Study On The Application Of Anderson-POM On SBA-15 In Oxidation And Esterification

Polyoxometalate?POM?is a kind of multinuclear inorganic polymer compound formed by bridging a metal atom with a kind of oxygen atom.It is divided into two kinds of polyacid and heteropoly acid.POM is composed of hetero atoms such as P and Si.Fe,Co,etc.constitute a central atom,and polyatoms such as Mo,V,W,etc.act as ligands,and are connected by a certain molecular structure through an oxygen atom coordination bridge.As a solid acid with a much higher acid strength than other inorganic acids,POM have been attracting attention in the field of catalysis.Among them,Anderson type polyoxometalates enters the researcher's field of vision with its unique structure and excellent catalytic performance.However,since the specific surface area of the polyoxometallate is small,the reaction rate is affected.Moreover,recovery after the reaction is difficult and it is difficult to recycle.In order to improve these problems,a SBA-15 mesoporous molecular sieve having a large specific surface area and a stable structure was used as a carrier.It is prepared as a supported Anderson polyoxometalates catalyst for several common catalytic oxidation reactions.These catalysts can catalyze different reactions by changing different central atoms,and have important research and application value in the field of catalysis.This paper is an investigation of the catalytic properties of supported Anderson polyoxometalates in oxidation and esterification reactions.Fe-POM is used as the active component of the catalyst and loaded onto the mesoporous molecular sieve to prepare a Fe-Anderson-type heteropolyacid catalyst.The catalyst loading was changed,and the catalyst with the optimum loading was controlled by the control variable to selectively catalyze the oxidation of benzaldehyde to controllize the formation of benzoic acid.In this process,the reaction conditions were screened to find the optimal experimental protocol.Through research,we found that when the reaction temperature is controlled between 65 and 75°C,with H₂O as the solvent,after 6 hours,the conversion of benzaldehyde can reach 97.8%.After 12 hours,the conversion rate reaches 99%or more.Fe-POM catalyst was applied to the oxidation process of other aldehydes,and the catalyst was found to have good universality and excellent yield and selectivity for most aromatic aldehydes and fatty aldehydes.Esterification is a very important part of organic synthesis.We synthesized a series of SBA-15 supported Anderson-type polyoxometallate catalysts with different central atoms for the esterification of different acids and alcohols.The esterification of isoamyl acetate was first selected as a model reaction to explore the activity of esterification of different central atom Anderson-type supported POM catalysts.Under the same conditions?108°C,1 atmosphere?,Cu-POM as the central atom had the best catalytic effect,and the yield of isoamyl acetate after heating for 1.5 hours was 97.3%.It shows that changing the central atom of POM does affect the esterification reaction.Then the effect of catalyst loading and addition amount on the catalytic effect is studied.It is found that the higher the loading,the faster the reaction rate and the higher the loading.Lead to blockage of the catalyst pores,and thus the yield is reduced;after exploring the optimal reaction conditions,the catalyst is used in the esterification reaction of other organic substances,and the substrate expansion experiment is conducted to find that the SBA-15 is loaded with Anderson-type polyoxometallate.The generality of the salt catalyst is good,and the esterification reaction of different types of macromolecular organic compounds has good yield and selectivity.The reaction condition is mild,the amount of catalyst is small,and it can be recycled and recycled,economical and environmentally friendly,and has good application prospect and potential in the industry.