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基于密度泛函理论的高覆盖氧吸附焦炭氧化机理研究

刘治港 田向红 李言钦

刘治港, 田向红, 李言钦. 基于密度泛函理论的高覆盖氧吸附焦炭氧化机理研究[J]. 燃料化学学报, 2022, 50(8): 974-983. doi: 10.1016/S1872-5813(22)60001-X
引用本文: 刘治港, 田向红, 李言钦. 基于密度泛函理论的高覆盖氧吸附焦炭氧化机理研究[J]. 燃料化学学报, 2022, 50(8): 974-983. doi: 10.1016/S1872-5813(22)60001-X
LIU Zhi-gang, TIAN Xiang-hong, LI Yan-qin. Study on CO/CO2 formation mechanism of Zigzag model coke with high oxygen coverage based on DFT theory[J]. Journal of Fuel Chemistry and Technology, 2022, 50(8): 974-983. doi: 10.1016/S1872-5813(22)60001-X
Citation: LIU Zhi-gang, TIAN Xiang-hong, LI Yan-qin. Study on CO/CO2 formation mechanism of Zigzag model coke with high oxygen coverage based on DFT theory[J]. Journal of Fuel Chemistry and Technology, 2022, 50(8): 974-983. doi: 10.1016/S1872-5813(22)60001-X

基于密度泛函理论的高覆盖氧吸附焦炭氧化机理研究

doi: 10.1016/S1872-5813(22)60001-X
基金项目: 国家自然科学基金(51676175)资助
详细信息
    通讯作者:

    E-mail: liyq@zzu.edu.cn

  • 中图分类号: O643.13

Study on CO/CO2 formation mechanism of Zigzag model coke with high oxygen coverage based on DFT theory

Funds: The project was supported by the National Natural Science Foundation of China (51676175).
  • 摘要: 碳资源在能源、材料及化工等领域的清洁高效利用日益重要,而焦炭氧化特别是脱附产生CO2/CO的机理研究并不充分。其中较高焦炭表面氧覆盖率相应于较低温度或较高压力的反应条件,对此,本研究基于第一性原理研究讨论了该情况下焦炭Zigzag结构碳环簇氧化脱附过程的反应路径。计算表明,表面吸附氧热解生成CO2过程需要经过重排形成含O−C−O团簇的结构,最终至CO2完成脱附需多个中间反应步,与对比文献中形成碳氧六元环再依次断掉两个C−O 键而脱附 CO2 不同,本研究得到了相关的两种路径,分别为形成 CO2−C−官能团再断掉 C−C 而脱附CO2以及基于碳氧六元环结构直接断裂两个C−O 键而脱附CO2的可能反应路径。另外,研究了CO脱附过程的不同反应路径。模型计算结果与相关文献理论和实验结果具有良好的符合。
  • FIG. 1767.  FIG. 1767.

    FIG. 1767.  FIG. 1767.

    图  1  Zigzag与Armchair焦炭表面模型示意图

    Figure  1  Zigzag (left) and Armchair (right) models of coke molecule

    图  2  高覆盖度Zigzag表面氧吸附模型示意图

    Figure  2  Oxygen adsorption model with high coverage along the Zigzag coke edge

    图  3  焦炭氧化基本反应过程计算与文献[9,10]对比

    Figure  3  Comparison between the calculation results and the literature[9,10]with respect to the basic reaction process of coke oxidation

    图  4  模型边缘活性位CO/CO2的生成与脱附过程对应构型变化(所框为路径最终产物)

    Figure  4  Corresponding configuration changes of the desorption of CO/CO2 at the edge of the coke molecule

    图  5  边缘活性位CO/CO2的脱附过程相对能量变化

    Figure  5  Diagram of relative energy with CO/CO2 desorption at the edge active sites

    图  6  初始构型X分别到B4及U+CO(图中所框为过程末端构型)过程的构型变化

    Figure  6  Configuration diagram of the initial configuration X to B4 and CO, respectively, with the frames denoting the final configurations (the frame is the final configuration)

    图  7  由B4到CO2脱附的各路径构型变化(框内为相应路径产物)

    Figure  7  Configuration changes of each path from B4 to CO2 desorption (the products of each path in the color boxes)

    图  8  初始吸附构型重排至B4过程相对能量变化

    Figure  8  Diagram of relative energy change from initial configuration rearrangement to B4

    图  9  碳氧六元环结构B4重排脱附CO2过程的相对能量变化

    Figure  9  Relative energy diagram of six-membered ring rearrangement to CO2 desorption

    图  10  上述六元环结构直接脱附CO2过程构型变化

    Figure  10  Configuration diagram of direct desorption of CO2 from a six-membered ring structure

    图  11  图10反应过程相对能量变化

    Figure  11  Diagram on relative energy of direct desorption of CO2 related to Figure 10

    图  12  各脱附反应路径速控步反应速率常数随温度的变化

    Figure  12  Diagram of rate constant of rate-controlled step vs temperature in each desorption pathway

    表  1  边缘活性位CO/CO2的生成与脱附过程的能垒、焓变及过渡态虚频

    Table  1  Energy barrier, enthalpy change and imaginary frequency of each step in the CO/CO2 formation and desorption process

    ReactionΔE/(kJ·mol−1)ΔH/(kJ·mol−1)Imaginary frequency/cm−1
    X → Yts → Y+CO562.9620.5691.42 i
    X→ Ats → A1196.65159.41411.10 i
    A1→ A1ts → A214.402.04271.17 i
    A2→ A2ts → A32.34−27.06155.45 i
    A2 → Zts → Z+CO8.28−21.45308.18 i
    A3→ A3ts → A4112.3817.58377.67 i
    A4→ A4ts →A552.97−293.34336.70 i
    A5→ A5ts →A6323.71309.16275.81 i
    A6→ A6ts →A76.65−57.24395.01 i
    A7→ A7ts →A8+CO234.73−35.15351.6 i
    下载: 导出CSV

    表  2  中间位点重排及脱附过程中各基元步的能垒、焓变以及虚频

    Table  2  Energy Barrier, enthalpy change and imaginary frequency of each step in the processes of rearrangement and desorption

    ReactionΔE
    /(kJ·mol−1)
    ΔH
    /(kJ·mol−1)
    Imaginary frequency
    /(kJ·mol−1)
    X → Yts → Y+CO 562.96 20.56 91.42 i
    X → Bts → B1 306.48 271.29 368.64 i
    B1→ B1ts →B2 20.08 −103.93 208.84 i
    B2→ B2ts → B3 30.62 −38.95 217.17 i
    B3→ Uts → U+CO 48.37 −71.72 727.24 i
    B3 → B3ts → B4 21.42 −247.52 712.15 i
    B4→ B4ts → B5 259.37 86.15 116.25 i
    B4 → αts → ɑ1 281.83 234.81 547.88 i
    α1 → α1ts → α2 8.41 −10.29 351.53 i
    α2 → α2ts → α2+CO2 25.90 −46.19 366.38 i
    B4 → βts → β1 295.26 198.44 582.07 i
    β1 → β1ts → β2 0.13 −12.26 207.88 i
    β2 → β2ts → β3+CO2 35.73 −22.64 352.48 i
    B5 → θts → θ1 228.19 162.46 551.45 i
    θ1 → θ1ts → θ2 24.86 13.89 325.85 i
    θ2 → θ2ts → θ3+CO2 20.62 −46.15 383.07 i
    B4→ Vts→ V+CO2 286.18 163.54 822.10 i
    下载: 导出CSV

    表  3  脱附过程活化能与文献[23,29,30]对比

    Table  3  Calculated activation energies of desorptions compared with literature[23,29,30]

    Calculation /(kJ·mol−1) Literature /(kJ·mol−1)
    Direct desorption of CO (Yts)562.96587.4[29]
    Indirect desorption of CO187.74/295.47160−400[23],
    150−420[30]
    Desorption of CO2310.71/295.47/298.18254.1[30]*
    *Result with temperature 820 K in Ref.[30]
    下载: 导出CSV
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  • 收稿日期:  2021-12-23
  • 录用日期:  2022-02-22
  • 修回日期:  2022-02-13
  • 网络出版日期:  2022-03-01
  • 刊出日期:  2022-08-26

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