Improved Gas Chromatograph Method for the Analysis of Trace Hydrocarbon Impurities in 1, 3-Butadiene

Significance of the Topic

Accurate analysis of trace hydrocarbons in 1,3-butadiene is essential for ensuring optimal performance of catalytic polymerization processes in synthetic rubber production. Even low-level impurities such as propadiene and methyl acetylene can disrupt polymer chain formation and degrade product quality.

Objectives and Study Overview

This work presents an improved gas chromatographic method using an Agilent 7890 Series GC, a High Pressure Liquid Injector (HPLI), and post-column backflushing to achieve high accuracy, precision, and reduced analytical cycles for detecting trace hydrocarbons in 1,3-butadiene.

Methodology and Instrumentation

• Instrument: Agilent 7890A GC configured with a High Pressure Liquid Injector and flame ionization detector (FID).
• Columns: Comparison of nonpolar HP-AL/KCl and polar GS-Alumina PLOT columns (50 m × 0.53 mm ID, 10–15 µm film).
• Sample introduction: HPLI ensured discrimination-free sampling of volatile liquid matrices.
• Chromatographic conditions: Helium carrier gas, tailored split ratios, programmed oven ramps, and a six-port valve for column backflushing.

Main Results and Discussion

The GS-Alumina column provided superior separation between 1,3-butadiene and propyne, enabling detection limits below 20 ppm with signal-to-noise ratios above 90. On HP-AL/KCl, reducing sample volume and adjusting split ratio mitigated coelution but offered lower sensitivity. Post-column backflushing eliminated a 30 min bake-out, shortened cycle time by over 50 %, and improved retention time repeatability (RSD ≤ 0.06 %). Analysis of a plant C4 sample confirmed robust detection of 4-vinylcyclohexene dimer alongside light hydrocarbons.

Benefits and Practical Applications

• Sensitive quantification of key trace impurities in monomer-grade butadiene.
• Significant reduction of analysis time and carryover through post-column backflushing.
• Enhanced retention time stability supporting routine QA/QC workflows.
• Unified method for both light hydrocarbons and heavier dimeric byproducts.

Future Trends and Potential Applications

Prospective developments include integration with mass spectrometric detection for confirmatory analysis, automated sampling for high-throughput quality control, and novel deactivated PLOT phases to extend the analytical scope to emerging contaminants.

Conclusion

The optimized GC method combining HPLI sampling, a polar GS-Alumina PLOT column, and post-column backflushing delivers rapid, reliable quantification of trace hydrocarbons in 1,3-butadiene, enhancing process control and product quality in petrochemical operations.

Used Instrumentation

• Agilent 7890A Gas Chromatograph
• High Pressure Liquid Injector (HPLI)
• Six-port backflushing valve
• GS-Alumina PLOT columns (50 m × 0.53 mm ID, 10–15 µm)
• Flame ionization detector (FID)

References

1. ASTM D2593-93 (2009) Standard Test Method for Butadiene Purity and Hydrocarbon Impurities by Gas Chromatography, ASTM International.
2. GBT 6017-2008 Butadiene for industrial use – Determination of Purity and Hydrocarbon Impurities by Gas Chromatography, Standardization Administration of China.
3. ASTM D2426-93 (2009) Standard Test Method for Butadiene Dimer and Styrene in Butadiene Concentrates by Gas Chromatography, ASTM International.
4. Agilent Technologies (2008) High-Pressure Injection Device for the Agilent 7890A and 6890 Series Gas Chromatographs, Publication 5989-8037EN.