TWI535683B - Preparation of p - dichlorobenzene - Google Patents

Description

Method for producing p-dichlorobenzene

The present invention relates to a method for producing p-dichlorobenzene, and more particularly to a catalyst comprising at least one of benzene (hereinafter also referred to as "Bz") and monochlorobenzene (hereinafter also referred to as "MCB"). A method of producing p-dichlorobenzene (hereinafter also referred to as "p-DCB" or "PDCB") by chlorination of chlorine as a catalyst. In the present specification, "zeolite catalyst" means "zeolite-containing catalyst".

p-DCB is a compound that is a raw material for medicines and pesticides, and is itself a pesticide and an insecticide, and is a material of high value for polyphenylene sulfide (PPS).

Previously, p-DCB has been known to produce a liquid phase chlorination of benzene and/or monochlorobenzene using a Lewis acid such as ferric chloride or antimony pentachloride as a catalyst. The activity of ferric chloride is high, and the chlorine conversion rate is 99.99% or more, and the unreacted chlorine gas in the by-produced hydrochloric acid gas is extremely small. However, the selectivity of the target para-substituent is about 60% when the catalyst is used alone, and is increased to about 75% after the addition of the accelerator.

In recent years, as a method of producing p-DCB in such a manner that the selectivity is 90.4% or more, as disclosed in Patent Document 1 or Patent Document 2, a method using L-type zeolite as a catalyst is disclosed. However, it is generally believed that the method of using zeolite as a catalyst is a laboratory-level method and is not a specific method that can be used as an actual device.

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 63-12450

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2001-213815

[Non-patent literature]

[Non-Patent Document 1] Masahiro Asaoka "Surface Design and Preparation Method of Nanoparticles Catalyst Catalysts", Chemical Engineering, April 2008, pp. 286-289

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for obtaining a target at a higher yield than before when operating p-DCB as a practical device, and which can be stably operated.

Other issues can be clarified by the following description.

The present invention for solving the problem is as follows.

[Invention of Patent Application No. 1]

A method for producing p-dichlorobenzene, which is produced by chlorinating at least one of benzene and monochlorobenzene, and is characterized in that: the raw material and the chlorine gas are introduced into a zeolite-containing catalyst. In the reactor as a fixed bed, the above-mentioned catalyst is obtained by molding a zeolite with a molding base containing an alumina sol as a main component.

[Invention of Patent Application No. 2]

A method for producing p-dichlorobenzene, which is produced by chlorinating at least one of benzene and monochlorobenzene, and is characterized by: a reactor having a plurality of stages containing a zeolite catalyst; The first stage reactor supplies the above raw materials, chlorine gas and/or unreacted chlorine gas in the latter stage, and supplies the reaction product of the preceding stage to the secondary reactor, and supplies the excess chlorine gas to the reactor after the second stage, and the reaction of the last stage is formed. Obtained p-dichlorobenzene.

[Invention of Patent Application No. 3]

A method for producing p-dichlorobenzene, which is produced by chlorinating at least one of benzene and monochlorobenzene, and is characterized by: a reactor having a plurality of stages containing a zeolite catalyst; The first stage reactor supplies the above raw materials, chlorine gas, and separates the reaction product of the previous stage into unreacted raw materials and products, and the unreacted raw materials are returned to the front stage reactor, and the product is supplied to the secondary reactor, and the reactor after the second stage is Chlorine gas is supplied, and p-dichlorobenzene is obtained from the reaction product of the last stage.

[Invention of Patent Application No. 4]

A method for producing p-dichlorobenzene, which is produced by chlorinating at least one of benzene and monochlorobenzene, and is characterized in that: the raw material and the chlorine gas are introduced into a zeolite-containing catalyst. In the reactor as a slurry bed.

[Invention of Patent Application No. 5]

The method for producing p-dichlorobenzene according to any one of claims 1 to 3, wherein at least one cooling medium of methyl chloride and ethyl chloride is introduced into each stage of the reactor to evaporate the cooling medium to suppress The temperature of the above chlorination reaction rises.

[Invention of Patent Application No. 6]

The method for producing p-dichlorobenzene according to the fifth aspect of the invention, wherein the evaporation gas component of the cooling medium is condensed outside the reactor, and the condensate is reused as the cooling medium.

[Invention of Patent Application No. 7]

A method for producing p-dichlorobenzene according to the second or third aspect of the invention, wherein the zeolite-containing catalyst is contained in the reactor as a fixed bed.

[Invention of Patent Application No. 8]

The method for producing p-dichlorobenzene according to any one of claims 2 to 4, wherein the zeolite-containing catalyst is obtained by molding a molding base containing zeolite as a main component of an alumina sol.

[Invention of claim 9]

The method for producing p-dichlorobenzene according to any one of claims 1 to 4, wherein the zeolite is a proton-type zeolite.

[Invention of Patent Application No. 10]

The method for producing p-dichlorobenzene according to any one of claims 1 to 4, wherein the zeolite is a zeolite beta.

[Invention of Patent Application No. 11]

The method for producing p-dichlorobenzene according to any one of claims 1 to 4, wherein the zeolite is an MFI zeolite.

[Invention of Patent Application No. 12]

The method for producing p-dichlorobenzene according to any one of claims 1 to 3, wherein the raw material and the chlorine gas are passed through a downflow.

[Invention of claim 13]

The method for producing p-dichlorobenzene according to any one of claims 1 to 4, wherein the chlorination reaction is carried out at a temperature of 40 to 130 ° C and a pressure of 10 atm or less.

[Invention of Patent Application No. 14]

The method for producing p-dichlorobenzene according to the first aspect of the invention, wherein the reactor has a plurality of stages, chlorine gas is supplied to each reactor in parallel, and the raw material and chlorine gas are supplied to the first stage reactor, and the reaction of the preceding stage is carried out. The product is supplied to the secondary reactor, and the reactor is supplied in parallel to the reactor after the second stage, and p-dichlorobenzene is obtained from the reaction product of the last stage.

[Invention of Patent Application No. 15]

The method for producing p-dichlorobenzene according to item 4 of the patent application, wherein the reactor has a plurality of stages, the first stage reactor is supplied with the raw material, chlorine gas, and the reaction product of the preceding stage is supplied to the second stage reactor, and The reactor after the second stage supplies chlorine gas in parallel, and p-dichlorobenzene is obtained from the reaction product of the last stage.

According to the present invention, it is possible to eliminate the disadvantages of the low selectivity of the p-DCB and the burden of the separation and recovery of the catalyst which are present in the homogeneous catalyst such as the ferric chloride of the prior art, and can be operated as an actual device. Runs steadily.

(the basic idea of the invention)

As described above, by using a homogeneous catalyst such as ferric chloride, not only the selectivity of p-DCB is low, but also the burden of the device for separating and recovering the catalyst becomes large. The present invention can increase the selectivity of p-DCB by using a zeolite catalyst, and can be reused by using a solid catalyst.

Further, as described above, the chlorination reaction is a severe exothermic reaction. Incidentally, if heat is not removed, the temperature is easily raised to 400 to 500 °C. Therefore, it is necessary to accurately suppress the temperature rise and maintain the operation within a certain temperature range. If the temperature is too low, the viscosity becomes high and the pressure loss increases. On the other hand, when it is at a high temperature, the chlorine gas dissolves to determine the reaction rate and suppress the reaction. Further, the boiling point of benzene is 80.1 ° C, and of course the reaction is inhibited under conditions in which benzene is evaporated. The reaction pressure must be determined in such a manner that an appropriate reaction temperature (reaction rate) can be maintained.

As a method of suppressing the exothermic reaction, there is a method of providing a cooling unit in a reactor such as a jacket or a coil, and a method of suppressing temperature rise by using a large amount of solvent (the candidate solvent may be considered as 1, 2 - 2) Ethyl chloride or MCB); and a method in which a cooling portion and a solvent are used in combination; of course, these methods can also be used. However, under the preferred reaction conditions (40 to 130 ° C, 10 atm or less), the gas-liquid mixed phase state is obtained, but the overall heat transfer rate of the reaction portion - the metal portion - the cooling portion is overwhelmed by the gas phase volume and the liquid phase volume. The advantage of the property, the thermal conductivity of the reaction part becomes the decisive factor, the total thermal conductivity is only about 10 ~ 30kcal / m ² hr ° C, under this condition must have a huge heat transfer area, specifically as a reactor has its difficulties.

Therefore, in the present invention, as a more preferable condition, a direct cooling method using the latent heat of vaporization of the cooling solvent is proposed. By allowing a compound having a boiling point equivalent to the reaction conditions to be present in the reaction system, the latent heat of vaporization accompanying evaporation of the compound is transferred to the compound, whereby the large heat of reaction generated can be absorbed.

The evaporated compound is condensed and reused, and when condensing, a general-purpose external heat exchanger which can ensure a total thermal conductivity of 600 to 1100 kcal/m ² hr ° C, such as a shell and tube, can be used.

The compound which can be utilized as such a direct cooling medium can be used as a condition for not reacting, and is suitable for the chlorination reaction of p-DCB synthesis, methylene chloride (Tb40.2 ° C), chloroform (Tb61.1). °C), chloroforms such as tetrachloromethane (Tb76.8 ° C), 1,1-dichloroethane (Tb 57 ° C), 1,1,1-trichloroethane (Tb 73.9 ° C), etc. class. Considering the desired reaction temperature, benzene and the boiling point of the direct cooling medium, stable temperature management can be achieved by selecting suitable pressure conditions.

In the procedure described below, the description is made by using an example of chloroform (alias: chloroform) having a boiling point of 61 ° C at normal pressure, but other chloromethane or chloroethane may be used, and it has also been confirmed. These can be used in a plurality of types.

Further, in the present invention, benzene and/or chlorobenzene and chlorine gas are used, and the above direct cooling medium (chloroform in the following examples) is used. After finishing it, it is as follows.

1) Raw materials and raw materials impurities: benzene, chlorobenzene, chlorine

2) Solvents ‧ solutions and impurities: chloroform, water

3) Reaction product: monochlorobenzene, dichlorobenzene, trichlorobenzene, hydrogen chloride

In consideration of the above components, appropriate separation means are combined to obtain the target p-dichlorobenzene.

When an example of a reaction formula is shown, it is as follows.

Bz(C ₆ H ₆ )→MCB(C ₆ H ₅ Cl)→PDCB, MDCB, ODCB (pC ₆ H ₄ Cl ₂ , oC ₆ H ₄ Cl ₂ , mC 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 →pC ₆ H ₄ Cl ₂ +HCl (2)

C ₆ H ₅ Cl+Cl ₂ →oC ₆ H ₄ Cl ₂ +HCl (3)

C ₆ H ₅ Cl+Cl ₂ →mC ₆ H ₄ Cl ₂ +HCl (4)◇

pC ₆ H ₄ Cl ₂ +Cl ₂ →C ₆ H ₃ Cl ₃ +HCl (5)

oC 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 chlorination reaction which may become an undesirable side reaction is as follows.

Formation of tetrachlorocyclohexene and hexachlorobenzene by chlorination of benzene:

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 hexachlorobenzene produced by undesired side reactions may become poisonous substances of the catalyst, and there is a concern that the catalyst is deteriorated.

Further, it is considered that a trace amount of moisture in the present reaction is necessary for the ionic reaction in the zeolite catalyst. However, exceeding the required amount of moisture causes corrosion of the device, and, in connection with the reaction, there is also a possibility that the reactivity is lowered and by-products are formed. Therefore, it is desirable to appropriately adjust the moisture in the raw material.

(Preferred form of zeolite catalyst)

A zeolite-containing catalyst is used in the present invention. Examples of the zeolite include erionite having a small pore diameter, offretite, ferrierite, a medium pore size L-form, ZSM-5 (MFI), and MCM-22 ( MWW), a large pore size type β (BEA), mordenite (MOR), X type, T type (FAU), etc., may be used. It is preferred to use a medium pore size type L type, ZSM-5 (MFI), MCM-22 (MWW), a large pore size type β type (BEA), a mordenite (MOR), an X type, a T type ( FAU), Y type (USY).

Zeolite monomer can not be formed, will become about 500 diameter Tiny powder. When used in a slurry bed, the zeolite catalyst of the present invention can also be used in the form of a powder, and can be used as a molded body to be granulated to have a diameter of 0.8 to 3.2 mm. Further, it may be molded into a special type such as a ring shape, a quadlobes shape, or a rib ring shape as needed. When it is considered that the zeolite catalyst is recovered after use and reused, it is preferably used to form a molded body which is more easily recovered. As the molding base material (forming aid) for molding the zeolite, for example, a niobium oxide aerosol having a nanoparticle size, an alumina sol or the like can be used, and it is particularly preferable to use an alumina sol alone. The proton-type BEA was formed by alumina sol and cerium oxide sol, respectively, and the yield and the selectivity of the DCB of the formed catalyst were compared. As a result, it was found that although the selectivity of the para-form was not observed, Large differences, but by the catalyst formed by alumina sol, a high yield can be stably obtained for a relatively long period of time (Fig. 3). As for the formation of zeolite, it has been previously carried out by a cerium oxide sol, which is preferable because it is difficult to form a new ion exchange point on the surface of the zeolite and does not hinder the reaction specificity of the zeolite. However, in the reaction of the present embodiment, by using an alumina sol, the selectivity of the counter body is not lowered, and the stability of the catalyst itself is improved. This suggests that the above reaction does not occur only in the pores of the zeolite, but also occurs at the ion exchange point formed by the alumina on the surface of the shaped catalyst. If the reaction occurs only in the pores of the zeolite, the catalyst may be deteriorated due to clogging of the pores, and if it is a reaction of the catalyst surface, the deterioration rate may be lower than before.

If the alumina on the surface of the zeolite is the ion exchange point as described above, the necessity of using no zeolite may be omitted. However, if the same reaction was carried out using a cerium oxide-alumina catalyst, the yield became very low, indicating that the catalyst activity was very low (Fig. 4). Also, the selectivity to the parasite is lower than when using zeolite. From this, it was found that in the production of p-DCB, in order to maintain a high yield and selectivity to the catalyst of alumina, it is necessary to use a specific skeleton of the zeolite as a carrier. Non-Patent Document 1 discloses that the activity of alumina can be increased by utilizing the structure of zeolite.

The zeolite framework varies greatly depending on the type of zeolite. Comparing the activities of ZSM-5 (MFI), β-type (BEA), Y-type (USY) alumina sol forming catalysts, which are typically used as medium pore size, large pore size zeolites, in zeolites, As a result, it was found that, as shown in Fig. 5, the DCB yield was low when USY was used (due to the large amount of TCB (not shown) generated in the side reaction), and the higher DCB yield was obtained when BEA and MFI were used. It is suggested that the difference in surface structure caused by the framework structure of the zeolite affects the catalytic activity of alumina. In the present invention, it can be said that it is particularly preferable to use ZSM-5 (MFI) or β type (BEA).

The molding base containing alumina as a main component is selected in an amount of 10% by weight to 50% by weight based on the total amount of the catalyst, and preferably 15% by weight to 35% by weight. If it is less than 10% by weight, the catalytic activity becomes low, and the binding property of the zeolite to the molding base deteriorates. If it is 50% by weight or more, the amount of the contact medium will be larger than necessary, and the characteristics of the above zeolite skeleton will not occur, and the catalytic activity will still be low.

The zeolite catalyst of this form is more preferably a proton type. This is due to the knowledge that if the ion exchange point of the zeolite is replaced with a metal cation, for example, a sodium ion, the initial activity is improved, but the catalytic activity is rapidly decreased in a short time (not shown). .

(Other forms of zeolite catalyst)

Hereinafter, a zeolite catalyst which does not use a molding base containing alumina as a main component is disclosed. In the present embodiment, a zeolite obtained by replacing an ion exchange point with a metal cation is used.

In the present embodiment, at least a part of the ion exchange point of the zeolite is used in a state occupied by a metal cation, preferably a sodium cation. In particular, when at least 10% or more, preferably 10% or more and 85% or less of the ion exchange point of the zeolite of the molding catalyst containing zeolite as a main component is occupied by the metal cation, the effect is large (Fig. 6). When the proportion of the metal cation is less than 10%, the efficiency of the above chlorination reaction is lowered, or the side reaction is increased.

In order to achieve a state in which at least a part of the ion exchange point of the zeolite is occupied by a metal cation, particularly a sodium cation, it can be used by ion exchange by a known method. When the ion exchange is a sodium cation, it is usually carried out by a plurality of ion exchange operations using an aqueous solution of a sodium salt, preferably an aqueous sodium chloride solution.

Further, it was found that when it is a homogeneous catalyst such as ferric chloride, the reaction proceeds not only gradually but also concurrently, whereas in the case of a zeolite catalyst, almost 100% of the reaction proceeds stepwise (Fig. 7). It is generally considered that when it is a homogeneous catalyst, at the stage of benzene residue, the monomer or dimer as a product reacts with the catalyst to form a complex with the catalyst, and in contrast, it is a zeolite touch. In the case of the medium, the reaction proceeds successively in the order of the ease of diffusion of the benzene, the monomer, the dimer, the tris, and the tetramer due to the resistance of the diffusion of the reactive molecules.

By comparing the molding catalysts containing the two kinds of zeolite as main components, it was found that the performance of the catalyst containing ZSM-5 (MFI) zeolite as a main component is insufficiently exhibited in the flow system, and the β type The zeolite is more excellent.

As for the resistance of the diffusion of the zeolite catalyst selected for the purpose of improving selectivity, it is required to significantly reduce the activity in a flow system which is required to be stably used in a reactor in which a catalyst is formed. Moreover, the result of the flow pattern of the reactor in which the molding catalyst containing β-type zeolite as a main component is contained is compared with the result of the batch type of the slurry reactor by powdering the molding catalyst, and the result is compared. It was found to be superior in both activity and selectivity.

The β-type zeolite which is a molding catalyst containing zeolite as a main component in the reactor preferably has a SiO ₂ /Al ₂ O ₃ ratio of 14 or more and 100 or less (more preferably 16 to 50). It is considered that if it is less than 14, octahedral aluminum may be present on the surface of the zeolite crystal or on the outer surface of the particle, which may form non-selective chlorination, either alone or in combination with a functional group present on the surface of the zeolite. The acid point of various strengths on the outer surface of the zeolite subjected to the reaction, that is, the metal (sodium) cation exchange point, or the alkali point at which the chlorination reaction proceeds, is not preferable. Moreover, when it is more than 100, the concentration of the active point in the pores of the zeolite becomes low, the diffusion distance becomes long, the reaction proceeds to the three bodies, and the diffusion of the raw material molecules in the pores is hindered by the product retention. Thereby hindering the progress of the target reaction.

Further, in order to carry out the ion exchange operation for a plurality of times in order to carry out the ion exchange to a target level for a short period of time, it is preferred to carry out the exchange of the aqueous solution of the sodium salt. Further, in the final operation, a method in which the pH of the solution side is completed on the acidic side and the adhered sodium chloride is washed and removed is selected. The concentration or amount of the aqueous solution of sodium chloride and the number of times of the ion exchange operation at this time can be appropriately selected.

However, it is considered that a state in which at least a part of the ion exchange point of the zeolite is occupied by the sodium cation is a point at which sodium ion can be ion-exchanged by sodium chloride. As such a point, it is generally considered to be a strong acid which exhibits strong acidity when formed into a proton type.

Incidentally, in the state of producing the zeolite catalyst of the present form, it is effective to form a zeolite or a molding catalyst containing zeolite as a main component into a proton type, and then to be strong by a metal, particularly sodium. The acid salt undergoes ion exchange to form at least 10% of the ion exchange point occupied by the sodium cation.

Further, in the case of producing the zeolite catalyst of the present embodiment, a matrix which does not form a new ion exchange point with the zeolite is preferred. As such a preferred substrate, for example, a nanoparticle size cerium oxide aerosol or the like can be used alone. If a plurality of molding bases are used at the same time, a new ion exchange point can be formed on the surface of the zeolite, which may adversely affect the activity of the catalyst. Further, since the zeolite is mainly composed of SiO ₂ , it is preferred to use SiO ₂ as a molding aid. It is also possible to use SiO ₂ as a forming aid after removing Al on the surface of the zeolite by an acid treatment.

The role as a molding base must be supplied to the molded body without impairing the catalytic properties of the zeolite and has an industrially usable strength. The amount of the molding base is from 10% by weight to 50% by weight, preferably from 15% by weight to 35% by weight. If it is less than 10% by weight, the binding property of the zeolite to the molding base is deteriorated. If it exceeds 50% by weight or more, the volume of the catalyst exceeds the necessary amount, and it is easily affected by the difficulty in reaching the diffusion point of the zeolite to the active site of the zeolite.

(summary of reaction device)

In the present invention, the zeolite catalyst is contained in the reactor. Since the zeolite catalyst is deteriorated, the reactor is preferably divided into a plurality of stages (lowest 2 stages) and used interchangeably. The zeolite catalyst can be used as a fixed bed to pass the raw material and the chlorine gas stream, and can also be used as a slurry bed (Fig. 11). By using a zeolite catalyst as a slurry bed, it is possible to efficiently suppress temperature rise and maintain operation in a certain temperature range.

When the catalyst is used as a fixed bed, the above-mentioned raw materials and chlorine gas may flow through the upward flow (Fig. 2), and more preferably flow through the downflow (Fig. 1). If it flows through the ascending flow, the reaction in the reactor becomes a continuous phase of the solution, causing the chlorine gas to dissolve into the solution to determine the reaction rate or cause the reverse mixing of the reaction product in the solution, but the reaction is caused by the downflow. The inside of the device becomes a continuous phase of gas, whereby the above problem can be solved.

In this case, it is desirable to ensure uniform dispersion of the gas phase centered on the chlorine gas and the liquid phase, and to eliminate the reverse mixing. The flow pattern of the gas-liquid mixed phase flow will vary depending on the reactor diameter employed. The flow pattern that can be used is the Pulsing and Foaming Flow or the Gas-continuous or Tricking Flow, and the ideal is the perfusion flow. The so-called pulsating flow is a state in which a large portion of a liquid hold-up alternates with a small portion, and the liquid of the liquid flow flows down from the catalyst particles by gravity, and the gas becomes a continuous phase. And the state of flowing through the space. As the flow velocity of the gas-liquid mixed phase flow becomes larger, the flow form changes from the pulsating flow to the perfusion flow.

Further, the number of stages of the fixed bed of the reactor has a plurality of stages, preferably three stages. When the deterioration of the solid catalyst is large, the active point due to the inflow of the substance causing the deterioration from the inlet portion disappears. As a countermeasure against this, the fixed bed can be connected in series by three independent grooves, and if it is deteriorated, the connection can be exchanged and used cyclically. The amount of chloroform added can also be used alternately by setting it as a plurality of stages, and the amount of chloroform circulating in the system can be suppressed.

As the reaction temperature, if the temperature is too low, the viscosity becomes high and the pressure loss increases. On the other hand, when the temperature is high, the chlorine gas dissolves to determine the reaction rate and suppress the reaction. Therefore, the reaction temperature is preferably 40 to 130 ° C, more preferably 55 to 90 ° C.

As the reaction pressure, as shown in Fig. 8 in which the reaction temperature is set to 80 ° C, it is preferable that the amount of chloroform added or the liquid phase recovery of PDCB is 950 to 1450 Torr (if 55 to 90 ° C). The same is true within the scope).

According to Fig. 8, the following judgment can be made. That is, (1) once the operating pressure is high, the reaction temperature cannot be maintained unless the chloroform/benzene ratio is increased; (2) chloroform does not evaporate at a pressure higher than the operating temperature, and a large amount is required to maintain the temperature. Chloroform; (3) Conversely, below the pressure of a certain operating temperature, chloroform is completely evaporated. At this time, PDCB is similarly evaporated; (4) Therefore, it is preferred that the conditions of chloroform or PDCB remain at the bottom of the reactor are appropriate. The recovery of chloroform or PDCB does not operate in a region where chloroform/benzene ratio is greatly affected, and it is preferable that the chloroform/benzene ratio is 16 to 20 and the PDCB recovery rate is 90 to 95%.

After the reaction, in order to recover the chloroform and the reaction product which are adiabatically evaporated, they are reused in the second stage to be cooled. In order to condense and cool the chloroform, a general-purpose external heat exchanger such as a shell tube can be used.

Although PDCB is also gasified, the melting point of PDCB is 53 ° C, so the environment in which PDCB is condensed alone cannot be set to 53 ° C or less. However, since chloroform exerts a function as a solvent for PDCB, if chloroform is present, it is experimentally confirmed that PDCB does not precipitate even in the vicinity of normal temperature. It is not impossible to drop below 40 °C.

The direct cooling medium of chloroform (chloroform) is converted to tetrachloromethane by reaction with chlorine. As a result, tetrachloromethane is not retained in the chloroform cycle system, and it is desirable to separate and remove chloroform from chloroform to the outside of the system.

In turn, a more detailed description of the preferred operation in the process construction is provided.

The reaction product of the reactor contains by-products (hydrocarbon compounds) and hydrogen chloride. Hydrogen chloride has a boiling point of -85 ° C and is extremely difficult to recover in liquid form and is therefore recovered as an aqueous solution. The concentration of hydrogen chloride recovered is preferably as high as possible, but can be easily recovered if it is 35% HCl.

That is, the reaction product in the reactor is sent to a hydrogen chloride removal column, and hydrogen chloride and a hydrocarbon compound accompanying it are separated from the top of the hydrogen chloride removal column, and hydrogen chloride and a small amount of a hydrocarbon compound accompanying the same are sent to a cooling tower for cooling. In the column, the water phase cooled by the attached condenser is dispersed in a column for cooling, thereby separating into an aqueous phase and a hydrocarbon compound at the bottom of the cooling tower, and the separated aqueous phase component can obtain a 35% aqueous HCl solution. The separated hydrocarbon compound is separated into water and a hydrocarbon compound by a later stage separation column, and is reused for the hydrocarbon compound.

For the reaction product collected at the bottom of the hydrogen chloride removal column, the target p-DCB can be crystallized and productized while removing TCB, m-DCB, and o-DCB.

In addition, the liquid in the system can be returned to the appropriate location within the process for reuse.

(First embodiment)

Next, an embodiment of the present invention will be described.

Fig. 1 shows a first embodiment of the present invention.

10 is a reactor, and in the embodiment, it has a three-stage configuration. The benzene 1 of the raw material is supplied from the top of the reactor 1 of the first stage after the water is removed in advance by a water removing means (not shown).

Chlorine gas 2 is supplied in parallel from the tops of the respective stages of reactors 10, 10, 10 to the respective stages of reactors 10, 10, 10. Condenators 12, 12, 12 are attached to each of the reactors 10, 10, 10. The chloroform (cooling medium) 3 is sent from the storage tank to the mixer 14, and is supplied from the top of the first stage reactor 10 to the first stage reactor 10 by the pump 16. Further, the recovered chloroform 3A recovered in the subsequent steps of the process flow not shown in detail is supplied from the top of the first-stage reactor 10 together with benzene 1. Further, the recovered chloroform 3B recovered in the subsequent step of the process flow not shown in detail is supplied to the mixer 14.

Each of the reactors 10, 10, and 10 contains a zeolite catalyst 18 (molded body) as a fixed bed, and the raw materials (benzene) and chlorine gas are circulated by flowing down. 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 introduced into the secondary reactors 10, 10 in sequence by pumps 20, 20. The evaporated components in the reactor 10 are condensed by the condensers 12, 12, and 12, and sent to the secondary reactors 10, 10 and the mixer 14. A portion of the unreacted small amount of reaction product is sent to the cooling tower 24.

The bottoms component of the last stage reactor 10 is sent to a hydrogen chloride removal column 22, and hydrogen chloride and associated hydrocarbon compounds are separated from the top of the hydrogen chloride removal column 22 by lower heating and sent to a cooling tower 24 for cooling. In the column 24, the water phase component cooled by the attached condenser 26 is dispersed in the column by the pump 28 for cooling, thereby separating into an aqueous phase and a hydrocarbon compound in the cooling tower 24, the separated aqueous phase. The ingredients obtained a 35% aqueous HCl solution. The hydrocarbon compound collected in the precipitation tank 30 provided at the lower portion of the bottom of the cooling tower 24 is separated into water and a hydrocarbon compound by a downstream separation column (not shown), and is reused for the hydrocarbon compound.

The reaction product collected at the bottom of the hydrogen chloride removal column 22 is then subjected to crystallization, and the target p-DCB is crystallized and processed by using appropriate treatment means to remove TCB, m-DCB, and o-DCB. Further, reference numeral 32 is a decompression pump.

(Second embodiment)

Fig. 9 shows a second embodiment of the present invention.

In the process for producing p-dichlorobenzene by chlorination of chlorine with benzene as a raw material, the reaction rate of monochlorobenzene as a reaction intermediate with chlorine gas is slower than that of benzene and chlorine (Fig. 12). Therefore, the amount of catalyst required is relatively large. This will result in a larger reactor filled catalyst and an increased investment in equipment.

Therefore, the second embodiment is a novel proposal for a method of supplying chlorine gas. Specifically, the method for producing p-dichlorobenzene is as follows: the reactor has a plurality of stages, and the first stage reactor is supplied with the raw material, the cooling medium, the chlorine gas, and/or the unreacted chlorine gas in the latter stage, and the reaction product of the preceding stage is supplied. In the sub-stage reactor, a cooling medium and an excess amount of chlorine gas are supplied to the reactor after the second stage, and crude dichlorobenzene is obtained from the final stage reaction product. By this method, the reaction rate of monochlorobenzene with chlorine gas can be increased (Fig. 12).

Further, when an excessive amount of chlorine gas is supplied, in the case of a homogenous catalyst of the prior art, dichlorobenzene containing p-dichlorobenzene as a target product is reacted with an excessive amount of chlorine gas to form trichlorobenzene, but in the present invention The formation of trichlorobenzene can be suppressed by using a zeolite catalyst. As shown in Fig. 13, even if p-dichlorobenzene is produced under conditions of Cl _{2 /} MCB = 1.0 or more, the chlorination degree of the reaction product is stopped at about 2.0, thereby suppressing the synthesis reaction of trichlorobenzene.

The reactor 10 of Fig. 9 has a three-stage configuration. The benzene 1 of the raw material is supplied from the top of the reactor 1 of the first stage, as long as it is necessary to remove water in advance by a water removing means (not shown).

Chlorine 2 is supplied in excess from the top of the last stage reactor 10. Each of the reactors 10, 10, and 10 contains an alumina catalyst 18 (molded body) as a fixed bed, and the raw materials (benzene), chlorine gas, and cooling medium are circulated by downflow. 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 introduced into the secondary reactors 10, 10 in sequence by pumps 20, 20. The evaporated components (mainly the cooling medium) in the reactor 10 are condensed by the condensers 12, 12, and 12, and sent to the secondary reactors 10, 10 and the mixer 14. The hydrogen chloride which is not reacted with chlorine gas and/or reacted in the reactor 10 is supplied from the top of the reactor 10 of the preceding stage. A portion of the unreacted small amount of the reaction product is sent to the cooling tower 24 with chloroform.

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

(Third embodiment)

Fig. 10 shows a third embodiment of the present invention.

The third embodiment is a novel proposal for a method of supplying a raw material to each stage. Specifically, the following method for producing p-dichlorobenzene: the above reactor has a plurality of stages, and the first stage reactor is supplied with the above raw materials, chlorine gas and/or a cooling medium, and the reaction product of the preceding stage is separated into unreacted raw materials and products. The unreacted raw material is returned to the front stage reactor, the product is supplied to the second stage reactor, and the chlorine gas and the cooling medium are supplied to the reactor after the second stage, and p-dichlorobenzene is obtained from the reaction product of the last stage.

By this method, the selectivity of the para-substrate in the reaction product can be improved as compared with the method of not supplying the reaction product of the first stage to the sub-stage reactor (Fig. 14).

The reactor 10 of Fig. 10 is constructed in two stages. The benzene 1 of the raw material is supplied from the top of the reactor 1 of the first stage, as long as it is necessary to remove water in advance by a water removing means (not shown).

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

The reaction product is introduced into the unreacted material separation columns 13, 13 in order by the pumps 20, 20. The evaporated component (mainly the cooling medium) in the reactor 10 is condensed by the condensers 12, 12, and sent to the secondary reactor 10 and the mixer 14. A portion of the unreacted small amount of the reaction product is sent to the cooling tower 24 with chloroform.

In the unreacted material separation column 13, the unreacted material in the preceding stage and the accompanying hydrogen chloride are separated from the column portion of the unreacted material separation column 13 by the lower portion heating. Further, the evaporated component in the unreacted material separation column 13 is condensed by the condenser 15, and the unreacted material is returned to the front stage reactor 10. A portion of the uncondensed hydrogen chloride and a small amount of unreacted material is sent to the cooling tower 24.

In the cooling tower 24, the water phase component cooled by the attached condenser 26 is dispersed in the tower by the pump 28 for cooling, thereby separating into an aqueous phase and a chloroform phase in the cooling tower 24, which is separated. The aqueous phase component gave a 35% aqueous HCl solution. The chloroform phase collected in the sedimentation tank 30 provided in the lower portion of the bottom of the cooling tower 24 is separated into water and chloroform by a downstream separation column (not shown), and is reused for chloroform.

The cooling medium from the last stage of the reactor 10 is cooled by the condenser 12 and introduced to the mixer 14 for supply of fresh chloroform.

For the reaction product collected at the bottom of the unreacted material separation column 13 in the last stage, the target p-DCB can be crystallized and productized by using appropriate treatment means to remove TCB, m-DCB, and o-DCB. .

(Fourth embodiment)

Fig. 11 shows a fourth embodiment of the present invention.

The reactor 10 has a three-stage configuration. The benzene 1 of the raw material is supplied to the first-stage reactor 10 as long as it is necessary to remove water in advance by a moisture removal means (not shown).

Chlorine 2 is supplied to each of the reactors 10, 10, and 10. Each of the reactors 10, 10, 10 contains an alumina catalyst 18 as a slurry bed. A cooling jacket 11 is provided on the peripheral wall of the reactor 10, and is cooled by a cooling medium such as water. Mixers 17, 17, and 17 are attached to each of the reactors 10, 10, and 10.

The reaction product is introduced into the separators 19, 19, 19 in sequence by pumps 20, 20, 20. The separation product 19, 19, 19 is separated into a reaction product and an alumina catalyst, and the separated alumina catalyst is returned to the front stage reactors 10, 10, and 10. The reaction product from which the alumina catalyst is separated is supplied to the secondary reactors 10, 10 and the hydrogen chloride removal column 22. The hydrogen chloride gas generated in each of the reactors 10, 10, 10 is sent to the secondary reactors 10, 10 or the cooling tower 24.

In the hydrogen chloride removal column 22, the hydrogen chloride and the accompanying hydrocarbon compound are separated from the top of the hydrogen chloride removal column 22 by heating in the lower portion, and sent to the cooling tower 24, in which the auxiliary condensation is carried out. The water phase component cooled by the unit 26 is dispersed in the column by the pump 28 for cooling, thereby separating into an aqueous phase and a hydrocarbon compound in the cooling tower 24, and the separated aqueous phase component can obtain a 35% aqueous HCl solution. The hydrocarbon compound collected in the precipitation tank 30 provided in the lower portion of the bottom of the cooling tower 24 is separated into water and a hydrocarbon compound by a downstream separation column (not shown), and can be reused for the hydrocarbon compound.

For the reaction product collected at the bottom of the hydrogen chloride removal column 22, the target p-DCB is crystallized and productized by removing TCB, m-DCB, and o-DCB using an appropriate treatment means.

[Examples]

(Example 1)

According to the procedure of Fig. 1, p-dichlorobenzene is produced by chlorinating chlorine with benzene as a raw material. An alumina shaped body of BEA zeolite was placed in the reactor as a fixed bed.

The reaction temperature was 75 ℃, chlorination reaction under a pressure of 1.8kg / cm ² of conditions. The degree of chlorination is about 2.0.

The obtained p-DCB has a selectivity of 77.7%, and can stably produce p-DCB with high selectivity.

(Example 2)

According to the procedure of Fig. 9, p-dichlorobenzene is produced by chlorinating chlorine gas using benzene as a raw material. A cerium oxide molded body of BEA zeolite catalyst was placed in the reactor as a fixed bed.

The chlorination reaction was carried out under the conditions of a reaction temperature of 80 ° C and a pressure of 1.8 kg/cm ² . The degree of chlorination is about 2.0.

The obtained p-DCB has a selectivity of 74.6%, and can stably produce p-DCB with higher selectivity.

(Example 3)

According to the procedure of Fig. 10, p-dichlorobenzene is produced by chlorinating chlorine gas using benzene as a raw material. A cerium oxide molded body of BEA zeolite catalyst was placed in the reactor as a fixed bed.

The chlorination reaction was carried out under the conditions of a reaction temperature of 80 ° C and a pressure of 1.8 kg/cm ² . The degree of chlorination is about 2.0.

The obtained p-DCB has a selectivity of 74.6%, and can stably produce p-DCB with higher selectivity.

(Example 4)

According to the flow of Fig. 11, p-dichlorobenzene is produced by chlorinating chlorine with benzene as a raw material. A cerium oxide molded body having a granulation of BEA zeolite catalyst of 0.8 to 3.2 mm was placed in the reactor as a slurry bed.

The chlorination reaction was carried out under the conditions of a reaction temperature of 80 ° C and a pressure of 1.8 kg/cm ² . The degree of chlorination is about 2.0.

The obtained p-DCB has a selectivity of 72.5%, and can stably produce p-DCB with higher selectivity.

(Comparative example)

A comparative example using ferric chloride FeCl ₃ which is a homogeneous catalyst of the prior art is shown. The reaction apparatus is a apparatus shown in Fig. 15 in which a chlorine gas is supplied from a supply blower using a fully-mixed reactor 50 with a jacket 51 and a stirrer 52, and benzene and FeCl _{3 are} supplied thereto, via the cooling water unit 53 via The sleeve 51 is cooled and reacted. The reaction product from the bottom is stored in the liquid storage tank 54 after cooling, and the gas-liquid component from the top is cooled and stored in the gas storage liquid tank 55.

The reaction conditions are as follows.

○ Catalyst FeCl ₃ concentration: 0.0088 catalyst mol / benzene mol

○ Raw material chlorine gas supply rate: 0.85mol / benzene mol

○ Reaction temperature: 80 ° C

If the degree of progress (degree of chlorination) is used to indicate the benzene in the reaction The change in chlorination product is shown in Figure 16.

According to Fig. 16, the homogeneous catalyst is used, and the reaction system is carried out successively and in parallel. The reason is generally believed to be because the homogeneous catalyst has no resistance to diffusion, and benzene reacts with the monomer, or with the monomer and the dimer. Therefore, the dimer selectivity stays at a maximum of 80% in the reaction.

The change in selectivity of PDCB in DCB with DCB yield is shown in Figure 17, and the change in PDCB yield with chlorination is shown in Figure 18. Since the homogeneous catalyst has no steric hindrance in the ortho-alignment alignment, the selectivity of the parasite is 60% as shown in Fig. 17, which is a lower value. Further, since the dimer selectivity stays at a maximum of 80%, the maximum yield of the ligand in the reaction is 50% as shown in FIG.

The experiment was carried out by reducing the reaction temperature of the standard conditions from 80 ° C to 70 ° C. The results are shown in Fig. 19. It is understood that the selectivity of the parallel does not change even if the reaction temperature is lowered.

Then, the amount of the catalyst was reduced from 0.0181 g-cat/g-Bz (0.0088 catalyst mol/benzene mol) to about 1/20 of 0.0010 g-cat/g-Bz (0.00049 catalyst mol/benzene mol), and the result was as a result. It can be clearly seen that there is no change in activity, and as shown in Fig. 20, it is organized into a curve with no change in selectivity.

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

[Industrial availability]

According to the present invention, a compound which is industrially valuable as a raw material of PPS can be continuously obtained.

1. . . benzene

2. . . Chlorine gas

3. . . Chloroform

3A, 3B. . . Recovery of chloroform

10. . . reactor

11. . . casing

12, 15, 26. . . Condenser

13. . . Unreacted material separation tower

14. . . mixer

16, 20, 28. . . Pump

17, 52. . . Mixer

18. . . Zeolite catalyst

19. . . Splitter

twenty two. . . Hydrogen chloride removal tower

twenty four. . . Cooling Tower

30‧‧‧Sedimentation tank

32‧‧‧Decompression pump

50‧‧‧Completely mixed reactor

51‧‧‧ casing

53‧‧‧Cooling water unit

54‧‧‧Liquid tank

55‧‧‧ gas storage tank

Fig. 1 is a flow chart of a first embodiment of the present invention.

Figure 2 is a flow chart for supplying raw materials and chlorine gas by upflow conditions.

Fig. 3 is a graph showing DCB yield and para-selectivity when BEA is used as a molding base for a cerium oxide sol or an alumina sol, respectively.

Fig. 4 is a graph showing DCB yield and para-selectivity when a ceria-alumina catalyst is used.

Fig. 5 is a graph showing DCB yield and para-selectivity when BEA, MFI, and USY using alumina sol as a molding base, respectively.

Fig. 6 is a graph showing changes in DCB yield and para-selectivity accompanying changes in the metal cation exchange rate at the ion exchange point of the zeolite catalyst.

Fig. 7 is a graph showing the progress of the reaction using a zeolite catalyst.

Fig. 8 is a view showing the relationship between the pressure at a reaction temperature of 80 ° C and a liquid phase cooling temperature of 58 ° C and the chloroform/benzene ratio, and the recovery ratio.

Fig. 9 is a flow chart showing a second embodiment of the present invention.

Figure 10 is a flow chart showing a third embodiment of the present invention.

Figure 11 is a flow chart showing a fourth embodiment of the present invention.

Fig. 12 is a view showing the progress of the reaction in the second embodiment of the present invention.

Figure 13 is a graph showing the degree of chlorination of a reaction product in a second embodiment of the present invention.

Figure 14 is a graph comparing the selectivity of the paramers under the conditions of the unresolved reaction product in the embodiment of the present invention.

Fig. 15 is a schematic configuration diagram of a reaction apparatus of the prior example (Comparative Example: using a homogeneous catalyst).

Figure 16 is a graph showing the composition change of each substance in the previous example (using a homogeneous catalyst).

Figure 17 is a graph showing the selectivity of p-DCB in the previous example (using a homogeneous catalyst).

Figure 18 is a graph of the yield of p-DCB accompanied by chlorination in the previous example (using a homogeneous catalyst).

Figure 19 is a graph showing the effect of the selectivity-reaction temperature in the previous example (using a homogeneous catalyst).

Figure 20 is a graph showing the effect of the amount of selective-catalyst in the previous example (using a homogeneous catalyst).

1. . . benzene

2. . . Chlorine gas

3. . . Chloroform

3A, 3B. . . Recovery of chloroform

10. . . reactor

11. . . casing

12, 26. . . Condenser

14. . . mixer

16, 20, 28. . . Pump

18. . . Zeolite catalyst

twenty two. . . Hydrogen chloride removal tower

twenty four. . . Cooling Tower

30. . . Precipitation tank

32. . . Decompression pump

Claims (10)

A method for producing p-dichlorobenzene, which is produced by chlorinating at least one of benzene and monochlorobenzene, and is characterized by: a reactor having a plurality of stages containing a zeolite catalyst; The first stage reactor supplies the raw material, chlorine gas, and separates the reaction product of the previous stage into unreacted raw materials and products, and the unreacted raw materials are returned to the previous stage reactor, and the product is supplied to the secondary reactor, and the reactor after the second stage is Chlorine gas is supplied, and p-dichlorobenzene is obtained from the reaction product of the last stage. The method for producing p-dichlorobenzene according to the first aspect of the patent application, wherein dichloromethane, chloroform, tetrachloromethane, 1,1-dichloroethane, 1,1 are introduced into each section of the reactor. At least one cooling medium of 1-trichloroethane causes the cooling medium to evaporate to suppress an increase in temperature of the chlorination reaction. The method for producing p-dichlorobenzene according to claim 2, wherein the vaporized gas component of the cooling medium is condensed outside the reactor, and the condensate is reused as the cooling medium. A method for producing p-dichlorobenzene according to the first aspect of the invention, wherein the zeolite-containing catalyst is contained in the reactor as a fixed bed. The method for producing p-dichlorobenzene according to the first aspect of the patent application, wherein the raw material and the chlorine gas flow are passed through a downflow. The method for producing p-dichlorobenzene according to the first aspect of the invention, wherein the zeolite-containing catalyst is obtained by molding a zeolite with a molding base containing an alumina sol as a main component. A method for producing p-dichlorobenzene according to the first aspect of the invention, wherein the zeolite is a proton-type zeolite. For example, the method for producing p-dichlorobenzene according to item 1 of the patent application, wherein The zeolite is a beta zeolite. A method for producing p-dichlorobenzene according to the first aspect of the invention, wherein the zeolite is an MFI zeolite. The method for producing p-dichlorobenzene according to the first aspect of the patent application, wherein the chlorination reaction is carried out at a temperature of 40 to 130 ° C and a pressure of 10 atm or less.