Synthesis And Modification Of SBA-15 And Its Catalytic Activity For Selective Hydrogenation Of Crotonaldehyde

Mesoporous molecular sieve SBA-15 not only have large surface area,thicker wall,uniform pore size distribution(1.5 nm～30 nm)and huge pore wolume,but also mechanical and chemical stability.They were widely used as catalysts,sorbents and separation materials in the past decade.Up to now,a great variety of functionalized and morphologic mesoporous materials have been developed in order to obetain higher selectivity and special active sites.In this thesis,a series of novel functionalized mesoporous material SBA-15 were synthesized.The main contents are as follows:1.Solid sphere SBA-15 have been synthesized by using noinonic surfactant P123 as template and strong electrolytes(NH₄F,Cu(NO₃)₂) under acidic conditions.The SBA-15 samples are characterized by X-ray diffraction(XRD),N₂ sorption,which show that the sample have a fine 2D-hexagonal structure.The morphology of SBA-15 is hexagonal prism of side-length of～0.5μm and height of～0.6μm in strong acid media. With increasing pH value of preparation medium,the resulting hexagonal prisms are stretched and distorted.With the participation of strong electrolytes(NH₄F,Cu(NO₃)₂),the mesoporous silica turn from curved forms to solid silica spheres.The structural transition accompanies the rearrangement of silicate micelles;a model for the templating mechanism pathway is proposed.2.CuO catalysts supported on SBA-15 were prepared by chelating of Cu²⁺withγ-aminopropyltrimethoxysilane(APTS)on the SBA-15 support and were tested for selective hydrogenation of crotonaldehyde. The CuO/SBA-15 catalysts with different CuO loadings were characterized by X-ray diffraction(XRD),N₂ sorption,and hydrogen temperature-programmed reduction(H₂-TPR).N₂ sorption results showed that the samples maintained a fine 2D-hexagonal structure after the CuO was loaded,whereas the BET surface area and pore volume decreased with increasing Cu content.H₂-TPR results revealed that there were three Cu species,finely dispersed CuO,bulk CuO,and Cu²⁺ions incorporated into the framework of SBA-15.Catalytic activity of each species was evaluated.The finely dispersed CuO had the highest activity,and the bulk CuO had medium activity,while the Cu²⁺in the SBA-15 framework was inactive in the reaction.These indicated that the finely dispersed Cu species were the active phase for the reaction.Furthermore,the catalyst calcined under N₂ instead of air could increase the content of the finely dispersed CuO,which could consequently enhance the catalytic activity.