Jocelyn Luche

The Low Temperature Oxidation of DME and Mutual Sensitization of the Oxidation of DME and Nitric Oxide: Experimental and Detailed Kinetic Modeling

Abstract The oxidation of dimethylelher (DME) has been studied experimentally at low-temperature {550-800 K) in a jet-stirred reactor operating at I atm. The mutual sensitization of the oxidation of dimethyl-ether and NO was also studied. It was shown that above 600 K, NO enhances the oxidation of DME in the cool flame regime and yields methylformate (not formed without NO) whereas NO is oxidized to NO2 Below 600 K, the oxidation of DME was inhibited by NO. A detailed chemical kinetic model was developed to simulate the present experiments and the ignition of DME/air mixtures in shock tube at 13 and 40 atm. 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 DME and NO proceeds through the following sequence: DME + OH →CH 3OCH2(R); R + O2→ RO2; R O2 + NO → RO + N O2; RO → methylformate + H; RO + O2 → methylformate + H O2; H O2 + NO → OH + N O2 The inhibition of DME oxidation below 600 K is due to R O2 + NO -→ R O2 + N O2 that reduces the production of OH by competition with the isomerization R O2 → Q O2H responsible for chain-branching: Q O2H + O2 → O2Q O2H → H O2QO + OH; Q O2H → 2CH2O + OH; H O2QO → OQO + OH.

Experimental and kinetic modeling of the reduction of NO by isobutane in a Jsr at 1 atm

A kinetic study of the reduction of nitric oxide (NO) by isobutane in simulated conditions of the reburning zone was carried out in a fused silica jet-stirred reactor operating at 1 atm, at temperatures ranging from 1100 to 1450 K. In this new series of experiments, the initial mole fraction of NO was 1000 ppm, that of isobutane was 2200 ppm, and the equivalence ratio was varied from 0.75 to 2. It was demonstrated that for a given temperature, the reduction of NO is favored when the temperature is increased and a maximum NO reduction occurs slightly above stoichiometric conditions. The present results generally follow those reported in previous studies of the reduction of NO by C1 to C3 hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiments was performed using an updated and improved kinetic scheme (979 reversible reactions and 130 species). An overall reasonable agreement between the present data and the modeling was obtained. Furthermore, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethylene, ethane, acetylene, a natural gas blend (methane-ethane 10:1), propene, and HCN. According to this study, the main route to NO reduction by isobutane involves ketenyl radical. The model indicates that the reduction of NO proceeds through the reaction path: iC4H10 C3H6 C2H4 C2H3 C2H2 HCCO; HCCO + NO HCNO + CO and HCN + CO2; HCNO + H HCN NCO NH; NH + NO N2 and NH + H followed by N + NO N2; NH + NO N2O followed by N2O + H N2.