Determination of Hydrocarbon Components in Petroleum Naphthas

Importance of the topic

The determination of hydrocarbon components in naphthas is crucial for process control, product quality, regulatory compliance, and mathematical modeling in refining operations. Detailed compositional data enables optimization of reforming, alkylation, and feedstock characterization.

Objectives and overview of the study

This study aimed to adapt ASTM D5134 methodology to a fast GC-TOFMS platform (LECO Pegasus II) to reduce analysis time from 122.5 min to 25 min, while maintaining accurate identification and quantification of hydrocarbons. Performance was evaluated using a PIANO standard and industrial naphtha process samples.

Used instrumentation

• Gas chromatograph: Agilent 6890 with EPC control
• Column: Supelco SPB-1, 30 m × 0.25 mm × 0.25 μm
• Injector: Split ratio 400:1 at 225 °C
• Oven program: 40 °C (2 min) to 250 °C at 10 °C/min (hold 2 min)
• Carrier flow: 1.8 ml/min constant
• Mass spectrometer: LECO Pegasus II GC-TOFMS in EI mode
• Mass range: 45–450 amu, acquisition rate: 25 spectra/s (up to 500 spectra/s capability)

Main results and discussion

GC-TOFMS achieved a five-fold reduction in runtime compared to standard D5134. Fast acquisition and spectral continuity enabled deconvolution of closely eluting peaks, as demonstrated with the PIANO standard. Automated peak finding and library search identified 139 components in the standard and up to 170 compounds in naphtha samples at S/N ≥ 200:1. Area percentage and retention index calculations were performed accurately despite coelutions.

Benefits and practical applications

• Reduced analytical cycle time improves throughput in petrochemical QA/QC laboratories.
• Enhanced resolution of coelutions ensures reliable qualitative and quantitative data.
• Automated data processing streamlines peak detection, deconvolution, and library matching.
• Method adaptability supports regulatory compliance and process modeling inputs.

Future trends and applications

Advances in TOF-MS hardware and software will further shorten analysis times and increase spectral fidelity. Integration with multidimensional GC and machine-learning algorithms promises improved discrimination of complex mixtures. The approach may be extended to other petroleum fractions and environmental monitoring.

Conclusion

The modified ASTM D5134 approach on a GC-TOFMS platform offers rapid, high-resolution hydrocarbon profiling in petroleum naphthas. Leveraging fast acquisition and deconvolution capabilities enhances analytical performance and operational efficiency.

References

• ASTM D5134—Standard Test Method for Hydrocarbon Types in Naphthas by Gas Chromatography
• LECO Pegasus II GC-TOFMS User Manual, LECO Corporation, 2010
• Agilent 6890 GC System Documentation
• Supelco SPB-1 Capillary Column Specifications