Study on the Formation Mechanism of NOx Precursors During Density Functional Theory Pyrolysis of Leucine and Proline

Abstract

ABSTRACT Incineration is an efficient method of resource utilization for kitchen waste. As an important stage of incineration, pyrolysis not only degrades kitchen waste but also generates pollutants such as nitrogen oxides. It is necessary to conduct in-depth research on the nitrogen conversion mechanism during its pyrolysis process. Most of the nitrogen in kitchen waste is concentrated in protein/amino acids. This article is based on the density functional theory calculation method, selecting typical compounds leucine and proline in kitchen waste as research objects, and studying their pyrolysis mechanism and the formation path of NOx precursors. A possible path for the cleavage of C-C/C-N bonds caused by hydrogen transfer to form NH3 and HCN has been proposed. Finally, it has been theoretically proven that the pyrolysis process of leucine tends to generate NH3 rather than HCN. And it was clarified that low energy barriers and high reaction rates are the reasons for the difference in production of these two NOx precursors. Meanwhile, the differences in the generation characteristics of NOx precursors for proline at different pyrolysis temperatures were theoretically explained. Finally, it was elucidated that leucine and proline preferentially undergo decarboxylation to complete the deoxygenation process, and the reason for the difference in CO production during the pyrolysis of the two amino acids was explained. In addition, this study found that the pyrolysis of leucine occurred preferentially than that of proline under the same conditions, and the yield of NOx precursor produced by leucine was higher than that of proline.