Quantitative on-line analysis of sulfur compounds in complex hydrocarbon matrices

Area of Science:

• Analytical Chemistry
• Petroleum Chemistry
• Process Engineering

Background:

• Accurate quantification of sulfur-containing compounds is crucial for process optimization and environmental compliance in the petrochemical industry.
• Traditional methods often lack the sensitivity and specificity required for complex hydrocarbon matrices.
• Steam cracking processes generate complex effluents with diverse sulfur species that require advanced analytical techniques.

Purpose of the Study:

• To develop and validate an improved on-line method for sensitive measurement of sulfur compounds in complex matrices.
• To enable precise quantification of various sulfur species generated during steam cracking.
• To establish a robust analytical methodology applicable to diverse sulfur-containing feedstocks and conversion processes.

Main Methods:

• Implementation of an on-line sampling system coupled with comprehensive two-dimensional gas chromatography (GC×GC).
• Utilized dual detection: flame ionization detector (FID) for hydrocarbon matrix analysis and sulfur chemiluminescence detector (SCD) for sulfur compound quantification.
• Incorporated a refinery gas analyzer (RGA) with a thermal conductivity detector for low molecular weight sulfur compounds (H2S, COS).
• Optimized GC×GC-FID/-SCD settings for ppm-level analysis in olefin-rich hydrocarbon matrices.
• Employed 3-chlorothiophene as an internal standard for accurate quantification in steam cracking effluent.

Main Results:

• Achieved unprecedented sensitivity down to 1 ppm-w for various sulfur-containing compounds in complex hydrocarbon matrices.
• Successfully closed the sulfur balance during steam cracking of vacuum gas oil, identifying sulfur distribution (75% H2S, 13% thiophenes, 12% benzothiophenes).
• Demonstrated the utility of FID for verifying internal standard concentration, crucial for quantification accuracy.

Conclusions:

• The developed GC×GC-SCD methodology provides a highly sensitive and accurate on-line tool for sulfur compound analysis in complex hydrocarbon streams.
• The method is effective for monitoring sulfur species during steam cracking and similar conversion processes.
• The methodology's versatility allows its application to a wide range of sulfur-containing feedstocks and industrial processes like hydrocracking and pyrolysis.