A kind of preparation method of methyl o-benzoylbenzoate

Abstract

The invention relates to a method for preparing methyl o-benzoylbenzoate. The method comprises the following steps: adding water to control the temperature for hydrolysis, wherein the obtained o-benzoylbenzoic acid is dissolved in a benzene phase, a first catalyst is dissolved in an aqueous phase, two-phase separation is achieved by liquid separation, and the benzene phase in which the o-benzoylbenzoic acid is dissolved is further concentrated to control the molar ratio of the o-benzoylbenzoic acid to be 1:2-4, and the benzene phase can be directly used as a raw material for an esterification reaction. The method does not require separation of an intermediate o-benzoylbenzoic acid solid, has lower energy consumption in the process, less material loss, and is conducive to obtaining higher product purity and yield.

Description

Technical Field

[0001] The invention belongs to the field of photoinitiators and relates to a method for preparing methyl o-benzoylbenzoate. Background Art

[0002] Photoinitiators are a class of compounds that can absorb energy of a certain wavelength in the ultraviolet or visible light region to generate free radicals, cations, etc., thereby initiating monomer polymerization, cross-linking and curing.

[0003] Methyl o-benzoylbenzoate (photoinitiator OMBB) is a commonly used low odor free radical type II photoinitiator that can be used in acrylate-based UV-curable coating and ink formulations for substrates such as paper, wood, metal and plastic; it has UV absorption at short wavelengths and is therefore ideal for promoting rapid surface cure.

[0004] In the traditional preparation process, after the o-benzoylbenzoic acid is obtained by hydrolysis reaction, the product o-benzoylbenzoic acid is generally precipitated, and the solid o-benzoylbenzoic acid is obtained by centrifugation and drying, and then used as a raw material for the esterification reaction; the above process not only has high energy consumption and large material loss, but also is complicated to operate and has high process cost.

[0005] Therefore, it is still of great significance to develop a method for preparing methyl o-benzoylbenzoate with low energy consumption, simple operation and low material loss. Summary of the invention

[0006] The object of the present invention is to provide a preparation method of methyl o-benzoylbenzoate, wherein the method comprises hydrolysis by adding water and controlling the temperature, wherein the obtained o-benzoylbenzoic acid is dissolved in a benzene phase, a first catalyst is dissolved in an aqueous phase, two-phase separation is achieved by liquid separation, and the benzene phase in which the o-benzoylbenzoic acid is dissolved is further concentrated to control the molar ratio of o-benzoylbenzoic acid to be 1:2-4, and the benzene phase can be directly used as a raw material for an esterification reaction; the method of the present invention does not require the separation of an intermediate o-benzoylbenzoic acid solid, has lower energy consumption in the process, less material loss, and is conducive to obtaining higher product purity and yield.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing methyl o-benzoylbenzoate, the preparation method comprising the following steps:

[0009] (1) mixing phthalic anhydride, benzene and a first catalyst to perform a Friedel acylation reaction;

[0010] (2) After the Friedel-Strauss acylation reaction in step (1) is completed, water is added to carry out a hydrolysis reaction, and then the liquids are separated to obtain an organic phase;

[0011] (3) heating and concentrating the organic phase in step (2) to obtain a mixed solution having a molar ratio of o-benzoylbenzoic acid to benzene of 1:2 to 4 (exemplary including 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8 or 1:3.9, etc.);

[0012] (4) mixing the mixed solution in step (3), the second catalyst and methanol, and performing an esterification reaction, refluxing and separating water during the reaction to obtain methyl o-benzoylbenzoate.

[0013] The reaction equation of the above preparation method of the present invention is as follows:

[0014]

[0015] Phthalic anhydride and benzene are used as raw materials to obtain o-benzoylbenzoic acid (BB acid) through Friedel-Strauss acylation reaction and hydrolysis reaction. In the traditional process, after the hydrolysis reaction, debenzening is usually performed and cold water is added to precipitate o-benzoylbenzoic acid, and then centrifugation and drying are performed to obtain o-benzoylbenzoic acid solid, which is used as a raw material for esterification reaction. During the above operation, the centrifugation and drying process consumes a lot of energy, and there is material loss during the collection process of o-benzoylbenzoic acid solid, thereby affecting the product yield; and o-benzoylbenzoic acid will adsorb part of the solid during the precipitation process. impurities, thereby affecting the purity of the product; based on solving the above problems, in the preparation method of the present invention, during the hydrolysis reaction after the Friedel acylation reaction is completed, water at room temperature is added, and the temperature is controlled for hydrolysis, so that the dissociated first catalyst is dissolved in the water phase, and the o-benzoylbenzoic acid is dissolved in the benzene phase, and the two are separated by liquid separation. After the organic phase is heated and concentrated, the molar ratio of o-benzoylbenzoic acid to benzene in the mixed solution is controlled to be 1:2-4, which can be directly used as a raw material for esterification reaction, and a higher product yield and purity can be obtained.

[0016] The present invention has found through research that a mixed solution of o-benzoylbenzoic acid and benzene as a raw material for an esterification reaction, wherein the content of benzene is controlled within the above-mentioned ratio, is directly used as a raw material for an esterification reaction, which not only has high production efficiency, but also is conducive to obtaining a higher product yield and purity. When the benzene content is too low, it may lead to an increase in impurities, and when the benzene content is too high, it will affect the production efficiency.

[0017] In the preparation method of the present invention, after the Friedel-Strauss acylation reaction is completed, normal temperature water is directly added, the hydrolysis process will heat up, and the temperature can be controlled within a specific range (60°C to 70°C) by adding cooling water to the reactor. On the one hand, the hydrolysis reaction is completed, and on the other hand, the hydrolysis heat is used to realize partial benzene desolvation, thereby reducing the energy consumption of subsequent debenzenization. After the hydrolysis is completed, the lower aqueous phase is separated and removed, and further heated and concentrated to remove part of the benzene in the organic phase. When the ratio of o-benzoylbenzoic acid to benzene reaches a specific ratio, a second catalyst and methanol are added thereto, and the esterification reaction process can be realized by heating, refluxing and water separation operation. The above-mentioned operation process avoids the centrifugation and drying process of o-benzoylbenzoic acid in the traditional process, has lower energy consumption, simpler operation process, less material loss in the process, and less impurities introduced, which is conducive to increasing the yield and purity of the target product.

[0018] Preferably, in the mixed solution of step (3), the molar ratio of o-benzoylbenzoic acid to benzene is 1:2.6-3.2, for example, 1:2.7, 1:2.8, 1:2.9, 1:3 or 1:3.1, etc.

[0019] Preferably, in step (1), the first catalyst is selected from anhydrous aluminum chloride.

[0020] Preferably, the method of mixing phthalic anhydride, benzene and the first catalyst in step (1) comprises mixing benzene and the first catalyst and then adding phthalic anhydride.

[0021] Preferably, in step (1), the molar ratio of phthalic anhydride, benzene and the first catalyst is 1:17-21:2-2.5, for example, 1:18:2.1, 1:19:2.2 or 1:20:2.4.

[0022] In the present invention, the Friedel acylation reaction adopts the above material ratio, which is conducive to obtaining a higher intermediate yield, and during the hydrolysis process, it is easy to control the intermediate o-benzoylbenzoic acid to dissolve in the benzene phase.

[0023] Preferably, the temperature of the Friedel-Crafts acylation reaction in step (1) is 60°C to 80°C, such as 65°C, 70°C or 75°C.

[0024] In the present invention, the temperature of the Friedel-Crafts reaction process is controlled within the above range, which is conducive to complete reaction; when the temperature is too low, the reaction is incomplete and the yield is too low; when the temperature is too high, exceeding the boiling point of the solvent is not conducive to the reaction.

[0025] Preferably, the ratio of the molar amount of the first catalyst in step (1) to the volume of water added in step (2) is 1.5 to 2.4 mol / L, for example, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L or 2.3 mol / L, etc.

[0026] Preferably, the temperature of the hydrolysis reaction in step (2) is 60°C to 70°C, such as 65°C.

[0027] In the preparation method of the present invention, the reaction temperature of the hydrolysis process is controlled within the above-mentioned temperature range, which can prevent the intermediate o-benzoylbenzoic acid from precipitating in solid form, so that o-benzoylbenzoic acid is dissolved in the benzene phase, and the first catalyst is dissolved in the water phase, which facilitates the separation of the two; secondly, utilizing the heat of hydrolysis and controlling the above-mentioned temperature range can achieve the effect of partial debenzenization, thereby reducing the energy consumption of subsequent debenzenization and saving costs.

[0028] Preferably, the temperature for heating and concentrating in step (3) is 80°C to 90°C, such as 85°C.

[0029] In the present invention, the heating concentration is carried out at the above temperature, which can achieve the desolventizing effect.

[0030] Preferably, the method of mixing the mixed liquid, the second catalyst and methanol in step (4) comprises adding the second catalyst to the mixed liquid, and then dripping methanol underwater.

[0031] Here, the submerged addition of methanol refers to the process in which the liquid outlet of the liquid adding tube is located below the liquid surface in the reaction device during the addition of methanol. The present invention adopts the above-mentioned submerged addition method, which can significantly improve the reaction effect and reduce the amount of methanol used. On the contrary, when the top-liquid addition method is adopted, due to the high temperature of the reaction process, part of the added methanol is vaporized, which not only affects the reaction effect, but also significantly increases the amount of methanol used.

[0032] Preferably, in step (4), the second catalyst is selected from sulfuric acid having a concentration of 95% to 98% (exemplary examples include 95.5%, 96%, 96.5%, 97% or 97.5%, etc.).

[0033] Preferably, in step (4), the molar ratio of methanol, the second catalyst and o-benzoylbenzoic acid is 1.3-2:0.06-0.1:1, for example, 1.35:0.07:1, 1.4:0.08:1, 1.45:0.09:1 or 1.8:0.08:1, etc., preferably 1.3-1.5:0.06-0.1:1.

[0034] In the present invention, methanol is added dropwise under liquid conditions, which can effectively reduce the amount of methanol used and improve the reaction efficiency.

[0035] Preferably, the temperature of the esterification reaction in step (4) is 80°C to 90°C, for example, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C or 89°C.

[0036] Preferably, after the esterification reaction in step (4) is completed, post-treatment is also included, and the post-treatment includes alkali washing, desolventizing, and purification to obtain methyl o-benzoylbenzoate.

[0037] Preferably, the purification method comprises distillation and crystallization.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) In the method of the present invention, after the Friedel-Strauss acylation reaction, water is added to control the temperature for hydrolysis to obtain a benzene phase in which the intermediate o-benzoylbenzoic acid is dissolved, and the benzene phase is heated and concentrated to obtain a mixed solution of o-benzoylbenzoic acid and benzene in a specific ratio, which can be directly used as a raw material for the esterification reaction and can obtain a higher product yield and purity;

[0040] (2) In the preparation process of the method of the present invention, there is no need to separate the solid of o-benzoylbenzoic acid, the process has lower energy consumption, simple operation and small material loss. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0042] Example 1

[0043] This embodiment provides a method for preparing methyl o-benzoylbenzoate, which specifically comprises the following steps:

[0044] (1) Benzene and AlCl3 were added to a reaction kettle. Under stirring, solid phthalic anhydride was added in batches at room temperature. As the addition process proceeded, the temperature gradually increased and was controlled at 70°C by cooling. After the addition was completed, the reaction was continued for 0.5h.

[0045] Wherein, the molar ratio of phthalic anhydride, benzene and AlCl3 is 1:19:2.2;

[0046] (2) After the Friedel-Strauss acylation reaction in step (1) is completed, adding room temperature water (25° C.) and controlling the temperature at 65° C. to carry out a hydrolysis reaction, standing and separating the liquids to obtain an organic phase;

[0047] Wherein, in step (1), the ratio of the molar amount of AlCl3 to the volume of the added water is 1.88 mol / L;

[0048] (3) heating and concentrating the organic phase in step (2) at 85° C. to obtain a mixed solution having a molar ratio of o-benzoylbenzoic acid to benzene of 1:2.9;

[0049] Taking the amount of phthalic anhydride added as the calculation basis, the yield of o-benzoylbenzoic acid was 96%;

[0050] (4) adding 97% sulfuric acid to the mixed solution of step (3), heating to 85° C., and dripping methanol under the liquid to carry out esterification reaction for about 8 hours, accompanied by reflux and water separation during the reaction; wherein the molar ratio of o-benzoylbenzoic acid, sulfuric acid and methanol is 1:0.08:1.4, followed by alkali washing, desolventizing, distillation and crystallization to obtain methyl o-benzoylbenzoate.

[0051] The purity of methyl o-benzoylbenzoate prepared in this example is 99.5%. Taking the amount of phthalic anhydride added as the calculation basis, the yield of methyl o-benzoylbenzoate is 86%.

[0052] Example 2

[0053] The only difference between this embodiment and embodiment 1 is that after heating and concentration in step (3), a mixed solution with a molar ratio of o-benzoylbenzoic acid to benzene of 1:2.5 is obtained, and it is used as a raw material for the esterification reaction in step (4). Other parameters and conditions are exactly the same as those in embodiment 1.

[0054] The purity of methyl o-benzoylbenzoate prepared in this example is 99.1%. Taking the amount of phthalic anhydride added as the calculation basis, the yield of methyl o-benzoylbenzoate is 85%.

[0055] Example 3

[0056] The only difference between this embodiment and embodiment 1 is that after heating and concentration in step (3), a mixed solution with a molar ratio of o-benzoylbenzoic acid to benzene of 1:3.5 is obtained, and it is used as a raw material for the esterification reaction in step (4). Other parameters and conditions are exactly the same as those in embodiment 1.

[0057] The purity of methyl o-benzoylbenzoate prepared in this example is 99.2%. Taking the amount of phthalic anhydride added as the calculation basis, the yield of methyl o-benzoylbenzoate is 85.5%.

[0058] Example 4

[0059] The only difference between this embodiment and embodiment 1 is that in step (4), the method of dropwise addition is adopted, and the molar ratio of o-benzoylbenzoic acid, sulfuric acid and methanol is replaced with 1:0.08:1.9, and the other parameters and conditions are exactly the same as those in embodiment 1.

[0060] The purity of methyl o-benzoylbenzoate prepared in this example is 99.0%. Taking the amount of phthalic anhydride added as the calculation basis, the yield of methyl o-benzoylbenzoate is 84%.

[0061] In this embodiment, methanol is added dropwise from the liquid surface. Since the temperature during the reaction is relatively high, the utilization rate of methanol is reduced and the reaction efficiency is reduced.

[0062] Comparative Example 1

[0063] The difference between this comparative example and Example 1 is that after heating and concentration in step (3), a mixed solution with a molar ratio of o-benzoylbenzoic acid to benzene of 1:1.5 is obtained, and it is used as a raw material for the esterification reaction in step (4). Other parameters and conditions are exactly the same as those in Example 1.

[0064] In this comparative example, the benzene content in the mixed solution used as the raw material for the esterification reaction is too low, and impurities increase in the esterification reaction, resulting in yellow color of the product.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that in step (3), the reaction mixture is heated and concentrated until benzene is completely removed, and then cold water is added to precipitate solids, which are filtered and dried to obtain o-benzoylbenzoic acid; then the mixture is mixed with benzene in a molar ratio of 1:2.9, and sulfuric acid with a concentration of 97% is added, the temperature is raised to 85° C., and methanol is added dropwise to carry out esterification reaction for about 8 hours, and the reaction is accompanied by reflux and water separation; wherein the molar ratio of o-benzoylbenzoic acid, sulfuric acid and methanol is 1:0.08:1.4, and then alkali washing, desolventization, distillation and crystallization are carried out to obtain methyl o-benzoylbenzoate;

[0067] The purity of the methyl o-benzoylbenzoate prepared in this comparative example is 99.0%. Taking the added amount of phthalic anhydride as the calculation basis, the yield of methyl o-benzoylbenzoate is only 82%.

[0068] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing methyl o-benzoylbenzoate, characterized in that: The preparation method comprises the following steps: (1) mixing phthalic anhydride, benzene and a first catalyst to perform a Friedel acylation reaction; (2) After the Friedel-Strauss acylation reaction in step (1) is completed, water is added to carry out a temperature-controlled hydrolysis reaction at a temperature of 60° C. to 70° C., and then the liquids are separated to obtain an organic phase; (3) heating and concentrating the organic phase in step (2) to obtain a mixed solution having a molar ratio of o-benzoylbenzoic acid to benzene of 1:2 to 4; (4) mixing the mixed solution in step (3), the second catalyst and methanol, and performing an esterification reaction, refluxing and separating water during the reaction to obtain methyl o-benzoylbenzoate.

2. The preparation method according to claim 1, characterized in that: In step (1), the first catalyst is selected from anhydrous aluminum chloride.

3. The preparation method according to claim 1, characterized in that: The method of mixing phthalic anhydride, benzene and the first catalyst in step (1) comprises mixing benzene and the first catalyst and then adding phthalic anhydride.

4. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of phthalic anhydride, benzene and the first catalyst is 1:17-21:2-2.

5.

5. The preparation method according to claim 1, characterized in that: The temperature of the Friedel-Strauss acylation reaction in step (1) is 60°C to 80°C.

6. The preparation method according to claim 1 or 2, characterized in that: The ratio of the molar amount of the first catalyst in step (1) to the volume of water added in step (2) is 1.5 to 2.4 mol / L.

7. The preparation method according to claim 1, characterized in that: The temperature for heating and concentrating in step (3) is 80°C to 90°C.

8. The preparation method according to claim 1, characterized in that: The method of mixing the mixed liquid, the second catalyst and methanol in step (4) comprises adding the second catalyst to the mixed liquid and then dripping methanol under the liquid.

9. The preparation method according to claim 1, characterized in that: In step (4), the second catalyst is selected from sulfuric acid with a concentration of 95% to 98%.

10. The preparation method according to claim 1, characterized in that: In step (4), the molar ratio of methanol, the second catalyst and o-benzoylbenzoic acid is 1.3-2:0.06-0.1:

1.

11. The preparation method according to claim 10, characterized in that: In step (4), the molar ratio of methanol, the second catalyst and o-benzoylbenzoic acid is 1.3-1.5:0.06-0.1:

1.

12. The preparation method according to claim 1, characterized in that: The temperature of the esterification reaction in step (4) is 80°C to 90°C.

13. The preparation method according to claim 1, characterized in that: After the esterification reaction in step (4) is completed, post-treatment is also included, and the post-treatment includes alkali washing, desolventizing, and purification to obtain methyl o-benzoylbenzoate.

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