Dimethyl Disulfide (DMDS)
Dimethyl Disulfide (DMDS) is the most commonly used chemical for sulfiding the hydrotreating and hydrocracking catalysts used to make clean fuels. These catalysts contain metal oxides that must be converted to the active metal sulfide prior to use. Sulfiding is carried out by introducing DMDS into the reactor with hydrogen at 390F or higher. Under these conditions, DMDS rapidly decomposes, forming the H2S that is required to convert the oxides to metal sulfides.
DMDS is also used to passivate furnace tubes in ethylene crackers, although Dimethyl Sulfide (DMS) is used more often in this application.
DMDS is ideal for sulfiding because of its high sulfur content (68%) and its decomposition temperature range of 360-400F. At this temperature level, it is much easier to control sulfiding exotherms that occur as the metal oxides are transformed to sulfides.
An additional advantage of DMDS is the by-product of its decomposition is simple methane (CH4) that will not cause premature coking of the catalyst bed. Other sulfiding chemicals, such as TBPS, can cause excess coking during the sulfiding process due to the by-products formed when they decompose.
In summary, the advantages of sulfiding with DMDS are:
- High Sulfur Content (68%)
- By-products will not cause premature coking
- Low Decomposition Temperature
- Chosen by Catalyst Manufactures for Activity Testing and Catalyst Development
Contact us to discuss the optimum sulfiding agent for your application.