Preparation Of High Pore Volume Pseudoboehmite And The Catalytic Properties Of CuO-γ-Al₂O₃Catalysts

With the development of the chemistry industrial, alumina, especially the porous Y-alumina (γ-Al2O3) is widely used as adsorbents and catalyst components in chemical processes, owing to its comparatively large surface area, unique surface characteristics and stable structural. To improve the catalytic efficiency, the preparation of porous y-alumina with a large pore volume and high surface area is becoming more and more important, y-alumina can be synthesized through the dehydration of pseudoboehmite under high temperature, therefore, it can be said that the properties of y-alumina are greatly determined by the quality and the characteristics of its precursor (pseudoboehmite).In this thesis, mesoporous pseudoboehmite was obtained via the direct precipitation method using A1(NO3)3-9H2O as the inorganic alumina precursor, NH3-H2O as the precipitating agent, in different micelles containing bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT), cetyltrimethylammonium bromide (CTAB), and tert-octylphenoxypolyethoxyethanol (Triton X-100), respectively. The as-synthesized mesoporous products were characterized by wide-angle X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption-desorption. The data indicated that pseudoboehmite prepared with anionic surfactant AOT was structured as densely distributed nanofibers with2-5nm diameters, nevertheless, surfactants Triton X-100and CTAB produced an aggregated particle-like morphology. In AOT micelles system, pure pseudoboehmite can be obtained as the final pH was between8and10.5. Furthermore, we investigated the influence of ions on the pore properties of pseudoboehmite. It was found that the specific surface area, the pore volume, and the average pore diameter of pseudoboehmite were improved in some degree through different metal introduced.In addition, the catalyst ability of CuO-y-Al2O3prepared in triblock copolymers polyoxyethylene-polyoxypropylene-polyoxyethylene (P123) and bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT) mixed surfactants system was examined towards styrene epoxidation. It was found that the main products of epoxidation of styrene were benzaldehyde and styrene oxide. After screening the temperature, solvent, molar ratio of oxidant and substrate influence on styrene conversion and styrene oxide selectivity, the suitable condition was obtained. The interrelated results indicated that very high conversion of styrene (97.43%) and fine selectivity of styrene oxide (85.15%) could be realized.