Palladium Membrane Formed in Macropores of Support Tube by Chemical Vapor Deposition with Crossflow through a Porous Wall

Palladium acetate vapor was sublimed at a reduced pressure and was evacuated through the porous wall of an α-alumina support tube of 1.8 mm i.d. and 2.4 mm o.d. Due to chemical vapor deposition (CVD), a thin palladium membrane was formed in macropores of the support. The membrane part was about 50 mm in length and was used without any pretreatment. The palladium membrane, prepared at a maximum CVD temperature of 400°C, showed hydrogen permeance and selectivity to nitrogen higher than 10−6 mol·m−2·s−1·Pa−1 and 1000 at 300–500°C, respectively. Even after the permeation temperature was repeatedly varied between 100 and 300°C in a hydrogen atmosphere, the membrane exhibited no hydrogen embrittlement. The amount of palladium deposited in pores of the support tube was 22 g/m2 of the outer surface of the tube. The thickness of the palladium membrane calculated from this value was 4.4 μm.