System and method for improving butyl acrylate yield

Abstract

The system comprises four reaction kettles which are sequentially connected in series, every two reaction kettles are jointly connected with a dehydrating tower, and each dehydrating tower is sequentially connected with a water segregator and a wastewater treatment system; the second dehydrating tower is sequentially connected with an extraction tower, a rectifying tower, a second condenser and a distributor through pipelines; according to the method for improving the yield of butyl acrylate, acrylic acid and butanol are subjected to esterification reaction in a reaction kettle under the action of an acidic catalyst; the light component steam is respectively fed into a dehydration tower; a gas-phase discharged material at the upper end of the dehydrating tower enters a water segregator for phase splitting; reflux at the bottom of the dehydrating tower is subjected to multi-stage extraction by an extraction tower, separation by a rectifying tower and heavy component water addition and then returns to the extraction tower, light component materials are distributed by a distributor and respectively flow into the rectifying tower and a third reaction kettle, and raffinate flows out from the bottom of the extraction tower to serve as a butyl acrylate product. The system and the method for improving the yield of butyl acrylate have the characteristics of improving the yield and reducing the production cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of new processes for the production of butyl acrylate, and particularly relates to a system for improving the yield of butyl acrylate, and also relates to a method for improving the yield of butyl acrylate. Background Art

[0002] n-Butyl acrylate belongs to a soft monomer and can copolymerize, crosslink, graft, etc. with various hard monomers such as methyl methacrylate, styrene, acrylonitrile, vinyl acetate, etc., and functional monomers such as (meth)acrylic acid hydroxyethyl ester, hydroxypropyl ester, glycidyl ester, (meth)acrylamide and its derivatives, etc., to make a variety of acrylic resin products, and is also widely used in many aspects such as coatings, adhesives, modification of acrylic fibers, modification of plastics, processing of fibers and fabrics, paper treatment agents, leather processing, and acrylic rubbers. Its copolymers have a wide range of uses in industries such as synthetic fibers, synthetic rubbers, synthetic resins, and as organic synthesis intermediates, adhesives, emulsifiers, coatings, papermaking, and textiles. The existing esterification reaction of n-butyl acrylate requires the use of pure acrylic acid and n-butanol raw materials. During the reaction process, due to the reaction activity of the double bonds of acrylic acid and butyl acrylate, other side reactions such as polymerization will occur. Among them, butyl acrylate and butanol will continue to react to form butyl β-butoxypropionate. Analyzing the composition of the reaction solution, it is found that butyl β-butoxypropionate accounts for more than 90% of the by-products. This part of the by-products needs to be treated subsequently, and at the same time, the increase in by-products leads to an increase in raw material consumption and an increase in production costs. Summary of the Invention

[0003] The purpose of the present invention is to provide a system for improving the yield of butyl acrylate, which has the characteristics of improving the yield and reducing the production cost.

[0004] Another purpose of the present invention is to provide a method for improving the yield of butyl acrylate, which reduces the content of by-products and improves the product yield.

[0005] The technical solution adopted by the present invention is: a system for improving the yield of butyl acrylate, including a first reaction kettle, a second reaction kettle, a third reaction kettle, and a fourth reaction kettle connected in series in sequence. The first reaction kettle and the second reaction kettle are jointly connected to a first dehydration tower, and the third reaction kettle and the fourth reaction kettle are jointly connected to a second dehydration tower. The first dehydration tower and the second dehydration tower are respectively connected to a condenser and a water separator in sequence through pipelines to form a loop. The water separator is connected to a wastewater treatment system; the bottom liquid phase outlet of the second dehydration tower is connected to an extraction tower through a pipeline. The extraction tower is provided with a raffinate extraction outlet at the bottom, and a first inlet and a second inlet are arranged at a position near the bottom on one side of the extraction tower. The top outlet of the extraction tower is connected to a rectification tower through a pipeline. The top outlet of the rectification tower is connected to a second condenser and a distributor in sequence through pipelines, and the distributor is communicated with the third reaction kettle through a shunt pipeline.

[0006] The characteristics of the present invention also lie in:

[0007] The middle part of the second dehydration tower is connected to the third reaction kettle through a pipeline. The bottom of the rectification tower is connected to the second inlet of the extraction tower through a pipeline. The distributor is connected to the top inlet of the rectification tower through a reflux pipeline.

[0008] Another technical solution adopted by the present invention is: a method for increasing the yield of butyl acrylate. Using the system for increasing the yield of butyl acrylate as described above, the steps are as follows:

[0009] Step 1: React acrylic acid and butanol respectively in four reaction kettles under the action of an acidic catalyst to carry out an esterification reaction;

[0010] Step 2: Feed the light component vapors generated by each reaction kettle into two dehydration towers respectively. Add an inhibitor from the top of the dehydration tower, and dehydrate while reacting to promote the forward progress of the reversible reaction;

[0011] Step 3: The gas-phase materials discharged from the upper ends of the two dehydration towers enter the water separator through condensers respectively for phase separation. The oil phase returns to the dehydration tower, and the water phase is transported to the wastewater treatment system; the bottom liquid of the second dehydration tower is taken out as reflux liquid;

[0012] Step 4: Add an extractant from the first inlet of the extraction tower. The reflux liquid enters from the top of the extraction tower. After multi-stage extraction and separation by the extractant, an extract is obtained. The extract is separated by rectification in a rectification tower. The heavy components after rectification are added with water and then returned to the extraction tower as an extractant. The light component materials pass through the second condenser to the distributor and are distributed according to a set ratio. Part of them returns to the rectification tower, and the other part refluxes to the third reaction kettle. The raffinate flows out from the bottom of the extraction tower as the butyl acrylate product.

[0013] Another feature of the technical solution of the present invention is:

[0014] In Step 1, add acrylic acid and an acidic catalyst to the first reaction kettle, and add butanol to the dehydration tower. The first reaction kettle and the second reaction kettle form a primary reactor, and the third reaction kettle and the fourth reaction kettle form a secondary reactor. The reaction temperature of the primary reactor is 94°C - 99°C, and the reaction pressure is 45 Kpa - 55 Kpa; the reaction temperature of the secondary reactor is 94°C - 99°C, and the reaction pressure is 33 Kpa - 43 Kpa.

[0015] In Step 1, the molar ratio of butanol to acrylic acid added is 1 - 1.2:1; the acidic catalyst includes at least one of methanesulfonic acid, p-toluenesulfonic acid, and sulfuric acid, and the added mass of the acidic catalyst is 5% - 8% of the added mass of acrylic acid.

[0016] In Step 2, the inhibitor is an 8% hydroquinone butanol solution, and the added mass of the inhibitor is 0.9% - 2% of the added mass of acrylic acid; the butanol discharged from the middle part of the second dehydration tower refluxes to the third reaction kettle.

[0017] The extractant is a mixture of polyols and water in a mass ratio of 1:0.1 - 1, and the mass flow rate of the added extractant is 1 - 3 times that of the reflux liquid.

[0018] The polyols are glycerol, propanetriol, butanediol or butanetriol.

[0019] In step 4, the multi-stage extraction is 2 - 5 stage extraction.

[0020] The mass flow rate of the fluid at the outlet of the fourth reaction kettle is 25% - 50% of the total mass flow rate of acrylic acid, butanol and the acidic catalyst.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1) The system for increasing the yield of butyl acrylate of the present invention utilizes the separation effect of the dehydration tower for promoting the forward progress of the reversible reaction during the reaction. While separating water, part of the butyl acrylate in the product is also separated, reducing the generation of by-products; the extraction separation method is used to separate most of the butyl acrylate generated by the reaction, reducing the product separation cost;

[0023] 2) The method for increasing the yield of butyl acrylate of the present invention adopts a completely mixed series reaction kettle. By separating the butyl acrylate in the reactants in a timely manner during the reaction, the content of butyl acrylate in the reaction solution is reduced, thereby blocking the further reaction of butyl acrylate and butanol to form butyl β - butoxypropionate, reducing the content of the by-product butyl β - butoxypropionate by 30 - 50%, achieving the purpose of increasing the yield and reducing the production cost. Description of the Drawings

[0024] Figure 1 is the process flow chart of the method for increasing the yield of butyl acrylate of the present invention;

[0025] In the figure, 1. The first reaction kettle, 2. The second reaction kettle, 3. The third reaction kettle, 4. The fourth reaction kettle, 5. The first dehydration tower, 6. The second dehydration tower, 7. The condenser, 8. The water separator, 9. The extraction tower, 10. The rectification tower, 11. The second condenser, 12. The distributor. Detailed Embodiments

[0026] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0027] The system for increasing the yield of butyl acrylate of the present invention has a structure as Figure 1As shown in the figure, a completely mixed series reaction kettle is adopted, including a first reaction kettle 1, a second reaction kettle 2, a third reaction kettle 3, and a fourth reaction kettle 4 connected in series in sequence. The first reaction kettle 1 and the second reaction kettle 2 are jointly connected to a first dehydration tower 5. The third reaction kettle 3 and the fourth reaction kettle 4 are jointly connected to a second dehydration tower 6. The first dehydration tower 5 and the second dehydration tower 6 are respectively connected to a condenser 7 and a water separator 8 in sequence through pipelines to form a loop. The water separator 8 is connected to a wastewater treatment system. The middle part of the second dehydration tower 6 is connected to the third reaction kettle 3 through a pipeline. The liquid phase outlet at the bottom of the second dehydration tower 6 is connected to an extraction tower 9 through a pipeline. An additional dehydration tower is added between the third reaction kettle 3 and the fourth reaction kettle 4 to separate the product in the reaction kettle through the dehydration tower. Part of the butanol returns to the third reaction kettle 3 from the middle of the dehydration tower for continuous reaction, and the reaction liquid at the bottom of the dehydration tower is taken out and enters the extraction tower for further separation. During the reaction dehydration process, the separated components of the tower are taken out to reduce the content of butyl acrylate in the reaction liquid and block the generation of by-products.

[0028] The extraction tower 9 is provided with a raffinate extraction outlet at the bottom. A first inlet and a second inlet are arranged at a position near the bottom on one side of the extraction tower 9. The top outlet of the extraction tower 9 is connected to a rectification tower 10 through a pipeline. The bottom of the rectification tower 10 is connected to the second inlet of the extraction tower 9 through a pipeline. The top outlet of the rectification tower 10 is connected to a second condenser 11 and a distributor 12 in sequence through pipelines. The distributor 12 is connected to the top inlet of the rectification tower 10 through a reflux pipeline. The distributor 12 is connected to the third reaction kettle 3 through a shunt pipeline.

[0029] The method for increasing the yield of butyl acrylate in the present invention uses the above system for increasing the yield of butyl acrylate, and the process flow is as Figure 1 shown, and is specifically implemented according to the following steps:

[0030] Step 1, reaction:

[0031] Acrylic acid and an acidic catalyst are added to the first reaction kettle 1, and butanol is added to the dehydration tower. The molar ratio of butanol to acrylic acid added is 1 - 1.2:1. The acrylic acid and butanol respectively undergo an esterification reaction in the presence of an acidic catalyst through four reaction kettles to generate butyl acrylate through four completely mixed reaction kettles.

[0032] The first reaction kettle 1 and the second reaction kettle 2 form a first-stage reactor. The reaction temperature of the first-stage reactor is 94°C - 99°C, and the reaction pressure is 45 Kpa - 55 Kpa;

[0033] The third reaction kettle 3 and the fourth reaction kettle 4 form a second-stage reactor. The reaction temperature of the second-stage reactor is 94°C - 99°C, and the reaction pressure is 33 Kpa - 43 Kpa.

[0034] The acidic catalyst includes at least one of methanesulfonic acid, p-toluenesulfonic acid, and sulfuric acid. The added mass of the acidic catalyst is 5% - 8% of the added mass of acrylic acid.

[0035] Step 2, dehydration and separation:

[0036] To separate the water in the reaction solution and promote the forward progress of the reversible reaction, a dehydration tower is connected to Reactors 1 and 2, and another dehydration tower is connected to Reactors 3 and 4. The light component vapors generated by each reactor are respectively sent into the two dehydration towers. A polymerization inhibitor is added from the top of the dehydration tower, and water is dehydrated while reacting to promote the forward progress of the reversible reaction. The butanol discharged from the middle of the second dehydration tower 6 is refluxed to the third reactor 3;

[0037] The polymerization inhibitor is an 8% hydroquinone butanol solution, and the added mass of the polymerization inhibitor is 0.9%-2% of the added mass of acrylic acid.

[0038] Step 3, the gas-phase materials discharged from the upper ends of the two dehydration towers respectively enter the water separator 8 through the condenser 7 for phase separation. The oil phase returns to the dehydration tower, and the water phase is transported to the wastewater treatment system. There is a draw at the bottom of the second dehydration tower 6 to draw 50%-75% of the reflux liquid to the extraction tower 9.

[0039] Step 4, extraction separation and rectification separation:

[0040] The reflux liquid drawn from the dehydration tower is connected to the extraction tower 9 and enters from the top of the extraction tower 9. An extractant is added from the first inlet of the extraction tower 9. The extractant is a mixture of polyols and water mixed in a mass ratio of 1:0.1-1, and the mass flow rate of the added extractant is 1-3 times that of the reflux liquid mass flow rate. After 2-5 stages of extraction separation, an extract is obtained. The extract is a mixture other than butyl acrylate, and the extract contains acrylic acid, butanol and other by-products. It is subjected to rectification separation through the rectification tower 10. After rectification, the heavy components are added with water and returned to the extraction tower 9 for use as an extractant. The light component materials pass through the second condenser 11 to the distributor 12 for distribution according to a set ratio. Part of it returns to the rectification tower 10, and the other part is refluxed to the third reactor 3 for continued reaction. The raffinate flows out from the bottom of the extraction tower 9 as the butyl acrylate product, and the butyl acrylate content reaches over 99%.

[0041] The polyols are glycerol, propanetriol, butanediol or butanetriol.

[0042] The mass flow rate of the fluid at the outlet of the fourth reactor 4 is 25%-50% of the total mass flow rate of acrylic acid, butanol and the acidic catalyst.

[0043] The method for increasing the yield of butyl acrylate of the present invention can reduce the content of butyl acrylate in the subsequent reaction solution, block the continuous reaction of butyl acrylate and butanol to form butyl β-butoxypropionate, reduce the generation of by-products, and reduce losses such as energy consumption.

[0044] Example 1

[0045] The system for improving the yield of butyl acrylate of the present invention adopts a fully mixed series reaction kettle, including a first reaction kettle 1, a second reaction kettle 2, a third reaction kettle 3, and a fourth reaction kettle 4 connected in series in sequence. The first reaction kettle 1 and the second reaction kettle 2 are jointly connected to a first dehydration tower 5. The third reaction kettle 3 and the fourth reaction kettle 4 are jointly connected to a second dehydration tower 6. The first dehydration tower 5 and the second dehydration tower 6 are respectively connected to a condenser 7 and a water separator 8 in sequence through pipelines to form a loop. The water separator 8 is connected to a wastewater treatment system. The middle part of the second dehydration tower 6 is connected to the third reaction kettle 3 through a pipeline. The bottom liquid phase outlet of the second dehydration tower 6 is connected to an extraction tower 9 through a pipeline. The bottom of the extraction tower 9 is provided with a raffinate extraction outlet. A first inlet and a second inlet are arranged at a position near the bottom on one side of the extraction tower 9. The top outlet of the extraction tower 9 is connected to a rectification tower 10 through a pipeline. The bottom of the rectification tower 10 is connected to the second inlet of the extraction tower 9 through a pipeline. The top outlet of the rectification tower 10 is connected to a second condenser 11 and a distributor 12 in sequence through pipelines. The distributor 12 is connected to the top inlet of the rectification tower 10 through a reflux pipeline. The distributor 12 is connected to the third reaction kettle 3 through a shunt pipeline.

[0046] The method for improving the yield of butyl acrylate of the present invention uses the above system for improving the yield of butyl acrylate, and the steps are as follows:

[0047] Step 1, reaction:

[0048] Four fully mixed reactors are adopted. Acrylic acid and an acidic catalyst are added to the first reaction kettle 1. Butanol is added to the dehydration tower. The acrylic acid and butanol respectively pass through the four reaction kettles to carry out an esterification reaction under the action of the acidic catalyst, and butyl acrylate is generated through the four fully mixed reaction kettles.

[0049] The molar ratio of butanol to acrylic acid added is 1.1:1. The acidic catalyst is a 20% butyl p-toluenesulfonate solution, and its addition amount is 6.5% of the addition amount of acrylic acid.

[0050] The first reaction kettle 1 and the second reaction kettle 2 share the first dehydration tower 5. The first reaction kettle 1 and the second reaction kettle 2 form a primary reactor. The reaction temperature is 97°C, and the reaction pressure is 50 Kpa. The third reaction kettle 3 and the fourth reaction kettle 4 share the second dehydration tower 6. The third reaction kettle 3 and the fourth reaction kettle 4 form a secondary reactor. The reaction temperature is 97°C, and the reaction pressure is 38 Kpa.

[0051] Step 2, dehydration tower separation:

[0052] The light component steam generated by each reaction kettle is respectively sent into the two dehydration towers. An inhibitor is added from the top of the dehydration tower, and water is dehydrated while reacting to promote the forward progress of the reversible reaction. Butanol is discharged and refluxed to the third reaction kettle 3 from the 5th to 8th trays in the middle of the second dehydration tower 6.

[0053] The inhibitor is a 8% hydroquinone butanol solution, and the addition amount is 1.5% of the addition amount of acrylic acid to prevent polymerization.

[0054] Step 3: The gas-phase materials discharged from the upper ends of the two dehydration towers respectively enter the water separator 8 through the condensers 7 for phase separation. The oil phase returns to the dehydration tower, and the water phase is transported to the wastewater treatment system; 62% of the reflux liquid is drawn from the bottom of the second dehydration tower 6 at the 2nd - 4th trays and sent to the extraction tower 9.

[0055] Step 4: Extraction separation and rectification separation:

[0056] The reflux liquid drawn from the dehydration tower is connected to the extraction tower 9 and enters from the top of the extraction tower 9. The extractant is added from the first inlet of the extraction tower 9. After 3 - stage extraction separation, the extract is obtained and subjected to rectification separation through the rectification tower 10. The heavy components after rectification are mixed with water and then returned to the extraction tower 9 for use as the extractant. The light - component materials pass through the second condenser 11 to the distributor 12 and are distributed according to a set ratio. Part of them returns to the rectification tower 10, and the other part refluxes to the third reaction kettle 3 for continuous reaction. The raffinate flows out from the bottom of the extraction tower 9 and is directly used as the butyl acrylate product, with the butyl acrylate content reaching 99.7%.

[0057] The extractant is a mixture of glycerol and water in a mass ratio of 1:0.5, and the mass flow rate of the added extractant is 2 times the mass flow rate of the reflux liquid.

[0058] The mass flow rate at the outlet of the fourth reaction kettle is 37% of the total mass flow rate of acrylic acid, butanol, and the acidic catalyst. The product at the outlet of the fourth reaction kettle 4 is analyzed by gas chromatography. The analysis results are as follows: the butyl acrylate content is 53.16%, the acrylic acid content is 0.2%, the butanol content is 40.29%, the β - butoxy propionic acid butyl ester content is 4.9%, and the others are 1.45.

[0059] Example 2

[0060] The system is the same as that in Example 1, and the difference in the method lies in:

[0061] In Step 1, the molar ratio of butanol to acrylic acid added is 1:1, and the acidic catalyst is a 20% p - toluenesulfonic acid butanol solution, and its addition amount is 8% of the addition amount of acrylic acid.

[0062] The reaction temperature in the first - stage reactor is 99°C, and the reaction pressure is 45 Kpa; in the second - stage reactor, the reaction temperature is 99°C, and the reaction pressure is 33 Kpa.

[0063] In Step 2, the inhibitor is an 8% hydroquinone butanol solution, and the addition amount is 2% of the addition amount of acrylic acid.

[0064] In Step 3, 75% of the reflux liquid is drawn from the bottom of the second dehydration tower 6 at the 2nd - 4th trays and sent to the extraction tower 9.

[0065] In Step 4, the extractant is changed to glycerol. The extractant is a mixture of glycerol and water in a mass ratio of 1:1. The mass flow rate of the added extractant is 1 times that of the reflux liquid. The multi-stage extraction is 2 stages. The raffinate is directly used as the butyl acrylate product, and the butyl acrylate content reaches 99.5%.

[0066] The product at the outlet of the fourth reactor 4 is analyzed by gas chromatography. The analysis results are as follows: the butyl acrylate content is 52.85%, the acrylic acid content is 0.23%, the butanol content is 40.31%, the butyl β-butoxypropionate content is 4.94%, and the others are 1.67%.

[0067] Example 3

[0068] The system is the same as that in Example 1. The difference in the method lies in:

[0069] In Step 1, the molar ratio of butanol to acrylic acid added is 1.2:1. The acidic catalyst is a 20% butanol solution of methanesulfonic acid, and its addition amount is 5% of the acrylic acid addition amount.

[0070] The reaction temperature in the first-stage reactor is 94°C, and the reaction pressure is 55 Kpa; for the second-stage reactor, the reaction temperature is 94°C, and the reaction pressure is 43 Kpa.

[0071] In Step 2, the inhibitor is an 8% butanol solution of hydroquinone, and its addition amount is 0.9% of the acrylic acid addition amount.

[0072] In Step 3, 50% of the reflux liquid is drawn from the 2nd - 4th trays at the bottom of the second dehydration tower 6 to the extraction tower 9.

[0073] In Step 4, the extractant is changed to butanetriol. The extractant is a mixture of butanetriol and water in a mass ratio of 1:0.5. The mass flow rate of the added extractant is 1.5 times that of the reflux liquid. The multi-stage extraction is 5 stages. The raffinate is directly used as the butyl acrylate product.

[0074] The mass flow rate of the fluid at the outlet of the fourth reactor 4 is 25% of the total mass flow rate of acrylic acid, butanol, and the acidic catalyst. The product at the outlet of the fourth reactor 4 is analyzed by gas chromatography. The analysis results are as follows: the butyl acrylate content is 53.26%, the acrylic acid content is 0.3%, the butanol content is 40.29%, the butyl β-butoxypropionate content is 4.64%, and the others are 1.51%.

[0075] Example 4

[0076] The system is the same as that in Example 1. The difference in the method lies in:

[0077] In Step 1, the molar ratio of butanol to acrylic acid added is 1.2:1. The acidic catalyst is a mixture of 20% methanesulfonic acid and p-toluenesulfonic acid (the molar ratio of methanesulfonic acid / p-toluenesulfonic acid = 6 / 4), and its addition amount is 5% of the acrylic acid addition amount.

[0078] The reaction temperature of the first-stage reactor is 94 °C, and the reaction pressure is 55 Kpa; for the second-stage reactor, the reaction temperature is 94 °C and the reaction pressure is 43 Kpa.

[0079] In step 2, the inhibitor is a 8% hydroquinone butanol solution, and the addition amount is 2% of the acrylic acid addition amount.

[0080] In step 3, 50% of the reflux liquid is drawn from the 2nd - 4th trays at the bottom of the second dehydration tower 6 to the extraction tower 9;

[0081] In step 4, the extractant is changed to glycerol. The extractant is a mixture of glycerol and water in a mass ratio of 1:0.1. The mass flow rate of the added extractant is 3 times that of the reflux liquid mass flow rate. The multi-stage extraction is 4 stages, and the raffinate is directly used as the butyl acrylate product;

[0082] The mass flow rate of the fluid at the outlet of the fourth reaction kettle 4 is 50% of the total mass flow rate of acrylic acid, butanol and the acidic catalyst. The product at the outlet of the fourth reaction kettle 4 is analyzed by gas chromatography. The analysis results are as follows: the butyl acrylate content is 53.86%, the acrylic acid content is 0.3%, the butanol content is 40.29%, the β-butoxy propionic acid butyl ester is 4.1%, and the others are 1.55%.

[0083] Comparative Example 1

[0084] Four continuous stirred-tank reactors. The four reaction kettles share a packed dehydration tower. The molar ratio of butanol to acrylic acid added is 1.1:1. The addition amount of the 20% p-toluenesulfonic acid butanol solution is 6.5% of the acrylic acid addition amount. The inhibitor is an 8% hydroquinone butanol solution added from the top of the dehydration tower. The addition amount is 0.9% - 2% of the acrylic acid addition amount. The reaction temperature of reaction kettles 1 and 2 is 97 °C, and the reaction pressure is 50 Kpa. For reaction kettles 3 and 4, the reaction temperature is 97 °C and the reaction pressure is 38 Kpa. No extractive distillation separation is carried out, and the outlet flow rate of the fourth reaction kettle 4 is all the reaction products.

[0085] The product at the outlet of the fourth reaction kettle 4 is analyzed by gas chromatography. The butyl acrylate content is 83.06%, the butanol content is 12.23%, the acrylic acid content is 0.24%, the β-butoxy propionic acid butyl ester is 3.0%, and the others are 1.47.

[0086] It can be seen from the comparison between Example 1 and Comparative Example 1 that for the method of increasing the butyl acrylate yield in this application, due to the use of extractive distillation separation, under different catalyst conditions and different extractant conditions, although the content of β-butoxy propionic acid butyl ester at the reactor outlet is higher, the total amount is only 25 - 50% of that in the comparative example, and the by-products generated are significantly reduced.

[0087] The method for increasing the yield of butyl acrylate in the present application timely removes the butyl acrylate generated in the reaction, prevents the further reaction to form butyl β-butoxypropionate due to the high content of butyl acrylate, and improves the reaction selectivity. The system for increasing the yield of butyl acrylate in the present application mainly removes the intermediate products, thereby reducing the generation of by-products, increasing the reaction yield, and reducing the production cost.

Claims

1. System for improving the yield of butyl acrylate, characterized in that, it comprises a first reactor (1), a second reactor (2), a third reactor (3), and a fourth reactor (4) connected in series in sequence. The first reactor (1) and the second reactor (2) are jointly connected to a first dehydration tower (5), and the third reactor (3) and the fourth reactor (4) are jointly connected to a second dehydration tower (6). The first dehydration tower (5) and the second dehydration tower (6) are respectively connected to a condenser (7) and a water separator (8) through pipelines to form a loop. The water separator (8) is connected to a wastewater treatment system. The bottom liquid phase outlet of the second dehydration tower (6) is connected to an extraction tower (9) through a pipeline. The bottom of the extraction tower (9) is provided with a raffinate extraction outlet. A first inlet and a second inlet are arranged at a position near the bottom on one side of the extraction tower (9). The top outlet of the extraction tower (9) is connected to a rectification tower (10) through a pipeline. The top outlet of the rectification tower (10) is sequentially connected to a second condenser (11) and a distributor (12) through pipelines. The distributor (12) is communicated with the third reactor (3) through a shunt pipeline.

2. The system for improving the yield of butyl acrylate according to claim 1, characterized in that, the middle part of the second dehydration tower (6) is communicated with the third reactor (3) through a pipeline. The bottom of the rectification tower (10) is connected to the second inlet of the extraction tower (9) through a pipeline. The distributor (12) is connected to the top inlet of the rectification tower (10) through a reflux pipeline.

3. Method for improving the yield of butyl acrylate, characterized in that, using the system for improving the yield of butyl acrylate according to claim 1 or 2, the steps are as follows: Step 1: Make acrylic acid and butanol respectively pass through four reactors to carry out an esterification reaction under the action of an acidic catalyst; Step 2: Send the light component vapors generated by each reactor into two dehydration towers respectively, add an inhibitor from the top of the dehydration tower, and dehydrate while reacting to promote the forward progress of the reversible reaction; Step 3: The gas-phase materials discharged from the upper ends of the two dehydration towers respectively enter the water separator (8) through the condenser (7) for phase separation. The oil phase returns to the dehydration tower, and the water phase is transported to the wastewater treatment system. The bottom liquid phase of the second dehydration tower (6) is taken out as a reflux liquid; Step 4: Add an extractant from the first inlet of the extraction tower (9). The reflux liquid enters from the top of the extraction tower (9). After multi-stage extraction and separation by the extractant, an extract is obtained. The extract is subjected to rectification separation through the rectification tower (10). The heavy components after rectification are added with water and then returned to the extraction tower (9) for use as an extractant. The light component materials pass through the second condenser (11) to the distributor (12) for distribution according to a set ratio. Part of them returns to the rectification tower (10), and the other part refluxes to the third reactor (3). The raffinate flows out from the bottom of the extraction tower (9) as a butyl acrylate product.

4. The method for improving the yield of butyl acrylate according to claim 3, characterized in that, In Step 1, acrylic acid and an acidic catalyst are added to the first reactor (1), and butanol is added to the dehydration tower. The first reactor (1) and the second reactor (2) form a primary reactor, and the third reactor (3) and the fourth reactor (4) form a secondary reactor. The reaction temperature of the primary reactor is 94°C - 99°C, and the reaction pressure is 45 Kpa - 55 Kpa; the reaction temperature of the secondary reactor is 94°C - 99°C, and the reaction pressure is 33 Kpa - 43 Kpa.

5. The method for increasing the yield of butyl acrylate according to claim 3, wherein, in Step 1, the molar ratio of the butanol to the acrylic acid added is 1 - 1.2:1; the acidic catalyst includes at least one of methanesulfonic acid, p-toluenesulfonic acid, and sulfuric acid, and the added mass of the acidic catalyst is 5% - 8% of the added mass of the acrylic acid.

6. The method for increasing the yield of butyl acrylate according to claim 3, wherein, in Step 2, the inhibitor is an 8% hydroquinone butanol solution, and the added mass of the inhibitor is 0.9% - 2% of the added mass of the acrylic acid; the butanol discharged from the middle of the second dehydration tower (6) is refluxed to the third reactor (3).

7. The method for increasing the yield of butyl acrylate according to claim 3, wherein, in Step 4, the extractant is a mixture of polyols and water in a mass ratio of 1:0.1 - 1, and the mass flow rate of the added extractant is 1 - 3 times the mass flow rate of the reflux liquid.

8. The method for increasing the yield of butyl acrylate according to claim 7, wherein, the polyols are glycerol, glycerin, butanediol, or butanetriol.

9. The method for increasing the yield of butyl acrylate according to claim 3, wherein, in Step 4, the multi-stage extraction is 2 - 5 stage extraction.

10. The method for increasing the yield of butyl acrylate according to claim 3, wherein, the mass flow rate of the fluid at the outlet of the fourth reactor (4) is 25% - 50% of the total mass flow rate of the acrylic acid, butanol, and acidic catalyst.

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