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

Abstract

Mo2C has previously been demonstrated as an effective catalyst layer to enable stable H2 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 ~ 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 H2 permeability of Mo2C/V membranes was significantly attenuated at lower temperatures (< 600°C). H2 permeation was also severely inhibited by the presence of N2 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 H2 permeability to 2 × 10−8molm−1s−1Pa−0.5 at 500°C for V based membranes. As an interlayer, Mo2C was demonstrated to be a stable barrier preventing Pd-V interdiffusion at 500°C while simultaneously allowing significant H2 permeation.