UOP 603-13: Analysis of Trace CO and CO2 in bulk H2 and Light Gaseous Hydrocarbons by GC

Importance of the Topic

Accurate measurement of trace carbon monoxide and carbon dioxide in hydrogen and light hydrocarbon streams is essential for refinery operations, natural gas processing, fuel cell feedstock preparation, and catalyst protection. Even low‐level impurities of CO and CO2 can compromise catalyst performance, product quality, safety, and overall process efficiency.

Objectives and Study Overview

This application note presents the updated UOP 603-13 method implemented by AC Analytical Controls. The goal is to achieve a rapid (<5 minutes), robust, and highly reproducible gas chromatographic analysis of trace CO and CO2 in bulk hydrogen, methane and similar light gas matrices, while avoiding matrix interferences and protecting the methanizer catalyst from high methane loads.

Methodology

The analytical sequence begins with a controlled sample injection into a pre-column. A deans switch and back-flush valve direct the bulk matrix and high methane concentrations to vent, isolating CO and CO2 for transfer to the main analysis column. During separation, both CO and CO2 are converted to methane in an AC proprietary methanizer reactor. Final detection is achieved with a flame ionization detector using the external standard calibration approach.

Instrumentation

• Gas chromatograph configured with three automated valves, two separation columns, one inlet, and one FID detector
• Electronic pressure control (EPC) on all gas flows
• AC proprietary methanizer combined with a four-port heart-cut switching valve and deans switch to prevent bulk matrix entry
• Gas sampling/back-flush valve for precise sample injection and venting of unwanted components

Results and Discussion

Separation efficiency was demonstrated by baseline resolution (R > 1.5) for CO, CO2, and methane, with resolution between CO and methane exceeding 7. Repeatability tests (n=10 at 200 ppm) yielded relative standard deviations below 0.05% for retention times and peak areas. Linearity studies across five calibration blends (1.19–210 ppm within method scope; extended to 1000 ppm) produced correlation coefficients (R²) above 0.9999 for all analytes. Methanizer conversion efficiency was confirmed as response factors for CO and CO2 fell within 5% of the methane factor. Detection limits were calculated at 0.03 ppm for CO, 0.04 ppm for methane, and 0.10 ppm for CO2 (LOD), with respective LOQs of 0.11, 0.14, and 0.32 ppm. For high methane samples, the heart-cut valve effectively vents excess methane, preserving catalyst life and analytical robustness.

Benefits and Practical Applications

• Fast analysis cycle under five minutes
• Exceptional repeatability and linearity across trace concentration ranges
• Minimal matrix interference through heart-cut and back-flush design
• Enhanced catalyst longevity and method robustness via selective venting of bulk methane
• Accurate quantitation using a stable FID detector and reliable methanizer conversion

Future Trends and Potential Applications

Ongoing developments may include integration of on-line and real-time monitoring, further miniaturization of GC systems, advanced methanizer catalysts for extended lifetime, and expanded applicability to heavier hydrocarbon streams and complex gas mixtures. Coupling with data-driven analytics and remote diagnostics will enhance process control and predictive maintenance.

Conclusion

The AC UOP 603-13 system offers a fast, precise, and robust solution for quantifying trace CO and CO2 in hydrogen and light hydrocarbon streams. By combining an optimized valve configuration, proprietary methanizer technology, and FID detection, the method achieves stringent separation, sensitivity, and repeatability requirements, ensuring reliable quality control in industrial gas analysis.