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摘要: 通过量子化学密度泛函理论研究了均相和煤焦催化的HCN还原NO反应机理，计算了反应动力学参数。结果表明，均相还原反应的活化能为306 kJ/mol，而煤焦催化的NO还原反应的活化能为136 kJ/mol。典型再燃温度1 400 K下，HCN异相还原NO的反应速率略小于煤焦异相还原NO的反应速率；HCN参与下的煤焦异相还原NO反应较CO参与下的煤焦异相促还原NO反应更易发生。各组分的吸附顺序对HCN异相还原NO的反应有明显的影响；在典型再燃温度下，NO先吸附时煤焦表面的异相还原反应速率常数为5.28×1010，比HCN先吸附时最快反应路径的反应速率常数大一个数量级。煤焦对NO还原具有显著的催化作用；煤焦表面作为NO的还原反应位点，对反应气体具有明显的活化作用。Abstract: The reaction mechanism of homogeneous and char-catalyzed heterogeneous NO reduction with HCN were investigated by density functional theory (DFT) of quantum chemistry; the reaction kinetic parameters were determined according to classical transition state theory (TST). The results indicate that the activation energy of homogeneous NO reduction is 306 kJ/mol, much higher than that of heterogeneously catalytic reduction of NO; the later can be as low as 136 kJ/mol. Under the typical reburning temperature (1 400 K), the reaction rate of heterogeneous reduction of NO with HCN is slightly lower than that of heterogeneous reduction catalyzed by char; in comparison with the heterogeneous NO reduction by CO, the heterogeneous NO reduction by HCN over char is more likely to occur. The adsorption sequence of various components has a significant effect on the heterogeneous NO reduction by HCN; the reaction rate coefficient of NO adsorbed on char surface with HCN is 5.28×1010, which is an order larger than that of the surface adsorbed HCN with NO. Char exhibits a significant catalytic effect on the NO reduction with HCN; char provides surface reaction sites for NO reduction which can effectively activate the reaction gas.
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Key words:
- HCN /
- char /
- NO /
- reduction mechanism /
- adsorption
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图 4 NO和HCN在煤焦表面的吸附构型示意图
Figure 4 Adsorption configurations of NO and HCN on char surface
图 5 HCN还原NO异相反应过程示意图
Figure 5 Heterogeneous reaction process of NO reduction by HCN (NO adsorbed on the char surface)
图 7 HCN还原NO异相反应过程示意图
Figure 7 Heterogeneous reaction process of NO reduction by HCN (HCN adsorbed on the char surface)
表 1 反应的动力学参数
Table 1 Reaction kinetic parameters
Reaction Pre-exponential
factor A/s-1Activation energy
Ea/(kJ·mol-1)Arrhenius equation k(1400K)
/s-1Homogeneous 4.31×1010 306.32 k=4.31×1010e-36835.02/T 1.61×10-1 Heterogeneous-HCN 3.86×1019 237.56 k=3.86×1019e-28573.49/T 5.28×1010 Heterogeneous-NO-1 7.67×1014 135.70 k=7.67×1014e-16321.87/T 6.63×109 Heterogeneous-NO-2 2.21×1014 230.29 k=2.21×1014e-27699.06/T 5.65×105 
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