Bromine number in pyrolysis gasoline

Significance of the Topic

Pyrolysis gasoline contains highly reactive unsaturated hydrocarbons that limit its direct use as motor fuel. Determining the bromine number, which reflects overall unsaturation, is essential for quality control and safe processing of these streams.

Objectives and Study Overview

This study aims to implement near-infrared spectroscopy (NIRS) as a rapid, chemical-free alternative to the standard titrimetric bromine number determination. A robust calibration model was developed to comply with ASTM D8321 and D6122, enabling quantification of unsaturation in less than one minute.

Methodology

A total of 180 pyrolysis gasoline samples were measured in transmission mode from 400 to 2500 nm at 40 °C. Chemometric models were built using Vision Air software to correlate spectral data with reference bromine number values obtained by wet chemistry.

Used Instrumentation

• DS2500 Liquid Analyzer (400–2500 nm range, 40 °C temperature control, 8 mm disposable vials)
• Vision Air 2.0 Complete software for spectral acquisition and model development

Main Results and Discussion

The NIR calibration achieved a coefficient of determination (R²) of 0.836, with a standard error of calibration of 1.84 and cross-validation error of 1.89. Correlation plots demonstrated strong agreement between NIR predictions and the reference titration method, validating the approach for routine analysis.

Benefits and Practical Applications

• No chemical reagents or sample cooling required
• Analysis time reduced from 30 minutes to 1 minute per sample
• Consumable cost lowered from $6 to $0.50 per measurement
• Annual running costs decrease from $12,533 to $1,125
• Capability to determine additional parameters, such as diene value, in the same measurement

Future Trends and Potential Applications

Expanded calibration libraries and advanced chemometric algorithms will further improve prediction accuracy. Integration with automated sampling and process control systems can enable real-time monitoring of unsaturation in petrochemical streams and other industrial contexts.

Conclusion

NIR spectroscopy using the DS2500 Liquid Analyzer provides a fast, cost-effective, and environmentally friendly alternative for bromine number determination in pyrolysis gasoline, offering significant benefits for quality control and process optimization.