Key Kinetic Interactions between NOX and Unsaturated Hydrocarbons: H Atom Abstraction from C3-C7 Alkynes, Dienes, and Trienes by NO2

Zhengyan Guo; Hongqing Wu; Ruoyue Tang; Xinrui Ren; Ting Zhang; Mingrui Wang; Guojie Liang; Hengjie Guo; Song Cheng

doi:10.1021/acs.jpca.4c07335

Key Kinetic Interactions between NO_X and Unsaturated Hydrocarbons: H Atom Abstraction from C₃-C₇ Alkynes, Dienes, and Trienes by NO₂

J Phys Chem A. 2025 Jan 2. doi: 10.1021/acs.jpca.4c07335. Online ahead of print.

Authors

Zhengyan Guo^{1

2}, Hongqing Wu³, Ruoyue Tang³, Xinrui Ren³, Ting Zhang³, Mingrui Wang³, Guojie Liang³, Hengjie Guo¹, Song Cheng^{3

4}

Affiliations

¹ School of Power and Energy, Northwestern Polytechnical University, Xi'an 710129, China.
² AECC Hunan Aviation Powerplant Research Institute, Zhuzhou 412002, China.
³ Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR 999077, China.
⁴ Research Institute for Smart Energy, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR 999077, China.

PMID: 39746216
DOI: 10.1021/acs.jpca.4c07335

Abstract

An adequate understanding of the NO_x interacting chemistry is a prerequisite for a smoother transition to carbon-lean and carbon-free fuels such as ammonia and hydrogen. In this regard, this study presents a comprehensive study on the H atom abstraction by NO₂ from C₃ to C₇ alkynes, dienes, and trienes forming 3 HNO₂ isomers (i.e., TRANS_HONO, HNO₂, and CIS_HONO), encompassing 8 hydrocarbons and 24 reactions. Through a combination of high-level quantum chemistry computation, electronic structures, single-point energies, C-H bond dissociation energies, and 1-D hindered rotor potentials of the reactants, transition state (TS), complexes, and products involved in each reaction are determined at DLPNO-CCSD(T)/cc-pVDZ//M06-2X/6-311++g(d,p), from which potential energy surfaces and energy barriers for each reaction are determined. Following this, the rate coefficients for all studied reactions, over a temperature range from 298 to 2000 K, are computed based on TS theory using the Master Equation System Solver program by considering unsymmetric tunneling corrections. Comprehensive analysis of branching ratios elucidates the diversity and similarities between different species, different HNO₂ isomers, and different abstraction sites. Incorporating the calculated rate parameters into a recent chemistry model reveals the significant influences of this type of reaction on model performance, where the updated model is consistently more reactive for all the alkynes, dienes, and trienes studied in predicting autoignition characteristics. Sensitivity and flux analyses are further conducted, through which the importance of H atom abstractions by NO₂ is highlighted. With the updated rate parameters, the branching ratios in fuel consumption clearly shift toward H atom abstractions by NO₂ while away from H atom abstractions by ȮH. The obtained results emphasize the need for adequately representing these kinetics in new alkyne, diene, and triene chemistry models to be developed by using the rate parameters determined in this study, and call for future efforts to experimentally investigate NO₂ blending effects on alkynes, dienes, and trienes.