Simultaneous recovery and production of pure xylenes from a c aromatic mixture

Claim 2

The process of claim 1 wherein said selective adsorption of step (d) comprises the steps of: i. contacting the mixed meta-xylene and para-xylene fraction with a mass of crystalline aluminosilicate contained in an adsorption zone maintained at adsorption conditions to effect the selective retention of an extract material containing meta-xylene or para-xylene; ii. withdrawing from said adsorption zone, a raffinate stream containing a less selectively retained xylene isomer; iii. contacting said adsorbent mass at desorption conditions with a desorbent material to effect a removal of the extract material from the adsorbent; and, iv. withdrawing from the adsorbent mass an extract stream comprising said extract material and desorbent.

Claim 3

The process of claim 3 wherein said extract stream comprises para-xylene.

Claim 4

The process of claim 3 wherein said adsorption and desorption are effected in the liquid phase.

Claim 5

The process of claim 3 wherein said desorbent is toluene or a diethylbenzene.

Claim 6

The process of claim 3 wherein said aluminosilicate is a Type X or Type Y structured zeolite.

Claim 7

The process of claim 7 wherein said zeolites contain cationic sites occupied by a member selected from the group consisting of potassium, barium, silver, cesium, praseodymium, neodymium, samarium, barium and potassium, beryllium and potassiUm, magnesium and potassium, rubidium and potassium, cesium and potassium, rubidium and barium, cesium and barium, copper and potassium and combinations thereof.

Claim 8

A process for the simultaneous recovery and production of meta-xylene, para-xylene and ortho-xylene from a C8 aromatic stream which comprises the steps of: a. separating, by fractional distillation, a C8 aromatic stream comprising ortho-xylene, meta-xylene, para-xylene and ethylbenzene to produce a relatively ortho-xylene free, ethylbenzene, meta-xylene and para-xylene overhead fraction and a relatively ethylbenzene free, meta-xylene, para-xylene and ortho-xylene bottoms fraction; b. contacting said overhead fraction in an isomerization zone with an isomerization catalyst maintained at isomerization conditions to produce a C8 aromatic mixture of ortho-xylene, meta-xylene, para-xylene and ethylbenzene. c. separating said C8 aromatic mixture produced in step (b) in step (a). d. contacting the bottoms fraction of step (a) with a crystalline aluminosilicate mass selective for para-xylene or meta-xylene at adsorption conditions to effect the retention of an extract material containing meta-xylene or para-xylene and to produce a raffinate stream containing the less selectively retained meta-xylene or para-xylene in admixture with ortho-xylene. e. withdrawing, from said adsorbent, at desorption conditions, said extract material relatively free of other C8 aromatic isomers; and f. separating by fractional distillation said raffinate stream to produce a relatively pure ortho-xylene stream and a relatively pure stream comprising the less selectively retained meta-xylene or para-xylene.

Claim 9

The process of claim 9 wherein para-xylene is selectively retained in the extract and the raffinate contains the less selectively retained meta-xylene.

Claim 10

The process of claim 9 wherein said aluminosilicate is a Type X or Type Y structured zeolite.

Claim 11

The process of claim 11 wherein said zeolite contain cationic sites occupied by a member selected from the group consisting of potassium, barium, silver, cesium, praseodymium, neodymium, samarium, barium and potassium, beryllium and potassium, magnesium and potassium, rubidium and potassium, cesium and potassium, rubidium and barium, cesium and barium, copper and potassium and combinations thereof.