Sulfur compounds - Analysis of sulfur compounds in hydrocarbons by selective detection

Significance of the Topic

Detection and quantification of sulfur compounds in hydrocarbon streams are critical for environmental compliance, product quality and protection of catalytic systems. Accurate profiling of thiols and sulfides helps optimize fuel processing, reduce emissions and prevent catalyst deactivation.

Objectives and Study Overview

This application note describes a method for simultaneous analysis of fourteen sulfur species in hydrocarbon matrices. Using capillary gas chromatography coupled with a sulfur chemiluminescence detector (SCD), the study aims to achieve baseline separation and selective detection of volatile sulfur compounds directly injected from a hexane solution.

Methodology and Instrumentation

The method utilizes an Agilent CP-Sil 5 CB fused silica capillary column (0.32 mm×50 m, 5 μm film thickness) under a temperature program starting at 100 °C (2 min) ramping to 270 °C at 15 °C/min. Helium at 0.7 bar serves as the carrier gas. Samples are introduced via a split injector (1:10) at 250 °C. The sulfur chemiluminescence detector provides selective response to sulfur-containing analytes, enabling detection at concentrations as low as 50 ppm.

Instrumentation Used

• Gas chromatograph with fused silica capillary column CP-Sil 5 CB (Part no. CP7690)
• Helium carrier gas (70 kPa, 10 psi)
• Sievers sulfur chemiluminescence detector (SCD)
• Split injection valve (1:10 split) with temperature control

Main Results and Discussion

The optimized method achieved baseline resolution for fourteen sulfur compounds, including hydrogen sulfide, carbonyl sulfide, a series of alkyl mercaptans and sulfides up to heptanethiol. Although hexane co-eluted with propyl mercaptan, quantification remained unaffected. Chromatograms exhibited sharp peaks and reproducible retention times, confirming the method’s robustness.

Benefits and Practical Applications

• High selectivity and sensitivity for sulfur species in complex hydrocarbon samples
• Minimal sample preparation through direct injection
• Applicability in quality control for petrochemical and fuel industries
• Enhanced catalyst protection via precise sulfur monitoring

Future Trends and Applications

Emerging developments may include coupling SCD with mass spectrometry for compound identification, miniaturized GC-SCD systems for on-site analysis, and automated high-throughput setups. Integration into process analytical technology (PAT) platforms could enable real-time sulfur monitoring in refining operations.

Conclusion

The described GC-SCD method offers a robust, selective and rapid approach for analyzing key sulfur compounds in hydrocarbon matrices. Baseline separation and low detection limits ensure reliable monitoring for industrial quality control and environmental applications.