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Patented Aug. 6, 1946 2,405,258 UNITED STATES PATENT OFFICE 2,405,258 PROCESS FOR DESULPHURIZING HYDROCARBONS George R. Lake, Long Beach, Calif., asslgnor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application December 8, 1942, Serial No. 468,220 17 Claims. (01. 202-42) ' 2 aforementioned change will be referred to as tion. An object of the present invention is to further the progress in preparing pure relatively sulphur free compounds from heterogeneous hydrocarbon 10 mixtures, using in this particular case a method 115 20 25 and sulphur compounds. A particular object of‘ my invention is to sep arate non-aromatic hydrocarbons and sulphur aromatic hydrocarbons by dis The fractional ture results in distilling 30 distillation residue ‘an aromatic hydrocarbon 85 fraction relatively free from non-aromatic hy drocarbons and sulphur compounds. The invention comprises adding to such hy drocarbon fractions from which it is desired to 40 segregate a speci?c hydrocarbon or hydrocarbon fraction, a substance or a mixture of substances hereinafter disclosed having a preferential ailin ity in the vapor state for one or more components contained in the fractions, thus causing a dis 45 turbance of the vapor pressure equilibrium that formerly existed in the fraction in such manner that the partial vapor pressure or fugacity of at su?iciently to permit its separation by controlled fractional distillation. This type of fractional distillation will be referred to hereinafter as azeo tropic distillation and the substance or substances which are added to the fraction which e?ect the 50 aromatic hydrocarbons and yet contains sulphur, the azeotropic distilla tion to remove sulphur from the remaining hy drocarbon mixture, such as one containing par a?ins and ole?ns and naphthenes, orv ole?ns and naphthenes or mixtures of para?ins, ole?ns and 65 naphthenes may be accomplished by azeotropic 2,405,258 4 toluene, xylene, etc, boiling range since it is pref distillation in which case the distillation residue azeotrope former which has a boiling point of not more than 50° F. difference - erable to employ an may consist of the relatively more aromatic hy drocarbons, i. e. the hydrocarbon which does not form an azeotrope with the azeotrope former or f0rms a higher boiling azeotrope therewith. In I." some cases, it may be desirable to remove only the from the average boiling point of the hydro carbon stock. I have found that acetone is particularly e?i ‘cient for desulphurizing complex hydrocarbon sulphur compounds from a hydrocarbon or hy fractions containing benzene and sulphur com drocarbon mixture. This may also be accome pounds and also non-aromatic hydrocarbons plished by azeotropic distillation but in such cases boiling between about 150 and 200° F. to produce it may be necessary to more carefully control the distillation to prevent substantial amounts of an azeotrope or azeotropes of the hydrocarbons from also distilling overhead in admixture with the sul substantially pure benzene. Acetone is an un usually efficient azeotrope former for separating benzene as it does not form an azeotrope with the benzene. Substantially pure benzene is required in the production of chemical compounds or de The type of distillation to be used depends 15' rivatives such as for producing phenols which the a‘ze'ot'ro‘p'e ' somewhat on the quantity of are used in making plastics, and ethyl benzene phur compounds. . . former used. I may take any proportion of the which may be converted to styrene and employed hydrocarbon fraction to the added mixture that in making synthetic rubber. I desire, depending on the ef?ciency of the oper I have also found that methyl ethyl ketone, 20 ation or the purity of the product desired,~ahd preferably containing water is an extremely e?i the technique to be usedin the distillation. The cient azeotrope former for separating pure tolu proportion of the azeotrope former may readily ene from complex hydrocarbon fractions con be adjusted on an ideal point, the de?nition of this point again depending on whether I desire taining toluene, non-aromatic hydrocarbons and sulphur compounds boiling between 200 and 240° the portion highin aromaticity to remain as 25 F. The production of substantially pure toluene bottoms in the distillation column in a practi cally pure state, i. e. free from non-‘aromatic is highly important when it is to housed in the manufacture of explosives by nitrating the tolu hydrocarbons and sulphur compounds, or wheth ene since small amounts of impurities seriously er I wish to distill'a portion of the non-aromatic impair the nitration process. Since this azeo hydrocarbons, leaving a portion of the non-aro 30 trope former does not form an azeotrope with matic hydrocarbons as bottoms together with toluene but forms an azeotrope with only the aromatic hydrocarbons. Also, the distillation non-aromatic hydrocarbons and sulphur oom- “ temperature and amount of. aze'otrop'e former may be adjusted to effect the distillation of all of pounds‘ in the mixture, the toluene will remain as a distillation bottoms substantially free from azeotrope former. While the foregoing description of my inven tion has been made with particular reference to the use of ketones for desulphurizing hydrocar the non-‘aromatic hydrocarbons and sulphur compounds together with a portion of the aro matic hydrocarbons. » In other words, the e?i ciency of separation of the aromatic from non aromatic hydrocarbons is ‘dependent upon the bons, other azeotrope formers may be used for a this purpose, it being understood that the choice proper adjustment of the amount ‘of 'azeotro-pe former used since a small amount may result in of azeotrope former for the most efficient opera tions will depend upon the character and boiling range of the stock undergoing treatment. Ex incomplete separation of the non-aromatic hy drocarbons while the use of an excess of the azeotrop'e former together with a relatively higher distillation temperature may "cause distillation 45 amples of such azeotrope formers include alco hols such as methyl, ethyl, propyl, butyl alcohol, fatty acids such as acetic, ‘propionic, butyric, valeric acid, polyglycols such as mono-, di-, tri-, of a portion of the aromatic hydrocarbons, par ticularly in the case where ‘the azeotrope former also forms an azeotrope with the aroma-tic hy tetra~, hexa-, mona-ethylene glycol, propylene drocarbons. In the foregoing separations, the and di-propylene glycol, ethers and esters of 50 sulphur compounds contained in the Stock will such polyglycols, phenolic compounds such as be distilled together with the non-aromatic hy phenol, resorcinol, naphthol, saturated hetero drocarbons or if desired the azeotropic distilla cy'clic compounds of four carbon atoms such as tion may be carried out to distill overhead sub dioxane, morpholine, di-oxolane, nitrogen bases stantially only sulphur compounds together with such as picoline, pyridine, quinoline, 'r‘nonoe, di-, azeotrope former. The latter is particularly de tri-amylamine, nitroparaf?ns such as nitro sirable in those cases where the stock is "essen ethane, nitromethane and nitropropane. tially aromatic containing only small amounts of Sulphur compounds which may be removed para?‘in, ole?n and/or naphthene hydrocarbons. from hydrocarbon fractions by aze'otropic dis I prefer, however, to carry out the distillation so tillation, of course, include those which form that at least a portion of the relatively less aro 60 azeotropes with the azeotrope former or those matic hydrocarbons will also ‘distill overhead together with the sulphur compounds. which in conjunction with relatively nonearo matic hydrocarbons form an azeotrope with the I have found that ketones, such as aliphatic azeotrope former. With some stock's, it is merely ketones, for example, acetone, methyl ethyl ke possible to remove by azeotropic distillation only 65 tone, diethyl ketone, methyl isopropyl ket‘one, a portion of the sulphurrcompounds contained diacetyl, acetonyl acetone and also ‘the cyclic in the stock, leaving a portion of the sulphur ketones, for example, cyclohexanone, methyl compounds in the residue together with the rel phenyl lieton , etc., are particularly emcient in atively aromatic hydrocarbons. Nevertheless, I separating substantially pure aromatic hydro have found that the sulphur compounds which carbons from complex hydrocarbon fractions of 7,0 are removable as overhead products either alone relatively narrow boiling range containing sul orv in admixture with relatively non-aromatic phur compounds. The choice-of the azeotrope hydrocarbons, together with the azeotro'pe form former to be employed will‘generally depend upon er, are not ordinarily removable from the stock the characteristics of the hydrocarbon stock to, by ordinary acid treatment. I have'also found be ‘treated, i. e. whether‘ it is in the benzene, 2,405,258 water to dissolve and remove ‘substantially all of the acetone contained therein. The 25 parts of thus extracted oil had a sulphur content of about by ‘ordinary acid treatment or extraction with 12%. solvents either in the liquid phase or vapor phase. The reasons that certain sulphur compounds contained in stocks are removable as overhead products together with azeotrope former by azeo tropic distillation while other types of sulphur sulphuric acid per barrel of bottoms and then 10 neutralized with caustic alkali which resulted in compounds do not distill overhead with the azeo producing a fraction having 0.014% trope former and relatively non-aromatic hydro carbons is not too clear. ‘However, one explana tion may be found in the fact that certain sul phur compounds such as thiophanes behave like non-aromatic hydrocarbons such as parai?ns 15 while other sulphur compounds such as thio phenes beh'ave like aromatic hydrocarbons. Thus, when a stock contains a mixture of such tures of sulphur compounds, it is nevertheless possible to remove substantially all of the sul phur compounds contained in the stock by a com bination of steps involving ?rst an azeotropic Example 2 1000 parts of the same hydrocarbon stock de sulphur compounds, the sulphur compounds which behave like non~aromatic hydrocarbons 20 are removed overhead by azeotropic distillation together with the relatively non-aromatic h'ydro carbons, while sulphur compounds which behave like aromatic hydrocarbons remain in the residue together with the aromatic hydrocarbons. In those cases where the stock contains such mix ‘ The undistilled bottoms of the azeotropic dis tillate had a sulphur content of 0.12%; This fraction was then treated with 20 pounds of 98% scribed in Example 1 and having a boiling range of 172-225° F. was fractionated in a fractionating column at a temperature of about 175° P. which resulted in distilling overhead 140 parts of the hydrocarbon fraction having a sulphur content of about 1.5% and leaving about 860 parts of an undistilled bottoms having a sulphur content of about 0.10%. The 140 parts of overhead fraction was con densed and then mixed with about 110 parts of acetone and the mixture was distilled at a tem perature of 130° .F. and‘ at atmospheric pressure distillation as described herein to remove over head sulphur compounds either together withor without the relatively non-aromatic hydrocar bons and azeotrope former and second, an acid treatment or extraction of the residue with a 35 traction with sufficient water, the fraction had a solvent to remove the remaining portion of the sulphur content of about 15%. The undistilled sulphur compounds from the aromatic hydrocar bottoms was substantially pure benzene having a bons. Selective solvent extraction processes are sulphur content of 0.04% and amounted to about 120 parts. well known and need not be described further herein. Processes of this character are described 40 The 860 parts of undistilled bottoms of the ini in the McKittrick 2,162,963 and Roelfsema tial fractionation was distilled at a temperature 2,069,329 patents. In general, the sulphur com of about 190° F. which resulted in distilling over pounds which may be removed by azeotropic dis head about 800 parts of substantially pure ben tillation include the th'iophanes, alkyl sulphides zene having a sulphur content of 0.04%, leaving and perhaps mercaptans and disulphides, while 45 as undistilled bottoms a fraction consisting main those which are not separable by azeotropic dis tillation or remain in the aromatic residue of an azeotropic distillation process include the thio phenes and thionaphthenes. ' tropic distillation to produce about 920 parts of Other objects, features and advantages of my 50 a benzene containing about 0.04% sulphur. invention will be apparent to those skilled in the blend was then treated with about 10 pounds of 98% sulphuric art from the following examples of the invention which are not to be taken as limiting but as illus trative of my invention. ' Example 1 In order to compare the above results with or 250 parts by volume of acetone were mixed with 1000 parts by volume of a. hydrocarbon fraction obtained from coal tar having a boiling range of approximately 172° F. to 225° F. and consisting of 60 approximately 92% benzene, 5% toluene, 1.5% dinary acid treatment of the same stock, a por tion of the same stock described above was treat ed with about 20 pounds of 98% sulphuric acid per barrel of stock and neutralized with caustic alkali. The thus treated product showed a sul phur content of about 0.20%. sulphur. compounds and 1.5% of non-aromatic hydrocarbons such as paraf?ns, naphthenes and Example 3 ole?ns. The hydrocarbon fraction had a sulphur A portion of the same stock described in the content of 0.29% as determined by the lamp sul 65 preceding examples was fractionated to produce phur method. The mixture of acetone and hy a benzene fraction substantially free from toluene drocarbon fraction was distilled in a fractionat and having a boiling range of about 172° F. to ing column at a temperature of about 130° F. and at atmospheric pressure. This resulted in dis 180° F. This fraction contained about 0.29% sul tilling overhead substantially all of the ‘acetone 70 phur. 600 parts of this fraction was then mixed and approximately 25 parts of the hydrocarbon with 1000 parts of methanol and the mixture was distilled at a temperature of about 138° F. The fraction which‘ consisted of approximately 15 parts of non-aromatic hydrocarbons and 10 parts distillate was separately collected in about 4% of sulphur compounds. This mixture was con outs and each fraction was analyzed. Methanol densed and subsequently extracted with sui?cient 75 distilled overhead with each out until all of the hydrocarbon fraction had distilled overhead, 2,405,255 leaving substantially pure methanol as a distilla tion residue. The methanol was removed from each cut by extraction with sufficient water and each hydrocarbon fraction was separately an alyzed for sulphur content with the following re sults: The ?rst 5% of distilled oil showed a sulphur content of about 2.0%; the next 5% showed a sulphur content of 0.31%, while the next 80% of distilled oil had an average sulphur content of 0.06%. The next 7% of oil had a sulphur content of 0.56% while the last 3% of oil con sulphur compounds comprising thiophanes and thiophenes to separate thiophanes therefrom, which comprises distilling said aromatic hydro carbon fraction in the presence of a su?icient amount of a polar organic azeotrope former hav ing a boiling point of not more than 50° F. dif ference from the average boiling point of said fraction to vaporize the sulphur compounds com prising thiophanes together with azeotrope former, thereby leaving aromatic hydrocarbons and thiophenes in the residue substantially com pletely separated from thiophanes. 5. A process for the treatment of a toluene fraction containing a mixture of sulphur com tained 3.0% sulphur. The foregoing experiment indicates that the pounds comprising thiophanes andthiophenes stock contained at least two types of sulphur com pounds, one of which was distilled overhead in to separate thiophanes therefrom, which com prises distilling said toluene fraction in the pres the ?rst few percent of azeotropic distillate, while the other type of sulphur compound remained as ence of a sufficient amount of a polar organic azeotrope former having a boiling point of not more than 50° F. difference from the average boil a distillation bottoms in the last 3% of oil which was subsequently distilled as an azeotrope with 20 ing point of said fraction to vaporize the sulphur the methanol. These sulphur compounds could compounds comprising thiophanes together with be recovered from the oil associated therewith by well known methods. The foregoing description of my invention is azeotrope former, thereby leaving toluene and thiophenes in the residue substantially completely separated from said thiophanes. 6. A process for the treatment of a benzene not to be taken as limiting my invention but only fraction containing a mixture of sulphur com as illustrative thereof since many variations may pounds comprising thiophane and thiophene to be made by those skilled in the art without de separate thiophane therefrom, which comprises parting from the scope of the following claims. distilling said benzene fraction in the presence of I claim: 1. A process for fractionating a mixture of sul 30 a su?icient amount of a polar organic azeotrope former having a boiling point of not more than phur compounds of the type contained in a coal tar fraction boiling in the benzene boiling range 50° F. difference from the average boiling point and comprising thiophane and thiophene which comprises distilling said mixture of sulphur com pounds in the presence of a suiiicient amount of of said fraction to vaporize thiophane together with azeotrope former, thereby leaving benzene and thiophane in the residue substantially com acetone adapted to form an azeotrope with thio pletely separated from thiophane. phane thereby vaporizing that portion of said sulphur compounds comprising thiophane to ‘7. A process for the treatment of a hydrocar bon fraction containing non-aromatic hydrocar gether with acetone and leaving the remaining portion of said sulphur compounds comprising thiophene in the residue substantially completely separated from thiophane. 40 2. A process for fractionating a mixture of sul phur compounds comprising thiophanes and thio phenes, which comprises distilling said mixture of sulphur compounds in the presence of a suf ?cient amount of a polar organic azeotrope former having a boiling point of not more than 50‘! F. difference from said mixture of sulphur compounds and adapted to form an azeotrope 50 bons, aromatic hydrocarbons and a mixture of sulphur compounds comprising thiophanes and thiophenes to separate non-aromatic hydrocar bons and thiophanes from aromatic hydrocar bons and thiophenes, said non-aromatic and aro matic hydrocarbons ordinarily distilling from the hydrocarbon fraction in the same temperature range as said aromatic hydrocarbons distill therefrom, which comprises distilling said hy drocarbon fraction in the presence of a sufficient - with said thiophanes, thereby vaporizing that amount of a polar organic azeotrope former hav ing a boiling point of not more than 50° F. differ ence from the average boiling point of said hy portion of said sulphur compounds comprising drocarbon fraction to vaporize substantially all thiophanes together with azeotrope former and leaving the remaining portion of said sulphur of said non-aromatic hydrocarbons and said thi ophanes together with azeotrope former, there compounds comprising thiophenes in the residue 55 by leaving said aromatic hydrocarbons and said thiophenes in the residue substantially com substantially completely separated from thio pletely separated from non-aromatic hydrocar phanes. 3. A process for fractionating a mixture of sul bons and thiophanes. 8. A process according to claim '7 in which said phur compounds of the type contained in a coal tar fraction boiling in the benzene boiling range 60 polar organic azeotrope former comprises a ke and comprising thiophane, and thiophane which tone. 9. A process for the treatment of a toluene comprises distilling said mixture of sulphur com fraction containing non-aromatic hydrocarbons pounds in the presence of sufficient amount of and a mixture of sulphur compounds comprising a polar organic azeotrope former having a boil ing point of not more than 50° F. difference from thiophanes and thiophenes to separate non-aro the average boiling point of said mixture of sul matic hydrocarbons and thiophanes therefrom, phur compounds and adapted to form an azeo said non-aromatic hydrocarbons and sulphur trope with thiophane, thereby vaporizing that portion of said sulphur compounds comprising compounds ordinarily distilling from the hydro carbon fraction in the same temperature range thiophane together with azeotrope former and 70 as said toluene distills therefrom, which com leaving the remaining portion of said sulphur prises distilling said toluene fraction in the pres compounds in the residue substantially complete ence of a sufiicient amount of a polar organic azeotrope former having a boiling point of not ly separated from thiophane, 4. A process for the treatment of an aromatic hydrocarbon fraction containing a- mixture of more than 50° F. difference from the average 2,405,258 i0 boiling point of said fraction to vaporize sulphur compounds comprising thiophanes and non-aro matic hydrocarbons together with azeotrope former, thereby leaving toluene and sulphur compounds comprising thiophenes in the residue substantially completely separated from non aromatic hydrocarbons and sulphur compounds matic hydrocarbons. 10. A process according to claim 9 in which said polar organic azeotrope former is methyl 14. A process according to claim 13 in which said small proportion of sulphur compounds comprising thiophenes is separated from said matic hydrocarbons and thiophanes and cori~ taining a small proportion of sulphur compounds comprising thiophenes and subsequently sepa rating said small proportion of sulphur com pounds comprising thiophenes from said aro comprising thiophanes. 10 aromatic hydrocarbons by treatment with sul ethyl ketone. phuric acid. 15. A process according to claim 13 in which said small proportion of sulphur compounds drocarbons and a mixture of sulphur compounds comprising thiophenes is separated from said comprising thiophane and thiophene to separate non-aromatic hydrocarbons and thiophane 15 aromatic hydrocarbons by extraction with a se lective solvent for said thiophenes. therefrom, said non-aromatic hydrocarbons and 16. A process for producing substantially pure sulphur compounds ordinarily distilling from the toluene from a hydrocarbon fraction containing benzene fraction in the same temperature range toluene, non-aromatic hydrocarbons and a mix as said benzene distills therefrom, which com ture of sulphur compounds comprising thio prises distilling said benzene fraction in the pres 11. A process for the treatment of a benzene fraction comprising benzene, non-aromatic hy phanes and thiophenes, said non-aromatic hy ence of a su?‘lcient amount of a polar organic drocarbons and mixture of sulphur compounds azeotrope former having a boiling point of not comprising thiophanes and thiophenes distilling more than 50° F. difference from the average in the same temperature range as toluene, which boiling point of said benzene fraction to vaporize thiophane and substantially all of said non-aro 25 comprises distilling said hydrocarbon fraction in the presence of sui?cient amount of methyl ethyl matic hydrocarbons together with azeotrope ketone to vaporize substantially all of said non former, thereby leaving benzene and thiophene aromatic hydrocarbons and said thiophanes to in the residue substantially completely separated from thiophane and non-aromatic hydrocarbons. gether with methyl ethyl ketone, thereby leaving 12. A process according to claim 11 in which 30 toluene in the residue substantially completely separated from non-aromatic hydrocarbons and said polar organic azeotrope former is acetone. thiophanes and containing small amounts of sul 13. A process for the treatment of a hydro carbon fraction containing non-aromatic hydro carbons, aromatic hydrocarbons and a mixture of sulphur compounds comprising thiophanes and thiophenes to separate sulphur compounds 35 phur compounds comprising thiophenes and sub sequently treating said toluene containing small amounts of sulphur compounds comprising thio phenes to separate said small amounts of sulphur compounds comprising thiophenes from said and non-aromatic hydrocarbons from aromatic toluene. hydrocarbons contained in said hydrocarbon 17. A process for producing substantially pure fraction, the non-aromatic and aromatic hydro carbons and said sulphur compounds ordinarily 40 benzene from a hydrocarbon fraction containing benzene, thiophane, thiophene and non-aromatic all distilling from said hydrocarbon fraction in hydrocarbons which distill in the same temper the same temperature range, which comprises ature range as benzene, which comprises dis distilling said hydrocarbon fraction in the pres tilling said hydrocarbon fraction in the presence ence of a su?icient amount of a polar organic azeotrope former having a boiling point of not 45 ' of acetone to vaporize sub more than 50° F. difference from the average boiling point of said hydrocarbon fraction to vaporize substantially all of said non-aromatic hydrocarbons and the sulphur compounds com prising thiophanes together with said polar or 50 stantially all of said non-aromatic hydrocarbons and said thiophane together with acetone, there by leaving a mixture of benzene and thiophene in ganic azeotrope former, thereby leaving said the residue substantially completely separated irom non-aromatic hydrocarbons and thiophane and subsequently treating said mixture of ben aromatic hydrocarbons in the residue substan tially completely separated from said non-aro zene and thiophene to separate said thiophene from said benzene. GEORGE R. LAKE.