A kinetics mechanism of NO X formation and reduction based on density functional theory

• Published in: The Science of the total environment Vol. 867; p. 161519
• Main Authors: Li, Zehong, Zhang, Wei, Chen, Zhaohui, Ren, Zhaoying, Ning, Shuo, Li, Mengting
• Format: Journal Article
• Language: English
• Published: Netherlands 01.04.2023
• Subjects: Transition state theory; Chemical kinetics analysis; Density functional theory; Combustion; NO(X) formation and reduction; Engine
• ISSN: 1879-1026

NO are serious pollutants emitted during combustion, which are greatly harmful to human health and the environment. However, previous studies have not accurately elucidated the NO conversion mechanism in complicated combustion reactions. To reveal the micro-chemical mechanism of NO conversion and obtain accurate kinetics data, advanced quantum chemistry methods are employed in this study to systematically explore the pathways of NO formation and reduction, and determine the new rate coefficients. An energy barrier analysis revealed that during NO formation (N → N O → NO→NO ), NO is primarily produced by a sequence of reactions (N + O → N O → NO) rather than the traditional reaction (O + N → NO+N). Meanwhile, NO formation (NO→NO ) largely depends on the O and HO radicals, while the active O atom can promote both the formation and destruction of NO . During NO reduction (NO → NO→N O → N ), NO reduction (NO → NO) is closely related to H, CO, and O, whereas CO plays a critical role in NO destruction. However, NO reduction (NO→N O) is unfavourable because of a high energy barrier, while N O reduction (N O → N ) is strongly affected by the O atom instead of CO. HONO is mainly formed when NO reacts with the HO and H radicals, and when NO reacts with OH radicals; thus, HONO consumption largely depends on OH and H radicals. Based on the transition state theory, we obtained new kinetic parameters for NO conversion, which supplement and correct critical kinetics data obtained from the current NO model. Performance assessment of the proposed NO kinetic mechanism reveals that it can improve the existing NO kinetic mode, which is in good agreement with experimental data.