The mechanism for the oxidation of benzoquinoline: A theoretical study

Abstract

The relationship between the coal nitrogen chemistry and the emission of NOx is a topic attracting wide-ranging interest due to its adverse impact on the environment. In this work, a comprehensive reaction network is proposed based on the DFT calculations to show the possible oxidation mechanisms of benzoquinoline that may result in the generation of NOx and/or other nitrogen-containing species. The kinetics of the reaction network is evaluated by Chemkin using the rate parameters computed from the transition state theory (TST). The first important contribution is the consideration of the role of O2 in the oxidation reaction, with the indication that the addition of O2 to N atom and neighboring CN bond that can activate the C(N) species will be more competitive than the addition of O2 to neighboring CC towards the benzoquinoline oxidation. Furthermore, benzoquinoline will be directly oxidated to NO and indirectly to HCN with the help of H radical. The H radical will promote the rupture of the CN bond, and thus accelerate the generation of HCN. The second important contribution is the obtained transition of the reaction mechanism over the temperature range of 1173–1273 K. The increase of the temperature will shift back the low-temperature formed NO to some important intermediates that can lead to the release of HCN. The mechanisms reported are capable of reproducing some general observations that previously did not have a fundamental explanation, and will be important for the future design of the low-NOx combustion technology.