Synthesis and Evaluation of Composite Ceramic Membrane in Hydrogen Purification for Fuel Cell Applications

An alumina microfiltration membrane (inside diameter=9 mm, outside diameter=l3 mm, length= 50 mm) with an average pore size of 0.4 microns was used as the support for composite membrane. This support was soaked in boehmite sols, with mean particle size adjusted in the range of 50 to 500 nm by carefully controlling hydrolysis time, and calcined at 650-700°C for two hours. This process was repeated with different boehmite solutions in order to achieve an intermediate layer with an average pore size of about 50 nm. The resulting substrate was then coated with a thin and dense layer of silica by chemical vapour deposition (CVD) method. SEM and XRD analysis were used to characterize different layers of the membrane. Single-component permeation tests were carried out for hydrogen, methane, and carbon dioxide at temperature range of 500-800 °C, and the outlet gases were analysed by an on-line gas chromatograph (Agilent 7890A) to measure total H2 permeation and selectivity. The results showed almost the same permeance in range of 5-8 x 10-7 mol.m2.Pa-1.s-1 and hydrogen selectivity values for hydrogen in range of 550-600, which means highly purified hydrogen of 99.9%. This hydrogen can be stored and used for fuel cell applications.