文摘
Grain boundary defects are normally formed in zeolite membranes during membrane preparation and calcination processes. In this work, a siloxane polymer coating with an imidazole group was grafted on the surface of defective SSZ-13 membranes by chemical liquid deposition to seal the defects. The parameters, such as silanization time, polymerization time, monomer type, and concentration, were optimized. Characterizations including Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy showed that siloxane polymers were coated on the surfaces of SSZ-13 crystals and membrane. Six modified membranes showed decreased CO2 permeance by only 21 卤 5% [average CO2 permeance of 1.9 脳 10鈥? mol/(m2 s Pa)] and increased CO2/CH4 selectivity by a factor of 9 卤 3 (average CO2/CH4 selectivity of 108) for an equimolar CO2/CH4 mixture at 298 K. CO2/CH4 and CO2/N2 selectivities of the modified membrane decreased with pressure and temperature. Membrane stability was investigated by a long-time test and exposures to water vapor at temperatures up to 378 K and to some organic solutions. This modification method is also effective in sealing the defects of other zeolite membranes, such as AlPO-18 membranes.