PALLADIUM MEMBRANE FORMED IN MACROPORES OF SUPPORT TUBE BY CHEMICAL-VAPOR-DEPOSITION WITH CROSS-FLOW THROUGH A POROUS WALL

Palladium acetate vapor was sublimed at a reduced pressure and was evacuated through the porous wall of an alpha-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 degrees C, showed hydrogen permeance and selectivity to nitrogen higher than 10(-6) mol . m(-2). s(-1). Pa-1 and 1000 at 300-500 degrees C, respectively. Even after the permeation temperature was repeatedly varied between 100 and 300 degrees 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/m(2) of the outer surface of the tube. The thickness of the palladium membrane calculated from this value was 4.4 mu m.