FTIR measurements of mid-IR absorption spectra of gaseous fatty acid methyl esters at T=25-500 °C

- Infrared spectra of 11 fatty acid methyl esters (C3-C11) have been measured.
- A linear relationship for predicting 3.39 μm cross section values is proposed.
- A molecule's integrated area is linearly related to its number of CH bonds.
- Mono-unsaturation decreases cross section values.

Gas-phase mid-infrared (IR) absorption spectra (2500-3400 cm−1) for eleven fatty acid methyl esters (FAMEs) have been quantitatively measured at temperatures between 25 and 500 °C using an FTIR spectrometer with a resolution of 1 cm−1. Using these spectra, the absorption cross section at 3.39 μm, corresponding to the monochromatic output of a helium-neon laser, is reported for each of these fuels as a function of temperature. The data indicate that the 3.39 μm cross section values of saturated FAMEs vary linearly with the logarithm of the number of CH bonds in the molecule.