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 o f HCN-natural gas blend (CH4-C2H6 10:1) mixtures at 1050 to 1450 K, with an d 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 re action sub-mechanism, was used to simulate the present experiments. A good agreement between the experimental results and the modeling was generally o btained. According to the proposed kinetic mechanism, in the present condit ions, the mutual sensitization of the oxidation of ethane and NO proceeds t hrough the following sequence: C2H6 + OH --> C2H5 + H2O; C2H5 + O-2 --> C2H 4 + HO2 followed by the oxidation of NO and production of OH sustaining eth ane oxidation, NO + HO2 --> NO2 + OH. Other reactions yield mutual sensitiz ation of the oxidation of ethane and NO: C2H5O2 + NO --> C2H5O + NO2 and CH 3O2 + NO --> CH3O + NO2 followed by thermal decomposition of alkoxy radical s (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 follow ed by NCO + CH4 --> HNCO + CH3, NCO --> C2H6 --> HNCO + C2H5 and HNCO + H - -> NH2+ CO. NO addition yields a strong sensitization of the oxidation proc ess. 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 experime nts, the NCO + NO reactions dominate resulting in an increased production o f N2O and a reduction of HNCO yield.