Catalytic MFI zeolite membranes supported on α-Al ₂O ₃ substrates for m-xylene isomerization

MFI zeolite membranes were synthesized on α-alumina substrates by in situ hydrothermal crystallization. The separation of p-/o-xylene (PX/OX) mixtures was performed to evaluate the quality of MFI zeolite membranes. EDS analysis showed that aluminum from the substrate was incorporated into the zeolite structure during membrane synthesis. The negatively charged aluminosilicate framework possessed ion-exchange properties due to the presence of charge-balancing cations, which could produce acidic sites for xylene isomerization. A membrane with a PX permeance of 2.58×10 ^-8mol/m ²sPa and a PX/OX separation factor of 19.3 at 300°C was modified by H ⁺ ion-exchange treatment and used for the isomerization of m-xylene (MX). The effects of the operating temperature, feed flow rate and sweep flow rate on the membrane reaction were investigated. For MX isomerization, a high PX selectivity of 92.1% and a MX conversion of 6.5% were achieved at 270°C over the catalytic membrane.