Construction Of Heteropolyacid Baced Solid Acid Catalyst And Its Catalytic Performance

As an indispensable part of human life,fine chemicals are widely used in food,medicine,industry and other fields,and its efficient and green production mode has been a topic of widespread concern.Heteropolyacids(HPAs),as a new type of solid acid catalyst,possess important applications in acid catalysis,photocatalysis and electrocatalysis due to their adjustable structure and different properties.However,due to the strong solubility of HPAs in polar solvents and BET surface area less than 5 m2g-1,it is difficult to separate and reuse.We designed and synthesized HPAs composite catalyst with unique morphology based on Keggin type heteropolyacid(phosphotungstic acid,H3PW12O40 ·H2O),zirconia(ZrO2)and organosilicon.Simultaneously,we systematically explored catalytic performance of PS@PMA-ZrO2-PW12 in the esterification of cellulose to produce cellulose acetate propionate(CAP)and the alkylation of benzyl alcohol as model reactions.1.A novel solid acid catalyst PS@PMA-ZrO2-PW12 with core-shell nanostructure was successfully constructed by cohydrolysis condensation and impregnation method with polystyrene(PS)as the core and CTAB as the structure directing agent.Simultaneously,the prepared catalyst PS@PMAZrO2-PW12 was used in the esterification of cellulose to produce CAP.In the preparation of CAP,PS@PMA-ZrO2-PW12 showed excellent catalytic performance,in which CAP exhibited Mw of 100644,DS of 2.73 and viscosity of 320 mPa s.Compared with commercially available catalysts such as Amberlyst-15 and liquid inorganic acids such as H2SO4 under the same reaction conditions,PS@PMA-ZrO2-PW12 exhibited the advantages of controllable reaction process with CAP of higher molecular weight(MW)and viscosity.At the same time,PS@PMA-ZrO2-PW12 could maintain its original morphology and excellent catalytic performance after at least five cycles.In addition,we further processed the above CAP products into film without addition of any plasticizers and investigated its optical and mechanical properties.It is found that the obtained CAP film displayed excellent optically transparent property,high flexibility and easy dyeability.2.Using PS as template,we have designed and constructed a new type of solid acid catalyst PMA-Si(Et)Si-ZrO2-PW12 HNs with a hollow structure of heteropolyacid and zirconium dioxide bifunctionalization by adjusting the ratio of zirconium precursor and heteropolyacid supported and introducing hydrophobic organosilane fragments to realize the control of the acidity of Br?nsted acid and Lewis acid as well as the construction of hydrophobic environment of the catalyst.The morphology,chemical structure and acidity of the PMA-Si(Et)Si-ZrO2-PW12 HNs were characterized by HRTEM and pyridine adsorption infrared spectroscopy and other measurement methods.At the same time,the catalytic activity of the PMA-Si(Et)Si-ZrO2-PW12 HNs was evaluated using toluene alkylation with benzyl alcohol as model reaction.The effects of acid strength,hydrophobicity of the PMA-Si(Et)Si-ZrO2-PW12 HNs on the catalytic performance were explored by regulating the ratio of Br?nsted acid and Lewis acid sites,the type of organosilane,the reaction conditions for alkylation and other conditions.The results displayed that the conversion of benzyl alcohol could reach 95.7%after reaction at 90℃ for 1 h.Simultaneously,the selectivity of diphenyl compounds was 75.9%.In addition,the as-prepared PMA-Si(Et)Si-ZrO2-PW12 HNs catalyst can maintain its original catalytic activity after four cycles.