Separation and purification method of vanillin reaction liquid

Abstract

The invention relates to a separation and purification method of vanillin reaction liquid, which comprises the following steps of: extracting the reaction liquid containing vanillin by using an organic solvent, adsorbing by using an adsorbent, and rectifying and crystallizing to obtain a vanillin product, wherein the adsorbent is a metal ion modified titanium silicalite molecular sieve. For impurities such as o-vanillin and methyl vanillin which are high in separation difficulty, a metal ion modified titanium silicalite molecular sieve is innovatively introduced in the process as an adsorbent, and the metal ion modified titanium silicalite molecular sieve can accurately adsorb o-vanillin and methyl vanillin due to a proper pore structure and size, so that effective separation from vanillin is realized; and carrying out subsequent rectification and crystallization purification to obtain a vanillin product with the purity of 99.9% or above.

Description

Technical Field

[0001] This invention belongs to the field of vanillin preparation, and specifically relates to a method for separating and purifying vanillin reaction solution. Background Technology

[0002] Vanillin, also known as vanillin aldehyde, has a rich milky and vanilla aroma and is widely used in food, daily chemicals, perfumes, and other fields. It is currently the largest marketable flavoring agent. The main synthesis process for vanillin is the guaiacol process, which uses guaiacol and glyoxylic acid as raw materials. Through steps such as condensation reaction, oxidation reaction, acidification and decarboxylation, distillation and crystallization, and wastewater treatment, pure vanillin is finally obtained. This process is characterized by readily available raw materials, high yield, and mild reaction conditions.

[0003] The guaiacol process for preparing vanillin produces a certain amount of o-vanillin (i.e., 2-hydroxy-3-methoxybenzaldehyde, also known as o-vanillin) and 6-methylvanillin as byproducts. These two impurities have boiling points close to vanillin, making them difficult to separate. The national standard for vanillin requires a purity of ≥99.5%, which is not met by conventional separation methods such as distillation. To further improve the purity of vanillin, patent CN101838188A uses a mixed solvent to recrystallize crude (ethyl)vanillin, achieving a yield of over 90% and reducing the amount used by half, enabling continuous production. However, the purity of vanillin only reaches 99.5%. Patent CN111548260A, based on crude vanillin obtained by distillation and toluene crystallization, uses alcohol-water extraction to achieve better separation of vanillin and 6-methylvanillin, reducing vanillin loss. However, this process is relatively cumbersome. Patent CN102718640 provides a method for separating vanillin and o-vanillin. The method involves distillation to obtain samples with high contents of both vanillin and o-vanillin. Crude vanillin is crystallized from toluene to obtain the vanillin product, while crude o-vanillin is dissolved, added to sodium bicarbonate and methanol, and then crystallized and separated to obtain the o-vanillin product. This process is mainly used for processing samples with high contents of both o-vanillin and vanillin, but the purity of the final vanillin product still cannot reach a high level.

[0004] Therefore, it is necessary to develop a post-processing method for vanillin that can efficiently separate o-vanillin and methylvanillin to obtain high-purity vanillin products. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies and obtain high-purity vanillin products, this invention provides a method for separating and purifying vanillin reaction solutions. The method involves extraction, adsorption, distillation, and crystallization of the vanillin-containing reaction solution to obtain vanillin with high purity. For impurities such as o-vanillin and methylvanillin, which are difficult to separate, a metal ion-modified titanium-silicon molecular sieve is introduced as an adsorbent, achieving effective separation from vanillin and yielding vanillin products with a purity of over 99.9%.

[0006] To achieve the above technical effects, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for separating and purifying vanillin reaction solution. The method involves extracting the vanillin-containing reaction solution with an organic solvent, then adsorbing it with an adsorbent, followed by distillation and crystallization to obtain the vanillin product.

[0008] The adsorbent is a metal ion-modified titanium-silicon molecular sieve.

[0009] The metal ion modified titanium-silicon molecular sieve of the present invention can be any material containing metal ions and titanium-silicon molecular sieve. The present invention does not specifically limit the combination of metal ions and titanium-silicon molecular sieve, and they can be combined in any way, such as loading, coating, grafting, etc.

[0010] The metal ion modified titanium-silicon molecular sieve of the present invention has no special requirements for the matrix material of the titanium-silicon molecular sieve. Conventional types such as TS-1 and MWW type can be used in the present invention.

[0011] Optionally, the specific surface area of ​​the titanium-silicon molecular sieve is ≥350㎡ / g, including but not limited to 350㎡ / g, 380㎡ / g, 400㎡ / g, 430㎡ / g, 450㎡ / g, 500㎡ / g, 600㎡ / g, 800㎡ / g, or any combination thereof.

[0012] Optionally, the silicon-to-titanium ratio of the titanium-silicon molecular sieve is 30-40, including but not limited to 30, 32, 34, 36, 38, 40, or any combination thereof;

[0013] Optionally, the pore size of the titanium-silicon molecular sieve is 0.4-0.6 nanometers, including but not limited to 0.4 nanometers, 0.45 nanometers, 0.5 nanometers, 0.55 nanometers, 0.6 nanometers, or any combination thereof.

[0014] In one embodiment of the present invention, the metal ion modified titanium-silicon molecular sieve may be selected from at least one of iron, copper, manganese, and cobalt ions.

[0015] In one embodiment of the present invention, the metal ion modified titanium-silicon molecular sieve has a metal ion mass content of 0.01-1%, including but not limited to 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, or any combination thereof, based on the total mass of the metal ion modified titanium-silicon molecular sieve.

[0016] The metal ion-modified titanium-silicon molecular sieve described in this invention has no particular requirements regarding its source. It can be a commercially available metal ion-modified titanium-silicon molecular sieve product that meets the above requirements, or it can be prepared by researchers using existing publicly available methods. Specific requirements are not specified. For example, a conventional impregnation method can be used to obtain an adsorbent with metal ions loaded on the surface of the titanium-silicon molecular sieve, or a bonding method, in-situ hydrothermal synthesis method, etc., can be used for preparation. Regarding the relevant operations and process conditions in the preparation method of this invention, as well as the apparatus used, those skilled in the art can optimize them based on existing known processes according to actual needs; these will not be elaborated upon here.

[0017] In one embodiment of the present invention, an example of a method for preparing a metal ion-modified titanium-silicon molecular sieve is provided. The method involves mixing the titanium-silicon molecular sieve with a metal salt solution, followed by filtration, washing, drying, and calcination.

[0018] The metal salt solution is selected from at least one of the sulfate, nitrate, chloride, and carbonate of metals, for example, it can be at least one of the sulfate, nitrate, chloride, and carbonate of iron, copper, manganese, and cobalt ions.

[0019] Optionally, the metal salt solution is an aqueous solution with a mass concentration of 1-5%, including but not limited to 1%, 2%, 3%, 4%, 5%, or any combination thereof.

[0020] The mass ratio of the titanium-silicon molecular sieve to the metal salt solution is 1:(2-20), including but not limited to 1:2, 1:4, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, or any combination thereof, and may be selected as 1:(5-10).

[0021] The titanium-silicon molecular sieve and the metal salt solution are mixed by stirring. Optionally, the stirring temperature is 40-100℃, including but not limited to 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, or any combination thereof, preferably 60-90℃; the stirring time is 1-6h, including but not limited to 1h, 2h, 3h, 4h, 5h, 6h, or any combination thereof, preferably 3-5h.

[0022] The filtration and washing process involves using negative pressure filtration after stirring, and washing the separated solids with deionized water 3-5 times. Optionally, the amount of washing water used is 10-20% of the mass of the titanium-silicon molecular sieve.

[0023] The roasting temperature is 300-700℃, including but not limited to 300℃, 400℃, 500℃, 600℃, 700℃, or any combination thereof, preferably 400-500℃; the roasting time is 2-10h, including but not limited to 2h, 4h, 6h, 8h, 10h, or any combination thereof, preferably 4-6h.

[0024] The vanillin-containing reaction solution of the present invention does not have any special requirements on the vanillin content in the raw material. The reaction solution with any vanillin content can be processed by this method. In one embodiment, the vanillin content can be 1-10%, including but not limited to 1%, 3%, 5%, 7%, 9%, 10% or any combination thereof, based on the total mass of the reaction solution as 100%.

[0025] In one embodiment, the vanillin-containing reaction solution of the present invention is a reaction solution obtained by preparing vanillin using the guaiacol method. Specifically, it is a reaction solution obtained by using guaiacol and glyoxylic acid as raw materials, through condensation reaction, oxidation reaction, and decarboxylation reaction stages. There are no specific requirements regarding its source; for example, it can be obtained commercially or prepared by any feasible method, including conventional operations of the guaiacol method in the art, or improved methods based on conventional operations in the art. In specific applications, for example, it can be prepared according to the method disclosed in patent CN102010310A. In specific applications, the relevant operations and process conditions used, as well as the equipment used, can all be selected according to the corresponding conventional choices in the art; the present invention does not have any special requirements. After the reaction, the reaction solution contains vanillin, o-vanillin, methylvanillin, 5-aldehyde vanillin, and vanillin dimer, with concentrations of 3-9%, 0.05-0.5%, 0.01-0.1%, and 0.01-0.05%, respectively, with the remainder being water.

[0026] For example, the reaction solution containing vanillin, based on its total mass of 100%, contains 3-9% vanillin, 0.05-0.5% o-vanillin, 0.01-0.1% methyl vanillin, 0.01-0.05% other impurities, and the remainder is water. The other impurities mainly include 5-aldehyde vanillin, vanillin dimers, etc., which are usually caused by excessive oxidation during the oxidation reaction. Specifically, the content of vanillin includes, but is not limited to, a range of 3%, 4%, 5%, 6%, 7%, 8%, 9%, or any combination thereof; the content of o-vanillin includes, but is not limited to, a range of 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any combination thereof; the content of methylvanillin includes, but is not limited to, a range of 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, or any combination thereof; and the content of other impurities includes, but is not limited to, a range of 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or any combination thereof.

[0027] This invention employs organic solvent extraction to extract vanillin from the reaction solution. Specifically, it uses an organic solvent to extract the reaction solution containing vanillin, separating an oil phase solution containing vanillin. In this step, the vanillin in the reaction solution is dissolved in an organic solvent, and the resulting oil phase solution containing vanillin inevitably contains small amounts of other phenolic impurities (mainly including o-vanillin, methylvanillin, 5-aldehyde vanillin, and vanillin dimers, etc.). These impurities are further removed in a subsequent adsorption unit, and the remaining phase, an aqueous solution, is sent to the wastewater treatment unit.

[0028] In one embodiment of the present invention, the organic solvent is a good solvent for vanillin, that is, a solvent with good solubility for vanillin, selected from alkanes, lipids, ketones, and ethers, and can be selected from at least one of benzene, toluene, ethyl acetate, butyl acetate, methyl isobutyl ketone, n-hexane, and anisole, preferably at least one of toluene and methyl isobutyl ketone.

[0029] In one embodiment of the present invention, the extraction temperature is 10-100℃, including but not limited to 10℃, 20℃, 30℃, 50℃, 70℃, 90℃, 100℃, or any combination thereof, and may be selected as 40-80℃.

[0030] In one embodiment of the present invention, the residence time of the extraction is 0.1-3h, including but not limited to 0.1h, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or any combination thereof, and may be selected as 0.5-1h.

[0031] The extraction pressure described in this invention is atmospheric pressure. Pressure generally does not significantly affect the extraction effect and can be carried out under reduced pressure, atmospheric pressure, or pressurized conditions, but is generally performed under atmospheric pressure. The extraction pressure is atmospheric pressure. This invention does not specify a particular extraction time; the extraction time is determined by technicians based on standard operating conditions and the actual situation.

[0032] In one embodiment of the present invention, the mass ratio of the organic solvent used for extraction to the reaction solution containing vanillin is 1:(3-15), including but not limited to 1:3, 1:5, 1:7, 1:9, 1:11, 1:13, 1:15, or any combination thereof, and may be selected as 1:(5-10).

[0033] In this invention, the extraction operation uses conventional extraction equipment in the field. In practical applications, the equipment used in the extraction step of this invention can be any one of a rotary extraction tower, a packed extraction tower, a centrifugal extraction tower, or a plate extraction tower, with a rotary extraction tower being preferred.

[0034] The vanillin-containing reaction solution of the present invention, after being extracted with an organic solvent, has an extraction efficiency of up to 99% or more in the oil phase solution obtained by phase separation.

[0035] The adsorption operation described in this invention primarily aims to remove two impurities: o-vanillin and methylvanillin. In existing technologies, the oil phase solution obtained from extraction is typically further separated by distillation. However, o-vanillin and methylvanillin have boiling points close to vanillin, making it difficult to obtain high-purity products using conventional distillation methods. This invention introduces an adsorption operation into the post-processing flow, employing a metal ion-modified titanium-silicon molecular sieve as the adsorbent. Its suitable pore structure and size enable precise adsorption of o-vanillin and methylvanillin, achieving effective separation from vanillin.

[0036] In one embodiment of the present invention, the adsorption temperature is 30-100℃, including but not limited to 10℃, 20℃, 30℃, 50℃, 70℃, 90℃, 100℃, or any combination thereof, and may be selected as 50-80℃.

[0037] In this invention, the adsorption operation employs conventional adsorption equipment within the field. In practical applications, the adsorption step of this invention can be carried out using a fixed-bed reactor. Specifically, the metal ion-modified titanium-silicon molecular sieve is placed in a fixed bed, and the extracted oil phase solution is used as the raw material to be adsorbed. The feed method is bottom-in, top-out. Optionally, the mass hourly space velocity (HSV) of the oil phase solution relative to the metal ion-modified titanium-silicon molecular sieve is 0.1-3.0 h⁻¹. -1 , including but not limited to 0.1h -1 0.5h -1 1h-1 1.5h -1 2h -1 2.5h -1 3.0h -1 The range consisting of or between any two of these, preferably 0.5-1.5h. -1 .

[0038] The method for separating and purifying vanillin reaction solution according to the present invention further includes distillation and crystallization operations after the oil phase solution is adsorbed. Distillation and crystallization are conventional post-treatment methods used in the vanillin preparation process.

[0039] Specifically, the oil phase solution is subjected to distillation to recover the organic solvent and obtain crude vanillin.

[0040] The crude vanillin was further crystallized to obtain pure vanillin.

[0041] In a specific example of the present invention, the selectively adsorbed oil phase solution enters a distillation unit. Optionally, the distillation unit consists of three columns, namely a solvent removal column, a light phase removal column, and a vanillin crude product column.

[0042] Optionally, the operating temperature of the desolventizing tower is 60-150℃, including but not limited to 60℃, 80℃, 100℃, 120℃, 140℃, 150℃, or any combination thereof, preferably 80-100℃; the operating pressure is 6-8kPa, including but not limited to 6kPa, 6.5kPa, 7kPa, 7.5kPa, 8kPa, or any combination thereof; and the residence time is 0.5-1h, including but not limited to 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, or any combination thereof.

[0043] Optionally, the operating temperature of the light-weight removal tower is 80-180℃, including but not limited to 80℃, 100℃, 120℃, 140℃, 160℃, 180℃, or any combination thereof, preferably 100-120℃; the operating pressure is 2-4 kPa, including but not limited to 2 kPa, 2.5 kPa, 3 kPa, 3.5 kPa, 4 kPa, or any combination thereof; and the residence time is 0.5-1 h, including but not limited to 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, or any combination thereof.

[0044] Optionally, the operating temperature of the vanillin crude product tower is 100-200℃, including but not limited to 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, or any combination thereof, preferably 150-180℃; the operating pressure is 1-2 kPa, including but not limited to 1 kPa, 1.5 kPa, 2 kPa, or any combination thereof; and the residence time is 0.2-0.5 h, including but not limited to 0.2 h, 0.3 h, 0.4 h, 0.5 h, or any combination thereof.

[0045] In one specific example of the present invention, crude vanillin is mixed with a crystallization solvent and then introduced into a crystallization unit for crystallization; optionally, the crystallization solvent is a mixture of water and alcohol.

[0046] Optionally, in the mixture of water and alcohol, the mixing mass ratio of water to alcohol is 1:(1-10), including but not limited to 1:1, 1:3, 1:5, 1:7, 1:9, 1:10, or any combination thereof, preferably 1:(2-6).

[0047] Optionally, the alcohol is at least one selected from methanol, ethanol, propanol, isopropanol, butanol, propanol, etc.

[0048] Optionally, the mass ratio of the crude vanillin to the crystallization solvent is 1:(3-20), including but not limited to 1:3, 1:5, 1:8, 1:10, 1:13, 1:15, 1:18, 1:20, or any combination thereof, preferably 1:(6-10).

[0049] Optionally, the crystallization temperature is 10-80℃, including but not limited to 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, or any combination thereof, preferably 20-40℃.

[0050] Optionally, the crystallization time is 1-8 hours, including but not limited to 1 hour, 3 hours, 5 hours, 7 hours, 8 hours, or any combination thereof, preferably 2-5 hours.

[0051] The method for separating and purifying vanillin reaction solution described in this invention can yield vanillin products with a purity of up to 99.9 wt%, wherein the content of o-vanillin is less than 0.01 wt% and the content of methylvanillin is less than 0.005 wt%.

[0052] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0053] The method for separating and purifying vanillin reaction solution provided by this invention can effectively separate vanillin from impurities, obtaining a vanillin product with high purity (>99.9%). The organic solvent extraction unit can separate vanillin from wastewater, avoiding distillation and significantly reducing energy consumption. The adsorption unit can effectively remove difficult-to-separate o-vanillin and methylvanillin impurities. High-purity vanillin product can then be obtained through conventional distillation and crystallization operations.

[0054] This invention utilizes metal ion-modified titanium-silicon molecular sieves to adsorb and separate vanillin, o-vanillin, and methylvanillin. By leveraging the different sizes of phenolic substances and the variations in pore size and channels of the molecular sieve, highly selective adsorption of o-vanillin and methylvanillin can be achieved. Furthermore, the metal ion-modified titanium-silicon molecular sieve used in this invention also exhibits high adsorption activity and high adsorption efficiency. Detailed Implementation

[0055] The following embodiments will further illustrate the method provided by the present invention, but the present invention is not limited to the listed embodiments, and should also include any other known modifications within the scope of the claims of the present invention.

[0056] It should be noted that the endpoints and any values ​​of the ranges disclosed in this specification are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0058] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0059] The main sources of raw materials used in the various embodiments and comparative examples of this invention are as follows:

[0060] Vanillin reaction solution: obtained from guaiacol and glyoxylic acid through condensation, oxidation and decarboxylation reactions. The synthetic route is based on the master's thesis: Research on the synthesis process of vanillin by glyoxylic acid method, author Xue Yue.

[0061] Adsorbent A: Iron-modified titanium-silicon molecular sieve, prepared according to the following method:

[0062] Purchased titanium-silicon molecular sieve (Zhongchumei New Materials Co., Ltd., model GCS231571, specific surface area 370㎡ / g, silicon-to-titanium ratio 35, pore size 0.5 nm) was mixed with 3wt% ferric sulfate solution at a mass ratio of 1:8 and stirred at 70℃ for 5 hours. After filtration and washing three times with deionized water, it was calcined at 500℃ for about 6 hours to obtain iron-modified titanium-silicon molecular sieve with an iron ion content of 0.1wt%.

[0063] Adsorbent B: Copper ion modified titanium-silicon molecular sieve, prepared by adjusting the operating parameters according to the method of adsorbent A above, wherein the copper ion content is 0.8 wt%;

[0064] Adsorbent C: Manganese ion modified titanium-silicon molecular sieve, prepared by adjusting the operating parameters according to the method of adsorbent A above, wherein the manganese ion content is 0.05 wt%;

[0065] Adsorbent D: Cobalt ion modified titanium-silicon molecular sieve, prepared by adjusting the operating parameters according to the method of adsorbent A above, wherein the cobalt ion content is 0.5 wt%.

[0066] Example 1

[0067] Vanillin reaction solution: The mass content composition includes 6% vanillin, 0.1% o-vanillin, 0.05% methyl vanillin, 0.03% 5-aldehyde vanillin and vanillin dimer, with the remainder being water.

[0068] The separation and purification steps are as follows:

[0069] 1) At 60℃, the vanillin reaction solution was mixed with toluene at a mass ratio of 5:1 for extraction. The extraction residence time was 1 hour. An oil phase solution containing vanillin and an aqueous phase solution were separated. The aqueous phase solution was sent to the wastewater treatment unit. The extraction efficiency of vanillin in the obtained oil phase solution was 99.88%.

[0070] 2) Adsorbent A was placed in a fixed bed, and the oil phase solution obtained from extraction was added for adsorption. The feed method was bottom inlet and top outlet. The adsorption temperature was 50℃, and the adsorption mass hourly space velocity was 1.5 h⁻¹. -1 .

[0071] 3) The solvent is then recovered in the solvent removal tower, which operates at a temperature of 100℃, a pressure of 8 kPa, and a residence time of 1 h. The light component impurities (mainly including o-vanillin, guaiacol, phenol, etc.) are then removed in the light component removal tower, which operates at a temperature of 120℃, a pressure of 2 kPa, and a residence time of 1 h. Finally, the crude vanillin is obtained in the crude vanillin tower, which operates at a temperature of 150℃, a pressure of 1 kPa, and a residence time of 0.4 h.

[0072] 4) The crude vanillin and the crystallization solvent (methanol:water = 1:3) were crystallized at a mass ratio of 1:6. The crystallization temperature was 40℃ and the crystallization time was 3h to obtain the vanillin product.

[0073] The vanillin product has a purity of approximately 99.95%, including 0.004% o-vanillin and 0.002% methylvanillin.

[0074] Example 2

[0075] Vanillin reaction solution: The mass content composition includes 4% vanillin, 0.04% o-vanillin, 0.03% methyl vanillin, 0.02% 5-aldehyde vanillin and vanillin dimer, with the remainder being water.

[0076] The separation and purification steps are as follows:

[0077] 1) At 40℃, the vanillin reaction solution was mixed with butyl acetate at a mass ratio of 5:1 for extraction. The extraction residence time was 0.2 h. An oil phase solution containing vanillin and an aqueous phase solution were obtained. The aqueous phase solution was sent to the wastewater treatment unit. The extraction efficiency of vanillin in the obtained oil phase solution was 99.92%.

[0078] 2) Adsorbent B was placed in a fixed bed, and the oil phase solution obtained from extraction was added for adsorption. The feed method was bottom inlet and top outlet. The adsorption temperature was 35℃, and the adsorption mass hourly space velocity was 0.2 h⁻¹. -1 .

[0079] 3) The solvent is then recovered in the solvent removal tower, which operates at 70°C, 7 kPa, and has a residence time of 0.6 h. Light component impurities (mainly including o-vanillin, guaiacol, phenol, etc.) are removed in the light component removal tower, which operates at 90°C, 2.5 kPa, and has a residence time of 0.6 h. Finally, the crude vanillin is obtained in the crude vanillin tower, which operates at 110°C, 1.1 kPa, and has a residence time of 0.25 h.

[0080] 4) The crude vanillin and the crystallization solvent (ethanol:water = 1:2) were crystallized at a mass ratio of 1:3. The crystallization temperature was 15℃ and the crystallization time was 4h to obtain the vanillin product.

[0081] The vanillin product has a purity of approximately 99.98%, including 0.003% o-vanillin and 0.001% methylvanillin.

[0082] Example 3

[0083] Vanillin reaction solution: The mass content composition includes 8% vanillin, 0.4% o-vanillin, 0.09% methyl vanillin, 0.04% 5-aldehyde vanillin and vanillin dimer, with the remainder being water.

[0084] The separation and purification steps are as follows:

[0085] 1) At 90℃, the vanillin reaction solution was mixed with methyl isobutyl ketone at a mass ratio of 9:1 for extraction. The extraction residence time was 0.9 h. An oil phase solution containing vanillin and an aqueous phase solution were separated. The aqueous phase solution was sent to the wastewater treatment unit. The extraction efficiency of vanillin in the obtained oil phase solution was 99.83%.

[0086] 2) Adsorbent C was placed in a fixed bed, and the oil phase solution obtained from extraction was added for adsorption. The feed method was bottom inlet and top outlet. The adsorption temperature was 90℃, and the adsorption mass hourly space velocity was 2.5 h⁻¹. -1 .

[0087] 3) The solvent is then recovered in the solvent removal tower, which operates at a temperature of 140℃, a pressure of 7.5 kPa, and a residence time of 0.9 h. The light component impurities (mainly including o-vanillin, guaiacol, phenol, etc.) are removed in the light component removal tower, which operates at a temperature of 160℃, a pressure of 3.5 kPa, and a residence time of 0.8 h. The crude vanillin is then obtained in the crude vanillin tower, which operates at a temperature of 180℃, a pressure of 2 kPa, and a residence time of 0.45 h.

[0088] 4) The crude vanillin product and the crystallization solvent (propanol:water = 1:8) were crystallized at a mass ratio of 1:18. The crystallization temperature was 70℃ and the crystallization time was 5h to obtain the vanillin product.

[0089] The vanillin product has a purity of approximately 99.94%, including 0.004% o-vanillin and 0.002% methylvanillin.

[0090] Example 4

[0091] Vanillin reaction solution: The mass content composition includes 5% vanillin, 0.1% o-vanillin, 0.05% methyl vanillin, 0.03% 5-aldehyde vanillin and vanillin dimer, with the remainder being water.

[0092] The separation and purification steps are as follows:

[0093] 1) At 50℃, the vanillin reaction solution was mixed with n-hexane at a mass ratio of 5:1 for extraction. The extraction residence time was 0.7 h. An oil phase solution containing vanillin and an aqueous phase solution were obtained. The aqueous phase solution was sent to the wastewater treatment unit. The extraction efficiency of vanillin in the obtained oil phase solution was 99.78%.

[0094] 2) Adsorbent D was placed in a fixed bed, and the oil phase solution obtained from extraction was added for adsorption. The feed method was bottom inlet and top outlet. The adsorption temperature was 60℃, and the adsorption mass hourly space velocity was 1.0 h⁻¹. -1 .

[0095] 3) The solvent is then recovered in the solvent removal tower, which operates at a temperature of 100℃, a pressure of 7 kPa, and a residence time of 0.8 h. The light component impurities (mainly including o-vanillin, guaiacol, phenol, etc.) are removed in the light component removal tower, which operates at a temperature of 120℃, a pressure of 3 kPa, and a residence time of 0.6 h. The crude vanillin is then obtained in the crude vanillin tower, which operates at a temperature of 160℃, a pressure of 1.5 kPa, and a residence time of 0.3 h.

[0096] 4) The crude vanillin and the crystallization solvent (isopropanol:water = 1:5) were crystallized at a mass ratio of 1:6. The crystallization temperature was 30℃ and the crystallization time was 5h to obtain the vanillin product.

[0097] The vanillin product has a purity of approximately 99.96%, including 0.005% o-vanillin and 0.003% methylvanillin.

[0098] Comparative Example 1

[0099] Referring to the method in Example 1, the difference is that adsorbent A is replaced with titanium-silicon molecular sieve (China Catalyst New Materials Co., Ltd., model GCS231571) without metal ion modification, while other operations and conditions remain unchanged, and vanillin product is obtained.

[0100] The vanillin product has a purity of approximately 99.86%, including 0.04% o-vanillin and 0.02% methylvanillin.

[0101] Comparative Example 2

[0102] Referring to the method in Example 1, the difference is that adsorbent A is replaced with macroporous resin (Tianjin Haoju Resin, model D101), while other operations and conditions remain unchanged, to obtain vanillin product.

[0103] The vanillin product has a purity of approximately 99.58%, including 0.2% o-vanillin and 0.1% methylvanillin.

[0104] Comparative Example 3

[0105] Referring to the method in Example 1, the difference is that the adsorption step of the adsorbent is omitted, while other operations and conditions such as distillation and crystallization remain unchanged, and vanillin product is obtained.

[0106] The vanillin product has a purity of approximately 99.45%, including 0.3% o-vanillin and 0.1% methylvanillin.

Claims

1. A method for separating and purifying vanillin reaction solution, characterized in that, The method involves extracting the reaction solution containing vanillin with an organic solvent, then adsorbing it with an adsorbent, followed by distillation and crystallization to obtain the vanillin product. The adsorbent is a metal ion-modified titanium-silicon molecular sieve.

2. The separation and purification method according to claim 1, characterized in that, The metal ion-modified titanium-silicon molecular sieve shall satisfy at least one of the following conditions: The specific surface area of ​​the titanium-silicon molecular sieve is ≥350㎡ / g; The silicon-to-titanium ratio of the titanium-silicon molecular sieve is 30-40; The pore size of the titanium-silicon molecular sieve is 0.4-0.6 nanometers; The metal ion modified titanium-silicon molecular sieve may be selected from at least one of iron, copper, manganese, and cobalt ions. The metal ion-modified titanium-silicon molecular sieve has a metal ion content of 0.01-1% and is based on the total mass of the metal ion-modified titanium-silicon molecular sieve.

3. The separation and purification method according to claim 1 or 2, characterized in that, The metal ion modified titanium-silicon molecular sieve is prepared by mixing titanium-silicon molecular sieve with a metal salt solution, followed by filtration, washing, drying, and calcination.

4. The separation and purification method according to claim 3, characterized in that, The metal salt solution is selected from at least one of the sulfate, nitrate, chloride, and carbonate of metals, and may be selected from at least one of the sulfate, nitrate, chloride, and carbonate of iron, copper, manganese, and cobalt ions; Optionally, the metal salt solution is an aqueous solution with a mass concentration of 1-5%; and / or, The mass ratio of the titanium-silicon molecular sieve to the metal salt solution is 1:(2-20), optionally 1:(5-10); and / or, The titanium-silicon molecular sieve is mixed with the metal salt solution by stirring. Optionally, the stirring temperature is 40-100℃, preferably 60-90℃; the stirring time is 1-6 hours, preferably 3-5 hours; and / or, The roasting temperature is 300-700℃, preferably 400-500℃; the roasting time is 2-10h, preferably 4-6h.

5. The separation and purification method according to any one of claims 1-4, characterized in that, The reaction solution containing vanillin has a vanillin content of 1-10%, calculated based on a total mass of 100% of the reaction solution. Optionally, the reaction solution containing vanillin is the reaction solution obtained by preparing vanillin using the guaiacol method; preferably, the reaction solution containing vanillin, based on its total mass of 100%, contains 3-9% vanillin, 0.05-0.5% o-vanillin, 0.01-0.1% methylvanillin, 0.01-0.05% other impurities, and the remainder is water.

6. The separation and purification method according to any one of claims 1-5, characterized in that, The organic solvent is a good solvent for vanillin, selected from alkanes, lipids, ketones, and ethers, and may be at least one of benzene, toluene, ethyl acetate, butyl acetate, methyl isobutyl ketone, n-hexane, and anisole, preferably at least one of toluene and methyl isobutyl ketone; and / or, The extraction temperature is 10-100℃, optionally 40-80℃; and / or, The extraction residence time is 0.1-3 h, optionally 0.5-1 h; and / or, The mass ratio of the organic solvent to the reaction solution containing vanillin is 1:(3-15), optionally 1:(5-10); and / or, The extraction operation uses any one of the following equipment: rotary extraction tower, packed extraction tower, centrifugal extraction tower, and plate extraction tower, with rotary extraction tower being preferred.

7. The separation and purification method according to any one of claims 1-6, characterized in that, The adsorption temperature is 30-100℃, optionally 50-80℃; and / or, The adsorption operation utilizes a fixed-bed reactor. Metal-ion-modified titanium-silicon molecular sieves are placed in the fixed bed, and the extracted oil phase solution is used as the adsorbate feedstock. The feed method is bottom-in, top-out. Optionally, the mass hourly space velocity (HSV) of the oil phase solution relative to the metal-ion-modified titanium-silicon molecular sieve is 0.1-3.0 h⁻¹. -1 Preferably, it is 0.5-1.5h. -1 .

8. The separation and purification method according to any one of claims 1-7, characterized in that, After adsorption treatment, the oil phase solution also includes distillation and crystallization operations: The oil phase solution is subjected to distillation to recover the organic solvent and obtain crude vanillin. The crude vanillin was further crystallized to obtain pure vanillin.

9. The separation and purification method according to any one of claims 1-8, characterized in that, The oil phase solution after adsorption treatment enters the distillation unit, which consists of three columns: a solvent removal column, a light phase removal column, and a vanillin crude product column, in sequence. Optionally, the operating temperature of the solvent removal tower is 60-150℃, preferably 80-100℃, the operating pressure is 6-8kPa, and the residence time is 0.5-1h; Optionally, the operating temperature of the light-weight removal tower is 80-180℃, preferably 100-120℃, the operating pressure is 2-4kPa, and the residence time is 0.5-1h; Optionally, the operating temperature of the crude vanillin tower is 100-200℃, preferably 150-180℃, the operating pressure is 1-2kPa, and the residence time is 0.2-0.5h.

10. The separation and purification method according to any one of claims 1-9, characterized in that, The crude vanillin is mixed with a crystallization solvent and then introduced into a crystallization unit for crystallization. Optionally, the crystallization solvent is a mixture of water and alcohol; preferably, the mass ratio of water to alcohol in the mixture is 1:(1-10), more preferably 1:(2-6); preferably, the alcohol is at least one selected from methanol, ethanol, propanol, isopropanol, butanol, and propanol. Optionally, the mass ratio of the crude vanillin to the crystallization solvent is 1:(3-20), preferably 1:(6-10; Optionally, the crystallization temperature is 10-80℃, preferably 20-40℃; Optionally, the crystallization time is 1-8 hours, preferably 2-5 hours.