Preparation,Characterization And Catalytic Performance Of Mesoporous Alumina-based Composite Oxide

The ordered mesoporous alumina（OMA）prepared by the solvent evaporation induced self-assembly（EISA）method has become one of the research hotspots in the world due to its simple synthesis process and excellent structure,which is promising for the efficient conversion of some macromolecules in the field of petrochemical industry.Studies have shown that the physical and chemical properties of OMA can be effectively adjusted by introducing appropriate amount of heteroatoms into EISA process.In this paper,Cu-Al composite oxides and Zr-Al composite oxides were synthesized by one-step method and characterized by XRD,N₂ adsorption-desorption,NH₃-TPD,H₂-TPR,and XPS.Various characterization tools were employed to understand the textural properties,acidity,interaction between metal oxide and alumina,and the distribution of metal on the surface.The catalytic activity was evaluated in the selective hydrogenation of phenylacetylene and isobutene/butane alkylation reaction.The research results of Cu-Al composite oxides show that:（1）When proper amount of Cu（NO₃）₂·3H₂O is introduced into the synthesis system,Cu species can modify the ordered mesoporous structure of amorphous alumina.If the amount of introduction is too much,excessive Cu will be unable to effectively participate in the cooperative self-assembly process,causing accumulation of pores on the wall.（2）When the Al/Cu atomic ratio is 20,the prepared material possesses the highest specific surface area of 448 m²/g with the largest pore volume of 0.72 cm³/g.The amount of Cu,calcination temperature and the introduction mode of Cu all affect the interaction between the support and the metal.A certain increase of temperature is conducive to strengthening the interaction between the metal and the alumina support.And the reduction of copper ion to the metal phase will be hindered by the surrounding amorphous alumina reservoir.（3）By comparing the introduction modes of Cu species,it is known that the simple and efficient one-step method can make the Cu species more dispersed and the mesoporous structure more ordered.Loading precious metal Pd on the surface of Cu-Al composite oxides,and the prepared material exhibites excellent hydrogenation activity and selectivity in the selective hydrogenation of phenylacetylene due to the efficient combination of Pd and Cu.When Al/Cu atomic ratio is 20,calcination temperature is 500?C and Pd loading is 0.5%,the phenylacetylene conversion rate is 99.9%,and the styrene selectivity can reach 90.7%.The research results of Zr-Al composite oxides show that:（1）Zr species can modify the ordered mesoporous structure of amorphous alumina when proper amount of Zr（NO₃）₂·3H₂O is introduced into the synthesis system.There are three Bragg diffraction peaks of（100）,（110）and（200）crystal planes belonging to the p6mm space group in the range of 2θ=0.5-5°for Zr-Al composite oxides with different atomic ratios.（2）The surface acidity of Zr-Al composite oxide was improved by the combination of the sulfate and Zr atoms.The total acid content increased by 280%compared with the pure OMA sample.（3）An isobutane/butene alkylation reaction device was established,and the prepared solid acid catalyst was applied to the reaction.The catalytic performance was investigated by changing the isobutane/butene molar ratio,reaction time,reaction temperature and other influence factors.