Xylene and Ethylbenzene Isomerization

Processes such as UOP s Isomar process are used to carry out isomerization of C8 aromatic species so that p-xylene can be removed selectively from the mixture of xylenes. The reaction is equilibrium controlled, so a continuous isomerization process is used. As is seen below, both aluminophosphate and aluminosilicate zeotypes are capable of catalyzing the reaction (Table 12.13). 

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Mordenite has been used since the second half of the 1970s in industrial xylene and ethylbenzene isomerization proeesses, chiefly for the production of paraxylene. the isomer for whieh there is the highest demand (Table 2). First, the isomerization of ethylbenzene into xylenes implies a bifunetional aeid catalyst. Second, it requires a temperature of around 400°C and hydrogen pressure in the region of 1-1.5 MPa. The catalyst is. therefore, composed of acid mordenite associated with a strong hydrogenation function, supplied by Pt. 

Isomerization is a reaction in which a molecule is transformed into a molecule having the same molecular formula but a different structure, i.e., isomers. Industrially important isomerization reactions are rearrangements of the carbon skeleton of C4-C8 hydrocarbons, and isomerization among alkyl benzene isomers such as xylenes and ethylbenzene.Isomerization including heteroatoms, such as propylene oxide to ally alcohol and Beckmann rearrangement of cyclohexanone oxime to e-caprolactam, are also significant industrial processes. 

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