Catalyzed oxidation of sulfur dioxide

Martin, L. R., and Good, T. W., Catalyzed oxidation of sulfur dioxide in solution The iron-manganese synergism. Atmos. Environ. 25A, 2395 (1991). 

A wide variety of interrelated homogenous gas-phase, solution-phase, and heterogenous chemistry may ultimately result in oxidation of SO2 to sulfuric acid in DUV exposure tools. The three main possible reaction pathways for the oxidation of sulfur dioxide to sulfuric acid in the exposure chamber may include (i) direct oxidation of sulfur dioxide by stable atmospheric oxygen, (ii) catalyzed oxidation of sulfur dioxide by metal ions, and (iii) photochemical oxidation of sulfur dioxide by ozone and hydroxyl radical. 

Catalyzed oxidation of sulfur dioxide by metal ions... 

Oxidation of sulfur dioxide in aqueous solution, as in clouds, can be catalyzed synergistically by iron and manganese (225). Ammonia can be used to scmb sulfur dioxide from gas streams in the presence of air. The product is largely ammonium sulfate formed by oxidation in the absence of any catalyst (226). The oxidation of SO2 catalyzed by nitrogen oxides was important in the eady processes for manufacture of sulfuric acid (qv). Sulfur dioxide reacts with chlorine or bromine forming sulfuryl chloride or bromide [507-16 ]. 

In the chamber process, nitric oxide catalyzes the oxidation of sulfur dioxide to trioxide ... 

The anaerobic reaction of sulfur dioxide with aqueous ammonia produces a solution of ammonium sulfite [10192-30-0]. This reaction proceeds efficiently, even with a gas stream containing as little 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 fertilizer (244) (see Fertilizers). In a variant of this process, the use of electron-beam radiation catalyzes the oxidation of sulfur dioxide in the presence of ammonia to form ammonium sulfate (245). 

The noble metals may assist in this process, since they are well known for catalyzing the oxidation of sulfur dioxide to sulfur trioxide species in an oxygen-rich environment... 

Besides providing high-energy adsorption sites for physical or specific adsorption, carbon, which consists of both small pores and functional groups, is able to catalyze surface reactions. A simple example is oxidation of sulfur dioxide where it was found that basic functional groups present on the surface of carbons... 

Oxidation of sulfur dioxide to sulfur trioxide occurs mostly in flames where (transient) atomic oxygen species are thought to be prevalent by interactions of hydrogen atoms with oxygen and by interactions of carbon monoxide with oxygen and therefore may not occur in the stoichiometric manner shown earlier. The process can, however, be catalyzed by the ferric oxides that form on boiler tube surfaces and show excellent catalytic activity for sulfur dioxide oxidation at approximately 600°C (1110 F), that is, at temperatures that occur in the superheater section of a boiler. 

Cesium is used as a catalyst in the hydrogenation of organic compounds. Some other catalysts are doped with cesium, giving an improved catalytic effect An important example is the vanadium pentoxide that catalyzes the oxidation of sulfur dioxide to sulfuric acid. The addition of cesium is expensive but profitable as it reduces the bed inlet temperature, saving energy and start-up time. It also maximizes the SO2 conversion and reduces emissions. 

Chamber An obsolete but formerly very important process for making sulfuric acid. Invented by J. Roebuck in Birmingham, England, in 1746, although the patent was not filed in Scotland until 1771. Progressively improved during the nineteenth century and finally abandoned everywhere in favor of the Contact process by 1980. Essentially, the Chamber process was the gas-phase oxidation of sulfur dioxide to sulfur trioxide, catalyzed by oxides of nitrogen, conducted in a lead-lined chamber, followed by dissolution of the sulfur trioxide in water. 

The first industrial catalyst was probably the niter pot, which was used in the early sulfuric acid lead chamber process when it became known that oxides of nitrogen catalyzed the oxidation of sulfur dioxide. How was this important process—on which chemical development soon depended—discovered Was it from the observation that cannons corroded or that condensation was acidic following the explosion of gunpowder All the ingredients for chamber acid were there—sulfur, saltpeter, atmospheric air, and heat. Ostwald noted that copious brown fumes were evolved as gunpowder exploded, but did not make any comment on sulfur oxides. Empirical observations, or inspired deductions, ditr-ing the 1800s led to the introduction of several more important catalytic processes. The inevitable development of a chemical industry based on the use of catalysts followed from a mass of experimental observations, such as those shown in Table 1.1, accumulated after Berzelius defined catalysts in 1835 (Figure 1.1). 

Claus A process for removing hydrogen sulfide from gas streams by the catalyzed reaction with sulfur dioxide, producing elementary sulfur. The process has two stages in the first, one third of the hydrogen sulfide is oxidized with air to produce sulfur dioxide in the second, this sulfur dioxide stream is blended with the remainder of the hydrogen sulfide stream and passed over an iron oxide catalyst at approximately 300°C. The resulting sulfur vapor is condensed to liquid sulfur. 

Katasulf A process for removing hydrogen sulfide and ammonia from coke-oven gas, developed by IG Farbenindustrie in Germany in the 1920s. The basic reaction involved is the catalyzed oxidation of hydrogen sulfide to sulfur dioxide and water at approximately 420°C ... 

Palladium alkoxide complexes are thought to be formed in the reactions of alcohols catalyzed by palladium(II) chloride. These reactions include the oxidation of alcohols, yielding acetals or ketones,137,138 and their carbonylation, yielding esters.139 Alkoxide intermediates are also thought to be involved in the reaction of sulfur dioxide with [PdCl2] suspended in alcohol (equation 15).140,141... 

The autoxidation of aqueous solutions of sulfur dioxide (sulfite, bisulfite) is a classic problem in chemistry. Basic features of this reaction have been known since early in this century, when it was established that the reaction is trace metal ion catalyzed (1 ) and most likely involves free radicals (2). Certain chemical effects associated with sulfite autoxidation were noted also. Before the turn of the century, it was noted that sulfite would induce the oxidation of transition metal ions (3) and it was reported later that the oxidation of organic compounds was brought about during sulfite autoxidation ( 0. Conversly, organic compounds were also shown to serve as inhibitors of sulfite autoxidation (5). 

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