Sulfur dioxide oxidation process

Conventional industrial processes operate continuously and at steady state. Steady-state operation, however, is sometimes less economical, particularly in cases where considerable energy effects are encountered. For example, classical sulfur dioxide oxidation processes involve a large reactor-heat exchanger system to force conversion of the reactant to an acceptable level. By non-steady-state operation, the reactor volume can be considerably diminished. Unconventional operation modes are much more sensitive than conventional steady-state modeling. Very advanced dynamic modeling concepts are thus needed. 

An additional benefit of adsorption-based sulfur dioxide removal processes is that nitrogen oxides, NO, are also removed by the sorbent. Nitrogen oxides desorb when the sorbent is heated using hot air. 

Sulfur dioxide removal processes can be used to treat flue gas from industrial boilers, heaters, or other process gases where sulfur compounds are oxidized. These processes have generally been proven in utility applications. More recently, several industrial SO2 removal installations have been completed. 

Both forms of iron disulfide are very stable at ordinary temperatures and also inert towards most chemicals. Ideating at elevated temperatures gives iron(III) oxide and sulfur dioxide. This process for producing sulfur dioxide is also applied to manufacture sulfuric acid ... 

The important commercial process of sulfur dioxide oxidation has been studied by a number of investigators. A set of steps that has been proposed for both platinum and vanadium oxide-based catalysis by Horiuti (7) for the overall reaction 2SOz + 02 2SOs is as follows ... 

Sulfur dioxide oxidation. The first use of SEP to study catalytic processes was made by Vayenas and Saltsburg. Vayenas and Saltsburg studied sulfur dioxide oxidation over platinum, silver and gold electrodes.39 The oxygen activity... 

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... 

The chemical reactions involved in this process were outlined in the patent, which laid the basis for this industry. However, many improvements in practice have been achieved from a more detailed knowledge of the gas phase kinetics of the sulfur dioxide oxidation step, as well as from a better understanding of the gas-liquid equilibria associated with the hydration step. 

At 600°C, the rate of reaction is some 30 to 50 times faster again, requiring an even smaller reactor for the same throughput, but the rate of dissociation of sulfur trioxide to sulfur dioxide becomes appreciable. The value of Kp drops to about 10, giving only about 60-65% of the sulfur as sulfur trioxide at this temperature, and the remainder as sulfur dioxide. For process purposes there is no point in considering the sulfur oxide equilibrium situation for any higher temperatures than this. With a promoted vanadium pentoxide catalyst bed at 600°C a 2-4 sec contact time is already sufficient to obtain essentially equilibrium concentrations at this temperature. 

The reverse-flow chemical reactor (RFR) has been shown to be a potentially effective technique for many industrial chemical processes, including oxidation of volatile organic compounds such as propane, propylene, and carbon monoxide removal of nitrogen oxides sulfur dioxide oxidation or reduction production of synthesis gas methanol formation and ethylbenzene dehydration into styrene. An excellent introductory article in the topic is given by Eigenberger and Nieken on the effect of the kinetic reaction parameters, reactor size, and operating parameters on RFR performance. A detailed review that summarizes the applications and theory of RFR operation is given by Matros and Bunimovich. 

The sulfone is a versatile functional group comparable to the carbonyl functionality in its ability to activate molecules for further bond construction, the main difference between these two groups being that the sulfone is usually removed once the synthetic objective is achieved. The removal most commonly involves a reductive desulfonylation process with either replacement of the sulfone by hydrogen (Eq. 1), or a process that results in the formation of a carbon-carbon multiple bond when a P-functionalized sulfone, for example a (3-hydroxy or (3-alkoxy sulfone, is employed (Eq. 2). These types of reactions are the Julia-Lythgoe or Julia-Paris-Kocienski olefination processes. Alkylative desulfonylation (substitution of the sulfone by an alkyl group, Eq. 3), oxidative desulfonylation (Eq. 4), and substitution of the sulfone by a nucleophile (nucleophilic displacement, Eq. 5) are also known. Finally, p-eliminations (Eq. 6) or sulfur dioxide extrusion processes (Eqs. 7, 8 and 9) have become very popular for the... 

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. 

Au particles supported on reducible oxides such as titania or ceria are also efficient catalysts for the water-gas shift, the destruction of sulfur dioxide (DeSOx processes), the complete oxidation of methane, the selective or partial oxidation of propene, the hydrogenation of CO and olefins, and the reduction of NO with hydrocarbons. Depending on the conditions, Au/TiOs... 

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. 

The global process of sulfur dioxide oxidation to sulfate and the catalytic action of nitrogen dioxide proposed in this work would correspond to the following general reactions ... 

The catalytic oxidation of sulfur compounds in gas streams is the basis for numerous gas purification proce,s.ses, most of which are covered in other sections of this book. The oxidation of SO2 to SOj as part of a sulfur dioxide removal process is discussed in Chapter 7. The oxidation of HiS to elemental sulfur by the Claus process and related technologies is covered in Chapter 8. The liquid-phase oxidation of H2S to elemental sulfur is described in Chapter 9, and the oxidation of H S and other sulfur compounds in dry boxes and in other sulfur scavenging processes is included in Chapter 16. An area of technology that is not covered... 

Sulfur dioxide oxidation to sulfuric acid (contact process). 

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