A method for the continuous synthesis of alpha-acetyl-gamma-butyrolactone

Abstract

The application discloses a method for continuously synthesizing alpha-acetyl-gamma-butyrolactone, which comprises the following steps: vaporizing 1,4-butanediol and then feeding the vaporized 1,4-butanediol into a first fixed-bed reactor filled with a nano copper oxide catalyst doped with Mn, Al, Yb, Sr and Cr to perform a reaction, so as to obtain gamma-butyrolactone gas; continuously feeding the gamma-butyrolactone gas, vaporized acetic anhydride and nitrogen into a second fixed-bed reactor filled with a silver-modified graphene / SiO2 composite catalyst under the protection of nitrogen to perform a reaction, and then performing rectification on a product obtained through multi-stage condensation, so as to obtain a target product. The method provided by the application has stable reaction conditions, high selectivity and specificity of a catalyst and high yield, and can realize continuous production of the product.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for the continuous synthesis of α-acetyl-γ-butyrolactone. Background Technology

[0002] α-Acetyl-γ-butyrolactone (ABL) is an important organic chemical raw material and a crucial organic intermediate in the synthesis of various drugs. It is primarily used as a raw material for vitamins and a key intermediate for chlorophyll synthesis. It is also used in the pharmaceutical industry to manufacture drugs such as the antianginal drug Yanxintong. Furthermore, it is an excellent reagent for pharmaceutical analysis, exhibiting colorimetric reactions with sulfonamides and primary amines, and is therefore frequently used in the analysis of these drug formulations.

[0003] α-Acetyl-γ-butyrolactone exists in small amounts in nature, and the process of separating it from natural products is quite complex and costly. Therefore, α-acetyl-γ-butyrolactone currently on the market is mass-produced through chemical synthesis.

[0004] Currently, there are two main methods for synthesizing α-acetyl-γ-butyrolactone: one involves the condensation and ring-closure of ethyl acetoacetate and ethylene oxide in ethanol solvent under the action of sodium ethoxide or sodium hydroxide; the other method uses γ-butyrolactone and ethyl acetate as starting materials, and synthesizes them through a condensation reaction in an inert solvent under the action of sodium ethoxide or metallic sodium. Although these two methods are relatively simple, the α-acetyl-γ-butyrolactone produced has low purity, and continuous production of α-acetyl-γ-butyrolactone cannot be achieved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for the continuous synthesis of α-acetyl-γ-butyrolactone, which addresses the shortcomings of the existing technology. This method has stable reaction conditions, strong catalyst selectivity and specificity, high yield, and can realize the continuous production of the product.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A method for the continuous synthesis of α-acetyl-γ-butyrolactone includes the following steps:

[0008] (1) 1,4-Butanediol is vaporized and then fed into a first fixed-bed reactor packed with catalyst 1 to react and produce γ-butyrolactone gas; the catalyst 1 is a nano-copper oxide catalyst doped with Mn, Al, Yb, Sr and Cr.

[0009] (2) The above-mentioned γ-butyrolactone gas, vaporized acetic anhydride and nitrogen are continuously fed into a second fixed-bed reactor containing catalyst 2 under nitrogen protection for reaction. The product obtained from the reaction is distilled after multi-stage condensation to obtain the target product. The catalyst 2 is a silver-modified graphene / SiO2 composite catalyst.

[0010] As an improved technical solution, in step (1), the diameter of the first fixed-bed reactor tube is 5-8 mm and the length is 0.1 m-1 m; when loading catalyst 1, the packing density of nano-copper oxide is ensured to be 6-7 g / cm³. 3 .

[0011] As an improved technical solution, in step (1), the contents of each component in the Mn, Al, Yb, Sr, and Cr doped nano-copper oxide catalyst are as follows: MnO2 5-10wt%, Al2O3 5-10wt%, Yb2O3 or SrO 0.1-0.5wt%, Cr2O3 0.1-0.5wt%, and the remainder is copper oxide, with each component content being 100%.

[0012] As an improved technical solution, in step (1), the reaction temperature is 230-250℃, the reaction residence time is 360s-600s, and the reaction pressure is 2MPa-10MPa.

[0013] As an improved technical solution, in step (2), the diameter of the second fixed-bed reactor tube is 5-8 mm, and the length is 1-3 m; when loading catalyst 2, the graphene packing density is ensured to be 2.21-2.26 g / cm³. 3 The packing density of silica is 2.2 g / cm³. 3 .

[0014] As an improved technical solution, in step (2), the molar ratio of γ-butyrolactone gas: acetic anhydride gas: nitrogen gas is 1:(1~2):0.1; the reaction temperature is 250~260℃, the reaction residence time is 720s~1800s, the vacuum is drawn to -0.07~-0.08MPa before the reaction, and then nitrogen gas is introduced to atmospheric pressure.

[0015] As an improved technical solution, in step (2), the distillation conditions are as follows: first, the byproduct acetic acid and unreacted raw materials are removed by distillation under the conditions of a temperature of 90-100℃ and a vacuum of -0.07--0.08MPa; then, the product α-acetyl-γ-butyrolactone is distilled off under the conditions of a temperature of 145-150℃ and a vacuum of -0.095--0.098MPa.

[0016] As an improved technical solution, in step (2), the preparation method of the silver-modified graphene / SiO2 composite catalyst includes the following steps:

[0017] 1. Nano-silica and graphene are placed in an ethanol solution and ultrasonically treated, then filtered and the solid is dried to obtain graphene / SiO2 material;

[0018] 2. The above graphene / SiO2 material is immersed in a mixed aqueous solution of silver nitrate, copper nitrate, and manganese nitrate, then dried, and the dried solid is calcined to obtain the final product.

[0019] As an improved technical solution, in step one, the mass ratio of the nano-silica to graphene is 1:(1-3); the power of the ultrasonic treatment is 500-1000W, and the ultrasonic treatment time is 30-60min.

[0020] As an improved technical solution, in step two, the concentrations of silver nitrate, copper nitrate, and manganese nitrate in the mixed aqueous solution are 1-2 wt%, 4-5 wt%, and 1-2 wt%, respectively; the ratio of the mixed aqueous solution to the graphene / SiO2 material is 200 ml: (20-30) g; and / or the soaking treatment time is 20-30 min; the calcination temperature is 300 °C, and the time is 2-3 h.

[0021] Furthermore, in this application, the Mn, Al, Yb, Sr, and Cr doped nano-copper oxide catalyst can be commercially available or prepared in-house using conventional co-precipitation methods in the prior art.

[0022] The reaction equation of this invention is as follows:

[0023]

[0024] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] 1. The reaction conditions provided by this invention are stable, the catalyst exhibits strong selectivity and specificity, and the yield is high. Compared with traditional processes, this process eliminates the traditional batch reactor method, avoids the use of sodium metal as a catalyst due to its explosive properties upon contact with water, and improves safety. Post-treatment requires no quenching, avoiding environmental pressures such as the use of phosphoric acid aqueous solutions. It significantly reduces the generation of waste, making it environmentally friendly.

[0026] 2. This invention employs a nano-copper oxide catalyst doped with Mn, Al, Yb, Sr, and Cr in the synthesis reaction of γ-butyrolactone. This catalyst improves reaction efficiency and enhances selectivity, thereby increasing the product yield. Furthermore, the catalyst exhibits good thermal stability and can be reused.

[0027] 3. Furthermore, this invention effectively controls the temperature of the synthesis and acylation reactions of γ-butyrolactone, ensuring not only the smooth progress of the reaction but also controlling the occurrence of side reactions. Simultaneously, the lower temperature helps extend the catalyst's lifespan.

[0028] 4. This invention employs a silver-modified graphene / SiO2 composite catalyst for acylation reactions. This catalyst exhibits high activity and selectivity. The addition of silver promotes the esterification reaction, while the graphene / SiO2 material has a large specific surface area, providing more active sites and catalyst-reactant contact area, thereby improving production efficiency. Attached image description:

[0029] Figure 1 This is a schematic diagram of the synthesis apparatus used in the reaction in the examples;

[0030] In the diagram, 1 is the first static mixer; 2 is the first fixed-bed reactor; 3 is the gas-liquid separator; 4 is the second static mixer; 5 is the acetic anhydride gas inlet; 6 is the second static mixer; 7 is the distillation column; 8 is the condenser; and 9 is the finished product tank. Detailed Implementation

[0031] The present invention is further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] Unless otherwise specified, all chemical reagents and materials used in the following examples are commercially available products.

[0033] In the following examples, the average particle size of the nano-silica is 20±2nm; the average diameter of the graphene is 1-2μm and the thickness is 30±5nm.

[0034] In the following embodiments, the preparation method of the silver-modified graphene / SiO2 composite catalyst includes the following steps:

[0035] 1. Nano-silica and graphene are placed in an ethanol solution and ultrasonically treated, then filtered and the solid is dried to obtain graphene / SiO2 material;

[0036] 2. The above graphene / SiO2 material is immersed in a mixed aqueous solution of silver nitrate, copper nitrate, and manganese nitrate, then dried, and the dried solid is calcined to obtain the final product.

[0037] As an improved technical solution, in step one, the mass ratio of the nano-silica to graphene is 1:(1-3).

[0038] In step one of this embodiment, the ultrasonic treatment power is 500-1000W, and the ultrasonic treatment time is 30-60 minutes. Further, the ultrasonic treatment power is preferably 500W, and the ultrasonic treatment time is preferably 30 minutes.

[0039] In step two of this embodiment, the concentrations of silver nitrate, copper nitrate, and manganese nitrate in the mixed aqueous solution are 1-2 wt%, 4-5 wt%, and 1-2 wt%, respectively; the ratio of the mixed aqueous solution to the graphene / SiO2 material is 200 ml: (20-30) g.

[0040] In step two of this embodiment, the soaking time is 20-30 minutes; the calcination temperature is 300°C and the time is 2-3 hours.

[0041] like Figure 1 As shown, the apparatus for synthesizing α-acetyl-γ-butyrolactone in the embodiment includes a first static mixer, a first fixed-bed reactor, a gas-liquid separator, a second static mixer, a second fixed-bed reactor, a condenser, and a finished product tank connected in series. The second static mixer is also provided with an acetic anhydride gas inlet.

[0042] The first fixed-bed reactor has a tube diameter of 5–8 mm and a length of 0.1 m–1 m. When loading the catalyst, the copper oxide packing density is ensured to be 6.31 g / cm³. 3 The second fixed-bed reactor has a tube diameter of 5–8 mm and a length of 1–3 m. When loading the catalyst, the graphene packing density is ensured to be 2.21–2.26 g / cm³. 3 The packing density of silica is 2.2 g / cm³. 3 .

[0043] Example 1

[0044] S1: Nano-silica and graphene are ultrasonically treated in an ethanol solution, then filtered, and the solid is dried to obtain graphene / SiO2 material; the mass ratio of nano-silica to graphene is 1:1.02; the ultrasonic treatment power is 500W, and the ultrasonic treatment time is 30min.

[0045] S2: The above-mentioned graphene / SiO2 material was immersed in a mixed aqueous solution of silver nitrate, copper nitrate, and manganese nitrate, then dried, and the dried solid was calcined to obtain catalyst 2; the concentrations of silver nitrate, copper nitrate, and manganese nitrate in the mixed aqueous solution were 1wt%, 4wt%, and 1wt%, respectively; the ratio of the mixed aqueous solution to graphene / SiO2 material was 200ml:30g; the immersion time was 30min; the calcination temperature was 300℃ and the time was 2h;

[0046] S3: The Mn, Al, Yb, Sr, and Cr-doped nano-copper oxide catalyst, used as catalyst 1, is loaded into the first fixed-bed reactor, and the packing density of the nano-copper oxide is controlled to be 6.31 g / cm³. 3 The catalyst contains the following components: 5wt% MnO2, 5wt% Al2O3, 0.1wt% Yb2O3, 0.1wt% Cr2O3, with the remainder being copper oxide, and each component is 100% present. The catalyst 2 prepared above is loaded into a second fixed-pack reactor, with the graphene packing density controlled at 2.25 g / cm³. 3 The packing density of silica is 2.2 g / cm³. 3 ;

[0047] S4: 1,4-Butanediol is introduced into the first fixed-bed reactor through the first static mixer to react and produce γ-butyrolactone gas; the reaction temperature is 230℃; the reaction residence time is 360s; and the reaction pressure is 2MPa.

[0048] S5: After the reaction is completed, the hydrogen gas in the product is removed by a gas-liquid separator, and the liquid enters the second static mixer to vaporize. After vaporization, it is continuously introduced into the second fixed-bed reactor containing catalyst 2 under nitrogen protection to carry out the reaction. During the reaction, the molar ratio of γ-butyrolactone gas:acetic anhydride gas:nitrogen gas is 1:1.2:0.1. The reaction temperature is 250℃, the reaction residence time is 720s, and the vacuum is drawn to -0.07MPa before the reaction, and then nitrogen gas is introduced to the atmospheric pressure.

[0049] S6: The product obtained from the reaction is first distilled at a temperature of 90℃ and a vacuum of -0.07MPa to remove the byproduct acetic acid and unreacted raw materials. Then, α-acetyl-γ-butyrolactone is distilled off at a temperature of 145℃ and a vacuum of -0.095MPa.

[0050] Example 2

[0051] S1: Nano-silica and graphene are ultrasonically treated in an ethanol solution, then filtered, and the solid is dried to obtain graphene / SiO2 material; the mass ratio of nano-silica to graphene is 1:1.02; the ultrasonic treatment power is 700W, and the ultrasonic treatment time is 40min.

[0052] S2: The above-mentioned graphene / SiO2 material was immersed in a mixed aqueous solution of silver nitrate, copper nitrate, and manganese nitrate, then dried, and the dried solid was calcined to obtain catalyst 2; the concentrations of silver nitrate, copper nitrate, and manganese nitrate in the mixed aqueous solution were 2wt%, 4.5wt%, and 1wt%, respectively; the ratio of the mixed aqueous solution to graphene / SiO2 material was 200ml:30g; the immersion time was 30min; the calcination temperature was 300℃ and the time was 2h.

[0053] S3: The Mn, Al, Yb, Sr, and Cr-doped nano-copper oxide catalyst, used as catalyst 1, is loaded into the first fixed-bed reactor, and the packing density of the nano-copper oxide is controlled to be 6.31 g / cm³. 3 The catalyst contains the following components: MnO2 6wt%, Al2O3 7wt%, Yb2O3 0.2wt%, Cr2O3 0.1%, with the remainder being copper oxide, and each component accounts for 100%. The catalyst 2 prepared above is loaded into a second fixed-pack reactor, with the graphene packing density controlled at 2.25 g / cm³. 3 The packing density of silica is 2.2 g / cm³. 3 ;

[0054] S4: 1,4-Butanediol is introduced into the first fixed-bed reactor through the first static mixer to react and produce γ-butyrolactone gas; the reaction temperature is 240℃; the reaction residence time is 400s; and the reaction pressure is 3MPa.

[0055] S5: After the reaction is completed, the hydrogen gas in the product is removed by a gas-liquid separator, and the liquid enters the second static mixer to vaporize. After vaporization, it is continuously introduced into the second fixed-bed reactor containing catalyst 2 under nitrogen protection to carry out the reaction. During the reaction, the molar ratio of γ-butyrolactone gas:acetic anhydride gas:nitrogen gas is 1:1.2:0.1. The reaction temperature is 255℃, the reaction residence time is 800s, and the vacuum is drawn to -0.075MPa before the reaction, and then nitrogen gas is introduced to the atmospheric pressure.

[0056] S6: The product obtained from the reaction is first distilled at a temperature of 95℃ and a vacuum of -0.075MPa to remove the byproduct acetic acid and unreacted raw materials. Then, α-acetyl-γ-butyrolactone is distilled off at a temperature of 145℃ and a vacuum of -0.096MPa.

[0057] Example 3

[0058] S1: Nano-silica and graphene are ultrasonically treated in an ethanol solution, then filtered, and the solid is dried to obtain graphene / SiO2 material; the mass ratio of nano-silica to graphene is 1:1.02; the ultrasonic treatment power is 800W, and the ultrasonic treatment time is 30min.

[0059] S2: The above-mentioned graphene / SiO2 material was immersed in a mixed aqueous solution of silver nitrate, copper nitrate, and manganese nitrate, and then dried. The dried solid was calcined to obtain catalyst 2. The concentrations of silver nitrate, copper nitrate, and manganese nitrate in the mixed aqueous solution were 1.5 wt%, 4 wt%, and 1 wt%, respectively. The ratio of the mixed aqueous solution to the graphene / SiO2 material was 200 ml: 20 g. The immersion time was 20 min. The calcination temperature was 300 °C and the time was 3 h.

[0060] S3: The Mn, Al, Yb, Sr, and Cr-doped nano-copper oxide catalyst, used as catalyst 1, is loaded into the first fixed-bed reactor, and the packing density of the nano-copper oxide is controlled to be 6.31 g / cm³. 3 The catalyst contains the following components: MnO2 7wt%, Al2O3 5wt%, SrO 0.2wt%, Cr2O3 0.3%, with the remainder being copper oxide, and each component accounts for 100%. The catalyst 2 prepared above is loaded into a second fixed-pack reactor, with the graphene packing density controlled at 2.25 g / cm³. 3 The packing density of silica is 2.2 g / cm³. 3 ;

[0061] S4: 1,4-Butanediol is introduced into the first fixed-bed reactor through the first static mixer to react and produce γ-butyrolactone gas; the reaction temperature is 245℃; the reaction residence time is 500s; and the reaction pressure is 5MPa.

[0062] S5: After the reaction is completed, the hydrogen gas in the product is removed by a gas-liquid separator, and the liquid enters the second static mixer to vaporize. After vaporization, it is continuously introduced into the second fixed-bed reactor containing catalyst 2 under nitrogen protection to carry out the reaction. During the reaction, the molar ratio of γ-butyrolactone gas:acetic anhydride gas:nitrogen gas is 1:1.2:0.1. The reaction temperature is 250℃, the reaction residence time is 1000s, and the vacuum is drawn to -0.07MPa before the reaction, and then nitrogen gas is introduced to atmospheric pressure.

[0063] S6: The product obtained from the reaction is first distilled at a temperature of 95℃ and a vacuum of -0.08MPa to remove the byproduct acetic acid and unreacted raw materials. Then, α-acetyl-γ-butyrolactone is distilled off at a temperature of 150℃ and a vacuum of -0.095MPa.

[0064] Example 4

[0065] S1: Nano-silica and graphene are ultrasonically treated in an ethanol solution, then filtered, and the solid is dried to obtain graphene / SiO2 material; the mass ratio of nano-silica to graphene is 1:1.02; the ultrasonic treatment power is 500W, and the ultrasonic treatment time is 30min.

[0066] S2: The above-mentioned graphene / SiO2 material was immersed in a mixed aqueous solution of silver nitrate, copper nitrate, and manganese nitrate, then dried, and the dried solid was calcined to obtain catalyst 2; the concentrations of silver nitrate, copper nitrate, and manganese nitrate in the mixed aqueous solution were 1wt%, 4wt%, and 1wt%, respectively; the ratio of the mixed aqueous solution to graphene / SiO2 material was 200ml:20g; the immersion time was 20min; the calcination temperature was 300℃ and the time was 2h.

[0067] S3: The Mn, Al, Yb, Sr, and Cr-doped nano-copper oxide catalyst, used as catalyst 1, is loaded into the first fixed-bed reactor, and the packing density of the nano-copper oxide is controlled to be 6.31 g / cm³. 3 The catalyst contains the following components: 10 wt% MnO2, 10 wt% Al2O3, 0.5 wt% SrO, 0.5 wt% Cr2O3, with the remainder being copper oxide, and each component accounts for 100%. The catalyst 2 prepared above is loaded into a second fixed-pack reactor, with the graphene packing density controlled at 2.25 g / cm³. 3 The packing density of silica is 2.2 g / cm³. 3 ;

[0068] S4: 1,4-Butanediol is introduced into the first fixed-bed reactor through the first static mixer to react and produce γ-butyrolactone gas; the reaction temperature is 250℃; the reaction residence time is 600s; and the reaction pressure is 10MPa.

[0069] S5: After the reaction is completed, the hydrogen gas in the product is removed by a gas-liquid separator, and the liquid enters the second static mixer to vaporize. After vaporization, it is continuously introduced into the second fixed-bed reactor containing catalyst 2 under nitrogen protection to carry out the reaction. During the reaction, the molar ratio of γ-butyrolactone gas:acetic anhydride gas:nitrogen gas is 1:1.2:0.1. The reaction temperature is 260℃, the reaction residence time is 1800s, and the vacuum is drawn to -0.08MPa before the reaction, and then nitrogen gas is introduced to the atmospheric pressure.

[0070] S6: The product obtained from the reaction is first distilled at a temperature of 100℃ and a vacuum of -0.08MPa to remove the byproduct acetic acid and unreacted raw materials. Then, α-acetyl-γ-butyrolactone is distilled off at a temperature of 150℃ and a vacuum of -0.098MPa.

[0071] The selectivity, conversion rate, yield, and purity of the raw materials in the methods provided in the above embodiments are shown in Table 1.

[0072] Table 1

[0073]

[0074] In summary, as the reaction temperature, reaction time, and reaction pressure increase, both the conversion rate of the raw materials and the selectivity of the product increase to some extent. However, beyond a certain range, with further increases in reaction temperature, reaction time, and reaction pressure, both the conversion rate of the raw materials and the selectivity of the product actually decrease. This is mainly because while high temperatures can accelerate the reaction rate, excessively rapid reaction rates can accelerate the occurrence of side reactions, thereby reducing the selectivity and purity of the desired product. Furthermore, high temperatures may also trigger side reactions, leading to a decrease in yield. Therefore, for economic, environmental, and safe production purposes, when preparing γ-butyrolactone using 1,4-butanediol, the reaction temperature of this invention is 230–250°C, the reaction residence time is 360–600 s, and the reaction pressure is 2 MPa–10 MPa.

[0075] In addition, the temperature and reaction pressure of γ-butyrolactone in the reaction with acetic anhydride also need to be strictly controlled. In order to ensure the high purity and high yield of the product, the present invention controls the reaction temperature to 250-260°C, evacuates to -0.07--0.08 MPa before the reaction, and then purges nitrogen to atmospheric pressure.

[0076] Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for the continuous synthesis of α-acetyl-γ-butyrolactone, characterized in that, Includes the following steps: (1) 1,4-Butanediol is vaporized and then fed into a first fixed-bed reactor packed with catalyst 1 to produce γ-butyrolactone gas; the catalyst 1 is a nano-copper oxide catalyst doped with Mn, Al, Yb, Sr, and Cr; the contents of each component in the nano-copper oxide catalyst doped with Mn, Al, Yb, Sr, and Cr are as follows: MnO2 5-10wt%, Al2O3 5-10wt%, Yb2O3 or SrO 0.1-0.5wt%, Cr2O3 0.1-0.5wt%, and the remainder is copper oxide, with each component content being 100%; (2) The above-mentioned γ-butyrolactone gas, vaporized acetic anhydride and nitrogen are continuously introduced into a second fixed-bed reactor containing catalyst 2 under nitrogen protection for reaction. The product obtained from the reaction is distilled after multi-stage condensation to obtain the target product. The catalyst 2 is a silver-modified graphene / SiO2 composite catalyst. The preparation method of the silver-modified graphene / SiO2 composite catalyst includes the following steps: ① Place nano-silica and graphene in an ethanol solution and sonicate, then filter and dry the solid to obtain graphene / SiO2 material; ② The above graphene / SiO2 material was immersed in a mixed aqueous solution of silver nitrate, copper nitrate and manganese nitrate, and then dried. The dried solid was then calcined to obtain the final product. The concentrations of silver nitrate, copper nitrate and manganese nitrate in the mixed aqueous solution were 1-2 wt%, 4-5 wt%, and 1-2 wt%, respectively.

2. The method for continuous synthesis of α-acetyl-γ-butyrolactone according to claim 1, characterized in that: In step (1), the diameter of the first fixed-bed reactor tube is 5-8 mm and the length is 0.1 m-1 m; when loading catalyst 1, the packing density of nano-copper oxide is ensured to be 6-7 g / cm³. 3 .

3. The method for continuous synthesis of α-acetyl-γ-butyrolactone according to claim 1, characterized in that: In step (1), the reaction temperature is 230-250℃, the reaction residence time is 360s-600s, and the reaction pressure is 2MPa-10MPa.

4. The method for continuous synthesis of α-acetyl-γ-butyrolactone according to claim 1, characterized in that: In step (2), the diameter of the second fixed-bed reactor tube is 5-8 mm, and the length is 1-3 m; when loading catalyst 2, the graphene packing density is ensured to be 2.21-2.26 g / cm³. 3 The packing density of silica is 2.2 g / cm³.

5. The method for continuous synthesis of α-acetyl-γ-butyrolactone according to claim 1, characterized in that: In step (2), the molar ratio of γ-butyrolactone gas: acetic anhydride gas: nitrogen gas is 1:(1~2):0.1; the reaction temperature is 250~260℃, the reaction residence time is 720s~1800s, the vacuum is drawn to -0.07~-0.08MPa before the reaction, and then nitrogen gas is introduced to atmospheric pressure.

6. The method for continuous synthesis of α-acetyl-γ-butyrolactone according to claim 1, characterized in that: In step (2), the distillation conditions are as follows: first, distillation is carried out at a temperature of 90-100℃ and a vacuum of -0.07--0.08MPa to remove the byproduct acetic acid and other unreacted raw materials; then, α-acetyl-γ-butyrolactone is distilled out at a temperature of 145-150℃ and a vacuum of -0.095--0.098MPa.

7. The method for continuous synthesis of α-acetyl-γ-butyrolactone according to claim 1, characterized in that: In step ①, the mass ratio of nano-silica to graphene is 1:(1-3); the ultrasonic treatment power is 500-1000W, and the ultrasonic treatment time is 30-60min.

8. The method for continuous synthesis of α-acetyl-γ-butyrolactone according to claim 1, characterized in that: In step ②, the ratio of the mixed aqueous solution to the graphene / SiO2 material is 200ml:(20-30)g; or the soaking time is 20-30min; and the calcination temperature is 300℃ and the time is 2-3h.

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