Decomposition of CH₃NH₂: Implications for CH_x/NH_y radical–radical reactions

Experiments on methylamine (CH₃NH₂) decomposition in shock tubes, flow reactors, and batch reactors have been re-examined to improve the understanding of hydrocarbon/amine interactions and constrain rate constants for CH_𝑥 +
NH_𝑦 reactions. In high-temperature shock tube experiments, the rapid thermal dissociation of CH₃NH₂ provides a fairly clean source of CH₃ and NH₂ radicals, allowing an assessment of reactions of CH₃ with NH₂ and NH. At the lower temperatures in batch and flow reactors, CH₃NH₂ is mostly consumed by reaction with H to form CH₂NH₂ +H₂; these results are useful in determining the fate of theCH₂NH₂ radical. Interpretation of these data, along with flow reactor data for the CH₃NH₂/H system at lower temperature, indicates that at temperatures up to about 1400 K at atmospheric pressure and above 2000 K at 100 atm, the CH₃ +NH₂ reaction forms mainly methylamine. At sufficiently high temperature, H abstraction to form CH₄ + NH and addition–elimination to form CH₂NH₂ + H become competitive. The CH₃ + NH reaction, with a rate constant close to collision frequency, forms CH₂NH + H, also leading into the hydrocarbon amine
pool. Thus, methylamine can be expected to be an important intermediate in co-combustion of natural gas and ammonia, and more work on the chemistry of CH₃NH₂ is desirable.