A theoretical insight into the mechanism of NO heterogeneous reduction on char surface: The catalytic effect of potassium

In this paper, the catalytic effect of K on the NO heterogeneous reduction over char surface was investigated using the quantum chemistry calculation. The adsorption performance and the detailed reaction pathways were obtained via density function theory before and after potassium decorating. Additionally, the mayer bond order, thermodynamic and kinetic analysis were studied to further clarify the effect of K on the NO-char reaction. The calculation results showed that K can promote the adsorption of NO molecules on char surface. It was found that the reaction energy barriers were reduced with the decoration of K, indicating that K can promote the chemical reaction. Four reaction pathways were obtained based on Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms, and the order of reaction activity was as follows: L-H@K > L-H > E-R@K > E-R. Moreover, thermodynamic analysis showed that the reaction equilibrium constants increased with the addition of K, sug-gesting that the reaction was more complete and irreversible. From kinetic analysis, the reaction rate constants increased with temperature, and the rate of reactions were more faster in the presence of K, which indicated that K can accelerate the NO heterogeneous reduction. Based on the thermodynamic and kinetic performances, it is concluded that K has a significant promotion on the NO heterogeneous reduction by char. The theoretical results systematically reveal the catalytic mechanism of K on the NO reduction by char, which can make contributions to the clean and efficient utilization of the potassium-containing fuels.