Preparation Of Pd/ZSM-5@ZSM-5Material And Its Catalytic Performances

Core-shell zeolite material is a kind of composite material with a zeolite film. By the use of separation and catalysis performance of zeolite membrane, the core-shell materials can protect the active metal from leaching, extend catalysts lifetime, exhibit selectivity to product or reactant, participate in the reaction and act as a microreactor.In this paper, Pd/ZSM-5@ZSM-5core-shell catalyst was designed, synthetised, characterized, and used in the Suzuki reaction:(1) Monodisperse zeolite ZSM-5particles were synthesized in the absence of a template using the seed-induced growth strategy. Synthesis parameters such as the effect of adding crystal, precursor composition and crystallization time were investigated. The obtained crystals were characterized by SEM and XRD analysis techniques. The results indicated that monodisperse zeolite ZSM-5particles were obtained by the synthesis solution that was composed of1Na2O:30SiO2:1A12O3:2000H2O, and crystallized in170℃for24h.(2) Monodisperse zeolite ZSM-5particles were used as support to introduce Pd nanoparticles by ion-exchange method, and the catalytic performance were investigated by probe reactions of Suzuki coupling reactions of bromo-benzene and5-Bromo-m-xylene. Results show that under the conditions of DMF/H2O solvent volume ratio of1/2,50℃and2h, the Pd/ZSM-5could catalyze the reaction of bromo-benzene with a best product yield. The obtained products were characterized by XRD, SEM, EDX and XPS analysis techniques.(3)A regrowth was outside the Pd/ZSM-5crystals to form the core-shell zeolite, and the obtained products were characterized by XRD, SEM, EDX and XPS analysis techniques, proving the shell thickness was250nm. The catalytic performance of the catalysts were investigated by probe reactions of Suzuki coupling reactions of bromo-benzene and5-Bromo-m-xylene. Relevant parameters were investigated such as shell thickness, Pd concentration, precursor solution and the influence of calcination. The results indicated that the catalyst express high activity, certain prison resistance and shape-selectivity.