JPH11228456A - Co-production of cyclohexanol and cyclohexane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for co-producing cyclohexanol and cyclohexane by hydrogenating benzene, separating the products and hydrating cyclohexene, capable of profitably giving the by-produced cyclohexane in high purity without requiring a complicated separation treatment process and capable of reducing the load of a separation process such as an extractive distillation process without accumulating impurities in a large amount in the reaction system. SOLUTION: This method for co-producing cyclohexanol and cyclohexane comprises a process for partially hydrolyzing benzene, the first separation process, a hydration process, the second separation process, a circulation process and a hydrogenating purification process. The cyclohexene, the cyclohexane and the unreacted benzene obtained by the hydrogenation of the benzene are separated in the first separation process comprising an extractive distillation process. The separated cyclohexene is fed into the hydration process as a hydration raw material, and the separated unreacted benzene is recycled to the hydrogenation process. The cyclohexanol is produced in the hydration process and subsequently separated from the unreacted cyclohexene in a hydrogenating purification process. The unreacted cyclohexene is recycled to the hydrogenation process. In order to prevent the accumulation of impurities comprising methylcyclopentene compounds in the recycling system, a part of the impurities are extracted, concentrated in a distillation calumn and subsequently purged. The cyclohexane separated in the first separation process is hydrogenatingly purified in the presence of a hydrogenation catalyst to give the highly pure cyclohexane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing cyclohexane, a main product, and cyclohexane, a by-product, from benzene with high purity.

[0002]

2. Description of the Related Art A hydrogenation reaction method for obtaining a reaction mixture consisting of cyclohexene (CHE), cyclohexane (CHX) and benzene (Bz) by partially hydrogenating benzene, a separation method for separating the respective components by extractive distillation, and A hydration reaction method for obtaining cyclohexanol (CHL) by hydrating the separated CHE in the presence of a zeolite catalyst or the like is known. Further, methylcyclopentenes (MCPN), which are by-products of the hydration reaction, and the raw material CHE are
A method of subjecting to CHL separation followed by extractive distillation is also known (for example, JP-A-4-41448).

Japanese Patent Application Laid-Open No. Hei 7-165646 describes a process in which the above-mentioned steps of hydrogenation, separation and hydration are integrated, but the remaining cyclohexene and cyclohexene obtained by separating cyclohexanol after the hydration reaction are described. It is described that methylcyclopentenes can be circulated to a previous extraction step, and at the same time, cyclohexane can be converted to benzene and circulated, thereby improving the utilization rate of raw materials used. At this time, a part of MCPN generated in the hydration reaction is circulated to the hydration reaction step, and the rest is circulated to the extraction step. As a result, MCPN is extracted out of the system together with CHX in the extractive distillation step.

[0004] One of the reasons for employing the method of circulating CHE containing MCPN in the extractive distillation step as described above is to prevent accumulation and effective use of CHX and Bz contained in the raw material of the hydration reaction. That is, the CHE separated in the extractive distillation step inevitably contains a small amount of CHX and Bz, but these are not consumed in the hydration reaction, and together with CHE in the next step of separating CHE and CHL. Taken out.
Since this component contains a large amount of CHE, it is usually circulated to the hydration step. However, this alone has a problem that CHX and Bz are accumulated in a high concentration in the hydration reaction system. In order to prevent this accumulation, a part of the CHE is recycled and used in the extraction step. From this viewpoint, such circulation of MCPN to the extractive distillation step is an effective method.

[0005] However, the above method has the following problems. That is, in this method, CHX is M
Since it is obtained in a form containing CPN, a complicated processing step is required to reuse this CHX. For example, in JP-A-3-287548, CHX containing MCPN is subjected to hydrogenation treatment to convert MCPN to methylcyclopentane, which is separated by distillation to obtain purified CX.
HX has been obtained. Whether CHX is used as it is for another purpose or CHX is converted to Bz and reused, it is not preferable that such a complicated process is required.

[0006] Another problem with this method is that the load of extractive distillation is heavy. That is, MCP
When CHE containing N is circulated to the extractive distillation column, the amount supplied to the extractive distillation step increases, and the amount of impurities also increases, so that the load on the reboiler and the condenser increases, the reflux ratio increases, and the column diameter increases. And so on, which leads to an increase in cost.

[0007]

Therefore, the present inventors did not substantially recycle the CHE containing MCPN to the extractive distillation step, but separated the MCPN from at least a part of the CHE containing MCPN. A method of purging this out of the system was studied. However, even such a method was not always sufficient in view of the problem of an increase in the load of extractive distillation. In other words, extractive distillation usually involves 3 to 4 columns.
A distillation column is required, and the load of distillation is considerably large even without containing MCPN. Moreover, CHX has various uses such as being used as a solvent as it is or being oxidized into a cyclohexanol / cyclohexanone mixture, unlike Bz reused in the reaction and CHE sent to the next step. Concentration matters. However, under normal conditions of extractive distillation, CHX usually contains about 200 ppm to 5% of Bz and CHE. To lower the concentration, it is necessary to further increase the load of extractive distillation. did not become.

The present invention has been made in order to solve the above-mentioned problems, and reduces the load of a separation step such as extractive distillation and is a by-product. Process, etc.).

[0009]

SUMMARY OF THE INVENTION The present invention resides in a method for co-producing cyclohexanol and cyclohexane having the following steps. (1) benzene obtained by partially hydrogenating benzene,
A first separation step of separating a hydrogenated reaction mixture containing cyclohexane and cyclohexene into components of benzene, cyclohexane and cyclohexene; (2) hydrating the separated cyclohexene to contain cyclohexene, cyclohexanol and methylcyclopentene (3) a second separation step of separating the hydration reaction mixture obtained in (2) above into a mixture of cyclohexene and methylcyclopentenes and cyclohexanol, ) Separating at least a part of the separated mixture of cyclohexene and methylcyclopentenes into a component having a high concentration of methylcyclopentenes and a component having a low concentration of methylcyclopentenes; , Above (1)
And the components having a low concentration of methylcyclopentenes are discharged out of the system without being circulated to the first separation step.
A circulation step of circulating the above-mentioned step (2), and (5) a hydrogenation purification step of hydrogenating and purifying the cyclohexane separated in the first separation step in the presence of a hydrogenation catalyst.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
As shown in FIG. 1, the process for co-producing cyclohexanol and cyclohexane of the present invention includes a hydrogenation reaction step, a first separation step, a hydration reaction step, a second separation step, a circulation step, and a hydrogenation purification step. . That is, in FIG. 1, cyclohexene, cyclohexane and unreacted benzene formed in the hydrogenation reaction step of benzene are separated in the extraction distillation step, cyclohexene becomes a raw material in the hydration reaction step, and unreacted benzene is used in the hydrogenation reaction step. Recycled. In the hydration reaction step, cyclohexanol is generated, and is separated from unreacted cyclohexene in the hydrogenation purification step. Unreacted cyclohexene is recycled to the hydration reaction step. To prevent methylcyclopentene from accumulating in the recycling system,
A part is withdrawn and purged after concentration in a distillation column. The cyclohexane separated in the first separation step is hydrogenated and refined in the presence of a hydrogenation catalyst to become high-purity cyclohexane.

Hereinafter, each of the above steps will be described. [Hydrogenation reaction step] In the partial hydrogenation reaction of benzene,
It is preferred to carry out the reaction in the presence of water. Although the amount of water varies depending on the reaction mode, it is generally 0.01 to 10 times by weight, preferably 0.1 to 5 times by weight of benzene. Under such conditions, an organic liquid phase (oil phase) mainly composed of raw materials and products and a liquid phase containing water (aqueous phase)
Two phases are formed without stirring. When the ratio between the oil phase and the aqueous phase is extreme, it is difficult to form two phases, and it is also difficult to perform liquid separation. If the amount of water is too small or too much,
The presence effect of water is reduced. Further, in the present invention, it is preferable to include a metal salt compound in water. Examples of the metal salt compound include sulfates, chlorides, acetates, and phosphates of metals such as Group 1 metals, Group 2 metals, zinc, manganese, and cobalt. The amount of the metal salt to be used is usually 1 × 10 ⁻⁵ to 1 times by weight, preferably 1 × 10 ⁻⁵ times by weight with respect to the water of the reaction system.
It is 1 × 10 ⁻⁴ weight times to 0.1 times weight.

The use of a ruthenium catalyst is preferred for this reaction. Examples of raw materials for the catalyst include ruthenium halides, nitrates, hydroxides, complex compounds such as ruthenium carbonyl and ruthenium ammine complexes, and ruthenium alkoxides. Among them, ruthenium chloride is preferably used. Ruthenium, which is the active component of the catalyst, can be used alone, but other metal components may be used in combination as co-catalyst components. By adding a co-catalyst, the effects of the present invention can be further exhibited. As the co-catalyst component, zinc, iron, cobalt, manganese, gold, lanthanum, copper and the like are effective, and zinc is particularly preferable. As a raw material of the promoter component, halides, nitrates, acetates, sulfates and complex compounds of each metal are used. When a promoter component is used, the atomic ratio of the promoter metal to ruthenium atoms is usually 0.01
-20, preferably 0.1-10.

The catalyst may be of a supported type supported on silica, alumina, silica-alumina, zeolite, activated carbon, or a common metal oxide, composite oxide, hydroxide or poorly water-soluble metal salt. . Specifically, as the carrier,
Metal salts such as barium sulfate and calcium sulfate, silica,
Examples thereof include oxides of alumina, zirconia, titania, chromina, and rare earth metals, or composite oxides such as silica-alumina, silica-zirconia, and zirconium silicate, and silica modified with a metal oxide such as zirconia. You. Further, among the above carriers, carriers having the following properties can be suitably used. When the pore volume and pore distribution are measured by the mercury intrusion method, the pore diameter is 75 to 100,0.
The total pore volume at 00 ° is 0.2 to 10 ml / g, preferably 0.3 to 5 ml / g, and the pore diameter is 75 to
For a total pore volume of 100,000 °, a pore volume having a pore diameter of usually 250 ° or more is 50% or more, preferably 7% or more.
It is a carrier having pores of 0% or more. 250 pore diameter
If the proportion of the pores smaller than す ぎ る is too large, the selectivity tends to decrease, which is not preferred.

The catalyst is preferably used after being activated as follows. As the activation method, a catalytic reduction method using hydrogen gas or a chemical reduction method using formalin, sodium borohydride, hydrazine or the like is used. Of these, a catalytic reduction method using hydrogen gas is preferable, which is usually carried out under a hydrogen-containing gas atmosphere at 80 to 50%.
It is fired under the condition of 0 ° C., preferably 100 to 450 ° C. and activated by reduction. If the reduction temperature is lower than 80 ° C., the reduction rate of ruthenium is remarkably reduced, and
When the ratio exceeds the above, ruthenium agglomeration tends to occur, which causes a decrease in the yield and selectivity of cyclohexene production.

In the present invention, the catalyst obtained by the above-described method is usually used. However, by subjecting such a catalyst to the water treatment described below, it is possible to obtain a catalyst having improved cyclohexene selectivity and the like. It is possible. Water treatment conditions are usually 0.01 to 100 times by weight, preferably 0.1 to 100 times the weight of the above-mentioned catalyst (ruthenium reduced product).
It is carried out, for example, by immersion in 10 to 10 times by weight of water. Other processing conditions are usually from normal pressure to pressurized, room temperature to 250
C., preferably at room temperature to 200.degree. C., usually for at least 10 minutes, preferably for 1 to 20 hours. The atmosphere for this water treatment is usually under an inert gas atmosphere or a hydrogen gas atmosphere, and preferably under a hydrogen gas atmosphere. Further, the catalyst after the water treatment is usually dried and subjected to a re-reduction treatment, particularly a contact treatment in a hydrogen gas atmosphere, so that a ruthenium catalyst with higher activity can be obtained. The water used for the above water treatment may be an aqueous solution containing a metal salt in addition to pure water.

As for the conditions of the hydrogenation reaction, the temperature is usually 50
To 250 ° C, preferably 100 to 220 ° C. If the temperature is higher than 250 ° C., the selectivity of cyclohexene decreases, and if the temperature is lower than 50 ° C., the reaction rate is remarkably reduced, which is not preferable. The pressure of hydrogen during the reaction is usually 0.1.
It is selected from the range of 1 to 20 MPa, preferably 0.5 to 10 MPa. If it exceeds 20 MPa, it is industrially disadvantageous, while if it is less than 0.1 MPa, the reaction rate is remarkably reduced, which is uneconomical in terms of equipment. The reaction may be performed batchwise or continuously using one or two or more reaction tanks, but a continuous method is preferred from an industrial viewpoint.

The reaction solution after the above hydrogenation reaction is a mixture of an aqueous phase in which a ruthenium catalyst is dispersed and an oily phase composed of an organic substance. Such a reaction solution is introduced into an oil / water separator illustrated as a stationary tank in FIG. 1 and subjected to oil / water separation. Such an oil-water separator may be installed inside the reactor, or may be installed outside the reactor as shown in FIG. The aqueous phase separated in the oil-water separator is preferably recycled to the reaction system and used again for the reaction. On the other hand, the oil phase is introduced into the first separation step. [First Separation Step] The hydrogenation reaction products containing benzene, cyclohexene and cyclohexane to be subjected to the first separation step usually have the boiling points of their components close to each other. A simple distillation method is employed.
Hereinafter, the case of extractive distillation, which is a preferred method, will be described.

FIG. 2 shows a separation method comprising three distillation columns. Extractive distillation is performed in the distillation column D1. An oil phase containing Bz, CHX, and CHE is supplied from line 1,
Extractant is supplied from line 2. After a component containing cyclohexane as the main component is extracted from the top of D1 and condensed by a condenser, a part of the component is returned to the distillation column D1 at a predetermined reflux ratio, and the rest is extracted from the line 3. From the bottom of the column, a component mainly composed of benzene, cyclohexene and an extractant is extracted through a line 4.

The cyclohexane extracted from the top of D1 is dehydrogenated to benzene and recycled to the hydrogenation step, or used as a raw material in other steps such as cyclohexanone or cyclohexanol by oxidation with cyclohexane. I do. Subsequently, extractive distillation is performed in the distillation column D2.
A line mainly composed of benzene, cyclohexene and an extractant is supplied from a line 4, and an extractant is supplied from a line 5. A fraction containing cyclohexene as a main component is withdrawn from the top of D2, condensed by a condenser, a part of which is returned to distillation column D2 at a predetermined reflux ratio, and the rest is withdrawn from line 6. And fed to the hydration step. A component mainly composed of benzene and an extractant is extracted from the bottom of the column D2 through the line 7, and supplied to the distillation column D3.

Further, in the distillation column D3, benzene and an extractant are separated by distillation, benzene is extracted from the top of the column, and is condensed by a condenser. A part of the benzene is returned to the distillation column D3 at a predetermined reflux ratio. The rest is withdrawn from line 8. The extracted benzene is recycled to the hydrogenation reaction. Extractant is withdrawn from the bottom of D3 through line 9, and is usually fed to distillation columns D2 and / or D3.
Reused.

The extractant used for such extractive distillation includes 1,3-dimethylacetamide, adiponitrile,
Sulfolane, dimethyl malonate, dimethyl succinate, γ
A known extractant such as 1-butyllactone and N-methylpyrrolidone, and a polar organic compound such as 1,3-dimethylimidazolidinone and ethylene glycol are used. In the method shown in FIG. 2 described above, Bz, C
In separating HE and CHX into their respective components,
Although the method of first separating CHX and then separating CHE and Bz has been illustrated, a method of first separating Bz and then separating CHX and CHE as shown in FIG. 3 can be adopted.

Each of the components separated in the first separation step contains other components to some extent. Particularly, the separated cyclohexane contains a considerable amount of CHE and Bz, which causes a problem when used as it is. However, since the present invention has a hydrogenation purification step described later, impurities in CHX are reduced to 5%. No problem up to about%
In order to reduce the load of the separation step, preferably 200p
It is preferable to contain CHE and Bz of about pm to 1%.

[Hydration reaction step] As the hydration catalyst used in this step, various catalysts used for hydration reaction of CHE can be used, but a solid acid catalyst is preferable. The solid acid catalyst is
An acidic solid substance, zeolite, a strongly acidic ion exchange resin containing sulfonic acid groups, etc.
Inorganic oxides such as hydrous tantalum oxide, zirconium dioxide, titanium dioxide, aluminum oxide, and silicon dioxide, or composite oxides thereof, and layered compounds such as smectite, kaolinite, and vermiculite are used in aluminum and silicon, titanium, and zirconium. Examples thereof include an ion-exchange layered compound treated with one or more metal oxides selected from the group consisting of zeolite, and zeolite is particularly preferred as the solid acid catalyst in the present invention. The form in which the solid acid catalyst is used is not particularly limited, but is usually used in the form of powder or granules. Alumina, silica, titania, or the like may be used as a carrier or a binder in the catalyst.

The zeolite catalyst is not particularly limited as long as it is a zeolite that can be used as a catalyst, and examples thereof include mordenite, erionite, ferrierite, ZSM-5, ZSM-4, ZSM-8 and Mozbil. ZSM
-11, ZSM-12, ZSM-20, ZSM-40,
Examples thereof include aluminosilicates such as ZSM-35 and ZSM-48 zeolites, and zeolites containing different elements such as borosilicate, gallosilicate, and ferroaluminosilicate. These zeolites are usually of the proton exchange type (H type), and some of them are alkali elements such as Na, K and Li, alkaline earth elements such as Mg, Ca and Sr, Fe, Co, Ni, and the like. It may be exchanged with a cation species selected from Group 8 elements such as Ru and Pd.

In the present invention, CHE is hydrated in the liquid phase in the presence of the above-mentioned catalyst. In the reaction system, another organic substance may be allowed to coexist as a solvent or an additive. Examples of the organic substance include oxygen-containing organic compounds such as benzoic acids, carboxylic acids, phenols, salicylic acids, alcohols, fluoroalcohols, ethers, esters, and ketones, and amide compounds. , Nitrogen-containing organic compounds such as nitriles, sulfur-containing organic compounds such as thiols and sulfonic acid, halogen-containing organic compounds such as halogenated carbon, aliphatic hydrocarbons, and aromatic hydrocarbons. .

This hydration reaction is preferably carried out continuously. In this case, CHE is continuously supplied to the catalyst slurry composed of the solid acid catalyst and water to carry out the hydration reaction to convert CHL. A method is employed in which the aqueous phase, which is a catalyst slurry, is separated from the reaction solution, and the oil phase containing CHL is separated from the reaction solution, and the oil phase is continuously collected. The reaction is usually carried out by mixing the aqueous phase and the oil phase by stirring or the like, in a suspended state, for example, a state in which the oil phase is dispersed in a continuous aqueous phase in the form of droplets. When the reaction mixture is weakened or stopped, the reaction solution usually separates into an aqueous phase and an oil phase, and the volume ratio of the oil phase to the aqueous phase is usually 0.01 to 10, preferably 0.1 to 10. ~ 1
It is. If the amount of CHE or water as the raw material is excessively large as compared with one of them, it is not preferable because the separation of the aqueous phase and the oil phase is poor and the reaction rate is reduced. The weight ratio of the catalyst to CHE is usually 0.01 to 20, preferably 0.05 to 5. If the amount of the catalyst is too small, the reaction speed is too slow and the reactor is too large. If the amount of the catalyst is too large, the cost of the catalyst increases, which is not preferable.

In this hydration reaction system, the aqueous phase mainly contains the solid acid catalyst, and the oil phase mainly contains the raw material CHE and the produced CHL. The aqueous phase containing the catalyst, after separation,
The catalyst slurry can be recycled to the reactor and reused. As the hydration reaction conditions, the reaction temperature is usually 50
-300 ° C, preferably 70-200 ° C, more preferably 80-160 ° C. The reaction pressure is not particularly limited, but is preferably a pressure capable of keeping CHE and water in a liquid phase,
Usually, it is 5 MPa or less, preferably 0.2 to 2 MPa. The reaction time or residence time is usually 1 minute to 10 hours, preferably 5 minutes to 5 hours. The reaction system is preferably maintained under an atmosphere of an inert gas such as nitrogen, helium, hydrogen, argon, carbon dioxide and the like. In this case, it is preferable that the content of oxygen in the inert gas is small, and one having an oxygen content of usually 100 ppm or less, preferably 20 ppm or less is used.

[Second Separation Step and Circulation Step] In the present invention, the second separation step is usually carried out by a method such as distillation.
HEPN and the by-products of the hydration reaction, MCPN and CHL, are separated. Hereinafter, a separation method by distillation will be described.

The reaction solution (CH) obtained in the above hydration reaction step
L, CHE and MCPN) are separated in a distillation column D4 shown in FIG.
E is distilled off, and CHL as a product is withdrawn from the bottom of the column. Bz, CHX and MCP were contained in the distilled CHE.
Since N is contained, at least a part thereof is withdrawn from the line 14 to prevent the accumulation thereof, and the distillation column D
The light boiling components such as MCPN are concentrated by 5 and extracted out of the system through a line 16. The bottom liquid from the bottom of the tower is recycled from the line 17 to the hydration reaction step. The portion of the distilled CHE that is not supplied to the distillation column D5 is
It is recycled from the line 15 to the hydration reaction step. In addition, by changing the conditions (reflux ratio, distilling ratio, supply amount to D5, etc.) of the distillation column D5, it becomes possible to control light boiling during recycling.

The process of the present invention is particularly useful for
A selectivity of CPN of 1% or less, preferably 0.5% or less;
It is particularly effective when the content is more preferably 0.2% or less. If the production rate of MCPN is too high, it is difficult to separate CHE and MCPN by distillation. As a result, a relatively large amount of MCPN is circulated in the hydration reaction, and as a result, the deterioration of the catalyst is easily accelerated.

One of the features of the present invention is that, after obtaining the desired product, CHL, from the product of the hydration reaction, CHE and MCPN are at least partially recycled without being substantially recycled to extractive distillation. The object is to separate a component having a high MCPN concentration and a component having a low MCPN concentration by means such as distillation. As a result, since MCPN is not substantially present in the extractive distillation system, a step of separating it from CHX is unnecessary, and therefore, CHX obtained by extractive distillation can be used as it is. The same composition and purity of CH
Even if X, CHE, and Bz are obtained, the load of the extractive distillation step can be greatly reduced. Further, there is no accumulation of MCPN in the hydration reaction system.

[Hydropurification Step] The CHX separated in the first separation step is subjected to hydrogenation purification in the presence of a hydrogenation catalyst.
In particular, CHE / CHX / B by partial hydrogenation of Bz
When a mixture is obtained, the CHX obtained in the first separation step contains substantially no B since there is substantially no other component.
It will not contain components other than z and CHE. Therefore, even if Bz or CHE is contained to some extent, high-purity CHX can be easily obtained by hydrogenating and purifying it.

As the hydrogenation catalyst used here, various metal catalysts usually used as a hydrogenation catalyst can be used. For example, noble metals such as Pd, Ru and Pt, Ni,
A metal such as Zn can be exemplified. These may be supported on a carrier. At this time, examples of the carrier include various carriers such as alumina, carbon, titania, silica, and zirconia. The reaction may be a fluidized bed or a fixed bed, but when a noble metal-supported catalyst such as Pd is used, a fixed bed is usually used.

The reaction conditions for hydrogenation purification vary depending on the catalyst used, but the purification temperature is usually 3
When using a noble metal catalyst such as Pd at 0 ° C. to 300 ° C., 30 ° C. to 200 ° C., preferably 40 ° C. to 15 ° C.
0 ° C, more preferably 60 ° C to 120 ° C. The pressure is generally 0.2 atm to 30 atm, preferably 0.5 atm to 10 atm, and more preferably 1 atm to 5 atm.

The LHSV varies depending on the type of reaction and the amount of impurities, but usually ranges from ¹ hr ^-1 to 100 hr ^-1 . C
If only the purity of HX is to be improved, it is not impossible to achieve it by making the separation conditions in the first separation step strict. However, in this case, the load of the first separation step such as extractive distillation is increased, that is, a large amount of extractant and a high reflux ratio are required, and therefore a huge distillation column or a large variable cost is required. However, in the present invention, the load of distillation can be reduced by including the hydrorefining step. Because if a hydrogenation catalyst is used, Bz or CH
It is very easy to convert E to CHX, since there is no need for a large distillation column or a large variable cost. CHX thus obtained is usually CHE
And Bz in an amount of about 10 ppm or less in total, and extremely high purity.

[0036]

FIG. 5 shows the flow of the embodiment. Hereinafter, the present embodiment will be described with reference to FIG. 5, but the present invention is not limited to the embodiment and the drawings at all without departing from the gist thereof. Benzene as a raw material is supplied to a hydrogenation reactor R1 from a line 1 and recycled benzene is supplied to a hydrogenation reactor R1 from a line 9. The conditions for the hydrogenation reaction were a pressure of 5.0MPa.
a, reaction temperature 150 ° C., conversion of benzene 67.3%,
The selectivity of cyclohexene is 64.5%. The reaction liquid is supplied to the distillation column D1 from the line 2 and 1,3-dimethylimidazolidinone as the extractant from the line 3, and is separated into cyclohexane and a mixture of cyclohexene, benzene and the extractant. The distillation column D1 is a packed column corresponding to 58 theoretical plates, in which the extractant is supplied from the fifth column from the top and the hydrogenation reaction liquid is supplied from the 37th column. The pressure at the top is 0.1
At 5 MPa, the reflux ratio is 6. At this time, the purity of cyclohexane as a distillate withdrawn from the line 4 is 9
9.95% by weight, with the balance being cyclohexene and benzene. The cyclohexene extracted from the line 4 is supplied to an upper part of a reactor R3 filled with a catalyst having Pd supported on alumina. At the same time, hydrogen is also supplied from line 19 to the upper part of the reactor R3. The reaction conditions of the reactor R3 were adjusted to a pressure of 0.17 MPa and a temperature of 80 ° C., and as a result of performing hydrogenation purification so that the LHSV was 40 hr ⁻¹ ,
As impurities such as cyclohexene and benzene, cyclohexane of 1 ppm or less was obtained (line 20).

The bottom liquid of the distillation column D1 is supplied to the distillation column D2 from the line 5 and the extractant is supplied to the distillation column D2 from the line 6, and separated into cyclohexene and a mixture of benzene and the extractant. The distillation column D2 is a packed column equivalent to 58 theoretical plates,
The extractant is supplied from the fourth stage from the top, and the bottom of the distillation column D1 is supplied from the 35th stage. At this time, the pressure at the top is 0.05 MPa
And the reflux ratio is 3. Cyclohexene is supplied from line 7 to the hydration reaction. The bottom liquid is supplied to the distillation column D3 via the line 8, and is separated into benzene and an extractant. Distillation column D3 is a packed column equivalent to 13 theoretical plates, and 6 columns from the top.
The stage includes a bottoms supply stage for the distillation column D2. At this time, the top pressure is 0.05 MPa and the reflux ratio is 1. Benzene, which is a distillate of the distillation column D3, is recycled from the line 9 to the hydrogenation reaction step (R1). On the other hand, the extractant is discharged from the line 10 and, after cooling, is recycled to the distillation tower D1 and / or the distillation tower D2.

As described above, the cyclohexene separated in the extraction step is supplied from the line 7 to the hydration reactor R2. The hydration reaction conditions were a pressure of 0.7 MPa and a reaction temperature of 120.
° C, cyclohexene conversion rate 11%, cyclohexanol selectivity 99.8%. The reaction liquid in the reactor R2 is supplied from the line 11 to the distillation column D4, where it is separated into cyclohexanol and light-boiling components containing unreacted cyclohexene and methylcyclopentenes. Distillation column D4 is theoretical plate 1
In a packed tower corresponding to five stages, the reaction liquid of R2 is supplied to the seventh stage from the top. At this time, the top pressure is normal pressure, and the reflux ratio is 0.3. The distillate of the distillation column D4 passes through the line 12, and a part thereof is supplied to the distillation column D5 via the line 14. The methylcyclopentenes are concentrated in the distillation column D5, and purge is performed from the top of the column. The distillation column D5 is a packed column corresponding to 30 theoretical stages, and the distillate from the distillation column D4 is supplied to the 23rd stage from the top. The top pressure of the distillation column D5 is normal pressure, and the reflux ratio is 30. The bottoms of the distillation column D5 are recycled from the line 17 to the hydration reactor R2. On the other hand, the cyclohexene distilled off by the line 12 and not supplied to the distillation column D5 is recycled from the line 15 to the hydration reactor.

Under these conditions, the mass balance of each line is as shown in Table 1, and it can be seen that methylcyclopentenes, benzene and cyclohexane do not accumulate in the recycle line. In addition, not only methylcyclopentenes are not mixed into cyclohexane, which is a by-product, but also high-purity cyclohexane having extremely low contents of CHE and Bz can be obtained.

[0040]

[Table 1]

[0041]

[Table 2]

Explanation of symbols in Table 1 CHX: cyclohexane, CHE: cyclohexene, BZ: benzene, DMI: 1,3-dimethylimidazolidinone, CHL: cyclohexanol, H2O: water, MCPN: methylcyclopentenes, H
B: high boiling, H2: hydrogen

[0043]

According to the present invention, in a method for producing cyclohexanol by hydrogenating benzene, and performing the separation and hydration steps in a consistent process, cyclohexane as a by-product is subjected to a complicated separation treatment step. There is no attempt to obtain a sufficiently high purity as it can be used for other purposes.

Further, in the method of the present invention, the load of the separation step such as extractive distillation is small, and MCPN which is an impurity is not accumulated in a large amount in the reaction system.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of all steps of the present invention.

FIG. 2 is a diagram schematically showing an example of a case where the first separation step in the present invention is performed by extractive distillation. (First CHX
Example of separating

FIG. 3 is a diagram schematically showing another example of the case where the first separation step in the present invention is performed by extractive distillation. (First B
Example of separating z)

FIG. 4 is a diagram schematically showing an example of a second separation step and a circulation step in the present invention.

FIG. 5 is a diagram showing the steps of the embodiment of the present invention.

[Explanation of symbols]

1 to 20 (number): line (piping), R1 to R3: reactor, D1 to D5: distillation column

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07C 7/163 C07C 7/163 29/04 29/04 35/08 35/08 // C07B 61/00 300 C07B 61/00 300

Claims (7)

[Claims] 1. A method for co-producing cyclohexanol and cyclohexane comprising the following steps. (1) benzene obtained by partially hydrogenating benzene,
A first separation step of separating a hydrogenated reaction mixture containing cyclohexane and cyclohexene into components of benzene, cyclohexane and cyclohexene; (2) hydrating the separated cyclohexene to contain cyclohexene, cyclohexanol and methylcyclopentene (3) a second separation step of separating the hydration reaction mixture obtained in (2) above into a mixture of cyclohexene and methylcyclopentenes and cyclohexanol, ) Separating at least a part of the separated mixture of cyclohexene and methylcyclopentenes into a component having a high concentration of methylcyclopentenes and a component having a low concentration of methylcyclopentenes; , Above (1)
And the components having a low concentration of methylcyclopentenes are discharged out of the system without being circulated to the first separation step.
A circulation step of circulating the above-mentioned step (2), and (5) a hydrogenation purification step of hydrogenating and purifying the cyclohexane separated in the first separation step in the presence of a hydrogenation catalyst. 2. The method according to claim 1, wherein the first separation step (1) is performed by extractive distillation using an extraction solvent. 3. The method according to claim 1, wherein the hydration step (2) is performed in the presence of a solid acid catalyst. 4. The process according to claim 3, wherein zeolite is used as the solid acid catalyst. 5. The method according to claim 1, wherein the selectivity of methylcyclopentene in the hydration step (2) is 1% or less. 6. The method according to claim 1, wherein the total amount of cyclohexene and benzene in the cyclohexane separated in the first separation step (1) is 5% or less. 7. In the circulation step (4), a part of the mixture of cyclohexene and methylcyclopentene obtained in the second separation step (3) is circulated to the hydration step (2), In addition, the remainder is separated into a component having a high concentration of methylcyclopentenes and a component having a low concentration of methylcyclopentenes by distillation, and the component having a high concentration of methylcyclopentenes is discharged out of the system. The method according to any one of claims 1 to 6, wherein a method of circulating a component having a low concentration in the step (2) is adopted.