Probing hydrogen–nitrogen chemistry: A theoretical study of important reactions in NxHy, HCN and HNCO oxidation

Abstract

As an indirect storage medium of hydrogen, ammonia (NH3) has drawn significant attention from academia and industry. Understanding nitrogen combustion chemistry is a major challenge in applying ammonia for converting chemical energy to thermal energy. Diazene (N2H2), diazenyl radical (NNH), amidogen radical (NH2), hydrogen cyanide (HCN) and isocyanic acid (HNCO) are the crucial intermediate species in the combustion of NH3 or its mixtures with other hydrocarbons. In light of that, this study provides advanced theoretical treatment of 14 important reactions in the oxidation of these intermediates, including isomerization, dissociation and abstraction reactions. The rate constants of all these reactions, and the temperature-dependent thermochemistry of the species involved in the reactions, were calculated utilizing high level quantum chemical methods. Ro-vibrational properties of the reactants, products and stationary points were determined at the M06-2X/6-311++G(d,p) level of theory. Coupled cluster (CCSD(T)) methods were employed, with two large basis sets (cc-pVTZ and cc-pVQZ), and complete basis set of extrapolation techniques to compute the energies of the resulting geometries. All calculated results were compared with experimental and theoretical results in the literature. Finally, the implications of this work for combustion modelling were investigated, and the simulated species' profiles of HCN and HNCO demonstrated the influence of the updated rate coefficients on kinetic model predictions.

New reactions of diazene and related species for modelling combustion of amine fuels

“…Earlier work on H-abstraction from HNNH has focused on the trans isomer or assumed the E and Z isomers to be equilibrated [46,54,55,5759]. However, Dievart and Catoire [46] reported that the energy barriers for cis-isomer are consistently lower than those of the trans-isomer, by 6.3, 10.…”

Experimental and numerical analyses of nitrogen oxides formation in a high ammonia-low hydrogen blend using a tangential swirl burner

“…The kinetic model has been revisited for the reactions related to NH 3 sub-mechanism. The thermodynamic data of nitrogen-related radicals, especially NH, NH 2 , NNH, and N 2 H 2 , were updated based on the work published by [49]. Also, the rate kinetics of the most important reactions, particularly those related to NO X formation, have been evaluated based on some experimental [50,51] and theoretical [43,49,[52][53][54][55] studies.…”

“…The thermodynamic data of nitrogen-related radicals, especially NH, NH 2 , NNH, and N 2 H 2 , were updated based on the work published by [49]. Also, the rate kinetics of the most important reactions, particularly those related to NO X formation, have been evaluated based on some experimental [50,51] and theoretical [43,49,[52][53][54][55] studies. Along with that, the numerical data from model prediction have been validated with JSR experimental measurements of oxidation on NH 3 -H 2 blended flames at atmospheric pressure, low -moderate temperatures (800-1280 K), different H 2 contents, 0-70VOL% in the fuel, and various equivalence ratios.…”

Theoretical study on the kinetics of hydrogen cyanide and hydrogen isocyanide reactions with the methyl radical

“…Hydrogen cyanide (HCN) and hydrogen isocyanide (HNC) are highly correlated in combustion and Titan atmosphere. [1][2][3][4][5][6] In the combustion processes, cyanides may be formed from the devolatilization of fuels containing organically bound nitrogen. Especially in fuel-rich hydrocarbon flames, it appears that HCN is the dominant nitrogenous species leaving the primary reaction zone.…”