GB592867A - Production of styrenes and other products - Google Patents

Abstract

Styrenes and their nuclear substituted derivatives are produced by heating asym. diaryl paraffins, and their nuclear substituted derivatives having at least 2 carbon atoms in the paraffin chain, to at least 350 DEG C., and passing them through a finely-divided siliceous catalyst, preferably a hydrated aluminium silicate, with a contact time of .004-.4 sec. Inert diluents such as water vapour, hydrocarbons, e.g. benzene or toluene or fixed gases, e.g. nitrogen or carbon dioxide, are preferably present in a molar ratio to the diaryl paraffin of 1 : 2 to 25 : 1. Initial materials include asym. diphenyl, phenyl tolyl, ditolyl, phenyl xylyl, tolyl xylyl, and dixylyl ethanes, a ,a -diphenyl, phenyl tolyl, phenyl xylyl, ditolyl, and tolyl xylyl propanes, and their nuclear halogen or hydroxy substituted derivatives, and hydrocarbon oils containing the same as obtained by distilling benzol still residues. These may be preheated and passed through a steel, silica or other converter containing the catalyst at the desired temperature of 350 DEG to about 600 DEG C. or even higher. Those catalysts with higher ratios of silica to alumina are most active. They may be formed into pellets, preferably of not more than 5 mm. greatest diameter. The contact time is computed on the assumption that the catalyst is 50 per cent voids and neglecting pressure drop and volume increase. Unconverted materials may be recirculated. Pressure may be atmospheric, reduced or elevated. The catalyst is reactivated with air, preferably mixed with steam, at about 590-650 DEG C. In examples: ditolyl ethane with benzene, water, nitrogen or carbon dioxide in molar ratios of 1 : 12.2, 16, 11.85 or 12.1 respectively is treated at between 440 DEG and 475 DEG C. using contact times of .08, .033 and .10, p-methyl styrene and toluene being recovered; di-(m-xylyl) ethane with 23.7 molar proportions of water is treated at 390 DEG C. with a contact time of .065 sec. giving dimethyl styrenes and m-xylene; while di-(chlorphenyl) ethane and di-(dichlorphenyl) ethane with water at between 630 DEG and 650 DEG C. and contact times of .1-.4 sec. give chlor- and dichlorstyrene respectively and chlorbenzene or o-dichlor-benzene. Specification 569,465 is referred to.