Synthesis of a Multilayer Ceramic Membrane Used for Hydrogen Separation at High Temperature

A multilayer composite ceramic membrane was prepared by depositing a nano-scale layer of SiO۲ on top of a modified porous alumina support by chemical vapor deposition (CVD) method. The modification of the support was carried out by adding a graded layer of Al۲O۳ (γ-alumina phase), using sol-gel method. An optimized temperature of ۷۰۰ K for intermediate layer calcination was gained by XRD analysis. Cross-sectional images obtained from SEM showed that the intermediate γ-alumina layer had a thickness of about ۲ μm and the top selective silica layer was quite dense and uniform with a thickness of about ۹۰-۱۰۰ nm. Permeation tests showed a very good flux of ۱۰-۶-۱۰-۷ mol m-۲ s-۲ Pa-۱ for H۲ with selectivities over CO۲, N۲ and CH۴ up to ۵۰۰. By performing different tests with various deposition times, it was concluded that by changing CVD time from ۳ h to ۶ h H۲/CO۲ selectivity increased from ۳۲ to ۵۷۳, although H۲  permeation flux reduced about ۵۰ percent.

Keywords:

Hydrogen Permeation , Ceramic Membrane , CVD , Selectivity