New Insights into the Heterogeneous Reduction Reaction between NO and Char-Bound Nitrogen

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• 作者：Hai Zhang ; Xiumin Jiang ; Jiaxun Liu ; Jun Shen
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2014
• 出版时间：April 16, 2014
• 年：2014
• 卷：53
• 期：15
• 页码：6307-6315
• 全文大小：454K
• 年卷期：v.53,no.15(April 16, 2014)
• ISSN：1520-5045

文摘

New insights into the heterogeneous reduction reaction between NO and char-bound nitrogen [char(N)] were obtained by a combination of density functional theory (DFT) and conventional transition state theory (TST). A detailed description of the nature of NO chemisorption is reported based on the HOMO and LUMO, Mulliken atomic charges, and spin densities. It is suggested that, during chemisorption, char(N) contributes electrons to NO. The seven most stable structures (I鈥揤II) resulting from NO chemisorption were identified, and the exothermicity was found to increase in the order III < V < IV < VI < VII< II < I. This finding is reasonable considering the fact that the HOMO of char(N) is predominantly reflected in the active C(2) atom and the LUMO of NO is mainly concentrated on the N(8) atom. Three stepwise reactions leading to N₂ formation have been characterized with low energetic penalty acceptable for occurring at the practical heterogeneous combustion temperature. The highest energy penalty was calculated to be 270.794 kJ/mol. A kinetic similarity over the temperature range of 850鈥?000 K between the rate-limiting step and char gasification was found (10^鈥?鈥?0⁰ compared to 10^鈥?鈥?0^鈥? s^鈥?, respectively). By comparison with previous experiments, the calculated results were validated, and on the basis of these results, the reburning of superfine bituminous coal is recommended.