(380am) Production of Hydrogen and H2/NH3 Mixtures from Ammonia at Elevated Pressure in a Catalytic Membrane Reactor

Ammonia is a leading hydrogen carrier owing to its high gravimetric hydrogen density in its liquid state at room temperature and moderate pressures, thereby addressing challenges associated with storage and transportation. The extraction of hydrogen from ammonia can be efficiently achieved through a catalytic membrane reactor (CMR), which offers process intensification by integrating both reaction and separation steps within a single unit operation. In addition, it is straightforward to produce H₂/NH₃ blends that can serve as carbon-free substitutes for conventional hydrocarbon fuels in combustion applications. Notably, CMRs boast higher ammonia conversions compared to conventional reactors, attributed to hydrogen removal from the reaction environment. Moreover, CMRs facilitate hydrogen recovery at elevated pressures, offering potential energy savings, particularly when the hydrogen stream is intended for applications at higher pressures, such as in fuel cells or internal combustion engines. In our previous experiments, we have showcased impressive outcomes, achieving nearly complete conversions (~100%) and substantial hydrogen recoveries (~80%) in CMR systems operating at 5 bar and 450°C. However, these systems relied on gas phase ammonia delivery which limited operating pressure to 5 bar to prevent ammonia condensation. In this study, we explore ammonia decomposition at pressures up to 20 bar by integrating liquid ammonia delivery and vaporization into the system. Additionally, we demonstrate enhanced conversion rates and hydrogen recovery by operating at higher pressures, culminating in the recovery of a high-purity permeate stream at pressures upwards of 15 bar. In the case of H₂/NH₃ blends the CMR permeate stream may be produced isobarically, eliminating compression costs.