Preparation of crystalline, reducible metal oxides for catalytic conversions

Abstract: Herein, we investigated the synthesis and characterization of crystalline reducible metal oxides, and their catalytic activities in chemical transformations. The inverse micelle method was adapted to synthesize numerous mesoporous metal oxide materials including cobalt, iron, cerium, aluminum, silicon, and titanium oxides. Much attention was given to cobalt oxide materials owing to its great catalytic activity. Alkali and alkaline earth metals such as lithium (Li), sodium (Na), potassium (K), cesium (Cs), magnesium (Mg) and calcium (Ca) were applied as doping agents in mesoporous materials in an attempt to increase their catalytic activity. Catalytic redox transformations were mainly conducted as chemical transformations to probe the newly designed mesoporous metal oxide materials’ catalytic activities. Several physicochemical techniques were used to characterize the as-prepared mesoporous metal oxide materials including their corresponding doped ones. Scanning electron microscopy (SEM) analysis provided the surface morphology of mesoporous metal oxide materials. Transmission electron microscopy (TEM) analysis served to view the intra-channels formed by the mesoporous structures and their average particle size estimation. Mesoporous metal oxide materials’ crystallite sizes were also calculated based on the resulting data from powder X-ray diffraction (XRD) analysis. Mesoporous metal oxide material porosities were investigated through nitrogen isotherm adsorption using Brunauer-Emmet-Teller (BET) analysis. Hydrogen temperature-programmed reduction (H2-TPR) analysis was conducted to investigate the mesoporous metal materials reducibility. Those physicochemical descriptions were critical for the understanding the redox catalytic activities displayed by the newly designed catalysts. Following the inverse micelle method, the synthesis of mesoporous Co3O4 materials resulted in mono-dispersed mesoporous materials described by the cubical crystalline system. The heat treatment influenced the physicochemical properties characterizing the mesoporous materials. Nitrogen gas sorption isotherm revealed surface area and diameter size variation for the pure mesoporous metal oxide materials as well as for their corresponding doped materials. With an immediate change in the diameter size of pure mesoporous Co3O4 materials shifting from 12.1 nm to 31.9 nm. In contrast, then doped mesoporous Co3O4 materials underwent a diameter change of 12.1 nm to 19.2 nm...Ph.D. (Chemistry