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United States Patent O?Ice Patented Aug 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.
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