Hydrogen permeation and surface properties of PdAu and PdAgAu membranes in the presence of CO, CO2 and H2S

Abstract

Using the electroless deposition technique with different deposition sequences, it was possible to obtain a single phase PdAgAu ternary alloy after treatment at 773 K during 7 days. Despite the order of deposition, the samples exhibited similar hydrogen permeation flux at the same temperature and pressure. In the presence of CO, the PdAgAu ternary alloy membranes showed a lower inhibition on the hydrogen permeance compared with the binary PdAu alloy at 623 and 673 K. On the contrary, under CO2 containing streams, the ternary alloy showed a higher inhibition with a complete hydrogen recovery after removing CO2 from the stream. When H2S was introduced in the 13% CO2/13% Ar/74% H2 stream, a higher permeance decrease was observed on both the PdAu and PdAgAu alloy membranes. After removal of H2S, a hydrogen recovery of 60% and 76% was measured for the PdAu and PdAgAu membranes, respectively. Pd surface segregation was observed on the Pd82Ag15Au3–873 K-5 d and the Pd78Au6Ag16–773 K-7 d samples upon exposure to CO containing streams. Instead, silver surface segregation was observed by XPS after exposing the PdAgAu ternary alloy to CO2 containing streams.