Process for the production of phenylethyl esters of diethyl carbonate with recycling of ethanol, rectification system

Abstract

The present application belongs to the technical field of production method of medical and pharmaceutical chemical products, and particularly relates to a production method of phenethyl ester with recycling of ethanol and reuse of diethyl carbonate, and a rectification system. The production method of phenethyl ester with recycling of ethanol and reuse of diethyl carbonate comprises the following steps: adding ethyl phenylacetate, sodium ethoxide and diethyl carbonate into a reaction kettle, mixing gas phase into a rectification tower, passing through a first condenser, a second condenser, a reflux tank, the rectification tower and the reaction kettle, and recycling ethanol by reflux; when the temperature at the top of the rectification tower exceeds 55 DEG C, recycling a mixed solution of diethyl carbonate and ethanol; dropping bromoethane into the reaction kettle for reaction by cooling; after the reaction is completed, adding water and sulfuric acid into the reaction kettle by distillation and cooling, acidizing, standing and separating into layers to obtain a crude phenethyl ester, and rectifying to obtain phenethyl ester. The production method provided by the present application has high purity and high yield of phenethyl ester, and can recycle and reuse once to reduce cost and increase efficiency. The present application further provides a rectification system of phenethyl ester.

Description

Technical Field

[0001] This invention belongs to the technical field of pharmaceutical and chemical production methods, specifically relating to a method for producing phenethyl ester by recovering ethanol and using diethyl carbonate, and a distillation system. Background Technology

[0002] Phenobarbital is a barbiturate sedative and hypnotic drug. Its synthesis mainly involves phenethyl esterification, condensation, crude product processing, and finished product processing. The phenethyl esterification process, as the first step in the synthesis chain, is the most crucial link. The condensation reaction is the most critical part of the phenethyl ester process; controlling the quality of phenethyl ester is key to ensuring the quality of phenobarbital products.

[0003] In existing technologies, the phenethyl ester process involves a condensation reaction of ethyl phenylacetate, diethyl carbonate, and sodium ethoxide, followed by alkylation with bromoethane. After post-treatment, crude phenethyl ester is obtained, which is then distilled to yield phenethyl ester. For example, the "Synthesis of Diethyl Phenylethyl Malonate" published in the 3rd issue of Ningxia Petrochemical in 1999 by Shi Wanli, discloses the following steps in section 2.5: First, sodium ethoxide is added to a dry reaction vessel, stirred, and samples are taken for analysis of total alkali and free alkali content. Based on the analysis results, ethyl acetate is added to neutralize the free alkali. Then, the temperature is raised to recover ethanol, and the sodium ethoxide is concentrated to 35%–40% of the total alkali. In the second step, after cooling, ethyl phenylacetate and diethyl carbonate are added. The reaction is maintained at 70–85°C; then, the pressure is reduced to -0.02 MPa, and ethanol (referred to as carbon ethanol) is fractionated and recovered for 6–8 hours until the vessel temperature rises to 120°C and no more distillate is obtained, at which point the condensation reaction is complete. The third step involves sealing all ports of the reactor and cooling it to 30°C, using the reactor's own negative pressure to draw in bromoethane. Then, the feed port is closed, and the system reacts in a closed state for 6–8 hours, with the temperature controlled between 65–95°C. The pressure should not exceed 0.15 MPa, at which point the alkylation reaction is complete. The fourth step involves cooling the reactor and recovering unreacted diethyl carbonate under negative pressure. The fifth step involves washing the feed solution with water and acidifying it (adjusting the pH to 1–2 with sulfuric acid). After settling and separating the layers, the sodium bromide mother liquor is separated, and the upper layer is transferred to the distillation process for vacuum distillation. The fraction reaching the required density is the final product, phenethyl ester. The yield of this step is 85%–92%. This process generates many byproducts, which must be recycled to reduce product costs. For example, the concentrated sodium bromide mother liquor can be used to synthesize bromoethane; the diethyl carbonate recovered under negative pressure can be directly reused after slight treatment; and the ethanol recovered during the concentration of sodium ethoxide can be used to synthesize sodium ethoxide, etc. This method is the conventional method. The recovered ethanol is carbon ethanol, which is a mixture of diethyl carbonate and ethanol. The ethanol content is low and does not meet the industrial ethanol standard (content ≥95%). It can only be treated as hazardous waste. Furthermore, the recovered diethyl carbonate needs to be treated before reuse, which increases the complexity of the process.

[0004] For example, CN115925543A discloses a method for synthesizing diethyl phenylmalonate. Diethyl phenylmalonate undergoes a substitution reaction with sodium ethoxide, followed by alkylation with bromoethane to obtain diethyl phenylmalonate. This method requires the condensation alkylation column used in existing preparation processes, has no special requirements for production equipment, and does not require vacuum control during the reaction. It employs a one-pot preparation method, directly esterifying, condensing, and alkylating after neutralization and substitution to obtain the product. The production process is simple, with high yield and short production cycle. The reaction process does not generate a large amount of organic solid waste, reducing industrial waste emissions compared to existing preparation processes, making it suitable for large-scale industrial production. The phenylethyl ester obtained by the one-pot preparation method has a content between 96.37% and 96.73%, which is relatively low. Furthermore, the distilled liquid is a mixture and can only be treated as hazardous waste.

[0005] The bottleneck of existing technology lies in the low purity of crude phenethyl ester, only 70%–80%, and the yield of finished phenethyl ester is only 65%, resulting in a low conversion rate. Furthermore, in the condensation reaction process, the existing technology recovers a low amount of ethanol in the early stages (approximately 70%–80%, with the remainder being diethyl carbonate), failing to meet industrial ethanol standards (ethanol content ≥95%), and thus requiring treatment as hazardous waste. The diethyl carbonate recovered in the later stages contains approximately 70%–80%, and a secondary recovery of diethyl carbonate is necessary for reuse. Existing technology is cumbersome, has a low reaction conversion rate, and suffers from significant waste of labor, power, and other energy resources, affecting the quality of crude phenethyl ester and generating substantial hazardous waste disposal costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate. The phenethyl ester prepared has high purity and high yield, can be recovered and reused in one step, has a high recycling rate, and reduces costs and increases efficiency. The present invention also provides a distillation system for phenethyl ester.

[0007] The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate according to the present invention includes the following steps:

[0008] (1) Add the measured amounts of ethyl phenylacetate, sodium ethoxide, and diethyl carbonate to the reactor, control the vacuum degree of the reactor to ≤0.06MPa, open the steam valve of the jacket to make the temperature inside the reactor high, and the mixed gas phase enters the distillation column. Part of it passes through the first-stage condenser and the second-stage condenser and enters the reflux tank. The reflux tank overflows to the distillation column and then flows back to the reactor from the distillation column. The other part is purified by the distillation column and directly refluxed to the reactor.

[0009] (2) After total reflux for 0.5 to 3 hours, control the top temperature of the distillation column to ≤55℃, open the feed valve of the ethanol receiver, and reflux to recover ethanol; open the steam valve of the reactor and control the steam pressure to ≤0.3MPa. When the top temperature of the distillation column exceeds 55℃, close the feed valve of the ethanol receiver, open the feed valve of the diethyl carbonate receiver, close the reflux valve, and recover diethyl carbonate until no liquid flows out of the sight glass of the diethyl carbonate receiver. The condensation reaction is over. The recovered diethyl carbonate can be directly reused to recover ethanol.

[0010] (3) Turn on the jacketed circulating water of the reactor to cool it down. When the temperature drops below 84°C, add bromoethane dropwise into the reactor and carry out the alkylation reaction for 6-8 hours. After the reaction is completed, open the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is over. Open the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure. When no liquid flows out of the sight glass of the diethyl carbonate acceptor, the distillation is over. Cool down to below 90°C, add water and sulfuric acid to the reactor until the pH is 1-2, let it stand and separate into layers. The upper layer is crude phenylethyl ester. The phenylethyl ester is obtained by distillation.

[0011] The diethyl carbonate recovered in step (2) has a purity of ≥95%.

[0012] In step (2), the ethanol receiver feed valve is opened to reflux and recover ethanol. The reflux ratio is controlled at (2:1) to (4:1). When ethanol is discharged, a ratio of 2:1 is preferred in the early stage when the top temperature of the column is relatively stable. As the top temperature of the distillation column gradually increases, the reflux ratio is gradually adjusted to 4:1. The reflux ratio in step (2) refers to the ratio of the total mass of refluxed into the distillation column to the mass of ethanol entering the ethanol receiver.

[0013] In step (1), the steam valve of the jacket is opened to bring the temperature inside the reactor to 80-120°C, preferably 80-100°C.

[0014] In step (1), the refrigerant of the first-stage condenser is low-temperature water with a temperature of 0 to 10°C, and the refrigerant of the second-stage condenser is ice-salt water with a temperature of -10 to -5°C.

[0015] Step (1) Open the steam valve of the jacket and control the steam pressure to ≤0.3MPa.

[0016] The aforementioned production system for recovering ethanol and reusing diethyl carbonate to produce phenethyl ester includes a distillation system comprising a reaction vessel, a distillation column, a primary condenser, a secondary condenser, and a reflux tank. The reaction vessel is connected to the distillation column, the distillation column is connected to the primary condenser, the primary condenser is connected to the secondary condenser, the secondary condenser is connected to the reflux tank, and the reflux tank is connected to the distillation column. The reflux tank is connected to both an ethanol receiver and a diethyl carbonate receiver.

[0017] The bottom outlet of the distillation column is connected to the reactor.

[0018] The outer layer of the reactor is sandwiched.

[0019] A reflux valve is installed on the pipeline connecting the reflux tank and the distillation column.

[0020] Specifically, the method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using the distillation system includes the following steps:

[0021] (1) Add the measured amounts of ethyl phenylacetate, sodium ethoxide, and diethyl carbonate to the reactor. Control the vacuum degree of the reactor to ≤0.06MPa. Open the steam valve of the jacket and control the steam pressure to ≤0.3MPa. Raise the temperature inside the reactor to 80-120℃. The mixed gas phase (ethanol and diethyl carbonate) enters the distillation column. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state. After passing through the first-stage condenser and the second-stage condenser, it enters the reflux tank. The overflow from the reflux tank goes to the distillation column and then back to the reactor. During this process, control the top temperature of the distillation column to ≤55℃ and the total reflux time to 0.5-3h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) is purified by the distillation column and directly refluxed to the reactor.

[0022] (2) Based on the top temperature of the distillation column, open the feed valve of the ethanol receiver and control the reflux ratio to (2:1) to (4:1) to recover ethanol. The recovered ethanol enters the ethanol receiver. Open the steam valve of the reactor and control the steam pressure to ≤0.3MPa. When the top temperature of the distillation column exceeds 55℃, close the feed valve of the ethanol receiver, open the feed valve of the diethyl carbonate receiver, close the reflux valve, and observe that no diethyl carbonate and ethanol mixture flows out of the sight glass of the diethyl carbonate receiver. The distillation of the diethyl carbonate and ethanol mixture is finished, the condensation reaction is finished, and the recovered diethyl carbonate (purity ≥95%) meets the application standard and can be directly applied. The recovered ethanol meets the industrial ethanol standard and is not treated as hazardous waste. It is sold directly.

[0023] (3) Turn on the jacketed circulating water of the reactor to cool it down. When the temperature drops below 84°C, add bromoethane dropwise into the reactor and carry out the alkylation reaction for 6-8 hours. Turn on the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is over. Turn on the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure. When no liquid flows out of the sight glass of the diethyl carbonate acceptor, the distillation is over. When the temperature drops below 90°C, add the measured amount of water and 30% sulfuric acid to the reactor and acidify it to pH 1-2. Let it stand and separate into layers to obtain crude phenylethyl ester. Then, distill it to obtain phenylethyl ester.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) The method for producing phenethyl ester by recovering ethanol and using diethyl carbonate of the present invention adopts the distillation system described above to separate ethanol and diethyl carbonate. The separation of ethanol and the reflux of diethyl carbonate in the reaction system can both promote the reaction in the forward direction, which is beneficial to the conversion of condensation reaction and improves the reaction conversion rate.

[0026] (2) The method for producing phenethyl ester by recovering ethanol and using diethyl carbonate of the present invention controls the reflux ratio, collects ethanol separately, and the ethanol content reaches the industrial ethanol standard, and is sold directly without being disposed of as hazardous waste, which greatly saves the cost of hazardous waste disposal.

[0027] (3) In the method of the present invention, after the ethanol is discharged, the diethyl carbonate content collected is ≥95%, which meets the applicable standard and can be directly used for production without secondary recycling. This eliminates the secondary recycling position, reduces the consumption of diethyl carbonate, reduces energy consumption, and greatly saves the costs of raw materials, labor, and power. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0029] Figure 1 This is a schematic diagram of the distillation system used in the production of phenethyl ester from diethyl carbonate, which is a product of the present invention, to recover ethanol.

[0030] Figure 1 In the middle: 1. Reactor; 2. Distillation column; 3. Primary condenser; 4. Secondary condenser; 5. Reflux tank; 6. Ethanol receiver; 7. Diethyl carbonate receiver; 8. Jacket; 9. Reflux valve.

[0031] Figure 2 The chromatogram is of the phenethyl ester prepared in Example 1.

[0032] Figure 3 The chromatogram is of the diethyl carbonate recovered in Example 1.

[0033] Figure 4 The chromatogram is of the phenylethyl ester prepared in Example 2.

[0034] Figure 5 The chromatogram is of the diethyl carbonate recovered in Example 2.

[0035] Figure 6 The chromatogram is of the phenylethyl ester prepared in Example 3.

[0036] Figure 7 The chromatogram is of the diethyl carbonate recovered in Example 3.

[0037] Figure 8 The chromatogram is of the phenylethyl ester prepared in Example 4.

[0038] Figure 9 The chromatogram is of the diethyl carbonate recovered in Example 4.

[0039] Figure 10 The chromatogram is of the phenethyl ester prepared in Example 5.

[0040] Figure 11 The chromatogram is of the diethyl carbonate recovered in Example 5.

[0041] Figure 12 The chromatogram is of the phenethyl ester prepared in Comparative Example 1.

[0042] Figure 13 The chromatogram is of the diethyl carbonate recovered in Comparative Example 1.

[0043] Figure 14 The chromatogram is of the phenethyl ester prepared in Comparative Example 2.

[0044] Figure 15 The chromatogram is of the diethyl carbonate recovered in Comparative Example 2.

[0045] Figure 16 The chromatogram is of the phenethyl ester prepared in Comparative Example 3.

[0046] Figure 17 The chromatogram is of the diethyl carbonate recovered in Comparative Example 3.

[0047] Figure 18 The chromatogram is of the phenethyl ester prepared in Comparative Example 4.

[0048] Figure 19 The chromatogram is of the diethyl carbonate recovered in Comparative Example 4. Detailed Implementation

[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0050] The distillation system used in the production of phenethyl ester from recovered ethanol and diethyl carbonate as described in this invention is, for example... Figure 1As shown, the apparatus includes a reaction vessel 1, a distillation column 2, a primary condenser 3, a secondary condenser 4, and a reflux tank 5. The reaction vessel 1 is connected to the distillation column 2, the distillation column 2 is connected to the primary condenser 3, the primary condenser 3 is connected to the secondary condenser 4, the secondary condenser 4 is connected to the reflux tank 5, and the reflux tank 5 is connected to the distillation column 2. The reflux tank 5 is connected to an ethanol receiver 6 and a diethyl carbonate receiver 7. The bottom outlet of the distillation column 2 is connected to the reaction vessel 1. A jacket 8 is provided on the outer layer of the reaction vessel 1. A reflux valve 9 is installed on the pipeline connecting the reflux tank 5 and the distillation column 2. The inlet, outlet, connecting pipelines, and connecting valves in the apparatus are all existing apparatus configurations and will not be discussed further. The primary condenser 3 uses low-temperature water as the refrigerant, with a temperature of 0–10°C, and the secondary condenser 4 uses ice-salt water as the refrigerant, with a temperature of -10–-5°C. The process of distilling bromoethane and the associated receivers are existing technologies and will not be described further.

[0051] The following embodiments are all implemented using the system described above.

[0052] Example 1

[0053] The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using the distillation system includes the following steps:

[0054] (1) Add 1200 kg of ethyl phenylacetate, 3130 g of sodium ethoxide (calculated based on free alkali), and 2600 kg of diethyl carbonate to reactor 1. Control the vacuum degree of reactor 1 to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa so that the temperature inside reactor 1 rises to 100℃. The mixed gas phase (ethanol and diethyl carbonate) enters distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The reflux tank 5 overflows to distillation column 2, and then flows back to reactor 1 from distillation column 2. During this process, control the top temperature of distillation column 2 to ≤55℃ and the total reflux time to 2 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) is purified by distillation column 2 and directly refluxed to reactor 1.

[0055] (2) Based on the top temperature of 48℃ in distillation column 2, open the feed valve of ethanol receiver 6 and control the reflux ratio to 2:1 (reflux flow rate 400kg / h: discharge flow rate 200kg / h) to recover ethanol. The recovered ethanol enters ethanol receiver 6. Open the steam valve of reactor 1 and control the steam pressure to ≤0.3MPa. When the top temperature of distillation column 2 exceeds 55℃, close the feed valve of ethanol receiver 6, open the feed valve of diethyl carbonate receiver 7, close the reflux valve 9, and observe that no diethyl carbonate and ethanol mixture flows out of the sight glass of diethyl carbonate receiver 7. The distillation of diethyl carbonate and ethanol mixture is finished, the condensation reaction is finished, and the recovered diethyl carbonate (purity ≥95%) meets the application standard and can be directly applied. The recovered ethanol meets the industrial ethanol standard and is not treated as hazardous waste. It is sold directly.

[0056] (3) Cool the reactor 1 by opening the jacket 8 with circulating water. When the temperature drops below 84℃, add 1160g of bromoethane dropwise to the reactor 1 and carry out the alkylation reaction for 8 hours. Open the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is complete. Open the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. When the temperature drops below 90℃, add 1200kg of water and 700g of 30% sulfuric acid to the reactor 1 and acidify to pH 1-2. Let it stand and separate into layers to obtain crude phenylethyl ester. Distill to obtain phenylethyl ester. The total yield of phenylethyl ester (diethyl phenyl ethyl malonate) is 77.24%, and the purity is 99.62%. The purity of the recovered diethyl carbonate is 98.10%.

[0057] Example 2

[0058] The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using the distillation system includes the following steps:

[0059] (1) Add 1500 kg of ethyl phenylacetate, 3910 g of sodium ethoxide (calculated based on free alkali), and 3250 kg of diethyl carbonate to reactor 1. Control the vacuum degree of reactor 1 to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa so that the temperature inside reactor 1 rises to 90℃. The mixed gas phase (ethanol and diethyl carbonate) enters distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The reflux tank 5 overflows to distillation column 2, and then flows back to reactor 1 from distillation column 2. During this process, control the top temperature of distillation column 2 to ≤55℃ and the total reflux time to 1.5 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) is purified by distillation column 2 and directly refluxed to reactor 1.

[0060] (2) Based on the top temperature of 45℃ in distillation column 2, open the feed valve of ethanol receiver 6 and control the reflux ratio to 3:1 (reflux flow rate 450kg / h: discharge flow rate 150kg / h) to recover ethanol. The recovered ethanol enters ethanol receiver 6. Open the steam valve of reactor 1 and control the steam pressure to ≤0.3MPa. When the top temperature of distillation column 2 exceeds 55℃, close the feed valve of ethanol receiver 6, open the feed valve of diethyl carbonate receiver 7, close the reflux valve 9, and observe that no diethyl carbonate and ethanol mixture flows out of the sight glass of diethyl carbonate receiver 7. The distillation of diethyl carbonate and ethanol mixture is finished, the condensation reaction is finished, and the recovered diethyl carbonate (purity ≥95%) meets the application standard and can be directly applied. The recovered ethanol meets the industrial ethanol standard and is not treated as hazardous waste. It is sold directly.

[0061] (3) Cool the reactor 1 by opening the jacket 8 with circulating water. When the temperature drops below 84°C, add 1450g of bromoethane dropwise to the reactor 1 and carry out the alkylation reaction for 8 hours. Open the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is complete. Open the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. When the temperature drops below 90°C, add 1500kg of water and 875g of 30% sulfuric acid to the reactor 1 and acidify to pH 1-2. Let it stand and separate into layers to obtain crude phenethyl ester. Distill to obtain phenethyl ester. The total yield of phenethyl ester is 76.77%, and the purity is 99.62%. The purity of the recovered diethyl carbonate is 98.00%.

[0062] Example 3

[0063] The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using the distillation system includes the following steps:

[0064] (1) Add 1300 kg of ethyl phenylacetate, 3390 g of sodium ethoxide (calculated based on free alkali), and 2810 kg of diethyl carbonate to reactor 1. Control the vacuum degree of reactor 1 to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa so that the temperature inside reactor 1 rises to 90℃. The mixed gas phase (ethanol and diethyl carbonate) enters distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The reflux tank 5 overflows to distillation column 2, and then flows back to reactor 1 from distillation column 2. During this process, control the top temperature of distillation column 2 to ≤55℃ and the total reflux time to 3 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) is purified by distillation column 2 and directly refluxed to reactor 1.

[0065] (2) Based on the top temperature of 52℃ in distillation column 2, open the feed valve of ethanol receiver 6 and control the reflux ratio to 4:1 (reflux flow rate 400kg / h: discharge flow rate 100kg / h) to recover ethanol. The recovered ethanol enters ethanol receiver 6. Open the steam valve of reactor 1 and control the steam pressure to ≤0.3MPa. When the top temperature of distillation column 2 exceeds 55℃, close the feed valve of ethanol receiver 6, open the feed valve of diethyl carbonate receiver 7, close the reflux valve 9, and observe that no diethyl carbonate and ethanol mixture flows out of the sight glass of diethyl carbonate receiver 7. The distillation of diethyl carbonate and ethanol mixture is finished, the condensation reaction is finished, and the recovered diethyl carbonate (purity ≥95%) meets the application standard and can be directly applied. The recovered ethanol meets the industrial ethanol standard and is not treated as hazardous waste. It is sold directly.

[0066] (3) Cool the reactor 1 by opening the jacket 8 with circulating water. When the temperature drops below 84°C, add 1250g of bromoethane dropwise to the reactor 1 and carry out the alkylation reaction for 8 hours. Open the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is complete. Open the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. When the temperature drops below 90°C, add 1296kg of water and 750g of 30% sulfuric acid to the reactor 1 and acidify to pH 1-2. Let it stand and separate into layers to obtain crude phenethyl ester. Distill to obtain phenethyl ester. The total yield of phenethyl ester is 76.67%, and the purity is 99.74%. The purity of the recovered diethyl carbonate is 98.23%.

[0067] Example 4

[0068] The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using the distillation system includes the following steps:

[0069] (1) Add 1200 kg of ethyl phenylacetate, 3130 g of sodium ethoxide (calculated based on free alkali), and 2600 kg of diethyl carbonate to reactor 1. Control the vacuum degree of reactor 1 to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa so that the temperature inside reactor 1 rises to 120℃. The mixed gas phase (ethanol and diethyl carbonate) enters distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The reflux tank 5 overflows to distillation column 2, and then flows back to reactor 1 from distillation column 2. During this process, control the top temperature of distillation column 2 to ≤55℃ and the total reflux time to 3 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) is purified by distillation column 2 and directly refluxed to reactor 1.

[0070] (2) Based on the top temperature of 54℃ in distillation column 2, open the feed valve of ethanol receiver 6 and control the reflux ratio to 4:1 (reflux flow rate 400kg / h: discharge flow rate 100kg / h) to recover ethanol. The recovered ethanol enters ethanol receiver 6. Open the steam valve of reactor 1 and control the steam pressure to ≤0.3MPa. When the top temperature of distillation column 2 exceeds 55℃, close the feed valve of ethanol receiver 6, open the feed valve of diethyl carbonate receiver 7, close the reflux valve 9, and observe that no diethyl carbonate and ethanol mixture flows out of the sight glass of diethyl carbonate receiver 7. The distillation of diethyl carbonate and ethanol mixture is finished, the condensation reaction is finished, and the recovered diethyl carbonate (purity ≥95%) meets the application standard and can be directly applied. The recovered ethanol meets the industrial ethanol standard and is not treated as hazardous waste. It is sold directly.

[0071] (3) Cool the reactor 1 by opening the jacket 8 with circulating water. When the temperature drops below 84°C, add 1160g of bromoethane dropwise to the reactor 1 and carry out the alkylation reaction for 8 hours. Open the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is complete. Open the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. When the temperature drops below 90°C, add 1200kg of water and 700g of 30% sulfuric acid to the reactor 1 and acidify to pH 1-2. Let it stand and separate into layers to obtain crude phenethyl ester. Distill to obtain phenethyl ester. The total yield of phenethyl ester is 77.24%, and the purity is 99.62%. The purity of the recovered diethyl carbonate is 98.28%.

[0072] Example 5

[0073] The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using the distillation system includes the following steps:

[0074] (1) Add 1200 kg of ethyl phenylacetate, 3130 g of sodium ethoxide (calculated based on free alkali), and 2600 kg of diethyl carbonate to reactor 1. Control the vacuum degree of reactor 1 to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa so that the temperature inside reactor 1 rises to 80℃. The mixed gas phase (ethanol and diethyl carbonate) enters distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The reflux tank 5 overflows to distillation column 2, and then flows back to reactor 1 from distillation column 2. During this process, control the top temperature of distillation column 2 to ≤55℃ and the total reflux time to 3 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) is purified by distillation column 2 and directly refluxed to reactor 1.

[0075] (2) Based on the top temperature of 43℃ in distillation column 2, open the feed valve of ethanol receiver 6 and control the reflux ratio to 2:1 (reflux flow rate 400kg / h: discharge flow rate 200kg / h) to recover ethanol. The recovered ethanol enters ethanol receiver 6. Open the steam valve of reactor 1 and control the steam pressure to ≤0.3MPa. When the top temperature of distillation column 2 exceeds 55℃, close the feed valve of ethanol receiver 6, open the feed valve of diethyl carbonate receiver 7, close the reflux valve 9, and observe that no diethyl carbonate and ethanol mixture flows out of the sight glass of diethyl carbonate receiver 7. The distillation of diethyl carbonate and ethanol mixture is finished, the condensation reaction is finished, and the recovered diethyl carbonate (purity ≥95%) meets the application standard and can be directly applied. The recovered ethanol meets the industrial ethanol standard and is not treated as hazardous waste. It is sold directly.

[0076] (3) Cool the reactor 1 by opening the jacket 8 with circulating water. When the temperature drops below 84°C, add 1160g of bromoethane dropwise to the reactor 1 and carry out the alkylation reaction for 8 hours. Open the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is complete. Open the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. When the temperature drops below 90°C, add 1200kg of water and 700g of 30% sulfuric acid to the reactor 1 and acidify to pH 1-2. Let it stand and separate into layers to obtain crude phenethyl ester. Distill to obtain phenethyl ester. The total yield of phenethyl ester is 76.64%, and the purity is 99.62%. The purity of the recovered diethyl carbonate is 98.23%.

[0077] Comparative Example 1

[0078] A method for producing phenethyl ester using a conventional tower includes the following steps:

[0079] (1) Add 1200 kg of ethyl phenylacetate, 3130 g of sodium ethoxide (calculated based on free alkali), and 2600 kg of diethyl carbonate to reactor 1. Control the vacuum degree of the reactor to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa to raise the temperature inside the reactor to 100℃. The mixed gas phase (ethanol and diethyl carbonate) enters tower 2. Part of it (low-boiling ethanol) enters the gas phase pipe in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The overflow from the reflux tank 5 goes to the distillation tower 2, and then refluxes from the distillation tower 2 back to reactor 1. During this process, control the top temperature of tower 2 to ≤55℃ and the total reflux time to 2.0 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) is directly refluxed to reactor 1 through tower 2.

[0080] (2) Control the temperature at the top of column 2 to 48°C, open the feed valve of ethanol acceptor 6, control the reflux ratio to 2:1 (reflux flow rate 400 kg / h: discharge flow rate 200 kg / h), recover ethanol, and the recovered ethanol enters ethanol acceptor 6; when the temperature at the top of column 2 exceeds 55°C, close the feed valve of ethanol acceptor 6, open the feed valve of diethyl carbonate acceptor 7, close the reflux valve 9, and observe that no liquid flows out of the sight glass of diethyl carbonate acceptor 7, the recovery of diethyl carbonate ends and the condensation reaction ends.

[0081] (3) Turn on the circulating water in the jacket 8 of reactor 1 to cool it down. When the temperature drops below 84℃, add 1160g of bromoethane dropwise to the reactor and carry out the alkylation reaction for 8 hours. After the reaction is completed, distill off the bromoethane. Open the feed valve of the diethyl carbonate acceptor 7 and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. The distillation is then complete. After the distillation is completed, cool down to below 90℃ and add 1200kg of water and 700kg of 30% sulfuric acid to reactor 1 to acidify to pH=1-2. After acidification, let it stand to separate the layers. The upper layer is crude phenylethyl ester, which is then distilled to obtain phenylethyl ester. The total yield of phenylethyl ester is 65.01%, and the purity is 98.98%. The recovered diethyl carbonate needs to be recovered twice. After the second recovery, the purity is 98.55%.

[0082] Comparative Example 2

[0083] A method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using a distillation system includes the following steps:

[0084] (1) Add 1200 kg of ethyl phenylacetate, 3130 g of sodium ethoxide (calculated based on free alkali), and 2600 kg of diethyl carbonate to reactor 1. Control the vacuum degree of the reactor to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa to raise the temperature inside the reactor to 100℃. The mixed gas phase (ethanol and diethyl carbonate) enters the distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The reflux tank 5 overflows to the distillation column 2, and then flows back to reactor 1 from the distillation column 2. During this process, control the top temperature of the distillation column 2 to ≤55℃ and do not perform total reflux. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) flows directly back to reactor 1 through the distillation column 2.

[0085] (2) Control the top temperature of the distillation column 2 to 48℃, open the feed valve of the ethanol acceptor 6, control the reflux ratio to 2:1 (reflux flow rate 400kg / h: discharge flow rate 200kg / h), recover ethanol, and the recovered ethanol enters the ethanol acceptor 6; when the top temperature of the distillation column 2 exceeds 55℃, close the feed valve of the ethanol acceptor 6, open the feed valve of the diethyl carbonate acceptor 7, close the reflux valve 9, and observe that no liquid flows out of the sight glass of the diethyl carbonate acceptor 7, the recovery of diethyl carbonate ends and the condensation reaction ends.

[0086] (3) Turn on the circulating water in the jacket 8 of reactor 1 to cool it down. When the temperature drops below 84℃, add 1160g of bromoethane dropwise to the reactor and carry out the alkylation reaction for 8 hours. After the reaction is completed, distill off the bromoethane. Open the feed valve of the diethyl carbonate acceptor 7 and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. The distillation is then complete. After the distillation is completed, cool down to below 90℃ and add 1200kg of water and 700kg of 30% sulfuric acid to reactor 1 to acidify to pH=1-2. After acidification, let it stand to separate the layers. The upper layer yields crude phenethyl ester, which is then distilled to obtain phenethyl ester. The total yield of phenethyl ester is 72.89%, and the purity is 99.61%. The purity of the recovered diethyl carbonate is 98.33%.

[0087] Comparative Example 3

[0088] A method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using a distillation system includes the following steps:

[0089] (1) Add 1200 kg of ethyl phenylacetate, 3130 g of sodium ethoxide (calculated based on free alkali), and 2600 kg of diethyl carbonate to reactor 1. Control the vacuum degree of the reactor to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa to raise the temperature inside the reactor to 100℃. The mixed gas phase (ethanol and diethyl carbonate) enters the distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The overflow from the reflux tank 5 goes to the distillation column 2, and then flows back to reactor 1 from the distillation column 2. During this process, the top temperature of the distillation column 2 is controlled to ≤55℃, and the total reflux time is 2.0 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) flows directly back to reactor 1 through the distillation column 2.

[0090] (2) Control the top temperature of the distillation column 2 to 48℃, open the feed valve of the ethanol acceptor 6, control the reflux ratio to 1:1 (reflux flow rate 300kg / h: discharge flow rate 300kg / h), recover ethanol, and the recovered ethanol enters the ethanol acceptor 6; when the top temperature of the distillation column 2 exceeds 55℃, close the feed valve of the ethanol acceptor 6, open the feed valve of the diethyl carbonate acceptor 7, close the reflux valve 9, and observe that no liquid flows out of the sight glass of the diethyl carbonate acceptor 7, the recovery of diethyl carbonate ends and the condensation reaction ends.

[0091] (3) Cool the reactor 1 by opening the jacket 8 with circulating water. When the temperature drops below 84℃, add 1160g of bromoethane dropwise to the reactor and carry out the alkylation reaction for 8 hours. After the reaction, distill off the bromoethane. Open the feed valve of the diethyl carbonate acceptor 7 and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. After distillation, cool the reactor to below 90℃ and add 1200kg of water and 700kg of 30% sulfuric acid to the reactor 1 to acidify to pH=1-2. After acidification, allow the mixture to stand and separate into layers. The upper layer yields crude phenethyl ester, which is then distilled to obtain phenethyl ester. The total yield of phenethyl ester is 71.52%, and the purity is 99.61%. The purity of the recovered diethyl carbonate is 98.27%.

[0092] Comparative Example 4

[0093] A method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate using a distillation system includes the following steps:

[0094] (1) Add 1200 kg of ethyl phenylacetate, 3130 g of sodium ethoxide (calculated based on free alkali), and 2600 kg of diethyl carbonate to reactor 1. Control the vacuum degree of the reactor to ≤0.06 MPa, open the steam valve of the jacket, and control the steam pressure to ≤0.3 MPa to raise the temperature inside the reactor to 100℃. The mixed gas phase (ethanol and diethyl carbonate) enters the distillation column 2. Part of it (low-boiling ethanol) enters the gas phase tube in the gas phase state, passes through the first-stage condenser 3 and the second-stage condenser 4, and enters the reflux tank 5. The overflow from the reflux tank 5 goes to the distillation column 2, and then flows back to reactor 1 from the distillation column 2. During this process, the top temperature of the distillation column 2 is controlled to ≤55℃, and the total reflux time is 2.0 h, thereby achieving the separation effect of ethanol and diethyl carbonate. The other part (high-boiling diethyl carbonate in the packing and low-boiling gas) flows directly back to reactor 1 through the distillation column 2.

[0095] (2) Control the top temperature of the distillation column 2 to 60℃, open the feed valve of the ethanol receiver 6, control the reflux ratio to 2:1 (reflux flow rate 400kg / h: discharge flow rate 200kg / h), recover ethanol, and the recovered ethanol enters the ethanol receiver 6; when the top temperature of the distillation column 2 exceeds 60℃, close the feed valve of the ethanol receiver 6, open the feed valve of the diethyl carbonate receiver 7, close the reflux valve 9, and observe that no liquid flows out of the sight glass of the diethyl carbonate receiver 7, the recovery of diethyl carbonate ends and the condensation reaction ends.

[0096] (3) Turn on the circulating water in the jacket 8 of reactor 1 to cool it down. When the temperature drops below 84℃, add 1160g of bromoethane dropwise to the reactor and carry out the alkylation reaction for 8 hours. After the reaction is completed, distill off the bromoethane. Open the feed valve of the diethyl carbonate acceptor 7 and distill the diethyl carbonate under reduced pressure until no liquid flows out of the sight glass of the diethyl carbonate acceptor. The distillation is then complete. After the distillation is completed, cool down to below 90℃ and add 1200kg of water and 700kg of 30% sulfuric acid to reactor 1 to acidify to pH=1-2. After acidification, let it stand to separate the layers. The upper layer yields crude phenethyl ester, which is then distilled to obtain phenethyl ester. The total yield of phenethyl ester is 71.06%, and the purity is 99.61%. The purity of the recovered diethyl carbonate is 97.84%.

[0097] The phenethyl esters prepared in the above examples and comparative examples were subjected to performance testing according to process parameters and quality standards. The statistical results are shown in Table 1.

[0098] Table 1 Statistical results of phenylethyl esters

[0099]

[0100] As can be seen from the table above, in Examples 1-5 of the present invention, the purity of phenethyl ester was 99.62%-99.74%, the yield was 76.64%-78.03%, and the purity of recovered diethyl carbonate was 98.00%-98.28%, all of which met the quality requirements.

[0101] Compared with the above embodiments, Comparative Example 1 did not use a distillation column, and within the specified process parameter range, the yield of phenethyl ester was only 65.01%, which was significantly lower than the yield of the above embodiments. Moreover, the recovered diethyl carbonate obtained in Comparative Example 1 required secondary recovery treatment, which was cumbersome and increased costs such as labor, power, and manufacturing expenses.

[0102] Compared with the above examples, Comparative Example 2 did not perform full reflux before recovering ethanol, but directly adjusted the reflux ratio for discharge, and the yield of phenethyl ester was 72.89%, which was lower than the yield of the examples.

[0103] Compared with the above examples, Comparative Example 3 controlled the reflux ratio at 1:1, which is outside the standard reflux ratio range, and the yield of phenethyl ester obtained was 71.52%, which was lower than the yield of the examples.

[0104] Compared with the above examples, the temperature at the top of the control column in Comparative Example 4 was 60°C, which exceeded the specified range of 55°C. The yield of phenethyl ester obtained was 71.06%, which was lower than the yield of the examples. Furthermore, the purity of the diethyl carbonate obtained was less than 98%. Although it met the quality standards, the quality was slightly lower than that of the examples.

[0105] Of course, the above description is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is also not limited to the above examples, and all equivalent changes and improvements made by those skilled in the art within the scope of the present invention should fall within the patent coverage of the present invention.

Claims

1. A method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate, characterized in that: Includes the following steps: (1) Add the measured amounts of ethyl phenylacetate, sodium ethoxide, and diethyl carbonate to the reactor, control the vacuum degree of the reactor to ≤0.06MPa, open the steam valve of the jacket to raise the temperature inside the reactor, and the mixed gas phase enters the distillation column. Part of it passes through the first-stage condenser and the second-stage condenser and enters the reflux tank. The reflux tank overflows to the distillation column and then flows back to the reactor from the distillation column. The other part is purified by the distillation column and directly refluxed to the reactor. (2) After total reflux for 0.5 to 3 hours, control the top temperature of the distillation column to ≤55℃, open the feed valve of the ethanol receiver, and reflux to recover ethanol; Open the steam valve of the reactor and control the steam pressure to ≤0.3MPa. When the temperature at the top of the distillation column exceeds 55℃, close the feed valve of the ethanol acceptor, open the feed valve of the diethyl carbonate acceptor, close the reflux valve, and recover diethyl carbonate until no liquid flows out of the sight glass of the diethyl carbonate acceptor. The condensation reaction is over. The recovered diethyl carbonate can be directly reused to recover ethanol. (3) Turn on the jacketed circulating water of the reactor to cool it down. When the temperature drops below 84°C, add bromoethane dropwise into the reactor and carry out the alkylation reaction for 6-8 hours. After the reaction is completed, open the feed valve of the bromoethane acceptor and distill the bromoethane at atmospheric pressure. When no bromoethane flows out of the sight glass of the bromoethane acceptor, the distillation is over. Open the feed valve of the diethyl carbonate acceptor and distill the diethyl carbonate under reduced pressure. When no liquid flows out of the sight glass of the diethyl carbonate acceptor, the distillation is over. Cool down to below 90°C, add water and sulfuric acid to the reactor until the pH is 1-2, let it stand and separate into layers. The upper layer is crude phenylethyl ester. The phenylethyl ester is obtained by distillation.

2. The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate according to claim 1, characterized in that: The diethyl carbonate recovered in step (2) has a purity of ≥95%.

3. The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate according to claim 1, characterized in that: In step (2), the ethanol receiver feed valve is opened to reflux and recover ethanol, and the reflux ratio is controlled to be (2:1)~(4:1).

4. The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate according to claim 1, characterized in that: In step (1), the steam valve of the jacket is opened to raise the temperature inside the reactor to 80-120°C.

5. The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate according to claim 1, characterized in that: In step (1), the refrigerant of the first-stage condenser is low-temperature water with a temperature of 0 to 10°C, and the refrigerant of the second-stage condenser is ice-salt water with a temperature of -10 to -5°C.

6. The method for producing phenethyl ester by recovering ethanol and reusing diethyl carbonate according to claim 1, characterized in that: Step (1) Open the steam valve of the jacket and control the steam pressure to ≤0.3MPa.

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