DMS Exact-S® Product Sheet



DMS Exact-S® Grade is an important sulfidation agent for ethylene manufacturers. It effectively regulates carbon monoxide (CO) generation during steamcracking and helps to control the formation of coke in the furnace. Gaylord Chemical is an on-purpose manufacturer of Dimethyl Sulfide (DMS).

Coke formation within the tubular coils of an the ethylene furnace continues to be a challenge faced by engineers. Coke deposition increases fuel consumption, reduces the furnace throughput and causes non-productive outages for decoking activities. Consequences of coking include:

  • Continuously rising external tube skin temperatures can reach its maximum allowable values. This fact can limit the on-stream time of the unit.
  • Pressure drops will increase with running time and can influence the process selectivity.
  • Furnace thermal efficiency is progressively reduced. Reaction volume progressively declines.

Sulfur-based compounds such as DMS have been traditionally dosed into the pyrolysis coils after a fresh decoke cycle or added to the feedstock . The sulfur compound converts the metal oxide sites on the tube wall surfaces into metal sulfides. Although the primary aim is to reduce carburization rate, it also reduces catalytic coking.


Select DMS Exact-S® Grade as your decoking agent. DMS Exact-S® Grade is:

  • The preferred decoking agent in North America due to its safety and operating advantages, environmental properties and product reliability.
  • The least toxic of commonly used decoking agents. Easily converted to usable sulfur and completely decomposes for effective decoking.
  • Free of impurities that may be harmful to your process such as nitrogen, water, hydrocarbons and non-volatiles even with pressure and temperature changes.
  • Is suited for pressure injection and is easily vaporized.

Representation Specification

Representative Test Method Values
Assay (% Min. by GLC) 99.2
Water (% Max.) 0.07
Color (APHA Max.) 10
Nitrogen (ppm Max.) 20
Methyl Mercaptan (ppm Max.) 500
Hydrogen Sulfide (ppm Max.) 200
Carbon Disulfide (ppm Max.) 20
Non-volatile Residue (ppm Max.) 10

This illustration does not constitute the specification. Specifications are available upon request.

DMS Exact-S® Grade at a Glance

Physical Parameter Values
Molecular weight 62.134
Percent sulfur (mass%) 51.5
Boiling point (°C) 37.34
Freezing point (°C) -98.27
Density (20°C) (g/cc) 0.847
Critical temperature (°C) 229
Critical pressure (mm Hg) 42,664
Heat of vaporization H v (25°C) (Cal/g) 106
Dielectric constant (20°C) 6.2
Flash point, closed cup (°C) -38
Autoignition temperature (°C) 206
Sulfur Agent Catalyst
Nickel-molybdenum Cobalt-molybdenum
DMS Exact-S® 435 °F 472 °F

Note: The temperatures shown above have been observed in hydrotreaters in the field to release sulfur for the generation of H 2 S. The catalyst determines the decomposition temperature for the spiking agent.




HMIS Hazard Ratings: Health ­2, Flammability ­4, Chemical Reactivity-0
NFPA Hazard Ratings: Health ­1, Flammability ­1, Chemical Reactivity-0


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The information in this bulletin is based on information available to us and on our observations and experiences. However, no warranty is expressed or implied regarding the accuracy of this data, the results to be obtained from the use thereof, or that any use will not infringe any patent. Each user must establish appropriate procedures for off-loading, handling, and use of the product(s). Since conditions for use are beyond our control, we will make no guarantee of results, and assume no liability for damages incurred by off-loading, handling, or use of the product(s). Nothing herein constitutes permission, or recommendation to practice any invention covered by any patent without license from the owner of the patent.