Thermochemical and Kinetics of Hydrazine Dehydrogenation by an Oxygen Atom in Hydrazine-Rich Systems: A Dimer Model

Autor(es)

Spada, Rene F. K. ^[1] ; Ferrao, Luiz F. A. ^[1] ; Roberto-Neto, Orlando ^[2] ; Lischka, Hans ^{[3, 4, 5]} ; Machado, Francisco B. C. ^[1]

Afiliação do(s) autor(es)

^[1] Inst Tecnol Aeronaut, Dept Quim, BR-12228900 Sao Paulo - Brazil

^[2] Inst Estudos Avancados, Div Aerotermodinam & Hiperson, BR-12228001 Sao Paulo - Brazil

^[3] Texas Tech Univ, Dept Chem & Biochem, Lubbock, TX 79409 - USA

^[4] Univ Vienna, Inst Theoret Chem, A-1090 Vienna - Austria

^[5] Tianjin Univ, Sch Pharmaceut Sci & Technol, Tianjin 300072 - Peoples R China

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry A; v. 119, n. 51, p. 12607-12614, DEC 24 2015.
• Citações Web of Science: 2

Resumo

The kinetics of the reaction of N2H4 with oxygen depends sensitively on the initial conditions used. In oxygen-rich systems, the rate constant shows a conventional positive temperature dependence, while in hydrazine-rich setups the dependence is negative in certain temperature ranges. In this study, a theoretical model is presented that adequately reproduces the experimental results trend and values for hydrazine-rich environment, consisting of the hydrogen abstraction from the hydrazine (N2H4) dimer by an oxygen atom. The thermochemical properties of the reaction were computed using two quantum chemical approaches, the coupled cluster theory with single, double, and noniterative triple excitations (CCSD(T)) and the M06-2X DFT approach with the aug-cc-pVTZ and the maug-cc-pVTZ basis sets, respectively. The kinetic data were calculated with the improved canonical variational theory (ICVT) using a dual-level methodology to build the reaction path. The tunneling effects were considered by means of the small curvature tunneling (SCT) approximation. Potential wells on both sides of the reaction ((N2H4)(2) + O -> N2H4 center dot center dot center dot N2H3 + OH) were determined. A reaction path with a negative activation energy was found leading, in the temperature range of 250-423 K, to a negative dependence of the rate constant on the temperature, which is in good agreement with the experimental measurements. Therefore, the consideration of the hydrazine dimer model provides significantly improved agreement with the experimental data and should be included in the mechanism of the global N2H4 combustion process, as it can be particularly important in hydrazine-rich systems. (AU)

• Processo FAPESP: 14/25734-0 - Estudo multiconfiguracional de reações elementares de diaminas (n2hx, x=1-4) com os átomos de hidrogênio, oxigênio e nitrogênio
• Beneficiário: Rene Felipe Keidel Spada
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 15/50018-9 - High-level quantum chemical investigations of defect structures in model graphene systems
• Beneficiário: Francisco Bolivar Correto Machado
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 14/24155-6 - Estudo de estados eletrônicos em hidrocarbonetos aromáticos policíclicos e suas propriedades eletrônicas como modelos de estruturas de grafeno
• Beneficiário: Francisco Bolivar Correto Machado
• Modalidade de apoio: Auxílio à Pesquisa - Regular