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

Abstract

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 (GC×GC‐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.

CoatAlloy Barrier Coating for Reduced Coke Formation in Steam Cracking Reactors: Experimental Validation and Simulations

“…It was demonstrated that the coking rates were increased when a certain amount of sulfur-containing compound was continu-ously added to the feed. 13,14,27,28 This is consistent with the measured lower amount of coke during this cycle compared to the previous cycles. This implies that the continuous addition of DMDS enhances coke deposition.…”

“…The formed thyil radicals can further react with radicals in the coke layer which leads to more active sites at the surface available to gas-phase radicals for noncatalytic heterogeneous coke formation. It was demonstrated that the coking rates were increased when a certain amount of sulfur-containing compound was continuously added to the feed. ,,, This is consistent with the measured lower amount of coke during this cycle compared to the previous cycles. This implies that the continuous addition of DMDS enhances coke deposition.…”

Investigation of the effect of presulphidation on coke deposition on 25Cr‐35Ni alloy during ethane steam cracking

“…Many scholars have widely studied the influence of sulphur species as coke inhibitors, which is unclear. [2,[11][12][13][14][15][16] Tan and Baker [12] studied the effects of different sulphides (DMDS, dimethyl sulphide [DMS], and H 2 S) on the rate of coke formation on nickel-iron particles. Also, Olahova et al [16] investigated the thermal decomposition of sulphide compounds such as CS2, DMDS, DMS, and DMSO and their effects on the rate of coke deposition and CO production during the heptane steam cracking process.…”

“…[2,[11][12][13][14][15][16] Tan and Baker [12] studied the effects of different sulphides (DMDS, dimethyl sulphide [DMS], and H 2 S) on the rate of coke formation on nickel-iron particles. Also, Olahova et al [16] investigated the thermal decomposition of sulphide compounds such as CS2, DMDS, DMS, and DMSO and their effects on the rate of coke deposition and CO production during the heptane steam cracking process. Parmar et al [17] studied the thermal decomposition of DMDS and DEDS (diethyl disulphide) in the temperature range of 200-800 C and realized decomposition conditions of sulphur compounds and their products affect product yield.…”

Effect of sulfur additives on coke formation during steam cracking of naphtha

“…Sulfur compounds are used to passivate the reactor inner wall either by presulfiding and/or by continuous addition of sulfur compounds in ppm level for coke reduction during steam cracking. Many additives reported include dimethyl sulfide (DMS), dimethyl disulphide, 15 hydrogen sulphide, [16][17][18][19] carbon disulphide, 22 benzothiophenes, bibenzyl sulphide, phosphorothioate, 20 methanedithione, (methyldisulfanyl) methane, (methylsulfanyl)methane, and dimethyl sulfoxide, 23 Benzyl diethyl phosphite, 24 sulfur and phosphorus, 21,25 phosphorus chemical (NALCO's COKE-LESS), sulphur-silicon liquid additives (Arkema/Technip CLX) and tin-based (tin/silicon mixtures: Chevron Phillips CCA500). Inorganic salts are also used as additive chemicals for coke reduction.…”