Homogeneous reaction mechanism in arsenic/hydrogen/oxygen system
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摘要: 采用量子化学的方法,利用量子化学软件Gaussian09和GaussView,在B3LYP/6-311G(3df, 3pd)理论水平下,对砷/氢/氧体系燃烧反应的微观机理进行研究。优化了13个基元反应的反应物、中间体、过渡态以及产物的构型,并通过振动频率和内禀反应坐标验证反应真实性。采用KiSThelP软件包基于传统过渡态理论拟合计算出动力学参数。本研究对砷燃烧体系中部分重要基元反应进行研究,便于后续建立砷的燃烧动力学模型。Abstract: Herein quantum chemistry methods were used to discuss the microscopic mechanism in the arsenic/hydrogen/oxygen reaction system during combustion by Gaussian09 and GaussView at the theoretical level of B3LYP/6-311G (3df, 3pd). Configuration of the reactants, intermediates, transition states, and products of 13 elementary reactions were optimized and the authenticity of these reactions were verified by frequency and intrinsic reaction coordinates. Finally, the kinetic parameters were calculated through KiSThelP based on the classic transition state theory. This study focused on some of the most important reations in the arsenic/hydrogen/oxygen system, which makes sense to establish arsenic dynamic model during combustion.
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Key words:
- coal combustion /
- arsenic /
- microscopic mechanism /
- DFT
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表 1 计算值与文献值对比
Table 1 Comparison of calculated values and literature values
Species Bond length(r/Å)
and angles(α/°)Calculated
resultReferenced
value[17]O2 r(O−O) 1.20255 1.239 AsO r(As−O) 1.62401 1.624 As2O3(D3H) r(As−O) 1.84376 1.836 r(As-As) 2.38940 2.375 α(As−O−As) 80.77769 80.6 As2O3(GAUCHE) r(As−O) 1.61949 1.610 r(O−As) 1.78284 1.794 α(As−O−As) 105.77862 106.3 α(O−As−O) 129.64809 133.8 表 2 砷参与的基元反应
Table 2 Elementary reactions of Arsenic
No. Elementary reactions 1 As+AsO2 = 2AsO 2 As+H2O = AsOH+H 3 AsO+H2O = AsOOH+H 4 AsOOH+H = AsO2+H2 5 AsO2+H2O = AsO2OH+H 6 AsO2OH+H = AsO(OH)2 7 AsOOH+H2O = As(OH)3 8 AsOOH+H = As(OH)2 9 As(OH)3+H = AsO(OH)2+H2 10 AsOH+H2O = As(OH)2 11 As(OH)2+H2O = As(OH)3+H 12 H3AsO4+H = AsO(OH)2+H2O 13 AsO2OH+H2O = H3AsO4 表 3 AsO2OH+H2O = H3AsO4反应各稳定点振动频率
Table 3 Frequencies of stable points of AsO2OH+H2O = H3AsO4
No. Vibrations frequencies/cm−1 AsO2OH 245.63, 281.93, 301.64, 459.23, 726.01, 947.36, 1018.14, 1073.63, 3771.60 H2O 1641.28, 3819.58, 3912.16 TS −1358.59, 165.93, 255.41, 266.03, 293.69, 370.60, 433.77, 553.71, 689.49,763.14, 806.75, 873.86, 1011.59, 1059.90, 1362.22, 1962.70, 3786.56, 3788.99 H3AsO4 123.08, 142.48, 208.18, 220.49, 281.94, 289.95, 300.96, 416.02, 548.75, 617.39, 718.8, 936.82, 1014.39, 1064.23, 1610.44, 3738.20, 3790.15, 3835.85 表 4 AsO2OH+H2O = H3AsO4反应过程能量变化
Table 4 Energy change in AsO2OH+H2O = H3AsO4 reaction process
B3LYP/(a.u.) ZEP/(a.u.) Etot/(a.u.) Erel/(kcal·mol−1) AsO2OH+ H2O −2538.657127 0.041458 −2538.615669 0 Initermediate −2538.679596 0.045239 −2538.634357 −14.2883 TS −2538.660815 0.041958 −2538.618857 −2.0000 H3AsO4 −2538.723255 0.044405 −2538.678850 −39.6467 Ea, for/(kcal·mol−1) 12.2883 Ea, rev/(kcal·mol−1) 37.6467 表 5 砷参与的各基元反应反应动力学参数
Table 5 Kinetic parameters of each elementary reaction of Arsenic
No. Elementary reactions A n Ea/(cal·mol−1) 1 As+AsO2 = 2AsO 3.312 × 1012 0.01 990 2 As+H2O = AsOH+H 5.74 × 105 2.53 9548 3 AsO2OH+H2 = AsOOH+H2O 8.07 × 102 2.81 43100 4 AsOOH+H = AsO2+H2 5.06 × 107 1.85 7303 5 AsO2+H2O = AsO2OH+H 5.00 ×10−2 3.95 48637 6 AsO2OH+H = AsO(OH)2 1.38 × 109 1.57 382 7 AsOOH+H2O = As(OH)3 1.09 × 109 0.53 7330 8 AsOOH+H = As(OH)2 6.56 × 108 1.57 119 9 As(OH)3+H = AsO(OH)2+H2 6.62 × 107 1.9 5403 10 AsOH+H2O = As(OH)2 3.991 × 10−1 4.04 40720 11 As(OH)2+H2O = As(OH)3+H 3.22 × 10−2 4.04 34765 12 H3AsO4+H = AsO(OH)2+H2O 2.97 × 108 1.67 10179 13 AsO2OH+H2O = H3AsO4 9.80 × 109 0.52 7982 -
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