Comparison of near infrared and Raman spectroscopies for determining the cetane index of hydrogenated gas oil

The standard method (ISO 4264) for determining the cetane index of hydrogenated gas oil is time-consuming and expensive for routine laboratory tests. Conversely, near infrared (NIR) and Raman spectroscopies are high-speed and cost-effective techniques. In this study, these tools were used to create two models for the determination of the hydrogenated gas oil cetane index. First, ISO 4264 was used to measure the cetane index for 45 real samples used as calibration standards. Then, to create the models, the same samples were measured using NIR and Raman spectroscopies. The model values were then correlated against the ISO values. The Raman model predicted cetane index values with a maximum absolute difference of 1.2 from the ISO, while the NIR model showed a difference of 0.3. Finally, 10 additional real samples were used as validation standards to compare the models. The NIR model predicted values with better cross-validation error and lower absolute differences (NIR 0.334, Raman 0.654) from the ISO values compared to the Raman model. Thus, the NIR model is a fast and accurate method that can partially substitute for ISO 4264 when performing routine laboratory tasks.