JPH11100351A - Purification of benzyl acetate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject compound in high yield by distilling crude benzyl acetate over an alkali metal compound. SOLUTION: Crude benzyl acetate containing 0.01-10 wt.% of impurities selected from phenyl acetate derivatives as cresyl acetate, phenol derivatives as cresol, and carboxylic acids as the total weight is distilled with heat over an alkali metal compound as sodium methoxide, for example, at 20-300 deg.C distillation column bottom temperature at a reduced pressure of 760 mm-0.01 mm Hg. During the purification, the impurities form alkali salt from the alkali metal compound and are separated as residues whereby the impurities are reduced in the range from 1-1,000 ppm and benzyl acetate of high purity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying benzyl acetate. More specifically, the present invention relates to a method for purifying benzyl acetate which economically removes impurities from crude benzyl acetate containing at least one impurity selected from the group consisting of an acetate ester having an aromatic group, a phenol derivative, and a carboxylic acid. It is.

[0002] Benzyl acetate is an important compound that is useful as a solvent for various fragrance components, alkyd resins and cellulosic resins, and is also a raw material for benzyl alcohol.

[0003]

2. Description of the Related Art As main methods for producing benzyl acetate, a method of acetylating benzyl alcohol and a method of oxidizing acetoxylation of toluene are known. Benzyl acetate obtained by a particular method contains phenyl acetate derivatives such as cresyl acetate and phenol derivatives such as cresol as impurities, and since these impurities have a peculiar odor, 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 acetate, so that distillation separation is difficult.

[0004]

[Table 1]

As a method for purifying an acetate ester, for example, Purification of Laborat
ory Chemicals, 2nd edition, 1980, 3
80, D.E. D. Perrin et al., Pergamon
Press describes a method of washing with an aqueous sodium carbonate solution, drying, and then distilling.

However, the above-mentioned method has a problem that phenol derivatives such as cresol and acetic acid esters having an aromatic group, such as cresyl acetate and phenyl acetate, which are contained as impurities in benzyl acetate, are hardly removed. .

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to select from the group consisting of phenylacetate derivatives such as cresyl acetate, phenol derivatives such as cresol, and carboxylic acids. Another object of the present invention is to provide a method for economically purifying benzyl acetate which produces high-purity benzyl acetate from crude benzyl acetate containing at least one impurity.

[0008]

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 efficiently purifying benzyl acetate, and have completed the present invention.

That is, the present invention relates to a method for purifying benzyl acetate, comprising distilling crude benzyl acetate in the presence of an alkali metal compound.

In the present invention, the impurities contained in the crude benzyl acetate include, for example, phenyl acetate, o-cresyl acetate, m-cresyl acetate, p-cresyl acetate, {2- (acetoxymethyl) phenyl} Aroma having 8 to 12 carbon atoms such as acetate, {3- (acetoxymethyl) phenyl} acetate, {4- (acetoxymethyl) phenyl} acetate, o-acetylsalicylic aldehyde, m-acetylsalicylic aldehyde, p-acetylsalicylic aldehyde, etc. Ester having a group: phenol, o-cresol, m-cresol, p-cresol, o-hydroxymethylphenol, m-hydroxymethylphenol, p-hydroxymethylphenol, o-salicylaldehyde, m-
C6-8 phenol derivatives such as salicylaldehyde and p-salicylaldehyde; 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. According to the method of the present invention, even if one or more of these impurities are present in benzyl acetate, the treatment can be performed without any problem. These impurities may be present in benzyl acetate in a total amount of about 0.01 to 10% by weight. Note that, apart from these impurities, benzyl alcohol may be present in benzyl acetate at about 0.05 to 2% by weight.

As the alkali metal compound used in the present invention, any compound can be used as long as it belongs to the alkali metal compound, and it is not particularly limited. For example, hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium hydroxide, alkoxides such as sodium methoxide, sodium ethoxide, sodium t-butoxide, sodium benzyl oxide and potassium methoxide, sodium amide And amides such as potassium amide, sodium diisopropylamide and lithium diisopropylamide, and hydrides such as sodium hydride and potassium hydride. These can be used alone or in combination of two or more. In the present invention, alkoxide is preferred because it is easily available and the purification efficiency of benzyl acetate is excellent, and sodium methoxide is particularly preferred. The amount of these alkali metal compounds used is not particularly limited as long as it does not deviate from the object of the present invention.Since the purification efficiency of benzyl acetate is excellent, the sum of the number of moles of the above impurities contained in crude benzyl acetate is excellent. It is preferably used in the range of usually 0.8 to 300 equivalents, preferably 0.9 to 200 equivalents. These alkali metal compounds can be used in either solid or solution form without any problem. When used as a solution,
Water; alcohols such as methanol and t-butanol; aromatic compounds such as benzene, toluene and xylene; diethyl ether, dibutyl ether, tetrahydrofuran,
Ether compounds such as dimethoxyethane are used.
The use amount of these solvents can be suitably used within 5% by weight based on benzyl acetate.

In the present invention, the conditions under which crude benzyl acetate is distilled in the presence of an alkali metal compound are not subject to any restrictions as long as it is possible to perform distillation of benzyl acetate in the presence of an alkali metal compound. Absent. For example, the temperature at the bottom of distillation is usually 20 to
The temperature is in the range of 300 ° C, particularly preferably in the range of 30 to 200 ° C, and the degree of reduced pressure is usually in the range of 760 to 0.01 mmHg, particularly preferably in the range of 100 to 0.1 mmHg. The impurities are separated as a residue of distillation by forming an alkali salt with the alkali metal compound. Therefore, the distillation apparatus is not particularly limited, and a distillation apparatus such as an evaporator can be used without any problem.
Before starting the distillation, it is also possible to take time to ripen the mixture of the crude benzyl acetate and the alkali metal compound, but in this case, the ripening time in the range of 1 minute to 1 hour is sufficient. Further, the distillation may be performed any number of times depending on the amount of impurities required. Specifically, a method can be employed in which an alkali metal compound is charged into the distillate of the first distillation, distillation is performed again, and the distillation is repeated. When the same amount of the alkali metal compound is used, the removal efficiency of impurities is better when, for example, half the amount is used and distillation is performed twice, than when the entire amount is used and distillation is performed once.

After the benzyl acetate of the present invention is distilled in the presence of an alkali metal compound, impurities in the benzyl acetate can be reduced to the range of 1 to 1000 ppm.

In the present invention, purified benzyl acetate is obtained by distillation, and impurities are removed to the residue as alkali metal salts. The higher the weight ratio of the fraction to the residue (hereinafter referred to as the evaporation rate), the higher the ratio. Benzyl acetate recovery is improved. However, if the alkali metal salt of the impurity has a high evaporation rate, it may be solidified depending on the temperature, and in some cases, it is preferable to complete the distillation before the solidification in operation of the apparatus. Therefore, the ratio of the weight of the fraction and the residue after distillation is 7
5: 25-99: 1, preferably 85: 15-98: 2
It is better to distill so that The residue contains sodium benzyl alkoxide, although the amount varies depending on the amount of the alkali metal compound used other than the alkali metal salt of the impurity.

[0015]

According to the present invention, at least one compound selected from the group consisting of phenylacetate derivatives such as cresyl acetate, phenol derivatives such as cresol, and carboxylic acids.
The present invention provides an economical purification method of benzyl acetate which produces high-purity benzyl acetate by subjecting crude benzyl acetate containing various kinds of impurities to heat distillation with an alkali metal compound, which is industrially extremely significant. .

[0016]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Example 1 100 ml equipped with a magnetic stirrer, a three-way cock for introducing nitrogen, a thermometer, and a Liebig tube for distillate cooling.
In a three-necked flask, 99.4% by weight of benzyl acetate,
63.88 g of a crude benzyl acetate solution composed of 0.6% by weight of cresyl acetate (ortho: meta: para ratio = 17: 53: 30) (cresyl acetate; 0.382 g,
2.56 mmol) and sodium methoxide 0.2
76 g (5.11 mmol, 2.0 of the total number of moles of impurities)
(Double equivalent) and heated to 60 ° C. After aging at 60 ° C. for 30 minutes, distillation was performed under reduced pressure of 1.4 mmHg. 6
61.97 g of a distillate from 1 ° C. to 62 ° C. were obtained, and the residue was 1.
44 g (weight ratio of fraction to residue = 97.7: 2.
3). When the distillate was analyzed by gas chromatography, cresyl acetate 5 ppm and cresol 10
ppm. Gas chromatography conditions; Column: FFAP-CB 25m × 0.32m
mID carrier: N2 0.95 ml / min Injection temperature: 280 ° C. Detector temperature (FID): 280 ° C. Column temperature: 65 ° C./3 minutes → temperature rise 15 ° C./minute→2
30 ° C./15 minutes.

Examples 2 to 4 The same operation as in Example 1 was repeated, except that the equivalents of sodium methoxide and the distillation conditions were the values shown in Table 2. Table 2 shows the results.

[0019]

[Table 2]

Examples 5 and 6 The same operations as in Example 1 were repeated except for the alkali metal compounds and their equivalents shown in Table 3. Table 3 shows these results.
Shown in

[0021]

[Table 3]

Comparative Example 1 Using 10% by weight aqueous sodium carbonate (5.0 equivalents),
52.85 g of crude benzyl acetate liquid used in Example 1
Was mixed in a separating funnel, washed, separated, and the organic phase was distilled under reduced pressure of 1.4 mmHg (boiling point 61).
-62 ° C, weight ratio of distillate and residue = 95.5: 4.5).
When the distillate was analyzed by gas chromatography, it contained 0.3% by weight of cresylacetate and 0.2% by weight of cresol, and was hardly removed.

Claims (3)

[Claims] 1. A method for purifying benzyl acetate, comprising distilling crude benzyl acetate in the presence of an alkali metal compound. 2. The method for purifying benzyl acetate according to claim 1, wherein the crude benzyl acetate is obtained by an oxidative acetoxylation reaction of toluene. 3. The method for purifying benzyl acetate according to claim 1, wherein the alkali metal compound is sodium methoxide.