Oxidation kinetics of methylhydrazine in a strictly single-phase medium studied in reconstituted air

The oxidation of methylhydrazine (monomethylhydrazine MMH) is studied in a strictly single-phase gaseous medium, in a reconstituted surrounding atmosphere. In order to work under such conditions, a specific apparatus was assembled to monitor the evolution of the reactants through time. The reaction kinetics was studied at 50°C to avoid condensation of the water formed and for O₂/MMH mole ratios between 1 and 4. Under these conditions, the partial pressures of O₂ were between 0.05 and 0.18 bar (4% MMH per volume). The main reaction products were monitored through time and identified by gas chromatography coupled with mass spectrometry (GC/MS). The products were: N₂, CH₄, CH₃-NH-N=CH₂ (formaldehyde monomethylhydrazone), NH₃, H₂O, CH₃OH, and CH₂=N-N=N-CH₃ (2,3,4-triazapenta-1,3-diene). The formation of nitrosamines was not observed under these experimental conditions. The rate laws related to the disappearance of the reagents were clearly established and can be described by 2 consecutive parallel reactions of order 2 whose rate constants are: k ₁ = 7.57 × 10⁻² bar⁻¹ min⁻¹ and k ₂ = 0.5 bar⁻¹ min⁻¹. Analysis of the products permitted establishing an approximated balance of the global reaction.