Heating Up Simulated Sistillation

Importance of the Topic

Simulated distillation (SimDist) is a cornerstone technique in petroleum analysis, providing detailed boiling point distributions that are essential for process optimization in refineries. Extending the detectable range of SimDist to very high boiling fractions allows operators to better understand the behavior of heavy crude oils, improve yield of valuable distillate streams, reduce vacuum residue, and even detect adulteration by heavy blending components.

Objectives and Study Overview

This work describes the development and application of a High Temperature Simulated Distillation (HTSD) method capable of measuring boiling points up to 1300–1380°F. The primary goals were to push beyond the established ASTM D2887 limit of 1000°F, demonstrate precise boiling point distribution for heavy petroleum cuts, and explore the method’s value in refinery operations and crude integrity assessment.

Methodology and Instrumentation

The HTSD approach relies on capillary gas chromatography with specialized thin-film columns:

• Column dimensions: 0.53 mm I.D., film thickness 0.05–0.15 µm (phase ratio 883–2650)
• Stationary phase: 100 % methyl silicone with enhanced deactivation for low bleed
• Column substrate: stainless steel tubing for thermal robustness up to 430 °C
• Injection: OPTIC temperature programmable vaporization (PTV) for reproducible sample introduction
• Carrier gas: inert gas (e.g., helium) at controlled flow to ensure sharp peaks

Thin films minimize retention of high-boiling hydrocarbons while offering sufficient capacity for early fractions. Sample concentrations (0.1–2 % wt/wt) and cool on-column or PTV techniques prevent discrimination of heavy components. All GC components, including high-temperature oven, injector, and column, were pushed to the upper limits of performance.

Main Results and Discussion

Chromatograms obtained with the DB-HT Sim Dis column show:

• Clear baseline return at the final boiling points, confirming minimal bleed and accurate endpoint detection
• Boiling point distribution spanning from n-C3 (via cryogenic injection) up to C110 equivalent with effective range from 156 °F (69 °C) to 1355 °F (735 °C)
• Reproducible profiles for two reference oils, validating precision for heavy crude applications

The extended range reveals detailed late-eluting fractions critical for assessing vacuum tower performance and detecting high-boiling contaminants or deliberate adulterants, such as pitch blends above 1000 °F.

Benefits and Practical Applications

The HTSD method offers multiple advantages:

• Refinery optimization: Accurate yields of gas oil and vacuum residue characterization
• Quality control: Detection of heavy-end adulteration in crude feedstocks
• Process monitoring: Tracking changes in crude composition during blending or upgrading
• Regulatory compliance: Meeting ASTM guidelines while extending analytical capabilities

Future Trends and Opportunities

Advances likely to further enhance HTSD include:

• New column materials with higher thermal limits and even lower bleed profiles
• Integration of high-resolution mass spectrometry for compound-specific distillation curves
• Automated sample handling and advanced data processing algorithms to improve throughput
• Application of HTSD to unconventional feedstocks, such as bitumen and bio-derived heavy oils

Conclusion

The High Temperature SimDist method significantly extends the boiling point range accessible by capillary GC SimDist, providing precise, reproducible data up to 1380 °F. This enables refineries and laboratories to optimize heavy crude processing, ensure product quality, and detect fraudulent blending. Continued innovation in column technology and detection systems will further solidify HTSD as an indispensable tool in modern petroleum analytics.

Instrumental Setup

• Gas chromatograph with high-temperature oven capable of 430 °C operation
• 0.53 mm I.D. stainless steel WCOT column, 0.05–0.15 µm methyl silicone stationary phase (DB-HT Sim Dis)
• OPTIC temperature programmable vaporization injector
• Carrier gas supply and cryogenic cooling accessories for low-boiling end calibration

References

1. Annual Books of ASTM Standards. Vols. 5.0, 5.02, and 5.03. American Society for Testing and Materials, Philadelphia, PA, 1990.
2. Villalanti, D.C. Personal communication, Triton Analytics Corp., Houston, TX, 1995.
3. Vickers, A.K., Hastings, M., Rood, D., Lautamo, R. An Improved Deactivation Process for Metal Tubing Used in Capillary Gas Chromatography Columns. Pittsburgh Conference and Exposition, New Orleans, LA, March 5–10, 1995.