In-situ Hydrothermal Synthesis And Catalytic Consequence Of Zeolite Encapsulated Ru Metal Clusters

Zeolite-supported noble metal particle is an important kind of bifunctional catalyst.The encapsulation of these noble metal within zeolite micropores can prepare small-scale and uniform metal particles,which is characteristic of excellent resistance to metal leaching and metal sintering.This thesis mainly focuses on the encapsulation of Ru metal clusters within Y zeolite and ZSM-5 zeolite,respectively.First,24 h aging was screened for the preparation of directing agent and silica-alumina gel in the synthesis of Y zeolite.Then the methods for the Y zeolite encapsulation of Ru metal clusters were developed.The physical properties of Y zeolite supported Ru metal particles were compared for the smaples from in-situ hydrothermal synthesis method,ion exchange method and impregnation method.Moreover,the sequence of the Ru Cl₃ addition for the in-situ hydrothermal synthesis method was investigated.It was found that successful Y zeolite-encapsulated Ru metal particles（Ru@Y）can be realized by the in-situ hydrothermal synthesis method,which high dispersed and small Ru metal clusters with～1 nm were obtained.During the in-situ hydrothermal synthesis process for Ru@Y zeolite,the introduction of Ru metal precursors after the including silicon sources when configurating silica-alumina gel,was shown to be good for the encapsulation of Ru metal species into zeolite micropores via a strong interaction with zeolite framework.Finally,the catalytic performance of Y zeolite supported Ru metal particles for isobutane hydroisomerization was investigated,and Ru@Y zeolite possessed the best performance.In order to overcome the difficulty in encapsulating metal clusters with low-silica ZSM-5 zeolite via the in-situ hydrothermal synthesis,a two-step in-situ hydrothermal crystallization method was developed to obtain ZSM-5 encapsulateed Ru metal clusters（Ru@ZSM-5）.Ru Cl₃ precursor was introduced after the nucleation of silica-alumino gel at low temperature,then these Ru metal species were encapsulated during the hydrothermal crystallization process at a higher temperature.The ²⁷Al NMR results showed that all Al species were successfully included as zeolite framework Al species.The transmission electron microscopy and chemisorption characterization results showed the as-prepared Ru@ZSM-5 sample possesses～1 nm size.The shape-selective hydrogenation reaction of toluene and 1,3,5-isopropylbenzene proved that～90%of the Ru metal was successfully encapsulated in the micropores of the low-silica ZSM-5 zeolite,which built-up of sub-nanometric intimacy between the Ru metal and acid sites of zeolite,which promoted the hydrogenation activity and stability in phenol hydrodeoxygenation（HDO）to cyclohexane.