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 sio2 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 al2o3 (γ-alumina phase), using sol-gel method. an optimized temperature of 700 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 2 µm and the top selective silica layer was quite dense and uniform with a thickness of about 90-100 nm. permeation tests showed a very good flux of 10 -6-10 -7 mol m2 s -2 pa -1 for h2 with selectivities over co2, n2 and ch4 up to 500. by performing different tests with various deposition times, it was concluded that by changing cvd time from 3 h to 6 h h2/co2 selectivity increased from 32 to 573, although h2 permeation flux reduced about 50 percent.