Shock tube/laser absorption studies of the decomposition of methyl formate
KAUST DepartmentClean Combustion Research Center
Physical Sciences and Engineering (PSE) Division
Mechanical Engineering Program
Chemical Kinetics & Laser Sensors Laboratory
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AbstractReaction rate coefficients for the major high-temperature methyl formate (MF, CH3OCHO) decomposition pathways, MF → CH3OH + CO (1), MF →CH2O+CH2O (2), and MF→ CH4 + CO2 (3), were directly measured in a shock tube using laser absorption of CO (4.6 μm), CH2O (306 nm) and CH4 (3.4 μm). Experimental conditions ranged from 1202 to 1607 K and 1.36 to 1.72 atm, with mixtures varying in initial fuel concentration from 0.1% to 3% MF diluted in argon. The decomposition rate coefficients were determined by monitoring the formation rate of each target species immediately behind the reflected shock waves and modeling the species time-histories with a detailed kinetic mechanism . The three measured rate coefficients can be well-described using two-parameter Arrhenius expressions over the temperature range in the present study: k1 = 1.1 × 1013 exp(-29556/T, K) s -1, k2 = 2.6 × 1012 exp(-32052/T, K) s-1, and k3 = 4.4 × 1011 exp(-29 078/T, K) s-1, all thought to be near their high-pressure limits. Uncertainties in the k1, k2 and k3 measurements were estimated to be ±25%, ±35%, and ±40%, respectively. We believe that these are the first direct high-temperature rate measurements for MF decomposition and all are in excellent agreement with the Dooley et al.  mechanism. In addition, by also monitoring methanol (CH3OH) and MF concentration histories using a tunable CO2 gas laser operating at 9.67 and 9.23 μm, respectively, all the major oxygen-carrying molecules were quantitatively detected in the reaction system. An oxygen balance analysis during MF decomposition shows that the multi-wavelength laser absorption strategy used in this study was able to track more than 97% of the initial oxygen atoms in the fuel. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
SponsorsThis work was supported by the Combustion Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001198, the Army Research Office (ARO) with Dr. Ralph Anthenien as contract monitor, and the Air Force Office of Scientific Research (AFOSR) with Dr. Julian Tishkoff as technical monitor.