Sulfurs, elemental reactions

This process is used to treat gas streams containing high concentrations of H2S. The chemistry of the units involves partial oxidation of hydrogen sulfide to sulfur dioxide and the catalytically promoted reaction of hh.S and SO2 to produce elemental sulfur. The reactions are staged and arc. is lollows ... 

Figure 7-8 represents a process flow diagram of the LOCAT process. The Hi.S is contacted with the reagent in an absorber it reacts with the dissolved iron to form elemental sulfur. The reactions involved are die following ... 

An analogous sulfur transfer reaction has been proposed for the thermal decomposition of neutral thiirane to give ethylene and elemental sulfur, on the basis of ah initio calculations at the G3(MP2) level of theory [135]. 

Solutions containing the nucleophiles and/or HS dissolve elemental sulfur by reactions according to the following equations (nucleophilic degradation) ... 

Plummer invented a process for the biodesulfurization of hydrocarbons [157], in which organic sulfur compounds contained in liquid hydrocarbons are converted to elemental sulfur. The reaction is carried out in the presence of a biocatalyst and hydrogen, by dissolving completely the liquid hydrocarbons in an organic solvent, such as a nucleophilic and/or electrophilic solvent(s). The nucleophilic solvent should have a pKa greater than 2, and the electrophilic solvent more negative than -2. Recommended nucleophilic solvents include -butylamine, diethylamine, butanediamine, ethylenimine, toluene, pyridine, aniline, and acetophenone. The electrophilic solvents could be methylethylketone, pyrrole, or benzaldehyde. 

Europeum generally is produced from two common rare earth minerals monazite, a rare earth-thorium orthophosphate, and bastnasite, a rare earth fluocarbonate. The ores are crushed and subjected to flotation. They are opened by sulfuric acid. Reaction with concentrated sulfuric acid at a temperature between 130 to 170°C converts thorium and the rare earths to their hydrous sulfates. The reaction is exothermic which raises the temperature to 250°C. The product sulfates are treated with cold water which dissolves the thorium and rare earth sulfates. The solution is then treated with sodium sulfate which precipitates rare earth elements by forming rare earth-sodium double salts. The precipitate is heated with sodium hydroxide to obtain rare earth hydrated oxides. Upon heating and drying, cerium hydrated oxide oxidizes to tetravalent ceric(lV) hydroxide. When the hydrated oxides are treated with hydrochloric acid or nitric acid, aU but Ce4+ salt dissolves in the acid. The insoluble Ce4+ salt is removed. 

In addition to the reactions that produce elemental sulfur, competing reactions also occur that produce undesirable by-products such as sodium thiosulfate. This is detrimental, because the thiosulfate remains in solution, and its concentration can generally be reduced only by bleeding off a portion of the solution inventory. This solution purge waste stream is hazardous, largely because it also contains vanadium compounds. The key to reducing the metal content of the waste stream is to reduce the rate of thiosulfate formation. 

Whereas (29) reacts with sulfides RSH via a radical mechanism to afford the cyclic product (30), in the presence of elemental sulfur the reaction takes an ionic course, giving the expected 1,2 adduct (31).42... 

The sulfonation of toluene proceeds via a complex scheme of elemental reactions with numerous side and consecutive reactions. Toluene sulfonic acid and sulfur trioxide can read in a consecutive process to give toluene pyrosulfonic acid, which can undergo further reactions [315,316]. Reaction of this acid with another molecule of toluene yields two molecules toluene sulfonic acid or ditolyl sulfone. In addition, toluene sulfonic anhydride may be formed via readion of toluene pyrosulfonic acid with toluene sulfonic acid. 

Thiosulfates are best made by the action of sulfites on elemental sulfur, a reaction analogous formally (and possibly mechanistically) to that yielding disulfides and thiocyanates (Exercise 10) ... 

Preparative Methods the title compound can be prepared by reaction of (R)-2-[l-(dimethylamino)ethyl]phenyllithium with elemental sulfur (eq 1). A solution of pure (R)-2-[l-(dimethyl-amino)ethyl]phenyllithium in THF is slowly added at —50°C to a suspension of a stoichiometric amount of freshly sublimed sulfur. The solution is warmed to room temperature and quenched with an equimolar amount of a 10 M aqueous HCl solution. All volatiles are evaporated at reduced pressure and the residue is sublimed at 120 °C in vacuo (0.1 mmHg). The nitrogen-functionalized derivatives (R)-2-[l-(l-pyrrolidinyl) ethyljbenzenethiol and (R)-2-[l-(l-piperidinyl)ethyl]benzen-ethioP may be prepared in a similar way. It should be noted that reaction with MesSiCl instead of HCl after the sulfur insertion reaction affords the corresponding trimethylsilyl thio ether, which also is a valuable catalyst precursor. ... 

Well dispersed iron oxide on silica of a specific surface area of 50 m /g has proven to be a very suitable catalyst for the selective oxidarion of hydrogen sulfide to elemental sulfur. Under reaction conditions the iron oxide is transformed into ironCII sulfate as revealed by X ray diffraction, Mbssbauer spectroscopy, and wet chemical analysis. The presence of an iron(III) component as observed by ex situ Mossbauer spectroscopy can not be excluded. Although the transfomiation of iTon(]Il) oxide into iron(II) sulfate causes initial deactivation, the increase in selectivity (96%) results in high sulfur yields (up to 94%). 

Sulfur Generation. During the SO2 removal step the gaseous SO2 is converted to nonvolatile sulfuric acid which remains sorbed in the carbon s pores. Conversion of this sulfuric acid to SO2 or elemental sulfur by reaction with hydrogen sulfide has been studied in bench scale. 

The oxidation of sulfur compounds in the sulfur-oxidizing bacteria is performed by the combination of several elemental reaction processes, and each of the processes is performed by a cooperation of several enzymes and cytochromes. The elemental reaction processes included in the bacterial oxidation of sulfur compounds will be described in the following section. 

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