Sulfur in Hydrocarbons*

Importance of the Topic

Sulfur content in hydrocarbon materials directly influences fuel performance, emissions, handling safety and compliance with environmental regulations. Accurate determination of sulfur levels is essential for predicting combustion behavior, meeting legal limits and optimizing downstream processing in industrial and research laboratories.

Study Objectives and Overview

The primary aim of this application note is to demonstrate a robust method for quantifying sulfur in hydrocarbons boiling above 177 °C using combustion–infrared detection. Key objectives include establishing blank precision, calibrating with reference materials, and validating method performance across typical fuel and oil samples.

Methodology and Used Instrumentation

The approach combines high-temperature combustion with infrared absorption to measure evolved sulfur dioxide. Steps include:

• Instrument setup and conditioning with coal samples to stabilize the furnace and detector.
• Blank determination using a catalyst matrix (Com-Cat) to ensure low background sulfur (≤ 5 ppm at 1 g).
• Calibration with hydrocarbon reference standards covering a range of sulfur concentrations.
• Sample analysis: weighing 0.10–0.13 g of hydrocarbon into the catalyst bed, combusting at 1350 °C and detecting sulfur dioxide by infrared.

Critical method parameters: furnace temperature 1350 °C, baseline and endline delays of 3 s and 1 s respectively, minimum analysis time 90 s and comparator level 0.30%.

Main Results and Discussion

Calibration and verification runs on Residual Fuel Oil, White Mineral Oil and #2 Diesel Fuel demonstrated high precision and accuracy:

• Residual Fuel Oil (approx. 2.15 % S): mean 2.17 % S, SD 0.02 %.
• White Mineral Oil (approx. 0.101 % S): mean 0.100 % S, SD 0.001 %.
• #2 Diesel Fuel (approx. 0.031 % S): mean 0.031 % S, SD 0.001 %.

These results confirm linear response and low variability across a broad concentration range, meeting regulatory and quality-control requirements.

Benefits and Practical Applications

The described method offers:

• High throughput with analysis times under two minutes per sample.
• Low detection limits suitable for regulatory sulfur thresholds.
• Minimal sample preparation and a wide working range for diverse hydrocarbon matrices.

It is well suited for routine QA/QC in refineries, petrochemical laboratories and environmental monitoring.

Future Trends and Applications

Advances may include integration of automated sample feeders, enhanced detector sensitivity for ultra-low sulfur fuels and coupling with chemometric tools for rapid data interpretation. Expanding applicability to lighter hydrocarbons and blended fuels will further align the technique with evolving fuel specifications and sustainability goals.

Conclusion

This application note demonstrates a reliable combustion-IR protocol for sulfur analysis in heavier hydrocarbons. The method achieves excellent precision, meets industry standards and supports critical regulatory and performance assessments in fuel analysis.

Used Instrumentation

• CHN628 Series Elemental Analyzer with Sulfur Add-On Module (S628).
• Ceramic Boats (528-203) and Com-Cat catalyst (502-321).

References

• ASTM D1552 Standard Test Method for Sulfur in Petroleum Products.