Fast Hydrocarbon and Sulfur Simulated Distillation Using the Agilent Low Thermal Mass (LTM) System on the 7890A GC and 355 Sulfur Chemiluminescence Detector

Importance of the Topic

The boiling point distribution of hydrocarbons and sulfur in petroleum streams is fundamental for process optimization, regulatory compliance, and product quality assessment. Fast simulated distillation (SimDis) enhances laboratory throughput and provides detailed composition profiles crucial for refining operations and environmental monitoring.

Objectives and Overview of the Study

This application note presents a rapid dual-element SimDis method combining hydrocarbon and sulfur analyses on an Agilent 7890A GC equipped with a Low Thermal Mass (LTM) column module. The goal is to reduce cycle time while maintaining agreement with ASTM D2887 specifications for reference gas oil samples.

Methodology and Instrumentation

The analysis used:

• Agilent 7890A GC with HT-PTV inlet (350 °C, split 30:1, 0.1 µL injection)
• LTM column module (DB-1, 5 m × 320 µm × 1 µm) with resistive heating (45→350 °C at 150 °C/min)
• Series detector configuration: flame ionization detector (FID) followed by Agilent 355 sulfur chemiluminescence detector (SCD)
• Helium carrier gas with pressure ramp 18→42 psi

The Agilent SimDis software performed two-channel processing, using calibration, blank, and quality control chromatograms for boiling point and sulfur recovery calculations.

Key Results and Discussion

The LTM-based method achieved a run time of approximately 2.5 minutes versus ~15 minutes on conventional air-bath ovens. For the ASTM D2887 reference gas oil:

• Boiling point percentiles (IBP to FBP) agreed within specification limits
• RSD across boiling range was 0.12–0.47 %

Retention time repeatability for C5–C40 calibration mixture showed RSDs of 0.02–0.15 %. Sulfur linearity (100–1500 ppm) yielded an R² above 0.999. Analysis of a high-sulfur light cycle oil resulted in hydrocarbon SimDis RSD <0.4 % and sulfur SimDis RSD <0.5 % (except FBP), with an average total sulfur of 260.8 ppm (RSD 4.83 %).

Benefits and Practical Applications

• Approximately six-fold reduction in analytical cycle time
• High precision and accuracy meeting ASTM D2887 criteria
• Simultaneous hydrocarbon and sulfur profiling in a single run
• Improved laboratory throughput for refinery QA/QC and research

Future Trends and Opportunities

Advancements in LTM technology may enable even faster temperature ramps and multi-column configurations for broader boiling range coverage. Integration with automated sampling and data-processing workflows will further increase productivity. Development of improved chemiluminescence detectors could enhance sulfur speciation capabilities.

Conclusion

The Agilent 7890A GC with LTM and dual detectors delivers rapid, precise simulated distillation of hydrocarbons and sulfur, aligning with ASTM D2887 requirements while significantly boosting sample throughput.

Reference

1. ASTM D2887-06a, Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography, ASTM International.
2. Agilent Low Thermal Mass (LTM) System for Gas Chromatography, Agilent Technologies publication 5989-8711EN.
3. Method Translation Software, Agilent Technologies.