Sulfuric acid production technology improvements

These three steps all produce significant amounts of waste. First, as discussed earlier, the nitration process results in the production of spent sulfuric acid. In the past the company had been able to sell much of this material to the coke and steel industries but declining demand meant that the acid now required disposing of, at additional cost. At the time green catalytic nitration technology was becoming available with clay, zeolite and lanthanide catalysts all providing possible alternatives to the use of sulfuric acid (see below). Improved selectivity to the desired para-isomer is an added benefit of some of these catalytic systems. However on the... 

Projections of Sulfuric Acid Production Trends and Technology Improvements... 

Production Technology. Processes for extraction of P2O3 from phosphate rock by sulfuric acid vary widely, but all produce a phosphoric acid—calcium sulfate slurry that requires soHds-Hquid separation (usually by filtration (qv)), countercurrent washing of the soHds to improve P2O3 recovery, and concentration of the acid. Volatilized fluorine compounds are scmbbed and calcium sulfate is disposed of in a variety of ways. 

Titanium dioxide (E171, Cl white 6) is a white, opaque mineral occurring naturally in three main forms rutile, anatase, and brookite. More than 4 million tons of titanium dioxide are produced per year and it is widely used for industrial applications (paints, inks, plastics, textiles) and in small amounts as a food colorant. ° "° Production and properties — Titanium oxide is mainly produced from ilmenite, a titaniferous ore (FeTiOj). Rutile and anatase are relatively pure titanium dioxide (Ti02) forms. Titanium oxide pigment is produced via chloride or sulfate processes via the treatment of the titanium oxide ore with chlorine gas or sulfuric acid, followed by a series of purification steps. High-purity anatase is preferred for utilization in the food industry. It may be coated with small amounts of alumina or silica to improve technological properties. 

To simplify the synthetic technology of 3-amino-5-nitroindazole and to improve the target product quality it is reasonable to use 2-cyano-4-nitroaniline. The latter is subjected to diazotization, and the azo compound thus formed is reduced with simultaneous closure of the indazole cycle with sulfur dioxide in 5-15% sulfuric acid [315],... 

Roasted pyrites release sulfur dioxide, which can then be converted to sulfuric acid. Commercial scale production of sulfuric acid from pyrites had taken place back in 1793, by M. Dartigues of France. To produce sulfuric acid from pyrites, the critical technology was the pyrites burner. A major technical breakthrough was an improved furnace, invented by Michel Ferret (1813 - 1900) in 1832 (Fr. Patent No. 1094, 1836 another modification by Ferret was made in 1845). Ferret built a sulfuric acid plant in Saint-Fons, near Lyons, in 1837. Later burner developments came from MacDougall Bros, of Liverpool and James Brown Herreshoff Sr. (1831 - 1930), brother of John Brown Herreshoff. 

In mineral technology, sulfur dioxide and sulfites are used as flotation depressants for sulfide ores. In electrowinning of copper from leach solutions from ores containing iron, sulfur dioxide prereduces ferric to ferrous ions to improve current efficiency and copper cathode quaHty. Sulfur dioxide also initiates precipitation of metallic selenium from selenous acid, a by-product of copper metallurgy (326). 

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