Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Sciences and Technology, Dalian University of Technology, Dalian 116024, People's Republic of China.
Environ Sci Technol. 2013 May 7;47(9):4528-35. doi: 10.1021/es3049898. Epub 2013 Apr 5.
The mechanism of selective catalytic reduction of NOx by propene (C3H6-SCR) over the Cu/Ti0.7Zr0.3O2 catalyst was studied by in situ Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) calculations. Especially, the formation and transformation of cyanide (-CN species) during the reaction was discussed. According to FTIR results, the excellent performance of the Cu/Ti0.7Zr0.3O2 catalyst in C3H6-SCR was attributed to the coexistence of two parallel pathways to produce N2 by the isocyanate (-NCO species) and -CN species intermediates. Besides the hydrolysis of the -NCO species, the reaction between the -CN species and nitrates and/or NO2 was also a crucial pathway for the NO reduction. On the basis of the DFT calculations on the energy of possible intermediates and transition states at the B3LYP/6-311 G (d, p) level of theory, the reaction channel of -CN species in the SCR reaction was identified and the role of -CN species as a crucial intermediate to generate N2 was also confirmed from the thermodynamics view. In combination of the FTIR and DFT results, a modified mechanism with two parallel pathways to produce N2 by the reaction of -NCO and -CN species over the Cu/Ti0.7Zr0.3O2 catalyst was proposed.
采用原位傅里叶变换红外（FTIR）光谱和密度泛函理论（DFT）计算研究了丙烯（C3H6-SCR）选择性催化还原 NOx 的铜/钛锆复合氧化物（Cu/Ti0.7Zr0.3O2）催化剂的反应机理。特别是讨论了反应过程中氰化物（-CN 物种）的形成和转化。根据 FTIR 结果，Cu/Ti0.7Zr0.3O2 催化剂在 C3H6-SCR 中具有优异的性能，这归因于通过异氰酸酯（-NCO 物种）和 -CN 物种中间体生成 N2 的两种平行途径的共存。除了 -NCO 物种的水解外，-CN 物种与硝酸盐和/或 NO2 之间的反应也是 NO 还原的关键途径。基于 B3LYP/6-311 G（d，p）水平理论上可能中间体和过渡态的能量的 DFT 计算，确定了 SCR 反应中 -CN 物种的反应通道，并从热力学角度证实了 -CN 物种作为生成 N2 的关键中间体的作用。结合 FTIR 和 DFT 的结果，提出了一种在 Cu/Ti0.7Zr0.3O2 催化剂上通过 -NCO 和 -CN 物种反应生成 N2 的两条平行途径的改进机理。
