Process for the preparation of high purity aconitate esters

Abstract

The application discloses a preparation method of high-purity aconitate, and belongs to the technical field of aconitate preparation. The preparation method comprises the following steps: (1) reacting aconitic acid obtained through fermentation with alcohol to obtain a solution containing aconitate, and after neutralizing the solution containing aconitate, the upper organic phase is taken by liquid separation; (2) adding hydrogen peroxide to the upper organic phase for one-step decolorization, and then washing, separating and desolubilizing to obtain a crude aconitate product; (3) adding a decolorizing agent to the crude aconitate product for two-step decolorization, and then filtering to obtain high-purity aconitate; the decolorizing agent is selected from at least one of activated carbon, diatomite, kaolin, basic aluminum oxide and neutral aluminum oxide. The preparation method removes pigment impurities carried in aconitic acid raw materials in the preparation process of aconitate, and can effectively improve the purity of aconitate on the basis of ensuring that the aconitate reaction proceeds smoothly.

Description

Technical Field

[0001] This application relates to a method for preparing high-purity aconitine esters, belonging to the field of aconitine ester preparation technology. Background Technology

[0002] Currently, aconitic acid production is mainly divided into fermentation and chemical synthesis. Fermentation mainly relies on strains to convert sugar into aconitic acid; chemical synthesis involves heating citric acid to remove one molecule of water to form aconitic acid. However, this process requires extremely high temperatures and is very demanding, making it difficult to achieve mass production of aconitic acid. Therefore, fermentation is currently the most widely used method. However, aconitic acid obtained by fermentation will produce many impurities during the preparation process, with the proportion of impurities ranging from 2% to 40%. These impurities are mainly polysaccharides, pigments, and trace amounts of mycelium and protein.

[0003] While pigments constitute a relatively small percentage, typically between 1% and 5%, their presence significantly impacts the product's color. Aconitic acid, as a raw material for aconitate synthesis, will remain as a pigment impurity in the synthesized aconitate if not decolorized. This pigment impurity will then greatly affect the final product's color and subsequent applications. Furthermore, the presence of polysaccharides significantly influences the purity and yield of aconitate. On one hand, polysaccharides hydrolyze into monosaccharides under acidic conditions. These monosaccharides, rich in hydroxyl groups and alcohols, compete with aconitic acid for esterification, resulting in impure aconitate products and reduced yield. On the other hand, polysaccharides undergo caramelization at high temperatures, increasing the color and decreasing the purity of aconitate, further affecting its usability.

[0004] Currently, for the decolorization and purification of acids, the following methods are used: For acids with low solubility, the dissolution and precipitation method is used. By preparing a concentrated solution of the acid and heating it, the acid precipitates as the temperature decreases due to its low solubility. At this point, the pigments and impurities have not yet reached the precipitation limit, thus achieving effective purification. For acids with high solubility, the salt precipitation method is used. A concentrated solution of the acid is prepared and a salt (such as a calcium salt) is added to form a precipitate with the acid. The high solubility allows as much of the acid as possible to precipitate, while the pigments and impurities precipitate less and can be further washed away, thus achieving effective purification as well.

[0005] Aconitic acid has high solubility. When its concentrated solution precipitates as the temperature decreases, pigment impurities also precipitate out. However, when using salt precipitation, the high solubility of aconitate salts makes effective precipitation difficult, and the precipitated product is even harder to retain during further washing and purification. Decolorizing and purifying aconitic acid requires extraction with polar organic solvents followed by decolorization with adsorbents. These steps are cumbersome, and incomplete removal of the organic extract can affect subsequent aconitate ester synthesis reactions. Therefore, fermented aconitic acid is difficult to separate from pigments, inevitably resulting in synthesized aconitate esters containing pigment impurities, leading to increased color and decreased purity in the aconitate ester product.

[0006] Chinese patent application number 200810195075.4 discloses a method for preparing tributyl citrate using a rare earth salt binary compound solid acid catalysis. This method involves simultaneously adding activated carbon and hydrogen peroxide to crude tributyl citrate without washing and solvent removal steps for decolorization. However, this method is ineffective. While it is effective for citrate esters with high purity and low color intensity, it struggles to effectively remove the pigments from aconitate esters, which have high pigment content and color intensity. Summary of the Invention

[0007] To address the aforementioned issues, a method for preparing high-purity aconitine esters is provided. This method involves a decolorization step prior to the solvent removal step, whereby the fat-soluble pigments in the aconitine esters are first destroyed and oxidized to reduce the color impact caused by these pigments. After solvent removal, a decolorizing agent is then used to selectively remove both the water-soluble pigments and the destroyed fat-soluble pigments from the aconitine esters. The combination of these two steps enhances the decolorization and impurity removal effect on aconitine esters, resulting in high-purity aconitine esters and expanding their application range.

[0008] This application provides a method for preparing high-purity aconitine ester, comprising the following steps:

[0009] (1) The aconitic acid obtained by fermentation is reacted with alcohols to obtain a solution containing aconitic acid esters. The solution containing aconitic acid esters is neutralized and the upper organic phase is separated.

[0010] (2) Hydrogen peroxide was added to the upper organic phase for one-step decolorization, followed by washing, separation and solvent removal to obtain crude aconitate ester product;

[0011] (3) Add a decolorizing agent to the crude aconitine ester product for two-step decolorization, and then filter to obtain high-purity aconitine ester;

[0012] The decolorizing agent is selected from at least one of activated carbon, diatomaceous earth, kaolin, and alumina.

[0013] Aconitic acid obtained through fermentation contains a significant amount of pigments, and different types of pigments exhibit distinct differences in their solubility in organic solvents and water. The pigments in fermented aconitic acid fall into two categories: fat-soluble pigments, primarily anthraquinone compounds, most of which contain double bonds and are highly compatible with aconitic acid esters, making them difficult to adsorb; and water-soluble pigments, which enter the organic phase with a small amount of water during washing and remain in the product after desolvation and dehydration, thus proving difficult to completely remove during the washing stage.

[0014] It typically reacts with oxidizing agents (such as hydrogen peroxide) (bleaching). This preparation method involves a one-step and two-step decolorization process during the preparation of aconitate esters. The one-step decolorization primarily oxidizes and destroys the structure of fat-soluble pigments. Hydrogen peroxide oxidizes and destroys the double bonds in these pigments, causing an oxidation reaction that decomposes the organic skeleton of the pigment, producing hydroquinone, aldehydes, etc. Therefore, by destroying the main structure of the fat-soluble pigments, the color intensity can be effectively reduced. Furthermore, while removing the color intensity of fat-soluble pigments, hydrogen peroxide also increases the absorption rate of fat-soluble pigments by the decolorizing agent. Combined with the two-step decolorization, this effectively reduces the content of fat-soluble pigments in aconitate esters. However, hydrogen peroxide and aconitate esters are immiscible, so washing with water is necessary after decolorization. Therefore, placing the hydrogen peroxide decolorization step before the washing and desolvation steps can not only fully decolorize fat-soluble pigments, but also ensure that the hydrogen peroxide is removed in the subsequent washing step. If the decolorization step is placed after the desolvation step, the introduction of hydrogen peroxide will cause aconitate to form oil-water separation, and further removal of hydrogen peroxide is still required, which makes the process cumbersome and reduces the removal rate of fat-soluble pigments.

[0015] A second-step decolorization process is performed after the solvent removal step, primarily to remove water-soluble pigments. The decolorizing agent used is evenly distributed in aconitine esters, and it only uniformly decolorizes aconitine esters in one phase, thereby effectively reducing the content of water-soluble pigments in aconitine esters. If the decolorizing agent is placed before the washing step or decolorized together with hydrogen peroxide, the decolorizing agent has different affinities with aconitine esters and solvent phases, resulting in the decolorizing agent being absorbed by different liquid phases and forming clumps. These clumps are dispersed in aconitine esters and are difficult to mix evenly with aconitine esters, resulting in insufficient contact between the decolorizing agent and aconitine esters, reduced decolorization effect, and decreased removal rate of water-soluble pigments.

[0016] Optionally, the concentration of the hydrogen peroxide is 33-40%, and the weight of the hydrogen peroxide accounts for 1-5% of the weight of the upper organic phase.

[0017] Optionally, the weight ratio of the decolorizing agent to the crude aconitate product is 1:(2-100).

[0018] The double bonds in fat-soluble pigments are alkyl chains, which are not significantly sterically hindered and are easily broken. In contrast, the double bonds in aconitine esters are located between two sterically hindered ester groups, making them difficult to break. Therefore, the concentration and weight of hydrogen peroxide mentioned above can quickly break the double bonds of fat-soluble pigments, thereby increasing the removal rate. Furthermore, this concentration and weight of hydrogen peroxide will not break the double bonds in aconitine esters, thus increasing the yield of aconitine esters. The strong oxidizing property of hydrogen peroxide oxidizes the chromophores in fat-soluble pigments into colorless functional groups. Therefore, the structure of the fat-soluble pigment with broken double bonds changes, and it no longer absorbs light. This concentration of hydrogen peroxide has the best bleaching effect on pigments in aconitine esters. This dosage ensures that the decolorizing agent is uniformly dispersed in the aconitine ester, improving the adsorption effect on both structurally altered fat-soluble and water-soluble pigments, and facilitating subsequent removal of the decolorizing agent. When the dosage exceeds 5%, hydrogen peroxide will cause hydrolysis of aconitine esters, thus affecting the yield.

[0019] Optionally, the hydrogen peroxide is decolorized in one step at a temperature of 20-70°C for a time of 15-30 minutes.

[0020] Optionally, the decolorizing agent is used for two-step decolorization at a temperature of 20-70°C for a time of 10-120 minutes.

[0021] Optionally, fat-soluble pigments include anthraquinone compounds; water-soluble pigments include terbinazone.

[0022] Temperature is a crucial factor in the decolorization of aconitic acid carrying pigment impurities. Higher temperatures result in lower viscosity and better flowability of the product system, leading to a more uniform distribution of the decolorizing agent. However, higher temperatures also intensify Brownian motion, making it more difficult for the decolorizing agent to adsorb pigments, thus reducing the removal rate of pigment impurities. In the decolorization of citrate esters, the presence of hydroxyl groups in the structure of citric acid facilitates hydrogen bonding with other hydroxyl groups and ester groups, causing product molecule aggregation. Activated carbon used for this process has poor adsorption performance; therefore, high temperatures are required to break down molecular aggregation and achieve decolorization.

[0023] The first-step and second-step decolorization temperatures of this application are relatively low. Firstly, this can reduce energy consumption in the decolorization process. Secondly, research has shown that the lower the decolorization temperature, the lower the Brownian motion of the molecules, and the better the decolorization effect. Therefore, the above-mentioned decolorization temperature and time can effectively improve the removal efficiency and removal rate of pigment impurities, thereby improving the purity of aconitate.

[0024] Optionally, the activated carbon has an iodine value > 800 and a cyanine value > 10; the diatomaceous earth has a particle size of 200-300 mesh; the kaolin has a particle size of 200-300 mesh; the alkaline alumina and neutral alumina both have a particle size of 100-200 mesh and a specific surface area of ​​60-90 m². 2 / g, with an average pore size of 10-20nm. The above-mentioned decolorizing agent configuration ensures uniform dispersion within the aconitate phase, preventing agglomeration or clustering. Furthermore, this decolorizing agent increases the contact area with water-soluble pigments and lipid-soluble pigments with broken double bonds, facilitating the adsorption and storage of these two pigments and other impurities within the pores of the decolorizing agent itself. This enhances the adsorption capacity for pigments, prevents pigments from escaping again after adsorption, and thus improves the removal efficiency of water-soluble and lipid-soluble pigments and impurities.

[0025] Alumina itself has a large adsorption area and pores for adsorbing pigments. In the above system, since sugars and pigment impurities are generally acidic, choosing alkaline alumina and neutral alumina as decolorizing agents can increase the adsorption capacity for sugars and pigment impurities and improve the removal rate of pigment impurities and sugars.

[0026] Optionally, the decolorizing agent is selected from activated carbon.

[0027] Optionally, the purity of the high-purity aconitate is not less than 99%.

[0028] Optionally, the color of the high-purity aconitine ester is not higher than 50 Pt-Co.

[0029] Traditional methods can produce aconitate esters with a purity of up to 95% and a color intensity above 500 Pt-Co, obtained using the platinum-cobalt colorimetric method. The preparation method described in this application involves a one-step and a two-step decolorization process during the synthesis of aconitate esters, resulting in an order-of-magnitude improvement in decolorization. This not only reduces the color intensity but also lowers the impurity content, increasing the product purity to at least 99%, demonstrating a significant purification effect.

[0030] Optionally, the content of fat-soluble pigments in the high-purity aconitine ester is less than 1000 ppm, and the content of water-soluble pigments is less than 1000 ppm.

[0031] The preparation method of this application is applicable to the reaction of aconitic acid with any alcohol. The alcohol can be a single alcohol, in which case a single aconitic acid ester is prepared, where the substituents on a single aconitic acid are the same. Alternatively, it can be a mixed alcohol, in which case a mixed aconitic acid ester is prepared, where the substituents on a single aconitic acid can be three of the same, two of the same and one different, or all three different.

[0032] Optionally, the alcohol in step (1) is selected from methanol, ethanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, propanol, isopropanol, n-butanol, isobutanol, tert-butanol, 4-methyl-2-butanol, 2-ethylbutanol, 3,3-dimethyl-2-butanol, 4-phenylbutanol, n-pentanol, isopentanol, tert-pentanol, 2-methylpentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-ethyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, n-hexanol, 2-hexanol, 3-hexanol, and 2-ethylhexanol. At least one of the following: 3,5,5-trimethylhexanol, n-heptanol, 2-heptanol, 3-heptanol, 2-methylheptanol, 4-methyl-3-heptanol, 3-propylheptanol, 2,6-dimethyl-4-heptanol, n-octanol, 2-octanol, n-nonanol, 2-nonanol, 3-nonanol, 5-ethyl-2-nonanol, 2,6,8-trimethyl-4-nonanol, n-decanol, isodecanol, undecanol, dodecanol, cyclohexanol, cyclohexylmethanol, chloroethanol, 1-chloro-2-propanol, 3-chloro-1-propanol and 2-chloro-1-propanol, benzyl alcohol and phenylethanol.

[0033] Optionally, the aconitic acid obtained from fermentation reacts with alcohols at a temperature of 75-145°C for a reaction time of 2-8 hours. Under the action of the catalyst of this application, the above-mentioned reaction temperature and reaction time can both improve the esterification reaction efficiency and avoid reducing the purity of aconitic esters and increasing the color of aconitic esters due to fermentation-derived aconitic acid.

[0034] Below 75℃, the efficiency of the esterification reaction decreases significantly. Higher utilization or yield requires a longer reaction time. Polysaccharides, due to their large steric hindrance, are difficult to esterify. However, a longer reaction time allows acidic catalysts to promote the hydrolysis of polysaccharides into monosaccharides, leading to competition between monosaccharides with abundant hydroxyl groups and alcohols for the esterification of aconitic acid. Above 145℃, polysaccharides undergo caramelization, producing dark brown sugar dehydration polymers, which deepen the color of aconitic esters. Small amounts of these sugar dehydration polymers can be absorbed by activated carbon, but excessive amounts are difficult to remove and clog the pores of activated carbon, reducing its adsorption efficiency. Therefore, only at this temperature and with effective treatment can low-color, high-purity aconitic esters be obtained.

[0035] The esterification time in this application is also determined by the aconitic acid from fermentation. Due to its high impurity content, fermented aconitic acid significantly affects the reaction rate. When the time is too short, the reaction is incomplete, making it difficult to obtain a high yield. When the time is too long, a large amount of polysaccharide hydrolysis occurs during the reaction, and the resulting monosaccharides compete with alcohols for the esterification reaction, leading to low product purity. Therefore, only by carrying out the esterification reaction within this time period can high-purity, low-color, and high-yield aconitic ester be obtained.

[0036] Optionally, in step (1), a dehydrating agent and catalyst are added to aconitic acid and alcohol solvent in a molar ratio of 1:(3-9), and the mixture is stirred at 75-145℃ for 2-8 hours to obtain a solution containing aconitic acid ester. The solution containing aconitic acid ester is neutralized by an alkaline washing solution and then separated to obtain the upper organic phase.

[0037] Preferably, the stirring speed is 100-1200 rpm.

[0038] Optionally, the dehydrating agent is selected from at least one of toluene, benzene, and cyclohexane, preferably toluene, and the molar ratio of the dehydrating agent to the aconitine is (0-5):1.

[0039] Optionally, the weight ratio of the catalyst to aconitic acid is 1:(2-100), and the catalyst is selected from homogeneous and heterogeneous catalysts. When a heterogeneous catalyst is used, no dehydrating agent is required, and the molar ratio of the dehydrating agent to aconitic acid is 0:1. When a homogeneous catalyst is used, a dehydrating agent needs to be added, and the molar ratio of the dehydrating agent to aconitic acid is (1-5):1.

[0040] Preferably, the homogeneous catalyst is selected from at least one of p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, dinitrobenzoic acid, diethylaminetetraacetic acid, trichloroacetic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, alkyl sulfuric acid, dodecylbenzenesulfonic acid, aminosulfonic acid, tetrabutyl titanate, isopropyl titanate, stannous octoate, stannous chloride, antimony acetate, cobalt acetate, and manganese acetate, preferably p-toluenesulfonic acid or p-toluenesulfonic acid monohydrate. The above-mentioned homogeneous catalyst can maximize the efficiency, completeness, and speed of the esterification reaction, reduce the formation of by-products, achieve high esterification reaction efficiency, good product quality, and low energy consumption. In the presence of this homogeneous catalyst, toluene, benzene, or cyclohexane are used as dehydrating agents to remove water from the reaction and separate the water content. Simultaneously, it can effectively mix aconitic acid with alcohols, promoting catalytic efficiency and increasing the reaction rate.

[0041] Preferably, the heterogeneous catalyst is selected from at least one of sodium bisulfate monohydrate, sodium bisulfate, potassium bisulfate, copper sulfate, ferric sulfate, titanium sulfate, aluminum sulfate, ferrous sulfate, cerium sulfate, lanthanum sulfate, magnesium sulfate, citric acid sulfate, ferrous sulfate, ferric ammonium sulfate, cerium methanesulfonate, ferric chloride, tin tetrachloride, titanium chloride, rare earth chloride, potassium hydroxide, sodium hydroxide, potassium bicarbonate, sodium bicarbonate, sodium carbonate, anion exchange resin, strong acid cation exchange resin, weak acid cation exchange resin, potassium aminosulfonate, sodium aminosulfonate, tetrabutylammonium chloride, tetrabutylammonium bromide, and copper methanesulfonate, preferably sodium bisulfate monohydrate or sodium bisulfate. This heterogeneous catalyst can maximize the efficiency, completeness, and speed of the esterification reaction under relatively low temperature conditions, reduce the formation of by-products, achieve high esterification reaction efficiency, good product quality, low energy consumption, and is easy to separate and process. The recovered catalyst can be reused, further reducing industrialization costs.

[0042] Traditional esterification reactions use concentrated sulfuric acid as a catalyst. Concentrated sulfuric acid possesses both strong oxidizing and strong acidic properties. While it can catalyze the reaction, it carbonizes the mycelium and proteins in the fermented aconitic acid, leading to complex and difficult-to-process aconitic esters. The aforementioned homogeneous and heterogeneous catalysts replace traditional concentrated sulfuric acid. These catalysts do not simultaneously possess strong oxidizing and acidic properties, effectively suppressing side reactions in the esterification reaction. For example, p-toluenesulfonic acid is a strong acid but has no oxidizing properties, and sodium bisulfate is inherently weaker than concentrated sulfuric acid, resulting in fewer side reactions and higher product color and purity. Therefore, the types of homogeneous and heterogeneous catalysts mentioned above are all based on fermented aconitic acid, further improving the yield and purity of aconitic esters and reducing the color of aconitic esters in the esterification reaction of aconitic acid with alcohols.

[0043] Optionally, when a heterogeneous catalyst is used, the reaction solution is obtained by filtration after the aconitic acid reacts with the alcohol.

[0044] Optionally, the reaction solution is neutralized by three alkaline washings with an alkaline washing solution, and the alkaline washing residue and salts generated by the alkaline washing reaction are removed by three water washings. The upper organic phase is then separated and collected.

[0045] Optionally, the solute in the alkaline washing solution is at least one of NaOH, NaHCO3, and Na2CO3.

[0046] Preferably, the mass fraction of the solute in the alkaline washing solution is 5-25%.

[0047] Preferably, the alkaline washing solution is used to neutralize the reaction solution at a temperature of 20-70°C for a time of 15-30 minutes.

[0048] Optionally, the desolventizing temperature in step (2) is 40-100℃ and the vacuum degree is 0.01mbar-100mbar.

[0049] Impurities in aconitic acid are mainly monosaccharides and polysaccharides. Monosaccharides, such as mannose, glucose, and galactose, have small molecular weights and contain a large number of hydroxyl groups, competing with alcohols for esterification and significantly reducing product purity. Polysaccharides have large molecular weights and complex structures, containing a large number of hydroxyl groups and also exhibiting significant steric hindrance. Although their reaction rate with aconitic acid is slow, once esterified, their significant steric hindrance makes it difficult for the other two carboxylic acids to esterify, thus affecting the product yield and purity. Therefore, both monosaccharides and polysaccharides greatly reduce the rate and purity of the aconitic acid esterification reaction.

[0050] Therefore, at the above temperature, the reaction rate of aconitic acid with alcohols is much greater than that with impurity sugars. The amount of catalyst and alcohol used allows aconitic acid to be esterified with alcohols as much as possible, improving the reaction conversion rate of aconitic acid. Furthermore, the unreacted sugars and other impurities mentioned above can also be removed through one-step and two-step decolorization processes, further improving the purity of aconitic acid esters.

[0051] The beneficial effects of this application include, but are not limited to:

[0052] 1. According to the preparation method of this application, the pigment impurities in the aconitic acid raw material obtained by fermentation are removed during the preparation of aconitic acid ester. On the basis of ensuring the smooth progress of the aconitic acid ester reaction, the purity of aconitic acid ester can be effectively improved, and the color problem of aconitic acid esterification products from fermentation is solved.

[0053] 2. According to the preparation method of this application, the fat-soluble pigments and water-soluble pigments of aconitic acid are decolorized and removed stepwise by one-step decolorization and two-step decolorization processes, which can improve the impurity removal effect on aconitic acid esters and increase the purity of aconitic acid esters from 95% to greater than or equal to 99%, so as to obtain high-purity aconitic acid esters.

[0054] 3. The aconitate obtained by the preparation method of this application has high purity and low color. When added to plastic products as a plasticizer, it will not affect the color of the plastic products themselves, but will improve the appearance quality and enhance the plasticizing effect on the plastic products.

[0055] 4. According to the preparation method of this application, the decolorization process of hydrogen peroxide and decolorizing agent can achieve decolorization at low temperature, which can reduce energy consumption in the decolorization process and improve decolorization efficiency and pigment removal rate.

[0056] 5. According to the preparation method of this application, the esterification reaction conditions of aconitic acid with alcohols, the type and amount of catalyst, the type and amount of dehydrating agent, the type of alkaline washing solution and the neutralization temperature are coordinated to improve the reaction conversion rate of aconitic acid. Combined with one-step decolorization and two-step decolorization processes, the synthesized aconitic acid ester has the characteristics of high purity, low acid value and low color. Attached Figure Description

[0057] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0058] Figure 1 This is a product diagram of aconitine tributyl aconitine involved in Comparative Example 1 of this application.

[0059] Figure 2 This is a product diagram of aconitine tributyl aconitine involved in Example 1 of this application.

[0060] Figure 3 This is a product diagram of tributyl citrate involved in Comparative Example 4 of this application.

[0061] Figure 4 This is a product diagram of tributyl citrate involved in Comparative Example 5 of this application.

[0062] Figure 5 This is the liquid phase spectrum of tributyl aconitate involved in Comparative Example 1 of this application.

[0063] Figure 6 This is the liquid phase spectrum of aconitine tributyl aconitine involved in Example 1 of this application. Detailed Implementation

[0064] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0065] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0066] Example 1

[0067] This embodiment provides a method for preparing pure aconitine tributyl ester, comprising the following steps:

[0068] (1) Mix 30g aconitic acid and 51g n-butanol and stir to dissolve. After the aconitic acid is completely dissolved, add 2.7g sodium bisulfate catalyst (purity 99%) and esterify at 125℃ and 300rpm for 6h. Separate the water produced by esterification in time during the reaction. After the reaction is completed, a solution containing aconitic acid ester is obtained. Add an equal volume of alkaline washing solution to the solution containing aconitic acid ester for neutralization reaction. Repeat three times and take out the upper organic phase. The mass fraction of solute in the alkaline washing solution is 5%, the solute is Na2CO3, the neutralization temperature is 40℃, and the neutralization time is 20min.

[0069] (2) Add 3% hydrogen peroxide (35% concentration) of the weight of the upper organic phase to the upper organic phase and decolorize at 30°C for 15 min. Then wash with water to remove hydrogen peroxide, alkaline washing residue and salts generated by alkaline washing reaction. Separate the upper layer and desolvent at 70°C and vacuum degree of 50mbar until no fraction is distilled off to obtain crude aconitine ester product.

[0070] (3) Add activated carbon with an iodine value of 810 and an alpha value of 12 to the crude aconitine product. The weight ratio of activated carbon to crude aconitine product is 1:7. Perform a two-step decolorization at 30°C for 30 minutes, and then filter to obtain pure tributyl aconitine product. See the product appearance picture below. Figure 2 The liquid phase spectrum is shown below. Figure 6 The detection wavelength is 230nm. Specific detection information is shown in Table 1 below. Peak 6 is tributyl cis-aconitate, and peak 8 is tributyl trans-aconitate. The purity of the product is 99.818%, which is rounded to 99.8%.

[0071] Table 1

[0072] 1 2.898 1632 367 0.015 2 3.209 3346 582 0.030 3 4.282 2300 288 0.021 4 5.375 4709 673 0.043 5 6.114 1551 228 0.014 6 7.547 125317 14261 1.134 7 9.273 4619 449 0.042 8 11.021 10901651 880085 98.684 9 13.226 1933 130 0.017

[0073] Example 2

[0074] This embodiment provides a method for preparing pure aconitine tri(2-ethylhexyl) ester, comprising the following steps:

[0075] (1) Mix 30g aconitic acid, 112g 2-ethylhexanol and 50g toluene dehydrating agent and stir to dissolve. After the aconitic acid is completely dissolved, add 15g p-toluenesulfonic acid monohydrate catalyst (purity 99%) and esterify at 145℃ and 1200rpm for 8h. Separate the water produced by esterification in time during the reaction. After the reaction is completed, a solution containing aconitic acid ester is obtained. Add an equal volume of alkaline washing solution to the solution containing aconitic acid ester for neutralization reaction. Repeat three times and take out the upper organic phase. The mass fraction of solute in the alkaline washing solution is 5%, the solute is Na2CO3, the neutralization temperature is 40℃ and the neutralization time is 20min.

[0076] (2) Add 1% by weight of 40% hydrogen peroxide to the upper organic phase and decolorize at 50°C for 20 min. Then wash with water to remove hydrogen peroxide, alkaline washing residue and salts generated by alkaline washing reaction. Separate the upper layer and desolvent at 90°C and vacuum degree of 10mbar until no fraction is distilled off to obtain crude aconitine ester product.

[0077] (3) Add activated carbon with an iodine value of 810 and an iodine value of 12 to the crude aconitine product. The weight ratio of activated carbon to crude aconitine product is 1:9. Decolorize in two steps at 50°C for 40 min. Then filter to obtain pure aconitine tri(2-ethylhexyl) ester product.

[0078] Example 3

[0079] This embodiment provides a method for preparing pure triethyl aconitate, comprising the following steps:

[0080] (1) Mix 30g aconitic acid, 71.4g ethanol and 50g toluene dehydrating agent and stir to dissolve. After the aconitic acid is completely dissolved, add 15g p-toluenesulfonic acid monohydrate catalyst (purity 99%) and esterify at 75℃ and 100rpm for 2h. Separate the water produced by esterification in time during the reaction. After the reaction is completed, a solution containing aconitic acid ester is obtained. Add an equal volume of alkaline washing solution to the solution containing aconitic acid ester for neutralization reaction. Repeat three times and take out the upper organic phase. The mass fraction of solute in the alkaline washing solution is 25%, the solute is NaOH, the neutralization temperature is 20℃ and the neutralization time is 30min.

[0081] (2) Add 5% by weight of 33% hydrogen peroxide to the upper organic phase and decolorize at 70°C for 30 min. Then wash with water to remove hydrogen peroxide, alkaline washing residue and salts generated by alkaline washing reaction. Separate the upper layer and desolvent at 40°C and vacuum degree of 100mbar until no fraction is distilled off to obtain crude aconitine ester product.

[0082] (3) Add diatomaceous earth with a particle size of 200 mesh to the crude aconitine ester product. The weight ratio of diatomaceous earth to crude aconitine ester product is 1:2. Decolorize in two steps at 50℃ for 120 min. Then filter to obtain pure aconitine tri(2-ethylhexyl) ester product.

[0083] Example 4

[0084] This embodiment provides a method for preparing pure aconitine mixed esters, comprising the following steps:

[0085] (1) Mix 30g aconitic acid, 25.5g n-butanol and 22.4g 2-ethylhexanol and stir to dissolve. After the aconitic acid is completely dissolved, add 2.7g sodium bisulfate catalyst (purity 99%) and esterify at 125℃ and 600rpm for 6h. Separate the water produced by esterification in time during the reaction. After the reaction is completed, a solution containing aconitic acid ester is obtained. Add an equal volume of alkaline washing solution to the solution containing aconitic acid ester for neutralization reaction. Repeat three times and take out the upper organic phase. The mass fraction of solute in the alkaline washing solution is 5%, the solute is NaHCO3, the neutralization temperature is 70℃ and the neutralization time is 15min.

[0086] (2) Add 3% by weight of 35% hydrogen peroxide to the upper organic phase and decolorize at 30°C for 15 min. Then wash with water to remove hydrogen peroxide, alkaline washing residue and salts generated by alkaline washing reaction. Separate the upper layer and desolvent at 100°C and vacuum degree of 0.01mbar until no fraction is distilled off to obtain crude aconitate ester product.

[0087] (3) Add kaolin with a particle size of 300 mesh to the crude aconitine ester product. The weight ratio of kaolin to crude aconitine ester product is 1:100. Decolorize in two steps at 30℃ for 10 min. Then filter to obtain pure aconitine mixed ester product.

[0088] Example 5

[0089] The difference between this embodiment and embodiment 1 is that the concentration of hydrogen peroxide in step (2) is 30%, while the amount and steps of the other substances are the same as in embodiment 1.

[0090] Example 6

[0091] The difference between this embodiment and embodiment 1 is that the concentration of hydrogen peroxide in step (2) is 45%, while the amount of other substances and the steps are the same as in embodiment 1.

[0092] Example 7

[0093] The difference between this embodiment and embodiment 1 is that the weight of hydrogen peroxide in step (2) accounts for 8% of the weight of the upper organic phase, while the amount and steps of the remaining substances are the same as in embodiment 1.

[0094] Example 8

[0095] The difference between this embodiment and embodiment 1 is that the weight of hydrogen peroxide in step (2) accounts for 0.5% of the weight of the upper organic phase, while the amount and steps of the remaining substances are the same as in embodiment 1.

[0096] Example 9

[0097] The difference between this embodiment and embodiment 1 is that the decolorization temperature of hydrogen peroxide in step (2) is 80°C, while the amount of other substances and steps are the same as in embodiment 1.

[0098] Example 10

[0099] The difference between this embodiment and embodiment 1 is that the decolorization time of hydrogen peroxide in step (2) is 10 minutes, while the amount of other substances and steps are the same as in embodiment 1.

[0100] Example 11

[0101] The difference between this embodiment and embodiment 1 is that the weight ratio of activated carbon to crude aconitine ester in step (3) is 1:120, while the amount of other substances and steps are the same as in embodiment 1.

[0102] Example 12

[0103] The difference between this embodiment and embodiment 1 is that the decolorization temperature of activated carbon in step (3) is 80°C, while the amount of other substances and steps are the same as in embodiment 1.

[0104] Example 13

[0105] The difference between this embodiment and embodiment 1 is that the decolorization temperature of activated carbon in step (3) is 10°C, while the amount of other substances and steps are the same as in embodiment 1.

[0106] Example 14

[0107] The difference between this embodiment and embodiment 1 is that the decolorization time of activated carbon in step (3) is 5 minutes, while the amount and steps of the other substances are the same as in embodiment 1.

[0108] Example 15

[0109] The difference between this embodiment and embodiment 1 is that the iodine value of the activated carbon in step (3) is 700 and the cyanine value is 10, while the amount of other substances and the steps are the same as in embodiment 1.

[0110] Example 16

[0111] The difference between this embodiment and Embodiment 1 is that: in step (3), a particle size of 200 mesh and a specific surface area of ​​90 m² are used. 2 / g, alkaline alumina with an average pore size of 15nm replaces activated carbon, and the amounts and steps of the remaining substances are the same as in Example 1.

[0112] Example 17

[0113] The difference between this embodiment and Example 1 is that in step (1), the raw materials are esterified at 200°C and 300 rpm for 6 hours, while the amount of other substances and the steps are the same as in Example 1.

[0114] Example 18

[0115] The difference between this embodiment and embodiment 1 is that the neutralization temperature in step (1) is 80°C, while the amount of other substances and the steps are the same as in embodiment 1.

[0116] Comparative Example 1

[0117] This comparative example provides a method for preparing pure aconitine tributyl ester, comprising the following steps:

[0118] (1) Mix 30g aconitic acid and 51g n-butanol and stir to dissolve. After the aconitic acid is completely dissolved, add 2.7g sodium bisulfate catalyst (purity 99%) and esterify at 125℃ and 300rpm for 6h. Separate the water produced by esterification in time during the reaction. After the reaction is completed, a solution containing aconitic acid ester is obtained. Add an equal volume of alkaline washing solution to the solution containing aconitic acid ester for neutralization reaction. Repeat three times and take out the upper organic phase. The mass fraction of solute in the alkaline washing solution is 5%, the solute is Na2CO3, the neutralization temperature is 40℃, and the neutralization time is 20min.

[0119] (2) The product was desolventized at 70℃ and a vacuum of 50mbar until no fraction was distilled off, yielding tributyl aconitate. See the product appearance image below. Figure 1 The liquid phase spectrum is shown below. Figure 5 The detection wavelength is 230nm. Specific detection information is shown in Table 2 below. Peak 16 is cis-tributyl aconitate, and peak 20 is trans-tributyl aconitate. The purity of the product is 93.854%, which is rounded to 93.9%.

[0120] Table 2

[0121]

[0122]

[0123] Comparative Example 2

[0124] This embodiment provides a method for preparing pure aconitine tributyl ester, comprising the following steps:

[0125] (1) Same as Example 1;

[0126] (2) Add activated carbon with an iodine value of 810 and an alpha value of 12 to the upper organic phase. The weight ratio of activated carbon to upper organic phase is 1:7. Decolorize at 30°C for 30 min, then filter and wash with water to remove alkaline washing residue and salts generated by alkaline washing reaction. Desolvate at 70°C and vacuum degree of 50 mbar until no fraction is distilled off to obtain crude aconitate ester.

[0127] (3) Add 3% hydrogen peroxide (35% concentration) of the crude aconitine to the crude aconitine product and decolorize in two steps at 30°C for 15 min. Then wash with water to remove hydrogen peroxide and desolvent at 70°C and 50 mbar until no fraction is distilled off to obtain the finished product of tributyl aconitine.

[0128] Comparative Example 3

[0129] This embodiment provides a method for preparing pure aconitine tributyl ester, comprising the following steps:

[0130] (1) Same as Example 1;

[0131] (2) Add 3% by weight of hydrogen peroxide with a concentration of 35% and an iodine value of 810 and an alpha value of 12 to the upper organic phase. The weight ratio of activated carbon to the upper organic phase is 1:7. Decolorize at 30°C for 30 min, then filter and wash with water to remove hydrogen peroxide, alkaline washing residue and salts generated by alkaline washing reaction. Desolvate at 70°C and vacuum degree of 50 mbar until no fraction is distilled off to obtain aconitine tributyl ester product.

[0132] Comparative Example 4

[0133] (1) Mix 33g citric acid and 51g n-butanol and stir to dissolve. After the citric acid is completely dissolved, add 2.7g sodium bisulfate catalyst (purity 99%) and esterify at 125℃ and 300rpm for 8h. Separate the water produced by esterification in time during the reaction. After the reaction is completed, a solution containing citrate ester is obtained. Add an equal volume of alkaline washing solution to the solution containing citrate ester for neutralization reaction. Repeat three times and take out the upper organic phase. The mass fraction of solute in the alkaline washing solution is 5%, the solute is Na2CO3, the neutralization temperature is 40℃, and the neutralization time is 20min.

[0134] (2) Desolventize at 70℃ and 50mbar until no fractions are distilled off to obtain tributyl citrate product. See the product appearance picture below. Figure 3 .

[0135] Comparative Example 5

[0136] The difference between this comparative example and comparative example 4 is that in step (2), hydrogen peroxide with a concentration of 35% and accounting for 3% of the weight of the upper organic phase is added to the upper organic phase, and activated carbon with an iodine value of 810 and an alpha value of 12 is added at the same time. The weight ratio of activated carbon to the upper organic phase is 1:7. The product is decolorized at 30°C for 30 minutes, then filtered, and washed with water to remove hydrogen peroxide, alkaline washing residue, and salts generated by the alkaline washing reaction. The product is desoluble at 70°C and a vacuum degree of 50 mbar until no fraction is distilled off, and tributyl citrate is obtained. The appearance of the product is shown in the figure. Figure 4 .

[0137] Test Example 1

[0138] The aconitate and citrate esters prepared in the above examples and comparative examples were tested for acid value, purity, color, yield, triester conversion rate, and water content. The specific test results are shown in Table 3 below, and the test methods are as follows:

[0139] 1. Acid value: Take 50 mL of ethanol, add 0.25 mL of phenolphthalein indicator solution, and prepare two aliquots for later use. Use 0.02 mol·L⁻¹ acid value solution. -1 Neutralize the potassium hydroxide aqueous solution to a light pink color and record the volume consumed, V0. Weigh 1 g of the sample (accurate to 0.01 g) into a ground-glass conical flask, then add one portion of the neutralized solution described above. After the sample is completely dissolved, use 0.02 mol·L⁻¹... -1 Titrate the sample with potassium hydroxide ethanol standard titration solution (the titration must be completed within 30 seconds) until a faint pink color appears and remains for 5 seconds without fading, which is the endpoint. Record the volume V consumed.

[0140] Acid value: X = (V - V0)cM) / m;

[0141] In the formula: X is the acid value of the sample (calculated as KOH), in milligrams per gram (mg·g). -1 V represents the volume of potassium hydroxide-ethanol standard titration solution consumed by the sample, in milliliters (mL); V0 represents the volume of potassium hydroxide-ethanol standard titration solution consumed by the blank test, in milliliters (mL); and c represents the exact concentration of the potassium hydroxide-ethanol standard titration solution, in moles per liter (mol·L⁻¹). -1 ), m is the mass of the sample in grams (g), and M is the molar mass of potassium hydroxide in grams per mole (g·mol⁻¹). -1 [M = 56.11].

[0142] 2. Purity: High-performance liquid chromatography (HPLC) was used. The instrument sensitivity and stability of the tester should comply with GB / T16631-2008. Column: C18 column; Injector: 10 μL microsyringe; Solvent: Acetonitrile (HPLC grade); Acquisition time: 15 min; Mobile phase: 80% acetonitrile (HPLC grade), 20% deionized water; Injection volume: 1 μL; Wavelength: 230 nm.

[0143] Experiment: Adjust the instrument according to the above specifications. After the baseline stabilizes, inject 0.2 μL of sample using a microsyringe. At the same time, start the integrator or chromatography workstation. The instrument will automatically provide the area percentage of each component.

[0144] Purity calculation formula: Purity = (Integrated area of ​​aconitine ester / Total integrated area) × 100%.

[0145] 3. Colorimetry: Preparation of Platinum-Cobalt Colorimetric Standard Solution No. 500: Weigh 1.2450g potassium chloroplatinate and 1.0000g cobalt chloride, accurate to 0.0002g, dissolve in 100mL hydrochloric acid, and then dilute with distilled water to 1000mL. This solution is the No. 500 colorimetric standard solution.

[0146] To prepare color standards of any number less than 500, take different amounts of the original 500 solution and dilute it with distilled water to the volume of the colorimetric tube. The calculation formula is as follows:

[0147] V = (N × V1) / 500

[0148] In the formula: V is the volume of the 500 standard stock solution taken to prepare the N color standard solution, mL; V1 is the volume of the colorimetric tube used, mL; N is the number of the color standard solution to be prepared.

[0149] After the sample is uniformly mixed, it is injected into a colorimetric tube and observed with the naked eye. It should be a transparent oily liquid with no turbidity and no obvious mechanical impurities. Colorimetric determination is carried out at 25℃.

[0150] 4. Yield: The efficiency of the reaction synthesis route is characterized by the yield. The yield calculation formula is: Yield = (mass of the final product / mass of the theoretically obtained aconitine ester) × 100%.

[0151] 5. Triester conversion rate: The characteristic peaks of aconitine esters (around 6.8) were analyzed by NMR spectrum. The formula for calculating the triester conversion rate is: Triester conversion rate = (Integrated area of ​​aconitine triester / Total area of ​​aconitine and aconitine esters (monoesters, diesters, and triesters) in this region) × 100%.

[0152] 6. Moisture content: The water content was measured using a Karl Fischer moisture analyzer (rounded to two decimal places).

[0153] 7. Residual amounts of fat-soluble pigments and water-soluble pigments:

[0154] High-performance liquid chromatography (HPLC) was used, and the instrument sensitivity and stability of the analyzer should comply with the requirements of GB / T16631-2008. Chromatographic column: C18 column; injector: 10 μL microsyringe; solvent: acetonitrile (HPLC grade); acquisition time: 15 min; mobile phase: 80% acetonitrile (HPLC grade), 20% deionized water; injection volume: 1 μL; wavelength: 230 nm.

[0155] Experiment: Adjust the instrument according to the above specifications. After the baseline stabilizes, inject 0.2 μL of sample using a microsyringe. Simultaneously start the integrator or chromatography workstation. Establish a pigment concentration-integral area standard curve by testing the integrated area of ​​pigments at different concentrations. When measuring pigment content, the instrument automatically provides the corresponding pigment integrated area. Compare the pigment concentration with the standard curve to obtain the pigment concentration. The ratio of pigment concentration to sample concentration is the pigment content.

[0156] Table 3

[0157]

[0158]

[0159] Based on the data in Table 3 and the comparison between Examples 5-8 and Example 1, it can be seen that the concentration and amount of hydrogen peroxide have a significant impact on the final color of the product. It needs to be within a reasonable range to achieve a color of less than 50. It is believed that excessive concentration or amount of hydrogen peroxide will increase the color of the product, and more hydrogen peroxide will participate in the hydrolysis of aconitine esters. Although the reaction rate is very slow, it will reduce the yield. Low amount or low concentration of hydrogen peroxide will cause incomplete bleaching of pigments in the product, and the pigments will not meet the requirements.

[0160] A comparison of Examples 9-10 and Example 1 shows that the higher the decolorization temperature of hydrogen peroxide, the more hydrogen peroxide decomposes, resulting in a poor oxidation effect on fat-soluble pigments. Consequently, the residual amount of fat-soluble pigments increases, leading to an increase in the color and a decrease in the purity of aconitine esters. At the same time, hydrogen peroxide promotes the hydrolysis of aconitine esters, resulting in a decrease in the yield of aconitine esters. Shortening the decolorization time of hydrogen peroxide affects its destructive effect on the main structure of fat-soluble pigments, further increasing the color and decreasing the purity of aconitine esters.

[0161] A comparison of Example 11 and Example 1 shows that when the amount of activated carbon is reduced, the amount of water-soluble pigments adsorbed decreases, thus increasing the residual amount of water-soluble pigments, resulting in an increase in the color and a decrease in the purity of aconitine ester.

[0162] A comparison of Examples 12-13 and Example 1 shows that the decolorization temperature of the decolorizing agent affects the decolorization effect on water-soluble pigments. The higher the temperature, the more intense the Brownian motion of the molecules, and the more difficult it is for the decolorizing agent to adsorb the pigments, which leads to a decrease in the removal rate of water-soluble pigment impurities. The lower the temperature, the lower the adsorption capacity of the decolorizing agent for water-soluble pigments. In addition, the high viscosity of aconitate is not conducive to the uniform dispersion of the decolorizing agent, which also leads to a decrease in the removal rate of water-soluble pigments, and consequently, a decrease in the purity and an increase in the color of aconitate.

[0163] A comparison between Example 14 and Example 1 shows that the shorter the decolorization time of the decolorizing agent, the worse the decolorization effect on water-soluble pigments, resulting in an increase in the color and a decrease in the purity of aconitate.

[0164] A comparison of Examples 15-16 and Example 1 shows that the type of decolorizing agent and the parameters of activated carbon can affect the removal effect of water-soluble pigments, thereby affecting the purity and color of aconitate products.

[0165] A comparison of Example 17 and Example 1 shows that an increase in esterification temperature leads to caramelization of polysaccharides. Under the same decolorization conditions, the content of both types of pigments in the final aconitate increases, resulting in increased product pigmentation and decreased purity. Furthermore, the monosaccharides produced by polysaccharide decomposition compete with alcohols for esterification with aconitic acid, leading to a decrease in the yield and triester conversion rate of aconitate.

[0166] A comparison of Example 18 and Example 1 shows that an increase in neutralization temperature leads to hydrolysis of the product in an alkaline environment, resulting in insufficient purity of the product. The decrease in purity increases the relative content of pigments in the product, which in turn affects the one-step and two-step decolorization processes, leading to an increase in the residual amount of fat-soluble and water-soluble pigments, an increase in the color and a decrease in the purity of aconitine ester, and a decrease in the yield of aconitine ester due to the loss caused by high-temperature hydrolysis.

[0167] Based on the comparison of Comparative Examples 1-3 and Example 1, it can be seen that the aconitate obtained without decolorization treatment has a high content of both water-soluble and fat-soluble pigments, the color of the product is greater than 500, and the purity decreases. When removing water-soluble pigments first and then fat-soluble pigments, or removing both types of pigments simultaneously, it not only increases the preparation process, but also affects the removal effect of the two types of pigments, resulting in an increase in the color of aconitate and a decrease in purity. Furthermore, when removing fat-soluble and water-soluble pigments simultaneously, activated carbon will agglomerate in the aqueous phase and distribute in the organic phase, resulting in poor decolorization effect of both pigments in the product, and the yield will decrease due to the agglomeration of activated carbon.

[0168] according to Figure 1-4 As can be seen from the comparison with Comparative Examples 4 and 5, the citrate ester itself has a low pigment content, so it is easy to decolorize and is not as difficult to decolorize as aconitate ester. Moreover, although the color intensity decreases before and after decolorization, the decrease in color intensity after decolorization is much smaller than that of this application.

[0169] Test Example 2

[0170] The aconitate and tributyl citrate prepared in the above examples and comparative examples were added to PVC resin as plasticizers to obtain PVC plastic, which included 100 parts of PVC resin, 35 parts of plasticizer, 2 parts of oxidized polyethylene wax, and 5 parts of octyltin maleate. After mixing the above raw materials, the same compounding process was used to prepare the PVC finished product. The performance of different plasticizers and the obtained PVC finished products in the above examples and comparative examples was tested. The results are shown in Table 4 below. The test methods are as follows:

[0171] 1. Hardness: Prepare and test specimens according to GB / T531-2008 "Indentation Hardness Test Method, Shore Hardness Tester Method". Select 3 points for each group of specimens, measure each point once, and take the median value.

[0172] 2.100% constant tensile stress, elongation at break, and modulus of elasticity: in accordance with GB / T1040–2006 "Test for tensile properties of plastics", the tensile speed is 50 mm / min and the temperature is 25℃.

[0173] 3. Compatibility: The water valence method was used for testing. Since water molecules are polar, the compatibility of plasticizers with water can characterize their compatibility with polar materials (PVC, PLA, and nitrile rubber). When a plasticizer has good compatibility with water, it has good compatibility with PVC, and vice versa. In the experiment, 2.5g of plasticizer and 25g of acetone were added to a beaker and titrated with a burette containing deionized water while stirring until turbidity appeared. The volume of deionized water consumed was recorded.

[0174] 4. Glass transition temperature (T) g Glass transition temperature was tested using a dynamic mechanical analyzer. Test conditions: nitrogen as carrier gas, test temperature range of -40 to 80℃, heating rate of 3℃ / min, and frequency of 1Hz.

[0175] Table 4

[0176]

[0177]

[0178] As shown in Table 4, the purity of aconitine esters has a significant impact on their performance as plasticizers. Lower purity aconitine esters result in lower hardness and TL of the composite material. g The higher the 100% constant tensile stress and elastic modulus, the worse the elongation at break and compatibility. In particular, comparing before and after decolorization, the hardness decreased by 12% and the toughness decreased by more than 14%. Therefore, decolorization can not only improve the color quality of the product itself, but its purification effect after decolorization can also improve the plasticizing performance of aconitate on PVC.

[0179] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing aconitate, characterized in that, Includes the following steps: (1) The aconitic acid obtained by fermentation and alcohol are reacted at 75-145℃ for 2-8h to obtain a solution containing aconitic acid ester. The solution containing aconitic acid ester is neutralized and the upper organic phase is taken by separation. (2) Hydrogen peroxide is added to the upper organic phase for one-step decolorization, followed by washing, separation, and solvent removal to obtain crude aconitate. The concentration of hydrogen peroxide is 33-40%, and the weight of hydrogen peroxide accounts for 1-5% of the weight of the upper organic phase. The temperature for one-step decolorization with hydrogen peroxide is 20-70 °C, and the time is 15-30 min. (3) Add a decolorizing agent to the crude aconitine ester product for two-step decolorization, and then filter to obtain aconitine ester. The weight ratio of the decolorizing agent to the crude aconitine ester product is 1:(2-100). The temperature for the two-step decolorization is 20-70 ℃ and the time is 10-120 min. The decolorizing agent is selected from at least one of activated carbon, diatomaceous earth, kaolin, alkaline alumina, and neutral alumina. The activated carbon has an iodine value >800 and a cyanine value >10. The diatomaceous earth has a particle size of 200-300 mesh. The kaolin has a particle size of 200-300 mesh. The alkaline alumina and neutral alumina both have a particle size of 100-200 mesh and a specific surface area of ​​60-90 m². 2 / g, average pore size 10-20 nm.

2. The preparation method according to claim 1, characterized in that, The decolorizing agent is selected from activated carbon.

3. The preparation method according to claim 1, characterized in that, The purity of the aconitate is not less than 99%.

4. The preparation method according to claim 1, characterized in that, The color of the aconitine ester is not higher than 50 Pt-Co.

5. The preparation method according to claim 1, characterized in that, The content of fat-soluble pigments in the aconitate is less than 1000 ppm, and the content of water-soluble pigments is less than 1000 ppm.

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