US 2025/0353800 A1Published application

Production of P-Xylene by Liquid-Phase Isomerization and Separation Thereof

AssigneeExxonMobil Chemical Patents Inc.

InventorsPaul Podsiadlo, Robert G. Tinger, Xiaobo Zheng

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Abstract

A feed mixture comprising one or more xylene isomers may be separated in a p-xylene recovery unit using simulated moving bed, chromatography with toluene as a desorbent to obtain a product stream rich in p-xylene and a raffinate stream lean in p-xylene. Optionally, an intermediate stream may be obtained as well. At least a portion of the raffinate stream or an isomerized raffinate stream may be separated in a distillation column to produce an overhead, stream comprising toluene, which may be fed to the p-xylene recovery unit as at least a portion of the desorbent. If present, the intermediate stream may be isomerized under liquid-phase isomerization conditions and fed to the p-xylene recovery unit. At least a portion of the raffinate stream or one or more lower streams obtained from the distillation column may be isomerized under liquid-phase isomerization conditions and fed to the p-xylene recovery unit.

Claims26

Dependent claims

A process comprising:

(I) providing a feed mixture comprising one or more xylene isomers and optionally ethylbenzene;
(II) separating the feed mixture in a p-xylene recovery unit using simulated moving bed chromatography with toluene as a desorbent to obtain a product stream rich in p-xylene, a raffinate stream lean in p-xylene, and optionally, an intermediate stream comprising p-xylene at a concentration higher than in the raffinate stream and lower than in the product stream, the raffinate stream comprising toluene, optionally ethylbenzene, and o-xylene, m-xylene, or any combination thereof,
(III) optionally, conducting liquid-phase isomerization under liquid-phase isomerization conditions in the presence of a liquid-phase isomerization catalyst upon at least a portion of the raffinate stream to obtain an isomerized raffinate stream;
(IV) separating at least a portion of the raffinate stream and/or, if present, at least a portion of the isomerized raffinate stream in a distillation column to obtain an overhead stream comprising at least a majority of the toluene in the raffinate stream and one or more lower streams each comprising one or more xylene isomers;
(V) feeding at least a portion of the overhead stream to the p-xylene recovery unit as at least a portion of the desorbent;
(VI) conducting liquid-phase isomerization under liquid-phase isomerization conditions in the presence of a liquid-phase isomerization catalyst and obtaining one or more isomerized recycle streams after conducting the liquid-phase isomerization, the liquid-phase isomerization being conducted upon at least one of:
(a) at least a portion of the one or more lower streams;
and/or
(b) if present, at least a portion of the intermediate stream;
and/or
(c) the liquid-phase isomerization of at least a portion of the raffinate stream is carried out in (III);
and
(VII) feeding at least a portion of the one or more isomerized recycle streams to the p-xylene recovery unit.

10 more elements

A process comprising:

(i) providing a feed mixture comprising one or more xylene isomers and optionally ethylbenzene;
(ii) separating the feed mixture in a p-xylene recovery unit using simulated moving bed chromatography with toluene as a desorbent to obtain a product stream rich in p-xylene and a raffinate stream lean in p-xylene, the raffinate stream comprising toluene, optionally ethylbenzene, and o-xylene, m-xylene, or any combination thereof,
(iii) conducting liquid-phase isomerization under liquid-phase isomerization conditions in the presence of a liquid-phase isomerization catalyst upon at least a portion of the raffinate stream to obtain an isomerized raffinate stream;
(iv) feeding the isomerized raffinate stream to a first side of a divided wall distillation column;
(v) feeding a portion of the raffinate stream to a second side of the divided wall distillation column;
(vi) obtaining a first lower stream rich in p-xylene from the first side of the divided wall distillation column, a second lower stream lean in p-xylene from the second side of the divided wall distillation column, and an overhead stream rich in toluene from the divided wall distillation column;
(vii) feeding at least a portion of the overhead stream to the p-xylene recovery unit as at least a portion of the desorbent;
and
(viii) feeding one or more isomerized recycle streams to the p-xylene recovery unit, the one or more isomerized recycle streams being obtained as at least a portion of the first lower stream.

6 more elements

A process comprising:

(A) providing a feed mixture comprising one or more xylene isomers and optionally ethylbenzene;
(B) separating the feed mixture in a p-xylene recovery unit using simulated moving bed chromatography with toluene as a desorbent to obtain a product stream rich in p-xylene, a raffinate stream lean in p-xylene, and optionally an intermediate stream comprising p-xylene at a concentration higher than in the raffinate stream and lower than in the product stream, the raffinate stream comprising toluene, optionally ethylbenzene, and o-xylene, m-xylene, or any combination thereof,
(C) separating at least a portion of the raffinate stream in a distillation column to obtain an overhead stream comprising at least a majority of the toluene in the raffinate stream and one or more lower streams each comprising one or more xylene isomers;
(D) feeding at least a portion of the overhead stream to the p-xylene recovery unit as at least a portion of the desorbent;
(E) conducting liquid-phase isomerization under liquid-phase isomerization conditions in the presence of a liquid-phase isomerization catalyst to produce one or more isomerized recycle streams, the liquid-phase isomerization being conducted upon at least one of:
(a) at least a portion of the one or more lower streams;
and/or
(b) if present, at least a portion of the intermediate stream;
and/or
(c) at least a portion of the raffinate stream;
and
(F) feeding at least a portion of the one or more isomerized recycle streams to the p-xylene recovery unit.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/872,371Filed 16 May 2023
Priority: 14 Jun 2022
Published: 20 Nov 2025
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

C07C 5/2737
Catalytic processes: with crystalline alumino-silicates, e.g. molecular sieves
C07C 7/12
Purification; Separation; Use of additives: by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with…
B01D 15/1821
Recycling of the fraction to be distributed: simulated moving beds
C07C 5/2708
Catalytic processes not covered by C07C5/2732 - C07C5/31; Catalytic processes covered by both C07C5/2732 and C07C5/277 simultaneously: with…