Analysis of Gas Products from Carbon Dioxide Use Technologies by Gas Chromatography

Importance of the Topic

The growing concentration of carbon dioxide in the atmosphere drives research into technologies that convert CO2 into valuable chemicals and fuels. Reliable analysis of gas products from these processes is essential for understanding reaction pathways, optimizing catalysts, and ensuring process efficiency and safety.

Objectives and Study Overview

This study presents a multidimensional gas chromatographic (GC) method designed to analyze gases produced by CO2 reduction technologies. The aim is to achieve sensitive, accurate detection of permanent gases (H2, O2, N2, CO, CO2, CH4) and hydrocarbons (C1–C6) across a wide concentration range (0.1 ppm to 100%).

Methodology

The method combines:

• A thermal conductivity detector (TCD) for high‐concentration detection (100 ppm to 100%) of H2, O2, N2, CH4, CO, and CO2.
• A flame ionization detector (FID) with a nickel catalyst for low‐level detection (0.1 ppm) of CH4, CO, CO2, and C2–C6 hydrocarbons.
• A heart‐cut design using a series of gas sampling valves and capillary columns to selectively direct CO and CO2 through the catalyst while bypassing heavier hydrocarbons.
• A sequence of column switching steps to resolve light permanent gases on one column and hydrocarbons on another, followed by catalytic conversion and FID detection.

Used Instrumentation

The key hardware components include:

• Agilent 8890 GC with options for TCD (Option 220) and FID (Option 211) and auxiliary electronic pressure control (Option 301).
• 10-port sampling valve (Option 801) with 0.5 mL loop (Option 503) and precolumn backflush.
• Series bypass and selection valves for heart‐cut operation.
• Capillary columns: HP-PLOT Q PT (30 m × 0.53 mm, 40 µm) and HP-PLOT Molesieve (30 m × 0.53 mm, 50 µm).
• Nickel catalyst module (Option 307) installed upstream of the FID.
• Fused-silica restrictors for flow balancing and column interfaces.

Key Results and Discussion

Chromatograms generated by TCD and FID demonstrate:

• Clear resolution of H2, O2, N2, and CH4 by TCD.
• Effective heart‐cutting of CO and CO2 through the catalyst, with conversion to CH4 and detection by FID at 0.1 ppm levels.
• Simultaneous quantification of C2–C6 hydrocarbons with high sensitivity.
• A combined dynamic range that exceeds the capability of a single detector, enabling comprehensive analysis from trace to bulk concentrations.

Benefits and Practical Applications

This GC configuration provides researchers and industrial laboratories with:

• Robust, automated analysis of complex gas mixtures from CO2 conversion reactors.
• Wide dynamic range for both permanent gases and hydrocarbons in a single run.
• Reduced catalyst poisoning through selective bypass of heavy hydrocarbons.
• Data critical for catalyst development, process optimization, and quality control in CO2 utilization projects.

Future Trends and Potential Applications

Advancements may include:

• Integration with online process monitoring and control systems for real‐time feedback.
• Miniaturized or portable GC systems tailored for field deployment.
• Improved catalysts to lower detection limits and expand the range of detectable compounds.
• Application of machine learning for automated peak identification and data interpretation.

Conclusion

The multidimensional GC method combining TCD and catalyst-enhanced FID provides a powerful tool for analyzing gas products from CO2 reduction technologies. Its broad dynamic range, selective heart‐cut design, and robust performance address the analytical challenges posed by complex reaction streams.

References

• NASA Global Climate Change. Vital Signs of the Planet: Carbon Dioxide. https://climate.nasa.gov/vital-signs/carbon-dioxide Accessed June 2021.
• Nitopi, S.; et al. Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte. Journal of the American Chemical Society 2019, 141, 7610–7672.