A method for improving the selectivity of the oxidation reaction of 3-methoxy-4-hydroxymandelic acid reaction solution

Abstract

The application discloses a method for improving the oxidation reaction activity of 3-methoxy-4-hydroxy mandelic acid reaction liquid. It is found for the first time that the benzene dimers and trimers exist in the oxidation reaction raw material. By controlling the content of the benzene dimers and trimers in the oxidation reaction raw material in the range of 100-500 ppm, the oxidation reaction selectivity is greater than or equal to 98%, and the yield of vanillin product can be effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of essence and flavor, and particularly relates to a method for improving the selectivity of oxidation reaction of 3-methoxy-4-hydroxymandelic acid reaction solution. BACKGROUND

[0002] 3-methoxy-4-hydroxymandelic acid is an important intermediate for preparing vanillin. Vanillin is widely used in the cosmetics, tobacco, pastry, candy and other industries, and plays a role in fragrance enhancement and fragrance fixation.

[0003] The industrial preparation process of 3-methoxy-4-hydroxymandelic acid is to use guaiacol and glyoxylic acid as raw materials, and prepare the product under the catalysis of sodium hydroxide. A series of patents such as CN102086151A, CN102086151A and CN102010310A all use sodium hydroxide as a catalyst and a large amount of deionized water to carry out condensation reaction. In these patent studies, liquid chromatography is mainly used to determine the reaction impurities, and the main reaction impurities are ortho-mandelic acid and ortho-p-mandelic acid. However, the detection of liquid chromatography cannot completely determine the composition and structure of all impurities, and the structure-activity relationship of other impurities in the reaction system cannot be determined.

[0004] Therefore, how to effectively control the content of other unknown impurities plays a crucial role in improving the selectivity of oxidation reaction of 3-methoxy-4-hydroxymandelic acid reaction solution. SUMMARY

[0005] The application adopts the combination of aqueous GPC detection and liquid chromatography detection to effectively monitor the impurities in the oxidation reaction raw materials. Not only the content of ortho-mandelic acid and ortho-p-mandelic acid can be monitored, but also the content of dimers and trimers in the raw material solution can be detected. The inventors have unexpectedly found that by controlling the content of dimers and trimers, the selectivity of oxidation reaction of 3-methoxy-4-hydroxymandelic acid is significantly improved.

[0006] To achieve the above application purposes, the technical solutions of the application are as follows:

[0007] On one hand, the application provides a method for improving the oxidation reaction activity of 3-methoxy-4-hydroxymandelic acid, which comprises the following steps:

[0008] 3-methoxy-4-hydroxymandelic acid reaction solution is used as a raw material to generate 3-methoxy-4-hydroxyphenone acid under the action of a catalyst and an oxidant.

[0009] In the reaction raw material, the content of benzene dimers and trimers is 50-1000 ppm, and preferably 100-500 ppm.

[0010] In the present application, the benzene dimers, trimers are mainly produced by polymerization of guaiacol, 3-methoxy-4-hydroxy mandelic acid, o,p-mandelic acid, o-mandelic acid. The molecular weight of the impurities produced can be determined by water-phase GPC test, so as to determine the degree of dimerization and trimerization. The possible structures of the dimers and trimers are shown as follows.

[0011]

[0012] In the present application, the 3-methoxy-4-hydroxy mandelic acid reaction solution is prepared by condensation reaction of glyoxylic acid and guaiacol as raw materials under the catalysis of sodium hydroxide, and the oxidation reaction raw material is obtained through the separation process of pH first adjustment, extraction, first adsorption, pH second adjustment, extraction, and second adsorption.

[0013] In the present application, the molar ratio of guaiacol, glyoxylic acid, and sodium hydroxide is 1:(0.4-0.6):(1.2-2); the reaction temperature is 10-40℃; and the reaction time is 8-20h. The water amount in the condensation reaction accounts for 70-90% of the total mass of the system.

[0014] The condensation reaction solution used in the present application is prepared by the above process, and the specific water amount used in the reaction is not described in detail, and the content of 3-methoxy-4-hydroxy mandelic acid in the obtained oxidation reaction raw material solution is used as the reference.

[0015] Preferably, the pH value of the reaction solution after the first pH adjustment is 6-8, and the pH value of the reaction solution after the second pH adjustment is 2-4; the chemical used for adjusting the pH is sulfuric acid.

[0016] Preferably, the extractant is selected from at least any one of methyl isobutyl ketone (MIBK), toluene, n-propyl acetate, and n-heptane; the amount of the extractant is 10%-50% of the mass of the condensation reaction solution, preferably 20%-40%.

[0017] Preferably, the adsorbent used in the first adsorption and the second adsorption is modified porous carbon material; the amount of the adsorbent used in the first adsorption is 10%-20% of the mass of the reaction solution, and the amount of the adsorbent used in the second adsorption is 5%-10% of the mass of the reaction solution.

[0018] Preferably, the modified porous carbon material is a commercial porous carbon material as a substrate, which is modified by mixed acid.

[0019] Preferably, the mixed acid is selected from at least any two of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and acetic acid; the mass ratio of the two acids in the mixed acid is 1:0.5-2; the amount of the mixed acid is 5%-20%, preferably 10%-15%, of the mass of the porous carbon material.

[0020] Preferably, the adsorbent modification treatment temperature is 20-80℃, preferably 40-60℃; the modification treatment time is 2-8h, preferably 4-6h.

[0021] The conventional treatment process for the condensation reaction liquid only adjusts the pH value of the condensation reaction liquid and then directly extracts the condensation reaction liquid. The pH adjustment range is wide, and any impurities cannot be removed. The separation process of the present application can not only separate guaiacol, but also effectively control the content of dimers and trimers. Among them, the purpose of the first pH adjustment and extraction is to extract and recover guaiacol; the purpose of the adsorption and secondary extraction is to control the content of dimer and trimer impurities.

[0022] Preferably, the content of 3-methoxy-4-hydroxymandelic acid in the oxidation reaction raw material liquid is 2%-10%, preferably 4%-8%.

[0023] Preferably, the pH value of the 3-methoxy-4-hydroxymandelic acid reaction liquid is 12-14, preferably 12.5-13.5.

[0024] Preferably, the oxidation agent is selected from a mixture of oxygen and nitrogen, and the oxygen content in the mixture is 5-100%, preferably 10-21%; the flow rate is 0.2-2.0L / min, preferably 0.5-1.0L / min.

[0025] Preferably, the catalyst is selected from at least one of copper sulfate, zinc sulfate, iron sulfate, cobalt sulfate, and manganese sulfate; the amount of the oxidation agent is 0.1%-5% of the mass of the reaction liquid, preferably 0.5%-2%.

[0026] Preferably, the reaction temperature of the oxidation reaction is 90-110℃, preferably 100-105℃; the reaction pressure is 0.3-2.0MPaG, preferably 0.5-1.0MPaG; and the reaction time is 0.5-3h, preferably 1-2h.

[0027] The present application has the following positive effects by adopting the above technical solutions:

[0028] The present application can control the content of unknown impurities dimers and trimers in the oxidation reaction raw material, and by controlling the content, the degree of excessive oxidation reaction can be effectively reduced, thereby improving the selectivity of the oxidation reaction. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The preparation flowchart of the 3-methoxy-4-hydroxymandelic acid reaction liquid DETAILED DESCRIPTION

[0030] In order to better understand the technical solutions of the present application, the following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any other known changes within the scope of the claims of the present application should also be included.

[0031] The preparation method of the present application will be described in more detail below through more specific examples, but the present application is not limited to the following examples.

[0032] The main raw material information used in the following examples and comparative examples is as follows:

[0033] Guaiacol, glyoxylic acid (50%), sodium hydroxide, potassium hydroxide, analytical pure, TCI; sulfuric acid, hydrochloric acid, nitric acid, acetic acid, phosphoric acid, MIBK, toluene, n-propyl acetate, n-heptane, analytical pure, Arlin; commercial porous carbon material SDG was purchased from Henan Shangzhi Purification Material Co., Ltd.

[0034] The liquid chromatography reaction test conditions of the present application are as follows: chromatography model: Agilent 1260; chromatography column: phenyl column; mobile phase: A: methanol, B: 0.1% phosphoric acid aqueous solution; column temperature: 40℃; flow rate: 0.5mL / min; sample size: 5μL; detection wavelength: 324nm.

[0035] The content of benzene dimers and trimers was tested by aqueous GPC; pH was tested by a pH meter.

[0036] Example 1

[0037] First, the modified porous carbon material was prepared, and the specific process was as follows: using the purchased commercial porous carbon as the substrate, using sulfuric acid and hydrochloric acid with a mass ratio of 1:0.5 as the mixed acid for modification treatment (the amount of mixed acid was 10% of the mass of porous carbon), the modification treatment temperature was 40℃, and the treatment time was 4h, to obtain the modified porous carbon material A. The condensation reaction liquid was adjusted to pH 6 using sulfuric acid, and the MIBK with a mass of 10% of the reaction liquid was used for extraction operation, and the aqueous phase reaction liquid was obtained, and then the modified porous carbon A was used for first adsorption, and the adsorbent amount was 10% of the mass of the reaction liquid, and then the pH value was adjusted to 2, and the MIBK with a mass of 10% of the reaction liquid was used for second extraction operation, and the aqueous phase was subjected to second adsorption, and the adsorbent amount was 10% of the mass of the reaction liquid, and the obtained reaction liquid was the oxidation reaction raw material. Using the raw material (3-methoxy-4-hydroxy mandelic acid content was 4%, dimer and trimer content was 102ppm) for oxidation reaction investigation, the pH value of the reaction liquid was adjusted to 12.5, and the oxygen gas with 21% oxygen content and nitrogen gas mixed gas (flow rate was 0.5L / min) was used as the oxidant, and 0.5% copper sulfate was used as the catalyst, and the reaction was carried out at 100℃, 0.5MPaG for 2h, and the reaction conversion rate was 100%, and the reaction selectivity was 98.2%.

[0038] Example 2

[0039] First, a modified porous carbon material was prepared. Specifically, a commercially available porous carbon was used as a base, and a mixed acid of hydrochloric acid and phosphoric acid in a mass ratio of 1:1 was used for modification treatment (the amount of the mixed acid was 5% of the mass of the porous carbon), the temperature of the modification treatment was 20°C, and the treatment time was 5 h, to obtain a modified porous carbon material C. The condensation reaction liquid was subjected to one-time pH adjustment to 8 using sulfuric acid, and extraction was performed using n-propyl acetate in an amount of 40% of the mass of the reaction liquid, and the obtained aqueous phase reaction liquid was subjected to one-time adsorption using the modified porous carbon C, the amount of the adsorbent was 20% of the mass of the reaction liquid, and the pH was adjusted to 4, and the obtained aqueous phase was subjected to two-time extraction using n-propyl acetate in an amount of 40% of the mass of the reaction liquid, and the obtained aqueous phase was subjected to two-time adsorption, the amount of the adsorbent was 20% of the mass of the reaction liquid, and the obtained reaction liquid was used as an oxidation reaction raw material. The oxidation reaction was performed using the raw material (3-methoxy-4-hydroxymandelic acid content: 6%, dimer and trimer content: 315 ppm), the pH of the reaction liquid was adjusted to 12, an oxygen-nitrogen mixed gas (flow rate: 2 L / min) with an oxygen content of 5% was used as an oxidizing agent, 0.1% of manganese sulfate was used as a catalyst, and the reaction was performed at 90°C and 0.3 MPaG for 3 h, and the conversion rate was 100%, and the reaction selectivity was 98.8%.

[0040] Example 3

[0041] First, a modified porous carbon material was prepared. Specifically, a commercially available porous carbon was used as a base, and a mixed acid of hydrochloric acid and phosphoric acid in a mass ratio of 1:1 was used for modification treatment (the amount of the mixed acid was 5% of the mass of the porous carbon), the temperature of the modification treatment was 20°C, and the treatment time was 5 h, to obtain a modified porous carbon material C. The condensation reaction liquid was subjected to one-time pH adjustment to 8 using sulfuric acid, and extraction was performed using n-propyl acetate in an amount of 40% of the mass of the reaction liquid, and the obtained aqueous phase reaction liquid was subjected to one-time adsorption using the modified porous carbon C, the amount of the adsorbent was 20% of the mass of the reaction liquid, and the pH was adjusted to 4, and the obtained aqueous phase was subjected to two-time extraction using n-propyl acetate in an amount of 40% of the mass of the reaction liquid, and the obtained aqueous phase was subjected to two-time adsorption, the amount of the adsorbent was 20% of the mass of the reaction liquid, and the obtained reaction liquid was used as an oxidation reaction raw material. The oxidation reaction was performed using the raw material (3-methoxy-4-hydroxymandelic acid content: 6%, dimer and trimer content: 315 ppm), the pH of the reaction liquid was adjusted to 12, an oxygen-nitrogen mixed gas (flow rate: 2 L / min) with an oxygen content of 5% was used as an oxidizing agent, 0.1% of manganese sulfate was used as a catalyst, and the reaction was performed at 90°C and 0.3 MPaG for 3 h, and the conversion rate was 100%, and the reaction selectivity was 98.8%.

[0042] Example 4

[0043] Firstly, the modified porous carbon material was prepared, and the specific process was as follows: using the purchased commercial porous carbon as the substrate, using the mixed acid with the mass ratio of 1:0.5 of sulfuric acid and phosphoric acid for modification treatment (the amount of the mixed acid was 20% of the mass of the porous carbon), the modification treatment temperature was 80°C, and the treatment time was 2h, to obtain the modified porous carbon material D. The condensation reaction liquid was adjusted to pH 6 by using sulfuric acid for the first time, and the n-heptane with 50% of the mass of the reaction liquid was used for extraction operation, and then the water phase reaction liquid was adsorbed by using the modified porous carbon D for the first time, the adsorbent amount was 15% of the mass of the reaction liquid, and then the pH value was adjusted to 4, and the n-heptane with 50% of the mass of the reaction liquid was used for the second extraction operation, and then the water phase was adsorbed for the second time, the adsorbent amount was 15% of the mass of the reaction liquid, and then the reaction liquid was obtained, which was the raw material for the oxidation reaction. The raw material (3-methoxy-4-hydroxymandelic acid content was 2%, and the dimer and trimer content was 49ppm) was used for oxidation reaction investigation, the pH value of the reaction liquid was adjusted to 14, the oxygen gas with 100% oxygen content and nitrogen mixed gas (flow rate was 0.2L / min) was used as the oxidant, the cobalt sulfate with 5% was used as the catalyst, the reaction was carried out at 110°C and 2MPaG for 0.5h, the reaction conversion rate was 100%, and the reaction selectivity was 98.1%.

[0044] Example 5

[0045] Firstly, the modified porous carbon material was prepared, and the specific process was as follows: using the purchased commercial porous carbon as the substrate, using the mixed acid with the mass ratio of 1:2 of hydrochloric acid and acetic acid for modification treatment (the amount of the mixed acid was 13% of the mass of the porous carbon), the modification treatment temperature was 50°C, and the treatment time was 8h, to obtain the modified porous carbon material E. The condensation reaction liquid was adjusted to pH 8 by using sulfuric acid for the first time, and the MIBK with 30% of the mass of the reaction liquid was used for extraction operation, and then the water phase reaction liquid was adsorbed by using the modified porous carbon E for the first time, the adsorbent amount was 20% of the mass of the reaction liquid, and then the pH value was adjusted to 3, and the MIBK with 30% of the mass of the reaction liquid was used for the second extraction operation, and then the water phase was adsorbed for the second time, the adsorbent amount was 20% of the mass of the reaction liquid, and then the reaction liquid was obtained, which was the raw material for the oxidation reaction. The raw material (3-methoxy-4-hydroxymandelic acid content was 10%, and the dimer and trimer content was 995ppm) was used for oxidation reaction investigation, the pH value of the reaction liquid was adjusted to 13, the oxygen gas with 15% oxygen content and nitrogen mixed gas (flow rate was 0.8L / min) was used as the oxidant, the iron sulfate with 1% was used as the catalyst, the reaction was carried out at 103°C and 0.8MPaG for 1h, the reaction conversion rate was 100%, and the reaction selectivity was 98.4%.

[0046] Comparative Example 1

[0047] The pH was adjusted to 1 again, and other conditions were the same as in Example 1. The content of benzene dimers and trimers in the oxidation reaction raw material was 5035 ppm, the reaction conversion rate was 97%, and the selectivity was 93.2%. This was because the content of dimers and trimers was too high, the reaction rate was slow, but at the same time, too many polymers caused excessive oxidation reaction, thereby reducing the selectivity.

[0048] Comparative Example 2

[0049] The porous carbon A was used in the amount of 40% for the first and second adsorption, and other conditions were the same as in Example 1. The content of benzene dimers and trimers in the oxidation reaction raw material was 15 ppm, the reaction conversion rate was 100%, and the selectivity was 92.1%. This was because the content of polymers was too low, which significantly increased the reaction rate, which would cause the oxidation products to further react with oxygen, thereby increasing the products of excessive oxidation reaction.

[0050] Comparative Example 3

[0051] No second adsorption was performed, and other conditions were the same as in Example 1. The content of benzene dimers and trimers in the oxidation reaction raw material was 1789 ppm, the reaction conversion rate was 97.9%, and the selectivity was 94.5%.

[0052] Comparative Example 4

[0053] The commercial catalyst was directly used for adsorption operation, and other conditions were the same as in Example 1. The content of benzene dimers and trimers in the oxidation reaction raw material was 1168 ppm, the reaction conversion rate was 99.1%, and the selectivity was 94.3%.

[0054] Although the content of the present application has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present application. Those skilled in the art can understand that some modifications or adjustments can be made to the present application under the teaching of the present specification. These modifications or adjustments should also be within the scope defined by the claims of the present application.

Claims

1. A method for improving the oxidation reaction activity of 3-methoxy-4-hydroxymandelic acid, the method comprising the following steps: generating 3-methoxy-4-hydroxybenzophenone acid from 3-methoxy-4-hydroxymandelic acid reaction liquid under the action of a catalyst and an oxidant; wherein the content of benzene dimers and trimers in the reaction raw material is 50-1000 ppm, the benzene dimers and trimers are generated by polymerization of guaiacol, 3-methoxy-4-hydroxymandelic acid, o,p-mandelic acid and o-mandelic acid; the 3-methoxy-4-hydroxymandelic acid reaction liquid is prepared by condensation reaction of guaiacol and glyoxylic acid under the catalysis of sodium hydroxide, and is obtained by the separation process of pH first adjustment, extraction, first adsorption, pH second adjustment, extraction and second adsorption; the molar ratio of guaiacol, glyoxylic acid and sodium hydroxide is 1:(0.4-0.6):(1.2-2); the reaction temperature is 10-40℃; the reaction time is 8-20h; the water content in the condensation reaction system is 70-90% of the total mass; the adsorbent used in the first adsorption and the second adsorption is modified porous carbon material; the modified porous carbon material is based on commercial porous carbon material, which is modified by mixed acid.

2. The method of claim 1, wherein, the content of benzene dimers and trimers in the reaction raw material is 100-500 ppm, the pH value of the reaction liquid after the first pH adjustment is 6-8, and the pH value of the reaction liquid after the second pH adjustment is 2-4; and / or, the extractant is at least one selected from methyl isobutyl ketone, toluene, n-propyl acetate and n-heptane; the amount of the extractant is 10%-50% of the mass of the condensation reaction liquid.

3. The method of claim 1, wherein, the amount of the extractant is 20%-40% of the mass of the condensation reaction liquid.

4. The method of claim 1, wherein the amount of the adsorbent in the first adsorption is 10%-20% of the mass of the reaction liquid, and the amount of the adsorbent in the second adsorption is 5%-10% of the mass of the reaction liquid.

5. The method of claim 1, wherein, the mixed acid is at least two selected from sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and acetic acid; the mass ratio of the two acids in the mixed acid is 1:0.5-2; the amount of the mixed acid is 5%-20% of the mass of the porous carbon material; and / or, the modification treatment temperature of the adsorbent is 20-80℃; the modification treatment time is 2-8h.

6. The method of claim 5, wherein, the amount of the mixed acid is 10%-15% of the mass of the porous carbon material; and / or, the modification treatment temperature of the adsorbent is 40-60℃; the modification treatment time is 4-6h.

7. The method according to any one of claims 1 to 6, wherein the content of 3-methoxy-4-hydroxymandelic acid in the oxidation reaction raw material liquid is 2%-10%, and the pH value of the 3-methoxy-4-hydroxymandelic acid reaction liquid is 12-14.

8. The method of claim 7, wherein, the content of 3-methoxy-4-hydroxymandelic acid in the oxidation reaction raw material liquid is 4%-8%, and the pH value of the 3-methoxy-4-hydroxymandelic acid reaction liquid is 12.5-13.

5.

9. The method according to any one of claims 1 to 6, wherein, the oxidant is mixed gas of oxygen and nitrogen, and the content of oxygen in the mixed gas is 5-100%; the flow rate is 0.2-2.0L / min.

10. The method of any one of claims 1-6, wherein, The catalyst is selected from at least one of copper sulfate, zinc sulfate, iron sulfate, cobalt sulfate, manganese sulfate; the amount of the oxidizing agent is 0.1%-5% of the mass of the reaction solution.

11. The method of any one of claims 1-6, wherein, The reaction temperature of the oxidation reaction is 90-110 DEG C; the reaction pressure is 0.3-2.0 MPaG; and the reaction time is 0.5-3 h.

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