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

Pyridine is one of the main nitrogen-containing compounds in coal, and its pyrolytic mechanism to generate NO x precursors (mainly NH 3 and HCN) remains unclear. In this work, the possible pathways for the pyrolysis of pyridine to form HCN and/or NH 3 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 NH 3 . The existence of H 2 O has significant effects on the decomposition of pyridine, as it participates in pyridine pyrolysis to form NH 3 rather than HCN as the major product.