Chlorates, manufacture

Sulfuric acid is an economical alternative source of acid and many commercial generators substitute concentrated sulfuric acid for HCl. Furthermore, the requited chloride ion needed as the reductant is already present or added as NaCl in the chlorate solution or crystal obtained from the chlorate manufacturer. This process, popular in the 1960s and 1970s, produces substantial amounts of Hquid effluent containing 20—35% sulfuric acid, 20—25% sodium sulfate, and minor amounts of sodium chloride and unreacted chlorate that must be neutralized with alkaH. 

The sodium chlorate manufacturing process can be divided into six steps (/) brine treatment 2 electrolysis (J) crystallisation and salt recovery (4) chromium removal (5) hydrogen purification and collection and (6) electrical distribution. These steps are outlined in Figure 3. 

Chromium Removal System. Chlorate manufacturers must remove chromium from the chlorate solution as a result of environmental regulations. During crystallization of sodium chlorate, essentially all of the sodium dichromate is recycled back to the electrolyzer. Alternatively, hexavalent chromium, Cr, can be reduced and coprecipitated in an agitated reactor using a choice of reducing agents, eg, sodium sulfide, sulfite, thiosulfate, hydrosulfite, hydrazine, etc. The product is chromium(III) oxide [1333-82-0] (98—106). Ion exchange and solvent extraction techniques have also... 

Platinum Platinum-coated titanium is the most important anode material for impressed-current cathodic protection in seawater. In electrolysis cells, platinum is attacked if the current waveform varies, if oxygen and chlorine are evolved simultaneously, or if some organic substances are present Nevertheless, platinised titanium is employed in tinplate production in Japan s. Although ruthenium dioxide is the most usual coating for dimensionally stable anodes, platinum/iridium, also deposited by thermal decomposition of a metallo-organic paint, is used in sodium chlorate manufacture. Platinum/ruthenium, applied by an immersion process, is recommended for the cathodes of membrane electrolysis cells. ... 

EMOS has to date been mostly used in chlorate manufacture, but R2 in Montreal, Canada has recently installed its system on an FM-21 1500-type cell chlor-alkali production facility. This is presently a pilot installation, with only six cells currently being monitored. This installation has led to the monitoring of cell currents rather than cell voltages owing to the monopolar design of these electrolysers. It is too soon to make detailed conclusions about this installation as it has only been fully operational since January 2000. 

Potassium perchlorate is made by converting sodium chlorate into sodium perchlorate in steel electrolytic cells that have platinum anodes and operate at a temperature of 65°C. Filtered potassium chloride solution is added to the sodium perchlorate, precipitating potassium perchlorate crystals, which are centrifuged, washed, and dried. The mother liquor now contains sodium chloride, which can be used as a cell feed for sodium chlorate manufacture. 

Because of the low hydrogen overvoltage iron is a suitable cathode material in the chlorate manufacture. The cathodic reaction proceeds according to the following equation ... 

K. Viswanathan and B.V. Tilak, Chemical, Electrochemical, and Technological Aspects of Sodium Chlorate Manufacture,/. Electrochem. Soc. 131, 1551—1559, July (1984). 

Calculated from the equation ln(H) = 11.04 —5196/T + 0.03998 1, where I is the ionic strength in molarity and T is the temperature in degree kelvin. This equation was obtained by linear regression of the data from Imakawa, H., Chemical reactions in the chlorate manufacturing electrolytic cell (part 1) the vapour pressure of hypochlorous add on its aqueous solution, J. Electrochem. Soc. Jpn., 18, 382, 1950 and Imagawa, H., Studies on chemical reactions of the chlorate cell (part 2) the vapour pressure of hypochlorous acid on its mixed aqueous solution with sodium chlorate, J. Electrochem. Soc. Jpn., 19, 271,1951. 

Imakawa, H., Chemical reactions in the chlorate manufacturing electrolytic cell (part 1) the vapour pressure of hypochlorous acid on its aqueous solution, J. Electrochem. Soc. Jpn., 18, 382, 1950. 

Cathode materials in the first years of chlorate manufacture were copper, nickel, and platinum. Today it is mainly steel, mild steel, or low-carbon steel and in some plants titanium or a Ti-0.2 % Pd alloy [3, 4]. A problem in chlorate electrolysis is the extremely corrosive electrolyte with active chlorine that attacks the steel cathodes when they are not under cathodic protection. This not only shortens the lifetime of the cathodes but also causes problems with pieces of steel in the... 

Chlorate Grade 50%--specially formulated for use in chlorate manufacture or processing. 

CH3C(0)CH2Br. Colourless liquid which rapidly becomes violet in colour it is a powerful lachrymator b.p. 1367725 mm. Manufactured by treating aqueous propanone with bromine at 30-40 C it is usual to add sodium chlorate(V) to convert the hydro-bromic acid formed by the reaction back to bromine. It is not very stable and decomposes on standing. 

It catalyses the decomposition of potassium chlorate(V). Mixed with zinc oxide, it is used as a catalyst in the manufacture of methanol. It is used as a pigment, being very resistant to weathering. 

Most of the chlorine produced is used in the manufacture of chlorinated compounds for sanitation, pulp bleaching, disinfectants, and textile processing. Further use is in the manufacture of chlorates, chloroform, carbon tetrachloride, and in the extraction of bromine. 

Three forms of caustic soda are produced to meet customer needs purified diaphragm caustic (50% Rayon grade), 73% caustic, and anhydrous caustic. Regular 50% caustic from the diaphragm cell process is suitable for most appHcations and accounts for about 85% of the NaOH consumed in the United States. However, it caimot be used in operations such as the manufacture of rayon, the synthesis of alkyl aryl sulfonates, or the production of anhydrous caustic because of the presence of salt, sodium chlorate, and heavy metals. Membrane and mercury cell caustic, on the other hand, is of superior quaUty and... 

Success in the chlorine industry led to the incorporation of DSA in sodium chlorate [7775-09-9] NaClO, manufacture. The unique stmctural characteristics of the anode allowed for innovative designs in ceU hardware, which in turn contributed to the extensive worldwide expansion of the sodium chlorate industry in the 1980s. 

Use of mercuric catalysts has created a serious pollution problem thereby limiting the manufacture of such acids. Other catalysts such as palladium or mthenium have been proposed (17). Nitration of anthraquinone has been studied intensively in an effort to obtain 1-nitroanthraquinone [82-34-8] suitable for the manufacture of 1-aminoanthraquinone [82-45-1]. However, the nitration proceeds so rapidly that a mixture of mono- and dinitroanthraquinone is produced. It has not been possible, economically, to separate from this mixture 1-nitroanthraquinone in a yield and purity suitable for the manufacture of 1-aminoanthraquinone. Chlorination of anthraquinone cannot be used to manufacture 1-chloroanthraquinone [82-44-0] since polychlorinated products are formed readily. Consequentiy, 1-chloroanthraquinone is manufactured by reaction of anthraquinone-l-sulfonic acid [82-49-5] with sodium chlorate and hydrochloric acid (18). 

Large-Scale Industrial Production. Large amounts of chlorine dioxide ate used in pulp bleaching and smaller quantities ate used for the manufacture of sodium chlorite. In these appHcations, sodium chlorate is the only commercially available taw material. Chlorine dioxide production from sodium chlorate is achieved by the reduction of the chlorate ion in the presence of strong acid. The reaction consumes acid, so that acid and reducing agents must be constantly added to maintain the reaction. 

The commercial manufacture of sodium chlorite is based almost entirely on the reduction of chlorine dioxide gas in a sodium hydroxide solution containing hydrogen peroxide [7722-84-1] as the reducing agent. The chlorine dioxide is generated from the chemical or electrochemical reduction of sodium chlorate under acidic conditions. 

Manufacture. Chloric acid is the precursor for generation of chlorine dioxide for pulp bleaching and other appHcations (see Bleaching agents), and is formed m situ by reaction of sodium chlorate [7775-09-9], NaClO, and a strong acid, eg. 

Manufacture. Most chlorate is manufactured by the electrolysis of sodium chloride solution in electrochemical cells without diaphragms. Potassium chloride can be electroly2ed for the direct production of potassium chlorate (35,36), but because sodium chlorate is so much more soluble (see Fig. 2), the production of the sodium salt is generally preferred. Potassium chlorate may be obtained from the sodium chlorate by a metathesis reaction with potassium chloride (37). 

Potassium chlorate is used mainly in the manufacture of matches (qv) and pharmaceutical preparation. In pyrotechnics, chlorate salts may be mixed with certain organic compounds such as lactose to give a relatively cool flame, so that certain dyes may be incorporated in the mixture to give colored flares. 

U. Kuhlmann, "Manufacture of Sodium Chlorate by Electrolysis," commercial brochure, PCUKProcess, 1978. 

Chloroanthraquinone [82-44-0] (41) is an intermediate for manufacturing vat dyes such as Cl Vat Brown 1. 1-Chloroanthraquinone is prepared by chlorination of anthraquinone-l-sulfonic acid with sodium chlorate in hydrochloric acid at elevated temperature (61). An alternative route from 1-nitroanthraquinone (18) using elemental chlorine at high temperature has been reported (62). 

In addition to being the most widely used disinfectant for water treatment, chlorine is extensively used in a variety of products, including paper products, dyestuffs, textiles, petroleum products, pharmaceuticals, antiseptics, insecticides, foodstuffs, solvents, paints, and other consumer products. Most chlorine produced is used in the manufacture of chlorinated compounds for sanitation, pulp bleaching, disinfectants, and textile processing. It is also used in the manufacture of chlorates, chloroform, and carbon tetrachloride and in the extraction of bromine. Among other past uses, chlorine served as a war gas during World War I. 

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