Wasson Chromatography Corner 8

Significance of the Topic

The accurate measurement of trace sulfur species and aromatic impurities is essential to maintain process efficiency, ensure product quality and comply with environmental regulations in the petroleum and polymer industries.

Objectives and Overview

The newsletter outlines two specialized analytical protocols:

• Quantitative sulfur speciation in light petroleum distillates following ASTM D5623.
• Benzene quantification in 1-hexene and xylene determination in 1-octene at ppb levels for LLDPE feedstock quality control.

Methodology and Instrumentation

• Trace sulfur analysis using an Agilent GC coupled with a Sulfur Chemiluminescence Detector; meets ASTM D5623 with a 0.1 ppm LDL for key sulfur compounds.
• Aromatic impurity analysis on an Agilent 6890N GC with Pulsed Discharge Helium Ionization Detector; achieves LQLs of 100 ppb for benzene and 150 ppb for xylenes via dual-column separation and helium purification.
• Gas chromatograph maintenance procedure for air switch leak diagnosis and replacement to ensure reliable valve actuation.

Main Results and Discussion

Sulfur compounds present in light petroleum streams were successfully quantified at sub-ppm levels, supporting feedstock purity and catalyst protection.
Aromatics in alpha-olefin co-monomers were separated and measured at low ppb, preventing catalyst poisoning and addressing safety concerns.
The outlined maintenance workflow effectively restores gas chromatograph performance by resolving air switch leaks.

Benefits and Practical Applications

• Enables precise sulfur removal to protect catalysts and meet environmental standards.
• Delivers reliable detection of toxic aromatics in polymer feedstocks for product safety and process control.
• Provides straightforward maintenance guidance to minimize instrument downtime and analytical variability.

Future Trends and Applications

Integration of advanced detectors and micro-column technology promises faster, more sensitive trace analyses.
Automation and predictive diagnostics will further improve instrument uptime and method robustness.
Expansion of these low-level detection strategies to biofuels and renewable feedstocks is anticipated.

Conclusion

The combined methodologies and maintenance practices described offer robust, reproducible protocols for trace-level GC analysis in petrochemical and polymer applications, enhancing laboratory efficiency and product integrity.

References

• ASTM D5623 – Standard Test Method for Trace Sulfur Compounds in Light Petroleum Liquids by GC/SCD.