Sulfur dioxide catalytic oxidation

I.M. Petrushina, V.A. Bandur, F. Cappeln, andN.J. Bjerrum, Electrochemical Promotion of Sulfur Dioxide Catalytic Oxidation, J. Electrochem. Soc. 147(8), 3010-3013(2000). 

Matros, Y.S. Noskov, A.S. Chumachenko, V.A. Goldman, O.V. Theory and application of unsteady catalytic detoxication of effluent gases from sulfur dioxide, nitrogen oxides and organic compounds. Chem. Eng. Sci. 1988, 43 (8), 2061-2066. 

Some of the advanced techniques used in postcombustion cleaning—such as the use of granular calcium oxide or sodium sulfite solutions—have already been described above. In the SNOX process, cooled flue gases are mixed with ammonia gas to remove the nitric oxide by catalytically reducing it to molecular nitrogen. The resulting gas is reheated and sulfur dioxide is oxidized catalytically to sulfur trioxide, which is subsequently hydrated by water to sulfuric acid, condensed, and removed. 

A derivative of the Claus process is the Recycle Selectox process, developed by Parsons and Unocal and Hcensed through UOP. Once-Thm Selectox is suitable for very lean acid gas streams (1—5 mol % hydrogen sulfide), which cannot be effectively processed in a Claus unit. As shown in Figure 9, the process is similar to a standard Claus plant, except that the thermal combustor and waste heat boiler have been replaced with a catalytic reactor. The Selectox catalyst promotes the selective oxidation of hydrogen sulfide to sulfur dioxide, ie, hydrocarbons in the feed are not oxidized. These plants typically employ two Claus catalytic stages downstream of the Selectox reactor, to achieve an overall sulfur recovery of 90—95%. 

Allied-Signal Process. Cyclohexanone [108-94-1] is produced in 98% yield at 95% conversion by liquid-phase catal57tic hydrogenation of phenol. Hydroxylamine sulfate is produced in aqueous solution by the conventional Raschig process, wherein NO from the catalytic air oxidation of ammonia is absorbed in ammonium carbonate solution as ammonium nitrite (eq. 1). The latter is reduced with sulfur dioxide to hydroxylamine disulfonate (eq. 2), which is hydrolyzed to acidic hydroxylamine sulfate solution (eq. 3). 

Snia Viscosa. Catalytic air oxidation of toluene gives benzoic acid (qv) in ca 90% yield. The benzoic acid is hydrogenated over a palladium catalyst to cyclohexanecarboxyhc acid [98-89-5]. This is converted directiy to cmde caprolactam by nitrosation with nitrosylsulfuric acid, which is produced by conventional absorption of NO in oleum. Normally, the reaction mass is neutralized with ammonia to form 4 kg ammonium sulfate per kilogram of caprolactam (16). In a no-sulfate version of the process, the reaction mass is diluted with water and is extracted with an alkylphenol solvent. The aqueous phase is decomposed by thermal means for recovery of sulfur dioxide, which is recycled (17). The basic process chemistry is as follows ... 

Catalytic Sulfur Dioxide Oxidation, Sulfuric acid [7664-93-9] is the largest volume chemical manufactured woddwide and is produced by... 

Metals and alloys, the principal industrial metalhc catalysts, are found in periodic group TII, which are transition elements with almost-completed 3d, 4d, and 5d electronic orbits. According to theory, electrons from adsorbed molecules can fill the vacancies in the incomplete shells and thus make a chemical bond. What happens subsequently depends on the operating conditions. Platinum, palladium, and nickel form both hydrides and oxides they are effective in hydrogenation (vegetable oils) and oxidation (ammonia or sulfur dioxide). Alloys do not always have catalytic properties intermediate between those of the component metals, since the surface condition may be different from the bulk and catalysis is a function of the surface condition. Addition of some rhenium to Pt/AlgO permits the use of lower temperatures and slows the deactivation rate. The mechanism of catalysis by alloys is still controversial in many instances. 

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 ... 

Commercially available hydrogen fluoride usually is not suitable for catalytic hydrogenation because of its sulfur dioxide content An oxidative treatment with manganese dioxide and distillation are needed for the preparation of hydrogena tion-grade hydrogen fluoride [d, 4]... 

Smelting iron ores produces large amounts of sulfur dioxide, which is catalytically oxidized to sulfur trioxide for sulfuric acid production. This process is declining due to pollution control measures and the presence of some impurities in the product acid. 

The chemical reactions appear simple. They begin with pure sulfur (which occurs in natural deposits in the elemental state). First, sulfur is burned to give gaseous sulfur dioxide, S02. Next, the S02 is further oxidized, catalytically, to sulfur trioxide, SO ,. Finally, addition of water forms sulfuric acid. The reactions are ... 

From the results of other authors should be mentioned the observation of a similar effect, e.g. in the oxidation of olefins on nickel oxide (118), where the retardation of the reaction of 1-butene by cis-2-butene was greater than the effect of 1-butene on the reaction of m-2-butene the ratio of the adsorption coefficients Kcia h/Kwas 1.45. In a study on hydrogenation over C03O4 it was reported (109) that the reactivities of ethylene and propylene were nearly the same (1.17 in favor of propylene), when measured separately, whereas the ratio of adsorption coefficients was 8.4 in favor of ethylene. This led in the competitive arrangement to preferential hydrogenation of ethylene. A similar phenomenon occurs in the catalytic reduction of nitric oxide and sulfur dioxide by carbon monoxide (120a). 

Reasonable NO conversion can be achieved using n-decane as reductant. In the absence of sulfur dioxide, the catalytic activity is roughly related to the r ucibility of the Cu phase of Cu ions in zeolites the reaction temperature needed to reach 20% NO conversion parallels that of the TPR peak (Table 7). This relation also practically holds for Cu on simple oxides, therefore a redox mechanism in which reduction of Cu + cations is the slow step could account for the results. 

Mathur and Thodos Chem. Eng. Sci., 21 (1191), 1966] used the initial rate approach to analyze the kinetics of the catalytic oxidation of sulfur dioxide. They summarized the most plausible rate controlling steps for the reaction as ... 

Olson, Schuler, and Smith (86) have studied the catalytic oxidation of sulfur dioxide in a differential fixed bed reactor. 

Industrial scale production of sulfuric acid is dependent on the oxidation of sulfur dioxide to sulfur trioxide in fixed bed catalytic reactors. 

CAT-OX [Catalytic oxidation] An adaptation of the Contact process for making sulfuric acid, using the dilute sulfur dioxide in flue-gases. A conventional vanadium pentoxide catalyst is used. Developed by Monsanto Enviro-Chemical Systems, and operated in Pennsylvania and Illinois in the early 1970s. 

Centaur A process for reducing sulfur dioxide emissions from sulfuric acid plants. An activated caibon with both absorptive and catalytic properties is used. The technology uses fixed beds of Centaur carbon to oxidize sulfur dioxide to sulfuric acid in the pores of the carbon. The sulfuric acid is recovered as dilute sulfuric acid, which is used a make-up water in the sulfuric acid production process. Developed by Calgon Carbon Corporation in the 1990s. Calgon Carbon and Monsanto Enviro-Chem operated a Centaur pilot plant at an existing sulfuric acid facility in 1996. 

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