Toward an Integrated Ceramic Micro-Membrane Network: Effect of Ethanol Reformate on Palladium Membranes
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Our research group has developed a cartridge-based, ceramic microchannel system capable of integrating multiple unique chemical processes within a single monolithic system, for rapid heat and mass transfer. In this manuscript, the authors report on the performance of palladium thin films incorporated within this ceramic microchannel system and their chemical compatibility with ethanol reforming chemistry. A dense, 9-m-thick palladium membrane for hydrogen purification from ethanol reformate was developed on a cordierite extruded ceramic support coated with successive alumina layers, and its compatibility was investigated via exposure to carbon dioxide, carbon monoxide, oxygen, water, and ethanol. The hydrogen permeability was determined to be 1.73 10 -9 mol m-1 s-1 Pa-0.5 at 350 C with an activation energy of 7.3 kJ mol-1 over the range 350-550 C. Exposure to carbon dioxide and oxygen had no effect on hydrogen permeation, while carbon monoxide and water exposure resulted in a 12% and 14% decrease in hydrogen flux, which was fully recovered upon the removal of contaminants. Exposure to ethanol vapor caused a 41% drop in hydrogen flux, which was restored to 91% of the initial steady-state value upon ethanol removal, indicating an irreversible surface modification of the palladium film, in addition to competitive adsorption. The hydrogen/helium selectivity of the membrane remained in excess of 1000:1 throughout all exposure tests, verifying the suitability of this system for integrated hydrogen purification and ethanol reforming. 2010 American Chemical Society.
