Uses of Sulfuric Acid

Other derivatives and some of the chemical uses of sulfuric acid are described in other sections. 

In the manufacture of fertilizers, sulfuric acid is used to digest phosphate rock (largely Ca3(P04)2 and Ca5(P04)3F) to make phosphoric acid or the calcium salts such as Ca(H2P04)2-Some of the phosphoric acid is also used to make ammonium phosphate. More details on the manufacture of fertilizer were presented in Chapter 13. 

In refining of petroleum, sulfuric acid is used as a catalyst for alkylation reactions and in the manufacture of other organic derivatives. Chemicals production includes virtually every heavy chemical industry. For example, the production of sodium and aluminum sulfates, hydrochloric and hydrofluoric acids, insecticides, detergents, and many other chemicals all involve the use of H2S04. 

Sulfuric acid is used in large quantities in the pickling of steel to remove oxide coatings by dissolving them. Another large use of sulfuric acid involves its reaction with ammonia obtained in the conversion of coal to coke  

In that process, a large quantity of ammonium sulfate is produced, and it is used in fertilizers because it is a relatively inexpensive source of nitrogen. Finally, a large quantity of sulfuric acid is used as the electrolyte in millions of automobile batteries. With so many processes that consume enormous quantities of H2S04, it is not surprising that the production and consumption of sulfuric acid provides a barometer to the general health of the economy  

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Organic Reactions. Nitric acid is used extensively ia iadustry to nitrate aHphatic and aromatic compounds (21). In many iastances nitration requires the use of sulfuric acid as a dehydrating agent or catalyst the extent of nitration achieved depends on the concentration of nitric and sulfuric acids used. This is of iadustrial importance ia the manufacture of nitrobenzene and dinitrotoluene, which are iatermediates ia the manufacture of polyurethanes. Trinitrotoluene (TNT) is an explosive. Various isomers of mononitrotoluene are used to make optical brighteners, herbicides (qv), and iasecticides. Such nitrations are generally attributed to the presence of the nitronium ion, NO2, the concentration of which iacreases with acid strength (see Nitration). 

Isopropyl Alcohol. Propylene may be easily hydrolyzed to isopropyl alcohol. Eady commercial processes involved the use of sulfuric acid in an indirect process (100). The disadvantage was the need to reconcentrate the sulfuric acid after hydrolysis. Direct catalytic hydration of propylene to 2-propanol followed commercialization of the sulfuric acid process and eliniinated the need for acid reconcentration, thus reducing corrosion problems, energy use, and air pollution by SO2 and organic sulfur compounds. Gas-phase hydration takes place over supported oxides of tungsten at 540 K and 25... 

The need for acid concentrators exists because many uses of sulfuric acid do not lead to its consumption. Instead, the acid is diluted and partially degraded and contaminated. In the past, large amounts of acid were disposed of either by usiag it ia the phosphate fertilizer iadustry to dissolve phosphate rock or by neutralization and subsequent discharge to waterways. 

Further Preparative Reactions. When pulps are to be used in the production of materials that do not retain the original fiber stmcture, such as rayon or ceUulose acetate film, the lignin, hemiceUulose, and other components must be reduced to the lowest possible concentrations. A surfactant (ionic or nonionic) is often added during a hot, weakly alkaline extraction step after chlorination. Another approach, sometimes used in addition to the surfactant step, is to treat the pulp with 6—10% NaOH after most of the oxidative bleaching is finished. This treatment removes most of the hemiceUulose. In most purification plants the final stage includes use of sulfuric acid chelators are optional. 

There are two main processes for the synthesis of ethyl alcohol from ethylene. The eadiest to be developed (in 1930 by Union Carbide Corp.) was the indirect hydration process, variously called the strong sulfuric acid—ethylene process, the ethyl sulfate process, the esterification—hydrolysis process, or the sulfation—hydrolysis process. This process is stiU in use in Russia. The other synthesis process, designed to eliminate the use of sulfuric acid and which, since the early 1970s, has completely supplanted the old sulfuric acid process in the United States, is the direct hydration process. This process, the catalytic vapor-phase hydration of ethylene, is now practiced by only three U.S. companies Union Carbide Corp. (UCC), Quantum Chemical Corp., and Eastman Chemical Co. (a Division of Eastman Kodak Co.). UCC imports cmde industrial ethanol, CIE, from SADAF (the joint venture of SABIC and Pecten [Shell]) in Saudi Arabia, and refines it to industrial grade. 

Indirect Hydration (Esterification—Hydrolysis) Process. The preparation of ethanol from ethylene by the use of sulfuric acid is a three-step process (Fig. 1) ... 

One of the important uses of sulfuric acid is that of an oxidizing agent. For example, when heated, it will even dissolve carbon. The reaction is... 

A second major use of sulfuric acid of commerce is in reactions with bases. In laboratory use it is diluted to a much lower concentration and can be used as a standard acid. A typical problem would be the titration of a base solution of unknown concentration using a sulfuric acid solution of known concentration. For example, What is the concentration of a sodium hydroxide solution if 25.43 ml of the NaOH solution just reacts with 18.51 ml of 0.1250 M HiSOt (to produce a neutral solution) ... 

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... 

C04-0146. The largest single use of sulfuric acid is for the production of phosphate fertilizers. The acid reacts with calcium phosphate in a 2 1 mole ratio to give calcium sulfate and calcium dihydrogen phosphate. The mixture is crushed and spread on fields, where the salts dissolve in rain water. (Calcium phosphate, commonly found in phosphate rock, is too insoluble to be a direct source of phosphate for plants.) (a) Write a balanced equation for the reaction of sulfuric acid with calcium phosphate, (b) How many kilograms each of sulliiric acid and calcium phosphate are required to produce 50.0 kg of the calcium sulfate-dihydrogen phosphate mixture (c) How many moles of phosphate ion will this mixture provide ... 

Sulfate solubility properties are the basis for other industrial uses of sulfuric acid. One example is in the metallurgy of titanium. One of the major ores of titanium is FeTi03, which is treated with sulfuric acid to separate titanium from iron ... 

The other advantages which sulfuric acid has as an inert electrolyte are (i) it increases the conductance of the bath (ii) it is inexpensive (iii) it strongly inhibits the hydrolysis of cuprous sulfate (iv) it is nonvolatile and may be used at high concentrations and temperatures and (v) it does not attack lead, so that it is possible to use this metal for plant construction. The only inconvenience of sulfuric acid is that copper dissolves in it essentially as the divalent ion this means that the current consumption is double of that which would be consumed if the electrolysis were to be carried out in an electrolyte solution containing Cu+ ions. Attempts to implement this alternative have not been very successful so that the use of sulfuric acid is yet to be challenged. 

Concerning the bisulfate salt, Sanofi presented evidence that "the prior art taught away from the use of sulfuric acid with the claimed enantiomer, for strong acids could encourage re-racemization [23]." "Teaching away" from, a separate secondary consideration trending toward patentability, is discussed in more detail in Section 7 of this chapter. 

The application of solvent extraction to copper recovery has been a major growth area since the last review of this series.11,13 Almost 30% of world production in 2000 involved the use of sulfuric acid heap leaching, solvent extraction, and electrowinning, far exceeding earlier predictions.136... 

In the absence of a catalyst the reaction proceeds more slowly and smaller yields are obtained. Phosphoric acid may be substituted for sulfuric acid, but the use of sulfuric acid results in the best yield in the shortest time. 

Sulfuric acid has found limited use in boiler cleaning operations. It is not feasible for removal of hardness scales due to the formation of highly insoluble calcium sulfate. It has found some use in cases where a high-strength, low-chloride solvent is necessary. Use of sulfuric acid requires high water usage in order to rinse the boiler sufficiently. 

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