Feasibility of a wide area illumination scheme for reliable Raman measurement of petroleum products.

A newly developed Raman collection scheme, a wide area illumination (WAI) scheme, was employed to demonstrate its utility for the analysis of petroleum products. For this purpose, the compositional analysis of simulated naphtha samples was attempted. The WAI scheme utilized a laser beam that illuminated a sample in a circular fashion with a diameter of 6 mm and a focal length of 250 mm. The reproducibility of the Raman measurement can be improved due to decreased sensitivity of the sample position as well as orientation with regard to the focal plane, as shown in a previous study. Near-infrared (NIR) spectroscopy, widely adopted in the field of petroleum refining, was also employed to compare with the prediction results obtained using the WAI scheme. Since the Raman spectral feature is more distinct and selective, the resulting calibration accuracy could be improved as long as reproducible Raman spectra could be collected. Overall prediction results using Raman spectroscopy were superior to those from NIR spectroscopy. The feasibility of the WAI scheme for reliable Raman analysis of petroleum products such as naphtha was demonstrated in this paper.