Oxidation of Acetylene−Ethanol Mixtures and Their Interaction with NO

Abstract

An experimental and theoretical study of the oxidation of acetylene−ethanol mixtures in the absence and presence of NO has been carried out. The experiments were conducted in an isothermal quartz flow reactor at atmospheric pressure in the 775−1375 K temperature range. The influence of the temperature, stoichiometry (by varying the O2 concentration for given C2H2 and C2H5OH initial concentrations), presence of different amounts of ethanol added to acetylene, and presence of NO on the concentrations of C2H2, C2H5OH, CO, CO2, NO, and HCN has been analyzed. The gas-phase kinetic mechanism used for calculations was that developed by Alzueta et al. (Alzueta, M. U.; Borruey, M.; Callejas, A.; Millera, A.; Bilbao, R. Combust. Flame 2008, 152, 377−386) for acetylene conversion, on the basis of a previous work by Skjøth-Rasmussen et al. (Skjøth-Rasmussen, M. S.; Glarborg, P.; Østberg, M.; Johannessen, J. T.; Livbjerg, H.; Jensen, A. D.; Christensen, T. S. Combust. Flame 2004, 136, 91−128), with reactions added from the ethanol oxidation mechanism of Alzueta and Hernández (Alzueta, M. U.; Hernández, J. M. Energy Fuels 2002, 16, 166−171), as well as reactions from the mechanism developed by Glarborg et al. (Glarborg, P.; Alzueta, M. U.; Dam-Johansen, K.; Miller, J. A. Combust. Flame 1998, 115, 1−27) to describe the interactions among C1/C2 hydrocarbons and nitric oxide. The experimental results show that the ethanol presence significantly modifies the acetylene conversion regime, inhibiting soot formation. An increase of the oxygen level and temperature favor acetylene conversion. The presence of NO results in some differences in relation to the oxidation regimes of the acetylene−ethanol blends. The reduction of NO by the mixture is favored at the highest temperatures of the considered range, above 1275 K, and for moderately fuel-rich conditions (λ = 0.7). In general, the kinetic model satisfactorily simulates the experimental trends. Model predictions indicate that, under the conditions of this study, HCCO + NO is the most important reaction in reducing NO. Moreover, the ethanol presence slightly inhibits the NO reduction in relation to the oxidation of pure acetylene.