Integrated selective adsorption and crystallization process for para-xylene recovery
AssigneeUop LLC
InventorJohn D. Swift
Life of this patent
Estimating the term…
Abstract
The eutectic limit of para-xylene crystallization is overcome by enriching the concentration of para-xylene of the crystallization feed. This is accomplished by passing the crystallization feed stream through a selective adsorption zone to produce a para-xylene-enriched stream and a para-xylene-depleted stream. The para-xylene-depleted stream is passed to an isomerization zone to re-equilibrate the xylene mixture, thereby producing additional para-xylene. The para-xylene-enriched stream is passed to a crystallization zone to produce high purity para-xylene. The result is an increase in the overall para-xylene recovery.
Claims22
A process for the production of a substantially pure para-xylene isomer from a mixed xylene feedstock comprising ortho-, meta- and para-xylene isomers and ethylbenzene which process comprises the steps of:
- (a) introducing at least a portion of said feedstock into a selective adsorption zone to produce a para-xylene-enriched stream and a para-xylene-depleted stream;
- (b) passing at least a portion of said para-xylene-depleted stream to an isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture;
- (c) recycling at least a portion of said isomerate stream to said selective adsorption zone;
- (d) passing at least a portion of said para-xylene-enriched stream to a crystallization zone to produce a para-xylene product stream and a mother liquor stream;
- and
- (e) recycling at least a portion of said mother liquor to said selective adsorption zone.
A process for the production of a substantially pure para-xylene isomer from a mixed xylene feedstock comprising ortho-, meta- and para-xylene isomers and ethylbenzene which process comprises the steps of:
- (a) introducing at least a portion of said feedstock into a selective adsorption zone to produce a para-xylene-enriched stream and a para-xylene-depleted stream;
- (b) passing at least a portion of said para-xylene-depleted stream to an isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture;
- (c) recycling at least a portion of said isomerate stream to said selective adsorption zone;
- (d) passing at least a portion of said para-xylene-enriched stream to a two-stage crystallization zone comprising a first stage crystallization zone which produces a first stage mother liquor and a second stage crystallization zone which produces a second stage mother liquor and a para-xylene product stream;
- (e) recycling at least a portion of said first stage mother liquor and admixing said first stage mother liquor with feed to said first stage crystallization zone;
- and
- (f) recycling at least a portion of said second stage mother liquor and admixing the second stage mother liquor with feed to the second stage crystallization zone.
A process for the production of a substantially pure para-xylene isomer from a mixed xylene feedstock comprising ortho-, meta- and para-xylene isomers and ethylbenzene which process comprises the steps of:
- (a) introducing at least a portion of said feedstock into a selective adsorption zone to produce a para-xylene-enriched stream and a para-xylene-depleted stream;
- (b) passing at least a portion of said para-xylene-depleted stream to an isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture;
- (c) recycling at least a portion of said isomerate stream to said selective adsorption zone;
- (d) passing at least a portion of said para-xylene-enriched stream to a two-stage crystallization zone comprising a first stage crystallization zone which produces a first stage mother liquor and a second stage crystallization zone which produces a second stage mother liquor and a para-xylene product stream;
- and
- (e) recycling at least a portion of said second stage mother liquor and admixing said second stage mother liquor with feed to said second stage crystallization zone.
A process for the production of a substantially pure para-xylene isomer from a mixed xylene feedstock comprising ortho-, meta- and para-xylene isomers which process comprises the steps of:
- (a) introducing at least a portion of said feedstock into a selective adsorption zone to produce a para-xylene-enriched stream and a para-xylene-depleted stream;
- (b) passing at least a portion of said para-xylene-depleted stream to an isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture;
- (c) recycling at least a portion of said isomerate stream to said selective adsorption zone;
- (d) passing said para-xylene-enriched stream to a two-stage crystallization zone comprising a first stage crystallization zone which produces a first stage mother liquor and a second stage crystallization zone which produces a second stage mother liquor and a para-xylene product stream, said para-xylene-enriched stream being fed to said second stage crystallization zone;
- and
- (e) recycling at least a portion of said second stage mother liquor and admixing said second stage mother liquor with feed to said second stage crystallization zone.
A process for the production of a substantially pure para-xylene isomer from a mixed xylene feedstock comprising ortho-, meta- and para-xylene isomers and ethylbenzene which process comprises the steps of:
- (a) introducing at least a portion of the feedstock into a selective adsorption zone to produce a para-xylene-enriched stream and a para-xylene-depleted stream;
- (b) passing at least a portion of the para-xylene-depleted stream to an isomerization zone containing an isomerization catalyst at conditions sufficient to produce an isomerate comprising an equilibrium xylene mixture;
- recycling at least a portion of the isomerate stream to the selective adsorption zone;
- (c) passing the para-xylene-enriched stream to a two-stage crystallization zone comprising a first stage crystallization zone which produces a first stage mother liquor and a second stage crystallization zone which produces a second stage mother liquor and a para-xylene product stream, the para-xylene-enriched stream being fed to the second stage crystallization zone;
- (d) recycling at least a portion of the second stage mother liquor and admixing the second stage mother liquor with feed to the second stage crystallization zone;
- and
- (e) recycling at least a portion of the second stage mother liquor to the first stage crystallization zone.
Dependencies are inferred from the claim text.