ABSTRACT
Zeolite membranes are synthesized by subjecting precursor solution to hydrothermal synthesis at certain temperature and autogenous pressure. In direct in situ hydrothermal synthesis, the surface of the porous support is in contact with zeolite precursor solution under controlled environment for nucleation and growth of a continuous zeolite membrane on the surface of the support. Microwave-assisted hydrothermal synthesis is able to form thinner zeolite membrane with narrower crystal size distribution. The utilization of ultrasonic-assisted hydrothermal synthesis offers a facile and versatile synthesis for nano and microstructure compounds, compared to long crystallization and low rate of mixing in conventional heating. Small pore zeolite membranes have been reported to be able to display high selectivities or separation factors for different gas systems of CO2/N2, CO2/CH4 and CO2/H2, depending on the conditions such as pressure and temperature. The presence of water vapor in the gas streams posted effect on the gas permeation and separation performance of several zeolite membranes.
