Restek's Capillary GC Columns for Simulated Distillation of Petroleum Fractions

Importance of the Topic

Simulated distillation (SimDist) is a cornerstone analytical technique in petroleum chemistry, enabling rapid and reproducible assessment of boiling point distributions for complex hydrocarbon mixtures. By replacing labor-intensive traditional distillation with gas chromatography (GC) under programmed temperature conditions, laboratories can achieve higher throughput, improved repeatability, and enhanced safety.

Objectives and Study Overview

The primary goal of the study is to demonstrate the performance of Restek’s Rtx®-2887 and MXT®-2887 capillary columns in ASTM D-2887 simulated distillation. Key objectives include verifying column resolution, bleed characteristics, and peak symmetry against standard specifications, and illustrating method calibration and sample analysis workflows.

Methodology and Instrumentation

Instrumentation and conditions were tailored to meet ASTM D-2887 requirements:

• Columns: 10 m × 0.53 mm ID, 2.65 μm film thickness Rtx®-2887 (fused silica) or MXT®-2887 (Silcosteel® stainless steel).
• Stationary Phase: Crossbond® 100% dimethyl polysiloxane.
• Carrier Gas: Nitrogen at 112 cm/s linear velocity (15 mL/min).
• Injection: 1.0 μL direct injection of a 0.1–0.01 wt % n-alkane standard in CS₂.
• Oven Program: 35 °C to 360 °C at 15 °C/min, holding 5 min.
• Injector/Detector Temperature: 360 °C.

Principal Results and Discussion

Calibration of n-alkanes from C₅ to C₄₄ was achieved in under 23 min, yielding a linear retention time–boiling point correlation. The columns delivered a C₁₆/C₁₈ resolution of 8.7 (ASTM range 3–10) and heptane skew factor of 0.92 (ASTM range 0.5–2.0). Baseline stability and low bleed confirmed robust stationary phase performance. Analysis of ASTM Reference Gas Oil #1 produced a reproducible boiling range profile, illustrating accurate cumulative area slicing for distillation curves. Limited theoretical plates align with the technique’s objective of obtaining boiling range distribution rather than full component resolution.

Benefits and Practical Applications

• High throughput analysis of jet fuels, kerosenes, diesels, and gas oils.
• Reduced analysis time and conditioning compared to packed columns.
• Extended column lifetime due to cross-bonded phase stability.
• Inter-laboratory comparability ensured by adherence to ASTM D-2887 parameters.

Future Trends and Opportunities

Advancements may include coupling SimDist with high-resolution detectors for compositional insight, applying alternative inert carriers (e.g., hydrogen) for faster runs, and integrating machine learning for automated curve fitting and anomaly detection. Ruggedized column formats like MXT®-2887 will support field-deployable GC systems in remote or harsh environments.

Conclusion

Restek’s Rtx®-2887 and MXT®-2887 capillary columns meet and exceed ASTM D-2887 requirements for simulated distillation of petroleum fractions. Their optimized dimensions, stationary phase robustness, and proven chromatographic performance offer laboratories a reliable, high-efficiency alternative to packed columns for boiling range determination.

References

1. L.E. Green, L.J. Schumauch, J.C. Worman, Anal. Chem. 36 (1964) 151.
2. L.E. Green, Hydrocarbon Processing, May 1976, p. 50.
3. ASTM Test Method D-2887, 1996 Annual Book of ASTM Standards, Vol. 5.02.