ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT aromatic distillate fuels where the sulfur compounds impart a n offensive odor, as well as poor color and poor stability,, and where aromatics impart adverse burning characteristics. Acknowledgment
The authors thank J. F. Deters for obtaining the data on furfural and D. A. McCaulay and Harold Shalit for supplying the data on hydrogen fluoride. Literature Cited (1) Am. SOC.Testing
Materials, “A.S.T.M. Standards on Petroleum Products and Lubricants,” p. 22, Method D 90-50T (1953).
Method D 129-52 (1953). (3) Arnold, R. C., U. S. Patent 2,673,830(March 30, 1954). (4) Arnold, R. C., and Lien, -4. P., Ibid., 2,646,390(July 21, 1953). (5) Ibid., 2,671,046(March 2, 1954) (6) Ibid., 2,671,047 (March 2 , 1954). (7) Lien, A. P., and Evering, B. L., IND.ENO. CHEM.,44, 874 (2) Ibid., p. 78,
(1952).
(8) Lien, A. P., McCaulay, D. A., and Evering, B. L., I b i d . , 41,2698 (1949).
(9) Lien, A. P., MeCaulay, D. A, and Evering, B. L.,Proc. Srd World Petroleum Congr., Sec. 111, 145 (1951). (10) McCaulay, D. A., and Lien, a.P., J . Am. Chem. Xoc., 73, 2013 (1951). (11)
McCaulay, D. A., Shoemaker, B. H., and Lien, A. P., IND. ENQ. CHEM.,42, 2103 (1950).
RECEIVED for review September 29, 1954.
ACCEPTEDDecember 14, 1954.
Sulfur Compounds in Kerosine Range of Middle East Crudes S. F. BIRCH, T. V. CULLUM, R. A. DEAN, AND R. L. DENYER Research Sfation, The British Petroleum Co., ttd., Sunbury-on-Thames, Middlesex, England
The mixture of sulfur compounds extracted from an Iranian kerosine by sulfuric acid and released on dilution has been investigated. Separation of individual compounds was effected b y fractional distillation, followed b y successive partial extractions of the fractions with aqueous mercuric acetate solution, and two-stage recovery from the extracts. Compounds were identified by physical properties and b y the hydrocarbons formed on desulfurization with Raney nickel. The main constituents identified were monocyclic and bicyclic sulfides (including bridged-ring compounds) and thiophenes; dialkyl sulfides contributed only 5 to 10%. No evidence of the presence of other types of sulfur compounds was obtained.
T
H E examination of the sulfurous oil (tar oil), which separates when sludge acid from the refining of light petroleum naphthas is diluted with water, has yielded much useful information concerning the sulfur bodies present in these distillates (14, 15, 17, 81, 38). This oil, provided the distillates treated are straight run products free from unsaturated hydrocarbons, consists mainly of unchanged sulfur compounds. Present in lesser amount are aromatic hydrocarbons (6) and traces of ketones (22) of unknown origin, the solubility of these substances in the acid being enhanced by the solubilizing effect of the sulfur compounds and sulfonic acids derived from the aromatics. The investigation of the sulfur bodies of petroleum distillates through the medium of a spent refining agent such as sludge acid is, however, open to several objections, not the least of which is that i t is difficult to establish any reliable quantitative relationship between the composition of the tar oil and that of the original distillate. Thus the solvent action of the acid is almost certainly selective for certain types of sulfur compounds and will also vary with molecular weight; extraction is often incomp1et.e and is affected by acid concentration, acid-hydrocarbon ratio, and temperature while the products of chemical reaction of the acid-e.g., aromatic sulfonic acids, water from oxidation of mercaptans, and sulfonation-have a marked effect on its solvent action. Nevertheless, tar oil undoubtedly provides a convenient source of those neutral compounds which are soluble in, but unaffected by, concentrated sulfuric acid. Sludge acid, being a waste material, is available in quantity. Separation of the tar oil is simple and, if desired, can be carried out on a very considerable scale. Alternative methods for concentrating the neutral sulfur bodies, which are dependent on the formation of metal salt or nonmetal-
240
lic halide complexes-e.g , mercuric salts, aluminum chloride ( I S ) . boron trifluoride, or on some form of adsorption-do not readily lend themselves to large scale operations nor are they as easy to conduct. With large quantities of material available, separation can be attempted on a scale adequate to provide samples of end products for physical and chemical examination. Certain of the compounds isolated in the present worlr were found t o be difficult to synthesize, and it proved easier to separate them directly from the tar oil, in sufficient quantity and of the required purity for determination of physical properties. Further. iarger scale working Lends to favor detection of substances present only in a small amount. Another advantage is that identification can sometimes be effected through desulfurization products, when isolation of individual sulfur compounds proves impossible The first investigation in these laboratories of the sulfur compounds recovered from acid sludge was concerned with material derived from the treatment of the sulfur dioxide extract of a 100” to 160” C. naphtha of mixed Persian origin ( 1 7 ) . Only alkane and simple cyclic sulfides could be identified; disulfides, if present, were not there in sufficient quantity to enable separation to be effected by the methods employed, mainly fractionation and adsorption on silica gel. The investigation haa now been extended to the kerosine boiling range, tar oil from the treatment of a refinery tractor fuel blend of similar origin being used. Since the boiling ranges of the naphtha and the tractor fuel blend overlapped, some of the compounds identified were found in both. Unlike the tar oil from the naphtha, that from the higher boiling kerosine contained only 5 to 10yoof alkane sulfides; the bulk consisted of cyclic sulfides and thiophenes. Of the
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 47, No. 2
HYDROCARBON SEPARATIONS former, bi- and tricyclic derivatives constituted significant proportions. No evidence was obtained for the presence in the tar oil of disulfides or of any type of sulfur body other than sulfides and thiophenes.
IO00
ZOO0
4000
3000
5000
6000 6 8 5 0
discussed with reference t o the fractions in which they occurred, the fractions examined being indicated by Roman numerals on the distillation curves (Figures 1 , 2 , 3 ) . Identification was largely dependent on physical properties, in particular boiling point, refractive index, and infrared absorption spectrum. Sulfides were characterized by their mercuric chloride complexes and the thiophenes by their acetoxymercuri derivatives. Desulfurization with Raney nickel followed by spectroscopic identification of the hydrocarbon formed was particularly used and possessed the advantage that i t gave helpful information with incompletely purified materials and even mixtures. It was discovered in t h e desulfurization of many of the sulfide fractions and particularly the higher molecular weight thiophenes, that appreciable amounts of olefins were present in the hydrocarbon products (4). The causes of this olefin formation are not known: 2,5-dimethylthiophene gave olefin-free n-hexane whereas Z-ethyl-3,4,5-trimethylthiophene (Fraction XVII) yielded a product having 33% olefins. Thiadamantane gave olefin-free bicyclo [3.3.1] nonarie whereas the liquid B sulfides associated with it gave a product containing some 60% olefins. Characterization of the sulfides by physical properties was badly hampered by lack of reliable data, a difficulty which applied equally to some of the higher paraffins and naphthenes obtained as desulfurization products. Concurrent with the present work the synthesis of a number of typical bicyclic sulfides and thiophenes has been in progress, and this has provided much useful data especially on sulfides containing fused 5- and 6-membered rings.
WEIGHT OF DISTILLATE, GRAMS
Figure 1.
Distillation curve of Fractions
I to
x
I n the present work separation was dependent almost entirely on fractional distillation and extraction with aqueous mercuric acetate solution. The latter technique, which has already been described (6), proved invaluable. Not only did it enable partial separation of open chain and cyclic sulfides to be effected, but it also assisted materially in concentrating mono- and bicyclic sulfides in different fractions. The order of extraction was found to be tricyclic > bicyclic > monocyclic > open chain sulfides. Regeneration followed the reverse order. A modification of the original procedure, involving recovery of the sulfides from the aqueous extract in two stages, first by steam distillation alone and then in the presence of hydrochloric acid, was found to give improved separation, the less stable complexes-i.e., those of the open chain and monocyclic sulfides breaking down before those of the more stable bicyclic and polycyclic compounds. For convenience in the experimental part, those sulfides regenerated by steam alone have been designated A sulfides and those in the presence of acid B sulfides. Gonversion of the mercuric acetate complexes to the corresponding chlorides by treatment of the aqueous extract with sodium chloride followed by fractional crystallization of the mercuric chloride complex failed as an alternative method of separation, largely owing to the tendency of the complexes to form oils. Mercuric acetate treatment offered an additional advantage in that it also provided a convenient method for the isolation of the thiophenes, the trisubstituted compounds yielding water-insoluble solid monoacetoxymercuri derivatives while the tetrasubstituted thiophenes remained unaffected by this treatment and were recovered from the residue. While the complete separation of sulfide types might be possible by reversible complex chromatography using mercuric acetate solution, under the conditions used only partial separation was achieved with this reagent. Other methods for effecting separation including adsorption chromatography, fractionation of sulfones, and azeotropic distillation were tried but with little success. The individual sulfur compounds identified in this work are
February 1955
6850
7680
8650
9650
10650
11650 12650 138M 14650
l56W
I6650
WEIGHT OF DISTILLATE, GRAMS
Figure 2.
Distillation curve of Fractions XI to XX
Desulfurization as a method of identification suffers from the disadvantage that i t provides no indication of the point of attachment of the sulfur atom to the carbon skeleton. Several alternatives may be possible and the selection of the most probable is a matter of some difficulty because of the paucity of data for the compounds involved. It has been assumed throughout that the cyclic compounds containing 5- and 6-membered rings and that any 4- or 7-membered ring compounds, if present, constitute only a minor portion of the cyclic bodies. The first indication of the presence of bicyclic sulfides (high refractive index of the B sulfides) was observed in the 187" to 191' C. region of the distillation curve (XII). This coincided with the appearance of cycloparaffins in the desulfurization products. Although naphthene hydrocarbons could have been formed
INDUSTRIAL AND ENGINEERING CHEMISTRY
241
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT The naphthenes identified in the hydrocarbons from the desulfurization of the B sulfides from Fraction XI1 were methylcyclohexane, ethylcyclopentane, and cycloheptane. There was also a considerable proportion of unidentified naphthenes. It was a t first thought possible that 3-thiabicyclo [3.3.0J octane wag one of the bicyclic sulfides present and that the methylcyclohexane had been formed by ring expansion during desulfurization.
,CH,
ng 1.4924, leaving unextractable material (19%)] n g 1.5022, b.p. 100" C. at 10 nim., consisting mainly of thiophenes. Desulfurization of the B sulfides yielded a complex mixture of O and bicyclic hydrohydrocarbons, largely Cg and C ~naphthenes carbons, containing some 60% olefins. The formation of these can best be explained by assuming that the sulfides are mainly bicyclic and tricyclic compounds. The A sulfides on desu1furizat)iongave a hydrocarbon product, b.p. 145' to 181" C. at 760 mm., n g 1.4290, which appeared to consist of CS naphthenes (9%) with some nonanes presumably from Cs bi- and monocyclic sulfides and Clo naphthenes and paraffins with traces of bicyclic hydrocarbons, mainly from Clo bi- and monocyclic sulfides. XXIII, XXIV, XXV, XXVI, and XXVII. In this boiling range, 233" to 248" C. at 760 mm., identification of individual compounds was not possible nor could any individual hydrocarbons be characterized in the desulfurization products. S5'it.h t,he aid of mercuric acetate extraction some indication of the nature of the fractions which comprised the five boiling ranges was obtained. Unusually high refract,ive indices of the B sulfides regenerated from XXIII, XXVI, and XXVII suggested the presence of polycyclic sulfides and sonie crystals of thiadamantane actually separated from XXIII on standing. A small quantity of a monoacetox3.mercurithiopheiie, m.p. 162' tjo 164' C. was obtained from XXT'II. Analysis
Calcd. for CiaHzaOsSHg Found
C 35.4 35.8
H 4.6
4.2
S 7.3 7.7
This has not been further investigated so far.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 2
HYDROCARBON SEPARATIONS Extraction of Sulfur Compounds from Hydrocarbon Solution. Solutions of I O sulfur compounds were prepared using a mixture of n-heptane (90% by volume) and thiophene-free benzene (10% by volume) as solvent to give a concentration of 1.3% by weight of sulfur in the final blend. Different quantities were contacted with 200-ml. portions of each (maximum blend of 5% by vol.) of 9801, sulfuric acid in a Wagner shaker for 30 minutes. After standing for 15 minutes the hydrocarbon layer was decanted, washed with caustic soda solution, and the sulfur content of this material and the original blend determined by the x-ray method ( 9 ) . The results of the extraction are given in Figures 5 and 6 which plot the weight of sulfur compound extracted against volume per cent of acid used. The acid also was neutralized with caustic soda solution and the products examined. With the following materials the original sulfur body was recovered substantially unchanged : di-nbutyl sulfide, di-n-butyl disulfide, 4-methylthiacyclohexane, 2-thiahydrindane (mixture of cis- and trans- isomers), 4-ethyl-2,3dimethylthiophene, and 2,3,4,5-tetramethylthiophene. 2-Methylthiophene and 2,3,5-trimethylthiophene were sulfonated] and no oil was liberated from the acid on neutralization. The oil recovered from 3-methylthiophene and 2,5-dimethylthiophene was much higher boiling and appeared to be polymeric material. Part of the oil from 3-methylthiophene boiled a t 130' to 160" C. at 22 mm.; n$ 1.6330; the remainder could not be distilled. Dehydrogenation of 2,315-Trimethylthiacyclopentane. A portion of Fraction VI (10.6 grams) was heated in sealed tubes at 300" to 310" C. with diphenyl disulfide (35.7 grams) for 11 hours. The product was steam distilled and the volatile portion distilled under reduced pressure. The portion boiling a t 46' to 58" C. at 12 mm. was dissolved in pentane and treated with aqueous mercuric acetate solution. After filtration, the pentane solution gave on removal of the solvent, an oil from which a solid separated. This was shown (mixed m.p.) to be 3-acetoxymercui-i2,4,5-trimethylthiophene.
Conclusions Much useful information concerning the sulfur compounds present in straight run naphthas can be obtained from the examination of tar oil recovered from sludge acid. The isolation and identification of compounds was greatly assisted by the availability of large quantities of material. One significant fact emerging from this work is that sulfur compounds in the kerosine distillate contain bi- and tricyclic sulfides of an unexpected type. Bridged-ring hydrocarbons are almost unknown in mineral oils, the only certain example being adamantane which, however, we have been unable to identify in the kerosine from which the acid sludge was derived. It is, therefore, interesting to find that bridged structures are to be found amongst the sulfur bodies. If, a6 seems likely, the latter bear a structural relationship to the hydrocarbons, some knowledge of their constitution may help in elucidating the nature of the hydrocarbons. Fortunately the sulfur atom in the molecule provides a convenient point of attack for chemical reagents which the hydrocarbon does not possess. It is not unreasonable to suppose that a knowledge of the sulfur bodies may eventually lead to useful information concerning the higher hydrocarbons, in particular those of the lubricating oil range of which very little is known. The investigation has been hampered by lack of knowledge of the properties of sulfur compounds and of hydrocarbons. The synthesis of some sulfur compounds has materially assisted and as more data become available, it is hoped that additional compounds in the tar oil may be identified. Methods of determining the structure of sulfur compounds other than by physical properties are being investigated, for example the dehydrogenation of substituted thiacyclopentanes to the corresponding thiophenes by such reagents as diphenyl disulfide which has already shown promise, and the preparation of thiacyclo-
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-
pentanes from available thiophenes by hydrogenation with plat inum as described by Mozingo (86) or with the aid of rhenium sulfide as recently described by Broadbent, Slaugh, and Jarvis (8). Some of the predictions with regard t o the boiling points of unknown compounds, which have been made, were later confirmed when data became available on physical properties.
Acknowledgment Our thanks are due to the chairman of the British Petroleum Co., Ltd., for permission to publish these results. We wish to acknowledge the help of D. H. Desty in the identification of hydrocarbons by gas chromatography and, with R. W. Willoughby, in carrying out the fractionations; we are also indebted to H. Powell and M. Flagg for their help in connection with the spectroscopic analyses.
Literature Cited (1) Alder, K., and Stein, G., Ann., 514, 1-33 (1934). (2) American Petroleum Institute Res. Proj. 44, Selected Values of the Properties of Hydrocarbons and Related Compounds, Table 115A, April 30, 1952. (3) Arnold, R. C., Launer, P. J., and Lien, A. P., presented at 121st Meeting, ACS, Milwaukee, Wis., March 30-April 3, 1952. (4) Birch, 9. F., and Dean, R. A., Ann., 585,234-40 (1954). (5) Birch, S. F., and McAllan, D. T., J . Inst. Petroleum, 37, 433-56 (1951). (6) Birch, S. F., and Norris, W. S. G. P., J ; Chem. Soc., 129,2545-54 (1926). (7) Bower, J. R., and Cooke, L. &I., IND. ENG.C m h i . , ANAL.ED., 15, 290-3 (1943). (8) Broadbent, H. S., Slaugh, L.. H., and Jarvis, h-. L., J . Am. Chem. Soc., 76, 1519-23 (1954). (9) Cranston, R. W., Matthews, F. W., and Evans, N., J. Inst. Petroleum, 40, 55-63 (1954). (10) Cullum, T. V., McAllan, D. T., Dean, R. A., and Fidler, F A., J . Am. Chem. Soc., 73, 3 6 2 7 3 2 (1951). (11) Desty, D. H., and Fidler, F. A., IND. ENQ.CHEM.,43, 905-10 (1951). (12) Doering, W. von E., Farber, M., Sprecher, M., and Wiberg, K. B., J . Am. Chem. Soc., 74, 3000-1 (1952). (13) Emmott, R., J . Inst. Petroleum, 39, 695-715 (1953). (14) Friedmann, W., and Canseco, C., Petroleum ReJiner, 22, 1-5 (1943). (15) Friedmann, W., and Rodriguez, C., Ibid., 25, 53-60 (1946). (16) Gaertner, R., and Tonkyn, R. G., J . Am. Chem. Soc., 73, 5872 (1951). (17) Haresnape, D., Fidler, F. A,, and Lowry, R. A,, IND. ENQ. CHEM..41. 2691-7 (1949). (18) Haitough, H.D., Anal. Chkm., 23, 1128-30 (1951). (19) Komppa, G., Ber., 68, 1267-72 (1935). (20) Landa, S., and MLchAEek, V., Collcction C~ech.Chem. Commun., 5, 1-5 (1933). (21) Mabery, C. F., andQuayle, W. O., Am. Chem. J., 35,404 (1906). (22) Mapstone, G., Petroleum. Refiner, 29, 142-150 (1950). (23) Meerwein, H., Kid, F., Klosgen, G., and Schoch, E., J . prakt. Chem., 104, 161- 206 (1922). (24) Meisel, S. L., Johnson, G. C., and Hartough, H. D., J . Am. Chem. SOC., 72, 1910-12 (1950). (25) Mozingo, R., Harris, S. A , , Wolf, D. E., Hoffine, C. E., Jr., Easton, N. R., and Folkers, K., Ibid., 67, 2092-5 (1945). (26) Nametkin, 9. S., and Sosnina, A. S., Doklady Akad. Nauk. S.S.S.R., 63, 391-4 (1948). (27) Owston, P. G., private communication, May 12, 1954. (28) Paty, M., and Deschamps, J., dompt. rend., 234, 2291-2 (1952). (29) Prelog, V., and Seiwerth, R., Ber., 74, 1644-8 (1941). (30) Rossini, F. D., Anal. Chem., 20, 110-21 (1948). (31) Semmler, F. W., and Bartelt, K., Ber., 40, 4844-9 (1907). (32) Thierry, E. H., J . Chem. Soc., 127, 2756-9 (1925). (33) Thompson, C. J., Coleman, H. H., Rall, H. T., and Smith, H. M., presented a t 126th Meeting, ACS, New York, N. Y . , September 11-17, 1954. (34) White, P. T., Barnard-Smith, D. G., and Fidler, F. A,, IND. ENG.CHEM.,44, 1430-8 (1952). (35) Whitehead, E. V., Dean, R. A., and Fidler, F. A., J . Am. Chem. SOC.,73, 3632-5 (1951). (36) Youtz, M. A., and Perkins, P. P., Ibid., 51, 3511-16 (1929). (37) Yur'ev, Yu. K., and Gragerov, I. P., J . Gen. Chem. U.S.S.R., 19, 724-9 (1949). (38) Yur'ev, Yu. K., Kondrat'eva, G. Ya., and Khartashevskii, A. J., Ibgd,, 22, 513-16 (1952). RECEIVED
for review September 9, 1954.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
ACCEPTED November 27. 1054.
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