Pore size control of carbonized BPDA-pp'ODA polyimide membrane by chemical vapor deposition of carbon

A BPDA-pp'ODA polyimide film was formed on the outer surface of a porous alumina support tube (outside diameter = 2.4 mm), and it was carbonized at an optimized temperature, 700 degrees C. The membrane obtained showed a permeance of 3 x 10(-9) mol . m(-2). s(-1). Pa-1 for O-2 and 2 x 10(-8) mol . m(-2). s(-1). Pa-1 for CO2 and a permselectivity of 10 for O-2/N-2 and 47 for CO2/N-2 at 35 degrees C. The membrane was then modified with carbon deposits formed by pyrolysis of propylene at 650 degrees C. The permselectivities for O-2/N-2 and CO2/N-2 at 35 degrees C were increased to 14 and 73, respectively. Coexisting water vapor decreased permeances of O-2 and N-2 but did not change the O-2/N-2 permselectivity.