Theoretical Kinetics of Radical-Radical Reaction NH2NH + NH2 and Its Implications for Monomethylhydrazine Pyrolysis Mechanism

作     者：Wang, Chunyu Zhao, Qian Zhao, Hao Pu, Binxu Huang, Zuohua Li, Longfei Zhang, Yingjia 

作者机构：Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Southwest Jiaotong Univ Dept Fire Protect Engn Chengdu 611756 Peoples R China Xian Aerosp Prop Inst Sci & Technol Liquid Rocket Engine Lab Xian 710100 Peoples R China 

出 版 物：《JOURNAL OF PHYSICAL CHEMISTRY A》 (J Phys Chem A)

年 卷 期：2024年第128卷第39期

页      面：8501-8511页

核心收录：

学科分类：081704[工学-应用化学] 07[理学] 070304[理学-物理化学(含∶化学物理)] 08[工学] 0817[工学-化学工程与技术] 0703[理学-化学] 0702[理学-物理学] 

基　　金：National Natural Science Foundation of China [U2141203] National Science and Technology Major Project [2020-JCJQ-ZD-197-021] 

主　　题：Free radical reactions 

摘      要：Significant discrepancies were observed between the experiments and the simulations for NH2 time-histories in monomethylhydrazine pyrolysis with the robust mechanism proposed by Pascal and Catoire. The rate of formation analyses for NH2 indicated the significance of the reaction NH2NH + NH2 = H2NN + NH3, which has not been well-defined. In this study, ab initio calculations were performed for the theoretical description of the NH2NH + NH2 chemistry. Most stationary points on the potential energy surface were quantified at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level, and the multireference methods were employed for barrier-less reaction and some transition states. The temperature- and pressure-dependent rate coefficients were determined using classical and microcanonical variational transition state theories. Four primary reaction channels were identified as competitive: 1) The H atom abstraction reaction yielding N2H2(T) + NH3, dominating at 1350-3000 K across the 0.001-100 atm pressure range. 2) The H atom abstraction reaction forming N2H2(S) + NH3, dominating at 800-1350 K and competing with the processes of chemical activation and collisional stabilization below 800 K. 3) The chemical-activated reaction resulting in H2NN(S) + NH3, dominating below 800 K at 0.001 atm. 4) The collisional-stabilized recombination reaction leading to N3H5, becoming significant as pressure increases and dominating below 600 and 650 K at 1 and 100 atm, respectively. The implications of newly calculated NH2NH + NH2 kinetics for the monomethylhydrazine pyrolysis mechanism were evaluated, and updates were implemented. Sensitivity analyses indicated the necessity of additional research efforts to comprehend the dynamics of CH3NH2 unimolecular and N2H2 + NH2 reaction systems. The rate coefficients presented in this study can be employed to develop the chemical kinetic model of nitryl-containing systems.