JPH0710783B2 - Selective separation method of cyclohexanone and cyclohexanol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for selectively separating cyclohexanone and cyclohexanol.

More specifically, it relates to a method for selectively separating cyclohexanone and cyclohexanol in a solution by using a membrane formed of a specific polymer having hydrogen bonding ability.

[Field of Industrial Application] The present invention relates to cyclohexanone, which is important as an intermediate for the production of nylon such as caprolactam and adipic acid,
Separate these from the solution containing cyclohexanol,
It is used when collecting and refining.

[Prior Art] Although cyclohexanone and cyclohexanol can be obtained by various methods, the most general method currently industrially practiced is by air oxidation of cyclohexane. However, since a large amount of unreacted cyclohexane remains in the reaction solution obtained by this method, in order to separate and recover a smaller amount of cyclohexanone and cyclohexanol, at present, first under pressure, then usually under constant pressure. It requires as many as three stages of cyclohexane distillation steps, under pressure and even under reduced pressure. Therefore, in these processes, a large amount of heat energy is consumed and the heat deterioration of the reaction product becomes a problem, leading to an increase in cost of not only caprolactam and adipic acid but also nylon products.

[Problems to be Solved by the Invention] In the present invention, a large amount of energy consuming type defect that multistage distillation is performed by utilizing boiling point difference when separating cyclohexanone and cyclohexanol from a solution containing cyclohexanone and cyclohexanol is a specific separation membrane. The present invention provides an energy-saving separation method for selectively permeating and separating by using.

[Means for Solving the Invention] The present invention provides a separation method for selectively permeating and separating cyclohexanone and cyclohexanol from a solution containing cyclohexanone and cyclohexanol by using a specific separation membrane.

In recent years, in a wide range of fields such as desalination of seawater, electrolysis of salt, food industry, and waste liquid treatment, separation technology using a membrane has been developed for separation of various solutions, recovery of solvent, etc. There is.

Generally, separation of organic liquid mixture has been carried out by distillation, but recently, as a new energy-saving separation method replacing distillation, a specific substance is selectively permeated based on the physicochemical interaction between the membrane and the permeate. Trying to separate,
Research on so-called permselective membranes is active. In the current distillation method, low-boiling substances were sequentially separated,
In this method, it becomes possible to selectively permeate and separate even a high boiling substance contained in a small amount by selecting a membrane material. In other words, in the development of highly selective membranes, it is important to select materials that cause a significant difference in the physicochemical interactions between the membrane and each component of the feed solution, such as radiation grafting, surface treatment, copolymerization, crosslinking and blending. Various methods have been proposed, and selective permeable membranes have been developed for mixed systems of water / alcohol, benzene / cyclohexane, m-xylene / p-xylene, and the like. However, for cyclohexanone and cyclohexanol obtained by aerial oxidation of cyclohexane, although a large amount of energy consumption is called out as a major problem in the separation and purification process, proposals for their selective permeation have not yet been made. Absent.

The proportions of cyclohexanone and cyclohexanol obtained by the above method in the reaction mixture are at most 2% cyclohexanone and 3% cyclohexanol. Therefore, in order to separate cyclohexanone and cyclohexanol from this, a large amount of conventional cyclohexanone remains. It is considered that the method using a membrane that selectively permeates cyclohexanone and cyclohexanol is more advantageous in terms of equipment, energy and physical properties than the method of distilling unreacted cyclohexane. Therefore, the present inventors have proposed a novel cyclohexanone / cyclohexanol selective separation method, particularly cyclohexanone, from a solution in which a large amount of cyclohexane coexists.
As a result of intensive studies on a method for selectively separating cyclohexanol, the present invention has been found out that a specific polymer membrane selectively permeates cyclohexanone and cyclohexanol, and has reached the present invention.

That is, it is to provide a selective separation method characterized by separating cyclohexanone and cyclohexanol from a solution containing cyclohexanone and cyclohexanol using a membrane made of a polymer represented by the following general formula.

General formula Here, R ₁ and R ₂ are hydrogen or an alkyl group, and R ₃ and R ₄ are hydrogen, hydroxyl group, carboxyl group, acid anhydride group, ester group, amide group, imide group and derivatives thereof. However,
Except when R ₃ and R ₄ are simultaneously hydrogen. m and n represent the mole fraction of each monomer structural unit, m is 0.1 to 0.7, and n is 0.3 to 0.9.
Is.

The polymer constituting the membrane used in the present invention is an acrylonitrile copolymer. Specific examples of other monomer constituent units constituting the copolymer include vinyl alcohol, acrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-methacrylic acid. Hydroxyethyl, vinyl acetate,
Acrylamide, N-vinyl 2-pyrrolidone, 3-vinyl-
1.4-Butyllactone, N-propenoyl-4-hydroxycyclohexylamine, maleic anhydride, maleimide, N-phenylmaleimide, 1-[(2-methylpropenoyl) oxy] succinimide, 1-[(2-methylpropenoyl) And oxy] phthalimide, and the like. It is preferable that these have a large hydrogen bonding ability. These are solubility parameters (δh) based on hydrogen bonding force.
Can be evaluated by

The molecular weight of the copolymer used in the present invention is not particularly limited as long as it can be formed into a film, and preferably n, 1
It is about 0,000 to 50,000. If the molecular weight is small, the membrane becomes brittle and inflexible and cannot withstand permeation experiments.

The film thickness used in the present invention is 0.1 μm to 500 μm, preferably 1 μm to 200 μm. When the film thickness is larger than this, the permeation flux becomes small, and when it is smaller than this, the mechanical properties deteriorate.

The m, n ratio of the copolymer used in the present invention is 0.05 to m.
0.9, n is 0.95 to 0.1, preferably m is 0.1 to 0.7, and n is 0.
3 to 0.9. When the m component is larger than this, swelling occurs and the selectivity (separation coefficient α) decreases. On the other hand, if it is less than 0.1, the permeation velocity will be significantly reduced.

There is no particular limitation on the method for producing the film formed from the above polymer in the present invention. For example, a homogeneous film in a film state can be obtained by dissolving in a suitable solvent, casting on a smooth surface, for example, a glass plate or the like, and then evaporating and removing the solvent. A so-called asymmetric membrane can also be obtained by stopping the evaporation of the solvent halfway and immersing it in the coagulating liquid. Further, it is possible to obtain a composite film by applying a dilute solution of a polymer on a porous substrate and evaporating the solvent to form an ultrathin film on the substrate. On the other hand, a homogeneous film can be obtained by hot pressing or extruding each polymer in a molten state. The shape of the membrane thus obtained is not particularly limited, and may be a flat membrane, spiral membrane, pleated membrane, tube membrane, hollow fiber membrane or the like. Also, these can be used as a separation membrane module.

To selectively separate cyclohexanone and cyclohexanol from a solution containing cyclohexanone and cyclohexanol according to the present invention, for example, a cyclohexane / cyclohexanone / cyclohexanol mixed solution is supplied to the supply side (one side) of the membrane, and the supply side and the permeate It suffices if the pressure difference from the side is the supply side ≧ the permeate side. Therefore, it suffices to only supply the mixed liquid to the supply side, but in general, a method is adopted in which the permeated liquid side is set to the current pressure without particularly pressurizing the supply side. At this time, the pressure on the permeate side is 0.01 to 500 mmHg, preferably 0.1 to 100 mmHg.
Is.

The operating temperature at this time is 10 to 80 ° C, preferably 30 to 60 ° C.
℃.

Further, the concentrations of cyclohexanone and cyclohexanol in the supply liquid are not particularly limited. A total of 5% is sufficient for both.

The solution containing cyclohexanone and cyclohexanol in the present invention is not particularly limited as long as it is a solution containing cyclohexanone and cyclohexanol, but cyclohexane / cyclohexane containing a large amount of cyclohexane obtained from the air oxidation step of cyclohexane in the process for producing caprolactam / Applies to cyclohexanone / cyclohexanol mixture.

Examples of the present invention will be shown below. Separation coefficient α in the examples
And the permeation flux J is defined by the following equation. The present invention is not limited to the examples below.

Xa: Cyclohexanone concentration in feed liquid (wt%) Xb: Cyclohexanol concentration in feed liquid (wt%) Xc: Cyclohexane concentration in feed liquid (wt%) Ya: Cyclohexanone concentration in permeate liquid (wt%) Yb : Cyclohexanol concentration in the permeate (wt%) Yc: Cyclohexane concentration in the permeate (wt%) J = P / A · t P: Permeation amount (g) A: Membrane area (m ² ) t: Permeation time (H) [Example] Example 1 Copoly (N-vinylpyrrolidone-acrylonitrile) having an N-vinylpyrrolidone amount of 0.228 in the copolymer, molecular weight 2
4,000, vapor pressure osmotic pressure method) was dissolved in N, N-dimethylformamide to prepare an 8 wt% solution. After casting this solution on a glass plate, evaporate the solvent at 40 ° C for 24 hours to obtain a thickness.
A uniform film of 20 μm was obtained. A cyclohexane / cyclohexanone / cyclohexanol mixed solution (95/2/3, wt%) was supplied to one side of this film, left at 50 ° C. for 8 hours, and then permeation started at a permeation side pressure of 0.2 mmHg to separate the film. The liquid was analyzed to obtain α = 15.4 and J = 24.5. The results are shown in Table 1 below.

Example 2 The same operation as in Example 1 was carried out except that a mixed solution having a composition of cyclohexane / cyclohexanone / cyclohexanol of 80/10/10, wt% was used as a supply liquid.

Example 3 The same operation as in Example 1 was carried out except that a mixed solution having a cyclohexane / cyclohexanone / cyclohexanol composition of 50/25/25, wt% was used as a supply liquid.

Example 4 The amount of N-vinylpyrrolidone in the copolymer was 0.111 (molecular weight 2
The same operation as in Example 1 was performed except that the membrane of (8,000) was used.

Example 5 The amount of N-vinylpyrrolidone in the copolymer was 0.483 (molecular weight 3
The same operation as in Example 1 was performed except that the membrane (3,000) was used.

Example 6 As a film material, the amount of methyl acrylate in the copolymer was 0.30.
8 copoly (methyl acrylate-acrylonitrile)
The same operation as in Example 1 was carried out except that (molecular weight 25,000) was used.

Example 7 As a membrane material, a copoly (maleimide-acrylonitrile) having a maleimide amount of 0.189 in a copolymer (molecular weight 18,00) was used.
The same operation as in Example 1 was carried out except that 0) was used.

Example 8 As a membrane material, copoly (vinyl acetate-acrylonitrile) having a vinyl acetate content of 0.214 in the copolymer (molecular weight 32,00
The same operation as in Example 1 was carried out except that 0) was used.

Example 9 As a membrane material, copoly (N) in which the amount of N-propenoyl-4-hydroxycyclohexylamine in the copolymer was 0.174.
-Propenoyl-4-hydroxycyclohexylamine-acrylonitrile) (molecular weight 13,000) was used and operated in the same manner as in Example 1.

Comparative Example 1 Polyacrylonitrile homopolymer (molecular weight 40,000)
It was dissolved in N, N-dimethylformamide to prepare a 5 wt% solution. After casting this solution on a glass plate, at 40 ℃
The solvent was evaporated for 24 hours to obtain a uniform film having a thickness of 20 μm. The same procedure as in Example 2 was carried out using this film. However, no substantial liquid permeation was observed even after several tens of hours.

Comparative Example 2 Copoly (styrene-containing 0.320 styrene)
Acrylonitrile, molecular weight 22,000) 6.8 wt% N, N-dimethylformamide solution was cast on a glass plate and kept at 40 ° C.
After evaporating the solvent for 24 hours, a uniform film having a thickness of 20 μm was obtained.

The same procedure as in Example 2 was carried out using this film.

Comparative Example 3 Copoly (N-vinyl-2-pyrrolidone-acrylonitrile, molecular weight 35,000) having an amount of N-vinyl-2-pyrrolidone of 0.810 in the copolymer was dissolved in N, N-dimethylformamide to prepare an 8 wt% solution. After casting this solution on a glass plate, the solvent was evaporated at 40 ° C. for 24 hours to obtain a uniform film having a thickness of 20 μm.

The same procedure as in Example 2 was carried out using this membrane.

[Effects of the Invention] The present invention is a method for selectively separating cyclohexanone and cyclohexanol using a film of an acrylonitrile copolymer. This method has higher efficiency and higher selectivity than the commonly used distillation method, and can be used for those having a small content of cyclohexanone and cyclohexanol. The operation is
It is an energy-saving type at low temperatures of 30 to 60 ° C, and has the effect of simplifying the equipment.

Specifically, as shown in the examples, the separation coefficient α is 6.3 to 20.
6. The permeation flux J is 15.4 to 48.7.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C07C 49/403 // C08F 220/44 MMY 7242-4J

Claims (2)

[Claims] 1. A selective separation method characterized in that cyclohexanone and cyclohexanol are separated from a solution containing cyclohexanone and cyclohexanol using a membrane made of a polymer represented by the following general formula. General formula Here, R ₁ and R ₂ are hydrogen or an alkyl group, and R ₃ and R ₄ are hydrogen, hydroxyl group, carboxyl group, acid anhydride group, ester group, amide group, imide group and derivatives thereof. However,
Except when R ₃ and R ₄ are simultaneously hydrogen. m and n represent the mole fraction of each monomer structural unit, m is 0.1 to 0.7, and n is 0.3 to 0.9.
Is. 2. The cyclohexanone according to claim 1, wherein the solution containing cyclohexanone and cyclohexanol is a solution containing cyclohexanone and cyclohexanol obtained from a cyclohexane oxidation tank in the process for producing caprolactam. , Cyclohexanol selective separation method.