Characterization of a Pd/Ta composite membrane and its application to a large scale high-purity hydrogen separation from mixed gas

Abstract

Group VB metals, as candidates for hydrogen separation metallic membrane, suffer from low surface catalytic activity and mechanical integrity issues due to hydrogen embrittlement, which limited their practical application for mixed gas purification. This study overcomes these problems and successfully demonstrates operation schemes of a Pd/Ta composite membrane, prepared by an electroless deposition of a thin Pd layer on a bulk Ta surface. The fabricated Pd/Ta composite membrane presented higher permeability (4.7 x 10(-8) mol m(-1) s(-1) pa(-0.5)) than that of Pd-based metallic membranes reported in the previous literatures, and gas chromatography analysis proved a fuel-cell grade high-purity hydrogen (purity of 99.999% and < 10 ppm CO) separation from the mixed gas (CO, CO2, H2O, and H-2) at between 400 and 500 degrees C. Moreover, a membrane module was also prepared for treating 26 L min(-1) of mixed gas feed flow and separating about 6.9 L min(-1) of pure hydrogen with feed side hydrogen partial pressure of 4.3 bar. Leak-free operation of the module was possible under pressurized conditions (< 10 bar), and hydrogen embrittlement issues of Ta could be successfully avoided by tailoring the operating conditions.