JPH0931001A - Production of cyclohexanol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain cyclohexanol in high purity through efficiently removing by-products by separating cyclohexene from a specific reaction mixture by extractive distillation followed by hydration of the cyclohexene to obtain a reaction product from which the aimed cyclohexanol is separated by distillation followed by circulating the residual liquid to both the extractive distillation and the hydration processes. SOLUTION: From a mixture of cyclohexene (A1 ), benzene (A2 ) and cyclohexane (A3 ) produced by partially hydrogenating benzene, the component A1 is separated by extractive distillation followed by hydration of the component A1 into a mixture of cyclohexanol (C1 ), the component A1 and methyl cycl, opentenes (C2 ), from which the component C1 is separated by distillation, and only part of the resultant residual liquid is circulated to the hydration process and the rest of the residual liquid to the extractive distillation process and the component C2 , together with the component A3 , is separated and removed out of the system, thus obtaining the objective cyclohexanol (C1 ).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing cyclohexanol. Specifically, it relates to a method for producing cyclohexanol by hydrating cyclohexene obtained mainly by partial hydrogenation of benzene. Cyclohexanol is an important intermediate raw material for adipic acid, hexamethylenediamine and ε-caprolactam which are precursors of nylon.

[0002]

2. Description of the Related Art As a main industrial production method of cyclohexanol, there are a method by nuclear hydrogenation of phenol and a conventional method via a mixture of cyclohexanone and cyclohexanol by air oxidation of cyclohexane. To be
These production methods have problems such as a large amount of by-products and a very low reaction conversion rate.

On the other hand, in recent years, attention has been focused on a method for producing cyclohexanol by hydrating cyclohexene obtained by partial hydrogenation of benzene. The partial hydrogenation reaction of benzene is usually performed in the presence of a ruthenium catalyst and water to obtain a reaction mixture containing cyclohexene, unreacted benzene and by-produced cyclohexane (Japanese Patent Publication No. 3-537).
0, Japanese Patent Publication No. 2-19098, Japanese Patent Laid-Open No. 04-074141, etc.)

As a method for hydrating cyclohexene to obtain cyclohexanol, a method using a solid acid catalyst such as zeolite as a catalyst is said to be preferable, and the hydration reaction of cyclohexene is an equilibrium reaction, A reaction mixture of the product cyclohexanol and unreacted cyclohexene is obtained (JP-A-58-112229, JP-A-58-194828, JP-A-60-104028-).
104031, JP-A-1-10639, etc.).

Separation and recovery of cyclohexene having a higher purity than a mixture of cyclohexene, benzene and cyclohexane obtained by the above-mentioned partial hydrogenation reaction of benzene is carried out in the usual manner because the boiling points of the three compounds are close to each other. Distillation is difficult, and the extractive distillation method is generally adopted. In this extractive distillation, N-methylpyrrolidone,
A method using various extraction agents such as dimethyl sulfoxide, dimethylformamide, γ-butyrolactone, N-dimethylacetamide, adiponitrile, sulfolane, dimethyl malonate and dimethyl succinate has been proposed (JP-A-52-5733, JP-A-52-5733). 52-170443, JP-A-52-144649, JP-A-52-144650, JP-A-58-1645724, and JP-A-58-164572.
5, JP-A-58-172323, JP-A-62-2953
11 etc.).

Further, a method of recovering cyclohexanol from a reaction mixture by hydration of cyclohexene is also known to some extent. The problem here is that an isomerization reaction of cyclohexene is unavoidable as a side reaction in the hydration of cyclohexene, which results in the by-production of methylcyclopentenes, and further a part of the methylcyclopentenes is hydrated. This is the point where it changes to methylcyclopentanols.

Cyclohexene and methylcyclopentenes, and cyclohexanol and methylcyclopentanol have a relative volatility close to 1. Therefore, when these mixtures are separated using a distillation column, methylcyclopentane is used. The nors are entrained as an impurity in cyclohexanol extracted from the bottom of the column, and the methylcyclopentenes remain in the residual liquid and are returned to the raw material for the hydration reaction. Therefore, when such an operation is continued, accumulation of methylcyclopentenes occurs in the starting cyclohexene of the hydration reaction,
As a result, in the product after the hydration reaction, methylcyclopentano- which is an equilibrium reaction product of methylcyclopentenes.
Content also increases, resulting in a significant decrease in cyclohexanol purity.

Therefore, a method for removing or controlling methylcyclopentenes has been proposed. For example, Japanese Examined Patent Publication (Kokoku) No. 55-34773 proposes a method of removing 1-methylcyclopentene in cyclohexene, which is a residual liquid obtained by separating cyclohexanol, by treating with nitric acid.
Further, Japanese Patent Publication No. 55-34774 proposes a method in which the same residual liquid as described above is treated with chlorine and then distilled to be removed.

On the other hand, according to the above-mentioned JP-A-60-104028, from the hydration reaction mixture of cyclohexene,
When cyclohexanol having a high boiling point is separated and obtained, and cyclohexene as a raw material for the hydration reaction in which cyclohexanol is separated is returned to the hydration reaction step, a part of the residual liquid is purified in advance. The method of removing methylcyclopentenes out of the system has been adopted. Also, Japanese Patent Laid-Open No. 4-41442.
Japanese Patent Laid-Open No. 4-41448 proposes extractive distillation as a purification method for removing the methylcyclopentenes out of the system. Especially,
Japanese Unexamined Patent Publication No. 4-41442 discloses that when removing methylcyclopentenes in crude cyclohexene, a method in which crude cyclohexene is mixed with cyclohexane and then extractive distillation is preferable.

[0010]

Conventionally, many proposals have been made for producing and purifying cyclohexene and cyclohexanol as described above, but each of them has some problems. The current situation is that the examination of rational methods in consideration of industrial implementation is insufficient. For example,
The method of treating methylcyclopentenes with nitric acid or chlorine described above has problems that a new treating agent needs to be added to the process and that a reactor for performing the treatment requires a high-grade material. Further, in the method of removing methylcyclopentenes from the residual liquid containing cyclohexene that has separated cyclohexanol by using extractive distillation, at least a distillation column for separating methylcyclopentenes and a distillation column for recovering cyclohexene from an extractant are used. Two distillation columns are newly required, which increases equipment cost and energy cost, which is an industrial problem.

[0011]

Means for Solving the Problems In view of the above problems, the present inventors have made earnest studies on the production of cyclohexanol using a partial hydrogenation reaction of benzene and a hydration reaction of cyclohexene. It came to construct a general process invention. That is, the gist of the present invention is cyclohexene obtained by partial hydrogenation of benzene, cyclohexene from a mixture of benzene and cyclohexane is separated by extractive distillation, and then cyclohexene is obtained by hydrating the cyclohexene, cyclohexene and methyl. In a method in which cyclohexanol is separated by distillation from a mixture of cyclopentenes, and the residual liquid is circulated in the hydration step, at least a part of the residual liquid is circulated in the extractive distillation step, and methylcyclopentenes are mixed with cyclohexane in a system. It exists in the manufacturing method of cyclohexanol characterized by separating and removing to the outside.

Hereinafter, the present invention will be described in detail. The production of cyclohexene in the present invention may be carried out by a known method for partially hydrogenating benzene, and is usually performed in the presence of a ruthenium catalyst and water. As the catalyst, ruthenium alone or ruthenium, iron, cobalt, manganese,
Zinc, gold and the like are used. The catalyst may be in the form of particles or may be used by being supported on silica or a metal oxide such as alumina or zirconia. Water is preferably used in a volume ratio of 0.1 to 5 times that of benzene. In addition, manganese, zinc,
Metal salts such as cobalt and lithium may coexist in water. The hydrogen pressure during the reaction is usually 0.5 to 10 MPa,
The reaction is usually carried out at 100 to 220 ° C.

Cyclohexene is isolated by extractive distillation of a mixture of cyclohexene, benzene and cyclohexane obtained by partial hydrogenation of benzene.
The separated purified cyclohexene is subjected to a hydration reaction.
Known conditions may be adopted for the extractive distillation. As the extractant, any one can be used as long as it can separate and obtain each component from a mixture of cyclohexane, cyclohexene, and benzene, and for example, N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, γ-butyrolactone, γ
-Valerolactone, γ-caprolactone, N, N-dimethylacetamide, adiponitrile, succinonitrile, glutaronitrile, malonnitrile, benzonitrile, pentenenitrile, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerol, triethylene Glycol, sulfolane, furfural, m-cresol, nitrobenzene, nitromethane, methyl isobutyl ketone, methyl pyruvate, dimethyl malonate, dimethyl succinate,
Examples thereof include a mixed solvent of N, N-dimethylacetamide and sulfolane, a mixed solvent of N, N-dimethylacetamide and adiponitrile, and the like. In addition, JP-A-4-4144
According to No. 1, the extractant preferably has a dielectric constant in the range of 10 to 60 at 20 ° C.

The order of separating cyclohexene, benzene and cyclohexane using extractive distillation is not particularly limited, but cyclohexane is distilled from the top of the first extractive distillation column and benzene and cyclohexene are extracted from the bottom together with the extractant. To extract cyclohexene from the top of the tower in the second extractive distillation of the bottom liquid, and then to extract benzene together with the extractant from the bottom of the tower, and cyclohexene and cyclohexane from the top of the first extractive distillation. Benzene is extracted from the bottom of the column together with the extractant, and cyclohexane is extracted from the top of the column by extraction distillation of the second column followed by the top liquid, and cyclohexene is extracted from the bottom of the column together with the extractant, and then extracted by ordinary distillation. A method of separating the agent and cyclohexene is exemplified. The separated benzene can be reused as a raw material in the partial hydrogenation step.

When performing extractive distillation, the theoretical plate number is usually 15
The above, preferably 20 or more distillation columns are used. Normal,
The extractant is supplied to the upper stage of the distillation column, and the mixture is supplied to the lower side of the middle stage of the distillation column. The amount of the extractant used is usually equal to or greater than the amount of the mixture, and the overhead pressure is usually 0.02 to
0.3 MPa. Further, the reflux ratio of the extractive distillation is usually 8 or more in the first column of the above method and the second column of the above method, and is 1 to 4 in the second column of the above method and the first column of the method.

As described in detail below, the present invention provides at least one of the residual liquid obtained by separating cyclohexanol from a mixture of cyclohexene, cyclohexene and methylcyclopentene obtained by subjecting cyclohexene to a hydration reaction. Part is circulated to the extractive distillation step to separate and remove methylcyclopentenes together with cyclohexane out of the system, but in the case of the above method, the residual liquid from which cyclohexanol was separated is the first column. Circulate to the extractive distillation column. Further, in the case of the above method, the same residual liquid from the hydration step may be normally circulated to the second extractive distillation column, but in consideration of the accumulation of a small amount of benzene in the residual liquid, A method of circulating in the tower may be adopted.

The cyclohexanol used in the present invention may be produced by a known cyclohexene hydration method, and examples of the catalyst include sulfuric acid, heteropolyacid, and solid acids such as zeolite. Is a zeolite. Preferred examples of zeolites include crystalline aluminosilicates such as mordenite, erionite, ferrierite and ZSM type zeolites announced by Mobil Co., and metallocontaining different elements such as boron, iron, gallium, titanium, copper and silver. Zeolites such as aluminosilicate and metallosilicate. The exchangeable cation species of zeolite is usually a proton exchange type, but it is also effective to exchange with a metal ion.

The hydration reaction is continuously carried out, for example, by mixing and suspending an aqueous phase containing a catalyst and an oil phase containing cyclohexene. The molar ratio of cyclohexene to water in the reaction system is usually 0.01 to 100, preferably 0.1.
~ 30. The weight ratio of the catalyst to cyclohexene in the reactor is usually 0.005 to 100, preferably 0.05 to 10. The reaction temperature is usually 50 to 30.
The temperature is 0 ° C, preferably 80 to 160 ° C. The reaction pressure is not particularly limited, but a pressure capable of keeping cycloalkene and water in a liquid phase is preferable, and usually 5 MPa or less, preferably 0.2 to 2 MPa. Further, the reaction residence time is usually 0.1 to 5 hours, preferably 0.2 to 3 hours.
In addition, it is preferable to replace the inside of the hydration reaction system with an inert gas such as nitrogen, hydrogen, helium, or argon. Further, in addition to cyclohexene, which is a reaction raw material, and water, ethanol, acetone, acetic acid, benzoic acid, phenol, or their derivatives may coexist in the reaction system.

In the hydration reaction liquid, the organic phase containing cyclohexanol can usually be separated and recovered by phase separation from the aqueous phase containing the catalyst. Examples of the method for separating the reaction liquid into an aqueous phase and an oil phase include a method in which an oil / water separation weir is provided in the reactor to take out only the oil phase. It is also conceivable to take out a part of the reaction liquid with a liquid circulation pump and supply it to an oil / water separation tank provided outside the reactor to separate it.The separated aqueous phase containing the catalyst circulates in the reactor. Can be reused.

The separated oil phase is cyclohexano-
A mixture of cyclohexene and methylcyclopentenes. Methylcyclopentenes are produced by the hydration reaction as described above. Methylcyclopentenes refer specifically to 1-methylcyclopentene, 3-methylcyclopentene and 4-methylcyclopentene, especially 1-methylcyclopentene and 3-methylcyclopentene. Methylcyclopentanols include 1-methylcyclopentanol, 2-methylcyclopentanol,
And 3-methylcyclopentanol, especially 1-
It means methylcyclopentanol and 3-methylcyclopentanol. The mixture also contains a trace amount of methylcyclopentanols, which are hydrates of methylcyclopentenes. It should be noted that there is no particular problem even if the mixture contains a small amount of benzene, cyclohexane, water or the like derived from partial hydrogenation of benzene or hydration of cyclohexene.

As a method for separating cyclohexanol from the above-mentioned mixture of cyclohexanol, cyclohexene and methylcyclopentene, ordinary distillation is carried out.
The most effective method is to obtain cyclohexanol from the bottom of the distillation column, but a combination of liquid-liquid extraction and distillation is also possible.

The present invention is characterized in that at least a part of the residual liquid from which cyclohexanol is separated is circulated in the extractive distillation step to separate and remove methylcyclopentenes together with cyclohexane out of the system. The residual liquid other than that circulated in the extractive distillation step is circulated as a starting material cyclohexene in the hydration reaction step. In the present invention, the step of removing methylcyclopentenes is also used as the step of separating the mixture of cyclohexene, benzene, and cyclohexane obtained by the partial hydrogenation reaction of benzene. The methylcyclopentenes can be removed to the outside of the system without particularly increasing. Further, conventionally, the separation efficiency of low-concentration methylcyclopentenes is not sufficient, and according to the above-mentioned Japanese Patent Laid-Open No. 4-41442, cyclohexane is intentionally added from outside the system for extractive distillation in order to improve the separation efficiency. However, in the method of the present invention, since the extractive distillation is carried out in the coexistence of cyclohexane, separation of low-concentration methylcyclopentenes is also good.

Furthermore, when continuously carrying out the present invention industrially, it is necessary to set the operating conditions concretely. In Japanese Patent Laid-Open No. 4-41448, there is a correlation between the amount of extractive distillation and the purity of cyclohexanol separated and obtained, particularly the concentration of methylcyclopentanol in cyclohexanol, and cyclohexanol It is stated that the purity of the phenol can be controlled by the conditions of extractive distillation. However, realistically, in the case of a process combining hydration reaction and distillation, the hydration reaction activity of the catalyst used for the hydration reaction, the methylcyclopentenes formation rate, the reaction temperature, the residence time, the number of reactor stages, etc. The equilibrium production rate of methylcyclopentanols, the distribution rate to the reaction solution, and the like remarkably change depending on the hydration reaction conditions, the separation conditions of the reaction solution, and the like, which is a complicated situation.

Therefore, in the present invention, as a result of a detailed study, the condition for the extractive distillation is α defined by the following formula (1).
It has been found that it is preferable to perform the operation so that the value is usually 10 to 80, preferably 15 to 60. By using this relational expression, the concentration of methylcyclopentanols in cyclohexanol to be separated and obtained can be easily 1% by weight or less, preferably 0.5% by weight.
It can be: The α value is not particularly understood, but when the α value exceeds 80, methylcyclopentanol in cyclohexanol that is separated and obtained usually reaches an equilibrium state at a high concentration. So not so good. Further, when the α value is less than 10, it is usually not preferable because it is necessary to increase the catalyst in the hydration reactor and to make the distillation conditions strict, which is not economical.

[0025]

Α = 1.20 × [(1-A) / A] × e ^{−23000 / (T + 273)} × B × 10 ³⁰ (1) (In the formula (1), A, B, and t are Each is as follows: A: Ratio of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step B: Methylcyclopentene per 1 kg of hydration catalyst at 100 ° C Generation rate (mol / hr / kg) T: Hydration reaction temperature (° C)

[0026]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. Reference Example 1 (Measurement of Methylcyclopentene Formation Rate in Hydration Reaction of Cyclohexene) Aluminosilicate H type ZSM-5 (SiO ₂ / Al ₂ O ₃ molar ratio) was added to an SUS-304 autoclave equipped with a stirrer. = 50) 370 g, water 1110 g, cyclohexene 5
55 g was charged, the system was replaced with nitrogen, and the temperature was raised to 100 ° C. While maintaining the pressure at 6 KG, 100 ℃, stirring number 10
After reacting for 20 hours under the condition of 00 rpm, stirring was stopped, and after standing for 20 minutes, only the oil phase was extracted from the sampling tube in the autoclave, and methylcyclopentenes were analyzed by gas chromatography. as a result,
The production rate of methylcyclopentenes at 100 ° C. is 4.3 × 10 ⁻⁴ mol / hr / k per 1 kg of catalyst.
g.

Example 1 The flow chart carried out is shown in FIG. The contents of implementation will be described below with reference to the drawings. Reference numeral 1 denotes a flow for supplying benzene as a raw material, which is mixed with a flow 5 of recovered unreacted benzene and is supplied to a hydrogenation reactor R1 having an oil / water separation weir in the reactor and capable of taking out only an oil phase. Stream 3 of the hydrogenation reaction solution is mixed with stream 18 which is a part of stream 16 of unreacted cyclohexene containing methylcyclopentenes recovered from cyclohexanol separation column T5 from the hydration reaction solution, It is supplied to the benzene separation column T1 and by extraction distillation, benzene and a solvent are obtained from the bottom (stream 4), and cyclohexene and cyclohexane containing methylcyclopentenes are obtained from the top (stream 7). Stream 7 is circulated to cyclohexane separation column T3, and cyclohexane and methylcyclopentenes are extracted from the top (stream 11) by extractive distillation. Cyclohexene and the extractant are withdrawn from the bottom of the column (stream 9), and the cyclohexene obtained from the top of the cyclohexene recovery column T4 (stream 12) is mixed with the cyclohexene stream 17 separated by T5 from the hydration reaction liquid. Then, it is supplied to the hydration reactor R2. Stream 14 containing unreacted cyclohexene, the desired product cyclohexanol, and by-products methylcyclopentenes and methylcyclopentanols is fed to T5, and cyclohexanol is fed from the bottom of the column (stream 15). Is obtained, and cyclohexene containing methylcyclopentenes is recovered from the top of the column (stream 16). A portion of stream 16 is fed to T1 as stream 18 and the remainder is recycled to hydration reactor R2 as stream 17.

The hydration reaction was carried out by using the ZS used in Reference Example 1.
After adding water to 2.5 kg of M-5 to make a slurry, the slurry was added to a hydration reactor R2 having an oil / water separation weir in the reactor and capable of taking out only an oil phase, at 120 ° C, reaction pressure 6K / G.
The feed to the reactor below (stream 13) was carried out at 2.5 kg / Hr. N, N-dimethylacetamide is used as the extractant for the extractive distillation, and the cyclohexane separation column T3 is 50
A staged distillation column was used. The flow rate of the cyclohexene stream 18 containing methylcyclopentenes circulated in the extractive distillation step is the same as that of the cyclohexene stream 12 supplied to the hydration step.
The ratio to the flow rate (corresponding to A in the above formula (1)) was 0.45. Further, the α value in the equation (1) is 24. Methylcyclopentano in cyclohexanol
Table 1 shows the composition after 25 hours when it was confirmed that the concentration of the rutiles reached an almost constant equilibrium value.

[0029]

[Table 1]

Example 2 The hydration reaction temperature T shown in the above formula (1) and the ratio A of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step. Table-
The same experiment as in Example 1 was performed except that the conditions shown in 3 were used. It was confirmed that the concentration of methylcyclopentanols in cyclohexanol reached an almost constant equilibrium value. 2
The concentration of methylcyclopentanol in cyclohexanol after 5 hours was 0.31% by weight. Table 3 shows the conditions and results.

Example 3 The hydration reaction temperature T shown in the above formula (1) and the ratio A of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step were determined. Table-3
An experiment similar to that of Example 1 was performed except that the conditions shown in (1) were used. It was confirmed that the concentration of methylcyclopentanols in cyclohexanol reached an almost constant equilibrium value. 2
The concentration of methylcyclopentanols in cyclohexanol after 0.5 hour was 0.54% by weight. Table 3 shows the conditions and results.

Comparative Example 1 Cyclohexene stream 18 containing methylcyclopentenes circulated in the extractive distillation step was set to a flow rate of 0, and stream 16 was used.
Flow of cyclohexene to supply all of the water to the hydration process 1
The same operation as in Example 1 was carried out except that 2 was mixed. The composition after 25 hours is shown in Table 2. Table-3
The conditions and results are shown in.

[0033]

[Table 2]

Reference Example 2 (Measurement of Methylcyclopentene Formation Rate in Cyclohexene Hydration Reaction) H-type gallium silicate (SiO ₂ / Ga ₂ O ₃ molar ratio = 5) which is a zeolite having an MFI structure as a hydration reaction catalyst.
When the same experiment as in Reference Example 1 was conducted except that 0) was used, the production rate of methylcyclopentenes was
It was 6.2 × 10 ⁻⁵ mol / hr / kg per g.

Example 4 Using the catalyst used in Reference Example 2 as a hydration reaction catalyst, the hydration reaction temperature T shown in the above formula (1) and extractive distillation after hydration with respect to the amount of cyclohexene supplied to the hydration step. The same experiment as in Example 1 was performed except that the ratio A of the amount of cyclohexene in the residual liquid circulated in the process was set to the conditions shown in Table-3.
It was confirmed that the concentration of methylcyclopentanols in cyclohexanol had an almost constant equilibrium value.
After a lapse of time, the concentration of methylcyclopentanols in cyclohexanol was 0.29% by weight. Table 3 shows the conditions and results.

Example 5 The hydration reaction temperature T shown in the above formula (1) and the ratio A of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step were determined. Table-3
An experiment similar to that in Example 4 was performed except that the conditions shown in (4) were used. It was confirmed that the concentration of methylcyclopentanols in cyclohexanol reached an almost constant equilibrium value. 2
The concentration of methylcyclopentanol in cyclohexanol after 5 hours was 0.31% by weight. Table 3 shows the conditions and results.

Example 6 Weight ratio A of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the hydration reaction temperature T shown in the above formula (1) and the amount of cyclohexene supplied to the hydration step. The same experiment as in Example 4 was performed except that the conditions shown in Table 3 were used. Methylcyclopentano in cyclohexanol
The concentration of methylcyclopentanols in cyclohexanol was 0.18% by weight after 500 hours when it was confirmed that the concentration of the polyols reached an almost constant equilibrium value. Table-3
The conditions and results are shown in.

Example 7 The hydration reaction temperature T shown in the above formula (1), the ratio A of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step was determined. Table-3
An experiment similar to that of Example 1 was performed except that the conditions shown in (1) were used. It was confirmed that the concentration of methylcyclopentanols in cyclohexanol reached an almost constant equilibrium value. 2
The concentration of methylcyclopentanol in cyclohexanol after 5 hours was 1.52% by weight. Table 3 shows the conditions and results.

Example 8 The hydration reaction temperature T shown in the above formula (1) and the ratio A of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step were determined. Table-3
An experiment similar to that in Example 4 was performed except that the conditions shown in (4) were used. It was confirmed that the concentration of methylcyclopentanols in cyclohexanol reached an almost constant equilibrium value. 2
The concentration of methylcyclopentanols in cyclohexanol after 5 hours was 1.59% by weight. Table 3 shows the conditions and results.

[0040]

[Table 3] *: In Comparative Example 1, the value is not in the equilibrium state, so that the methylcyclopentanol concentration further increases when the operation is continued.

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, methylcyclopentenes by-produced in cyclohexene hydration can be separated and removed with high efficiency and economically, and highly pure cyclohexanol can be stably obtained. it can.

[Brief description of drawings]

FIG. 1 is a flow chart showing a first embodiment.

Continuation of the front page (72) Inventor Tsutomu Yonemori 1-1 Kurosaki Shiroishi, Hachimannishi-ku, Kitakyushu, Fukuoka Prefecture Mitsubishi Chemical Corporation Kurosaki Development Laboratory

Claims (6)

[Claims] 1. A cyclohexene obtained by partial hydrogenation of benzene, cyclohexene is separated from a mixture of benzene and cyclohexane by extractive distillation, and then cyclohexene is hydrated to obtain cyclohexanol, cyclohexene and methylcyclopentenes. In the method in which cyclohexanol is separated by distillation from the mixture and the residual liquid is circulated in the hydration step, at least a part of the residual liquid is circulated in the extractive distillation step, and methylcyclopentenes are separated from the system together with cyclohexane. A method for producing cyclohexanol, which comprises removing the cyclohexanol. 2. The method according to claim 1, wherein the α value defined by the following formula (1) is 10 to 80 under the condition of the extractive distillation. ## EQU1 ## α = 1.20 × [(1-A) / A] × e ^{−23000 / (T + 273)} × B × 10 ³⁰ (1) (In the formula (1), A, B, and t are Each is as follows: A: Ratio of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step B: Methylcyclopentene per 1 kg of hydration catalyst at 100 ° C Generation rate (mol / hr / kg) T: Hydration reaction temperature (° C) 3. A mixture of cyclohexene, benzene and cyclohexane is supplied to a first extractive distillation column, cyclohexane is distilled off from the top of the column, an extractant, benzene and cyclohexene are extracted from the bottom of the column, and the bottom liquid is subjected to a second extraction. It is a method of distilling cyclohexene from the top of a distillation column and extracting benzene and an extractant from the bottom of the column, and cyclohexene is obtained by hydrating cyclohexene, cyclohexene from a mixture of cyclohexene and methylcyclopentenes. The ethanol is separated by distillation, and at least a part of the residual liquid is circulated to the first extractive distillation column, and methylcyclopentenes are distilled out together with cyclohexane from the top of the first extractive distillation column to separate them out of the system. The method for producing cyclohexanol according to claim 1 or 2, wherein 4. A mixture of cyclohexene, benzene and cyclohexane is supplied to a first extractive distillation column, benzene and an extractant are extracted from the bottom of the column, cyclohexene and cyclohexane are distilled off from the top of the column, and the top liquid is subjected to a second extraction. It is a method of distilling cyclohexane from the top of the column, distilling cyclohexane from the top of the column, extracting cyclohexene and a solvent mixture from the bottom of the column, and separating cyclohexene by distillation from the mixture, which is obtained by hydrating cyclohexene. Cyclohexanol was separated by distillation from a mixture of sanol, cyclohexene and methylcyclopentene, and at least a part of the residual liquid was circulated to the first extractive distillation column, and methylcyclopentene was collected from the top of the second extractive distillation column. The cyclohexane according to claim 1 or 2, wherein the cyclohexane is distilled off together with cyclohexane to separate and remove it from the system. Method for producing xanol. 5. A mixture of cyclohexene, benzene and cyclohexane is supplied to a first extractive distillation column, benzene and an extractant are extracted from the bottom of the column, cyclohexene and cyclohexane are distilled off from the top of the column, and the top liquid is subjected to a second extraction. It is a method of distilling cyclohexane from the top of the column, distilling cyclohexane from the top of the column, extracting cyclohexene and a solvent mixture from the bottom of the column, and separating cyclohexene by distillation from the mixture, which is obtained by hydrating cyclohexene. Cyclohexanol was separated by distillation from a mixture of sanol, cyclohexene and methylcyclopentene, and at least a part of the residual liquid was circulated to the second extractive distillation column, and methylcyclopentene was collected from the top of the second extractive distillation column. The cyclohexane according to claim 1 or 2, wherein the cyclohexane is distilled off together with cyclohexane to separate and remove it from the system. Method for producing xanol. 6. Cyclohexanol is separated by distillation from a mixture of cyclohexanol, cyclohexene and methylcyclopentene obtained by hydrating cyclohexene,
In the method in which the residual liquid is circulated in the hydration step, and at least a part of the residual liquid is subjected to extractive distillation, and the separated cyclohexene is circulated in the hydration step, the condition of the extractive distillation is represented by the following formula (1). The method for producing cyclohexanol, wherein the α value defined in is 10 to 80. ## EQU2 ## α = 1.20 × [(1-A) / A] × e ^{−23000 / (T + 273)} × B × 10 ³⁰ (1) (In the formula (1), A, B, and t are Each is as follows: A: Ratio of the amount of cyclohexene in the residual liquid circulated in the extractive distillation step after hydration to the amount of cyclohexene supplied to the hydration step B: Methylcyclopentene per 1 kg of hydration catalyst at 100 ° C Generation rate (mol / hr / kg) T: Hydration reaction temperature (° C)