Catalytic dehydrogenation of ethylbenzene to styrene in a zeolite silicalite-1 membrane reactor

A novel membrane reactor containing stainless-steel-supported zeolite silicalite-1 membrane was used for the catalytic dehydrogenation of ethylbenzene to styrene packed with an iron oxide catalyst. The zeolite silicalite-1 membrane was formed on a porous, tubular stainless-steel (PTSS) support by a two-stage varying-temperature in situ synthesis. The dehydrogenation of ethylbenzene to styrene was carried out in both the zeolite silicalite-1 membrane reactor and fixed-bed reactor at temperatures from 580 to 640 degrees C and 0.8 atm pressure with a water/ethylbenzene volumetric ratio of 2.0. The conversion of ethylbenzene in the membrane reactor increased with the increasing purge gas flow rate originally and then decreased slightly. The conversion in the silicalite-1 membrane reactor was about 7% higher than the fixed-bed reactor for temperatures above 600 degrees C without decreasing the styrene selectivity as the ratio of the purge gas to the reactant feed was kept at two. For example, the conversion of ethylbenzene in the membrane reactor reached 74.8% at 610 degrees C, compared with the fixed-bed reactor value 67.5%. The improvement of conversion is mainly attributed to the instantaneous, removal of hydrogen from the reaction zone through the zeolite silicalite-1 membrane during reaction process. (C) 2007 Elsevier B.V. All rights reserved.