CATALYTIC ISOBUTANE DEHYDROGENATION IN A DENSE SILICA MEMBRANE REACTOR

The dehydrogenation of isobutane on a commercial chromia-alumina catalyst was studied using a conventional and a membrane reactor. A series of differential runs were conducted varying the temperature and feed composition. Extensive loss of catalyst activity was observed within the first two or three hours on stream and this deactivation intensified with temperature and olefin content but was inhibited by hydrogen. The membrane reactor utilized a dense silica membrane prepared by chemical vapor deposition on a porous Vycor substrate. The membrane permeance was 0.3 cm3/cm2-min-atm and the hydrogen to hydrocarbon permeance ratio was 80-300. Integral runs were conducted to compare the performance of the membrane reactor with that of a conventional reactor. At all temperatures and space times the membrane reactor gave higher isobutene yield and selectivity, the difference increasing with the space time. The membrane exhibited stable permeance and permselectivity during several days of operation.