Silicalite-1 zeolite membrane reactor packed with HZSM-5 catalyst for meta-xylene isomerization

A silicalite-1/α-Al₂O₃ zeolite membrane with high para-xylene (PX) selectivity was tested for isomerization of meta-xylene (MX) to PX. Two HZSM-5 catalyst packing methods were compared in the membrane reactor: (1) catalyst in contact with the Al₂O₃ substrate and (2) catalyst in contact with the membrane layer. The second packing method exhibited higher efficiency for MX isomerization. Compared with a conventional reactor, the membrane reactor with the second catalyst packing method had increased rates of 26.0% and 31.2% for the PX yield and selectivity, respectively, at a temperature of 270 °C. PX selectivity and yield increased as the flow rate of the sweep gas increased because of the enhanced PX flux through the zeolite membrane. Increasing the gas hourly space velocity (GHSV) could reduce the contribution of membrane permeation to PX productivity. It was also revealed that MFI zeolite membranes exhibit a high stability for xylene isomerization.