Sulfur poisoning studies of high permeance Pd/Cu alloy membranes for H_2 separation from coal gas

摘要

Bath agitation enabled uniform, ultra-thin Cu layers to be deposited on Pd surfaces which drastically reduced the annealing time and temperature needed for the fcc alloy formation. Furthermore, the membranes made with the ultra-thin Cu layer had a permeance similar to the Pd membranes due to the confinement of the Pd/Cu alloy to the surface. The poisoning of the Pd/Cu membranes was partly irreversible. XPS results showed that the reversible and irreversible poisoning was mostly due to the formation of less energetically favorable Pd sulfides and more energetically favorable Cu sulfides, respectively. Both reversible and irreversible poisonings were due to surface sulfide formation, rather than a bulk sulfide scale. The tolerance of the fcc Pd/Cu alloy in comparison to Pd could be due to the preferential adsorption of sulfur on Cu, allowing H_2 to continue to adsorb onto Pd and permeate through the layer.