Effect of Alkali Metal Ions on the Formation Mechanism of HCN During Pyridine Pyrolysis

Abstract The present work aims at the effects of alkali metal ions (Na+, K+) on the NOx precursor formation during coal pyrolysis by employing the N-containing pyridine as the model compound. Density functional theory (DFT) calculations were used to elucidate the pyridine pyrolysis mechanism and pathways for the HCN formation. The calculation results indicate that Na+ and K+ have distinct influences on different pyrolysis reactions. The two alkali metal ions can facilitate the initial hydrogen transfer from C1 to N and C2, while it is the opposite situation for other hydrogen migration reactions. Both Na+ and K+ significantly reduce the activation energies for the C-C bond breakage and the formation of the triple bond, whereas the activation energies are increased for isomerization reactions. The two alkali metal ions modulate the rate-determining step of the pyrolysis process and promote the formation of HCN from pyridine by decreasing the activation energies of the rate-determining steps in different pathways.