| An indium tin oxide/alumina nanoparticle catalyst was used for the selective oxidation of CH3OH to form H2 and CO2. At 68% CH3OH conversion, the H2 selectivity was 73%, and CO was only 1--2% of the products. Four reactors were used, and the highest H2 selectivity was obtained in a tank reactor that contained a thin catalyst film. A packed bed reactor did not effectively remove the heat of reaction, but coating the catalyst as a thin film gave better control. The product selectivity dependence on temperature and the CH 3OH/O2 feed ratio was measured.; Palladium-copper alloy membranes, which were deposited on porous ceramic tubular supports by electroless plating, separated H, from a water gas shift mixture and a H2S/H2 mixture at 623 to 723 K. Annealing the membrane in CO2 and CO increased the height of micron-scale conical hillocks and defect sizes on the membrane surface; H2 and He post-treatments decreased the hillock heights and defects sizes. The defects allowed gases other than H2 to permeate through the membrane. Surface topology changes may partially be due to the removal of carbon impurities by CO2 to form CO. Hydrogen sulfide at concentrations below complete inhibition of H2 permeation decreased permeation through electroless-plated Pd and Pd-Cu alloy membranes by blocking H2 dissociation sites. At complete inhibition of H2 permeation, an adsorbed sulfur mass transfer resistance layer that did not allow H2 to penetrate to the Pd-Cu surface or react with the sulfided surface formed. The addition of H2O to the H2S mixture increased inhibition of H 2 permeation and rate of sulfidation. Hydrogen must be present at the membrane surface to decrease the thermodynamically favored sulfidation reactions. The mass transfer resistance layer increased Pd and Cu sulfidation, which formed micron size pores. Membrane failure depended on H2S concentration, not time of exposure; at concentration below complete inhibition, steady state permeation was obtained.; Decreasing membrane surface roughness, increasing membrane thickness, and minimizing carbon impurities decreased defect formation associated with surface rearrangement. Different gas exposures segregated the metals and changed the membrane alloy composition and phase structure. The change in phase structure increased surface rearrangement and decreased H2 permeance through the membrane. |
