Kinetic study of hydrogen abstraction and unimolecular decomposition reactions of diethylamine during pyrolysis and oxidation

Diethylamine (DEA) represents a nitrogen-containing bio-oil model compound and an amine-model compound during the co-combustion of ammonia and hydrocarbons. Kinetics of the hydrogen abstraction reactions by H, O, OH, O2, HO2, CH3, and C2H5, and unimolecular decomposition reactions including 1,3-elimination, 1,2-hydrogen transfer, and C-N/C-C bond dissociations of DEA are theoretically investigated. Using the DLPNOCCSD(T)/CBS(T-Q) method as a benchmark, cost-effective M06-2X/def2-TZVP method is selected for kinetic investigation. High-pressure-limit rate constants for the reactions with tight saddle points are determined by canonical variational transition-state theory with the multi-structural torsional anharmonicity and small- curvature tunneling. Hydrogen abstraction reactions at the C site connecting to the N site dominant in the low-to-mediate temperature range. Pressure dependent rate constants for the unimolecular decomposition reactions are determined by SS-QRRK/MSC-Dean approach. 1,3-elimination and C-C dissociation reactions dominant at the low-to-mediate and high temperature ranges, respectively.