Microemulsion-gel Method Preparation MoO₃/SiO₂ Complex Nanocatalsts For Selective Catalytic Oxidation Cyclohexane

The objective of this disquisition is to synthesize MoO₃/SiO₂ complex nanocatalysts by Reverse Microemulsion-Gel Method (RMGM) and investigate their use in transforming gaseous cyclohexane into oxide cyclohexene by selective catalytic oxidation. A series of silica supported MoO₃ were prepared using inorganic and oraganometallic precursors as the metal source by MGM and sol-gel method. The target reaction was systematically researched in preparation catalyst, activation catalyst, characterization catalyst and tests for catalytic activity. The experiments manifested that the catalyst activity is influenced by the catalyst preparation methods, the component of catalysts and the conditions of catalysis reactions.RMGM is a new technology for synthesis complex nanocatalysts. It was necessary for the formation of reverse microemulsion-gel (RMG) that the homogeneous steady reverse microemulsion could be prepared and the microemulsion-gel of the catalyst precursors could be formed in non-microemulsion systems. The appearance and structure of the complex nanocatalysts were systematically investigated by the changes of the different parameters in RMG. The optimal scheme of preparation complex nanocatalysts was found in RMG.The nanocatalysts were characterized by Differential Scanning Calorimetry-Thermogravimetry (DSC-TG), X-ray Diffraction (XRD), Transmission Electron Microscope (TEM) and Fourier transform infrared (FT-IR). The DSC-TG analysis results showed that the prepared nanocatalysts were subjected to thermal treatment at 300℃. The solid-solid interactions between the different constituents of the nanocatalysts were studied using XRD. The appearance of the complex nanocatalysts was characterized by TEM. The results showed that the active contents of nanocatalysts were dispersed on the silica supporters very well. The FT-IR analysis showed that there were interaction between SiO₂ and MoO₃. The results of characterization indicated that the appearance of nanocatalysts and the dispersion of active contents preparation by RMGM were better than by sol-gel method.The surface structure model of nanocatalysts was deduced from these characterization facts. Based on the surface structure model of nanocatalysts, the active sites offering active oxygen of the complex nanocatalysts surface were analyzed. The variation rule was deduced that the offering active oxygen abilities of nanocatalysts increase in nonlincarity with the decrease of nanocatalyst granularity.The assessment standard of catalyst activity was the conversation of cyclohexane and...