103b: Enviro-S Presulfiding Agent for Petroleum Catalysts
Many organosulfur compounds are available for pretreating catalysts. The choice of a presulfiding agent should be guided by these factors:
- Operational and environmental safety
- Maximum sulfiding capability
- Cost effectiveness
Preference for ENVIRO-S ® dimethyl sulfoxide (DMSO) is growing, due in large part to its low toxicity and odor. DMSO is easier and safer for plant personnel to handle than many other sulfur compounds. No toxicity problems have been encountered with ENVIRO-S ® DMSO since it became available in the late 1960's. Risks to workers are minimal. The Gaylord presulfiding equipment and experience help insure a leak and odor-free process. If a leak or spill occurs, ENVIRO-S ® DMSO may be diluted and flushed to the wastewater treatment facility where it is fully biodegradable by typical activated sludge bacteria.
DMSO is a fully saturated, low-molecular weight, sulfur-containing compound that begins to decompose at its boiling point of 372ºF. The presence of oxygen in DMSO appears to have no adverse effect on catalyst activity and is insignificant compared to that released from the catalyst. Water that may be present to control the freezing point would be in the vapor phase.
Inhalation Toxicity of Presulfiding Agents in Common Use (LC 50 for Rats )
| ENVIRO-S ® ® DMSO | None at levels tested |
| Ethyl mercaptan | 4,420 ppm |
| Butyl Mercaptan | 4,020 ppm |
| Dimethyl disulfide | 805 ppm |
| Methyl mercaptan | 675 ppm |
| Hydrogen sulfide | 444 ppm |
Representative Specification
| Specification | Values |
| Assay, % Min. by GLC | 99.7 |
| Water, % Max. by KF | 0.15 |
| Titrable Acid, meq/g Max. | 0.001 |
*This illustration does not constitute the specification. Specifications are available upon request.
ENVIRO-S ® DMSO at a Glance
| Physical Parameter | Value |
| Molecular weight | 78.13 |
| Percent sulfur (mass %) | 41.0% |
| Boiling point | 189°C |
| Freezing point | 18.45°C |
| Density (20°C) | 1.099 g/cc |
| Heat of vaporization H v (70°C) | 11.3 kcal/mol |
| Dielectric constant (20°C) | 48.9 |
| Flash point, open cup | 95°C |
| Autoignition temperature | 300-302°C |
Catalysts Decomposition Temperatures Hydrotreating Catalysts in Hydrogen Atmosphere
| Catalyst | ||
| Sulfur Agent | Nickel-molybdenum | Cobalt-molybdenum |
| ENVIRO-S ® DMSO | 420°F (216°C) | 457°F (236°C) |
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 decom- position temperature for the spiking agent.
Regulatory
CAS:67-68-5, EINECS:200-664-3
HMIS and NFPA Hazard Ratings: Health 1, Flammability 1, Chemical
Reactivity-0
Packaging
45,000 lb Tank Truck
