Preparation Of Spherical Catalyst With Hierarchical Porous Structure By Microfluidic Technology

In recent years,more and more researchers have paid their attention to porous materials.There are a large number of pores in the structure of porous materials.The porous materials have smaller density,lighter weight,and larger surface area compared with none-porous materials.The research on porous materials has become an essential branch in the field of materials science.The hierarchical porous materials contained two or more kinds of pores in their structure at the same time and combined the advantages of different sized pores.Therefore the hierarchical porous materials were widely used in catalysis,adsorption separation,energy storage,and other fields.In this thesis,multi-functional silica?SiO₂?microspheres were prepared by microfluidic technology and electric field spraying.The main research results are as follows:?1?Firstly,mesoporous SiO₂ nanoparticles were synthesized.The catalytic elements?ZrO₂-SiO₂,MgO-SiO₂?with acid,base catalytic were prepared by the solution impregnation method,respectively.Secondly,a bi-functional catalyst was prepared by microfluidic technology.Magnetic Fe₃O₄ nanoparticles were assembled with other elements to obtain multi-functional microspheres.Finally,composite microspheres were used to catalyze the deacetalization-Knoevenagel cascade reactions.The average diameter of composite microspheres was about 150?m,the monodispersity was good?CV=4.7%?.The microspheres have a specific surface area of more than 400 m²·g^-1.When the content of solid particles was10%,and the ratio of ZrO₂-SiO₂ to MgO-SiO₂ was 7:3,the catalytic activity of the composite microspheres was the highest.The yield of product was 92%.The composite microspheres have a magnetic susceptibility of 7.2 emu·g^-1 and can be removed from the reaction system easily by applying an external magnetic field.?2?Porous SiO₂ microspheres were prepared by sol-gel method and electric field spraying technique under acidic conditions.Tetramethoxysilane?TMOS?was used as a precursor,and polyethylene glycol?PEG 10000?was used as a pore-forming agent.When the solvent volume in the sol was 13 mL,and the amount of PEG was 2.4 g,the skeleton structure of the obtained gel microspheres was the most complete.The specific surface area of the microspheres was 160 m²·g^-1,and the pore volume was 0.99 mL·g^-1.The average pore diameter was 25 nm.The raw SiO₂ microspheres were modified to obtain SO₃H-SiO₂ and NH₂-SiO₂ microspheres,respectively.The above microspheres were used to catalyze the deacetalization reaction and Knoevenagel reaction,respectively.The results showed that the catalytic activity of both two catalysts was good enough.