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INDUSTRIAL AND ENGINEERING CHEMISTRY
On the basis of the work reported in this paper and data in the literature, the present knowledge concerning the reactions under consideration may be summarized as follows: Some crude oils contain elemental sulfur. This elemental sulfur begins to react with some components of t h e crude oil a t about 200" to 300" F., with evolution of hydrogen sulfide. The reaction reaches its maximum observable rate at about 400' F., accompanied by a maximum evolution of hydrogen sulfide and rapid depletion of the elemental sulfur content. Approximately 50% of the elemental sulfur can be accounted for by the hydrogen sulfide evolved at 400" F. The remaining sulfur forms thermally labile compounds that decompose a t temperatures above 400' F., releasing hydrogen sulfide. Sulfur reacts with n-tetradecane and tetrahydronaphthalene (Tetralin) a t 176" F. (80" C . ) , and with paraffin wax (melting point 160" to 170' F.) a t 240" F. (110' C.), withincipient evolution of hydrogen sulfide. There is some knowledge of the reaction of sulfur with hydrocarbons (1-3, 6, 8),but most of the data pertain to temperatures above 395" F. (200" C.) and pressures above atmospheric. Tri- and pol sulfides react with components of crude oil in the same way as ecmental sulfur in that hydrogen sulfide is formed but they also form thiols in much greater quantity than does the equivalent quantity of elemental sulfur. Crude oils containing sulfur compounds but no elemental sulfur react like Bradford crude, with sulfur or polysulfide added after the initial release of hydrogen sulfide at 400 F. Asphaltic constituents contain thermally labile sulfur compounds t h a t decompose t o yield hydrogen sulfide a t temperatures of 500" F. and above.
Vol. 45, No, 12
Some implications from this work relate to the refining of crude oil. Obviously, if a crude oil contains polysulfides and even though no thiols are originally present, upon distillation a t a temperature of 400" or 500' F. thiols will be produced and a sour distillate obtained. The reaction of crude-oil constituents with sulfur to yield hydrogen sulfide suggests the possibility of field treatment for certain crude oils in which the elemental sulfur content is high. If it were economical t o heat these crude oils in the field in a closed system to 400' F., a considerable portion of the sulfur would be released as hydrogen sulfide, and this reaction would not occur in costly refinery equipment where it might cause more serious replacement problems. Possible removal of the elemental sulfur as such from the crude oil before any heat treatment is worthy of thought. It is obvious that the answer to some of the questions posed would be helpful in refinery operations. It is hoped that means will be found to study further the reaction of sulfur, polysulfide, and hydrocarbons a t atmospheric pressure. ACKNOWLEDGMENT
The authors are indebted to the Phillips Petroleum Co. for the tri- and polysulfides used in this work, and to the Union Oil Co. of California for the Santa Maria Valley California crude-oil samples.
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A review of the foregoing statements raises many questions, of which the following are typical. With what hydrocarbons in the crude oil does elemental sulfur react? Is there any preferential selection based on type, structure, or molecular weight, and if so, what? Do the threshold temperatures of the reactions differ with hydrocarbon type, structure, or molecular weight? What are the threshold temperatures for these reactions? What type or types of sulfur compounds are formed in addition to hydrogen sulfide? What hydrocarbons, if any, are formed by the reaction of sulfur with hydrocarbons? What are the kinetics of these reactions? What is the effect of pressure on these various reactions? If the reaction can proceed slowly a t low temperature, what ia the significance of the presence or absence of elemental sulfur in crude oil as regards its origin? Will a disulfide plus elemental sulfur act like a trisulfide? Are polysulfides present in crude oils? Can all the sulfur compounds present in a crude oil be attributed to the results of previous reaction with elemental sulfur? An example of the significance of the answers to these questions is the question of the origin of elemental sulfur and hydrogen sulfide in crude oils and the relationship of the content of these compounds to the temperature of the producing formation. Certainly, if the sulfur has been indigenous to the oil, the oil must have had a very low temperature history. On the other hand, if the sulfur dissolved in crude oil results from contact between sulfur and oil after the formation of the oil, there would be no proof of a low temperature thermal history before solution of the sulfur in the oil, but a low temperature environment after the solution of the sulfur in the crude oil would be indicated. Finally, it seems probable that, although the reaction does not appear to proceed rapidly a t temperatures below 300' F., it could be progressing slowly and, over a relatively short geological period, could well account for the hydrogen sulfide found in some crude oils, and thus the difference between the hydrogen sulfide, elemental sulfur, and sulfur compound content of crude oils might be accounted for by the temperature differences of the producing horizons. The authors have been unable t o obtain bottom-holetemperature data for the wells from which samples were obtained, but this information would also be an interesting field of study from a geological as well as a chemical point of view.
REFERENCES Baker, R. B., and Reid, E. E., J . Am. Chem. SOC.,51, 1566 (1929). Friedmann, Walter, Be?. 49, 1344 (1916). Friedmann, Walter, Petroleum, 11, 978 (1916). Eccleston, B. H., Morrison, Marilyn, and Smith, H. M., Anal. Chem., 24,1745 (1952). Farmer, H. E., and Shipley, F. W., J . Polymer Sci., 1, 293 (1946). Hoffert, W. H., and Wendtner, K., J . Inst. Petroleum, 35, 171 (1949). Schuhe,' W. A., Short, G. H., and Crouch, W. W., IND.ENG. CHEX.,42,916 (1950). Shepard, A. F., Henne, A. L., and Midgley, Thos., Jr., J . Am. Chem. SOC.,56,1355 (1934). RECEIVED for review June 8, 1953. ACCEPTEDAugust 17, 1953. Presented before the Division of Petroleum Chemistry at the 123rd Meeting of the AMERICAN CHEMICAL SOCIETY,Los hgeles. Calif. Part of the work of American Petroleum Institute Research Project 48A on "Production, Isolation, and Purification of Sulfur Compounds and Measurement of Their Properties," which the Bureau of Mines conducts at Bartlesville, Okla., and Laramie, Wyo.
Corrections Influence of Hydrogen Sulfide on Flame Speed of Propane-Air Mixtures I n the article on "Influence of Hydrogen Sulfide on the Flame Speed of Propane-Air Mixtures" [ I N D . ENG.CHEM., 45, 2361-6 (1953)l on page 2364 in the paragraph below Figure 9 the fourth sentence should read: For rich mixtures Zc,/c*, < 1 and for lean mixtures 2 c,,/c*. > 1, indicating inhibition in both instances. PHILIP F. KURZ
Chemigum SL-An Elastomeric Polyester-Urethane I n the article on "Chemigum SL-An Elastomeric PolyesterUrethane" [Seeger, K. V., et al., IND.EXG.CHEW., 45, 2538 (1953)l an error was made in Table VI. I n the last column the entries under Chemigum SL should have been: 0, 0.32, 0.48, 0.56, 0.64, 0.88, 1.04, 1.36, and 2.24. N. V. SEEGER
