Dealkylation of toluene and xylenes to benzene

The dealkylation of toluene and xylenes to benzene is carried out not only catalyt-ically but also as a purely thermal reaction in the presence of hydrogen. In the catalytic process, pressures ranges from 35 to 70 bar and temperatures from 550 to 650 °C chromium oxides on alumina are used as catalysts. Thermal dealkylation takes place at temperatures up to 750 °C and pressures of around 45 bar. 

1 and 2 Prefractionation column 3 Vaporizer 4 Prehydrogenation reactor 5 Litol reactors 6 Flash vessel 7 Stabilizer 8 Benzene column 9 Toluene column 10 Gas purification 11 Low temperature gas separation 

The Houdry Litol process is widely used to produce benzene by dealkylation the following processes occur concurrently  

Yields with and without toluene recycling are shown in Table 4.12. 

After a long period of operation, carbon deposited on the surface of the catalyst reduces its effectiveness. The carbon is burned off with oxygen, after the system has been purged with nitrogen. 

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