The Preparation Of Acid/base-modified Metal Nanocatalysts And The Study Of Their Structure And Catalytic Performance

Metal oxides, such as spinel materials, are one of the most important inorganic functional nanomaterials, which have been paid more and more attention due to their low cost, stable properties and excellent performance. Very recently, metal oxides have been in-depth insight by researchers in the field of supercapacitors, catalysis, magnetic materials and semiconductor ceramics.In view of several problems in the traditional synthesis method of spinel material such as long reaction time, high energy consumption, easy introduction of impurities, the development of new synthesis routes are necessary. In this paper, we develop a simple solvothermal method to synthesis the zinc-aluminium spinel (ZnAl2O4) material under mild conditions, which exhibit high surface specific area and thermal stability. Based on this, surface acid/base-modified ZnAl2O4 were designed via the doped or composite with different components and used as the catalyst supports. The catalytic activity and selectivity have been deeply studied under the regulation of surface nature of different catalyst.In this paper, Mg was introduced into the framework of ZnAl2O4 to adjust the surface basic sites of the spinel material. Highly dispersed Zn1-xMgxAl2O4 supported gold nanocatalysts were obtained by a one step reduction route with KBH4. The catalysts were applied to the selective oxidation of benzyl without any solvent. The relationship between the structure of catalysts and the catalytic activity has been investigated. On the other hand, a novel Zr4/ZnAl2O4 composite was designed for the catalyst support with improved surface acid nature. Well-dispersed Cu nanocatalysts were obtained by the deposition-precipitation method followed by a calcined/reduced process, and applied to the hydrogenation of biomass y-valerolactone.(1) Mg-doped ZnAl2O4 support Au nanocatalyst was obtained by a simple reduction route. The relationship of structure and catalytic activity was investigated by XRD, BET, CO2-TPD, XPS, and HRTEM. The results showed that the abundant micro-mesoporous in the high-specific-surface-area-catalysts are benefit for the diffusion of reactant molecule. Suitable surface basicity could promote the formation of alkoxide intermediates with the hydroxyl of benzyl alcohol, which is benefit for the reaction. Moreover, the existence of Au+ species could adsorb the benzyl alcohol molecular and further improve the activity. Under mild and green conditions (120℃,0.2MPa, solvent-free), the as-synthesized catalyst exhibits high catalytic performence in the selective oxidation of benzyl alcohol to produce benzaldehyde.(2) ZrO2/ZnAl2O4 support Cu nanocatalyst was obtained by deposition precipitation method followed by a calcined/reduced route. The structure of catalysts was studied by XRD, BET, HRTEM, H2-TPR, Py-IR, NH3-TPD, and XPS. The results revealed that Cu nanoparticles were well-depersed on the support under the metal-support interaction. The synergistic effect of appropriate surface acidity (Lewis acid and Bransted acid) and Cu+ species significantly facilitate the activity and selectivity in the hydrogenation of y-valerolactone. When using pentanol as solvent, y-valerolactone can be effectively hydrogenated to pentyl valerate by as-synthesized Cu/ZZA-0.2 catalyst.