Thermal Decomposition of Sulfur Compounds and their Role in Coke Formation during Steam Cracking of Heptane

Sulfur-containing compounds play a key role in many industrial processes. Particularly for the steam cracking process, they have been linked with increased olefin selectivity, CO formation, and coke inhibition. The influence of four different sulfur-containing additives, methanedithione, (methyldisulfanyl)methane, (methylsulfanyl) methane, and dimethyl sulfoxide, on product selectivity, coke deposition, and CO production during steam cracking of a surrogate light naphtha feed is investigated. The use of online comprehensive 2D gas chromatography with sulfur chemiluminescence detection (GCxGC-SCD) is the key enabling technology to characterize the sulfur compounds. Steam cracking in a pilot-plant unit revealed that all studied sulfur compounds are efficient in reducing the CO yield. Simultaneously, they strongly promote coke.