Production of hydrogen and H2/NH3 mixtures from ammonia at elevated pressures in a catalytic membrane reformer

Abstract

Hydrogen delivery at elevated pressures is often required for fuel cell and combustion applications to improve volumetric energy density. Catalytic membrane reformers (CMRs) integrate hydrogen production and purification from reforming liquid hydrogen carriers, such as ammonia, enabling direct recovery of pressurized, purified hydrogen. In this study, high-pressure ammonia is supplied to a catalytic membrane reformer (CMR) to enhance both performance and hydrogen recovery pressures. Increasing operating pressure in the CMR resulted in nearly doubling the hydrogen flux from 17.2 to 34 sccm cm⁻² compared to our previous work. However, as the recovery pressure of the permeate increased, the performance notably decreased with hydrogen recovery dropping from 98 % at atmospheric pressure to 44 % at 10 bar. Nevertheless, the system demonstrated rates of ammonia conversion, hydrogen flux, and hydrogen recovery comparable to leading literature reports when supplying ammonia at 20 bar and recovering the permeate up to 10 bar. Additionally, by using ammonia as both a feed and sweep gas, we demonstrate the direct production of high-pressure NH₃/H₂ fuel blends, including a 70:30 mixture representative of natural gas, without loss in CMR performance. These results highlight the potential of CMR technology to reduce hydrogen compression costs and enable on-demand generation of ammonia-derived fuel blends.