Pyridine-H_5PMo_(10)V_2O_(40) hybrid catalysts for liquid-phase hydroxylation of benzene to phenol with molecular oxygen  

作　　者：GE HanQing1,LENG Yan1,ZHANG FuMin1,PIAO JiaRui2,ZHOU ChangJiang1 & WANG Jun1 1 State Key Laboratory of Materials-Oriented Chemical Engineering,College of Chemistry and Chemical Engineering,Nanjing University of Technology,Nanjing 210009,China 2 Petrochemical Research Institute,PetroChina Company Ltd.,Beijing 100083,China 

出　　处：《Science China Chemistry》2009年第8期1264-1269,共6页中国科学（化学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant Nos. 20476046 and 20776069);the "Qinglan" Project of Jiangsu Province for Young Researchers

摘　　要：Pyridine(Py)-modified Keggin-type vanadium-substituted heteropoly acids(PynPMo10V2O40,n=1 to 5) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene to phenol in a pressured batch reactor and their structures were detected by FT-IR.Among various catalysts,Py3PMo10V2O40 exhibits the highest catalytic activity(yield of phenol,11.5%),without observing the formation of catechol,hydroquinone and benzoquinone in the reaction with 80 vol% aqueous acetic acid,molecular oxygen and ascorbic acid used as the solvent,oxidant and reducing reagent,respectively.Influences of reaction temperature,reaction time,oxygen pressure,amount of ascorbic acid and catalyst on yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.Pyridine can greatly promote the catalytic activity of the Py-free catalyst(H5PMo10V2O40),mostly because the organic π electrons in the hybrid catalyst may extend their conjugation to the inorganic framework of heteropoly acid and dramatically modify the redox properties,at the same time,pyridine adsorbed on heteropoly acids can promote the effect of "pseudo-liquid phase",thus accounting for the enhancement of phenol yield.Pyridine(Py)-modified Keggin-type vanadium-substituted heteropoly acids(PynPMo10V2O40,n=1 to 5) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene to phenol in a pressured batch reactor and their structures were detected by FT-IR.Among various catalysts,Py3PMo10V2O40 exhibits the highest catalytic activity(yield of phenol,11.5%),without observing the formation of catechol,hydroquinone and benzoquinone in the reaction with 80 vol% aqueous acetic acid,molecular oxygen and ascorbic acid used as the solvent,oxidant and reducing reagent,respectively.Influences of reaction temperature,reaction time,oxygen pressure,amount of ascorbic acid and catalyst on yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.Pyridine can greatly promote the catalytic activity of the Py-free catalyst(H5PMo10V2O40),mostly because the organic π electrons in the hybrid catalyst may extend their conjugation to the inorganic framework of heteropoly acid and dramatically modify the redox properties,at the same time,pyridine adsorbed on heteropoly acids can promote the effect of "pseudo-liquid phase",thus accounting for the enhancement of phenol yield.

关 键 词：HYDROXYLATION benzene ORGANIC/INORGANIC hybrid catalyst PHENOL HETEROPOLY acid PYRIDINE 

分 类 号：O621.2[理学—有机化学]