Recycling method of condensation reaction sodium hydroxide solution in vanillin synthesis process

Abstract

The invention relates to a method for recycling a condensation reaction sodium hydroxide solution in a vanillin synthesis process, which comprises the following steps of: firstly, respectively preparing guaiacol and glyoxylic acid with the sodium hydroxide solution into sodium salt solutions in the vanillin synthesis process, then adding the glyoxylic acid sodium salt solution into the guaiacol sodium salt solution, and carrying out condensation reaction; and recovering the sodium hydroxide solution by using a bipolar membrane electrodialysis device, and recycling the recovered sodium hydroxide solution in the condensation reaction. Compared with the prior art, the condensation liquid obtained by the condensation reaction does not need to be added with acid to adjust the pH value, so that the production of a large amount of salt-containing wastewater and solid waste is avoided, the purpose of recovering the sodium hydroxide solution is achieved, the cyclic utilization of resources is realized, and the content of the finally synthesized vanillin is increased.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic fragrances, in particular to a method for recycling a sodium hydroxide solution produced in a condensation reaction during the synthesis of vanillin. Background Art

[0002] Vanillin is one of the most widely used monomeric spices in the world, and the current global consumption of vanillin has reached more than 20,000 tons. Vanillin is widely found in plants such as beets, vanilla beans, benzoin gum, and Peruvian balsam. It is white or light yellow in appearance and has a strong milky flavor. It is widely used in the food, daily chemical products, and pharmaceutical industries.

[0003] There are many methods for synthesizing vanillin, and the main method is the guaiacol glyoxylic acid method. Cao Zhongliang et al. reported the glyoxylic acid method for synthesizing vanillin in the 2016 issue of Applied Chemical Industry 45(8). This method uses guaiacol as a raw material and sodium hydroxide solution as an alkali solution. During the synthesis process, guaiacol and glyoxylic acid condense to form the sodium salt of guaiacol glyoxylic acid. At the same time, the excess guaiacol is converted into sodium phenol salt. Then, sulfuric acid is used to adjust the pH value to 4-5, and toluene is used to extract the excess guaiacol. Then, sodium hydroxide solution is used to strip the guaiacol in toluene. Finally, the condensation liquid is oxidized and decarboxylated to generate vanillin. However, in the process of synthesizing vanillin and recovering the excess guaiacol, a large amount of salt-containing wastewater and solid waste will be generated, and the waste treatment is expensive. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for recycling the sodium hydroxide solution in the condensation reaction during the synthesis of vanillin, so as to solve the problem of large amount of sodium hydroxide solution and high cost.

[0005] The conception process of the present application is as follows: the present invention recovers sodium hydroxide from the alkaline condensation liquid of guaiacol and glyoxylic acid in the production process of vanillin through a bipolar membrane electrodialysis method, and recycles the recovered sodium hydroxide solution in the condensation reaction.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The invention discloses a method for recycling a sodium hydroxide solution in a condensation reaction during the synthesis of vanillin. In the synthesis of vanillin, guaiacol and glyoxylic acid are respectively prepared with a sodium hydroxide solution to form a sodium salt solution, and then the glyoxylic acid sodium salt solution is added to the guaiacol sodium salt solution for a condensation reaction to obtain an alkaline condensation liquid, and then a bipolar membrane electrodialysis device is used to recover the sodium hydroxide solution, and the recovered sodium hydroxide solution is recycled in the condensation reaction.

[0008] Preferably, the molar ratio of the sodium salt solution of guaiacol to the sodium salt solution of glyoxylic acid is 1:0.7.

[0009] Furthermore, the pH value of the sodium hydroxide solution used to prepare the sodium salt solution of guaiacol and glyoxylic acid is 11-12.

[0010] Furthermore, the bipolar membrane electrodialysis device includes: a bipolar membrane electrodialysis membrane stack and polar water separators, a tightening plate, an anode plate and a cathode plate located on both sides of the bipolar membrane electrodialysis membrane stack.

[0011] Furthermore, the bipolar membrane electrodialysis membrane stack is formed by alternatingly stacking a plurality of bipolar membranes and a plurality of cationic membranes, and the bipolar membrane electrodialysis membrane stack adopts a BP-C structure to form a raw material chamber and an alkali chamber, which are separated by a raw material partition and an alkaline water partition, wherein the raw material chamber is connected to the alkaline condensation liquid through a raw material channel, and the alkali chamber is connected to the sodium hydroxide solution through an alkali channel.

[0012] Preferably, the number of the bipolar membranes is 6 to 12 and the number of the male molds is 6 to 12.

[0013] Furthermore, the method for using the bipolar membrane electrodialysis device is: 10 alkaline condensation liquid is passed into the raw material chamber, pure water is passed into the alkali chamber, the bipolar membrane electrodialysis device is connected to a power supply, and electrolysis is performed, and finally the raw material channel obtains a neutral condensation liquid, and the alkali channel obtains a recovered sodium hydroxide solution.

[0014] Furthermore, the voltage of the electrolysis is 10-24V, and the current is 2-4.4A.

[0015] Furthermore, the pH value of the neutral condensation liquid is 6-9.

[0016] Furthermore, the pH value of the recovered sodium hydroxide solution is 13-14, and the concentration of the recovered sodium hydroxide solution is 0.5-1 mol / L.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) In the process of synthesizing vanillin, the present invention does not need to add acid to adjust the pH value, thereby avoiding the production of a large amount of saline wastewater and solid waste. At the same time, it also achieves the purpose of recycling sodium hydroxide solution, realizes the recycling of resources, and increases the content of the finally synthesized vanillin.

[0019] (2) The concentration of the sodium hydroxide solution recovered by the present invention is 0.5-1 mol / L, which can be adjusted according to production needs; when recovering the sodium phenolate of guaiacol, the pH value can be accurately controlled according to the recovery extraction requirements to reduce costs.

[0020] (3) The present invention is conducive to the clean production of vanillin synthesis and is easy to scale up and intelligentize. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the bipolar membrane electrodialysis membrane stack structure in Examples 1 to 3 of the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Any features such as preparation means, materials, structures or composition ratios not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0023] Example 1

[0024] Firstly, guaiacol and glyoxylic acid are respectively prepared with a sodium hydroxide solution with a concentration of 0.5 mol / L to form a sodium salt solution, and then the glyoxylic acid sodium salt solution is added to the guaiacol sodium salt solution for condensation reaction (molar ratio 0.7:1) to obtain an alkaline condensation solution with a pH value of 11-12.

[0025] Take 1kg of alkaline condensation liquid and put it into the raw material channel, add 800g of pure water into the alkali channel, and Figure 1 The bipolar membrane electrodialysis membrane stack is connected to a power supply, the voltage is set to 20V, the current is set to 4.4A, and electrolysis is performed. Finally, the raw material channel obtains a condensation liquid with a pH value of 7-8, and the alkali channel obtains a recovered sodium hydroxide solution with a pH value of 13.78 and a concentration of 0.59moL / L. The weight of the recovered sodium hydroxide solution is 820g.

[0026] The condensation liquid obtained from the raw material channel is used to extract unreacted guaiacol with toluene, and the extracted liquid is oxidatively decarboxylated in the presence of a copper salt catalyst to synthesize vanillin. The content of vanillin analyzed by HPLC is 90.64%.

[0027] Example 2

[0028] First, guaiacol and glyoxylic acid were respectively prepared with the sodium hydroxide solution with a concentration of 0.59 mol / L recovered in Example 1 to form a sodium salt solution, and then the glyoxylic acid sodium salt solution was added to the guaiacol sodium salt solution for condensation reaction (molar ratio 0.7:1) to obtain an alkaline condensation solution with a pH value of 11 to 12.

[0029] Take 1kg of alkaline condensation liquid and put it into the raw material channel, add 500g of pure water into the alkali channel, and Figure 1 The bipolar membrane electrodialysis membrane stack is connected to a power supply, the voltage is set to 24V, the current is set to 2A, and electrolysis is performed. Finally, the raw material channel obtains a condensation liquid with a pH value of 6 to 7, and the alkali channel obtains a recovered sodium hydroxide solution with a pH value of 14 and a concentration of 1 mol / L. The recovered sodium hydroxide solution is 520.5g.

[0030] The condensation liquid obtained from the raw material channel is used to extract unreacted guaiacol with toluene, and the extracted liquid is oxidatively decarboxylated in the presence of a copper salt catalyst to synthesize vanillin. The content of vanillin analyzed by HPLC is 90.24%.

[0031] Example 3

[0032] First, guaiacol and glyoxylic acid were respectively prepared with the sodium hydroxide solution with a concentration of 1 mol / L recovered in Example 2 to form a sodium salt solution, and then the glyoxylic acid sodium salt solution was added to the guaiacol sodium salt solution for condensation reaction (molar ratio 0.7:1) to obtain an alkaline condensation solution with a pH value of 11 to 12.

[0033] Take 1kg of alkaline condensation liquid and put it into the raw material channel, add 1000g of pure water into the alkali channel, and Figure 1 The bipolar membrane electrodialysis membrane stack is connected to a power supply, the voltage is set to 10V, the current is set to 4.4A, and electrolysis is performed. Finally, the raw material channel obtains a condensation liquid with a pH value of 8-9, and the alkali channel obtains a recovered sodium hydroxide solution with a pH value of 13.68 and a concentration of 0.5moL / L. The recovered sodium hydroxide solution is 1020.5g.

[0034] The condensation liquid obtained from the raw material channel is used to extract unreacted guaiacol with toluene, and the extracted liquid is oxidatively decarboxylated in the presence of a copper salt catalyst to synthesize vanillin. The content of vanillin analyzed by HPLC is 90.55%.

[0035] The total recovery rate of the sodium hydroxide solution in Examples 1-3 is close to 100%.

[0036] Comparative Example 1

[0037] Firstly, guaiacol and glyoxylic acid are respectively prepared with a sodium hydroxide solution with a concentration of 0.5 mol / L to form a sodium salt solution, and then the glyoxylic acid sodium salt solution is added to the guaiacol sodium salt solution for condensation reaction (molar ratio 0.7:1) to obtain a condensation solution with a pH value of 11-12.

[0038] The pH value was adjusted to 4-5 with 50% sulfuric acid, and the unreacted guaiacol was extracted with toluene in the alkaline condensation liquid. The extracted liquid was oxidized and decarboxylated in the presence of a copper salt catalyst to synthesize vanillin. The content of vanillin was 89.04% as analyzed by HPLC.

[0039] Table 1 is a comparison table of HPLC spectral analysis data of Example 1 and Comparative Example 1. It can be seen from the table that the condensation liquid after being treated by the bipolar membrane electrodialysis device does not need to add acid to adjust the pH value, and continues to react under the same conditions. The content of vanillin finally prepared is higher and the content of other by-products is lower.

[0040] Table 1 Comparison of HPLC spectrogram analysis data of Example 1 and Comparative Example 1

[0041] Peak name Condensation liquid Dialdehyde Vanillin o-Vanillin Other unknown impurities Example 1 0.25％ 6.11％ 90.64％ 0.44％ 2.54％ Comparative Example 1 0.79％ 6.76％ 89.04％ 0.36％ 3.05％

[0042] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for recycling sodium hydroxide solution from condensation reaction in the synthesis process of vanillin, characterized in that: In the process of vanillin synthesis, guaiacol and glyoxylic acid are firstly prepared with sodium hydroxide solution to form sodium salt solution, and then the glyoxylic acid sodium salt solution is added to the guaiacol sodium salt solution for condensation reaction to obtain an alkaline condensation liquid of guaiacol and glyoxylic acid, and then the sodium hydroxide solution is recovered by a bipolar membrane electrodialysis device, and the recovered sodium hydroxide solution is recycled in the condensation reaction.

2. The method for recycling sodium hydroxide solution from condensation reaction in a vanillin synthesis process according to claim 1, characterized in that: The pH value of the sodium hydroxide solution used to prepare the sodium salt solution of guaiacol and glyoxylic acid is 11-12.

3. The method for recycling sodium hydroxide solution from condensation reaction in a vanillin synthesis process according to claim 1, characterized in that: The bipolar membrane electrodialysis device comprises: a bipolar membrane electrodialysis membrane stack and polar water separators, a tightening plate, an anode plate and a cathode plate located on both sides of the bipolar membrane electrodialysis membrane stack.

4. The method for recycling the sodium hydroxide solution of the condensation reaction in the synthesis process of vanillin according to claim 3, characterized in that: The bipolar membrane electrodialysis membrane stack is formed by alternatingly stacking a plurality of bipolar membranes and a plurality of cation membranes. The bipolar membrane electrodialysis membrane stack adopts a BP-C structure to form a raw material chamber and an alkali chamber, which are separated by a raw material partition and an alkaline water partition, wherein the raw material chamber is connected to the alkaline condensation liquid through a raw material channel, and the alkali chamber is connected to the sodium hydroxide solution through an alkali channel.

5. The method for recycling sodium hydroxide solution from condensation reaction in the synthesis process of vanillin according to claim 4, characterized in that: The number of the bipolar membranes is 6 to 12, and the number of the male molds is 6 to 12.

6. The method for recycling sodium hydroxide solution from condensation reaction in the synthesis process of vanillin according to claim 4, characterized in that: The method for using the bipolar membrane electrodialysis device is as follows: an alkaline condensation liquid is passed into a raw material chamber, pure water is passed into an alkali chamber, the bipolar membrane electrodialysis device is connected to a power source, and electrolysis is performed, and finally a neutral condensation liquid is obtained in the raw material channel, and a recovered sodium hydroxide solution is obtained in the alkali channel.

7. The method for recycling sodium hydroxide solution from condensation reaction in the synthesis process of vanillin according to claim 6, characterized in that: The voltage of the electrolysis is 10-24V, and the current is 2-4.4A.

8. The method for recycling sodium hydroxide solution from condensation reaction in the synthesis process of vanillin according to claim 6, characterized in that: The pH value of the neutral condensation liquid is 6-9.

9. The method for recycling sodium hydroxide solution from condensation reaction in the synthesis process of vanillin according to claim 6, characterized in that: The pH value of the recovered sodium hydroxide solution is 13-14.

10. The method for recycling sodium hydroxide solution from condensation reaction in the synthesis process of vanillin according to claim 6, characterized in that: The concentration of the recovered sodium hydroxide solution is 0.5-1 mol / L.

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