Using Alternative Carrier Gases with Accelerated ASTM D2887 Simulated Distillation Analysis

Significance of the Topic

Simulated distillation by ASTM D2887 is a cornerstone technique for characterizing petroleum fractions (C5–C44) by boiling point distribution. Accelerated SimDist (Procedure B) enables faster turnaround for refinery monitoring, product specification, and process optimization. Recent amendments allowing hydrogen or nitrogen as carrier gases offer potential cost savings and supply reliability compared to helium.

Objectives and Study Overview

• Demonstrate the feasibility of replacing helium with hydrogen or nitrogen while preserving retention times and chromatographic resolution.
• Apply Restek’s EZGC online method translator to establish equivalent method parameters for each carrier gas.
• Simplify method revalidation, maintain accuracy for process control, and reduce operating costs.

Methodology and Instrumentation

• Column: MXT®-1HT SimDist, 10 m × 0.53 mm ID, 0.88 µm PDMS stationary phase.
• Gas chromatograph: Agilent 7890B GC with flame ionization detector at 360 °C.
• Temperature program: 60 °C initial (hold) to 360 °C at 35 °C/min.
• Carrier gases (constant flow): helium 26 mL/min; hydrogen 22.35 mL/min; nitrogen 25.5 mL/min.
• Make-up and auxiliary flows: N₂ make-up 20–30 mL/min; H₂ 30–40 mL/min; air 360–400 mL/min.

Main Results and Discussion

• Retention Time Preservation
  • Method translation produced retention times for C5–C44 that matched helium-based results for both hydrogen and nitrogen methods.
• Chromatographic Performance
  • Hydrogen: demonstrated superior efficiency at fast linear velocities (>100 cm/s), yielding the narrowest peaks. Relative response factor deviations were <10%, and asymmetry ranged from 0.96 to 1.19.
  • Nitrogen: showed broader peaks due to lower optimal velocity, but resolution remained within ASTM criteria. Response factor deviations were <5%, asymmetry between 1.01 and 1.15.
• Blank and Reference Gas Oil Analysis
  • Stable baselines with no crossover between blank and sample chromatograms for all gases.
  • Boiling point distributions of the reference gas oil fell within allowable ASTM D2887 windows, confirming method accuracy.

Benefits and Practical Applications

• Significant cost reduction by switching from helium to in-house–generated hydrogen or nitrogen.
• Streamlined method translation minimizes revalidation efforts and preserves compound identification tables.
• Maintained analytical performance supports quality control, refinery optimization, and contractual specifications.
• Accelerated analysis timelines improve laboratory throughput and real-time decision making.

Future Trends and Potential Applications

• Wider adoption of automated method translation tools integrated with laboratory information management systems.
• Extension of carrier gas alternatives to other simulated distillation methods and column chemistries.
• Adaptive carrier gas selection strategies based on sample matrix complexity and throughput demands.
• Coupling SimDist with advanced detection (e.g., mass spectrometry) or multidimensional GC for enhanced hydrocarbon profiling.

Conclusion

By leveraging method translation software, laboratories can smoothly replace helium with hydrogen or nitrogen in accelerated ASTM D2887 SimDist without compromising accuracy or resolution. Both alternative gases meet performance criteria, reduce costs, and simplify validation, supporting efficient petroleum analysis and process control.