Xylenes separation process

In a continuous process for the separation of a feedstock containing a major proportion of mixed xylene isomers into substantially pure o- and p-isomer fractions by feeding the feedstock to a fractional distillation column in which a fraction containing a major portion of the o-xylene in the feedstock is removed from the bottom of the column and further fractionated to recover substantially pure o-xylene and a major portion of the p-xylene in the feedstock is removed in an overhead fraction, the p-xylene being removed from the overhead fraction by crystallization and the mother liquor therefrom being recycled to the feed after contact with an isomerization catalyst, the improvement which comprises, prior to contacting said mother liquor remaining after crystallization with an isomerization catalyst, the steps of combining said mother liquor with additional mother liquor and contacting said combined mother liquor with a crystalline alumino-silicate active for the selective adsorption of p-xylene the hydrated form of which has the formula:

• M.sub.2 /.sub.n O :
• Al.sub.2 O.sub.3 :
• wSiO.sub.2 :
• yH.sub.2 O (I)
• wherein M is a cation which balances the electrovalance of the tetrahedra, n represents the valence of the cation, w represents the number of moles of SiO.sub.2 and y represents the number of moles of water;
• and, thereafter recovering the adsorbed p-xylene from said substrate, the amount of said mother liquor added being substantially equal to the quantity of p-xylene recovered from said crystalline alumino-silicate in any given time.