JP2016074640A - Method for refining cyclohexene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To industrially produce cyclohexene of high quality by safely reducing cyclohexenyl hydroperoxide having a possibility of explosion.SOLUTION: Cyclohexene including cyclohexenyl hydroperoxide is brought into contact with a reducing agent to decompose the cyclohexenyl hydroperoxide and then the cyclohexene is distilled.SELECTED DRAWING: None

Description

  The present invention relates to a method for purifying cyclohexene that industrially obtains high-quality cyclohexene.

  Cyclohexene is a useful compound as a synthetic intermediate for polyamide raw materials such as lactams and dicarboxylic acids, various organic chemical products such as adipic acid, maleic anhydride, and cyclohexanecarboxylic acid, pharmaceuticals, and agricultural chemicals. With respect to the production method of cyclohexene, for example, a production method for dehydrating cyclohexanol, a production method for dehydrohalogenating halogenated cyclohexane (for example, see Patent Document 1), and a production method for partially hydrogenating benzene and subjecting it to extractive distillation (for example, patents) Document 2) is known. In addition, a production method for purifying cyclohexane produced as a by-product in the production process of synthesizing dicyclohexyl disulfide by reacting sodium disulfide with chlorocyclohexane is also conceivable.

  However, the cyclohexane obtained by any of the production methods contains a trace amount of cyclohexenyl hydroperoxide. In addition, since cyclohexane is unstable to light and air, cyclohexenyl hydroperoxide may increase when stored for a long period of time. For example, cyclohexenyl hydroperoxide in cyclohexane may increase by about 0.5% by weight over 3 months. This hydroperoxide is a highly explosive compound and needs to be purified and removed before use.

  As a method for decomposing cyclohexenyl hydroperoxide, for example, a method is known in which hexafluoroacetone trihydrate and pyridine are added to cyclohexene containing cyclohexenyl hydroperoxide and heated (see, for example, Patent Document 3). A method for decomposing cyclohexenyl hydroperoxide in the presence of a chromium-based compound and pyridines having 7 or more carbon atoms is known (see, for example, Patent Document 4). In these decomposition methods, the selectivity for decomposing cyclohexenyl hydroperoxide to produce 2-cyclohexenone is high, and the purity of cyclohexene cannot be increased. For this reason, it is difficult to say that it is a purification method of cyclohexene suitable for industrialization.

Japanese Patent Laid-Open No. 7-100384 JP-A-11-29505 JP 58-72533 A JP-A-6-21727

  Thus, in the prior art, there is currently no purification method for safely decomposing and removing cyclohexenyl hydroperoxide and increasing the purity of cyclohexene, and both the yield and the purification effect of cyclohexene are satisfactory. The creation of an efficient industrial purification method has been strongly desired.

  An object of the present invention is to provide a method for purifying cyclohexene that can safely reduce cyclohexenyl hydroperoxide, which may explode, and industrially obtain high-quality cyclohexene.

  As a result of intensive studies on a method for solving the above-mentioned problems, the present inventors have found that cyclohexene can be efficiently purified by bringing cyclohexenyl hydroperoxide into contact with a reducing agent and decomposing it, thereby reaching the present invention.

  The method for purifying cyclohexene according to the present invention is characterized in that cyclohexene is distilled after contacting a cyclohexene containing cyclohexenyl hydroperoxide with a reducing agent to decompose the cyclohexenyl hydroperoxide.

  According to the method for purifying cyclohexene of the present invention, cyclohexenyl hydroperoxide is decomposed by bringing it into contact with a reducing agent, so that cyclohexenyl hydroperoxide can be decomposed safely and efficiently.

  As the reducing agent, sodium bisulfite or sodium sulfite is preferable, and cyclohexenyl hydroperoxide can be efficiently decomposed.

  As cyclohexene containing cyclohexenyl hydroperoxide, cyclohexene by-produced in the production process of synthesizing dicyclohexyl disulfide by reacting sodium disulfide with chlorocyclohexane can be used. By purifying the by-produced cyclohexene, the production cost of cyclohexene can be reduced.

  The present invention is described in detail below.

  The present invention is a process for purifying cyclohexene, including cyclohexenyl hydroperoxide. The cyclohexene is not particularly limited as long as it contains cyclohexenyl hydroperoxide. For example, this purification method can be applied to cyclohexene obtained by a usual production method or cyclohexene stored for a long time. Moreover, this purification method may be applied using cyclohexene by-produced when other compounds are produced. For example, when dicyclohexyl disulfide is produced by reacting sodium disulfide with chlorocyclohexane, cyclohexene is by-produced. It is preferable to separate and purify this cyclohexene. Thereby, the manufacturing cost of cyclohexene can be reduced.

  In the present invention, the chemical purity of cyclohexene before purification is preferably 90% or more, more preferably 95% or more, and further preferably 99% or more. By setting the chemical purity of cyclohexene before purification to 90% or more, the purification efficiency for decomposing and removing cyclohexenyl hydroperoxide can be further increased. In the present specification, the chemical purity of cyclohexene is calculated from the ratio (area%) of peak areas measured by gas chromatography.

  The purification method of the present invention includes a reduction step in which a reducing agent is contacted with cyclohexene containing cyclohexenyl hydroperoxide, and a distillation step in which cyclohexene obtained in the reduction step is distilled. Moreover, the liquid separation process which isolate | separates the liquid mixture of the cyclohexene obtained at the reduction | restoration process into the oil layer containing a water layer and cyclohexene can be performed, and the obtained oil layer can be distilled.

In the reduction step, cyclohexenyl hydroperoxide in cyclohexene is decomposed by contacting with a reducing agent. The reducing agent is not particularly limited as long as it decomposes cyclohexenyl hydroperoxide, and examples thereof include sodium bisulfite (NaHSO ₃ ) and sodium sulfite (Na ₂ SO ₃ ). Of these, sodium bisulfite is preferable. By using these reducing agents, the purity of cyclohexene is not affected while efficiently decomposing cyclohexenyl hydroperoxide.

  The method for contacting the reducing agent is not particularly limited, and the reducing agent can be contacted by a usual method. For example, an aqueous solution in which a reducing agent is dissolved in water can be added to cyclohexene and mixed. Alternatively, a trace amount of reducing agent may be added to cyclohexene and mixed. Furthermore, an organic solvent etc. can be added and a reducing agent can also be contacted. Preferably, an aqueous solution in which a reducing agent is dissolved in water is added to cyclohexene and mixed, and cyclohexenyl hydroperoxide can be decomposed safely and efficiently. Further, since cyclohexene produced by the decomposition of cyclohexenyl hydroperoxide is present in the oil layer of the mixed solution, the reducing agent and the compound derived from the hydroperoxide group are present in the aqueous layer, cyclohexene can be easily separated.

  The amount of the reducing agent added to cyclohexene is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of cyclohexene. If the amount of the reducing agent added is less than 0.01 parts by weight, cyclohexenyl hydroperoxide cannot be efficiently decomposed. On the other hand, if the amount of the reducing agent added is more than 10 parts by weight, the amount of waste increases after the purification of cyclohexene.

  The concentration when the reducing agent is dissolved in water is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. If the concentration of the reducing agent aqueous solution is less than 0.1% by weight, the cyclohexenyl hydroperoxide may not be sufficiently decomposed. If the concentration of the reducing agent aqueous solution exceeds 10% by weight, mixing with cyclohexene may be poor.

  The temperature at which the reducing agent is brought into contact with cyclohexene is preferably 0 to 80 ° C, more preferably 5 to 50 ° C. If the reaction temperature of the reducing agent is less than 0 ° C, cyclohexenyl hydroperoxide may not be sufficiently decomposed. If the reaction temperature of the reducing agent exceeds 80 ° C., side reactions may occur.

  The time for bringing the reducing agent into contact with cyclohexene is not particularly limited, but is preferably 1 to 400 minutes, more preferably 10 to 100 minutes. If the reaction time is less than 1 minute, cyclohexenyl hydroperoxide may not be sufficiently decomposed. On the other hand, if the reaction time exceeds 400 minutes, the purification efficiency is lowered.

  In the purification method of the present invention, a liquid separation step can be performed as necessary. The liquid separation step is a step of separating the mixed liquid of cyclohexene obtained in the reduction step into an aqueous layer and an oil layer containing cyclohexene. By separating an oil layer containing cyclohexene and subjecting it to a distillation step, the energy cost for distillation can be reduced. As a method for liquid separation, a liquid separation method that is usually used can be applied.

  In the present invention, the distillation step is a step of distilling the cyclohexene mixed solution or the oil layer containing cyclohexene obtained in the reduction step. Examples of the distillation method include atmospheric distillation, low pressure distillation, vacuum distillation, molecular distillation, simple distillation, rectification, continuous distillation, batch distillation, and the like. Among them, atmospheric distillation, low pressure distillation, and vacuum distillation are examples. preferable.

  In this invention, the internal temperature at the time of distilling the oil layer containing a cyclohexene liquid mixture or cyclohexene is 90 degrees C or less, Preferably it is 50-85 degreeC. By distilling at an internal temperature of 85 ° C. or lower, it is possible to suppress the decomposition of cyclohexene and to prevent the generation of odor due to the decomposition.

  Moreover, the pressure at the time of distilling cyclohexene becomes like this. Preferably it is 10-120 kPa, More preferably, it is 20-105 kPa. By distilling at such a pressure, the decomposition of cyclohexene can be suppressed and the increase in odor can be suppressed.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Method for measuring cyclohexenyl hydroperoxide content in cyclohexene]
Take 25 ml of isopropanol and 1.0 ml of acetic acid in a 50 ml Erlenmeyer flask, put small pieces of dry ice, and exclude air. About 5 g of cyclohexene was collected and weighed there, and 1.0 ml of a saturated aqueous potassium iodide solution was added, followed by stirring for 1 hour while heating to about 40 ° C. As the content of cyclohexenyl hydroperoxide in cyclohexene increases, the color changes from yellow to brown. The solution is titrated with a 0.1N sodium thiosulfate aqueous solution, and the point at which the solution becomes colorless is the end point. The content of cyclohexenyl hydroperoxide in cyclohexene (hereinafter referred to as HPO content. The unit is% by weight) is calculated by the following formula.
HPO content (% by weight) = T × 10 ⁻⁴ × (1/2) × 114 × 100 / S
T: Titration volume (ml)
S: Amount of cyclohexene collected (g)
114: Molecular weight of cyclohexenyl hydroperoxide

[Cyclohexene purity measurement method]
The purity of cyclohexene was measured by a gas chromatography (hereinafter referred to as GC) method, and the purity was determined from the ratio of peak areas.
Apparatus: Shimadzu GC-17A (Shimadzu Corporation)
Detector: FID
Column: NB-1, length 60 m × inner diameter 0.25 mm, film thickness 0.40 μm
Carrier gas: helium Column temperature: 40 → 270 ° C., 5 ° C./min temperature rise, 270 ° C. maintained.
Sample: 0.2 μl
Carrier gas flow rate: 1.1 ml / min
Analysis time: 45 minutes

[Reference example]
In a 1 L autoclave, 150 g of 60 wt% sodium sulfide (crystal water 60 g, sodium sulfide amount 90 g, 1.15 mol (molecular weight 78.1)), sulfur 30 g (0.94 mol (atomic weight 32.1)), methanol 120 g, and 100 g of water was charged and heated at 70 ° C. and a gauge pressure of 80 kPa for 1 hour to prepare sodium disulfide. After cooling, the autoclave was opened and charged with 250 g of 95 wt% chlorocyclohexane (chlorocyclohexane amount 237 g, 2.00 mol (molecular weight 118.6)) (total 650 g), and heated and reacted for 11 hours at 100 ° C., gauge pressure 180 kPa. . After cooling, by-product insoluble matter containing sodium chloride by-produced from the reaction mixture was filtered out and rinsed with 5 mL of methanol to obtain 120 g of insoluble matter.

  Subsequently, the filtrate was separated and separated into 280 g of an aqueous layer and 228 g of an oil layer. Gas chromatographic analysis of the oil layer revealed that the dicyclohexyl disulfide concentration in the oil layer was 77.2% by weight (dicyclohexyl disulfide content 176 g, 0.76 mol (molecular weight 230.4), reaction yield 76%). The cyclohexene concentration in the oil layer was 10.0% by weight (cyclohexene amount 22.8 g, 0.28 mol (molecular weight 82.14), reaction yield 14%).

  This oil layer was rectified under reduced pressure (80 kPa), and methanol and the like were distilled off, and then 20.0 g of cyclohexene (chemical purity 99%) was obtained.

  The HPO content in the obtained cyclohexene was 0.15% by weight after storage in January.

[Example 1]
To 10.0 g of cyclohexene (HPO content 0.15 wt%), 1.0 g of a 10 wt% aqueous sodium hydrogen sulfite solution was added as a reducing agent, and the mixture was stirred at room temperature of 25 ° C. for 1 hour. The HPO content in the cyclohexene oil layer was 0.005% by weight.

[Examples 2 to 5]
Cyclohexene was purified in the same manner as in Example 1 except that cyclohexene and reducing agent having different HPO contents shown in Table 1 were changed. Table 1 shows the HPO content in the obtained cyclohexene oil layer.

[Comparative Examples 1-6]
Cyclohexene was purified in the same manner as in Example 1 except that it was changed to cyclohexene and a decomposing agent having different HPO contents described in Table 2. Table 2 shows the HPO content in the obtained cyclohexene oil layer.

[Example 6]
To 100 g of cyclohexene (chemical purity 98.88 area%, HPO content 0.28 wt%, boiling point 83 ° C.), 2.0 g of water and 1.0 g of sodium bisulfite were added and stirred at room temperature of 25 ° C. for 1 hour. The HPO content in the cyclohexene oil layer was 0.03% by weight.

  Subsequently, the liquid separation process which liquid-separates a cyclohexene oil layer and removes an aqueous layer was performed. The obtained cyclohexene oil layer was transferred to 200 ml of an eggplant flask, and distillation was started in a single distillation apparatus equipped with a Liebig condenser 20 cm while gradually heating the eggplant flask from room temperature under normal pressure in an oil bath. 5 g of the initial distillation from the low boiling point to the distillation temperature of 80 ° C. and 88 g of the main distillation having a distillation temperature of 80 ° C. or more were obtained, and 3 g of residue remained in the eggplant flask. The HPO contents were 0.01% by weight for the initial fraction, 0.03% by weight for the main fraction and 0.11% by weight for the residue, respectively, and the cyclohexene purity of the main fraction was 99.20 area%. The method for purifying cyclohexene of Example 6 was high in the quality (chemical purity) of main-chain cyclohexene, and decomposed and removed cyclohexenyl hydroperoxide to reduce the HPO content in the residual component and to be excellent in safety. It was.

[Example 7]
Cyclohexene was purified in the same manner as in Example 6 except that the same cyclohexene as in Example 6 was used as a raw material and the liquid separation step was not performed. Table 3 shows the analysis results of the main distillate cyclohexene, the first distillate component and the residue component. The method for purifying cyclohexene of Example 7 was high in the quality (chemical purity) of main-chain cyclohexene, and decomposed and removed cyclohexenyl hydroperoxide to reduce the HPO content in the residual component and to be excellent in safety. It was.

[Comparative Example 7]
Cyclohexene was purified in the same manner as in Example 6 except that the same cyclohexene as in Example 6 was used as a raw material, no reducing agent / decomposing agent was added, and no liquid separation step was performed. Table 3 shows the analysis results of the main distillate cyclohexene, the first distillate component and the residue component. The purification method of cyclohexene of Comparative Example 7 has a problem in safety because the quality (chemical purity) of main-chain cyclohexene is low, the concentration of cyclohexenyl hydroperoxide in the residual component is high.

Claims (3)

  A method for purifying cyclohexene, comprising: bringing cyclohexene containing cyclohexenyl hydroperoxide into contact with a reducing agent to decompose the cyclohexenyl hydroperoxide, and then distilling cyclohexene.   The method for purifying cyclohexene according to claim 1, wherein the reducing agent is sodium bisulfite or sodium sulfite.   The method for purifying cyclohexene according to claim 1 or 2, wherein cyclohexene by-produced in the production process of synthesizing dicyclohexyl disulfide by reacting sodium disulfide with chlorocyclohexane is brought into contact with the reducing agent.