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Study of the reaction mechanism of oxygen to heterogeneous reduction of NO by char

机译：氧对焦炭非均相还原NO反应机理的研究

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摘要

Quantum chemistry theoretical calculations were carried out to investigate the influence mechanism of different oxygen concentrations on the heterogeneous reduction of NO by char. The results show that there are two reaction paths for the heterogeneous reduction of NO by char using the char edge model with one hydroxyl group (R1). One is to reduce the NO adsorbed on the surface of R1 to N2O, which can be decomposed on the surface of char or react with CO. Three stepwise reactions with the highest energy barrier of 274.2 kJ/mol are found responsible for the desorption of CO and production of new active sites, on which N2O desorption can occur barrierlessly. The other path with a moderate energy barrier (139.6 kJ/mol) takes place to reduce NO to N-2. The rate-determining step in the heterogeneous reduction of NO by the char edge with two hydroxyl groups (R2), a ring opening reaction, with a higher-barrier (398.03 kJ/mol), is less effective to the reduction of NO. From the kinetic analysis it is known that the reaction rate constants increase with the increase of temperature, indicating that temperature has a great influence on the reduction of NO and a higher combustion temperature contributes to lower NO emission. At a high temperature (1800 K), the rate constant of rate-determining step of R1 is 10(3) times higher than that of R2, which shows that R1 is more beneficial to the reduction of NO. The results reveal that the mechanism of NO reduction by char is promoted by oxygen at the char surface.
机译：进行了量子化学理论计算，研究了不同氧浓度对焦炭非均相还原NO的影响机理。结果表明，使用具有一个羟基（R1）的炭边模型，通过炭进行异质还原NO的反应路径有两种。一种是将吸附在R1表面的NO还原为N2O，该NO可以分解成炭或与CO反应。发现了三个步阶反应，其最高能垒为274.2 kJ / mol，这是导致CO解吸的原因以及生产新的活性位点，N2O的解吸可以无障碍地发生。发生另一条具有中等能垒（139.6 kJ / mol）的路径将NO还原为N-2。带有两个羟基（R2）的炭边缘不均匀还原NO的速率确定步骤，开环反应，较高的阻挡层（398.03 kJ / mol），对NO的还原效果较差。从动力学分析可知，反应速率常数随温度的升高而增加，这表明温度对NO的还原影响很大，较高的燃烧温度有助于降低NO的排放。在高温（1800 K）下，R1的速率决定步骤的速率常数比R2的速率常数高10（3）倍，这表明R1更有利于NO的还原。结果表明，炭表面的氧促进了炭还原NO的机理。

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  • 来源
    《Fuel》 |2019年第15期|1213-1225|共13页
  • 作者

    Chen Ping; Gu Mingyan; Chen Xue; Chen Jinchao;

  • 作者单位

    Anhui Univ Technol, Sch Energy & Environm, Maanshan 243002, Anhui, Peoples R China;

    Anhui Univ Technol, Sch Met Engn, Maanshan 243002, Anhui, Peoples R China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Hydroxyl group; Char; NO; Active site; Kinetic analysis;

    机译：羟基;焦炭;NO;活性部位;动力学分析;

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