The structure-performance evolution of Co/N-AC catalyst during ethylene oligomerization was investigated in detail. It was found that the catalytic activity sharply decreased in the first 30 h with the ethylene conversion decreasing from 64 to 4%. Butene selectivity increased gradually in the first 10 h then remained about 74%, while the selectivity for hexene and octene exhibited an opposite trend. The ratio of α-olefin to isomers for butene increased greatly with time on stream and most of the generated butene was 1-butene. Based on the structure characterization at different reaction stages, CoO x was suggested to be major active phase and the coverage of long-chain hydrocarbons as well as the loss of surface CoO x active sites due to size growth of Co 3 O 4 nanoparticles were the main reasons for catalytic deactivation. Graphic Abstract The structure-performance evolution of Co/N-AC catalyst during ethylene oligomerization was investigated and the coverage of long-chain hydrocarbons as well as the loss of surface CoO x active sites due to size growth of Co 3 O 4 nanoparticles were the main reasons for catalytic deactivation
Dong-hong Nan,Cheng-bo Zhang,Qi Niu,Shi-yu Feng,Bin Hu,Ji Liu,Kai Li,Qiang Lu
Nitrogen-doped activated carbon (NAC) has shown great potential in selectively catalyzing the pyrolysis of biomass to produce alkoxyphenols, with the structural characteristics being key to influencing alkoxyphenol yields. In this study, a method for preparing nitrogen-doped hydrothermal carbon (HY-NAC) by hydrothermal carbonization coupled with ammonia water activation was proposed. The resulting carbon was then used as catalyst in the selective preparation of alkoxyphenols by catalytic pyrolysis of biomass, with the 9,10-dihydroanthracene (DHA) being selected as the hydrogen donor. The physical and chemical properties of HY-NAC were systematically studied. Based on the pyrolysis-gas chromatography/mass spectrometry, the effects of the carbonization method and ammonia concentration during HY-NAC preparation, and the pyrolysis temperature, catalyst/pine ratio, and DHA/pine ratio during the pyrolysis process on the yields of alkoxyphenols were investigated. The results showed that, compared to the activated carbon prepared by pyrolytic carbonization method, HY-NAC had a larger specific surface area, higher nitrogen content, and higher contents of pyridinic nitrogen and pyrrolic nitrogen, thus exhibiting stronger catalytic performance. At an ammonia concentration of 10 %, the specific surface area of HY-NAC was 947.488 m 2 /g, and the relative contents of pyridinic nitrogen and pyrrolic nitrogen were 38.04 % and 33.22 %, respectively. Under pyrolysis temperature of 500 °C, HY-NAC/pine ratio of 3:1, and DHA/pine ratio of 1:1, the alkoxyphenol yield reached the maximum of 7.42 wt%.
Zhenjia Liu,Xinxin Pi,Guangshun Chai,Lingtao Ran,Mulin Wang,Junhan He,Yanhui Li,Yan He
Catalysts based on Fe 3 C suffer from metal dissolution and strong adsorption of oxygen intermediates. In this work, a stable Fe 3 C@C/N–C heterojunction is constructed by combining Fe-induced graphitization of coal-tar carbon with ammonia-activated porous carbon nanotubes. The CNTs provide a conductive framework and abundant anchoring sites, enabling uniform in situ formation of Fe 3 C nanoparticles encapsulated within graphitic layers. The catalyst delivers excellent bifunctional performance, with an ORR onset potential of 1.052 V, a half-wave potential of 0.844 V, and an OER overpotential of 270 mV at 10 mA cm −2 . A Zn–air battery using this catalyst achieves a peak power density of 167.4 mW cm −2 and retains 95 % capacity over 160 h. Finite-element simulations reveal enhanced fields, and DFT calculations confirm an optimized electronic structure with reduced reaction barriers. This work offers a strategy for designing durable, high-efficiency catalysts for metal–air batteries.
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