Identifying the adsorbed active intermediates on Pt surface and promotion of activity through the redox CeO2 in preferential oxidation of CO in H2

A series of non-and modified with niobia and ceria alumina-supported Pt catalysts with different Pt content (0.3-2 wt%) were prepared by wetness impregnation method and characterized by N-2 adsorption-desorption isotherms, XRD, TPR, DRIFT, in situ EXAFS and Delta XANES. The effect of the content of Pt and promoter on the change of catalyst electronic structure and behaviors in the reaction of preferential oxidation of CO in the presence of H, was studied. A strong interaction of Pt with CO and O-2 in atmospheres of H-2/CO and H-2/CO/O-2 mixtures was detected by Delta XANES. Different steps of activation of reagents molecules were observed. The increase of activity with increasing the Pt content was related to the presence of Pt nanoparticles with high electron density. While, the highest metal dispersion of the low metal-loaded Pt catalyst was responsible for its high CO oxidation selectivity. Addition of ceria to Pt catalysts caused significantly increase of activity and CO oxidation selectivity at lower reaction temperatures. Niobia addition did not improve the catalysts behaviors. The promotion effect of ceria was related to the oxygen mobility at Pt-O-Ce interface. The coda-promoted Pt catalysts with the highest ceria loading of 12 wt% exhibited the highest activity and CO oxidation selectivity, but at higher reaction temperatures of about 110 degrees-130 degrees C it was begin slowly to decrease. This was attributed to going on the reverse of WGS reaction and high O-2 consumption to Hy oxidation during the PROX-CO reaction on ceria alumina-supported Pt catalysts at high temperatures.