Preparation and Microstructural Characterization of Activated Carbon-Metal Oxide Hybrid Catalysts: New Insights into Reaction Paths

In catalysis processes, activated carbon (AC) and metal oxides (MOs) are widely used either as catalysts or as catalyst supports because of their unique properties. A combination of AC and MO nanoparticles in a single hybrid material usually entails both chemical and microstructural changes, which may largely influence the potential catalytic suitability and performance of the resulting product. Here, the preparation of a wide series of AC−MO hybrid catalysts is studied. Three series of such catalysts are prepared by support first of MO (Al2O3, Fe2O3, SnO2, TiO2, WO3, and ZnO) precursors on a granular AC by wet impregnation and oven-drying at 120 °C, and by subsequent heat treatment at 200 or 850 °C in inert atmosphere. Both the chemical composition and microstructure are mainly investigated by powder X-ray diffraction. Yield and ash content are often strongly dependent on the MO precursor and heat treatment temperature, in particular for the Sn catalysts. With the temperature rise, trends are towards the transformation of metal hydroxides into metal oxides, crystallinity improvement, and occurrence of drastic composition changes, ultimately leading to the formation of metals in elemental state and even metal carbides. Reaction paths during the preparation are explored for various hybrid catalysts and new insights into them are provided.