Other Sulfur Compounds

Of the general formula, R - S — H, where R represents an aliphatic or cyclic radical, the thiols —also known as mercaptans— are acidic in behavior owing to their S—H functional group they are corrosive and malodorous. Their concentration in crude oils is very low if not zero, but they are created from other sulfur compounds during refining operations and show up in the light cuts, as illustrated in Table 8.6. 

Mercaptans are naturally present in crude oil (Chapters 1 and 8), or they result from the decomposition of other sulfur compounds during thermai or catalytic cracking operations. 

Other sulfur compounds such as thiourea, ammonium dithiocarbamate, or hydrogen sulfide also lead to 2-mercaptothiazoles. Thus thiourea has been used in the syntheses of 4,5-dimethyl (369) and 4-aryl-2-mercapto-thiazoles (Table 11-30) (519). The reactions were carried out by condensing the ia -thiocyanatoketones with thiourea in alcohol and water acidified with hydrochloric acid. By this procedure, 4-aryl-2-mercaptothiazoles were obtained in yields of 40 to 80% with bis-(4-aryl-2-thiazolyl) sulfides as by-products (519). These latter products (194) have also been observed as a result of the action of thiourea on 2-chloro-4-arylthiazole under the same experimental conditions. They can be separated from 2-mercaptothiazoles because of their different degrees of solubility in sodium hydroxide solution at 5%. In this medium bis-(4-phenyl-2-thiazolyl)sulfide is... 

A large use of molecular sieves ia the natural gas industry is LPG sweetening, in which H2S and other sulfur compounds are removed. Sweetening and dehydration are combined in one unit and the problem associated with the disposal of caustic wastes from Hquid treating systems is eliminated. The regeneration medium is typically natural gas. Commercial plants are processing from as Htde as ca 30 m /d (200 bbl/d) to over 8000 m /d (50,000 bbl/d). 

Alternative means for removal of carbonyl sulfide for gas streams iavolve hydrogenation. For example, the Beavon process for removal of sulfur compounds remaining ia Claus unit tail gases iavolves hydrolysis and hydrogenation over cobalt molybdate catalyst resulting ia the conversion of carbonyl sulfide, carbon disulfide, and other sulfur compounds to hydrogen sulfide (25). 

Conversion Processes. Most of the adsorption and absorption processes remove hydrogen sulfide from sour gas streams thus producing both a sweetened product stream and an enriched hydrogen sulfide stream. In addition to the hydrogen sulfide, this latter stream can contain other co-absorbed species, potentially including carbon dioxide, hydrocarbons, and other sulfur compounds. Conversion processes treat the hydrogen sulfide stream to recover the sulfur as a salable product. 

Most natural gas is substantially free of sulfur compounds the terms. sweet and. sour are used to denote the absence or presence of HgS. Some wells, however, dehver gas containing levels of hydrogen sulfide and other sulfur compounds (e.g., thio enes, mercaptans, and organic sulfides) that must be removed before transfer to commercial pipehnes. Pipehne-company contracts typically specify maximum allowable Emits of impurities HgS and tot sulfur compounds seldom exceed 0.023 and 0.46 g/m (1.0 and 20.0 gr/100 std fF),... 

Gas treating is defined here as removal of H2S and CO2. Other sulfur compounds are discussed where applicable. Dehydration and sulfur production are not included, except for discussing sulfur production in the Stretford Process and for selective H2S removal. H2S must be removed from natural gas and process streams for health reasons and prevention of corrosion. Natural gas pipeline specifications require no more than % grain/100 SCF. This is equivalent to 4ppmv or 7ppmw (for a 0.65 specific gravity gas). By comparison, the human nose can detect... 

In addition to heavy hydrocarbons and water vapor, natural gas often contains other contaminants that may have to be removed. Carbon dioxide (CO2), hydrogen sulfide (H2S), and other sulfur compounds such as mercaptans are compounds that may require complete or partial removal for acceptance by a gas purchaser. These compounds are known as acid gases. H2S combined with water forms a weak form of sulfuric acid, while CO2 and water forms carbonic acid, thus the term acid gas. ... 

Natural gas with H2S or other sulfur compounds present is called sour gas, while gas with only CO2 is called sweet. Both H2S and CO2 are undesirable, as they cause corrosion and reduce the heating value and thus the sales value of the gas. In addition, H2S may be lethal in very small quantities. Table 7-1 shows physiological effects of H2S concentrations in air. 

The disulfide has a special interest as the catalyst in the carbon disulfide-catalyzed iodine-azide reaction. No perceptible nitrogen evolution will take place in a solution containing iodine and azide ions without the presence of a catalyst. Thiosulfates, sulfides, and many other sulfur compounds act as catalysts. In 1922 Browne et found that carbon disulfide is a powerful catalyst in this... 

The overhead product is totally liquefied in the overhead condensers. A portion of the overhead liquid is pumped and returned to the tower as reflux. The remainder is sent to a treating unit to remove H2S and other sulfur compounds. The mixed Cj s and C s stream can then be fed to an ether or an alkylation unit. It can be fed to a depropanizer tower where the Cj s are separated from C4 s. The Cj s are processed for petrochemical feedstock and the C4 s are alkylated. 

The exact mechanisms of the Raney nickel reactions are still in doubt, though they are probably of the free radical type. It has been shown that reduction of thiophene proceeds through butadiene and butene, not through 1-butanethiol or other sulfur compounds, that is, the sulfur is removed before the double bonds are reduced. This was demonstrated by isolation of the alkenes and the failure to isolate any potential sulfur-containing intermediates. 

Oxidation of Thiois and Other Sulfur Compounds to Sulfonic Acids... 

Abstract Molecular spectroscopy is one of the most important means to characterize the various species in solid, hquid and gaseous elemental sulfur. In this chapter the vibrational, UV-Vis and mass spectra of sulfur molecules with between 2 and 20 atoms are critically reviewed together with the spectra of liquid sulfur and of solid allotropes including polymeric and high-pressure phases. In particular, low temperature Raman spectroscopy is a suitable technique to identify single species in mixtures. In mass spectra cluster cations with up to 56 atoms have been observed but fragmentation processes cause serious difficulties. The UV-Vis spectra of S4 are reassigned. The modern XANES spectroscopy has just started to be applied to sulfur allotropes and other sulfur compounds. 

The sulfur-rich oxides S 0 and S 02 belong to the group of so-called lower oxides of sulfur named after the low oxidation state of the sulfur atom(s) compared to the best known oxide SO2 in which the sulfur is in the oxidation state +4. Sulfur monoxide SO is also a member of this class but is not subject of this review. The blue-green material of composition S2O3 described in the older literature has long been shown to be a mixture of salts with the cations S4 and Ss and polysulfate anions rather than a sulfur oxide [1,2]. Reliable reviews on the complex chemistry of the lower sulfur oxides have been published before [1, 3-6]. The present review deals with those sulfur oxides which contain at least one sulfur-sulfur bond and not more than two oxygen atoms. These species are important intermediates in a number of redox reactions of elemental sulfur and other sulfur compounds. 

Study on applicability of MoNi/zeolite catalysts to the HDS reactions of other sulfur compounds is ongoing in our laboratory. 

Metabolism of this thiosulfate or of other sulfur compounds... 

Sulfur compounds such as furfuryl mercaptans have a rotten odor but in small amounts are coffee-like.15 Furfuryl mercaptan itself has an odor threshold of 0.005 ppb in water but at 10 ppb in water it imparts a distinctly stale odor.19 The particular precursors of furfuryl mercaptan seem to be the coffee cell wall material which contains both arabinogalactan as a pentose sugar source and protein such as glutathione.84 Other sulfur compounds such as kahweofuran and methyldithiofurans impart a meaty odor if their concentrations are high enough.19... 

Conventional wastewater treatment techniques consist of physical/chemical treatments, including oil separation, dissolved gas flotation, and ammonia distillation (for removal of free cyanides, free sulfides, and ammonia) followed by biological treatment (for organics removal) and residual ammonia nitrification. Almost all residuals from coke-making operations are either recovered as crude byproducts (e.g., as crude coal tar, crude light oil, ammonium sulfate, or other sulfur compounds)... 

Puacz et al. (1995) developed a catalytic method, based on the iodine-azide reaction, for the determination of hydrogen sulfide in human whole blood. The method involves the generation of hydrogen sulfide in an evolution-absorption apparatus. In addition, the method allows for the determination of sulfide in blood without interference from other sulfur compounds in blood. A detection limit of 4 g/dm3 and a percent recovery of 98-102% were achieved. Although the accuracy and precision of the catalytic method are comparable to those of the ion-selective electrode method, the catalytic method is simpler, faster, and would be advantageous in serial analysis. 

Other sulfur compounds are known to undergo photoelimination and fragmentation reactions(85 6S) ... 

In this equation, B stands for adsorption coefficients and C for concentrations. The thermodynamic control imposes the use of very high pressures, low space velocities, and very active catalysts. For the specific case of aromatic saturation and in the presence of H2S or any other sulfur compound, NiW is the recommended catalyst [66], However, in those cases where a precious metal catalyst may be used then, it becomes the preferred choice [67],... 

The data reported identifies sulfur substrates tested for growth as sole sulfur source for the various strains. The strains may metabolize other sulfur compounds (not listed). A complete name of listed strains in Table 3 comprises Rhodococcus sp. SY1 Rhodococ-cus sp. H-2 Rhodococcus sp. D-l Rhodococcus ECRD-1 Gordona CYKS1 Nocar-dia sp. CYKS2 Paenibacillus All-2 Mycobacterium sp. WU-F1 Mycobacterium sp. WU-0103 Mycobacterium phlei sp. GTIS10 and Agrobacterium MC501. 

Constanti, M. Giralt, J., and Bordens, A., Degradation and Desulfurization of Dibenzothiophene Sulfone and Other Sulfur Compounds by Agrobacterium MC501 and a Mixed Culture. Enzyme and Microbial Technology, 1996. 19 pp. 214-219. 

Sulfur dioxide is an economically important gas that is used as a refrigerant, disinfectant, and reducing atmosphere for preserving food. Although it is also used in the manufacture of many other sulfur compounds, the most important use of S02 is as a precursor in producing sulfuric acid. It can be obtained by burning sulfur, but it is also produced in numerous other reactions. Sulfites react with acids by liberating so2. 

Econ-Abator A process for oxidizing hydrogen sulfide and other sulfur compounds in waste gases by fluid bed combustion in the presence of an oxide catalyst. Licensed by ARI Technologies. In 1992 there were 90 installations. 

Z-Sorb A process for removing hydrogen sulfide and other sulfur compounds from gas streams by absorption in a proprietary granular absorbent containing zinc oxide. The process can be operated at temperatures between 315 and 555°C. Chem. Eng. (N.Y.), 1998,105(2), 25. 

Alkanolamines, generally referred to as amines, are organic compounds of the form Hn-N-(R0H)3-n (3) the hydroxyl group generally provides for the compounds solubility in water, while the HN group provides the alkalinity in water solutions to cause the absorption of acid gases. Amine processes used commercially are shown in Table I. These compounds are chemical solvents they combine chemically with H2S, C02, and other sulfur compounds. They are customarily regenerated by the application of heat. 

Selectivity - solvents generally have different affinities for H2S and CO2. Some processes can remove essentially all of the H2S and many of the other sulfur compounds while leaving most of the CO2 in the treated gas, potentially reducing the cost of the downstream sulfur recovery facilities (4). However, such... 

Sulfur recovery processes convert acid gases containing H2S and other sulfur compounds to elemental sulfur and sulfuric acid. Table II is a summary of many of the available sulfur recovery processes. 

It is more than likely that when sulfur occurs in a crude oil or in coal (other than the pyrites), it is organically bound in one of the three forms listed in Table 8.3—the thiols, sulfides, or disulfides. The combustion of these compounds is very much different from that of other sulfur compounds in that... 

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