Synthesis And Application Of Solid Acid Catalysts Of Heteropoly Acid In Reaction Of Acid Catalyzed

The traditional acid catalysts in organic synthesis reaction are usually heterogeneous catalyst,such as concentrated sulfuric acid,phosphoric acid,hydrofluoric,hydrochloric acid.There are lots of problems of corroding equipment,polluting the environment and almost not recycle after the reaction.Heteropolyacid catalyst is a kind of mult oxygen mental complex formed by the combination of the central atom and the coordination atom through a combination of the oxygen atom.It has both of the structural characteristics of coordination complexes and metal oxides,and has acidity and oxidability.It can be not only used in homogeneous reaction system,but also in heterogeneous reaction system.The heteropolyacid and its salts are neotype catalytic material with characteristics of special acidic compounds,“pseudo-liquid phase”and multi-functional and have outstanding catalytic effect in organic synthesis reactions such as esterification,condensation,etherification,asymmetric reaction,isomerization,dehydration and cracking.Heteropolyacid catalyst has a great potential for application in acid catalysis,but there are still many disadvantages such as smaller surface area,poor stability,high solubility in polar solvent and difficult to recycle.In view of disadvantages of heteropolyacid,various methods of modified heteropolyacid were reported.The coordination ability of heteropolyanion is strong.Organic-polyoxometalates were prepared by the interaction between organic ligand and heteropolyanion,such as organic-silicotungstate,organic-phosphotungstate and organic-molybdovanadophosphoric heteropolyacid salts.The prepared catalyst was researched by X-ray powder diffraction?XRD?,infraredspectroscopy?IR?,automaticchemicaladsorption instrument?NH₃-TPD?,scanning electron microscope?SEM?,electron spectroscopy for chemical analysis?XPS?,thermogravimetry?TG?and potentiometric titration.In order to estimate the catalytic property of organic-polyoxometalates,these catalysts were used to catalyze oleic acid esterification,levulinic acid esterification,glyceride esterification and ketalation.The applicability of catalyst can be explore by altering reaction substrates and explore their durability by the method of filtration.