A shock tube and laser absorption study of ignition delay times and OH reaction rates of ketones: 2-Butanone and 3-buten-2-one

Ketones are potential biofuel candidates and are also formed as intermediate products during the oxidation of large hydrocarbons or oxygenated fuels, such as alcohols and esters. This paper presents shock tube ignition delay times and OH reaction rates of 2-butanone (C2H5COCH3) and 3-buten-2-one (C2H3COCH3). Ignition delay measurements were carried out over temperatures of 1100–1400 K, pressures of 3–6.5 atm, and at equivalence ratios (Ф) of 0.5 and 1. Ignition delay times were monitored using two different techniques: pressure time history and OH absorption near 306 nm. The reaction rates of hydroxyl radicals (OH) with these two ketones were measured over the temperature range of 950–1400 K near 1.5 atm. The OH profiles were monitored by the narrow-line-width ring-dye laser absorption of the well-characterized R1(5) line in the OH A–X (0, 0) band near 306.69 nm. We found that the ignition delay times of 2-butanone and 3-buten-2-one mixtures scale with pressure as P−0.42 and P−0.52, respectively. The ignition delay times of 3-buten-2-one were longer than that of 2-butanone for stoichiometric mixtures, however, for lean mixtures (Ф = 0.5), 2-butanone had longer ignition delay times. The chemical kinetic mechanism of Serinyel et al. [1] over-predicted the ignition delay times of 2-butanone at all tested conditions, however, the discrepancies were smaller at higher pressures. The mechanism was updated with recent rate measurements to decrease discrepancy with the experimental data. A detailed chemistry for the oxidation of 3-buten-2-one was developed using rate estimation method and reasonable agreements were obtained with the measured ignition delay data. The measured reaction rate of 2-butanone with OH agreed well with the literature data, while we present the first high-temperature measurements for the reaction of OH with 3-buten-2-one. The following Arrhenius expressions are suggested over the temperature range of 950–1450 K: kC2H5COCH3+OH=6.78×1013exp(-2534/T)cm3mol-1s-1kC2H3COCH3+OH=4.17×1013exp(-2350/T)cm3mol-1s-1