Reactions of sulfur dioxide

Rhenium oxides have been studied as catalyst materials in oxidation reactions of sulfur dioxide to sulfur trioxide, sulfite to sulfate, and nitrite to nitrate. There has been no commercial development in this area. These compounds have also been used as catalysts for reductions, but appear not to have exceptional properties. Rhenium sulfide catalysts have been used for hydrogenations of organic compounds, including benzene and styrene, and for dehydrogenation of alcohols to give aldehydes (qv) and ketones (qv). The significant property of these catalyst systems is that they are not poisoned by sulfur compounds. 

At present, thionyl chloride is produced commercially by the continuous reaction of sulfur dioxide (or sulfur trioxide) with sulfur monochloride (or sulfur dichloride) mixed with excess chlorine. The reaction is conducted in the gaseous phase at elevated temperature over activated carbon (178). Unreacted sulfur dioxide is mixed with the stoichiometric amount of chlorine and allowed to react at low temperature over activated carbon to form sulfuryl chloride, which is fed back to the main thionyl chloride reactor. 

The Claus process, which involves the reaction of sulfur dioxide with hydrogen sulfide to produce sulfur in a furnace, is important in the production of sulfur from sour natural gas or by-product sulfur-containing gases (see Sulfurremoval and recovery). 

The anaerobic reaction of sulfur dioxide with aqueous ammonia produces a solution of ammonium sulfite [10192-30-0]. This reaction proceeds efficientiy, even with a gas stream containing as Httie as 1 wt % sulfur dioxide. The sulfur dioxide can be regenerated at a high concentration by acidulation or by stream stripping of the ammonium sulfite solution, or the sulfite can be made to precipitate and the ammonia recovered by addition of lime (243). The process can also be modified to produce ammonium sulfate for use as fertili2er (244) (see Fertilizers). In a variant of this process, the use of electron-beam radiation cataly2es the oxidation of sulfur dioxide in the presence of ammonia to form ammonium sulfate (245). 

The reaction of sulfur dioxide with olefins under free-radical-cataly2ed conditions produces copolymers which, ia most cases, are of an alternating 1 1 type (249,250) ... 

Other reactions of sulfur dioxide forming sulfinic acids or sulfones have been reviewed (254). 

The thermodynamic properties of sulfur trioxide, and of the oxidation reaction of sulfur dioxide are summarized in Tables 3 and 4, respectively. Thermodynamic data from Reference 49 are beheved to be more accurate than those of Reference 48 at temperatures below about 435°C. 

Sodium sulfite [7757-83-7] which is used in pulp and paper bleaching, is usually produced by the reaction of sulfur dioxide with either caustic soda or soda ash. 

Catalysis. Catalytic properties of the activated carbon surface are useful in both inorganic and organic synthesis. For example, the fumigant sulfuryl fluoride is made by reaction of sulfur dioxide with hydrogen fluoride and fluorine over activated carbon (114). Activated carbon also catalyzes the addition of halogens across a carbon—carbon double bond in the production of a variety of organic haUdes (85) and is used in the production of phosgene... 

Sulfur dioxide emissions may affect building stone and ferrous and nonferrous metals. Sulfurous acid, formed from the reaction of sulfur dioxide with moisture, accelerates the corrosion of iron, steel, and zinc. Sulfur oxides react with copper to produce the green patina of copper sulfate on the surface of the copper. Acids in the form of gases, aerosols, or precipitation may chemically erode building materials such as marble, limestone, and dolomite. Of particular concern is the chemical erosion of historical monuments and works of art. Sulfurous and sulfuric acids formed from sulfur dioxide and sulfur trioxide when they react with moisture may also damage paper and leather. 

Formed as an intermediate in the Pb chamber process for sulfuric acid by the reaction of sulfur dioxide, nitrogen trioxide, oxygen and w (chamber crystals) (Refs 1 2). Can be prepd from Ag acid sulfate and nitrosyl bromide (Ref 4)... 

Two-component methods represent the most widely applied principles in sulfone syntheses, including C—S bond formation between carbon and RSOz species of nucleophilic, radical or electrophilic character as well as oxidations of thioethers or sulfoxides, and cheletropic reactions of sulfur dioxide. Three-component methods use sulfur dioxide as a binding link in order to connect two carbons by a radical or polar route, or use sulfur trioxide as an electrophilic condensation agent to combine two hydrocarbon moieties by a sulfonyl bridge with elimination of water. 

Beside these free radical reactions of sulfur dioxide, its electrophilic reactions generating sulfinates with organometallic compounds453,454 or sulfinic acids with arenes under Friedel-Crafts conditions455 are well known. To complete these three-component syntheses, the sulfinates prepared first are transformed to sulfones by reactions with appropriate electrophiles, discussed earlier in this chapter, i.e. equation 82. 

The simultaneous reaction of sulfur dioxide and chlorine with paraffins, named sulfochlorination, was discovered by Reed and Horn in the 1930s [9]. The primary products of this reaction are the alkanesulfochlorides [10], which can be saponified to alkanesulfonates by sodium hydroxide solution or treated with substituted phenolates to give plasticisers. In a short time the process was industrially realized to secure detergent production during World War II in Germany [11]. 

The oxidation number of sulfur in sulfur dioxide and the sulfites is +4, an intermediate value in sulfur s range from —2 to +6. Hence, these compounds can act as either oxidizing agents or reducing agents. By far the most important reaction of sulfur dioxide is its slow oxidation to sulfur trioxide, S03 (13), in which sulfur has the oxidation number +6 ... 

The reversible reaction between butadiene and sulfur dioxide, which yields sulfolene, has been known for a long time. Such cycloaddition reactions of sulfur dioxide, and of other sulfur oxides, have been reviewed by Block.49... 

The S02 molecule has unshared pairs of electrons on both the sulfur and oxygen atoms. As a result, it forms numerous complexes with transitions metals in which it is known to attach in several ways. These include bonding through the sulfur atom, through an oxygen atom, by both oxygen atoms, and various bridging schemes. In most cases, the complexes involve soft metals in low oxidation states. Another important reaction of sulfur dioxide is known as the insertion reaction, in which it is placed... 

Scheme 2 Photochemical reaction of sulfur dioxide with hydrocarbons...

Timmons, R. B. The photochemically induced reactions of sulfur dioxide with alkanes and carbon monoxide. Photochem. Photobiol. 12 219-230, 1970. 

The reaction of sulfur dioxide and hydrogen selenide in water yields an orange precipitate of the approximate composition Se S the nature of which has not been elucidated. The product is partly soluble in carbon disulfide. 

Frederick Frey and Walter Shultze were instrumental early researchers. Frey was among the first to dehydrogenate paraffins catalytically to olefins and then the olefins to diolefins that serve as feedstocks to the production of many of today s polymers. In competition with Bakelite, he discovered the preparation of polysulfone polymers made from the reaction of sulfur dioxide and olefins creating a hard Bakelite-like material. Frey and Schultz also developed a process that allowed the production of 1,3-butadiene from butane that allowed the synthesis of SR. 

Baldwin, A. C., Heterogeneous Reactions of Sulfur Dioxide with Carbonaceous Particles, Int. J. Chem. Kinet., 14, 269-277 (1982). 

Britton, L. G., and A. G. Clarke, Heterogeneous Reactions of Sulfur Dioxide and S02/N02 Mixtures with a Carbon Soot Aerosol, Atmos. Environ, 14, 829-839 (1980). 

Here PNO2 partial pressure of nitrogen dioxide in pascals (1 Pa = 0.000145 psi), and the activation energy is 3870 kJ/mol. Other saturated polymers are less susceptible to attack by NO2 than most unsaturated polymers such as synthetic rubbers (polyiso-prene, polybutadiene, and butyl rubber). The presence of oxygen also tends to accelerate degradation by NO2. The reaction of sulfur dioxide with saturated polymers is complex, but appears to be activated by ultraviolet radiation. 

Scheme 15. The reactions of sulfur dioxide with dioxygen complexes of iridium.

The reaction of sulfur dioxide and chlorine with paraffin hydrocarbons to yield alkane sulfonyl chlorides (RH + S02 + Cl2 - RS02C1 + HC1) (the Reed reaction) was patented in 1939.221 This reaction has usually been run in the liquid phase under strong illumination with short wavelength visible or ultraviolet light.107,218 267... 

Sulfur dioxide is another commonly used chemical for chromium reduction. The reduction occurs when sulfurous acid, produced by the reaction of sulfur dioxide and water, reacts with chromic acid as follows ... 

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