Reduction of NO by n-butane in a JSR: Experiments and kinetic modeling

A study of the reduction of nitric oxide (NO) by n-butane, in simulated con ditions of a reburning zone, has been undertaken in a fused silica jet-stir red reactor operating at 1 atm. The temperatures ranged from 1100 to 1450 K , the initial mole fraction of NO was 1000 ppm,and that of n-butane was 200 0-2200 ppm. The equivalence ratio (phi = [fuel%/O-2%]/[fuel%/O-2%](at phi=1 )) was varied from 0.68 to 2. It was demonstrated that the reduction of NO varies as the temperature and that for a given temperature, a maximum NO re duction occurs, slightly above stoichiometric conditions. Generally, the pr esent results follow those obtained in previous studies involving simple hy drocarbons or natural gas as reburn-fuel. The oxidation of n-butane was als o studied without NO in the same conditions of temperature, pressure, and r esidence time. A detailed chemical kinetic modeling of the present experime nts was performed using an updated and improved kinetic scheme (892 reversi ble reactions and 113 species). An overall reasonable agreement between the present data and the modeling was obtained. Furthermore, the proposed kine tic mechanism can be successfully used to model the reduction of NO by etha ne, ethylene, a natural gas blend (methane-ethane 10:1), acetylene, propene , and propane. According to this study, NO reduction by n-butane mainly occ urs via reaction with ketenyl radical (HCCO): n-C4H10 --> C3H6, C2H4 --> C2 H2 --> HCCO, CH; HCCO + NO --> HCNO + CO, and HCN + CO2; CH + NO --> HCN; H CNO + H --> HCN + OH; HCN + O --> NCO --> NH; NH + H -->N; N + NO --> N-2; NH + NO --> N2O followed by N2O + H --> N-2.