Room-temperature ionic liquids modified zeolite SSZ-13 membranes for CO2/CH4 separation

Abstract A new modification strategy using precursors of silanized imidazolium-based room temperature ionic liquids (RTILs) has been developed for surface modification of zeolite membranes by the gentle liquid-phase silanization reaction. The advantage of RTILs in selective adsorption of CO 2 could enhance the CO 2 -selective separation for the RTILs-modified membranes. The parameters, such as the precursor and the anion type of RTILs were optimized. Characterizations including Fourier transform infrared spectroscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy, showed that silanized imidazolium-based RTILs were grafted on the surface of SSZ-13 crystals and membrane. Carbon dioxide/methane selectivity of the modified membranes was strongly depended on the type of the balanced anion of RTILs. Single-gas permeation for H 2 , CO 2 , N 2 , CH 4 , C 2 H 6 and i -C 4 H 10 and mixture CO 2 /CH 4 separation through the fresh and modified membranes were investigated. When [TESPMIM][BF 4 ] precursor was used, the average CO 2 permeance of three modified membranes decreased by only 44% (average CO 2 permeance of 1.0×10 −7  mol m −2  s −1  Pa −1 ) and CO 2 /CH 4 selectivity increased by a factor of 7 (average CO 2 /CH 4 selectivity of 87) for an equilmolar CO 2 /CH 4 mixture at room temperature compared with those of the fresh membranes.