JPH11199532A - Method for producing cyclohexanol - Google Patents

Abstract

(57) [Summary] (Problem corrected) [Problem] In a method for integrated production of cyclohexanol (CHL) from benzene (Bz), there is a problem that cyclohexane (CHX) and Bz accumulate at a high concentration in a hydration reaction system. The present invention eliminates the need for circulation to extractive distillation to prevent accumulation and complicated purification steps, reduces the load of extractive distillation, and reduces costs. SOLUTION: From Bz to CH having the steps of 1) to 4)
A method for continuously producing L. 1) A first separation step of separating a hydrogenation reaction mixture containing Bz, CHX, and CHE obtained by partially hydrogenating Bz into components. 2) A hydration step in which the CHE separated in 1) is hydrated to obtain a mixture containing CHE, CHL and methylcyclopentene (MCPN). 3) A second separation step of separating the hydration reaction mixture of 2) into a CHE-MCPN mixture and CHL. 4) At least a part of the CHE-MCPN mixture separated in 3) is separated into a high concentration component and a low concentration component of MCPN,
A circulating step of discharging high-concentration components out of the system and circulating low-concentration components in 2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing cyclohexanol in which the purity of cyclohexanol and by-product cyclohexane is improved in producing cyclohexanol from benzene.

[0002]

2. Description of the Related Art Conventionally, benzene is partially hydrogenated to form cyclohexene (hereinafter sometimes referred to as "CHE"), cyclohexane (hereinafter sometimes referred to as "CHX"), and benzene (hereinafter referred to as "Bz"). Hydrogenation reaction method to obtain a reaction mixture comprising: a reaction mixture comprising: There is known a hydration reaction method for obtaining “CHL”. After CHL separation from the product of this hydration reaction, methylcyclopentene (hereinafter sometimes referred to as “MCPN”) as a by-product and unreacted C
It is also known that HE and extract are subjected to extractive distillation (for example, JP-A-4-41448, etc.). Further, the above hydrogenation, separation and hydration are performed consistently, and after CHL separation,
In particular, it is possible to improve the utilization rate of the raw materials used by circulating MCPN and unreacted CHE to the extractive distillation step and dehydrogenating the CHE to Bz and circulating it to the hydrogenation reaction step. It is described in Kaihei 7-165646. That is, MC by-produced in the hydration reaction
PN will be recycled to the hydration step or extractive distillation step with unreacted CHE.

[0003]

As described above, the MCP
One of the reasons for adopting a method of circulating unreacted CHE containing N to the extractive distillation step is to effectively utilize CHX and Bz simultaneously contained in the unreacted CHE, and to directly describe in the above-mentioned known literature. However, it is considered that CHX and Bz are prevented from accumulating in the hydration reaction system. That is, although the CHE separated in the extractive distillation step inevitably contains a small amount of CHX and Bz, these are not consumed in the hydration reaction, and the next step of separating unreacted CHE and CHL. And is taken out together with CHE. This unreacted component containing CHE is usually circulated to the hydration step as a raw material, but this alone has the problem that CHX and Bz accumulate at a high concentration in the hydration reaction system. To prevent this accumulation,
When the unreacted components containing CHE are recycled to the extractive distillation step, CHX and Bz can be separated and used effectively. Therefore,
During this extractive distillation, MCPN contained in unreacted CHE
Is distilled with CHX.

[0004] However, the above method has the following problems. That is, since CHX is obtained in a form containing MCPN, a complicated process is required to reuse it. For example, Japanese Patent Application Laid-Open No. 3-28754
In JP-A-8, CHPN containing MCPN is subjected to hydrogenation treatment to convert MCPN to methylcyclopentane, which is separated by distillation to obtain purified CHX. When CHX is used for another purpose as it is,
It is not preferable that such a complicated purification step be required in any case where the compound is converted to Bz and reused in the method for producing cyclohexene or cyclohexanol from benzene as in the present invention.

[0005] The method of circulating CHE containing MCPN to the extractive distillation step also has a problem that the load of extractive distillation is large. That is, since the supply amount is increased and impurities are increased as compared with the case where this CHE is not circulated in the extractive distillation step, the reflux ratio is increased, the tower diameter has to be increased, etc. The load also increases, leading to an increase in cost.

The present invention has been made in order to solve the above-mentioned problems, and it has been proposed to improve the purity of cyclohexane as a by-product without requiring a complicated process, and to perform the process in another process (such as a cyclohexane oxidation process). It is intended to provide a method that can be used and does not increase the cost compared to the conventional method.

[0007]

The gist of the present invention resides in a method for continuously producing cyclohexanol from benzene having the following steps (1) to (4). (1) benzene obtained by partially hydrogenating benzene,
A first separation step of separating a hydrogenation reaction mixture containing cyclohexane and cyclohexene into components of benzene, cyclohexane and cyclohexene; (2) A hydration step of hydrating the cyclohexene separated in the first separation step of (1) to obtain a hydration reaction mixture containing cyclohexene, cyclohexanol and methylcyclopentene.

(3) A second separation step of separating the hydration reaction mixture obtained in the hydration step (2) into a mixture of cyclohexene and methylcyclopentene and cyclohexanol. (4) separating at least a part of the mixture of cyclohexene and methylcyclopentene separated in the second separation step of (3) into a component having a high concentration of methylcyclopentene and a component having a low concentration of methylcyclopentene; The component having a high concentration of methylcyclopentene is discharged out of the system without being circulated to the first separation step (1), and the component having a low concentration of methylcyclopentene is circulated to the hydration step (2). Circulating process.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The method for consistently and continuously producing cyclohexanol from benzene according to the present invention includes at least a hydrogenation step, a first separation step, a hydration reaction step, and a second separation step, as shown in FIG. In FIG. 1, cyclohexene, cyclohexane and unreacted benzene generated 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. And the cyclohexane is discharged out of the system. In the hydration reaction step, cyclohexanol is generated,
In the second separation step, unreacted cyclohexene is separated.
Unreacted cyclohexene is recycled to the hydration reaction step. In order to prevent methylcyclopentene from accumulating in the hydration reaction recycling system, a part of the unreacted cyclohexene is withdrawn, concentrated in a distillation column, and purged without being circulated to extractive distillation.

Hereinafter, each of the above steps will be described. Hydrogenation Reaction Step In the partial hydrogenation reaction of benzene, the reaction is preferably performed 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 these conditions, an organic liquid phase (oil phase) containing the raw material and the product as main components and a liquid phase (water phase) containing water form two phases without stirring. When the ratio between the oil phase and the aqueous phase is extremely deviated, it is difficult to form two phases, and it is difficult to perform liquid separation. Also, if the amount of water is too small or too large, the presence effect of water decreases.

Further, in the present invention, it is preferred that a metal salt compound is contained in water. Examples of the metal salt compounds include Group 1 metals, Group 2 metals, and sulfates, chlorides, acetates, and phosphates of metals such as zinc, manganese, and cobalt. The amount of the metal salt used is usually 1 × with respect to the water of the reaction system.
It is 10 ^-5 times by weight to 1 times by weight, preferably 1 × 10 ^-4 times by weight to 0.1 times by weight.

The use of a ruthenium catalyst is preferred for this reaction. Examples of the ruthenium raw material 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 an active component of the catalyst, can be used alone, but it is preferable to use another metal component in combination as a promoter component. As the promoter component, zinc, iron, cobalt, manganese,
Gold, lanthanum, copper and the like are effective, and zinc is particularly preferable. As a raw material of the co-catalyst component, halides, nitrates, acetates, sulfates, and complex compounds containing each metal of each metal are used. When a co-catalyst metal is used, the atomic ratio of the co-catalyst metal to ruthenium atoms is usually from 0.01 to 20, preferably from 0.1 to 10.

[0013] The catalyst may be of an unsupported type,
The carrier may be a carrier supported on a carrier such as alumina, silica-alumina, zeolite, activated carbon, or a common metal oxide, composite oxide, hydroxide, or poorly water-soluble metal salt. The carrier used in such a supported catalyst is preferably a poorly soluble oxide or metal salt generally used as a catalyst carrier, and specifically, barium sulfate, a metal salt such as calcium sulfate, or the like. Silica, alumina, zirconia, titania, chromina, oxides of rare earth metals, or composite oxides such as silica-alumina, silica-zirconia, zirconium silicate, and silica modified with a metal oxide such as zirconia, etc. Is exemplified. Further, when the pore volume and the pore distribution were measured by the mercury intrusion method in the above-mentioned carrier, the diameter was 75 to 100,000Å.
Has a total pore volume of 0.2 to 10 ml / g, preferably 0.3 to 5 ml / g, and a diameter of 75 to 1 ml.
For a total pore volume of 0.00000 ° pores, a diameter of 2
The carrier has a ratio of the total pore volume of the pores of 50 ° or more to 50% or more, preferably 70% or more. Also this 250
If the ratio of the pore volume of pores smaller than Å is too large, the selectivity tends to decrease, which is not preferred.

The catalyst is preferably used after being activated by an appropriate method. As the activation method, for example, a catalytic reduction method using hydrogen gas or a chemical reduction method using formalin, sodium borohydride, hydrazine or the like is used. Of these, catalytic reduction with hydrogen gas is preferred,
Specifically, for example, under a hydrogen-containing gas atmosphere, usually 80 to
It is calcined under the condition of 500 ° C., preferably 100 to 450 ° C. to activate by reduction. If the reduction temperature is lower than 80 ° C., the reduction ratio of ruthenium is significantly reduced, and if it is higher than 500 ° C., aggregation of ruthenium is liable to occur, which causes a decrease in the yield and selectivity of cyclohexene formation.

In the present invention, the catalyst obtained by the above-described method is usually used as a catalyst. By subjecting such a catalyst to a water treatment described below, the selectivity of cyclohexene and the like can be further improved. It is possible to obtain a catalyst. The water treatment conditions are usually 0.01 to 100 with respect to the above-mentioned catalyst (ruthenium reduced product).
For example, immersion in water by weight, preferably 0.1 to 10 times by weight may be mentioned. The treatment conditions are usually room temperature to 250 ° C., preferably room temperature to 200 ° C. under normal pressure to pressure.
And is usually 10 minutes or more, preferably 1 to 20 hours.
The atmosphere of the water treatment is usually under an inert gas atmosphere or a hydrogen gas atmosphere, 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, whereby a ruthenium catalyst with higher activity can be obtained. In addition, as water used for the above water treatment,
It may be an aqueous solution containing a metal salt in addition to pure water.

As the conditions for the hydrogenation reaction, the reaction temperature is usually selected from the range of 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 generally selected from the range of 0.1 to 20 MPa, preferably 0.5 to 10 MPa. If it exceeds 20 MPa, it is industrially disadvantageous. On the other hand, if it is less than 0.1 MPa, the reaction rate is remarkably reduced, which is uneconomical in terms of equipment.

The reaction solution after the above reaction is a mixture of an aqueous phase in which a ruthenium catalyst is dispersed and an oil phase composed of an organic substance.
Such a reaction solution is introduced into an oil / water separator exemplified 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 outside the reactor. The aqueous phase separated in such an oil-water separator is preferably recycled to the reaction system and used again for the hydrogenation reaction. On the other hand, the oil phase is introduced into the first separation step of extractive distillation.

First Separation Step The oil phase subjected to the first separation step mainly contains benzene, cyclohexene and cyclohexane, but since these boiling points are close to each other, this first separation step is carried out. As the process, extractive distillation or azeotropic distillation is usually employed.
Hereinafter, the case of extractive distillation, which is a preferred method, will be described as an example.

FIG. 2 shows a separation method comprising three distillation columns. Extractive distillation is performed in the distillation column D1. Line 1
From the line 2 and an extractant (hereinafter referred to as “s
olv ”). After a component containing cyclohexane as the main component is extracted from the top of the column 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 column bottom, components containing benzene and cyclohexene as main components are extracted through a line 4. Cyclohexane extracted from the top is dehydrogenated to benzene and recycled to the hydrogenation step, or it is effectively used as a raw material in other steps such as cyclohexane oxidation to cyclohexane and cyclohexanol, and mixtures thereof. Used.

Extractive distillation is also performed in the distillation column D2. A fraction mainly composed of benzene, cyclohexene and an extractant is supplied from a line 4, and an extractant is supplied from a line 5. After a fraction containing cyclohexene as the main component is extracted from the top of the column and condensed by a condenser, a part thereof is returned to the distillation column D2 at a predetermined reflux ratio, and the rest is extracted from the line 6. From the bottom of the column, a component containing benzene and an extractant as main components is extracted through a line 7, and the distillation column D3
Supplied to The extracted cyclohexene fraction is supplied to a hydration step.

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

The extractant used in the extractive distillation includes:
Known extractants such as 1,3-dimethylacetamide, adiponitrile, sulfolane, dimethyl malonate, dimethyl succinate, γ-butyllactone, N-methylpyrrolidone, and polarities such as 1,3-dimethylimidazolizonone and ethylene glycol Is used.
In the method of FIG. 2 described above, a method of first separating cyclohexane and then separating cyclohexene and benzene in separating each component is illustrated in FIG.
As shown in (1), a method of first separating benzene and then separating cyclohexane and cyclohexene can be adopted (detailed description is omitted).

Hydration Reaction The catalyst used in the hydration step is not particularly limited as long as it can be used for the hydration reaction of cyclohexene, but is preferably a solid acid catalyst. The solid acid catalyst is an acidic solid substance and is a strongly acidic ion exchange resin containing zeolite, sulfonic acid group, etc., and inorganic oxides such as hydrated niobium oxide, hydrated tantalum oxide, zirconium dioxide, titanium dioxide, aluminum oxide, silicon dioxide, etc. Products or composite oxides thereof, and ion-exchange layered compounds obtained by treating a layered compound such as smectite, kaolinite, vermiculite with one or more metal oxides selected from aluminum, silicon, titanium and zirconium. However, 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. Further, as a carrier or binder, alumina,
Silica, titania or the like may be used.

The zeolite catalyst is not particularly limited as long as it is a zeolite that can be used as a catalyst. Examples thereof include mordenite, erionite, ferrierite, and ZSM-5, ZSM-4, ZSM-8, and ZSM published by Mobil. −
11, ZSM-12, ZSM-20, ZSM-40, Z
Illustrative are aluminosilicates such as SM-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 metal elements such as Na, K and Li, alkaline earth metal elements such as Mg, Ca and Sr, Fe, Co, It may be exchanged with a cation species selected from Group 8 metal elements such as Ni, Ru, and Pd.

In the present invention, the hydration of cyclohexene can be carried out in the liquid phase in the presence of the solid acid catalyst as described above. A solvent or another organic substance may be allowed to coexist as an additive in the reaction system. Examples of the organic substance include benzoic acids, carboxylic acids, phenols, salicylic acids,
Oxygen-containing organic compounds such as alcohols, fluoroalcohols, ethers, esters and ketones; nitrogen-containing organic compounds such as amide compounds and nitriles; sulfur-containing compounds such as thiols and sulfonic acids. Examples include organic compounds, halogen-containing organic compounds such as halogenated carbon, and aliphatic hydrocarbons and aromatic hydrocarbons.

The hydration reaction is preferably carried out continuously. In this case, the hydration reaction is carried out by continuously supplying cyclohexene to a catalyst slurry composed of a solid acid catalyst and water, and the hydration reaction is carried out. It is carried out by separating the aqueous phase, which is a catalyst slurry, and the oil phase containing the product cyclohexanol, and continuously collecting the oil phase. The reaction is usually performed by mixing an aqueous phase and an oil phase by stirring or the like, thereby dispersing the oil phase in a suspended state, for example, a continuous aqueous phase in a droplet state. The reaction solution is usually separated into an aqueous phase and an oil phase when the mixing is weakened or stopped, and the volume ratio of the oil phase to the aqueous phase is usually 0.01 to 10, preferably 0 to 10. .1 to 1. If the amount of the supplied cyclohexene or water is too large as compared with one, the separation of the water phase and the oil phase is poor, and the reaction rate is undesirably reduced. The weight ratio of the catalyst to cyclohexene is usually 0.01 to 20, preferably 0.05 to 5. When the amount of the catalyst is too small, the reaction rate is slow and the reactor is too large. When the amount 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 contains the raw material cyclohexene and the generated cyclohexanol. After separation, the aqueous phase containing the catalyst can be recycled to the hydration reactor as a catalyst slurry and reused.

As the hydration reaction conditions, the reaction temperature is usually 50 to 300 ° C, preferably 70 to 200 ° C, more preferably 80 to 160 ° C. The reaction pressure is not particularly limited, but is preferably a pressure that can keep the cycloalkene and water in a liquid phase, and is usually 5 MPa or less, preferably 0.2 to 2 M.
Pa. The reaction time or residence time is usually from 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 the oxygen content is usually 100 ppm or less, preferably 20 ppm or less.

Second Separation Step and Circulation Step In the second separation step, cyclohexene and methylcyclopentene which is a by-product of the hydration reaction are separated from cyclohexanol by a method such as distillation. Hereinafter, a separation method by distillation will be described with reference to FIG.

The reaction solution (mainly containing cyclohexanol, cyclohexene and methylcyclopentene) obtained in the hydration step is separated in a distillation column D4 in FIG. 4, and unreacted cyclohexene is distilled off from the top of the column. Product cyclohexanol is withdrawn from the bottom of the column. Distilled cyclohexene contains benzene, cyclohexane and methylcyclopentene, and when this methylcyclopentene is circulated to the hydration reaction step, these are not used for the hydration reaction, thus preventing accumulation in these reaction systems. For this reason, a part of the distilled cyclohexene is withdrawn from the line 14, these light-boiling components such as methylcyclopentene are concentrated by the distillation column D 5, and then withdrawn from the line 16 out of the system. The bottom liquid of D5 is recycled from the line 17 to the hydration reaction step. Also, what is not supplied to the distillation column D5 is recycled from the line 15 to the hydration reaction step. Here, conditions of the distillation column D5 (reflux ratio, distilling ratio, supply amount of D5, etc.)
The amount of light-boiling components during recycling can be controlled by changing the value of.

One of the features of the present invention is that cyclohexene and methylcyclopentene obtained after obtaining the desired product cyclohexanol from the hydration reaction product are at least partially recycled without being substantially recycled to extractive distillation. Is separated into components having a high concentration of methylcyclopentenes and components having a low concentration of methylcyclopentenes by distillation.
As a result, methylcyclopentene does not substantially exist in the extractive distillation system, and a step of separating from cyclohexane becomes unnecessary, so that cyclohexane obtained by extractive distillation can be used as it is in other reactions. Even if cyclohexane, cyclohexene and benzene having the same composition are obtained, the load can be greatly reduced. Also, there is an effect that methylcyclopentene does not accumulate at a high concentration in the hydration reaction system.

The process of the present invention is particularly useful for
This is effective when the CPN selectivity is 1% or less, preferably 0.5% or less, and more preferably 0.2% or less.
If the generation rate of MCPN is too high, CHE and MCP
Since it is difficult to separate by distillation from N, a large amount of MC
PN circulates, and as a result, deterioration of the catalyst is easily accelerated, which is not preferable.

[0032]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples. FIG. 5 shows the flow of the following embodiment. The raw material benzene is supplied to the hydrogenation reactor R1 from line 1 and the benzene to be recycled is also supplied from line 9 to the hydrogenation reactor R1. The conditions of the hydrogenation reaction were a pressure of 5.0 MPa, a reaction temperature of 150 ° C., a conversion of benzene of 67.3%, and a selectivity of cyclohexene of 6.
It is 4.5%. The reaction liquid is supplied to the distillation column D1 from the line 2 and also the extractant 1,3-dimethylimidazolizonone from the line 3, and is separated into cyclohexane and a mixture of cyclohexene, benzene and the extractant. The distillation column is a packed column equivalent to 58 theoretical plates, and 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 of the column is 0.15 MPa and the reflux ratio is 6.
At this time, the purity of the distillate, cyclohexane, was 99.9.
5% by weight, with the balance being cyclohexene and benzene. D1 bottoms from line 5 and 1,3 of extractant
-Dimethylimidazolizonone is also supplied from line 6 to distillation column D2.
And separated into a mixture of cyclohexene, benzene and an extractant. D2 is a packed column corresponding to 58 theoretical plates, in which the extractant is supplied from the fourth column from the top and the bottom liquid of D1 is supplied from the 35th column. At this time, the pressure at the top is 0.05 MPa
And the reflux ratio is 3. The distillate, cyclohexene, is supplied to the hydration reactor R2 from the line 7. On the other hand, the bottom product of D2 is separated into benzene and an extractant by the distillation column D3.
D3 is a packed column equivalent to 13 theoretical stages, and the sixth stage from the top has a supply stage for the bottoms of D2. At this time, the top pressure is 0.05 MPa and the reflux ratio is 1. Benzene, the distillate of D3, is recycled from line 9 to the hydrogenation step. On the other hand, the extractant is recycled to D1 and D2 after cooling.

The cyclohexene separated in the extraction step is supplied from line 7 to a hydration reactor R2. The hydration reaction conditions were as follows: pressure 0.7 MPa, reaction temperature 120 ° C., cyclohexene conversion 11%, cyclohexanol selectivity 99.8%.
It is. The reaction solution is supplied from line 11 to distillation column D4, where it is separated into cyclohexanol and light-boiling components containing unreacted cyclohexene and methylcyclopentene. D
Reference numeral 4 denotes a packed tower corresponding to 15 theoretical stages, and the reaction solution 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. Distillate is from line 12 to part line 1
4 to a distillation column D5. At D5, methylcyclopentene is concentrated and purged from the top. D5 is a packed column corresponding to 30 theoretical plates, and the distillate of D4 is 2
It is supplied to the third stage. The top pressure is normal pressure and the reflux ratio is 30. D5 bottoms are recycled from line 17 to the hydration reactor. On the other hand, cyclohexene not supplied to D5 is recycled from the line 15 to the hydration reactor.

Under the above conditions, the mass balance of each line is as shown in Table 1, and it can be seen that methylcyclopentene, benzene and cyclohexane do not accumulate in the recycle line. That is, the MCPN of the line 11 feeding the distillation column is suppressed to 1%. If distillation column D
If the condition (5) is relaxed, the MCPN concentration in the line 11 increases, which causes deterioration of the hydration catalyst. In the cyclohexane obtained as a by-product from line 4,
It can be seen that highly pure cyclohexane containing no methylcyclopentene can be obtained.

[0035]

[Table 1]

[0036]

[Table 2]

In Table 1, Bz is benzene, CHX is cyclohexane, CHE is cyclohexene, MCPN is methylcyclopentene, CHL is cyclohexanol, H
B represents a high-boiling substance, and DMI represents 1,3- represents dimethylimidazolidinone.

[0038]

The feature of the present invention described in detail above is that, after obtaining the desired product cyclohexanol from the product of the hydration reaction, cyclohexene and methylcyclopentene are extracted as in the prior art. Without circulating in distillation, at least a part thereof is separated into a component having a high concentration of methylcyclopentene and a component having a low concentration of methylcyclopentene by means of distillation or the like, and the former is extracted out of the system, and the latter is hydrated. Circulation to the reaction process. As a result, even in a method for consistently producing cyclohexanol from benzene, since methylcyclopentene is substantially absent in the extractive distillation system, a separation step from cyclohexane is unnecessary, and thus, it is obtained by extractive distillation. Cyclohexane can be used for other purposes as it is. Also, cyclohexane of the same composition,
Even if cyclohexene and benzene are obtained, the load can be greatly reduced. In addition, there is an effect that a large amount of methylcyclopentene does not accumulate in the hydration reaction system, and this is extremely advantageous as a method industrially adopted.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing all steps of a manufacturing method of the present invention.

FIG. 2 schematically shows a method of first separating cyclohexane and then separating cyclohexene and benzene using three distillation columns in a first separation step (extraction separation step) of the production method of the present invention. FIG.

FIG. 3 schematically shows a method of separating benzene and then separating cyclohexane and cyclohexene using four distillation columns in a first separation step (extraction separation step) of the production method of the present invention. FIG.

FIG. 4 is a diagram schematically showing a hydration step and a second separation step of the production method of the present invention.

FIG. 5 is a diagram showing a process flow of an embodiment of the present invention.

[Explanation of symbols]

R1 and R2 are reactors. D1, D2, D3, D4 and D5
Is a distillation tower. Numbers 1 to 18 are tubes (lines). Bz is benzene. CHX is cyclohexane. CHE is cyclohexene. MCPN is methylcyclopentene. CHL is cyclohexanol. solv is an extractant.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁶ Identification code FI C07C 29/04 C07C 29/04 29/80 29/80 // C07B 61/00 300 C07B 61/00 300

Claims (6)

[Claims] 1. A method for continuously producing cyclohexanol from benzene having the following steps (1) to (4). (1) benzene obtained by partially hydrogenating benzene,
A first separation step of separating a hydrogenation reaction mixture containing cyclohexane and cyclohexene into components of benzene, cyclohexane and cyclohexene; (2) A hydration step of hydrating the cyclohexene separated in the first separation step of (1) to obtain a hydration reaction mixture containing cyclohexene, cyclohexanol and methylcyclopentene. (3) A second separation step of separating the hydration reaction mixture obtained in the above hydration step (2) into a mixture of cyclohexene and methylcyclopentene and cyclohexanol. (4) separating at least a part of the mixture of cyclohexene and methylcyclopentene separated in the second separation step of (3) into a component having a high concentration of methylcyclopentene and a component having a low concentration of methylcyclopentene; The component having a high concentration of methylcyclopentene is discharged out of the system without being circulated to the first separation step (1), and the component having a low concentration of methylcyclopentene is circulated to the hydration step (2). Circulating process. 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 circulation step of (4) includes the second step of (3).
Part of the mixture of cyclohexene and methylcyclopentene obtained in the separation step is circulated to the hydration step (2), and the remainder is distilled to remove the components having a high concentration of methylcyclopentene and the components having a low concentration of methylcyclopentene. And discharging the component having a high concentration of methylcyclopentene to the outside of the system, and circulating the component having a low concentration of methylcyclopentene to the hydration step (2). The method according to any of the above.