The effect of Na/K on the NO adsorption behavior and heterogeneous reduction of internal nitrogen-containing char: A DFT study

[Display omitted] •The stability of Na/K doped on zigzag structures was better than that of armchair structures.•The adsorption stability of NO on Na/K-doped char is Z-N@Na/K > A-N@Na/K > G-N@Na/K.•The adsorption effect of nitrogen-containing saturated char with NO is significantly improved after doping with Na/K.•The addition of sodium and potassium lowers the highest energy barrier and increases the exotherm of the reaction. Sodium and potassium in high alkali coal have an effect on the heterogeneous reduction of NO with char. The microscopic mechanisms of the effect of Na and K on the adsorption behavior and heterogeneous reduction roads of NO on the surface of internal nitrogen-containing char were investigated at the GGA-PBE level using DFT. The adsorption energy of NO on the surface of nitrogen-containing char doped with Na and K was calculated using zigzag, armchair and saturated structures, and the reaction path of Z-N-2 with NO was also calculated. The results showed that the adsorption effects of the three types of nitrogen-containing char on NO ranked from strong to weak were: Z-N > A-N > G-N. The addition of Na and K both promoted the adsorption of NO with char structure. The highest energy barrier for the reaction of the Z-N-2 structure with NO was 232.80 kJ/mol, which decreased to 180.52 kJ/mol when Na doped and 176.04 kJ/mol when K doped. The exotherm of the reaction increases from 378.59 to 1245.26 kJ/mol, it appears that the addition of sodium and potassium facilitates the reaction. The study will provide a theoretical pavement for the continued study of the heterogeneous reduction process, which is of great significance for the clean use of high alkali coals.