High-Temperature Simulated Distillation System Based on the 6890N GC

Significance of the Topic

The boiling point distribution of mid and heavy petroleum distillates is a critical quality parameter for refinery feedstocks and products. Simulated distillation by gas chromatography offers a faster, safer, and more cost effective alternative to traditional laboratory distillation methods. By accurately mapping the boiling range, refiners can optimize processes such as hydrocracking, hydrotreating, visbreaking and deasphalting while meeting product specifications.

Objectives and Study Overview

This work presents an integrated simulated distillation system based on the Agilent 6890N GC configured for high-temperature performance. The goals are to implement ASTM D6352 and the extended D2887X protocols for boiling point distributions from 174 to 700 °C and 100 to 615 °C, respectively, and to demonstrate method accuracy, repeatability and ease of use with the Agilent SimDis software.

Methodology and Instrumentation

The system employs a 6890N GC with electronic pneumatic control, a flame ionization detector, and a 5 m×530 μm×0.15 μm DBHT-SIMD column. Sample introduction uses a high temperature programmable temperature vaporizer inlet air-cooled PTV for rapid heating to 420–440 °C at 200 °C/min followed by controlled hold and cooling. The Agilent 7683B autosampler delivers injection volumes of 0.05 to 2.0 μL. Calibration mixtures consist of Polywax standards and n-alkane blends covering carbon ranges from C5 to C100. The SimDis module within the GC ChemStation automates baseline correction, boiling point vs retention time calibration, start- and end-elute selection, and cut point calculation.

Main Results and Discussion

Blank runs with carbon disulfide establish a stable baseline. Calibration plots of boiling point versus retention time exhibit linearity across the required temperature range. Analysis of ASTM D6352 reference material shows boiling points at specific percent cuts matching consensus values within allowable tolerances. Eight replicate injections display high precision with standard deviations below 2 °C for most cut points. Heavy vacuum gas oil samples processed under D2887X conditions demonstrate repeatable distillation profiles with less than 4 °C variability for mid-range cuts.

Benefits and Practical Applications

• Substantial time savings compared to manual distillation, enabling higher sample throughput
• Reduced solvent usage and safer operation due to automated microinjections
• High reproducibility and compliance with ASTM methods D6352, D2887 and extended D2887X
• Flexible calibration to cover a wide boiling range from C5 to C100
• Integrated software simplifies setup, validation, reporting and data archiving

Future Trends and Applications

Advances may include coupling simulated distillation with mass spectrometry for compositional analysis, development of more thermally robust stationary phases to extend the boiling range beyond 700 °C, and incorporation of predictive machine learning models to anticipate refining behavior. Portable or field-deployable GC SimDis systems may support real-time process monitoring at remote sites.

Conclusion

The Agilent 6890N high-temperature simulated distillation system provides a robust, accurate and efficient solution for determining boiling point distributions of petroleum fractions. By combining a high temperature PTV inlet, stable metal column, precise autosampler, and dedicated SimDis software, the method meets stringent ASTM requirements and delivers reliable data for refinery process control and product specification.

References

• C Wang, R Firor Simulated Distillation System for ASTM D2887 Agilent Technologies publication 5989-2726EN 2005
• ASTM D6352-02 Standard Test Method for Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700 °C by Gas Chromatography Annual Book of Standards Volume 05.02 ASTM West Conshohocken PA USA