Alcohol dehydrogenation over Pd versus PdAg membranes

The dehydrogenation of methanol and ethanol and the subsequent permeation o f hydrogen through Pd and Pd-70Ag30 membranes, respectively, have been stud ied. In order to keep a continuous hydrogen permeation rate, oxygen needs t o be added to the alcohol supply. Without oxygen, the decomposition product s will form a contaminating layer on the upstream membrane surface. The ext raction of hydrogen from ethanol is six times more effective through a Pd-7 0Ag30 membrane than through a pure Pd membrane (at optimum conditions). For methanol, the hydrogen permeation is 30% larger through a Pd-70Ag30 membra ne than through a membrane of pure Pd. The increased hydrogen permeation yi eld through Pd-70Ag30 compared to Pd can be attributed mainly to a lower up stream consumption of hydrogen due to water formation, but also to an incre ased conversion of the alcohol in the presence of oxygen. (C) 2001 Elsevier Science B.V. All rights reserved.