Preparation And Surface Modification Of Sulfonated Mesoporous Silica Solid Acid Catalyst

Compared with traditional liquid acids,solid acid catalysts have the advantages of easy separation,non-corrosiveness and continuous production.At the same time,they conform to the concept of green environmental protection and are widely used in various acid catalytic reactions.In view of the problems of mass transfer,acid loss and inactivation of solid acid,the new type of mesoporous silica foam was used as the carrier to anchor the sulfonic group onto the carrier.By adjusting the hydrophobicity of the catalyst,different esterification reactions,reactant properties and different hydrophobic groups were grafted to increase the adsorption capacity of the reactants and the concentration of the reactants on the surface of the catalyst.At the same time,the by-product water is quickly discharged from the surface of the catalyst to avoid hydrolysis and improve the water resistance and stability of the catalyst.In this paper,the effects of 1,3,5-trimethylbenzene content on the structure and surface hydroxyl groups of MCF molecular sieves synthesized by hydrothermal method were systematically studied.The effects of pore structure of support,temperature-sensitive polymers and carbon-chain phenyl rings on the catalytic performance of hydrophobic regulation of solid acids were emphatically studied.1.MCF molecular sieves with different pore sizes and hydroxyl groups were synthesized by changing the content of 1,3,5-trimethylbenzene.It is found that with the increase of 1,3,5-three methyl benzene content,the mesoporous silicon material will gradually change from the two-dimensional six party structure of SBA-15 to the three-dimensional cubic structure.When 1,3,5-three toluene is added to a certain amount,the foamed MCF material will be obtained.When the 1,3,5-three methylbenzene reaches the maximum amount,the three-dimensional vertical foam structure will be destroyed.The pore structures of MCF and SBA-15 are different.The catalytic properties of support with different pore structures for sulfonation were investigated.The results showed that the sulfonated MCF solid acid catalyst had higher esterification activity than the sulfonated SBA-15 solid acid catalyst.2.The prepared poly-N-isopropylacrylamide was chemically bonded to the surface of the sulfonated MCF solid acid to investigate its effect on the synthesis of ethyl acetate.Studies have shown that the temperature-sensitive material is grafted onto the surface of the solid acid,so that the solid acid has a significant temperature stimulating response,causing a switchable catalytic effect.The hydrogen bond between the grafted poly-N-isopropylacrylamide and ethanol increases the adsorption of the reactant ethanol and accelerates the reaction rate.In the unmodified sulfonated MCF,collapse of the skeleton and the pores occurred,and the modified solid acid exhibited high stability.3.Phenyltrimethoxysilane was used to regulate the nonpolar hydrophobicity of sulfonated MCF solid acid surface,and its effect on the synthesis of methyl benzoate was studied.The results showed that the pi-pi bond formed between the benzene ring on the surface of solid acid and the benzoic acid,which enriched the reactants.The concentration of the reactants on the surface of catalyst increased the reaction rate and the water resistance and stability of the catalyst.