Low temperature CO Oxidation and Preferential Oxidation of CO Over Nano-Structured Base Metal Oxide Catalysts

Demand of pure hydrogen is considerably increased by the development of polymer electrolyte membrane fuel cell technology. Hydrogen produced from the hydrocarbon sources with steam reforming followed by water gas shift reaction contains carbon monoxide (CO), which is not suitable for the efficient functioning of the PEM fuel cells. Preferential CO oxidation is the most effective and economic ways to reduce trace amounts of CO from the hydrogen stream. Present PhD work deals with the development of base metal oxide catalyst combinations for CO oxidation and preferential CO oxidation reaction. Four base metal oxide catalyst systems are investigated for CO oxidation in the presence and absence of hydrogen. The catalyst combinations investigated for the reactions include copper-cobalt, iron-cobalt, copper-cerium and a tri-component copper-cerium-iron oxide. Copper-cobalt, iron-cobalt, copper-cerium and cerium-iron oxide catalysts combinations were prepared by hard template method. Chelating-impregnation and incipient wetness impregnation techniques used to deposit copper on the cerium-iron oxide support. Gold deposited iron-cobalt and cerium-iron oxide catalysts were also prepared for comparing the catalytic activity with iron-cobalt and copper-cerium-iron oxide catalyst. All the catalysts were characterized as to their structure, morphology, texture and redox features by X-ray diffraction, transmission electron microscopy, N2 physisorption and temperatureprogrammed reduction with hydrogen, respectively. It was observed that doping cobalt oxide structure with copper and iron are beneficial for improving the activity of the oxide. Superiority of copper-cobalt is observed above 100°C for CO oxidation. In preferential oxidation, higher CO and oxygen conversions were observed over such system, compared to pure cobalt oxide. Gold deposited on iron-cobalt oxide was highly active for CO oxidation in the absence of hydrogen, but its activity was not maintained in the presence of hydrogen. Iron-cobalt oxide catalyst was the highly active catalyst in PROX. Copper-cerium oxide catalysts showed similar activity in CO oxidation and preferential oxidation reaction. No remarkable differences between the catalysts were observed. Catalytic activity for both CO oxidation and preferential oxidation reactions on the cerium-iron support was improved by the presence of copper. Copperbased catalyst showed improved activity and selectivity in preferential oxidation compared to gold based catalysts.