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Efficient Ammonia Decomposition in a Catalytic Membrane Reactor To Enable Hydrogen Storage and Utilization

Zhang, Zhenyu, Liguori, Simona, Fuerst, Thomas F., Way, J. Douglas, Wolden, Colin A.
ACS sustainable chemistry & engineering 2019 v.7 no.6 pp. 5975-5985
ammonia, catalysts, ceramics, hydrogen, infrastructure, liquids, models, palladium, ruthenium, temperature
Liquid ammonia is a high-density (17.7 wt %) hydrogen carrier with a well-established production and distribution infrastructure. Efficient decomposition and purification are essential for its use as a hydrogen-storage material. Here we demonstrate the production of high-purity (>99.7%) H₂ from NH₃ using a catalytic membrane reactor (CMR) in which a Ru catalyst is impregnated within a porous yttria-stabilized zirconia (YSZ) tube coated with a thin, 6 μm Pd film by electroless deposition. The intimate proximity of catalyst and membrane eliminates transport resistances that limit performance in the conventional packed-bed membrane reactor (PBMR) configuration. The addition of a Cs promoter enabled complete NH₃ conversion at temperatures as low as 400 °C, exceeding equilibrium constraints without the need for a sweep gas. A reactor model was developed that captured CMR performance with high fidelity. NH₃ decomposition was observed to follow first-order kinetics due to efficient H₂ removal. Relative to a comparable PBMR, the Ru loading in the CMR was reduced an order of magnitude and the H₂ recovery increased 35%, enabling record volumetric productivity rates (>30 mol m–³ s–¹) that validate its promise for efficient, compact H₂ delivery from ammonia.