Fabrication and operational considerations of hydrogen permeable Mo2C/V metal membranes and improvement with application of Pd

Mo2C has previously been demonstrated as an effective catalyst layer to enable stable H-2 permeation through vanadium foils at high temperatures. In this study, this approach was extended to several group V metal foils (V, Nb, and Ta) as well as mixed gas testing. The best permeability was achieved with V, and an activation process was developed to recover the performance of V foils displaying evidence of oxidation. Nb foils yielded similar to 20% the permeability of V, while Ta was too brittle to operate effectively. Mo2C/V membranes were operated at feed conditions well above the ductile-to-brittle transition pressure without embrittlement; however, the H-2 permeability of Mo2C/V membranes was significantly attenuated at lower temperatures (< 600 degrees C). H-2 permeation was also severely inhibited by the presence of N-2 or CO2 in mixed gas environments due to strong competitive adsorption. The addition of a Pd catalyst layer on top of Mo2C improved mixed gas stability and increased H-2 permeability to 2 x 10(-8) mol m(-1) s(-1) Pa-0.5 at 500 degrees C for V based membranes. As an interlayer, Mo2C was demonstrated to be a stable barrier preventing Pd-V interdiffusion at 500 degrees C while simultaneously allowing significant H-2 permeation.