CARACTERIZACIÓN DE CATALIZADORES 0,8% PD/TIO2 SOL-GEL USADOS EN REACCIONES DE HIDRODECLORACIÓN CATALÍTICA EN FASE LÍQUIDA

Abstract

Selected samples of fresh and used 0.8% Pd/TiO2 sol-gel catalyst were characterized by a wide range of physicochemical techniques. This catalyst was used in reactions of hydrodechlorination of tetrachloroethylene in the liquid phase, with pure hydrogen, in the presence of NaOH, under mild conditions. The purpose was to study the physical and chemical properties of the catalyst which enabled a high catalytic activity and identify the effects of the reaction conditions on these properties. The results indicate that the method of synthesis and pre-treatment used to prepare the catalyst helped to obtain a mesoporous material, with a relatively high surface area, weakly hydroxylated with type Lewis acidity and with Pd0 and Pd2+  superficial species. However, the characterizations of the used catalyst showed some changes, such as: decrease in surface area, increase in surface acidity, the presence of some organic compounds, decrease in dispersion and, thereby, increase in the size of palladium particles. However, some features like the crystalline structure of the support, the metal charge, the shape of palladium particles and their oxidation states remained almost constant.