Patented Nov. 15, 1949 2,488,479

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' 2,488,479 ‘SEPARATION 9F PHENGLS ,FROIVI THIOPHENOLS Hans ‘Schindler, Pet-rolia, Pa., iassignor ‘to T'Ehe Pure iOil ‘ Company, Chieagoglll, a ‘corporation of Ohio No Drawing. Applicationseptember 2%,..1948, Serial No. 51,123 19 Claims. (01. 260-609) "1 2 This invention relates to a method of separat ring sulfur, wherein: the oxygen and‘sulfur are ‘at ' ing phenols from thiophenols and, in particular, it ‘:tached rclirectly 1‘ to: the nucleus. relates to an adsorption process of separating “In accordance :with- my invention, EI prefer to phenols from thiophenols whichhave' closely re ‘filter the'mixture of a “phenol and thiophenol lated ‘structures. 5 :through aibed of-silicagel until analysis: of the This application is a-continuation-in-ipart of e?luent‘liquid or '?ltratesshows that phenol‘ isl-no my'application Serial Number 547,989, now aban longer being iadsorbed zaon‘the-silica gel as indi doned, filed August “3, 1944. vcated lby-lthe ‘fact that'the- effluent has substan Phenols recovered ‘from 'coaltars ‘and petro tially thesamercomposition as thezcharge. The leum oils are frequently admixed with thiophe 10 asijlicargel-bed isitheniwashed with "a suitable-‘sol nols which occur naturally in the same media and vent, preferably 'a1.low'-'boiling hydrocarbon sol because of the chemical similarity .of the two =.vent, such as hexane?benzene or hydrocarbons types of compounds, separation is very dimcult fbo'iling :in the-gasoline range, ‘capable-of ‘remov when purely chemical means are used. This in 1mg unadsorbed :materiali held ‘in “the :?lter vbed, particular is "true when phenols are extracted 15111115 incapable of rextractingthe adsorbed con virom , their.naturallmedialbylmeans of caustical :istituents :from :the :silica gel; Following ithis vkali solution. A common source of mixtures of washing, the adsorbed phenols a-raextracted from phenols and thiophenols is the alkaline prewash the silica gel by means ofasuitable solvent, pref used in re?ning cracked gasolines. Quitegener erably a low-boiling 'ketone, such as acetone, sally ‘in such operations, ;an ;acid oil fraction is 20 butanone, or pentanone. Any hydrocarbon sol ‘sprung .from the :alkaline > was-h solution, which vent boiling up to approximately 200°,C.,is suita jfraction-hassa boiling :range ::from about 359° to ble-Ior the‘preliminary washing of the silica gel about 450311, land-1a desirable cresol content. ‘and any "aliphatic sketone 'boiling "up ‘to - approxi However, the economic’ valuev of the ‘ material --is mately 200°C. is suitable for the extraction of the seriouslyrreducedbecause it contains thiophenols 25 phenols from the silica gel. ‘ Zin ‘substantial :amounts. To apply the process to a speci?c-mixture-of Accordingly,__itnis :a ‘fundamental 1 object of ‘ the >_ phenols anclthiophenols, consideration should'be :instant invention toprovide .armethod which can given to the possibility that the phenol to be re ‘serve as abasisforla-processcfor separating;phe covered may be substituted'to such an-extent that nols. from thiophenols and serve totconcentrate a 30;it .will not be adsorbed preferentially. I have :mixture :of :the compounds ;into fractions rela .zfound that if .thesphenol to berecovered'from ad tively :richer ‘:in phenol and thiophenol, respect ;mixture with1anthiophenol is soluble in sodium ively. lhydroxidezsolution .of :a concentration about :10 ;It is :asecond :object of ,the:invention to pro per . cent‘ :.by ‘weight, it will “be preferentially ad ~_vide an adsorption'process-jfor the separation of .vsorbed from admixture with very closely related aphenols ‘from ;thiopheno1s. athiophenols. :fIlhezsolubilitynof ‘the phenol in any alt isianother-gobject of vtheinvention to provide zalk'altmetal hydroxidesolutioncan be used, for \a-cmethod of'recovering a useful;phenol fraction iexamplejsodium, ipotassium, lithium, rubidium, :Irom .acid zoiil. , ' ,iforitiistheccapacity of the phenol-t0 form phe Ii'have discovereclsthatrelatively pure phenols ‘19 enolatewhichgis beingrrtested, :becauselit is those can be separated from :mixtures :of-pheno-ls :and :y‘vhich xform 531K811 zphenolates which are readily "thiophen'ols ;by;contactir.g ;the jnixtures with adsorbed. In general, .imsu-bstitutedphenols v‘will zsilica ‘gel aatordinarytemperatures. Mixtures "-of be adsorbed from admixture with unsubstituted phenol and thiop'henol- :which :are zrathericlosely thiophenols; 'likewisa'sub'stituted phenols will be related in‘structurebyyirtue ofrhavingesubstam adsorbedzfrom admixture with substitute'rlthio "tially similar 'substituents > onithe» respective ben -,phenols. 2 It iswhen atsubstituted phenol is to be recovered from admixture with unsubstituted ‘ ' zene rings are readily-separated,'=for the'phenols thiophenol that the degree of substitution of the are preferentially“adsorbed onisilica gel'andloan phenol or ‘the degree of di?erence'between‘the ‘be extracted therefrom‘by using, a-suitable solvent . ,structuresof the compounds should be consid ‘from which ‘theycan‘ibe recovered. "'Thel- process ered. If the phenol is soluble in sodium hydrox~ is applicable generally 'to mixtures ‘toil-aromatic ide ‘solution .of about “10 percent concentration, compounds-of carbon,fhydrogennoxygenwand sul itwill be‘preferentially adsorbed by silica‘gel. vfur, the onrelgroup-offcompounds:containing oxy~ 'As an "example 'of the above procedure, ‘the ‘gen and thelother group invthe mixture :contain- ’ 55 eseparationrof thiop'hen'o'l vfrom 2,4,‘G-tertiarybutyl 2,488,479 3 4 phenol might be attempted. Because the hy cent by weight of cresols and 2.4 per cent by droxyl group on the 2,4,6-tertiary butyl phenol is weight of thiocresols. Measured in terms of so hindered by alkyl groups, the thiophenol would barrels of cresols per ton of silica gel, the yield be preferentially adsorbed. The 2,4,6-tertiary was 1.6 barrels per ton. The cresols obtained butyl phenol has no signi?cant solubility in 10 were slightly better in quality than commercial per cent sodium hydroxide solution. However, cresols marketed by a well-known company. 2,4-tertiary butyl phenol can be preferentially ad Commercial cresols, with which a sample pre- sorbed from a mixture thereof with thiophenol pared in accordance with my invention was com and it is found to be readily soluble in 10 per pared, contained 2.6 per cent of thiocresols. cent sodium hydroxide solution. 10 The cresols from the ?rst extraction were Thus, the application of the process to the again percolated through the silica gel and four recovery of phenols from thiophenols as they cuts of ?ltrate were taken and analyzed for occur in admixture, is well exempli?ed in the thiocresols. The data on these four cuts are rendering of acid oils. These oils as they are given in Table III: sprung from spent caustic, may contain very low TABLE III boiling aliphatic acids, but will include phenolic and thiophenolic compounds of closely related Per Cent by Per Cent by Per Cent by structures in the fraction boiling from about 300° Cut No. W gt. of Wgt. of W gt. of to 450° F. The phenolic bodies are easily recov Charge Thiocresol Crcsol ered by successive adsorptive fractionations car 20 ried out with silica gel in accordance with the instant invention as illustrated by the following asap-q examples in which the separation of mixtures Hwww I-‘CRHD-l caDcow otocozo FIST‘? representing typical acid oil cuts is illustrated. In order to demonstrate the invention, 125 The silica gel was then washed with 200 milli grams of silica gel having a mesh size of approxi liters of hexane to wash it free of unadsorbed mately 8 to 14 was packed in a glass tube. The material and thereafter washed with 150 milli silica gel occupied a volume of 200 milliliters. liters ci acetone to extract the adsorbed ma Two hundred (200) grams of a mixture, con terial. The data on the extracts obtained are taining 25 per cent by weight of meta-thlocresols 30 given in Table IV: and 75 per cent by weight of mixed meta- and TABLE IV para-cresols was percolated by gravity at room temperature through the bed of silica gel at the rate of 1.3 barrels per ton per hour. The ?ltrate 91i o vent P $36113.“'_ 1 Pcrvcentfbygt. 0 Pervcentfbygt. 0 was divided into seven separate equal cuts and solvggtugtree Thiocrcsol Cresol each was analyzed for thiocresols. The data are given in the following table: Hexane ______41.0 2.3 97.7 TABLE I Acetone...“ 11.0 1.4 98.6

Per Cent by Per Cent by Per Cent by It will be seen from the table that 11 per cent Cut No. Wgt. of Wgt. of Wgt. of of the initial charge of 35 grams containing 97.6 Charge Thiocresol Cresols per cent of cresols and 2.4 per cent by weight of thiocresols was obtained as cresols having a 5. 2 5B. 1 41. 9 5. 2 32. 5 67.5 purity of 98.6 per cent by weight. 5. 2 27.0 73.0 It will be apparent that larger yields of cre 5. 2 25. 6 74. 4 7. 7 25. 9 71. 1 sols may be obtained by recontacting any or all l2. 9 25. 8 74. 2 of the ?ltrate cuts with silica gel. For example, 7. 7 24. 6 75. 4 the process can be carried out in series with the ?ltrate from one ?lter bed passing through After 98.4 grams of the mixture had drained 50 successive ?lter beds followed by separate ex from the silica gel bed, hexane was admitted in traction of each bed with hydrocarbon solvent order to remove all non-adsorbed material. The and ketone. In this manner it is possible to amount of hexane used in the washing step was obtain a series of fractions of cresols of gradu approximately 200 milliliters. After the unad .. ally decreasing purity from each bed and these sorbed material was removed from the silica gel fractions can be again treated in a series of con by hexane washing, the silica gel was washed tact steps with silica gel to increase the purity with approximately 150 milliliters of acetone to thereof. After contacting mixed phenols and remove the adsorbed material. The hexane and thiophenois with silica gel, followed by extrac acetone were separated by fractional distillation tion with hydrocarbon solvent and ketone, silica from their respective extracts and these were gel can be re-used for further treatment of analyzed for thiocresols. Data with respect to phenol-thiophenol mixtures. the extracts appear in Table II: In additional testing of the process, a mixture TABLE II of phenol and thiophenol containing 25 per cent by weight of thiophenol and 75 per cent by weight of phenol was subjected to the adsorp Pe{vc‘gngfby Per Cent by Per Cent by tion process. A column of silica gel containing Solvent sdVegn?Ftee Wgt. of Wgt. oi Extract Thiocresols Cresols 100 grams of 200 mesh activated silica gel was maintained at a temperature of about 110° F. in

Hexane ______31. 5 24. 6 75. 4 order to insure the retention of the percolating Acetone ______17. 5 2. 4 97. 6 mixture in the liquid phase. One hundred (100) milliliters (approximately 105 grams) of the It is apparent from Table II that 17.5 per blend of phenol and thiophenol was added to cent by weight of the original charge or 35 grams the column and subjected to a pressure of 6 of cresols were recovered, containing 97.6 per pounds per square inch gauge of nitrogen. Frac has 5 6 'tions :of effluent were collected "and their - volume compounds, as ‘shown, it is possible to develop an :and weight recorded as follows: appreciable concentration of the phenol in a-given fraction by means of a single pass through an 'TABLEV adsorption bed. As an empirical testof the type 10f phenol which "can be separated from a thio Fraction Interval ' Volume Weight phenol by means of the ‘process, the solubility of the compounds in 10 per cent sodium hydroxide I M in. -Cc ‘ ‘Grams solution can be used. Where a phenol and a Sample-‘entered '0 ______.L _. ______. .85 5. 0 ‘5:108 =thiophenol ‘have substantial solubility in sodium 2 .31 5. 0 5. O3 hydroxide solution and are rather closely'related 3"- _. ’56 633 7/20 10 in structure, it is quite possible to base a sep aration on ‘this adsorption process. For most Fractions ofthe e?luent from 'the column were reliable operation of 5the process, therefore, the .takenafter the ‘intervals indicated and after the degree of hindranceof the hydroxyl-group in the ‘third ‘fraction ‘had been taken, nitrogen com phenol should be about the same as the degree menced issuing from the column. At ‘this point, ‘of hindrance of the sulfhydryl group in the thio the test was ended, nitrogen ‘pressure released, phenol. If the structures are verydifierent, the andheating discontinued. One hundred‘ (100) one compound being relatively unsubstituted and milliliters of redistilled commercial ‘hexane was the other carrying many hydrocarbon substitu "introduced ‘into ‘the top of the column at "70° ‘ents, 'it is quite-possible that the difierenceinad Eundera pressure of 15 p'ounds'per square inch sorptivity between the compounds will be-altered gauge ‘of ‘nitrogen and 1:05 milliliters of liquid to the point that the polarities will change. collected from the ‘column before nitrogen again For example, a very highly substituted phenol, ‘began to ‘issue therefrom. Following the same such as 2,¢l,6-tertiary butyl phenol, ‘cannot vbe ‘technique, "76 milliliters of acetone was passed 25 vpreferentially adsorbed from admixture with 'into the column under a pressure ‘of 6 pounds ‘thiophenol by this process; it is the 'thiophenol ‘.per square .inch gauge of nitrogen and during a which is adsorbed. If the thiophenol is highly period of four hours 190 milliliters of eliluent was substituted and the phenol is not, sharp adsorp collected. The hexane and acetone solutions tion of the phenol is aided. ‘thus recovered were separately distilled in ‘the 30 In a similar manner, other mononuclear absence of air ‘and ‘the residues weighed. They phenols, such as 70-, m-, or p- mono .n-bu‘tyl were also analyzed for phenol and thiophenol phenol are separable from corresponding mono ‘with the‘followingresults: n-butyl ‘thiophenols. 'The compounds are-of very TABLE VI similar structure, molecular weight and'chemical Distribution of thiophenol and phenol reactivity, ‘but the OH group of the phenol ‘is free and the phenol can be adsorbed-out of mix [From acid-base titration usingphenolphthalcin indicator] tures. Various propyl and isopropyl phenols are ‘common and can be separated from correspond Per cent Per cent Per cent Sample Weight Thiophenol Phenol-in ing thiophenols-by adsorption in accordance with Charge in Fraction Fraction 40 the» process described. Xylenols constitute an other type of phenol which ‘is readily separated Grams from admixture with thiophenols. Thus, the Original vCharge ______22. 6 77. 4 Fraction #1 ...... _ _ 5.08 A4. 8 88. 4 11.6 various xylenols, some of which occur in mixtures 'Fraction #2 ______.; ‘5: (13' "4.8 40.8 59. 2 such as the acid oils mentioned, are readily Fraction #3.. _ _ _. _____ 7. 2O .9 23. O 17.0 Residue from Hex separated from “thiophenols or their correspond 'ane Wash ______.1 ‘56. '2 v53.5 24.8 '75. 2 ing thioxylenols, because the OH group of the Residue ‘from ‘Ace tone Wash ______._ 19.0 18. l 1. 2 98. 8 xylenol ‘is -essentially unhindered and available for adsorption. 1 92. 51 1 88.1 It will be seen, ;-therefore, that I ‘have ‘found a simple method for separating phenols from lOriginal charge was approximately 105 grams, so there was apparently a loss of some 12.5 grams (probably due to hold-up). thiophenols. Similar tests made with activated Per cents are calculated on basis of 105 gram charge. charcoal and activated alumina indicated that From these data, the ?gures showing the phenol neither of these materials was effective to sepa content of the acetone extract, it was determined rate thiocresols from cresols. that about 2s per cent of the phenol present in 55 What is claimed is: the original mixture charged to the silica gel ad 1. The method of separating a mixture of sorption column was recovered in a state of about phenols and thiophenols of similar structure into 99 per cent purity and that approximately 19 at least two fractions, the phenol being soluble per cent of the thiophenol present in the mixture in caustic alkali solution of about 10 per cent charged to the column was recovered with a 60 concentration, one of which is richer in phenols purity of approximately 93 per cent. and the other of which is richer in thiophenols Contact between the material undergoing than the original mixture comprising, contacting treatment and the silica gel may be by contact the mixture with silica gel, removing the un ?ltration or percolation. Where percolation is adsorbed mixture from the silica gel and then used, upward or downward percolation may be 65 solvent extracting a mixture richer in phenols practiced and the contact may be carried out from the silica gel. at atmospheric pressure or at superatmospheric 2. Method in accordance with claim 1 in which pressure. the unadsorbed mixture is removed from the The process as has been pointed out is par~ silica gel by washing it with a low-boiling hydro ticularly useful for the separation of phenols and 70 carbon solvent and the fraction richer in phenols thiophenols of closely related structure which is extracted from the silica gel with a low-boiling would have substantially similar boiling points ketone. and reactivities and, therefore, complicate chemi 3. The method in accordance with claim 1 in cal processes for separation. By basing the which the fraction richer in phenols is extracted process on the difference in adsorptivity of the from the silica gel with acetone. 2,488,479 7 8 4. The method in accordance with claim 1 in 13. The method of recovering concentrated which the fraction richer in phenols is extracted cresols from a mixture containing cresols and from the silica gel with butanone. thiocresols comprising, contacting the mixture 5. The method in accordance with claim 1 in with silica gel, removing unadsorbed constituents which the mixture is an acid oil fraction boiling from the silica gel and then solvent extracting from about 300° to 450° F‘. the adsorbed constituents from the silica gel. 6. The method of separating a mixture of 14. The method in accordance with claim 13 monohydroxy phenols and thiophenols of similar in which the unadsorbed constituents are re structure into at least two fractions, the phenol moved from the silica gel by washing with a being soluble in caustic alkali of about 10 per 10 low-boiling hydrocarbon solvent and the ad cent concentration, one of which is richer in sorbed constituents are removed from the silica phenols and another of which is richer in thio gel by extraction with a low-boiling ketone. phenols than the original mixture comprising, 15. The method in accordance with claim 13 percolating a mixture of phenols and thiophenols in which the adsorbed constituents are extracted through a bed of silica gel, removing unadsorbed with acetone. mixture from said bed and then solvent extract 16. The method in accordance with claim 13 ing the adsorbed fraction richer in phenols from in which the adsorbed constituents are extracted the silica gel. with butanone. 7. The method in accordance with claim 6 in 17. The method of obtaining concentrated which the mixture is percolated through the bed cresols from a mixture of cresols and thiocresols until the e?iuent liquid is of substantially the comprising, percolating said mixture through same composition as the charge. silica gel until the composition of the e?‘luent 8. The method in accordance with claim 6 in is substantially the same as the charging mix which the unadsorbed mixture is removed from ture, washing the silica gel with hexane until the silica gel by washing with a low-boiling substantially all hexane-extractable material is hydrocarbon solvent and the adsorbed fraction removed, then washing the silica gel with acetone richer in phenols is removed from the silica gel and separating the acetone from the material by extraction with a low-boiling ketone. extracted from the silica gel. 9. Method in accordance with claim 8 in which 18. The method in accordance with claim 1 in the ketone is acetone. 30 which the mixture is contacted with silica gel at 10. Method in accordance with claim 8 in which approximately atmospheric temperature. the ketone is butanone. 19. The method in accordance with claim 11 in 11. The method of separating monohydroxy which the mixture is contacted with silica gel mononuclear phenols from thiophenols of closely at approximately atmospheric temperature. related structure comprising, percolating a mix HANS SCHINDLER. ture of phenols and thiophenols through a bed of silica gel until the effluent liquid has substan REFERENCES CITED tially the same composition as the charging mix ture, washing the silica gel with hexane until The following references are of record in the substantially all unadsorbed mixture is removed ?le of this patent: and then extracting a fraction richer in phenols UNITED STATES PATENTS than the original mixture from the silica gel with acetone. Number Name Date 12. The method of recovering phenol from a 1,537,260 Patrick ______May 12, 1925 mixture containing phenol and thiophenol com 1,882,146 Holmes ______Oct. 11, 1932 prising, contacting the mixture with silica gel, 2,098,779 Gericke et al. ______Nov. 9, 1937 removing unadsorbed constituents from the silica 2,343,165 Adler ______Feb. 29, 1944 gel, and then solvent extracting the adsorbed constituents from the silica gel.