Propionaldehyde infrared cross-sections and band strengths

- High resolution IR spectra of propionaldehyde were measured by FTIR spectrometer.
- The discrepancy between the present study and PNNL database was less than 2%.
- The fundamental vibrational frequencies were reported at high resolution.
- The rovibrational Q transitions were higher than previously reported values.

The use of oxygenated biofuels reduces the greenhouse gas emissions; however, they also result in increased toxic aldehyde by-products, mainly formaldehyde, acetaldehyde, acrolein, and propionaldehyde. These aldehydes are carcinogenic and/or toxic and therefore it is important to understand their formation and destruction pathways in combustion and atmospheric systems. Accurate information about their infrared cross-sections and integrated strengths are crucially needed for development of quantitative detection schemes and modeling tools. Critical to the development of such diagnostics are accurate characterization of the absorption features of these species. In this study, the gas phase infrared spectra of propionaldehyde (also called propanal, CH3-CH2-CHO), a saturated three carbon aldehyde found in the exhaust emissions of biodiesel or diesel fuels, was studied using high resolution Fourier Transform Infrared (FTIR) spectroscopy over the wavenumber range of 750−3300 cm−1 and at room temperature 295 K. The absorption cross sections of propionaldehyde were recorded at resolutions of 0.08 and 0.096 cm−1 and at seven different pressures (4−33 Torr). The calculated band-strengths were reported and the integrated band intensity results were compared with values taken from the Pacific Northwest National Laboratory (PNNL) database (showing less than 2% discrepancy). The peak positions of the 19 different vibrational bands of propionaldehyde were also compared with previous studies taken at a lower resolution of 1 cm−1. To the best of our knowledge, the current FTIR measurements provide the first highest resolution infrared cross section data for propionaldehyde.