Ethyl sulfuric acid, catalytic formation

Ethyl mercaptan, IV, 93, 94 Ethyl sulfuric acid, catalytic formation, V, 52... 

It is in the very nature of the catalytic process that the intermediate compound formed between catalyst and reactant is of extreme lability therefore not many cases are on record where the isolation by chemical means, or identification by physical methods, of intermediate compounds has been achieved concomitant with the evidence that these compounds are true intermediaries and not products of side reactions or artifacts. The formation of ethyl sulfuric acid in ether formation, catalyzed by HjSO , and of alkyl phosphates in olefin polymerization, catalyzed by liquid phosphoric acid, are examples of established intermediate compound formation in homogeneous catalysis. With regard to heterogeneous catalysis, where catalyst and reactant are not in the same... 

Reaction (1) is easily applicable to the preparation of the lower simple alkyl ethers which boil below the boiling point of the alcohol. For example, when ethyl alcohol is mixed with sulfuric acid in the cold, ethyl sulfuric acid is formed. When more alcohol is allowed to flow into such a mixture at 140-150°, ether, water, and some unchanged alcohol distill over. The mechanism of the reaction is assmned to involve, first the formation of ethyl sulfuric acid, and then the reaction of this with alcohol to form ether and regenerate the sulfuric acid. The regenerated acid combines with fresh alcohol and repeats the cycle until the water produced in the reaction by dilution diminishes its catalytic activity. Olefin formation takes place even at this temperature and decreases the yield. Further decrease in the yield results from the oxidizing action of sulfuric acid. 

Traditionally, ethanol has been made from ethylene by sulfation followed by hydrolysis of the ethyl sulfate so produced. This type of process has the disadvantages of severe corrosion problems, the requirement for sulfuric acid reconcentration, and loss of yield caused by ethyl ether formation. Recently a successful direct catalytic hydration of ethylene has been accomplished on a commercial scale. This process, developed by Veba-Chemie in Germany, uses a fixed bed catalytic reaction system. Although direct hydration plants have been operated by Shell Chemical and Texas Eastman, Veba claims technical and economic superiority because of new catalyst developments. Because of its economic superiority, it is now replacing the sulfuric acid based process and has been licensed to British Petroleum in the United Kingdom, Publicker Industries in the United States, and others. By including ethanol dehydrogenation facilities, Veba claims that acetaldehyde can be produced indirectly from ethylene by this combined process at costs competitive with the catalytic oxidation of ethylene. 

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