Detailed Separation of C1-C5 Light Hydrocarbons on CP-Al2O3/Na2SO4 PLOT GC Column

Importance of the Topic

Detailed separation of C1–C5 light hydrocarbons is essential for quality control, safety and process optimization in refinery, natural gas and LPG streams. Accurate quantification of impurities at trace to percent levels supports regulatory compliance and efficient downstream processing.

Objectives and Study Overview

This application demonstrates the use of a CP-Al2O3/Na2SO4 PLOT GC column to resolve 18 C1–C5 hydrocarbons, including structural and positional isomers, within a 20-minute run. The goal is to showcase selectivity, peak shape and robustness for routine hydrocarbon profiling.

Methodology and Instrumentation

The analysis employed gas chromatography with flame ionization detection (GC-FID) using the following setup:

• Column: CP-Al2O3/Na2SO4 PLOT, 50 m × 0.32 mm ID, film thickness 5 µm
• Carrier gas: hydrogen at constant pressure (100 kPa)
• Oven program: 70 °C hold, 3 °C/min to 170 °C
• Injection: split 1:50, injector at 250 °C, 5 µL gas sample
• Detector: FID at 275 °C

Main Results and Discussion

The CP-Al2O3/Na2SO4 column achieved baseline separation of saturated and unsaturated C1–C5 species in under 20 minutes. Peak shapes were generally sharp, with slight tailing observed for acetylene and propyne due to stronger interactions with the polar Na2SO4 deactivation layer. Molar concentrations ranged from 0.199 % to 24.9 %, demonstrating reliable quantitation across a wide dynamic range.

Benefits and Practical Applications

The polar Na2SO4 deactivation on alumina enhances retention of unsaturated and branched hydrocarbons, improving isomeric resolution over non-polar columns. The column tolerates bake-out to 200 °C without loss of performance, offering stability for high-throughput quality assurance in petrochemical plants, natural gas monitoring and LPG specification testing.

Future Trends and Opportunities

Advancements may include novel deactivation chemistries to reduce tailing of polar species, integration with mass spectrometry for definitive identification and development of shorter, high-efficiency PLOT columns for faster cycle times. Online GC-FID systems are expected to further automate process monitoring in real time.

Conclusion

The CP-Al2O3/Na2SO4 PLOT GC column provides a robust and selective solution for routine detailed analysis of C1–C5 hydrocarbons. Its high resolving power and thermal stability make it well suited for petrochemical and gas industry requirements.

Reference

• Provoost L. Detailed Separation of C1–C5 Light Hydrocarbons on CP-Al2O3/Na2SO4 PLOT GC Column. Agilent Technologies Application Note SI-02644, 2010.
• Gasterra. What Is Natural Gas? http://www.gasterra.com/naturalgas/Pages/Whatisnaturalgas.aspx
• WiseGeek. What Is Refinery Gas? http://www.wisegeek.com/what-is-refinery-gas.htm
• Australian Government Dept. of Environment. LPG Fuel Quality Standards FAQ. http://www.environment.gov.au/atmosphere/fuelquality/standards/lpg/faq.html#lpg