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. The CO2 through the column after the interstitial alcoholic salt form of the resin is preferred in this latter instance solution has been drained. A liberal excess of base even to minimize loss of suifolene by formation of ether with up to, say, 800% of the stoichiometric amount may be the alcohol which is catalyzed by a resin in strong base desirable to obtain complete conversion to the OH form, form. but usually from about 150 to 200% of the stoichiometric 30 Example amount will be economically more advantageous. Sulfur dioxide can also be removed by anion ex Conditioning of the Resin-A portion of Dowex 1-X8 changers of the above-mentioned type in the SOs form. standard grade anion exchanger resin was conditioned The mechanism of SO2 uptake then is exclusively reaction by repeated anion exchange cycles alternately with 1 2. The advantage of this method is that the column can M. NaOH and 1 M HCl (about 4 liters per 50 grams of be regenerated for renewed use simply by washing with resin per cycle for 4 hours), and washing with distilled solvent, thus reverting reaction 2. However, the capacity Water (about 4 iiiers) after each conversion. Condition of the resin for SO2 uptake when used in the SOs form ing was carried out on a Buchner funnel in such a man is only half as high as when used in the CO3 form. ner that the resin never became dry. The resin so-con The invention contemplates the use of strong base 40 ditioned was stored in Cl form under about 0.1% anionic exchange resins, and, in fact, practically any NaCl solution. strong base anionic exchange resin may be employed. Preparation of the Column-About 500 grams of the As a class, these resins are high molecular weight poly resin were converted to COs form in a column of 2 bases which are virtually insoluble in the media wherein inches in diameter by passing therethrough about 8 liters they are to be used. They consist of a 3-dimensional 45 of 1 M aqueous Na2CO3 solution. Tests for Cl- in polymer network to which are attached a plurality of the last fractions of the effluent were negative. The resin cationic radicals which maintain their cationic character was then washed with 4 liters of methanol and subse regardless of pH. These act as the anion exchangers. quently with 8 liters of isopropyl alcohol. 60 ml. of Especially suitable are the quaternary ammonium anion the resin were transferred into a column of 1 inch internal exchange resins, typical of which are the products of 50 diameter. The bed was backwashed with isopropyl amination with the trimethyl amine or dimethyl ethanol alcohol. amine of chloromethylated polymers, for example, chloro reparation of Feed-A feed containing 450 p.p.m. methylated styrene-divinyl benzene copolymers. Repre SO2 and major amounts of Suffolene was produced from sentative commercially available exchangers of these types the condensation reaction of butadiene with SO, in iso are Amberlite RA-400, IRA-401 and RA-410 of Rohn propyl alcohol, followed by stripping most of the un and Haas Company; DoweX-1 and DoweX-2 of Dow treated SO2 therefron. Chemical Company, Nalcite SBR and SAR of National Columin Operation.-The feed was passed through the Aluminate Corporation, Permutit S-2 of Permutit Corn column at a flow rate of about 3 to 5 bed volumes per pany and Duolite A-42 and A-40 of Chemical Process hotif. Regular titration checks for the appearance of Company. U.S. Patents 2,388,235 and 2,591,573 describe 60 SO in the effluent were performed. SO in the effluent processes for producing ammonium exchange resins which was first detected when 200 bed volumes of feed had can be converted to salts useful in practicing the inven passed through the column. The total effluent up to this tion. The Dowex and Nalcite resins are of the general point contained less than 3 p.p.m. SO, the first 50 bed formula RN+A, in which one of the R's is derived volutes less than 0.2 p.p.m. from polystyrene which has been cross-linked with divinyl 65 Hydrogenation.-The sulfolene thus freed from con benzene. In the case of DoweX 2 and Nalcite SAR, two taminating SO was fed into a hydrogenation zone where R groups are methyl groups and one R group is a hydroxy in sulfolane was produced by hydrogenating in the pres ethyl group. In the case of DoweX-1 and Nalcite SBR, ence of a Raney nickel catalyst. The life of this cata the three remaining R groups are methyl groups. The lyst was prolonged indefinitely and substantially pure sul resultant ammonium exchange resin is a highly dissociated 70 folane resulted therefrom. organic base, in which the large cationic body is immobile Regeneration of Resin.--An excess of Na2CO3 was used and the relatively small and mobile anion is free to ex as regenerant after draining the column. Such excess change. Particular success has been achieved in practic was several times the stoichiometric amount and the so ing the process of the present invention through the use diurn carbonate solution was passed into the column up of DoweX -X8, which is representative of the group Set wardly and withdrawn from the top thereof. The resin 3,077,479 5 6 was then found to be in renewed condition for further 3. Process in accordance with claim 1 wherein the SO removal. ationic exchanger is in the form of the anion of an acid With regard to the particular type of alcohol to be with K. les than 10-2. used in the condensation reaction between the alkadiene 4. Process in accordance with claim wherein the and the Sulfur dioxide, isopropyl alcohol has proven par strong base anionic exchanger is in SO form. ticularly useful in that it reduces the formation of poly 5. Process in accordance with claim 1 wherein the sulfone and improves separation by filtration of any poly alkadiene is butadiene. sulfone which may be formed. 6. Process in accordance with claim wherein the The sulfolanes manufactured in this manner are par alkadiene is isoprene. ticularly useful as selective solvents for the separation O 7. Process in accordance with claim 1 wherein the of organic compounds. They are specifically applicable Sulfolene contaminated wtih sulfur dioxide is treated with to the separation of mixtures of hydrocarbons of dif a strong base anion exchanger in the form of a salt of ferent degrees of saturation such as, for example, the a weak acid in the presence of a monohydric alcohol con separation of aromatics from non-aromatics, olefins from taining from one to four carbon atoms. diolefins and monoolefins from saturates. The sulfolanes 8. Process in accordance with claim 7 wherein said produced by this invention possess an enhanced stability monohydric alcohol is isopropanol. in the processes involved in such extractions. 9. Process in accordance with claim 1 wherein the We claim as our invention: hydrogenating of the sulfolene is effected prior to the 1. In a process for the synthesis of a sulfoane which reversion of substantial amounts of the sulfolene. comprises reacting a conjugated alkadiene with sulfur 20 dioxide to form a reaction product containing essentially References Cited in the file of this patent a corresponding sulfolene and catalytically hydrogenat UNITED STATES PATENTS ing a sulfolene to a corresponding sulfolane in the 2,360,859 Evans et al. ------Oct. 24, 1944 presence of asulfur-sensitive hydrogenation catalyst, the 2,451,298 Morris et al. ------Oct. 12, 1948 improvement of treating the reaction product contain 25 2,578,565 Mahan et al. ------Dec. 11, 1951 ing the Sulfolene with a strong base anionic exchange resin consisting essentially of a high molecular weight FOREIGN PATENTS polymeric network to which are attached a plurality of 936,442 Germany ------Dec. 15, 1955 cationic radicals to substantially remove sulfur-contain OTHER REFERENCES ing poisons of catalytic hydrogenation catalysts. Calman et al.: Ion Exchangers in Organic and Bio 2. Process in accordance with claim 1 wherein the chemistry, 1957, Interscience Publishers, Inc., New York, strong base anionic exchanger is in COr form. New York, page 642,