Controllable Preparation Of Palladium Nanoparticles Encaged Hollow Mesoporous Silica Nanoreactors And Their Application In Selective Oxidation Of Alcohol Derivatives

This thesis aims at controllably synthesizing hollow mesoporous silica catalytic nanoreactors with Pd nanoparticles(NPs)inside their cavities(Pd@HMSNs),and studies their catalytic performance for selective oxidation reactions of a series of alcohol derivatives.The catalytic results suggest that the mesopores facilitate the mass transportation of reactants and products,the presence of active NPs inside large hollow cavities greatly enhances the contact of reactant molecules and active NPs with an improved activity,and the silica shells provide the protection for inner active NPs with a good stability.(1)Controlled synthesis of Pd@HMSNs.Pd@HMSNs were synthesized by a new method that includes using charge-driven self-assembly micelles as templates,deposition of silica onto the mentioned micelles,and following calcination and reduction.The micelles were prepared by charge-driven self-assembly through mixing the corresponding aqueous solutions of Pd ions,triple ligands with three dipicolinic acid groups grafted on a benzene ring(L3),and P2MVP128-b-PEO477 with quaternary pyridinium groups.The hollow mesoporous nanostructures with Pd NPs inside were confirmed by a series of XRD,BET and TEM.The prepared Pd@HMSNs have a large BET specific surface area of 498 m2/g,an average pore size of 7.7 nm and a Pd loading of 3.0 wt%.(2)Application of Pd@HMSNs in selective oxidations of benzyl alcohol derivatives to corresponding aldehydes.Pd@HMSNs obtained at 600? calcination and 300? reduction show the best performance for selective oxidation of benzyl alcohol.The influences of reaction conditions such as temperature,substrate concentration and solvents on the catalytic performance are also studied.The optimum reaction conditions are the followings:reaction tempareture-100?;reaction pressure-0.1 MPa;substrate concentration-0.5 vol%in water.In addition,selective oxidations of several benzyl alcohol derives over Pd@HMSNs at the optimum conditions are further investigated.Compared with the traditional supported Pd nanocatalysts,Pd@HMSNs illustrate enhanced catalytic activities for selective oxidizations of benzyl alcohol derivatives to corresponding aldehydes.