Gas Permeation Properties and Methylation of Toluene by MFI Zeolite Membranes with Different Si/Al Ratios

摘要

MFI zeolite membranes having different Si/Al ratios were prepared by secondary growth of crystalline colloidal seeds under hydrothermal conditions. An MFI membrane of Si/Al = infinity showed a n-C_4H_(10) permeance of 1.5 X 10~(-5) m~3 (STP) m~(-2)s~(-1)kPa~(-1) and a n/I-C_4H_(10) selectivity of 15 at 150 deg C. By addition of Al into MFI membranes, the zeolite layers appeared to be randomly oriented, and n/I-C_4H_(10) selectivities were decreased. Methylation of toluene using MFI catalytic membrane reactors was carried out at 400-500 deg C. Toluene conversions increased with reaction temperature and a maximal p-xylaene selectivity of 80% was achieved. suggesting the effectiveness of MFI catalytic membrane reactors.