2024 AIChE Annual Meeting
(728a) Nanoscale Engineering of Ceramic Supports for High Permeance Membranes
Catalytic membrane reformers (CMRs) are an emerging reactor technology capable of intensifying chemical production and separation. One application of this technology is in the production of hydrogen for fuel. Storing pure hydrogen is challenging, but storing hydrogen chemically within the bonds of a liquid such as ammonia is much easier. However, re-forming hydrogen from a carrier currently employs a packed bed reactor and subsequent separation, requiring significant energy input. We have developed a CMR that combines the steps of hydrogen reforming by employing a thin, hydrogen-selective palladium membrane plated onto a porous, catalyst-impregnated ceramic support. The removal of reformed hydrogen through the membrane favors hydrogen production thermodynamically and kinetically. Accordingly, improving hydrogen flux through the CMR becomes paramount in improving CMR productivity. Previous experiments revealed that hydrogen permeance is presently limited by the resistance through the ceramic support. Namely, this resistance is caused by a ~25-micron-thick mesoporous layer coating the macroporous bulk of the commercially-available supports used for the project. This work aims to engineer a support with surface geometry that can still facilitate a defect-free membrane, but minimizes the mesoporous layer to improve flux. This will be achieved through the modification of symmetric macroporous supports via exposure-limited atomic layer deposition (ALD). In this work we identified appropriate exposure-limited ALD recipes for both zirconia and alumina. This technique was applied to provide nanoscale engineering of symmetric supports with the goal of reducing the external pore size without compromising permeance. It was shown pore diameters could be closed off by 60% before making any significant change in permeance. Future work will employ scanning electron microscopy to quantity the depth of ALD penetration and subsequent refinement of ALD parameters to further enhance CMR performance.