2,899,444 United States Patent O?ice Patented Aug. 11, 1959

2 Under the presently described conditions, it has been found that tetrahydrothiophene is obtained in high yields 2,899,444 and is separated from the reaction product as a clear, SYNTHESIS OF TETRAHYDROTHIOPHENE colorless product. The extremely pure, colorless product obtained is directly useful, without further processing, as Bernard Loev, Philadelphia, and John T. Massengale, a chemical intermediate, fuel odorant, or for other pur West Chester, Pa., assignors to Pennsalt Chemicals poses for which tetrahydrothiophene is adapted. Corporation, a corporation of Pennsylvania Space velocity, a variable to which particular atten No Drawing. Application April 3, 1957 tion is directed in the present synthesis, is a measure of Serial No. 650,287 the rapidity with which a reactant is passed through the effective reaction zone, that is, the zone in which con 10 Claims. (Cl. 260-329) ditions, such as temperature, the presence of catalyst, and the like, are conducive to reaction. The higher the space velocity, the more reactant is passed through the This invention relates to synthesis of a sulphur com reaction zone in a given time; accordingly, the higher the pound, and more particularly, to a process for the prep space velocity, the less time does any given portion of aration of tetrahydrothiophene by reaction of tetrahy the reactants spend in the reaction zone, or, in other drofuran with hydrogen sulphide under conditions con words, the shorter is the dwell time or contact time. ducive to maximum yields with minimum color body For the present catalytic reaction, the catalyst bed forms formation. the reaction zone, and space velocity is measured as the Tetrahydrothiophene is used as an odorant for fuel gas, in which application it is of particular importance be gaseous volume of reactant per volume of catalyst per hour, corrected to 0° C. and one atmosphere pressure. cause of superior oxidation stability as compared to mer captans used for this purpose. It is also of value as a Catalyst volume is taken as the gross volume of the cat chemical intermediate: the sulphoxide of tetrahydrothio— 25 alyst bed. Space velocity for the reaction of multiple phene is used to improve ignition characteristics of diesel reactants may be measured with respect to the totality of fuel; the sulphone is useful as a solvent, in extraction reactants, or as regards any individual reaction compo of aromatic compounds from petroleum and in synthesis nent. In accordance with this invention, it has been found of polyacrylonitriles; chlorinated tetrahydrothiophene is that in the synthesis of tetrahydrothiophene, the tetra used in preparation of insecticides, fungicides and germi 30 hydrofuran space velocity is an individually controlling cides, and so forth. factor. A variety of syntheses of tetrahydrothiophene are pro In one embodiment of the invention, tetrahydrofuran is posed in the prior art. All of these procedures suffer contacted with hydrogen sulphide in the presence of from various disadvantages, such as expensiveness of re alumina as catalyst. The hydrogen sulphide should be agents and low yields. Under conditions conducive to 35 present in excess, in a molar ratio, with respect to tetra high yields, formation of color bodies has been observed. hydrofuran, ranging from about 6:1 to about 2:1. A These are impurities of unknown composition which are greater excess of hydrogen sulphide than about 6:1 gen probably reaction byproducts. To remove these colored erally does not improve the yields of tctrahydrothiophene impurities and purify the tetrahydrothiophene requires additional, troublesome and costly processing steps. 40 obtained, and is therefore uneconomical, while the yield It is an object of this invention to provide a novel becomes less as the molar ratio decreases, and ratios be synthesis of tetrahydrothiophene. low 2:1 are unfavorable. A particular object of this invention is to provide a If desired, part or all of the hydrogen sulphide em novel process for conversion of tetrahydrofuran to ployed as a reactant may be replaced by carbon disul tetrahydrothiophene, by reaction of tetrahydrofuran with 45 phide. A reaction mixture comprising either (a) a mix hydrogen sulphide in the presence of alumina as catalyst, ture of tetrahydrofuran, hydrogen sulphide and carbon whereby tetrahydrothiophene is obtained in high conver disulphide, or (b) a mixture of tetrahydrofuran, carbon sions and yields, in substantially colorless form. disulphide and water may be used. Only half so much A further object is to provide a synthesis of tetrahy CS2 is required as H25, on a molar basis to supply a drothiophene from tetrahydrofuran wherein the space 50 molar equivalent quantity with respect to sulphur fur velocity of the tetrahydrofuran is controlled so as to in nished, and the quantity of CS2 employed is adjusted ac hibit color body formation. cordingly, to produce the S:tetrahydrofuran ratio of from Another object is to provide a novel process com about 2:1 to about 6:1 also preferred with hydrogen prising contacting tetrahydrothiophene with carbon disul sulphide alone, as described above. Water need be phide in the presence of water to form tetrahydrothio 55 phene. present only in trace amounts in the reaction mix ture, and may be supplied by the reaction of the These and other objects of the present invention will be apparent from a consideration of the following speci tetrahydrofuran with the hydrogen sulphide. Effec ?cation and claims. tively, it is believed, hydrogen sulphide, formed by re In accordance with this invention, tetrahydrothiophene 60 action of carbon disulphide with water under the re is prepared by reaction of tetrahydrofuran with hydro action conditions, is the active reagent producing con gen sulphide in the presence of alumina at a tempera version of the tetrahydrofuran to tetrahydrothiophene. ture of from about 350—380° C., preferably about 375° Thus, where reference is made herein and in the ap C., and at a tetrahydrofuran space velocity of from about pended claims to contacting tetrahydrofuran with hy 100 to about 110, preferably about 105 gas volume/cat 65 drogen sulphide, this language is intended to refer to the alyst volume/hour. use of reaction mixtures comprising hydrogen sulphide, 2,899,444 3 4 or carbon disulphide in the presence of water, or mix unit time is commercially and economically undesirable, tures of hydrogen sulphide and carbon disulphide. The and the productivity of the process is diminished, While at use of carbon disulphide as a reactant has the advantage space velocities above this range, color body formation of eliminating the quantities of water formed as a reaction is encountered. product by a reaction mixture employing hydrogen sul— In the present reaction, when hydrogen sulphide is the phide as the sulphur-containing reactant, and may lead, sole or chief sulphur-containing reactant, water is formed, furthermore, to improved yields, under some reaction as represented by the equation conditions. The catalyst for the reaction comprising alumina, that is aluminum oxide. Generally, alumina itself will ad— 0 vantageously be employed to form the catalyst bed. The presence of adjuvants and promoters in the catalyst com O S position is usually unnecessary, but the use of substan tially pure alumina is not required, and a technical grade When the e?luent from the reaction Zone is condensed, of alumina, containing various impurities, such as thoria, water will be present in the condensate. If at least part silica or chromia, may be used if desired. Preferably, of the hydrogen sulphide is replaced by carbon disulphide, the catalyst is in granulated or pulverized form, and of water is consumed in hydrolysis of carbon disulphide to a size ranging from about 30 mesh up to about one inch hydrogen sulphide and carbon dioxide, and the ellluent pellets; advantageously, about 14 mesh size up to 1/2 inch will contain less aqueous component. In addition to pellets of alumina will be used. Ordinarily special pro 20 water, besides product tetrahydrothiophene, the conden cedures to avoid problems of local overheating or poor sate may contain unreacted tetrahydrofuran and also, de‘ heat transfer, such as the use of a ?uidized catalyst bed, pending on the temperature of condensation, unreacted are not required, and the catalyst life usually is in hydrogen sulphide. The tetrahydrothiophcne may con de?nitely long. As noted above, the catalyst bed size veniently be separated from the condensate by distilla is a factor affecting the space velocity of the reactants, tion: tetrahydrofuran is distilled off at 50-70“ C., water and will be adjusted accordingly, in relation to the rc~ is azeotroped out at about 88° C., and tetrahydrothio actor volume and the rate of gas flow of the tetrahydro phene is collected as a limpid, water-white product at 119° C. furan reactant. The factors of temperature and space velocity are It will be understood that in commercial operation, un converted reactants may be recycled and the process interrelated in their effect on the present reaction. In ac 30 cordance with this invention, the conversion of tetra made continuous if desired. Furthermore, instead of hydrofuran to tetrahydrothiophene in good yields and to atmospheric pressure, the present process may be car produce a product substantially free of color bodies is ried out at either sub- or super-atmospheric pressure. In an illustrative operation, the description of which carried out at a temperature of from about 350° to about 380° C., and at a tetrahydrofuran space velocity of is non-limiting, the process of the invention is carried out as follows: from about 100 to about 110 gas volume/catalyst vol~ The apparatus employed is constructed of stainless steel ume/ hour. It has been found that either at a tempera and comprises metering feed pumps from which tetra ture of 400° C. or above, within the preferred space hydrofuran and hydrogen sulphide are fed into a pre velocity range, or at a space velocity exceeding the pre sently preferred range, but at lower temperatures, the 40 heater tube in which the reactants are mixed and the tetrahydrothiophene product obtained in accordance with tetrahydrofuran is gasi?ed. The preheater tube leads this process is contaminated by colored impurities which into the top of a heated reactor tube, in which a hori~ zontal catalyst bed of 8~l4 mesh alumina lies across the are dil?cult or impossible to remove by puri?cation proc path of the gaseous reactant mixture. The effluent from esses such as distillation. On the other hand, when oper the reactor is passed through a condenser, cooled with ated under the presently adduced conditions, the present ~15 process leads to formation of extremely pure tetrahy ice or a Dry-Ice-acetone mixture, and collected in a chilled receiver. drothiophene, as a substantially colorless and water In starting up, hydrogen sulphide is passed through white liquid product. Temperature as referred to herein is the temperature the apparatus at the rate to be used in the reaction, for 50 at least one hour, to condition the catalyst. The tempera of the reactants initially, as they contact the catalyst bed. ture just above the catalyst bed is adjusted to the desired Within the catalyst bed, the temperature is generally reading by adjusting the temperature of the bath sur somewhat, irregularly, higher, by about 35—40° C., as a result of the heat evolved by the reaction. The preferred rounding the reactor tube, and then the tetrahydrofuran is passed in at the rate used in the run. temperature of the reactants for the process is about In a one-inch diameter reactor tube, at a tetrahydro 375° C. As the temperature is diminished, yields de- ' furan flow rate of 0.01 mole per minute, a catalyst bed crease, and temperatures below about 350° C. give un~ 1 inch in diameter and 10 inches deep is used to produce a favorably low yields. Above about 380° C., the for tetrahydrofuran space velocity of 105 cc./cc./hr. In mation of color bodies may occur. As noted in the above discussion of space velocity comparative runs, showing the effect of higher space measurement, at a high space velocity, the reactant spends velocities, a bed 1 inch in diameter and 3.5 inches deep is used at the same ?ow rate, to produce a space velocity less time in the reaction zone than at a lower space velocity. It would be expected that, the less time spent of 300 cc./cc./hr. The total space velocity of the re in the reaction zone, the less opportunity ‘would there be actants varies, from 1500 cc./cc./hr. at a 4:1 HzS/tetra for undesired side reactions to proceed. Thus, for ex hydrofuran ratio and a 300 cc./cc./hr. tetrahydrofuran ample, in the conversion of an alcohol to a mercaptan space velocity to 315 cc./ cc./ hr. at a 2:1 H2S/tetrahydro— by reaction with hydrogen sulphide, as the space velocity furan ratio and a 105 cc./cc./hr. tetrahydrofuran space decreases, byproduct formation increases. It is side re velocity. The passage of tetrahydrofuran into the re actions and byproduct formation which are responsible action zone together with the hydrogen sulphide is con for color body formation. Tto the contrary, however, it tinued for 4-6 hours, while the reactor ef?uent is collected has been found that in the present reaction, low tetra- " in the condenser receiver. hydrofuran space velocities, and consequent longer dwell When the introduction of reactants is terminated, the times, favor production of a pure, colorless product. A receiver is warmed to room temperature, whereupon the tetrahydrofuran space velocity of from about 100 to hydrogen sulphide is evolved. The water layer is sepa about 110 gas volume/ catalyst volume/ hour is preferred. rated from the crude product, after which the organic At lower space velocities, the decrease in throughput per layer is distilled and tetrahydrothiophene collected. 2,899,444 5 6 In the following table are summarized a number of 5. The process of claim 4 wherein a mixture of said experiments carried out under varying conditions. tetrahydrofuran and said hydrogen sul?de is passed into the presence of said alumina. Hi8! space temp, conver- color of 6. In the process of preparing tetrahydrothiophene THF 1 THE 1 ° 0.6 sion, per- distilled on wherein tetrahydrofuran is reacted with a sulphurizing cent 4 THF agent, the improvement whereby color body formation 1. 2:1 315 375 41 yellow is avoided which comprises reacting said tetrahydro?uran 2:1 315 375 66 Do. with a mixture of hydrogen sulphide and carbon di~ 3:1 300 380 50 Do. 4:1 300 400 70 Do. sulphide, in a molar ratio of said tetrahydrofuran to the 2:1 300 400 67 Do. total sulphur in said mixture of hydrogen sulphide and 2:1 105 410 63 Do. 5. 5:1 105 410 86 Do. carbon disulphide of ‘from about 1:2 to about 1:6, at a 6: 1 105 375 94 colorless temperature of from about 350° to 380° C., in the 2:1 105 375 86 Do. I 2:1 105 375 90 Do. presence of alumina as a catalyst, and at a space velocity 2:1 105 350 71 Do. of said tetrahydrofuran in respect to said alumina of from 15 about 100 to about 110 gas volume/ catalyst volume/hour. 1 Molar ratio of hydrogen sulphide to tetrahydrofuran in feed. 7. The process of claim 6, wherein said molar ratio 1 Space velocity of tetrahydroiurau, calculated as gaseous volume of tetrahydrofuran in cubic centimeters, per gross volume of catalyst in is about 1:2. cubic centimeters, per hour. a Reactor bath temperature. 8. The process of claim 7, wherein said temperature is 4 Conversion, based on tetrahydrofuran fed into system. about 375 ° C., and said space velocity is about 105 gas i 0.005 mole CS2 plus 0.01 mole H28; the HQS:CS2:TIIF molar ratio is voL/ catalyst vol./ hour. 1:0.5z1, giving an effective S:THF ratio of 2:1. 9. In the process of preparing tetrahydrothiophene As will be evident from the above data, at a space wherein tetrahydrofuran is reacted with a sulphurizing velocity on the order of 300 oc./cc./hr. or above, only agent, the improvement whereby color body formation low conversions are obtained at varying temperatures and is avoided which comprises reacting said tetrahydrofuran H2S:THF ratios. At a space velocity of 105 cc./oc./hr., 25 with carbon disulphide in the presence of Water, in a decreasing the temperature from 410“ to 375 ° is found to molar ratio of said tetrahydrofuran to said carbon di increase the conversion, which is generally contrary to sulphide from about 1:1 to 1:3, at a temperature from usual temperature effects in chemical reactions; as the about 350° to about 380° C., in the presence of alumina temperature is further decreased, however, the expected as a catalwt, and at a space velocity of said tetrahydro drop in conversion produced is noted at 350° C. The 30 furan with respect to said alumina of from about 100 to hydrogen sulphide to tetrahydrofuran ratio is advan about 110 gas volume/catalyst volume/hour. tageously 6:1, for maximum yields, but good yields are 10. The process of claim 9, wherein said molar ratio obtained at down to 2: 1. Finally, to obviate color forma is about 1:3, said temperature is about 375° C., and said‘ tion, both temperatures and space velocities within the space velocity is about 105 gas vol./catalyst vol./hour. ranges speci?ed herein are required. While the invention has been described with reference References Cited in the ?le of this patent to various particular preferred embodiments thereof, it UNITED STATES PATENTS will be appreciated that variations and modi?cations can be made within the scope of the appended claims. 2,539,325 Prochazka ______Jan. 23, 1951 What is claimed is: 40 1. In the process of preparing tetrahydrothiophene OTHER REFERENCES wherein tetrahyd-rofuran is reacted with hydrogen sul Fischer: Chemical Abstracts, vol. 18, p. 17141 (1924). ?de, the improvement whereby color body formation is Abstract of: Biochemische Zeitschrift, vol. 141, pp. 540-4 avoided which comprises reacting said tetrahydrofuran (1923). with said hydrogen sul?de in a molar ratio, respectively, 45 Hirao et al.: Chemical Abstracts, vol. 49, p. 6909c of from about 1:2 to about 1:6, at a temperature of from (1955). Abstract of: Journal of the Pharmaceutical about 350° C. to about 380° C., in the presence of Society of Japan, vol. 74, pp. 446-449 (1954). alumina as catalyst, and at a space velocity of said tetra Tronova et al.: Chemical Abstracts, vol. 45, p. 94241’ hydrofuran with respect to said alumina of from about ( 1951). Abstract of: Zhurnal Obschei Khimii (Journal 100 to about 110 gas volume/catalyst volume/hour. 50 of General Chemistry), vol. 21, pp. 742-9 (1951). 2. The process of claim 1 wherein said molar ratio is Dubrovina et al.: Chemical Abstracts, vol. 41, p. 1653i, about 1:6. and l654a,b 1947). Abstract of: Journal of General 3. The process of claim 2 wherein said temperature is Chemistry (U.S.S.R.), vol. 16, pp. 843-50 (1940). about 375° C. Prokina et al.: Chemical Abstracts, vol. 31, p. 1399' 4. The process of claim 3 wherein said space velocity 55 ( 1937). Abstract of: Journal of General Chemistry is about 105 gas volume/catalyst volume/hour. (U.S.S.R.), vol. 7, pp. 1868-73 (1937). UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,899,444 August 11 , 1959 Bernard Loev et :11. It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below. Column 3, line 9, for "comprising" read —- comprises ——; line 69f for "Tto" read —- To -—; column 5, in the table, heading to column 5 thereof‘ for "color of distilled THF" read -- color of distilled tetrahydrothiophene -~-. ‘ Signed and sealed this 25th day of October 1960.

(S EAL) Attest: KARL H. AXLINE' ROBERT C. WATSON Attesting Of?cer Commissioner of Patents