Revisiting the kinetics of pyridine pyrolysis. Part 1: H atom abstraction reactions

High-temperature decomposition of pyridine, C 5 H 5 N, occurs during waste incineration, pyrolysis of biomass and coal. In the present work, the rate constants of H atom abstraction from C 5 H 5 N by H, CH 3 , CN, C 2 H 3 , CHCHCN and nC 4 H 3 radicals have been calculated at the DLPNO-CCSD(T)-F12/cc-pVDZ-F12//M06-2×/def2-TZVP level of theory from 300 to 2000 K. The new rate constants obtained in the present work, in most cases are notably different from the expressions suggested in the earlier studies on pyridine pyrolysis or derived in theoretical calculations. Only for reactions of H atom abstraction by H, a reasonable agreement was found. It was revealed that the formation of ortho-, meta-, and para-pyridyls could be of equal importance and, therefore, all pyridyl isomers should be considered in detailed kinetic mechanisms for pyridine. • Theoretical kinetic study of H atom abstraction reactions from pyridine • Formation of all pyridyl radicals is important and cannot be neglected • Significant disparity with the rate constants previously estimated or calculated • The new kinetic data will make kinetic mechanisms of pyridine pyrolysis consistent.