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 phen...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.展开更多
Title molybdogadolinium heteropoly compound has been synthesized and used to catalize the hydroxylation of phenol with hydrogen peroxide. The effects of reaction time, temperature, pH value, n(phOH)/n(H 2O 2) and solv...Title molybdogadolinium heteropoly compound has been synthesized and used to catalize the hydroxylation of phenol with hydrogen peroxide. The effects of reaction time, temperature, pH value, n(phOH)/n(H 2O 2) and solvent on the catalytic activity for phenol hydroxylation have been investigated. The results show that the title compound in the presence of V 2O 5 shows an excellent catalytic activity for phenol hydroxylation. When methanol is used as solvent at n(phOH)/n(H 2O 2)=1∶2, pH=5, at 343 K and for 4 h, hydroquinone in yield of 42 10% is obtained with phenol conversion of 40.50%.展开更多
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
文摘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.
文摘Title molybdogadolinium heteropoly compound has been synthesized and used to catalize the hydroxylation of phenol with hydrogen peroxide. The effects of reaction time, temperature, pH value, n(phOH)/n(H 2O 2) and solvent on the catalytic activity for phenol hydroxylation have been investigated. The results show that the title compound in the presence of V 2O 5 shows an excellent catalytic activity for phenol hydroxylation. When methanol is used as solvent at n(phOH)/n(H 2O 2)=1∶2, pH=5, at 343 K and for 4 h, hydroquinone in yield of 42 10% is obtained with phenol conversion of 40.50%.
