Alternative Carrier Gases for ASTM D7213 Simulated Distillation Analysis

Significance of the topic

The boiling point distribution of crude oil and its fractions is a fundamental parameter for refinery feed characterization and process optimization. Simulated distillation (SimDist) by gas chromatography offers a rapid, reproducible, and automated approach to determine this distribution. Traditionally, helium has been the carrier gas of choice for ASTM Method D7213; however, recent approvals for nitrogen and hydrogen present cost, supply, and sustainability advantages.

Objectives and overview of the study

This work evaluates nitrogen and hydrogen as alternative carrier gases for ASTM D7213 SimDist analysis. Key aims include assessing chromatographic performance against method requirements (resolution between C50 and C52 >1, skewness between 0.5 and 2), comparing efficiencies and run times, and demonstrating method translation from helium to these substitutes.

Methodology and instrumentation

The study used a 5 m × 0.53 mm ID, 0.88 µm MXT®-1HT SimDist column on an Agilent 7890B GC with FID at 390 °C. A C5–C72 retention standard in carbon disulfide (1 wt % concentration) was injected (1 µL) via a programmable temperature vaporizing on-column inlet. Oven programs and carrier flows were adjusted for each gas:

• Helium: constant flow at 12 mL/min, oven 40 °C→380 °C at 10 °C/min (hold 10 min).
• Nitrogen: constant flow at 11.9 mL/min, same oven program as helium.
• Hydrogen: constant flow at 20 mL/min, translated oven ramp of 40 °C→380 °C at 16.9 °C/min (hold 5 min) using EZGC method translator.

Main results and discussion

Nitrogen provided the highest column efficiency at its optimum linear velocity but required much slower carrier flow, elongating run times. When substituted directly at the helium flow rate, the MXT-1HT column still met ASTM resolution and skewness criteria, though with reduced peak heights. Hydrogen exhibited an optimal velocity faster than helium, enabling a 25 % reduction in analysis time. A translated oven program delivered a 15-minute shorter elution of C72 compared to the helium method while preserving resolution (R(C50/C52)≈2.7). The column’s low bleed and robust stationary phase showed no performance loss after over 80 injections with hydrogen, and retention time RSDs for selected components remained below 1.1 %, typically under 0.1 %.

Benefits and practical applications

• Cost and supply resilience: nitrogen and hydrogen are more abundant and economical than helium.
• Method flexibility: MXT-1HT columns maintain ASTM D7213 criteria across gases without extensive revalidation.
• Throughput gains: hydrogen reduces run times by up to 25 %, improving laboratory productivity.
• Robustness: column coatings withstand high-temperature cycles and reducing environments.

Future trends and potential applications

Anticipated developments include broader adoption of hydrogen for faster SimDist workflows, integration of real-time method translation software, and design of specialty columns optimized for alternative gases. Advances in gas generation technologies (on-site H2 and N2) and enhanced stationary phases will further drive sustainable and high-throughput distillation analyses.

Conclusion

Alternative carrier gases, particularly nitrogen and hydrogen, are viable substitutes for helium in simulated distillation of petroleum fractions under ASTM D7213. With MXT-1HT SimDist columns and method translation tools, laboratories can achieve required resolution and repeatability while addressing helium scarcity, reducing costs, and improving analysis speed.

References

No external literature citations were provided in the original document.