Sulfur Detection at ppb Levels in Light Hydrocarbon Streams

Importance of the Topic

Light hydrocarbon streams used as feeds for polyolefin production often contain sulfur compounds at concentrations below 100 ppb. Even trace levels of hydrogen sulfide, carbonyl sulfide and mercaptans can poison Ziegler‐Natta and metallocene catalysts, leading to drastically reduced polymer yields.

Study Objectives and Overview

The primary goal of this work is to assess a new super‐permeable porous layer open tubular column (“Select for Low Sulfur”) for its ability to separate and detect sulfur species at low ppb levels in propylene and ethylene matrices using gas chromatography.

Methodology

Standard gas mixtures containing H2S, COS and methyl mercaptan in nitrogen and hydrocarbon matrices were injected via a 1 mL sample loop with variable split ratios. Temperature programming and isothermal conditions were applied to optimize separation. Detection was performed primarily with a pulsed flame photometric detector.

Used Instrumentation

• Agilent J&W Select for Low Sulfur PLOT column, 60 m × 0.32 mm ID, super‐permeable porous stationary phase
• Gas chromatograph equipped with PFPD; compatible with sulfur chemiluminescence detector (SCD) and atomic emission detector (AED)
• Gas sample loops, helium carrier gas

Key Results and Discussion

The new column achieved near‐100% recovery of H2S at ppb levels with excellent chromatographic resolution between sulfur compounds and C1–C4 hydrocarbons.

Detection limits for H2S, COS and methyl mercaptan were in the range of 20–30 ppb. Calibration curves exhibited linearity with R² > 0.997 over a 0–60 ppb range. Repeatability studies using SCD showed relative standard deviations below 2% for all three sulfur species.

In propylene and ethane/propane/propylene matrices, hydrogen sulfide and carbonyl sulfide peaks were well separated from co‐eluting hydrocarbons, minimizing detector quenching and ensuring reliable quantitation.

Benefits and Practical Applications

The Select for Low Sulfur column offers a one‐dimensional GC method with robust separation of sulfur species from light hydrocarbons, high sensitivity at low ppb levels and mechanical stability without particle bleed. This makes it well suited for quality control of polymer feedstocks, refinery stream monitoring and catalyst performance studies.

Future Trends and Opportunities

Further development may focus on extending the approach to ethylene matrices, coupling with mass spectrometry for structural identification, and integrating on‐line monitoring systems for continuous process control. Advances in stationary phase materials and detector technologies could push detection limits into the sub‐ppb range.

Conclusion

The Agilent J&W Select for Low Sulfur column demonstrates superior recovery, selectivity and sensitivity for low‐level sulfur analysis in hydrocarbon streams, providing a reliable tool for industrial and research laboratories concerned with catalyst protection and feedstock quality.