Thermal Decomposition Mechanism of Aqueous Hydroxylammonium Nitrate (HAN): Molecular Simulation and Kinetic Modeling

Kaiqiang Zhang, Stefan Thynell

Research output: Contribution to journalArticle

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Abstract

A detailed mechanism has been developed for thermal decomposition of hydroxylammonium nitrate (HAN) solutions, based on quantum mechanical calculations using the SMD-ωB97X-D method. The mechanism describes multiple kinetic processes, including nitration and nitrosation of hydroxylamine, HNO dimerization, and HONO-regeneration pathways involving H-abstraction reactions. Rate constants of elementary reactions were estimated using transition state theory with consideration of species' diffusion effect. Kinetic modeling was performed to predict species' evolutions in 0.1 m HAN in the temperature range of 463-523 K, and results show reasonable agreement with the experimental data from flow reactor studies. For more concentrated solutions, strong autocatalytic behaviors were predicted with the late emergence of NO2 and HONO, whose regeneration was previously considered as the major autocatalytic pathway. Sensitivity analysis results suggest an acid-catalyzed nitration-nitrosation pathway, based on which the autocatalysis should be caused by the rise of solution acidity. A linear correlation can be observed in the previously reported apparent Arrhenius parameters, which may be reconciled via a kinetic compensation effect.

Original languageEnglish (US)
Pages (from-to)8086-8100
Number of pages15
JournalJournal of Physical Chemistry A
Volume122
Issue number41
DOIs
StatePublished - Oct 18 2018

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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