Experimental and kinetic modeling study of the effect of NO and SO2 on the oxidation of CO-H2 mixtures

The effect of NO and SO2 on the oxidation of a CO-H-2 mixture was studied in a jet-stirred reactor at atmospheric pressure and for various equivalence ratios (0.1, 1, and 2) and initial concentrations of NO and SO2 (0-5000 ppm). The experiments were performed at fixed residence time and variable temperature ranging from 800 to 1400 K. Additional experiments were conducted in a laminar flow reactor on the effect of SO2 on CO-H-2 oxidation in the same temperature range for stoichiometric and reducing conditions. It was demonstrated that in fuel-lean conditions, the addition of NO increases the oxidation of the CO-H-2 mixture below 1000 K and has no significant effect at higher temperatures, whereas the addition of SO2 has a small inhibiting effect. Under stoichiometric and fuel-rich conditions, both NO and SO2 inhibit the oxidation of the CO-H-2 mixture. The results show that a CO-H-2 mixture has a limited NO reduction potential in the investigated temperature range and rule out a significant conversion of HNO to NH through reactions like HNO + CO double left right arrow NH + CO2 or HNO + H-2 double left right arrow NH + H2O. The chain terminating effect of SO2 under stoichiometric and reducing conditions was found to be much more pronounced than previously reported under How reactor conditions and the present results support a high rate constant for the H + SO2 + M double left right arrow HOSO + M reaction. The reactor experiments were used to validate a comprehensive kinetic reaction mechanism also used to simulate the reduction of NO by natural gas blends and pure C-1 to C-4 hydrocarbons. (C) 2003 Wiley Periodicals, Inc.