Preparation, Characterization And Application Of Aquivion Perfluorosulfonic Acid Resin Organic-inorganic Composite Solid Acid Catalyst

The extensive use of homogeneous acid catalysts in industrial catalytic processes has raised a series of problems such as severe waste liquid emission,environmental pollution,high cost and equipment corrosion.This paper is dedicated to the development of an easily separable,recyclable composite solid acid catalyst,i.e.,Aquivion perfluorosulfonic acid resin?PFSA?with excellent acidic catalytic activity immobilized on mesoporous silica?m-SiO₂?to prepare organic-inorganic Aquivion@m-SiO₂ composite solid acid catalyst.The main research contents of this dissertation include three parts:?i?the preparation and characterization of Aquivion@m-SiO₂ catalysts and their applications in?ii?the catalytic dehydration of _D-fructose to 5-hydroxymethylfurfural?5-HMF?and?iii?the catalytic etherification of5-HMF with isobutene?IB?to biodiesel additives.The catalytic activities of Aquivion@m-SiO₂ catalysts for the two model reactions are investigated and the structure-activity correlation is discussed by intergrading the characterization results and catalytic results of the catalysts.In this paper,an amphiphilic sulfonic acid resin was used as template and acid medium,and tetraethoxysilane?TEOS?was used as silicon source.The m-SiO₂ support was prepared by sol-gel method followed by calcination.The m-SiO₂ support displayed a rich pore structure and a large specific surface area.Aquivion@m-SiO₂ catalyst was prepared by impregnation and the loading of Aquivion resin was tuned.The Aquivion@m-SiO₂ catalyst showed both the characteristic properties of Aquivion resin and m-SiO₂ support,and exhibited stable catalytic performance in the consecutive recycling test.A facile proton exchange of the used Aquivion@m-SiO₂ catalyst with diluted nitric acid enabled the acid sites to be regenerated,indicating that the Aquivion resin and the m-SiO₂ support were closely interacted together.The blank experiments confirmed that the catalytic activity of the catalyst came only from the sulfonic acid groups in the Aquivion resin.Thermogravimetric analysis showed that the catalyst afforded good thermal stability when working below 280?C.In the catalytic dehydration of fructose to 5-HMF,an Aquivion@m-SiO₂ catalyst with 10%loading of Aquivion resin exhibited excellent catalytic performance.Dimethyl sulfoxide?DMSO?with a strong polarity was used as solvent.The targeted product?5-HMF?was fairly stable in DMSO,moreover DMSO can also act as an electron acceptor and/or donor to improve the catalytic dehydration of fructose to 5-HMF.The optimization tests were carried out to investigate the influence of reaction parameters,the conversion of fructose reached 100%,and the yield of 5-HMF was of 85%.Compared with the recently reported catalytic systems over Br?nsted solid acids,the Aquivion@m-SiO₂ catalyst demonstrated a higher yield(mol _HMF/mol _H⁺).In the catalytic etherification of 5-HMF with IB,an Aquivion@m-SiO₂ catalyst with 45%loading of Aquivion resin exhibited excellent catalytic performance.The medium polar tetrahydrofuran?THF?was used as solvent to balance adsorption of the reactants and desorption of the products on the catalyst.The optimization tests were carried out to investigate the influence of reaction parameters,the optimal conversion of5-HMF reached 76%,and the optimal yield of tert-butoxymethylfurfural?tBMF?was of61%.Compared with the previously reported catalytic systems over solid acids,the Aquivion@m-SiO₂ catalyst demonstrated the highest tBMF yield.The excellent performance of the Aquivion@m-SiO₂ catalyst can be attributed to the fact that the m-SiO₂ support exhibits a rich pore structure with an average pore size up to 11 nm.After being effective immobilization and fully dispersed of the Aquivion resin in the Aquivion@m-SiO₂ catalyst,it also retains some pore structure,which promotes the contact between the acid sites and the reactants and facilitates the transport of the substances.The distribution density of the resin on the m-SiO₂ support increases with increasing resin loading in the Aquivion@m-SiO₂ catalyst,and the number of acid sites increases by per unit area.The reactants can contact more acidic sites after being adsorbed on the catalyst,corresponding to an acid-catalyzed reaction at a stronger acid environment.A suitable acid strength is beneficial for an acid-catalyzed reaction.Therefore,Aquivion@m-SiO₂ catalysts with different resin loadings exhibit excellent catalytic performance in catalytic dehydration and etherification reactions.