Pyrolysis of Oil Shale in Hydrogen at Elevated Pressure

Significance of the topic

Determining the hydrocarbon potential of oil shale is essential for energy exploration and resource evaluation. Analytical pyrolysis coupled with gas chromatography–mass spectrometry (GC–MS) provides a rapid approach to characterize complex kerogen-derived compounds. Integrating catalytic conversion under hydrogen pressure can enhance molecular transformation, yielding deeper insight into shale composition and potential upgrading pathways.

Objectives and study overview

This application brief describes an on-line sample preparation strategy in which ground oil shale undergoes pyrolysis in a hydrogen atmosphere at elevated pressures (200 and 400 PSI), followed by catalytic treatment in a platinum reactor. The goal is to compare product distributions under inert versus hydrogen environments and to demonstrate pressure-driven aromatic formation.

Methodology and instrumentation

A CDS Pyroprobe 5200 HP-R interface was used for flash pyrolysis of shale at 750 °C for 15 s. Evolved vapors were transferred through a heated transfer line and valve oven (both at 325 °C) into a platinum reactor held at 500 °C under hydrogen flow (40 mL/min). Two hydrogen pressures, 200 PSI and 400 PSI, were evaluated. Separation and detection employed a PerkinElmer Clarus® GC/MS system with a 30 m × 0.25 mm 5% phenyl column, helium carrier (50:1 split), and an injector temperature of 325 °C. The GC oven was programmed from 40 °C to 300 °C at 10 °C/min, and the mass spectrometer scanned m/z 35–600.

Main results and discussion

Under conventional pyrolysis (no hydrogen), chromatograms display a complex mixture of long-chain aliphatics, aromatics, and branched compounds. Introducing hydrogen at 200 PSI and passing products through the Pt reactor reduces unsaturated bonds, induces additional cracking, and produces some aromatics. At 400 PSI, further pressure-promoted cyclization and dehydrogenation markedly increase aromatic yields. These trends illustrate how hydrogen pressure and catalytic treatment shift product distributions toward more stable, lower-polarity species.

Benefits and practical applications

• Enhanced compositional profiling of kerogen and bound oil fractions.
• Simultaneous pyrolysis and catalytic upgrading in a single workflow.
• Potential to simulate in-situ hydrogenation conditions for resource evaluation.
• Rapid screening tool for QA/QC in shale oil research and processing.

Future trends and potential applications

Further developments may include alternative catalysts (e.g., nickel, palladium), variable pressure and temperature regimes, and coupling with high-resolution MS or two-dimensional GC to achieve finer compound speciation. Portable pyrolysis reactors with real-time data processing could enable field-based shale evaluation. Integration with chemometric analysis and machine learning may improve prediction of reservoir quality.

Conclusion

On-line pyrolysis of oil shale in hydrogen at elevated pressure, combined with catalytic conversion, offers a powerful approach to generate and analyze simplified hydrocarbon profiles. Pressure-dependent aromatic formation underscores the method’s versatility for resource characterization and potential process simulation.

Reference

Greenwood P., Sherwood N., Willett G., Chemical examination of some petroleum source rocks by laser pyrolysis mass spectrometry and flash pyrolysis gas chromatography mass spectrometry, J. Anal. Appl. Pyrolysis, 31 (1995) 177–202.