On-line determination of fuel quality parameters using near-infrared spectrometry with fibre optics and multivariate calibration

Near-infrared spectrometry with multivariate calibration has been widely used in the food and chemical industries for the determination of quality parameters. The use of fibre optics opens the possibility of using this technique for on-line analysis. With fuels such as gasoline and diesel, most of the parameters used for their characterization are measured using empirical and sometimes subjective tests. These tests might also require costly and complicated equipment as in the measurement of octane number, cetane number and paraffin, olefin, naphthene and aromatics content (PONA). Near-infrared spectrometry using fibre optics in combination with multivariate calibration was used for the determination of fuel quality parameters. The octane number of gasolines was measured. The sampling problems encountered when this method is implemented on-line were evaluated by monitoring the research and motor octane numbers in a gasoline line. Other applications, such as the determination of PONA in gasolines and the measurement of cetane number in diesel fuels, are discussed. In all instances the results obtained by the proposed technique agree with the values measured with conventional methods.