(73c) A Computational Investigation into the Kinetics of NO + CH2CCH and Its Effect on NO Reduction | AIChE

(73c) A Computational Investigation into the Kinetics of NO + CH2CCH and Its Effect on NO Reduction

Authors 

Danilack, A. - Presenter, Brown University
Goldsmith, C. F., Brown University
Reduced emissions of nitrogen oxides (NOx = NO + NO2) is a critical goal in the development of advanced internal combustion engines. Chemical kinetic modeling plays a key role in the design process by quantifying rates of reactions that involve NO and NO2. Due to the stability of NO, most NO-consuming pathways involve reaction with another radical. One potential sink for NO is reaction with the propargyl radical, CH2CCH. Since the recombination of propargyl is crucial to the formation of aromatic soot precursors, the oxidation of CH2CCH by NO has important implications for kinetic models of nascent soot chemistry.

A computational investigation into the kinetics of the NO + CH2CCH reaction is presented. The stationary points on the C3H3N1O1 potential energy surface are analyzed using the high-accuracy compound method ANL0, with key regions of the potential energy surface computed using multi-reference methods. The temperature- and pressure-dependent rate constants are computed using the RRKM/Master Equation. The results reveal multiple pathways that enable the reduction of NO (and oxidation of CH2CCH) with the dominant bimolecular products being CH2CO + HCN and CO + CH3CN. Additional calculations for the thermal decomposition of an unimolecular intermediate, isoxazole, are in good agreement with the available experimental data.

The new rate constants are implemented in a detailed chemical kinetic mechanism, taken from literature, for the oxidation of C2H4 by O2 + NO. Additional propargyl formation reactions were also included from a recently developed kinetic mechanism. Analysis of a constant temperature, constant pressure batch reaction suggests that NO + CH2CCH accounts for a significant portion of the total NO chemistry at lower temperatures under fuel-rich conditions. Accordingly, this reaction could be an important pathway for both NO reduction and CH2CCH oxidation in reburn chemistry.