Air-promoted selective hydrogenation of phenol to cyclohexanone at low temperature over Pd-based nanocatalysts  

作　　者：Qing Guo Shiguang Mo Pengxin Liu Weidong Zheng Ruixuan Qin Chaofa Xu Youyunqi Wu Binghui Wu Nanfeng Zheng 

机构地区：[1]Department of Chemical and Biochemical Engineering,National Engineering Laboratory for Green Chemical Productions of Alcohols-Ethers-Esters,State Key Laboratory for Physical Chemistry of Solid Surfaces,Collaborative Innovation Center of Chemistryfor Energy Materials,and Engineering Research Center for Nano-Preparation Technology of Fujian Province,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China

出　　处：《Science China Chemistry》2017年第11期1444-1449,共6页中国科学（化学英文版）

基　　金：supported by the Ministry of Science and Technology of China(2017YFA0207302,2015CB93230);the National Natural Science Foundation of China(21420102001,21333008)

摘　　要：Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy （Ea, 55-70 kJ/mol）. Here we report a simple and efficient strategy for phenol hydrogenation catalyzed by Pd in aqueous phase at 30 ℃ by introducing air to promote the catalysis. With the assistance of air, 〉99% conversion and 〉99% selectivity were achieved over Pd（111）/Al2O3 with an overall turnover frequency （TOF） of 621 h-1, -80 times greater than that of the state-of-art Pd catalyst at 30 ℃. Mechanism studies revealed that phenol was activated to generate phenoxyl radicals. The radicals were yielded from the reaction between phenol and hydroxyl radicals in the presence of hydrogen, oxygen and protic solvent on Pd. The phenoxyl pathway resulted in a low apparent Ea （8.2 kJ/mol） and thus high activity. More importantly, this strategy of activating substrate by air can be adapted to other Pd based catalysts, offering a new thinking for the rational design of cyclohexanone production in industry.Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy(E_a, 55–70 kJ/mol). Here we report a simple and efficient strategy for phenol hydrogenation catalyzed by Pd in aqueous phase at 30 °C by introducing air to promote the catalysis. With the assistance of air, >99% conversion and >99% selectivity were achieved over Pd(111)/Al_2O_3 with an overall turnover frequency(TOF) of621 h^(-1), ~80 times greater than that of the state-of-art Pd catalyst at 30 °C. Mechanism studies revealed that phenol was activated to generate phenoxyl radicals. The radicals were yielded from the reaction between phenol and hydroxyl radicals in the presence of hydrogen, oxygen and protic solvent on Pd. The phenoxyl pathway resulted in a low apparent E_a(8.2 kJ/mol) and thus high activity. More importantly, this strategy of activating substrate by air can be adapted to other Pd based catalysts, offering a new thinking for the rational design of cyclohexanone production in industry.

关 键 词：selective hydrogenation PHENOL PALLADIUM NANOCATALYSIS RADICAL 

分 类 号：O643.36[理学—物理化学] TQ234.21[理学—化学]