Sulfur dioxide production using acid

Uses. The dominant use of sulfur dioxide is as a captive intermediate for production of sulfuric acid. There is also substantial captive production in the pulp and paper industry for sulfite pulping, and it is used as an intermediate for on-site production of bleaches, eg, chlorine dioxide or sodium hydrosulfite (see Bleaching agents). There is a substantial merchant market for sulfur dioxide in the paper and pulp industry. Sulfur dioxide is used for the production of chlorine dioxide at the paper (qv) mill site by reduction of sodium chlorate in sulfuric acid solution and also for production of sodium dithionite by the reaction of sodium borohydride with sulfur dioxide (315). This last appHcation was growing rapidly in North America as of the late 1990s. 

Sulfur dioxide is used for refrigeration and also serves as raw material for the production of sulfuric acid. It is also used as a bleaching agent in the textile and food industries. It is an effective disinfectant and is employed as such for wooden kegs and barrels and brewery apparatus and for the prevention of mold in the drying of fruits. Sulfur dioxide efficiently controls fermentation in the making of wine. It is used in the sulfite process for paper pulp, as a liquid solvent in petroleum refining, and as a raw material in many plants in place of sulfites, bisulfites, or hydrosulfites. 

Extraction hoods serve a number of useful purposes. These include removal of carbon dioxide and steam (the commonest combustion products) and of other, less desirable combustion products, such as sulfur dioxide and other acidic gases from some sample solutions, and of whatever elements were present in the samples. They also remove soot from excessively fuel-rich flames, which otherwise can make a real mess in the laboratory. It is unwise to run instruments for extended periods without fume extraction, even if there is nothing obviously toxic in the sample solutions. This is especially true for the nitrous oxide-acetylene flame. It is well worth considering interfacing the fume extraction switch with the instrument power supply, because it is easy to forget to turn on the extractor when everything else is automated. 

In the reduction of an arsonic acid, the end product depends largely on the reducing agent used. For instance, sulfur dioxide and hydnodic acid together convert the arsonic radical into the arsinoxide group,... 

The Flakt-Boliden version of the citrate process uses thermal regeneration of the citrate absorbing solution to obtain stripped citrate solution and a stream of up to 90% sulfur dioxide. Recovery of a sulfur dioxide product gives flexibility to the final stage of processing as to whether liquid sulfur dioxide, sulfuric acid, or sulfur are obtained as the final product. This process has recently been reexamined [42]. 

So-called Raffo or LaMer sulfur sols are used most frequently. These can be prepared by dropwise addition of aqueous sodium thiosulfate to concentrated sulfuric acid followed by coohng and precipitation of the hydrophilic sol by a saturated solution of sodium chloride. The sol originates from the spontaneous decomposition of the primary product thiosulfuric acid (H2S2O3) which disproportionates in a series of complex redox reactions producing elemental sulfur, hydrogen sulfide, sulfur dioxide and polythionic acids ... 

Apply Coal and petroleum products are sometimes contaminated with sulfur. When coal or petroleum containing sulfur is burned, sulfur dioxide (SO2) can be released into the atmosphere. Use the information about the reactions involved in industrial sulfuric-acid production to infer how atmospheric sulfur dioxide contributes to acid precipitation. 

In some countries, sulfur dioxide is used as a preservative in meat products. Sulfur dioxide occvus in many forms in food but quantitative tests for the material in meat products are normally for total (free plus bound) sulfur dioxide. The AOAC method applied to meat products consists of liberation of sulfur dioxide from the sample by heating with hydrochloric acid, distillation into hydrogen peroxide solution. 

Sulfur dioxide is produced on a large scale by burning sulfur, Sg. It is also obtained as a by-product of the roasting of sulfide ores (such as FeS2, CuS, ZnS, and PbS). Most of this sulfur dioxide is used to prepare sulfuric acid. Some is used as a bleach for wood pulp and textiles (Figure 22.46) and as a disinfectant and food preservative (for example, in wine and dried fruit). Its use as a food preservative depends on the fact that sulfur dioxide is especially toxic to yeasts, molds, and certain bacteria. Because some people are allergic to sulfur dioxide, foods containing it must be properly labeled. 

In 1839 Kuhlmann described ammonia oxidation to produce nitrogen oxides for nitric acid production using a platinum sponge catalyst at 300 C. At the same time he was also granted a patent for the oxidation of sulfur dioxide and used the process in his factoiy at Loos. He was apparently unaware of the Phillips patent granted in the United Kingdom, but he attempted to make sulfuric acid with a platinum catalyst. 

Benzene. The reaction of sulfur trioxide and ben2ene in an inert solvent is very fast at low temperatures. Yields of 90% ben2enesulfonic acid can be expected. Increased yields of about 95% can be reali2ed when the solvent is sulfur dioxide. In contrast, the use of concentrated sulfuric acid causes the sulfonation reaction to reach reflux equiUbrium after almost 30 hours at only an 80% yield. The by-product is water, which dilutes the sulfuric acid estabhshing an equiUbrium. 

Because sulfur suppHes, either as elemental sulfur or by-product sulfuric acid, have grown owiag to iacreased environmental awareness, demand for sulfur has decreased ia some consuming iadustries for the same reason. Industries such as titanium dioxide productions, which traditionally utilized sulfuric acid, have concerted to more environmentally friendly processes. In addition, many consumers who contiaue to use sulfuric acid are puttiag an emphasis on regenerating or recycling spent acid. 

Sulfuric acid is the most important sulfur-containing intermediate product. More than 85% of the sulfur consumed in the world is either converted to sulfuric acid or produced direcdy as such (see Sulfuric acid and sulfur trioxide). Worldwide, well over half of the sulfuric acid is used in the manufacture of phosphatic fertilizers and ammonium sulfate for fertilizers. The sulfur source may be voluntary elemental, such as from the Frasch process recovered elemental from natural gas or petroleum or sulfur dioxide from smelter operations. 

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 ]. 

Pan and cascade burners are generally more limited ia flexibiHty and are useful only where low sulfur dioxide concentrations are desired. Gases from sulfur burners also contain small amounts of sulfur trioxide, hence the moisture content of the air used can be important ia achieving a corrosion-free operation. Continuous operation at temperatures above the condensation poiat of the product gases is advisable where exposure to steel (qv) surfaces is iavolved. Pressure atomiziag-spray burners, which are particularly suitable when high capacities are needed, are offered by the designers of sulfuric acid plants. 

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