MFI型分子筛膜的两段变温合成及对二甲苯异构体的分离性能

MFI zeolite membranes were prepared in situ on alumina supports by constant temperature and two-stage varying-temperature synthesis methods, respectively. The MFI zeolite membranes synthesized by the constant temperature method were composed of large crystals and had no separation performance for PX/OX due to the large defects caused by template removal at high temperature. The membranes synthesized by two-stage varying-temperature synthesis method were composed of the zeolite crystals with smaller sizes in a and b directions, and the formation of defects can be avoided during template removal at high temperature. A good separation performance for PX/OX at 300 ℃ with a separation factor of 42 and the PX permeance of 9.57×10^-9 mol•m^-2•s^-1•Pa^-1 can be obtained. Detemplation at low temperature in ozone atmosphere can effectively avoid the formation of large defects to improve the membranes, performance by reducing the stress caused by the thermal shrinkage of zeolite crystals. The membranes synthesized by both the two methods showed separation abilities for the xylene isomer after detemplating at low temperature in ozone atmosphere. The MFI zeolite membranes synthesized by variable synthesis temperature showed a PX/OX separation factor up to 76 and PX permeance of 1.02×10^-8 mol•m^-2•s^-1•Pa^-1.