阅读说明：本技术 一种苯甲酸苄酯的纯化方法 (Method for purifying benzyl benzoate ) 是由 曹金 田佳 黄虎 冉文华 李盛 张阳洋 刘淦 张吉 彭丽芳 初玎鲒 吴琼 李文 于 2020-06-24 设计创作，主要内容包括：本发明公开了一种苯甲酸苄酯的纯化方法。该纯化方法包括将苯甲酸苄酯粗品溶液与苯甲酸苄酯晶种混合之后,再固液分离,得到的固体即为苯甲酸苄酯；苯甲酸苄酯粗品溶液由苯甲酸苄酯粗品和溶剂组成；所述溶剂为异丙醇和水；所述苯甲酸苄酯粗品与所述溶剂的质量比为2：(1.4～4.0)；所述异丙醇与所述水的质量比为2：(0.5～1.2)；所述混合之前所述苯甲酸苄酯粗品溶液的温度为5～15℃；所述混合的温度为5～15℃。本发明的苯甲酸苄酯的纯化方法收率高,同时得到的产物纯度高、色号值低、杂质含量少,也便于工业化生产。(The invention discloses a method for purifying benzyl benzoate. Mixing a crude benzyl benzoate solution with a benzyl benzoate seed crystal, and carrying out solid-liquid separation to obtain a solid, namely benzyl benzoate; the benzyl benzoate crude product solution consists of a benzyl benzoate crude product and a solvent; the solvent is isopropanol and water; the mass ratio of the crude benzyl benzoate to the solvent is 2: (1.4-4.0); the mass ratio of the isopropanol to the water is 2: (0.5 to 1.2); the temperature of the crude benzyl benzoate solution before mixing is 5-15 ℃; the mixing temperature is 5-15 ℃. The method for purifying the benzyl benzoate has high yield, and simultaneously, the obtained product has high purity, low color number value and low impurity content, and is convenient for industrial production.)

1. A method for purifying benzyl benzoate is characterized in that the method comprises the steps of mixing a crude solution of benzyl benzoate with a seed crystal of benzyl benzoate, and then carrying out solid-liquid separation to obtain a solid, namely benzyl benzoate; the crude benzyl benzoate solution consists of a crude benzyl benzoate and a solvent;

the solvent is isopropanol and water; the mass ratio of the crude benzyl benzoate to the solvent is 2: (1.4-4.0); the mass ratio of the isopropanol to the water is 2: (0.5 to 1.2);

the temperature of the crude benzyl benzoate solution before mixing is 5-15 ℃;

the mixing temperature is 5-15 ℃.

2. The method of purifying benzyl benzoate according to claim 1, wherein the crude benzyl benzoate has a purity of 96 to 99.6%, such as 96.6%, 99.18%, 99.19%, 99.2%, 99.3%, 99.35%, 99.36%, 99.42%, 99.58%, 99.6% or 99.64%, preferably 99 to 99.6%;

and/or the crude benzyl benzoate has a color number of 150Hazen or less, such as 18Hazen, 20Hazen, 65Hazen, 70Hazen, 75Hazen or 150Hazen, preferably 18-75 Hazen;

and/or, the content of benzyl chloride in the crude benzyl benzoate is less than 2.83%, preferably 0.2-0.4%, for example, 0.25%, 0.27%, 0.3%, 0.32%, 0.33%, 0.35% or 0.37%, and the percentage is the mass percentage of benzyl chloride in the total mass of the crude benzyl benzoate.

3. The method of purifying benzyl benzoate according to claim 2, wherein the crude benzyl benzoate is prepared by a process comprising the steps of: in the presence of quaternary ammonium salt, sodium benzoate and benzyl chloride are subjected to nucleophilic substitution reaction.

4. The method of purifying benzyl benzoate according to claim 3, wherein in the nucleophilic substitution reaction, the quaternary ammonium salt has the structure of a compound according to formula A:

in the formula, the R₁Independently is C₁～C₆Alkyl groups of (a); the R is₂Is C₁～C₁₆Alkyl or C substituted by phenyl₁～C₆Alkyl groups of (a); the X is F, Cl, Br or I;

and/or, in the nucleophilic substitution reaction, the molar ratio of the quaternary ammonium salt to the benzyl chloride is (0.015-0.1): 1, such as 0.016: 1. 0.026:1, 0.038: 1. 0.0392:1, 0.0625: 1. 0.06722:1, 0.0811:1 or 0.1: 1;

and/or, in the nucleophilic substitution reaction, the molar amount of the sodium benzoate is more than that of the benzyl chloride; the molar ratio of the sodium benzoate to the benzyl chloride is preferably (1.01-1.7): 1, e.g. 1.196:1, 1.277: 1. 1.289:1, 1.328:1, 1.4:1, 1.439: 1. or 1.68: 1;

and/or, the nucleophilic substitution reaction is carried out in a reaction solvent;

wherein, the reaction solvent is preferably an alkane solvent and/or an ester solvent, and more preferably an alkane solvent.

5. The method of purifying benzyl benzoate of claim 4 wherein R in said compound of formula A₁Is one or more of methyl, ethyl, n-propyl and n-butyl;

and/or, R in the compound shown in the formula A₂Is one or more of ethyl, n-butyl, benzyl and n-hexadecyl;

and/or the temperature of the nucleophilic substitution reaction is 60-140 ℃, preferably 60-100 ℃;

and/or the time of the nucleophilic substitution reaction is 2-8 h;

when the nucleophilic substitution reaction is carried out in the reaction solvent, the mass ratio of the benzyl chloride to the reaction solvent in the nucleophilic substitution reaction is 1: (0.5 to 2.13);

in the nucleophilic substitution reaction, when the reaction solvent contains an alkane solvent, the alkane solvent is an alkane solvent with 4-8 carbon atoms; preferably one or more of n-hexane, n-octane, isooctane and n-heptane;

in the nucleophilic substitution reaction, when the reaction solvent contains an ester solvent, the ester solvent is an ester solvent with 4-8 carbon atoms; preferably ethyl acetate and/or isoamyl acetate.

6. The method of purifying benzyl benzoate according to claim 5, wherein the quaternary ammonium salt is one or more of triethylbenzylammonium chloride, tetrabutylammonium iodide and 1-hexadecyltrimethylammonium bromide, such as triethylbenzylammonium chloride, tetrabutylammonium iodide or 1-hexadecyltrimethylammonium bromide;

when the quaternary ammonium salt comprises triethylbenzylammonium chloride, the triethylbenzylammonium chloride is preferably generated in situ from triethylamine and an equivalent amount of benzyl chloride.

7. The process for the purification of benzyl benzoate according to claim 6, characterized in that the nucleophilic substitution reaction is followed by a preliminary work-up operation to remove unreacted sodium benzoate, salts formed during the reaction;

wherein, when said nucleophilic substitution reaction is carried out in said reaction solvent, said preliminary post-treatment preferably further comprises an operation of removing said reaction solvent;

wherein, the preliminary post-treatment preferably further comprises a decoloring treatment; the decoloring treatment preferably includes the steps of: mixing the crude benzyl benzoate and active metal and inorganic acid for reaction.

8. The method of purifying benzyl benzoate according to claim 7, wherein the species of active metal comprises one or more of magnesium, zinc, iron, and aluminum;

and/or, the inorganic acid comprises one or more of hydrochloric acid, sulfuric acid and acetic acid;

and/or in the decoloring treatment, the molar ratio of the active metal to the crude benzyl benzoate is 1: 0.005 to 0.07, preferably 1: 0.06 to 0.07;

and/or in the decoloring treatment, the molar ratio of the inorganic acid to the crude benzyl benzoate is 1: 0.01 to 0.2, preferably 1: 0.01 to 0.04;

and/or in the decoloring treatment, the temperature of the mixing reaction is 50-90 ℃;

and/or in the decoloring treatment, the mixing reaction time is 1-3 h;

and/or, the operations of filtering, first extraction, reduced pressure distillation and second extraction are generally carried out after the decoloring treatment and before the crude benzyl benzoate solution is prepared.

9. The method for purifying benzyl benzoate according to claim 8, wherein the mass ratio of the crude benzyl benzoate to the solvent in the crude benzyl benzoate solution is 2: (2.5-4), such as 2:4, 2:3, or 2: 2.8;

and/or the mass ratio of the isopropanol to the water is 2: (0.8 to 1);

and/or the mass ratio of the crude benzyl benzoate to the seed crystals of benzyl benzoate is 1: (0.0005 to 0.005), preferably 1: (0.001 to 0.002), for example, 1: 0.0011, 1: 0.0016 or 1: 0.0019;

and/or the purity of the benzyl benzoate crystal seed is more than or equal to 99 percent;

and/or, the mixing further comprises the operation of stirring;

and/or the mixing time is 30-60 min;

and/or the temperature of the crude benzyl benzoate solution before mixing is 8-10 ℃;

and/or the mixing temperature is 8-10 ℃;

and/or, the mixing also comprises heat preservation crystallization.

10. The method of purifying benzyl benzoate according to claim 9, wherein said benzyl benzoate seed crystals are prepared by a process comprising the steps of: placing benzyl benzoate with the purity of more than or equal to 99% at the temperature of between 20 ℃ below zero and 5 ℃ below zero until the benzyl benzoate is crystallized into solid, thus obtaining the benzyl benzoate seed crystal;

and/or, benzyl benzoate obtained by the process for purifying benzyl benzoate according to claim 1 is used as said benzyl benzoate seed crystal;

and/or the rotating speed of the stirring is 30 r/min-120 r/min;

and/or the temperature of the heat-preservation crystallization is-5-3 ℃;

and/or the time for heat preservation and crystallization is 30-60 min.

Technical Field

The invention relates to a method for purifying benzyl benzoate.

Background

Benzyl benzoate, also known as benzyl benzoin, is a colorless or pale yellow oily liquid with a light almond-like aroma. Benzyl benzoate is often used as a setting agent and a flavoring agent of floral essence, and is also widely applied to edible essence. The product is also widely used as a plasticizer or solvent. In the medical field, benzyl benzoate is often used in combination with natural oils as a solvent or solubilizer in injection products.

Shen Guo, the research on the toluene air oxidation process reported in Heiping and the comprehensive utilization of byproducts (database of Chinese Master thesis, 2009.5), disclose a process for decolorizing and recrystallizing a crude benzyl benzoate product by the decolorizing and recrystallizing process. In the literature, it is described that for a small-scale experiment, a crude benzyl benzoate product with the purity of 97.8-99.3% is purified by recrystallization, the yield of recrystallization is only 68.5-75.6%, the purity is only 99.75-99.87, and the color number value is 15-30 Hazen. In the industrial scale-up test, the crystal yield is only 65.49-67.93%. The document also discloses an operation of purifying benzyl benzoate by adopting a rectification process, but instruments such as a rectification device, a condenser and the like are required, the heating cost is higher, the industrial production is not facilitated, the purity of the obtained product is also lower, and the obtained product still contains more impurities. The above technical problems remain to be solved.

Disclosure of Invention

The invention solves the technical problem of overcoming the defects of low purity, high color number value and high impurity content of benzyl benzoate in the prior art, and provides a method for purifying benzyl benzoate. The method for purifying the benzyl benzoate has high yield, and simultaneously, the obtained product has high purity, low color number value and low impurity content, and is convenient for industrial production.

The invention solves the technical problems through the following technical scheme.

The invention provides a method for purifying benzyl benzoate, which comprises the steps of mixing a crude solution of benzyl benzoate with a seed crystal of benzyl benzoate, and then carrying out solid-liquid separation to obtain a solid, namely benzyl benzoate;

the crude benzyl benzoate solution consists of a crude benzyl benzoate and a solvent;

the solvent is isopropanol and water; the mass ratio of the crude benzyl benzoate to the solvent is 2: (1.4-4.0); the mass ratio of the isopropanol to the water is 2: (0.5 to 1.2);

the temperature of the crude benzyl benzoate solution before mixing is 5-15 ℃;

the mixing temperature is 5-15 ℃.

In the present invention, the skilled person knows the purification method of benzyl benzoate, and the crude solution of benzyl benzoate is generally a supersaturated solution.

In the present invention, the crude benzyl benzoate can be a crude benzyl benzoate conventional in the art.

Wherein the purity of the benzyl benzoate crude product can be 95-99.8%; preferably 96-99.6%, such as 96.6%, 99.18%, 99.19%, 99.2%, 99.3%, 99.35%, 99.36%, 99.42%, 99.58%, 99.6% or 99.64%, more preferably 99-99.6%. The purity is the content of benzyl benzoate measured by gas chromatography.

Wherein, the color number of the crude benzoic acid can be below 150Hazen, such as 18Hazen, 20Hazen, 65Hazen, 70Hazen, 75Hazen or 150Hazen, preferably 18-75 Hazen. In the invention, the color number is determined by adopting a platinum-cobalt colorimetric method, and is detected by using an automatic colorimeter according to the standard of color determination method (Hazen unit-platinum-cobalt color number) of liquid chemical products.

The content of benzyl chloride in the crude benzyl benzoate is preferably less than 2.83%, for example, 0.2 to 0.4%, specifically, for example, 0.25%, 0.27%, 0.3%, 0.32%, 0.33%, 0.35%, or 0.37%, where the percentage is the mass percentage of benzyl chloride in the total mass of the crude benzyl benzoate.

In the present invention, the crude benzyl benzoate can be obtained by the method of benzyl benzoate conventional in the art. The preparation method of the crude benzyl benzoate can comprise the following steps: in the presence of quaternary ammonium salt, sodium benzoate and benzyl chloride are subjected to nucleophilic substitution reaction.

The nucleophilic substitution reaction can be carried out in a conventional order in the art, for example, by sequentially adding the benzyl chloride, the quaternary ammonium salt, and the sodium benzoate to a reactor.

In the nucleophilic substitution reaction, the structure of the quaternary ammonium salt can be a compound shown as a formula A:

in the formula, the R₁Can independently be C₁～C₆Alkyl of (a), for example, one or more of methyl, ethyl, n-propyl and n-butyl; the R is₂Can be C₁～C₁₆Alkyl or C substituted by phenyl₁～C₆The alkyl group of (a) is,for example, one or more of ethyl, n-butyl, benzyl, and n-hexadecyl; and X is Cl, Br or I.

In the nucleophilic substitution reaction, the quaternary ammonium salt is preferably one or more of triethylbenzylammonium chloride, tetrabutylammonium iodide and 1-hexadecyltrimethylammonium bromide, such as triethylbenzylammonium chloride, tetrabutylammonium iodide or 1-hexadecyltrimethylammonium bromide. When the quaternary ammonium salt comprises triethylbenzylammonium chloride, it may be generated in situ from triethylamine with an equivalent amount of benzyl chloride.

In the nucleophilic substitution reaction, the amount of the quaternary ammonium salt may be an amount of a catalyst conventional in the art. The molar ratio of the quaternary ammonium salt to the benzyl chloride may be (0.015-0.1): 1, for example 0.016: 1. 0.026:1, 0.038: 1. 0.0392:1, 0.0625: 1. 0.06722:1, 0.0811:1 or 0.1: 1.

in the nucleophilic substitution reaction, the molar ratio of the sodium benzoate to the benzyl chloride may be a molar ratio conventional in the art, typically the molar amount of the sodium benzoate is greater than the molar amount of the benzyl chloride. The ratio of the molar amount of the sodium benzoate to the molar amount of the benzyl chloride is preferably (1.01-1.7): 1, e.g. 1.196:1, 1.277: 1. 1.289:1, 1.328:1, 1.4:1, 1.439: 1. or 1.68: 1.

in the nucleophilic substitution reaction, the temperature of the nucleophilic substitution reaction may be 60 to 140 ℃, preferably 60 to 100 ℃, for example, 70 ℃, 80 ℃, 90 ℃ or 100 ℃.

In the nucleophilic substitution reaction, the time for the nucleophilic substitution reaction may be a reaction time conventional in the art, and generally may be after the completion of the benzyl chloride reaction. Generally, the time is 2-8 h, such as 2h, 3h, 5h or 6 h.

The nucleophilic substitution reaction is preferably carried out in a reaction solvent. The reaction solvent may be a solvent conventionally used in the art for carrying out the nucleophilic substitution reaction. The reaction solvent is preferably an alkane solvent and/or an ester solvent, more preferably an alkane solvent.

When the nucleophilic substitution reaction is carried out in the reaction solvent, the nucleophilic substitution reaction may be carried out by, for example, sequentially adding the benzyl chloride, the quaternary ammonium salt, the reaction solvent, and the sodium benzoate to a reactor.

When the nucleophilic substitution reaction is performed in the reaction solvent, the mass ratio of the benzyl chloride to the reaction solvent in the nucleophilic substitution reaction may be 1: (0.5 to 2.13), specifically 1: 0.515, 1:0.728, 1: 0.86, 1: 1.08, 1: 1.55 or 1: 2.13.

when the reaction solvent comprises an alkane solvent, the alkane solvent may be one conventional in the art. The alkane solvent preferably contains 4-8 carbon atoms, and may be one or more of n-hexane, n-octane, isooctane and n-heptane, such as n-hexane, n-octane, isooctane or n-heptane.

When the reaction solvent includes an ester solvent, the ester solvent may be a solvent having an ester bond, which is conventional in the art. The ester solvent preferably has a carbon number of 4 to 8, and may include ethyl acetate and/or isoamyl acetate, for example.

It should be noted that the alkane solvent or the ester solvent may satisfy the following conditions:

(1) said sodium benzoate being insoluble in said reaction solvent;

(2) the reaction solvent does not react with benzyl chloride, sodium benzoate and amine;

(3) the reaction solvent is mutually soluble with benzyl chloride and benzyl benzoate;

(4) the reaction solvent is insoluble with quaternary ammonium salt and is layered with water; the insolubility means that the solubility of the sodium benzoate in the reaction solvent is less than 0.01g/100g at 20 ℃.

After the nucleophilic substitution reaction, it is generally necessary to perform a preliminary post-treatment to remove unreacted sodium benzoate and salts formed during the reaction. When the nucleophilic substitution reaction is carried out in the reaction solvent, the preliminary post-treatment may further include an operation of removing the reaction solvent.

Wherein, the primary post-treatment can be further followed by decolorization treatment.

The operation and conditions of the decoloring treatment may be a decoloring treatment which is conventional in the art. Preferably comprising the steps of: mixing the crude benzyl benzoate and active metal and inorganic acid for reaction.

The species of active metal may be one conventional in the art, including, for example, one or more of magnesium, zinc, iron, and aluminum. The person skilled in the art knows that the active metal generally takes part in the reaction in the form of a powder.

The inorganic acid species may be those conventional in the art, including, for example, one or more of hydrochloric acid, sulfuric acid, and acetic acid. The mass fraction of the inorganic acid can be the mass fraction of the inorganic acid which is conventional in the art, and is generally 5 to 20 percent, for example 10 percent.

The molar ratio of the active metal to the crude benzyl benzoate can be any molar ratio conventional in the art, typically 1: 0.005 to 0.07, preferably 1: 0.06 to 0.07.

The molar ratio of the inorganic acid to the crude benzyl benzoate may be any conventional in the art, and is typically 1: 0.01 to 0.2, preferably 1: 0.01 to 0.04.

In the decoloring treatment, the temperature of the mixing reaction may be a decoloring temperature that is conventional in the art, and is generally 50 to 90 ℃, for example, 70 ℃, 80 ℃ or 90 ℃.

In the decoloring treatment, the time of the mixing reaction may be a decoloring time which is conventional in the art, and is generally 1 to 3 hours, for example 2 hours.

The decoloring treatment and the preparation of the crude benzyl benzoate solution can also generally comprise operations of filtering, first extraction, reduced pressure distillation and second extraction in sequence. The filtration is to remove unreacted metal powder. The aqueous phase of the extraction may be a saturated sodium chloride solution. The number of the first extraction may be 1 to 3, for example 2. The temperature of the reduced pressure distillation can be 50-80 ℃, such as 60 ℃ or 70 ℃. The vacuum degree of the reduced pressure distillation can be-0.09 MPa to-0.096 MPa. The aqueous phase of the second extraction may be a saturated sodium chloride solution.

In the present invention, as known to those skilled in the art, the preparation method of the crude solution of benzyl benzoate generally comprises the following steps, and the crude benzyl benzoate is mixed with the solvent to obtain the benzyl benzoate. Wherein, the mixing is preferably also carried out by stirring. Wherein, the mixing is preferably further performed with an operation of raising the temperature, so that the crude benzyl benzoate is dissolved in the solvent.

In the solution of the crude benzyl benzoate, the mass ratio of the crude benzyl benzoate to the solvent may be 2: (2.5-4), for example 2:4, 2:3 or 2: 2.8.

In the solvent of the present invention, the mass ratio of the isopropyl alcohol to the water may be 2: (0.8 to 1).

In the "mixture of the crude solution of benzyl benzoate and the seed crystals of benzyl benzoate" of the present invention, the mass ratio of the crude solution of benzyl benzoate to the seed crystals of benzyl benzoate may be conventional in the art, and may be, for example, 1: (0.001 to 0.002), for example, 1: 0.0011, 1: 0.0016 or 1: 0.0019.

in the present invention, the benzyl benzoate seed crystal may be a seed crystal that is conventional in the art.

Wherein the purity of the benzyl benzoate crystal can be more than or equal to 99%.

The preparation method of the benzyl benzoate seed crystal comprises the following steps: and (3) placing benzyl benzoate with the purity of more than or equal to 99% at the temperature of between 20 ℃ below zero and 5 ℃ below zero until the benzyl benzoate is crystallized into solid, thus obtaining the benzyl benzoate seed crystal. The temperature of the mixture is between-20 ℃ and-5 ℃ for 2 to 5 days. As known to those skilled in the art, the benzyl benzoate seed crystals are stored at a temperature of 2-8 ℃. The benzyl benzoate with the purity of more than or equal to 99 percent is sold in the market, is usually oily liquid, and can be used as a seed crystal when being prepared into solid.

Wherein, the benzyl benzoate seed crystal also can contain benzyl benzoate prepared by the method for purifying benzyl benzoate as the benzyl benzoate seed crystal.

In the present invention, the mixing preferably further comprises an operation of stirring.

Wherein the rotating speed of the stirring can be conventional in the field, and is generally 30 r/min-120 r/min.

In the present invention, the mixing time may be a conventional crystallization time in the art, and may be, for example, 30 to 60 min.

In the invention, the temperature of the crude benzyl benzoate solution before mixing is preferably 8-10 ℃.

In the present invention, the mixing temperature is preferably 8 to 10 ℃.

In the present invention, it is preferable that the mixing further comprises crystallization under heat.

Wherein the temperature of said incubation crystallization may be conventional in the art, preferably lower than the temperature of said mixing. The temperature of the heat-preservation crystallization can be-5-3 ℃, such as 0 ℃, 1 ℃ or 2 ℃.

The time for the heat preservation crystallization can be conventional in the field, and is preferably 30-60 min.

In the present invention, the solid-liquid separation operation may be an operation conventional in the art, and generally includes suction filtration or centrifugation, preferably centrifugation.

Wherein the centrifugation process may be a centrifugation process conventional in the art.

Wherein, the time of centrifugation is preferably 4-6 min, more preferably 5 min. The mother liquor can be better removed within the range of the centrifugation time, and if the centrifugation time is too long, the obtained filter cake is easy to melt after being heated, so that the material loss is caused.

Wherein the rotation speed of the centrifugation is preferably 1500-2500 rpm, such as 2000 rpm.

In the present invention, the centrifugation may be followed by a solvent removal operation, as known to those skilled in the art. The solvent removal operation may be conventional in the art, and generally includes heating and melting the filter cake obtained after the centrifugation, and then distilling the filter cake under reduced pressure.

The heating and melting temperature is generally 60-70 ℃. The temperature of the reduced pressure distillation is generally 60-70 ℃, and the vacuum degree of the pressure distillation is generally below-0.09 Mpa.

The above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention without departing from the common general knowledge in the art.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows: in the purification method of the invention, a specific recrystallization process is adopted. The crude benzyl benzoate product has high purification efficiency, and the finally obtained benzyl benzoate has high purity and yield, low impurity content and low color number. The method can prepare the pharmaceutical grade benzyl benzoate meeting the standard of the European and American daily pharmacopoeia, wherein the content of the benzyl benzoate in the pharmacopoeia is required to be 99.0-100.5 percent by adopting a titration method, the benzyl benzoate is colorless in appearance, the content of aldehydes is less than or equal to 0.05 percent, and benzyl chloride is genotoxic impurities. According to the ICH guideline, benzyl chloride should be less than or equal to 0.05 percent generally. And the impurities are less than or equal to 0.005 percent of benzyl chloride, less than or equal to 0.001 percent of benzaldehyde, less than or equal to 0.005 percent of benzyl alcohol and less than or equal to 0.001 percent of benzoic acid.

Drawings

FIG. 1 is an infrared spectrum of benzyl benzoate prepared in example 1.

FIG. 2 is an infrared spectrum of a benzyl benzoate standard.

FIG. 3 is a GC spectrum of the final benzyl benzoate product of example 1.

FIG. 4 is a GC spectrum of the crude benzyl benzoate of example 1.

Fig. 5 is an HPLC profile of the determination of the impurity content of benzyl benzoate obtained in example 1 and an enlarged view thereof. Wherein FIG. 5a is an HPLC chart for measuring the impurity content of benzyl benzoate obtained in example 1, and FIG. 5b is an enlarged view of the HPLC chart for measuring the impurity content of benzyl benzoate obtained in example 1.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

The benzyl benzoate seed crystal used in the embodiments 1, 2, 8 and 9 of the invention is powder which is obtained by placing the seed crystal with the purity of more than or equal to 99% at the temperature of minus 20 ℃ for 2 to 5 days for solidification and then scraping.

The benzyl benzoate seed crystals of examples 3 to 7 of the present invention and comparative example 3 were filter cakes obtained by centrifuging the crystals of example 2 described below.

In the following examples and comparative examples of the present invention, the reduced pressure distillation in step 1 is only for removing the solvent, and the parameters of temperature, time and vacuum degree are set so that the influence on the purity, yield, impurity content and color number of the crude benzyl benzoate in the filtrate is within the error range and can be ignored.

In the following examples 1 to 9 and comparative example 3, the filter cake obtained in the step of purifying benzyl benzoate is transferred to a reaction kettle, and the operations of heating and melting, reduced pressure distillation and temperature reduction are performed to remove the solvent to obtain solid benzyl benzoate, and the above operations have influences on the content of benzyl benzoate, the content of impurities and the color number in the filter cake within error ranges, and the influences are negligible.