JPH11322661A - Production of cyclohexanone and production of epsilon-caprolactam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing cyclohexanone from benzene without waste by utilizing byproduct cyclohexane from CHE process (a combination of the partial hydrogenation of benzene with the hydration reaction of cyclohexene), and to provide a method for producing ε-caprolactam without waste in a similar manner. SOLUTION: This method for producing cyclohexanone comprises a combination of the following two processes: (1) in the CHE process intended for producing cyclohexanol by hydration of cyclohexene formed by partial hydrogenation of benzene, byproduct cyclohexane is oxidized with molecular oxygen to form cyclohexanone, and (2) the cyclohexanol obtained by the CHE process is dehydrogenated to form cyclohexanone. The other objective method for producing ε-caprolactam comprises using the cyclohexanone produced by the process 1 as a feedstock.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing cyclohexanone from benzene. More specifically, the present invention relates to a method for producing cyclohexanone using a by-product effectively and a method for producing ε-caprolactam using cyclohexanone obtained by the method as a raw material.

[0002]

2. Description of the Related Art Cyclohexanone is a compound useful as an intermediate material or a solvent for caprolactams used as a nylon material. As a method for producing cyclohexanone, a method for oxidizing cyclohexane with molecular oxygen in the presence of a heavy metal catalyst such as cobalt or a boric acid catalyst has been widely known. In this method, since cyclohexanol is usually produced together with cyclohexanone as a reaction product, cyclohexanol is dehydrogenated to cyclohexanone. However, this method not only has a low conversion, but also has a large amount of by-products, resulting in a complicated process.

In order to solve such problems, a method for producing cyclohexene by a partial hydrogenation reaction of benzene using a Ru catalyst and a method for producing cyclohexanol by a hydration reaction of a cyclohexene using a zeolite catalyst are combined. Thus, a method for producing cyclohexanol from benzene and dehydrogenating it to form cyclohexanone has been studied. According to this method, in the hydrogenation reaction, substantially only cyclohexane is generated as a by-product, and the selectivity in the hydration reaction is extremely high, so that the carbon yield is high and the process is very simple. There is a feature. However, in a method combining the above partial hydrogenation reaction of benzene and the hydration reaction of cyclohexene (hereinafter referred to as “CHE method”), the presence of cyclohexane generated in the hydrogenation reaction becomes a problem. In a conventional partial hydrogenation reaction of benzene, the conversion is 60% at the maximum and the selectivity is about 80%. That is, as much as 12% of cyclohexane is produced with respect to the raw material benzene. Cyclohexane also has uses as an organic solvent and release agent, but considering industrial processes,
It is not preferable that the production of cyclohexanone be restricted due to various factors (demand, price, etc.) in the above applications of cyclohexane, and there is a problem in using cyclohexane for another application.

In order to solve such a problem, CH
It has also been proposed that cyclohexane produced by the method E is dehydrogenated to benzene, which is then used again as a raw material for the partial hydrogenation reaction (Japanese Patent Application Laid-Open No. Hei 7-165646).

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a novel method for solving the above-mentioned problems, and it is intended to provide a novel
It is an object of the present invention to solve the problem of by-product cyclohexane in the method E and to obtain cyclohexanone from benzene without waste. According to the study of the present inventors, such objects are achieved by a method of oxidizing cyclohexane obtained by the CHE method with molecular oxygen to cyclohexanone, and a method of dehydrogenating cyclohexanol obtained by the CHE method. The present invention has been accomplished by finding that the above-mentioned effects can be achieved by combining the above.

[0006]

That is, the gist of the present invention is a method for producing cyclohexanone using benzene as a raw material, comprising the following steps (1) to (5): It is about the method. (1) Partial hydrogenation of benzene to obtain a hydrogenated reaction mixture containing cyclohexane and cyclohexene (2) The hydrogenated reaction mixture obtained in the above (1) is added to each component of cyclohexane and cyclohexene Separation step for separation (3) Hydration step of hydrating the separated cyclohexene and obtaining cyclohexanol from the reaction product (4) Dehydrogenating the cyclohexanol obtained in the above (3) to produce cyclohexanone Obtained dehydrogenation step (5) Oxidation step of oxidizing cyclohexane separated in the above step (2) with molecular oxygen to obtain cyclohexanone Another gist of the present invention is to oxidize cyclohexane with molecular oxygen. A method for producing cyclohexanone to obtain an oxidation reaction mixture containing cyclohexanone,
The present invention relates to a method for producing cyclohexanone using cyclohexane obtained through the following steps (1) to (5) as a raw material cyclohexane. (1) Partial hydrogenation of benzene to obtain a hydrogenated reaction mixture containing cyclohexane and cyclohexene (2) The hydrogenated reaction mixture obtained in the above (1) is added to each component of cyclohexane and cyclohexene Separation step for separation (3) Hydration step of hydrating cyclohexene separated in (2) above to obtain a hydration reaction mixture containing cyclohexanol (4) hydration reaction mixture obtained in (3) above A cyclohexanol separation step of separating into a low-boiling component containing cyclohexene and methylcyclopentenes and a high-boiling component containing cyclohexanol. (5) The light-boiling component obtained in the above (4) is separated into the (2) After removing at least a portion of the methylcyclopentenes in the light-boiling component without recycling to the separation step of (3), the remainder is recycled to the above (3). Concentration Step of Methylcyclopentenes Used Further, the present invention also relates to a process for producing ε-caprolactam by subjecting cyclohexanone obtained by the above method to oximation and further Beckmann rearrangement to obtain ε-caprolactam.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. (Partial hydrogenation step) In the present invention, the partial hydrogenation fixation
In this step, benzene is partially hydrogenated in the presence of a hydrogenation catalyst to obtain a partially hydrogenated reaction mixture containing cyclohexane and cyclohexene. Usually, the mixture also contains unreacted benzene.

[0008] In the partial hydrogenation reaction, it is preferable 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) containing a raw material and a product as main components and a liquid phase containing water (aqueous phase) will form two phases unless stirring is performed. However, when the ratio of the oil phase and the aqueous phase is extreme, 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 preferable that a metal salt compound is contained in water. The metal salt compound is a Group 1 metal, a Group 2 metal, or zinc,
Sulfates, chlorides, acetates of metals such as manganese and cobalt,
Phosphates and the like are exemplified. The amount of the metal salt used is usually 1 × 10 ⁻⁵ weight to 1 weight, preferably 1 × 10 ⁻⁴ weight to 0.1 weight, based on the water of the reaction system.

In the present reaction, the use of a Group 8 metal catalyst is preferred. A particularly preferred metal is ruthenium. Examples of the raw material for the catalyst include halides, nitrates, hydroxides, complex compounds, and alkoxides. The catalyst may use another metal component in combination as a promoter component. By adding a co-catalyst, the effects of the present invention can be further exhibited. As the promoter component, zinc, iron, cobalt,
Manganese, gold, lanthanum, copper and the like are effective, and zinc is particularly preferable. When a promoter metal is used, the atomic ratio of the promoter metal to ruthenium atoms is usually 0.01 to 2%.
0, preferably 0.1 to 10.

The catalyst used is a metal oxide such as silica, alumina, titania and chromina; a complex oxide such as silica-alumina, silica-zirconia and zirconium silicate; a zeolite; an activated carbon; a metal such as barium sulfate and calcium sulfate. Salt: A supported type supported on a carrier such as a hydroxide or a poorly water-soluble metal salt, or a non-supported type may be used. In addition, among the above carriers, carriers having the following properties can be suitably used. That is, when the pore volume and the pore distribution are measured by the mercury intrusion method, the pore diameter is 75 to
100,000 Å total pore volume of 0.2
The pore volume is usually from 10 to 10 ml / g, preferably from 0.3 to 5 ml / g, and the pore diameter is usually 250 angstroms or more, based on the total pore volume of 75 to 100,000 angstroms. Is a carrier having pores of 50% or more, preferably 70% or more. Pore diameter 2
If the proportion of pores smaller than 50 angstroms is too large, selectivity tends to decrease, which is not preferred.

As a method for activating the catalyst, 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 by hydrogen gas is preferred,
A method of firing in a hydrogen-containing gas atmosphere at a temperature of usually 80 to 500 ° C., preferably 100 to 450 ° C. for reduction activation is mentioned.

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 as described below, a catalyst having improved cyclohexene selectivity and the like can be obtained. It is also possible to get The water treatment conditions are usually 0.01 to 100 times by weight based on the catalyst (ruthenium reduced product),
It is preferably carried out by immersion in 0.1 to 10 times by weight of water. Also, 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 water used for the contact treatment may be an aqueous solution containing a metal salt in addition to pure water. Further, the catalyst after the water contact 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.

As the reaction conditions for the partial hydrogenation, the reaction temperature is usually 30 to 500 ° C., preferably 50 to 300 ° C.
More preferably, it is selected from the range of 100 to 250 ° C. If the temperature is too high, the selectivity for cyclohexene will decrease, and if it is too low, the reaction rate will decrease significantly. 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. 20MPa
If it is more than 0.1 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 equipment. As the reaction type, using one or two or more reaction tanks, the reaction can be performed batchwise or continuously, and is not particularly limited, but is performed industrially continuously. The method is preferred.

[0015] The partial hydrogenation reaction is usually carried out with an aqueous phase containing water,
The reaction is carried out in a four-phase system consisting of an oil phase containing raw materials and products, a solid phase containing a catalyst present in an aqueous phase, and a gas phase containing hydrogen. In this case, the reaction proceeds with these phases suspended in each other. The reaction solution obtained by performing 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 by a stationary tank, 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 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 a separation step described below.

(Separation Step) Next, since cyclohexene and cyclohexane to be subjected to the separation step have boiling points close to each other, a distillation method such as extractive distillation or azeotropic distillation is usually employed. Further, in the partial hydrogenation reaction as described above, benzene is usually included in addition to the one to be subjected to the separation step, but also in this case, since the boiling points are close to each other, the distillation method as described above is used. It is suitable. Hereinafter, a case where extractive distillation, which is a preferred method, is used for a partial hydrogenation reaction mixture containing benzene, cyclohexane, and cyclohexene will be described with reference to the drawings.

FIG. 1 shows a separation method comprising three distillation columns. Extractive distillation is performed in the distillation column D1. The oil phase is supplied from the line 1, and the extractant is supplied from the line 2. After the component whose main component is cyclohexane 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. A component containing benzene and cyclohexene as main components is extracted from the bottom of the distillation column D1 through a line 4.

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

In the distillation column D3, benzene and an extractant are separated by distillation, benzene is extracted from the top of the column and condensed by a condenser, and a part thereof is distilled at a predetermined reflux ratio.
And 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 is usually fed to D2 and / or D3 for reuse.

Examples of the extractant used for the extractive distillation in the present invention include known extractants such as 1,3-dimethylacetamide, adiponitrile, sulfolane, dimethyl malonate, dimethyl succinate, γ-butyl lactone, N-methylpyrrolidone, and the like. Organic compounds having polarity such as 1,3-dimethylimidazolizonone and ethylene glycol are used.

In the above method, benzene (B
z), cyclohexene (CHE) and cyclohexane (CHX) were separated into their respective components by first separating CHX and then separating CHE and Bz. As shown in FIG. To separate
Next, a method of separating CHX and CHE can be adopted.

The separation step is preferably performed continuously. In the separation step as described above, each of the separated components contains other components to some extent. Especially in extractive distillation, the load required for distillation is large,
It is necessary to determine the impurity concentration in each component according to the subsequent use form of each component.

For example, in the case of cyclohexane, it is subjected to an oxidation reaction step described later. However, there is a problem that benzene and cyclohexene contained as impurities are accumulated at a high concentration in the oxidation reaction system. Therefore, the total amount of cyclohexene and benzene in cyclohexane is
It is preferable to keep it at 10 ppm or less. On the other hand, in order to obtain cyclohexane having a small amount of impurities, it is industrially problematic to make the separation conditions extremely strict. Therefore, as described later, preferably, the cyclohexane obtained by the separation is first treated with water. It is preferable that substantially all of benzene and cyclohexene be converted to cyclohexane after subjecting to refining and then used for the oxidation reaction. That is, if only the purity of cyclohexane is improved, it is not impossible to achieve strict separation conditions in the separation step. However, in this case, the load of the separation step such as extractive distillation is large, 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. Therefore, as described above, the load of distillation can be reduced by including the hydrotreating step before the oxidation step. This is because if a hydrogenation catalyst is used, it is extremely easy to convert BZ or CHE to CHX, and there is no need for a huge distillation column or large variable costs.

In the case of performing such hydrogenation purification, the cyclohexane obtained by separation may contain a considerable amount of CHE or BZ, and there is usually no problem if it is up to about 5%. Further, in order to reduce the load of the separation step, it is preferable to contain CHE and BZ in a total amount of about 200 PPM to 1%.

(Hydration reaction) As the hydration catalyst used in the hydration reaction step, various catalysts usually used for a hydration reaction of cyclohexene can be used, but a solid acid catalyst is preferable. In this case, the hydration reaction is a three-phase system consisting of an aqueous phase containing water, an oil phase containing raw materials and reaction products, and a solid phase containing a solid acid catalyst in the aqueous phase. The reaction proceeds with these suspended in each other.

The solid acid catalyst used is an acidic solid substance, such as zeolite, a strongly acidic ion exchange resin containing a sulfonic acid group, etc., as well as hydrous niobium hydroxide, hydrous tantalum, zirconium dioxide, titanium dioxide, aluminum oxide, Inorganic oxides such as silicon dioxide or their composite oxides, and further layered compounds such as smectite, kaolinite, vermiculite, aluminum and silicon,
Examples include an ion-exchange layered compound treated with one or more metal oxides selected from titanium and zirconium, 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. Further, as a carrier or binder, alumina,
Silica, titania and the like may be used.

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

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

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. To produce cyclohexanol,
A method is employed in which a water phase, which is a catalyst slurry, and an oil phase containing cyclohexanol are separated from the reaction solution and the oil phase is continuously collected. The phase separation can be performed by providing an oil-water separation weir inside the reactor, or once the oil phase is taken out of the reactor and phase-separated by an oil-water separator provided outside,
It can also be carried out by circulating the aqueous phase through the reaction system.

The reaction is usually carried out by mixing an aqueous phase and an oil phase by stirring or the like to disperse the oil phase in a suspended state, for example, a continuous aqueous phase in a droplet state. When the reaction mixture is weakly mixed or in a stopped state, it usually separates into an aqueous phase and an oil phase, and the volume ratio of the oil phase to the aqueous phase is usually 0.0%.
It is 1-10, preferably 0.1-1. If the amount of the raw material cyclohexene or water is excessively large as compared with one, 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 cyclohexene is usually 0.01 to 20, preferably 0.05 to 5. When the amount of the catalyst is too small, the reaction speed is slow and the size of the reactor becomes large. When the amount is too large, the cost of the catalyst increases, which is not preferable. In the 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 reactor as a catalyst slurry and reused.

As the hydration reaction conditions, the reaction temperature is usually 5
The temperature is 0 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 capable of keeping cyclohexene and water in a liquid phase, usually 5 MPa or less, preferably 0.2 to 2 MPa.
a. The reaction time or residence time is usually 1 minute to 1 minute.
0 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,
The content of oxygen in the inert gas is preferably small, and the oxygen content is usually 100 ppm or less, preferably 20 pp.
m or less are used. In the hydration reaction step, a small amount of methylcyclopentene is usually produced as a by-product in addition to cyclohexanol, which is a target product.

(Cyclohexanol Separation Step and Circulation Step) Since the oil phase obtained by the hydration reaction usually contains cyclohexanol and cyclohexene, these are distilled to obtain a high-boiling component containing cyclohexanol and a low-boiling component containing cyclohexene. Separate from boiling components. Methylcyclopentenes are usually entrained on the cyclohexene side. Preferably, at least a portion of the separated cyclohexene is recycled to the hydration reaction.

Hereinafter, a method for separation by distillation will be described. That is, the reaction liquid [containing cyclohexanol, cyclohexene and methylcyclopentenes (hereinafter, may be referred to as “MCPN”) which is obtained from the hydration reactor R2 is separated in the distillation column D4 in FIG. Unreacted cyclohexene is distilled off from the top, and the product cyclohexanol is withdrawn from the bottom. In industrial processes, it is preferred that at least a portion of the unreacted cyclohexene in the distillate is recycled to the hydration reaction. However, this cyclohexene contains trace amounts of benzene and cyclohexane, as well as methylcyclopentenes.If this methylcyclopentene accumulates in the hydration reaction system, it will adversely affect the hydration catalyst, so it has been separated. It is preferable that at least a part of cyclohexene is subjected to the following treatment (I) or (II). (I) A method of circulating a part of the separated cyclohexene to a hydration step and circulating the remainder to a separation step such as the extraction step, and (II) distilling at least a part of methylcyclopentenes in the separated cyclohexene. However, in the case of the above method (I), in the extractive distillation,
Methylcyclopentenes are entrained in cyclohexane, but the methylcyclopentenes are introduced into the separation step, resulting in increased separation loads. Moreover, since cyclohexane and methylcyclopentenes have boiling points close to each other and are difficult to separate by distillation, complicated separation is required. Therefore, a more preferable method is the method (II).

In the method (II), since methylcyclopentenes are not substantially present in the separation step, the load of separation is small, and complicated separation of cyclohexane and methylcyclopentene is not required. Furthermore, methylcyclopentenes do not exist at a high concentration in the hydration reaction system. As a specific method of (II), a part of the separated cyclohexene is circulated to the hydration reaction, and the remaining part is subjected to distillation to obtain a component having a high concentration of methylcyclopentenes from the top of the column, A method in which a component having a low concentration of methylcyclopentene is obtained, a component having a high concentration of methylcyclopentene is discharged out of the system, and the component having a low concentration is circulated to a hydration reaction can be exemplified.

The specific method of the above (II) will be described with reference to FIG. 3. A part of cyclohexene is extracted from the line 14, the light-boiling components such as MCPN are concentrated by the distillation column D5, Extract to The bottom is recycled from the line 17 to the hydration reaction step. The distillate from the distillation column D4 that is not supplied to the distillation column D5 is recycled from the line 15 to the hydration reaction step. The conditions (reflux ratio, distillate ratio, D
5), it becomes possible to control light boiling components during recycling.

In this method, in particular, the selectivity of MCPN in the hydration reaction is 1% or less, preferably 0.5%.
It is particularly effective when it is at most 0.2%. If the selectivity of MCPN is too high, cyclohexene (hereinafter sometimes referred to as “CHE”) and M
Since it is difficult to separate from CPN by distillation, a relatively large amount of MCPN is circulated in the hydration reaction, and as a result, deterioration of the catalyst is easily accelerated.

The method (II) is particularly suitable for preparing the starting material cyclohexane in the oxidation of cyclohexanone of the present invention with molecular oxygen. That is, it is obtained through a method of partial hydrogenation of benzene, separation of each component from a hydrogenation reaction mixture, hydration of cyclohexene, separation of cyclohexanol by the method (II), and circulation of unreacted cyclohexene. When cyclohexane is reacted with molecular oxygen, there is an advantage that the cyclohexane is substantially free of methylcyclopentenes, which may ordinarily be contained to some extent. Further, according to this method, there is no need to perform a complicated operation of removing methylcyclopentene from the raw material cyclohexane.

(Dehydrogenation Step) The cyclohexanol obtained by the above hydration reaction is subjected to a dehydrogenation step to become cyclohexanone. The dehydrogenation reaction is preferably carried out as a gas-phase flow reaction. As the reaction system, the catalyst may be either a fixed bed or a fluidized bed, but a fixed bed is preferred industrially. The dehydrogenation catalyst is not particularly limited as long as it can be generally used for dehydrogenation of cycloalkanol such as cyclohexanol, and metal oxide catalysts such as copper, chromium, zinc, and cobalt, and alkali metal and alkali Examples to which an earth metal is added can be given. Specifically, a copper-zinc catalyst (U.S. Pat.
No. 18), a copper-chromium catalyst (JP-A-58-157).
No. 741, U.S. Pat. No. 4,310,703, British Patent No. 1,444,484, and No. 1500884.
Specification), a copper-cobalt catalyst (JP-A-55-1362).
No. 41), a zinc-calcium catalyst (Japanese Patent Publication No. 52-4)
8977, and Canadian Patent No. 826799). A plurality of these catalysts may be used in combination.

The temperature of the dehydrogenation reaction varies depending on the type of the catalyst used, but since the dehydrogenation reaction is an endothermic reaction, it is preferable that the reaction temperature be high within the heat-resistant limit of the catalyst, and usually from 200 to 200. 500 ° C, preferably 200 to 40
0 ° C. If the temperature is too low, the conversion will be small, and if it is too high, the conversion will be large, but the by-products will be undesirably large. The reaction pressure is not particularly limited and can be applied from reduced pressure to increased pressure.
Preferably it is 0.1 to 10 kg / cm ² , particularly preferably 0.5 to 5.0 kg / cm ² . The feed rate of the reaction raw material mixture is usually 0.1 hour by liquid hourly space velocity (LHSV).
It is ¹ to 100 hr ^-1 , preferably 0.5 to 20 hr ^-1 , and the reaction raw material mixture may be supplied after being diluted with an inert gas such as nitrogen.

(Hydrogenation purification step) The cyclohexane (hereinafter sometimes referred to as “CHX”) separated in the separation step such as the extraction distillation is subjected to hydrogenation purification preferably in the presence of a hydrogenation catalyst. (Described above). CHE / CH by partial hydrogenation of benzene (hereinafter sometimes referred to as “BZ”)
When an X / BZ mixture is obtained, since no other components are substantially present, CHX obtained in the separation step contains substantially no components other than BZ and CHE. Therefore, even if BZ and CHE are contained to some extent, high-purity CHX can be easily obtained by hydrogenating and purifying this.

When the method (I) of recycling part of the cyclohexene obtained in the cyclohexanol separation step to the separation step is employed, methylcyclopentenes also exist in the separation system. As the hydrogenation catalyst to be used, various commonly used metal catalysts can be used, and examples thereof include noble metals such as Pd, Ru, and Pt, and metals such as Ni and Zn. These may be supported on a carrier or may be non-supported. Examples of the carrier include alumina, carbon, titania, silica, zirconia and the like.
The catalyst may be a fluidized bed or a fixed bed,
When a noble metal-supported catalyst such as d is used, it is usually preferable to use a fixed bed.

The conditions for purification differ depending on the catalyst used, but the purification temperature is usually from 30 ° C. to 300 ° C.
When a noble metal catalyst such as Pd is used, the temperature is 30 ° C.
To 200 ° C, preferably 40 ° C to 150 ° C, more preferably 60 ° C to 120 ° C. Further, the pressure is generally 0.2 atm to 30 atm, preferably 0.5 atm to 10 atm, more preferably,
It is 1 atm to 5 atm. Also, LHSV, the reaction format may vary depending the amount of impurities, usually 1 Hr ^-1 10
It is 0Hr- ¹ . The CHX thus obtained usually contains only 10 ppm or less of CHE and BZ in total, and has extremely high purity.

(Oxidation Step) As described above, the cyclohexane obtained in the separation step such as extractive distillation is preferably hydrogenated and purified as described above, and then oxidized with molecular oxygen to form cyclohexanone. This reaction is usually carried out in a liquid phase, but as a result of the oxidation reaction, cyclohexanol and the like are produced in addition to cyclohexanone.

As the catalyst used for the oxidation reaction, there are usually known boron compounds and cobalt compounds (RAShel).
don and JKKochi Metal-Catalyzed Oxidations of Or
ganic Compounds; Academic Press: New York, 1981; p
p.344-345), a copper catalyst (see Japanese Patent Application No. 4-208888), a metal-containing catalyst such as a chromium catalyst, and the like.

Specific examples of the boron compound include boric acids such as orthoborane, metaboric acid, tetraboric acid, and boric anhydride, and boric esters such as trimethyl borate and tributyl borate. Is preferred. These boron compounds are generally used in an amount of 1/3 mole or more of boron per mole of cyclohexanol generated by oxidation. In addition, when the reaction is performed in a batch system, even if the boron compound is present as a solid, there is little problem, so that it can be used in a large excess. In order to avoid inconvenience, it is preferable to reduce the amount of the solid boron compound as much as possible. Usually, the amount of the boron compound is preferably carried in the range of 0.5 to 5 mol atoms of boron per mol of cyclohexanol.

Further, specific examples of the cobalt compound include:
For example, cobalt acetate, cobalt chloride, cobalt sulfate,
Examples include cobalt naphthenate, cobalt octoate, cobalt laurate, cobalt palmitate, cobalt stearate, cobalt acetylacetonate, and mixtures thereof. Usually, the amount of the cobalt compound used is such that the cobalt ion concentration in the reaction mixture is 0.0
The amount is from 01 to 100 ppm, preferably from 0.5 to 5 ppm.

Further, specific examples of the copper-based catalyst include:
For example, Cu, CuCl, CuCl _Two・ NH_TwoO, CuB
r, CuBr_Two , CuI, CuF_Two , CuSO_Four・ NH_Two
O, Cu (NO_Three)_Two・ NH_TwoO, Cu (ClO_Four)_Two・ N
H_TwoO, Cu (OCH_Three)_Two, Cu (PO_Four)_Two・ NH_TwoO,
CuO, Cu_TwoO, Cu (OOCH_Three)_Two・ NH_TwoO, Cu
(OCH_ThreeOCH_Three)_Two, Cu (OH)_TwoEtc.
(However, n is usually an integer of 0 to 6). Use of catalyst
The amount is not particularly limited, but is usually based on cyclohexane.
0.001 to 200 mol%, preferably 0.01 to 5 mol
%.

In the present oxidation reaction, a solvent can be used. Examples of the solvent used include halogenated hydrocarbons such as dichloromethane, chloroform and ethylene dichloride, esters such as ethyl acetate, nitriles such as acetonitrile, and aromatic hydrocarbons such as benzene, toluene, xylene, monochlorobenzene and dichlorobenzene. And the like.

As the gas containing molecular oxygen used for the oxidation, oxygen, air, or a gas obtained by diluting these with an inert gas can be used, but usually air may be used. It is preferable that the oxygen concentration be relatively low, and it is usually preferable to use a gas of about 5 to 25% by volume. The temperature of the oxidation reaction is usually 10 to
400 ° C, preferably 100-250 ° C, especially 140-
180 ° C. is preferred. When the temperature is too low, the oxidation reaction does not proceed, while when it is too high, the generation of by-products increases, which is not preferable. The reaction pressure may be either normal pressure or pressurization, and may be appropriately selected in consideration of the vapor pressure and the oxygen partial pressure at the reaction temperature of the raw material cyclohexane.
kg / cm ² G or less, preferably 5 to 25 kg / cm ² G
And pressurizing with an inert gas such as nitrogen.

The method of the present invention can be carried out in any of a batch system, a semi-batch system and a continuous system according to well-known procedures, but is preferably a continuous system. When a boron compound is used as a catalyst, the resulting oxidation reaction mixture contains
May contain boric esters of cyclohexanol. In this case, by hydrolyzing the ester, it can be converted to cyclohexanol.

In the present invention, in the oxidation step, cyclohexane is oxidized in the absence of a catalyst to produce cyclohexyl hydroperoxide, which is decomposed in another step to form a reaction mixture containing cyclohexanone and cyclohexanol. You can also get. The obtained oxidation reaction mixture is usually obtained by removing unreacted cyclohexane by distillation and then contacting it with an alkali to be subjected to a saponification treatment, thereby removing impurities such as organic acids and organic acid esters to the aqueous phase side. After the saponification treatment, unreacted cyclohexane can be removed by distillation. Examples of the alkali used for the saponification treatment include caustic alkalis such as caustic soda and potassium caustic, and alkali carbonates such as sodium carbonate and potassium carbonate. The temperature at the time of the saponification treatment is usually about 30 to 200 ° C.

It is extremely preferable that the reaction mixture obtained in this way further recovers by-product cyclohexanol and dehydrogenates it to obtain cyclohexanone. The cyclohexanol can be recovered by distillation, and is separated into a low-boiling component such as cyclohexanone and a high-boiling component such as cyclohexanol. It is also possible to remove other high-boiling impurities and low-boiling impurities by distillation. The separated cyclohexanol is subjected to dehydrogenation to form cyclohexanone. The conditions for this dehydrogenation are the same as the conditions for the dehydrogenation of cyclohexanol obtained by hydration of cyclohexene. Of course, the cyclohexanol obtained in the oxidation step,
The cyclohexanol obtained in the hydration step can be subjected to a separate dehydrogenation reaction, and these are combined,
This can be subjected to one dehydrogenation reaction.

(Use) The obtained cyclohexanone has ε
-Can be used as a raw material for caprolactam. For example, cyclohexanone can be oximed by reacting it with hydroxylamine or with ammonia and oxygen to form cyclohexanone oxime. The obtained cyclohexanone oxime can be converted to ε-caprolactam by Beckmann rearrangement in the presence of fuming sulfuric acid or a solid acid catalyst.

Further, the obtained cyclohexanone can be used as a raw material for adipic acid or hexamethylenediamine. For example, adipic acid can be obtained by oxidative cleavage of cyclohexanone. Further, hexamethylenediamine can be obtained by reduction with NH ₃ .

[0055]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. FIG. 4 shows the flow performed in this embodiment. Figure 4 below
According to the description, the contents of the implementation will be described.

[Cyclohexanol Production Process] Benzene as a raw material is supplied from a line 1 and recycled benzene is supplied from a line 9 to a hydrogenation reactor R1 to be reacted. The conditions of the hydrogenation reaction were as follows: a pressure of 5.0 MPa, a reaction temperature of 150 ° C., an oil-water ratio of 4: 6, and a catalyst concentration of 30 wt%.
The conversion of benzene is 67.3% and the selectivity of cyclohexene is 64.5%. The reaction solution was supplied from line 2 and the extractant 1,3-dimethylimidazolizonone was added to line 3.
Then, the mixture is supplied to the distillation column D1 to be separated into cyclohexane and a mixture of cyclohexene, benzene and an extractant. The distillation column D1 is a packed column equivalent to 58 theoretical plates, and the extractant is supplied to the fifth column from the top, and the hydrogenation reaction liquid is supplied to the 37th column. The pressure at the top is 0.15 MPa and the reflux ratio is 6. At this time, the purity of cyclohexane as the distillate (line 4) is 99.95% by weight, and the balance is cyclohexene and benzene. D1 bottoms are on line 5
And the extractant is also supplied from line 6 to the distillation column D2,
It is separated into cyclohexene and a mixture of benzene and extractant. D2 is a packed column corresponding to 58 theoretical stages, in which the extractant is supplied to the fourth stage from the top and the bottom liquid of D1 is supplied to the 35th stage. At this time, the pressure at the top of the column was 0.05 MPa, and the reflux ratio was 3. Cyclohexene is supplied from line 7 to the hydration reactor R2. The bottom liquid is supplied to a distillation column D3 through a line 8, and separated into benzene and an extractant in the distillation column D3. D3 is a packed column equivalent to 13 theoretical stages, and has a supply stage at the sixth stage from the top of the column. At this time, the top pressure is 0.05
At MPa, the reflux ratio is 1. Benzene, a distillate, is recycled from line 9 to the hydrogenation step. On the other hand, the cooling agent 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 are a pressure of 0.7 MPa, a reaction temperature of 120 ° C., an oil-water ratio of 1: 2, a catalyst concentration of 30 wt%, a conversion of cyclohexene of 11%, and a selectivity of cyclohexanol of 99.8%.
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 methylcyclopentenes. D4 is a packed column corresponding to 15 theoretical stages, and the reaction solution is supplied to the seventh stage from the top of D4. At this time, the top pressure is normal pressure, and the reflux ratio is 0.3. The distillate is supplied from the line 12 to the distillation column D5 via the first line 14. At D5, methylcyclopentenes are concentrated and purged from the top of the column. D5
Is a packed column equivalent to 30 theoretical plates, and is supplied to the 23rd plate from the top. The top pressure of D5 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 line 15 to hydration reactor R2.

[Cyclohexanone Production Process] Line 13
The obtained cyclohexanol is introduced into a reactor R4 filled with a copper-based catalyst, and is subjected to a dehydrogenation reaction at a temperature of 250 ° C. in a gas phase. Here, the conversion of the dehydrogenation reaction is 57%, and the selectivity is 99.4%. Cyclohexanone and unreacted cyclohexanol are supplied from line 21 to a cyclohexanone distillation system. The cyclohexanone distillation system comprises a low-boiling separation column D6, a rectifying column D7, and a high-boiling separation column D8. The low-boiling separation column D6 distills low-boiling impurities from the top of the column through a line 23 at a column pressure of 200 Torr. Purge out. The bottom product of the low-boiling separation tower is supplied to the rectification tower D7, and cyclohexanone is distilled from the top of the tower at a top pressure of 50 Torr (line 24). The bottom product of the rectification column D7 is supplied to the high-boiling separation column D8. At a top pressure of 30 Torr, cyclohexanol is distilled from the top of the column, and is supplied again from the line 25 to the dehydrogenation reaction system. The bottom liquid of D8 is a high boiling impurity, and is purged from the line 26 to the outside of the system.

[Cyclohexane Purification Step] The cyclohexane extracted from the line 4 is supplied to the upper part of the reactor R3 filled with a catalyst having Pd supported on alumina. At the same time, hydrogen (H ₂ ) is supplied from line 19 to the upper part of the reactor R3. The reactor R3 has a pressure of 0.17 MPa and a temperature of 80.
It has been adjusted to ° C. Further, a hydrogenation reaction was carried out by filling a catalyst so that the LHSV became 40 Hr ^-1 , and cyclohexane containing impurities such as cyclohexene and benzene of 1 ppm or less was obtained.

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

[Cyclohexane Oxidation Step and Cyclohexanone Production Step] The cyclohexane obtained in the cyclohexane purification step is supplied from a line 20 to a cyclohexane oxidation reactor R5. Also, boric acid from line 37
Air is supplied from line 31. The cyclohexane oxidation reaction was performed at 10 kg / cm ² G at 170 ° C.
A conversion of 5% and a selectivity of 93% are obtained. The mixture obtained by the cyclohexane oxidation reaction is supplied to the flash tower D9 from the line 32, and a part of the unreacted cyclohexane is recovered from the top of the line from the line 34 and recycled to the cyclohexane oxidation reactor R5. The remaining mixture is supplied from the bottom to the hydrolysis reactor R6 through a line 33. In the hydrolysis reactor R6, water is supplied from a line 35, the reaction is carried out at a reaction temperature of 80 ° C. and a pressure of 1 kg / cm ² , and the oil phase side is sent from a line 38 to a saponification step (reactor R7). The boric acid in the aqueous phase is dehydrated in the crystallizer Q1, and
7, is recycled to the cyclohexane oxidation reactor R5. In the saponification step, NaOH is supplied from a line 39, and the reaction is carried out at a reaction temperature of 80 ° C. and a pressure of 1 kg / cm ² . At the outlet of the step, the oil phase side is supplied to the cyclohexane distillation system D10 from a line 40, and the remaining cyclohexane is separated as a distillate, extracted from a line 41, and recycled to a cyclohexane oxidation step. Cyclohexanol containing some cyclohexanone has D
It is supplied to the dehydrogenation reactor R8 from the line 42 as 10 bottoms. The mixture obtained in the dehydrogenation reactor R8 is subjected to low-boiling impurities, high-boiling impurities in the low-boiling separation column D11, the rectifying column D12, and the high-boiling separation column D13 under the same conditions as in the above-mentioned cyclohexanone purification step. Cyclohexanone and cyclohexanol are separated from each other, and low-boiling impurities are
The high boiling impurities are purged out of the system through line 48. Cyclohexanol is distilled from D13 and
7 to the dehydrogenation reactor R8. Table 1 below shows the mass balance of each step.

[0062]

According to the present invention, cyclohexanone can be produced from benzene without waste by effectively utilizing cyclohexane by-produced by the CHE method.

[Brief description of the drawings]

FIG. 1 is a schematic view showing steps in a case where a method for separating a partial hydride of benzene into components of cyclohexane and cyclohexene is performed by extractive distillation in the present invention. (The separation step (1) above, in which cyclohexane is separated first, and then cyclohexene and benzene are separated.)

FIG. 2 is a schematic diagram showing steps in a case where a method for separating a partial hydride of benzene into components of cyclohexane and cyclohexene is performed by extractive distillation in the present invention. (The separation step of the above (1). A method of first separating benzene and then separating cyclohexane and cyclohexene.)

FIG. 3 In the present invention, cyclohexene is hydrated,
It is the schematic which showed the process in the case of utilizing distillation in obtaining cyclohexanol from the reaction product. (Step (3))

FIG. 4 is a diagram showing a flow performed in an embodiment of the present invention.

[Explanation of symbols]

D1 to D13: distillation column, R1 to R8: reactor, Q1: crystallizer, number (1 to 48): tube BZ: benzene, Solv: extractant, CHE: cyclohexene, LB: low boiling point, CHL: cyclo Hexanol, H
B: high boiling substance, CHN: cyclohexanone, MCPN: methylcyclopentenes

Claims (11)

[Claims] 1. A method for producing cyclohexanone using benzene as a raw material, the method comprising the following steps (1) to (5): (1) Partial hydrogenation of benzene to obtain a hydrogenated reaction mixture containing cyclohexane and cyclohexene (2) The hydrogenated reaction mixture obtained in the above (1) is added to each component of cyclohexane and cyclohexene (3) Hydration of cyclohexene separated in (2) above to obtain cyclohexanol from the reaction product (4) Dehydrogenation of cyclohexanol obtained in (3) above (5) Oxidation step of oxidizing cyclohexane separated in the above (2) with molecular oxygen to obtain cyclohexanone 2. In the above (3), the hydration reaction product is separated into a light-boiling component containing cyclohexene and methylcyclopentene and a high-boiling component containing cyclohexanol, and the obtained light-boiling component is separated. The method for producing cyclohexanone according to claim 1, wherein after removing at least a part of the methylcyclopentenes in the component, the remainder is reused in the reaction (3). 3. The method according to claim 1, wherein the cyclohexane obtained in the separation step (2) is hydrogenated and purified in the presence of a hydrogenation catalyst, and is subjected to the oxidation step (5). A method for producing cyclohexanone. 4. The method for producing cyclohexanone according to claim 1, wherein cyclohexanol obtained as a by-product in the oxidation step (5) is subjected to a dehydrogenation reaction to form cyclohexanone. 5. The separation in the separation step (2),
5. The method according to claim 1, wherein the extraction is performed by extraction distillation using an extraction solvent.
The method for producing cyclohexanone according to any one of the above. 6. The method for producing cyclohexanone according to claim 1, wherein the partial hydrogenation reaction (1) is performed in the presence of a Group 8 metal catalyst and water. 7. The method for producing cyclohexanone according to claim 1, wherein the hydration reaction of (3) is performed in the presence of a solid acid catalyst. 8. The method for producing cyclohexanone according to claim 7, wherein zeolite is used as the solid acid catalyst. 9. The method for producing cyclohexanone according to claim 1, wherein the oxidation reaction (5) is performed in the presence of a metal-containing catalyst. 10. A method for oxidizing cyclohexane with molecular oxygen to obtain an oxidation reaction mixture containing cyclohexanone, wherein the starting cyclohexane is as described in the following (1) to (10).
A method for producing cyclohexanone using cyclohexane obtained through the step (5). (1) Partial hydrogenation of benzene to obtain a hydrogenated reaction mixture containing cyclohexane and cyclohexene (2) The hydrogenated reaction mixture obtained in the above (1) is added to each component of cyclohexane and cyclohexene Separation step for separation (3) Hydration step of hydrating cyclohexene separated in (2) above to obtain a hydration reaction mixture containing cyclohexanol (4) hydration reaction mixture obtained in (3) above A cyclohexanol separation step of separating into a low-boiling component containing cyclohexene and methylcyclopentenes and a high-boiling component containing cyclohexanol. (5) The light-boiling component obtained in the above (4) is separated into the (2) After removing at least a portion of the methylcyclopentenes in the light-boiling component without recycling to the separation step of (3), the remainder is recycled to the above (3). Concentration process of methylcyclopentenes used 11. A method according to claim 1, wherein the cyclohexanone obtained by the method according to claim 1 is converted into an oxime,
Further, a method for producing ε-caprolactam by Beckmann rearrangement to obtain ε-caprolactam.