Preparations of metal impregnated porous inorganic membranes for hydrogen separation by multi-step pore modifications

In this research porous inorganic membranes for hydrogen separation were pr epared with alpha-alumina support by multi-step pore modification method. P orous inorganic membranes were made by three consecutive steps: sol-gel met hod in-situ hydrolysis of tetraethylorthosilicate (TEOS) and soaking and va por deposition (SVD) method. In order to enhance the hydrogen selectivity, we used nickel (Ni) and palladium (Pd) particles in the first and final por e modification steps. Although both nickel and palladium induced surface di ffusion, palladium was shown more effective for hydrogen selective adsorpti on than nickel. This multi-step method produced porous membranes with a mod erate hydrogen selectivity and excellent hydrogen permeability at high temp erature up to 773 K and at transmembrane pressure (Delta P) as high as 310 kPa. The separation factor of hydrogen relative to nitrogen was maintained at about 7 even when the transmembrane pressure was 70 kPa, and the hydroge n permeability was still much higher than that of non-porous polymeric memb ranes. Furthermore, the distributions of nickel and palladium within the in termediate layer formed at the membrane cross-section were examined by scan ning electron microscopy (SEM) and energy dispersive X-ray analysis.