Effects of sodium addition on the performance of PtCo/Al2O3 catalysts for preferential oxidation of carbon monoxide from hydrogen-rich fuels

Preferential oxidation (PROX) of carbon monoxide from a hydrogen-rich gas stream was performed over sodium-added platinum-cobalt catalyst. The process was analyzed based on the two major reactions involved in PROX, viz. the oxidation of carbon monoxide and the H2-O2 reaction. The modification of sodium enhances the performance of platinum-cobalt catalysts greatly, whereas the extent of the enhancement is relatively small for platinum catalysts. Selectivity for carbon monoxide oxidation is not influenced by sodium addition for any of the platinum and platinum-cobalt catalysts. The BET surface area of alumina is reduced by sodium addition, because sodium forms Na-O-Al bonds due to the migration of sodium ions into the alumina support. The incorporation of sodium with alumina inhibits the formation of the surface spinel cobalt species and promotes the formation of the Pt-Co bimetallic interphase.