Hydrocarbons, C1-C3 - Analysis of trace cyclopropane in propylene

Significance of the topic

Gas chromatography (GC) analysis of trace cyclopropane in propylene matrices is vital for petrochemical quality control. Cyclopropane impurities, even at low ppm levels, can affect downstream processes such as polymerization catalysts and product specifications. Achieving reliable detection and quantification supports regulatory compliance and process optimization.

Objectives and study overview

This application note evaluates the performance of the Agilent CP-SilicaPLOT column for selective separation of cyclopropane from a propylene matrix. The study aims to demonstrate high resolution, reproducible retention times, and quantifiable detection limits at the ppm scale.

Methodology

The analysis employs a capillary GC approach:

• Column: Agilent CP-SilicaPLOT (0.32 mm × 30 m, 4 μm film thickness)
• Temperature program: 50 °C (5 min), ramp at 5 °C/min to 100 °C, then 20 °C/min to 200 °C
• Carrier gas: Helium at 124 kPa
• Injection: Valve-based split injection (1:10) at 250 °C
• Detection: Flame ionization detector at 250 °C
• Sample volume: 250 μL of ppm-level standards in propylene

Main results and discussion

The CP-SilicaPLOT column exhibited unique selectivity by eluting cyclopropane ahead of propylene with baseline separation. Peak order included methane, ethane, ethylene, acetylene, propane, cyclopropane, propylene, and C4 hydrocarbons. The resolution between cyclopropane and propylene allows detection limits in the low ppm range with excellent repeatability and minimal peak tailing.

Benefits and practical applications

• High sensitivity for trace-level cyclopropane in propylene streams
• Short analysis time due to optimized temperature programming
• Robust separation minimizes interference from hydrocarbon matrix
• Simple method adapts to quality control and R&D laboratories

Future trends and potential applications

Advances may include coupling GC with mass spectrometry for enhanced selectivity, integration with automated sampling systems for online monitoring, and extending this methodology to other cyclic impurities in light hydrocarbon mixtures. Ongoing column development may further improve resolution and reduce analysis time.

Conclusion

The Agilent CP-SilicaPLOT column provides a reliable and highly selective GC solution for detecting trace cyclopropane in propylene. The method achieves low ppm quantification with robust performance, supporting critical quality control in petrochemical operations.