Study on the mechanism of oxidation of nitrogen-containing char by CO<sub>2</sub> based on density functional theory

ZHOU Sai; LIU Hu; YU Peng-fei; YUAN Mao-bo; XUE Jing-wen; CHE De-fu

doi:10.19906/j.cnki.JFCT.2021061

Volume 50 Issue 1

Jan. 2022

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Article Navigation > Journal of Fuel Chemistry and Technology > 2022 > 50(1): 19-27

ZHOU Sai, LIU Hu, YU Peng-fei, YUAN Mao-bo, XUE Jing-wen, CHE De-fu. Study on the mechanism of oxidation of nitrogen-containing char by CO2 based on density functional theory[J]. Journal of Fuel Chemistry and Technology, 2022, 50(1): 19-27. doi: 10.19906/j.cnki.JFCT.2021061

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ZHOU Sai, LIU Hu, YU Peng-fei, YUAN Mao-bo, XUE Jing-wen, CHE De-fu. Study on the mechanism of oxidation of nitrogen-containing char by CO₂ based on density functional theory[J]. Journal of Fuel Chemistry and Technology, 2022, 50(1): 19-27. doi: 10.19906/j.cnki.JFCT.2021061

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Study on the mechanism of oxidation of nitrogen-containing char by CO₂ based on density functional theory

doi: 10.19906/j.cnki.JFCT.2021061

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China

Funds: The project was supported by the Postdoctoral Research Foundation of China (2018M633507) and Natural Science Basic Research Plan in Shaanxi Province of China (2020JQ-063)

Received Date: 2021-04-14
Rev Recd Date: 2021-06-03

Available Online: 2021-06-25

Publish Date: 2022-01-25

Abstract

Abstract

In order to obtain the NO formation mechanism during the coal combustion, the heterogeneous oxidation of nitrogen-containing char by CO₂ were investigated based on density functional theory. Simplified char models containing pyrrole nitrogen or pyridine nitrogen were selected as the carbonaceous surfaces. Geometric optimizations were carried out at the B3LYP-D3/6-31G(d) level. Energies of optimized geometries were calculated at the B3LYP-D3/def2-TZVP level. The results show that CO₂ oxidation of nitrogen-containing char is composed of three stages: namely CO₂ adsorption, CO desorption and NO desorption. In the reaction of CO₂ heterogeneous oxidation of pyrrole nitrogen-containing char, CO₂ molecules tend to absorb in the C−O−down mode (C−C bonding, N−O bonding) to form a five-membered heterocyclic structure containing nitrogen and oxygen atoms. Then, the surface carbonyl groups and N(O) are formation as the C−O bonds of the original CO₂ molecules in the five-membered ring broken to desorb CO and NO, respectively. The reaction is 401.2 kJ/mol endothermic, and the highest energy barrier is 197.6 kJ/mol. In the reaction of CO₂ heterogeneous oxidation of pyridine nitrogen-containing char, CO₂ molecules tend to form six-membered heterocyclic ring containing nitrogen and oxygen atoms after adsorption in the C−O−down and C−C bonding and C−O bonding mode. And then CO and NO molecules are desorbed. The reaction is 598.6 kJ/mol endothermic, and the energy barrier of rate-determining step is 292.0 kJ/mol.
- CO₂,
- nitrogen-containing char,
- heterogeneous oxidation,
- CO,
- NO,
- density functional theory

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References(33)

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