Mercaptans by catalytic cleavage of organic sulfides

#This invention pertains to the preparation of mercaptans. In a more specific aspect of this invention it pertains to the preparation of mercaptans by the cleavage reaction of organic sulfides with hydrogen sulfide. In another of its aspects this invention relates to the catalyzed cleavage of organic sulfides. In yet another of its aspects this invention relates to the cleavage of n-alkyl sulfides. In yet another aspect of this invention it pertains to the improvement in the conversion of reactants in the process of preparing mercaptans from the cleavage reaction of organic sulfides with hydrogen sulfide in the presence of a sulfactive catalyst.

#It is well known in the art to prepare mercaptans by the cleavage of organic sulfides with hydrogen sulfide in the presence of a sulfactive catalyst. This reaction has been modified by the use of various promoters for the catalysts and by the presence of modifying compounds along with the reactants. It has been found, however, that the cleavage reaction of n-alkyl sulfides is difficult with conventionally used catalysts. The cleavage of n-alkyl sulfides requires higher temperature than does the cleavage of secondary and tertiary sulfides. This causes the cleavage reaction of normal alkyl sulfides to lead to more by-products which are difficult to separate and which can be undesirable for other reasons.

#A catalyst has now been discovered with which higher conversion and higher selectivity can be obtained in the cleavage of organic sulfides to the corresponding mercaptans using hydrogen sulfide. Higher conversion and higher selectivity in the reaction of normal alkyl sulfides has been noted particularly. It has also been discovered that the presence of carbon disulfide in the reaction mixture enhances the conversion of reactants to the desired mercaptan products.

#1.0 g phosphotungstic acid (Mallinckrodt P.sub.2 O.sub.5 .multidot. 24WO.sub.3 .multidot. XH.sub.2 O) was dissolved in 100 ml. distilled water and 50 g alumina (A1.sub.2 O.sub.3) was added and thoroughly stirred to insure complete contact of the fresh acid solution with the support. The water was stripped and the catalyst was dried at 260.degree. C for 2 hours in a stream of H.sub.2 S. No further activation was required.

#A stainless steel tubular reactor with heaters (1/2 .times. 18 inch diameter .times. length) was charged with 10 ml. glass beads, 50 g (70 ml.) of catalyst as prepared in Example I and another 10 ml. layer of glass beads. The reactor was heated to the operating temperature and pressurized with H.sub.2 S at 450 or 500 psig. n-Dibutyl sulfide was fed at the rate of 3.0 ml./minute. 810 g H.sub.2 S, 348 g sulfide, and, optionally 6 g of CS.sub.2 were passed through the apparatus. The results are tabulated below:

#Table I ______________________________________ Conversion of sulfide % Conversion with 6 g of CS.sub.2 T.degree. C No CS.sub.2 present in the feed present in the Feed % ______________________________________ 204 6.4 7.8 232 8.1 28.7 260 23.4 69.2 288 61.2 79.1 315.5 73.9 87.9 ______________________________________