Formation mechanism of NO_x precursors during the pyrolysis of glutarimide and succinimide

Kitchen waste incineration technology is one of the effective technologies for achieving waste resource utilization with heat recovery and large-scale volume reduction. Pyrolysis is the most fundamental and important stage in the incineration process. Hence, this paper selects glutarimide and succinimide are abundant initial products during kitchen waste pyrolysis. Glutarimide and succinimide are the main N -containing heterocycles (33.55 wt %) in soybean protein pyrolysis from kitchen waste. The pyrolysis mechanism of glutarimide/ succinimide and the reaction pathways of NOx precursors (NH3, HCN, and HNCO) are studied by using density functional theory (DFT) calculation. The possible pathways of NOx precursors formation from cleavage of C-N/C-C bond caused by H -transfer and homolysis of C-N/C-C bond are proposed. The favorable pathways for the formation of HNCO have low energy barrier (430.9 kJ/mol,418.5 kJ/mol) and high reaction rate constant throughout the entire temperature range. At the same time, the hydrogenation and decomposition of HNCO have explained the trend of NH3 and HCN formation under low temperature condition in pyrolysis experiment. Finally, this study theoretically proves that the yield of NH3 is higher than that of HCN. This finely explains the phenomenon that NH3 release is greater than HCN release in the experiment. In addition, this study found that the yield of NOx precursor formed by glutarimide cracking is higher, and the structure of the five membered ring succinimide (minimum energy barrier value of an open loop,334.3 kJ/mol) is more stable than that of the six membered ring glutarimide (347.0 kJ/mol).