Katzschmann process

Witten A process for making dimethyl terephthalate by the concurrent oxidation and esterification of p-xylene. Similar to the Imhausen and Katzschmann processes. Developed by Chemische Werke Witten and subsequently operated by Dynamit Nobel in Germany. World production capacity for this process in 1993 was 3 million tonnes. 

The Witten process, which is also known as the Imhausen or Katzschmann process [3a-f], involves the oxidation of p-xylene to p-toluic acid as a reaction intermediate. For activity reasons, the p-toluic acid is esterified with methanol to methyl toluate, which is then oxidized to monomethyl terephthalate. The two oxidation reactions take place simultaneously in one oxidation system likewise... 

An alternative route to DMT was introduced in 1953. This was based on air oxidation of y -xylene to /Moluic acid, which was esterified by methanol to form methyl /Moluate, which was oxidised by air to monomethyl terephthalate [40], which in turn was esterified by methanol to make DMT. The two oxidations could be combined so that p-xylene and methyl p-toluate were oxidised in the same vessel, and so could the two esterifications [41], The process was due to Katzschmann of Imhausen, a firm based at Witten and later known as Chemische Werke Witten. This process, known variously by its inventor s name and by various combinations of the names of the companies involved in its development, i.e. Hercules, Imhausen, Witten, and Dynamit Nobel, rapidly replaced the rather unsatisfactory and sometimes hazardous nitric acid oxidation route to DMT. 

Imhausen A process for making dimethyl terephthalate. See Katzschmann. 

Katzschmann E. (1966) Oxidation of alkyl aromatic compounds. Chem. Ing. Tech., 38 1-10. Kenig E, Seferhs P. (2009) Modeling reactive absorption. Chem. Eng. Prog., 105(l) 65-73. Knochen J, Guttel R, Knobloch C, Turek T. (2010) Fischer-Tropsch synthesis in milli-struc-tured fixed-bed reactors experimental study and scale-up considerations. Chem. Eng. Process., 49 958-964. 

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