Preparation method of citraconic acid

Abstract

The invention discloses a preparation method of citraconic acid, and relates to the technical field of preparation of citraconic acid. According to the invention, itaconic acid is used as a reaction raw material, water is used as a reaction solvent, a combination of nickel acetylacetonate and a tertiary amine compound is used as a catalyst, and citraconic acid is prepared through an isomerization reaction. The citraconic acid prepared by the preparation method disclosed by the invention is high in purity and high in yield, specifically, the purity of the citraconic acid prepared by the preparation method disclosed by the invention is 99.1%-99.5%, and the yield of the citraconic acid prepared by the preparation method is 80%-95%. The preparation method for preparing the citraconic acid is low in reaction temperature and low in production energy consumption, the citraconic acid can be prepared by adopting a one-pot end method, the operation is simple, the synthesis is simple and convenient, and a new reaction thought is provided for industrial large-scale production of the citraconic acid.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of citraconic acid, and particularly relates to a method for preparing citraconic acid. Background Art

[0002] Citraconic acid, with the molecular formula C5H6O4, is the cis - stereoisomer of mesaconic acid and belongs to the isomeric dicarboxylic acid derived from citric acid. Its structural formula is The unique chemical structure and reactivity of citraconic acid have attracted much attention in many fields such as materials science, polymer chemistry, and biomedicine. Specifically, citraconic acid can be used as an antioxidant for the protection of oils and fats; it can participate in regulating cell metabolism, oxidative and electrophilic stress responses, and immune responses, and is used to prepare anti - inflammatory and anti - tumor drugs; it can be used to produce liquid curing agents for epoxy resins. For example, citraconic acid undergoes a Diels - Alder reaction with isoprene to synthesize a non - hygroscopic curing agent that is liquid at room temperature; it can also be used as a comonomer in the synthesis of copolymers with antiviral and antibacterial activities.

[0003] Currently, there are mainly two methods for synthesizing citraconic acid: one is to use citric acid as a raw material and heat it under the action of a catalyst to prepare citraconic acid, but this synthesis method has the problem of low yield; the other is to use citraconic anhydride as a raw material and obtain citraconic acid through hydrolysis reaction, but citraconic anhydride itself is prone to polymerization reaction, resulting in difficult post - treatment of citraconic anhydride and thus low yield of citraconic acid. In the prior art, the literature (Org.Synth.1931, 11, 28) discloses the preparation of citraconic acid using itaconic anhydride as a raw material. The specific synthesis process is as follows:

[0004]

[0005] In the above synthesis method, itaconic anhydride will isomerize to citraconic anhydride at high temperature, but the reaction yield is not high, about 62-66%. The main reason for the low reaction yield is that itaconic anhydride and citraconic anhydride are prone to polymerization at high temperature, generating a large amount of red tarry substances. Moreover, this method has a large amount of solid waste, low product purity, and poor product color. The literature "Journal of Polymer Science: Polymer Chemistry Edition" (1981, Vol 19, 2243-2253) discloses a method for isomerizing itaconic anhydride to citraconic anhydride using a weak base and a polar solvent acetone. Among them, the weak base is triethylamine, trimethylamine, and pyridine. However, this method is greatly affected by factors such as the substrate structure, solvent polarity, and pH of the reaction system, and has low applicability. The literature (Journal of the Society of Chemical Industry, London, Transactions and Counications, 1950, 69, 97-9) and US3701805A disclose the preparation of citraconic acid using citric acid as a raw material and alkali metal or alkaline earth metal salts such as K2HPO4 as catalysts. However, the yield of this reaction is only 64% and the reaction temperature needs to be controlled as high as 260°C during the reaction process.

[0006] It can be seen that the current production methods of citraconic acid generally have the defects of low yield, high energy consumption, and high preparation cost. Therefore, it is of great practical significance to develop a preparation method of citraconic acid that can ensure simple synthesis, easy operation, low energy consumption, and high yield. Summary of the Invention

[0007] In view of the above prior art, the object of the present invention is to provide a preparation method of citraconic acid. The present invention uses itaconic acid as a reaction raw material, water as a reaction solvent, and a combination of nickel acetylacetonate and a tertiary amine compound as a catalyst, and prepares citraconic acid through an isomerization reaction. The citraconic acid prepared by the preparation method of the present invention has high purity and high yield. Specifically, the purity of the citraconic acid prepared by the present invention is 99.1%-99.5%, and the yield is 80%-95%. The preparation method of the present invention for preparing citraconic acid has a low reaction temperature, low production energy consumption, and can obtain citraconic acid by a one-pot method. The operation is simple and the synthesis is simple, providing a new reaction idea for the industrial large-scale production of citraconic acid.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a preparation method of citraconic acid, comprising the following steps:

[0010] (1) Mix itaconic acid and water, dropwise add a tertiary amine compound and stir to obtain a mixed solution, then add nickel acetylacetonate dihydrate to the mixed solution for reaction. After the reaction is completed, cool it down, let it stand, and separate the aqueous phase to obtain a solution containing citraconic acid;

[0011] (2) After decolorizing the solution containing citraconic acid, add alkali and stir to make it layer. Collect the aqueous phase to obtain a sodium citrate solution;

[0012] (3) Acidify the sodium citrate solution, concentrate, crystallize, filter and dry to obtain citraconic acid.

[0013] Preferably, in step (1), the structural formula of the tertiary amine compound is shown as formula (I),

[0014]

[0015] In formula (I), R1, R2 and R3 are independently selected from -Ar or C l -alkyl of C8.

[0016] Furthermore, the alkyl of C l -C8 includes branched-chain alkyl of C l -C8, straight-chain alkyl of C l -C8.

[0017] Preferably, in step (1), the tertiary amine compound is selected from one of triethylamine, tripropylamine, N,N-dimethylisobutylamine, N,N-dimethylbutylamine, and N,N-diethylaniline.

[0018] Furthermore, the tertiary amine compound is one of triethylamine, tripropylamine, and N,N-diethylaniline.

[0019] Preferably, in step (1), the molar ratio of itaconic acid, nickel acetylacetonate dihydrate, tertiary amine compound and water is 1:(0.012 - 0.015):(3.5 - 6.5):(7.2 - 21.7).

[0020] Furthermore, the molar ratio of itaconic acid, nickel acetylacetonate dihydrate, tertiary amine compound and water is 1:0.012:6.4:21.7.

[0021] Preferably, in step (1), when dropping the tertiary amine compound, control the temperature of the solution to be 20±5°C.

[0022] Preferably, in step (1), the stirring time is 25 - 35 min.

[0023] Preferably, in step (1), the reaction temperature is 90 - 100°C and the reaction time is 4 - 6 h.

[0024] Furthermore, the reaction temperature is 100 °C and the reaction time is 6 h.

[0025] Preferably, in step (1), the temperature is lowered to 10 - 30 °C. Further preferably, the temperature is lowered to 10 °C.

[0026] Preferably, in step (2), the specific operation for decolorizing the solution containing citraconic acid is as follows:

[0027] Activated carbon is added to the solution containing citraconic acid, and decolorization is carried out at 50 - 60 °C;

[0028] Among them, the addition amount of activated carbon is 2% - 4% of the mass of the solution containing citraconic acid.

[0029] Preferably, in step (2), the base is a NaOH solution with a mass fraction of 30 - 35%, and the molar ratio of NaOH to itaconic acid in the NaOH solution is (1.5 - 2.5):1.

[0030] Preferably, in step (2), the stirring temperature is 20 - 30 °C and the stirring time is 8 - 12 min.

[0031] Preferably, in step (3), the acid is hydrochloric acid with a mass fraction of 35 - 37%, and the pH after acidification is 3.5 - 4.5.

[0032] Preferably, in step (3), the crystallization temperature is 10 - 30 °C.

[0033] Preferably, in step (3), the drying method is vacuum drying and the drying temperature is 65 - 75 °C.

[0034] Advantages of the present invention:

[0035] 1. The present invention uses itaconic acid as a reaction raw material, water as a reaction solvent, and a combination of nickel acetylacetonate and a tertiary amine compound as a catalyst to prepare citraconic acid through an isomerization reaction. The citraconic acid prepared by the preparation method of the present invention has high purity and high yield. Specifically, the purity of the citraconic acid prepared by the present invention is 99.1% - 99.5%, and the yield is 80% - 95%.

[0036] 2. The present invention uses nickel acetylacetonate and a tertiary amine compound as a catalyst. Nickel acetylacetonate can complex carbonyl and double bonds to form a cyclic-like structure, and then isomerize under the action of the tertiary amine compound to obtain citraconic acid. Using a combination of nickel acetylacetonate and a tertiary amine compound as a catalyst can improve the yield of citraconic acid.

[0037] 3. The present invention uses water as a solvent, ruthenium acetylacetonate and a tertiary amine compound as catalysts. Utilizing the immiscibility between the catalyst and water at a certain temperature, after the reaction is completed, the temperature is first lowered and then the mixture is allowed to stand for phase separation. The citraconic acid enters the aqueous phase, enabling the separation of the citraconic acid from the tertiary amine compound.

[0038] 4. When preparing citraconic acid by the preparation method of the present invention, the reaction temperature is low, the production energy consumption is low, and citraconic acid can be obtained by a one-pot method. The operation is simple and the synthesis is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 : HNMR spectrum of the citraconic acid prepared in Example 1 1 HNMR spectrum. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0041] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0042] The experimental materials used in the embodiments of the present invention are all conventional experimental materials in the art and can be obtained through commercial channels.

[0043] Example 1: Preparation method of citraconic acid

[0044] (1) 0.1538 mol of itaconic acid and 3.33 mol of water were mixed, the temperature in the system was 20 °C, 0.988 mol of triethylamine was added dropwise, and the system temperature was controlled at 20 ± 5 °C. After the addition was completed, stirring was continued for 30 min, 0.002 mol of nickel acetylacetonate dihydrate was added, the temperature was raised to 100 °C and the reaction was carried out for 6 h. After the reaction was completed, the temperature was lowered to 10 °C and allowed to stand for phase separation, and the aqueous phase was separated to obtain a solution containing citraconic acid;

[0045] (2) Activated carbon was added to the solution containing citraconic acid, and decolorization treatment was carried out at 60 °C. The addition amount of the activated carbon was 2% of the mass of the solution containing citraconic acid; then 40 g of a NaOH solution with a mass fraction of 32% was added to the decolorized solution, and stirring was carried out at 25 °C for 10 min to make it layer, and the aqueous phase was collected to obtain a sodium citraconate solution;

[0046] (3) Add hydrochloric acid with a mass fraction of 36% to the sodium citraconate solution and acidify it to pH 4.0. After concentration under reduced pressure and dehydration, a concentrated solution is obtained. Then, the concentrated solution is cooled and crystallized at 10 °C, filtered, and the filtered solid is collected and dried in vacuo at 70 °C to obtain the target product citraconic acid.

[0047] For the citraconic acid prepared in this example 1 HNMR is as Figure 1 shown. In this example, the purity of citraconic acid is 99.5% and the yield is 95%.

[0048] Example 2: Preparation method of citraconic acid

[0049] (1) Mix 0.1538 mol of itaconic acid and 3.33 mol of water, with the temperature in the system at 20 °C. Dropwise add 0.68 mol of tripropylamine, control the system temperature at 20 ± 5 °C. After the addition is complete, continue stirring for 30 min, add 0.0023 mol of nickel acetylacetonate dihydrate, raise the temperature to 90 °C and react for 6 h. After the reaction is completed, cool to 30 °C and let it stand for liquid separation, and separate the aqueous phase to obtain a solution containing citraconic acid;

[0050] (2) Add activated carbon to the solution containing citraconic acid and perform decolorization treatment at 50 °C. Among them, the addition amount of activated carbon is 4% of the mass of the solution containing citraconic acid; then add 40 g of a NaOH solution with a mass fraction of 32% to the decolorized solution, stir at 25 °C for 10 min to make it layer, collect the aqueous phase to obtain a sodium citraconate solution;

[0051] (3) Add hydrochloric acid with a mass fraction of 36% to the sodium citraconate solution and acidify it to pH 4.0. After concentration under reduced pressure and dehydration, a concentrated solution is obtained. Then, the concentrated solution is cooled and crystallized at 15 °C, filtered, and the filtered solid is collected and dried in vacuo at 65 °C to obtain the target product citraconic acid.

[0052] In this example, the purity of citraconic acid is 99.1% and the yield is 80%.

[0053] Example 3: Preparation method of citraconic acid

[0054] (1) Mix 0.1538 mol of itaconic acid and 3.33 mol of water, with the temperature in the system at 20 °C. Dropwise add 0.68 mol of tripropylamine, control the system temperature at 20 ± 5 °C. After the addition is complete, continue stirring for 30 min, add 0.002 mol of nickel acetylacetonate dihydrate, raise the temperature to 100 °C and react for 4 h. After the reaction is completed, cool to 30 °C and let it stand for liquid separation, and separate the aqueous phase to obtain a solution containing citraconic acid;

[0055] (2) Activated carbon was added to the solution containing citraconic acid, and decolorization treatment was carried out at 50 °C. Among them, the addition amount of activated carbon was 2% of the mass of the solution containing citraconic acid; then 45 g of a NaOH solution with a mass fraction of 32% was added to the decolorized solution, and it was stirred at 25 °C for 10 min to make it stratified, and the aqueous phase was collected to obtain a sodium citraconate solution;

[0056] (3) The sodium citraconate solution was acidified with hydrochloric acid with a mass fraction of 36% to a pH of 4.0, dehydrated after reduced pressure concentration to obtain a concentrated solution, and then the concentrated solution was cooled and crystallized at 30 °C, filtered, and the solid after filtration was collected and dried in vacuo at 70 °C to obtain the target product citraconic acid.

[0057] In this example, the purity of citraconic acid was 99.0% and the yield was 85%.

[0058] Example 4: Preparation method of citraconic acid

[0059] 0.1538 mol of itaconic acid and 1.12 mol (20 g) of water were mixed, the temperature in the system was 20 °C, 0.988 mol of triethylamine was added dropwise, the temperature of the system was controlled at 20 ± 5 °C, after the addition was completed, stirring was continued for 30 minutes, 0.0022 mol of nickel acetylacetonate dihydrate was added, the temperature was raised to 95 °C and reacted for 5 h, after the reaction was completed, the temperature was lowered to 15 °C and allowed to stand and stratify, and the aqueous phase was separated to obtain a solution containing citraconic acid;

[0060] (2) Activated carbon was added to the solution containing citraconic acid, and decolorization treatment was carried out at 60 °C. Among them, the addition amount of activated carbon was 3% of the mass of the solution containing citraconic acid; then 42 g of a NaOH solution with a mass fraction of 32% was added to the decolorized solution, and it was stirred at 25 °C for 10 min to make it stratified, and the aqueous phase was collected to obtain a sodium citraconate solution;

[0061] (3) The sodium citraconate solution was acidified with hydrochloric acid with a mass fraction of 36% to a pH of 4.0, dehydrated after reduced pressure concentration to obtain a concentrated solution, and then the concentrated solution was cooled and crystallized at 20 °C, filtered, and the solid after filtration was collected and dried in vacuo at 75 °C to obtain the target product citraconic acid.

[0062] In this example, the purity of citraconic acid was 99.2% and the yield was 87%.

[0063] Example 5: Preparation method of citraconic acid

[0064] Mix 0.1538 mol of itaconic acid and 3.33 mol (60 g) of water. The temperature in the system is 20°C. Dropwise add 0.56 mol of N,N-dimethylisobutylamine, controlling the system temperature at 20 ± 5°C. After the dropwise addition, continue stirring for 30 minutes. Then add 0.0018 mol of nickel acetylacetonate dihydrate, and raise the temperature to 100°C for reaction for 4 h. After the reaction is completed, cool down to 30°C and let it stand for liquid separation. Separate the aqueous phase to obtain a solution containing citraconic acid;

[0065] (2) Add activated carbon to the solution containing citraconic acid and perform decolorization treatment at 60°C. The addition amount of activated carbon is 2% of the mass of the solution containing citraconic acid. Then add 40 g of a NaOH solution with a mass fraction of 32% to the decolorized solution, stir at 25°C for 10 min to make it layer, and collect the aqueous phase to obtain a sodium citraconate solution;

[0066] (3) Acidify the sodium citraconate solution with hydrochloric acid with a mass fraction of 36% to a pH of 4.0, perform vacuum concentration to dehydrate, obtain a concentrated solution, then place the concentrated solution at 20°C for cooling and crystallization, filter, collect the filtered solid and dry it under vacuum at 70°C to obtain the target product citraconic acid.

[0067] In this example, the purity of citraconic acid is 99.5% and the yield is 91%.

[0068] Comparative Example 1:

[0069] The difference between this comparative example and Example 1 is that only triethylamine is used as the catalyst. The specific steps are as follows:

[0070] Mix 0.1538 mol of itaconic acid and 3.33 mol of water. The temperature in the system is 20°C. Dropwise add 0.988 mol of triethylamine, controlling the system temperature at 20 ± 5°C. After the dropwise addition, continue stirring for 30 minutes. Then raise the temperature to 100°C for reaction for 6 h. After the reaction is completed, cool down to 10°C and let it stand for liquid separation. Separate the aqueous phase to obtain a solution containing citraconic acid; Purify the solution containing citraconic acid to obtain citraconic acid, where the purification operation and parameters are the same as those in Example 1.

[0071] The yield of citraconic acid prepared in this comparative example is 62.9%.

[0072] Comparative Example 2:

[0073] The difference between this comparative example and Example 1 is that only nickel acetylacetonate is used as the catalyst. The specific steps are as follows:

[0074] 0.1538 mol of itaconic acid and 3.33 mol of water were mixed, and the temperature in the system was 20 °C. After stirring for 30 minutes, 0.002 mol of nickel acetylacetonate dihydrate was added, and the temperature was raised to 100 °C for reaction for 6 h. After the reaction was completed, the temperature was lowered to 10 °C and allowed to stand for liquid separation. The aqueous phase was separated to obtain a solution containing citraconic acid; the solution containing citraconic acid was purified to obtain citraconic acid, wherein the purification operation and parameters were the same as those in Example 1.

[0075] The yield of citraconic acid prepared in this comparative example was 30.7%.

[0076] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing citraconic acid, characterized in that, It includes the following steps: (1) Mix itaconic acid and water, then dropwise add a tertiary amine compound and stir to obtain a mixed solution. Then add nickel acetylacetonate dihydrate to the mixed solution for reaction. After the reaction is completed, cool down and let it stand, and separate the aqueous phase to obtain a solution containing citraconic acid; (2) After decolorizing the solution containing citraconic acid, add alkali and stir to make it layer, collect the aqueous phase to obtain a sodium citrate solution; (3) Acidify the sodium citrate solution, and through concentration, crystallization, filtration and drying, citraconic acid is obtained.

2. The preparation method of citraconic acid according to claim 1, characterized in that, The tertiary amine compound is one of triethylamine, tripropylamine, N,N-dimethylisobutylamine, N,N-dimethylbutylamine, N,N-diethylaniline.

3. The preparation method of citraconic acid according to claim 1, wherein, In step (1), the molar ratio of itaconic acid, nickel acetylacetonate dihydrate, tertiary amine compound and water is 1:(0.012 - 0.015):(3.5 - 6.5):(7.2 - 21.7).

4. The preparation method of citraconic acid according to claim 1, wherein, In step (1), the reaction temperature is 90 - 100 °C and the reaction time is 4 - 6 h.

5. The preparation method of citraconic acid according to claim 1, characterized in that, In step (1), when dropping the tertiary amine compound, control the temperature of the solution at 20 ± 5 °C, the stirring time is 25 - 35 min, and cool down to 10 - 30 °C.

6. The preparation method of citraconic acid according to claim 1, characterized in that, In step (2), the specific operation of decolorizing the solution containing citraconic acid is: add activated carbon to the solution containing citraconic acid and carry out decolorization treatment at 50 - 60 °C; the addition amount of activated carbon is 2% - 4% of the mass of the solution containing citraconic acid.

7. The preparation method of citraconic acid according to claim 1, wherein In step (2), the alkali is a NaOH solution with a mass fraction of 30 - 35%, and the molar ratio of NaOH to itaconic acid in the NaOH solution is (1.5 - 2.5):

1.

8. The preparation method of citraconic acid according to claim 1, characterized in that, In step (2), the stirring temperature is 20 - 30 °C and the stirring time is 8 - 12 min.

9. The preparation method of citraconic acid according to claim 1, characterized in that, In step (3), the acid is hydrochloric acid with a mass fraction of 35 - 37%, and the pH after acidification is 3.5 - 4.

5.

10. The preparation method of citraconic acid according to claim 1, characterized in that, In step (3), the crystallization temperature is 10 - 30 °C, the drying method is vacuum drying, and the drying temperature is 65 - 75 °C.

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