Analysis of Impurities in Ethylene/Ethane and Propylene/Propane Streams Using a Pulsed Flame Photometric Detector (PFPD)

Significance of the Topic

Trace sulfur compounds such as hydrogen sulfide (H2S) and carbonyl sulfide (COS) in ethylene/ethane and propylene/propane streams pose serious risks by corroding equipment and poisoning catalysts, leading to reduced yields and compromised product quality.

Objectives and Study Overview

This study aims to develop a fast, reliable and robust gas chromatographic method coupled to a pulsed flame photometric detector (PFPD) to quantify sub-ppm levels of H2S and COS in C2 and C3 petrochemical feedstocks. An automated gas loop injection and optimized chromatographic separation ensure accuracy and speed.

Methodology

The analytical workflow involves automated gas loop injection into a gas chromatograph, separation on a low-sulfur capillary column, and detection using the PFPD in linearized mode. Calibration is achieved with certified permeation devices held at constant temperature to generate known sulfur concentrations.

Used Instrumentation

• OI Analytical S-Pro Select GC System with 5383 Pulsed Flame Photometric Detector (PFPD)
• Agilent J&W Select Low Sulfur GC Column (60 m × 0.32 mm ID)
• Permeation oven and wafer devices for H2S and COS calibration
• Automated 4-port/6-port valve system with Sulfinert®-coated sample path
• Split/splitless inlet, helium carrier gas, and volatiles interface at 200 °C

Main Results and Discussion

Calibration curves for H2S (0.17–6.60 ppmv) and COS (0.39–15.48 ppmv) showed excellent linearity (R = 0.999). Method detection limits were 0.013 ppm for H2S and 0.019 ppm for COS. System stability tests yielded deviations of 3.1% for H2S and 2.2% for COS. Chromatograms of real samples in various matrices confirmed clear separation of sulfur peaks from hydrocarbons with run times around 15 minutes.

Benefits and Practical Applications

The method provides rapid analysis with high sensitivity, benefiting quality control in petrochemical plants. The inert Sulfinert® pathway minimizes sample adsorption and allows routine verification of system integrity with gas standards.

Future Trends and Potential Applications

Future work may extend this approach to other trace sulfur species and more complex matrices. Integration with real-time monitoring, advanced column chemistries, and hyphenated detectors could further enhance sensitivity and throughput in industrial settings.

Conclusion

The described GC-PFPD method offers a robust and efficient solution for trace sulfur analysis in ethylene/ethane and propylene/propane streams, combining simple calibration, reliable detection, and strong system stability.

References

1. Ceresana, Market Study: Polypropylene, 3rd edition, Dec. 2014.
2. ASTM International, ASTM D-6228 Standard Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Flame Photometric Detection.
3. OI Analytical Application Note, Fast Determination of Impurities in Propane-Propylene Streams Using a Pulsed Flame Photometric Detector (PFPD) and a New Capillary PLOT Column, 2011.