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Xylenes
and ethylbenzene are C8 homologues with
the molecular formula C8H10. The three xylene
isomers are o-oxylene, m-xylene and pxylene,which
differ in the positions of two methyl groups
on the ring. The term mixed xylenes describes
a mixture of ethylben
zene and the three xylene isomers. Mixed xylenes are derived
largely from petroleum.While xylene aren’t
as important as many other products of the
chemical industry they certainly serve as
an indicator of the nations’petrochemical
prowess. Xylene production’s close link
to petrochemical production ensures that
its supply is interwined with the production
of other chemicals. Ethylbenzene, an isomer
of the xylenes, is always present in small
amounts and can influence the economics,
of the process as being a diluent it accumulates
in the recycle and hence has to be periodically
removed. Xylene separations are complicated
by the fact that the physical and chemical
properties of all the isomers are similar.
This necessities the use of other expensive
procedures and the use of large distillation
columns to achieve high purity.
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