Ethylene Oxide and Propylene Oxide Analysis Using the Agilent 990 Micro GC

Importance of the Topic

Epoxides such as ethylene oxide (EO) and propylene oxide (PO) are key intermediates in the production of solvents, surfactants, and polymers. Rapid and accurate analysis of EO and PO, along with synthesis-related permanent gases, is critical for process optimization in both traditional high-temperature reactions and emerging electrocatalytic methods. The ability to detect ppm-level concentrations in under four minutes supports real-time monitoring in industrial and research environments.

Objectives and Article Overview

This application note describes a fast micro gas chromatography method using the Agilent 990 Micro GC to separate and quantify hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, ethylene, EO, propylene, and PO. The goal is to achieve high repeatability, low detection limits, and a short cycle time under four minutes by employing two backflush column configurations.

Methodology

• Dual backflush channels: 3+10 m CP-Molsieve 5Å for permanent gases and 1+10 m PoraPLOT U for CO2, olefins, and epoxides.
• Helium carrier gas with optimized pressures (125–150 kPa) and column temperatures (65–110 °C).
• Injection parameters: 40 ms injection time, 60 s sampling time, backflush times of 14–18 s.
• Analysis of two standard gas mixtures simulating EO and PO synthesis conditions.

Instrumentation

• Agilent 990 Micro GC with thermal conductivity detector.
• Agilent J&W CP-Molsieve 5Å (3+10 m backflush) channel for H2, O2, N2, CO separation.
• Agilent J&W PoraPLOT U (1+10 m backflush) channel for CO2, ethylene, EO, propylene, and PO separation.
• Standard gases from Air Liquide used for method validation.

Main Results and Discussion

• Full separation and quantification achieved in less than four minutes per run.
• Retention time repeatability below 0.2% RSD and area repeatability below 2.5% RSD over ten injections.
• Detection limits down to 1 ppm for CO2, 2 ppm for olefins, and 5 ppm for EO and PO.
• Backflush operation allowed venting of high-boiling compounds and maintained short analysis times.

Benefits and Practical Applications

• Enables online and field monitoring of epoxide synthesis processes.
• Low gas and power consumption facilitates portable and remote analysis.
• Supports rapid catalyst screening and batch analysis through sequential sampling.

Future Trends and Potential Uses

• Integration with automated sampling and control systems for continuous process optimization.
• Application to other epoxide production pathways and reactive gas monitoring.
• Use in environmental and safety applications due to low detection limits and high selectivity.

Conclusion

The Agilent 990 Micro GC with dual-column backflush configuration provides a rapid, robust, and sensitive method for analyzing EO, PO, and related permanent gases. Its high repeatability, sub-ppm detection limits, and cycle times under four minutes make it suitable for both industrial process control and laboratory research.

Reference

• Wan Ru, L et al. Chloride-Mediated Selective Electrosynthesis of Ethylene and Propylene Oxides at High Current Density. Science 2020, 368, 1228–1233.
• Yixuan, S. Research Progress on Electrochemical Synthesis of Ethylene Oxide and Propylene Oxide. Petrochemical Technology 2023, 52 11, 1596–1601.
• Hanyu, W et al. Boosting Electrocatalytic Ethylene Epoxidation by Single Atom Modulation. Angew Chem Int Ed 2024, 63, e202402950.
• Jie, Z. Fast Analysis of Natural Gas using the Agilent 990 Micro GC Natural Gas Analyzer. Agilent Technologies application note 2019.
• Toonen, A; van Loon, R. Hydrogen Detection with a TCD using Mixed Carrier Gas on the Agilent Micro GC. Agilent Technologies application note 2013.