PYROLYSIS-GC×GC-QTOF FOR IMPROVED CHARACTERIZATION OF CRUDE OILS

Importance of the Topic

Detailed characterization of crude oils is essential for optimizing refinery processes, monitoring product quality and assessing environmental impact. The vast complexity and diversity of compounds in crude demand advanced analytical strategies.

Study Objectives and Overview

This study demonstrates how pyrolysis coupled to comprehensive two-dimensional gas chromatography with quadrupole time-of-flight detection (py-GC×GC-QTOF) can improve compositional profiling and comparison of crude oil samples from different origins.

Methodology and Instrumentation

Three crude oils (Samples A, B and C) were analyzed by direct pyrolysis at 750 °C for 15 s. The analytical setup included:

• CDS Pyroprobe 5200 for controlled thermal degradation
• Agilent 7890B GC with Zoex ZX2 cryogen-free modulator for two-dimensional separation
• Agilent 7200B QTOF in Extended Dynamic Range mode at 50 Hz for high-resolution mass detection
• GC Image HR software for visualization, differential imaging and template-based processing

Main Results and Discussion

Two-dimensional chromatograms resolved overlapping classes and elucidated chemical distributions:

• Sample B: predominance of aromatics with moderate paraffins and low naphthenes.
• Sample A and C: naphthenic-rich profiles; Sample C contained more paraffins and fewer aromatics.

The differential imaging tool highlighted subtle sample-specific peaks. High-resolution mass accuracy enabled confident identification of sulfur-containing heterocycles, including isomeric dibenzothiophenes with varied alkyl substitution. Automated template screening quantified benzothiophene and dibenzothiophene groups, revealing differences in total and subgroup sulfur distributions.

Benefits and Practical Applications

The py-GC×GC-QTOF approach offers:

• Superior separation of complex hydrocarbon mixtures at class and isomer levels.
• Effective fingerprinting for rapid sample comparison.
• High selectivity and accurate mass identification of target and unknown compounds.
• Enhanced detection of heteroatom species crucial for industry quality control.

Future Trends and Potential Applications

Emerging developments may include automated chemometric workflows for predictive modeling of crude properties, expanded spectral libraries for unknown screening, and faster or miniaturized modulators to increase throughput or enable field analysis.

Conclusion

Pyrolysis-GC×GC-QTOF delivers enhanced resolution, comprehensive profiling and reliable heteroatom speciation for crude oils, supporting improved decision-making in refining, quality assurance and research.

Reference

• Peroni D. Pyrolysis-GC×GC-QTOF for Improved Characterization of Crude Oils. JSB Application Note, 2018.