Direct hydroxylation of benzene catalyzed by vanadium-con- taining heteropoly compounds with Keggin or Dawson structure has been investigated.The effects of several factors upon the hydroxylation reaction have also be...Direct hydroxylation of benzene catalyzed by vanadium-con- taining heteropoly compounds with Keggin or Dawson structure has been investigated.The effects of several factors upon the hydroxylation reaction have also been examined.It is indicated that the highest yield of phenol reached 76%(based on H_2O_(?))with 99.4～100% selectivity.展开更多
A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilizedon dealuminated ultra-stable Y zeolite (DUSY) were prepared. Their specific surface area and acidstrength were characterized, and t...A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilizedon dealuminated ultra-stable Y zeolite (DUSY) were prepared. Their specific surface area and acidstrength were characterized, and their catalytic activity, selectivity and stability were evaluated in theliquid-phase esterification of acetic acid with n-butanol. It was found that the catalytic activity could beimproved remarkably by introducing PW onto dealuminated USY (from 49.5% to 86.4%). Howeverthis obvious promotion effect of PW could not be observed on USY supported PW catalyst, whichshowed rather low conversion of less than 25.0%. The supported cesium salt of PW on DUSY catalysgave a very high conversion of n-butanol of 94.6% and the 100% selectivity for n-butyl acetate. Thecatalytic stability test revealed that after 5 reaction cycles, the catalytic activity over PW/DUSY drastically dropped to 47.6%, by contrast, the PW cesium salt/DUSY still showed a high conversion o81.6%. The leaching test for catalysts in water showed that the decrease of activity was closely associated with the solubility of the active heteropoly components on supports into the polar solvent, whichindicates that the catalytic deactivation was mainly due to the lose of the heteropoly species in thereaction medium. The high catalytic stability of the supported cesium salts of PW is suggested to bederived from the water-tolerance of cesium salts of PW in the polar reaction system.展开更多
Heteropoly complexes as double-function catalysts have been reported. Their ability of oxidation and acidity can be adjusted by changing their constituent, which is achieved by synthesizing mixed heteropoly complexes....Heteropoly complexes as double-function catalysts have been reported. Their ability of oxidation and acidity can be adjusted by changing their constituent, which is achieved by synthesizing mixed heteropoly complexes. The synthetic method and characterization of the salts of tungstomolybdoniobophosphoric acids are reported in this note.展开更多
文摘Direct hydroxylation of benzene catalyzed by vanadium-con- taining heteropoly compounds with Keggin or Dawson structure has been investigated.The effects of several factors upon the hydroxylation reaction have also been examined.It is indicated that the highest yield of phenol reached 76%(based on H_2O_(?))with 99.4～100% selectivity.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 20306011 & 20476046) the Ph.D. Program Foundation of Chinese University (No. 20040291002).
文摘A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilizedon dealuminated ultra-stable Y zeolite (DUSY) were prepared. Their specific surface area and acidstrength were characterized, and their catalytic activity, selectivity and stability were evaluated in theliquid-phase esterification of acetic acid with n-butanol. It was found that the catalytic activity could beimproved remarkably by introducing PW onto dealuminated USY (from 49.5% to 86.4%). Howeverthis obvious promotion effect of PW could not be observed on USY supported PW catalyst, whichshowed rather low conversion of less than 25.0%. The supported cesium salt of PW on DUSY catalysgave a very high conversion of n-butanol of 94.6% and the 100% selectivity for n-butyl acetate. Thecatalytic stability test revealed that after 5 reaction cycles, the catalytic activity over PW/DUSY drastically dropped to 47.6%, by contrast, the PW cesium salt/DUSY still showed a high conversion o81.6%. The leaching test for catalysts in water showed that the decrease of activity was closely associated with the solubility of the active heteropoly components on supports into the polar solvent, whichindicates that the catalytic deactivation was mainly due to the lose of the heteropoly species in thereaction medium. The high catalytic stability of the supported cesium salts of PW is suggested to bederived from the water-tolerance of cesium salts of PW in the polar reaction system.
文摘Heteropoly complexes as double-function catalysts have been reported. Their ability of oxidation and acidity can be adjusted by changing their constituent, which is achieved by synthesizing mixed heteropoly complexes. The synthetic method and characterization of the salts of tungstomolybdoniobophosphoric acids are reported in this note.
