Supported Cobalt Oxide Nanoparticles: The Influence of Mesoporous Materials and their Role in Methyl Phenyl Sulfide Oxidation Reactions

The effect of the support in the incorporation of cobalt oxide nanoparticles on mesoporous materials (SBA-15) and mesoporous cellular foam (MCF) was investigated. The materials were characterized using various techniques. The XRD diffraction patterns showed that the porous structures remained after cobalt incorporation, while high-angle XRD of the MCF showed CoO peaks, in contrast to Co-SBA-15 which exhibited Co3O4. This was confirmed by XPS technique. The SEM-EDS and HRTEM-STEM microscopy indicate a distribution of cobalt oxides uniform in the samples synthesized and the average size of the particles is 1.88 nm. H2-TPR analysis highlighted the interaction between the support surfaces and the metal oxide (SMSI). It was observed that in the SBA-15 structure, small clusters of cobalt oxide formed with a strong interaction with silica, leading to high reduction temperatures. The catalysts activity was characterized in oxidation reactions of Methyl Phenyl Sulfide and a correlation was observed between the characterization results and the enhanced selectivity and yield towards sulfone exhibited by Co-MCF. Mesostructured MCF and SBA-15 materials with cobalt oxide nanoclusters were designed. The pore topology of each mesostructure favors a certain oxidation state of cobalt, with the mesoporous cellular foam showing higher Co2+/Co3+ ratios. The influence of each support on the support metal interaction (SMSI) was determined by different techniques. A higher amount of Co2+ is required in methylphenylsulfone oxidation reactions. image