Mercaptans, liquid

Grace Letterflex Polyurethane with allyl groups Mercaptan Liquid Air knife or water... 

Mercaptans. liquid, flammable, toxic. 1228 28 Mercury Nucleate 1639 53... 

Mercaptan LIQUIDS point salt thioether sulphone... 

Mercaptans and thiophenols (thiols). The thiols are generally liquids with penetrating and disagreeable odours, which persist even at extremely low concentrations in the air. They are soluble in dilute sodium hydroxide solution. Thiols are best characterised as the crystalline 2 4-dinitrophenyl thioethers or as the corresponding sulphones (see Section 111,168). 

Disulphides. Disulphides are liquids or low m.p. solids and have un pleasant odours, particularly if liquid. They are reduced by zinc and dilute acids to the mercaptans ... 

Dissociation extraction is the process of using chemical reac tion to force a solute to transfer from one liquid phase to another. One example is the use of a sodium hydroxide solution to extract phenolics, acids, or mercaptans from a hydrocarbon stream. The opposite transfer can be forced by adding an acid to a sodium phenate stream to spring the phenolic back to a free phenol that can be extrac ted into an organic solvent. Similarly, primary, secondary, and tertiary amines can be protonated with a strong acid to transfer the amine into a water solution, for example, as an amine hydrochloride salt. Conversely, a strong base can be added to convert the amine salt back to free base, which can be extracted into a solvent. This procedure is quite common in pharmaceutical production. 

Low molecular weight liquid nitrile rubbers with vinyl, carboxyl or mercaptan reactive end groups have been used with acrylic adhesives, epoxide resins and polyesters. Japanese workers have produced interesting butadiene-acrylonitrile alternating copolymers using Ziegler-Natta-type catalysts that are capable of some degree of ciystallisation. 

Observable Characteristics - Physical State (as shipped) Liquid Color Yellow to dark brown Odor Characteristic skunk-like mercaptan. 

However, a strong caustic solution is used to remove mercaptans from gas and liquid streams. In the Merox Process, for example, a caustic solvent containing a catalyst such as cobalt, which is capable of converting mercaptans (RSH) to caustic insoluble disulfides (RSSR), is used for streams rich in mercaptans after removal of H2S. Air is used to oxidize the mercaptans to disulfides. The caustic solution is then recycled for regeneration. The Merox process (Fig. 1-3) is mainly used for treatment of refinery gas streams. ... 

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. 

In the extraction process, the LPG from the prewash tower enters the bottom of an extractor column. The extractor is a liquid/liquid contactor in which the LPG is counter-currently contacted by a caustic solution. Another option is the use of a fiber film contacting device. The mercaptans dissolve in the caustic (Equation 1-14). The treated LPG leaves the top of the extractor and goes on to a settler, where entrained caustic is separated. 

Mercaptans RSH (also thioethers or sulphides R SR and disulphides R SSR ) are generally liquids and possess unpleasant odours. 

Caustic washing. Here, caustic solution 5-15% strength is reacted with liquid gasoline or gaseous hydrocarbons. This interacts with H2S and lower molecular-weight mercaptans and they are thus removed. 

As one more common example of liquid fuels present reference may be drawn to liquified petroleum gas (LPG) or bottled gas or refinery gas. This fuel is obtained as a by-product during the cracking of heavy oils or from natural gas. It is dehydrated, desulfurized and traces of odours organic sulfides (mercaptans) are added in order to identify whether a gas leak has occurred. Supply of LPG is carried out under pressure in containers under different trade names. It consists of hydrocarbons of great volatility such that they can occur in the gaseous state under atmospheric pressure, but are readily liquifiable under high pressures. The principal constituents of LPG are n-butane, iso-butane, butylene and propane,... 

Spent caustic solutions from petroleum refining. Petrochemical refineries use caustics to remove acidic compounds such as mercaptans from liquid petroleum streams to reduce produced odor and corrosivity as well as to meet product sulfur specifications. Spent liquid treating caustics from petroleum refineries are excluded from the definition of solid waste if they are used as a feedstock in the manufacture of napthenic and cresylic acid products. U.S. EPA believes that spent caustic, when used in this manner, is a valuable commercial feedstock in the production of these particular products, and is therefore eligible for exclusion. 

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