Pt Nanoparticles Supported On Dispersed Alumina Coated Inside Mesoporous Materials And Its Catalytic Application

Active alumina has attracted much attention due to its application in adsorption and catalysis in recent years. Pt/Al2O3catalyst has already been successfully applied to the heterogeneous enantioselective hydrogenation of α-functionalized prochiral carbonyl compounds and many researchers have worked on it. The catalytic performance of Pt/MA (mesoporous alumina) catalyst is better than the Pt/Al2O3catalyst in many fields, so a series of composites of alumina coated inside the mesoporous channels of SBA-15with different alumina loadings were prepared by using different alumina sources and several methods.The samples were characterized by XRD, N2-sorption, SEM and TEM. The characterization of the resulted composites confirmed that Al2O3was dispersed inside the mesoporous channels of SBA-15host, and all the catalysts remained the similar p6mm meso-structure as the SBA-15host even after the support was soaked in H2PtCl6solution and sodium formate aqueous solution for several hours. The Pt nanoparticles sizes ranged in2-4nm with high dispersion.The Pt/Al2O3@SBA-15catalysts were used in the asymmetric hydrogenation of ethyl2-oxo-4-phenylbutyrate after they were chirally modified with cinchonidine. EOPB conversion and their ee values increased with increasing alumina loading. The Pt/xAS catalysts show higher conversion and enantioselectivity than the Pt/SBA-15catalyst and Pt/Al2O3catalyst. As the Pt/xAS catalysts have high stability even under acidic conditions, some Pt/xAS catalysts can reuse for several times. The Al2O3@SBA-15composites have strong Lewis acid sites which is easier for the dispersion of Pt nanoparticles, the adsorption of the substrate and so on. Another influencing factor for the catalytic performance maybe the proper effect of metal-support interation, the positive charge of Pt atoms, Ptδ+sites, while the Ptδ+species would enhanced the adsorption of cinchonidine and the substrate.We also prepared other series of alumina composites coated inside the mesoporous silicon materials such as KIT-6, SBA-16, and organic periodic mesoporous resols such as FDU-14. The aim was to investigate the effect of the mesopore arrangement and different materials for the alumina dispersion. These supports loaded Pt nanoparticles in order to investigate the effect of mesopore arrangement and different materials in the enantioselectivity.