Preparation And Characteriztion Of Mesoprous-based Composite Catalytic Materials

Aiming at the applications of mesoporous materials in catalysis, several functionalized mesoporous-based composite materials, such as noble metal/transitional metal oxide colloidal layer coated mesoprous silica materials, Rh2O3-loaded mesoporous Al2O3 hybid materials, and mesoporous Co3O4 materials, Fe3O4 core/oxide shell nanocomposite, etc., were fabricated using different approaches. The preparation process and catalytic properties of these composite materials have been investigated in detail.Ultra-thin Pd colloid layer had been synthesized and coated on the surface of mesoporous material SBA-15 by on step in-situ process. In this material, the incorporated Pd attached on the pore wall surface and occupied very limited space, and therefore almost all of the nano-pore channels of the host silica remained open. The catalytic experiments showed that this kind of composite material had relatively high catalytic activity to Heck reactions, it only about one tenth the amount of catalyst was needed to reach the same conversion under the same reaction conditions compared with analogous catalysts reported in literatures. The catalytic experiment also indicated that the modified material had very high stability against the leaching of the active species and it could be repeatedly used without any apparent decrease in its catalytic activity. We also developed this method to functionalize the surface of mesoporous silica with the colloids of cerium oxide and manganese oxides. The H2-TPR experiments clearly showed that thes transitional metal oxide-loaded mesoporous composite materials demonstrated an effect of hydrogen spillover. This was the first time that this phenomenon was observed on the transitional metal oxides-loaded materials.A Micro-Electro-Mechanical System (MEMS) sensor for methane catalytive combustion has been successfully developed, and the system showed minimized power consumpotion and ultra-high signal/noise ratio. It was found that in sensors where traditional matrix and catalyst were used, the signal was very low companied with the large signal noise ration (SNR). This can be attributed to the little heating area of the active element. The straightforward and effective way to improve the sensivity of the MEMS sensor is the enlargement of the valid contact area between catalyst and detected gases. In this thesis, mesoporous Rh2O3/Al2O3 hybride were successfully fabricated and introduced into MEMS sensor structure. In the MEMS sensors developed in this study, the signal/noise ratio was only about one percent of that of a traditional catalytic combustion sensor. The catalytic experiment indicated that this heterogeneous catalyst had high catalytic activity to methane combustion reaction. The power consumption was only one fifth of that traditional LEL sensor and the sensitivity of sensor could be 5mV/%CH4.Mesoporous CO3O4 (Co)/Co-Mn-O materials were fabricated in the thesis by a simple controlled decomposition of the corresponding metal oxalate precursors under a certain heating rate. The therraml decomposition conditions, especially the temperature, were decisive in affect the mesoporosity of the mesoporous structure. The synthesized materials under optimized conditions had uniform mesoporous structure, high surface area and the inherited morphology from its precusors. The catalytic experiments showed that mesoporous CO3O4 had high catalytic activity to CO oxidation reaction. The further reduction of the mesoporous CO3O4 and Co-Mn-O materials could lead to the formation of corresponding porous metal Co and Co-Mn.Fe3O4 core/oxide shell nanocomposite was syntheisised by layer-by-layer assembly and calcination methods, which combines both versatile anion loading capability and high separation efficiency, making it an ideal support for recoverable anionic functional materials. The success in the assembly of theW7O246- catalyst provide a general route to the facile and direct fabrication of magnetic core/various anion-functionalized shell composite structures. The magnetic nanocomposite catalyst system demonstrated is expected to find many important applications in catalysis, drug storage/release system and so on.