A theoretical investigation on the thermal decomposition of pyridine and the effect of H₂O on the formation of NO_x precursors

Abstract

Pyridine is one of the main nitrogen-containing compounds in coal, and its pyrolytic mechanism to generate NO_x precursors (mainly NH₃ and HCN) remains unclear. In this work, the possible pathways for the pyrolysis of pyridine to form HCN and/or NH₃ were investigated by the density functional theory method, and the effects of H₂O on pyridine pyrolysis were also investigated. The results show that there are two possible reactions for the initial pyridine pyrolysis, i.e., internal hydrogen transfer and C–H bond homolysis, and that internal hydrogen transfer is more favorable. Nine possible reaction pathways following internal hydrogen transfer are obtained and analyzed. Among these pathways, pyridine prefers to produce HCN instead of NH₃. The existence of H₂O has significant effects on the decomposition of pyridine, as it participates in pyridine pyrolysis to form NH₃ rather than HCN as the major product.

Key words： coal; pyridine; pyrolysis mechanism; NO_x precursors; DFT

Acknowledgments

The authors thank the National Natural Science Foundation of China (Grant Nos. 51922040 and 51821004), China Postdoctoral Science Foundation (Grant No. 2019TQ0091), Grants from Fok Ying Tung Education Foundation (Grant No. 161051), and Fundamental Research Funds for the Central Universities (Grant Nos. 2020DF01, 2020 MS020, 2018ZD08) for financial support.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-020-2024-8 and is accessible for authorized users.

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