Green Synthesis Of Functionalized SAPO-34 And ZSM-5 Zeolite Molecular Sieves

Zeolite is a kind of microporous crystalline material with ordered distribution.It has become a hot research topic in scientific research because it exhibited excellent shape selectivity,strong adsorption and ion exchange capacity,high chemical stability and adjustable acid site.SAPO-34 and ZSM-5,in particular,have recently become the focus of research as ideal supports for metal-supported catalysts.As the main traditional method of synthesizing zeolite,hydrothermal method has many disadvantages,such as time-consuming,low yield,high energy consumption and pollution of water resources,which seriously hinder the sustainable development of zeolite.Under the environment of national ecological civilization construction,Solvent-free method and steam-assisted conversion（SAC）method have the advantages of small solvent consumption,short crystallization time and high yield and become the preferred paths for green synthesis of zeolite molecular sieve.Therefore,in this paper,the synthesis process of SAPO-34 is briefly described based on solvent-free method.Meanwhile,the structure of Silicalite-1and the structure and performance of metal-supported catalyst prepared with this support are studied in depth by using steam-assisted method.The main research details and achievements are divided into the following three parts:Without adding additional solvent,SAPO-34 zeolite was successfully synthesized by solvent-free method using silica wastes as silicon source,pseudo-bauxite as aluminum source and morpholine as template.The obtained samples have uniform size,larger specific surface area and higher pore volume.In addition,the strategy can also be used to load metallic Fe functional materials in situ.This synthesis strategy provided reference for industrial production,because it possesses the advantages of simple operation,short crystallization time,high yield,low energy consumption and low environmental pollution,etc.Using ethylenediamine ligand to stabilize the metal source,Pd@Silicalite-1 zeolite functional materials with different metal loads were synthesized in situ under condition of steam-assisted（SAC）conversion.The ultra-small Pd nanoparticles（about 1 nm）in Pd@silicalite-1 catalyst can be firmly fixed in silicalite-1 support and have good dispersion.Moreover,Pd@silicalite-1 has high crystallinity,large specific surface area and pore volume.Therefore,it showed superior sintering resistance and superior catalytic performance in the hydrogenation reaction of biomass furfural.Moreover,this steam-assisted conversion（SAC）-amine ligand stability-in-situ encapsulation strategy can be extended to other noble/non-noble species such as Ru.Using ethylenediamine complexes of Pd and Cu as metal precursors,Pd_xCu_1-x@S-1（x=0.2,0.5,0.8）bimetallic functionalized zeolite materials with different Pd/Cu ratios were successfully synthesized by SAC using in situ strategy.It was found that the size of Pd/Cu NPs in the prepared bimetallic catalyst was extremely small（about 0.8 nm）and dispersed evenly on the molecular sieve support.Moreover,the obtained catalyst has the synergistic advantages of high selectivity of Cu catalyst and high activity of Pd catalyst,Therefore,the conversion and selectivity of furfural to furfuryl alcohol were significantly improved under the action of Pd_xCu_1-x@S-1（x=0.2,0.5,0.8）.