Method for separating paraxylene from toluene

Abstract

The present invention provides a method and apparatus for the separation of para-xylene. A stream of para-xylene is separated from a stream of toluene in a fractionating column. The overhead stream of the fractionating column is compressed and then transferred to a heat recovery zone to transfer heat from the overhead stream to another process stream, such as in a heat exchanger. The fractionating column can separate effluent from a toluene methylation reactor.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for separating para-xylene, and more particularly, to a method for separating para-xylene from toluene. Background Art

[0002] Aromatic hydrocarbons, especially benzene, toluene, ethylbenzene and xylene (ortho, meta and para isomers), which are commonly referred to as "BTEX" or more simply as "BTX", are extremely useful chemicals in the petrochemical industry. They represent components of materials such as polystyrene, styrene-butadiene rubber, polyethylene terephthalate, polyesters, phthalic anhydride, solvents, polyurethanes, benzoic acid and many other components. Conventionally, BTEX for the petrochemical industry is obtained by separation and processing of fossil fuel petroleum fractions, for example in catalytic reforming or cracking refinery process units. Different aromatic compounds can be separated individually in an aromatics complex, which has various separation units and processing units for improving the recovery of specific compounds.

[0003] In particular, p-xylene and m-xylene are important raw materials in the chemical and fiber industries. Terephthalic acid derived from p-xylene is used to make polyester fabrics and other products that are currently widely used. One method for making p-xylene is the toluene methylation process.

[0004] The toluene methylation process uses methanol to produce para-xylene with very high (90+%) selectivity relative to total xylenes. Fractionation of the reaction effluent is ultimately necessary to separate components, including light ends, water, oxygenates and acids, benzene, unconverted toluene, xylenes, and products of heavier components. Separation can be achieved by first performing a "loose" split using a first fractionating tower that is operated to remove light ends and recover crude para-xylene. The resulting product stream can then be directed to a second fractionating tower within a larger aromatics complex for further separation of toluene from the desired xylene product. Alternatively, xylene separation can be achieved solely via a fractionating tower, wherein nearly all of the benzene and toluene are recycled internally, so that the only end products are xylenes and heavier aromatics.

[0005] A disadvantage of a configuration utilizing two columns with a "loose" split on the first column is that oxygenates produced in the toluene methylation reaction that azeotropes with toluene are given more opportunity to migrate to and damage downstream units in the aromatics complex. For example, oxygenates can damage the adsorbent in a para-xylene separation unit. This problem is particularly concerning for a para-xylene separation unit utilizing toluene as a photodesorbent. However, one advantage is that the first fractionator is easier to thermally integrate within the aromatics complex relative to the second fractionator due to the lower bottom temperature.

[0006] However, either configuration requires a significant increase in the fractionation requirements (ie, condenser and reboiler duties) in the fractionation column to achieve a desired or acceptable separation of toluene and xylenes.

[0007] Therefore, there remains a need for an effective and efficient process for separating xylene from toluene. In addition, it is desirable that such a process reduce the risk of oxygenates migrating downstream. Summary of the invention

[0008] One or more methods and apparatus have been invented that provide an effective and efficient method for separating xylenes from toluene. According to the method and apparatus of the present invention, a heat pump is incorporated into a fractionation column that separates toluene from xylenes.

[0009] Generally, the compressed overhead stream can be used to partially reboil the fractionation column and for other heat recovery purposes, such as preheating the feed within the toluene methylation unit. Overall, the heat pump improves the energy efficiency of the fractionation column while achieving the above-mentioned configuration benefits (i.e., limiting oxygenate migration).

[0010] Thus, in at least one aspect, the invention can be characterized as providing a process for para-xylene separation by: alkylating toluene with methanol in a toluene methylation zone to provide a methylation effluent comprising para-xylene and toluene; separating the methylation effluent in a fractionation column into at least an effluent stream comprising para-xylene, a recycle stream comprising toluene, and a C-containing effluent stream; 1 -C 6 recovering paraxylene from an effluent stream comprising paraxylene in a paraxylene recovery zone; compressing the overhead stream in a first compression zone to provide a compressed overhead stream; and transferring heat from the compressed overhead stream after the overhead stream has been compressed.

[0011] In one or more aspects, the present invention may also be characterized by providing a method for paraxylene separation, which is carried out by the following steps: passing a toluene feed stream to a toluene methylation zone; passing a methanol feed stream to a toluene methylation zone, the toluene methylation zone being operated under conditions to convert toluene to paraxylene and provide a methylation effluent containing paraxylene and toluene; passing the methylation effluent to a fractionation tower, the fractionation tower being configured to separate the methylation effluent into at least an effluent stream containing paraxylene, a recycle stream containing toluene, and an overhead stream; passing the effluent stream containing paraxylene to a paraxylene recovery zone, the paraxylene recovery zone being configured to provide a paraxylene product stream; passing the overhead stream to a compression zone, the compression zone being configured to compress the overhead stream and provide a compressed overhead stream; and passing the compressed overhead stream to a heat recovery zone, the heat recovery zone being configured to remove heat from the compressed overhead stream in at least one heat exchanger.

[0012] In one or more aspects, the features of the present invention may be broadly that a device for separating para-xylene from toluene is provided. The device may include a fractionating tower having an inlet and a plurality of outlets, and is configured to receive a stream containing toluene and para-xylene via an inlet, separate the stream and provide an effluent stream containing para-xylene via at least a first outlet in the plurality of outlets, provide a recycle stream containing toluene via a second outlet in the plurality of outlets, and provide a tower top stream via a third outlet in the plurality of outlets. The device may also include a compression zone, which has been configured to compress the tower top stream to provide a compressed tower top stream. The device may also include a heat recovery zone, which includes at least one heat exchanger, and the at least one heat exchanger is configured to remove heat from the compressed tower top stream.

[0013] Further aspects, embodiments and details of the invention (all of which may be combined in any manner) are set forth in the following detailed description of the invention.

[0014] definition

[0015] As used herein, the terms "stream", "feed", "product", "component" or "portion" may include various hydrocarbon molecules such as linear, branched or cyclic alkanes, olefins, alkadienes and alkynes, and optionally other substances such as gases, for example hydrogen, or impurities such as heavy metals, and sulfur and nitrogen compounds. Each of the above may also contain aromatic hydrocarbons and non-aromatic hydrocarbons.

[0016] The hydrocarbon molecule can be abbreviated as C 1 , C 2 , C 3, Cn, where "n" represents the number of carbon atoms in one or more hydrocarbon molecules, or the abbreviation can be used as an adjective, such as a non-aromatic compound or compound. Similarly, aromatic compounds can be abbreviated as A 6 , A 7 , A 8 , An, where "n" represents the number of carbon atoms in one or more aromatic hydrocarbon molecules. In addition, the superscript "+" or "-" may be used with the abbreviated hydrocarbon symbol or symbols, such as C 3+ or C 3- , which includes one or more hydrocarbons abbreviated. As an example, the abbreviation "C 3+ ” means one or more hydrocarbon molecules having three or more carbon atoms.

[0017] As used herein, the term "zone" may refer to an area that includes one or more equipment items and / or one or more sub-zones. Equipment items may include, but are not limited to, one or more reactors or reactor vessels, separation vessels, distillation columns, heaters, exchangers, pipelines, pumps, compressors, and controllers. In addition, equipment items such as reactors, dryers, or containers may also include one or more zones or sub-zones.

[0018] As used herein, the term "rich" may mean that the amount of one compound or class of compounds in a stream is generally at least 50 mole %, and preferably 70 mole %. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] One or more exemplary embodiments of the present invention will be described below in conjunction with the following drawings, in which:

[0020] Figure 1 shows a process flow diagram according to one aspect of the present invention; and,

[0021] Figure 2 A process flow diagram according to another aspect of the present invention is shown.

[0022] In the several views of the accompanying drawings, corresponding reference numerals represent corresponding parts. It will be appreciated by the skilled person that the elements in the accompanying drawings are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the sizes of some elements in the accompanying drawings may be exaggerated relative to other elements to help improve the understanding of the various embodiments of the present disclosure. Moreover, in order to facilitate less obstruction to the viewing of the various embodiments of the present disclosure, generally available or necessary and well-known elements in commercially feasible embodiments are not usually depicted. DETAILED DESCRIPTION

[0023] As mentioned above, in embodiments described herein, heat pump is combined with the fractionating tower separating toluene from dimethylbenzene.For example, two compression stages can be used to obtain enough driving force for the exchange of overhead stream and tower side reboiler on fractionating tower.In order to maximize the energy recovery rate from compression process, overhead stream can be shunted as required and distributed to other heat exchange areas, such as preheating of water for main toluene methylation injection and / or preheating of liquid fed to fractionating tower.Therefore, another beneficial effect of heat pump is to reduce the fuel demand (fired heater load) in the unit.As mentioned previously, fractionation causes the separation (benzene / toluene is limited to internal toluene methylation unit recycling, and only dimethylbenzene and heavier materials leave the unit as pure product) of expectation at the expense of high energy demand.Fracturing tower is therefore transformed with the lower pump heated via exchanging with compressed overhead stream.This supplementary heat offsets a part of main (tower bottom) reboiling load.

[0024] With these general principles in mind, one or more embodiments of the invention will be described with the understanding that the following description is not intended to be limiting.

[0025] like Figure 1 As shown, toluene stream 10 is passed to toluene methylation zone 14 along with methanol stream 12. Toluene stream 10 may come from a larger aromatics complex that receives a toluene methylation zone of the general formula C 6 H (6-n) R n An alkyl aromatic hydrocarbon feedstock, wherein n is an integer from 0 to 5, and each R can be any combination of CH 3 , C 2 H 5 , C 3 H 7 or C 4 H 9Such aromatic feed streams contain benzene, toluene and aromatics and typically contain higher aromatics and aliphatic hydrocarbons (including cycloalkanes). Aromatic-rich feeds can be derived from a variety of sources, including, but not limited to, catalytic reforming, steam pyrolysis of naphtha, distillates or other hydrocarbons to produce light olefins and heavier aromatic-rich byproducts (including gasoline-range materials, commonly referred to as "pyrolysis gasoline"), and catalytic or thermal cracking of distillates and heavy oils to produce gasoline-range products. In order to remove sulfur, olefins and other compounds that will affect product quality and / or damage the catalysts and adsorbents used therein, the products obtained from pyrolysis or other cracking operations are typically hydrotreated according to processes well known in the industry before being loaded into the combined unit. Light cycle oil obtained from catalytic cracking can also be advantageously hydrotreated and / or hydrocracking according to known techniques to produce gasoline-range products; hydrotreating also preferably includes catalytic reforming to produce an aromatic-rich feed stream. Known reforming zones typically include a reforming unit that receives a feed. The reforming unit will typically include a reforming catalyst. Typically, such streams will also be treated to remove olefinic compounds and light fractions (e.g., butanes and light hydrocarbons and preferably pentanes), however, such removal is not necessary for practicing the broad aspects of the present disclosure and is not shown. Although not shown as such, a typical aromatics complex includes, for example, an aromatics extraction zone, a transalkylation zone, a toluene methylation zone 14, and a para-xylene extraction zone and a xylene isomerization zone.

[0026] return Figure 1 , toluene stream 10 may be mixed with hydrocarbons from a recycle stream 16 (discussed below) and then injected into a toluene methylation zone 14. Toluene methylation zone 14 may be a fluidized bed reaction zone that includes a reactor 18 that receives toluene stream 10, methanol stream 12, and a lift water stream 20 that is used to fluidize or "lift" the catalyst and reactants upwardly through reactor 18. Reactor 18 is operated under known conditions such that toluene is alkylated with methanol to produce xylenes.

[0027] The toluene methylation effluent stream 22 is passed to a separation zone 24, which includes, among other things, a fractionation column 26 having an inlet for receiving at least a portion of the toluene methylation effluent stream 22 and separating the toluene methylation effluent stream 22. The separation zone 24 may also include other separation vessels 27, 28, 30 that produce water streams 32, 34, 36, some of which may include some methanol. A hydrocarbon stream 38 from the last vessel 30 is passed to the fractionation column 26.

[0028] As discussed above, the separation of xylene from toluene is energy intensive. Therefore, the fractionation column 26 may include a bottom reboiler 40, a side reboiler 42, and at least one exchanger 44 located on one of the feed streams to the fractionation column 26. The fractionation column 26 provides a feed stream comprising C 1 -C6 A hydrocarbon overhead stream 46 provides a bottoms stream 48 via a second outlet and a side draw stream 50 via a third outlet that can be recycled to the toluene methylation zone 14. The bottoms stream 48 contains paraxylene which can be sent to a paraxylene extraction unit (not shown) to recover the paraxylene.

[0029] According to the process of the present invention, heat is recovered from the top stream 46 before the top stream 46 is separated in the vessel 52 into a water-containing stream 54, a fuel gas stream 56, and a liquid hydrocarbon stream 57, which contains toluene and can be recycled to the toluene methylation zone 14 as the above-mentioned recycle stream 16. Therefore, the energy efficiency of the separation in the fractionation column 26 is improved by recovering the heat in the top stream 46.

[0030] Therefore, if Figure 2 As shown, overhead stream 46 is compressed in a first compression zone 58 having a compressor, and compressed overhead stream 59 may then be used to transfer heat in heat exchange zone 60. Condenser 62 is used to cool the stream from heat exchange zone 60 before transferring it to receiver vessel 52 (as discussed above, see Figure 1 ).

[0031] In an exemplary embodiment, compressed stream 59 is passed to a second compression zone 64 having, for example, a knockout drum 66, which separates a liquid phase 68 from the compressed overhead stream before the compressed overhead stream is further compressed in a second compressor 70. The compressed overhead stream after second compression zone 64 may be passed to heat exchange zone 60. Liquid phase 68 from knockout drum 66 may be passed to vessel 52.

[0032] In the exemplary heat exchange zone 60, the compressed overhead stream is split into two or more portions 72a, 72b. The first portion 72a is passed to at least one heat exchanger, such as heat exchanger 74 for an aqueous recycle stream 75 (which may be formed, for example, from at least a portion of the aqueous stream 36, 54 separated from the toluene methylation effluent stream 22). Figure 1 The first portion 72a may also be passed to the feed exchanger 44 of the fractionation column 26 (see Figure 1 The second portion 72b may be transferred to the side reboiler 42 of the fractionation column 26 (see Figure 1 ), lifting water exchanger 76 (see Figure 1 ) or both. The heat exchange zone 60 shown is merely exemplary, and any number of portions of compressed stream 59 and exchangers may be used.

[0033] It will be appreciated by those skilled in the art that embodiments of the present invention provide an economical way to better balance heat transfer and recovery within a toluene methylation unit, preferably within an aromatics complex, when there is severe product fractionation within the toluene methylation unit. This benefit may vary with alternative feed conditions or with situations where the overall energy balance of the complex is different.

[0034] According to a theoretical evaluation, the economic savings within two years will offset the initial investment costs associated with introducing the additional equipment specified herein. The theoretical evaluation is based on a combined plant operating 8,000 hours / year to obtain 1,700 KMTA of paraxylene from 3,400 KMTA of feed to the toluene methylation unit.

[0035] Those of ordinary skill in the art will recognize and appreciate that various other components such as valves, pumps, filters, coolers, etc. are not shown in the accompanying drawings because it is believed that their details are well within the knowledge of those of ordinary skill in the art and their description is not necessary for the practice or understanding of the embodiments of the present invention.

[0036] Any of the above-mentioned pipelines, conduits, units, equipment, containers, surrounding environments, zones or the like may be equipped with one or more monitoring components, including sensors, measuring devices, data capture devices or data transmission devices. Signals, process or state measurements and data from monitoring components can be used to monitor conditions in, around and related to process equipment. Signals, measurements and / or data generated or recorded by monitoring components can be collected, processed and / or transmitted via one or more networks or connections, which can be private or public, general or dedicated, direct or indirect, wired or wireless, encrypted or unencrypted, and / or combinations thereof; the present specification is not intended to be limiting in this regard.

[0037] The signals, measurements and / or data generated or recorded by the monitoring components may be transmitted to one or more computing devices or systems. The computing device or system may include at least one processor and a memory storing computer-readable instructions, which, when executed by at least one processor, causes one or more computing devices to perform a process that may include one or more steps. For example, one or more computing devices may be configured to receive data related to at least one piece of equipment associated with the process from one or more monitoring components. One or more computing devices or systems may be configured to analyze the data. Based on the data analysis, one or more computing devices or systems may be configured to determine one or more recommended adjustments to one or more parameters of one or more processes described herein. One or more computing devices or systems may be configured to transmit encrypted or unencrypted data, which includes one or more recommended adjustments to one or more parameters of one or more processes described herein.

[0038] Specific implementation plan

[0039] While the following is described in conjunction with specific embodiments, it should be understood that this description is intended to illustrate and not to limit the scope of the foregoing description and the appended claims.

[0040] A first embodiment of the present invention is a process for para-xylene separation, the process comprising alkylating toluene with methanol in a toluene methylation zone to provide a methylation effluent comprising para-xylene and toluene; separating the methylation effluent in a fractionation column into at least an effluent stream comprising para-xylene, a recycle stream comprising toluene, and a C-containing effluent stream; 1 -C 6A tower overhead stream of hydrocarbons; recovering paraxylene from an effluent stream comprising paraxylene in a paraxylene recovery zone; compressing the tower overhead stream in a first compression zone to provide a compressed tower overhead stream; and transferring heat from the compressed tower overhead stream after the tower overhead stream has been compressed. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes compressing the compressed tower overhead stream in a second compression zone before transferring heat from the compressed tower overhead stream, wherein the second compression zone includes at least one compressor and at least one separation vessel. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes transferring heat from the compressed tower overhead stream to the first exchanger stream in at least one heat exchanger. One embodiment of the invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, further comprising splitting the compressed overhead stream into at least a first portion and a second portion; transferring heat from the first portion of the compressed overhead stream to the first exchanger stream in a first heat exchanger; and transferring heat from the second portion of the compressed overhead stream to the second exchanger stream in a second heat exchanger. One embodiment of the invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, further comprising condensing the first portion and the second portion in a condenser to provide a condensed stream after heat has been transferred from the first portion and the second portion; separating the condensed stream into a fuel gas stream and at least one liquid stream in a receiver vessel. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which further includes transferring heat from the first portion of the compressed overhead stream to the third exchanger stream downstream of the first exchanger in the third heat exchanger; and transferring heat from the second portion of the compressed overhead stream to the fourth exchanger stream downstream of the second exchanger in the fourth heat exchanger. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which further includes condensing the compressed overhead stream in a condenser to provide a condensed stream after heat has been transferred from the compressed overhead stream; separating the condensed stream into a fuel gas stream and at least one liquid stream in a receiver vessel. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, wherein the receiver vessel also receives a liquid phase of the compressed overhead stream. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which further includes recycling the at least one liquid stream from the receiver vessel to the toluene methylation zone.

[0041] A second embodiment of the present invention is a method for paraxylene separation, which includes passing a toluene feed stream to a toluene methylation zone; passing a methanol feed stream to a toluene methylation zone, the toluene methylation zone being operated under conditions to convert toluene to paraxylene and provide a methylation effluent comprising paraxylene and toluene; passing the methylation effluent to a fractionation tower, the fractionation tower being configured to separate the methylation effluent into at least an effluent stream comprising paraxylene, a recycle stream comprising toluene, and an overhead stream; passing the effluent stream comprising paraxylene to a paraxylene recovery zone, the paraxylene recovery zone being configured to provide a paraxylene product stream; and delivering the overhead stream to a compression zone, the compression zone being configured to compress the overhead stream and provide a compressed overhead stream; and passing the compressed overhead stream to a heat recovery zone, the heat recovery zone being configured to remove heat from the compressed overhead stream in at least one heat exchanger. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, wherein the heat recovery zone includes a plurality of heat exchangers. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, wherein the compressed overhead stream is passed to a compression zone including a compressor and a container before the compressed overhead stream is passed to the heat recovery zone. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, which also includes splitting the compressed overhead stream into a plurality of compressed overhead streams; and passing each compressed overhead stream in the plurality of compressed overhead streams to at least one heat exchanger. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, wherein each compressed overhead stream in the plurality of overhead streams is passed to at least two heat exchangers. One embodiment of the invention is one, any or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, which also includes, after removing heat from the compressed overhead stream in at least one heat exchanger in the heat recovery zone, passing the compressed overhead stream to a condenser to provide a condensed stream; and passing the condensed stream to a receiver vessel configured to separate the condensed stream into a fuel gas stream, at least one stream, and at least one liquid hydrocarbon stream. One embodiment of the invention is one, any or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, which also includes recycling the at least one liquid hydrocarbon stream to the toluene methylation zone.

[0042] The third embodiment of the present invention is an apparatus for separating paraxylene from toluene, the apparatus comprising a fractionation tower, the fractionation tower comprising an inlet and a plurality of outlets, the fractionation tower being configured to receive a stream comprising toluene and paraxylene via the inlet, separate the stream and provide an effluent stream comprising paraxylene via at least a first outlet of the plurality of outlets, provide a recycle stream comprising toluene via a second outlet of the plurality of outlets, and provide an overhead stream via a third outlet of the plurality of outlets; a compression zone, the compression zone having been configured to compress the overhead stream to provide a compressed overhead stream; and a heat recovery zone, the heat recovery zone comprising at least one heat exchanger, the at least one heat exchanger being configured to remove heat from the compressed overhead stream. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the third embodiment of this paragraph, wherein the heat recovery zone further comprises a plurality of heat exchangers. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the third embodiment of this paragraph, which further includes a first conduit configured to transfer a first portion of the compressed overhead stream to a first heat exchanger; and a second conduit configured to transfer a second portion of the compressed overhead stream to a second heat exchanger. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the third embodiment of this paragraph, wherein the compression zone includes at least two compressors and a container.

[0043] Although there is no further detailed description, it is believed that those skilled in the art can utilize the present invention to the greatest extent by using the foregoing description and can easily determine the essential characteristics of the present invention without departing from the spirit and scope of the present invention to make various changes and modifications of the present invention and adapt it to various usages and conditions. Therefore, the aforementioned preferred specific embodiments should be understood as merely illustrative and not to limit the rest of the present disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0044] In the foregoing, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

[0045] Although at least one exemplary embodiment has been presented in the foregoing specific embodiments of the present invention, it should be understood that there are a large number of variations. It should also be understood that an exemplary embodiment or multiple exemplary embodiments are only examples and are not intended to limit the scope, applicability or configuration of the present invention in any way. On the contrary, the foregoing specific embodiments will provide a convenient roadmap for those skilled in the art to implement the exemplary embodiments of the present invention, and it should be understood that various changes can be made to the functions and arrangements of the elements described in the exemplary embodiments without departing from the scope of the present invention as set forth in the attached claims and their legal equivalents.

Claims

1. A method for separating p-xylene, the method comprising: alkylating toluene with methanol in a toluene methylation zone (14) to provide a methylation effluent (22) comprising para-xylene and toluene; separating the methylation effluent (22) in a fractionation column (26) into at least an effluent stream (48) comprising paraxylene, a recycle stream (50) comprising toluene, and an overhead stream (46) comprising C1-C6 hydrocarbons; recovering paraxylene from the effluent stream (48) comprising paraxylene in a paraxylene recovery zone; Recovering heat from the overhead stream (46) prior to separating the overhead stream (46) into an aqueous stream (54), a fuel gas stream (56), and a liquid hydrocarbon stream (57) comprises: compressing the overhead stream (46) in a first compression zone (58) to provide a compressed overhead stream (59); as well as, After the overhead stream (46) has been compressed, heat is transferred from the compressed overhead stream (59).

2. The method according to claim 1, further comprising: Prior to transferring heat from the compressed overhead stream (59), the compressed overhead stream (59) is compressed in a second compression zone (64), wherein the second compression zone includes at least one compressor (70) and at least one separation vessel (66).

3. The method according to claim 1, further comprising: Heat is transferred from the compressed overhead stream (59) to a first exchanger stream in at least one heat exchanger (42, 44, 74, 76).

4. The method according to any one of claims 1 to 3, further comprising: splitting the compressed overhead stream (59) into at least a first portion (72a) and a second portion (72b); transferring heat from said first portion (72a) of said compressed overhead stream (59) to a first exchanger stream in a first heat exchanger (42, 44, 74, 76); as well as, Heat is transferred from the second portion (72b) of the compressed overhead stream (59) to a second exchanger stream in a second heat exchanger (42, 44, 74, 76).

5. The method according to claim 4, further comprising: condensing the first portion (72a) and the second portion (72b) in a condenser (62) after heat has been transferred from the first portion (72a) and the second portion (72b) to provide a condensed stream; The condensed stream is separated in a receiver vessel (52) into a fuel gas stream (56) and at least one liquid stream (54, 57).

6. The method according to claim 4, further comprising: transferring heat from said first portion (72a) of said compressed overhead stream (59) in a third heat exchanger (42, 44, 74, 76) to a third exchanger stream downstream of said first exchanger (42, 44, 74, 76); and, Heat is transferred from the second portion (72b) of the compressed overhead stream (59) in a fourth heat exchanger (42, 44, 74, 76) to a fourth exchanger stream downstream of the second exchanger (42, 44, 74, 76).

7. The method according to claim 1, further comprising: condensing the compressed overhead stream (59) in a condenser (62) after heat has been transferred from the compressed overhead stream (59) to provide a condensed stream; The condensed stream is separated in a receiver vessel (52) into a fuel gas stream (56) and at least one liquid stream (56, 57).

8. The method of claim 7, wherein the receiver vessel (52) also receives a liquid phase (68) of the compressed overhead stream (59).

9. The method according to claim 7, further comprising: The at least one liquid stream (57) is recycled from the receiver vessel (52) to the toluene methylation zone (14).

10. An apparatus for separating paraxylene from toluene, the apparatus comprising: a fractionation tower (26) comprising an inlet (38) and a plurality of outlets (46, 48, 50), the fractionation tower (26) being configured to receive a stream (38) comprising toluene and para-xylene via the inlet, separate the stream and provide an effluent stream (48) comprising para-xylene via at least a first outlet of the plurality of outlets, provide a recycle stream (50) comprising toluene via a second outlet of the plurality of outlets, and provide an overhead stream (46) via a third outlet of the plurality of outlets; a compression zone (58) configured to compress the overhead stream (46) to provide a compressed overhead stream (59); and and a heat recovery zone (60) comprising at least one heat exchanger (42, 44, 74, 76) configured to remove heat from the compressed overhead stream (59) prior to separating the overhead stream (46) into an aqueous stream (54), a fuel gas stream (56), and a liquid hydrocarbon stream (57).

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