Use of glacial acetic acid in circular production system for α-acetyl-γ-butyrolactone

Abstract

The present invention relates to the use of glacial acetic acid in a circular production system for α-acetyl-γ-butyrolactone. The use comprises the following steps: adding glacial acetic acid to an α-acetyl-γ-butyrolactone sodium solution generated by a condensation reaction of γ-butyrolactone, an acetate and sodium metal, performing a neutralization reaction, then performing solid-liquid separation, and then adding an esterification reaction catalyst to the obtained α-acetyl-γ-butyrolactone solution, performing reactive rectification, subjecting a byproduct, i.e., alkyl alcohol, and glacial acetic acid to an esterification reaction so as to generate an acetate, and recycling the produced acetate into the condensation reaction. It is proposed for the first time in the present invention that glacial acetic acid is used as a neutralizing agent during the synthesis process of α-acetyl-γ-butyrolactone, the raw material, i.e., glacial acetic acid and the by-product, i.e., alkyl alcohol (ROH), are converted into an acetate by means of subsequent reactive rectification, and the produced acetate is directly recycled into the condensation reaction, thereby constructing a circular production system for α-acetyl-γ-butyrolactone.

Description

Application of anhydrous acetic acid in the recycling production system of α-acetyl-γ-butyrolactone Technical Field

[0001] The invention belongs to the technical field of chemical synthesis and relates to application of anhydrous acetic acid in an α-acetyl-γ-butyrolactone circulation production system. Background Art

[0002] α-Acetyl-γ-butyrolactone (ABL) is an important pharmaceutical intermediate and organic chemical raw material. It is a key intermediate in the preparation of vitamins and chlorophyll, and is also a pharmaceutical intermediate in the synthesis of drugs such as the antipsychotic drug risperidone, the anticonvulsant and sedative-hypnotic drugs clomethiazole, acetaminophen, and chloroquine. Currently, there are two main routes for the preparation of α-acetyl-γ-butyrolactone: one using ethylene oxide and ethyl acetoacetate as starting materials, and the other using γ-butyrolactone and acetate as starting materials.

[0003] The process for preparing α-acetyl-γ-butyrolactone from γ-butyrolactone and acetate esters primarily involves a condensation reaction, a neutralization reaction, and a subsequent distillation step. In the neutralization step, aqueous phosphoric acid and dilute sulfuric acid are often used as neutralizing agents. However, using these neutralizing agents is not conducive to the recycling of materials and byproducts, and also results in low product yields.

[0004] For example, in the synthesis method for α-acetyl γ-butyrolactone disclosed in Chinese Patent CN107857745A, after the condensation reaction is completed, ethanol and ethyl acetate are first distilled off, followed by neutralization with the addition of dilute sulfuric acid. The resulting organic phase is then allowed to stand for separation, and then vacuum distilled to produce ABL. The byproduct, ethanol, is distilled off along with the ethyl acetate, resulting in a significant waste of resources. Furthermore, the maximum yield of ABL is only 93.0%.

[0005] Another example is the α-acetyl-γ-butyrolactone process provided by Chinese patent CN111018810A. A phosphoric acid solution is added during the neutralization reaction step, followed by stratification. The resulting organic phase is then distilled under atmospheric pressure and then under reduced pressure to produce ABL. After neutralization with the phosphoric acid solution and stratification, the aqueous phase, which includes water, ethanol, sodium phosphate, and phosphoric acid, is separated and purified. This process requires significant energy consumption and cannot be effectively separated, resulting in a waste of resources. Most importantly, none of these substances can be converted into raw materials for recycling within the entire reaction system. Furthermore, the maximum yield of ABL is only 94.0%. Technical issues

[0006] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to provide an application of anhydrous acetic acid in a recycling production system of α-acetyl-γ-butyrolactone, so as to realize the recycling of materials in the entire reaction system. Solution

[0007] The technical solution adopted by the present invention to solve the technical problem is to provide an application of anhydrous acetic acid in an α-acetyl-γ-butyrolactone circulation production system, a α-acetyl-γ-butyrolactone circulation production system and α-acetyl-γ-butyrolactone prepared by the above circulation production system.

[0008] The first object of the present invention is achieved through the following technical solutions:

[0009] The application of anhydrous acetic acid in an α-acetyl-γ-butyrolactone recycling production system comprises the following steps:

[0010] Anhydrous acetic acid is added to the α-acetyl-γ-butyrolactone sodium salt solution generated by the condensation reaction of γ-butyrolactone, acetate and metallic sodium to carry out a neutralization reaction. After solid-liquid separation, an esterification reaction catalyst is added to the obtained α-acetyl-γ-butyrolactone-containing solution to carry out reactive distillation. The by-product alkyl alcohol reacts with anhydrous acetic acid to produce acetate, and the recovered acetate is recycled and reused in the condensation reaction.

[0011] In the above application, the metallic sodium used can be solid metallic sodium or liquid metallic sodium.

[0012] If the metallic sodium is solid metallic sodium, the solid metallic sodium is directly added into the reaction system to carry out the reaction.

[0013] If the metallic sodium is liquid metallic sodium, solid metallic sodium is first prepared into liquid metallic sodium, and then the liquid metallic sodium is added into the reaction system for reaction.

[0014] For example, the method for synthesizing liquid sodium metal includes the following steps: adding solid sodium metal into a reactor under an inert gas atmosphere, heating and melting the solid sodium metal to obtain liquid sodium metal. The melting temperature is greater than the melting point of the sodium metal and can be selected from 100 to 150°C.

[0015] Preferably, the metallic sodium is liquid metallic sodium.

[0016] In the above applications, the chemical formula of the acetate used is CH3COOR, where R is an alkyl group.

[0017] Preferably, in the chemical formula of the acetate, the molecular formula of R is C n H 2n+1 , n is an integer from 1 to 20.

[0018] More preferably, n is an integer of 1 to 10.

[0019] More preferably, n is an integer of 1 to 5.

[0020] Preferably, the acetate is one or more of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, tert-butyl acetate, n-pentyl acetate, isopentyl acetate, sec-pentyl acetate, tert-pentyl acetate, and 3-pentyl acetate.

[0021] More preferably, the acetate is one or more of ethyl acetate, n-propyl acetate, and n-butyl acetate.

[0022] Most preferably, the acetate is ethyl acetate.

[0023] Preferably, during the condensation reaction, the molar mass ratio of γ-butyrolactone to acetate is 1:1.0 to 20.0, more preferably 1:1.5 to 10.0, for example, 1:1.5, 1:2, 1:2.5, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the molar mass ratio of γ-butyrolactone to sodium metal is 1:1.0~15.0, more preferably 1:1.0~8.0, for example, it can be 1:1.0, 1:1.5, 1:2, 1:2.5, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the condensation reaction is a reflux reaction at a reflux temperature of 70-180°C, the specific reflux temperature depending on the type of acetate used. The reflux reaction time is 1-50 hours, more preferably 2-30 hours, and even more preferably 3-20 hours. For example, it can be 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, or 20 hours, but is not limited to the values ​​listed above. Other values ​​within the numerical range not listed are also applicable.

[0026] During the condensation reaction, the chemical reaction equation is as follows:

[0027] .

[0028] Acetate, γ-butyrolactone and metallic sodium react to generate α-acetyl-γ-butyrolactone sodium salt and alkyl alcohol ROH.

[0029] During the neutralization reaction, only anhydrous acetic acid can be used for the neutralization reaction. In this way, the by-product alkyl alcohol ROH formed by the reaction can undergo esterification with the remaining acetic acid after the neutralization reaction to form acetate, and the acetate can be recovered by distillation and recycled to the condensation reaction.

[0030] Preferably, the molar amount of the added anhydrous acetic acid is ≥ the molar amount of γ-butyrolactone.

[0031] More preferably, the molar amount of the added anhydrous acetic acid is greater than or equal to the sum of the molar amounts of γ-butyrolactone and metallic sodium.

[0032] Still more preferably, the molar amount of the added anhydrous acetic acid is the sum of the molar amounts of γ-butyrolactone and metallic sodium.

[0033] The molar amount of acetic acid added to the neutralization reaction is further controlled to be the sum of the molar amounts of γ-butyrolactone and sodium metal. In this way, the remaining acetic acid and by-product ROH after the neutralization reaction can be completely consumed in the subsequent esterification reaction process to avoid excess acetic acid or by-product ROH, which affects the reaction distillation and reduces the recovery of acetate, while avoiding waste of resources. In addition, in theory, the amount of acetate extracted after the reaction distillation is the same as the amount of acetate added in the condensation reaction, but in the actual process, the acetate extracted will be lost, which is different from the amount of acetate added in the condensation reaction, but the difference is not large. The extracted acetate can be directly recycled to the condensation reaction without the need to add additional acetate in the condensation reaction, or only a small amount of acetate needs to be added to make up for the loss in the actual process, thereby realizing the closed recycling of acetate.

[0034] Preferably, the neutralization reaction is carried out at 20-60° C. for 1-100 min.

[0035] The chemical reaction equation for the neutralization reaction process is as follows:

[0036] .

[0037] The solid-liquid separation after the neutralization reaction can be exemplified by centrifugal separation or filtration separation.

[0038] After solid-liquid separation, the collected solid is sodium acetate, and the collected liquid is an ABL-containing solution, which includes ABL, ROH, and acetic acid. Alternatively, if an excess of acetate is added during the condensation reaction, the ABL-containing solution includes ABL, ROH, acetic acid, and acetate.

[0039] The esterification reaction catalyst used is used to catalyze the esterification reaction between anhydrous acetic acid and alkyl ROH. Any catalyst that can be used to catalyze the esterification reaction between anhydrous acetic acid and ROH is within the scope of protection of the present invention.

[0040] Preferably, the esterification reaction catalyst is an acid catalyst, which can be sulfuric acid, phosphoric acid, p-toluenesulfonic acid, etc.

[0041] More preferably, the esterification reaction catalyst is sulfuric acid.

[0042] Still more preferably, the esterification reaction catalyst is concentrated sulfuric acid with a mass fraction of 92% or more.

[0043] Still more preferably, the esterification reaction catalyst is concentrated sulfuric acid with a mass fraction of 95% or more.

[0044] Optimally, the esterification reaction catalyst is concentrated sulfuric acid with a mass fraction of 98% or more.

[0045] Preferably, the reactive distillation is atmospheric pressure reactive distillation, which is carried out in a distillation tower with a bottom temperature of 90-200°C and a top temperature of 70-150°C, which is lower than the bottom temperature.

[0046] The esterification reaction of anhydrous acetic acid and alkyl ROH is carried out in the bottom of the distillation tower.

[0047] The reactive distillation process specifically includes: adding an esterification reaction catalyst to a solution containing ABL, feeding the mixed solution into the bottom of a distillation tower, wherein acetic acid and ROH undergo an esterification reaction under high temperature conditions in the bottom of the tower to produce acetate, and collecting an azeotrope of acetate and water. After separation, crude acetate is obtained, and the crude acetate is dehydrated to obtain pure acetate, which is directly applied to the condensation reaction.

[0048] Preferably, the acetate produced by reactive distillation is recycled to the condensation reaction, and the residue after reactive distillation is further subjected to vacuum distillation to obtain α-acetyl-γ-butyrolactone.

[0049] Preferably, the vacuum distillation is carried out in a vacuum distillation tower, the pressure of the vacuum distillation tower is 1-50 kPa, the bottom temperature of the vacuum distillation tower is 110-200°C, the top temperature is 80-130°C, and the top temperature is lower than the bottom temperature.

[0050] The second object of the present invention is achieved through the following technical solutions:

[0051] The cyclic production system of α-acetyl-γ-butyrolactone comprises the following steps:

[0052] Condensation reaction: γ-butyrolactone, acetate and metallic sodium undergo condensation reaction to generate α-acetyl-γ-butyrolactone sodium salt solution;

[0053] Neutralization reaction: adding anhydrous acetic acid to the α-acetyl-γ-butyrolactone sodium salt solution for neutralization, and obtaining a solution containing α-acetyl-γ-butyrolactone after solid-liquid separation;

[0054] Reactive distillation: add esterification catalyst to the solution containing α-acetyl-γ-butyrolactone, perform reactive distillation, and produce acetate;

[0055] Vacuum distillation: The residue after reactive distillation is further subjected to vacuum distillation to obtain α-acetyl-γ-butyrolactone.

[0056] In the method provided by the second object of the present invention, the specific description and preferred embodiments of the condensation reaction step and the neutralization reaction step are the same as those of the application provided by the first object of the present invention.

[0057] In the reactive distillation step, the produced acetate can be directly recycled to the condensation reaction, realizing the recycling of acetate in the synthesis method of α-acetyl-γ-butyrolactone; or the produced acetate can be added to the condensation reaction alone, or used in other reaction processes, realizing the green recovery of acetate.

[0058] Preferably, the acetate produced in the reactive distillation step is recycled to the condensation reaction. Thus, the entire ABL preparation process is a cyclic production system, with the byproducts being esterified to form acetate, which is then recycled to the reaction.

[0059] Preferably, the vacuum distillation is carried out in a vacuum distillation tower, the pressure of the vacuum distillation tower is 1-50 kPa, the bottom temperature of the vacuum distillation tower is 110-200°C, the top temperature is 80-130°C, and the top temperature is lower than the bottom temperature.

[0060] Preferably, in the synthesis method of the present invention, the purity of the synthesized α-acetyl-γ-butyrolactone is ≥99%, more preferably ≥99.5%; the yield of the synthesized α-acetyl-γ-butyrolactone is ≥95%, more preferably ≥96%.

[0061] The third object of the present invention is achieved through the following technical solutions:

[0062] An α-acetyl-γ-butyrolactone is prepared by a synthesis method comprising the following steps:

[0063] Condensation reaction: γ-butyrolactone, acetate and metallic sodium undergo condensation reaction to generate α-acetyl-γ-butyrolactone sodium salt solution;

[0064] Neutralization reaction: adding anhydrous acetic acid to the α-acetyl-γ-butyrolactone sodium salt solution for neutralization, and obtaining a solution containing α-acetyl-γ-butyrolactone after solid-liquid separation;

[0065] Reactive distillation: add esterification catalyst to the solution containing α-acetyl-γ-butyrolactone, perform reactive distillation, and produce acetate;

[0066] Vacuum distillation: The residue after reactive distillation is further subjected to vacuum distillation to obtain α-acetyl-γ-butyrolactone.

[0067] The specific description and preferred embodiments of the synthesis steps of α-acetyl-γ-butyrolactone provided by the third object of the present invention are the same as those of the α-acetyl-γ-butyrolactone recycling production system provided by the second object of the present invention.

[0068] Preferably, the purity of the α-acetyl-γ-butyrolactone is ≥99%, more preferably ≥99.5%. Beneficial effects

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] 1. The present invention proposes for the first time the use of anhydrous acetic acid as a neutralizing agent in the synthesis process of α-acetyl-γ-butyrolactone. Through subsequent reaction and distillation, the raw material anhydrous acetic acid and the by-product alkyl alcohol ROH are converted into acetate. The recovered acetate is directly recycled and reused in the condensation reaction, thus forming a circular production system for α-acetyl-γ-butyrolactone.

[0071] 2. In the cyclic production system for α-acetyl-γ-butyrolactone of the present invention, the γ-butyrolactone raw material reacts completely; the sodium metal raw material ultimately produces sodium acetate, which is recycled in the solid-liquid separation step; the acetate raw material reacts partially to produce ABL, and the remainder is withdrawn in the reactive distillation step and recycled to the condensation reaction; the neutralizing agent, anhydrous acetic acid, undergoes a partial neutralization reaction to produce sodium acetate, which is recycled in the solid-liquid separation step as described above; the remainder and the by-product, alkyl alcohol ROH, undergo an esterification reaction in the reactive distillation step to produce acetate, which is withdrawn and recycled to the condensation reaction. In other words, in the cyclic production system for α-acetyl-γ-butyrolactone provided by the present invention, all raw materials and by-products are recycled. In particular, the reaction raw materials, acetate, anhydrous acetic acid, and by-product alkyl alcohol ROH, undergo special treatment to convert them into acetate, which is directly recycled to the condensation reaction. The entire ABL preparation process is a cyclic reaction system, and the by-products produced undergo an esterification reaction to produce acetate, which is recycled to the reaction, forming a closed loop. It effectively reduces production costs, avoids waste of resources, and is environmentally friendly.

[0072] 3. The present invention further controls the molar amount of anhydrous acetic acid added in the neutralization reaction to be the sum of the molar amounts of γ-butyrolactone and metallic sodium. In this way, the remaining anhydrous acetic acid and the by-product ROH after the neutralization reaction can be completely consumed in the subsequent esterification reaction to produce acetate, thereby preventing excess acetic acid or by-product ROH from affecting the reaction distillation and resulting in a reduced acetate recovery, while also avoiding waste of resources.

[0073] 4. The α-acetyl-γ-butyrolactone recycling production system provided by the present invention is conducive to improving the ABL yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] FIG1 is a flow chart of the α-acetyl-γ-butyrolactone recycling production system provided by the present invention. Modes for Carrying Out the Invention

[0075] Below by specific embodiment and accompanying drawing, technical scheme of the present invention is further described explanation, it should be understood that specific embodiment described herein is only for helping to understand the present invention, is not used for specific limitation of the present invention.And accompanying drawing used herein, is only for better illustrating the disclosure of the present invention, does not have limiting effect on protection scope.If no special instructions, the raw materials adopted in the embodiment of the present invention are all raw materials commonly used in this area, and the method adopted in the embodiment is all conventional method in this area.

[0076] 1. Example 1

[0077] Under nitrogen atmosphere, 1.2 mol of metallic sodium was put into a storage tank, and the temperature was raised to 130°C and kept at this temperature for 2 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0078] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 4 mol of ethyl acetate, stir, and then slowly heat to 80°C. Open the dripping valve of the storage tank and drip liquid sodium metal into the condensation reactor. After the dripping is complete, keep the system reflux for 10 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0079] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 40°C, 2.2 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 30 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for later use. The ABL-containing solution included ethyl acetate, acetic acid, ethanol, and ABL.

[0080] 5 g of 98% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 120°C, and the top temperature was 72°C. Acetic acid and ethanol underwent esterification reaction in the bottom of the tower to produce ethyl acetate. The azeotrope of ethyl acetate and water was collected from the top of the tower and separated by layers to obtain crude ethyl acetate. The crude ethyl acetate was dehydrated to obtain 3.6 mol of pure ethyl acetate, which was directly used in the condensation reaction.

[0081] The residue in the distillation tower kettle was subjected to reduced pressure distillation again at a pressure of 5 kPa, a kettle temperature of 130°C, and a tower top temperature of 98°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.5%, with a yield of 97.5%.

[0082] The flow chart of the entire α-acetyl-γ-butyrolactone recycling production system is shown in Figure 1.

[0083] 2. Example 2

[0084] Under nitrogen atmosphere, 1.1 mol of metallic sodium was put into a storage tank, and the temperature was raised to 135°C and kept warm for 2.5 hours to melt all the metallic sodium to obtain liquid metallic sodium.

[0085] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 3 mol of methyl acetate, stir, and then slowly heat to 75°C. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system under reflux for 9 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone.

[0086] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 42°C, 2.1 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 35 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for future use. The ABL-containing solution included methyl acetate, acetic acid, methanol, and ABL.

[0087] 4.5 g of 96% concentrated sulfuric acid was added to the ABL solution and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 120°C and the top temperature was 65°C. Acetic acid and methanol underwent esterification reaction in the bottom of the tower to produce methyl acetate. The azeotrope of methyl acetate and water was extracted from the top of the tower and separated to obtain crude methyl acetate. The crude methyl acetate was dehydrated to obtain 2.6 mol of pure ethyl acetate, which was directly used in the condensation reaction.

[0088] The residue in the distillation tower bottom was subjected to reduced pressure distillation again at a pressure of 1 kPa, a tower bottom temperature of 125°C, and a tower top temperature of 92°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.1%, with a yield of 97.0%.

[0089] 3. Example 3

[0090] Under nitrogen atmosphere, 1.3 mol of metallic sodium was put into a storage tank, and the temperature was raised to 140°C and kept at this temperature for 2 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0091] In a fully dried condensation reactor equipped with an electric stirrer, a condenser, and a thermometer, add 1 mol of γ-butyrolactone and 5 mol of n-propyl acetate, stir, and then slowly heat to reflux. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system at reflux for 12 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone.

[0092] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 38°C, 2.3 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 40 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for future use. The ABL-containing solution included n-propyl acetate, acetic acid, n-propanol, and ABL.

[0093] 6 g of 97% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 130°C, and the top temperature was 102°C. Acetic acid and n-propanol underwent an esterification reaction in the bottom of the tower to produce n-propyl acetate. The azeotrope of n-propyl acetate and water was collected from the top of the tower and separated to obtain crude n-propyl acetate. The crude n-propyl acetate was dehydrated to obtain 4.3 mol of pure n-propyl acetate, which was directly used in the condensation reaction.

[0094] The residue in the distillation tower bottom was subjected to reduced pressure distillation again at a pressure of 3 kPa, a tower bottom temperature of 120°C, and a tower top temperature of 94°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.3%, with a yield of 96.6%.

[0095] 4. Example 4

[0096] Under nitrogen atmosphere, 1.4 mol of metallic sodium was put into a storage tank, and the temperature was raised to 135°C and kept warm for 3 hours to melt all the metallic sodium to obtain liquid metallic sodium.

[0097] In a fully dried condensation reactor equipped with an electric stirrer, a condenser, and a thermometer, add 1 mol of γ-butyrolactone and 5.5 mol of n-butyl acetate, stir, and then slowly heat to reflux. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system at reflux for 13 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone.

[0098] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 45°C, 2.4 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 30 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for future use. The ABL-containing solution included n-butyl acetate, acetic acid, n-butanol, and ABL.

[0099] 6.5 g of 98% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 135°C, and the top temperature was 120°C. Acetic acid and n-butanol underwent esterification in the bottom of the tower to produce n-butyl acetate. An azeotrope of n-butyl acetate and water was extracted from the top of the tower. After layering, crude n-butyl acetate was obtained. The crude n-butyl acetate was dehydrated to obtain 4.5 mol of pure n-butyl acetate, which was directly used in the condensation reaction.

[0100] The residue in the distillation tower bottom was subjected to reduced pressure distillation again at a pressure of 4 kPa, a bottom temperature of 122°C, and a top temperature of 95°C. The ABL product was taken out from the top of the tower. The ABL content was determined to be 99.2% and the yield was 96.3%.

[0101] 5. Example 5

[0102] Under nitrogen atmosphere, 1.6 mol of metallic sodium was put into a storage tank, and the temperature was raised to 135°C and kept warm for 3 hours to melt all the metallic sodium to obtain liquid metallic sodium.

[0103] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 6 mol of n-pentyl acetate, stir, and then slowly heat to reflux. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system at reflux for 14 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0104] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 45°C, 2.6 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 40 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for future use. The ABL-containing solution included n-pentyl acetate, acetic acid, n-pentanol, and ABL.

[0105] 8 g of 95% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 160°C, and the top temperature was 150°C. Acetic acid and n-pentanol underwent an esterification reaction in the bottom of the tower to produce n-pentyl acetate. The azeotrope of n-pentyl acetate and water was collected from the top of the tower and separated to obtain crude n-pentyl acetate. The crude n-pentyl acetate was dehydrated to obtain 5.0 mol of pure n-pentyl acetate, which was directly used in the condensation reaction.

[0106] The residue in the distillation tower kettle was subjected to reduced pressure distillation again at a pressure of 5 kPa, a kettle temperature of 135°C, and a tower top temperature of 96°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99%, with a yield of 95.2%.

[0107] 6. Example 6

[0108] Under nitrogen atmosphere, 2 mol of metallic sodium was put into a storage tank, and the temperature was raised to 135°C and kept at this temperature for 2.5 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0109] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 6.5 mol of isopropyl acetate, stir, and then slowly heat to reflux. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system at reflux for 15 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0110] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 45°C, 3 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 35 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for future use. The ABL-containing solution included isopropyl acetate, acetic acid, isopropyl alcohol, and ABL.

[0111] 7.5 g of 98% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 125°C, and the top temperature was 88°C. Acetic acid and isopropyl alcohol underwent esterification in the bottom of the tower to produce isopropyl acetate. The azeotrope of isopropyl acetate and water was collected from the top of the tower. After layering, crude isopropyl acetate was obtained. The crude isopropyl acetate was dehydrated to obtain 5.5 mol of pure isopropyl acetate, which was directly used in the condensation reaction.

[0112] The residue in the distillation tower kettle was subjected to reduced pressure distillation again at a pressure of 5 kPa, a kettle temperature of 135°C, and a tower top temperature of 96°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.2%, with a yield of 95.9%.

[0113] 7. Example 7

[0114] Under nitrogen atmosphere, 3 mol of sodium metal was put into a storage tank, heated to 140°C, and kept warm for 3 hours to melt all the sodium metal to obtain liquid sodium metal.

[0115] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 7 mol of isobutyl acetate, stir, and then slowly heat to reflux. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system at reflux for 16 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0116] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 40°C, 4 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 40 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for future use. The ABL-containing solution included isobutyl acetate, acetic acid, isobutanol, and ABL.

[0117] 9 g of 97% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 145°C, and the top temperature was 116°C. Acetic acid and isobutanol underwent an esterification reaction in the bottom of the tower to produce isobutyl acetate. An azeotrope of isobutyl acetate and water was extracted from the top of the tower. After layering, crude isobutyl acetate was obtained. The crude isobutyl acetate was dehydrated to obtain 5.7 mol of pure isobutyl acetate, which was directly used in the condensation reaction.

[0118] The residue in the distillation tower kettle was subjected to reduced pressure distillation again at a pressure of 6 kPa, a kettle temperature of 140°C, and a tower top temperature of 100°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.0%, with a yield of 95.4%.

[0119] 8. Example 8

[0120] Under nitrogen atmosphere, 4 mol of metallic sodium was put into a storage tank, heated to 140°C, and kept warm for 2 hours to melt all the metallic sodium to obtain liquid metallic sodium.

[0121] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 8 mol of ethyl acetate, stir, and then slowly heat to 85°C. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system under reflux for 13 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone.

[0122] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 40°C, 5 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 40 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for future use. The ABL-containing solution included ethyl acetate, acetic acid, ethanol, and ABL.

[0123] 10 g of 98% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 125°C, and the top temperature was 73°C. Acetic acid and ethanol underwent esterification in the bottom of the tower to produce ethyl acetate. The azeotrope of ethyl acetate and water was collected from the top of the tower and separated to obtain crude ethyl acetate. The crude ethyl acetate was dehydrated to obtain 7.5 mol of pure ethyl acetate, which was directly used in the condensation reaction.

[0124] The residue in the distillation tower kettle was subjected to reduced pressure distillation again at a pressure of 5 kPa, a kettle temperature of 136°C, and a tower top temperature of 97°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.6%, with a yield of 97.9%.

[0125] 9. Example 9

[0126] The difference between Example 9 and Example 1 is that Example 9 directly uses solid metallic sodium, and the specific steps are as follows:

[0127] In a fully dried condensation reaction kettle equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 4 mol of ethyl acetate, stir, then add sodium metal, slowly heat to 80°C, and keep the system under reflux for 10 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0128] The subsequent steps are the same as in Example 1.

[0129] 3.6 mol of pure ethyl acetate was obtained. The ABL product was taken from the top of the tower, and the ABL content was determined to be 99.1%, with a yield of 94.9%.

[0130] 10. Example 10

[0131] Under nitrogen atmosphere, 1.5 mol of metallic sodium was put into a storage tank, and the temperature was raised to 150°C and kept at this temperature for 2 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0132] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 4 mol of ethyl acetate, stir, and then slowly heat to 85°C. Open the dripping valve of the storage tank and dropwise add liquid sodium metal to the condensation reactor. After the addition is complete, maintain the system under reflux for 15 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone.

[0133] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 50°C, 2.5 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 50 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for later use. The ABL-containing solution included ethyl acetate, acetic acid, ethanol, and ABL.

[0134] 6 g of 98% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 125°C, and the top temperature was 75°C. Acetic acid and ethanol underwent esterification in the bottom of the tower to produce ethyl acetate. An azeotrope of ethyl acetate and water was collected from the top of the tower and separated by stratification to obtain crude ethyl acetate. The crude ethyl acetate was dehydrated to obtain 3.7 mol of pure ethyl acetate, which was stored for future use.

[0135] The residue in the distillation tower bottom was subjected to reduced pressure distillation again at a pressure of 5 kPa, a tower bottom temperature of 140°C, and a tower top temperature of 96°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.2%, with a yield of 97.3%.

[0136] 11. Example 11

[0137] Under nitrogen atmosphere, 1.2 mol of metallic sodium was put into a storage tank, and the temperature was raised to 130°C and kept at this temperature for 2 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0138] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 4 mol of ethyl acetate, stir, and then slowly heat to 80°C. Open the dripping valve of the storage tank and drip liquid sodium metal into the condensation reactor. After the dripping is complete, keep the system reflux for 10 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0139] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 40°C, 2.0 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 30 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for later use. The ABL-containing solution included ethyl acetate, acetic acid, ethanol, and ABL.

[0140] 5 g of 98% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 120°C, and the top temperature was 72°C. Acetic acid and ethanol underwent esterification in the bottom of the tower to produce ethyl acetate. An azeotrope of ethyl acetate, ethanol, and water was collected from the top of the tower. After layering, crude ethyl acetate was obtained. The crude ethyl acetate was dehydrated and purified to obtain 3.2 mol of pure ethyl acetate, which was directly used in the condensation reaction.

[0141] The residue in the distillation tower kettle was subjected to reduced pressure distillation again at a pressure of 5 kPa, a kettle temperature of 130°C, and a tower top temperature of 98°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.4%, with a yield of 96.8%.

[0142] 12. Example 12

[0143] Under nitrogen atmosphere, 1.2 mol of metallic sodium was put into a storage tank, and the temperature was raised to 130°C and kept at this temperature for 2 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0144] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 4 mol of ethyl acetate, stir, and then slowly heat to 80°C. Open the dripping valve of the storage tank and drip liquid sodium metal into the condensation reactor. After the dripping is complete, keep the system reflux for 10 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0145] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to a neutralization reactor. When the material temperature dropped to 40°C, 2.5 mol of anhydrous acetic acid was added to the neutralization reactor under stirring, and stirring was continued for 30 minutes. Then, solid-liquid separation was performed to obtain sodium acetate solid and ABL-containing solution. The sodium acetate solid was recovered for later use. The ABL-containing solution included ethyl acetate, acetic acid, ethanol, and ABL.

[0146] 5 g of 98% concentrated sulfuric acid was added to the ABL solution, and the solution was transferred to the bottom of a distillation tower. The bottom temperature of the distillation tower was 120°C, and the top temperature was 72°C. Acetic acid and ethanol underwent esterification reaction in the bottom of the tower to produce ethyl acetate. The azeotrope of ethyl acetate and water was collected from the top of the tower and separated by layers to obtain crude ethyl acetate. The crude ethyl acetate was dehydrated to obtain 3.5 mol of pure ethyl acetate, which was directly used in the condensation reaction.

[0147] The residue in the distillation tower kettle was subjected to reduced pressure distillation again at a pressure of 5 kPa, a kettle temperature of 130°C, and a tower top temperature of 98°C. The ABL product was taken out from the tower top, and the ABL content was determined to be 99.3%, with a yield of 96.5%.

[0148] Comparative Example 1

[0149] Under nitrogen atmosphere, 1.2 mol of metallic sodium was put into a storage tank, and the temperature was raised to 130°C and kept at this temperature for 2 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0150] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 4 mol of ethyl acetate, stir, and then slowly heat to 80°C. Open the dripping valve of the storage tank and drip liquid sodium metal into the condensation reactor. After the dripping is complete, keep the system reflux for 10 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0151] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to the neutralization reactor. When the material temperature dropped to 40°C, 50% phosphoric acid aqueous solution (2.2 mol of phosphoric acid) was added to the neutralization reactor under stirring and continued stirring for 30 minutes. The mixture was then allowed to stand and the layers were separated, and the aqueous phase was removed.

[0152] The organic phase was transferred to the bottom of the distillation tower with a bottom temperature of 120°C and a top temperature of 72°C to remove light components. The residue in the bottom of the distillation tower was again subjected to reduced pressure distillation at a pressure of 5 kPa, a bottom temperature of 130°C, and a top temperature of 98°C. The ABL product was taken from the top of the tower, and the ABL content was determined to be 99.1%, with a yield of 92%.

[0153] Comparative Example 2

[0154] Under nitrogen atmosphere, 1.2 mol of metallic sodium was put into a storage tank, and the temperature was raised to 130°C and kept at this temperature for 2 hours to melt all the metallic sodium and obtain liquid metallic sodium.

[0155] In a fully dried condensation reactor equipped with an electric stirrer, condenser, and thermometer, add 1 mol of γ-butyrolactone and 4 mol of ethyl acetate, stir, and then slowly heat to 80°C. Open the dripping valve of the storage tank and drip liquid sodium metal into the condensation reactor. After the dripping is complete, keep the system reflux for 10 hours to generate a sodium salt solution of α-acetyl-γ-butyrolactone;

[0156] The α-acetyl-γ-butyrolactone sodium salt solution in the condensation reactor was transferred to the neutralization reactor. When the material temperature dropped to 40°C, 50% acetic acid aqueous solution (acetic acid amount was 2.2 mol) was added to the neutralization reactor under stirring conditions and continued to stir for 30 minutes. The mixture was then allowed to stand and the layers were separated, and the aqueous phase was removed.

[0157] The organic phase was transferred to the bottom of the distillation tower with a bottom temperature of 120°C and a top temperature of 72°C to remove light components. The residue in the bottom of the distillation tower was again subjected to reduced pressure distillation at a pressure of 5 kPa, a bottom temperature of 130°C, and a top temperature of 98°C. The ABL product was taken from the top of the tower, and the ABL content was determined to be 99.2%, with a yield of 89.5%.

[0158] Table 1 Raw material parameters and results in Examples and Comparative Examples

[0159]

[0160] By comparing Example 9 with Example 1, it can be seen that using solid metallic sodium to react with γ-butyrolactone and ethyl acetate will reduce the yield of the product compared to using liquid metallic sodium.

[0161] Comparison of Examples 1, 11, and 12 reveals that when too little acetic acid is added, the byproduct ethanol cannot be fully converted to ethyl acetate, and the remaining ethanol is extracted together with the ethyl acetate, significantly increasing the energy consumption of ethyl acetate dehydration and reducing the amount of acetate recovered. Adding too much acetic acid, on the other hand, increases the light fraction during ABL distillation and reduces the ABL yield.

[0162] Excessive or small amounts of acetic acid are not conducive to the recovery of acetate. The amount of acetate recovered in Examples 11 and 12 is less than that in Example 1.

[0163] Comparative Examples 1 and 2 used aqueous phosphoric acid solution and aqueous acetic acid solution for neutralization, respectively. Comparative Examples 1-2 were unable to convert the by-product ethanol into ethyl acetate, and the ABL yield obtained in Comparative Examples 1-2 was greatly reduced.

[0164] The various aspects, embodiments, and features of the present invention should be considered in all respects as illustrative and not limiting, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0165] In the synthetic methods of the present invention, the order of the steps is not limited to the order listed. Persons skilled in the art will appreciate that varying the order of the steps without inventive effort is within the scope of the present invention. Furthermore, two or more steps or actions may be performed simultaneously.

[0166] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit its implementation. Persons skilled in the art may make various modifications, additions, or substitute similar methods for the described specific embodiments. It is not necessary and impossible to provide comprehensive examples of all implementations here. However, obvious variations or modifications arising from the essential spirit of the present invention remain within the scope of protection of the present invention, and interpreting them as any additional limitations would be contrary to the spirit of the present invention.

Claims

1. The application of anhydrous acetic acid in the α-acetyl-γ-butyrolactone circulation production system is characterized in that: The application comprises the following steps: Anhydrous acetic acid is added to the α-acetyl-γ-butyrolactone sodium salt solution generated by the condensation reaction of γ-butyrolactone, acetate and metallic sodium to carry out a neutralization reaction. After solid-liquid separation, an esterification reaction catalyst is added to the obtained α-acetyl-γ-butyrolactone-containing solution to carry out reactive distillation. The by-product alkyl alcohol reacts with anhydrous acetic acid to produce acetate, and the recovered acetate is recycled and reused in the condensation reaction.

2. A circulating production system for α-acetyl-γ-butyrolactone, characterized in that: The following steps are involved: Condensation reaction: γ-butyrolactone, acetate and metallic sodium undergo condensation reaction to generate α-acetyl-γ-butyrolactone sodium salt solution; Neutralization reaction: adding anhydrous acetic acid to the α-acetyl-γ-butyrolactone sodium salt solution for neutralization, and obtaining a solution containing α-acetyl-γ-butyrolactone after solid-liquid separation; Reactive distillation: add esterification catalyst to the solution containing α-acetyl-γ-butyrolactone, perform reactive distillation, and produce acetate; Vacuum distillation: The residue after reactive distillation is further subjected to vacuum distillation to obtain α-acetyl-γ-butyrolactone.

3. An α-acetyl-γ-butyrolactone, characterized in that Prepared by a synthetic method comprising the following steps: Condensation reaction: γ-butyrolactone, acetate and metallic sodium undergo condensation reaction to generate α-acetyl-γ-butyrolactone sodium salt solution; Neutralization reaction: adding anhydrous acetic acid to the α-acetyl-γ-butyrolactone sodium salt solution for neutralization, and obtaining a solution containing α-acetyl-γ-butyrolactone after solid-liquid separation; Reactive distillation: add esterification catalyst to the solution containing α-acetyl-γ-butyrolactone, perform reactive distillation, and produce acetate; Vacuum distillation: The residue after reactive distillation is further subjected to vacuum distillation to obtain α-acetyl-γ-butyrolactone.

4. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The metallic sodium is solid metallic sodium and / or liquid metallic sodium.

5. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The metallic sodium is liquid metallic sodium.

6. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The chemical formula of the acetate is CH3COOR, wherein R is an alkyl group, and the molecular formula of R is C n H 2n+1 , n is an integer from 1 to 20.

7. The use or recycling production system or α-acetyl-γ-butyrolactone according to claim 6, characterized in that The acetate is one or more of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, tert-butyl acetate, n-pentyl acetate, isopentyl acetate, sec-pentyl acetate, tert-pentyl acetate, and 3-pentyl acetate.

8. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The molar mass ratio of γ-butyrolactone to acetate is 1:1.0~20.0; The molar mass ratio of γ-butyrolactone to metallic sodium is 1:1.0-15.

0.

9. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The condensation reaction is a reflux reaction, the reflux temperature is 70-180° C., and the reflux reaction time is 1-50 hours.

10. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The molar amount of the added anhydrous acetic acid is ≥ the molar amount of γ-butyrolactone.

11. The use or recycling production system or α-acetyl-γ-butyrolactone according to claim 10, characterized in that The molar amount of the added anhydrous acetic acid is ≥ the sum of the molar amounts of γ-butyrolactone and metallic sodium.

12. The use or recycling production system or α-acetyl-γ-butyrolactone according to claim 11, characterized in that The molar amount of the added anhydrous acetic acid is the sum of the molar amounts of γ-butyrolactone and metallic sodium.

13. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The esterification reaction catalyst is an acid catalyst.

14. The use according to claim 1 or the cyclic production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The esterification reaction catalyst is sulfuric acid.

15. The use or recycling production system or α-acetyl-γ-butyrolactone according to claim 14, characterized in that The esterification reaction catalyst is concentrated sulfuric acid with a mass fraction of 92% or more.

16. The use according to claim 1 or the circulating production system according to claim 2 or the α-acetyl-γ-butyrolactone according to claim 3, characterized in that: The reactive distillation is atmospheric pressure reactive distillation, the bottom temperature of the atmospheric pressure reactive distillation is 90~200℃, and the top temperature of the tower is 70~150℃.

17. The use according to claim 1, characterized in that The acetate produced by reactive distillation is recycled to the condensation reaction and then subjected to vacuum distillation to obtain α-acetyl-γ-butyrolactone.

18. The circular production system according to claim 2, characterized in that: In the reactive distillation step, the acetate extracted is recycled to the condensation reaction.

19. The use according to claim 17 or the circular production system according to claim 2, characterized in that: The vacuum distillation is carried out in a vacuum distillation tower. The pressure of the vacuum distillation tower is 1~50kPa, the bottom temperature of the vacuum distillation tower is 110~200℃, and the top temperature of the tower is 80~130℃.

20. The use according to claim 17 or the circular production system according to claim 2, characterized in that: The purity of the synthesized α-acetyl-γ-butyrolactone is ≥99%, and the yield of the synthesized α-acetyl-γ-butyrolactone is ≥95%.

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