Synthetic method of anhydrous potassium citrate

Abstract

The invention provides a synthetic method of anhydrous potassium citrate, and relates to the technical field of organic salt crystallization. The synthesis method provided by the invention comprises the following steps: mixing citric acid and potassium ethoxide in absolute ethyl alcohol to react, and separating to obtain a potassium citrate crude product; dissolving the potassium citrate crude product in the eutectic solvent to prepare a potassium citrate crude solution; adding potassium citrate microcrystals into the potassium citrate crude solution, cooling, crystallizing and separating to obtain potassium citrate crystals; and immersing the potassium citrate crystal in molten citric acid, aging, separating, and washing to obtain the anhydrous potassium citrate. The synthesis method provided by the invention can effectively improve the particle size uniformity and fluidity of the anhydrous potassium citrate, and at the same time helps to improve the purity of the anhydrous potassium citrate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic salt crystallization, in particular to a synthesis method of anhydrous potassium citrate. BACKGROUND

[0002] Anhydrous potassium citrate (C6H5K3O7) is a colorless or white crystalline powder of citrate, which is widely used as an important additive in food, medicine, chemical industry and other fields. In the food industry, anhydrous potassium citrate is mainly used as an acidity regulator, a buffer, a stabilizer and an emulsifier; in the pharmaceutical industry, potassium citrate is used to prevent and treat hypokalemia and alkalize urine, help prevent and treat uric acid or cystine kidney stones; and in the chemical industry, potassium citrate can be used for the synthesis of chemical fertilizers, papermaking, electroplating and other industries.

[0003] The most basic synthesis method of potassium citrate at present is to carry out acid-base neutralization reaction of citric acid and potassium hydroxide or potassium bicarbonate in aqueous solution, and then obtain potassium citrate crystals by decolorizing and removing impurities, filtering, reducing pressure concentration, crystallization and other processes. In order to improve the purity of potassium citrate crystals, potassium hydroxide prepared by ion membrane method can be used as raw material to react with food-grade citric acid, for example, a preparation method of potassium citrate is provided in Chinese patent CN107286010A, citric acid aqueous solution is reacted with ion membrane liquid potassium hydroxide, then glucose is added for heat preservation, and anhydrous potassium citrate is prepared by reducing pressure concentration and evaporation crystallization.

[0004] However, glucose is added to remove excess chlorate in the reaction system, but glucose can also produce new impurity components which have a negative impact on the purity and transmittance of the crystalline product. In addition, the potassium citrate crystals prepared by it are easy to generate amorphous powder, which reduces the flowability of the crystals, and the uneven particle size distribution of the crystals and the decrease of the purity of the product are easy to occur in the disordered crystallization process. Therefore, it is urgent to provide a method to improve the above problems. SUMMARY

[0005] The purpose of the present application is to provide a synthesis method of anhydrous potassium citrate, which can effectively improve the uniformity of the particle size and the flowability of the anhydrous potassium citrate, and help to improve the purity of the anhydrous potassium citrate.

[0006] The synthesis method of anhydrous potassium citrate provided by the present application comprises: mixing citric acid and potassium ethoxide in anhydrous ethanol to obtain potassium citrate crude product after reaction; dissolving the potassium citrate crude product in a eutectic solvent to obtain a potassium citrate crude solution; adding potassium citrate microcrystals to the potassium citrate crude solution and then crystallizing and separating to obtain potassium citrate crystals; and immersing the potassium citrate crystals in molten citric acid for aging, then separating and washing to obtain anhydrous potassium citrate.

[0007] Optionally, the molar ratio of citric acid to potassium ethoxide is 1:(3.02-3.05).

[0008] Optionally, the reaction can be refluxed at 40°C-50°C.

[0009] Optionally, the mixture reaction can be carried out for 3-5 hours.

[0010] Optionally, the mixture is separated by vacuum filtration after the reaction.

[0011] Optionally, citric acid and potassium ethoxide are dissolved in anhydrous ethanol to prepare citric acid ethanol solution and potassium ethoxide ethanol solution, respectively, and then the citric acid ethanol solution is added dropwise to the potassium ethoxide ethanol solution for mixing and reaction.

[0012] Alternatively, citric acid and potassium ethoxide can be reacted ultrasonically in anhydrous ethanol.

[0013] Optionally, after mixing and reaction, the product is separated and dried to obtain crude potassium citrate.

[0014] Optionally, the eutectic solvent includes a group consisting of choline chloride and glycerol, and choline chloride and lactic acid.

[0015] Optionally, the mixing ratio of crude potassium citrate to the eutectic solvent is 0.3 mg / mL to 0.5 mg / mL.

[0016] Optionally, the crude potassium citrate is stirred and mixed in a eutectic solvent for 1-2 hours.

[0017] Optionally, crude potassium citrate can be dissolved in a eutectic solvent at 60°C-70°C.

[0018] Alternatively, potassium citrate can be ultrasonically dissolved in a eutectic solvent.

[0019] Optionally, the density of the crude potassium citrate solution is 1.40 g / cm³. 3 -1.60g / cm 3 .

[0020] Optionally, the particle size of the potassium citrate microcrystals is 1μm-5μm.

[0021] Optionally, the potassium citrate microcrystals are cubic microcrystals.

[0022] Optionally, the mass ratio of the crude potassium citrate to the microcrystals of potassium citrate is 100:(0.05-0.10).

[0023] Optionally, crystallization can be carried out by cooling at a rate of 0.1℃ / min to 1.0℃ / min.

[0024] Optionally, crystallization can be achieved by cooling the machine at a speed of 40 rpm to 60 rpm.

[0025] Optionally, cooling to 30-35℃ crystallization.

[0026] Optionally, holding for 6-8h crystallization after cooling.

[0027] Optionally, after cooling crystallization, the potassium citrate crystals are separated by ultrafiltration.

[0028] Optionally, cooling crystallization under ultrasonic.

[0029] Optionally, the volume ratio of the potassium citrate crystals to the molten citric acid is 1:(1.2-1.5).

[0030] Optionally, aging for 3-5h in the molten citric acid.

[0031] Optionally, aging in the molten citric acid at 155-160℃.

[0032] Optionally, the potassium citrate crystals are immersed in the molten citric acid under an inert atmosphere, which includes one of helium atmosphere, neon atmosphere, argon atmosphere.

[0033] Optionally, ultrafiltration separation after aging.

[0034] Optionally, drying after washing with anhydrous ethanol to obtain anhydrous potassium citrate.

[0035] In a second aspect, the present application further provides an anhydrous potassium citrate synthesized by any of the above synthesis methods.

[0036] The synthesis method of the anhydrous potassium citrate provided by the present application has at least one of the following beneficial technical effects compared with the prior art: 1. By neutralizing the citric acid and potassium ethoxide in anhydrous ethanol, no water molecules are introduced during the reaction, and the generated potassium citrate is insoluble in ethanol, thereby directly precipitating to obtain a potassium citrate crude product, which can effectively avoid the formation of potassium citrate hydrate, and the reaction of citric acid and potassium ethoxide is rapid, complete and has few side reactions, which helps to improve the purity of the generated potassium citrate; 2. By dissolving the potassium citrate crude product in a eutectic solvent and adding microcrystalline to induce crystallization, the eutectic solvent can effectively inhibit the nucleation rate and growth rate of the crystal, thereby promoting the epitaxial growth of potassium citrate with microcrystals as the center, controlling the ordered crystallization of potassium citrate, and improving the uniformity of potassium citrate crystal size distribution and the regularity of crystal form; 3. By immersing the potassium citrate crystals in the molten citric acid and aging treatment, impurities attached to the surface of the crystals during the crystallization process can be effectively removed, and the surface of the crystals can be reconstructed and defects repaired, thereby improving the integrity and purity of the potassium citrate crystals. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A flow chart of a synthesis method of anhydrous potassium citrate according to the present application. DETAILED DESCRIPTION

[0038] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application. Unless otherwise defined, the technical terms or scientific terms used herein should be understood as their common meanings to those of ordinary skill in the art to which the present application belongs.

[0039] Reference Figure 1 The present application provides a synthesis method of anhydrous potassium citrate, comprising the following steps: S1, mixing citric acid and potassium ethoxide in anhydrous ethanol to react and then separating to obtain potassium citrate crude product; S2, dissolving the potassium citrate crude product in a eutectic solvent to obtain a potassium citrate crude solution; S3, adding potassium citrate microcrystals to the potassium citrate crude solution to crystallize and separate to obtain potassium citrate crystals; S4, immersing the potassium citrate crystals in molten citric acid to age, and then separating and washing to obtain anhydrous potassium citrate.

[0040] In fact, in the step S1, when citric acid and potassium ethoxide are reacted in anhydrous ethanol, citric acid is acidic, and potassium ethoxide is strongly basic. In the mixing reaction process, acid-base neutralization occurs to generate potassium citrate and ethanol. Since potassium citrate is insoluble in ethanol, potassium citrate is directly precipitated to obtain potassium citrate crude product.

[0041] In some embodiments, in the step S1, the citric acid and potassium ethoxide can be dissolved in anhydrous ethanol respectively to prepare citric acid ethanol solution and potassium ethoxide ethanol solution, and then the citric acid ethanol solution is added dropwise into the potassium ethoxide ethanol solution to mix and react. In fact, adding the citric acid solution dropwise into the potassium ethoxide solution is beneficial to inhibit side reactions in the acidic environment, and can promote the reaction system to be in an environment of excessive potassium ions, thereby improving the generation rate and uniformity of potassium citrate.

[0042] In some embodiments, the molar ratio of the total amount of citric acid to the total amount of potassium ethoxide used in step S1 can be 1:(3.02-3.05). In fact, by controlling the excess of potassium ethoxide, it is beneficial to promote the full reaction of citric acid and to promote the precipitation of potassium citrate. Specifically, in step S1, the citric acid and potassium ethoxide can be incubated and refluxed in a water bath environment at 40-50°C for 3-5h.

[0043] In some embodiments, in step S1, the citric acid and potassium ethoxide can be ultrasonically mixed in anhydrous ethanol, and the ultrasonic cavitation effect is used to promote the uniform dispersion of citric acid and potassium ethoxide to improve the reaction efficiency, while the generated potassium citrate can form fine crystal grains, which is beneficial to avoid the formation of large crystal nuclei of potassium citrate crude product wrapping impurities.

[0044] In some embodiments, after mixing the citric acid and potassium ethoxide in anhydrous ethanol in step S1, the mixture can be separated by suction filtration to obtain a solid, and the solid can be further washed with anhydrous ethanol to remove alcohol-soluble impurities on the surface, and then transferred to a vacuum drying oven for drying to constant weight to obtain the potassium citrate crude product.

[0045] In some embodiments, the eutectic solvent used in step S2 includes one of choline chloride and glycerol, choline chloride and lactic acid. In fact, in the eutectic solvent, choline chloride is a hydrogen bond acceptor, and glycerol and lactic acid are hydrogen bond donors. By dissolving the potassium citrate crude product in the eutectic solvent, it is beneficial to regulate the crystal size and morphology of potassium citrate during crystallization upon cooling.

[0046] In some embodiments, the mixing ratio of the potassium citrate crude product used in step S2 to the eutectic solvent used can be 0.3-0.5mg / mL. In fact, the potassium citrate crude product can be stirred and mixed in the eutectic solvent at 60-70°C for 1-2h to promote the full dissolution of the potassium citrate crude product in the eutectic solvent at high temperature, and then facilitate the crystallization during the cooling process.

[0047] In some embodiments, in step S2, the potassium citrate can be ultrasonically dissolved in the eutectic solvent to obtain a uniform solution, and the density of the potassium citrate crude solution can be controlled to be 1.40-1.60g / cm 3 3 In order to promote the uniform crystallization of the potassium citrate crude solution during the subsequent cooling process. Specifically, the potassium citrate microcrystals added in step S3 are cubic system microcrystals with a particle size of 1-5μm.

[0048] ​In some embodiments, the mass ratio of the potassium citrate microcrystals used in step S3 to the potassium citrate crude product dissolved in step S2 is (0.05-0.10) : 100. In fact, the microcrystals are used as crystal nuclei and the low eutectic solvent in the cooling crystallization process to promote the ordered growth of potassium citrate, thereby obtaining potassium citrate crystals with uniform particle size and high fluidity.

[0049] In some embodiments, the cooling crystallization in step S3 is performed at a rate of 0.1°C / min-1.0°C / min to 30°C-35°C. In fact, a two-step cooling method can be used in the cooling crystallization process, for example, pre-cooling at a rate of 0.5°C / min-1.0°C / min to 50°C-55°C and constant temperature stirring for 1 h, and then cooling at a rate of 0.1°C / min-0.5°C / min to 30°C-35°C and holding for 6 h-8 h. Specifically, the stirring speed can be controlled to be 40 rpm-60 rpm during constant temperature stirring.

[0050] In some embodiments, the cooling crystallization process in step S3 is performed with external ultrasonic treatment. The potassium citrate crystals can be further refined by ultrasonic treatment, and after the crystallization treatment, the obtained potassium citrate crystals and mother liquor are separated by ultrafiltration using an ultrafiltration membrane with a pore size of 0.2 μm. The mother liquor can be reused. In addition, after obtaining the potassium citrate crystals, they can be washed with anhydrous ethanol and dried to constant weight.

[0051] In some embodiments, the volume ratio of the potassium citrate crystals used in step S4 to the molten citric acid used is 1: (1.2-1.5). In fact, the citric acid can be heated to a molten state, and then the potassium citrate crystals are immersed in the molten citric acid, so that the potassium citrate crystals are completely submerged in the molten citric acid. Specifically, the citric acid can be heated to 155°C-160°C for sufficient melting.

[0052] In some embodiments, in step S4, the citric acid is heated to a molten state under an inert atmosphere, and then the potassium citrate crystals are immersed in the molten citric acid and aged for 3 h-5 h to improve the purity and integrity of the crystal grains. Further, the inert atmosphere includes one of helium atmosphere, neon atmosphere, and argon atmosphere, and the gas pressure of the inert atmosphere can be standard atmospheric pressure.

[0053] In some embodiments, after the potassium citrate crystals are aged in the molten citric acid in step S4, the obtained solid is cooled to room temperature, washed with anhydrous ethanol, and then transferred to a vacuum drying oven for drying at 50°C-60°C to constant weight to obtain anhydrous potassium citrate.

[0054] Example 1

[0055] The embodiment 1 provides a synthesis method of anhydrous potassium citrate, which comprises the following steps: S1, food-grade citric acid and potassium ethoxide are respectively dissolved in anhydrous ethanol to prepare citric acid ethanol solution and potassium ethoxide ethanol solution, then the potassium ethoxide ethanol solution is heated to 45 DEG C under a nitrogen atmosphere, the citric acid ethanol solution is added dropwise into the potassium ethoxide ethanol solution for reflux reaction, the total amount of citric acid added is controlled to have a molar ratio of 1:3.03 to potassium ethoxide, the reflux reaction is carried out for 4 h, and 200 W of intermittent ultrasonic treatment is additionally provided during the reflux reaction, the ultrasonic treatment is intermittently carried out in a mode of 3 s ultrasonic treatment and 2 s pause, after the reflux reaction, hot filtration separation is carried out, and the obtained solid is transferred into a vacuum drying box for drying until a constant weight to obtain potassium citrate crude product; S2, choline chloride and glycerol are uniformly mixed to prepare a eutectic solvent in a molar ratio of 1:2, then the potassium citrate crude product is added into the eutectic solvent in a mixing ratio of 0.4 mg / mL, heated to 70 DEG C and stirred (compound ultrasonic treatment) at a rotating speed of 100 rpm for 2 h, so that the potassium citrate crude product is completely dissolved in the eutectic solvent to obtain a potassium citrate crude solution; S3, under the condition of 70 DEG C, 0.08% of cubic system potassium citrate microcrystal with an average particle size of 3 μm is added into the potassium citrate crude solution and ultrasonically mixed, then the temperature is lowered to 52 DEG C at a rate of 0.8 DEG C / min, constant temperature stirring is carried out at a rotating speed of 60 rpm for 1 h, then the temperature is lowered to 32 DEG C at a rate of 0.3 DEG C / min and incubated for 7 h, and then ultrafiltration separation and drying are carried out to obtain potassium citrate crystals; during the temperature lowering process, 200 W of intermittent ultrasonic treatment is additionally provided, and the ultrasonic treatment is intermittently carried out in a mode of 3 s ultrasonic treatment and 2 s pause; S4, citric acid is heated to 160 DEG C under an argon atmosphere until completely melted, then the potassium citrate crystals are immersed in the molten citric acid, and the volume ratio of the potassium citrate crystals to the molten citric acid is controlled to be 1:1.3; after incubation and aging in the molten citric acid for 3 h, hot ultrafiltration separation is carried out, and then anhydrous ethanol is used for washing, then the potassium citrate crystals are transferred into a vacuum drying box and dried at 50 DEG C until a constant weight to obtain anhydrous potassium citrate.

[0056] Embodiment 2

[0057] The embodiment 2 provides a synthesis method of anhydrous potassium citrate, which comprises the following steps: S1, dissolve food-grade citric acid and potassium ethoxide in anhydrous ethanol respectively to prepare citric acid ethanol solution and potassium ethoxide ethanol solution, then heat the potassium ethoxide ethanol solution to 45℃ under nitrogen atmosphere, and then add the citric acid ethanol solution dropwise into the potassium ethoxide ethanol solution for reflux reaction, control the molar ratio of the total amount of citric acid to potassium ethoxide to be 1:3.03, reflux for 4h, and add 200W of intermittent ultrasound during the reflux reaction, the ultrasound is intermittent in the form of 3s ultrasound and 2s pause, after the reflux reaction, separate by hot filtration and dry the obtained solid in a vacuum drying oven until constant weight to obtain potassium citrate crude product; S2, uniformly mix choline chloride and lactic acid at a molar ratio of 1:2 to prepare a deep eutectic solvent, then add the potassium citrate crude product to the deep eutectic solvent at a mixing ratio of 0.4mg / mL, heat to 70℃ and stir at a speed of 100rpm (complex ultrasound treatment) for 2h to completely dissolve the potassium citrate crude product in the deep eutectic solvent to obtain a potassium citrate crude solution; S3, under the condition of 70℃, add 0.08% of cubic system potassium citrate microcrystal with an average particle size of 3μm to the potassium citrate crude solution, then mix by ultrasound, then reduce the temperature to 52℃ at a rate of 0.8℃ / min, then stir at a constant temperature of 60rpm for 1h, then reduce the temperature to 32℃ at a rate of 0.3℃ / min and keep the temperature for 7h for crystal growth, then separate by ultrafiltration and dry to obtain potassium citrate crystals; during the temperature reduction process, add 200w of intermittent ultrasound, and the ultrasound is intermittent in the form of 3s ultrasound and 2s pause; S4, heat citric acid to 160℃ under argon atmosphere until completely melted, then immerse the potassium citrate crystals in the molten citric acid, control the volume ratio of potassium citrate crystals to molten citric acid to be 1:1.3, keep the temperature for 3h, then separate by ultrafiltration while hot and rinse with anhydrous ethanol, then transfer to a vacuum drying oven and dry at 50℃ until constant weight to obtain anhydrous potassium citrate.

[0058] Comparative Example 1 Comparative Example 1 provides a synthesis method of anhydrous potassium citrate, which comprises the following steps: D1, stir and dissolve food-grade citric acid in deionized water to prepare a citric acid aqueous solution, mix the citric acid aqueous solution with ion membrane liquid potassium hydroxide, and keep the temperature at 50℃ for 3h, control the molar ratio of citric acid to potassium hydroxide to be 1:3.03, after the reaction, add glucose solution, keep the temperature at 80℃ for 2h, then evaporate and concentrate to crystallize to obtain potassium citrate crude product; D2, after the choline chloride and glycerol are uniformly mixed in a molar ratio of 1:2 to configure a eutectic solvent, potassium citrate crude product is added into the eutectic solvent in a mixing ratio of 0.4 mg / mL, heated to 70℃ and stirred (ultrasonic treatment) at a rotating speed of 100 rpm for 2 h to promote the complete dissolution of the potassium citrate crude product in the eutectic solvent to obtain a potassium citrate crude solution; D3, under the condition of 70℃, 0.08% cubic potassium citrate microcrystal with an average particle size of 3 μm is added into the potassium citrate crude solution and ultrasonically mixed, then cooled to 52℃ at a rate of 0.8℃ / min, stirred at a constant temperature of 60 rpm for 1 h, then cooled to 32℃ at a rate of 0.3℃ / min and kept for 7 h for crystal growth, then separated by ultrafiltration and dried to obtain potassium citrate crystals; during the cooling process, 200w of intermittent ultrasonic treatment is applied, and the ultrasonic treatment is intermittent in the mode of 3s ultrasonic treatment and 2s pause; D4, under an argon atmosphere, citric acid is heated to 160℃ until completely melted, then the potassium citrate crystals are immersed in the melted citric acid, and the volume ratio of the potassium citrate crystals to the melted citric acid is controlled to be 1:1.3; after being kept and aged in the melted citric acid for 3 h, the potassium citrate crystals are separated by hot ultrafiltration and rinsed with anhydrous ethanol, then transferred to a vacuum drying oven and dried at 50℃ until constant weight to obtain anhydrous potassium citrate.

[0059] Comparative Example 2 The present comparative example 2 provides a synthesis method of anhydrous potassium citrate, comprising the following steps: D1, food-grade citric acid and potassium ethoxide are respectively dissolved in anhydrous ethanol to obtain a citric acid ethanol solution and a potassium ethoxide ethanol solution, then the potassium ethoxide ethanol solution is heated to 45℃ under a nitrogen atmosphere, and the citric acid ethanol solution is added dropwise into the potassium ethoxide ethanol solution for reflux reaction, and the molar ratio of the total amount of citric acid to potassium ethoxide is controlled to be 1:3.03; the reflux reaction is carried out for 4 h, and 200w of intermittent ultrasonic treatment is applied during the reflux reaction, and the ultrasonic treatment is intermittent in the mode of 3s ultrasonic treatment and 2s pause; after the reflux reaction is completed, the obtained solid is separated by hot filtration and transferred to a vacuum drying oven for drying until constant weight to obtain potassium citrate crude product; D2, the potassium citrate crude product is dissolved in deionized water to obtain a potassium citrate crude solution, under the condition of 70℃, 0.08% cubic potassium citrate microcrystal with an average particle size of 3 μm is added into the potassium citrate crude solution and ultrasonically mixed, then cooled to 52℃ at a rate of 0.8℃ / min, stirred at a constant temperature of 60 rpm for 1 h, then cooled to 32℃ at a rate of 0.3℃ / min and kept for 7 h for crystal growth, then separated by ultrafiltration and dried to obtain potassium citrate crystals; during the cooling process, 200w of intermittent ultrasonic treatment is applied, and the ultrasonic treatment is intermittent in the mode of 3s ultrasonic treatment and 2s pause; D3, after heating citric acid to 160℃ until completely melted under argon atmosphere, immerse potassium citrate crystals into the melted citric acid, control the volume ratio of potassium citrate crystals and melted citric acid to be 1:1.3; after aging for 3h in the melted citric acid, separate by hot ultrafiltration and rinse with anhydrous ethanol, then transfer to vacuum drying oven and dry at 50℃ until constant weight to obtain anhydrous potassium citrate.

[0060] Comparative Example 3 Comparative Example 3 provides a method for synthesizing anhydrous potassium citrate, comprising the following steps: D1, dissolve food-grade citric acid and potassium ethoxide in anhydrous ethanol respectively to obtain citric acid ethanol solution and potassium ethoxide ethanol solution, then heat the potassium ethoxide ethanol solution to 45℃ under nitrogen atmosphere, and add the citric acid ethanol solution dropwise into the potassium ethoxide ethanol solution for reflux reaction, control the molar ratio of the total amount of citric acid added to potassium ethoxide to be 1:3.03; reflux for 4h, and add 200W of intermittent ultrasound outside during the reflux reaction, the ultrasound is intermittent in the form of 3s ultrasound and 2s pause; after the reflux reaction is completed, separate by hot filtration and transfer the obtained solid to a vacuum drying oven for drying until constant weight to obtain potassium citrate crude product; D2, uniformly mix choline chloride and glycerol at a molar ratio of 1:2 to prepare a deep eutectic solvent, then add the potassium citrate crude product to the deep eutectic solvent at a mixing ratio of 0.4mg / mL, heat to 70℃ and stir at a speed of 100rpm (complex ultrasound treatment) for 2h to completely dissolve the potassium citrate crude product in the deep eutectic solvent to obtain a potassium citrate crude solution; D3, under the condition of 70℃ heat preservation, add 0.08% of cubic system potassium citrate microcrystals with an average particle size of 3μm to the potassium citrate crude solution, then ultrasound mix, reduce the temperature to 52℃ at a rate of 0.8℃ / min, then stir at a constant temperature of 60rpm for 1h, then reduce the temperature to 32℃ at a rate of 0.3℃ / min and keep the temperature for 7h for crystal growth, then separate by ultrafiltration and dry to obtain anhydrous potassium citrate; during the temperature reduction process, add 200w of intermittent ultrasound outside, the ultrasound is intermittent in the form of 3s ultrasound and 2s pause.

[0061] Performance detection Detect the D90 particle size and D50 particle size of the anhydrous potassium citrate in Example 1 to Example 2 and Comparative Example 1 to Comparative Example 3 respectively, and calculate the ratio of D90 / D50 as shown in Table 1; detect the angle of repose of the anhydrous potassium citrate in Example 1 to Example 2 and Comparative Example 1 to Comparative Example 3 respectively as shown in Table 1; detect the purity of the anhydrous potassium citrate in Example 1 to Example 2 and Comparative Example 1 to Comparative Example 3 respectively as shown in Table 1.

[0062] Table 1 Performance detection of anhydrous potassium citrate D90 / D50 Resting angle / ° Purity / % Example 1 2.12 23.1 99.99 Example 2 2.13 23.4 99.99 Comparative Example 1 2.25 24.8 99.92 Comparative Example 2 3.08 32.6 99.82 Comparative Example 3 2.86 29.5 99.76 As can be seen from Table 1, the anhydrous potassium citrate provided in Examples 1 to 2 of the present application has good uniformity and flowability, purity. As can be seen from Comparative Example 1, the use of potassium hydroxide as a raw material inevitably introduces impurity components, thereby reducing the purity and crystal grain properties of potassium citrate, and as can be seen from Comparative Example 2, the use of a eutectic solvent to regulate the crystallization process is advantageous in improving the purity and crystal grain properties.

[0063] While the embodiments of the present application have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to the embodiments. However, it should be understood that such modifications and changes are within the scope and spirit of the present application described in the claims. Furthermore, the present application described herein can have other embodiments and can be practiced or implemented in various ways.

Claims

1. A method for synthesizing anhydrous potassium citrate, characterized in that, include: Citric acid and potassium ethoxide were mixed and reacted in anhydrous ethanol to obtain crude potassium citrate. The crude potassium citrate was dissolved in a eutectic solvent to prepare a crude potassium citrate solution. Potassium citrate microcrystals were added to the crude potassium citrate solution and then cooled and crystallized to obtain potassium citrate crystals. The potassium citrate crystals were immersed in molten citric acid for aging, and then separated and washed to obtain anhydrous potassium citrate.

2. The synthesis method according to claim 1, characterized in that: The molar ratio of citric acid to potassium ethoxide is 1:(3.02-3.05); and / or, the reaction is carried out under reflux at 40℃-50℃; and / or, the reaction is carried out for 3-5 hours; and / or, the reaction is carried out by filtration after the reaction.

3. The synthesis method according to claim 1, characterized in that: Citric acid and potassium ethoxide were dissolved in anhydrous ethanol to prepare citric acid ethanol solution and potassium ethoxide ethanol solution, respectively. The citric acid ethanol solution was then added dropwise to the potassium ethoxide ethanol solution to mix and react.

4. The synthesis method according to claim 1, characterized in that: Citric acid and potassium ethoxide are ultrasonically reacted in anhydrous ethanol; and / or, after mixing and reacting, the mixture is separated and dried to obtain crude potassium citrate; and / or, the eutectic solvent includes one group of choline chloride and glycerol, or choline chloride and lactic acid.

5. The synthesis method according to claim 1, characterized in that: The mixing ratio of the crude potassium citrate to the eutectic solvent is 0.3 mg / mL to 0.5 mg / mL; and / or, the crude potassium citrate is stirred and mixed in the eutectic solvent for 1 h to 2 h; and / or, the crude potassium citrate is dissolved in the eutectic solvent at 60℃ to 70℃.

6. The synthesis method according to claim 1, characterized in that: Potassium citrate is dissolved ultrasonically in a eutectic solvent; and / or, the density of the crude potassium citrate solution is 1.40 g / cm³. 3 -1.60g / cm 3 ; and / or, the particle size of the potassium citrate microcrystals is 1μm-5μm; and / or, the potassium citrate microcrystals are cubic crystal system microcrystals.

7. The synthesis method according to claim 1, characterized in that: The mass ratio of crude potassium citrate to potassium citrate microcrystals is 100:(0.05-0.10); and / or, cooling and crystallizing at a rate of 0.1℃ / min-1.0℃ / min; and / or, cooling and crystallizing at a rotation speed of 40rpm-60rpm; and / or, cooling to 30℃-35℃ and crystallizing; and / or, maintaining the temperature for 6h-8h after cooling and crystallizing.

8. The synthesis method according to claim 1, characterized in that: Potassium citrate crystals are obtained by ultrafiltration after cooling crystallization; and / or by ultrasonic cooling crystallization; and / or by a volume ratio of the potassium citrate crystals to the molten citric acid of 1:(1.2-1.5); and / or by aging in molten citric acid for 3-5 hours; and / or by aging in molten citric acid at 155℃-160℃.

9. The synthesis method according to claim 1, characterized in that: Potassium citrate crystals are immersed in molten citric acid under an inert atmosphere, wherein the inert atmosphere includes one of helium, neon, or argon; and / or, after aging, they are separated by ultrafiltration; and / or, after washing with anhydrous ethanol, they are dried to obtain anhydrous potassium citrate.

10. Anhydrous potassium citrate synthesized by the synthetic method according to any one of claims 1 to 9.

Images