Exploring the Potential of Raman Spectroscopy for Characterizing Olefins in Olefin-Containing Streams

Olefins are highly reactive hydrocarbon compounds that are often found in cracked petroleum and renewable-based products and may be responsible for the formation of gums and solid deposits in storage tanks, refining equipment, and vehicle fuel systems. Several government environmental regulations and industrial specifications are in place to control the levels of olefins in both unprocessed and finished petroleum products. This creates an urgent need for rapid monitoring of olefin levels in petroleum products. Most of the analytical methods currently used for olefin determination have several significant shortcomings, including long analysis times, the need for expensive equipment, high solvent usage, the requirement for high-purity gases (carrier or swift gases), and poor suitability for process monitoring. This paper presents a qualitative and semi-quantitative study of olefins in petroleum samples using Raman spectroscopy. A mixture of unsaturated model hydrocarbons was prepared to demonstrate the suitability of Raman spectroscopy for the determination of olefin contents in petroleum samples. The Raman spectra of the mixture and its individual components were obtained, and the C=C region was used to calculate the integrated area of the region against the olefin concentration. The results show that semi-quantitative analyses for similar mixtures are feasible, and the limit of detection of olefinic species in this particular naphtha is estimated to be approximately 1 vol %. The study also shows that different olefinic species generally do not exhibit the same molar C=C intensities, which may limit the accuracy of quantitative work. The proposed approach for olefin determination may be limited, but it can be developed and utilized for the determination of olefin concentrations in samples containing similar types of olefins and blended in a similar naphtha matrix. The study emphasizes the importance of the calibration procedure being sensitive to the type of selected olefin standards and the nature of the hydrocarbon matrix in the blend.