Mutual sensitization of the oxidation of nitric oxide and simple fuels over an extended temperature range: Experimental and detailed kinetic modeling

The sensitization of ethane oxidation by NO above 800 K and the oxidation of HCN-natural gas blend (CH4-C2H6 10:1) mixtures at 1050 to 1450 K, with and without NO, have been studied in a fused silica jet-stirred reactor (JSR) at 1 atm. A derailed chemical kinetic model developed for NO-reburning by natural gas (754 reactions and 102 species), including a low-temperature reaction sub-mechanism, was used to simulate the present experiments. A good agreement between the experimental results and the modeling was generally obtained. According to the proposed kinetic mechanism, in the present conditions, the mutual sensitization of the oxidation of ethane and NO proceeds through the following sequence: C2H6 + OH --> C2H5 + H2O; C2H5 + O-2 --> C2H4 + HO2 followed by the oxidation of NO and production of OH sustaining ethane oxidation, NO + HO2 --> NO2 + OH. Other reactions yield mutual sensitization of the oxidation of ethane and NO: C2H5O2 + NO --> C2H5O + NO2 and CH3O2 + NO --> CH3O + NO2 followed by thermal decomposition of alkoxy radicals (C2H5O --> CH3HCO + H, CH3O --> CH2O + H) and production of HO2, H + O-2 --> HO2. The present modeling also shows that the oxidation of HCN-natural gas blend proceeds through the following routes: HCN + O --> NCO + H followed by NCO + CH4 --> HNCO + CH3, NCO --> C2H6 --> HNCO + C2H5 and HNCO + H --> NH2+ CO. NO addition yields a strong sensitization of the oxidation process. The proposed kinetic model indicates that the reaction path is: HCN + O --> NCO + H followed by NCO + NO --> N2O, CO, CO2, and N-2. N2O is mostly converted to N-2 through reaction with H and CO. In the NO-seeded experiments, the NCO + NO reactions dominate resulting in an increased production of N2O and a reduction of HNCO yield.