Sulfur dioxide oxidation temperature

Kagawa and Toyama in Tokyo followed 20 normal 11-yr-old school children once a week from June to December 1972 with a battery of pulmonary-function tests. Environmental factors studied included oxidant, ozone, hydrocarbon, nitric oxide, nitrogen dioxide, sulfur dioxide, particles, temperature, and relative humidity. Temperature was found to be the most important environmental factor affecting respiratory tests. The observers noted that pulmonary-function tests of the upper airway were more susceptible to increased temperature than those of the lower airway. Although the effect of temperature was the most marked, ozone concentration was significantly associated with airway resistance and specific airway conductance. Increased ozone concentrations usually occur at the same time as increased temperature, so their relative contributions could not be determined. 

Temperature profiles, reactors ammonia synthesis, 582, 584 cement kiln, 590 cracking of petroleum, 595 endo- and exothermic processes, 584 jacketed tubular reactor, 584 methanol synthesis, 580 phosgene synthesis, 594 reactor with internal heat exchange, 584 sulfur dioxide oxidation, 580... 

DOCs also convert sulfur dioxide to sulfur trioxide, which forms sulfuric acid droplets or solid sulfate particles. These add to the amount of particulates emitted and can put an engine out of compliance. One approach to this problem is to lower fuel sulfur from the 1994 level to 0.01 wt% or less. A second approach is to develop a catalyst that oxidizes HC and CO but not sulfur dioxide. Newly developed catalysts that make almost no sulfate at temperatures as high as 400 C have brought this approach a step closer to reality. A third approach concerns catalyst placement. Sulfur dioxide oxidizes above 350-400°C over a EXX, while hydrocarbons do so below this temperature. A DOC could be located to have an inlet temperature favoring HC conversion. 

Sulfonation of alkylbenzene, 23-25 Sulfur dioxide, optimum temperature for oxidation of 8-9... 

Figure 9 Temperature of the reaction mixture, T, and of the coolant, Ta, in the plug flow reactor for sulfur dioxide oxidation according to Johannessen and Kjelstrup ...

The reason for limiting the temperature in sulfur dioxide oxidation is based on two factors excessive temperatures decrease the catalyst activity, as just mentioned, and the equilibrium yield is adversely affected at high temperatures. This last point is the important one in explaining the need to maintain the temperature level in the dehydrogenation of butene. Still other factors, such as physical properties of the equipment, may require limiting the temperature level. For example, in reactors operated at very high temperatures, particularly under pressure, it may be necessary to cool the reactor-tube wall to preserve the life of the tube itself. 

Formation of combustion particles also involves nucleation and condensation of vapors, although the processes occur at elevated temperatures inside the combustion source and during cooling of the plume. Like secondary aerosols, combustion particles have a major semivolatile component composed of sulfates from sulfur dioxide oxidation and organic oxidation products, and of unburned fuel and oil as well. Furthermore, they contain a large non-volatile component consisting of soot, metals, and metal oxides. 

The first supported molten salt catalyst systems date from 1914, where BASF filed a patent on a silica-supported V20s-alkali pyrosul te sulfur dioxide oxidation catalyst [48], which even today - as a slightly modified catalyst system - is still the preferred catalyst for sulfuric acid production [49]. However, it took many years to realize in the 1940s [50,51], that the catalyst system actually was a molten salt SLP-type system which is best described by a mixture of vanadium alkah sulfate/hydrogensulfate/pyrosulfate complexes at reaction conditions in the temperature range 400-600 °C with the vanadium complexes playing a key role in the catalytic reaction [49]. 

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. 

Nikolov, I., I. Vitanova, V. Najdenov, T. Milusheva, and T. Vitanov (1997). Effect of pyrolysis temperature of the catal54ic activity of active carbon -I- cobalt phthalocya-nines in sulfur dioxide oxidation by oxygen. J. Appl. Electrochem. 27, 77-82. 

Most catalysts supported on titanium dioxide reach an optimum NOX reduction temperature that depends on the catalyst composition and the treated gas. Activity then declines as the secondary reactions compete for the armnonia reductant and sulfur dioxide oxidation becomes excessive. Typical operation is in the range 300°-425°C although zeolite catalysts operate from 300°-600°C. ... 

Catalysts may therefore be designed for nse in specific duties. For power plant, the design must balance the reaction rates of NOX reduction and sulfur dioxide oxidation in the restricted range of temperature of flue gas leaving the boiler, or at the dust and sulfur dioxide removal stages. A low activity catalyst that reaches maximum NOX reduction between, say 380°-400°C, can be more efficient than a catalyst that is more active between 300°-350°C because, overall, it produces less sulfur trioxide at the fixed operating temperature. ... 

Sulfur dioxide [7446-09-5] is formed as a result of sulfur oxidation, and hydrogen chloride is formed when chlorides from plastics compete with oxygen as an oxidant for hydrogen. Typically the sulfur is considered to react completely to form SO2, and the chlorine is treated as the preferred oxidant for hydrogen. In practice, however, significant fractions of sulfur do not oxidi2e completely, and at high temperatures some of the chlorine atoms may not form HCl. 

High Temperature Corrosion. The rate of oxidation of magnesium adoys increases with time and temperature. Additions of berydium, cerium [7440-45-17, lanthanum [7439-91-0] or yttrium as adoying elements reduce the oxidation rate at elevated temperatures. Sulfur dioxide, ammonium fluoroborate [13826-83-0] as wed as sulfur hexafluoride inhibit oxidation at elevated temperatures. 

In a vacuum, uncoated molybdenum metal has an unlimited life at high temperatures. This is also tme under the vacuum-like conditions of outer space. Pure hydrogen, argon, and hehum atmospheres are completely inert to molybdenum at all temperatures, whereas water vapor, sulfur dioxide, and nitrous and nitric oxides have an oxidizing action at elevated temperatures. Molybdenum is relatively inert to carbon dioxide, ammonia, and nitrogen atmospheres up to about 1100°C a superficial nitride film may be formed at higher temperatures in the latter two gases. Hydrocarbons and carbon monoxide may carburize molybdenum at temperatures above 1100°C. 

Nickel sulfate also is made by the reaction of black nickel oxide and hot dilute sulfuric acid, or of dilute sulfuric acid and nickel carbonate. The reaction of nickel oxide and sulfuric acid has been studied and a reaction induction temperature of 49°C deterrnined (39). High purity nickel sulfate is made from the reaction of nickel carbonyl, sulfur dioxide, and oxygen in the gas phase at 100°C (40). Another method for the continuous manufacture of nickel sulfate is the gas-phase reaction of nickel carbonyl and nitric acid, recovering the soHd product in sulfuric acid, and continuously removing the soHd nickel sulfate from the acid mixture (41). In this last method, nickel carbonyl and sulfuric acid are fed into a closed-loop reactor. Nickel sulfate and carbon monoxide are produced the CO is thus recycled to form nickel carbonyl. 

It is apparent from these equations that significant quantities of sulfur dioxide are generated. For selenium, the reaction shown for oxidation of elemental selenium reverses itself at the lower temperatures employed for water scmbbing, thus regenerating sulfuric acid. The tellurium dioxide remains in the sulfated slimes. 

Chemical Properties. Anhydrous sodium sulfite is stable in dry air at ambient temperatures or at 100°C, but in moist air it undergoes rapid oxidation to sodium sulfate [7757-82-6]. On heating to 600°C, sodium sulfite disproportionates to sodium sulfate and sodium sulfide [1313-82-2]. Above 900°C, the decomposition products are sodium oxide and sulfur dioxide. At 600°C, it forms sodium sulfide upon reduction with carbon (332). 

Physical Properties. Sodium metabisulfite (sodium pyrosulfite, sodium bisulfite (a misnomer)), Na2S20, is a white granular or powdered salt (specific gravity 1.48) and is storable when kept dry and protected from air. In the presence of traces of water it develops an odor of sulfur dioxide and in moist air it decomposes with loss of part of its SO2 content and by oxidation to sodium sulfate. Dry sodium metabisulfite is more stable to oxidation than dry sodium sulfite. At low temperatures, sodium metabisulfite forms hydrates with 6 and 7 moles of water. The solubiHty of sodium metabisulfite in water is 39.5 wt % at 20°C, 41.6 wt % at 40°C, and 44.6 wt % at 60°C (340). Sodium metabisulfite is fairly soluble in glycerol and slightly soluble in alcohol. 

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