Permeation properties and hydrothermal stability of allylhydridopolycarbosilane (AHPCS)-derived silicon carbide (SiC) membranes

Among various membrane materials used for gas separation, silicon carbide (SiC) is promising because of its structural stability and mechanical strength. In this study, allylhydridopolycarbosilane (AHPCS) was used as a precursor for SiC membranes to improve gas permeance and hydrothermal stability. The membrane was prepared by coating AHPCS sols on a SiO 2 -ZrO 2 intermediate layer as the top layer, followed by firing at 500-800 °C. The highest H 2 permeance of (2.3-3.0) × 10 −6 mol m −2 s −1 Pa −1 with H 2 /N 2 of 10-30 and a H 2 /SF 6 permeance ratio higher than 1000 was obtained on AHPCS-derived SiC membranes fired at 500-700 °C. The AHPCS-derived SiC membranes were then subjected to hydrothermal treatment. After being exposed to steam, the N 2 permeance decreased from 2.4 × 10 −8 and reached stable permeances of ∼3 × 10 −9 mol m −2 s −1 Pa −1 . In the separation of binary mixtures of H 2 O/N 2 at 400 °C, the AHPCS membrane showed an excellent water selectivity, and permeance ratio for H 2 O/N 2 of approximately 100, with an H 2 O permeance of (5.5-8.0) × 10 −7 mol m −2 s −1 Pa −1 . The temperature dependence of gas permeance in binary mixtures was measured in the range of 200-400 °C. The AHPCS-derived SiC membranes are promising materials for future applications in high temperature dehydration processes. Among various membrane materials used for gas separation, silicon carbide (SiC) is promising because of its structural stability and mechanical strength.