Sulfur high purity

Grade Technical (lumps, roll, flour), rubber maker s, NF (sublimed), crude, refined, precipitated (milk of sulfur), high purity (impurities less than 10 ppm), also available in prilled form. 

High-purity sulfur is commercially available in purities of 99.999+%. 

From Acetylene. Although acetaldehyde has been produced commercially by the hydration of acetylene since 1916, this procedure has been almost completely replaced by the direct oxidation of ethylene. In the hydration process, high purity acetylene under a pressure of 103.4 kPa (15 psi) is passed into a vertical reactor containing a mercury catalyst dissolved in 18—25% sulfuric acid at 70—90°C (see Acetylene-DERIVED chemicals). 

In another development (32), the sodium sulfate solution produced during the desulfurization of paste with caustic soda is electrolyzed in a membrane ceU to produce caustic soda and high purity sulfuric acid. The caustic soda is recycled to the desulfurization stage the sulfuric acid, after concentration, can be reused in battery production. 

The advent of a large international trade in methanol as a chemical feedstock has prompted additional purchase specifications, depending on the end user. Chlorides, which would be potential contaminants from seawater during ocean transport, are common downstream catalyst poisons likely to be excluded. Limitations on iron and sulfur can similarly be expected. Some users are sensitive to specific by-products for a variety of reasons. Eor example, alkaline compounds neutralize MTBE catalysts, and ethanol causes objectionable propionic acid formation in the carbonylation of methanol to acetic acid. Very high purity methanol is available from reagent vendors for small-scale electronic and pharmaceutical appHcations. 

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. 

Sulfonation. Aniline reacts with sulfuric acid at high temperatures to form -aminoben2enesulfonic acid (sulfanilic acid [121 -57-3]). The initial product, aniline sulfate, rearranges to the ring-substituted sulfonic acid (40). If the para position is blocked, the (9-aminoben2enesulfonic acid derivative is isolated. Aminosulfonic acids of high purity have been prepared by sulfonating a mixture of the aromatic amine and sulfolane with sulfuric acid at 180-190°C (41). 

The indirect hydration, also called the sulfuric acid process, practiced by the three U.S. domestic producers, was the only process used worldwide until ICI started up the first commercial direct hydration process in 1951. Both processes use propylene and water as raw materials. Early problems of high corrosion, high energy costs, and air pollution using the indirect process led to the development of the direct hydration process in Europe. However, a high purity propylene feedstock is required. In the indirect hydration process, C -feedstock streams from refinery off-gases containing only 40—60 wt % propylene are often used in the United States. 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

Toluenesulfonic Acid. Toluene reacts readily with fuming sulfuric acid to yield toluene—sulfonic acid. By proper control of conditions, /)i7n7-toluenesulfonic acid is obtained. The primary use is for conversion, by fusion with NaOH, to i ra-cresol. The resulting high purity i7n -cresol is then alkylated with isobutylene to produce 2 (i-dii-tert-huty -para-cmso (BHT), which is used as an antioxidant in foods, gasoline, and mbber. Mixed cresols can be obtained by alkylation of phenol and by isolation from certain petroleum and coal-tar process streams. 

Beryllium Oxide. Beryllium oxide [1304-56-9], BeO, is the most important high purity commercial beryllium chemical. In the primary industrial process, beryllium hydroxide extracted from ore is dissolved in sulfuric acid. The solution is filtered to remove insoluble oxide and sulfate impurities. The resulting clear filtrate is concentrated by evaporation and upon cooling high purity beryllium sulfate, BeSO 4H20, crystallizes. This salt is... 

Methods of Purification. Although carbon dioxide produced and recovered by the methods outlined above has a high purity, it may contain traces of hydrogen sulfide and sulfur dioxide, which cause a slight odor or taste. The fermentation gas recovery processes include a purification stage, but carbon dioxide recovered by other methods must be further purified before it is acceptable for beverage, dry ice, or other uses. The most commonly used purification methods are treatments with potassium permanganate, potassium dichromate, or active carbon. 

High purity sulfur with low ash and organic content is desirable. If the raw sulfur is in soHd form, it is first melted and filtered or otherwise treated for purification. Liquid sulfur must be handled between the melting point (132°C) and about 150°C to avoid its pecuflar high viscosity range (see Sulfur). 

The neutralized, alumina-free sodium chromate solution may be marketed as a solution of 40° Bh (specific gravity = 1.38), evaporated to dryness, or crystallized to give a technical grade of sodium chromate or sodium chromate tetrahydrate [1003-82-9] Na2Cr04 4H2O. If the fuel for the kilns contains sulfur, the product contains sodium sulfate as an impurity. This compound is isomorphous with sodium chromate and hence difficult to separate. High purity sodium chromate must be made from purified sodium dichromate. 

Another process depends on the addition of a large excess of sulfuric acid to a concentrated solution or slurry of sodium dichromate. Under the proper conditions, a high purity chromic acid, may be precipitated and separated (77,85). 

Silver [7440-22-4]—The coloi additive silvei (EEC No. E 174) is a crystaUine powdei of high purity silver prepared by die reaction of silver nitrate with ferrous sulfate in the presence of nitric, phosphoric, and sulfuric acids. Poly(vinyl alcohol) is used to prevent the agglomeration of crystals and the formation of amorphous silver. 

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