A method for producing propionic acid ester by hydrogenation of acrylic acid ester

Abstract

The present application is a kind of catalyst and process for preparing electronic grade propionic acid ester by hydrogenation of acrylic acid ester. The process uses activated carbon supported Ni-based catalyst, and one or two of Re, B or Ag as additives. The process is to mix acrylic acid ester containing trace amount of polymerization inhibitor or mixture with corresponding propionic acid ester with hydrogen and preheat into gas phase, then enter the fixed bed reactor containing catalyst to carry out gas phase reaction under very mild conditions, which avoids problems such as raw material self-polymerization and catalyst sintering, the catalyst can be stably operated for more than 2000 hours, the conversion rate of acrylic acid ester and the selectivity of propionic acid ester still maintain nearly 100%, which shows excellent stability, the purity of propionic acid ester in the reactor outlet sample can reach more than 99.6%, therefore, electronic grade propionic acid ester product can be obtained by simple rectification and molecular sieve dehydration treatment.

Description

Technical Field

[0001] This invention belongs to the technical field of gas-phase hydrogenation catalysts for carbon-carbon double bonds and their processes, specifically relating to catalysts and processes for the hydrogenation of acrylates to propionate under mild conditions. Background Technology

[0002] Methyl propionate is an important chemical raw material, used as a solvent for nitrocellulose, nitrocellulose lacquer, coatings, and varnishes, as well as for fragrances and flavorings, and as an intermediate in organic synthesis. Its most important application is the aldol condensation reaction with formaldehyde to produce methyl methacrylate (MMA), which is mainly used in polymer materials such as plexiglass. As a crucial step in this process, the hydrogenation of methyl acrylate to methyl propionate is an indispensable step. Furthermore, propionate esters, including methyl propionate, such as ethyl propionate, propyl propionate, and butyl propionate, are used as co-solvents for carbonate solvents in lithium-ion battery electrolytes, which helps improve the low-temperature conductivity of the electrolyte and significantly improves the low-temperature performance of the battery. It is expected that in the future, high-quality propionate esters with a purity of over 99.995% and free of ppm-level fusel oils, ethers, and acids will be in high demand both domestically and internationally.

[0003] The esterification method for preparing propionate esters involves thermodynamic equilibrium, resulting in incomplete conversion of reactants, difficult separation, and high propionic acid prices, making this route uneconomical. The carbonylation method for synthesizing propionate esters uses precious metal catalysts, which are also expensive and currently remain in the laboratory stage. Patent CN110639511A briefly describes a method for producing methyl propionate from methyl acrylate by hydrogenation using modified alumina supported on a 0.1-0.2% Pd catalyst, with alkali metals K and / or P as promoters, at 60°C and 1.5 MPa. Patent CN104513163A also describes a method for producing methyl methacrylate from methyl acetate and formaldehyde, where methyl acrylate is hydrogenated to methyl propionate using a fixed-bed reactor at 120–300°C with precious metals such as Pd. Patents CN111054390 and CN117920173 use cerium oxide and modified silica gel as supports, respectively, to load Pd / Ru / Pt, supplemented with Ni, Cu, and other additives, in the hydrogenation reaction of methyl acrylate at a reaction temperature of 100-110℃ and a pressure of 1 MPa. Patents CN111905745A and CN118807765 use alumina-supported non-precious metal Ni-Mo catalysts, reacting at 80℃ and 1 MPa. Most related reports only mention using fixed-bed reactors with Pd or Ni catalysts, achieving yields and selectivity up to 99%, without systematically considering the continuous operation of methyl acrylate hydrogenation to methyl propionate. Furthermore, the reaction substrates are limited to methyl acrylate, without mentioning other acrylates such as ethyl acrylate and propyl acrylate.

[0004] In terms of process, acrylates are prone to self-polymerization and clogging of reactors and pipelines in the liquid phase. Furthermore, the hydrogenation of acrylates is a strongly exothermic reaction, easily causing catalyst sintering and deactivation. Therefore, patent CN 112851505 B proposes a continuous gas-phase hydrogenation process for methyl acrylate to methyl propionate. First, the raw material is heated into a gaseous phase in a vaporization tower before entering the reactor. Simultaneously, a polymerization inhibitor remains in the tower bottom as a liquid phase, acting as a separator. The concentration of the raw material is significantly reduced due to its gaseous state, effectively inhibiting self-polymerization. After condensation, the material exiting the reactor is recycled in the gas phase, while the liquid phase proceeds to the next separation step. However, the reaction temperature remains above 80°C, and the possibility of self-polymerization is still high without a polymerization inhibitor. Furthermore, the patent does not mention how long the reaction can be stably maintained.

[0005] This invention provides a catalyst and process for the hydrogenation of acrylate to prepare propionate. The catalyst used is Ni-Re-B supported on activated carbon. The acrylate raw material containing the polymerization inhibitor is preheated and vaporized, and the gas phase enters the fixed bed reactor along with H2. It operates stably for more than 2000 hours at relatively low temperatures (40-70℃) and pressures (0.4-1.0MPa). The conversion rate of acrylate and the selectivity of propionate are both above 99.99%, exhibiting excellent stability and no self-polymerization problem. The process is simple, and the product does not contain the polymerization inhibitor or difficult-to-separate acrylate. Electronic grade propionate product can be obtained by distillation and molecular sieve dehydration. Summary of the Invention

[0006] To address the shortcomings of existing research, the present invention aims to provide a catalyst and process for the hydrogenation of acrylates to prepare propionate esters. This process utilizes a high-performance catalyst to completely convert acrylates to the corresponding propionate esters under mild conditions. The catalyst exhibits high stability and low subsequent separation costs. The specific details are as follows (see...). Figure 1 ):

[0007] 1. The acrylates used include methyl acrylate, ethyl acrylate, n-propyl acrylate, or n-butyl acrylate;

[0008] 2. The catalyst is supported on activated carbon and the promoter is one or more of Re, B or Ag; the Ni content is 1-20%, preferably 5-15%, more preferably 5-10%; the promoter is one or more of Re, B or Ag and its content is 0.01-0.5%, preferably 0.02-0.4%, more preferably 0.05-0.15%; the activated carbon support is preferably coconut shell carbon.

[0009] 3. The catalyst is prepared by impregnation method. Nickel nitrate, ammonium rheniumate, boric acid or silver nitrate are weighed according to the ratio, dissolved in an appropriate amount of solvent water, and then qualified activated carbon (coconut shell activated carbon is treated with a 1-5% (preferably 2-4%) dilute nitric acid solution at 60-95℃ (preferably 80-90℃) for 1-8h (preferably 2-4h) before impregnation, then washed with water until neutral, dried, and the qualified activated carbon carrier is obtained). The mixture is stirred evenly, air-dried at room temperature, and then treated at 80-120℃ for 1-30h.

[0010] 4. After the catalyst is loaded into the reactor, it needs to be reduced in situ. The reducing atmosphere is 2-90% N2 / H2, and the gas space velocity is 100-5000 h⁻¹. -1 Reduce at 200-400℃ for 4-20 hours.

[0011] 5. To prevent the self-polymerization of the raw material acrylate, a polymerization inhibitor must be added, generally p-diphenol or p-hydroxyanisole, preferably p-hydroxyanisole, with a concentration of about 10-300 ppm, preferably 50-100 ppm;

[0012] 6. The raw materials, acrylate and hydrogen, must be preheated to 50-90℃ and enter the vaporization tower from the middle and lower parts, respectively. The liquid phase containing the polymerization inhibitor remains at the bottom of the vaporization tower, while the gas phase enters the tubular fixed-bed reactor.

[0013] 7. To ensure that the feedstock enters the fixed-bed reactor in the gas phase, the reaction conditions must be carefully controlled: temperature 40-100℃, preferably 50-80℃, more preferably 60-70℃; reaction pressure 0.1-2MPa, preferably 0.3-1.5MPa, more preferably 0.5-1.0MPa; hydrogen-to-ester ratio 5-100, preferably 10-60, more preferably 20-50; feedstock space velocity 0.2-1.5h⁻¹. -1 Preferably 0.3-1.0h -1 More preferably 0.5-0.9h -1 .

[0014] 8. The material coming out of the reactor is frozen to -5 to -15°C and then sent to the gas-liquid separator. A portion of the gas phase is released to control the reaction pressure, while the majority is circulated through the compressor to the fresh hydrogen feed line.

[0015] Liquid phase to distillation column.

[0016] 9. The liquid phase from the bottom of the gas-liquid separator is preheated and then sent to a distillation column, which is either a tray type or a packed type, with an operating pressure of 0.1-0.2 MPa. Part of the material at the top of the column is refluxed, and part is collected to the light component tank. The material collected from the bottom of the column is sent to the heavy component tank. The propionate product is collected from the lower part of the column, cooled, and then dehydrated by a molecular sieve to finally obtain the electronic grade product (see Table 2).

[0017] The process involves mixing acrylates containing trace amounts of polymerization inhibitors, or mixtures thereof with corresponding propionates, with hydrogen and preheating them into a gaseous phase before introducing them into a fixed-bed reactor containing a catalyst. The gaseous reaction takes place under very mild conditions, avoiding problems such as raw material self-polymerization and catalyst sintering. The catalyst can operate stably for more than 2000 hours, and the conversion rate of acrylates and the selectivity of propionates remain close to 100%, demonstrating excellent stability. The purity of propionates in the reactor outlet sample can reach more than 99.6%. Therefore, electronic-grade propionates can be obtained by simple distillation and molecular sieve dehydration. Attached Figure Description

[0018] Figure 1 The reaction process flow diagram of this invention; in the diagram: 1 heat exchanger; 2 vaporization tower; 3 tubular fixed-bed hydrogenation reactor; 4 gas-liquid separator; 5 circulating compressor; 6 distillation tower; 7A and 7B are molecular sieve dehydration tanks.

[0019] Figure 2 Figure showing the stability test results after 1800 hours of reaction in Example 6.

[0020] Figure 3 Figure showing the stability test results after 2000 hours of reaction in Example 7. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] like Figure 1 As shown, the acrylate hydrogenation reaction feedstock is pumped into the feed line and mixed with hydrogen (the reactants and hydrogen are heat-exchanged separately by heat exchanger 1). (After heat exchange, the reactants and hydrogen enter the vaporization tower 2 from the top and bottom, respectively. The liquid phase containing the polymerization inhibitor remains at the bottom of the vaporization tower, while the gas phase enters the tubular fixed-bed hydrogenation reactor 3. A circulation pump is installed at the bottom of the vaporization tower, and the material returns to the bottom of the vaporization tower through the heat exchanger via the circulation pump.) The gas phase at the top of the vaporization tower passes through the catalyst bed in the fixed-bed reactor from top to bottom.

[0023] The product from the bottom of the reactor is then subjected to distillation to remove light and heavy components and molecular sieve dehydration to obtain electronic-grade propionate. Specifically, the product from the bottom of the reactor is cooled to -5 to -15°C by gas-liquid separator 4, and then separated into gas and liquid phases. A portion of the gas phase is released to control the reaction pressure, while the majority is circulated to the fresh hydrogen feed line by circulating compressor 5. The liquid phase enters the distillation column, where light and heavy components are removed (light components flow out from the top of the column, and heavy components flow out from the bottom of the column). The propionate is then collected from the bottom of the distillation column 6, cooled, and then dehydrated by molecular sieve dehydration tanks 7 (two in parallel) to finally obtain the electronic-grade product.

[0024] The distillation column is either a tray type or a packed type, and operates at atmospheric pressure.

[0025] Example 1

[0026] Coconut shell activated carbon was treated with a 2% dilute nitric acid solution at 85℃ for 2 hours before impregnation, then washed with water until neutral, drained, and dried at 120℃ for 12 hours to obtain a qualified activated carbon support. 50.0g Ni(NO3)2·6H2O, 1.44g NH4ReO4, and 0.57g boric acid H3BO3 were added to 130mL of deionized water. After the metal salts were completely dissolved and homogenized, the solution was impregnated onto 100g of the qualified activated carbon support. After natural air-drying, it was dried at 87℃ for 20 hours. The resulting catalyst was labeled A, with a composition of 10% Ni - 1% Re - 0.1% B (the numbers preceding the elements represent their mass content in the catalyst based on the support mass, the same below).

[0027] The hydrogenation reaction of acrylate was carried out in a fixed-bed reactor (9 mm inner diameter). The amount of the above catalyst was 5 mL. Before the reaction, 10% H2 / N2 (space velocity 5000 h⁻¹) was used. -1 The reaction mixture was reduced at 300℃ for 8 hours, then cooled to the reaction temperature. A final concentration of 50 ppm MQ was added to the raw material methyl acrylate, pumped into the feed line, and mixed with hydrogen gas. The mixture was preheated to 40℃ via a heat exchanger and then passed from top to bottom through the catalyst bed in a fixed-bed reactor. The reaction conditions were 40℃, 0.5 MPa, and LHSV = 0.4 h. -1 The hydrogen-ester molar ratio was 10. After the reaction, the material was collected after being cooled to room temperature by condensation. The results of the reaction after 1000 hours are shown in Table 1.

[0028] Example 2

[0029] The catalyst preparation process and conditions are the same as in Example 1, except that the salts added to 130 mL of deionized water are: 74.3 g Ni(NO3)2·6H2O, 1.73 g NH4ReO4, and 2.86 g H3BO3. The resulting catalyst is labeled as B, and its composition is 15% Ni-1.2% Re-0.5% B.

[0030] The catalyst evaluation process and conditions are the same as in Example 1, except that the catalyst reduction conditions are: 50% H2 / N2 mixed gas (volume concentration) and a gas space velocity of 1000 h⁻¹. -1 Reduction at 350℃ for 4 hours; Reaction conditions: Ethyl acrylate containing a final concentration of 150 ppm HQ as the hydrogenation feedstock, 60℃, 1 MPa, LHSV = 0.8 h. -1 The hydrogen-to-ester ratio was 50. The reactants were collected after condensation and cooling. The results of the reaction after 1000 hours are shown in Table 1.

[0031] Example 3

[0032] The catalyst preparation process and conditions are the same as in Example 1, except that the salts added to 130 ml of deionized water are: 24.8 g Ni(NO3)2.6H2O, 4.75 g NH4ReO4, and 4.58 g H3BO3. The resulting catalyst is labeled C, and its composition is 5% Ni-3.3% Re-0.8% B.

[0033] The catalyst evaluation process and conditions are the same as in Example 1, except that the catalyst reduction conditions are: 90% H2 / N2 mixed gas (volume concentration) and a gas space velocity of 1000 h⁻¹. -1 Reduction at 400℃ for 4 hours; Reaction conditions: using propyl acrylate containing 100 ppm MQ and 4% propyl propionate as hydrogenation feedstock, 80℃, 2 MPa, LHSV = 1 hour. -1 The hydrogen-to-ester ratio was 20. The reactants were collected after condensation and cooling. The results of the reaction after 1000 hours are shown in Table 1.

[0034] Example 4

[0035] The catalyst preparation process and conditions are the same as in Example 1, except that the salt added to 130 ml of deionized water is: 49.6 g Ni(NO3)2·6H2O, 1.30 g NH4ReO4, and 1.72 g H3BO3. The resulting catalyst is labeled as D, and its composition is 10% Ni-0.9% Re-0.3% B.

[0036] The catalyst evaluation process and conditions are the same as in Example 1, except that the catalyst reduction conditions are: 5% H2 / N2 mixed gas (volume concentration) and a gas space velocity of 500 h⁻¹. -1 Reduction at 200℃ for 14 hours; Reaction conditions: using n-butyl acrylate with a final concentration of 200 ppm as the hydrogenation feedstock, 100℃, 1 MPa, LHSV = 1.2 h. -1 The hydrogen-to-ester ratio was 40. The reactants were collected after condensation and cooling. The results of the reaction after 1000 hours are shown in Table 1.

[0037] Example 5

[0038] The catalyst preparation process and conditions are the same as in Example 1, except that the salts added to 130 ml of deionized water are: 12.39 g Ni(NO3)2.6H2O, 0.72 g NH4ReO4, and 0.32 g AgNO3. The resulting catalyst is labeled as E, and its composition is 2.5Ni-0.5Re-0.2Ag.

[0039] The catalyst evaluation process and conditions are the same as in Example 1, except that the catalyst reduction conditions are: 20% H2 / N2 mixed gas (volume concentration) and a gas space velocity of 3000 h⁻¹. -1 Reduction at 290℃ for 6 hours; Reaction conditions: Ethyl acrylate containing 150 ppm MQ and 5% ethyl propionate as hydrogenation feedstock, 65℃, 0.8 MPa, LHSV = 1.5 h. -1 The hydrogen-to-ester ratio was 50. The reactants were collected after condensation and cooling. The results of the reaction after 1000 hours are shown in Table 1.

[0040] Example 6

[0041] The catalyst preparation process and conditions are the same as in Example 1, except that the salts added to 130 ml of deionized water are: 49.55 g Ni(NO3)2.6H2O, 2.37 g AgNO3, and 4.58 g H3BO3. The resulting catalyst is labeled F and its composition is 10% Ni-1.5% Ag-0.8% B.

[0042] The catalyst evaluation process and conditions are the same as in Example 1, except that the catalyst reduction conditions are: 40% H2 / N2 mixed gas (volume concentration) and a gas space velocity of 9000 h⁻¹. -1 Reduction at 400℃ for 10 hours; Reaction conditions: methyl acrylate containing 80 ppm MQ and 10% methyl propionate as hydrogenation feedstock, 55℃, 0.7 MPa, LHSV = 0.5 h. -1 The hydrogen-to-ester ratio was 60. The reactants were collected after condensation and cooling. The reaction results are shown in Table 1. Its 1800-hour stability test is shown in... Figure 2 It can be seen that the catalyst performance is very stable, and the content of methyl acrylate in the material coming out of the reactor is basically above 99.9%.

[0043] Example 7

[0044] The catalyst preparation process and conditions are the same as in Example 1, except that the salts added to 130 ml of deionized water are: 74.33 g Ni(NO3)2.6H2O, 2.16 g NH4ReO4, and 5.73 g H3BO3. The resulting catalyst is labeled G, and its composition is 15% Ni-1.5% Re-1% B.

[0045] The catalyst evaluation process and conditions are the same as in Example 1, except that the catalyst reduction conditions are: 90% H2 / N2 mixed gas (volume concentration) and a gas space velocity of 5000 h⁻¹. -1 Reduction at 250℃ for 9 hours; Reaction conditions: Ethyl acrylate containing 40 ppm MQ and 15% ethyl propionate as hydrogenation feedstock, 70℃, 1.5 MPa, LHSV = 0.5 h. -1 The hydrogen-to-ester ratio was 25. The reactants were collected after condensation and cooling. The reaction results are shown in Table 1, and the 2000-hour stability test results are shown in [Table 1]. Figure 3 As can be seen, the catalyst performance is very stable, and the content of ethyl acrylate in the material coming out of the reactor is basically above 99.7%.

[0046] Example 8

[0047] The catalyst evaluation process and conditions were the same as in Example 1, except that: catalyst A prepared in Example 1 and its reduction method (process and conditions were the same as in Example 1) were used, the feed was n-propyl acrylate containing 250 ppm HQ, and the treatment was carried out at 55°C, 0.8 MPa, and LHSV = 0.7 h. -1 The reaction was carried out under a hydrogen-to-ester ratio of 50, and the experimental results after 1000 hours are shown in Table 1.

[0048] Example 9

[0049] The catalyst evaluation process and conditions were the same as in Example 1, except that: catalyst B prepared in Example 2 and its reduction method (process and conditions were the same as in Example 2) were used; the feed was a mixture of ethyl acrylate containing a final concentration of 120 ppm MQ and a final mass concentration of 10% ethyl propionate; and the reaction was carried out at 75°C, 0.7 MPa, and LHSV = 0.4 h. -1 The reaction was carried out under a hydrogen-to-ester ratio of 40, and the experimental results after 1000 hours are shown in Table 1.

[0050] Example 10

[0051] The catalyst evaluation process and conditions were the same as in Example 1, except that: catalyst D prepared in Example 4 and its reduction method (process and conditions were the same as in Example 4) were used; the feed was a mixture of methyl acrylate containing a final concentration of 150 ppm MQ and a final mass concentration of 20% methyl propionate; and the reaction was carried out at 65°C, 1 MPa, and LHSV = 1.0 h. -1The reaction was carried out under a hydrogen-to-ester ratio of 45, and the experimental results after 1000 hours are shown in Table 1.

[0052] Example 11

[0053] The catalyst evaluation process and conditions were the same as in Example 1, except that: catalyst G prepared in Example 7 and its reduction method (process and conditions were the same as in Example 7) were used; the feed was a mixture of n-butyl acrylate containing a final concentration of 60 ppm MQ and a final mass concentration of 30% n-butyl propionate; and the reaction was carried out at 60°C, 0.7 MPa, and LHSV = 0.6 h. -1 The reaction was carried out under a hydrogen-to-ester ratio of 50, and the experimental results after 1000 hours are shown in Table 1.

[0054] Comparative Example 1

[0055] The catalyst evaluation process and conditions were the same as in Example 1, except that the same catalyst A, reduction method, and hydrogenation feedstock prepared in Example 1 were used, but the reaction conditions were 55°C, 2 MPa, and LHSV = 0.8 h⁻¹. -1 With a hydrogen-to-ester ratio of 6, the reaction proceeds in a trickle bed state. After 100 hours of operation, the catalyst bed becomes clogged due to the self-polymerization of the raw materials, and the reaction cannot continue.

[0056] Comparative Example 2

[0057] The catalyst evaluation process and conditions were the same as in Example 1, except that the catalyst F prepared in Example 6, along with its reduction method and hydrogenation feedstock, were used, but the reaction conditions were 50°C, 1.8 MPa, and LHSV = 1 h. -1 With a hydrogen-to-ester ratio of 4, the reaction proceeds in a trickle bed state. After 80 hours of operation, the catalyst bed becomes clogged due to the self-polymerization of the raw materials, and the reaction cannot continue.

[0058] These two comparative examples demonstrate that ensuring the conditions for gas-phase reactions is crucial for the stable operation of the device.

[0059] Table 1

[0060]

[0061]

[0062] Table 2

[0063]

[0064] As shown in Table 1, all catalysts in the examples efficiently converted acrylates, producing propionate esters with 100% selectivity. Therefore, the propionate ester content in the material exiting the reactor was generally above 99.5%, and the metal content was below 100 ppb. The impurities all originated from the raw materials; thus, selecting a stable source of raw materials is crucial for the design of the subsequent distillation column. After removal of light and heavy components and dehydration using molecular sieves, the propionate ester content was above 99.99%, the acetate content was below 0.003%, the water content was below 0.002%, and the metal ion content was below 1 ppm, achieving electronic-grade quality (see Table 2).

[0065] The foregoing is a detailed description of several embodiments of the present invention, but the present invention is not limited to the specific implementations described herein. Those skilled in the art can make other modifications and variations without departing from the technical scope of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for hydrogenating acrylate to propionic acid ester, characterized in that, It employs a supported catalyst, with activated carbon as the support, preferably coconut shell carbon, Ni as the active component, and one or more of Re, B, or Ag as the auxiliary agent; in a fixed-bed reactor packed with the supported catalyst, the raw material acrylate is converted into the corresponding propionate by gas-phase hydrogenation.

2. The method according to claim 1, characterized in that, The acrylates used include one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate and n-butyl acrylate; the corresponding propionate esters are one or more of methyl propionate, ethyl propionate, n-propyl propionate or n-butyl propionate.

3. The method according to claim 1, characterized in that, The active component used in the supported catalyst is Ni, and its mass content relative to the support (based on the mass of the support) is 1-20%, preferably 5-15%, and more preferably 5-10%; the promoter used in the catalyst is one or more of Re, B or Ag, and the promoter mass content relative to the support (based on the mass of the support) is 0.01-0.5%, preferably 0.02-0.4%, and more preferably 0.05-0.15%.

4. The method according to claim 1 or 3, characterized in that, The supported catalyst is prepared by impregnation. Nickel nitrate, and one or more of ammonium rhenium, boric acid or silver nitrate are added to the required solvent water in the required amount to dissolve them. Then, activated carbon support that has been acid washed and water washed in sequence is added, stirred evenly, air-dried at room temperature, and then dried at 80-120℃ for 2-10 hours.

5. The method according to claim 1 or 3, characterized in that, After the supported catalyst is loaded into the reactor, it needs to be reduced in situ under the following conditions: N2 / H2 atmosphere with a volume concentration of 2-90% and a gas space velocity of 100-5000 h⁻¹. -1 Reduce at 200-400℃ for 4-20 hours. After the reduction is complete, lower the temperature to the reaction temperature and then feed the material to continue the reaction.

6. The method according to claim 1, characterized in that, The acrylate raw material for hydrogenation reaction must be added with a polymerization inhibitor, which is generally one or more of hydroquinone (HQ) or p-hydroxyanisole (MQ), preferably MQ, and its concentration in the hydrogenation reaction raw material is about 10-300 ppm, preferably 50-100 ppm. Preferably, the acrylate raw material for hydrogenation reaction does not contain or may contain propionate, a hydrogenation product corresponding to the acrylate raw material, with a mass concentration of 0.5-90% in the hydrogenation reaction raw material, preferably 5-50%.

7. The method according to claim 1 or 6, characterized in that, The raw materials and hydrogen for the hydrogenation reaction of acrylate must be preheated to 40-90°C and enter the vaporization tower from the top and bottom, respectively. The liquid phase containing the polymerization inhibitor remains at the bottom of the vaporization tower, while the gas phase enters the tubular fixed-bed reactor.

8. The method according to claim 1 or 7, characterized in that, To ensure that the feedstock enters the fixed-bed reactor in the gas phase, appropriate reaction conditions must be maintained: temperature 40-100℃, preferably 50-80℃, more preferably 60-70℃; reaction pressure 0.1-2MPa, preferably 0.3-1.5MPa, more preferably 0.5-1.0MPa; hydrogen-ester molar ratio 5-100, preferably 10-60, more preferably 20-50; feedstock space velocity 0.2-1.5h⁻¹. -1 Preferably 0.3-1.0h -1 More preferably, it is 0.5-0.9h. -1 .

9. The method according to claim 1, characterized in that, The product from the reactor is then subjected to distillation to remove light and heavy components and molecular sieve dehydration to obtain electronic-grade propionate; specifically: After the product from the reactor is frozen to -5 to -15°C, gas-liquid separation occurs. A portion of the gas phase is released to control the reaction pressure, while the majority is circulated through a compressor to the fresh hydrogen feed line. The liquid phase enters a distillation column, where light and heavy components are removed. The propionate ester is collected from the bottom of the column, cooled, and then dehydrated through a molecular sieve to finally obtain the electronic grade product.

10. The method according to claim 9, characterized in that, The distillation column is either a tray type or a packed type, and operates at atmospheric pressure.

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