US 5,705,726 A · Xylene isomerization on separate reactors · patentgrep

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Abstract

A mixture of aromatic hydrocarbons, comprising ethylbenzene and at least one xylene, is isomerized using a two reactor system to convert the ethylbenzene to compounds that may be removed from the aromatic hydrocarbon stream and to produce a product stream wherein the para-xylene concentration is approximately equal to the equilibrium ratio of the para-isomer. The catalyst present in the first reactor is one that is effective for ethylbenzene conversion with minimal xylene loss when operated under suitable conversion conditions, e.g., a catalyst comprising silica bound ZSM-5 that has been selectivated by one or more silicon impregnations or that has been coke selectivated. The catalyst present in the second reactor is one which is effective to catalyze xylene isomerization when operated under suitable conditions. Each of the catalysts of this invention may contain one or more hydrogenation or dehydrogenation components.

Claims20

Dependent claims

A process for isomerizing xylenes in a feed comprising ethylbenzene and xylenes, the process comprising the steps of:

(a) contacting the feed with a first catalyst in a first reactor under ethylbenzene conversion conditions, wherein the first catalyst comprises an intermediate pore size zeolite having a constraint index ranging from 1 to 12 and a silica to alumina ratio of at least about 5, said intermediate pore size zeolite having been modified by being exposed to at least one selectivation sequence that comprises the steps of contacting the zeolite with a silicon compound to obtain a selectivated zeolite and subsequently calcining the selectivated zeolite, to form an ethylbenzene depleted product;
and
(b) contacting at least a portion of the ethylbenzene depleted product with a second catalyst in a second reactor under xylene isomerization conditions, the second catalyst being effective to isomerize a mixture of xylenes to approximately equilibrium conditions.

A xylene isomerization process, wherein the process comprises the steps of:

(a) directing a mixed xylene feed comprising ethylbenzene, para-xylene and ortho-xylene into a xylene splitter which fractionates the mixed xylene feed into a first stream containing at least a portion of the para-xylene present in the mixed xylene feed and a second stream containing at least a portion of any aromatics heavier than C.sub.8 present in the mixed xylene stream, and optionally, containing a portion of the ortho-xylene present in the mixed xylene feed;
(b) passing the first stream produced in step (a) through a para-xylene separation operation wherein a para-xylene rich stream and a para-xylene depleted stream are produced;
(c) directing the para-xylene depleted stream produced in step (b) along with hydrogen into a first reactor containing a first catalyst under ethylbenzene conversion conditions, wherein the first catalyst comprises an intermediate pore size zeolite having a constraint index ranging from 1 to 12 and a silica to alumina ratio of at least about 5, said intermediate pore size zeolite having been modified by being exposed to at least one selectivation sequence that comprises the steps of contacting the zeolite with a silicon compound to obtain a selectivated zeolite and subsequently calcining the selectivated zeolite, to form an ethylbenzene depleted product;
(d) directing the ethylbenzene depleted product of step (c) to a second reactor containing a second catalyst, wherein the effluent contacts the second catalyst under xylene isomerization conditions, the second catalyst and xylene isomerization conditions being effective to isomerize a mixture of xylenes to approximately equilibrium concentrations;
(e) separating and removing at least one component having a boiling point lower than ethylbenzene from the effluent of the reactor of step (d) to thereby produce a mixed xylene recycle stream;
and
(f) combining the mixed xylene recycle stream produced in step (e) with the mixed xylene feed stream of step (a) and directing the combined mixed xylene stream thereby produced to the xylene splitter of step (a).

4 more elements

A xylene isomerization process, wherein the process comprises the steps of:

(a) directing a mixed xylene feed stream comprising ethylbenzene, para-xylene, and ortho-xylene along with hydrogen into a first reactor containing a first catalyst under ethylbenzene conversion conditions to thereby produce an ethylbenzene depleted stream, wherein the first catalyst comprises an intermediate pore size zeolite having a constraint index ranging from 1 to 12 and a silica to alumina ratio of at least about 5, said intermediate pore size zeolite having been modified by being exposed to at least one selectivation sequence that comprises the steps of contacting the zeolite with a silicon compound to obtain a selectivated zeolite and subsequently calcining the selectivated zeolite, to form an ethylbenzene depleted product;
(b) removing at least one compound having a boiling point lower than ethylbenzene from the ethylbenzene depleted product of step (a) to thereby produce a stream comprising ethylbenzene;
(c) directing the stream comprising ethylbenzene of step (b) to a xylene splitter which fractionates the stream comprising ethylbenzene into a first stream containing at least a portion of the para-xylene present in the stream comprising ethylbenzene and a second stream containing at least a portion of any aromatics heavier than C.sub.8 present in the stream comprising ethylbenzene, and optionally containing a portion of the ortho-xylene present in the stream comprising ethylbenzene;
(d) passing the first stream produced in step (c) through a para-xylene separation operation wherein a para-xylene rich stream and a para-xylene depleted stream arm produced;
(e) directing the para-xylene depleted stream produced in step (d) to a second reactor containing a second catalyst, wherein the para-xylene depleted stream contacts the second catalyst under xylene isomerization conditions the second catalyst and xylene isomerization conditions being effective to isomerize a mixture of xylenes to approximately equilibrium concentrations;
and
(f) combining the effluent from step (e) with the ethylbenzene depleted stream of step (a) and removing the compounds having boiling points lower than ethylbenzene from the combined stream according to step (b) to thereby produce the stream comprising ethylbenzene of step (b).

4 more elements

A xylene isomerization process, wherein the process comprises the steps of:

(a) directing a mixed xylene feed comprising ethylbenzene, para-xylene and ortho-xylene into a xylene splitter which fractionates the mixed xylene feed into a first stream containing at least a portion of the para-xylene present in the mixed xylene feed and a second stream containing at least a portion of any aromatics heavier than C.sub.8 present in the mixed xylene stream, and optionally contains a portion of any ortho-xylene present in the mixed xylene feed;
(b) passing the first stream produced in step (a) through a para-xylene separation operation wherein a para-xylene rich stream and a para-xylene depleted stream are produced;
(c) directing the para-xylene depleted stream produced in step (b) along with hydrogen into a first reactor containing a first catalyst under ethylbenzene conversion conditions, the first catalyst being effective to produce less than 12 weight % para-xylene when tested by contacting a test feed containing 60 weight % meta-xylene, 20 weight % ortho-xylene and 20 weight % ethylbenzene at a temperature of 800EF, a pressure of 150 psig, a weight hourly space velocity of 20 hr.sup.-1, and a hydrogen to hydrocarbon molar ratio of 1;
(d) directing the effluent of the reactor of step (c) to a second reactor containing a second catalyst, wherein the effluent contacts the second catalyst under xylene isomerization conditions, the second catalyst and xylene isomerization conditions being effective to isomerize a mixture of xylenes to approximately equilibrium concentrations;
(e) separating and removing at least one component having a boiling point lower than ethylbenzene from the effluent of the reactor of step (d) to thereby produce a mixed xylene recycle stream;
and
(f) combining the mixed xylene recycle stream produced in step (e) with the mixed xylene feed stream of step (a) and directing the combined mixed xylene stream thereby produced to the xylene splitter of step (a).

4 more elements

A xylene isomerization process, wherein the process comprises the steps of:

(a) directing a mixed xylene feed stream comprising ethylbenzene, para-xylene, and ortho-xylene along with hydrogen into a first reactor containing a first catalyst under ethylbenzene conversion conditions to thereby produce an ethylbenzene depleted stream, the first catalyst being effective to produce less than 12 weight % para-xylene when tested by contacting a test feed containing 60 weight % meta-xylene, 20 weight % ortho-xylene and 20 weight % ethylbenzene at a temperature of 800.degree. F., a pressure of 150 psig, a weight hourly space velocity of 20 hr.sup.-1, and a hydrogen to hydrocarbon molar ratio of 1;
(b) removing at least one compound having a boiling point lower than ethylbenzene from the ethylbenzene depleted stream of step (a) to thereby produce a stream comprising ethylbenzene;
(c) directing the stream comprising ethylbenzene of step (b) to a xylene splitter which fractionates the stream comprising ethylbenzene into a first stream containing at least a portion of the para-xylene present in the stream comprising ethylbenzene and a second stream containing at least a portion of any aromatics heavier than C.sub.8 present in the stream comprising ethylbenzene, and optionally containing a portion of any ortho-xylene present in the stream comprising ethylbenzene;
(d) passing the first stream produced in step (c) through a para-xylene separation operation wherein a para-xylene rich stream and a para-xylene depleted stream are produced;
(e) directing the para-xylene depleted stream produced in step (d) along with hydrogen to a second reactor containing a second catalyst, wherein the para-xylene depleted stream contacts the second catalyst under xylene isomerization conditions, the second catalyst and xylene isomerization conditions being effective to isomerize a mixture of xylenes to approximately equilibrium concentrations;
and
(f) combining the effluent from step (e) with the ethylbenzene depleted stream of step (a) and removing the compounds having boiling points lower than ethylbenzene from the combined stream according to step (b) to thereby produce the stream comprising ethylbenzene of step (b).

4 more elements

A xylene isomerization process, wherein the process comprises the steps of:

(a) directing a mixed xylene feed comprising ethylbenzene, para-xylene and ortho-xylene into a xylene splitter which fractionates the mixed xylene feed into a first stream containing at least a portion of the para-xylene present in the mixed xylene feed and a second stream containing at least a portion of any aromatics heavier than C.sub.8 present in the mixed xylene stream, and optionally contains a portion of any ortho-xylene present in the mixed xylene feed;
(b) passing the first stream produced in step (a) through a para-xylene separation operation wherein a para-xylene rich stream and a para-xylene depleted stream are produced;
(c) directing the para-xylene depleted stream produced in step (b) along with hydrogen into a first reactor containing a first catalyst under ethylbenzene conversion conditions, the first catalyst comprising a silica bound intermediate pore size zeolite that has been modified by being exposed to two to six selectivation sequences, each selectivation sequence comprising the steps of contacting the zeolite with a selectivating agent and subsequently calcining the selectivated zeolite, wherein the selectivating agent contains silicon;
(d) directing the effluent of the reactor of step (c) along with hydrogen to a second reactor containing a second catalyst, wherein the effluent contacts the second catalyst under xylene isomerization conditions, the second catalyst and xylene isomerization conditions being effective to isomerize a mixture of xylenes to approximately equilibrium concentrations;
(e) separating and removing at least one component having a boiling point lower than ethylbenzene from the effluent of the reactor of step (d) to thereby produce a mixed xylene recycle stream;
and
(f) combining the mixed xylene recycle stream produced in step (e) with the mixed xylene feed stream of step (a) and directing the combined mixed xylene stream thereby produced to the xylene splitter of step (a).

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/555,693Filed 14 Nov 1995 · continuation in part
Priority: 18 Nov 1994
Granted: 6 Jan 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification26 codes

C07C 15/08
C8H10 hydrocarbons: xylenes
B01J 29/40
Crystalline aluminosilicate zeolites; Isomorphous compounds thereof: of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by…
B01J 29/44
Containing iron group metals, noble metals or copper: noble metals
B01J 29/80
Crystalline aluminosilicate zeolites; Isomorphous compounds thereof: mixtures of different zeolites

Family

Serial342,322Parent of this continuation-in-part · filed 18 Nov 1994
Serial469,602Parent of this continuation-in-part · filed 6 Jun 1995
Serial471,631Parent of this continuation-in-part · filed 6 Jun 1995
US 5,516,956 AParent of this continuation-in-part
US 5,625,104 AParent of this continuation-in-part
US 5,705,726 AThis patent

From the US filing history. Foreign family members aren’t listed.

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