Abstract:
The objective of this study was to examine the effects of design parameters on the physical properties and on preferential CO oxidation (PROX) activity of Pt-Co-Ce/Al2O3 catalysts. The major catalyst design parameters considered were the metal loadings of Pt, Co and Ce, calcination temperature and calcination time. Ten different Pt-Co-Ce/Al2O3 catalysts were prepared using incipient to wetness impregnation method. The total surface areas, pore volumes, solid and envelope densities of the catalysts were measured in order to investigate the effect of design parameters on physical properties. A realistic gas mixture simulating the exit stream of a typical fuel processor and containing 1% O2, 1% CO, 60% H2, 25% CO2, 10% H2O and inert He as balance was used in the PROX experiments. Activity tests were performed on five of the ten catalysts studied. CO and O2 conversions were measured at 30-minute intervals up to two hours. It was found that Al2O3-supported catalysts with Pt loadings between 1.4-1.8 wt%, Co and Ce loadings between 1.25-3.75 wt% and calcined at 450oC for 2 h all achieve 100% CO conversion with a selectivity of 50% and are successful PROX catalysts. Among the catalysts studied, 1.4%Pt-1.25%Co-1.25%Ce/Al2O3 calcined at 450oC for 2 h is the optimum PROX catalyst since it yields 100% CO conversion both in the presence and in the absence of carbon dioxide and water vapor in the feed.
