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钠的液氨溶液还原炔烃反应机理探讨 被引量:2
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作者 李彦如 《承德民族师专学报》 2004年第2期42-43,共2页
根据炔烃及氨合电子的性质,提出炔烃被钠的液氨溶液还原的反应机理,并对产物的构型给予了理论解释。
关键词 溶液 炔烃 还原反应 氨合电子 离子型自由基 反应产物
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A theoretical study of electrocatalytic ammonia synthesis on single metal atom/MXene 被引量:3
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作者 Yijing Gao Han Zhuo +6 位作者 Yongyong Cao Xiang Sun Guilin Zhuang Shengwei Deng Xing Zhong Zhongzhe Wei Jianguo Wang 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2019年第2期152-159,共8页
Electrocatalytic ammonia synthesis under mild conditions is an attractive and challenging process in the earth’s nitrogen cycle,which requires efficient and stable catalysts to reduce the overpotential.The N2 activat... Electrocatalytic ammonia synthesis under mild conditions is an attractive and challenging process in the earth’s nitrogen cycle,which requires efficient and stable catalysts to reduce the overpotential.The N2 activation and reduction overpotential of different Ti3C2O2-supported transition metal(TM)(Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn,Mo,Ru,Rh,Pd,Ag,Cd,and Au)single-atom catalysts have been analyzed in terms of the Gibbs free energies calculated using the density functional theory(DFT).The end-on N2 adsorption was more energetically favorable,and the negative free energies represented good N2 activation performance,especially in the presence Fe/Ti3C2O2(﹣0.75 eV).The overpotentials of Fe/Ti3C2O2,Co/Ti3C2O2,Ru/Ti3C2O2,and Rh/Ti3C2O2 were 0.92,0.89,1.16,and 0.84 eV,respectively.The potential required for ammonia synthesis was different for different TMs and ranged from 0.68 to 2.33 eV.Two possible potential-limiting steps may be involved in the process:(i)hydrogenation of N2 to*NNH and(ii)hydrogenation of*NH2 to ammonia.These catalysts can change the reaction pathway and avoid the traditional N–N bond-breaking barrier.It also simplifies the understanding of the relationship between the Gibbs free energy and overpotential,which is a significant factor in the rational designing and large-scale screening of catalysts for the electrocatalytic ammonia synthesis. 展开更多
关键词 Electrocatalytic ammonia synthesis Single atom catalyst MXene Transition metal Density functional theory OVERPOTENTIAL Gibbs free energy
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Does Muller Cell Differentiation Occur Prior to the Emergence of Synapses in Embryonic Turtle Retina?
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作者 Yolanda Segovia Rosa Maria Perez +1 位作者 Norberto Mauricio Grzywacz Joaquin De Juan 《Journal of Life Sciences》 2012年第11期1200-1205,共6页
MOiler cells are the main glial cells in the retina, and are related to plexiform layer activity. Recent studies have demonstrated that Muller cells are involved in the synaptic conservation, plasticity, development a... MOiler cells are the main glial cells in the retina, and are related to plexiform layer activity. Recent studies have demonstrated that Muller cells are involved in the synaptic conservation, plasticity, development and metabolism of glutamate. During turtle retinal development, layers, cells and synapses appear at different times. The aim of this research is to study the emergence of Muller cells during embryonic development and their relationship with the synaptogenesis. The authors used retinas from Trachemys scripta elegans embryos at stages S14, 18, 20, 23, and 26. Some retinas were processed with immunocytochemistry in order to detect the presence of glutamine synthetase in Muller cells, which was used as a marker of these ceils. Other retinas from the same stages were processed for ultrastructural studies. Samples were observed in confocal and transmission electron microscopes, respectively. The present results show that glutamine synthetase expression in MOiler cells occurs at S18, before the emergence of the retinal layers and the early synapses. 展开更多
关键词 SYNAPTOGENESIS retinal development glutamine synthetase ULTRASTRUCTURE immunochemistry.
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Efficient synthesis of 1,6-hexamethylene diurethane through coupling transesterification and methoxycarbonylation with methyl phenyl carbonate as intermediate
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作者 杨勇 汤吉海 +3 位作者 陈献 费兆阳 崔咪芬 乔旭 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2015年第7期1147-1152,共6页
A reaction coupling system of transesterification and methoxycarbonylation with methyl phenyl carbonate (MPC) as intermediate was established to efficiently prepare 1,6-hexamethylene diurethane (HDU) from 1,6- bex... A reaction coupling system of transesterification and methoxycarbonylation with methyl phenyl carbonate (MPC) as intermediate was established to efficiently prepare 1,6-hexamethylene diurethane (HDU) from 1,6- bexametbylene diamine (HDA). The feasibility of the system was explored using the thermodynamics analysis, the reaction mechanism and the experiment results. The optimal reaction was carried out to get higher HDU yield. The thermodynamic analysis showed that the metboxycarbonylation of HDA with MPC, the Gibbs free energy of which was negative, was a spontaneous process. Furthermore, the equilibrium constant of the methoxycarbonylation of HDA with MPC was much greater than that of the transesterification of dimethyl carbonate (DMC) with phenol, so the reaction coupling could be realized under mild conditions. The reaction mechanism analysis indicated that phenoxy anion was the key spedes for reaction coupling. Higher MPC concentration was detected when sodium phenoxide was used as transesterification reactant with DMC, since the phenoxy anion of sodium phenoxide could be dissociated more easily. Sodium pbenoxide was more suitable to prepare HHDU through reaction coupling. A yield of HDU as high as 98.3% could be reached under the optimal conditions of mPhONa/mDMC = 0.027 and nDMC/nHDa = 8/1 at 90 ℃ in 2 h. 展开更多
关键词 Methyl phenyl carbonate 1 6-Hexamethylene diurethane Transesterification Methoxyl carbonate Reaction coupling
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Atomically dispersed Au_1 catalyst towards efficient electrochemical synthesis of ammonia 被引量:25
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作者 Xiaoqian Wang Wenyu Wang +13 位作者 Man Qiao Geng Wu Wenxing Chen Tongwei Yuan Qian Xu Min Chen Yan Zhang Xin Wang Jing Wang Jingjie Ge Xun Hong Yafei Li Yuen Wu Yadong Li 《Science Bulletin》 SCIE EI CSCD 2018年第19期1246-1253,共8页
Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispe... Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispersed Au_1 catalyst is synthesized and applied in electrochemical synthesis of ammonia under ambient conditions. A high NH+4 Faradaic efficiency of 11.1 % achieved by our Au_1 catalyst surpasses most of reported catalysts under comparable conditions. Benefiting from efficient atom utilization, an NH+4 yield rate of 1,305 μg h-1 mg-1Au has been reached, which is roughly 22.5 times as high as that by sup- ported Au nanoparticles. We also demonstrate that by employing our Au_1 catalyst, NH+4 can be electro- chemically produced directly from N_2 and H_2 with an energy utilization rate of 4.02 mmol kJ-1. Our study provides a possibility of replacing the Haber-Bosch process with environmentally benign and energy-efficient electrochemical strategies. 展开更多
关键词 NH_3 synthesis Metal single sites ELECTROCATALYSIS Haber-Bosch process Nitrogen reduction
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