Theoretical investigation of the ethylbenzene with NH_2 radical: H abstraction and addition reactions pathways

摘要

Thermal processes like pyrolysis of biomass and coal account for the interaction of alkylbenzenes with amidogen (NH_2) radical. The NH_2 radical evolves from the oxidation of ammonia and hydrogen cyanide in processes encompassing the transformation of nitrogenous fuels, with significant propositions to atmospheric and combustion systems. In this study, for the first time, we investigate the gas-phase mechanisms governing the reactions of ethylbenzene, as modelled alkylbenzene species, with NH_2 radical. More specifically, we determine H abstractions and addition reactions of ethylbenzene with NH_2. We compute standard reaction (Δ_rH_(298)~o) and activation (Δ~≠H_(298)~o) enthalpies for H removal from the alkyl side chains (primary H and benzylic H) in ethylbenzene, as well as the addition of NH_2 at the four possible sites (ipso, ortho, meta and para) of the ethylbenzene phenyl ring. The kinetic analysis of the interaction of ethylbenzene with NH_2 shows that abstraction of benzylic H atom represents the exclusive plausible corridor at all temperatures. The computed mechanistic and kinetic parameters (fitted in the temperature range of 300-2000 K) entail high accuracy level and corroborate with the available literature measurements.