Industrial manufacture sulfuric acid, Contact Process

Sulfuric acid (H2S04), the world s most important industrial chemical, is manufactured by the contact process, a three-step reaction sequence in which (1) sulfur burns in air to give S02, (2) S02 is oxidized to S03 in the presence of a vanadium(V) oxide catalyst, and (3) S03 reacts with water to give H2S04 ... 

The industrial conditions employed ensure that sufficient ammonia is produced at a fast enough rate. The principles which underpin equilibrium processes such as this are discussed below and in Chapter 12 (the Contact process for manufacturing sulfuric acid, p. 199). 

The first industrial method, the lead-chamber process, is not commonly used now because its purity is low and its percent yield is only 60 to 80 percent. But it is much cheaper than the later and more productive contact process. The lead-chamber process is used for manufacturing sulfuric acid for applications that do not demand high purity. 

Sulfuric acid is the strong acid most widely used by the chemical industry, due to its low cost of synthesis. It is manufactured by the contact process, which is covered in detail earlier in this Book. Here we will concentrate only on one stage — which illustrates some of the principles important in plant design — the combination of sulfur dioxide with oxygen to give sulfur trioxide in the presence of a catalyst (usually V2O5) ... 

Sulfuric Acid. Essentially all sulfuric acid manufactured in this industry is produced by the contact process, in which SO2 and oxygen contact each other on the surface of a catalyst (vanadium pentaoxide) to form SO3 gas. Sulfur trioxide gas is added to water to form sulfuric acid. The sulfur dioxide used in the process is produced by burning elemental sulfur in a furnace. 

We begin our discussion with what is by far the largest volume chemical produced in the United States sulfuric acid. It is normally manufactured at about twice the amount of any other chemical and is a leading economic indicator of the strength of many industrialized nations. Since about 80% of all sulfuric acid is made by the contact process which involves oxidation of sulfur, we will examine this raw material in detail. The average per capita consumption of sulfur in the United States is a staggering 135 Ib/yr. 

Sulfuric acid is manufactured by two processes namely, the chamber process and the contact process. The chamber process was discovered in 1746 and was used to produce sulfuric acid for over a century. This process was replaced hy the contact process which has a lower production cost and yields a more concentrated acid needed for most industrial applications. The chamber process is obsolete now but for historical interest it is outlined below. 

Industrial manufacture of sulfuric acid - the Contact process Uses of sulfuric acid Properties of sulfuric acid... 

Contact process The industrial manufacture of sulfuric acid using the raw materials sulfur and air. 

In the industrial process used today to manufacture salicylic acid, dry sodium phenoxide obtained from phenol and soda is contacted with C02 under 0.5 MPa and at temperatures around 373 K. After absorption of approximately one molar equivalent of C02, the temperature is raised and held at 423—433 K for several hours to fulfill the reaction [16]. The final technical-grade salicylic acid is obtained after successive purification steps and, eventually, upon acidification with sulfuric or hydrochloric acid (Figure 5.1). 

Miles, F.D., The Manufacture of Sulfuric Acid by the Contact Process, Gurney Jackson, London, 1925. Trickett, A.A., in Industrial Inorganic Chemicals Production and Use, Thompson, R., Ed., Royal Society of Chemistry, Cambridge, UK, 1995, 93. 

Manufactured in greater amounts than any other chemical, sulfuric acid is usually produced by the contact process, which is described in Chapter 3. About 60% of the sulfuric acid manufactured in the United States is used to produce fertilizers from phosphate rock (see Section 19.3). The other 40% is used in lead storage batteries, in petroleum refining, in steel manufacturing, and for various other purposes in the chemical industry. 

The growth in world population necessitated the increased use of fertilisers to augment increased supply of food. In the fertiliser industry the manufacturing process involves the use of sulfuric acid, hydrochloric acid and phosphoric acid. The plant, equipment and piping system that come into contact with the acids must be dependably protected against the corrosive attack. Rubber as a construction material is well able to satisfy the variety of requirements on it in this area, which are [9] ... 

The oxidation of SO2 by atmospheric O2 (equation 15.90) is very slow, but is catalysed by V2O5 (see Section 26.7). This is the first step in the Contact process for the manufacture of sulfuric acid operating conditions are crucial since equilibrium 15.90 shifts further towards the left-hand side as the temperature is raised, although the yield can be increased somewhat by use of high pressures of air. In practice, the industrial catalytic process operates at 750K and achieves conversion factors >98%. 

Sulfuric Acid. Until the 1940 s the manufacture of heavy chemicals in India was insignificant. The production of sulfuric acid was only 18,000 tons as contrasted with 7,000,000 tons in the United States at the same time. Until the establishment of the first contact acid plant in 1948, all production used the chamber process. Installed annual capacity in 1948 was 175,000 tons, distributed among 49 different units. Because India does not have a source of free sulfur, the production of sulfuric acid is one of the critical chemical industries. India, however, has large deposits of iron pyrite in the northern part of the country and development of these is being undertaken to alleviate the problem of the lack of sulfur. 

The development of the less expensive and less easily contaminated vanadium pentoxide (V2O5) catalyst by BASF in Germany in 1915, combined with increasing demand for concentrated sulfuric acid by the chemical industry, has led to the gradual replacement of the lead-chamber process by the Contact Process. In 1930, sulfuric acid produced by the Contact Process accounted for only 25% of sulfuric acid production, while today nearly all sulfuric acid is manufactured in this way. 

The sulfuric acid industry got a head start in the 1940s due to the invention of vanadium pentoxide as catalyst to convert sulfur dioxide to sulfur trioxide, popularly known as the contact process. This enabled large sulfuric acid plants of high capacity to be built to produce phosphoric acid for the manufacture of phosphatic fertilizers. 

The contact process is an industrial method for the manufacture of sulfuric acid. It consists of the reaction of sulfur dioxide with oxygen to form sulfur trioxide using a catalyst of vanadium(V) oxide, followed by the reaction of sulfur trioxide with water. Because the direct reaction of sulfur trioxide with water produces mists that are unmanageable, the sulfur trioxide is actually dissolved in concentrated sulfuric acid, which is then diluted with water. ... 

The heterogeneous catalytic oxidation of sulfur dioxide to sulfur trioxide is well established. The industrial manufacture of sulfuric acid is based on the well-known contact process where the overall stoichiometry is as shown in reaction 8.5.5.3. 

Sulfuric acid is manufactured commercially by the contact process (see also the Case Study Industrial Inorganic Chemistry). Sulfur dioxide mixed with air is passed over a catalyst (usually vanadium pentoxide, V2O5) whereupon it is oxidized to sulfur trioxide ... 

Sulfuric acid is used in the laboratory to dry gases (except ammonia), to prepare nitric acid and ethene, and to absorb alkenes. In industry, it is used to manufacture fertilizers (e.g. ammonium sulfate), rayon, and detergents, to clean metals, and in vehicle batteries. See contact process. 

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