Determination of RON, aromatics, benzene, olefins, and density in reformate by NIRS

Importance of the Topic

The catalytic reforming process produces high-octane reformate essential for premium gasoline blending and petrochemical applications. Traditional methods for determining research octane number (RON), aromatic content, benzene, olefins, and density are time-consuming, labor-intensive, and generate chemical waste. Near‐infrared spectroscopy (NIR) offers a rapid, reagent-free alternative, delivering multiparameter results in under one minute.

Objectives and Study Overview

This study evaluates the capability of the Metrohm DS2500 Liquid Analyzer for simultaneous quantification of RON (ASTM D2699), aromatics (ASTM D5769), benzene, olefins, and density in reformate. A robust calibration model was developed and validated against reference methods to demonstrate accuracy, precision, and operational efficiency.

Methodology and Instrumentation

507 reformate samples were analyzed in transmission mode over 400–2500 nm using the DS2500 Liquid Analyzer fitted with 8 mm disposable vials. The instrument was temperature-controlled at 35 °C. Spectral data acquisition, calibration, and prediction were performed with Vision Air Complete software using full cross-validation to assess model performance.

Instrumentation Used

• DS2500 Liquid Analyzer (Article No. 2.929.0010)
• DS2500 Holder for 8 mm vials (Article No. 6.7492.020)
• Vision Air 2.0 Complete software (Article No. 6.6072.208)

Main Results and Discussion

All analytes exhibited excellent correlation between NIR predictions and reference methods, with R2 values exceeding 0.98:

• RON: R2 = 0.996, SEC = 0.34, SECV = 0.36
• Aromatics: R2 = 0.999, SEC = 0.88 vol%, SECV = 0.91 vol%
• Benzene: R2 = 0.984, SEC = 0.066 vol%, SECV = 0.088 vol%
• Olefins: R2 = 0.982, SEC = 0.71 vol%, SECV = 0.87 vol%
• Density: R2 = 0.993, SEC = 0.0029 kg/L, SECV = 0.0034 kg/L

These figures of merit confirm that NIR spectroscopy can match conventional methods in accuracy while reducing analysis time dramatically.

Benefits and Practical Applications

• Rapid results in under one minute without sample preparation
• Elimination of chemical reagents and associated waste
• Enhanced throughput for routine quality control in refineries
• Reduced operational costs and improved laboratory efficiency

Future Trends and Applications

Integration of NIR analyzers directly into production lines and automated sampling systems will support real-time process monitoring. Advances in chemometric algorithms and machine learning will further refine calibration models, enabling broader analyte coverage and adaptive maintenance. Industry 4.0 implementations may link NIR data with centralized control systems for predictive quality assurance.

Conclusion

The Metrohm DS2500 Liquid Analyzer offers a fast, accurate, and environmentally friendly solution for multi-parameter reformate analysis. Its high correlation with standard methods, minimal sample handling, and sub-minute measurement time make it an ideal tool for modern refinery quality control.

Reference

• Metrohm AG. Application Note AN-NIR-114: Determination of RON, Aromatics, Benzene, Olefins, and Density in Reformate by NIRS.