Nanocomposite MFI–alumina membranes prepared via pore-pugging synthesis: Application as packed-bed membrane reactors for m-xylene isomerization over a Pt-HZSM-5 catalyst

In this paper, we present m-xylene isomerization in an extractor-type catalytic membrane reactor using nanocomposite MFI–alumina membrane tubes packed with a Pt-HZSM-5 catalyst. The catalytic performance of the membrane reactor was compared with that of a conventional fixed-bed reactor with similar dimensions and at comparable operation conditions. The influence of the reaction temperature, gas hourly space velocity, reaction time and reactor configuration on the performance of membrane reactor was explored. The membrane reactor displayed a maximum p-xylene yield of 5.1% at 523 K when computed at permeate-only mode, decreasing with temperature. At combined mode, the p-xylene yield was ca. 28%, showing an increase of about 18% compared to an equivalent fixed-bed reactor. The catalytic membrane reactor showed 100% selectivity towards p-xylene at permeate-only mode, displaying a maximum value of ca. 42% at 523 K at combined mode. Higher performance was obtained when the catalyst packing was close to the inner top layer of the membrane support. In this configuration, xylene permeate compositions higher than 95% could be achieved on the basis of the high p/o and p/m-xylene separation factors offered by the membrane.