Heterogeneous reduction mechanism of NO on the surface of nitrogen-containing char was investigated at molecular level using density functional theory.The char model

products

stable intermediates and transition states were optimized at B3LYP/6-31G(d）level.The whole potential energy surface was obtained by calculating single point energies with zero point energy corrections for geometries.The results are as follows.The first step of the heterogeneous reduction is NO adsorption on the surface of nitrogen-containing char

releasing heat energy of 98.1 kJ·mol-1 .N and O atoms tend to separate after chemisorption.N2 is desorbed with the production of P1 by a series of rearrangement reactions

in which the highest energy barrier is 87.7 kJ·mol-1.The highest energy barrier for CO desorption is 253 kJ·mol-1 and P2 is left on the char surface.Desorption of N2 and CO from reactions between NO and nitrogen-containing char are 187 kJ·mol-1 exothermic and 302 kJ·mol-1 endothermic

respectively.CO is further released from P1 with 138 kJ·mol-1 endothermic

and N2 is desorbed from P2 with 352 kJ·mol-1 released.About 49 kJ·mol-1 is released throughout the overall heterogeneous reduction of NO on the surface of nitrogen-containing char.