Mid-IR absorption spectra of C1-C4 alkyl acetates at high temperatures

We present measurements of the temperature-dependent absorption cross-section of C1-C4 alkyl acetates (methyl acetate, ethyl acetate, n-propyl acetate, n‑butyl acetate) covering their strongest infrared absorption band near 1250 cm⁻¹. The methodology employed here consists of a broadband rapid-tuning MIRcat-QT™ laser in conjunction with a shock tube. The spectral measurements were performed over the wavelength range of 7.52 – 8.62 μm (1160 – 1330 cm⁻¹), temperatures of 580 – 980 K, and pressures near 1.3 bar. The reported IR spectra are the first experimental measurements of the high-temperature absorption spectra of these species, and the measured spectra showed strong temperature dependence. We provide herein absorption cross-section correlations for a wide range of spectra and a wide range of temperatures. Rapid measurements of alkyl acetate in transient environments may be performed in a fixed-wavelength mode by choosing a suitable wavelength. Based on our analysis, we propose a wavelength of 1221.27 cm⁻¹ which exhibited minimal temperature and pressure dependence over the range of investigated conditions. We utilized this strategy for measuring methyl acetate concentration during its high-temperature pyrolysis.