Diaz, Isabel (Professor)Chebude, Yonas (PhD)Awoke, Yaregal2021-07-212023-11-092021-07-212023-11-092020-06-18http://etd.aau.edu.et/handle/12345678/27283This study focusses on obtaining heterogeneous Ti-containing catalysts through the design and optimization of pure silica SBA-15 and hybrid organic-inorganic PMO mesostructured materials in which the pore size, the particle morphology, and the surface chemistry are controlled to enhance the accessibility of the active sites and to avoid diffusion problems of substrates and products. The synthesis conditions of pure silica SBA-15 and hybrid organosilica PMO materials with different particle morphologies and pore sizes have been optimized. Ti has been incorporated in the framework/on the channel of both types of ordered mesoporous materials by using either co-condensation or grafting methods. To do this, the optimum SBA-15 and PMO materials, which have different pore diameters have been selected for Ti-grafting. A strategy has been designed to incorporate Ti in the framework of the mesoporous material during the support synthesis step (cocondensation). A detailed study has been undertaken to analyze the use of different surfactants, different Ti-source precursors, additives and different Ti/Si ratios of the synthesis gel to obtain Ti-incorporation in the Td structure and thereby avoiding or minimizing the agglomeration of TiO2 species. The prepared samples were characterized by X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), N2 adsorptiondesorption isotherms, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Inductively Coupled Plasma Optical Emission Spectroscopy (ICPiv OES) and Diffuse Reflectance UV-vis Spectroscopy (DRS UV-vis). The following Ticontaining SBA-15 and PMO with different particle morphologies and pore sizes with isolated Ti (IV) species have been synthesized: - Ti-containing SBA-15 and PMO materials with hexagonal plate-like and fiber-like particle morphology using Pluronic P104 and P123 surfactants; - Ti-containing SBA-15 materials with hexagonal pore structure and large pore diameters (> 10 nm) using TIPB micelle expander; - Ti-containing PMO materials with moderately ordered hexagonal pore structure and large pore diameters (> 8.5 nm) using TIPB micelle expanders; - Ti-grafted SBA-15 and PMO materials with highly populated isolated Td Ti (IV) species and without formation of anatase TiO2 species. The catalytic activities of selected catalysts were tested for the epoxidation of cyclohexene using TBHP (5.5 M in decane solution) as an oxidant. The catalysts which give good conversion and epoxide selectivity in the epoxidation of cyclohexene were selected for epoxidation of vernonia oil. Solvent-free epoxidation of vernonia oil with anhydrous TBHP (5.5 M TBHP in decane solution) in the presence of selected Ti-containing SBA-15 and PMO catalysts was investigated. Ti-grafted materials show better catalytic activity than their corresponding Ti-containing materials, synthesized by the co-condensation method. Ti-containing SBA-15 materials are better in conversion when compared to PMO type of materials. Among them, Ti-grafted SBA-15 with large pore diameter (TiG-ESBA-L) gives the highest conversion (71%) with 80% of epoxide selectivity. Ti-containing PMO materials are better in epoxide selectivity in epoxidation of vernonia oil (achieving more than 90% epoxide selectivity) when compared to their corresponding Ti-SBA-15 materials.enDesignSynthesis and CharacterizationTi-Containing OrderedMesoporous MaterialsEpoxidationVernonia OilThesis