Sulfonating Agents and Derivatives Based on Sulfuric Acid
Sulfuric acid is called the king of chemicals. The first step to produce a useful product is sulfonation. Since the direct use of sulfuric acid is not feasible in all applications, the following auxiliary agents do play an important role. These are:
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Sulfonating Agents and Derivatives Based on Sulfuric Acid
4.1 Summary Sulfuric acid is called the king of chemicals. The first step to produce a useful product is sulfonation. Since the direct use of sulfuric acid is not feasible in all applications, the following auxiliary agents do play an important role. These are: 1. 25% oleum 2. 65% oleum 3. Liquid SO3 4. Chlorosulfonic acid 5. Diethyl sulfate 6. Dimethyl sulfate 7. Chloro-oleums 8. Liquid sulfur dioxide 9. Sulfamic acid 10. Methane sulfonic acid Outotec from Germany are suppliers of technology for large size (5,000 tonnes per day (TPD)) sulfuric acid plants and have innovated processes for sulfonation. See Appendix. Outotec have developed the Hero process which should also be considered for sulfonations.
4.2 Detailed Account of Sulfonating Agents 4.2.1 25% Oleum 4.2.1.1 Introduction Until the mid-1950s all sulfonations were carried out using sulfuric acid of different strengths. The reactions carried out by sulfuric acid were unable to give the conversion efficiencies that were economical, especially in the manufacture of detergents.
N.G. Ashar and K.R. Golwalkar, A Practical Guide to the Manufacture of Sulfuric Acid, Oleums, and Sulfonating Agents, DOI 10.1007/978-3-319-02042-6_4, © Springer International Publishing Switzerland 2013
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4 Sulfonating Agents and Derivatives Based on Sulfuric Acid
In certain dye intermediates the higher strength sulfuric acid was found to be essential part of the chemical reaction. This led many of the sulfuric acid plants to manufacture “fuming sulfuric acid,” popularly known as oleum. The initial product was in the range 20–25% oleum which meant 20–25% free SO3 dissolved in sulfuric acid.
4.2.1.2 Technical Considerations The basic reaction carried out in the oleum tower is absorption of SO3 in sulfuric acid to form an adduct – H2SO4 + SO3 = H2S2O7. This would correspond to 45% free SO3 dissolved in sulfuric acid. Since the freezing point of 40–45% oleum is in the range 90–95 °F there is always a possibility of solidification and consequent choking of equipment and pipelines at ambient temperatures, especially in the cold season. Hence, the industrial preference for manufacturing fuming sulfuric acid was in the range 20–25% free SO3. This needs removal of exothermic heat of heat of dilution together with heat of absorption of SO3 by specially designed coolers. Some plants have a gas heated oleum boiler for boiling the 25% oleum to produce pure SO3 vapor. 4.2.1.3 Manufacturing The manufacture of oleum is usually carried out in accordance with the block diagram in Chap. 1. The plant gases from the contact sulfuric acid plant (based on sulfur) having an SO3 strength of 10–12% are first cooled by counter current heat in the cold heat exchanger (CHE) after pass 3. The temperature of gases leaving the CHE will be in the range 270–280 °C and this is further cooled by an economiser for pre-heating the boiler feed water. The cold gases in the range 140–160 °C from the economiser outlet are fed to the oleum towe
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