US 2018/0002252 A1Published application

Processes for Recovering Paraxylene

AssigneeExxonMobil Chemical Patents Inc.

InventorsMichael Salciccioli, Gaurav Agrawal, Michael W. Weber, Dana L. Pilliod, Catherine M. Dorsi

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Abstract

Disclosed is a process for recovering paraxylene in which a first simulated moving bed adsorption unit is used to produce two extract streams—one rich in paraxylene and a paraxylene-rich extract stream that is lean in ethylbenzene and an ethylbenzene-rich extract stream that is lean in paraxylene- and a paraxylene-depleted raffinate stream. A significant amount of the ethylbenzene is removed in the ethylbenzene-rich extract stream (at least enough to limit buildup in the isomerization loop), so the paraxylene-depleted raffinate stream may be isomerized in the liquid phase. Avoiding vapor phase isomerization saves energy and capital, as liquid phase isomerization requires less energy and capital than the vapor phase isomerization process due to the requirement of vaporizing the paraxylene-depleted stream and the use of hydrogen, which requires an energy and capital intensive hydrogen recycle loop.

Claims24

Dependent claims

A process for recovering paraxylene, the process comprising:

(a) introducing a first hydrocarbon feed stream into a first simulated moving bed adsorption unit, wherein the first hydrocarbon feed stream comprises a mixture of paraxylene (PX), metaxylene (MX), orthoxylene (OX), and ethylbenzene (EB);
(b) introducing a desorbent stream into the first simulated moving bed adsorption unit, wherein the desorbent stream comprises a desorbent;
(c) withdrawing a first PX-rich extract stream, which comprises desorbent and PX, from the first simulated moving bed adsorption unit, wherein the PX-rich extract stream is withdrawn at a location downstream of the desorbent introduction location and upstream of the feed introduction location;
(d) withdrawing an EB-rich extract stream, which comprises desorbent, EB, and PX, from the first simulated moving bed adsorption unit, wherein the EB-rich extract stream is withdrawn at a location downstream of the PX-rich extract stream withdrawal location and upstream of the feed introduction location;
(e) withdrawing a first PX-depleted raffinate stream, which comprises desorbent, MX, OX, and EB, from the first simulated moving bed adsorption unit;
(f) isomerizing at least a portion of the first PX-depleted raffinate stream at least partially in the liquid phase to produce a first isomerized stream having a higher PX concentration than the first PX-depleted raffinate stream;
and
(g) recycling at least a portion of the first isomerized stream to the first simulated moving bed adsorption unit.

5 more elements

A process for recovering paraxylene, the process comprising:

(a) providing a first hydrocarbon feed stream and a desorbent stream to a first simulated moving bed adsorption unit, wherein the first hydrocarbon feed stream comprises a mixture of paraxylene (PX), metaxylene (MX), orthoxylene (OX), and ethylbenzene (EB), and wherein the desorbent stream comprises desorbent;
(b) withdrawing from the first simulated moving bed adsorption unit:
(i) a first PX-rich extract stream, which comprises desorbent and PX;
(ii) an EB-rich extract stream, which comprises desorbent, EB, and PX;
and
(iii) a first PX-depleted raffinate stream, which comprises desorbent, MX, OX, and EB,
wherein the PX-rich extract stream is withdrawn at a location downstream of the desorbent introduction location and upstream of the feed introduction location and the EB-rich extract stream is withdrawn at a location downstream of the PX-rich extract stream withdrawal location and upstream of the feed introduction location;
(c) isomerizing at least a portion of the first PX-depleted raffinate stream at least partially in the liquid phase to produce a first isomerized stream having a higher PX concentration than the first PX-depleted raffinate stream;
(d) recycling at least a portion of the first isomerized stream to the first simulated moving bed adsorption unit;
(e) providing the EB-rich extract stream to a second simulated moving bed adsorption unit to produce a second PX-rich extract stream and a second PX-depleted raffinate;
and
(f) recovering a pure EB stream from the second PX-depleted raffinate stream in a distillation column.

9 more elements

A process for recovering paraxylene, the process comprising:

(a) providing a first hydrocarbon feed stream and a desorbent stream to a first simulated moving bed adsorption unit, wherein the first hydrocarbon feed stream comprises a mixture of paraxylene (PX), metaxylene (MX), orthoxylene (OX), and ethylbenzene (EB), and wherein the desorbent stream comprises desorbent;
(b) withdrawing from the first simulated moving bed adsorption unit:
(i) a first PX-rich extract stream, which comprises desorbent and PX;
(ii) an EB-rich extract stream, which comprises desorbent, EB, and PX;
and
(iii) a first PX-depleted raffinate stream, which comprises desorbent, MX, OX, and EB,
wherein the PX-rich extract stream is withdrawn at a location downstream of the desorbent introduction location and upstream of the feed introduction location and the EB-rich extract stream is withdrawn at a location downstream of the PX-rich extract stream withdrawal location and upstream of the feed introduction location;
(c) isomerizing at least a portion of the first PX-depleted raffinate stream at least partially in the liquid phase to produce a first isomerized stream having a higher PX concentration than the first PX-depleted raffinate stream;
(d) recycling at least a portion of the first isomerized stream to the first simulated moving bed adsorption unit;
(e) providing the EB-rich extract stream to a second simulated moving bed adsorption unit to produce a second PX-rich extract stream and a second PX-depleted raffinate;
(f) isomerizing at least a portion of the second PX-depleted raffinate stream in the vapor phase to produce a second isomerized stream having a higher PX concentration than the second PX-depleted raffinate stream;
and
(g) recycling at least a portion of the second isomerized stream to the first simulated moving bed adsorption unit or second simulated moving bed adsorption unit.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/600,494Filed 19 May 2017
Priority: EP 16185649.725 Aug 2016
Published: 4 Jan 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification11 codes

C07B 63/04
Purification; Separation ; Stabilisation; Use of additives: use of additives
B01D 15/1828
Simulated moving beds: characterised by process features
B01D 15/185
Simulated moving beds: characterised by the components to be separated
C07C 5/2708
Catalytic processes not covered by C07C5/2732 - C07C5/31; Catalytic processes covered by both C07C5/2732 and C07C5/277 simultaneously: with…