Activation of Hydroprocessing Catalysts: An in depth understanding of Dimethyldisulfide (DMDS) decomposition chemistry on Hydroprocessing Catalysts during their activation via Sulfiding

摘要

The progress in the improvement of hydroprocessing catalysts has been impressivesince the discovery of Type-Ⅱ acid sites. Strict regulations on the sulphur and nitrogen levelsin finished transportation fuels are being enforced globally, and this has promulgated the needto capture all the available activity of these new catalysts. The new generations of CoMo andNiMo catalysts have to be carefully activated via sulfiding to accomplish this task. Dimethyldisulfide (DMDS) has been and continues to be the agent of choice to sulphide "in-situ", andobtain optimal activity from these catalysts. The decomposition of DMDS, while verified underlaboratory conditions, has not been clearly understood under actual refinery unit conditions.The DMDS decomposition chemistry under a range of commercial unit conditions has beeninvestigated. Experimental data obtained have been used to build a kinetic model based onthe fundamental decomposition mechanism. The data can be used beneficially to fine tuneexisting sulfiding procedures established by Catalyst Manufacturers and Refining Companies soas to make them optimal for and applicable to different types of units in the refinery.Additionally, this information can be used to ascertain essentially complete use of the 'sulfur'introduced via DMDS and prevent SO_2 excursions due to inadvertent loss of sulphurintermediates to the flare or flue gas, during the catalyst sulfiding and activation. Being theleader in DMDS manufacture, Arkema has recently introduced a new formulation, "DMDSEvolution~? E2" that has an improved user-friendly odor. Details of this formulation and of the"Carelflex~? Service" that Arkema provides to sulfide these catalysts in-situ will be described.