filtering the feed stock prior to fractional distillation toluene is alkylated to form ethyltoluene by any suitable method known to those of skill in the art the ethyltoluenes formed are dehydrogenated by vaporizing the hydrocarbons by means of heat exchangers passing a stream of the vapors into admixture with steam to form a vapor mixture comprising from 1 to 10 advantageously from 2 to 3 parts by weight of steam per part of hydrocarbons and passing the vapor mixture into a reactor containing a solid granular dehydrogenation catalyst at a reaction temperature between 550 u00b0 and 700 u00b0 c preferably between 560 u00b0 and 650 u00b0 c any of the known catalysts which are suitable for use in dehydrogenating ethyltoluene may be used a considerable number and variety of such catalysts are known and are commercially available catalysts of the self regenerative type are preferably used a vapor mixture containing steam and vinyltoluene then leaves the dehydrogenation reactor and passes through one or more heat exchangers a polymerization inhibitor is then injected into the vaporous mixture any of the inhibitors which are suitable for use in preventing the formation of undesirable thermal polymers in vinyltoluene and are soluble in the organic phase of.