Sulfides and mercaptans

Sodium chlorite has also been used for treatment and removal of toxic and odorous gases such as hydrogen sulfide and mercaptans. Chlorine dioxide from chlorite is also useful for microbial and slime control in paper mills and alkaline paper machine systems (164,165). The use of sodium chlorite in textile bleaching and stripping is well known. Cotton is not degraded by sodium chlorite because the oxidation reactions are specific for the hemiceUulose and lignin components of the fibers. 

Water and sulfur compounds are the principal non-hydrocarbon impurities present in light ends which frequently require removal. The sulfur compounds of concern are concerned with here are hydrogen sulfide and mercaptans, both of which have to be removed almost quantitatively from any light ends cut which is going to be marketed. There are two reasons for this First, they have an objectionable odor, even in minute concentrations. Second, they may cause corrosion either by themselves or through their combustion products. 

Molecular sieves (dehydrated zeolite) purify petroleum products with their strong affinity for polar compounds such as water, carbon dioxide, hydrogen sulfide, and mercaptans. The petroleum product is passed through the sieve until the impurity is sufficiently removed after which the sieve may be regenerated by heating to 400 - bOO F. 

The LPG stream containing a mixture of C s and C4 s must be treated to remove hydrogen sulfide and mercaptan. This produces a noncorrosive, less odorous, and less hazardous product. The C s and C4 s from the debutanizer accumulator flow to the bottom of the H S contactor. The operation of this contactor is similar to that of the fuel gas absorber, except that this is a liquid-liquid contactor. 

Sweetening of petroleum products implies the removal of dissolved free sulfur and its compounds like hydrogen sulfide, and mercaptans in order that the product has no bad odour and does not tend to cause corrosion. The removal of these is accomplished by oxidation processes, solvent processes or catalytic desulfurization processes. 

Lacy-Keller A process for removing hydrogen sulfide and mercaptans from natural gas by absorption in a proprietary solution. Elemental sulfur precipitates as a colloid and is separated from the solution by means of an electrolytic flotation cell. The process does not remove carbon dioxide. 

SulfaTreat A process for removing hydrogen sulfide and mercaptans from natural gas or carbon dioxide streams, using a proprietary solid absorbent, which is subsequently dumped. Over 600 plants were in operation or planned in 1996. Licensed by Gas Sweetner Associates. 

The manufacturing processes for liquefied petroleum gas are designed so that the majority, if not all, of the sulfur compounds are removed. The total snlfnr level is therefore considerably lower than for other petrolenm fuels, and a maximnm limit for sulfur content helps to define the prodnct more completely. The snlfnr compounds that are primarily responsible for corrosion are hydrogen snlfide, carbonyl sulfide, and sometimes, elemental sulfur. Hydrogen sulfide and mercaptans have distinctive unpleasant odors. 

Aromatic Compounds with Sulfides and Mercaptans. Alkyl sulfides and mercaptans function very similarly to ethers and alcohols. Hydrogen sulfide is produced and it escapes as a gas not being significantly soluble in liquid hydrogen fluoride. In this respect the technique of procedure is similar to that used for alkyl halides. 

More than 80% of all sodium chlorite produced is used for the generation of chlorine dioxide. Sodium chlorite is also used in disinfectant formulations and sterilization. Like chlorine dioxide, it must be registered with EPA under FIFRA for each specific application use as a disinfection. Sodium chlorite is used in other industrial settings in NO and SO combustion flue gas scrubber systems in the treatment and removal of toxic and odorous gases such as hydrogen sulfide and mercaptans and as a solution formulation to oxidize copper surfaces in multilayer circuit boards (Kaczur and Cawlfield 1993). 

A drop in media pH may result in odor problems caused by the system s inability to treat organic sulfides and mercaptan compounds. 

Hydrogen sulfide and mercaptans Sour crudes formed by decomposition of sulfur compounds during distillation, cracking, reforming, and hydroprocessing... 

Corrosion inhibitor Two inhibitors could be used a. Copper corrosion inhibitor to help prevent sulfur, hydrogen sulfide, and mercaptan attack on copper b. Ferrous metal corrosion inhibitor to prevent water/oxygen initiated corrosion of iron and steel system components... 

Hydrogen sulfide, mercaptans, active elemental sulfur, inorganic acids, and ammonia can all attack and corrode copper. The presence of these compounds in fuel can lead to destruction of copper heating lines, cooling coils, and nonferrous metal fittings. Also, hydrogen sulfide and mercaptans can contribute to fuel odor problems. 

Merox Sweetening A process used in fuel refining to remove primarily hydrogen sulfide and mercaptans from fuel. This is a patented, proprietary process. 

Types of sulfur compounds fall into two main classes, the acidic compounds such as hydrogen sulfide and mercaptans, and the neutral compounds which include sulfides both alkyl and cyclic, thiophenes, and disulfides. 

When heated to decomposition it emits toxic fumes of SOx and Na20. See also SULFIDES and MERCAPTANS. 

SAFETY PROFILE Poison by intravenous and intraperitoneal routes. Moderately toxic by ingestion. A human skin irritant. This material yields hydrogen sulfide on decomposition. A death has been attributed to the absorption of toxic decomposition products from the use of this material in a hair permanent-waving solution. When heated to decomposition it emits toxic fumes of SOx and Na20. See also SULFIDES and MERCAPTANS. 

Hydrogen sulfide is easily separated from the other constituents after hydrogenation by stripping or fractionation. Hydrogen sulfide and mercaptans (thiols) may also be removed from refinery streams by washing with aqueous sodium hydroxide (lye treating, Eq. 18.31, 18.32). 

Natural gas or light hydrocarbons that serve as feed gas in the synthesis of ammonia contain sulfur compounds that act as poisons for the nickel catalyst used in synthesis gas production. Hydrogen sulfide and mercaptans are the dominant sulfur species in natural gas, while the light hydrocarbons may contain higher boiling sulfur species. A fixed-bed reactor containing zinc oxide is often used to desulfurize the feed gas. The chemical reaction with hydrogen sulfide is... 

A large number of chemical devulcanization agents for natural and synthetic rubbers have been developed. These include phosphines and phosphates, numerous sulfides and mercaptans, metal salts such as methyl iodide, phenyl lithium, lithium aluminum hydride, and phase-transfer catalysts. ... 

Included in the list of sulfides and mercaptans are diphenyl disulfide, dibenzyl disulfide, diamyl disulfide, bis(alkoxy aryl) disulfides, butyl mercaptan and thio-phenols, xylene thiols and other mercaptans, phenol sulfides and disulfides. ... 

Shaw, J. A., Ibid., 12, 668 (1940). Rapid Determination of Hydrogen Sulfide and Mercaptan... 

Control of the total sulfur content, hydrogen sulfide, and mercaptans ensures that the product is not corrosive or nauseating. Stipulating a satisfactory copper strip test further ensures control of corrosion. 

Refining treatment includes among its objects the removal of such undesirable products as hydrogen sulfide, mercaptan sulfur, and free or corrosive sulfur. Hydrogen sulfide and mercaptans cause objectionable odors, and both are corrosive. The presence of such compounds can be determined by the Doctor test (ASTM D-484, ASTM D-4952, IP 30). The Doctor test (which is pertinent for petroleum product specifications ASTM D-235) ensures that the concentration of these compounds is insufficient to cause such problems in normal use. In the test, the sample is shaken with sodium plumbite solution, a small quantity of sulfur is added, and the mixture is shaken again. The presence of mercaptans, hydrogen sulfide, or both is indicated by discoloration of the sulfur floating at the oil-water interface or by discoloration of either of the phases. 

---