Reactions and carbide formation on thin Pd membranes during separation of CH4/H2 and CO/H2 mixtures in the limit of maximum H2 extraction

Inhibitive effects of CO and CH4 on H2 permeation through 2-3 μm thick Pd membranes were studied by comparing their impact to that of inert N2. CO lead to reduction of the H2 permeance at all temperatures while it increased in the presence of CH4. Below 623 K CO adsorption was the main reason for the decrease of H2 permeation while carbon deposition due to CO decomposition became important at higher temperatures. The larger H2 fluxes from mixtures with CH4 resulted from decomposition of that hydrocarbon, leading to carbonaceous phases above 723 K. Apparently the presence of 50% H2 cannot completely suppress carbon deposition from CO at elevated temperatures.