JPH11193256A - Purification of benzyl alcohol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purification method of benzyl alcohol that permits benzyl alcohol of high purity to be economically produced. SOLUTION: Crude benzyl alcohol containing one or more than two of impurities selected from the group consisting of phenol derivatives, acetic esters bearing aromatic groups and carboxylic acids, an alkali metal compound and water, if a metal alkoxide is used as an alkali metal alkoxide, are fed to a distiller 1 and they are heated and distilled in the distiller 1 into the distillate mainly consisting of benzyl alcohol and the distillation residue mainly containing alkali metal salts formed by their reactions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for purifying benzyl alcohol. More specifically, a method for purifying benzyl alcohol which economically removes impurities from crude benzyl alcohol containing one or more impurities selected from the group consisting of phenol derivatives, acetates having aromatic groups and carboxylic acids It is about.

[0002] Benzyl alcohol is a solvent having excellent solubility and is non-toxic in addition to its use as a paint, a resin release agent, a gloss imparting agent, a volatile retention agent for perfume, a color development aid for photography, and the like. It is a very important compound also as an intermediate for pharmaceutical additives, agricultural chemicals and medicines.

[0003]

2. Description of the Related Art The following processes are known as main processes for producing benzyl alcohol.

A method for hydrolyzing benzyl chloride.

[0005] Direct oxidation of toluene.

A method for oxidizing acetoxylation of toluene.

A method for hydrogenating benzaldehyde.

[0008] Although there are some differences in the types and concentrations of impurities included in the production methods, advanced purification techniques are required for each. Among them, the benzyl alcohol obtained by the method of-includes, as impurities, phenol derivatives such as phenol and cresol, and acetates having an aromatic group such as benzyl acetate and cresyl acetate, and these impurities have a peculiar strong odor and Since they have the property of easily discoloring, it is desired to separate and remove them particularly highly.

However, as shown in Table 1, these impurities have a boiling point close to that of benzyl alcohol, so that it is difficult to separate them by distillation.

[0010]

[Table 1]

As a method for removing cresols from benzyl alcohol, there is a method of separating a cresol as an alkali metal salt by bringing a solution of benzyl alcohol in a vapor state containing the cresol and an alkali metal benzylate into countercurrent contact with each other to separate the cresol as an alkali metal salt. No. 38324.
This method is an effective method for removing only cresols.

[0012]

However, in the method described in JP-B-45-38324, an excess amount of alkali metal benzylate must be used relative to the cresols to be removed. And Tokiko 45-3232.
Patent Document 4 does not disclose any method for separating an alkali metal benzylate used in excess of cresols from an alkali metal cresylate produced by a reaction. Depending on the method of separation, a large amount of benzyl alcohol is lost as excess unreacted alkali metal benzylate, and the embodiment of the separation method is an important factor in determining the economics, that is, practicality of the process.
When the method described in JP-B-45-38324 is used for the purification of benzyl alcohol containing an acetic acid ester having an aromatic group such as benzyl acetate or cresyl acetate and cresols, the cresols react to some extent and are removed. However, there is a problem that benzyl acetate is hardly removed.

[0013] The present invention has been made in order to compensate for the above-mentioned drawbacks of the prior art, and has as its object one or two types selected from the group consisting of phenol derivatives, acetates having an aromatic group, and carboxylic acids. An object of the present invention is to provide a method for economically purifying benzyl alcohol which produces high-purity benzyl alcohol from crude benzyl alcohol containing the above impurities.

[0014]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found a method for economically purifying benzyl alcohol, and have completed the present invention.

That is, the present invention relates to (1) a crude benzyl alcohol containing one or more impurities selected from the group consisting of phenol derivatives, acetates having an aromatic group, and carboxylic acids; The distillate containing benzyl alcohol as a main component is supplied to the distillate 1,
A method for purifying benzyl alcohol, which is separated into a distillation residue having an alkali metal salt as a main component produced by the reaction, and (2) a method for producing crude benzyl alcohol containing an acetate ester having an aromatic group as an impurity and an alkali metal. Alkoxide and, when water is not contained in the crude benzyl alcohol, water is further supplied to the still 1 and subjected to heat distillation treatment in the still 1 to obtain a distillate mainly composed of benzyl alcohol. (3) The method for purifying benzyl alcohol, wherein the distillation residue is separated into a distillation residue having an alkali metal salt as a main component produced by the reaction. (3) The purification method according to (1) or (2), An aqueous solution of alkali metal hydroxide or water is added to the distillation residue from the mixture, and the mixture is settled and separated into an organic phase and an aqueous phase, and a part or all of the organic phase is circulated to the still 1. (4) The method for purifying benzyl alcohol according to any one of (1) to (3), wherein the distillate from the still 1 is mixed with a hydroxide of an alkali metal and an alkali. One or more alkali metal compounds selected from the group consisting of metal alkoxides, and an acetate ester having an aromatic group in the distillate from the still 1 using an alkali metal alkoxide as the alkali metal compound Is contained and water is not contained, water is further supplied to another still 2 and subjected to heat distillation treatment in the still 2 to obtain a distillate mainly composed of benzyl alcohol; A method for purifying benzyl alcohol, characterized in that the reaction product is separated into a distillation residue containing an alkali metal salt as a main component,
(5) The method for purifying benzyl alcohol according to (4), wherein part or all of the distillation residue from the still 2 is circulated to the still 1.
(6) One or two selected from the group consisting of phenol derivatives, acetates having an aromatic group, and carboxylic acids
Crude benzyl alcohol containing more than one kind of impurities
And a distillate having benzyl alcohol as a main component is obtained by subjecting the distillate to heat distillation in the still 1. The distillate from the still 1 is mixed with an alkali metal hydroxide and an alkali metal alkoxide. One or more alkali metal compounds selected from the group consisting of: and an alkali metal alkoxide is used as the alkali metal compound, and the distillate from the still 1 contains an acetate ester having an aromatic group. In the case where water is not contained, water is further supplied to another still 2 and subjected to heat distillation treatment in the still 2 to form a reaction with a distillate mainly composed of benzyl alcohol. A method for purifying benzyl alcohol, comprising separating the distillation residue into a distillation residue having an alkali metal salt as a main component, and circulating a part or all of the distillation residue to the still 1; In the purification method according to (6), an aqueous solution or water of an alkali metal hydroxide is added to the distillation residue from the still 1 and mixed, and the mixture is settled and separated into an organic phase and an aqueous phase. A method for purifying benzyl alcohol, wherein part or all of the benzyl alcohol is circulated to the still 1.

In the present invention, the crude benzyl alcohol may be any as long as it contains one or two or more impurities selected from the group consisting of phenol derivatives, acetates having an aromatic group and carboxylic acids. Any method can be used, but the crude benzyl alcohol produced by the above-mentioned production methods and above, particularly, the oxidative acetoxylation of toluene, can be suitably used. Usually, benzyl alcohol obtained by these production methods contains phenol derivatives, acetates having an aromatic group, carboxylic acids, and the like as impurities, although there are some differences in components and amounts depending on the production methods.

Examples of the impurities referred to in the present invention include phenol, o-cresol, m-cresol and p-cresol.
-Cresol, o-hydroxymethylphenol, m-
C6-8 phenol derivatives such as hydroxymethylphenol, p-hydroxymethylphenol, o-salicylaldehyde, m-salicylaldehyde, p-salicylaldehyde; phenylacetate, benzylacetate, o-cresylacetate, m-crete Acetates having an aromatic group having 8 to 14 carbon atoms, such as silacetate and p-cresyl acetate; formic acid, acetic acid, propionic acid, benzoic acid, o-salicylic acid, m-salicylic acid, p-
Examples thereof include carboxylic acids having 1 to 8 carbon atoms such as salicylic acid. In the present invention, even if one or more of these impurities are present in the crude benzyl alcohol, the treatment can be performed without any problem. The total amount of these impurities may be present in crude benzyl alcohol in a total weight ratio of 0.01 to 10%.

The alkali metal compounds used in the present invention include hydroxides such as sodium hydroxide, potassium hydroxide and cesium hydroxide, sodium methoxide, sodium ethoxide, sodium t-butoxide, sodium benzyl oxide, and the like. Alkoxides of alkali metals such as potassium methoxide. However, when the alkoxide is used when the crude benzyl alcohol contains an acetate having an aromatic group as an impurity and does not contain water, water is supplied and used in the presence of water.
In this case, the amount of coexisting water is related to the treatment time. If the amount is too small, the treatment takes a long time, and if the amount is too large, separation in a subsequent step becomes difficult. In the present invention, the supply amount of water is usually 0.8 to 2000 times, preferably 3 to 1000 times, the molar ratio of the aromatic group-containing acetate ester, though it depends on the concentration of impurities contained therein. These alkali metal compounds can be used alone or in combination of two or more. In the present invention, sodium hydroxide is preferred because it is easily available and has excellent purification efficiency of benzyl alcohol.

In the present invention, the amount of the alkali metal compound used is not particularly limited as long as it does not deviate from the object of the present invention. It is preferable to use 0.8 to 300 equivalents, preferably 0.9 to 200 equivalents, based on the total number of moles of the impurities.

In the present invention, the alkali metal compound can be used in any form of solid or solution without any problem. In the case of a solution, the solvent is preferably water; alcohols such as methanol and 1-butanol are preferred, and water is particularly preferred. The amount of these solvents to be used is preferably within 10% by weight based on benzyl alcohol in consideration of later separation and the like.

In the present invention, the heat distillation treatment in the still is carried out by distillation of an alkali metal salt formed by a reaction between an alkali metal hydroxide and an impurity, and an alkali metal benzylate formed by excess alkali metal hydroxide and benzyl alcohol. The purpose is to separate and remove the residue from benzyl alcohol and volatile impurities in advance. By this operation, it is possible to avoid scaling and clogging troubles in the subsequent distillation purification step of the distilled benzyl alcohol. Distillation residue is discharged from the bottom of the still to prevent accumulation of formed salts. The bottom discharge mixture is usually a slurry, depending on the amount of impurities in the crude benzyl alcohol as the raw material, the amount of the alkali metal compound used, and the concentration ratio by heat distillation. Therefore, in order to prevent the discharge line from being blocked, it is possible to discard the accumulated amount of the generated salts while circulating a part of the bottom mixture.

In the present invention, the type of the still is not limited at all. However, it is preferable that the solid such as crude benzyl alcohol is hardly scaled or clogged with solids precipitated by the heat distillation treatment. A scraping-type thin film evaporator can also be used to reduce the loss of benzyl alcohol discharge from the bottom by increasing the evaporation rate. As illustrated in FIG. 3, the residue discharged from the bottom of the still is mixed with water or an aqueous solution of an alkali metal hydroxide and subjected to a static separation treatment to reduce the waste loss of benzyl alcohol. it can. In this case, the distillation treatment in the still can be performed within a range where the bottom residue has fluidity, and the simplest simple distillation apparatus can be employed. In this case, the ratio between the distillate and the distillation residue from the bottom discharge is usually 60:40 to 40% by weight.
98: 2, preferably 65:35 to 95: 5.

In the present invention, a multi-stage distillation column can be employed for the still 1. The supply method in this case is not particularly limited, but the alkali metal compound is supplied from the top of the column, and the crude benzyl alcohol is supplied to the bottom or the bottom of the column. When an alkoxide is used as the alkali metal compound, when the crude benzyl alcohol contains an acetate having an aromatic group as an impurity and does not contain water, the water may be the same as the crude benzyl alcohol supply location or The mixture is supplied to the lower portion, and the impurities in the crude benzyl alcohol and the alkoxide of the alkali metal are brought into countercurrent contact in the presence of water. The amount of water coexisting with impurities is not particularly limited because it depends on the amount of impurities contained and the purity of the required product benzyl alcohol, but the molar ratio to the acetate having an aromatic group contained as impurities is not limited. 0.8 to 2000 times, preferably 3 to
It is 1000 times. When an alkali metal hydroxide is used as the alkali metal compound, such coexistence of water is not essential, but the coexistence of water not only improves the reactivity but also causes scaling due to precipitates in the reaction section in the column. This is also a preferable method because it is also effective in suppressing a blockage trouble. In this case, the amount of coexisting water is based on the total amount of the phenol derivative and the carboxylic acid when the acetic acid ester having an aromatic group is contained as an impurity, or when the acetic acid ester is not contained. 1 to 2000 times, preferably 3 to 100 times in molar ratio to the amount
It is 0 times.

The bottom temperature of the still is in the range of 20 to 300 ° C., and is preferably 30 to 30 in view of the thermal stability and reactivity of the components.
The temperature is 200 ° C, more preferably 40 to 180 ° C. The pressure is correlated to the temperature and composition of the bottom,
0.01 to 760 mmHg, preferably 20 to 300
mmHg.

When a single-stage distillation apparatus is used for the still,
In order to make the reaction between the alkali metal compound and the impurity more complete, the crude benzyl alcohol and the alkali metal compound are mixed in advance so that some or all of the reactive impurities with the alkali metal compound are reacted and then distilled. It is also possible to supply to the vessel, which is a preferred method. The reaction temperature and the reaction pressure in this case can be used as long as the temperature and pressure are such that the impurities exist in a liquid. The reaction temperature is typically 20 to 300 ° C., preferably 30 to 200 ° C., more preferably 40 to 180 ° C. in consideration of the reactivity and the thermal stability of the components. The reaction time is 1 minute to 1
Within the time range is enough.

It should be noted that the present invention can be partially or entirely implemented in a batch system or a continuous system, and is not limited to this.

[0027]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 1 shows a basic flow of the present invention. That is, the crude benzyl alcohol is supplied from the conduit 1
Further, the alkali metal compound is supplied from the conduit 2 to the still D1.

When an alkali metal alkoxide is used as the alkali metal compound and the crude benzyl alcohol contains an acetate ester having an aromatic group as an impurity and does not contain water, water is supplied from the conduit 14. .
When an alkali metal hydroxide is used as the alkali metal compound, it is preferable to actively supply water from the conduit 14 when the crude benzyl alcohol does not contain water. The water may be supplied as a mixture as shown in FIG. 1 or separately. Distiller D1
In this method, the reaction between the impurities and the alkali metal compound is performed, and benzyl alcohol and volatile impurities are separated by distillation from the alkali metal salt produced by the reaction. Although not shown in FIG. 1, when the bottom mixture forms a slurry, the bottom of the still D1 is preferably agitated with a stirrer or pumped. The bottom distillation residue of the still D1 is discharged from the bottom conduit 3. In order to prevent the discharge line of the conduit 3 from being blocked, a circulation line may be provided as shown by a dotted line in FIG. When a single-stage distillation apparatus is used for the distillation apparatus D1, a method in which the crude benzyl alcohol and the alkali metal hydroxide are preliminarily mixed and supplied to the distillation apparatus D1 is such that a part or all of the impurities are reacted and supplied. Therefore, the amount of impurities distilled out unreacted with benzyl alcohol is reduced, which is a preferable method.

When a multi-stage distillation column is used for the still D1, the upper conduit 2 of the still D1, as shown in FIG.
And the crude benzyl alcohol is supplied to the lower conduit 1 or the bottom of the still D1. Further, when the supply of water is necessary as described in FIG. In the case of supply, water is supplied from a conduit 14 which is the same as or lower than the supply place of the crude benzyl alcohol, and the impurities in the crude benzyl alcohol and the alkali metal compound are brought into countercurrent contact in the presence of water. . This makes it possible to efficiently remove impurities without scaling or clogging due to precipitates in the reaction section in the column. Although the number of stages of the distillation column is not particularly limited, the theoretical number of stages from the lower crude benzyl alcohol supply stage to the upper alkali metal compound supply stage is usually 2
The number of stages is from 30 to 30, preferably from 2 to 10, but several stages are provided above the supply stage of the alkali metal compound so that the alkali metal compound is not distilled out by entrainment, and a part of the distillate is refluxed. Alternatively, it is preferable to provide a facility such as a demister to suppress entrainment.

The benzyl alcohol-based distillate withdrawn from the top of the still D1 is sent via line 4 to a further distillation purification step of benzyl alcohol, if necessary. For example, as shown by dotted lines in FIGS. 1 and 2, low-boiling substances such as water are removed from the conduit 11 by the low-boiling substance removal column L, and high-boiling substances are separated from the conduit 12 by the product column P to form a conduit 13. From the product benzyl alcohol.

FIGS. 3 and 4 show a flow chart in consideration of the step of recovering benzyl alcohol from the distillation residue of each still D1 in FIGS. 1 and 2, respectively. That is, the distillation residue discharged from the conduit 3 at the bottom of the distiller D1 and the aqueous solution of water or the alkali metal hydroxide supplied from the conduit 5 are sent to the mixing and stabilizing device E to be mixed and settled. Then, an organic phase and an aqueous phase are separated (hereinafter, this operation is referred to as an extraction operation). The aqueous phase is taken out of the system through a conduit 6, and the organic phase is circulated through a conduit 7 to a still D1. On this occasion,
The organic phase may be mixed with crude benzyl alcohol supplied from conduit 1 and an alkali metal compound supplied from conduit 2 as shown in FIG.
It may be circulated directly to the still D1. Water can be supplied from the conduit 14 when the supply of water is necessary or when water is actively supplied. However, when water is dissolved in the organic phase circulated from the conduit 7, The step of supplying water from the conduit 14 can be omitted. The excess alkali metal and benzyl alcohol reactant in the distillation residue discharged from the conduit 3, ie, the alkali metal benzylate, is decomposed by mixing with the water supplied from the conduit 5, and the benzyl alcohol and the alkali metal water are decomposed. Oxides are distributed and separated into an organic phase and an aqueous phase, respectively, based on a distribution coefficient determined by conditions such as the concentration of constituent components and temperature at that time. The alkali metal salt generated by the reaction between the alkali metal compound and the impurities is distributed more to the aqueous phase and taken out of the system from the conduit 6 as the aqueous phase. As the alkali metal hydroxide to be added instead of water, those described in the above description of the alkali metal compound can be used.
Sodium hydroxide is particularly preferred. If an alkali metal hydroxide is used as the alkali metal compound used to remove impurities, the addition of the alkali metal hydroxide in this extraction operation can be omitted or reduced by adjusting the amount of alkali metal hydroxide used. Can be minimized. In this extraction operation, the alkali metal concentration in the aqueous phase after the stabilization is important. The preferred alkali metal concentration in the aqueous phase varies depending on the type and concentration of the constituent components, the type of alkali metal used, and the like, and cannot be determined unconditionally.
It is 5 to 10% by weight, particularly preferably 0.8 to 5% by weight. By incorporating this extraction operation, the amount of benzyl alcohol loss outside the system becomes the amount of benzyl alcohol dissolved in the aqueous phase, and the amount of benzyl alcohol discharge outside the system is greatly reduced compared to the method shown in FIG. Can improve the economics of the process. In particular, the method of using a multi-stage distillation column for the still D1 shown in FIG. 4 is an economically superior method that is simple in process, has a high effect of removing impurities, and has little loss of benzyl alcohol outside the system. . The distillate mainly composed of benzyl alcohol taken out from the top of the still D1 is sent to a further benzyl alcohol distillation and purification step as shown in FIG. 1 as necessary.

FIG. 5 shows a method for minimizing the concentration of impurities in the product benzyl alcohol by employing two simple distillation apparatuses D1 and D2. That is, a method of minimizing the impurity concentration in benzyl alcohol by reacting the remaining unreacted impurities in the distillate containing benzyl alcohol as the main component, which is distilled from the top of the still D1, with the alkali metal compound again. It is.
The alkali metal compound supplied from the conduit 8 and the distillate from the distiller D1 supplied from the conduit 4 are separately supplied directly to another simple distillation apparatus, a distiller D2, or as shown in FIG. The alkali metal compound supplied from the conduit 8 is supplied to the distiller D2 in a form preliminarily mixed with the distillate of the distiller D1. The alkali metal compound supplied from the conduit 2 may be omitted, and the entire required amount may be supplied from the conduit 8, or may be supplied from both the conduit 2 and the conduit 8 at an appropriate ratio. An alkoxide of an alkali metal is used as an alkali metal compound, and a distillate of the still D1 from the conduit 4 contains an acetate having an aromatic group as an impurity and does not contain water. When supplying
Water is supplied from a conduit 15. The distillation residue discharged from the bottom of the still D2 passes directly through the conduit 9 to the still D1.
Or mixed with an organic phase circulated from a conduit 7, crude benzyl alcohol supplied from a conduit 1, an alkali metal compound supplied from a conduit 2, and the like, as shown in FIG. Circulate. On the other hand, the benzyl alcohol-based distillate taken out from the conduit 10 at the top of the still D2 is sent to a further benzyl alcohol distillation / purification step as shown in FIG. 1 if necessary. According to this method, high purity benzyl alcohol can be economically produced by using two structurally simple simple distillation apparatuses, as in the case of FIG.

[0034]

According to the present invention, crude benzyl alcohol containing one or more selected from the group consisting of a phenol derivative, an acetic ester having an aromatic group and a carboxylic acid as impurities is heat-distilled together with an alkali metal compound. By doing so, it is possible to produce high-purity benzyl alcohol. Furthermore, the alkali metal compound and the alkali metal benzylate in the distillation residue can be recovered and used, so that the amount of waste can be reduced and the environment is also preferable, and an economically advantageous and industrially valuable purification method can be provided. .

[0035]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. In addition,% shows weight% unless there is a notice.

Example 1 In a 200 ml round bottom flask equipped with a magnetic stirrer, a three-way cock for introducing nitrogen, a thermometer, and a distilling condenser, 98.6% of benzyl alcohol and benzyl acetate.
0%, Cresol 0.3% (ortho: meta: para ratio 1
7:53:30) and 161.70 g of a crude benzyl alcohol solution containing 0.1% of acetic acid were charged and heated to 80 ° C. 3.59 g of a 40% aqueous NaOH solution (35.9 mmol
1, 2.0 equivalents of the total number of moles of impurities). 8
After reacting at 0 ° C. for 5 minutes, simple distillation was performed under reduced pressure of 20 mmHg until no distilling was observed. Distillate from 30 ° C to 104 ° C (azeotropic distillate of water and benzyl alcohol) 2.93
g, 1045.5 g of a fraction at 104 ° C., and the distillation residue was 6.61 g. (Weight ratio of total distillation amount to residue amount = 9
6.0: 4.0). As a result of analyzing the distillate by gas chromatography, it was found that benzyl acetate was 70 ppm, cresol (total value of ortho, meta and para, the same applies hereinafter) 105
ppm and acetic acid 0 ppm.

Gas chromatography conditions: Model: Shimadzu Corporation GC-14A Detector: Flame ionization detector Column: FFAP-CB manufactured by Chrome Pack 0.32 mm ID × 25 m Film thickness 0.3 μm Carrier gas: He 0.93 ml / min Injection Temperature: 260 ° C Detector temperature: 260 ° C Column temperature: 65 ° C (3 minutes) → Temperature rise 15 ° C / min → 230 ° C (15 minutes) Split ratio: 1/60 Sample injection volume: 1 μl Internal standard: 1 In this example, the bottom mixture was concentrated until the fluidity of the bottom mixture was lost and no distillate was generated. Benzyl alcohol in the distillation residue was 4.21 g in terms of benzyl alcohol including sodium benzylate, and 2.62% of the total benzyl alcohol (including the benzyl acetate reaction component) in the crude benzyl alcohol as the raw material. there were. This value indicates the minimum discharge loss of benzyl alcohol discharged from the bottom as a distillation residue.

Comparative Example 1 In a 1000 ml round bottom flask equipped with a stirrer, a three-way cock for introducing nitrogen, a thermometer and a distilling cooler, 1043.43 g of benzyl alcohol and 39.93 g of a methanol solution of 28% sodium methylate were placed. The batch simple distillation was started under reduced pressure.

The pressure and the temperature were raised to 150 mmHg and 156 ° C., and almost all of methanol and a part of benzyl alcohol were distilled off to prepare a benzyl alcohol solution of sodium benzylate.

Using this sodium benzylate benzyl alcohol solution, benzyl acetate 1.0
%, Cresol 0.67% (ortho: meta: para ratio 1)
7:53:30), acetic acid 0.04%, water 0.0149
%. 26.93 g of sodium benzylate (0.201
mol) containing 1005.73 g of benzyl alcohol solution
Was prepared. The moisture was measured using a Karfisher moisture meter MKA-210 manufactured by Kyoto Electronics Industry Co., Ltd. This solution was charged into a 1000 ml round bottom flask equipped with a stirrer, a three-way cock for introducing nitrogen, a thermometer, and a distilling cooler.
C., and batch distillation was started under a reduced pressure of 55 mmHg. Distillation rate (ratio of distilling amount to total charged amount) 90.1%
The simple distillation was carried out. The distillation time was about 3 hours. A total distillation amount of 906.47 g was obtained, and the distillation residue was 99.26 g. (Weight ratio of total distillate amount to residue amount = 90.1: 9.
9). As a result of analyzing the distillate by gas chromatography, benzyl acetate 7800 ppm and cresol 1
89 ppm and acetic acid 0 ppm.

Examples 2 to 7 The same operation as in Example 1 was carried out except that the alkali metal compounds and their equivalents shown in Table 2 were used. Table 2 shows the results.

[0042]

[Table 2]

Example 8 In a 1000 ml round bottom flask equipped with a stirrer, a three-way cock for introducing nitrogen, a thermometer and a distilling condenser, 98.29% of benzyl alcohol, 1.0% of benzyl acetate and 0.67 of cresol were added. % (Ortho: meta: para ratio 17:53:
30), 100.88 g of a crude benzyl alcohol solution containing 0.04% of acetic acid was charged, and the temperature was raised to 100 ° C. 4
19.95 g of 0.25% NaOH aqueous solution (0.201 m
and 1.49 equivalents of the total number of moles of impurities), and at the same time, batch simple distillation was started under reduced pressure of 55 mmHg. Distillation rate (ratio of distilling amount to total charged amount) 90.1%
The simple distillation was carried out. The distillation time was about 3 hours. A total distillation amount of 919.77 g was obtained, and the distillation residue was 101.06 g. (Weight ratio of total distillate amount to residue amount = 90.1: 9.
9). The distillate was analyzed by gas chromatography to find that benzyl acetate 1020 ppm and cresol 8
It was 59 ppm and acetic acid was 0 ppm.

Example 9 In a 2000 ml round bottom flask equipped with a stirrer, a three-way cock for introducing nitrogen, a thermometer, and a distilling condenser, 98.29% of benzyl alcohol, 1.0% of benzyl acetate, and 0.67 of cresol were added. % (Ortho: meta: para ratio 17:53:
30), 2001.76 g of a crude benzyl alcohol solution containing 0.04% of acetic acid was charged, and the temperature was raised to 100 ° C. 4
39.90 g of a 0.25% NaOH aqueous solution (0.401 m
ol, 1.49 equivalents of the total number of moles of impurities). After reacting at 100 ° C. for 5 minutes, the mixture was subjected to batch simple distillation under reduced pressure of 55 mmHg. A total distillation amount of 1843.38 g was obtained, and a distillation residue was 198.28 g. (Weight ratio of total distillate to residue) = 90.3: 9.7). As a result of analyzing the distillate by gas chromatography, it was found that benzyl acetate was 127 ppm, cresol was 338 ppm, and acetic acid was 0 ppm.
Met.

The amount of benzyl alcohol in the evaporation residue was 163.36 g in terms of benzyl alcohol including the sodium benzylate component, and was calculated based on the total amount of benzyl alcohol (including the benzyl acetate reaction component) in the crude benzyl alcohol raw material. 2%.

[Extraction operation] 195.74 g of the distillation residue obtained by the above simple distillation was charged into a 500 ml mixer settler (separable flask equipped with a stirrer and with a jacket drawn out from the bottom), and 319.96 g of water was added. After stirring at 50 ° C. for 5 minutes, the mixture was settled and separated into an organic phase and an aqueous phase. The weight and composition of the obtained phases were as shown in Table 3. In the composition analysis, both phases were neutralized with hydrochloric acid to a pH of 1 or less and analyzed by gas chromatography. The cresol Na salt was calculated from the cresol amount, and the sodium acetate was calculated from the acetic acid amount.
The water concentration was determined from the material balance (the same applies hereinafter).

[0047]

[Table 3]

Example 10 In a 1000 ml round bottom flask equipped with a stirrer, a three-way cock for introducing nitrogen, a thermometer and a distilling condenser, 76.25 g of the organic phase obtained by the extraction operation of Example 9 and crude benzyl were added. 792.73 g of alcohol (98.36% of benzyl alcohol,
Benzyl acetate 1%, Cresol 0.6% (ortho, meta, para ratio = 17: 53: 30), acetic acid 0.04
%, And the temperature was raised to 100 ° C. 40.25% NaO
15.19 g of H aqueous solution (0.153 mol, 1.5 equivalents of the total mole number of impurities) was added. After reacting at 100 ° C. for 5 minutes, the mixture was subjected to batch simple distillation under reduced pressure of 55 mmHg. A total distillation amount of 795.75 g was obtained, and a distillation residue was 88.4.
2 g. (Weight ratio of total distillation amount to residue amount = 90: 1
0). As a result of analyzing the distillate by gas chromatography, benzyl acetate 113 ppm, cresol 42
It was 5 ppm and acetic acid was 0 ppm.

[Extraction operation] 86.0 g of the distillation residue obtained by the above simple distillation was charged into the 500 ml mixer settler described in Example 9, and 111.0 g of water was added thereto.
After stirring for 5 minutes, the mixture was settled and separated into an organic phase and an aqueous phase. Table 4 shows the weight and composition of the obtained two phases.

[0050]

[Table 4]

This embodiment is an application of the process shown in FIG. 2 and uses 40.25% NaO as an alkali metal compound.
In this example, the sodium salt of impurities in the distillation residue after simple distillation was extracted and separated with water using an H aqueous solution, and the organic phase was recycled.

The recycling of the organic phase slightly increases the load of impurities, and the use amount of the same alkali metal compound slightly reduces the effect of removing the same. However, all benzyl alcohol (benzyl acetate reaction component) in the crude benzyl alcohol as a raw material is reduced. Benzyl alcohol (discharge loss) in the aqueous phase discharged to the outside of the system (including discharge loss) is 0.78%, and the benzyl alcohol discharge loss can be greatly reduced as compared with the case where no extraction operation is performed.

Example 11 887.34 g of the distillate obtained by simple distillation in Example 9 was charged and heated to 100 ° C. After adding 19.31 g of a 40.25% NaOH aqueous solution and reacting at 100 ° C. for 5 minutes, the mixture was subjected to batch simple distillation under reduced pressure of 100 mmHg. 94 ° C
74.08 g of a distillate (azeotropic distillate of water and benzyl alcohol) of from 144 ° C. to 144 ° C. and a distillate 6 of from 144 ° C. to 149 ° C.
63.24 g was obtained, and the distillation residue was 169.33 g. (Weight ratio of total distillate amount and residue amount = 81.3: 18.
7). As a result of analyzing the distillate by gas chromatography, it was found that benzyl acetate was 0 ppm and cresol was 7 pp.
m and acetic acid were 0 ppm.

This example shows that the amount of impurities can be significantly reduced by performing the second simple distillation process in the first simple distillation process of the ninth embodiment.

Example 12 [First Simple Distillation] In the same simple distillation apparatus as in Example 10, 68.68 g of the organic phase obtained by the extraction operation of Example 9 and the simple distillation of Example 11 were used instead of the alkali metal compound. 133.62 g of crude benzyl alcohol and 797.76
g (benzyl alcohol 98.36%, benzyl acetate 1%, cresol 0.6% (ortho, meta, para ratio = 17: 53: 30), acetic acid 0.04%), and 1
The temperature was raised to 00 ° C. and kept for 5 minutes for reaction. Then 5
Batch simple distillation was performed under a reduced pressure of 5 mmHg. 76 ° C to 11
Distillate at 0 ° C (azeotropic distillate of water and benzyl alcohol) 1
0.78 g and a distillate of 110 ° C. to 130 ° C. 904.4
8 g was obtained, and the distillation residue was 87.86 g (weight ratio of total distillate amount and residue amount = 91.2: 8.8). As a result of analyzing the distillate by gas chromatography, it was found that benzyl acetate was 119 ppm, cresol was 428 ppm, and acetic acid was 0 pp.
m.

The benzyl alcohol in the evaporation residue was 73.26 g in terms of benzyl alcohol including the sodium benzylate component, and was 9 to the total benzyl alcohol (including 100% benzyl acetate reaction component) in the crude benzyl alcohol as the raw material. 0.3%.

[Extraction operation] The distillation residue (85.22 g) obtained in the first simple distillation was used in 500 ml as described in Example 9.
129.46 g of water was added, and the mixture was stirred at 50 ° C. for 5 minutes, settled and separated into an organic phase and an aqueous phase. Table 5 shows the weight and composition of both phases obtained.

[0058]

[Table 5]

The benzyl alcohol (discharge loss) in the aqueous phase discharged out of the system relative to all the benzyl alcohol (containing 100% of benzyl acetate in the reaction mixture) in the crude benzyl alcohol as the raw material was 0.80%.

[Second Simple Distillation] In the same simple distillation apparatus as above, 907.43 g of the distillate obtained in the first simple distillation was charged, and the temperature was raised to 100 ° C. After adding 40.25% NaOH aqueous solution (15.40 g) and reacting at 100 ° C. for 5 minutes, the mixture was subjected to batch simple distillation under reduced pressure of 100 mmHg. 94
59.18 g of a distillate (azeotropic distillate of water and benzyl alcohol) at a temperature of from 144 ° C. to 144 ° C. and 724.16 g of a distillate from 144 ° C. to 149 ° C. were obtained, and the distillation residue was 139.49 g (total distillation). Weight ratio of output amount and residue amount = 81.3: 18.
7). As a result of analyzing the distillate by gas chromatography, benzyl acetate was 0 ppm and cresol was 19 pp.
m and acetic acid were 0 ppm.

In the present embodiment, in the process shown in FIG. 3, an aqueous solution of NaOH of 40.25% is supplied as the alkali metal compound in the second stage, and the alkali metal source of the first reaction is 2
By using the distillation residue of the simple distillation of the first stage and extracting and removing the sodium salt of the impurities in the distillation residue of the first stage with water and recycling the organic phase, it is possible to reduce the amount of NaOH used. This is an example in which a high impurity removal effect is obtained, and at the same time, the emission loss of benzyl alcohol is suppressed to a low level.

Example 13 [First Simple Distillation] In a 300 ml round bottom flask equipped with the same equipment as in Example 1, 98.3% of benzyl alcohol, 1.0% of benzyl acetate, 0.6% of cresol (ortho:
Meta: para ratio 17:53:30) and 223.74 g of a crude benzyl alcohol solution containing 0.1% of acetic acid were charged.
The temperature was raised to 80 ° C. 40.0% NaOH aqueous solution 3.13
g (31.3 mmol, 1.0 equivalent of the total moles of impurities) was added. After reacting at 80 ° C for 5 minutes, 20m
Batch simple distillation was performed under reduced pressure of mHg. Distillate 204.18
g was obtained and the residue was 22.69 g. (Weight ratio of total distillate amount and residue amount = 90.0: 10.0). The distillate was analyzed by gas chromatography. As a result, benzyl acetate 3 was obtained.
12 ppm, 1505 ppm cresol, 0 pp acetic acid
m.

[Second Simple Distillation] In the same apparatus as above, 200.0 g of the distillate from the first single distillation (benzyl acetate:
62 mg, cresol: 301 mg, acetic acid: 0 g) were charged, and the temperature was raised to 80 ° C. 3.13 g of a 40.0% NaOH aqueous solution (31.3 mmol, 9.8 equivalents of the total number of moles of impurities, the same charge as in the first simple distillation) was added. After reaction at 80 ° C. for 5 minutes, batch simple distillation was performed under a reduced pressure of 20 mmHg. 3.29 g of a distillate (azeotropic fraction) at 30 ° C. to 104 ° C., 184.85 g of a distillate at 104 ° C.
Was obtained and the residue was 18.28 g (weight ratio of the total amount of distillate to the amount of residue = 91.0: 9.0).

As a result of analyzing the distillate by gas chromatography, it was found that benzyl acetate was 12 ppm, cresol was 39 ppm, and acetic acid was 0 ppm.

In this example, the first simple distillation treatment
This shows that the amount of impurities can be significantly reduced by performing the second simple distillation treatment.

Example 14 A continuous aldershaw column having a column diameter of 32 mm and having five distillation sections and two upper and lower feed sections sandwiching the distillation section was used. The still has a stirrer and a liquid level controller, and is heated by a mantle heater. The top has a condenser and a reflux controller. Operation was performed at an overhead pressure of 150
Continuous distillation was performed under the reduced pressure of mmHg with the following feed amount. From the lower feed section, 451.3 g / h of crude benzyl alcohol (0.994% of benzyl acetate,
o-cresol 0.100%, m-cresol 0.29
8%, p-cresol 0.199%, benzaldehyde 0.048%, water 0.358%). On the other hand, benzyl alcohol containing neither benzyl acetate nor cresol and 47.62 from the upper feed section.
75.6 g / h (NaOH aqueous solution mixture)
4.05%, water 4.52%, benzaldehyde 0.04
5%, benzyl alcohol 91.38%).
The molar ratio of feed NaOH to the total amount of benzyl acetate and cresol in the feed was 1.40.
The molar ratio of water to benzyl acetate, which was heat-treated in the presence of impurities such as benzyl acetate and cresol, was 3.0. Still heating by a mantle heater was adjusted so that the ratio of the distillate amount to the total feed amount (hereinafter, referred to as the distillate ratio) when all were distilled without reflux from the top was 70%. . The distillate amount after reaching the steady state is 375.7 g / h, and the distillate rate is 71.3%.
Met. When the obtained distillate was analyzed by gas chromatography, the benzyl acetate concentration was 340 pp
m, the cresol was 0 ppm. The moisture in the distillate was measured by a Karl Fischer moisture meter to be 1.45%. The liquid in the still and the bottom liquid were cloudy due to the precipitation of solids, but there was no sign of precipitation or scaling of the solids in the column.

Comparative Example 2 (Example of application of the method described in Japanese Patent Publication No. 45-38324) Example 14 was repeated except that the same apparatus as in Example 14 was used and the feed amount and composition from the upper and lower feed sections were changed. The same was done. That is, from the lower feed section, 451.3 g / h of crude benzyl alcohol (1.000% of benzyl acetate, 0.100% of o-cresol, m
-Cresol 0.300%, p-cresol 0.200
%, 0.032% of benzaldehyde and 0.066% of water). On the other hand, from the upper feed section, a benzyl alcohol solution of sodium benzylate obtained by removing NaOH from benzyl alcohol after adding NaOH to the benzyl alcohol and removing the produced water was 451.3 g / h (13.82% sodium benzylate, 0.1% water). 07%, benzaldehyde 0.032%, benzyl alcohol 86.08%). The molar ratio of sodium benzylate in the feed to the total amount of benzyl acetate and cresol in the feed was 1.43. In this example, there is no active water supply, and only a small amount of water contained in the starting benzyl alcohol is brought in. For reference, the molar ratio of water to benzyl acetate was 0.55. The distillation rate was 70.2%. When the obtained distillate was analyzed by gas chromatography, cresol was 0 ppm, but the benzyl acetate concentration was as high as 5550 ppm.

Examples 15-17 Changing the molar ratio of water to benzyl acetate in crude benzyl alcohol by varying the amount of water supplied with crude benzyl alcohol from the lower feed section; Example 14 was carried out in the same manner as in Example 14 except that the mixing ratio of the 62% NaOH aqueous solution and benzyl alcohol was changed to change the molar ratio of NaOH in the upper feed to the total number of moles of benzyl acetate and cresol in crude benzyl alcohol. The results were as shown in Table 6.

[0069]

[Table 6]

Example 18 After the crude benzyl acetate was subjected to a methanolysis reaction, low-boiling components were separated by distillation to obtain crude benzyl alcohol. 305.43 g / h of the crude benzyl alcohol (0.05% methanol)
8%, benzaldehyde 0.072%, benzyl alcohol 97.8%, benzyl acetate 0.074%, o
-Cresol 0.084%, m-cresol 0.253
%, P-cresol 0.168%, other sodium salts, etc.) and an organic phase obtained by adding water and extracting and separating the mixture, and 185.69 g / h (benzyl alcohol 81.69 g / h).
9%, benzaldehyde 0.065%, cresols 1.37%, sodium acetate 0.065%, water 16.6
%) Was supplied from the lower feed section described in Example 14. Meanwhile, from the upper feed section, 47.6
Mixed solution of 2% NaOH aqueous solution and benzyl alcohol 8
1.55 g / h (NaOH 3.49%, water 3.83%,
Benzyl alcohol 92.6%, benzaldehyde 0.
045%). The operation was carried out at a top pressure of 150 mmHg, and all distillation was performed without reflux from the top. Distillation rate is 7
Driving at 9.5%.

Both benzyl acetate and cresols in the distilled benzyl alcohol were 0 ppm. On the other hand, the bottom liquid was stirred and mixed with 122.75 g / h of water, settled and separated into an organic phase and an aqueous phase, and the organic phase was circulated to the lower feed section. The NaOH concentration in the aqueous phase is 3.42%
Met. In addition, when sodium acetate and cresol Na salt in the aqueous phase were decomposed with hydrochloric acid and analyzed by gas chromatography, acetic acid and cresol in amounts corresponding to benzyl acetate and cresols in crude benzyl alcohol as a raw material were detected.

[Brief description of the drawings]

FIG. 1 is a process chart showing a specific example when carrying out the method of the present invention.

FIG. 2 is a process chart showing a specific example when carrying out the method of the present invention.

FIG. 3 is a process chart showing a specific example when carrying out the method of the present invention.

FIG. 4 is a process chart showing a specific example when carrying out the method of the present invention.

FIG. 5 is a process chart showing a specific example when carrying out the method of the present invention.

[Explanation of symbols]

 1-14 Conduit D1, D2 Distiller E Mixing and stabilizing device L Low boiling substance removal tower P Product tower

Claims (11)

[Claims] 1. A crude benzyl alcohol containing one or more impurities selected from the group consisting of a phenol derivative, an acetate having an aromatic group, and a carboxylic acid;
The alkali metal hydroxide is supplied to the still 1 and subjected to heat distillation treatment in the still 1, whereby a distillate containing benzyl alcohol as a main component and a distillate containing a reaction product of an alkali metal salt as a main component are obtained. A method for purifying benzyl alcohol, which is separated into a residue and a residue. 2. The method for purifying benzyl alcohol according to claim 1, wherein the alkali metal hydroxide is sodium hydroxide. 3. A crude benzyl alcohol containing an acetic acid ester having an aromatic group as an impurity and an alkoxide of an alkali metal, and if the crude benzyl alcohol does not contain water, water is further supplied to the still 1 By subjecting the distillate 1 to a heat distillation treatment, a distillate mainly composed of benzyl alcohol and a distillation residue mainly composed of an alkali metal salt produced by the reaction are separated into benzyl alcohol. Purification method. 4. The purification method according to claim 1, wherein an aqueous solution or water of an alkali metal hydroxide is added to the distillation residue from the still 1 and mixed. A method for purifying benzyl alcohol, comprising separating a phase and an aqueous phase, and circulating a part or all of the organic phase to the still 1. 5. The purification method according to claim 1, wherein one or two selected from the group consisting of a distillate from the still 1 and an alkali metal hydroxide and an alkali metal alkoxide. When at least one kind of alkali metal compound and an alkoxide of an alkali metal are used as the alkali metal compound, and the distillate from the still 1 contains an acetate having an aromatic group and does not contain water, the distillate further contains: Water is supplied to another still 2 and subjected to heat distillation in the still 2 to obtain a distillate mainly composed of benzyl alcohol and a distillation residue mainly composed of an alkali metal salt produced by reaction. A method for purifying benzyl alcohol, comprising: separating benzyl alcohol; 6. The method for purifying benzyl alcohol according to claim 5, wherein a part or all of the distillation residue from the still 2 is circulated to the still 1. 7. A crude benzyl alcohol containing one or more impurities selected from the group consisting of a phenol derivative, an acetic ester having an aromatic group and a carboxylic acid is supplied to the still 1. A distillate containing benzyl alcohol as a main component is obtained by the heat distillation treatment, and one or more selected from the group consisting of a distillate from the still 1 and an alkali metal hydroxide and an alkali metal alkoxide. When two or more alkali metal compounds and an alkoxide of an alkali metal are used as the alkali metal compound, and the distillate from the still 1 contains an acetate ester having an aromatic group and does not contain water, More water,
The mixture is supplied to another distillation apparatus 2 and subjected to heat distillation treatment in the distillation apparatus 2 to convert a distillate mainly composed of benzyl alcohol and a distillation residue mainly composed of an alkali metal salt produced by reaction. A method for purifying benzyl alcohol, comprising separating and circulating a part or all of the distillation residue to the still 1. 8. The purification method according to claim 7, wherein an aqueous solution or water of an alkali metal hydroxide is added to the distillation residue from the still 1 and mixed, and the mixture is settled and separated into an organic phase and an aqueous phase. A method for purifying benzyl alcohol, wherein a part or all of the organic phase is circulated to the still 1. 9. The method for purifying benzyl alcohol according to claim 1, wherein the still 1 is a single-stage still. 10. The method for purifying benzyl alcohol according to claim 1, wherein the distiller 1 is a multi-stage distiller. 11. The method for purifying benzyl alcohol according to claim 5, wherein the still 1 and / or the still 2 are single-stage stills.