Preparation of thin palladium composite membrane tube by a CVD technique and its hydrogen permselectivity

A thin and firmly deposited palladium membrane applicable to surface catalysis is attempted to be prepared. The technique and equipment developed in this study is based on chemical vapor deposition (CVD) under a forced flow, where due to a pressure difference applied between the outside and the inside of the support tube the chemical vapors enter into the porous layer of the support where they decompose. Palladium diacetate, (CH3COO)2Pd, was used as a palladium source. The tubular support made from α-alumina powder is porous and has an average pore diameter of 0.15 μm. The forced-flow CVD was carried out by heating according to a temperature program under regulated vacuum pressure. The palladium membrane thus obtained was as thin as 2–4 μm and had a good H2/N2 selectivity exceeding 5000.