US2562238A - Thiophene by-product tar and triglyceride oil reaction product - Google Patents

Description

i atentecl 31 THI'OPHENEBY+1RODUCT1TAR:AND tra I GLYCERIQE on, REACTION PRODUCT Sigmund "J.'-Lukasiewicz and Alexander" N. Sachanen, -Woodbury, N. -J.,--assignors 'to so- -cony-Vacuum Oil Company, Incorporated, a corporation oflNew'York Nb Drawing- Original application Marchil3,.1946,

Serial No. 654,222. Divided and this application April"17 ,f1947, Serial No, 742,202

ii-Claims. (01. 260-3322) This invention'h as to do with-'the development of improved lubricating compositions. More specifically, the present invention relates to;the development of a novel class of characterizing agents which, when incorporated in hydrocarbon lubricating oils, inhibit the deleterious-effects'of oxidation upon the'oils.

As is well'known to those familiar with theart, various characterizingagents have been proposed for use in lubricants to counteract the chemical and physical shortcomings thereof. Among such shortcomings are, for example, tendencies to: oxidize, corrode metalswvith which they are in contact, form sludge and lacquer films onmetal parts, deposit insoluble materials from acid bodies, etc. The present'invention is concerned with overcoming some of these tendencies, -notably with fortifying lubricants against the'deleterious effects ofoxidation and theformationof acid and sludge. I r

The present invention is-based uponthe discovery of a novel class of sulfur-containingreaction products which, when used in'lubri cating oils, effectively increase the resistance of's'aidoils to oxidation. 'I'hus, thisiinvention-is predicated upon the discovery that a new and novelclass of reactionproducts, namely, sulfur-containing'reaction products obtained by'reactio'n of ananimal, mineral, vegetable or essential oil, withl'a sulfur-containing tar obtained from'aprocesslfor preparing thiophene and certain alkyl -thiophenes, will so characterize lubricating, oils. a

The characterizing agents, as indicated above, are formed from an oil such" as an animaLEmi neral, vegetable or essential oil. Typical of these oils which may be usedherein are: .animal -lard oil, sperm, oil, etc.; mineralp araflinic, naphtheme and, aromatic oils or mixtures thereof;

vegetable-.-'rapeseed oil, soybean oil, cotton-seed oil, corn oil, 'palmbil, castorfoil,:oiticica;and

essential-turpentine oil, lemon'oil peppermint oil, etc. Preferred of such oils are animal oils; of

which lard oil isparticularly preferred.

The sulfur-containing tars reacted herein with the aforesaid oils are obtained byjreactingf'certain aliphatic hydrocarbons, with 'sulfur as described at length in copending application Serial No. 601,758, filed June 2'7, 1945, by. o ne' of the present applicants, Alexander N.'Sa'chanen, 'with V "H. E. Rasmussen and Rowland C. I-lansfo rd, now abandoned, ,and in copending applicatiomserial No. 601,759, filed June27, 1945, by said Basmussen andHansford, now issued as'UI S. 'Patent No. 2,450,686. For convenience. herein, however, the following is offered as a description'of the process in which the tar-is obtained as abyproduct. a

Thiophene and a by-product tar areprepared by separately preheating sulfurand one or more normal'aliphatic hydrocarbonsselected from the group consisting of normal butane, normal butenes and butadienes to temperatures such that combiningthe sulfur and the hydrocarbon material will provide a mixture having a temperature'in excess of-about 450 C.,=mixin'g.zthe preheated sulfur and preheated hydrocarbon,

maintaining -=the temperature of themixture at mal butane, normalbutenes'butadienes,pentanes,

pentenes,penta'diens, hexanes, hexenes andhexadienes,al1 havingat least 4 carbon'atom's in a chain, or mixtures -thereof,l lt will be clear that a tar and thiophene areobtained from the aforesaid -4-carbon hydrocarbons; tarsand :alkyl derivatives of thio'phene are obtained" from the aforesaid 5 and *6 carbonhydrocarbons. 7 "As stated herein, and-in the appended claims there'- for, the term s'ulfur-containing by-producti tar is:used" generically to describe those tars which 'areformed along with thiophene andthose which are formed'withalkyl-derivatives thereof; such as the methyl and ethyl derivatives'. v f v It hasbeen' fou'd in 'the operation=of this processthat the relative proportions of sulfur and hydrocarbon material-in the charge may "be varied over wide limits. Too" inuch'sulfur, howeyer, 1resultspoor'efiiciency in sulfur utilization per pass, and favors the complete 'sulfurizationof hydrocarbon material to'carbon disulfied. Yet, too low a proportion ;of sulfur lowers the conversion per pass and the ultimate yield by increasing the;overall-thermaldegradationof hydroc'arbon material. f Generally speaking; l best results are-obtained fusing a-weight "ratio 0f suifur to a hydrocarbon material varying between about 0.5 and abont ;-alth'oug'h when butehs,

butadienes; pent'enes, pentadiene's, -he'xenes,-' or hexadienes "constitute *thebulls of the hydrocharge.

carbon material in the charge, the lower limit of the weight ratio may be lower than 0.5. It should be observed however, that for economical operation of the process, it is preferred not to use a hydrocarbon charge consisting of butadienes, pentadienes, or hexadienes, because of their tendency to polymerize under the conditions of the process.

The selectivity of the reaction involved for the preparation of the tars and thiophenes depends, primarily, upon two variables, namely, reaction temperature at which the normal aliphatic hydrocarbon or hydrocarbons are contacted with sulfur and the reaction time or the time during which contact between the reactants is maintained at the reaction temperature.

The limits of operating temperature are fixed by the kinetics of the desired reaction and the kinetics of possible side or secondary reactions. It has been found, in this connection, that the reaction temperature may vary between about 450 C. and about 760 C. and preferably between about 540 C. and about 650 C. when normal butane is the predominant hydrocarbon reactant in the charge, and between about 480 C. and about 590 C. when butenes and butadienes are the predominant hydrocarbon reactants in the charge. With the and 6 carbon hydrocarbons mentioned hereinabove, the reaction temperature may vary between about 450 C. and about 700 C. and preferably, between about 480 C. and between about 590 C. Below the lower limit of the temperature range (about 450 C.) the reaction is so slow as to require a large throughput of sulfur and a higher ratio of hydrocarbon recycle for a fixed amount of end product, therefore detracting from the economics of the operation. Above the upper limit of the temperature range which, as indicated hereinabove varies with the number of carbon atoms in the hydrocarbon reactant, the secondary reaction of degradation of hydrocarbon material in the charge takes precedence, therefore decreasing the yield of desired product. In addition to this, high temperatures favor the formation of carbon disulfide. It must be noted also that at these high temperatures corrosion problems are at a maximum, corrosion increasing perceptibly with increasing temperature.

It has been found, in connection with this process, that the optimum reaction time depends upon the temperature employed. In general, other variables remaining constant, the lower the temperature, the longer the reaction time. The reaction or contact time and the reaction temperature are somewhat fixed, one in relation to the other, between degree of degradation of the hydrocarbon material in the charge and between the extent or formation of undesirable products which may be tolerated. Thus, too long a con-.

tact time at high temperature results in severe cracking of the hydrocarbon material in the The reaction proceeds with extreme speed, the only limitation apparently being the rapidity with which heat can be supplied to the reaction mixture. The reaction is highly endothermic requiring, by experimental measurement, approximately 28,000 calories per gram molecular weight of thiophene produced from normal butane. The lower limit of the range of reaction time is fixed, therefore, by the engineering problem of heat transfer and by mechanical limitations, such as allowable pressure drop across the reactor. Relatively long reaction times at temperatures in the neighborhood of carbon disulfide.

of the lower limit of the temperature range results in lower yields of thiophene and increased yields of thiophene tar. Too short a reaction time, however, at temperatures in the neighborhood of the lower limit of the temperature range results in insufi'icient reaction. Accordingly, it has been found that for best results the time of reaction is fixed by the reaction temperature.

In view of the foregoing, the criteria to be used in determining optimum operating temperatures within the range 450 C.760 C. with 4 carbon hydrocarbons and 450 C.-700 C. for 5 and 6 carbon hydrocarbons and reaction times, are to chose the degree of conversion desired, commensurate with operating costs such as heat input and equipment costs, bearing in mind that within the limits, the shorter the reaction time, and correspondingly, the higher the temperature, the larger amount of end product which can be realized from a unit of given size per day.

It is recognized that the relationship between the temperature of reaction and reaction time is not singular with this process. It is a well established and fairly well understood relationship in numerous reactions. In this process, it has been found that a sulfur-containing, by-product tar and thiophene may be produced by reacting sulfur and the aforesaid 4 carbon hydrocarbons at a temperature between about 450 C. and about 760 C., and the tars and alkyl derivatives of thiophene may be produced by reacting sulfur and the aforesaid 5 and 6 carbon hydrocarbons at a temperature between about 450 C. and about 700 0., for a period of time selected to minimize the yields of secondary reaction products, such as carbon disulfide, coke-like materials, etc. at the selected temperature. Under such conditions, when operating continuously with the reactor coil of suitable size and at a particular charge rate, it has been found that the lowest practical limit of the time of reaction isof the order of 0.01 second at about 760 C. The upper practical limit of the reaction time, other variables remaining constant, will correspond to the lower limit of the temperature of reaction and may be of the order of several seconds.

Separate preheating of the hydrocarbon reactant and sulfur and quenching of the reaction mixture are necessary for achieving the relatively close control of the reaction time at a given reaction temperature. This is very important in the specific reaction producing thiophene and. tars. It is suspected that a number of reactions occur in the reaction between thehydrocarbon reactant and sulfur. In this connection the following should be noted: cracking of the hydrocarbon reactant destroying the 4 carbon atom chain structure (prerequisite for the formation of thiophene and alkyl derivatives thereof); formation of tars higlrin sulfur; and formation These reactions compete with one another. It has been found that the rates of the formation of lighter hydrocarbons and of the formation of carbon disulfide are somewhat slower than those required for the formation of thiophene and tars. Accordingly, a proper control of the reaction time at a given reaction temperature achieved by separate preheating, mixing, heating at a given temperature for an increasing period of time and quenching is necessary to produce high yields of thiophene and tars with limited yields of carbon disulfidc, coke-like materials, and fixed gases due to a limited decomposition of the hydrocarbon reactant. The rate of the reaction producing tars pressure.

a reaction variable.

teases is fairly close to that required for the formation of thiophene and the yields of tars and of thiophenes are approximately the same.

In carrying out the process for preparing tars, it is essential to separately preheat the reactants.

' Heating the hydrocarbon material and sulfur together is undesirable, in that heavy tars are produced and these are subsequently crackedin the reactor causing undue coke formation. Tests have shown that whenthe reactants are heated together, up to temperatures within theaforementioned reaction temperature ranges, tar formation is favored as'is subsequent cracking thereof with the result that the reaction zone iseventually filled with a heavy, carbonaceous deposit. Therefore,'it is essential to separately preheat each cfthe rea ctants, i. e., the hydrocarbon or mixtures of hydrocarbons'arid sulfur l to such temperatures'that 'when' they are'brought together, under proper conditionsof flow, a temperature falling within the reaction temperature range is achieved before effecting contact be tween them. In practice, this is effected ordinarily by separately preheating each of the re- H actants to temperatures within the reaction temperature range.

After the separately preheated hydrocarbon reactant and sulfur are mixed and allowed to 'react for the reaction time indicated by the operating temperature, the temperatures of the reaction mixture are immediately lowered to below about 450 C., in practice, appreciably below 450 C. in order to avoid over reaction in the system after leaving the reactor. achieved suitably by spraying the efiiuent of the reactor with a liquid. In preparing the tars, reaction is eifected preferably at atmospheric pressure or sufficient pressure caused to flow the be achieved with a pressure drop of about l-20 pounds across the coil, depending upon the size of the pipe and thelength of the coil. Turbulent flow promotes heat transfer and assures good testing of the reacting variables of sulfur and hydrocarbon reactants.

The following detailed example is for the purpose of illustrating the production of thiophene and tar, in accordance with the foregoing process.

EXAMPLE I Preparation of sulfur-containing lay-product tar Normal butane was charged into a preheater at the rate of 39 grams per minute and heated to a temperature of 645 C. Sulfur was charged to a separate preheater at a rate of 145 grams per minute and heated to a temperature of 645 C. The two streams were sent through a mixing nozzle and thence through a baffled tube reactor of 200 cc. volume constructed of 27 per cent chromium, stainless steel maintained at a temperature of 665 C. The reaction product'was quenched with a water spray passed through a emu cottreu precipitator to remove tar inist This may be With this fandscrubbed through a hot countercurrent" caustic toweri separatedin a water cooler and ice trap. The

Liquid product was condensed and residual gas was metered. Of the hydrocarbon material charged, per cent was converted to light product and tar, in approximately equal amounts. Fractionation of a portion of thestabilized (i. e.,- afterremoval of C4 hydrocarbon and lighter constituents) light product showed the following composition:

The tar thus obtainedwas a dark, viscous mass having the following characteristics:

Composition:

Carbon l- 25 per cent Hydrogen 1.8 per cent Sulfur -c 73.0 per cent Properties:

Molecular weight (average) 317 Specific gravity 1.5066 at(82F. -Pour point --15 F.

SJU. V 46 seconds at 210 F.

The tar described in Example I above is illustrative of the tars reacted herein with an oil of the type described above. The tar is substantially soluble in benzene and in aqueous alkaline solutions indicating the acidic nature of its constituents. It has been found, however, that the composition of the tars varies with the aliphatic hydrocarbon from which they are prepared and varies as wellwith the conditions under which they are prepared. As such, it is not possible at this time to ascribe any representative formula or formulae to thetars, and they can be more I accurately defined, therefore, as reaction products in terms of the reactants from which they are derived and the reaction conditions under which they are derived.

The reaction products contemplated herein are illustrated in the following example:

' EXAMPLE II Preparation of lard oil-tar (Example I) reaction product Lard oil (280 grams) and the tar of Example I (57 grams) wereheated together at approxi mately 180 C. fora period of 4 hours and 45 minutes. During this time the reaction mixture was continuously agitated and during the greater part of this period, hydrogen sulfide was evolved which is indicative of reaction taking place between the reactants. The reaction product was cooled andfiltered through Super Filtrol. The filtrate was a dark-colored liquid containing 11.8

per cent of sulfur (product I).

The reaction product-was tested in order to de- 'termine its corrosive or non-corrosive nature. in

the following "manner. One per cent by weight "of the reaction product was blended in neutral mineral oil (S. U. V. 53 secondsat'210" F.) and a bright copper strip was immersed in the resulting blend. "'A fter'24 hours at 100 C. the copper strip was only slightly stained. A second, one per cent blend ofthe reaction product in a highly aromatic-fraction (boiling range 91 C. to 141C.)

was agitatedwith a small amount of metallic mercury for 3 minutes. The mercury was not --'tarnished by tliis treatment. Accordingly, the

reaction product is substantially non-corrosive.

The foregoing example of a typical reaction product is but illustrative, inasmuch as the reaction temperatures used in preparing the same may be varied considerably. For example, temperatures of the order of 160 C. to about 250C. are generally used, with preference being given to those within the range from about 180 C. to about 200 C. Similarly, the reaction time may be varied and depends, to a large degree, upon the quantities of materials which are reacted together and upon the reaction temperatures used. In general, longer reaction times should be used, .all other conditions being constant, with lower temperatures of the aforesaid temperature ranges; correspondingly, shorter reaction times may be used with temperatures at the upper end of the aforesaid temperature ranges. As a guide to preparing sulfur-containing reaction products of the aforesaid type, it is preferred that the re- This characteristic may be determined as indicated -.above in Example II, wherein the corrosive nature of hydrocarbon blends of the reaction product were tested with a copper strip and with metallic :mercury. A reaction product is considered substantially non-corrosive when the copper strip is not discolored or is only slightly stained, or when the mercury in contact therewith is not tarnished.

Considerable variation also obtains in regard to the relative proportions of oil and tar reactants. The sulfur content of the reaction product may be controlled, by varying the proportions of lard oil and tar. Increasing the ratio of lard oil decreases the sulfur content and increasing the ratio of tar increases the sulfur content. Thus, if a sulfur content of 10-12 per cent is desired, the relative proportions are: 1 part of tar by weight to 5 parts of lard oil.

To demonstrate the effectiveness of the reaction products of this invention as oil-improving agents, lubricating oil blends containing typical reaction products were subjected to the tests described below:

CORROSION TEST A section of a bearing containing a cadmiumsilver, alloy surface and weighing about 6.0 grams, was placed in a solvent-refined Pennsylvania oil of S. U. V. of 53 seconds at 210 F. The oil was heated to 175 C. for 22 hours while a stream of air was bubbled against the surface of the bearing. The loss in weight, in mgms, of the bearing is indicative of the corrosiveness of the oil. In each case a sample of the oil containing the characterizing agent was run concurrently with a sample of straight or uninhibited oil. Each sample contained a section cut from the same bearing. The results are set forth in Table I below:

The oil employed in this test was a solventrefined oil having a S. U. V. of 45 seconds at 210 F. and the test procedure involves the following: The tests were carried out in a single cylinder lauson engine operated continuously over a time interval of 36 hours with a cooling medium held at a temperature of about 212 F. and the oil temperature held at about 280 F. The engine was operated at a speed of about 1830 R. P. M. At the end of the test, the oil was tested for acidity (in terms of the Neutralization Number or N. N.) and viscosity. The results of these tests are tabulated in Table II below.

It will be apparent from the foregoing test data that the reaction products contemplated herein are efiective corrosion and oxidation inhibitors. When incorporated in oil, these reaction products may be used in relatively small amounts, depending upon the intended purpose and upon the oil with which they are used. When used as corrosion and oxidation inhibitors, concentrations from about 1 per cent to about 3 per cent are generally satisfactory, with concentrations of the order of 2 per cent being preferred. They may also be used in cutting oils or as cutting oils per se. Cutting oils, however, may contain substantially larger amounts such as of the order of 10-20 per cent.

These reaction products may also be used as rubber accelerators. Numerous other uses and applications will be readily apparent to those skilled in the art from the foregoing discussion of the composition of these reaction products and from the typical procedures for preparing them.

It is to be understood that although certain preferred reaction products and certain preferred procedures for preparing the reaction products contemplated herein have been illustrated hereinabove, the invention is not limited to the said products or procedures, but includes within its scope such changes and modifications as fairly come within the spirit of the appended claims.

This application is a division of an application, Serial No. 654,222, filed March 13, 1946, now matured into U. S. Patent No. 2,480,650, issued August 30, 1949.

We claim:

1. As a new composition of matter, a sulfurcontaining reaction product obtained by reacting about 5 parts by weight of a triglyceride oil with about 1 part by weight of a sulfur-containing by-product tar, at a temperature of from about C. to about 250 0., said tar being obtained by: separately preheating sulfur and a hydrocarbon selected from the group consisting of normal butane, normal butenes, butadienes, pentanes, pentenes, pentadienes, hexanes, hexenes and hexadienes, said hydrocarbon having at least four carbon atoms in a straight chain, to temperatures such that combining said sulfur and said hydrocarbon will provide a reaction mixture having a temperature varying between 450 C. and about 760 C. when the said hydrocarbon is one of the aforesaid four-carbon hydrocarbons, and between 450 C. and about 700 C. whenthe said hydrocarbon is one of the aforesaid fiveand six-carbon hydrocarbons; mixing the preheated sulfur and the preheated hydrocarbon in a weight ratio of sulfur to hydrocarbon varying between about 0.5 and about 4.0; reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C. and about 760 C. when the said hydrocarbon is one of the aforesaid four-carbon hydrocarbons, and between 450 C. and about 700 C. when the said hydrocarbon is one of the aforesaid fiveand six-carbon hydrocarbons, for a contact time of from about 0.01 second to several seconds, to produce a reaction mixture containing thiophene and a sulfur-containing tar; reducing the temperature of said reaction mixture to less than 450 C.; and separating said tar from said mixture.

2. As a new composition of matter, a sulfurcontaining reaction product obtained by reacting about 5 parts by weight of lard oil with about 1 part by weight of sulfur-containing lay-product tar, at a temperature of from about 160 C. to

' about 250 0., said tar being obtained by: separately preheating sulfur and a hydrocarbon selected from the group consisting of normal butane, normal butenes, butadienes, pentanes, pentenes, pentadienes, hexanes, hexenes and hexadienes, said hydrocarbon having at least four carbon atoms in a straight chain, to temperatures such that combining said sulfur and said hydrocarbon will provide a reaction mixture having a temperature varying between 450 C. and about 760 C. when the said hydrocarbon is one of the aforesaid four-carbon hydrocarbons, and between 450 C. and about 700 C. when the said hydrocarbon is one of the aforesaid fiveand six-carbon hydrocarbons; mixing the preheated sulfur and the preheated hydrocarbon in a weight ratio of sulfur to hydrocarbon varying between about 0.5 and about 4.0; reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C. and about 760 C. when the said hydrocarbon is one of the aforesaid four-carbon hydrocarbons and between 450 C. and about 700 C. when the said hydrocarbon is one of the aforesaid fiveand six-carbon hydrocarbons, for

a contact time of from about 0.01 second to sev- 10 eral seconds, to produce a reaction mixture containing thiophene and a sulfur-containing tar; reducing the temperature of said reaction mixture to less than 450 C.; and separating said tar from said mixture.

3. As a new composition of matter, a sulfurcontaining reaction product obtained by reacting about 5 parts by weight of lard'oil with about 1 part by weight of a sulfur-containing by-product tar, at a temperature of from about C. to about 250 C., said tar being obtained by: separately preheating sulfur and normal butane to temperatures such that combining said sulfur and normal butane will provide a reaction mixture having a temperature varying between 450 C. and about 760 C, mixing the preheated sulfur and the preheated normal butane in a weight ratio of sulfur to butane varying between about 0.5 and about 4.0; reacting said preheated sulfur and said preheated normal butane at a temperature falling between 450 C'. and about 760 C. for a contact time of from about 0.01second to several seconds to produce a reaction mixture containing thiophene and a sulfur-containing tar; reducing the temperature of said reaction mixture to less than 450 C., and separating said tar from said mixture.

SIGMUND J. LUKASIEWICZ. ALEXANDER N. SACHANEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,167,439 Kaufman July 25, 1939 2,181,964 Chittick Dec. 5, 1939 OTHER REFERENCES Winslow and Eichhorn, Veterinary Material Medica, ed. 8, pp. 462-463, American Veterinary Publishing Co-., Chicago, 1919.

Hagers Handbuch der Pharmazeutischen Praxis, vol. 2, p. 2.82, Springer, Berlin, 1927.

Sollmann, Manual of Pharmacology, ed. 7, pp. 129-130, Saunders, Philadelphia, 1948.

Claims (1)

1. AS A NEW COMPOSITION OF MATTER, A SULFURCONTAINING REACTION PRODUCT OBTAINED BY REACTING ABOUT 5 PARTS BY WEIGHT OF A TRIGLYCERIDE OIL WITH ABOUT 1 PART BY WEIGHT OF A SULFUR-CONTAINING BY-PRODUCT TAR, AT A TEMPERATURE OF FROM ABOUT 160* C. TO ABOUT 250* C., SAID TAR BEING OBTAINED BY: SEPARATELY PREHEATING SULFUR AND A HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF NORMAL BUTANE, NORMAL BUTENES, BUTADIENES, PENTANES, PENTENES, PENTADIENES, HEXANES, HEXENES AND HEXADIENES, SAID HYDROCARBON HAVING AT LEAST FOUR CARBON ATOMS IN A STRAIGHT CHAIN, TO TEMPERATURES SUCH THAT COMBINING SAID SULFUR AND SAID HYDROCARBON WILL PROVIDE A REACTION MIXTURE HAVING A TEMPERATURE VARYING BETWEEN 450* C. AND ABOUT 760* C. WHEN THE SAID HYDROCARBON IS ONE OF THE AFORESAID FOUR-CARBON HYDROCARBONS, AND BETWEEN 450* C. AND ABOUT 700* C. WHEN THE SAID HYDROCARBON IS ONE OF THE AFORESAID FIVE- AND SIX-CARBON HYDROCARBONS; MIXING THE PREHEATED SULFUR AND THE PREHEATED HYDROCARBON IN A WEIGHT RATIO OF SULFUR TO HYDROCARBON VARYING BETWEEN ABOUT 0.5 AND ABOUT 4.0; REACTING SAID PREHEATED SULFUR WITH SAID PREHEATED HYDROCARBON AT A REACTION TEMPERATURE VARYING BETWEEN 450* C. AND ABOUT 760* C. WHEN THE SAID HYDROCARBON IS ONE OF THE AFORESAID FOUR-CARBON HYDROCARBONS, AND BETWEEN 450* C. AND ABOUT 700* C. WHEN THE SAID HYDROCARBON IS ONE OF THE AFORESAID FIVE- AND SIX-CARBON HYDROCARBONS, FOR A CONTACT TIME OF FROM ABOUT 0.01 SECOND TO SEVERAL SECONDS, TO PRODUCE A REACTION MIXTURE CONTAINING THIOPHENE AND A SULFUR-CONTAINING TAR; REDUCING THE TEMPERATURE OF SAID REACTION MIXTURE TO LESS THAN 450* C.; AND SEPARATING SAID TAR FROM SAID MIXTURE.