2,410,042 Patented Oct. 29, 1946 U‘NlTED STATES PATENT, orrlcs ‘ PURIFICATION OF STYRENE ANDJITS HOMOLOGUES ' ' ‘ George R. Bond, JrQ, Paulsboro, N. J., assignor to Houdry Process Corporation, Wilmington, Del, a corporation of Delaware ‘N0 Drawing. Application March 31, 1944, Serial No. 528,949 4 Claims. (01. 2.605669) + . 2 1 The present invention relates to improved methods for the puri?cation of styrene and its homologues produced in the cracking of high boiling hydrocarbon oils. ’ r . I-Ieretofore the commercial preparation of com pounds having a. styrene nucleus has been in accordance with the classical methods, such as molecular dehydration of betaJ-phenyl ethyl alco hol. Recently dehydrogenation methods have been employed such as the dehydrogenation of ethyl benzene and iso-propyl benzene for the ' . tages of‘ the‘present invention will be apparent as the description proceeds. ' ‘ ‘ In‘ accordance with the preferred form of the present invention a cut of a cracked hydrocarbon oil containing'a styrene type ‘compound is‘puri ?ed o‘f‘fthe reactive materials by effecting reac- . tion of theimpur‘ities in ‘the presence of sulphur dioxide and by separating the high boiling'reac—‘ ; tion ‘products from the cut. ‘ The cracked hydrocarbon, which is preferably a narrow cut relatively rich innstyrene‘ or in a homologue of styrene, is treated with sulphur di-‘ oxide;' ‘The cut may conveniently be saturated‘ spectively. The puri?cation of the dehydrogena with sulphur dioxide by bubbling the gas through‘ tion product of these processes is relatively sim the out, though obviously liquid phase sulphur‘ ple and involves the fractionation of the product dioxide may be added to the cut‘in limited amount to separate the ‘unsaturate from the saturate. insufficient to leave any liquid phase sulphur ‘di- , It has heretofore been known in the arttthat‘ oxide undissolved in the. cut. ‘The cut contain compounds having a‘styrene nucleus, by which it ing dissolved sulphur dioxide is maintained at a is intended to include. styreneand its homologues, are obtained both in thermal and catalytic crack 20 temperature below about 130° F. for. at least 15 minutes; No catalyst is needed to effect the reac: ing of gas oils. The percentage of such materials tion and it is preferred )not‘to employ any’ inas produced depends in both thermal and catalytic much as catalysts will generally promote reaction cracking to a substantial extent upon the condi . of the‘ sulphur dioxide ‘with ‘styrene type ‘come tionsof cracking, particularly upon the tempera ture, higher temperatures being conducive to 25 pounds. Temperatures substantially below room temperature are not desirable since'the rate of .' higher yields of styrene and its homologues. reaction is reduced. Operation at such tempera Various methods have been proposed for the puri production of styrene and tic-methyl styrene, re tures though is within the scope of this invention. The sulphur dioxide treatment causes the for eral involve fractionation, and concentration by , 30 mation of a tarrymaterial without anysubstantial solvent extraction. loss of either the styrene'materials or the prin I have found that cuts of cracked hydrocarbon cipal ole?ns present. It is not known de?nitely oils containing styrenes also contain small per what the impurities are which are removed or centages of reactive materials which interfere what the tarry material is, whether a polymer of with the customary uses of styrene. These ma-v the highly reactive ole?ns or a product of inter terials also interfere with some of the purifica action of the sulphur dioxide with the highlyreac tion methods employed and in many instances tive impurities. It is to be noted that under the with the production of styrene derivatives. In ?cation of the styrenes so produced and in gen general, these reactive materials can not readily be separated from the styrene by known puri? conditions of treatment‘ole?ns generally do not react to any substantial extent with sulphur‘ dioxide. > 7 cation methods, but remain with the styrene, this 40 Following the sulphur dioxide treatment the being true both in conjunction with fractionation tarry material formed from the reactive compo-f and solvent extraction. An example'of the inter nents is removed from the unreacted materials. ference of these reactive materials with styrene Likewise it is desirable to remove unreacted sul is found in the preparation of nitrosites of the phur dioxide. Convenient methods for the re styrene. When nitric oxide is reacted with the moval of these two are to distill the cut, prefer styrene compounds in the hydrpcarbon oil the ably with steam, whereby the tarry material is product which. is produced is of a dark gummy consistency instead of being in the form of the separated, and to wash the wt either before or' after steam distillation with an alkaline wash characteristic light yellow crystals. 50 such as a solution of caustic soda. to provide methods for the puri?cation of styrene When it is desired to separate the styrene from a cracked gasoline the sulphur dioxide treat . compounds produced by cracking of hydrocarbon oils and to free the styrene compounds of highly ment may be effected either before or after mak ing a narrow cut of the'gasoline, which cut con Among the objects of the present invention are reactive impurities. Other objects and advan 56 tains the desired styrene components. In ‘the " ' 2,410,042 3 case of styrene itself the~cut will ordinarily con tain styrene, ethyl benzene, xylene, and the paraf ?ns, naphthenes and less reactive ole?ns which boil in substantially the styrene range. By sol vent extraction the para?ins and naphthenes may 4 below 130° F. for at least 15 minutes in the ab sence of undissolved liquid phase sulphur diox ide, whereby reactive impurities are caused to re ~-act to form a high boiling reaction product and :separating the reaction product and excess sul be separated so that the fraction contains sty- 7 V phur dioxide from the hydrocarbon oil. mm, ethyl benzene,xylene and‘ the less reactive 2. The process of purifying a crudestyrene ole?ns. By close fractionation it is possible to compound produced by the cracking of a higher obtain a relatively pure styrene. The sulphur boiling hydrocarbon oil resulting in the com dioxide treatment may be employed at any stage 10 pound containing reactive impurities, which com in the preparation, though it is preferred to treat prises dissolving sulphur dioxide in the com the relatively narrow out prior to solvent extrac pound, maintaining sulphur dioxide dissolved in said compound for a period of at least 15 min A 120° to 150° C. cut of a naphtha obtained by utes at a temperature below about 130° F. in the thermal cracking of gas oil was saturated with absence of undissolved liquid phase sulfur diox sulphur dioxide by bubbling the sulphur dioxide ide, whereby the reactive impurities are caused through the cut at room temperature. The cut to react to form a high boiling reaction product, so saturated was allowed to stand for one ‘hour and separating the reaction product from the compound. v . at room temperature. It was then washed with caustic solution to remove free sulphur dioxide 20 3. The process of purifying cracked naphtha tion. . . and ‘steam distilled. ,A dark red gummy residue was vleft following the distillation. A sample of the cut prior to S02 treatment ‘was saturated with nitrogen trioxide at roomtemperaturet0 of highly reactive impurities which comprises dissolving sulphur dioxide in'the naphtha, main taining the naphtha together with dissolved sul phur dioxide at a temperature ‘below about 130° form‘ the nitrosite of the styrene. vThis produced‘ 25 F. for at least about 15 minutes in‘ the absence a nitrosite which was a dark’ reddish brown oily’v of liquid ‘phase sulphur dioxide and in the 'ab precipitate] The yieldoflnitrosit'e' after alcohol sence of a catalyst whereby the reactive impuri puri?cation ‘showed the naphtha ‘contained 25.5% ties ‘are caused to react to form alhigh boiling' styrene. Following SOzpuri?c'ation of the origi reaction product, and separating the reaction nal cut a nitrosite was formed by the same meth od; which nitrosite was a relatively pure, pale yellow crystalline precipitate which was easily 30 product from the] naphtha by distillation. ‘ 4. The method of purifying a hydrocarbon oil containing a styrene compound, which hydrocar ?ltered. ' The yield of nitrosite showed that the bon oil was produced by cracking a gas oil,,which naphtha‘ after treatment contained 25.1% sty comprises dissolving sulphur dioxide in the hydro; rene. .The difference .in the indicated styrene 35 carbon oil, maintaining the oil with the sulphur content was probablydue to the. difficulty of puri dioxidedissolved therein “at a temperature below ?ca'tio'n of the oily nitrosite. . ‘ 130° F. for at least 15’ minutesin the absence of ‘ What ,Ilclaim is: . ' .1. The method of purifying a hydrocarbon oil’ containinga styrene compound, which hydrocar bonoiliwas produced by cracking a gas oil, which comprises dissolving sulphur dioxide in the hy drocarbon oil, maintaining the oil with the sul phur dioxide ‘dissolved therein at a temperature liquid phase sulphur dioxide undissolved in the oil,'whereby reactive impurities are caused to re-' 40 act to form a high boiling reaction product and separating the reaction product and excess sul phur dioxide from the hydrocarbon oil. GEORGE R. BOND, JR. '