Density Functional Theory Investigation on the Catalytic Reduction of NO by CO on the Char Surface: the Effect of Iron

Abstract

The catalytic reduction of NO with the presence of CO was investigated by density functional theory (DFT) calculations with consideration of the iron involved in the char (Fe-adsorbed char). The quantitative information of reaction kinetics was also evaluated by the canonical variational transition-state theory (CVT) in the temperature range of 500-1800 K. The analysis of associated adsorption energies indicates that the affinity of carbon active site toward NO and CO is stronger than Fe site, and the NO adsorption on the carbon site in N-down mode is the most energetically favorable. Following the chemisorption step, the reactions proceed for N2O, N2 and CO2 desorption by different reduction mechanisms, depending on whether CO exists. The FeO group formed and transformed during the NO reduction is of significant importance for the whole catalytic process. The results show that the heterogeneous reduction of NO is promoted much more dramatically under the help of CO, which brings about a decrease in the activation energies accompanied by an increase in the reaction rate constants. The effectiveness of Fe-adsorbed model derives from its prominent effect on NO-CO reaction, and becomes more realistic than the original metal-free structure.