Design And Application Of Polyaniline-Supported Tungsten Catalyst

Supported catalyst is a kind of common catalyst with wide applications in catalytic synthesis reactions.There are many kinds of catalyst support,such as:polymer derived ceramics(PDCs),graphene,polyaniline,etc.Polyaniline has been widely studied for its good redox ability,stability,non-toxicity,adjustable substituents and easy synthesis.In recent years,tungsten,as a transition metal,has gradually attract much attention due to its good chemical properties.The toxicity of tungsten is low,and it is safe to the environment.The excellent properties of polyaniline catalyst support and tungsten metal inspire us to develop the novel polyaniline-supported tungsten catalyst.We developed two types of tungsten-containing catalysts using polyaniline as the catalyst support:W@PANI and Pd/W@PANI.They were used in oxidation of alcohol,alkylation of alcohol ketone and coupling reaction respectively.The main research content of the paper is as follows:In chapter 2,four catalysts,such as W@PANI,W@PANI-F,W@PANI-pMe and W@PANI-pOMe,were prepared.The catalytic activities of these four catalysts and sodium tungsten were evaluated by the benzyl alcohol oxidation reactions,and W@PANI was screened out to be the best catalyst.By tunning the reaction conditions such as the amount of catalyst required for the reaction,the amount of oxidant,and the reaction temperature,benzaldehyde was finally produced in a high yield of 78%.The reaction process is simple,the reaction conditions are mild,and the catalyst material has a good range of applicability for the substrate,especially good for controlling the selectivity of the reaction of the primary alcohols.In addition,the possible mechanism of this oxidation reaction was supposed on the basis of the result of XPS analysis of the catalyst before and after the reaction.In chapter 3,the W@PANI catalyst was applied in the C-C bonded alkylation reaction of benzyl alcohol with acetophenone.The experimental results showed that the W@PANI catalyst could catalyze not only the alcohol oxidation reaction but also the alkylation reaction of benzyl alcohol with acetophenone.Through further studies,we screened out the optimized reaction conditions and finally obtained the corresponding reaction products in 76%yield.The reaction conditions were mild and the generation of by-products were well restrained.In addition,the tungsten metal used in the reaction was inexpensive,thus reducing the reaction cost.In chapter 4,we initially performed the Suzuki coupling reactions using W@PANI as catalyst,but the results were not satisfied.Therefore,we tried to improve the catalytic activity by doping palladium into the catalyst.It was found that although tungsten could not directly catalyze the coupling reaction,it could enhance the catalytic activity of metallic palladium to generate the coupling product in a yield of up to 92%.Through a series of comparative experiments and material analysis tests,we elucidated the mechanism by which tungsten enhances the catalytic activity of palladium.The reaction employs clean ethanol as the reaction solvent,thus making it greener.