Mercaptans applications

R. H. Buck and K. Krummen, High-performance liquid chromatographic determination of enantiomeric amino acids and amino alcohols after derivatization with o-phthaldialdehyde and various chiral mercaptans Application to peptide hydrolysates,/. Chromatogr., A, 1987,357, 255-265. 

LPG is considered to be non-toxic witli no chronic effects, but the vapour is slightly anaesthetic. In sufficiently high concentrations, resulting in oxygen deficiency, it will result in physical asphyxiation. The gases are colourless and odourless but an odorant or stenching agent (e.g. methyl mercaptan or dimethyl sulphide) is normally added to facilitate detection by smell down to approximately 0.4% by volume in air, i.e. one-fifth of the lower flammable limit. The odorant is not added for specific applications, e.g. cosmetic aerosol propellant. 

Effect of Catalyst The catalysts used in hydrotreating are molybdena on alumina, cobalt molybdate on alumina, nickel molybdate on alumina or nickel tungstate. Which catalyst is used depends on the particular application. Cobalt molybdate catalyst is generally used when sulfur removal is the primary interest. The nickel catalysts find application in the treating of cracked stocks for olefin or aromatic saturation. One preferred application for molybdena catalyst is sweetening, (removal of mercaptans). The molybdena on alumina catalyst is also preferred for reducing the carbon residue of heating oils. 

Washing light hydrocarbons with water is a common refinery practice. It finds application on the feed to catalytic polymerization plants. It is used to remove any entrained caustic from the mercaptan removal facilities as well as any other impurities such as amines which tend to poison the polymerization catalyst. Another use for water wash is in alkylation plants to remove salts from streams, where heating would tend to deposit them out and plug up heat exchanger surfaces. Water washing can be carried out in a mixer- settler, or in a tower if more intimate contacting is necessary. 

The water (moisture) content can rapidly and accurately be determined in polymers such as PBT, PA6, PA4.6 and PC via coulometric titration, with detection limits of some 20 ppm. Water produced during heating of PET was determined by Karl Fischer titration [536]. The method can be used for determining very small quantities of water (10p,g-15mg). Certified water standards are available. Karl Fischer titrations are not universal. The method is not applicable in the presence of H2S, mercaptans, sulfides or appreciable amounts of hydroperoxides, and to any compound or mixture which partially reacts under the conditions of the test, to produce water [31]. Compounds that consume or release iodine under the analysis conditions interfere with the determination. 

Electrodes of the first kind have only limited application to titration in non-aqueous media a well-known example is the use of a silver electrode in the determination of sulphides and/or mercaptans in petroleum products by titration in methanol-benzene (1 1) with methanolic silver nitrate as titrant. As an indicator electrode of the second kind the antimony pH electrode (or antimony/antimony trioxide electrode) may be mentioned its standard potential value depends on proton solvation in the titration medium chosen cf., the equilibrium reaction on p. 46). 

The LP grades are liquid polymers used in sealant and mastic applications, and are formed by breaking down a high molecular weight polymer in a controlled manner. The liquid polymer again has mercaptan end groups. 

This one-step procedure is a convenient and general method for the preparation of carbamates. It is substantially simpler, quicker, and safer than the multistep methods hitherto used for the preparation of carbamates of tertiary alcohols. This procedure is applicable to the preparation of carbamates of primary, secondary, and tertiary alcohols and mercaptans, polyhydric alcohols, acetylenic alcohols, phenols, and oximes. It has also been extended to the preparation of carbamyl derivatives (i.e., ureas) of inert (non-basic) amines.10... 

During oxide lead flotation, the choice of collector is rather limited to xanthates, which are used in operating plants. Dithiophosphates and mercaptans are used as secondary collectors. This is due to the fact that natural ores contain a variety of floatable gangues, for which the anionic flotation process is not applicable. The use of chelating agents as flotation collectors for oxide lead flotation have been extensively examined [5,6], Oximes/fuel oil... 

Dinitrobenzenesulfenyl chloride is a versatile analytical reagent for the characterization of a wide variety of organic compounds, including alcohols, mercaptans, ketones, olefins, amines, aromatic compounds, olefin oxides, and hydroxysteroids. Review articles summarize these applications.9 10... 

By 2000, the alpha olefin market had grown to more than 3. billion pounds. Technology had brought down the cost of producing them and simultaneously, a broad range of applications for all the alpha olefins expanded rapidly—surfactants, synthetic lubricants, plasticizer alcohols, fatty acids, mercaptans, comonomers, biocides, paper and textile sizing, oil field chemicals, lube oil., additives, plastic processing aids, and cosmetics. 

Soil. Hydrolyzes in soil forming ethyl mercaptan, carbon dioxide, and dialkylamine (half-life approximately 2-5 wk) (Hartley and Kidd, 1987). At recommended rates of application, the half-life of molinate in moist loam soils at 21-27 °C was approximately 3 wk (Humburg et al., 1989). Rajagopal et al. (1984) reported that under flooded conditions, molinate was hydroxylated at the 3- and 4-position with subsequent oxidation forming many compounds including molinate sulfoxide, carboxymethyl molinate, hexahydroazepine-l-carbothioate, 4-hydroxymolinate, 4-hy-droxymolinate sulfoxide, hexahydroazepine, 5-methyl hexahydroazepine-l-carbothioate, 4-keto-molinate, 4-hydroxyhexahydroazepine, 4-hydroxy-Wacetyl-hexahydroazepine, carbon dioxide, and bound residues. 

The first major attempt at precombustion desulphurisation was in the coal gas industry and a number of efficient and effective techniques for removal of H2S, COS, CS2, mercaptans and other volatile sulphur containing products of the gasification process were developed. Many of these techniques found application in the subsequent development of sour natural gas processing where large volumes of hydrogen sulphide had to be removed from the hydrocarbon component. 

For a particular application the molecular weight of the polystyrene obtained in Problem 3-10 is too high. What concentration of n-hutyl mercaptan should be used to lower the molecular weight to 85,000 What will he the polymerization rate for the reaction in the presence of the mercaptan ... 

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). 

The most important applications of hydrogen sulfide involve the production of sodium sulfide and other inorganic sulfides. Hydrogen sulfide obtained as a by-product often is converted into sulfuric acid. It also is used in organic synthesis to make thiols or mercaptans. Other applications are in metallurgy for extracting nickel, copper, and cobalt as sulfides from their minerals and in classical qualitative analytical methods for precipitation of many metals (see Reactions). It also is used in producing heavy water for nuclear reactors. 

Lead sulfide occurs in nature as the mineral galena. Most lead comes from this ore. Additionally, lead sulfide has several industrial applications. It is used in infrared detectors transistors photoconductive cells high temperature lubricants and for glazing earthenware. It also is used as a catalyst in petroleum refining for removal of mercaptans from petroleum distillates. 

Two of the more recently developed polysulfide polymers are the mercaptan-terminated polyoxypropylene urethane polymer and the polythioether polymer. The urethane-backbone-based polymer is used in many sealant formulations for insulating glass applications. The thioether backbone contains sulfur, but no S—S bonds, which are the weakest part of the conventional polysulfide polymer. This polymer improves the thermal stability and reduces the gas—liquid permeability. 

Applications of these methods to various synthetic objectives have been reported the preparation of organosilicon-containing pseudothiuronium salts [66], mercaptans from alcohols [9, 67], 2-alkylpseudothiuronium picrates for the estimation of tertiary alcohols [68, 69], and alkylsulfonyl chlorides from pseudothioureas by chlorination of pseudothiourea-HCl salts [55]. (CAUTION May cause an explosion [70].)... 

Surprisingly it was reported that when potassium cyanate is substituted for sodium cyanate the yields of carbamates are reduced to less than 5 %. The reason for this drastic effect is not known at this time. In addition, the use of other alkali or alkaline metal cyanates in this reaction has not been investigated. The Loev [28] procedure appears applicable to the synthesis of carbamates from primary, secondary, and tertiary alcohols (2 hr reaction time affords 60-90% yields), cyclic and acyclic 1,3-diols, phenols, oximes, ald-oximes, and ketoximes, and primary, secondary, and tertiary mercaptans. Carbamates could not be obtained from diphenylethylcarbinol (dehydrated to 1,1-diphenylethylene) or trichloro- and trifluoromethylcarbinols. 

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