Effect of Si-doping on thermal stability and diesel oxidation activity of Pt supported porous γ-[Al.sub.2][O.sub.3] monolithic catalyst

A series of different contents of Si-stabilized aluminas with high thermal stability were synthesized by the coprecipitation method and were used as the support of Pt diesel oxidation catalysts. The physicochemical properties of Si[O.sub.2]-[Al.sub.2][O.sub.3] (SA) and the catalytic performance of Pt/Si[O.sub.2]-[Al.sub.2][O.sub.3] (Pt/SA) were characterized in detail by TG-DTA, XRD, infrared spectroscopy, [N.sub.2] adsorption, NMR, CO-TPD, and the catalytic activity evaluation of CO and [C.sub.3][H.sub.6] oxidations as well as NO reduction in simulating diesel exhaust. The results indicate that the presence of Si can remarkably enhance the thermal stability and phase transition temperature of alumina. It was also found that the catalytic activity is virtually independent of surface area, and only appropriate amount of Si doping can improve the diesel oxidation activity, as compared to pure Pt/[Al.sub.2][O.sub.3] under the same conditions as a result of the better dispersion of Pt on SA-W supports.