Dec. 11, 1951 J. E. MAHAN ET AL 2,578,565 HYDROGENATING SULFOLENES TO SULFOLANES Filed Dec. 28, 1948

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INVENTORS J.E. MAHAN BY S.C. FAUSKE Rudo-at-thur A 77OAPAVA 1S Patented Dec. 11, 1951 2,578,565 UNITED STATES PATENT OFFICE 2,578,565 HYDROGENATING SULFOLENESTO SULFOLANES John E. Mahan and Sig C. Fauske, Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Application December 28, 1948, Serial No. 67,745 15 Claims. (CI. 260-332.1) 1. 2 This invention relates to the production of the generic term “a sulfolane' or "a Sulfolane Sulfolanes by the hydrogenation of the corre compound' covering not only the above Com sponding unsaturated Sulfolenes. In One par pound but also the substituted derivatives there ticular embodiment it relates to an improved of, particularly those in which various radicals process for the production of 2,3,4,5-tetrahy mentioned in the preceding paragraph are Sub drothiophene-1,1-dioxide, commercially known stituted for one or more of the hydrogen atoms as sulfolane, by the catalytic hydrogenation of of the above structure. Where such a radical the corresponding unsaturated cyclic butadiene is hydrogenatable under the conditions of our monosulfone, i. e. 2,5-dihydrothiophene-1,1- process, it will be understood that the sulfolane dioxide, commercially known as Sulfolene, in the 0. containing the hydrogenated radical is included presence of a novel solvent. when reference is made to a sulfolane compound The term “a sulfolene compound' as employed which “corresponds' to a given sulfolene com herein and in the appended claims, defines ge pound. Thus, an alkyl Sulfolane, Such as a nerically the unsubstituted and Substituted un propyl or butyl sulfolane, corresponds to the al Saturated compounds comprising or containing 5 kenyl, such as allyl or butenyl respectively, Sul a sulfolene nucleus, i. e. a five-membered ring foLee. of four carbon atoms and a sulfur atom, a sin The material known as sulfolane, i. e. 2,3,4,5- gle olefinic linkage between any two adjacent tetrahydrothiophene-1,1-dioxide, has found val carbon atoms of Said ring, and two oxygen luable uses as an intermediate in the produc atoms each of which is directly attached to the 20 tion of other useful organic chemicals, and as sulfur atom thereof. The generic term “a sul a selective solvent for hydrocarbons of various folene' or "a sulfolene compound,' therefore types, fatty acids or fatty acid esters, and the covers the simple unsubstituted sulfolenes, like. Various derivatives thereof have also been viz. the 3-sulfolene having the general struc likewise employed, particularly 2,4-dimethyl ture 25 sulfolane, which has been used as a selective HCasas CE solvent to separate aromatic hydrocarbons from Hé ch, petroleum fractions. A convenient type of raw Ys/ material for the preparation of these various 2 Sa sulfolene compounds is found in the conjugated 2 n. O 30 diolefins, which are readily converted by reac and the 2-sulfolene having the structure tion with sulfur dioxide in known manner to unsaturated cyclic sulfones or sulfolenes. Thus, IC-CI 2-methyl-1,3-pentadiene by reaction with Sull H. &H, fur dioxide forms 2,4-dimethyl-3-sulfolene, N s^ 35 which may then be hydrogenated to the cor of2 SaSo responding sulfolane. This is true of the various unsubstituted and substituted aliphatic conju as well as the various substituted derivatives gated diolefins, such as those ranging up to 12 thereof, i.e. sulfolene compounds in which war carbon atoms per molecule. Similarly bu ious organic and/or inorganic and particularly 40 tadiene is reacted with Sulfur dioxide to form hydrocarbon radicals, i. e. alkyl, alkenyl, aryl, the cyclic butadiene Sulfone (Sulfolene) which aralkyl, alkaryl, allicyclic and/or heterocyclic is convertible by hydrogenation to sulfolane. radicals, and/or such inorganic radicals as do However since butadiene cyclic Sulfone is a Solid not interfere with the hydrogenation reaction, at room temperature, its hydrogenation to Sul are substituted for one or more of the hydro 45 gen atoms of the above unsubstituted Sulfolenes, foane must be carried out either in the presence provided the total molecule contains not over of a Suitable Solvent or at temperatures above twelve carbon atoms. its melting point. As practiced in the past, both Similarly, the term “a sulfoliane compound' of these processes have disadvantages which referS to a Saturated Sulfolene compound. In 50 make them undesirable. When operating in a other words, the sulfoliane compound contains Solvent medium according to methods of the Or consists of a saturated five-membered ring prior art recovery of catalyst, solvent, and prod of four carbon atoms and a sulfur atom, the uct are necessary and time consuming opera latter having two oxygen atoms directly at tions. The catalyst is usually removed from the tached thereto. The structural formula of the System by filtration after which the solution is 55 fractionated to separate the Solvent from the re simple unsubstituted sulfolane, therefore, is action product. This necessitates the use of ex H2C-CH pensive fractionation equipment and greatly ex tends the probability of handling losses. When H N oil, 80 pure butadiene cyclic sulfone is hydrogenated 22’s n. in the absence of a Solvent medium at temper O O atures aboves its melting point with the usual 2,578,565 3 4. hydrogenation catalysts, hydrogen absorption tageous to effect the hydrogenation reaction at is normally incomplete. This proceSS also has this latter temperature. It may be pointed out several disadvantages such as low yields, quick that use of a sulfolane compound as Solvent for catalyst poisoning, and decomposition of reac its corresponding sulfolene is advantageous even tants as evidenced by the pronounced odor of when hydrogenating at temperatures above the Sulfur dioxide in the reactor effluent. Similar meiting point of the sulfolene, in that reduced considerations are involved in the hydrogena catalyst poisoning and/or more complete con tion of the Substituted Suifoleines. version is often obtained as compared With hy It is an object of this invention to produce drogenation of the sulfolene alone, and there sulfolane compounds by an in proved inlethod is no necessity of distilling off an extraneous of hydrogenating the corresponding sulfolenes. solvent from the reactor effluents. The inven A further object is to obtain practically theo tion in its broadest aspects may be practiced retical yields of Sulfolane in the hydrogeiation at any temperature at which decomposition is of sulfolene. Yet another object is to minimize not so excessive as to stop the hydrogenation or prevent decomposition of Sulfolene compounds short of an economic yield, though of course it during catalytic hydrogenation thereof. An is preferred to avoid any decomposition, which other object is to avoid the necessity of remov is readily done in using the Sulfolane as the ing a Solvent by distillation from a Sulfolane Solvent. product obtained by hydrogenation of a sulfolene Any cf the more active hydrogenation cata in a Solvent. Yet another object is to reduce 20 lysts may be employed in our process. For eco greatly the amount of material which must be nomic reasons however we have preferred to filtered to remove a suspended catalyst from the use the more active base metal catalystS Such effluent of a Sulfolene hydrogenation reaction. as nickel, cobalt, chromium, copper-chronium Further objects and advantages of the inven oxide, and the like. These may be used ini. tion Will be apparent, to one skilled in the art, finely divided form such as, for example, Rafiey from the accompanying disclosure and discus nickel, or may be suitably supported on kiesel S.O. guhr, aluminum oxide, diatomaceous earth, and We have now found that many advantages the like. A supported catalyst in pelleted form and greatly improved results may be obtained which we have found satisfactory comprises 70 in hydrogenations of the type described by first 30 to 80 per cent nickel on diatonnaceous earth. dissolving the Sulfolene to be hydrogenated, not It is an advantage of our process that rio Sol in an extraneous solvent as has heretofore been vent recovery steps are necessary and no catalyst done in the prior art, but rather in the corre poisoning is observed. It is a further advantage Sponding Sulfoliane as a solvent. As applied of our process that relatively mild conditions Specifically to the hydrogenation of butadiene of operation provide substantially complete hy Cyclic Sulfone, a significant feature of our proc drogenation with little, if any, loss resulting from eSS lies in the high solvent power of the solvent decomposition. It is still a further advaitage employed, namely sulfolane, for the sulfolene. of our method that the product is ready for We have found that two parts by weight of shipment or immediate use as it flows from the Sulfolane will dissolve about three parts by ...) process. These and other advantages of the in Weight of Sulfolene at room temperature (30° vention will be further apparent from a descrip C.). This is advantageous in that larger tion of the accompanying drawing in which is amountS of the butadiene cyclic sulfone are shown diagrammatically one form of apparatus processed per unit equipment capacity when in which our process can be carried out. The using Sulfolane as an initially present solvent -i. 5 invention will be illustrated by Specific refei' than With other, formerly used solvents of lower ence to the hydrogenation of the simple but3 Solvent power. Additionally, as will be shown diene cyclic monosulfone known as sulfolene (3- hereinafter, the extent of conversion and the sulfolene) to form sulfolane, but the invention, maintenance of catalytic activity are remarkably is readily adapted to the various substituted improved by the practice of our invention. Fur 3) sulfolenes and sulfolanes with suitable modifi thermore the former necessity of distilling off cation wherever niecessary which will be ap great quantities of extraneous solvents to obtain parent to one skilled in the art. the final Sulfolane product, which involves not In the drawing, butadiene cyclic sulfone (Sui Only equipment and operating expense of great folene) is withdrawn from storage f, either aS magnitude but also the decomposition and de 5 5 an unmelted solid or in the melted form (since terioration of the product due to the tempera the material is reasonably stable for limited tures employed, is completely avoided. It will periods of time and in the absence of catalyst at also be noted that the hydrogenation can be temperatures somewhat above its melting point initiated and effected at reasonable tempera and is passed via line 2 to mixing chamber S. tures, even those below the melting point of the 60 Sulfoliane is passed, preferably at about 30° C. Sulfolene starting material, with the result, that at which temperature it is a liquid, from Sul decomposition of reactants and products does foliane storage 5 or recycle line 6, via line 4 to not occur. Thus, while sulfolene melts at about mixing chamber 3. The sulfolene-sulfolane Solu 65 C., the corresponding sulfolane melts at tion prepared in mixing chamber 3 is passed via 27-28 C. However, mixtures of the two are (35 line to reactor 8. Reactor 8 may be filled with molten even down to 10° C. so that the hydogena a pelleted catalyst of the type mentioned above, tion can be started and carried to partial com or a finely divided catalyst may be Suspended pletion at a temperature below the melting point in the liquid reaction mixture therein. Hydro of either pure compound if desired. Of course, gen is admitted to the reactor from storage 7 for complete hydrogenation the final reaction via line 9 which terminates in a perforated disc temperature will be at least as high as the melt f providing even distribution of the gas Over ing point of the sulfolane solvent-product. The the bottom of the reactor. In order to insure 2,4-dimethyl-3-sulfoiene melts at 39° C. while its adequate contact of the reactants hydrogen gas hydrogenated product, 2,4-dimethylsulfolane may be removed from the top of reactor 8 melts at -3.3° C.; however, it is seldom advan through line i? containing a blower 8 or other 2,578,565 S 6 suitable circulating device and recycled with the sulfur dioxide by methods well known in the hydrogen feed in line 9. The product is carried art. Any sulfolene compound may be employed from reactor 8 via line 3 to storage 5. as the starting material to produce the corre When operating with a fixed bed catalyst agi sponding sulfolane compound. These Sulfolene tating means will not ordinarily be required since 5 compounds may contain an olefinic or double the countercurrent stream of hydrogen through bond in the 2-, 3- or 4-position in the ring, the the catalyst bed usually provides adequate agi various unsatisfied bonds of the nuclear carbon tation. Flow rates of reactants are adjusted to atoms of the sulfolene ring being taken up by provide a space velocity from about 1 to about hydrogen atoms and/or hydrocarbon radicals, 10 volumes of butadiene cyclic sulfone-sulfolane O particularly saturated aliphatic radicals. As solution per volume catalyst per hour. We have examples of these sulfolene compounds which generally preferred to operate using flow rates may be subjected to hydrogenation to produce from about 2 to about 4 volumes of sulfolane a Sulfolane compound corresponding to the solution per volume catalyst per hour. starting sulfolene compound employed, reference When it is desirable to use a finely divided 5 is made to the following: 3-sulfolene, 2-sulfolene, catalyst, the reactor 8 should be fitted with a 2 - methyl - 3 - sulfolene, 3 - methyl - 3 - Sulfo stirrer or other agitating means, and a catalyst lene, 3 - methyl - 2 - Sulfolene, 3 - ethyl-3-sul recovery step which is indicated diagrammati folene, 3 - ethyl - 2 - Sulfolene, 2,4 - dimethyl cally by element 4 and which may comprise a 3 - Sulfolene, 2,4 - dimethyl - 2 - sulfolene, 2,4- centrifuge, filter, or other suitable apparatus will 20 dimethyl-4-Sulfolene, and the like, and their normally be required. In this event, that por homologues, as well as similar Sulfolene com tion of the reactor effluent required as solvent pounds wherein other hydrocarbon radicals, as for the reaction is passed without catalyst sepa Well as Substituted hydrocarbon radicals which ration through lines 3, 6 and 4 to mixing Zone may be aliphatic, alicyclic, aromatic and/or 3 and thence via line 7 into reactor 8, whereas 25 a portion which corresponds in quantity to the heterocyclic, or other radicals, are directly at Sulfolene feed is passed via line 9 to catalyst tached to the various nuclear carbon atoms. recovery unit 4 and thence via lines 20 and 3 The following examples are offered as illus to Sulfolane storage vessel 5. Recovered catalyst trative of certain Specific aspects of the inven is conveyed via line 5 either to catalyst storage tion, and to show some of the advantages thereof. unit 6 or on through line 5 into mixing zone It will be apparent that the materials treated 3. Catalyst concentrations in the range from and the conditions employed are exemplary and 0.5 to 5 per cent by weight of the solution being that the broad scope of the invention is not processed are usually satisfactory although larger limited thereto. amounts may be used if desired. We have gen 35 Eacample I erally preferred to use these catalytic materials in concentrations of from 1 to 2 per cent by To show the advantages of using sulfolane as weight of reactants. a solvent two runs were made. In the first (A), Temperatures in the range from about 10 to three parts by weight of butadiene cyclic sul about 100° C. are suitable for the operation of 40 fone was dissolved in two parts by weight of sul this process and in fact any temperature is op folane in a pressure reactor at 30° C. Raney erable at which the reaction mixture is liquid, nickel equivalent to one per cent by weight of and which is below that at which the materials the butadiene cyclic Sulfone was added as cata decompose severely. However, to avoid any lyst and the reactor sealed. Hydrogen was then possibility of thermal decomposition we usually pressured in at about 1000 pounds per square operate below 50° C., preferably in the range from 45 inch gauge with agitation until absorption ceased 10 to 40° C. While the melting point of sulfolane (about 20 hours). In the second run (B), buta is about 27°C., and the melting point of sulfolene diene cyclic sulfone without a solvent was quite considerably higher (65° C.), solutions of charged to the reactor. Raney nickel equivalent the two are liquid as low as 10° C. So that the to two per cent by weight of the charge was hydrogenation can be readily initiated at such a added and the reactor sealed. The temperature temperature if desired and completed at 27-28 was then raised to about 65° C. to melt the charge C. or higher. Hydrogenation proceeds at hydro and hydrogen was pressured in at about 1000 gen pressures above 50 pounds per square inch pounds per Square inch gauge with agitation gauge and is effected quite rapidly and smoothly 5 until absorption ceased (1942 hours). Results between 500 and 1500 pounds per square inch of the two runs are shown in the following tabu gauge. Pressures above this range may be em lation: ployed if desired. A two to threefold mol excess of hydrogen over the sulfolene fed is usually Run. A Run B maintained in the reactor at all times. Ordi 6) Conversion of Butadiene narily the ratio of Sulfolene compound, to sul Cyclic Sulfone to Sul SubstantiallyComplete. 33 Per cent. folane compound will be within the range of folane. Catalyst Condition at 0.5:1 to 4:1 by weight, the maximum being End of Ruth, Active------Inactive. limited by the solubility of the particular sul Deconposition.------...--- None Detected.---- Pronounced Odor folene in Sulfolane at the temperatures employed. 65 of Sulfur Dioxide. Thus, at 30° C. the ratio of 3-sulfolene to sulfolane is limited to 1.5:1, but is higher at higher tem Eacample II peratures. Ratios lower than 0.5:1 are seldom advantageous, while above 4:1 usually provides A run was made where in three parts by weight insufficient Sulfolane solvent for realizing all of () of butadiene cyclic sulfone was dissolved in two the benefits of the process. Ratios within the e parts by Weight of Sulfolane in a pressure re i’ange of 1:1 to 2:1 are generally preferred. actor at 30 C. Raney nickel equivalent to two Butadiene cyclic sulfone may be obtained from any suitable source. We have found it convenient per cent by weight of the solution was added as to prepare it by the interaction of butadiene and thencatalyst pressured and the inreactor at about sealed. 1000 Hydrogen pounds wasper 2,578,565 7 8 square inch guage with agitation until absorption convert said sulfolene to sulfolane, and remov ceased (about 20 hours). At the end of this pe ing from said hydrogenation Zone a quantity of riod the catalyst was allowed to settle and about sulfolane equivalent to the qualltity of Sulfolene half of the sulfolane decanted. This portion hydrogenated. was replaced with an equal amount of butadiene 5 5. A process which comprises catalytically hy sulfone and after it was hydrogenated in like drogenating 3-sulfolene dissolved in Sulfolane, at manner a third portion was processed. Exam a temperature below the melting point of 3-sul ination of the product by distillation indicated folene, in a reaction mixture consisting eSSen that hydrogenation was substantially complete. tially of 3-sulfoiene, Sulfolane, hydrogen, and an active. base metal hydrogenation catalyst. The product had a boiling range of 139.5-140° C. 10 6. A process which comprises catalytically hy at 10 inm. drogenating 2,5-dimethyl-3-sulfolene dissolved in Eacample III 2,5-dimethylsulfoliane, at a temperature below the melting point of the former, in a reaction A run was made according to the method mixture consisting essentially of 2,5-dimethyl-3- shown in the accompanying diagram using a sulfolene, 2,5-dimethylsulfolane, hydrogen, and pelieted catalyst comprising 72 per cent, nickel an active base metal hydrogenation catalyst. on diatomaceous earth. The ratio of butadiene 7. A process which comprises forming a mix cyclic sulfone (3-sulfolene) to Sulfolane in the ture consisting of a liquid solution of a Sulfolene mixing chamber was maintained between about 20 compound dissolved in its corresponding Sul i.3:1 and .5:1 and flow of reactantS WaS ad foliane compound, passing Said mixture into Con justed to provide a space velocity of 3 volumes of tact with hydrogen and an active base metal butadiene cyclic sulfone-sulfolane solution per hydrogenation catalyst in a reaction mixture con Voiune catalyst per hour. Hydrogen Was intro sisting essentially of said hydrogen, Said catalyst, duced concurrently at a rate such that a twofold said sulfolene compound, and Said Sulfolane Com molar excess of gas to Sulfolene charged WaS pound, maintaining said contact at a tempera maintained at all times. The temperature of the ture avoiding decomposition of said sulfolene catalyst chamber Was maintained between 27 compound to an extent detrinental to the hydro and 30° C. Tests made on the effluent stream genation reaction and for a time effective to hy indicate that Substantially pure sulfolane was dirogenate said sulfolene compound to form its produced. 30 corresponding sulfolane compound, and recover We claim: 1. A process of producing a sulfoliane which ing from contact With Said hydrogein and hydro cožilplises catalytically hidrogenating a Sulfolene genation catalyst the sulfolane compound formed in a reaction mixture consisting essentially of by said hydrogenation plus the sulfolane com 35 pound originally present in said mixture as Said sulfolene, hydrogen, an active base metal Solvent, hydrogenation catalyst, and an initially-present 8. A process which comprises forming a solu Sulfolane as a Solvent. -- 2. A process of producing sulfolane which tion of 3-sulfolene in sulfoliane and contacting comprises catalytically hydrogenating Sulfolene same as a liquid at a temperature below the melt in a reaction mixture consisting essentially of 40 ing point of the former with sufficient hydrogen sulfoiene, hydrogen, an active base metal hydro to convert all of said 3-sulfolene into Sulfolane genation catalyst, and initially-present Suifolane in the presence of an active base metal hydro as a solvent, the weight ratio of Sulfolene to Sul genation catalyst, in a reaction mixture con folane in the initial reaction mixture being Within sisting essentially of said catalyst, hydrogen, 3 the range of 1:1 to 2:1. 45 Sulfolene, and Sulfolane. 3. A process for the formation of a Sulfolane 9. A process according to claim 8 Wherein a from a corresponding sulfolene which comprises nickel catalyst is used and wherein hydrogen dissolving Said Sulfolene in Said Sulfolane to for il is used at a pressure of at least about 500 pounds a catalyst-free solution, introducing said solution per Square inch gauge. into a hydrogenation zone containing an active 50 10. A process according to claim wherein a base metal hydrogenation catalyst, introducing temperature not exceeding 100° C. is employed. Sficient, hydrogen into Said hydrogenation Zone 11. A process according to claim 2 Wherein a to Saturate the unsaturated double bond of the tenperature below 50° C. is employed. suifolene, the contents of said hydrogenation 12. A process which comprises hydrogenating 55 3-sulfolene dissolved in Sulfolane at temperatures zone consisting essentially of said sulfolene, said below the melting point of 3-sulfolene but above Sulfolane, said catalyst, and said hydrogen, and the melting point of Sulfolane and in the ab being maintained at hydrogenation conditions sence of an extraneous solvent, in a reaction for a time sufficient to convert said Sulfolene to mixture consisting essentially of 3-sulfolene, Said Sulfolane, and removing from said hydro Sulfoliane, hydrogen, and an active base metal genation zone a quantity of the sulfolane equiv 60 dehydrogenation catalyst. alent to the quantity of the sulfolene hydro 13. A continuous process for the conversion of genated. 3-sulfolene to Sulfolane in high yields by cata 4. A process for the formation of sulfolane lytic-hydrogenation, Which comprises continu from Sulfolene which comprises dissolving sul 85 ously passing a liquid Solution of 3-sulfolene in folene in Sulfolane to form a catalyst-free solu Sulfolane into a reaction zone containing an ac tion, introducing said solution into a hydrogena tive base metal hydrogenation catalyst, continu tion Zone containing an active base metai hydro ously passing hydrogen into said zone and main genation catalyst, introducing sufficient hydrogen taining Same therein at a pressure of at least 50 into Said hydrogenation zone to saturate the un- 70 pounds per Square inch gauge, maintaining in Saturated double bond of the sulfolene, the con Said Zone a reaction mixture consisting essential tents of Said hydrogenation zone consisting es ly of Said catalyst, hydrogen, 3-sulfolene, and Sentially of Sulfolene, sulfoliane, said catalyst, Sulfolane, maintaining a hydrogenating tem and Said hydrogen, and being maintained at perature in Said Zone such that decomposition hydrogenation conditions for a time sufficient to 75 of Said 3-sulfolene to sulfolane does not occur 2,578,565 O to an extent preventing the hydrogenation re 15. A process according to claim 1 wherein action, continuously removing liquid sulfolane said catalyst is Raney nickel. from said zone at a rate permitting complete hydrogenation of 3-sulfolene fed to said Zone, re JOHN E. MAHAN. cycling a portion of the thus-withdrawn Sulfolane SIG. C. FAUSKE, as the Sole solvent to form said Solution of 3 REFERENCES CITED Sulfolene in Sulfolane, and recovering sulfolane as a product of the process in an amount equiv The following references are of record in the alent to the 3-sulfolene fed to the process. file of this patent: 14. A process according to claim 1 wherein 10 UNITED STATES PATENTS said catalyst is selected from the group consist Number Name Date ing of nickel, cobalt, chromium, and copper 2,435,404 Morris ------Feb. 3, 1948 chromium oxide, 2,451,298 Morris ------Oct. 12, 1948