Reparation Of Supported Gold Catalysts And Their Performance For One Pot Hydrogenation Of Nitrobenzene And Benzaldehyde

Supported gold catalysts are a kind of promising catalysts for selective hydrogenation based on their good activity and selectivity for the reduction of many compounds.In this paper, using Fe2O3-SBA-15as the support, which was prepared by impregnation, a series of Au catalysts were prepared using the deposition-precipitation method. The catalysts were tested in the one-pot hydrogenation of nitrobenzene and benaldehyde. The effects of the type of the support, the amount of promoter, the calcination temperature and the reduction temperature on the performance of Au/Fe2O3-SBA-15catalysts were investigated. The catalysts were characterized by XRD and SEM.The results show that the structure of SB A-15makes the distributing of the gold particles more even on the surface of catalysts. The presence of Fe2O3makes the pore wall keep mechanism strength and thermal stability, and avoids the supports collapsing. The preparation conditions of catalysts were optimized as follows:2wt%of gold content,25%of Fe2O3, calcination temperature300℃and reduction temperature200℃.Using2%Au/25%Fe2O3-SBA-15as the catalyst, The reaction conditions were optimized as follows:reaction temperature95℃, hydrogen pressure 1.4MPa, the amount of catalyst0.72g, methanol as solvent. At the above reaction conditions, the conversion of nitrobenzene can reach98.7%, and the selectivity to benzalaniline can be up to98.7%for reaction19h.Secondly, a series of Au-Ru/TiO2bimetallic catalysts were prepared by the deposition-precipitation (DP) method. The catalysts were tested in the reaction that one-pot hydrogenation of nitrobenzene and benaldehyde. The effects of the amout of ruthenium, the calcination temperature and the reduction temperature on the performance of Au-Ru/TiO2calalysts were investigated. The catalysts were characterized by XRD, TEM, SEM and TPR. The results show that Ru cooperates with Au, promotes hydrogenation reaction. The preparation conditions of the catalysts were optimized as follows:1.5wt%of Ru content, calcination temperature300℃and reduction temperature200℃.Using2%Au-1.5%Ru/TiO2as the catalyst, the reaction conditions were optimized as follows:reaction temperature80℃, hydrogen pressure1.1MPa, the amout of catalyst0.36g, and toluene as solvent. At the above reaction conditions, the conversion of nitrobenzene is100%, and the selectivity to benzylaniline is88.2%for reaction6h.