Alcohol dehydrogenation over Pd versus PdAg membranes

Abstract

The dehydrogenation of methanol and ethanol and the subsequent permeation of hydrogen through Pd and Pd 70Ag 30 membranes, respectively, have been studied. In order to keep a continuous hydrogen permeation rate, oxygen needs to be added to the alcohol supply. Without oxygen, the decomposition products will form a contaminating layer on the upstream membrane surface. The extraction of hydrogen from ethanol is six times more effective through a Pd 70Ag 30 membrane than through a pure Pd membrane (at optimum conditions). For methanol, the hydrogen permeation is 30% larger through a Pd 70Ag 30 membrane than through a membrane of pure Pd. The increased hydrogen permeation yield through Pd 70Ag 30 compared to Pd can be attributed mainly to a lower upstream consumption of hydrogen due to water formation, but also to an increased conversion of the alcohol in the presence of oxygen.