GC Analysis of Sulfur Components in Propylene using a Pulsed Flame Photometric Detector

Significance of the Topic

The presence of hydrogen sulfide, carbonyl sulfide and methyl mercaptan in propylene streams poses significant risks due to corrosion, toxicity and odor issues. Trace level quantification of these sulfur compounds is essential to protect equipment integrity, ensure product quality and comply with environmental regulations.

Objectives and Study Overview

This application note evaluates the performance of a capillary PLOT column featuring a novel stationary phase for the separation of H2S, COS and CH3SH in a propylene matrix. The study aims to achieve baseline resolution of target analytes from the bulk hydrocarbon stream while minimizing matrix interference and quenching effects.

Methodology and Instrumentation

The analytical setup consisted of gas chromatography coupled to a pulsed flame photometric detector. Key parameters included:

• Column: Agilent J&W Select Low Sulfur, 60 m x 0.32 mm
• Oven: 65 °C isothermal
• Carrier gas: Helium at 2.0 mL/min
• Injector: Split 1:20 at 200 °C
• Detector: PFPD at 200 °C
• Sample: Propylene spiked with approximately 500 ppb of each sulfur compound

Main Results and Discussion

The novel column achieved baseline separation of H2S, COS and CH3SH from the propylene matrix, effectively preventing quenching and signal suppression. A representative chromatogram demonstrated distinct peaks for each analyte with detection limits down to 20 ppb for H2S. The system employed a gas sampling valve to improve sample introduction consistency.

Benefits and Practical Applications

This methodology offers high sensitivity and selectivity for trace sulfur analysis in light hydrocarbons. It supports routine quality control in petrochemical processes, helps prevent catalyst poisoning and reduces environmental emissions of odorous compounds.

Future Trends and Potential Applications

Advancements may include integration of online sampling systems for real-time monitoring, development of enhanced stationary phases for even lower detection limits and adaptation of the approach to other hydrocarbon matrices and sulfur compounds.

Conclusion

The Agilent J&W Select Low Sulfur column combined with GC-PFPD provides reliable trace analysis of sulfur compounds in propylene streams. Its excellent separation capabilities eliminate matrix interferences, enabling accurate quantification at ppb levels.

References

1. W. Wardencki (1998) Problems with the determination of environmental sulphur compounds by gas chromatography J Chromatogr A 793 1-19
2. Roger L Firor and Bruce D Quimby Comparison of Sulfur Selective Detectors for Low-Level Analysis in Gaseous Streams Agilent Technologies publication 5988-2426EN