Ammonia (NH3), a liquid at moderate temperatures and pressures, is a leading carrier that mitigates many of the challenges associated with the storage and transport of pure hydrogen. Catalytic membrane reformers (CMR) offer process intensification and greater efficiency for on-site and on-demand hydrogen delivery. We have developed a CMR configuration based on composite palladium (Pd) membranes that have a ruthenium (Ru) catalyst impregnated in the support as well as additional catalyst within the lumen. Although excellent performance has been achieved, both reductions in cost and improvements in productivity are required to enhance commercial viability. In this presentation, we describe multiple advances over our previous design. First, using an ultrasonic-assisted electroless plating method, we have been able to achieve <1 micron palladium membranes while maintaining high selectivity, a 4-fold reduction in Pd inventory. Second, the asymmetrically porous yttria-stabilized zirconia (YSZ) supports were replaced with low cost symmetrically porous alumina. The latter forms an improved palladium/support interface, enabling composite membranes with double the hydrogen permeance than that of the YSZ composite membrane. The performance of the current CMR, without additional catalyst added to the lumen, saw over a 4-fold higher throughput relative to our original design. The productivity can be further enhanced by the addition of catalyst to the lumen. In the past, this has been a commercially sourced Ru/Al2O3 catalyst. To further reduce the platinum group metal content, we have developed a Ni/La2O3 catalyst whose initial performance approaches that of Ru but is more strongly inhibited by released hydrogen. Our hypothesis is that the improved membranes will enable the Ni-based catalyst to maintain high activity. In this presentation, we will report on performance (ammonia conversion, hydrogen recovery, and hydrogen productivity) and material costs among the various CMR configurations. In addition, we will compare the performance for the production of hydrogen as well as zero carbon NH3/H2 fuel blends.
