JP2010254582A - Method for producing para-dichlorobenzene - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing para-dichlorobenzene, by which the objective compound can be obtained in a high yield in stable operation on work as a real apparatus. <P>SOLUTION: This method for producing the para-dichlorobenzene, comprising chlorinating at least one of benzene and monochlorobenzene as a raw material with chlorine gas, is characterized by supplying the chlorine gas to each of reactors in which a catalyst containing alumina as a main component is disposed and which are arranged at a plurality of stages, in parallel, supplying the raw material and the chlorine gas to the first stage reactor, supplying the first stage reaction product to the next stage reactor, supplying the chlorine gas to the next and further continuing reactors in parallel, and obtaining the para-dichlorobenzene from the final stage reaction product. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing paradichlorobenzene, and in particular, chlorination with chlorine gas using at least one of benzene (hereinafter also referred to as “Bz”) and monochlorobenzene (hereinafter also referred to as “MCB”) as a raw material using alumina as a catalyst. The present invention relates to a method for producing chlorobenzene (hereinafter also referred to as “p-DCB” or “PDCB”). In the present specification, “alumina catalyst” indicates “a catalyst mainly composed of alumina”.

  p-DCB is a compound with extremely high industrial value as a raw material for pharmaceuticals and agricultural chemicals, itself as an insecticide and insect repellent, and as a raw material for polyphenylene sulfide (PPS).

  Conventionally, p-DCB has been known to be a liquid phase chlorination of benzene and / or monochlorobenzene using a Lewis acid such as ferric chloride or antimony pentachloride as a catalyst. Ferric chloride has a high activity, the chlorine conversion rate reaches 99.99% or more, and a very small amount of unreacted chlorine in the by-produced hydrochloric acid gas remains. However, the selectivity of the desired para-substituted product is at most about 60% with the catalyst alone, and is increased to about 75% by adding a cocatalyst.

  In recent years, as a method for producing p-DCB with a selectivity of 90% or more, as shown in Patent Document 1, Patent Document 2, and the like, a method using L-type zeolite as a catalyst has been disclosed. However, the zeolite catalyst is expensive, and there are problems such as deterioration in a relatively short time depending on conditions.

  Patent Document 3 discloses a method of using activated alumina as a catalyst in producing dichlorobenzene by chlorinating benzene and / or monochlorobenzene. This method shows a high para-selectivity of 75%, a high chlorine conversion rate of 99.8%, and shows that no catalyst deterioration is observed over a long period of time. However, the method disclosed in Patent Document 3 is of a laboratory level and is not considered to be a specific one that can be operated as an actual apparatus. Moreover, since the chlorination reaction of benzene is a vigorous exothermic reaction, in an actual apparatus, it is very important to appropriately suppress the temperature rise and maintain the operation within a certain temperature range. It does not teach an effective solution to this point.

Japanese Examined Patent Publication No. 63-12450 JP 2001-213815 A Japanese Patent No. 2518095

  The problem to be solved by the present invention is to provide a method capable of stable operation at a lower cost when operating as an actual apparatus when manufacturing p-DCB. Other issues will become apparent from the following description.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
In a method of producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, each reactor of a reactor having a plurality of stages containing a catalyst mainly composed of alumina is supplied with chlorine gas. Supply in parallel, supply the raw material and chlorine gas to the first-stage reactor, supply the reaction product of the previous stage to the reactor of the next stage, supply chlorine gas to the reactors of the subsequent stage, in parallel, A process for producing parachlorobenzene, characterized in that paradichlorobenzene is obtained from the final stage reaction product.

[Invention of Claim 2]
In a method of producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, among the reactors having a plurality of stages containing a catalyst mainly composed of alumina, the raw material is provided in the first stage reactor. , Supply chlorine gas and / or unreacted chlorine gas in the subsequent stage, supply the reaction product in the previous stage to the reactor in the next stage, supply an excess amount of chlorine gas to the reactors in the subsequent stage and the final stage. A process for producing paradichlorobenzene, comprising obtaining paradichlorobenzene from a reaction product of

[Invention of Claim 3]
In a method of producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, among the reactors having a plurality of stages containing a catalyst mainly composed of alumina, the raw material is provided in the first stage reactor. , Supplying chlorine gas, separating the reaction product of the previous stage into unreacted raw material and product, returning the unreacted raw material to the reactor of the previous stage, supplying the product to the reactor of the next stage, A process for producing paradichlorobenzene, characterized in that chlorine gas is supplied to the reactor and paradichlorobenzene is obtained from the reaction product in the final stage.

[Invention of Claim 4]
The method for producing paradichlorobenzene according to any one of claims 1 to 3, wherein the reactor is a reactor in which a catalyst mainly composed of alumina is incorporated as a fixed bed.

[Invention of Claim 5]
The manufacturing method of the para dichlorobenzene of Claim 4 which distribute | circulates the said raw material and chlorine gas by a down flow.

[Invention of Claim 6]
The paradigm according to any one of claims 1 to 5, wherein at least one kind of cooling medium of chloromethane and chloroethane is introduced into each stage of the reactor, and the temperature of the chlorination reaction is suppressed by evaporating the cooling medium. A method for producing chlorobenzene.

[Invention of Claim 7]
The method for producing paradichlorobenzene according to any one of claims 1 to 6, wherein the evaporated gas content of the cooling medium is condensed outside the reactor, and the condensed liquid is reused as the cooling medium.

[Invention of Claim 8]
In a method of producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, the raw material and the chlorine gas are led to a reactor equipped with a catalyst mainly composed of alumina as a slurry bed. A method for producing paradichlorobenzene, which is characterized.

[Invention of Claim 9]
The method for producing paradichlorobenzene according to any one of claims 1 to 8, wherein the alumina is nano alumina having a high specific surface area.

[Invention of Claim 10]
The method for producing paradichlorobenzene according to claim 9, wherein the nanoalumina is produced from a nanoparticle gel and / or a nanoparticle sol.

[Invention of Claim 11]
The method for producing paradichlorobenzene according to any one of claims 1 to 10, wherein the chlorination reaction is performed at a temperature of 40 to 130 ° C and a pressure of 10 atm or less.

  According to the present invention, although the chlorination reaction of benzene and / or monochlorobenzene is a violent exothermic reaction, the temperature rise can be accurately suppressed and stable operation can be performed for a long time when operating as an actual device. become.

1 is a flowchart of a first embodiment of the present invention. It is a flow sheet that supplies raw material and chlorine gas under up-flow conditions. It is an electron micrograph of γ-alumina and a schematic structure diagram. (A) Electron micrograph of hydrogel, (B) Electron micrograph after firing, (C) Structural schematic after firing, (D) Fractal structure of pores. It is a flow sheet of a 2nd embodiment of the present invention. It is a flow sheet of a 3rd embodiment of the present invention. It is a flow sheet of a 4th embodiment of the present invention. It is a graph which shows the dichlorobenzene yield and para selectivity in the system which used γ-alumina (nanoparticle gel), β zeolite, and silica alumina as a catalyst. It is a graph which shows the dichlorobenzene yield and para selectivity in the system which used nanoparticle gel and (gamma) -alumina of nanoparticle sol as a catalyst. It is a graph which shows the reaction stability of 20 hours in the system which used (gamma) -alumina (nanoparticle gel) as a catalyst. It is a general | schematic block diagram of the reaction apparatus of a prior art example (comparative example: use of a homogeneous catalyst). It is a composition change graph of each substance in a conventional example (use of a homogeneous catalyst). It is a graph of the selectivity of p-DCB in a conventional example (using a homogeneous catalyst). It is a graph of the p-DCB yield accompanying chlorination in a conventional example (use of a homogeneous catalyst). It is a graph which shows the influence of the reaction temperature of the selectivity in a prior art example (use of a homogeneous catalyst). It is a graph which shows the influence of the catalyst amount of the selectivity in a prior art example (use of a homogeneous catalyst).

(Basic idea of the invention)
As described above, a homogeneous catalyst such as ferric chloride not only has low p-DCB selectivity, but also increases the equipment load for catalyst separation and recovery. In the present invention, the use of an alumina catalyst increases the selectivity of p-DCB, and the use of a solid catalyst enables reuse.

  Further, as described above, the chlorination reaction is a violent exothermic reaction. Incidentally, if the heat is not removed, the temperature is easily raised to 400 to 500 ° C. Therefore, it is necessary to appropriately suppress the temperature rise and maintain the operation within a certain temperature range. If the temperature is too low, the viscosity increases and the pressure loss increases. On the other hand, when the temperature is high, the chlorine dissolution rate is controlled and the reaction is suppressed. Further, the boiling point of benzene is 80.1 ° C., and naturally the reaction is suppressed under the condition that benzene evaporates. It is also necessary to determine the reaction pressure so that an appropriate reaction temperature (reaction rate) can be maintained.

As a method for suppressing an exothermic reaction, a method in which a reactor such as a jacket or a coil is provided with a cooling part, a method for suppressing a temperature rise by using a large amount of solvent (1.2 dichloroethane and MCB are considered as solvent candidates. )), And a method using a combination of a cooling part and a solvent, etc., and naturally these methods can also be used. However, under suitable reaction conditions (40 to 130 ° C., 10 atm or less), a gas-liquid mixed phase state is obtained, but the overall heat transfer rate of the reaction part—the metal part—the cooling part is overwhelmed with the liquid phase volume. Therefore, the heat transfer rate in the reaction section becomes dominant, and the overall heat transfer coefficient is only about 10 to 30 kcal / m ² hr ° C. Under this condition, a huge heat transfer area is required, which is embodied as a reactor. Difficult to do.

  Therefore, the present invention proposes a direct cooling method using latent heat of vaporization of the cooling solvent as a more preferable condition. It is possible to absorb the enormous reaction heat generated by transferring the latent heat of vaporization caused by the evaporation of the compound to the compound by having a compound having the same boiling point as the reaction conditions in the reaction system. It becomes.

Evaporated compounds can be condensed and reused. When condensing, a general-purpose external heat exchanger such as a shell and tube that can secure a general heat transfer coefficient of 600 to 1100 kcal / m ² hr ° C. can be used. It is.

  Such a compound that can be directly used as a cooling medium is required not to react, and suitable for the chlorination reaction of p-DCB synthesis is dichloromethane (Tb 40.2 ° C.), trichloromethane (Tb 61.1 ° C.), tetra Chloromethanes such as chloromethane (Tb 76.8 ° C.), 1.1-dichloroethane (Tb 57. ° C.), 1.1.1-trichloroethane (Tb 73.9 ° C.), and chloroethanes. Stable temperature control is possible by selecting a suitable pressure condition in consideration of the desired reaction temperature and the boiling point of benzene and the direct cooling medium.

  In the process described below, an example using trichloromethane (also known as chloroform) having an atmospheric pressure boiling point of 61 ° C. will be described, but the use of other chloromethanes and chloroethanes described above is also possible. It has been confirmed that more than one can be used.

By the way, the present invention uses benzene and / or chlorobenzene and chlorine gas and the direct cooling medium (chloroform in the following example). This is summarized as follows.
1) Raw materials and raw material impurities: benzene, chlorobenzene, chlorine 2) Solvents / solutions and their impurities: chloroform, water 3) Reaction products: Monochlorobenzene, dichlorobenzene, trichlorobenzene, hydrogen chloride Appropriately considering the above components In order to obtain paradichlorobenzene for the purpose.

An example of the reaction formula is as follows.
Bz (C ₆ H ₆ ) → MCB (C ₆ H ₅ Cl) → PDCB, MDCB, ODCB (p-C ₆ H ₄ Cl ₂ , o-C ₆ H ₄ Cl ₂ , m-C ₆ H ₄ Cl ₂ → TCB (C ₆ H ₃ Cl ₃ )
PDCB synthesis reaction system:
C ₆ H ₆ + Cl ₂ → C ₆ H ₅ Cl + HCl (1)
C ₆ H ₅ Cl + Cl ₂ → p-C ₆ H ₄ Cl ₂ + HCl (2)
C ₆ H ₅ Cl + Cl ₂ → o-C ₆ H ₄ Cl ₂ + HCl (3)
C ₆ H ₅ Cl + Cl ₂ → m-C ₆ H ₄ Cl ₂ + HCl (4)
p-C ₆ H ₄ Cl ₂ + Cl ₂ → C ₆ H ₃ Cl ₃ + HCl (5)
o-C ₆ H ₄ Cl ₂ + Cl ₂ → C ₆ H ₃ Cl ₃ + HCl (6)
C ₆ H ₃ Cl ₃ + Cl ₂ → C ₆ H ₂ Cl ₄ + HCl (7)

An example of a chlorine addition reaction, which is an undesirable side reaction, is as follows.
Formation of tetrachlorocyclohexene and benzenehexachloride by benzene chlorination:
C ₆ H ₆ + 2Cl ₂ → C ₆ H ₆ Cl ₄ (8)
C ₆ H ₆ + 3Cl ₂ → C ₆ H ₆ Cl ₆ (9)
Tetrachlorocyclohexene and benzene hexachloride produced by undesirable side reactions can be poisonous substances of the catalyst, and there is a concern that the catalyst may be deteriorated.

  In this reaction, a small amount of moisture is considered necessary for the ionic reaction on the alumina catalyst. However, excessive moisture causes corrosion of the apparatus, and there is a possibility that the reactivity of the reaction is lowered and a by-product is generated. Therefore, it is desirable that the water content in the raw material is appropriately adjusted.

(Preferred form of alumina catalyst)
In the present invention, a catalyst containing alumina is used. Alumina (Al ₂ O ₃ ) is mainly classified into α type, γ type, δ type, and θ type from its crystal form. Among these, γ-alumina has a high specific surface area and is frequently used as a catalyst or a catalyst carrier. Many of alumina having catalytic activity and other activities called activated alumina are mainly composed of γ-alumina. The stable phase α-type alumina is produced by heating and sintering the γ-type to 1000 ° C. or higher, and is widely used mainly as a ceramic material. The δ type and the θ type are intermediates generated in the process of sintering the γ type and converting it to the α type.

  FIG. 3 shows an electron micrograph and structural schematic diagram of nanoparticles of γ-alumina. FIG. 3A shows the state of the gel generated by neutralization precipitation, and FIG. 3B shows γ-alumina particles after drying at 550 ° C. As shown in FIG. 3C, the γ-alumina particles have a nano-order step shape, and the pores formed as gaps between such γ-alumina particles are also shown in FIG. Thus, since it has a fractal structure with many nano-order irregularities, the specific surface area is large and the reaction activity is also high.

  α-type, δ-type, and θ-type alumina is formed by phase transition of γ-alumina at a high temperature, and at that time, the specific surface area is significantly reduced. Therefore, these aluminas do not have a high catalytic activity like γ-alumina. Therefore, it is preferable to use γ-alumina having a high specific surface area and high catalytic activity as the alumina catalyst used in the present invention. In addition, although gamma-alumina can be suitably manufactured from any form of nanoparticle gel and nanoparticle sol, when used as a fixed bed, manufacture from nanoparticles is more preferable.

(Outline of reactor)
In the present invention, the alumina catalyst is installed in the reactor. Although the alumina catalyst is a stable catalyst for a long time, the reactor is used in multiple stages (minimum of two stages) in preparation for catalyst deterioration and used interchangeably. The alumina catalyst may be used as a fixed bed, and the raw material and chlorine gas may be circulated, or may be used as a slurry bed (FIG. 6). The slurry bed requires the separation of reaction products, unreacted components and catalyst, which makes the operation complicated. On the other hand, since the temperature rise can be suppressed by stirring in the reactor, heat removal with a solvent described later is not required, and the jacket Since the temperature rise can be sufficiently suppressed only by the water cooling, it can be preferably used.

  When the catalyst is used as a fixed bed, the raw material and the chlorine gas can be circulated in an up flow (FIG. 2), but are preferably circulated in a down flow (FIG. 1). When flown up-flow, the reactor becomes a continuous phase of the liquid, so the problem remains that the dissolution of chlorine gas in the solution becomes rate-limiting and back-mixing of reaction products in the liquid occurs. By making the flow down, it is possible to solve the above problem by making the inside of the reactor a continuous phase of gas.

  In this case, it is desirable to ensure the dispersion of the gas phase centered on chlorine gas and the uniform flow of the liquid phase, and to eliminate backmixing. The flow pattern of the gas-liquid multiphase flow changes depending on the diameter of the reactor used. The flow pattern to be adopted is a pulsating flow (Fulsing and Foaming Flow) or a perfusion flow (Gas-continuous or Tricking Flow), and preferably a perfusion flow. Pulsating flow is a state where large and small portions of liquid hold-up flow alternately. Perfusion flow is a state in which liquid flows down on the catalyst particles in the form of a film due to gravity, and gas becomes a continuous phase in the space. It is a flowing state. As the flow velocity of the gas-liquid multiphase flow increases, the flow pattern changes from pulsating flow to perfusion flow.

  Further, the number of stages of the reactor fixed bed has a plurality of stages, and preferably has three stages. In many cases, the solid catalyst is deteriorated due to the loss of active sites due to the inflow of the deterioration-causing substance from the inlet. As countermeasures against this, it is possible to connect each fixed floor in a series of 3 independent tanks and replace the connections when they are deteriorated to operate cyclically. By adding multiple amounts of chloroform, it can be reused and the amount of chloroform circulating in the system can be suppressed.

  As the reaction temperature, when the temperature is too low, the viscosity increases and the pressure loss increases. On the other hand, when the temperature is high, the chlorine dissolution rate is controlled and the reaction is suppressed. Therefore, as reaction temperature, it is 40-130 degreeC, More preferably, it is 55-90 degreeC.

  After the reaction, the adiabatic evaporated chloroform and the reaction product are recovered and cooled for reuse in the next stage. For condensation cooling of chloroform, a general-purpose external heat exchanger such as a shell and tube can be used.

  Although PDCB is also vaporized, the melting point of PDCB is 53 ° C., so it cannot be reduced to 53 ° C. or less in an environment where PDCB condenses alone. However, since chloroform functions as a solvent for PDCB, it has been experimentally confirmed that if chloroform is present, precipitation of PDCB does not occur even at around room temperature. It is not impossible to lower the temperature below 40 ° C.

  The direct cooling medium trichloromethane (chloroform) reacts with chlorine and is converted to tetrachloromethane. As a result, it is desirable to separate tetrachloromethane from trichloromethane and remove it from the system so that tetrachloromethane does not accumulate in the trichloromethane circulation system.

Next, operations desirable for process construction will be supplementarily described.
By-products (hydrocarbon compounds) and hydrogen chloride are contained in the reaction product in the reactor. Since the boiling point of hydrogen chloride is -85 ° C. and liquid recovery is extremely difficult, it is recovered as an aqueous solution. The concentration of hydrogen chloride to be recovered is preferably as high as possible, but if it is about 35% HCl, it can be easily recovered.

  That is, the reaction product in the reactor is sent to the hydrogen chloride removal tower, and hydrogen chloride and the hydrocarbon compounds accompanying it are separated from the top of the hydrogen chloride removal tower, and hydrogen chloride and a small amount of hydrocarbons accompanying it are separated. The compound is sent to the cooling tower, and in this cooling tower, the aqueous phase cooled by the attached condenser is sprayed into the tower and cooled, so that the water phase and the hydrocarbon compound are separated at the bottom of the cooling tower, A 35% aqueous HCl solution is obtained as the separated aqueous phase. The separated hydrocarbon compound is separated into water and a hydrocarbon compound by a subsequent separation tower, and the hydrocarbon compound is reused.

The reaction product collected at the bottom of the hydrogen chloride removing column can be commercialized by crystallizing the desired p-DCB while removing TCB, m-DCB, and o-DCB.
The liquid in the system can be returned to an appropriate position in the process and reused.

(First embodiment)
Next, an embodiment of the present invention will be described.
FIG. 1 shows a preferred embodiment of the present invention.
Reference numeral 10 denotes a reactor, which has a three-stage configuration in the embodiment. The benzene 1 as a raw material is supplied from the top of the first-stage reactor 10 after moisture is removed in advance by a moisture removing means (not shown) if necessary.
The chlorine gas 2 is supplied from the tops of the reactors 10, 10, 10 in each stage in parallel. Capacitors 12, 12, 12 are attached to each reactor 10, 10, 10. Chloroform (cooling medium) 3 is sent from the storage tank to the mixer 14, and is supplied from the top to the first stage reactor 10 by the pump 16. Further, the recovered chloroform 3A recovered in the subsequent step of the processing flow not shown in detail is supplied together with benzene 1 from the top of the first stage reactor 10. The mixer 14 is also supplied with recovered chloroform 3B recovered in a subsequent step of the processing flow, the details of which are not shown.
In each reactor 10, 10, 10, an alumina catalyst 18 (molded body) is installed as a fixed bed, and raw materials (benzene) and chlorine gas are circulated in a down flow. A cooling jacket 11 is provided on the peripheral wall of the reactor 10 and is cooled by a cooling medium such as water.

  The reaction product is sequentially led to the next reactors 10 and 10 by the pumps 20 and 20. In the reactor 10, the evaporated component is condensed by the condensers 12, 12, 12 and then sent to the reactors 10, 10 and the mixer 14 in the next stage. A part of a small amount of the reaction product that has not been condensed is sent to the cooling tower 24.

  The bottom component of the reactor 10 in the final stage is sent to the hydrogen chloride removing tower 22, and by lower heating, hydrogen chloride and the hydrocarbon compounds accompanying it are separated from the top of the hydrogen chloride removing tower 22, and this is separated. The cooling water is fed to the cooling tower 24, and the water phase cooled by the attached condenser 26 is sprayed into the cooling tower 24 by the pump 28 and cooled. Separate and obtain 35% aqueous HCl as the separated aqueous phase. The hydrocarbon compounds collected in the precipitation tank 30 provided at the bottom of the cooling tower 24 are separated into water and hydrocarbon compounds by a subsequent separation tower (not shown), and the hydrocarbon compounds are recycled. Use.

  The reaction product collected at the bottom of the hydrogen chloride removal tower 22 is then crystallized from the target p-DCB while removing TCB, m-DCB and o-DCB using an appropriate treatment means. Can be commercialized. Reference numeral 32 denotes a decompression pump.

(Second Embodiment)
FIG. 4 shows a second embodiment of the present invention.
The reactor 10 has a three-stage configuration. The benzene 1 as a raw material is supplied from the top of the first-stage reactor 10 after moisture is removed in advance by a moisture removing means (not shown) if necessary.
Chlorine gas 2 is supplied in excess from the top of reactor 10 in the final stage. In each reactor 10, 10, 10, an alumina catalyst 18 (molded body) is housed as a fixed bed, and raw materials (benzene), chlorine gas, and a cooling medium are circulated in a down flow. A cooling jacket 11 is provided on the peripheral wall of the reactor 10 and is cooled by a cooling medium such as water.

  The reaction product is sequentially led to the next reactors 10 and 10 by the pumps 20 and 20. In the reactor 10, the evaporation component (mainly the cooling medium) is condensed by the condensers 12, 12, 12 and then sent to the reactors 10, 10 and the mixer 14 in the next stage. Unreacted chlorine gas in the reactor 10 and / or hydrogen chloride produced by the reaction are supplied from the top of the reactor 10 in the preceding stage. A part of a small amount of the reaction product that has not been condensed and chloroform are sent to the cooling tower 24.

  The bottom components of the final stage reactor 10 and the subsequent flow of the uncondensed reaction product and chloroform sent to the cooling tower 24 are the same as those in the first embodiment.

(Third embodiment)
FIG. 5 shows a third embodiment of the present invention.
The reactor 10 has a two-stage configuration. The benzene 1 as a raw material is supplied from the top of the first-stage reactor 10 after moisture is removed in advance by a moisture removing means (not shown) if necessary.

  The chlorine gas 2 is supplied from the tops of the reactors 10 and 10 in each stage in parallel. Capacitors 12 and 12 are attached to each reactor 10 and 10. Chloroform (cooling medium) 3 is sent from the storage tank to the mixer 14, and is supplied from the top to the first stage reactor 10 by the pump 16. Further, the recovered chloroform 3A recovered in the subsequent step of the processing flow not shown in detail is supplied together with benzene 1 from the top of the first stage reactor 10. The mixer 14 is also supplied with recovered chloroform 3B recovered in a subsequent step of the processing flow, the details of which are not shown.

  The reaction product is sequentially led to unreacted substance separation towers 13 and 13 by pumps 20 and 20. In the reactor 10, the evaporation component (mainly the cooling medium) is condensed by the condensers 12, 12, and then sent to the reactor 10 and the mixer 14 in the next stage. A part of a small amount of the reaction product that has not been condensed and chloroform are sent to the cooling tower 24.

  In the unreacted substance separation tower 13, the unreacted substance in the previous stage and the hydrogen chloride accompanying it are separated from the tower portion of the unreacted substance separation tower 13 by lower heating. Further, after the vaporized component in the unreacted substance separation tower 13 is condensed by the condenser 15, the unreacted substance is returned to the previous reactor 10. Uncondensed hydrogen chloride and a small amount of unreacted material are sent to the cooling tower 24.

  In the cooling tower 24, the aqueous phase cooled by the attached condenser 26 is dispersed in the tower by the pump 28 and cooled, so that the cooling tower 24 separates the water phase and the chloroform phase, and the separated water phase is separated. A 35% aqueous HCl solution is obtained as the aqueous phase. The chloroform phase collected in the precipitation tank 30 provided at the bottom of the bottom of the cooling tower 24 is separated into water and chloroform by a subsequent separation tower (not shown), and the chloroform is reused.

  The cooling medium from the final stage of the reactor 10 is cooled by the condenser 12 and then led to the mixer 14 and can be used for supplying new chloroform.

  The reaction product collected at the bottom of the final stage unreacted substance separation column 13 is then subjected to removal of TCB, m-DCB, and o-DCB by using an appropriate treatment means, and the target p- DCB can be crystallized to produce a product.

(Fourth embodiment)
FIG. 6 shows a preferred embodiment of the present invention.
The reactor 610 has a three-stage configuration. The benzene 1 as a raw material is supplied to the first-stage reactor 610 after moisture is removed in advance by a moisture removing unit (not shown) if necessary.

  The chlorine gas 2 is supplied to the reactors 610, 610, and 610 of each stage. In each reactor 610, 610, 610, an alumina catalyst 618 is installed as a slurry bed. A cooling jacket 611 is provided on the peripheral wall of the reactor 610 so as to be cooled by a cooling medium such as water. Each reactor 610, 610, 610 is provided with a stirrer 617, 617, 617.

  The reaction products are sequentially led to separators 619, 619, 619 by pumps 20, 20, 20. Separators 619, 619, and 619 separate the reaction product and the alumina catalyst, and the separated alumina catalyst is returned to the preceding reactors 610, 610, and 610. The reaction product from which the alumina catalyst has been separated is supplied to the subsequent reactors 610 and 610 and the hydrogen chloride removing tower 22. Hydrogen chloride gas generated in each reactor 610, 610, 610 is sent to the next reactor 610, 610 or the cooling tower 24.

  In the hydrogen chloride removal tower 22, hydrogen chloride and a hydrocarbon compound accompanying the hydrogen chloride removal tower 22 are separated from the top of the hydrogen chloride removal tower 22 by lower heating, and this is sent to the cooling tower 24. The water phase cooled by the condenser 26 is sprayed into the tower by the pump 28 and cooled, so that the water phase and the hydrocarbon compound are separated in the cooling tower 24, and the separated water phase is 35%. An aqueous HCl solution is obtained. The hydrocarbon compounds collected in the precipitation tank 30 provided at the bottom of the bottom of the cooling tower 24 are separated into water and hydrocarbon compounds by a subsequent separation tower (not shown), and the hydrocarbon compounds are reused. To do.

  The reaction product collected at the bottom of the hydrogen chloride removal tower 22 is then crystallized from the target p-DCB while removing TCB, m-DCB and o-DCB using an appropriate treatment means. Can be commercialized.

(Examples 1 and 2 and Comparative Examples 1 and 2)
γ-alumina (nanoparticle gel, Example 1), γ-alumina (nanoparticle sol, Example 2), β zeolite (BEA, Comparative Example 1), and silica alumina (Comparative Example 2) were fixed to the reactor as catalysts. The interior was constructed as a floor, and p-DCB was produced by chlorination with chlorobenzene using benzene as a raw material according to the flow of FIG. The reaction conditions were a temperature of 80 ° C. and a pressure of 1.8 kg / cm ² , and dichlorobenzene yield and paraselectivity of dichlorobenzene were examined.

  The results of Example 1 and Comparative Examples 1 and 2 are shown in FIG. When γ-alumina (nanoparticle gel) was used as a catalyst, it was found that a yield of dichlorobenzene equivalent to that of BEA was obtained, and that the para selectivity was higher than that of BEA. A catalyst containing alumina and silica alumina widely used as a catalyst support have a low yield in this reaction system and are not suitable for use.

  A comparison of the results of Examples 1 and 2 is shown in FIG. It has been found that γ-alumina exhibits a high yield and para selectivity even when it is produced from either nanoparticle gel or nanoparticle sol.

  About Example 1, reaction for a total of 20 hours was performed intermittently and reaction stability was examined. As shown in FIG. 9, it was shown that the catalytic activity and reaction selectivity of γ-alumina (nanoparticle gel) were not deteriorated even after 20 hours of reaction.

(Comparative Example 3)
Showing a comparative example 3 using the homogeneous catalyst of ferric chloride FeCl ₃ is a conventional method. As a reaction apparatus, as shown in FIG. 10, a fully mixed reactor 50 with a jacket 51 and a stirrer 52 is used. To this, chlorine is supplied from a blower, benzene and FeCl ₃ are supplied, and a cooling water unit 53 supplies a jacket. The reaction is conducted while cooling through 51. The reaction product from the bottom was stored in the liquid storage tank 54 after cooling, and the gas liquid component from the top was stored in the gas liquid storage tank 55 after cooling.

The reaction conditions are as follows.
○ Catalyst FeCl ₃ concentration: 0.0088 catalyst mol / benzene mol
○ Raw material chlorine gas supply rate: 0.85 mol / benzene mol
○ Reaction temperature: 80 ℃

FIG. 11 shows the change in the product of chlorination of benzene in this reaction process, expressed as the reaction progress (degree of chlorination).
It can be seen from FIG. 11 that the homogeneous catalyst proceeds in a sequential and concurrent manner. This is probably because the homogeneous catalyst has no resistance to diffusion, and benzene and the Mono isomer, or the Mono isomer and the Di isomer reacted at the same time. Therefore, the Di body selectivity in the reaction remains at a maximum of 80%.

  FIG. 12 shows the change in the selectivity of PDCB in DCB accompanying the DCB yield, and FIG. 13 shows the transition of the PDCB yield accompanying chlorination. Since the homogeneous catalyst has no steric hindrance in the Ortho-Para orientation, the Para body selectivity is as low as 60% as shown in FIG. Further, since the Di isomer selectivity remains at a maximum of 80%, the maximum Para isomer yield in the reaction is 50% as shown in FIG.

  The experiment was conducted by reducing the reaction temperature from 80 ° C. under standard conditions to 70 ° C. The results are shown in FIG. It can be seen that the para-isomer selectivity does not change even when the reaction temperature is lowered.

  Next, the catalyst amount was changed from 0.0181 g-cat / g-Bz (0.0088 catalyst mol / benzene mol) to about 1/20 0.0010 g-cat / g-Bz (0.00049 catalyst mol / benzene). As a result, the activity was not changed, and it was clarified that the selectivity was arranged with a single curve as shown in FIG. 15 and the selectivity was not changed.

  As described above, it has been clarified that p-DCB cannot be produced with high selectivity as long as a homogeneous catalyst is used.

  According to the present invention, a compound having an extremely high industrial value can be continuously obtained as a raw material for PPS.

DESCRIPTION OF SYMBOLS 1 ... Benzene, 2 ... Chlorine gas, 10,610 ... Reactor, 11,611 ... Jacket, 12 ... Condenser, 13 ... Unreacted substance separation tower, 18 ... Alumina catalyst, 20 ... Pump, 22 ... Hydrogen chloride removal tower, 24 ... cooling tower, 26 ... condenser, 28 ... pump, 30 ... sedimentation tank, 32 ... vacuum pump, 617 ... stirrer, 619 ... separator.

Claims (11)

  In a method for producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, each reactor of a reactor having a plurality of stages containing a catalyst mainly composed of alumina contains chlorine gas. Supply in parallel, supply the raw material and chlorine gas to the first-stage reactor, supply the reaction product of the previous stage to the reactor of the next stage, supply chlorine gas to the reactors of the subsequent stage, in parallel, A process for producing parachlorobenzene, characterized in that paradichlorobenzene is obtained from the final stage reaction product.   In the method for producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, among the reactors having a plurality of stages containing a catalyst mainly composed of alumina, the raw material is provided in the first stage reactor. , Supply chlorine gas and / or unreacted chlorine gas in the subsequent stage, supply the reaction product in the previous stage to the reactor in the next stage, supply an excess amount of chlorine gas to the reactors in the subsequent stage and the final stage. A process for producing paradichlorobenzene, comprising obtaining paradichlorobenzene from a reaction product of   In a method of producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, among the reactors having a plurality of stages containing a catalyst mainly composed of alumina, the raw material is provided in the first stage reactor. , Supplying chlorine gas, separating the reaction product of the previous stage into unreacted raw material and product, returning the unreacted raw material to the reactor of the previous stage, supplying the product to the reactor of the next stage, A process for producing paradichlorobenzene, characterized in that chlorine gas is supplied to the reactor and paradichlorobenzene is obtained from the reaction product in the final stage.   The method for producing paradichlorobenzene according to any one of claims 1 to 3, wherein the reactor is a reactor in which a catalyst mainly composed of alumina is incorporated as a fixed bed.   The manufacturing method of the para dichlorobenzene of Claim 4 which distribute | circulates the said raw material and chlorine gas by a down flow.   The paradigm according to any one of claims 1 to 5, wherein at least one kind of cooling medium of chloromethane and chloroethane is introduced into each stage of the reactor, and the temperature of the chlorination reaction is suppressed by evaporating the cooling medium. A method for producing chlorobenzene.   The method for producing paradichlorobenzene according to any one of claims 1 to 6, wherein the evaporated gas content of the cooling medium is condensed outside the reactor, and the condensed liquid is reused as the cooling medium.   In the method of producing paradichlorobenzene by chlorinating with chlorine gas using at least one of benzene and monochlorobenzene as a raw material, the raw material and the chlorine gas are led to a reactor equipped with a catalyst mainly composed of alumina as a slurry bed. A method for producing paradichlorobenzene, which is characterized.   The method for producing paradichlorobenzene according to any one of claims 1 to 8, wherein the alumina is nano alumina having a high specific surface area.   The method for producing paradichlorobenzene according to claim 9, wherein the nanoalumina is produced from a nanoparticle gel and / or a nanoparticle sol. The method for producing paradichlorobenzene according to any one of claims 1 to 10, wherein the chlorination reaction is performed at a temperature of 40 to 130 ° C and a pressure of 10 atm or less.