Improvement of the Pd/Al2O3 catalyst by the control of the sol-gel preparative parameters

In this work, the metal dispersion of the Pd/Al2O3 catalyst prepared by sol-gel method is improved by an adequate optimisation of the preparative variables. First, the gelation temperature and the ageing time are selected, in order to avoid the reduction of the metal precursor (palladium acetylacetonate, Pd(acac)(2)) by the solvent (sec-butanol, sB). The metal sintering effect on the catalysts treated in oxygen at 500degreesC is then minimized when the alumina pore size is controlled by the variation of the aluminum alkoxide (AsB) concentration and the acetic acid amount ([AcA]/[AsB]). The appearance of new palladium particles on the alumina surface and the matching between the particle diameters and the pore sizes were also effective for the metallic surface area improvement on the samples treated in oxygen at 800degreesC. Compared to the reference catalysts, the higher metal dispersion obtained on the sol-gel ones was the determinant factor for their higher catalytic activity in methane combustion.