Probing the combustion kinetics of dimethylformamide: A theoretical study of H-atom abstraction reactions

The DMF vapor in the exhaust gas is needed to be recovered and incinerated to eliminate NOx emissions. This process will also provide the required heat for the production process. To verify the combustion chemistry of DMF in control of its ignition in fuel-lean combustion, 16H-atom abstraction reactions of DMF were systematically studied by high-level quantum chemical calculation in this work. The reactions include abstracting two types of H-atom from DMF molecule: H-atom of aldehyde and methyl groups respectively. Moreover, eight abstractors: Ḣ, ȮH, O2, ĊH3, CH3Ȯ, CH3OȮ, NO2, and HȮ2 were involved. In ab initio calculation, the M06-2X/6–311++G(d,p) method was used for geometry optimization, vibration frequency, and dihedral scan calculation. CCSD/cc-pVXZ (X = T, Q) method was employed for the single point energy (SPE) calculation. The rate constants of all abstraction reactions and the thermochemical quantities of the DMF and corresponding two radical products were carried out simultaneously. The calculation results show that abstracting the H-atom of the aldehyde group is dominant over the methyl group H-atom abstraction. Moreover, for both the aldehyde and methyl groups, H-atom abstraction, ȮH, Ḣ, and CH3Ȯ abstractors produce the fastest rates. From the application point of view, one detailed kinetic model of DMF was developed by adopting our calculation results. The model accurately predicts the ignition delay times (IDTs) of DMF at a wide range of temperatures and equivalence ratios. The sensitivity analysis indicates that the branching ratio of abstracting aldehyde group H-atom and methyl group H-atom is crucial for the reactivity prediction of DMF.