JPH04208234A - Device and method for producing xylenes - Google Patents

Abstract

PURPOSE:To effectively utilize the energy contained in toluene vapor by disposing two condensers at the top of a toluene tower and employing the condensers as a reboiler of a benzene tower and as a waste heat-recovering device, respectively, when xylenes are produced by the disproportionation reaction of the toluene. CONSTITUTION:Toluene as a raw material is subjected to a disproportionation reaction to produce a reaction solution containing at least benzene, toluene and xylenes. The reaction solution is distilled to separate into benzene, toluene and xylenes, and para-xylene is separated and recovered from the xylene distillate. In the process, toluene vapor distilled out from the top of the toluene tower for the separation of the toluene is divided into at least two fractions, one of the fractions is employed as a heat source for the reboiler of a benzene tower, and the remaining fraction is employed as a heat source for a equipment (e.g. a heat source for a reboiler of an ammonia distillation tower in a xylene- recovering process, or a heat source for a reflux condenser of a vertical purification tower) in the production plant.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an apparatus and method for producing xylenes, and more particularly, to a method for efficiently producing xylene using at least toluene as a raw material. Concerning equipment and manufacturing methods.

゛ [Conventional technology 9 Problems to be solved by the invention]□
Traditionally, xylene has been produced primarily by disproportionation of toluene and, in some cases, by transalkylation or the disproportionation and transalkylation of reacting toluene with a C1 aromatic hydrocarbon, such as, for example, trimethylbenzene. It is manufactured using a combination of However, in this production, a large amount of energy is consumed for separating and recovering the xylenes.

In particular, the substance generally contained in the largest amount in the reaction product liquid is unreacted toluene, and its separation requires a large amount of energy, and the energy carried away by the separated toluene is large. Despite the amount, this energy was wasted without being utilized effectively.

[Means for Solving the Problems 1 Effect] The present inventors have conducted intensive research to overcome the above-mentioned drawbacks in the conventional method for producing xylene using Tornidium as a raw material, and in separating toluene, it has been found that The present invention was finally achieved by developing an apparatus and method for efficiently producing xylenes by effectively utilizing the large amount of energy that had been available.

That is, one aspect of the present invention is a reaction process including a reactor for disproportionating toluene into xylene and benzene using at least toluene as a raw material, and at least benzene, toluene and benzene discharged from the reaction process. A distillation process having at least a benzene column and a toluene column for separating each of benzene, toluene and xylene from a reaction product liquid containing xylene by distillation, and a distillation process for separating and recovering para-xylene from the xylene fraction from the distillation process. In a system for producing xylenes in which varaxyl 1F recovery processes are sequentially connected, two condensers are installed at the top of the toluene column, one of which is used as a rewheeler for the benzene column, and the other This is an apparatus for producing xylenes, characterized in that the two condensers are used as condensers for waste heat recovery.

Another aspect of the present invention is to obtain a reaction product liquid containing at least benzene, toluene, and xylene using at least toluene as a raw material, and to separate benzene, toluene, and xylenes from the reaction product liquid by distillation, respectively. Next, in a method for producing xylenes in which para-xylene is separated and recovered from the xylene fraction, toluene vapor distilled from the top of a toluene column for separating toluene by distillation is divided into at least two parts, and one is passed through a benzene column. This is a method for producing xylenes, characterized in that the remaining part is used as an energy source for equipment in the toluene production apparatus.

The apparatus of the present invention includes a reaction step, a distillation step, and a pump reactor. Although either a batch type or a continuous type reactor can be used, a continuous type is practically preferred. In addition, hydrogen gas is generally fed into the reactor, but in this case, the hydrogen gas mixed with the reaction product liquid at the reactor outlet is separated by a flash separator and recovered. The hydrogen produced is pressurized by a compressor and returned to the reactor for reuse. This compressor may be either a turbo type or a positive displacement type, but a turbo type or a rotary positive displacement type is preferred.

The reaction product liquid after hydrogen gas has been removed is sent to a distillation process.

In the distillation process, from the upstream side, low-boiling components in the reaction product liquid, benzene, toluene, xylene, and low-boiling groups for separating high-boiling components by distillation, benzene tower, toluene tower, xylene tower, and high-boiling groups are generally used. It is arranged.

There are no particular restrictions on the type of distillation column, but either a plated column or a packed column may be used.

In addition, if the reaction product liquid contains fewer components with a boiling point higher than xylenes, the content of single xylene is high, and the content of single xylene in the bottom liquid of the toluene tower is high, the xylene tower is omitted. be able to.

In addition, in order to further separate xylenes into each xylene, an adsorption separation method, IP-BP, is used instead of distillation.

It can also be obtained by a method that utilizes a complex reaction between xylene and xylene, or by a solvent extraction method.

The xylene fractions, such as the toluene column bottom liquid or the xylene column top liquid, containing xylene obtained in the distillation process are sent to a para-xylene recovery process to separate and recover xylene.

The paraxylene recovery process is usually performed using a crystallization method.

As the crystallization method, both a high pressure crystallization method and a cooling crystallization method can be used, but the cooling crystallization method is preferable. This is a powerful cooling crystallization method. This "countercurrent cooling melting refining method" has a cooling type crystallization tank with a clarification section at the top, a clarification section at the top, and a heater at the bottom.
It is combined with a vertical refining tower that operates at a higher temperature than the crystallization tank, and the crystals generated in the crystallization tank are heated and melted by a heater at the bottom on the refining tower, and a part of the melt is taken out as a product. In this method, the other part is raised as a reflux liquid to wash the crystal layer moving to the lower part, and the clarified liquid at the upper part of the purification tower is led to the clarification sedimentation part of the crystal tank.

The crystallization tank used here is not particularly limited as long as it has a clarification section at the top, but for example, the crystallization tank used in JP-A No. 55, No.
- The "scraping circulation crystallizer" described in IQ9403 is preferably used.

This "scraping circulation type crystallizer" is equipped with a draft tube in the scraping mechanism that rotates inside the scraping type crystallization tank, and a stirring blade is attached to create a circulation flow inside and outside the draft tube. , a baffle having a certain curvature inserted into the outside and inside of the draft tube from the upper lid and bottom plate of the crystallization tank to near the support boom of the scraping mechanism for changing the swirling flow upstream and downstream. It is a crystal tank.

Moreover, as the vertical purification column used here, for example, the "purification apparatus" described in Japanese Patent Publication No. 62-596.03 is suitably used. This "purification device" is a device provided with a heatable partition shelf having an opening.

Although there are no particular restrictions on the refrigerant for cooling this crystallization tank, ammonia is usually used. Further, as the refrigeration method using ammonia as a refrigerant, either a so-called compression refrigeration method or an absorption refrigeration method can be used, but the latter is preferred in practice.

Of the toluene vapor distilled from the top of the toluene column, a portion is used as a heat source for the benzene column, and the energy of the remaining toluene vapor is used, for example, as a reboiler heat source for an ammonia distillation column in an absorption refrigeration method in a para-xylene recovery process. As a heat source for the flux in the vertical purification tower, as a power source for a compressor for hydrogen compression, or as an energy source for a turbine generator to obtain power for lighting, controls, pumps, etc. in the equipment, or as a solvent. It can be used as a heat source for removing the solvent used for extraction.

Usually, most of the energy of the remaining toluene vapor will be consumed by the foregoing or the former two, but if there is a surplus, it can also be used as the other energy source.

That is, when this toluene vapor is used directly as an energy source, the waste heat condenser is, for example, a reboiler at the bottom of the ammonia distillation column.

On the other hand, when this toluene vapor is used as a heat source to generate water vapor and this water vapor is used as an energy source, the waste rust condenser is used as a steam boiler.

This water vapor has a low pressure as it is, so for example,
When used as a power source for a turbine-driven compressor for hydrogen compression, a turbine-type generator, etc., medium- to high-pressure steam that has been heated and pressurized must be used.

Although the toluene tower boiler can be heated using a heat medium such as high-temperature heat transfer oil, the heat source of the toluene tower reboiler is a turbine generator for the power supply of the xylene equipment of the present invention. It is possible and preferred to use back pressure steam driven and/or back pressure steam of a steam turbine for driving a hydrogen compressor.

In addition, B, F, and W (boiler supply water - the same shall apply hereinafter) of the boiler that generates steam for the above-mentioned turbine generator and steam turbine for driving the hydrogen compressor are generally supplied by a direct heating furnace, but some or all of them may be Steam from a waste heat condenser at the top of the toluene column can also be used.

FIG. 1 shows a flow sheet of a typical example of the apparatus for producing xylenes of the present invention. The xylene production equipment shown in the flow sheet in Figure 1 does not include a xylene tower, and the recovery system uses a countercurrent cooling crystallization purification equipment with three crystal tanks and a vertical purification tower. In addition, ammonia, which is the refrigerant in this countercurrent cooling crystallization refiner, is cooled by absorption refrigeration.

The raw material toluene is combined with the toluene separated and recovered and condensed in the toluene column 17, preheated in the heat exchanger 3 by the reaction product liquid from the reactor 2, and further heated to a predetermined temperature in the heating furnace 1 to undergo a reaction. is supplied to vessel 2. Meanwhile, hydrogen gas is supplied to the reactor 2. Toluene is reacted in the reactor 2, and the reaction product liquid from the reactor 2, which mainly contains toluene, benzene, and xylene, as well as low-boiling components and hydrogen gas, is sent to a flash separator 4, where hydrogen gas is separated. This hydrogen gas is combined with newly supplied hydrogen gas if desired, pressurized by the hydrogen compressor 5, and circulated to the reactor 2. After exchanging heat with the feed liquid, the reaction product liquid discharged from the flash separator lake 4 is sent to the pressure release fludge tank 6, where the vapor components in the reaction product liquid flashed under pressure are condensed and discharged. Furthermore, the liquid component is sent to the low boiling column 10 from the bottom of the pressure release flash tank 6.

In the low-boiling column 10, low-boiling components such as light hydrocarbons in the reaction product liquid are removed by distillation. The removed low-boiling components are condensed in the low-boiling column condenser 11, a portion of which is refluxed and the remainder is taken out of the column. The reaction product liquid from which the low-boiling components have been removed is sent to the benzene tower 14 as a low-boiling column bottom liquid. Here, benzene in the bottom liquid of the low-boiling column is removed by distillation, and this benzene is condensed in the benzene column condenser 15, a part of which is refluxed, and the remainder is discharged to the outside of the column. Furthermore, the benzene tower bottom liquid that does not substantially contain benzene is sent to the toluene tower 17. Here, toluene in the bottom liquid of the benzene tower is separated by distillation.
This toluene is discharged from the top of toluene column 17, and 2
One stream is used as a heat source for the benzene tower boiler 16 and is condensed. The other stream is sent to the waste heat recovery condenser 18 and used as a heat source for steam generation, while toluene is condensed. Part of the toluene that has been coagulated in the benzene column reboiler 16 and the waste heat recovery condenser 18 is refluxed, and the remainder is combined with the raw material toluene and returned to the reactor 2.

The bottom liquid of the 1.luene column, which is essentially made up of only xylenes, is sent to a para-xylene recovery step. The three crystallization tanks in the paraxylene recovery process are scraping circulation type crystallizers described in JP-A-55-109403, in which the upper part is the clarification section. Liquid ammonia is flowed into the shells of these crystallization tanks and is cooled by the latent heat of vaporization of the liquid ammonia.

The first of these crystallization tanks is connected to a vertical purification tower. This vertical purification column is a purification device described in Japanese Patent Publication No. 62-59603.

The toluene column bottom liquid is supplied to the first crystallization tank 50. 1st
The clarified liquid in the upper part of the crystallization tank 50 is sent to the second crystallization tank 51,
Similarly, the clarified liquid in the upper part of the second crystallization tank 51 is sent to the third crystallization tank 52, and the clarified liquid in the upper part of the third crystallization tank 52 is discharged out of the apparatus as a residue. Further, the crystal slurry in the third crystal tank 52 is sent to the second crystal tank 51, the crystal slurry in the second crystal tank 51 is sent to the first crystal tank 50, and the crystal slurry in the first crystal tank 50 is vertically refined. It is sent to the top of tower 53.

Here, the crystal slurry settles and moves to the lower part of the heater 54.
It is heated and melted. A portion of the melt is taken out from the bottom of the vertical purification tower 53 to obtain high purity xylene as a product. The remaining molten material ascends within the vertical purification tower 53 and is brought into contact with the crystals descending within the tower to wash the crystals. The clarified liquid at the top of the vertical purification tower 53 is returned to the first crystallization tank 50.

The ammonia vapor from the jacket of the third crystallization tank 52 passes through the first superheater 41 to the first ejector where it is mixed with dilute ammonia water, and this mixture is then transferred to the first low pressure condenser 34, the first diluted The liquid is sent to the second ejector via the liquid receiving tank and the first booster pump gauge 6 in sequence.

Ammonia vapor from the outer shells of the second crystal tank 51 and the first crystal tank 50 passes through the second super heater 40 and reaches the second ejector, where the first boost pump 3
The mixture is mixed with the pressurized dilute ammonia water sent through the second ammonia distillation column heat exchanger. 33 to the second ammonia tower 29
sent to. Here, ammonia vapor is separated by distillation. The bottom liquid of the second ammonia column 29 is dilute ammonia water, and this bottom liquid passes through the second ammonia distillation column exchanger 33 to the first ejector, where it is mixed with ammonia vapor.

Ammonia vapor from the top of the second ammonia distillation column 29 passes through a second ammonia distillation column condenser 30 and a second ammonia distillation column reflux drum 31 to remove a liquid component. This ammonia vapor is mixed with dilute ammonia water, which is the bottom liquid of the first ammonia distillation column 20, and is made into concentrated ammonia water. The ammonia vapor is sent via the heat exchanger 24 to the first ammonia distillation column 20, where the pressurized ammonia vapor is separated by distillation. The bottom liquid of the first ammonia distillation column 20 is pressurized dilute ammonia water. is mixed with pressurized ammonia vapor from

The pressurized ammonia vapor from the first ammonia distillation column 20 is liquefied in the first ammonia distillation column condenser 22, sent to the liquefied ammonia beam flux drum 23, and a part of it is refluxed to the ammonia distillation column 20,
The remainder is divided into two streams, one stream is sent to the outer part of the first crystal tank 50 via the second super heater 40, and the other stream is sent to the outer part of the first crystal tank 50 via the first super heater 41. The liquid is sent to the mantles of the second crystal tank 51 and the third crystal tank 52, respectively.

Steam obtained in the waste heat condenser 18 using toluene vapor from the toluene column 17 as a heat source is led to the first ammonia distillation column reboiler 21 and the second ammonia distillation column reboiler 32, and is used as a heat source for both distillation columns. The remaining steam is led to the vertical purification column heater 54 and used as a heat source for the vertical purification column.

A typical example of a heating method for a toluene column will be explained with reference to flow sheets shown in FIGS. 2 and 3.

In FIG. 2, B, F, 'W are supplied to a boiler 61 and converted into steam. The obtained steam (high pressure steam) rotates a steam turbine 62 to drive a generator 63,
Waste heat steam (medium pressure steam) after rotating the turbine 62 is led to the toluene tower boiler 19 and used as a heat source for the toluene tower 17.

In Figure 3, water vapor (
The steam turbine 71 (high pressure steam) is used to rotate the steam turbine 71 to drive the generator 72, and the hydrogen compressor 5 is also driven to rotate the steam turbine 71.The waste steam (medium pressure steam) is guided to the toluene tower wheeler 19. , is used as a heat source for the toluene column 17.

In addition, in the above, B, F, and W to the boiler 61.

It is also possible to use the steam generated by the waste heat compressor 18 to preheat some or all of the waste heat compressor 18.

In reactor 1, it is possible to disproportionate toluene and/or to transalkylate toluene with a C9 aromatic hydrocarbon, such as, for example, trimethylbenzene. These reactions are performed, for example, in the presence of a solid acid catalyst such as silica alumina and a catalyst in which a noble metal is supported on silica alumina at 30 to 60 bar.
The reaction is carried out at a temperature of 00 to 350°C under normal conditions in which the amount of hydrogen used is 3 to 8 times the molar amount of toluene fed.

For example, the TATORAY process by Toshi Co., Ltd., Atlantic
A R□ by ic R4chfiekd Co,)
CO-xylene plus method and 5T by Mopil
DP (Selective Toluence di)
Reaction conditions such as sproportionation can be adopted.

Among these, it is preferable to adopt the reaction conditions for 5TDP because paraxylene, which has high utility value, has high selectivity and can be obtained efficiently.

Note that the toluene used in this reaction can be one that is used as a general industrial raw material. For example, A'STM
f Testing Material - American Society for Testing Materials - Standard) Specified in D362-80 and with a purity of 99.9% by weight or more is used.

The conditions may vary depending on the composition of the reaction product liquid, etc., but the conditions normally employed may be sufficient.
Bensen tower Toluene tower number (
stage) 15-2525-30 stage 30-35 stage supply stage (
Steps) 7-105-8 steps 5-8 steps In addition,
When a xylene tower is installed, the number of stages is 20 to 30, the supply stage is 5 to 10 stages, the temperature is 160 to 180°C at the top of the tower, 190 to 2.30°C at the bottom, and the pressure is 1 to 2.30°C at the top of the tower. It is said to be 3 bar. In this case, if a xylene tower condenser is used as a waste heat boiler, steam at a temperature of 140 to 160° C. can be obtained, and this steam can also be used as an energy source in the same plant, which is preferable.

In the para-xylene recovery process, various temperatures when using a self-flow cooling crystallization purification device vary depending on the composition of the xylene-containing toluene column bottom liquid and the xylene column top liquid supplied to the first crystallization tank. .

For example, when the xylene content of the liquid supplied to the first crystallization tank is 60 to 80 wt%, the first crystallization tank -5 to 0%
°C, 2nd crystal tank -15 °C1 3rd crystal tank -25 to -35
°C and the fourth crystallization tank to -65 to -45 °C and the upper part of the vertical purification column to -3 to 3 °C.

In addition, when the content of paraxylene is 25 to 35 wt%, the feed liquid is supplied to the second crystallization tank, the first crystallization tank is -10 to -15°C, the second crystallization tank is -30°C, the third crystallization tank is -10 to -15°C, Preferably, the temperature is -45°C in the crystallization tank, -65°C in the fourth tank, and -2°C in the upper part of the vertical purification column.

Further, conditions for freezing ammonia, which is a refrigerant in this para-xylene recovery process, are appropriately determined depending on the composition and amount of the liquid supplied to the para-xylene recovery process.

〔Example〕

The present invention will be explained in more detail with reference to Examples.

Note that the present invention is not limited to the examples.

Example 1 p-xylene was produced using the apparatus shown in the flow sheet of FIG. 7 1. Reaction step The reaction was carried out using a zeolite catalyst ZSM=5. That is, (11 catalyst ZSM-5 (2) Toluene ASTM D362 crude product 1 toluene purity 99.9 wt% (3) Toluene supply rate 5 kg/catalyst 1' kg/hr
(Replenishment toluene: Circulating toluene-1:3.3>(4) Hydrogen supply rate 2 kg-mol/Tolue, M
kg-mol/hr (5) Pressure 30 bar (6) Temperature
400 ℃ (7) Reaction product liquid discharge amount 8403 kg/hr (8
) Reaction product liquid composition (after hydrogen gas removal) mo1% C5 or less: 5.20 Benzene: 15.83 Toluene: 66.80 P-xylene:' 10.14 M-xylene: 1.80 0-xylene: 0. 19 C7 or higher: 0.04 The reboiler of the toluene column uses high-temperature heat transfer oil, and its inlet and outlet temperatures are 240°C and 200°C, respectively.
'C.

3. All three crystal tanks in the xylene recovery process have a diameter of 1.8 m and a height of 2.4 m.
m, and the heat transfer area was 10M.

Further, the operating conditions in the three crystallization tanks were as follows.

Crystallization temperature ("c) 2.0 -13
-30 Amount of heat removed 47 44
20 (103Kcal/hr) Refrigerant evaporation temperature ("c) -10-25-45 Refrigerant evaporation amount (kg/hr) 162 150
68 Feed liquid amount kg/lr 1232"
6.7 kg/hr was emitted.

Composition of residue (mo1%) Toluene 1.50 Ethylbenzene 13.93 p-xylene 28.84 0 to xylene 37.18 m-xylene 6.53 C7 or higher 12.02 Also, the specifications and operating conditions of the vertical purification tower was done as follows.

Column diameter mφ 750 Height m3.0 Clear liquid discharge amount kg/hr Composition Mol% Toluene 0.4 Ethylbenzene 4. O p-xylene 79.4 0-xylene 10.8 m-xylene 1.9 C1 or more 3.5 Crystal slurry supply kg/hr 1172.0 Slurry concentration ivt% 45 Melt discharge amount kr/hr 293. Op-xylene purity % 99.9 Primary ammonia Secondary ammonia distillation column
Distillation column top pressure ata 12.0 5.8 Column top temperature °C 4489 Column bottom temperature °c 106 106 Vapor amount kg / hr 515 342 Concentrated ammonia water Supply in the tank 1 k
g/H843Q'+3 Ammonia concentration wtχ 75
28 rare ammonia water discharge kg/H293663 29^^・t Φ Ammonia concentration weak t% 28
16 Top gas discharge kg/H550110 Ammonia vol Z 99.
9 90.2 Reflux ratio
0.15 0.3 Primary ammonia
27th dry near absorption tower Absorption tower condenser Condenser pressure ata 0.07 0.
8 Temperature "C3838 5. Comparison of energy content Product p-xylene in distillation process and recovery process 1
The amount of energy required per kg was 1.8 kilojoules in this example. On the other hand, when the waste heat of toluene in the toluene tower was not utilized, the amount was 3.3 kilojoules.

〔Effect of the invention〕

In the present invention, high purity xylene can be efficiently obtained with a relatively small amount of energy.

[Brief explanation of the drawing]

1 to 3 are flow sheets showing embodiments of the present invention. In the drawing, 1 - heating furnace 2 - reactor 4 - flash separator 5 - hydrogen compressor 6 - decompression Franch tank 10 - low boiling group 14 - Hensen tower 17 - toluene tower 18 - waste heat recovery condenser 2 - primary ammonia Distillation column 26 - Reflux strum 27 - Solution pump 29 - Second ammonia distillation column 35 - First diluted liquid receiver 36 - First booster pump 38 - Second diluted liquid receiver 39 - Third booster pump 40 - No. 2 super heater 41 - first super heater 50 - first crystal tank 51 - second crystal tank 52 - third crystal tank 53 - vertical purification column 61 - boiler 6
2-Steam turbine 63-generator 71-steam turbine 72-generator

Claims (8)

[Claims] (1) A reaction process using at least toluene as a raw material and including a reactor for disproportionating toluene into benzene and xylene; benzene from the reaction product liquid containing at least benzene, toluene and xylene discharged from the reaction process; In an apparatus for producing xylenes, which has a distillation step having at least a benzene column and a toluene column for separating toluene and xylene by distillation, and a xylene recovery step for separating and recovering para-xylene from the xylene fraction from the distillation step. ,
A xylene compound characterized in that two condensers are installed at the top of the toluene column, one of which is used as a reboiler for the benzene column, and the other one is used as a waste heat recovery condenser. manufacturing equipment. (2) The apparatus for producing xylenes according to claim (1), wherein the para-xylene recovery step is based on a cooling crystallization method. (3) The apparatus for producing xylenes according to claim 1 or 2, wherein the para-xylene recovery step is based on a countercurrent cooling melt purification method. (4) The apparatus for producing xylenes according to claim 2 or 3, wherein the equipment for producing the refrigerant for cooling the para-xylene recovery process by the cooling crystallization method is of an absorption refrigeration system. (5) A claim where, of the two condensers installed at the top of the toluene column, a condenser other than the reboiler of the benzene column is connected to the reboiler of the ammonia distillation column in the absorption refrigeration system. Item (1) or (4)
) The apparatus for producing xylenes described in ). (6) Claim (1) in which of the two condensers installed at the top of the toluene column, the condenser other than the reboiler of the benzene column is connected to the lower part of the vertical purification column in the paraxylene recovery process. Or the apparatus for producing xylenes according to (3). (7) The para-xylene recovery process is based on a countercurrent cooling melt refining method, and the equipment for producing the cooling refrigerant in the para-xylene recovery process is based on an absorption refrigeration system, and is installed at the top of the toluene column. 2. A condenser other than the reboiler of the benzene column out of the two condensers is connected to an ammonia distillation column in the refrigeration equipment and a lower part of the vertical purification column in the xylene recovery step. (1), (3), (4), (5) or (
6) The apparatus for producing xylenes as described above. (8) Using at least toluene as a raw material, obtain a reaction product liquid containing at least benzene, toluene, and xylene, separate benzene, toluene, and xylenes from the reaction product liquid by distillation, and then separate paraxylene from the xylene fraction. In a method for producing xylenes that is separated and recovered, toluene vapor distilled from the top of a toluene column for separating toluene by distillation is divided into at least two parts, one of which is used as a reboiler heat source for a benzene column, and the remaining part is A method for producing xylenes, which is used as an energy source for equipment in the toluene production apparatus.