- Understanding the mechanism of the competitive adsorption in 8-methylquinoline hydrogenation over a Ru catalyst
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The competitive adsorption of 8-methylquinoline (8-MQL) and partially hydrogenated product, 4H-8-MQL, was studied by performing a combination of experiments and first-principles calculations over a selected Ru catalyst. A series of hydrogenation reactions were conducted with 8-MQL and 4H-8-MQL as initial reactants, respectively. 8-MQL exhibits stronger adsorption on catalyst surface active sites compared with 4H-8-MQL and the massive adsorption of 8-MQL hampers the further adsorption of 4H-8-MQL. The effects of temperature, pressure and solvent on the selectivity in 8-MQL hydrogenation were investigated as well. Full hydrogenation of 8-MQL to 10H-8-MQL was achieved within 120 min when the catalyst dosage increased from 5 wt% to 7 wt% under 160 °C and a hydrogen pressure of 7 MPa. The electronic charge of the N-heteroatom in 8-MQL and 4H-8-MQL was analyzed and the adsorption geometries of 8-MQL and 4H-8-MQL on the Ru(001) surface were optimized by DFT calculations to explain the competitive adsorption behaviors of 8-MQL and 4H-8-MQL.
- Cheng, Hansong,Dong, Yuan,Liu, Zhenjie,Yang, Ming,Zhang, Zhenlin,Zhao, Haoming,Zhu, Ting
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p. 11039 - 11045
(2020/04/03)
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- Highly efficient one-pot multi-directional selective hydrogenation and N-alkylation catalyzed by Ru/LDH under mild conditions
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Atomic economy, non-toxicity, harmlessness and multidirectional selectivity advocated by green chemistry have increasingly become a hot and difficult research topic. Herein, we present a highly efficient, one-pot tandem and easy-to-operate method through which we could directly produce a broad range of multi-directional selective hydrogenated amines or N-alkyl aliphatic amines using aromatic nitro compounds as raw materials. Ru/LDH with characteristics of layered mesoporous structure, well dispersed small Ru nanoparticles and LDH stabilization to the Ru NPs was employed as the catalyst. It is remarkable that multi-directional superb chemoselectivity to aromatic amines, alicyclic amines as well as N-alkyl aliphatic amines could be achieved with excellent catalytic activity and recyclability by tuning reaction conditions over 5wt%Ru/LDH-2. Additionally, this catalytic system also exhibited attractive activity and multi-directional chemoselectivity in the hydrogenation of quinoline and its derivatives with solvents of different polarity. Chemoselectivity to 5,6,7,8-tetrahydroquinoline derivatives could reach as high as 95.6 %.
- Zhang, Sishi,Xu, Jie,Cheng, Hongmei,Zang, Cuicui,Sun, Bin,Jiang, Heyan,Bian, Fengxia
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supporting information
(2020/03/30)
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- Unique nanocages of 12CaO·7Al2O3 boost heterolytic hydrogen activation and selective hydrogenation of heteroarenes over ruthenium catalyst
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The chemoselective hydrogenation of heteroarenes is one of the most important synthetic reactions for the production of key intermediates in agrochemicals, pharmaceuticals and various fine chemicals. The development of new heterogeneous catalysts for the environmentally benign synthesis of heterocycle hydrogenated products is a fundamental objective for chemists. Here, we report that 12CaO·7Al2O3 with a unique sub-nanocage structure loaded with Ru nanoparticles exhibits higher activity, chemoselectivity and sustainability for the hydrogenation of heteroarenes in a solvent-free system than traditional oxide-supported metal catalysts. Conversion of >99% and a selectivity close to 99% were achieved for the hydrogenation of quinoline under mild conditions. This catalyst was also successfully applied to the hydrogenation of a variety of N- and O-heteroarenes with high yields. The superior catalytic performance can be attributed to a cooperative effect between the hydrogen-storage ability and large amount of strong basic sites on the surface of the support, which promotes heterolytic H2 cleavage and prevents poisoning of the metal surface caused by the adsorption of heteroarenes.
- Ye, Tian-Nan,Li, Jiang,Kitano, Masaaki,Hosono, Hideo
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p. 749 - 756
(2017/05/22)
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- Hydrogenation Pathway of Quinolines over Raney Nickel and Ru/C
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Quinoline, 2-methylquinoline, and 8-methylquinoline were hydrogenated over Raney Nickel (R-Ni) under 10 atm hydrogen pressure at about 200 deg C and over ruthenium on carbon (Ru/C) under 100 atm hydrogen pressure at 150 deg C.All the substrates were commonly hydrogenated into the initial products, 1,2,3,4-tetrahydroquinolines.The initial products were competitively converted over R-Ni to the final products, decahydroquinolines, directly or via 5,6,7,8-tetrahydroquinolines which were mainly formed from the initial products by isomerization.Ru/C promoted exclusively the direct hydrogenation of 1,2,3,4-tetrahydro derivatives to the final products.The hydrogenation and isomerization of 1,2,3,4-tetrahydroquinoline was completely inhibited in the competitive hydrogenation of quinoline and isoquinoline over R-Ni.Such features of these substrates are explained by the strong basicity of 1,2,3,4-tetrahydroisoquinoline.Roles of 1,2,3,4-tetrahydroisoquinoline are much moderate on Ru/C, where the ?-coordination may be important.The effects of methyl substituent and different reactivities of quinoline and isoquinoline are discussed in terms of the steric hindrance on adsorption, heats of hydrogenation, basicities, and electronic properties of the related compound, which are calculated according to the MNDO-PM3 method.
- Okazaki, Hiroshi,Onishi, Kiyotaka,Soeda, Mahito,Ikefuji, Yoshio,Tamura, Ryuji,Mochida, Isao
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p. 3167 - 3174
(2007/10/02)
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