A method of recrystallization of propionic acid salts

Abstract

This invention provides a method for recrystallizing propionate, characterized in that the method includes dissolving crude propionate in a recrystallization solvent at a first temperature, then adding seed crystals and cooling to a second temperature for recrystallization, followed by filtration and drying to obtain purified propionate; wherein the recrystallization solvent comprises alcohol and water; the volume ratio of water to alcohol in the recrystallization solvent is 1:1-20; and the second temperature is 10-90°C lower than the first temperature. The method of this invention is not only simple in process and convenient to operate, with high yield, but also yields propionate crystals with high purity.

Description

Technical Field

[0001] This invention relates to the field of propionate purification technology, and in particular to a method for recrystallizing propionate. Background Technology

[0002] Propionates, including sodium propionate, calcium propionate, and ammonium propionate, are safe and reliable food and feed preservatives approved by the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO). They are widely used in agriculture, food, medicine, and textile industries. Propionates have advantages such as high temperature resistance, non-volatility, unaffected by other components in feed, low corrosivity, low irritation, and suitability for long-term feed storage. They overcome many shortcomings of propionic acid as a direct preservative, such as: 1) propionic acid has a low boiling point (79℃) and is easily volatile; 2) propionic acid is rapidly lost during feed storage, resulting in a short duration of efficacy, which is not conducive to long-term feed preservation; 3) propionic acid is easily neutralized by proteins in feed, thus reducing or eliminating its activity. Therefore, in the application of edible preservatives, propionates are recognized as the most economical, safe, and effective edible preservatives, and are widely used as preservatives and anti-mold agents in pastries, soy products, canned goods processing, and beer production. In addition, propionates such as sodium propionate, calcium propionate, and ammonium propionate can be used as silage preservatives and are widely used in cattle, sheep, and poultry feed. In the textile industry, propionates are used as masking agents in leather making to improve the alkali resistance and tanning uniformity of leather.

[0003] Currently, propionate is mainly produced through a neutralization reaction of propionic acid with sodium hydroxide, sodium carbonate, or calcium hydroxide. However, the production process of propionic acid is relatively complex. First, propionaldehyde is produced by hydroformylation of ethylene under the catalysis of rhodium and cobalt metal complexes at 70-150℃ and 2-100 atm pressure. The resulting propionaldehyde is then oxidized to propionic acid under the catalysis of manganese, cobalt, vanadium, etc., at 40-45℃ and 3-7 atm pressure. The overall process is lengthy and requires high equipment investment.

[0004] CN108191637A discloses a method for synthesizing sodium propionate, specifically a method for producing sodium propionate under slurry conditions using solid sodium carbonate and liquid propionic acid. Sodium carbonate and propionic acid are added to a reaction vessel and mixed, then stirred at high speed to form a slurry for direct reaction, yielding a sodium propionate product with quality and properties comparable to those produced by conventional processes.

[0005] US10239813B2 discloses a method for producing calcium dipropionate in a batch process within a single pressure-resistant reaction vessel. Calcium oxide, calcium hydroxide, calcium carbonate, or a mixture thereof are added to the reaction vessel. Then, pure, high-concentration propionic acid is added to the solid feedstock, and the mixture is heated to a maximum temperature of 160°C. After a reaction time of 3–6 hours, pure calcium dipropionate with a water content of less than 1% is obtained. However, this method involves a relatively long reaction temperature and time.

[0006] The prepared propionate often requires purification through recrystallization due to purity issues. Currently, recrystallization in aqueous solution is the main method for purification. However, since propionate is highly soluble in water, the yield of the first recrystallization is usually less than 60%. To obtain high-yield propionate crystals, multiple recrystallization stages are required to achieve a higher recrystallization yield.

[0007] CN117482559A discloses a calcium propionate crystallization preparation apparatus, including a crystallization vessel, support legs, a heating wire, a stirring motor, a discharge pipe, and a branch pipe. The crystallization vessel has a double-layer design, with heat-conducting oil filling the gap between the two layers. A heating rod with a spiral design is installed in the gap and connected to the heating wire. A narrow-diameter tube is installed inside the crystallization vessel. The crystallization apparatus uses the heating rod and heat-conducting oil to ensure uniform heating of the crystallization vessel, thereby improving the crystallization efficiency of calcium propionate.

[0008] However, existing crystallization devices mostly use heating rods or heating kettles to heat the solution, resulting in poor temperature uniformity and easily leading to excessively fine crystals. Furthermore, since propionate is highly soluble in water, existing propionate recrystallization processes are lengthy, complex, and energy-intensive in order to improve the efficiency and yield of propionic acid crystallization.

[0009] In summary, because propionate is highly soluble in water, existing recrystallization processes for propionate are lengthy, complex, and energy-intensive in order to improve the efficiency and yield of propionic acid crystallization.

[0010] Moreover, propionates usually contain chloride impurities. Although chloride impurities in propionates are highly soluble in water, they are easily encapsulated by the precipitated propionate crystals during recrystallization, making it difficult to improve the purity of propionate crystals.

[0011] If propionate recrystallization can be achieved in a single operation with high yield using simple methods, thereby producing high-purity propionate, it will greatly promote the development of the propionate industry. Summary of the Invention

[0012] To address the aforementioned problems in the prior art, this invention provides a method for recrystallizing propionate. The method of this invention has a simple process flow, low cost, high recrystallization yield, and the obtained propionate crystals have high purity.

[0013] The objective of this invention is mainly achieved through the following technical solutions.

[0014] This invention provides a method for recrystallizing propionate, the method comprising dissolving crude propionate in a recrystallization solvent at a first temperature, then adding seed crystals and cooling to a second temperature for recrystallization, and obtaining purified propionate after filtration and drying; wherein the recrystallization solvent comprises alcohol and water; and the volume ratio of water to alcohol in the recrystallization solvent is 1:1-20.

[0015] The second temperature is 10-90°C lower than the first temperature.

[0016] Preferably, the second temperature is 40-80°C lower than the first temperature, and more preferably 70-75°C lower.

[0017] Preferably, the crude propionate is dissolved in a recrystallization solvent by a method comprising the following steps: the crude propionate is dissolved in water at a first temperature of 30°C-70°C, and then alcohol is added and stirred until completely dissolved.

[0018] Preferably, the recrystallization conditions include: a second temperature of -40-50℃, more preferably -25-0℃; and a time of 1-24h, more preferably 2-7h.

[0019] Preferably, the recrystallization is carried out under stirring at a speed of 100-1000 rpm, more preferably 300-500 rpm.

[0020] Preferably, the volume ratio of water to alcohol in the recrystallization solvent is 1:4-20, more preferably 1:4-5.

[0021] Preferably, the weight ratio of the crude propionate to the volume ratio of water is 1:0.3-1, more preferably 1:0.5-0.6.

[0022] Preferably, the weight ratio of the crude propionate to the seed crystals is 1:0.001-0.1, more preferably 1:0.01-0.06.

[0023] Preferably, the recrystallization solvent comprises a monohydric alcohol having 1-16 carbon atoms, and more preferably a monohydric alcohol having 1-8 carbon atoms.

[0024] Preferably, the monohydric alcohol is selected from at least one of methanol, ethanol, isopropanol, butanol and isooctyl alcohol.

[0025] Preferably, the method further includes preparing crude propionate, specifically comprising: reacting propionate with a metal hydroxide in the presence of water and an organic solvent at a reaction temperature of 50-130°C; concentrating, crystallizing, and filtering the reaction solution obtained after the reaction; and drying the filtered product to obtain crude propionate; wherein the weight ratio of the organic solvent to water is 1:1.2-10; and the organic solvent is selected from at least one of alcohols, ketones, nitriles, and ethers.

[0026] Preferably, the reaction temperature is 50-110℃, and more preferably 50-70℃.

[0027] Preferably, the contact reaction time is 1-10 hours, more preferably 1-3 hours.

[0028] Preferably, the contact reaction is carried out under stirring, and the stirring speed is preferably 300-1000 rpm, more preferably 500-1000 rpm, and even more preferably 500-700 rpm.

[0029] Preferably, the weight ratio of the organic solvent to the propionate ester is 1:0.1-2, more preferably 1:0.5-1.

[0030] Preferably, the weight ratio of the organic solvent to water is 1:1.2-5, and more preferably 1:1.5-2.5.

[0031] Preferably, the molar ratio of the propionate ester to the metal hydroxide is 1:1-10, more preferably 1:1.2-5, and even more preferably 1:1.7-2.

[0032] Preferably, the alcohol in the organic solvent is a monohydric alcohol with 1-16 carbon atoms, more preferably a monohydric alcohol with 1-8 carbon atoms.

[0033] Preferably, the organic solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isooctyl alcohol, acetone, and acetonitrile.

[0034] Preferably, the metal hydroxide is selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and zinc hydroxide.

[0035] Preferably, the propionate is selected from one of methyl propionate, ethyl propionate, butyl propionate and isooctyl propionate.

[0036] Preferably, the reaction solution is concentrated to less than 1 / 3 of its original volume.

[0037] Preferably, the pore size of the filter membrane used for filtration is 1-10 μm, and more preferably 3-5 μm.

[0038] Preferably, the drying method is selected from at least one of vacuum drying, spray drying, freeze drying, and infrared drying.

[0039] Preferably, the impurities in the crude propionate include chloride impurities.

[0040] The recrystallization method for propionate disclosed in this invention has the following advantages:

[0041] (1) The recrystallization method of the present invention has simple procedures and is easy to operate;

[0042] (2) The recrystallization method of the present invention has a high propionate yield and the obtained propionate crystals have high purity. Detailed Implementation

[0043] The inventors of this invention have discovered through research that combining water and alcohol in a specific ratio as a recrystallization solvent, under specific temperature conditions, can effectively remove chloride impurities such as potassium chloride and sodium chloride from crude propionate (e.g., potassium propionate or sodium propionate).

[0044] Based on the above research, in a preferred embodiment of the present invention, the method further includes dissolving the crude propionate obtained from the contact reaction in a recrystallization solvent at a first temperature, then adding seed crystals and cooling to a second temperature for recrystallization, and obtaining purified propionate after filtration and drying; wherein the recrystallization solvent includes alcohol and water; the volume ratio of water to alcohol is 1:1-20; and the second temperature is 10-90°C lower than the first temperature.

[0045] The recrystallization method of this invention uses a specific ratio of water and alcohol as the recrystallization solvent and strictly controls the temperature difference between the dissolution temperature and the recrystallization temperature, thereby achieving high yield and purity. Analysis suggests that, under the combined action of the specific recrystallization solvent and the specific temperature control of this invention, not only can a low amount of impurities be guaranteed, but the amount of propionate crystals precipitated is also effectively increased, and impurities such as chlorides encapsulated in the propionate crystals are reduced or even avoided.

[0046] In a preferred embodiment of the present invention, the second temperature is 40-80°C lower than the first temperature, preferably 70-75°C lower.

[0047] In a preferred embodiment of the present invention, the crude propionate is dissolved in a recrystallization solvent by a method comprising the following steps: the propionate is dissolved in water at a first temperature of 30°C-70°C, and then the alcohol is added and stirred until completely dissolved.

[0048] In a preferred embodiment of the present invention, the first temperature is 30℃-60℃, preferably 50-60℃.

[0049] In a preferred embodiment of the present invention, the recrystallization conditions include: a second temperature of -40-50°C, preferably -25-0°C; and a time of 1-24 hours, preferably 2-7 hours.

[0050] In a preferred embodiment of the present invention, the recrystallization is carried out under stirring at a speed of 100-1000 rpm, preferably 300-500 rpm, and more preferably 400-450 rpm. This preferred stirring speed avoids excessively rapid crystallization, promotes crystal precipitation and formation, and helps improve crystal purity.

[0051] In a preferred embodiment of the present invention, the volume ratio of water to alcohol in the recrystallization solvent is 1:4-20, more preferably 1:4-5. This preferred water-to-alcohol volume ratio is more conducive to the precipitation of propionate crystals.

[0052] In this invention, if the amount of water is too small, it is insufficient to dissolve the propionate; if the amount of water is too large, it is not conducive to the precipitation of crude propionate in the recrystallization solvent composed of water and alcohol, resulting in a low yield of propionate crystals and also reducing the purity of propionate crystals. In order to further improve the yield and purity of propionate crystals, in a preferred embodiment, the weight ratio of the crude propionate to the volume ratio of water is 1:0.3-1, more preferably 1:0.5-0.6.

[0053] In a preferred embodiment of the present invention, the recrystallization solvent comprises a monohydric alcohol having 1-16 carbon atoms, preferably a monohydric alcohol having 1-8 carbon atoms.

[0054] In a preferred embodiment of the present invention, the monohydric alcohol is selected from any one of methanol, ethanol, isopropanol, butanol, and isooctanol, more preferably from any one of methanol, ethanol, and isopropanol, and even more preferably from methanol. Using this preferred alcohol is more conducive to the precipitation of propionate crystals, and can further improve the yield and purity of propionate crystals.

[0055] In a preferred embodiment of the present invention, the propionate is selected from one of sodium propionate, potassium propionate, lithium propionate, calcium propionate and zinc propionate, preferably one of sodium propionate, potassium propionate and calcium propionate, and more preferably sodium propionate or potassium propionate.

[0056] In a preferred embodiment of the present invention, the weight ratio of crude propionate to seed crystals is 1:0.001-0.1, preferably 1:0.01-0.06, and more preferably 1:0.01-0.03. This preferred weight ratio of crude propionate to seed crystals is more conducive to crystal precipitation, and can further improve the yield and purity of propionate crystals.

[0057] In this invention, the seed crystal is selected from the same compound as the substance to be recrystallized.

[0058] The present invention does not impose any special requirements on the method of filtering the mother liquor obtained by recrystallization, as long as the propionate crystals can be separated. The pore size of the filter membrane used for filtration is 1-100 μm, preferably 30-70 μm.

[0059] In this invention, the method of drying products containing propionate crystals is not particularly limited, and the drying method includes vacuum drying, freeze drying or atmospheric pressure drying.

[0060] In this invention, the drying temperature is not particularly limited. Preferably, the drying temperature is 70-300℃, and more preferably 100-170℃.

[0061] In a preferred embodiment of the present invention, the method further includes preparing crude propionate. The specific preparation method includes: in the presence of water and an organic solvent, reacting propionate and metal hydroxide at a reaction temperature of 50-130°C, concentrating, crystallizing and filtering the reaction solution obtained after the reaction, and drying the filtered product to obtain crude propionate.

[0062] The weight ratio of the organic solvent to water is 1:1.2-10;

[0063] The organic solvent is selected from at least one of alcohols, ketones, nitriles and ethers.

[0064] In this invention, the reaction of propionate ester and metal hydroxide to produce propionate in a system containing both water and an organic solvent at 50-130°C exhibits higher propionate conversion and selectivity. Analysis suggests that the different polarities of propionate and metal hydroxide solutions, coupled with their varying solubilities in a single-solvent reaction system, make it difficult to mix propionate and sodium hydroxide uniformly, resulting in poor contact reaction and low yield. Typically, higher reaction temperatures are required to drive the reaction, leading to increased energy consumption and, more importantly, increased byproducts, further reducing selectivity and product purity. The method of this invention uses water and an organic solvent to form a homogeneous reaction system, significantly improving the conversion rate and product yield of propionate ester and metal hydroxide at a lower reaction temperature. Furthermore, the controlled low reaction temperature greatly reduces byproduct formation, improving reaction selectivity and product purity.

[0065] In this invention, the conversion rate of propionate refers to the proportion of the amount of propionate that participated in the reaction after the reaction to the total amount of propionate before the reaction; that is, conversion rate = (weight of propionate before reaction - weight of propionate after reaction) ÷ weight of propionate before reaction × 100%.

[0066] In this invention, selectivity refers to the ratio of the amount of propionate that generates propionate to the amount of propionate that participates in the reaction; that is, selectivity = amount of propionate that generates propionate ÷ amount of propionate that participates in the reaction × 100%.

[0067] In this invention, the purity of propionate refers to the proportion of the mass of the generated propionate to the total mass of the generated product.

[0068] In this invention, yield refers to the ratio of the actual amount of product generated to the theoretical amount of product generated, i.e., yield = actual amount of product generated ÷ theoretical amount of product generated × 100%.

[0069] In a preferred embodiment of the present invention, the reaction temperature is 50-110℃, preferably 50-70℃. Using this preferred reaction temperature not only ensures higher conversion rate and selectivity but also further reduces energy consumption.

[0070] In this invention, the degree of reaction increases with the extension of time. However, when the conversion rate of propionate reaches a certain level, it is difficult to achieve a significant improvement even if the time is extended further. Instead, it leads to an increase in by-products and increases production costs.

[0071] In a preferred embodiment of the present invention, the contact reaction time is 1-10 hours, preferably 1-3 hours; using this preferred reaction time not only ensures a high conversion rate and selectivity, but also saves reaction time and reduces the amount of by-products.

[0072] In a preferred embodiment of the present invention, the contact reaction is carried out under stirring, and the stirring speed is 300-1000 rpm, preferably 500-1000 rpm, and more preferably 500-700 rpm.

[0073] In a preferred embodiment of the present invention, the weight ratio of the organic solvent to the propionate ester is 1:0.1-2, preferably 1:0.5-1. Using this preferred weight ratio of organic solvent to propionate ester effectively improves the solubility of propionate ester in the reaction system formed by water and organic solvent, while ensuring that the metal hydroxide maintains good solubility as the reaction proceeds, thereby improving the conversion rate and reaction selectivity of propionate ester.

[0074] In a preferred embodiment of the present invention, the weight ratio of the organic solvent to water is 1:1.2-5, more preferably 1:1.5-2.5. Using this preferred weight ratio of organic solvent to water can effectively improve the solubility of the metal hydroxide and propionate in the water and organic solvent system, enabling the metal hydroxide and propionate to have better contact reaction effects, and further improving the conversion rate and reaction selectivity of the propionate.

[0075] In this invention, the molar amount of metal hydroxide is in excess relative to the molar amount of propionate, which ensures that the reaction system is alkaline and promotes the hydrolysis reaction of propionate. To further promote the hydrolysis reaction of propionate, and in a preferred embodiment, the molar ratio of propionate to metal hydroxide is 1:1-10, preferably 1:1.2-5, and more preferably 1.7-2.

[0076] In a preferred embodiment of the present invention, the weight ratio of the metal hydroxide to water is 1:1-15, preferably 1:2-5. This preferred weight ratio of metal hydroxide to water effectively maintains the good solubility of the metal hydroxide in the reaction system formed by water and organic solvent, allowing for better contact reaction between the metal hydroxide and propionate ester, further improving the conversion rate and reaction selectivity of the propionate ester.

[0077] In a more preferred embodiment of the present invention, the alcohol in the organic solvent is a monohydric alcohol with 1-16 carbon atoms, more preferably a monohydric alcohol with 1-8 carbon atoms.

[0078] In this invention, propionate ester is hydrolyzed to form the corresponding alcohol. In a preferred embodiment, the organic solvent is the same as the alcohol obtained after hydrolysis of propionate ester. This preferred embodiment can further improve the conversion rate and reaction selectivity of propionate ester.

[0079] In a more preferred embodiment of the present invention, the organic solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isooctanol, acetone, and acetonitrile, more preferably methanol and / or ethanol. Using methanol and / or ethanol can achieve higher propionate conversion and reaction selectivity. The inventors' analysis shows that the combined action of methanol and / or ethanol with water is more conducive to improving the solubility of metal hydroxide and propionate in the water and organic solvent reaction system, thereby promoting the contact reaction effect between the two. Further research revealed that when the organic solvent and the alcohol produced after hydrolysis of propionate are the same, the conversion rate and reaction selectivity of propionate are further improved.

[0080] In a preferred embodiment of the present invention, the metal hydroxide is selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and zinc hydroxide; preferably, it is selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide, and more preferably, it is sodium hydroxide and / or potassium hydroxide.

[0081] In a preferred embodiment of the present invention, the alcohol providing the hydroxyl group in the propionate contains a substituted or unsubstituted C1-C. 10 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C 6- C 30 One of the aryl groups. The C1-C 10 This refers to C3-C having 1-10 carbon atoms. 12 and C6-C 30 Similarly.

[0082] In a preferred embodiment of the present invention, the propionate is selected from one of methyl propionate, ethyl propionate, butyl propionate and isooctyl propionate, preferably methyl propionate or ethyl propionate.

[0083] In this invention, the propionate ester generally has a high purity, such as 99% or higher. However, the technical solution of this invention is also applicable to propionate esters with lower purity. In a preferred embodiment, the propionate ester has a purity of ≥95%, preferably ≥99%.

[0084] In this invention, the propionate ester can be derived from the product of propionate esterification or prepared by ethylene carbonylation. The propionate esterification method refers to the esterification of propionic acid to produce propionate ester.

[0085] In this invention, the contact reaction is carried out under alkaline conditions. In order to further improve the conversion rate and reaction selectivity of propionate, it is necessary to maintain the alkaline conditions of the reaction system throughout the reaction process. In a preferred embodiment, the pH value of the reaction endpoint of the contact reaction is >7, and preferably the pH value of the reaction endpoint is 7-12.

[0086] In this invention, the reaction solution is concentrated to less than one-third of its original volume; during the concentration process, the concentration temperature is controlled at 50-130℃, preferably 50-90℃. Any known method in the art can be used to concentrate and crystallize the propionate reaction solution to separate the crude propionate. The volume of the concentrated reaction solution can be controlled experimentally or theoretically to ensure complete precipitation of propionate while minimizing or eliminating the precipitation of impurities.

[0087] In this invention, the filtration method is not particularly limited, and suction filtration, pressure filtration or centrifugal filtration can be selected.

[0088] In a preferred embodiment of the present invention, the pore size of the filter membrane used for filtration is 1-10 μm, preferably 3-5 μm.

[0089] In a preferred embodiment of the present invention, the drying method is selected from at least one of vacuum drying, spray drying, freeze drying and infrared drying, preferably spray drying.

[0090] In this invention, the impurities in the crude propionate include chloride impurities, which mainly originate from metal hydroxides in the raw materials. Typically, the cation element of the chloride impurities is the same as that of the propionate; for example, the main impurity of sodium propionate is sodium chloride, the main impurity of potassium propionate is potassium chloride, and the main impurity of calcium propionate is calcium chloride.

[0091] In this invention, the propionate ester can be derived from commercially available products or can be prepared in-house. The preparation method of the propionate ester includes:

[0092] Step (1): Mix the palladium catalyst, ligand, acid and ethylene evenly in the solvent system;

[0093] Step (2): Introduce carbon monoxide to carry out the reaction;

[0094] The ligand is ROH, and R is selected from substituted or unsubstituted C1-C. 10 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C6-C 30 One of the aryl groups.

[0095] In a preferred embodiment of the present invention, the acid is selected from at least one of methanesulfonic acid, sulfuric acid, benzenesulfonic acid and hydrochloric acid, preferably methanesulfonic acid and / or sulfuric acid; using this preferred acid helps to improve the catalytic performance of the catalyst.

[0096] In a preferred embodiment of the present invention, the weight ratio of the ligand, acid, ethylene and carbon monoxide is (1-10):(2-200):(10000-10000000):(10000-10000000).

[0097] In a preferred embodiment of the present invention, the preparation method of the propionate ester includes the following reaction conditions: reaction temperature of 50-120℃; and reaction time of 3-13h.

[0098] In a preferred embodiment of the present invention, the propionate is prepared under stirring conditions.

[0099] In a preferred embodiment of the present invention, the solvent system in step (1) includes an alcohol and an auxiliary solvent miscible with the alcohol; more preferably, the solvent system includes an alcohol having 1-16 carbon atoms, and even more preferably an alcohol having 1-8 carbon atoms;

[0100] In a preferred embodiment of the present invention, the auxiliary solvent is selected from at least one of tetrahydrofuran, toluene, acetone and acetonitrile, more preferably tetrahydrofuran.

[0101] The following detailed description of preferred embodiments of the present invention illustrates the principles of the invention and is not intended to limit the scope of the invention.

[0102] The yield of sodium propionate powder product = actual weight of propionate powder product ÷ theoretical weight of propionate to propionate × 100%;

[0103] Yield of propionate crystals = (weight of propionate crystals - weight of seed crystals) ÷ weight of crude propionate × 100%;

[0104] Ammonium propionate: purchased from Sinopharm Chemical Reagent Co., Ltd., with a purity of 95%.

[0105] Example 1

[0106] 1) Add 100g water, 50g methanol, 30g NaOH and 35g methyl propionate to the reaction vessel, and stir at 600rpm for 20min until the mixture is homogeneous;

[0107] 2) Heat to 70℃, stir at 600 rpm for 2 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 10.7.

[0108] 3) At 80℃, the volume of the reaction mixture is concentrated to 1 / 3 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0109] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0110] Example 2

[0111] 1) Add 100g water, 67g methanol, 54g NaOH and 67g methyl propionate to the reaction vessel, and stir at 600rpm for 20min until the mixture is homogeneous;

[0112] 2) Heat to 70℃, stir at 600 rpm for 2 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 11.3.

[0113] 3) At 80℃, the volume of the reaction mixture is concentrated to 1 / 3 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0114] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0115] Example 3

[0116] 1) Add 100g water, 40g methanol, 16g NaOH and 20g methyl propionate to the reaction vessel, and stir at 600rpm for 20min until the mixture is homogeneous;

[0117] 2) Heat to 90℃, stir at 600 rpm for 2 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 11.9.

[0118] 3) At 75°C, the volume of the reaction mixture is concentrated to 1 / 4 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5 μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0119] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0120] Example 4

[0121] 1) Add 100g water, 50g acetone, 30g NaOH and 35g methyl propionate to the reaction vessel, and stir for 30 minutes until the mixture is homogeneous;

[0122] 2) Heat to 70℃, stir at 400 rpm for 4 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 12.

[0123] 3) At 85℃, the volume of the reaction mixture is concentrated to 1 / 3 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0124] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0125] Example 5

[0126] 1) Add 100g water, 50g acetonitrile, 30g NaOH and 35g methyl propionate to the reaction vessel, and stir for 30 minutes until the mixture is homogeneous;

[0127] 2) Heat to 70℃, stir at 500 rpm for 4 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 12.3.

[0128] 3) At 75°C, the volume of the reaction mixture is concentrated to 1 / 3 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5 μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0129] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0130] Example 6

[0131] 1) Add 100g water, 50g methanol, 30g Ca(OH)2 and 35g methyl propionate to the reaction vessel, and stir for 30 minutes until the mixture is homogeneous;

[0132] 2) Heat to 90℃, stir at 350 rpm for 5 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 12.0.

[0133] 3) At 80℃, the volume of the reaction mixture is concentrated to 1 / 5 of the original volume. Then, the concentrated liquid is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain calcium propionate powder product (crude calcium propionate).

[0134] The conversion rate and reaction selectivity of propionate, the yield and purity of calcium propionate powder were determined, and the results are shown in Table 1.

[0135] Example 7

[0136] 1) Add 100g water, 50g methanol, 30g KOH and 35g methyl propionate to the reaction vessel and stir for 10 minutes until the mixture is homogeneous;

[0137] 2) Heat to 80℃, stir at 300 rpm for 2 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 11.2.

[0138] 3) At 70℃, the volume of the reaction mixture is concentrated to 1 / 3 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 10μm. The filter residue obtained by filtration is spray-dried to obtain potassium propionate powder product (crude potassium propionate).

[0139] The conversion rate and reaction selectivity of propionate, the yield and purity of potassium propionate powder were determined, and the results are shown in Table 1.

[0140] Example 8

[0141] 1) Add 100g water, 50g ethanol, 30g NaOH and 35g ethyl propionate to the reaction vessel and stir for 10 minutes until the mixture is homogeneous;

[0142] 2) Heat to 90℃, stir at 500 rpm for 3 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 12.0.

[0143] 3) At 80℃, the volume of the reaction mixture is concentrated to 1 / 4 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0144] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0145] Example 9

[0146] 1) Add 100g water, 50g butanol, 30g Ca(OH)2 and 35g butyl propionate to the reaction vessel, and stir for 30 minutes until the mixture is homogeneous;

[0147] 2) Heat to 100℃, stir at 500 rpm for 3 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 10.5.

[0148] 3) At 80℃, the volume of the reaction mixture is concentrated to 1 / 3 of the original volume. Then, the concentrated liquid is filtered using a filter membrane with a pore size of 10μm. The filter residue obtained by filtration is spray-dried to obtain calcium propionate powder product (crude calcium propionate).

[0149] The conversion rate and reaction selectivity of propionate, the yield and purity of calcium propionate powder were determined, and the results are shown in Table 1.

[0150] Example 10

[0151] 1) Add 100g water, 50g isooctyl alcohol, 30g Ca(OH)2 and 35g isooctyl propionate to the reaction vessel, and stir for 30 minutes until the mixture is homogeneous;

[0152] 2) Heat to 110℃, stir at 500 rpm for 5 hours and then stop stirring to obtain a reaction mixture. The pH at the reaction endpoint was measured to be 10.8.

[0153] 3) At 80℃, the volume of the reaction mixture is concentrated to 1 / 4 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 10μm. The filter residue obtained by filtration is spray-dried to obtain calcium propionate powder product (crude calcium propionate).

[0154] The conversion rate and reaction selectivity of propionate, the yield and purity of calcium propionate powder were determined, and the results are shown in Table 1.

[0155] Example 11

[0156] 1) Add 100g water, 50g isooctyl alcohol, 30g NaOH and 35g isooctyl propionate to the reaction vessel, and stir for 10 minutes until the mixture is homogeneous;

[0157] 2) Heat to 80℃, stir at 300 rpm for 5 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 12.0.

[0158] 3) At 80℃, the volume of the reaction mixture is concentrated to 1 / 5 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0159] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0160] Example 12

[0161] Sodium propionate was prepared according to the method of Example 1, except that methanol was replaced with an equal amount of ethanol.

[0162] Sodium propionate powder product (crude sodium propionate) was obtained.

[0163] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0164] Example 13

[0165] Sodium propionate was prepared according to the method in Example 1, except that 25g of methanol was used.

[0166] Sodium propionate powder product (crude sodium propionate) was obtained.

[0167] The conversion rate and reaction selectivity of propionate, as well as the yield and purity of sodium propionate powder, were determined, and the results are shown in Table 1.

[0168] Example 14

[0169] Sodium propionate was prepared according to the method in Example 1, except that the amount of sodium hydroxide used was 48g.

[0170] Sodium propionate powder product (crude sodium propionate) was obtained.

[0171] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0172] Example 15

[0173] Sodium propionate was prepared according to the method in Example 1, except that the reaction time in step 2) was 8 hours.

[0174] Sodium propionate powder product (crude sodium propionate) was obtained.

[0175] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0176] Example 16

[0177] Take 10g of the crude sodium propionate prepared in Example 1, add 5mL of water to dissolve it, then add 20mL of methanol, and stir at 50°C until the sodium propionate dissolves.

[0178] Cool to -25℃, add 0.1g of seed crystals, stir for 2 hours at a stirring speed of 300rpm;

[0179] The filter residue was filtered using a 15 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 8.9 g of granular sodium propionate crystals.

[0180] The yield of sodium propionate crystals was 88%, and the purity was 98%.

[0181] Example 17A

[0182] Take 10g of the crude sodium propionate prepared in Example 1, add 5mL of water to dissolve it, then add 20mL of methanol, and stir at 50°C until the sodium propionate dissolves.

[0183] 2) Cool down to -25℃, add 0.1g of seed crystals, stir for 2 hours at a stirring speed of 450rpm;

[0184] 3) The filter was filtered using a 15μm pore size filter membrane, and the resulting filter residue was vacuum dried for 16 hours to obtain 8.9g of granular sodium propionate crystals.

[0185] The yield of sodium propionate crystals was 88%, and the purity was 99%.

[0186] Example 17B

[0187] Recrystallization was performed according to the method of Example 17A, except that methanol was replaced with an equal amount of ethanol.

[0188] 8.3g of granular sodium propionate crystals were obtained.

[0189] The yield of sodium propionate crystals was 82%, and the purity was 99%.

[0190] Example 17C

[0191] Recrystallization was performed according to the method of Example 17A, except that 20 mL of methanol was replaced with 10 mL of isopropanol.

[0192] 7.9g of granular sodium propionate crystals were obtained.

[0193] The yield of sodium propionate crystals was 78%, and the purity was 99%.

[0194] Example 18

[0195] Sodium propionate was purified by recrystallization according to Example 16, except that methanol was replaced with an equal amount of ethanol.

[0196] 8.3g of granular sodium propionate crystals were obtained.

[0197] The yield of sodium propionate crystals was 82%, and the purity was 98%.

[0198] Example 19

[0199] Take 10g of the crude sodium propionate prepared in Example 1, add 5mL of water to dissolve it, then add 10mL of isopropanol, and stir at 60°C until the sodium propionate dissolves.

[0200] Cool to -25℃, add 0.3g of seed crystals, and stir for 2 hours at a stirring speed of 300 rpm;

[0201] The filter residue was filtered using a 15 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 7.9 g of granular sodium propionate crystals.

[0202] The yield of sodium propionate crystals was 76%, and the purity was 99%.

[0203] Example 20A

[0204] Take 10g of the crude potassium propionate prepared in Example 7, add 5mL of water to dissolve it, then add 20mL of methanol, and stir at 50℃ until sodium propionate dissolves; cool down to -25℃, add 0.1g of seed crystals, and stir for 2h at a stirring speed of 400rpm;

[0205] The filter residue was filtered using a 15μm pore size membrane and then vacuum dried for 16 hours.

[0206] 9.1g of granular potassium propionate crystals were obtained.

[0207] The yield of potassium propionate crystals was 90%, and the purity was 99%.

[0208] Example 20B

[0209] Take 10g of the crude sodium propionate prepared in Example 1, add 6mL of water to dissolve it, then add 30mL of methanol, and stir at 70°C until the sodium propionate dissolves.

[0210] Cool to 0℃, add 0.3g of seed crystals, and stir for 2 hours at a stirring speed of 400 rpm;

[0211] The filter residue was filtered using a 15 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 8.3 g of granular sodium propionate crystals.

[0212] The yield of sodium propionate crystals was 80%, and the purity was 99%.

[0213] Example 20C

[0214] Take 10g of the crude sodium propionate prepared in Example 1, add 7mL of water to dissolve it, then add 70mL of methanol, and stir at 40°C until the sodium propionate dissolves.

[0215] Cool to -5℃, add 0.6g of seed crystals, stir for 2 hours at a stirring speed of 300rpm;

[0216] The filter residue was filtered using a 10 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 8.8 g of granular sodium propionate crystals.

[0217] The yield of sodium propionate crystals was 82%, and the purity was 99%.

[0218] Example 20D

[0219] Take 10g of the crude sodium propionate prepared in Example 1, add 10mL of water to dissolve it, then add 10mL of methanol, and stir at 50°C until the sodium propionate dissolves.

[0220] Cool to 0℃, add 1g of seed crystals, and stir for 2 hours at a stirring speed of 500rpm.

[0221] The filter residue was filtered using a 20 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 9.0 g of granular sodium propionate crystals.

[0222] The yield of sodium propionate crystals was 80%, and the purity was 99%.

[0223] Example 20E

[0224] Take 10g of the crude sodium propionate prepared in Example 1, add 3mL of water to dissolve it, then add 30ml of methanol, and stir at 45℃ until the sodium propionate dissolves.

[0225] Cool to 0℃, add 0.01g of seed crystals, and stir for 2 hours at a stirring speed of 400rpm;

[0226] The filter residue was filtered using a 10 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 8.8 g of granular sodium propionate crystals.

[0227] The yield of sodium propionate crystals was 88%, and the purity was 99%.

[0228] Example 21

[0229] Take 10g of ammonium propionate, add 5mL of water to dissolve it, then add 20mL of butanol and stir at 50℃ until the ammonium propionate dissolves.

[0230] Cool to -25℃, add 0.5g of seed crystals, and stir for 2 hours at a stirring speed of 400 rpm;

[0231] The filter residue was filtered using a 15 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 7.9 g of granular ammonium propionate crystals.

[0232] The yield of ammonium propionate crystals was 74%, and the purity was 98%.

[0233] Example 22

[0234] Take 10g of the crude calcium propionate prepared in Example 6, add 7mL of water to dissolve it, then add 25ml of methanol, and stir at 60°C until the calcium propionate dissolves.

[0235] Cool to -25℃, add 0.6g of seed crystals, and stir for 2 hours at a stirring speed of 500 rpm;

[0236] The filter residue was filtered using a 10 μm pore size filter membrane and then vacuum dried for 16 h to obtain 9 g of granular calcium propionate crystals.

[0237] The yield of calcium propionate crystals was 84%, and the purity was 99%.

[0238] Example 23

[0239] Take 10g of the crude calcium propionate prepared in Example 6, add 9mL of water to dissolve it, then add 20mL of ethanol, and stir at 50°C until the calcium propionate dissolves.

[0240] Cool to -25℃, add 0.7g of seed crystals, and stir for 2 hours at a stirring speed of 300 rpm;

[0241] The filter residue was filtered using a 10 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 8.5 g of granular calcium propionate crystals.

[0242] The yield of calcium propionate crystals was 78%, and the purity was 99%.

[0243] Example 24

[0244] Take 10g of the crude calcium propionate prepared in Example 6, add 9mL of water to dissolve it, then add 15mL of isopropanol, and stir at 60°C until the calcium propionate dissolves.

[0245] Cool to -25℃, add 0.3g of seed crystals, and stir for 2 hours at a stirring speed of 300 rpm;

[0246] The filter residue was filtered using a 15 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 8.3 g of granular sodium propionate crystals.

[0247] The yield of calcium propionate crystals was 80%, and the purity was 99%.

[0248] Example 25

[0249] Take 10g of the crude sodium propionate prepared in Example 1, add 6mL of water to dissolve it, then add 30mL of methanol, and stir at 60°C until the sodium propionate dissolves.

[0250] The mixture was cooled to -10℃, 0.3g of seed crystals was added, and the mixture was stirred for 2 hours at a stirring speed of 400 rpm. The mixture was then filtered using a 15μm pore size filter membrane, and the resulting filter residue was vacuum dried for 16 hours to obtain 9.3g of granular potassium propionate crystals.

[0251] The yield of sodium propionate crystals was 90%, and the purity was 99%.

[0252] Example 26

[0253] Take 10g of the crude sodium propionate prepared in Example 1, add 6mL of water to dissolve it, then add 30mL of methanol, and stir at 70°C until the sodium propionate dissolves.

[0254] The temperature was lowered to -15℃, 0.3g of seed crystals were added, and the mixture was stirred for 2 hours at a stirring speed of 400 rpm. The mixture was then filtered using a 15μm pore size filter membrane, and the resulting filter residue was vacuum dried for 16 hours to obtain 8.6g of granular potassium propionate crystals.

[0255] The yield of sodium propionate crystals was 83%, and the purity was 99%.

[0256] Example 27

[0257] Recrystallization was performed according to the method of Example 20A, except that 100 mL of methanol was used.

[0258] 8.9g of granular potassium propionate crystals were obtained.

[0259] The yield of potassium propionate crystals was 88%, and the purity was 99%.

[0260] Example 28

[0261] Recrystallization was performed according to the method of Example 20B, except that the amount of seed crystals used was 1.5g.

[0262] 9.5g of granular potassium propionate crystals were obtained.

[0263] The yield of potassium propionate crystals was 80%, and the purity was 99%.

[0264] Comparative Example 1

[0265] 1) Add 100g water, 30g NaOH and 35g methyl propionate to the reaction vessel and stir for 30 minutes until the mixture is homogeneous;

[0266] 2) Heat to 90℃, stir at 600 rpm for 5 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 12.5.

[0267] 3) At 100℃, the volume of the reaction mixture is concentrated to 1 / 3 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0268] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0269] Comparative Example 2

[0270] 1) Add 100g water, 30g NaOH and 35g isooctyl propionate to the reaction vessel and stir for 10 minutes until the mixture is homogeneous;

[0271] 2) Heat to 80℃, stir at 750 rpm for 5 hours and then stop stirring to obtain a reaction mixture. The pH value at the reaction endpoint was 12.8.

[0272] 3) At 90℃, the volume of the reaction mixture is concentrated to 1 / 4 of the original volume. Then, the concentrated solution is filtered using a filter membrane with a pore size of 5μm. The filter residue obtained by filtration is spray-dried to obtain sodium propionate powder product (crude sodium propionate).

[0273] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0274] Comparative Example 3

[0275] Sodium propionate was prepared according to the method of Example 1, except that the temperature was raised to 135°C in step 2).

[0276] Sodium propionate powder product (crude sodium propionate) was obtained.

[0277] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0278] Comparative Example 4

[0279] Sodium propionate was prepared according to the method of Example 1, except that water was replaced with an equal amount of methanol.

[0280] Sodium propionate powder product (crude sodium propionate) was obtained.

[0281] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0282] Comparative Example 5

[0283] Sodium propionate was prepared according to the method in Example 1, except that 100g of methanol was used.

[0284] Sodium propionate powder product (crude sodium propionate) was obtained.

[0285] The conversion rate and reaction selectivity of propionate, the yield and purity of sodium propionate powder were determined, and the results are shown in Table 1.

[0286] Comparative Example 6

[0287] Recrystallization was performed according to the method of Example 16, except that water was not added.

[0288] 8.8g of granular sodium propionate crystals were obtained.

[0289] The yield of sodium propionate crystals was 87%, and the purity was 85%.

[0290] Comparative Example 7

[0291] Take 10g of sodium propionate prepared in Example 1 and dissolve it in 5mL of water;

[0292] Cool to room temperature, add 0.3g of seed crystals, and stir for 2 hours at a stirring speed of 400 rpm;

[0293] The filter residue was filtered using a 15 μm pore size filter membrane, and then vacuum dried for 16 h to obtain 4.9 g of granular sodium propionate crystals.

[0294] Comparative Example 8

[0295] Recrystallization was performed according to the method of Example 17A, except that methanol was replaced with an equal amount of acetonitrile.

[0296] 6.3g of granular sodium propionate crystals were obtained.

[0297] The yield of sodium propionate crystals was 62%, and the purity was 99%.

[0298] Comparative Example 9

[0299] Recrystallization was performed according to the method of Example 17A, except that methanol was replaced with an equal amount of acetone.

[0300] 6.9g of granular sodium propionate crystals were obtained.

[0301] The yield of sodium propionate crystals was 68%, and the purity was 99%.

[0302] Table 1

[0303]

[0304]

[0305] As can be seen from Examples 1-15 and Comparative Examples 1-5, the propionate prepared in Examples 1-3 using the preferred technical solution of the present invention achieved a propionate conversion rate, propionate selectivity, and propionate yield of 99%, and the purity of the prepared propionate reached 93%. Furthermore, the reaction temperature was low, the reaction time was short, and the efficiency was high.

[0306] Compared to ethanol as the organic solvent in Example 12, methanol was chosen as the organic solvent in Example 1, and it is the same as the alcohol produced after the hydrolysis of methyl propionate. Using this preferred organic solvent, the propionate was prepared with a higher conversion rate and yield, and the prepared propionate had higher purity.

[0307] Compared to Example 14, where the molar ratio of propionate to metal oxide was 1:3, Example 1, using a molar ratio of 1:1.89 (within the preferred range of 1:1.7-2), prepared propionate with higher purity.

[0308] Compared to Comparative Example 3, which used a reaction temperature of 135°C, the propionate prepared in Example 1 at a reaction temperature of 70°C exhibited higher purity. Analysis suggests that excessively high reaction temperatures promote the formation of more byproducts.

[0309] Compared to Comparative Example 4, which prepared propionate only in the presence of an organic solvent, Example 1 prepared propionate in the presence of both water and an organic solvent, resulting in higher propionate conversion and yield, and the obtained propionate had higher purity.

[0310] Compared to Comparative Example 5, where the weight ratio of organic solvent to water was 1:1, the propionate was prepared in Example 1 with a preferred weight ratio of 1:2, resulting in a significantly higher conversion rate and yield of propionate compared to Comparative Example 5.

[0311] As can be seen from Examples 16-28 and Comparative Examples 6-9, the recrystallization yield of Examples 20A and 25, which adopt the most preferred technical solution of the present invention, reached 90%, and the purity of the propionate crystals obtained by recrystallization reached 99%.

[0312] Compared to Comparative Example 8, which used a combination of acetonitrile and water as a recrystallizing agent, and Comparative Example 9, which used a combination of acetone and water as a recrystallizing agent, Examples 17A to 17C of the present invention have higher yields in the preparation of propionate crystals using a combination of alcohol and water as a recrystallizing agent.

[0313] Compared to Example 16, where the recrystallization raw material was sodium propionate, Example 20A used potassium propionate as the recrystallization raw material. The yield of potassium propionate crystals obtained by recrystallization was 90%, which was higher than the 88% of Example 16. Moreover, under the condition of increasing the stirring speed, the purity of the potassium propionate crystals obtained in Example 20A was also higher than that in Example 16.

[0314] Compared to Example 17B, which uses a combination of ethanol and water as a recrystallizing agent, and Example 17C, which uses isopropanol and water as a recrystallizing agent, Example 17A of the present invention, which uses a combination of methanol and water as a recrystallizing agent, has a higher yield in preparing propionate crystals.

[0315] Compared to Example 16, which used a stirring speed of 300 rpm for recrystallization, Example 17A used a stirring speed of 450 rpm, and the resulting propionate crystals achieved a purity of 99%, which is higher than the 98% purity of Example 16.

[0316] Compared to Example 20B, which uses a dissolution temperature of 70°C and a recrystallization temperature of 0°C, and Example 26, which uses a dissolution temperature of 70°C and a recrystallization temperature with a temperature difference of 85°C between the dissolution and dissolution temperatures, the dissolution temperature, recrystallization temperature, and temperature difference between the recrystallization and dissolution temperatures in Example 25 of the present invention are all within the optimal range. The yield of propionate obtained by recrystallization under these temperature conditions reached 90%, which is much higher than the 80% of Example 20B and the 83% of Example 26.

[0317] Compared to the methanol-to-water ratio of 20 in the recrystallizing agent of Example 27, the methanol-to-water ratio of the recrystallizing agent of Example 20A is 4. Under these preferred recrystallizing agent combination conditions, the yield of propionate obtained by recrystallization reached 90%, which is higher than the 88% yield of Example 27.

[0318] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for recrystallizing propionate, characterized in that, The method includes dissolving crude propionate in a recrystallization solvent at a first temperature, then adding seed crystals and cooling to a second temperature for recrystallization, followed by filtration and drying to obtain purified propionate. The recrystallization solvent includes alcohol and water; The volume ratio of water to alcohol in the recrystallization solvent is 1:1-20; The second temperature is 10-90°C lower than the first temperature.

2. The method according to claim 1, characterized in that, The second temperature is 40-80°C lower than the first temperature, preferably 70-75°C lower; And / or, the crude propionate is dissolved in a recrystallization solvent by a method comprising the following steps: dissolving the crude propionate in water at a first temperature of 30°C-70°C, then adding alcohol and stirring until completely dissolved; And / or, the recrystallization conditions include: a second temperature of -40-50°C, preferably -25-0°C; and a time of 1-24 hours, preferably 2-7 hours; And / or, the recrystallization is carried out under stirring at a speed of 100-1000 rpm, preferably 300-500 rpm.

3. The method according to claim 1 or 2, characterized in that, The volume ratio of water to alcohol in the recrystallization solvent is 1:4-20, more preferably 1:4-5; And / or, the weight ratio of the crude propionate to the volume ratio of water is 1:0.3-1, more preferably 1:0.5-0.6; And / or, the weight ratio of the crude propionate to the seed crystals is 1:0.001-0.1, preferably 1:0.01-0.

06.

4. The method according to any one of claims 1-3, characterized in that, The recrystallization solvent includes a monohydric alcohol having 1-16 carbon atoms, preferably a monohydric alcohol having 1-8 carbon atoms; Preferably, the monohydric alcohol is selected from at least one of methanol, ethanol, isopropanol, butanol and isooctyl alcohol.

5. The method according to any one of claims 1-4, characterized in that, The method further includes preparing crude propionate, specifically comprising: reacting propionate with metal hydroxide in the presence of water and organic solvent at a reaction temperature of 50-130°C; concentrating, crystallizing and filtering the reaction solution obtained after the reaction; and drying the filtered product to obtain crude propionate. The weight ratio of the organic solvent to water is 1:1.2-10; The organic solvent is selected from at least one of alcohols, ketones, nitriles and ethers.

6. The method according to claim 5, characterized in that, The reaction temperature is 50-110℃, preferably 50-70℃; And / or, the contact reaction time is 1-10 hours, preferably 1-3 hours; And / or, the contact reaction is carried out under stirring, preferably at a speed of 300-1000 rpm, more preferably 500-1000 rpm, and even more preferably 500-700 rpm.

7. The method according to claim 5 or 6, characterized in that, The weight ratio of the organic solvent to the propionate ester is 1:0.1-2, preferably 1:0.5-1; And / or, the weight ratio of the organic solvent to water is 1:1.2-5, preferably 1:1.5-2.5; And / or, the molar ratio of the propionate ester to the metal hydroxide is 1:1-10, preferably 1:1.2-5, more preferably 1:1.7-2.

8. The method according to any one of claims 5-7, characterized in that, The alcohol in the organic solvent is a monohydric alcohol with 1-16 carbon atoms, more preferably a monohydric alcohol with 1-8 carbon atoms; Preferably, the organic solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isooctyl alcohol, acetone, and acetonitrile; And / or, the metal hydroxide is selected from one of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and zinc hydroxide; And / or, the propionate ester is selected from one of methyl propionate, ethyl propionate, butyl propionate and isooctyl propionate.

9. The method according to any one of claims 5-8, characterized in that, The reaction solution is concentrated to less than 1 / 3 of its original volume; And / or, the pore size of the filter membrane used for filtration is 1-10 μm, preferably 3-5 μm; And / or, the drying method is selected from at least one of vacuum drying, spray drying, freeze drying and infrared drying.

10. The method according to any one of claims 1-9, characterized in that, The crude propionate contains impurities including chloride impurities.

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