5 September 2014 Use of the characteristic Raman lines of toluene (C7H8) as a precise frequency reference on the spectral analysis of gasoline-ethanol blends
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In order to reduce some of the toxic emissions produced by internal combustion engines, the fossil-based fuels have been combined with less harmful materials in recent years. However, the fuels used in the automotive industry generally contain different additives, such as toluene, as anti-shock agents and as octane number enhancers. These materials can cause certain negative impact, besides the high volatility implied, on public health or environment due to its chemical composition. Toluene, among several other chemical compounds, is an additive widely used in the commercially-available gasoline-ethanol blends. Despite the negative aspects in terms of toxicity that this material might have, the Raman spectral information of toluene can be used to achieve certain level of frequency calibration without using any additional chemical marker in the sample or any other external device. Moreover, the characteristic and well-defined Raman line of this chemical compound at 1003 cm−1 (even at low v/v content) can be used to quantitatively determine certain aspects of the gasoline-ethanol blend under observation. By using an own-designed Fourier-Transform Raman spectrometer (FT-Raman), we have collected and analyzed different commercially-available and laboratory-prepared gasoline-ethanol blends. By carefully observing the main Raman peaks of toluene in these fuel blends, we have determined the frequency accuracy of the Raman spectra obtained. The spectral information has been obtained in the range of 0 cm−1 to 3500 cm−1 with a spectral resolution of 1.66 cm−1. The Raman spectra obtained presented only reduced frequency deviations in comparison to the standard Raman spectrum of toluene provided by the American Society for Testing and Materials (ASTM).
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Valentin Ortega Clavero, Valentin Ortega Clavero, Nicolas Javahiraly, Nicolas Javahiraly, Andreas Weber, Andreas Weber, Werner Schröder, Werner Schröder, Dan Curticapean, Dan Curticapean, Patrick P. Meyrueis, Patrick P. Meyrueis, "Use of the characteristic Raman lines of toluene (C7H8) as a precise frequency reference on the spectral analysis of gasoline-ethanol blends", Proc. SPIE 9202, Photonics Applications for Aviation, Aerospace, Commercial, and Harsh Environments V, 92020A (5 September 2014); doi: 10.1117/12.2064371; https://doi.org/10.1117/12.2064371

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