace impurities, were examined to see if such influences were merely additive or were in some way synergistic. The rates of deposit formation were measured in the Advanced Kinetic Unit a t 69 atm with the temperature zones a t 371-540 O C . The molecular oxygen content of fuel mixture was reduced to 1ppm of 0 2 or lower. The JP-5 fuel alone, without added compounds, was tested similarly and for purposes of comparison. The results of the effects of various added nitrogen compounds on deposit formation in JP-5 are summarized in Table I. Some representative Arrhenius plots are shown in Figures 1 and 2. None of these compounds studied promoted deposit formation to any appreciable extent in the deoxygenated systems. The total deposits observed were of the same order of those obtained from the base fuel (Table I). This effect is in contrast to their deleterious nature in oxygen-saturated fuels (Nixon, 1962; Taylor, 1968b). The Arrhenius plots for fuels with pyrrolic compounds added have different slopes than that for the base fuel (Figure 1). All showed slightly higher deposits in the lower temperature regime when compared to the base fuel. Other heterocyclic
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978
88
Table 11. The Effect of Individual Oxygen Compounds on Total Deposit Formation in a Deoxygenated Jet Fuel
Class of added oxygen compounda
Added compound
Oxygen content, ppm of 02
Peroxide
a
Di-tert-butylperoxide 0.2 Cumene hydroperoxide 0.1 tert- Butylhydroperoxide 0.2 Carboxylic acid Cyclohexanecarboxylicacid 0.1 n-Decanoic acid 0.1 Cyclohexanebutyric acid 0.2 2-Ethylbutyric acid 0.2 2,4-Dimethylbenzoic acid 0.3 Phenol 2-Methylphenol 0.2 2,6-Dimethylphenol 0.1 2,4,6-Trimethylphenol 0.1 Furan Benzo(b)furan 0.2 Dibenzofuran 0.2 Alcohol n-Dodecyl alcohol 0.9 4-Methylcyclohexanol 0.3 Ketone 5-Nonanone 0.7 4-Methylcyclohexanone 0.3 Ester Cyclohexyl formate 0.2 Methyl benzoate 0.7 Pentyl formate 0.8 Base fuel 0.4 All compounds added to the 100 ppm 0 level. See Table I for run conditions.
N@ ADDED ACIDS
;
120
2879 7219 8934 1563 2997 1730 1291 1801 1561 2048 1451 1505 1410 2046 1356 2422 1244 1318 2488 1894 1485
1.49 3.73 4.62 0.82 1.54 0.89 0.67 0.93 0.81 1.06 0.75 0.78 0.73 1.06 0.70 1.26 0.64 0.68 1.29 0.98 0.77
fi
L-LLdl
5 10 1 0
Total deposits wg As PPm of carbon based on fuel
1.30
140
1.50
1.60
1.70
IOOU'F 10
700°F
'\,,
500-F
300'F
1
1000/'K
Figure 3. Deoxygenated fuel at 69 atm (0.2 ppm of 0 2 ) : 0 ,with added cyclohexanecarboxylicacid; m, with added mixed naphthenic acids; A,with added n-decanoic acid. All compounds added at 100 ppm of 0.
amines such as pyridines and quinolines showed similar effects. Primary amines, on the other hand, appeared to have no influence either in total deposits formed (Table I) or on the shape of the Arrhenius plots (Figure 2). The effects of various oxygen compounds studied are summarized in Table I1 and representative Arrhenius plots are shown in Figures 3 and 4. These compounds varied considerably in their influence on fuel instability. The furans, most carboxylic acids, and alcohols were generally not harmful t o fuel stability. An exception was n-decanoic acid. It promoted significantly higher deposit formation rates than either the aromatic or naphthenic acids studied (Table 11,Figure 3). Carboxylic esters were only mildly harmful and their influence also varied with structure. The aromatic ester, methyl benzoate, was mildly deleterious. The naphthenic ester, cyclohexyl formate, exerted no apparent influence on deposit for-
mation. The purely aliphatic ester, pentyl formate, was intermediate in its effect. Of the two ketones studied, 5-nonanone was mildly harmful while 4-methylcyclohexanone had no observable effect (Table 11). Peroxidic compounds, regardless of structure, cause significantly higher deposit formation rates and may be classed as highly deleterious (Table 11, Figure 4). The most active peroxide studied, tert-butylhydroperoxide, afforded a 600% increase in total deposits over the base fuel even though it was added only a t the 100 ppm 0 level. This increase in deposit is of the same order of magnitude as that observed with the most harmful sulfur compounds which were present a t the 3000 ppm S level (Taylor, 1976). An interesting result, obtained in all classes studied, is the consistently lower deposits observed with naphthenic (cy-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17,No. 1, 1978
Table 111. Interaction Study of t h e Presence of Pyrrole and a n Acid in Deoxygenated JP-5 Total pg of carbon Presence of a pyrrolea No Yes
Presen ce of an acidb
1485 1310 No 2997 5071 Yes a 100 ppm of N as 2,5-dimethylpyrrole added to base JP-5. 100 ppm of 0 as n-decanoic acid added to base JP-5; see Table I for run conditions. cloalkane) compounds. This result is especially noteworthy for the esters and ketones where the naphthenic compounds, cyclohexyl formate, and 4-methylcyclohexanone, afforded only half the deposits of their aromatic or open chain analogues. However, the effect is also significant among the alcohols, phenols, and carboxylic acids (Table 11). In order to test for interactive effects of synergisms, a 2 X 2 factorial experiment was designed (Bennett and Franklin, 1954) using the presence of the two added compounds as variables. An example is given in Table 111. In the example shown, a strong interaction between 2,5-dimethylpyrrole and n-decanoic acid was uncovered. The total deposits for the interaction run, in excess of 5000 pg of carbon, are considerably greater than expected from the sum of the additive contributions (2822 p g from a contribution of 1485 wg from the base fuel plus 1512 pg for the effect of the addition of the acid, minus 175 pg for the effect of the addition of the pyrrole). Several interesting interactions were observed when two different compounds were added simultaneously to the base fuel. For some, the total deposits formed were significantly higher than could be accounted for by additive effects alone. For others, stabilizing interactions were encountered. T h a t is, lower deposit formation rates were observed than would be expected from either of the added compounds alone. A summary of the more important interactions is given in Table IV. The two compounds showing the greatest tendency to interact were 2,5-dimethylpyrrole and n-decanoic acid. These compounds also exhibited strong interactions with sulfur-containing impurities and olefins (Taylor and Frankenfeld, unpublished observations). Significantly, all of the interactions among purely oxygenated species were stabilizing; that is, they tended to reduce deposit formation. Other combinations of compounds from Tables I and I1 were studied but gave no significant interactive effects. Discussion As pointed out previously (Taylor, 1974), not all fuels exhibit enhanced thermal stability when rigorously deoxygenated. Since those fuels which fail to show the expected improved stability are of generally poor quality, the presence of trace impurities is a likely cause. Taylor (1976) has shown that
89
the presence of certain sulfur compounds can markedly increase deposit formation in deoxygenated jet fuels. The present study indicates that certain other trace impurities, especially oxygen containing, can also contribute significantly to high-temperature instability. The formation of deposits in jet fuels is known to involve both chemical and physical changes (Taylor, 1974; Boss and Hazlett, 1969). In oxygen-saturated systems below the pyrolysis temperatures, deposits form as a result of free radical chain reactions (autoxidation). However, in deoxygenated fuels, the process appears different and even more complex (Taylor, 1976). Previous studies have shown that nitrogen compounds can be highly deleterious to air-saturated fuels both under storage (Nixon, 1962) and “empty” wing tank conditions (Taylor, 1968b). However, in deoxygenated fuel, nitrogen compounds have little effect on deposit formation under high-temperature conditions. This is apparent from data in Table I and the Arrhenius plots given in Figures 1and 2. None of the nitrogen compounds caused a significant increase in total deposits over the entire temperature range. In the low-temperature regimes, however, the heterocyclic amines 2,5-dimethylpyrrole, indole, and carbazole promoted deposit formation to a small extent when compared to the base fuel (Figure 1).The primary amines studied had no observable influence on deposit formation throughout the temperature range (Figure 2). The foregoing observations pertain to an effect on deposit formation on the tube surface at high temperatures (700-1000 OF). I t should be noted that during storage a t ambient temperatures, some heterocyclic amines, in particular 2,5-dimethylpyrrole, promoted the formation of considerable flocculent sediment in both air-saturated and deoxygenated fuels. The appearance of dark colored sediment was evident within a few hours after the pyrrole had been added to the fuel. This was observed previously in air-saturated fuels and has been attributed to autoxidation of the pyrrole (Oswald and Noel, 1961; Dinneen and Bickel, 1951; Angeli, 1916). It is somewhat surprising, however, to find such sediment in rigorously deoxygenated systems where autoxidation would be very slow. A preliminary analysis of the sediment from deoxygenated JP-5 suggests that it is quite different from that reported by others in air-saturated fuel. At any rate, the sediment formed at low temperatures, suggesting that it was either broken down to fuel-soluble fragments at high temperatures or that it did not adhere to the surface walls and form a deposit. The compounds containing oxygen were considerably more deleterious than those containing nitrogen (Table 11). Particularly noteworthy were peroxides although n-decanoic acid, methylbenzoate, and 5-nonanone also increased deposit formation by a t least 50% over the base fuel. Several aliphatic alcohols and phenols produced a moderate increase in deposit formation. This effect with phenols is in contrast to air-sat-
Table IV. Interactions between Oxvgen and Nitrogen Containing Imouritiesa
Compounds 2,5-Dimethylpyrrole + n-decanoic acid 2,5-Dimethylpyrrole + 2,4,6-trimethylphenol 2,5-Dimethylpyridine n-decanoic acid 2,4,6-Trimethylphenol + n-decanoic acid 5-Nonanone n-decanoic acid Dibenzofuran n-decanoic acid 2,4,6-TrimethylphenoI + Methylbenzoate
+
+ +
Total deDosits. pg of carbonb ExpectedC Obsd 2822 1276 3489 2963 3934 2922 2454
5071 1784 1993 1484 1741
1566 1808
Interaction effect Le., increase or reduce deposits Increase Increase Reduce Reduce Reduce Reduce Reduce
a Compounds present at levels of 100 ppm of N or 0 in deoxygenatedJP-5; run conditions in Table I. Predicted from data in Tables I and I1 assuming each component acting independently. c See Table I for run conditions.
90
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978
urated fuels where they often act as antioxidants and, therefore, stabilizing agents. On the other hand, the cyclic ethers, benzofuran and dibenzofuran, showed no tendency to promote deposit formation. It appears that oxygenated impurities behave similarly to their sulfur analogues in deoxygenated JP-5. Taylor (1976) reported that di- and polysulfides, analogues of peroxides, were highly deleterious to fuel stability while thiophenes, analogous to furans, were inert. The stabilizing effects of napthenic rings is illustrated by data in Table I1 and Arrhenius plots in Figure 3. As shown in Figure 3, the aliphatic acid, n-decanoic, afforded significantly greater deposits than either of the two napthenic acids shown. The napthenic alcohol, 4-methylcyclohexanol, gave lower deposits than any of the phenols or aliphatic alcohols (Table 11).The same trend is noted for both ketones and esters. This difference cannot be due to increased stability to pyrolysis since methyl benzoate is much more resistant to thermal decomposition than esters of formic aci& (Hurd, 1929). Similarly, alicyclic alcohols appear a t least as heat sensitive as their aliphatic counterparts and phenols are much more stable than either (Hurd, 1929).It would appear that the lower deposit formation rates observed with the napthenic compounds are due to the enhanced solubility of their pyrolysis products rather than to any enhanced stability to heat. One of the salient features of deposit formation with airsaturated fuels is the complex Arrhenius plot which results from the sharp drop in rates in the 350-430 "C (650-806 O F ) range. This was pointed out by Taylor (1974)and is illustrated by the typical curve for the air-saturated fuel given in Figure 4. Deposit formation rates show a sharp drop in this temperature range before continuing upward again a t even higher temperatures. Previous studies at sub-atmospheric pressures have shown that as a hydrocarbon jet fuel is heated, the rate of autoxidative deposit formation increases until the liquid phase is lost, at which point the rate of deposit formation drops sharply (Taylor and Wallace, 1967). I t would appear that much of this drop can be attributed to a reduction in the autoxidative reaction rate revealing the concentration of reactive species as the system passes from the liquid phase to the vapor phase (Mayo, 1968). With increasing temperature, the autoxidative rate constants continue to increase, so that ultimately this concentration effect is overcome and the overall rate of reaction again increases. The very similar shape of the curves obtained when deoxygenated fuels are doped with various peroxides (Figure 4) suggests that peroxides formed by autoxidation of air-saturated fuels are, indeed, the reactive species, whose drop in concentration with the phase change causes this discontinuity. The curve for the rigorously deoxygenated fuel, with no added peroxides, does not exhibit this effect. Furthermore, the deoxygenated fuels doped with various peroxides show an immediate increase in deposit formation (low-temperature regimes in Figure 4) while the air-saturated base fuel, with no added peroxides, exhibits a gradual increase in deposits. This suggests a steady generation of peroxidic compounds due to autoxidation of the base fuel by dissolved oxygen. These results strongly suggest that peroxides are a major cause of deposit formation in air-saturated fuel systems. A number of interactions between trace impurities were observed in the present study. In some instances, these led to
significantly increased deposits over those expected from additive effects alone while at other times the interactions actually tended to inhibit the formation of deposits. The most important interactions between 0- and N-containing impurities are summarized in Table IV. The most active material tested was 2,5-dimethylpyrrole, which interacted in a deleterious manner with both acids and phenols. A deleterious interaction with olefins was also observed which will be reported later. Significantly, the interactions between oxygen compounds were nondeleterious. That is, they tended to reduce deposit formation rates below that expected from additive effects. These findings suggest that trace impurities must be taken into account when assessing the thermal stability of fuel for high-speed aircraft. Deoxygenation procedures will be of optimal effectiveness only when trace impurity effects are considered and eliminated or controlled. Acknowledgments Helpful discussions with C. J. Nowack, L. Maggitti, Jr., and J. R. Pichtelberger are gratefully acknowledged. Literature Cited Angeli, A,, Gazz. Chim. Ita/., 46 (II), 279 (1916). Back, M. H., Sehon, A. H., Can. J. Chem., 38, 1076 (1960). Bail, J. S., Proc. Am. Pet. Inst., Sect. 8, 42, 27 (1962). Bennett, C. A., Franklin, N. L., "Statistical Analysis in Chemistry and the Chemical industry", Wiley, New York, N.Y., 1954. Boss, B. D., Hazlett, R. N., Can. J. Chern., 47, 4175 (1969). Braye, E. H., Sehon, A. H., Darwent, B. de B., J. Am. Chem. SOC., 77, 5282
(1955). Coleman, H. J., Hopkins, R. L., Thompson, C. J., Am. Chern. Sm.,DIv. Pet. Chern. Prepr., 15 (3),A17 (1970). Churchiii, A. V., Hager, J. A., Zengel, A. E., SA€ Trans., 74, 641 (1966). Dinneen, G. U., Bickei, W. D., Ind. Eng. Chern., 43, 1604 (1951). Fabuss, B. M., Duncan, D. A., Smith, F. O., Satterfield, C. N., Ind. Eng. Chern. Process Des. Dev., 4, 117 (1965). Hendrickson, Y. G., Am. Chern. SOC., Div. Pet. Chem., Prepr., 4 (l),55
(1959). Hodgson, G. W., Adv. Chem. Ser., No. 103 (1971). Hurd, C. D., "The Pyrolysis of Carbon Compounds", American Chemical Society, Monograph Series, Chemical Catalog Co., Inc., New York, N.Y., 1929. Mayo, F. R., Acc. Chem. Res., 1, 193 (1968). Nixon, A. C., in "Autoxidation and Antioxidants", Vol. 11, W. 0. Lundberg, Ed., Interscience, New York, N.Y., 1962. Oswald, A., Noel, F.,J. Chern. Eng. Data, 6, 294 (1961). Pryor, W. A., "Mechanisms of Sulfur Reactions", McGraw-Hili, New York, N.Y.,
1962. Rall. H. T., Thompson, C. J., Coleman, H. J., Hopkins, R. L., Roc. Am. Pet. Inst., Sect. 8, 42, 19 (1962). Reid. E. M.. "Organic Chemistry of Bivalent Sulfur", Voi. i, p 110,Chemical Publishing Co.,New York, N.Y., 1958. Reid, E. M.. "Organic Chemistry of Bivalent Sulfur", Vol. ii, p 60,Chemical Publishing Co., New York. N.Y., 1960. Reid, E. M., "Organic Chemistry of Bivalent Sulfur", Vol. Ill, p 369,Chemical Publishing Co., New York, N.Y., 1960. Rudneko, M. G.. Gromova, V. N., Dokl. Akad. Nauk SSSR, 81,297(1951). Sauer, R. W.. et ai., Id.Eng. Chem., 44, 2606 (1952). Sehon, A. H., Darwent, B. de B., J. Am. Chem. SOC., 76, 4806 (1954). Taylor, W. F., Wallace, T. J. Ind. Eng. Chern. Prod. Res. Dev., 6, 258 (1967). Taylor, W. F..Wallace, T. J., Ind. Eng. Chem. Prod. Res., 7, 198 (1968). Taylor, W. F., J. Appl. Chem., 18,251 (1968a). Taylor, W. F., SA€ Trans., 76, 281 1 (1968b). Taylor, W. F., J. Appl. Chem., 19,222 (1969a). Taylor, W. F., Ind. Eng. Chem. Prod. Res. Dev., 8,375 (1969b). Taylor, W. F., Ind. Eng. Chem. Prod. Res. Dev., 13, 133 (1974). Taylor, W. F.,Ind. Eng. Chem. Prod. Res. Dev., 15, 64 (1976). Thompson, R. B., Druge. L. W., Chenicek, J. A,, Ind. Eng. Chem., 41, 2715 ( 1949).
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Receiued for reuieu, June 9,1977 Accepted September 29,1977 T h i s work was sponsored by the D e p a r t m e n t of t h e Navy under Contracts N00140-73-C-0547 a n d N00140-74-C-0618.
