Adsorption process for paraxylene purifacation using Cs SSZ-25 adsorbent with benzene desorbent
AssigneeChevron Corporation
InventorJohn J. Cain
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Abstract
An adsorption process for the recovery of paraxylene from mixed xylenes using a molecular sieve adsorbent comprising SSZ-25, MCM-22, PSH-3, ERB-1, or ITQ-1. A preferred desorbent for the process is benzene. A hybrid adsorption/crystallization PX purification process is also described using the molecular sieve adsorbent.
Claims17
A process for the separation and purification of paraxylene from a hydrocarbon feed comprising a mixture of C8 aromatic hydrocarbons, comprising:
- a) contacting the feed, at adsorption conditions, with an adsorbent bed comprising an adsorbent selected from the group consisting of SSZ-25, MCM-22, PSH-3, ERB-1, and ITQ-1 thereby adsorbing paraxylene from the feed;
- b) contacting the adsorbent bed at desorption conditions with a desorbent material comprising benzene;
- c) withdrawing a stream comprising desorbent and less selectively adsorbed components of the feed from the adsorbent bed;
- and
- d) withdrawing from the adsorbent bed a stream comprising desorbent and said paraxylene,
- e) separating the stream comprising desorbent and less selectively adsorbed components into a stream comprising desorbent and a stream comprising less selectively adsorbed components;
- and
- f) separating the stream comprising desorbent and said paraxylene into a stream comprising desorbent and a stream comprising paraxylene.
A two stage process for the production of paraxylene from a feed comprising C8 aromatic isomers, comprising:
- a) an adsorption step, using an adsorbent selected from the group consisting of SSZ-25, MCM-22, PSH-3, ERB-1, and ITQ-1 to form a stream concentrated in paraxylene from the feed comprising C8 aromatic isomers;
- and
- b) a crystallization step to purify the stream concentrated in paraxylene to obtain high purity paraxylene product suitable for use in the production of terephthalic acid or dimethylterephthalate.
A process for the production of high purity paraxylene from a feed comprising paraxylene and at least one other C8 aromatic hydrocarbon, comprising:
- a) adsorption of the paraxylene from the feed on an adsorbent selected from the group consisting of SSZ-25, MCM-22, PSH-3, ERB-1, and ITQ-1 at adsorption conditions;
- b) desorption of the paraxylene from the adsorbent using a desorbent to form a stream comprising desorbent and paraxylene;
- and
- c) separation of the stream comprising desorbent and paraxylene to form a stream comprising paraxylene and a stream comprising desorbent.
Dependencies are inferred from the claim text.