Rapid analysis of heavy oil catalytic cracking products using pyrolysis GC (2) Analysis of short-chain hydrocarbons (C2-C6) produced by different catalysts

Importance of the Topic

Catalytic cracking of heavy oil is crucial for converting high-boiling hydrocarbons into valuable lighter fractions used as fuels and chemical feedstocks. Rapid and precise analysis of short-chain products informs catalyst efficiency and process optimization in refining operations.

Study Objectives and Overview

This study evaluates the formation of C2–C6 hydrocarbons generated from direct-desulfurized heavy oil subjected to catalytic cracking with three zeolite-type catalysts. It aims to compare product distributions and intensities to assess catalyst performance.

Methodology and Instrumentation

The experimental workflow involved dissolving heavy oil in toluene, mixing with catalyst at an 18:1 mass ratio, evaporating solvent, and pyrolyzing at 500 °C using a Multi-Shot Pyrolyzer directly interfaced with a GC/MS system. Cryo-focusing of volatiles was performed with a MicroJet Cryo-Trap, followed by separation on a UA+-1 dimethylpolysiloxane column under programmed temperature conditions. Three catalysts were tested: equilibrium catalyst, ZSM-5 (SiO2/Al2O3=150), and beta zeolite (SiO2/Al2O3=300).

Main Results and Discussion

• All catalysts produced C2–C6 paraffins and olefins, with propylene as the dominant product.
• ZSM-5 yielded lower overall signal intensities compared to the equilibrium catalyst and beta zeolite, indicating different cracking activity or selectivity.
• Beta zeolite and equilibrium catalyst showed comparable peak distributions but varied intensities for individual C4–C6 species.

Key chromatographic trends highlight the influence of zeolite structure and acidity on light hydrocarbon production.

Benefits and Practical Applications

• Allows rapid catalyst screening for refining processes by directly correlating catalyst type with light fraction yields.
• Supports optimization of catalytic cracking conditions to maximize valuable olefins, particularly propylene for petrochemical uses.
• Provides a streamlined method for on-site analysis without extensive sample preparation.

Future Trends and Potential Applications

The integration of high-throughput pyrolysis GC/MS platforms with advanced data analytics could further accelerate catalyst development. Emerging catalysts with tailored acidity and pore structures may enable selective production of targeted olefins. Furthermore, coupling with real-time process monitoring could enhance refinery efficiency and adaptability to feedstock variations.

Conclusion

This work demonstrates that pyrolysis GC/MS with cryo-trapping is an effective approach for rapid evaluation of catalyst performance in heavy oil cracking. The contrasting behaviors of equilibrium catalyst, ZSM-5, and beta zeolite underscore the importance of catalyst selection in controlling product distributions.

Reference

• Frontier Laboratories Ltd. Multi-functional Pyrolyzer® Technical Note PYA1-105E: Rapid analysis of heavy oil catalytic cracking products using pyrolysis GC (2) Analysis of short-chain hydrocarbons (C2-C6) produced by different catalysts.