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The Isomar Process is used to convert a mixture of C 8 aromatic compounds depleted in one isomer to an equi-librium mixed xylene stream. The Isomar Process is
most often used in integrated complexes where para-xylene is produced from mixed xylenes, but it can also be used to maximize the production of ortho-xylene or meta-xylene. The term “mixed xylenes” is used to describe a mixture of C 8 aromatic isomers containing an equilibrium distribution of para-xylene, ortho-xylene, meta-xylene, and ethyl benzene (EB). In the case of para-xylene product, a mixed xylenes feed is charged to a Parex TM unit where the para-xylene isomer is referentially separated at 99.9 wt-% purity and 97 wt-% recovery per pass. The raffinate from the Parex unit, almost entirely depleted of para-xylene, is then sent to the Isomar unit. The Isomar unit re-establishes an equilibrium distribution of xylene isomers, essentially creating addi- tional para-xylene from the remaining ortho- and meta-xylenes. Effluent from the Isomar unit is then recycled back to the Parex unit for recovery of additional para-xylene. In this way, the ortho-and meta- xylenes and EB are recycled to extinction. Depending on the type of catalyst in the Isomar unit, EB is converted into additional xylenes or benzene