High-Purity H2 Produced from NH3 via a Ruthenium-Based Decomposition Catalyst and Vanadium-Based Membrane

Ammonia is a prospective hydrogen transport intermediate due to its high volumetric and gravimetric H2 densities, and existing production and distribution infrastructure. However, its ultimate use in mobile proton exchange membrane (PEM) fuel cells necessitates decomposition and purification at or near the point of use. In this study, the production of high purity H2 from NH3 using a two-stage process has been demonstrated by coupling separate decomposition (150 g of 1 wt % Ru on Al2O3 catalyst) and purification (a single 150 cm2, Pd-coated tubular vanadium membrane) stages. Equilibrium NH3 decomposition and >90% H2 recovery was demonstrated with a catalyst temperature of 450 °C and membrane temperature of 340 °C, with an overall H2 production rate of 0.75 kg/day. Mass spectrometry showed that levels of N2 and NH3 impurities were below detection limits. This configuration is readily scalable by increasing the catalyst loading and membrane area (through use of multiple tubes in parallel), and could enable a pathway for distributed use of H2 from NH3 in mobile and stationary power generation.