United States Patent [191 [11] 3,968,155 Gue'rin [451 July 6, 1976 [541 PROCESS FOR PREPARED PERCHLOROMETHYL MERCAPTAN BY Primary Examiner—Lewis Gotts CHLORINATION OF CARBON DISULFIDE Assistant Examiner—D. R. Phillips Attorney, Agent, or Firm—-Pennie & Edmonds [75] Inventor: Jean Guérin, Grenoble, France [73] Assignee: Produits Chimiques Ugine [57] ABSTRACT Kuhlmann, Paris, France Perchloromethyl mercaptan is prepared with about [22] Filed: Apr. 28, 1975 10% saving in raw materials by an improved process [21] Appl. No.: 571,919 comprising (i) chlorinating carbon disul?de in the presence of iodine to produce a ?rst chlorinated li quor, (ii) separating said liquor by distillation into a [30] Foreign Application Priority Data high-boiling fraction of technical-grade per June 21, 1974 France ............................ .. 74.21586 chloromethyl mercaptan and a low-boiling fraction, A, (iii) chlorinating fraction A in the presence of iodine [52] US. Cl. ....................... .. 260/543 H; 260/607 R and absence of any substantial amount of metallic ha [51] Int. Cl.2 .............. .. C07C 145/00; C07C' 149/16 lides to produce a second chlorinated liquor, (iv) sep [58] Field of Search ............. ..'. .............. .;. 260/543 1-1 arating said second liquor by distillation into a high boiling fraction of crude perchloromethyl mercaptan [56] References Cited and a second low-boiling fraction, B, consisting essen UNITED STATES PATENTS tially of sulfur dichloride, and (v)' heating fraction B at about 90°—150°C in presence of a metallic halide to 2,664,442 12/1953 Kamlet .......................... .. 260/543 H form sulfur_monochloride and regenerate chlorine. OTHER PUBLICATIONS Chem. Review vol. 58 pp. 509-512 (1958). 5 Claims, 5 Drawing Figures US. Patent July 6, 1976 Sheet1of2 3,968,155 v IiIilil lllll 1 II I (Tl °°\, >>/ Now_m HWVW IIJII || ON 'WX 1 N9Nowwon I U.S. Patent July 6, 1976 Sheet 2of2 ’ 3,968,155 FIG. 2 35 @ 36 JUL 1 32 i77 33 3,968,155 1 2 In most of the prior processes, the higher boiling PROCESS FOR PREPARED PERCI-ILOROMETI-IYL PCMM and sulfur monochloride are isolated by distil MERCAPTAN BY CHLORINATION OF CARBON lation under reduced pressure being delivered at the DISULFIDE " tail end or foot of the distillation unit while the lower boiling fractions comprising carbon disul?de, sulfur The present invention provides an improved process dichloride and carbon tetrachloride are delivered at the for preparing perchloromethyl mercaptan by chlorina head of the distillation unit and are then transformed tion of carbon disul?de. Perchloromethyl mercaptan, into a mixture of carbon tetrachloride and sulfur mono CCl3SCl, hereinafter abbreviated as PCMM, is known chloride by chlorination according to the overall equa also as trichloromethanesulfenyl chloride. Reduction tion VI, using a metallic chloride as catalyst: of PCMM with stannous chloride or tin and hydrochlo 2.5 SCI; + 0.5 CS2 + 0.25 Clz -> 0.5 CCL, + l.75 ric acid produces thiophosgene or thiocarbonyl chlor SQCIL, (VI) ide CSCI2. Both thiophosgene and PCMM itself are commercially useful as raw materials in the production of many organic sulfur compounds. See KIRIQ SUMMARY OF THE INVENTION OTHMER, ENCYCLOPEDIA OF CHEMICAL Present inventor has now surprisingly established TECHNOLOGY, Second Edition, Volume 4, page 372 that if the above mentioned chlorination of the low (1964); and, for example, US. Pat. Nos. 2,553,771; boiling fraction is, in contrast to the usual practice, 2,653,155; and 2,713,058. 20 carried out in the substantially complete absence of such metallic halide catalyst but in the presence, in BACKGROUND OF THE INVENTION stead, of iodine, the’ chlorine action takes place accord According to the known procedures, PCMM is pro ing to the overall equation (VII) with the formation of duced by chlorination of carbon disul?de in the pres a mixture of PCMM, sulfur monochloride and sulfur ence of small quantities of iodine, about 0.005 to 2% 25 dichloride: ' (based on weight of carbon disul?de) as catalyst, ac 2.5 sci2 + 0.5 cs2 + 1.4 cl2 -» 0.5 CCI,,SC] + 0.1 cording to the overall reaction I: $2012 + 2.8 sci2 _ > (vn) Present inventor has furthermore ascertained that 30 when the (second) liquor, chlorinated according to This reaction theoretically consumes 409 g of carbon equation VII is submitted to distillation under reduced disul?de and 1.145 grams of chlorine per kilogram of pressure i.e., between 50 to 400 torrs, two fractions can PCMM formed, corresponding to a molar ratio Cl2/CS2 be separated, one being crude PCMM containing about equal to 3.0. However, in industrial practice the chlo 10-15% sulfur monochloride, the other being very rich rine is charged in an amount considerably smaller than 35 in sulfur dichloride but substantially free of carbon theoretical, the molar ratio Cl2/CS2 scarcely exceeding disul?de; and that this (“second”) low-boiling fraction 2.50 in order not to risk destruction of part of the (i.e., coming from the “second” distillation) decome‘ formed PCMM in the following well-known side reac poses in the presence of a metallic chloride like molyb ' tions: denum pentachloride at about 90°—l50°C to form sul- ' 40 fur monochloride and regenerate chlorine. A combina CCl_-,SCI + Clz -> CCI. + SCIZ (II) tion of these steps in succession has been found to effect an overall saving of about 10% in the raw materi CCIQSCI + $02 -> CCI, + 82C!2 (III) als required to make a given total weight of technical grade PCMM. Simultaneously reation (IV), forming carbon tetrachlo Brie?y stated, the present invention is an improved ride directly by the action of chlorine and carbon disul process for preparing perchloromethyl mercaptan ?de, can take place, particularly in the presence of light which comprises (i) chlorinating carbon disul?de in the and traces of metallic chlorides: presence of iodine to produce a ?rst chlorinated liquor, (ii) separating said liquor by distillation into a high cs2 + sci2 -> cc], + szcl2 (iv) 50 boiling fraction of technical grade perchloromethyl The extent of this reaction corresponds to at least 5% mercaptan and a low-boiling fraction, A, (iii) chlorinat of the charged carbon disul?de. After separating the ing fraction A in the presence of iodine and absence of low-boiling products by distillation (preferably at re any substantial amount of metallic halides to produce a second chlorinated liquor, (iv) separating said second duced pressure), a minimum of 1.5% of sulfur mono liquor by distillation into a high-boiling fraction of chloride remains, being difficult to remove because-its crude perchloromethyl mercaptan and a second low boiling point (138°C) is so close to that of PCMM boiling fraction, B, comprising sulfur dichloride and (v) (148°C.) heating fraction B at about 90°—l50°C in presence of a In practice, then, equation V represents the overall metallic halide (about 0.5 to 10% of molybdenum pen reaction which takes place with at best 95% yield based 60 tachloride, or ferric chloride, or tungsten chloride...) to on carbon disul?de charged: form sulfur monochloride and regenerate chlorine. This invention also provides for optional steps of acs2 + 7.5012 -> 2.5 cc], — SCI + 2.5 scl2 + 0.5 ‘ CS, (V) processing the crude perchloromethyl mercaptan. Ac cording to one embodiment of the invention, the crude Under these conditions, the consumption of reactants 65 PCMM obtained in step (iv) above is reintroduced into is raised from theoretical to at least 508 grams of car the distillation of step (ii). According to an alternative bon disul?de and 1.188 grams of chlorine per kilogram embodiment of the overall process, the crude PCMM of technical grade of PCMM, 98.5% pure. I from step (iv) is separately puri?ed by chlorination 3,968,155 3 4 under pressure lower than one bar in the presence of ing large capacity, it is advantageous to set up the pro about 100 to 2000 ppm of iodine, based on weight of cess continuously, carrying out in successive steps a PCMM. The sulfur dichloride thus formed is then elim multistage chlorination of carbon disul?de, a distilla inated by distillation to produce a high-purity technical tion under reduced pressure drawing off the technical grade of PCMM containing about 96% to 99% by grade PCMM obtained, the chlorination of the head weight of pure PCMM. ‘ fraction i.e. low-boiling‘ fraction followed by separation by distillation under reduced pressure of 'the PCMM DETAILED DESCRIPTION obtained in this chlorination and recycling this PCMM Thus, the instant invention relates to an improvement in the ?rst distillation column from the second head in the conventional method of preparing PCMM by 0 fraction, and decomposing by heat of the SCl2 in this iodine-catalyzed chlorination of carbon disul?de and second head-fraction with recovery of chlorine and separating the formed PCMM by distilling off a low reintroduction of said chlorine into the ?rst cycle of boiling fraction. In the conventional method, the low chlorination and formation of sulfur monochloride boiling fraction is chlorinated over a metallic chloride S2Cl2. ' catalyst to produce carbon tetrachloride and sulfur The following examples illustrate modi?cations of monochloride. In the improvement of the instant inven the present invention in non-limiting fashion, using tion, metallic chlorides are avoided and the same low equipment described schematically in FIGS. 1 and 2. boiling fraction is chlorinated in the presence of iodine The equipment of FIG. 1 includes three tubular chlo to produce more PCMM. The distillation of this second rinators l, 2 and 3, provided with cooling jackets and a chlorinated product then yields a crude PCMM and a 20 “ripener” or ?nishing-off reactor 4 for the purpose of second low-boiling fraction containing sulfur dichlo effecting the reaction of some 3 or ‘4% with CS2 which ride which is then converted to a sulfur monochloride has not reacted in the three chlorinators as well as by-product and to chlorine which is recycled in the effecting the reaction of SCl2-on the residual CS2 in treatment of fresh carbon disul?de.