The disclosed invention relates to a process for converting ethylbenzene to styrene, comprising: flowing a feed composition comprising ethylbenzene in at least one process microchannel in contact with at least one catalyst to dehydrogenate the ethylbenzene and form a product comprising styrene; exchanging heat between the process microchannel and at least one heat exchange channel in thermal contact with the process microchannel; and removing product from the process microchannel. Also disclosed is an apparatus comprising a process microchannel, a heat exchange channel, and a heat transfer wall positioned between the process microchannel and heat exchange channel wherein the heat transfer wall comprises a thermal resistance layer.