Novel Catalysts For Propane Selective Oxidation: Preparation, Characterization, Catalytic Reaction And Related Sduties

In this thesis the research was focused on the selective oxidation of propane on mesoporous alumina based metal oxide catalysts, the exploration of novel methods for the preparation of nano metal oxide materials, and the theoretical study on polyanions.Mesoporous alumina was used as the support of catalysts. Three kinds of catalysts containing P-Mo-V, Mg-V, and Nb-V were prepared by both impregnation and co-synthesis methods. P-Mo-V, Mg-V, and Nb-V were introduced into the frame of mesoporous alumina by co-synthesis methods. The co-synthesized samples have disordered pores with wide pore distribution. 5-coordinated Al exists in the co-synthesized samples proved by the ²⁷A1 MAS NMR technique. The amount of 5-coordinated Al species is related to the amount of P-Mo-V, Mg-V, and Nb-V. In contrast there are only 4- and 6-coordinated Al species in impregnated samples, meso-Al₂O₃, and γ-Al₂O₃. The effects of space velocity, propane/oxygen ratio, reaction temperature, and contents of active constituent were explored. The results showed that co-synthesized P-Mo-V-Al-O catalysts have higher conversion of propane, higher selectivity of acetone, but lower selectivity of propene. Both the ratio and amount of Mg/V in co-synthesized catalysts influence the activity of Mg-V-Al-O catalysts. However, the impregnated Nb-V-Al-O catalysts has better reaction results than the related co-synthesized ones. The reaction looks like through the [CH₃CH(OH)CH₃] intermediate, because acetone was detected in the products. PMoV-Al-C4 has the highest yield of acetone (7.4%) with reaction temperature of 550 ℃, space velocity of 4800 mL·g^-1·h^-1 and C₃H₈/O₂ ratio of 1.0/0.9. With the same reaction condition, MgV-A1-C4 had the highest selectivity of propene (77.4%).Zinc and iron nitrates with molar ratio of 1:2 were introduced into mesoporous silica host SBA-15 via a "two-solvent" route. The thermal decomposition of the precursors inside SBA-15 and the formation of spinel phase were monitored by X-ray diffraction, thermogravimetric and differential thermal analysis. The one-dimensional nanostructured spinel zinc ferrite in mesopores and pure spinel ZnFe₂O₄ nanowires, obtained through complete removal of the silica template with aqueous NaOH solution, were confirmed by TEM. The nanowires exhibited superparamagnetism at room temperature, whereas the bulk spinel ZnFe₂O₄ showed weak paramagnetism. The method may be extended to prepare nano metal oxides with defined compositions.Density functional method was employed to study geometry, bonds, valances, MEP, NMR, etc. of ployanions [W₁₀O₃₂]^n- and [PMo₁₀V₂O₄₀]^5-. Bridged oxygen (O_b) was proved to be the active site in ployanions from MEP and other information. Solvation had some effects to the stability of [W₁₀O₃₂]^n-. The more polarity of solvent, the higher stable energy was obtained. The more negative charge of [W₁₀O³²]^n-, the more stable energy was obtained. The order of the stability is: Mo₁₀V₂-E > Mo₁₀V₂-C > Mo₁₀V₂-D > Mo₁₀V₂-A > Mo₁₀V₂-B. The results also showed the calculations of NMR are successful.