Experimental and DFT research on role of sodium in NO reduction on char surface under H2O/Ar atmosphere

The catalytic mechanism of Na during NO reduction on char surface is proposed to provide fundamental information for minimizing NOx emissions. A molecular modeling study was carried out using density functional theory to clarify the NO reduction and CO release pathways on char surface. The calculation results explain the promotion phenomenon caused by Na catalysis, and the fluctuation of the CO release curve in the experiment. Under H2O/Ar atmosphere, besides the NO-char heterogeneous reaction, simultaneous occurrence of the NO homogeneous reaction with lower energy barrier improved the NO reduction rate. According to the simulation results, the catalytic effect of Na is manifested in that it can weaken the conjugated components of the aromatics structure, and form a stable H-C-O-Na structure to weaken the connected C-C bond, thereby facilitating the CO release. Mayer bond order and RDG analyses indicate that the participation of Na can prevent the C-O bond from being stretched, and generate the strong attractive interaction to promote the NO reduction.