Thermal decomposition sulfur

H2S is found with the reservoir gas and dissolved in the crude (< 50 ppm by weight), but it is formed during refining operations such as catalytic cracking, hydrodesulfurization, and thermal cracking or by thermal decomposition of sulfur[Pg.322]

Synthetic Iron Oxides. Iron oxide pigments have been prepared synthetically since the end of the seventeenth century. The first synthetic red iron oxide was obtained as a by-product of the production of sulfuric acid from iron sulfate containing slate. Later, iron oxide pigments were produced direcdy by the thermal decomposition of iron sulfates. In the 1990s, about 70% of all iron oxide pigments consumed are prepared synthetically. 

Thermal decomposition of spent acids, eg, sulfuric acid, is required as an intermediate step at temperatures sufficientiy high to completely consume the organic contaminants by combustion temperatures above 1000°C are required. Concentrated acid can be made from the sulfur oxides. Spent acid is sprayed into a vertical combustion chamber, where the energy required to heat and vaporize the feed and support these endothermic reactions is suppHed by complete combustion of fuel oil plus added sulfur, if further acid production is desired. High feed rates of up to 30 t/d of uniform spent acid droplets are attained with a single rotary atomizer and decomposition rates of ca 400 t/d are possible (98). 

An excess of crotonaldehyde or aUphatic, ahcyhc, and aromatic hydrocarbons and their derivatives is used as a solvent to produce compounds of molecular weights of 1000—5000 (25—28). After removal of unreacted components and solvent, the adduct referred to as polyester is decomposed in acidic media or by pyrolysis (29—36). Proper operation of acidic decomposition can give high yields of pure /n j ,/n7 j -2,4-hexadienoic acid, whereas the pyrolysis gives a mixture of isomers that must be converted to the pure trans,trans form. The thermal decomposition is carried out in the presence of alkaU or amine catalysts. A simultaneous codistillation of the sorbic acid as it forms and the component used as the solvent can simplify the process scheme. The catalyst remains in the reaction batch. Suitable solvents and entraining agents include most inert Hquids that bod at 200—300°C, eg, aUphatic hydrocarbons. When the polyester is spHt thermally at 170—180°C and the sorbic acid is distilled direcdy with the solvent, production and purification can be combined in a single step. The solvent can be reused after removal of the sorbic acid (34). The isomeric mixture can be converted to the thermodynamically more stable trans,trans form in the presence of iodine, alkaU, or sulfuric or hydrochloric acid (37,38). 

Inorganic Reactions. Thermal decomposition of Hquid sulfamic acid begins at 209°C. At 260°C, sulfur dioxide, sulfur trioxide, nitrogen, water, and traces of other products, chiefly nitrogen compounds, result. 

For solvent extraction of pentavalent vanadium as a decavanadate anion, the leach solution is acidified to ca pH 3 by addition of sulfuric acid. Vanadium is extracted in about four countercurrent mixer—settler stages by a 3—5 wt % solution of a tertiary alkyl amine in kerosene. The organic solvent is stripped by a soda-ash or ammonium hydroxide solution, and addition of ammoniacal salts to the rich vanadium strip Hquor yields ammonium metavanadate. A small part of the metavanadate is marketed in that form and some is decomposed at a carefully controlled low temperature to make air-dried or fine granular pentoxide, but most is converted to fused pentoxide by thermal decomposition at ca 450°C, melting at 900°C, then chilling and flaking. 

Carbenes of type (113), generated by thermal decomposition of the appropriate tosyl-hydrazone salts, undergo ring opening more readily when the ring heteroatom is oxygen rather than when it is sulfur (78JA7927). 

Thermodynamic parameters have been obtained from kinetic HNMR spectroscopic studies of the thermal decomposition of ethyl 2,7-di-to7-butyl-5-methylthiepin-4-carboxylaten and two 1-benzothiepin compounds.12 The activation parameters for sulfur extrusion are AH = 93.7 kJ mol - 1 and AS = — 112.6 J Kmol-1 (in [2H18]Decalin) for the thiepin derivative,11 and AH = 75.3 and 87.9 kJ mol1 and AS = —100.4 and —104.6J Kmol-1 (in [2Hs]toluene) for the benzothiepin compounds.12 The large negative activation entropy values are consistent with a high degree of order in the anticipated thianorcaradiene transition state of the sulfur extrusion reaction. 

It has been generally assumed that thermal decomposition of thiirane oxides proceeds stereospecifically to the corresponding olefins by elimination of sulfur monoxide, possibly through a concerted nonlinear chelatropic reaction96 with retention of configuration of the liberated olefin. 

It is highly probable that the lesser stability of thiirene dioxides compared with that of the thiirene oxides simply reflects the more facile extrusion of sulfur dioxide relative to that of sulfur monoxide. In fact, the same effect is probably operative in the case of the cis- and trans-diphenylthiirane oxides (16g,h)110 compared with cis- and trans-diphenylthiirane dioxides (17d,e)99 the former were found to be more stable toward thermal decomposition than the latter. 

Write the balanced chemical equation for (a) the thermal decomposition of potassium chlorate without a catalyst (b) the reaction of bromine with water (c) the reaction between sodium chloride and concentrated sulfuric acid, (d) Identify each reaction as a Bronsted acid—base, Lewis acid—base, or redox reaction. 

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]. 

The spontaneous thermal decomposition of S2O on condensation at low temperatures and of some of the homocychc sulfuroxides on storage at 20 °C results in polysulfuroxides (PSO) of composition S 0 with n>3. These products are mixtures of molecules of unknown molecular mass which slowly decompose at 20 °C to elemental sulfur and SO2. Consequently, their composition depends on the preparation and changes with time. At 100 °C this decomposition is quantitative within a few minutes. 

The materials obtained by this idealized equation have also been termed polysulfuroxides in the older hterature. However, more recent results showed that they also contain hydrogen and therefore are probably polysulfane oxides of the types HS(S 0)xSH or HS(S 0)xOH [3, 88]. Due to the simultaneous thermal decomposition with formation of SO2 the sulfur content is higher than expected from Eq. (38) and from the general formula. All these compounds produce S2O on heating in a high vacuum which is a typical reaction for compounds containing oxidized sulfur chains or rings. 

Reichle, W. T. Preparation, Properties, and Thermal Decomposition Products of Organoazides of Silicon, Germanium, Tin, Lead, Phosphorus, and Sulfur. Inorg. Chem. 3, 402 (1964). 

Corriu et al. also described an alternative synthetic method for internally coordinated silanethiones starting from the pentacoordinated diaminosilanes.28 As shown in Scheme 9, the pentacoordinated diaminosilanes 32 are allowed to react with sulfur-containing heterocumulenes such as carbon disulfide or phenyl isothiocyanate to give the corresponding insertion products 33, which undergo thermal decomposition to produce the corresponding silanethiones 31, 34, and 35.28... 

The acid is prepared by sulfonation of nitrobenzene with oleum, and the reaction product consists essentially of a hot solution of the acid in sulfuric acid. A completed 270 1 batch exploded violently after hot storage at 150C for several hours. An exotherm develops at 145°C, and the acid is known to decompose at 200 C [ 1], A similar incident arose from water leaking from a cooling coil into the fuming sulfuric acid reaction medium, which caused an exotherm to over 150°C and subsequent violent decomposition [2], Detailed examination of the thermal decomposition of the acid shows that it is much slower for the isolated acid than for the reaction mass, and that the concentration of sulfur trioxide in the oleum used for sulfonation bears... 

Sulfuric acid, Sulfur trioxide Vervalin, H. C., Hydrocarbon Process., 1976, 55(9), 323 Dining sulfonation of 4-nitrotoluene at 32° C with 24% oleum in a 2000 1 vessel, a runaway decomposition reaction set in and ejected the contents as a carbonaceous mass. The thermal decomposition temperature was subsequently estimated as 52°C (but see above). 

For the synthesis ofthiepins and oxepins, [(ri3-C3Hs)PdCl]2-catalyzed decomposition of 4-diazomethyl-4-methyl-4/f-thiopyrans 387) or -pyrans38] ) is the method of choice. Purely thermal decomposition of the former diazo compounds would require higher temperatures and thus would cause extrusion of sulfur from the primarily formed thiepin, yielding a benzene derivative. 

Hundreds of cycles have been studied from the viewpoint of the feasibility of component chemical reactions in terms of conversion ratio or product separation, theoretical thermal efficiency of hydrogen production, etc. [16]. Among them, those that utilize thermal decomposition of sulfuric acid, which are categorized as "sulfur cycles," have been considered one of the most promising cycles. 

Thermal decomposition of sulfuric acid, reaction 4.1, proceeds in the following two steps ... 

The metal and ammonium salts of dithiophosphinic acids tend to exhibit far greater stability with respect to this thermal decomposition reaction, and consequently these acids are often prepared directly in their salt form for convenience and ease of handling. Alkali-metal dithiophosphinates are accessible from the reaction of diphosphine disulfides with alkali-metal sulfides (Equation 22) or from the reaction of alkali-metal diorganophosphides with two equivalents of elemental sulfur (Equation 23). Alternatively, they can be prepared directly from the parent dithiophosphinic acid on treatment with an alkali-metal hydroxide or alkali-metal organo reagent. Reaction of secondary phosphines with elemental sulfur in dilute ammonia solution gives the dithiophosphinic acid ammonium salts (Equation 24). 

The thermal decomposition of />-nitrotriphenylmethyl hydroperoxide in benzene gives -nitrophenol 32%, phenol 9%, >-nitro-triphenylcarbinol 23%, -nitrobenzophenone 14%, and no benzo-phenone the decomposition in ether plus sulfuric acid gives -nitro-benzophenone 94% and phenol 81%.817 The latter reaction is very probably ... 

---