3,077,479 United States Patent Office Patiented Feb. 12, 1963 2 The condensation product of sulfur dioxide with 3,077,479 butadiene is, as has been set forth heretofore, sulfolene. PURE FICATION OF SULFGLENE It is preferred to carry out this reaction so as to obtain 3 Daniel B. Lateia, Sr., and Friedrich G. Hefferica, Berke Sulfolene isomer which is more readily hydrogenated than ey, Calif., assignac's to Sheil Gi Co, nasay, New York, 2-sulfoiene. This material, after treatment to deactivate N.Y., a corporation of Delaware catalyst poisons, is then hydrogenated at about 30° C. No Drawing. Fied May 5, 1961, Ser. No. 107,931 over Raney nickel catalyst with a conversion of about 9 Cains. (C. 260-332.1) 97%. In general, this hydrogenation should be carried This invention relates to the manufacture of sulfolane out within about 12 hours, and preferably within about 6 and homologues thereof, particularly lower alkyl Sul 0. hours, following the purification treatment; substantially folanes of up to about eight carbon atoms. More partic immediate hydrogenation is advantageous. ularly, it relates to an improvement in the reaction of 1,3- Sulfolene can also be produced by reacting sulfur di diolefins with sulfur dioxide to form sulfolenes and the oxide and butadiene at about 95 C. in an isopropanol catalytic hydrogenation of the sulfolenes to sulfolanes. solution. At 1:1 mole ratio of sulfur dioxide to buta The sulfolanes are well known solvents useful in extrac 5 diene the conversion to sulfolene of the butadiene is tive distillations, solvent extractions, and the like, especial about 60-65%. According to earlier procedures both ly in petroleum processing for the separation of hydro unreacted sulfur dioxide and butadiene are removed by carbon mixtures. They are prepared by reacting a con boiling at about 60° C. and 15 p.s.i.a. Following this, jugated diolefin with sulfur dioxide and hydrogenating the the composition of the reactant mixture is predominantly resulting sulfolene to the corresponding Sulfolane. Thus, 20 as indicated in Table . sulfolane and the mono- and dimethyl sulfolanes are pre TABLE pared by reacting butadiene, methylbutadiene (isoprene, Component: Percent wt. trans-piperylene), and dimethylbutadienes with sulfur di Isopropanol ----------------------------- 66.5 oxide to form sulfolene, methyl sulfolene, and dimethyl Sulfur dioxide---------------------------- 3.0 sulfolene, respectively, and then catalytically hydrogenat 25 ing the particular sulfolene, as by using a Raney nickel Polysulfone ----------------------------- 0.5 catalyst, to the corresponding sulfolane. Sulfolene ------------------------------- 30.0 The crude reaction product from the reaction of the From the foregoing Table I, it will be appreciated that diolefin with sulfur dioxide, even after conventional re 3% by weight sulfur dioxide still remains. Even if this moval of excess SO2 and any insoluble polysulfones, is 30 existing sulfur dioxide were completely removed by not readily hydrogenated with any practical degree of stripping, decomposition of sulfoiene during storage or eficiency due to short catalyst life, The exact nature of extended handling will produce additional suifur dioxide. the catalyst poison(s) is not known. There seem to be it is important that Suffolene solution be stored in a slight various possibilities. Neutralization with caustic followed ly Warm environment in view of its solubility limitations. by separation from inorganic sulfite salt formed from The decomposition rate constant at 40° C. is 5X 10-7 per excess sulfur dioxide, or simply stripping with an inert gas, minute. Calculations based on this rate constant indicate have not solved the problem. Heretofore, the difficulty that after one week's storage of 30% w. Solution of sul has been reduced by fractional crystallization of the Sul folene at 40 C., the material will contain about 770 folene from the reaction product in an attempt to provide p.p.m. sulfur dioxide. a purer sulfolene for the hydrogenation. This technique, 40 In accordance with the present invention the sulfur di however, is not only time-consuming and requires con oxide present in the reaction products from the sulfoiene siderable capital expenditure for plant-scale operation, but synthesis in a solution of alcohol is removed by means of it results in a substantial reduction in yield of sulfolane. anionic exchange with a "strong base' anion exchanger A well known method for producing the sulfolene com resin in Salt form. Sulfur dioxide can be removed from prises conducting the reaction between the conjugated the suifolene by an anion exchanger in OH- form, but alkadiene and sulfur dioxide in a solution of a mono the OH ions catalyze the addition of alcohols (as well hydric alcohol having from 1 to 4 carbon atoms, such as, as any water present) to the sulfolene double bond. It for example, isopropanol. The product sulfolene is sub has, however, been found that the use of the anion ex sequently hydrogenated to form sulfolane usually in the changer in the CO form effectively removes the sulfur presence of Raney nickel catalyst. This type of catalyst, 50 dioxide without adversely affecting the sulfolene. In as has been considered hereinbefore, is suscpetible to accordance therewith, the primary process for the sulfur poisoning by Sulfur-containing materials, and especially dioxide removal is delineated by the following equation: by sulfur dioxide. Moreover, the diolefin plus sulfur di oxide reaction is reversible, and upon standing the Sul (R+)3COs --SO-> (R+)SO---CO, (1) folene product reverts in part into its constituents includ 55 where R represents a fixed cationic group, e.g., quater ing sulfur dioxide. nary annonium ion, of the exchange resin. The carbon It is therefore a principal object of this inventon to dioxide byproduct is easily removed by heating where such provide improved means for the treatment of the reaction removal is found necessary, although its presence may products of butadiene and related conjugated diolefins, be tolerated in relatively large amounts during the sub e.g., butadienes of 4 to 8 carbon atoms, with sulfur di 60 sequent hydrogenation. In actual practice, it has been oxide whereby a sulfolene is formed. It is a further found that the sulfur dioxide removal is twice that indi object to provide an improved and greatly refined Sul cated by the foregoing Equation 1 and, in view of the fact folene product for hydrogenation with a sulfur-sensitive that traces of water are generally present in the alcohol, catalytic material, as for example, Raney nickel. the additional uptake probably occurs according to Another important object of the invention is to remove sulfur dioxide from sulfolene, thereby providing a feed of (Ri)SO---SO--HO-> 2R+SOE - (2) higher quality for further chemical processing. A still Over-all the reaction then can be represented as: further object of the invention is to provide an improved (R)2CO3-4-2SO--HO->2(R+) (SOH) --CO(3) process for the synthesis of sulfolane. Other objects and 70 features of advantage will be apparent from a considera in view of the fact that the reversion of sulfolene on tion of the following description of the invention. standing forms undesired SO2, it is most advantageous to 3,077,479 3. 4. provide for the removal of the contaminating SO2 im forth hereinbefore. An exchanger in the form of the mediately prior to the catalytic hydrogenation step. anion of an acid with ionization constant (Ka) less than As a further important advantage of the invention the 108 is particularly desirable. ion exchange bed can be readily regenerated with aqueous It has been found that the equilibrium of the reaction Na2OO. In performing the regeneration, it is advan set forth in Equation 3 is driven virtually to completion tageous to drain the column and to effect the regeneration on the resin. Moreover, the front boundary of the SO2 by upflow therethrough in view of the fact that the resin Zone in the bed is thus self-sharpening. It has also been expands when it is brought into contact with an aqueous found that the break-through capacity of the resin is solution. Moreover, if water is particularly objection about 1.11 moles of SO per liter of resin bed. This is able in the product, it can be removed from the column 10 more than 85% of over-all ion exchange capacity of the following regeneration by washing briefly with an alcohol resi11. Moreover, it has been found in the commercial such as methanoi or isopropyl alcohol. A liberal excess preparation of Suifolane that with a feed containing 450 of Na2CO3 may be found desirable even up to, say,800% p.p.m. SO2, about 200 bed volumes can be processed in of the stoichiometric amount. The regeneration efficiency one cycle. Under such conditions the removal of SO depends to a great degree on such variables as column di contaminant from the suifolene is in excess of 99.3%. mensions, conditions of operation, and purity required The use of alcohol, such as isopropyl alcohol, does not of the product. In plant-scale operations, from about adversely affect the resin life. 150 to 250% of the stoichiometric amount will be found In accordance with the invention, when the ion ex sufficient. change is conducted in the absence of alcohol, such as Alternatively, the exhausted resin which is the HSO isopropyl alcohol, the resin may then be in the base or form can be regenerated without contacting it with an hydroxy form. On the other hand, it is a preferred em aqueous solution. For this purpose, the resin is first con bodiment to use the ion exchanger in the presence of verted to the OH form by treatment with a base such as alcohol which may or may not contain minor amounts of KOH in alcoholic solution, and then the OH form is Water, when the resin may then be in the form of a salt converted to the desired COs form by passing gaseous 25 Such as, for example, the acetate or carboxylate salt.