Effect of preparation conditions on the stability of Pt/Al2O3 catalysts inmethane combustion

Alumina supported platinum catalysts were prepared by sol-gel method using aluminum-sec-butoxide, platinum acetylacetonate and sec-butanol. Various ge lation process were performed either by the help of a gelation agent (water or acetic acid) or by a slow condensation without hydrolysis source. The t extural and the structural study of the catalysts using the nitrogen physic al adsorption and the hydrogen chemisorption showed that the BET surface ar ea and the metal dispersion varied when the hydrolysis and the gelation pro cesses were modified. The catalytic activities for methane combustion perfo rmed on the fresh and aged catalysts were correlated to the metal dispersio n values. In addition the catalytic activity loss under reaction mixture se emed to be caused by the metal dispersion decrease. When the catalysts were aged under the reaction mixture at 600 degreesC for 72 h, a BET surface ar ea decrease and a metallic surface area loss were observed. The resistance to sintering observed to be dependant on the hydrolysis and the gelation pr ocesses was in favor of the catalyst prepared by acetic acid.