Sulfur dioxide heterogeneous reactions

As mentioned before, heterogeneous sulfur dioxide oxidation reactions... 

In furnaces using residual oils, heterogeneous catalysis is a possible route for the conversion of S02 to S03. Sulfur dioxide and molecular oxygen will react catalytically on steel surfaces and vanadium pentoxide (deposited from vanadium compounds in the fuel). Catalytic reactions may also occur at lower temperatures where the equilibrium represented by reaction (8.94) favors the formation of S03. 

The Henry s law constant in water was used in the McJilton et al. uptake model to determine the equilibrium concentration of ozone and sulfur dioxide at the surface of a simulated mucus film along the airways in Weibel s symmetric model.It is also used to determine the concentration of absorbed gas at the surface of the mucus when the pollutant gas undergoes a homogeneous or heterogeneous chemical reaction within the mucus layer. 

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). 

A. Disodium Nitrosodisulfonate. In a 1-1. resin kettle, equipped with a mechanical stirrer, a thermometer, a gas-inlet tube suspended about 0.5 cm. above the bottom of the vessel, and an ice-cooling bath, are placed 15.0 g. (0.217 mole) of sodium nitrite (Note 1), 16.8 g. (0.200 mole) of sodium bicarbonate (Note 1), and 400 g. of ice. Sulfur dioxide (25.6 g. or 0.40 mole, Note 2) is passed into the cold, initially heterogeneous mixture with stirring over a period of 40 minutes. Near the end of the sulfur dioxide addition, the light brown color of the reaction mixture fades almost completely. The resulting colorless to pale yellow solution of disodium hydroxyl-aminedisulfonato (Note 3), which has an approximate pH of 4,... 

Procedure for preparation of wood-styrene-sulfur dioxide graft copolymer was almost the same as described in our previous paper (3), except that wood was grafted instead of cellulose and that the reaction proceed heterogeneously. 

However, this reaction is very slow in the absence of a catalyst. One of the mysteries during early research on air pollution was how the sulfur dioxide produced from the combustion of sulfur-containing fuels is so rapidly converted to sulfur trioxide in the atmosphere. It is now known that dust and other particles can act as heterogeneous catalysts for this process (see Section 15.9). In the preparation of sulfur trioxide for the manufacture of sulfuric acid, either platinum metal or vanadium(V) oxide (V205) is used as a catalyst, and the reaction is carried out at approximately 500°C, even though this temperature decreases the value of the equilibrium constant for this exothermic reaction. 

Heterogeneous reduction processes still involve the reaction of gases, but in these cases the reaction occurs in the presence of a suitable solid phase catalyst. Sulfur dioxide may be reduced to sulfur with hydrogen sulfide, if this is available, and the sulfur vapor condensed out of the gas stream by cooling, as in the second half of the Claus process (Eq. 3.17). 

Sulfur dioxide (SO ) and nitrogen oxides (NO ) are oxidized to sulfate and nitrate aerosols either homogeneously rn the gas phase or heterogeneously in atmospheric microdroplets and hydrometeors Gas-phase production of nitric acid appears to be the dominant source of aerosol nitrate because the aqueous phase reactions of NO (aq) are slow at the nitrogen oxide partial pressures typically encountered in the atmosphere (5,i5). Conversely, field studies indicate that the relative importance of homogeneous and heterogeneous SO2 oxidation processes depends on a variety of climatological factors such as relative humidity and the intensity of solar radiation (4, -1 ). 

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. 

MCM-41 and silica gel as efficient and reusable heterogeneous catalyst for the Knoevenagel Condensation reactions. Burwell and Leal (1974) first reported selective chemisorption of sulfur dioxide on amine-modified silica gel. Leal et al. (1995) studied carbon dioxide adsorption on amine surface-bonded silica gel, although their CO2 adsorption amount (0.3 mmol/g-sorbent at 1 atm CO2) was low. Further work by Huang et al. (2003) produced high-capacity and selective sorbents for both CO2 and H2S. 

The heterogeneous catalytic oxidation of sulfur dioxide to sulfur trioxide is well established. The industrial manufacture of sulfuric acid is based on the well-known contact process where the overall stoichiometry is as shown in reaction 8.5.5.3. 

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