Aromatics transalkylation process

Abstract

Aromatic transalkylation processes that reduce the hydrogen makeup gas requirement for aromatic transalkylation units and improve the energy efficiency of aromatic complex are described. The processes can utilize a hot separator, optionally one or more flash drums, and optionally a stripping column. The aromatic transalkylation separator bottoms liquid can be preheated and flashed to a low pressure drum to separate light hydrocarbons such as C1 to C5 as a vapor stream from a liquid hydrocarbon stream rich in aromatics. A portion of the flash drum liquid can be recycled back to the product condenser inlet as sponge liquid to absorb light hydrocarbons from the reactor effluent stream and thereby improve the hydrogen purity of the recycle gas (RG) without purging the RG.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Patent Application No. 63 / 611,580, filed December 18, 2023, the entire contents of which are incorporated herein by reference. Background Technology

[0002] A typical aromatics complex includes an aromatics alkyl transfer reactor, in which toluene and C9-C... 11 Aromatic hydrocarbons, preferably C9-C 10 Aromatic hydrocarbons undergo alkylation in the presence of hydrogen to form xylene. The reactor effluent contains benzene, toluene, xylene, C1-C5 light hydrocarbons, and hydrogen. In a product separator, the reactor effluent is separated into an overhead gas stream containing C1-C5 light hydrocarbons and hydrogen; and an unconverted aromatic compound containing benzene, toluene, and 9 to 11 carbon atoms, preferably C9-C5. 10 The bottom liquid stream of aromatic compounds and xylene. The bottom liquid stream of the product separator is separated in the stripping column into an overhead stream containing some benzene, non-aromatic compounds and light hydrocarbons; and an overhead stream containing the remaining benzene, toluene, and unconverted C9-C. 11 The bottom streams of the aromatics and xylene are used. The overhead gas stream from the stripping tower is used as fuel gas. The bottom stream from the stripping tower is sent to the benzene / toluene (BT) tower for further separation into benzene stream, toluene stream, and unconverted C9-C. 11 Aromatic hydrocarbons and xylene feed stream.

[0003] The overhead feed stream from the product separator is recycled to the aromatic alkyl transfer reactor. The recycled hydrogen stream requires a minimum hydrogen purity of 55 mol% to 95 mol%, preferably 75 mol%, in the reactor section. To maintain this hydrogen purity level, the recycled stream needs to be extensively purged. The purging gas stream, containing a significant amount of hydrogen, is used as fuel gas, and hydrogen is lost.

[0004] In addition, the stripping tower reboiler consumes a large amount of high-end energy to separate C6 range non-aromatic hydrocarbons and some benzene from the remaining benzene, toluene and xylene products.

[0005] Therefore, there is a need for an aromatic alkyl transfer method that reduces the operating costs of aromatic complexes. Attached Figure Description

[0006] Figure 1 This is one embodiment of the aromatic alkyl transfer method of the present invention.

[0007] Figure 2 This is another embodiment of the aromatic alkyl transfer method of the present invention.

[0008] Figure 3This is another embodiment of the aromatic alkyl transfer method of the present invention.

[0009] Figure 4 This is another embodiment of the aromatic alkyl transfer method of the present invention.

[0010] Figure 5 This is another embodiment of the aromatic alkyl transfer method of the present invention. Detailed Implementation

[0011] This invention addresses this need by providing an aromatic alkyl transfer method that reduces the hydrogen replenishment gas requirement for the aromatic alkyl transfer unit and improves the energy efficiency of the aromatic complex. The method eliminates the need for recirculated gas purging while maintaining a minimum hydrogen purity of 55 mol% to 95 mol%, preferably 75%, thereby reducing hydrogen replenishment costs.

[0012] In some embodiments, the method utilizes a thermal separator, optionally one or more flash tanks, and optionally a stripping column. In some methods, the bottom liquid of the aromatic alkyl transfer separator is preheated and flashed into a low-pressure tank to separate light hydrocarbons, such as C1 to C5, as a vapor stream from the aromatic-rich liquid hydrocarbon stream. A portion of the flash tank liquid is recycled back to the product condenser inlet as a sponge liquid to absorb light hydrocarbons from the reactor effluent stream and thereby increase the hydrogen purity of the RG without purging the recycle gas (RG). With this arrangement, a recycle gas purity of 75 mol% can be achieved with zero purging.

[0013] In some embodiments, the method includes a thermal separator in the alkyl transfer reactor section, which eliminates the need for an aromatic alkyl transfer stripping tower and related equipment. Hot and cold flash tank liquids are heated in a series of heat exchangers and fed directly to the downstream BT tower. The method utilizes bulk separation at the BT tower reboiler load due to the inclusion of the aromatic alkyl transfer thermal separator and flash tank. This reduces fuel consumption in the flame heater.

[0014] In some embodiments, the aromatic alkyl transfer stripping column and related equipment are replaced with a BT side-stripping column to achieve benzene product specifications (e.g., 99.94% by weight purity). Separation between C6 aromatics and non-aromatics is carried out in a low-operating-pressure BT column and side-stripper, rather than in a high-operating-pressure aromatic alkyl transfer stripper. The side-stripper also receives extracts from the sulfolane extraction unit.

[0015] In some implementations, the method includes: containing toluene, C9-C 11 Aromatics (preferably C9-C) 10 The combined feed stream of aromatics and hydrogen undergoes alkyl transfer, resulting in a mixture containing benzene, xylene, toluene, and unconverted C9-C hydrocarbons. 11A reactor effluent stream of aromatics, light hydrocarbons having 1 to 5 carbon atoms, and hydrogen is formed. The reactor effluent stream is cooled with a high-pressure liquid stream from a high-pressure product separator, resulting in a cooled reactor effluent stream and a heated high-pressure liquid stream. The cooled reactor effluent stream is separated in the high-pressure product separator, resulting in a hydrogen stream and a high-pressure liquid stream. The heated high-pressure liquid stream is flashed in a first flash tank to form a first flash tank vapor stream containing light hydrocarbons and a stream containing benzene, xylene, toluene, and unconverted C9-C. 11 The first flash tank liquid stream of aromatics is divided into a first portion and a second portion. The first portion of the first flash tank liquid stream is recycled to the product condenser upstream of the product high-pressure separator. In the aromatics separation zone containing the benzene-toluene tower, at least a portion of the second portion of the first flash tank liquid stream is separated into a benzene stream, or a toluene stream, or a xylene stream, or a combination thereof.

[0016] In some embodiments, the method further includes: introducing a first flash tank vapor stream into a stripper at a first location, and introducing a second portion of the first flash liquid stream into the stripper at a second location below the first location. The first flash tank vapor stream and the second portion of the first flash tank liquid stream are separated in the stripper into a stripper overhead stream containing a portion of benzene, non-aromatic compounds, and light hydrocarbons; and a stripper bottom stream containing the remaining benzene, xylene, unconverted aromatic compounds, and toluene. In this case, separating at least a portion of the second portion of the first flash tank liquid stream in the aromatics separation zone includes separating the stripper bottom stream in the aromatics separation zone.

[0017] In some embodiments, the method further includes precooling the reactor effluent stream with a combined feed stream before cooling it with a high-pressure liquid stream from a high-pressure product separator, thereby forming a precooled reactor effluent stream. The precooled reactor effluent stream is separated into a thermal separator vapor stream and a thermal separator liquid stream in a thermal separator, wherein cooling the reactor effluent stream with the high-pressure liquid stream from the high-pressure product separator includes cooling the thermal separator vapor stream with the high-pressure liquid stream from the high-pressure product separator. The high-pressure thermal separator liquid stream is separated into a second flash tank vapor stream and a second flash tank liquid stream in a second flash tank. The second flash tank vapor stream is fed to a first flash tank. A second portion of the first flash tank liquid stream is fed at a first location to a benzene-toluene tower, and the second flash tank liquid stream is fed at a second location below the first location to a benzene-toluene tower. The aromatics separation zone also includes a benzene-toluene side fractionation tower. The method further includes feeding an aromatic-rich feed stream from a sulfolane extraction process to a benzene-toluene side fractionation column, the aromatic-rich feed stream comprising benzene and toluene. The aromatic-rich feed stream from the extraction process is separated into a benzene feed stream, a toluene feed stream, or both in the benzene-toluene side fractionation column. The benzene feed stream comprises the overhead or side fraction feed stream from the benzene-toluene side fractionation column, located above the point where the aromatic-rich feed stream from the extraction process enters the benzene-toluene side fractionation column. The toluene feed stream comprises the bottom feed stream from the benzene-toluene side fractionation column, and the xylene feed stream comprises the bottom feed stream from the benzene-toluene column.

[0018] In some embodiments, the method further includes conveying a side distillate stream from the benzene-toluene column to the benzene-toluene side distillate column at a position above where the aromatic-rich feed stream from the extraction process enters the benzene-toluene side distillate column. The overhead feed stream from the benzene-toluene side distillate column is then conveyed to the benzene-toluene column at a position above where the side distillate stream from the benzene-toluene column exits the benzene-toluene side distillate column. The benzene feed stream exits the benzene-toluene side distillate column at a position below where the side distillate stream from the benzene-toluene column enters the benzene-toluene side distillate column and above where the aromatic-rich feed stream from the extraction process enters the benzene-toluene side distillate column.

[0019] In some embodiments, the method further includes dividing the hydrogen stream into a first portion and a second portion. The first portion of the hydrogen stream is compressed in a purge gas compressor to form a compressed first portion, and the compressed first portion of the hydrogen stream is separated in a membrane separation unit into a permeate stream containing hydrogen and a hydrogen-lean waste gas stream. The second portion of the hydrogen stream is compressed in a recirculation gas compressor to form a compressed second portion, and the permeate stream and the compressed second portion are combined to form a combined hydrogen stream, and the combined hydrogen stream is recirculated to the combined feed stream.

[0020] In some embodiments, the method further includes precooling the reactor effluent stream with a combined feed stream before cooling it with a high-pressure liquid stream from a high-pressure product separator, thereby forming a precooled reactor effluent stream. The precooled reactor effluent stream is separated into a thermal separator vapor stream and a thermal separator liquid stream in a thermal separator, wherein cooling the reactor effluent stream with the high-pressure liquid stream from the high-pressure product separator includes cooling the thermal separator vapor stream with the high-pressure liquid stream from the high-pressure product separator. The thermal separator liquid stream is flashed in a second flash tank to form a second flash tank vapor stream and a second flash tank liquid stream. The second flash tank vapor stream is fed to a first flash tank. A second portion of the first flash tank liquid stream is fed at a first location to a benzene-toluene tower, and the second flash tank liquid stream is fed at a second location below the first location to a benzene-toluene tower. The aromatics separation zone also includes a benzene-toluene side fractionation column, and the method further includes feeding an aromatics-rich feed stream containing benzene and toluene from the sulfolane extraction process into the benzene-toluene side fractionation column. The aromatics-rich feed stream is separated into a benzene feed stream, a toluene feed stream, or both in the benzene-toluene side fractionation column. The benzene feed stream includes the overhead or side fraction feed stream from the benzene-toluene side fractionation column, located above the point where the aromatics-rich feed stream enters the benzene-toluene side fractionation column; the toluene feed stream includes the bottom feed stream from the benzene-toluene side fractionation column; and the xylene feed stream includes the bottom feed stream from the benzene-toluene column.

[0021] In some embodiments, the method further includes dividing the hydrogen stream into a first portion and a second portion. The first portion of the hydrogen stream is compressed in a purge gas compressor to form a compressed first portion. The compressed first portion of the hydrogen stream is separated in a membrane separation unit into a permeate stream containing hydrogen and a hydrogen-lean waste gas stream. The second portion of the hydrogen stream is compressed in a recirculation gas compressor to form a compressed second portion. The permeate stream and the compressed second portion of the hydrogen stream are combined to form a combined hydrogen stream, and the combined hydrogen stream is recycled to a combined feed stream.

[0022] In some embodiments, the method further includes separating the overhead stream of the benzene-toluene column into an overhead waste gas stream containing hydrogen, light hydrocarbons having one to five carbon atoms, and a portion of benzene; and an overhead liquid stream containing hydrogen, light hydrocarbons having one to five carbon atoms, and a second portion of benzene. The overhead waste gas stream is compressed to form a compressed overhead waste gas stream. The compressed overhead waste gas stream and the overhead liquid stream are then fed to a stabilizer column.

[0023] In some implementations, the method further includes compressing the hydrogen feed stream and recycling the compressed hydrogen feed stream back into the combined feed stream.

[0024] In some embodiments, the method further includes preheating the combined feed stream in a heat exchanger with a reactor effluent or a flame heater or both before transferring the alkyl groups of the combined feed stream.

[0025] In some implementations, the method includes making a mixture containing toluene, C9-C 11 The combined feed stream of aromatics and hydrogen undergoes alkyl transfer, resulting in a mixture containing benzene, xylene, toluene, and unconverted C9-C hydrocarbons. 11 A reactor effluent stream of aromatics, light hydrocarbons having 1 to 5 carbon atoms, and hydrogen is separated in a thermal separator into a thermal separator vapor stream and a thermal separator liquid stream. The thermal separator vapor stream is cooled with a high-pressure liquid stream from a high-pressure product separator, resulting in a cooled thermal separator vapor stream and a heated high-pressure liquid stream. The cooled thermal separator vapor stream is separated in a high-pressure product separator, resulting in a hydrogen stream and a high-pressure liquid stream from the high-pressure product separator. The thermal separator liquid stream is separated in a second flash tank into a second flash tank vapor stream and a second flash tank liquid stream. The heated high-pressure liquid stream and the second flash tank vapor stream are flashed in a first flash tank to form a first flash tank vapor stream containing light hydrocarbons and a first flash tank liquid stream containing benzene, xylene, and toluene. The first flash tank liquid stream is conveyed at a first location to an aromatics separation zone including a benzene-toluene tower, and the second flash tank liquid stream is conveyed at a second location below the first location to a benzene-toluene tower. In the aromatics separation zone, the liquid streams from the first flash tank and the second flash tank are separated into a benzene stream, or a toluene stream, or a xylene stream, or a combination thereof.

[0026] In some embodiments, the method further includes precooling the reactor effluent stream with a combined feed stream before separating the reactor effluent stream in a thermal separator, thereby forming a precooled reactor effluent stream. The reactor effluent stream separated in the thermal separator comprises the precooled reactor effluent stream. The aromatics separation zone also includes a benzene-toluene side fractionation column, and the method further includes feeding an aromatics-rich stream containing benzene and toluene from a sulfolane extraction process to the benzene-toluene side fractionation column. The aromatics-rich stream is separated in the benzene-toluene side fractionation column into a benzene stream, a toluene stream, or both. The benzene stream comprises the overhead stream or side fraction stream from the benzene-toluene side fractionation column located above the point where the aromatics-rich stream enters the benzene-toluene side fractionation column; the toluene stream comprises the bottom stream from the benzene-toluene side fractionation column; and the xylene stream comprises the bottom stream from the benzene-toluene column.

[0027] In some embodiments, the method further includes feeding a side fraction of the benzene-toluene column into the benzene-toluene side fraction at a position above where the aromatic-rich feed stream enters the benzene-toluene side fraction, and feeding a top fraction of the benzene-toluene side fraction into the benzene-toluene column at a position above where the side fraction feed stream exits the benzene-toluene column. The benzene feed stream exits the benzene-toluene side fraction at a position below where the side fraction feed stream from the benzene-toluene column enters the benzene-toluene side fraction.

[0028] In some embodiments, the method further includes dividing the hydrogen stream into a first portion and a second portion. The first portion of the hydrogen stream is compressed in a purge gas compressor to form a compressed first portion, and the compressed first portion of the hydrogen stream is separated in a membrane separation unit into a permeate stream containing hydrogen and a hydrogen-lean waste gas stream. The second portion of the hydrogen stream is separated in a recirculation gas compressor to form a compressed second portion. The permeate stream and the compressed second portion of the hydrogen stream are combined to form a combined hydrogen stream, and the combined hydrogen stream is recirculated to a combined feed stream.

[0029] In some implementations, the method includes making a mixture containing toluene, C9-C 11 The combined feed stream of aromatics and hydrogen undergoes alkyl transfer to form a reactor effluent stream containing benzene, xylene, toluene, unconverted aromatic compounds having 9 to 11 carbon atoms, light hydrocarbons having 1 to 5 carbon atoms, and hydrogen. The reactor effluent stream is cooled with a high-pressure separator liquid stream from a high-pressure product separator, resulting in a cooled reactor effluent stream and a heated high-pressure separator liquid stream. The cooled reactor effluent stream is separated in the high-pressure product separator, resulting in a hydrogen stream and a high-pressure separator liquid stream. The heated high-pressure liquid stream is heated with a stripper side stream from a stripper, resulting in a second heated high-pressure liquid stream and a cooled side stream. The second heated high-pressure liquid stream is separated in the stripper into a stripper overhead stream containing a portion of benzene, non-aromatic compounds, and light hydrocarbons, including benzene, xylene, and unconverted C9-C4 hydrocarbons. 11 The stripping column side fraction of aromatic compounds and toluene, as well as the fraction containing benzene, xylene, and unconverted C9-C... 11 The stripper bottom stream contains aromatic compounds and toluene. A second heated, high-pressure stream enters the stripper above the location where the side fraction stream exits the stripper. The cooled stripper side fraction stream is combined with the cooled reactor effluent stream. In the aromatics separation zone, the stripper bottom stream is separated into a benzene stream, or a toluene stream, or a xylene stream, or a combination thereof.

[0030] In some implementations, the method further includes heating the second heated liquid stream with the bottom stream of the stripper before separating the second heated high-pressure liquid stream in the stripper.

[0031] In some implementations, the method further includes compressing the hydrogen feed stream and recycling the compressed hydrogen feed stream back into the combined feed stream.

[0032] Figure 1 An example of aromatic alkyl transfer method 100 is illustrated. The C9-C... 11 Aromatic feed stream 105, toluene feed stream 110, and hydrogen feed stream 115 are combined into a combined feed stream 120. The combined feed stream 120 is fed to a combined feed heat exchanger 125, where it is heated together with the reactor effluent stream 130. The heated combined feed stream 135 is further heated in a charge heater 140, and then fed to an aromatic alkyl transfer reactor 150.

[0033] The reactor effluent stream 130, containing benzene, toluene, xylene, and light hydrocarbons (e.g., C1 to C5 hydrocarbons), is cooled in a combined feed heat exchanger 125. The cooled reactor effluent stream 155 exchanges heat with the high-pressure bottom liquid stream 160 from the high-pressure product separator 165 in a heat exchanger 170, thereby forming a heated high-pressure liquid stream 175 and a cooled reactor effluent stream 180.

[0034] The cooled reactor effluent stream 180 is condensed in the product condenser 185, and the condensed reactor effluent stream 190 is sent to the high-pressure product separator 165, where it is separated into an overhead gas stream 195 and a high-pressure bottom liquid stream 160. The hydrogen-containing overhead gas stream 195 is compressed in the compressor 200 to form a compressed hydrogen stream 205. The compressed hydrogen stream 205 is combined with the supplemental hydrogen stream 210 to form a hydrogen stream 115.

[0035] The heated high-pressure liquid stream 175 is sent to a flash tank 215, where it is flashed into a flash tank vapor stream 220 containing C1 to C5 light hydrocarbons and a flash tank bottom liquid stream 225 containing benzene, toluene and xylene.

[0036] A portion 230 of the flash tank bottom liquid stream 225 is combined with the cooled reactor effluent stream 180 and sent to the product condenser 185. Another portion 235 of the flash tank bottom liquid stream 225 exchanges heat with the stripper bottom stream 240 in a heat exchanger 245. Optionally, the A8 stripper overhead stream 250 may be combined with a portion 235 of the flash tank bottom liquid stream 225.

[0037] The heated flash tank bottom liquid stream 255 and flash tank steam stream 220 are sent to the stripper 260 and separated into stripper top stream 265 and stripper bottom stream 240.

[0038] The overhead stream 265 of the stripping tower is condensed in the overhead condenser 270, and the condensed stream 275 is separated into an overhead vapor stream 285 and an overhead liquid stream 290 in the overhead separator 280. The overhead vapor stream 285 is further separated into a waste gas stream 300 and a liquid stream 305 in the separator 295. The waste gas stream 300 is sent to the fuel gas header. The liquid stream 305 is sent to the overhead separator 280.

[0039] The overhead liquid stream 290 from the top separator 280 is divided into a portion 310 that returns to the stripper 260 and a portion 315 that is sent to the stabilizer.

[0040] The cooled stripper bottom stream 320 from heat exchanger 245 is sent to BT column 325, where it is separated into benzene stream 330, toluene stream 335, toluene stream (supplementary desorbent) 340 and xylene stream 345.

[0041] Optionally, the feed stream 350 containing benzene and toluene from the extraction process can be sent to BT tower 325.

[0042] Figure 2 An example of aromatic alkyl transfer method 400 is illustrated. The C9-C... 11 Aromatic feed stream 405, toluene feed stream 410, and hydrogen feed stream 415 are combined into a combined feed stream 420. The combined feed stream 420 is fed to a combined feed heat exchanger 425, where it is heated together with the reactor effluent stream 430. The heated combined feed stream 435 is further heated in a charge heater 440, and the heated combined feed stream 445 is then fed to an aromatic alkyl transfer reactor 450.

[0043] The reactor effluent stream 430, containing benzene, toluene, xylene, and light hydrocarbons (e.g., C1 to C5 hydrocarbons), is cooled in a combined feed heat exchanger 425. The cooled reactor effluent stream 455 is separated in a thermal separator 460 into a thermal separator vapor stream 465 and a thermal separator liquid stream 470.

[0044] The thermal separator vapor stream 465 exchanges heat with the high-pressure bottom liquid stream 475 from the high-pressure product separator 480 in a heat exchanger 485, thereby forming a cooled thermal separator vapor stream 490 and a heated high-pressure bottom liquid stream 495. The cooled thermal separator vapor stream 490 is condensed in the product condenser 500, and the condensed thermal separator vapor stream 505 is sent to the high-pressure product separator 480. The condensed thermal separator vapor stream 505 is separated into an overhead gas stream 510 and a high-pressure bottom liquid stream 475. The overhead gas stream 510, containing hydrogen, is compressed in a compressor 515, thereby forming a compressed hydrogen stream 520. The compressed hydrogen stream 520 is combined with a supplementary hydrogen stream 525 to form a hydrogen stream 415.

[0045] The heated high-pressure tower bottom liquid stream 495 is sent to the first flash tank 530, where it is flashed into a first flash tank top stream 535 containing C1 to C5 light hydrocarbons and a first flash tank bottom liquid stream 540 containing benzene, toluene and xylene.

[0046] A portion 545 of the liquid stream 540 from the bottom of the first flash tank is combined with the cooled vapor stream 490 from the heat separator and sent to the product condenser 500. Another portion 550 of the liquid stream 540 from the bottom of the first flash tank is sent to the BT column 555. Optionally, the overhead stream 560 of the A8 stripping column may be combined with a portion 550 of the liquid stream 540 from the bottom of the first flash tank.

[0047] The liquid stream 470 from the thermal separator is fed to the second flash tank 565, where it is separated into a second flash tank vapor stream 570 and a second flash tank liquid stream 575. The second flash tank vapor stream 570 is combined with the heated high-pressure tower bottom liquid stream 495 and sent to the first flash tank 530. The second flash tank liquid stream 575 is sent to the BT tower 555 at a location below the entry point of a portion 550 of the first flash tank tower bottom liquid stream 540.

[0048] The top stream 535 from the first flash tank is fed to a separator 580 and separated into a waste gas stream 585 and a liquid stream 590. The waste gas stream 585 can be sent to the fuel gas header. The liquid stream 590 can be combined with a portion 550 of the bottom liquid stream 540 from the first flash tank and sent to the BT tower 555.

[0049] A portion 550 of the bottom liquid stream 540 from the first flash tank and a portion 575 of the liquid stream 575 from the second flash tank are separated in the BT tower 555 into a top stream 595 containing C1-C5 hydrocarbons, a side stream 600 containing benzene and toluene, a toluene stream 605, a toluene stream (supplementary desorbent) 610, and a xylene stream 615.

[0050] The overhead stream 595 is condensed in condenser 620. The condensed overhead stream 625 is separated into an exhaust gas stream 635 and an overhead liquid stream 640 in overhead separator 630. The exhaust gas stream 635 can be sent to the fuel gas header. The overhead liquid stream 640 is divided into a portion 645 that is returned to BT tower 555 and a portion 650 that is sent to the stabilizer tower.

[0051] Side fraction stream 600 is fed to BT side fractionation column 655, where it is separated into overhead stream 660, benzene stream 665, and toluene stream 670, each containing benzene and residual non-aromatic compounds. Overhead stream 660 is returned to BT column 555 at a position above where side fraction stream 600 exits. Optionally, benzene and toluene stream 675 from the extraction process can be fed to BT side fractionation column 655.

[0052] Figure 3 An example of aromatic alkyl transfer method 400' is illustrated. C9-C 11 Aromatic feed stream 405, toluene feed stream 410, and hydrogen feed stream 415 are combined into a combined feed stream 420. The combined feed stream 420 is fed to a combined feed heat exchanger 425, where it is heated together with the reactor effluent stream 430. The heated combined feed stream 435 is further heated in a charge heater 440, and the heated combined feed stream 445 is then fed to an aromatic alkyl transfer reactor 450.

[0053] The reactor effluent stream 430, containing benzene, toluene, xylene, and light hydrocarbons (e.g., C1 to C5 hydrocarbons), is cooled in a combined feed heat exchanger 425. The cooled reactor effluent stream 455 is separated in a thermal separator 460 into a thermal separator vapor stream 465 and a thermal separator liquid stream 470.

[0054] The thermal separator vapor stream 465 exchanges heat with the high-pressure bottom liquid stream 475 from the high-pressure product separator 480 in a heat exchanger 485, thereby forming a cooled thermal separator vapor stream 490 and a heated high-pressure bottom liquid stream 495. The cooled thermal separator vapor stream 490 is condensed in the product condenser 500, and the condensed thermal separator vapor stream 505 is sent to the high-pressure product separator 480. The condensed thermal separator vapor stream 505 is separated into an overhead gas stream 510 and a high-pressure bottom liquid stream 475. The overhead gas stream 510, containing hydrogen, is compressed in a compressor 515, thereby forming a compressed hydrogen stream 520. The compressed hydrogen stream 520 is combined with a supplementary hydrogen stream 525 to form a hydrogen stream 415.

[0055] The heated high-pressure tower bottom liquid stream 495 is sent to the first flash tank 530, where it is flashed into a first flash tank top stream 535 containing C1 to C5 light hydrocarbons and a first flash tank bottom liquid stream 540 containing benzene, toluene and xylene.

[0056] A portion 545 of the liquid stream 540 from the bottom of the first flash tank is combined with the cooled vapor stream 490 from the heat separator and sent to the product condenser 500. Another portion 550 of the liquid stream 540 from the bottom of the first flash tank is sent to the BT column 555. Optionally, the overhead stream 560 of the A8 stripping column may be combined with a portion 550 of the liquid stream 540 from the bottom of the first flash tank.

[0057] The liquid stream 470 from the thermal separator is fed to the second flash tank 565, where it is separated into a second flash tank vapor stream 570 and a second flash tank liquid stream 575. The second flash tank vapor stream 570 is combined with the heated high-pressure tower bottom liquid stream 495 and sent to the first flash tank 530. The second flash tank liquid stream 575 is sent to the BT tower 555 at a location below the entry point of a portion 550 of the first flash tank tower bottom liquid stream 540.

[0058] The top stream 535 from the first flash tank is fed to a separator 580 and separated into a waste gas stream 585 and a liquid stream 590. The waste gas stream 585 can be sent to the fuel gas header. The liquid stream 590 can be combined with a portion 550 of the bottom liquid stream 540 from the first flash tank and sent to the BT tower 555.

[0059] A portion 550 of the bottom liquid stream 540 from the first flash tank and a portion 575 of the liquid stream 575 from the second flash tank are separated in the BT tower into a top stream 595 containing benzene, a toluene stream 605, a toluene stream (supplementary desorbent) 610, and a xylene stream 615.

[0060] The overhead stream 595 is condensed in condenser 620. The condensed overhead stream 625 is separated into a waste gas stream 635 and an overhead liquid stream 640 in overhead separator 630. The waste gas stream 635 can be sent to the fuel gas header. The overhead liquid stream 640 is divided into a portion 645 that returns to BT tower 555 and a portion 650 that is sent to the stabilizer tower.

[0061] BT side fractionation column 655 separates from BT column 555. Stream 675, containing benzene and toluene, from the extraction process can be fed to BT side fractionation column 655, where it is separated into a benzene-containing overhead stream 680 and a toluene-containing bottom stream 685. Overhead stream 680 is condensed in condenser 690. The condensed top stream 695 is sent to column receiver 700. Liquid stream 705 from top receiver 700 is divided into a portion 710, which is returned to BT side fractionation column 655, and a benzene stream 715, which is recovered as a benzene product. Alternatively, benzene stream 715 can also be withdrawn from BT side fractionation column 655.

[0062] Figure 4 An example of aromatic alkyl transfer method 800 is illustrated. The C9-C... 11 Aromatic feed stream 805, toluene feed stream 810, and hydrogen feed stream 815 are combined into a combined feed stream 820. The combined feed stream 820 is fed to a combined feed heat exchanger 825, where it is heated together with the reactor effluent stream 830. The heated combined feed stream 835 is further heated in a charge heater 840 and then fed to an aromatic alkyl transfer reactor 850.

[0063] The reactor effluent stream 830, containing benzene, toluene, xylene, and light hydrocarbons (e.g., C1 to C5 hydrocarbons), is cooled in a combined feed heat exchanger 825. The cooled reactor effluent stream 855 is separated in a thermal separator 860 into a thermal separator vapor stream 865 and a thermal separator liquid stream 870.

[0064] The thermal separator vapor stream 865 exchanges heat with the high-pressure bottom liquid stream 875 from the high-pressure product separator 880 in the heat exchanger 885, thereby forming a cooled thermal separator vapor stream 890 and a heated high-pressure bottom liquid stream 895. The cooled thermal separator vapor stream 890 is condensed in the product condenser 900, and the condensed thermal separator vapor stream 905 is sent to the high-pressure product separator 880. The condensed thermal separator vapor stream 905 is separated into a top gas stream 910 and a high-pressure bottom liquid stream 875.

[0065] The overhead gas stream 910 containing hydrogen is divided into a first portion 915 and a second portion 920. The first portion 915 is compressed in a compressor 925, and the compressed first portion 930 is sent to a membrane separation unit 935, where it is separated into an exhaust gas stream 940 containing light hydrocarbons (e.g., C1 to C5 hydrocarbons) and a permeate stream 945 containing hydrogen.

[0066] The second portion 920 of the overhead gas stream 910 is compressed in compressor 950 to form a compressed hydrogen stream 955. The compressed hydrogen stream 955 is combined with the permeate stream 945 and the supplementary hydrogen stream 960 to form a hydrogen stream 815.

[0067] The heated high-pressure tower bottom liquid stream 895 is sent to the first flash tank 965, where it is flashed into a first flash tank top stream 970 containing C1 to C5 light hydrocarbons and a first flash tank bottom liquid stream 975 containing benzene, toluene and xylene.

[0068] The liquid stream 975 from the bottom of the first flash tank is sent to the BT tower 980. Optionally, the overhead stream 985 of the A8 stripping tower can be combined with the liquid stream 975 from the bottom of the first flash tank.

[0069] The liquid stream 870 from the thermal separator is fed to the second flash tank 990, where it is separated into a second flash tank vapor stream 995 and a second flash tank liquid stream 1000. The second flash tank vapor stream 995 is combined with the heated high-pressure tower bottom liquid stream 895 and sent to the first flash tank 965. The second flash tank liquid stream 1000 is sent to the BT tower 980 at a position below the entry point of the first flash tank tower bottom liquid stream 975.

[0070] The top stream 970 from the first flash tank is fed to separator 1005 and separated into waste gas stream 1010 and liquid stream 1015. Waste gas stream 1010 can be sent to the fuel gas manifold. Liquid stream 1015 can be combined with the bottom liquid stream 975 from the first flash tank and sent to BT tower 980.

[0071] The bottom liquid stream 975 from the first flash tank and the liquid stream 1000 from the second flash tank are separated in the BT tower 980 into a top stream 1020 containing benzene, a side stream 1025 containing benzene and toluene, a toluene stream 1030, a toluene stream (supplementary desorbent) 1035, and a xylene stream 1040.

[0072] The overhead stream 1020 is condensed in condenser 1045. The condensed overhead stream 1050 is separated into a waste gas stream 1060 and an overhead liquid stream 1065 in overhead separator 1055. The waste gas stream 1060 can be sent to the fuel gas header. The overhead liquid stream 1065 is divided into a portion 1070 that is returned to BT tower 980 and a portion 1075 that is sent to the stabilizer tower.

[0073] Side fraction stream 1025 is fed to BT side fractionation column 1080, where it is separated into overhead stream 1085 containing benzene and residual non-aromatics, benzene stream 1090, and toluene stream 1095. Overhead stream 1085 is returned to BT column 980 at a position above where side fraction stream 1025 exits. Optionally, benzene and toluene stream 1100 from the extraction process can be fed to BT side fractionation column 1080.

[0074] Figure 5 An example of aromatic alkyl transfer method 1200 is illustrated. The C9-C... 11 Aromatics stream 1205, toluene stream 1210, and hydrogen stream 1215 are combined into a combined feed stream 1220. The combined feed stream 1220 is fed to a combined feed heat exchanger 1225, where it is heated together with the reactor effluent stream 1230. The heated combined feed stream 1235 is further heated in a charge heater 1240, and then fed to an aromatics alkyl transfer reactor 1250.

[0075] The reactor effluent stream 1230, containing benzene, toluene, xylene, and light hydrocarbons (e.g., C1 to C5 hydrocarbons), is cooled in a combined feed heat exchanger 1225.

[0076] The cooled reactor effluent stream 1255 exchanges heat with the high-pressure bottom liquid stream 1260 from the high-pressure product separator 1265 in a heat exchanger 1270, thereby forming a cooled reactor effluent stream 1275 and a heated high-pressure bottom liquid stream 1280. The cooled reactor effluent stream 1275 is condensed in a product condenser 1285, and the condensed reactor effluent stream 1290 is sent to the high-pressure product separator 1265. The condensed reactor effluent stream 1290 is separated into a hydrogen-containing overhead gas stream 1295 and a high-pressure bottom liquid stream 1260.

[0077] The overhead gas stream 1295 containing hydrogen is compressed in compressor 1300 to form a compressed hydrogen stream 1305. The compressed hydrogen stream 1305 is combined with the supplementary hydrogen stream 1310 to form a hydrogen stream 1215.

[0078] In heat exchanger 1330, the heated high-pressure bottom liquid stream 1280 exchanges heat with the stripper side stream 1320 from stripper 1325, thereby forming a second heated high-pressure bottom liquid stream 1335 and a cooled stripper side stream 1340. The cooled stripper side stream 1340 is combined with the cooled reactor effluent stream 1275 and sent to product condenser 1285.

[0079] The second heated high-pressure bottom liquid stream 1335 exchanges heat with the stripper bottom stream 1345 from the stripper 1325 in the heat exchanger 1350. The third heated high-pressure bottom liquid stream 1355 is sent to the stripper 1325 at a position above where the stripper side distillate stream 1320 leaves.

[0080] The cooled stripper bottom stream 1360 is sent to the BT column 1365, where it is separated into a benzene overhead stream 1370, a benzene stream 1375, a toluene stream 1380, a toluene stream (supplementary desorbent) 1385, and a xylene stream 1390.

[0081] The overhead feed stream 1370 is condensed in condenser 1395. The condensed overhead feed stream 1400 is sent to receiver 1405, and the overhead liquid feed stream 1410 is returned to BT column 1365.

[0082] The feed stream 1415 containing benzene and toluene from the extraction process can be sent to BT tower 1365.

[0083] Specific implementation plan

[0084] While the following description is presented in conjunction with specific embodiments, it should be understood that the description is intended to be illustrative and not to limit the scope of the foregoing description and the appended claims.

[0085] A first embodiment of the present invention is a method comprising alkyl transfer of a combined feed stream containing toluene, an aromatic compound having 9 to 11 carbon atoms, and hydrogen to form a reactor effluent stream containing benzene, xylene, toluene, unconverted aromatic compound having 9 to 11 carbon atoms, a light hydrocarbon having 1 to 5 carbon atoms, and hydrogen; cooling the reactor effluent stream with a high-pressure liquid stream from a high-pressure product separator to form a cooled reactor effluent stream and a heated high-pressure liquid stream; separating the cooled reactor effluent stream in the high-pressure product separator to form a hydrogen stream and the high-pressure liquid stream. Liquid stream; flashing the heated high-pressure liquid stream in a first flash tank into a first flash tank vapor stream containing the light hydrocarbons and a first flash tank liquid stream containing the benzene, xylene, toluene and unconverted aromatic compounds having 9 to 11 carbon atoms; dividing the first flash tank liquid stream into a first portion and a second portion; recycling the first portion of the first flash tank liquid stream to a product condenser upstream of a product high-pressure separator; separating at least a portion of the second portion of the first flash tank liquid stream into a benzene stream, or a toluene stream, or a xylene stream, or a combination thereof in an aromatic separation zone containing a benzene-toluene tower. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph further includes introducing the first flash tank vapor stream into a stripping tower at a first location, and introducing a second portion of the first flash liquid stream into the stripping tower at a second location below the first location; separating the first flash tank vapor stream and the second portion of the first flash tank liquid stream in the stripping tower into a stripping tower overhead stream containing a portion of the benzene, non-aromatic compounds, and the light hydrocarbons, and a stripping tower bottom stream containing the remaining portion of benzene, xylene, unconverted aromatic compounds having 9 to 11 carbon atoms, and toluene; and wherein separating at least a portion of the second portion of the first flash tank liquid stream in the aromatic separation zone includes separating the stripping tower bottom stream in the aromatic separation zone.An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph further includes precooling the reactor effluent with the combined feed stream before cooling the reactor effluent with the high-pressure liquid stream from the high-pressure product separator, thereby forming a precooled reactor effluent; separating the precooled reactor effluent into a thermal separator vapor stream and a thermal separator liquid stream in a thermal separator, wherein cooling the reactor effluent with the high-pressure liquid stream from the high-pressure product separator includes cooling the thermal separator vapor stream with the high-pressure liquid stream from the high-pressure product separator; flashing the thermal separator liquid stream into a second flash tank vapor stream and a second flash tank liquid stream in a second flash tank; transferring the second flash tank vapor stream to the first flash tank; and transferring the first flash tank liquid stream... The second portion of the feed stream is conveyed to the benzene-toluene tower at the first position; the liquid feed stream from the second flash tank is conveyed to the benzene-toluene tower at the second position below the first position; wherein the aromatic separation zone further includes a benzene-toluene side fractionation tower, and further includes conveying an aromatic-rich feed stream from the sulfolane extraction process to the benzene-toluene side fractionation tower, the aromatic-rich feed stream containing benzene and toluene; separating the aromatic-rich feed stream from the extraction process in the benzene-toluene side fractionation tower into the benzene feed stream, the toluene feed stream, or both; wherein the benzene feed stream includes the overhead feed stream or side fraction feed stream from the benzene-toluene side fractionation tower, the overhead feed stream or side fraction feed stream being located above the position where the aromatic-rich feed stream from the extraction process enters the benzene-toluene side fractionation tower; wherein the toluene feed stream includes the bottom feed stream from the benzene-toluene side fractionation tower; and wherein the xylene feed stream includes the bottom feed stream from the benzene-toluene tower. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment in this paragraph further includes feeding a side fraction of the benzene-toluene column into the benzene-toluene side fraction at a position above where the aromatic-rich feed from the extraction process enters the benzene-toluene side fraction; and feeding a top feed from the benzene-toluene side fraction into the benzene-toluene column at a position above where the side fraction feed exits the benzene-toluene column; wherein the benzene feed exits the benzene-toluene side fraction below the position where the side fraction feed from the benzene-toluene column enters the benzene-toluene side fraction and above the position where the aromatic feed from the extraction process enters the benzene-toluene side fraction.An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, further includes dividing the hydrogen feed stream into a first portion and a second portion; compressing the first portion of the hydrogen feed stream in a purge gas compressor to form a compressed first portion; separating the compressed first portion of the hydrogen feed stream into a permeate stream containing hydrogen and a hydrogen-lean waste gas stream in a membrane separation unit; compressing the second portion of the hydrogen feed stream in a recirculation gas compressor to form a compressed second portion; merging the permeate stream and the compressed second portion to form a merged hydrogen feed stream; and recirculating the merged hydrogen feed stream to the merged feed stream. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph further includes precooling the reactor effluent stream with the combined feed stream before cooling the reactor effluent stream with the high-pressure liquid stream from the high-pressure product separator, thereby forming a precooled reactor effluent stream; separating the precooled reactor effluent stream into a thermal separator vapor stream and a thermal separator liquid stream in a thermal separator, wherein cooling the reactor effluent stream with the high-pressure liquid stream from the high-pressure product separator includes cooling the thermal separator vapor stream with the high-pressure liquid stream from the high-pressure product separator; flashing the thermal separator liquid stream into a second flash tank vapor stream and a second flash tank liquid stream in a second flash tank; and sending the second flash tank vapor stream to the first flash tank. A flash tank; conveying the second portion of the liquid stream from the first flash tank at a first position to the benzene-toluene tower; conveying the liquid stream from the second flash tank at a second position below the first position to the benzene-toluene tower; wherein the aromatic separation zone further includes a benzene-toluene side fractionation tower, and further includes conveying an aromatic-rich stream containing benzene and toluene from the sulfolane extraction process to the benzene-toluene side fractionation tower; separating the aromatic-rich stream in the benzene-toluene side fractionation tower into a benzene stream, a toluene stream, or both; wherein the benzene stream includes the overhead stream or side fraction stream from the benzene-toluene side fractionation tower, the overhead stream or side fraction stream being located above the position where the aromatic-rich stream enters the benzene-toluene side fractionation tower; wherein the toluene stream includes the bottom stream from the benzene-toluene side fractionation tower; and wherein the xylene stream includes the bottom stream from the benzene-toluene tower.An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, further includes dividing the hydrogen feed stream into a first portion and a second portion; compressing the first portion of the hydrogen feed stream in a purge gas compressor to form a compressed first portion; separating the compressed first portion of the hydrogen feed stream into a permeate stream containing hydrogen and a hydrogen-lean waste gas stream in a membrane separation unit; compressing the second portion of the hydrogen feed stream in a recirculation gas compressor to form a compressed second portion; merging the permeate stream and the compressed second portion of the hydrogen feed stream to form a merged hydrogen feed stream; and recirculating the merged hydrogen feed stream to the merged feed stream. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph further includes separating the overhead stream of a benzene-toluene column into an overhead waste gas stream containing hydrogen, a light hydrocarbon having one to five carbon atoms, and a portion of said benzene, and an overhead liquid stream containing hydrogen, a light hydrocarbon having one to five carbon atoms, and a second portion of said benzene; compressing the overhead waste gas stream to form a compressed overhead waste gas stream; and feeding the compressed overhead waste gas stream to a stabilizer column and feeding the overhead liquid stream to the stabilizer column. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph further includes compressing the hydrogen stream; and recycling the compressed hydrogen stream to the combined feed stream. An embodiment of the invention described in the preceding embodiments to the first embodiment in this paragraph, any one embodiment, or all embodiments, further includes preheating the combined feed stream in a heat exchanger with the reactor effluent stream or a flame heater or both before alkyl transfer of the combined feed stream.

[0086] A second embodiment of the present invention is a method comprising alkyl transfer of a combined feed stream containing toluene, an aromatic compound having 9 to 11 carbon atoms, and hydrogen to form a reactor effluent stream containing benzene, xylene, toluene, unconverted aromatic compound having 9 to 11 carbon atoms, a light hydrocarbon having 1 to 5 carbon atoms, and hydrogen; separating the reactor effluent stream into a thermal separator vapor stream and a thermal separator liquid stream in a thermal separator; cooling the thermal separator vapor stream with a high-pressure liquid stream from a high-pressure product separator to form a cooled thermal separator vapor stream and a heated high-pressure liquid stream; separating the cooled thermal separator vapor stream in the high-pressure product separator to form a hydrogen stream and the hydrogen from the high-pressure product separator. A high-pressure liquid stream; in a second flash tank, the liquid stream from the thermal separator is flashed into a second flash tank vapor stream and a second flash tank liquid stream; in a first flash tank, the heated high-pressure liquid stream and the second flash tank vapor stream are flashed into a first flash tank vapor stream containing the light hydrocarbons and a first flash tank liquid stream containing the benzene, the xylene, and the toluene; the first flash tank liquid stream is sent to an aromatics separation zone, which includes a benzene-toluene tower at a first location; the second flash tank liquid stream is sent to the benzene-toluene tower at a second location below the first location; in the aromatics separation zone, the first flash tank liquid stream and the second flash tank liquid stream are separated into a benzene stream, or a toluene stream, or a xylene stream, or a combination thereof. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding to the second embodiments of this paragraph further includes precooling the reactor effluent stream with the combined feed stream before separating the reactor effluent stream in the thermal separator, thereby forming a precooled reactor effluent stream; wherein separating the reactor effluent stream in the thermal separator includes separating the precooled reactor effluent stream in the thermal separator; wherein the aromatic separation zone further includes a benzene-toluene side fractionation column, and further includes a fractionation column from cyclobutane... Aromatic hydrocarbon-rich feed containing benzene and toluene in a sulfone extraction process is fed to the benzene-toluene side fractionation column; the aromatic hydrocarbon-rich feed in the benzene-toluene side fractionation column is separated into a benzene feed, a toluene feed, or both; wherein the benzene feed includes the overhead feed or side fraction feed from the benzene-toluene side fractionation column, the overhead feed or side fraction feed being located above the point where the aromatic hydrocarbon-rich feed enters the benzene-toluene side fractionation column; wherein the toluene feed includes the bottom feed from the benzene-toluene side fractionation column; and wherein the xylene feed includes the bottom feed from the benzene-toluene column.An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the second embodiments described in this paragraph further includes feeding a side distillate from the benzene-toluene side distillate column to the benzene-toluene side distillate column at a position above where the aromatic-rich feed stream enters the benzene-toluene side distillate column; and feeding a top feed stream from the benzene-toluene side distillate column to the benzene-toluene column at a position above where the side distillate stream exits the benzene-toluene column; wherein the benzene feed stream exits the benzene-toluene side distillate column at a position below where the side distillate stream from the benzene-toluene column enters the benzene-toluene side distillate column. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the second embodiments described in this paragraph further includes dividing the hydrogen feed stream into a first portion and a second portion; compressing the first portion of the hydrogen feed stream in a purge gas compressor to form a compressed first portion; separating the compressed first portion of the hydrogen feed stream into a permeate stream containing hydrogen and a hydrogen-lean waste gas stream in a membrane separation unit; compressing the second portion of the hydrogen feed stream in a recirculation gas compressor to form a compressed second portion; merging the permeate stream and the compressed second portion of the hydrogen feed stream to form a merged hydrogen feed stream; and recirculating the merged hydrogen feed stream to the merged feed stream. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the second embodiments described in this paragraph further includes compressing the hydrogen feed stream; and recirculating the compressed hydrogen feed stream to the merged feed stream. An embodiment of the invention described in the preceding embodiments to the second embodiments of this paragraph, any one of the embodiments, or all of the embodiments, further includes preheating the combined feed stream in a heat exchanger with the reactor effluent stream or a flame heater or both before alkyl transfer of the combined feed stream.

[0087] A third embodiment of the present invention is a method comprising alkyl transfer of a combined feed stream containing toluene, an aromatic compound having 9 to 11 carbon atoms, and hydrogen to form a reactor effluent stream containing benzene, xylene, toluene, unconverted aromatic compound having 9 to 11 carbon atoms, a light hydrocarbon having 1 to 5 carbon atoms, and hydrogen; cooling the reactor effluent stream with a high-pressure separator liquid stream from a high-pressure product separator to form a cooled reactor effluent stream and a heated high-pressure separator liquid stream; separating the cooled reactor effluent stream in the high-pressure product separator to form a hydrogen stream and the high-pressure separator liquid stream; and heating the heated high-pressure liquid stream with a stripper side fraction stream from a stripper to form a hydrogen stream. The second heated high-pressure liquid stream and the cooled side distillate stream are separated in the stripper into a stripper overhead stream containing a portion of the benzene, non-aromatic compounds, and the light hydrocarbons; a stripper side distillate stream containing benzene, xylene, unconverted aromatic compounds, and toluene; and a stripper bottom stream containing the benzene, xylene, unconverted aromatic compounds, and toluene, wherein the second heated high-pressure stream enters the stripper at a position above where the side distillate stream exits the stripper; the cooled stripper side distillate stream is combined with the cooled reactor effluent stream; and the stripper bottom stream is separated in the aromatic separation zone into a benzene stream, or a toluene stream, or a xylene stream, or a combination thereof. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the third embodiment described in this paragraph further includes heating the second heated liquid stream with the bottom stream of the stripper before separating the second heated high-pressure liquid stream in the stripper. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the third embodiment described in this paragraph further includes compressing the hydrogen stream and recycling the compressed hydrogen stream to the combined feed stream. An embodiment of the invention according to any one, any one, or all of the embodiments described in the preceding embodiments to the third embodiment described in this paragraph further includes preheating the combined feed stream in a heat exchanger with the reactor effluent stream or a flame heater or both before alkyl transfer of the combined feed stream.

[0088] Although no further detailed description has been provided, it is believed that those skilled in the art will be able to make full use of the invention by employing the foregoing description and will be able to readily identify the essential features of the invention without departing from its spirit and scope, and to make various changes and modifications to adapt it to various uses and situations. Therefore, the foregoing preferred embodiments should be understood as illustrative only and not as limiting the remainder of this disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0089] In the foregoing, all temperatures are expressed in degrees Celsius, and all portions and percentages are by weight unless otherwise specified.

Claims

1. A method, the method comprising: An alkyl transfer is performed on a combined feed stream (120) containing toluene, an aromatic compound having 9 to 11 carbon atoms, and hydrogen to form a reactor effluent stream (130) containing benzene, xylene, toluene, unconverted aromatic compounds having 9 to 11 carbon atoms, light hydrocarbons having 1 to 5 carbon atoms, and hydrogen. The reactor effluent stream (130) is cooled by a high-pressure liquid stream (160) from a high-pressure product separator (165), thereby forming a cooled reactor effluent stream (180) and a heated high-pressure liquid stream (175). The cooled reactor effluent stream (180) is separated in the high-pressure product separator (165) to form a hydrogen stream (195) and the high-pressure liquid stream (160). In the first flash tank (215), the heated high-pressure liquid stream (175) is flashed into a first flash tank vapor stream (220) containing the light hydrocarbons and a first flash tank liquid stream (225) containing the benzene, xylene, toluene and unconverted aromatic compounds having 9 to 11 carbon atoms. The liquid flow (225) in the first flash tank is divided into a first part (130) and a second part (235); The first portion (230) of the liquid stream (225) from the first flash tank is recirculated to the product condenser (185) upstream of the product high-pressure separator (165); and In the aromatic separation zone containing the benzene-toluene tower (325), at least a portion of the second portion (235) of the first flash tank liquid stream (225) is separated into a benzene stream (330), or a toluene stream (335), or a xylene stream (345), or a combination thereof.

2. The method according to claim 1, further comprising: The first flash tank steam stream (220) is introduced into the stripping tower (260) at a first position, and the second portion (235) of the first flash liquid stream (225) is introduced into the stripping tower (260) at a second position below the first position; In the stripping tower (260), the second portion (235) of the first flash tank vapor stream (220) and the first flash tank liquid stream (225) is separated into a stripping tower overhead stream (265) containing a portion of the benzene, non-aromatic compounds, and the light hydrocarbons, and a stripping tower bottom stream (240) containing the remaining benzene, xylene, unconverted aromatic compounds having 9 to 11 carbon atoms, and toluene; and At least the portion of the second part (235) of separating the liquid stream (225) from the first flash tank in the aromatic separation zone includes separating the bottom stream (240) from the stripping tower in the aromatic separation zone.

3. The method according to any one of claims 1 to 2, further comprising: Before cooling the reactor effluent stream (430) with the high-pressure liquid stream (475) from the high-pressure product separator (480), the reactor effluent stream (430) is pre-cooled with the combined feed stream (420) to form a pre-cooled reactor effluent stream (455). In a thermal separator (460), the pre-cooled reactor effluent stream (455) is separated into a thermal separator vapor stream (465) and a thermal separator liquid stream (470), wherein cooling the reactor effluent stream (430) with the high-pressure liquid stream (475) from the high-pressure product separator (480) includes cooling the thermal separator vapor stream (465) with the high-pressure liquid stream (475) from the high-pressure product separator (480). In the second flash tank (565), the liquid stream (470) of the heat separator is flashed into a second flash tank vapor stream (570) and a second flash tank liquid stream (575). The steam stream (570) from the second flash tank is transferred to the first flash tank (530). The second portion (550) of the liquid flow (540) from the first flash tank is conveyed at the first location to the benzene-toluene tower (555). The liquid stream from the second flash tank (575) is delivered to the benzene-toluene tower (555) at a second position below the first position. The aromatics separation zone further includes a benzene-toluene side fractionation column (655), and the method further includes: An aromatic-rich feed stream (675) from a sulfolane extraction process is fed to the benzene-toluene side fractionation column (655), the aromatic-rich feed stream (675) comprising benzene and toluene; The aromatic-rich feed stream (675) from the extraction process in the benzene-toluene side fractionation column (655) is separated into a benzene feed stream (665), a toluene feed stream (670), or both. The benzene feed stream (665) includes the overhead feed stream (715) or side stream stream (665) from the benzene-toluene side distillation column (655), which is located above the position where the aromatic-rich feed stream (675) from the extraction process enters the benzene-toluene side distillation column (655). The toluene feed stream (670) comprises the bottom feed stream from the benzene-toluene side fractionation column (655); and The xylene stream (615) includes the bottom stream from the benzene-toluene tower (555).

4. The method according to claim 3, further comprising: At a position above the point where the aromatic-rich feed stream (675) from the extraction process enters the benzene-toluene side distillation column (655), the side distillate stream (600) from the benzene-toluene column (555) is conveyed to the benzene-toluene side distillation column (655); and The overhead stream (660) from the benzene-toluene side distillate column (655) is fed to the benzene-toluene column (555) at a position above the position where the side distillate stream (600) leaves the benzene-toluene column (555). The benzene feed stream (665) exits the benzene-toluene side distillation column (655) at a position below where the side distillate stream (600) from the benzene-toluene column (555) enters the benzene-toluene side distillation column (655) and above where the aromatic-rich feed stream (675) from the extraction process enters the benzene-toluene side distillation column (655).

5. The method according to claim 3, further comprising: The hydrogen flow (910) is divided into a first part (915) and a second part (920); The first portion (915) of the hydrogen feed stream (910) is compressed in the purge gas compressor (925) to form the compressed first portion (930). In the membrane separation unit (935), the first compressed portion (930) of the hydrogen stream (910) is separated into a permeate stream (945) containing hydrogen and a hydrogen-lean waste gas stream (940). The second portion (920) of the hydrogen feed stream (910) is compressed in the recirculating gas compressor (950) to form the compressed second portion (955). The permeate stream (945) and the compressed second portion (955) are combined to form a combined hydrogen stream (815); and The combined hydrogen stream (815) is recycled back to the combined feed stream (820).

6. The method according to any one of claims 1 to 2, further comprising: Before cooling the reactor effluent stream (830) with the high-pressure liquid stream (875) from the high-pressure product separator (880), the reactor effluent stream (830) is pre-cooled with the combined feed stream (820) to form a pre-cooled reactor effluent stream (855). In a thermal separator (860), the pre-cooled reactor effluent stream (855) is separated into a thermal separator vapor stream (865) and a thermal separator liquid stream (870), wherein cooling the reactor effluent stream (830) with the high-pressure liquid stream (875) from the high-pressure product separator (880) includes cooling the thermal separator vapor stream (865) with the high-pressure liquid stream (875) from the high-pressure product separator (880). In the second flash tank (990), the liquid stream (870) of the heat separator is flashed into a second flash tank steam stream (995) and a second flash tank liquid stream (1000). The steam stream (995) from the second flash tank is transferred to the first flash tank (965). The liquid flow from the first flash tank (975) is conveyed at the first location to the benzene-toluene tower (980). The liquid stream (1000) from the second flash tank is delivered to the benzene-toluene tower (980) at a second position below the first position. The aromatics separation zone further includes a benzene-toluene side fractionation column (1080), and the method further includes: The aromatic stream (1100) containing benzene and toluene from the sulfolane extraction process is fed to the benzene-toluene side fractionation column (1080). The aromatic-rich stream (1100) in the benzene-toluene side distillation column (1080) is separated into the benzene stream (1090), the toluene stream (1095), or both. The benzene feed stream (1090) includes a side stream (1090) from the benzene-toluene side distillation column (1080), the side stream being located above the position where the aromatic-rich feed stream (1100) enters the benzene-toluene side distillation column (1080); The toluene feed stream (1095) comprises the bottom feed stream from the benzene-toluene side fractionation column (1080); and The xylene stream (1040) comprises the bottom stream from the benzene-toluene tower (980).

7. The method according to claim 6, further comprising: The hydrogen flow (910) is divided into a first part (915) and a second part (920); The first portion (915) of the hydrogen feed stream (910) is compressed in the purge gas compressor (925) to form the compressed first portion (930). In the membrane separation unit (935), the first compressed portion (930) of the hydrogen stream (910) is separated into a permeate stream (945) containing hydrogen and a hydrogen-lean waste gas stream (940). The second portion (920) of the hydrogen feed stream (910) is compressed in the recirculating gas compressor (950) to form the compressed second portion (955). The compressed second portion (955) of the permeate stream (945) and the hydrogen stream (910) are combined to form a combined hydrogen stream (815); and The combined hydrogen stream (815) is recycled back to the combined feed stream (820).

8. The method according to any one of claims 1 to 2, further comprising: The overhead stream of the benzene-toluene tower (1020) is separated into an overhead waste gas stream (1060) containing hydrogen, light hydrocarbons having 1 to 5 carbon atoms and a portion of the benzene, and an overhead liquid stream (1065) containing hydrogen, light hydrocarbons having 1 to 5 carbon atoms and a second portion of the benzene. The exhaust gas stream at the top of the tower (1060) is compressed to form a compressed exhaust gas stream at the top of the tower; The compressed overhead exhaust gas stream (1060) is conveyed to the stabilizer tower; as well as The liquid stream (1075) at the top of the tower is transferred to the stabilizer tower.

9. The method according to any one of claims 1 to 2, further comprising: Compress the hydrogen gas stream (195); as well as The compressed hydrogen stream (205) is recycled to the combined feed stream (120).

10. The method according to any one of claims 1 to 2, further comprising: Before alkylation of the combined feed stream (120), the combined feed stream (120) is preheated in a heat exchanger (125) with the reactor effluent stream (130) or a flame heater (140) or both.

Images