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

• Published in: Journal of quantitative spectroscopy & radiative transfer 2023-05, Vol.300, p.108522, Article 108522
• Main Authors: Adil, Mohammad, Giri, Binod Raj, Elkhazraji, Ali, Farooq, Aamir
• Format: Article
• Language: English
• Subjects: Absorption spectra; Acetate; High temperature; Pyrolysis; Shock tube
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2023.108522

•A rapid-tuning laser is applied in a shock tube to measure high-temperature absorption spectra over a wide spectral window.•Absorption spectra of methyl acetate, ethyl acetate, n-propyl acetate and n‑butyl acetate are reported for their strongest infrared absorption band between 7.52 – 8.62 μm over 580 – 980 K near 1.3 bar.•Absorption cross section correlations are provided for the wide range of spectra over the studied temperature range for easy use of the measured spectra.•A fixed-wavelength laser diagnostic is developed for methyl acetate that exhibits minimal dependence on pressure and temperature.•Pyrolysis of methyl acetate is studied by measuring its decay profiles. 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.