2,410,166 Patented Oct. 29, 1946 g ‘I ” [STAT _ j' F‘Thomasi rnocnss Bi’Kimball, :OVFFSIEPARATINQ Hammond, Incl‘, TOLUENEI assignor to - SinclairRe?nin'g Company, New York, N. Y., a ‘ " corporation of Maine ‘I v - 1 . -; "Application-May '1'4,1941>,,SerialNo.393,338 - H , 3HCl'aims. (o1. goof-#674) This invention relates to improvementsin the ‘ separation of, toluene from para?in hydrocarbons of similar boiling point, and to the production of quite pure toluene from its mixturésfwith parafe ?n hydrocarbons. ' ‘ k In the production of gasoline or other low'boil the toluene from the high boiling para?‘m hydro carbons, i. e., the kerosene or thelike, a rela tively simple distillation operation in view of the substantial di?ereri‘ce in boiling points. Sub stantially allof the toluene may thus, be recov-z erediin quite pure form,_e. g.,,98,% or better.’ ingv hydrocarbons from crude oil, there is pro duced, in admixture with paraffin hydrocarbons, substantial amounts of the aromatic hydrocar ' Thesecond prO-du'ct'the kerosene or wash oil production of a distilled fraction having a boil-v ing point about that of toluene, it can be more _ or other high boiling hydrocarbon from the low , boiling para?in hydrocarbons and toluene which rei?inate, is subjected to distillationvto remove the sulfur dioxide it contains, which is recycled, bon toluene. By fractional distillation, i. e., the 10 and then is fractionated to separate the kerosene itcontains, the lighter fraction being returned to or less concentrated‘, with the production of, mix tures of toluene and paraffin hydrocarbons‘which - may contain around 30-,-,50% of toluene. Further concentration by distillation‘ operations is im , practical, and for this reas0n,'further concentra the feed tov the system if its toluene content is 15 su?icientto warrant'this, and the heavier free: 1 tion beingrecycled. Operation in ‘accordance with the invention tion of the toluene is accomplished by selective extraction with sulfur dioxide, which preferen tially dissolves the toluene. In such" operations, has importantadvantages in providing inexpen containing naphtha to separate the toluene from like from?light hydrocarbons’in the kerosene raf ?nate is simple because of .the relatively small sive yet quite complete recovery of toluene in highly puri?ed form from admixture with par a?in ‘hydrocarbons of similar boiling point. The however, di?iculties are encountered because of ?nal distillation for the separation of the toluene the distribution ratios between the extract and from kerosene or the like is easily carried out the ra?inate layers. . ' ‘ . because of the wide difference in boiling points. The present invention is directed to improve ments in the sulfur dioxide extraction of toluene 25 fsimilarly,v the separation of the kerosene or the the para?in hydrocarbons, ‘ ' 'In accordance‘ with ‘the, present invention, a mixture of toluene with para?in'hydrocarbonsof similar boiling point‘ is subjected to extraction, usually countercurrenhwith sulfur dioxide, and after separation of the extract from the raf proportion of light boiling hydrocarbons in this ' mixture.‘ In addition; because of this'small vol ume of the lighthydrocarbons in this mixture, they may be recycled to the feed, for recovery of the toluene therein. The invention will be further ‘described in con '?nate,,_the extract, with or‘without the addition nection with the appended drawing, which illus of more sulfur dioxide, iswashed or counter-cur rently extracted with a kerosene OI‘OthBI' paraf 35 trates in» a_ diagrammatic manner, apparatus ?n hydrocarbon oil of ‘substantially higher boil ing T point than toluene!“ This'jwashin'g or lcolln tercurrent , extraction of. the' naphthabxtract with kerosene or other relatively'high boiling,v 7 suitable for the practice of the invention. _> ‘In the apparatus illustrated, there is provided a tower l0 divided into two sections 12 and I4, packed in the usual fashion for countercurrent ,para?in hydrocarbon, causes the replacement, to 40 extraction of one liquid by another immiscible in it. Liquid sulfur dioxide is supplied toward a substantial extent, of the ‘light para?in hydro the top of the: upper section l2 throughthe inlet carbons carried’ by the extract with‘heavier pars l6, ‘while the feed, containing toluene and paraf a?in hydrocarbons, and results in .two products, one being a sulfur dioxide extract containing most of the toluene, a‘small proportion oflparaf ?n hydrocarbons of boiling point close to that of - ?n hydrocarbons of ‘similar boiling point issup plied somewhat below the middle of the upper ' section through the line [8. The sulfur dioxide passes downwardly through the tower countercurrent' to the hydrocarbon feed, and extracts from the hydrocarbon sub second being a ra?inate containing kerosene or , other wash ‘oil. the light para?in, hydrocarbons 50 stantially all of the toluene which it contains. The sulfur dioxide extract is removed from the extracted from the’ sulfur dioxide extract and a bottom of the upper section through the line 20, small proportion of toluene and sulfur dioxide. and as removed, it containsthe sulfur dioxide, The ?rst product is subjected to distillation nearly all of the toluene and a substantial to remove the sulfur dioxide, which is recycled, and then is subjected to treatment to separate 55 amount of para?in hydrocarbons having a boil , toluene and‘a substantial‘r-proportion of paraf?n hydrocarbons of higher boiling point, and the 2,410,166 3 ing point about the same as that of toluene. The naphtha ra?inate taken from the top of the tower through the line 22 contains most of the paraffin hydrocarbon together with small I claim: 1. The process of separating toluene from a _ mixture of toluene and parai?n hydrocarbons of similar boiling point which comprises intimately contacting said mixture with sulphur dioxide in an extracting treatment, separating the com amounts of sulfur dioxide and toluene. It is in troduced into the sulfur dioxide still 24 in which the sulfur dioxide is removed - for recycling posite mixture; into two component parts consist through the storage tank 26 while the hydrocar ingfof a raf?nate phaseand a primary extract bon bottoms are led through the line 28 for use in gasoline. The sulfur dioxide extract removed from the phase, bringing said primary extract phase With 10 out removal of sulphur dioxide therefrom into intimate contact with a paraf?n hydrocarbon having a‘, boiling point substantially higher than is supplied through the line 30 to the upper part thatyof toluene in a washing treatment, separat of the lower section of the tower. lierosene ,or , '1" i-ngithe produotsi‘of said washing treatment into bottom of the upper section through the line 20 ; ' other hydrocarbon oil having a boiling point sub two,‘ component parts consisting of a washed ex stantially higher than toluene, for example, hav tract component and a spent Wash oil component, separating hydrocarbons having boiling points ing a boiling range of 363-490'3 F. is ‘supplied to the lower portion of this section through the line .similar to'toluene from said spent wash oil com 32. The kerosene and sulfur dioxide pass through ponent by distillation, and recovering toluene the tower countercurrently and in intimate con 20 from said washed extract component by distil tact, with replacement of most of the light par affin hydrocarbons in the extract by heavier pare lation. ' ' ' ' ' ~ 2. The process ‘of separating toluene from' a mixture of toluene and para?in hydro-carbons of ' similar boiling point which comprises intimately The kerosene raf?nate is removed from the top of this section through the line 34',‘ and intro—' 25 contacting said mixture with sulphur vdioxide in an extracting treatment, separating the com duced intothe sulfur dioxide still 36, where‘the posite mixture into two component parts consist sulfur, dioxide which it contains is removed and ing of a ramnate phase and a primary extract returned to the vsulfur dioxide tank through the phase, bringing said primary extract phase with lines.36 ‘and lit. The kerosene raf?nate contain ing light hydrocarbons is then passedthrough the out removal of sulphur dioxide therefrom into af?n hydro-carbons from the kerosene. ' . linel'ii! to the splitter or still 44‘ in which the light hydrocarbons are removed from the kerosene. The light hydrocarbons are passed. through the intimate contact with a paraffin hydrocarbon line 453 and introduced with the, original feed to ing the products of said-washing treatment into the upper section l2 of the column'l@,'_if it con two component ‘parts consisting of a Washed ex tract component and a spent wash oil component, having a boiling point substantially higher than that of toluene, in a washing treatment, separat— tains suf?cient toluene to warrant further proc essing for its recovery. The'kerosene fraction is recycled through the line 138 to the lower section separating hydrocarbons having boiling points of the column ML The kerosene washed extract is removed from the bottom of the section ill through the line 50,v and introduced into the sulfur dioxide still .52. The sulfur dioxide removed in this still is recycled through the line ‘Ml, while the hydrocarbon frac tion containing kerosene and nearlyall of the toluene is removed through the‘line 5t‘, treated with acid in the acid‘treater 56 and then sub jected to distillation in the still 58 to 'separate'the similar to toluene from said spent wash oil com ponent by distillation and returning the thus sep arated hydrocarbons to the ?rst-mentioned ex tracting treatment, and recovering toluene from said washed extract component by distillation. 3. The process of separating toluene from a mixture of toluene and para?in hydrocarbons of similar boiling .pointwhich comprises intimately contacting said mixture with sulphur dioxide in an extracting treatment, separating the com posite mixture into two component parts consist toluene from the kerosene and any ‘heavier prod- . ~ ing of a ra?inate phase and a primary extract line Gil as a relatively pure product which may phase,‘ bringing said primary extract phase‘ with out removal of sulphur dioxide therefrom and in the absence of additional sulphur dioxide from contain 98.5% or more toluene; ' an extraneous source into intimate contact with ucts that may have been formed. The toluene is removed from the top of the tower through the " ' Sulfur dioxide and kerosene to replace losses may be supplied through the'lines 62‘ and 6.4, re-& spectively. ‘ ~. . ' . _‘ " ' In operatiomfor each 10G“parts of'a' hydrocar bon fraction containing about 40%itolue'ne, about 100 parts of sulfur dioxide and H50,‘ parts of kero a paraiiin hydrocarbon having a, boiling point substantiallyhigherthan that of‘ toluene in a washing treatment," separating, the products fof saidwashing treatment into two componentparts consisting of a‘waished extract component‘ and aspen't wash oil component, separatin'ghydro sene may be used, with recovery of substantially 60 carbons having boiling points similarto toluene all of the toluene as a 98.5% product. _ > ' If desired, to reduce the amount ,of “toluene removed through the line 34, additional'sulfur dioxide may be supplied through the line 66, but this is not necessary; particularly‘ifl the light hydrocarbon separated‘ from’ theikero‘sene still 44 is recycled to the feed. ' " the ' ‘from said‘ spent wash oil component by distilla tionand returning the thus separated hydrocar-f bone, to ‘the ‘?rst-mentioned extracting treatment, and recovering toluene‘ from said washed extract component by‘ distillation. ' .. THOMAS E. KIMBALL.