Copolymer alcoholysis system and method thereof

Abstract

The application discloses a copolymer alcoholysis system and a method thereof, and the system comprises a reactive rectifying tower, a heating device, a condenser and a blowing pipeline, an oil collection groove, a separation element and an overflow groove are sequentially arranged in a top section, a middle section and a bottom section of the reactive rectifying tower, a feeding pipe is connected to the top section of the reactive rectifying tower, an air inlet pipe is connected to the bottom section of the reactive rectifying tower, the feeding pipe and the air inlet pipe are respectively connected with the blowing pipeline capable of blowing inert gas, the heating device is located outside the reactive rectifying tower and connected with the top section and the bottom section of the reactive rectifying tower to realize external circulation heating, the condenser is connected to an air outlet of the top section of the reactive rectifying tower, and the condenser is also connected to a reflux outlet of the top section of the reactive rectifying tower. The application has the advantages of simple design, low investment cost and suitability for continuous large-scale production.

Description

Technical Field

[0001] This application relates to the field of chemical technology, and in particular to a copolymer alcoholysis system and method thereof. Background Technology

[0002] Alcohol copolymers, such as ethylene-vinyl acetate alcohol copolymer (EVOH), are generally obtained through the alcoholysis reaction of ethylene-vinyl acetate copolymer (EVAC). However, the alcoholysis reaction of ethylene-vinyl acetate copolymer (EVAC) is a reversible equilibrium reaction, making it difficult to obtain the required high alcoholysis rate (above 99.5%) in traditional reaction vessels. Since the alcoholysis process produces methyl acetate as a byproduct with a relatively low boiling point, methyl acetate can be removed in situ using reactive distillation, breaking the equilibrium limitation of the alcoholysis reaction and obtaining a high-alcohol-rate EVOH product. Traditional reactive distillation columns are difficult to operate stably for long periods in alcoholysis reactions, making it difficult to consistently obtain a high degree of alcoholysis product. Summary of the Invention

[0003] Therefore, it is necessary to provide a copolymer alcoholysis system. The copolymer alcoholysis system of the present invention has a simple structure, low investment cost, and is suitable for continuous large-scale production. It can solve the problems of traditional schemes that are difficult to operate for a long time or have low alcoholysis rate. It has strong alcoholysis rate stability, flexible and convenient start-up and shutdown operation, can be operated intermittently or continuously, and the reaction temperature and residence time can be reliably controlled. The system has good anti-clogging properties, strong system stability, can be operated for a long time, and the method is simple and easy to implement.

[0004] One embodiment of this application provides a copolymer alcoholysis system.

[0005] A copolymer alcoholysis system includes a reactive distillation column, a heating device, a condenser, and a gas blowing pipe. The reactive distillation column has an oil collection tank, a separation element, and an overflow tank respectively installed in its top, middle, and bottom sections. A feed pipe is connected to the top section of the reactive distillation column, and an inlet pipe is connected to the bottom section. Gas blowing pipes capable of continuously blowing inert gas are connected to both the feed pipe and the inlet pipe. The heating device is located outside the reactive distillation column and connected to both the top and bottom sections to achieve external circulation heating. The condenser is connected to the outlet of the top section of the reactive distillation column for condensing the gas phase. The condenser is also connected to the reflux port of the top section of the reactive distillation column to allow some of the condensate to flow back into the reactive distillation column.

[0006] In some embodiments, the blowing pipe is a long blowing nitrogen pipe connected to a nitrogen source.

[0007] In some embodiments, the reactive distillation column is further provided with a demister located at the top of the column, above the oil collection tank.

[0008] In some embodiments, the copolymer alcoholysis system further includes a first delivery pump connected to a heating circulation pipeline between the heating device and the reactive distillation column. The first delivery pump is used to discharge the reaction products from the bottom section of the reactive distillation column or to reflux products that have not reached the degree of alcoholysis into the oil collection tank after heating by the heating device.

[0009] In some embodiments, the copolymer alcoholysis system further includes a second transfer pump connected to a reflux pipe between the outlet of the condenser and the reflux port of the condenser. The second transfer pump is used to discharge the condensate from the condenser to the outside or reflux it back to the condenser and the reactive distillation column.

[0010] In some embodiments, the condenser is provided with a first nozzle that communicates with the condenser's return port.

[0011] In some embodiments, the top section of the reactive distillation column is provided with a second nozzle that communicates with the reflux port of the top section.

[0012] In some embodiments, the number of oil collection tanks is one or more, and the residence time of the oil collection tanks is set to 0.1hr to 3hr.

[0013] In some embodiments, a downcomer is provided in the oil collection tank, and the downcomer is also connected to the separation element, through which liquid in the oil collection tank overflows to the separation element.

[0014] In some embodiments, the temperature within the oil collection tank can be regulated by the heating device.

[0015] In some embodiments, the oil collection trough has an annular groove structure.

[0016] In some embodiments, the feed pipe and the downcomer in the oil collection tank are positioned relative to each other.

[0017] In some embodiments, the separation element includes packing and / or trays.

[0018] In some embodiments, the top section of the reactive distillation column is connected to a gas phase pipe communicating with the condenser, the gas phase pipe is inclined upward, and the angle between the gas phase pipe and the horizontal plane is greater than 30°.

[0019] In some embodiments, the bottom section of the reactive distillation column is provided with a first baffle and a second baffle. The first baffle is connected to the inner wall of the reactive distillation column and extends toward the bottom surface of the bottom section, and is spaced apart from the bottom surface of the bottom section. The second baffle is connected to the bottom surface of the bottom section and extends toward the middle section of the column. There is a gap between the first baffle and the second baffle, and the gap forms an overflow channel. The first baffle and the second baffle divide the bottom section of the reactive distillation column into an independent constant liquid level space and an external discharge space. The constant liquid level space is connected to the separation unit, and the external discharge space is connected to the outlet of the bottom section.

[0020] An embodiment of this application also provides a method for copolymer alcoholysis.

[0021] A copolymer alcoholysis method, employing the above-mentioned copolymer alcoholysis system, includes the following steps:

[0022] The copolymer to be hydrolyzed is controlled to enter the top section of the reactive distillation column through the feed pipe, and the hydrolysis gas is controlled to enter the bottom section of the reactive distillation column through the inlet pipe. The heating device is controlled to heat the reactive distillation column, driving the reaction raw materials in the reactive distillation column to circulate. The hydrolysis gas and the copolymer to be hydrolyzed undergo an ester exchange reaction. The reaction products are separated by a separation element. The gas phase containing the hydrolysis gas and ester products enters the condenser for condensation, while the alcohol copolymer is discharged from the outlet of the bottom section of the reactive distillation column. The product that has not reached the degree of hydrolysis is controlled to be heated by the heating device and then returned to the oil collection tank.

[0023] The above-mentioned copolymer alcoholysis system is flexible and convenient to shut down, and can be operated intermittently or continuously. The reaction temperature and residence time are reliably controlled, the system has good anti-clogging properties, and the system design is simple with low investment costs, making it suitable for continuous large-scale production. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0026] Figure 1 This is a schematic diagram of a copolymer alcoholysis system according to an embodiment of the present invention;

[0027] Figure 2This is a schematic diagram of the oil collection tank according to an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures

[0029] 10. Copolymer alcoholysis system; 100. Reactive distillation column; 101. Top section of the column; 102. Middle section of the column; 103. Bottom section of the column; 200. Heating device; 300. Condenser; 410. Feed pipe; 420. Gas inlet pipe; 430. Gas blowing pipe; 440. Reflux pipe; 500. Oil collection tank; 600. Separation element; 700. Overflow tank; 800. Demister; 910. First transfer pump; 920. Second transfer pump; 1010. First nozzle; 1020. Second nozzle; 1100. Downcomer; 1200. Vapor phase pipe; 1310. First baffle; 1320. Second baffle; 1410. Constant liquid level space; 1420. External discharge space. Detailed Implementation

[0030] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0034] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0035] In this document, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain."

[0036] In this application, when numerical intervals (i.e., numerical ranges) are mentioned, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] This application provides a copolymer alcoholysis system to address the problem that existing reactive distillation columns are difficult to operate stably for long periods and to consistently obtain high-degree-of-alcoholization products when applied to alcoholysis reactions. The copolymer alcoholysis system will be described below with reference to the accompanying drawings. The following description uses the alcoholysis of ethylene-vinyl acetate copolymer as an example, where methanol is used as the alcoholysis gas.

[0039] The copolymer alcoholysis system provided in this application is exemplary; please refer to [link to example]. Figure 1 As shown, Figure 1 This is a schematic diagram of the copolymer alcoholysis system provided in an embodiment of this application. The copolymer alcoholysis system of this application can be used to stably obtain ethylene-vinyl acetate copolymer products with high degrees of alcoholysis.

[0040] To more clearly illustrate the structure of the copolymer alcoholysis system, the following description, in conjunction with the accompanying drawings, will be presented.

[0041] For example, please refer to Figure 1 As shown, a copolymer alcoholysis system 10 includes a reactive distillation column 100, a heating device 200, a condenser 300, and a gas blowing pipe 430. The top section 101, middle section 102, and bottom section 103 of the reactive distillation column 100 are respectively equipped with an oil collection tank 500, a separation element 600, and an overflow tank 700. The top section 101 of the reactive distillation column 100 is connected to a feed pipe 410, which is used to input a solution of the copolymer to be alcoholyzed, such as ethylene-vinyl acetate copolymer (EVAC). The bottom section 103 of the reactive distillation column 100 is connected to a gas inlet pipe 420, which is used to input alcoholysis gas, such as methanol gas. Gas blowing pipes 430, capable of continuously blowing inert gas (such as nitrogen), are connected to both the feed pipe 410 and the gas inlet pipe 420. The heating device 200 is located outside the reactive distillation column 100 and connects the top section 101 and the bottom section 103 of the reactive distillation column 100 to achieve external circulation heating. The condenser 300 is connected to the outlet of the top section 101 of the reactive distillation column 100 for condensing the gas phase. The condenser 300 is also connected to the reflux port of the top section 101 of the reactive distillation column 100 to allow a portion of the condensate to be refluxed back into the reactive distillation column 100.

[0042] In some embodiments, the blowing pipe 430 is a long-blowing nitrogen pipe connected to a nitrogen source. To achieve good distribution, the copolymer to be hydrolyzed, such as the ethylene-vinyl acetate copolymer (EVAC) solution, and the hydrolysis gas, such as methanol gas, are preferably fed into the oil collection tank 500 or below the bottom liquid level. In practice, blockage of the feed pipe 410 or material backflow can easily occur. Therefore, this application adds a long-blowing nitrogen pipe 430 to both the feed pipe 410 and the gas inlet pipe 420, which can effectively prevent pipe blockage. The nitrogen pressure in the blowing pipe 430 is controlled to be slightly higher than the pressure of the reactive distillation column 100 but lower than the pressure of the feed pipe 410 and the gas inlet pipe 420, ensuring that the nitrogen flow does not stop throughout the entire operating cycle. Through multiple experiments, the applicant has found that in addition to achieving anti-blockage of the feed pipe 410, the addition of long-blowing nitrogen in the blowing pipe 430 is beneficial for controlling the overall column pressure. Compared to check valves and other similar devices, the long-blowing nitrogen pipeline of this application is more durable. Unlike check valves, which are easily jammed by polymer adhesion and lose their backflow prevention function, the long-blowing nitrogen pipeline is suitable for long-term equipment operation.

[0043] In some of these embodiments, please refer to Figure 1 As shown, a demister 800 is also installed in the top section 101 of the reactive distillation column 100. The demister 800 is located above the oil collection tank 500. The working principle of the demister 800 is usually based on physical methods, such as gravity sedimentation, centrifugal separation, filtration, etc., and sometimes it is combined with chemical methods, such as adding defoaming agents. Different types of demisters 800 are suitable for different application scenarios. Common types include: (1) Baffle demister: By setting baffles, the liquid containing bubbles flows through. By utilizing the difference in density between bubbles and liquid, the bubbles adhere to the baffles and gradually rise to the liquid surface, thereby removing the bubbles. (2) Cyclone demister: The centrifugal force generated by high-speed rotation is used to separate the bubbles from the liquid. (3) Wire mesh demister: The bubbles are captured by a fine metal wire mesh. When the bubbles pass through the wire mesh, they will gather and eventually form larger bubbles, making it easier to separate them from the liquid. (4) Packed tower demister: A specific material, such as ceramic rings or plastic balls, is filled inside the tower. When liquid containing bubbles flows through the packing, the bubbles will gather and merge on the surface of the packing, and eventually rise to the top and be discharged. The demister 800 in this application may be selected from one or more of the following: baffle demister, cyclone demister, wire mesh demister and packed tower demister.

[0044] In some of these embodiments, please refer to Figure 1As shown, the copolymer alcoholysis system 10 also includes a first transfer pump 910. The first transfer pump 910 is connected to the heating circulation pipeline between the heating device 200 and the reactive distillation column 100. The first transfer pump 910 is used to discharge the reaction products from the bottom section 103 of the reactive distillation column 100 or to reflux products that have not reached the degree of alcoholysis into the oil collection tank 500 after heating by the heating device 200.

[0045] In some embodiments, the heating device 200 is preferably a vertical single-pass shell-and-tube heat exchanger or a spiral plate heat exchanger. In this application, during continuous operation, the overall temperature control of the reactive distillation column 100 mainly depends on the feed and inlet gas temperatures and the external circulation temperature, while during batch operation, the overall temperature control mainly depends on the external circulation temperature; the external circulation heating device 200 is mainly used to meet heating requirements. Therefore, using a vertical single-pass shell-and-tube heat exchanger or a spiral plate heat exchanger as the heating device 200 can reduce flow dead zones and improve anti-clogging capabilities.

[0046] In some of these embodiments, please refer to Figure 1 As shown, the copolymer alcoholysis system 10 also includes a second transfer pump 920. The second transfer pump 920 is connected to the reflux pipe 440 between the liquid outlet of the condenser 300 and the reflux port of the condenser 300. The second transfer pump 920 is used to discharge the condensate from the condenser 300 to the outside or reflux it back to the condenser 300 and the reactive distillation column 100.

[0047] In some of these embodiments, please refer to Figure 1 As shown, a first nozzle 1010 communicating with the return port of the condenser 300 is provided inside the condenser 300. The first nozzle 1010 helps to spray some of the condensate back towards the demister 800, reducing the clogging of the demister 800 structure.

[0048] In some of these embodiments, please refer to Figure 1 As shown, the top section 101 of the reactive distillation column 100 is equipped with a second nozzle 1020 that communicates with the reflux port of the top section 101. The first nozzle 1010 helps to spray some of the condensate back towards the oil collection tank 500, reducing the blockage of the oil collection tank 500 structure.

[0049] In some embodiments, the number of oil collection tanks 500 is one or more, and the residence time of the oil collection tanks 500 is set to 0.1hr to 3hr. For example, when the copolymer to be alcoholyzed is EVAC and the alcoholysis gas is methanol, the EVAC solution contains ethylene-vinyl acetate copolymer and a catalyst (e.g., sodium hydroxide). At a certain temperature, EVAC undergoes alcoholysis to generate ethylene-vinyl acetate alcohol copolymer (EVOH) and ester products. The reactive distillation column 100 is equipped with oil collection tanks 500, and the number of oil collection tanks 500 can be one or more. The residence time of the oil collection tanks 500 is 0.1hr to 3hr. The EVAC solution should enter from the bottom of the oil collection tank 500 and be uniformly mixed with the hot material from the external circulation heating device 200. The hot material from the external circulation heating device 200 is required to enter the tower tangentially along the inner wall of the equipment, ensuring as few dead zones as possible in the oil collection tank 500 and guaranteeing smooth gas flow. The liquid in the oil collection tank 500 overflows into the separation element 600 through the downcomer 1100. Since the volume of the oil collection tank 500 is fixed, the residence time of the EVAC solution in the oil collection tank 500 is also fixed. Furthermore, the temperature in the oil collection tank 500 can be determined by the EVAC solution feed temperature or the external circulation temperature. Therefore, the oil collection tank 500 provides a fixed residence time and reaction temperature for the EVAC solution.

[0050] In some embodiments, a downcomer 1100 is provided inside the oil collecting tank 500. The top opening of the downcomer 1100 is at a certain height from the bottom surface of the oil collecting tank 500, so that the oil collecting tank 500 has a certain residence time. The downcomer 1100 is also connected to the separation element 600, and the liquid in the oil collecting tank 500 overflows to the separation element 600 through the downcomer 1100.

[0051] Preferably, please refer to Figure 1 As shown, in some embodiments, the downcomer 1100 is in a bent state.

[0052] Further preferably, please refer to Figure 1 As shown, one end of the downcomer 1100 is located inside the oil collection tank 500 and is higher than the bottom surface of the oil collection tank 500 and lower than the top surface of the oil collection tank 500. The other end of the downcomer 1100 extends to the separation element 600.

[0053] In some embodiments, the temperature within the oil collection tank 500 can be regulated by the heating device 200.

[0054] In some embodiments, the separation element 600 includes packing and / or a tray. For example, when the copolymer to be hydrolyzed is EVAC and the hydrolysis gas is methanol, the reaction of EVAC with methanol to produce EVOH and methyl acetate is an equilibrium reaction with an equilibrium constant between 0.1 and 10. To achieve a certain hydrolysis rate requirement, such as 99.5%, methyl acetate must be removed in time to break the reaction equilibrium. At the same time, methyl acetate is the substance with the lowest boiling point in the system and forms the lowest azeotrope with methanol. Therefore, methyl acetate in the reaction liquid phase can be removed by distillation to obtain a satisfactory hydrolysis rate. The distillation process mainly occurs on the separation element 600, which can be packing or a tray. If packing is selected, packing with good anti-clogging and wettability is preferred. If a tray is selected, since the viscosity of the system is relatively high, the influence of viscosity on the flow and distribution of the tray needs to be considered to avoid leakage, flooding, and flow deviation.

[0055] In some of these embodiments, see Figure 2 As shown, the oil collection tank 500 has an annular groove structure.

[0056] In some embodiments, the oil collection tank 500 provides a defined residence time for the alcoholysis reaction, specifically requiring that the inlet of the feed pipe 410 and the outlet of the downcomer 1100 within the oil collection tank 500 be in relative positions, see [reference]. Figure 2 As shown, the connection point between the feed pipe 410 and the oil collection tank 500 is at a 180° angle relative to the inlet of the downcomer 1100 on the circumference. This is to avoid short circuits; otherwise, the alcoholysis effect will not meet expectations. Since the feed material has been mixed evenly and is homogeneous in phase, there is no need for mixing equipment such as a stirrer in the oil collection tank 500. Set up one or more oil collection tanks 500 with a residence time of 0.1hr to 3hr. The total number of trays in the tower should not be less than 30. Alternatively, packing with the same efficiency can be used. The first oil collection tank 500 is set at the top of the tower, and an oil collection tank 500 is set at intervals of a certain number of trays. No oil collection tank 500 is needed under the bottom tray. In this application, the relative positions of the feed pipe 410 and the downcomer 1100 in the oil collection tank 500 ensure that the feed pipe 410 can pass through the semi-circular path of the oil collection tank 500, thus extending the flow path of the feed in the oil collection tank 500 and avoiding dead corners in the oil collection tank 500.

[0057] In some embodiments, the top section 101 of the reactive distillation column 100 is connected to a gas phase pipe 1200 communicating with the condenser 300. The gas phase pipe 1200 is inclined upward and the angle between the gas phase pipe 1200 and the horizontal plane is greater than 30°. Because the gas phase in the top section 101 of the reactive distillation column 100 is prone to polymer entrainment, causing blockages in the top gas phase pipeline 1200 or condenser 300, this application makes corresponding designs at locations prone to polymer entrainment and deposition blockage in order to achieve a stable anti-blockage effect. For example, a demister 800 is installed in the top section 101 and a second nozzle 1020 is used for intermittent or continuous spray cleaning. The top gas phase pipeline 1200 adopts a large-angle piping, with an angle greater than 30° with the horizontal plane to avoid material retention in the horizontal gas phase pipeline 1200. A small amount of liquid droplets entrained in the gas phase pipeline 1200 can flow downwards under the action of gravity to avoid deposition blockage. The second nozzle 1020 is installed on the end cap of the condenser 300 to avoid polymer deposition blockage. The above-mentioned setup structure is simple and feasible to operate, with low operational requirements.

[0058] In some of these embodiments, please refer to Figure 1 As shown, the bottom section 103 of the reactive distillation column 100 is provided with a first baffle 1310 and a second baffle 1320. The first baffle 1310 is connected to the inner wall of the reactive distillation column 100 and extends toward the bottom surface of the bottom section 103, with a gap between them. The second baffle 1320 is connected to the bottom surface of the bottom section 103 and extends toward the middle section 102. There is a gap between the first baffle 1310 and the second baffle 1320, and this gap forms an overflow channel 700. The first baffle 1310 and the second baffle 1320 divide the bottom section 103 of the reactive distillation column 100 into an independent constant liquid level space 1410 and an external discharge space 1420. The constant liquid level space 1410 communicates with the separation unit, and the external discharge space 1420 communicates with the outlet of the bottom section 103. In this application, in order to pursue the stability of high alcoholysis degree and avoid product defects caused by operational fluctuations, such as a sudden increase in feed and direct extraction of material that has not reached the required alcoholysis degree from the reactive distillation column 100, resulting in an alcoholysis degree below 99.5%, a constant liquid level space 1410 is set up as a buffer area. By modifying the structure of the bottom section 103 of the column, a constant liquid level space 1410 is formed through the cooperation of the first baffle 1310 and the second baffle 1320. This space provides a buffer function for the liquid at the bottom of the column. For example, when there are operational fluctuations, a small amount of material with a low alcoholysis degree enters the bottom of the column and is first "forced" into the constant liquid level space 1410. After accumulating to a certain level over a certain period of time, it will enter the discharge space 1420 on the right side, instead of being directly extracted as product. Experiments have shown that this design significantly reduces the probability of unqualified alcoholysis degree during operational adjustments.

[0059] An embodiment of this application also provides a method for copolymer alcoholysis.

[0060] It should be noted that, unless otherwise stated, the reaction steps may be performed in the order described herein or not. For example, other steps may be included between reaction steps, and the order of reaction steps may be appropriately interchanged. This is something that those skilled in the art can determine based on conventional knowledge and experience. Preferably, the reaction methods described herein are performed sequentially.

[0061] A copolymer alcoholysis method, employing the aforementioned copolymer alcoholysis system 10, includes the following steps:

[0062] The copolymer to be hydrolyzed is controlled to enter the top section 101 of the reactive distillation column 100 through the feed pipe 410, and the hydrolysis gas is controlled to enter the bottom section 103 of the reactive distillation column 100 through the gas inlet pipe 420. The heating device 200 is controlled to heat the reactive distillation column 100, driving the reaction raw materials in the reactive distillation column 100 to circulate. The hydrolysis gas and the copolymer to be hydrolyzed undergo an ester exchange reaction. The reaction products are separated by the separation element 600. The gas phase containing the hydrolysis gas and ester products enters the condenser 300 for condensation, and the copolymer containing alcohol is discharged from the outlet of the bottom section 103 of the reactive distillation column 100. The product that has not reached the degree of hydrolysis is controlled to be heated by the heating device 200 and then returned to the oil collection tank 500.

[0063] In some embodiments, the mass ratio of the copolymer to be hydrolyzed to the catalyst is 1:2 to 1:5. Preferably, the mass ratio is 1:3.

[0064] In some embodiments, the mass ratio of the copolymer to be alcoholyzed to the alcoholysis gas is 100:1 to 300:1. Preferably, the mass ratio of the copolymer to be alcoholyzed to the alcoholysis gas is 200:1.

[0065] In some embodiments, the catalyst comprises sodium hydroxide. Preferably, the catalyst is a 10% to 20% sodium hydroxide methanol solution.

[0066] In some embodiments, the reaction temperature inside the reactive distillation column 100 is controlled to be 40°C to 80°C by the heating device 200.

[0067] Example 1

[0068] This embodiment provides a copolymer alcoholysis system 10, which can be used for the alcoholysis of ethylene-vinyl acetate alcohol copolymer.

[0069] See Figure 1As shown, the ethylene-vinyl acetate copolymer alcoholysis system 10 of this embodiment includes a reactive distillation column 100, a heating device 200, a condenser 300, a gas blowing pipe 430, a first transfer pump 910, and a second transfer pump 920. The gas blowing pipe 430 is a long nitrogen blowing pipe connected to a nitrogen source. The top section 101, middle section 102, and bottom section 103 of the reactive distillation column 100 are respectively equipped with an oil collection tank 500, a separation element 600, and an overflow tank 700. There are multiple oil collection tanks 500, and the residence time of the oil collection tanks 500 is set to 1 hour. A downcomer 1100 is installed in the oil collection tank 500, and the downcomer 1100 is in a bent state. One end of the downcomer 1100 is located inside the oil collection tank 500 and is lower than the top surface of the oil collection tank 500; the other end of the downcomer 1100 extends to the separation element 600. The separation element 600 includes a tray.

[0070] The top section 101 of the reactive distillation column 100 is connected to a feed pipe 410. A baffle-type demister 800 is also installed inside the reactive distillation column 100, located above the oil collection tank 500. The bottom section 103 of the reactive distillation column 100 is connected to an inlet pipe 420. Both the feed pipe 410 and the inlet pipe 420 are connected to purge pipes 430 capable of continuously blowing inert gas. A heating device 200 is located outside the reactive distillation column 100 and connects to the top section 101 and the bottom section 103 to achieve external circulation heating. The heating device 200 is preferably a vertical single-pass shell-and-tube heat exchanger. A condenser 300 is connected to the outlet of the top section 101 of the reactive distillation column 100 via a gas phase pipe 1200 for condensing the gas phase. Vertically, the condenser 300 is located diagonally above the reactive distillation column 100, and the vapor phase pipe 1200 is inclined upwards, forming an angle of 35° with the horizontal plane. The condenser 300 is also connected to the reflux port of the top section 101 of the reactive distillation column 100 to allow partial condensate reflux back into the reactive distillation column 100. A first transfer pump 910 is connected to the heating circulation pipe between the heating device 200 and the reactive distillation column 100. A second transfer pump 920 is connected to the reflux pipe 440 between the liquid outlet and the reflux port of the condenser 300. A first nozzle 1010 communicating with the reflux port of the condenser 300 is installed inside the condenser 300. A second nozzle 1020 communicating with the reflux port of the top section 101 of the reactive distillation column 100 is installed.

[0071] A downcomer 1100 is provided inside the oil collection tank 500. One end of the downcomer 1100 is located inside the oil collection tank 500 and is lower than the top surface of the oil collection tank 500. The other end of the downcomer 1100 extends to the separation element 600.

[0072] The bottom section 103 of the reactive distillation column 100 is provided with a first partition 1310 and a second partition 1320. The first partition 1310 is connected to the inner wall of the reactive distillation column 100 and extends toward the bottom surface of the bottom section 103, and is spaced apart from the bottom surface of the bottom section 103. The second partition 1320 is connected to the bottom surface of the bottom section 103 and extends toward the middle section 102. There is a gap between the first partition 1310 and the second partition 1320, and the gap forms an overflow channel 700. The first partition 1310 and the second partition 1320 divide the bottom section 103 of the reactive distillation column 100 into an independent constant liquid level space 1410 and an external discharge space 1420. The constant liquid level space 1410 is connected to the separation unit, and the external discharge space 1420 is connected to the outlet of the bottom section 103.

[0073] Example 2

[0074] This embodiment provides a method for alcoholysis of ethylene-vinyl acetate copolymer. The alcoholysis method of this embodiment uses the copolymer alcoholysis system 10 in Example 1.

[0075] An efficient alcoholysis method for ethylene-vinyl acetate copolymers includes the following steps:

[0076] The feed pipe 410 and air inlet pipe 420 are controlled to continuously blow nitrogen through the air blowing pipe 430 to maintain a slight positive pressure in the system.

[0077] The ethylene-vinyl acetate copolymer (EVAC) solution is controlled to enter the top section 101 of the reactive distillation column 100 through feed pipe 410, and the methanol gas is controlled to enter the bottom section 103 of the reactive distillation column 100 through inlet pipe 420. The EVAC solution contains ethylene-vinyl acetate copolymer and sodium hydroxide catalyst, with a mass ratio of 1:3. The catalyst is a 10% sodium hydroxide methanol solution. The mass ratio of ethylene-vinyl acetate copolymer to methanol gas is 300:1.

[0078] The heating device 200 heats the reactive distillation column 100 to 60°C, driving the reaction feedstock within the column to circulate. Methanol undergoes a transesterification reaction with the ethylene-vinyl acetate copolymer. The reaction products are separated by the separation element 600. The vapor phase containing methanol and methyl acetate enters the condenser 300 for condensation, while the vapor phase containing the ethylene-vinyl acetate copolymer is discharged from the outlet of the bottom section 103 of the reactive distillation column 100. When a product with insufficient degree of alcoholysis is formed, it is controlled to accumulate in the constant liquid level space 1410 and overflow through the overflow tank 700 to the discharge space 1420. After being heated by the heating device 200, it flows back to the oil collection tank 500 for further alcoholysis.

[0079] Ethylene-vinyl acetate copolymer, methanol, and sodium hydroxide catalyst undergo alcoholysis at a certain temperature to produce ethylene-vinyl acetate alcohol copolymer (EVOH) and methyl acetate, as shown in formula (1):

[0080] Equation (1).

[0081] In Example 2, the product alcoholysis rate of the copolymer alcoholysis system 10 can be stably maintained above 99.5%. Even under fluctuating feed conditions, the buffering capacity of the copolymer alcoholysis system 10 is very strong. If the oil collection tank 500 is missing or the bottom of the oil collection tank 500 is not open, the residence time of the oil collection tank 500 will be close to 0, and the product alcoholysis rate will be at most 98-98%. This is because the system does not provide sufficient residence time for the alcoholysis process, and the liquid holding capacity of the trays or packing is relatively limited and unstable due to the influence of gas-liquid flow rate, temperature, pressure, etc. The absence of the first nozzle 1010 and the second nozzle 1020 does not have a short-term impact on the continuous nitrogen blowing of the feed pipe 410 and the air inlet pipe 420, but long-term operation will cause system blockage and affect normal operation. After shutdown inspection, it was found that the polymer precipitated at the key position caused the blockage.

[0082] In summary, the copolymer alcoholysis system 10 described above, coupled within the reactive distillation column 100, includes an oil collection tank 500 and an overflow tank 700 to provide reliable residence time for the reactants; a separation element 600 to break reaction equilibrium and remove ester products such as methyl acetate; a top demister 800 to prevent blockage of the top gas pipeline or condenser 300; a first nozzle 1010; a second nozzle 1020; a continuous nitrogen flow to prevent blockage of the feed pipe 410 and gas inlet pipe 420 and to facilitate pressure control; an external circulation heating device 200 to control the overall column temperature; a bottom section 103 structure of the reactive distillation column 100 to prevent short circuits in the reaction liquid; and optimized selection criteria for dynamic and static equipment and pipeline layout. The resulting copolymer alcoholysis system 10 offers flexible and convenient shutdown operation, allowing for intermittent or continuous operation. It features reliable control of reaction temperature and residence time, good anti-clogging properties, simple system design, low investment cost, and is suitable for continuous large-scale production.

[0083] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0084] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A copolymer alcoholysis system, characterized in that, The system includes a reactive distillation column, a heating device, a condenser, and a gas blowing pipe. The top, middle, and bottom sections of the reactive distillation column are respectively equipped with an oil collection tank, a separation element, and an overflow tank. The top section of the reactive distillation column is connected to a feed pipe, and the bottom section is connected to an inlet pipe. Both the feed pipe and the inlet pipe are connected to gas blowing pipes capable of continuously blowing inert gas. The heating device is located outside the reactive distillation column and is connected to the top and bottom sections to achieve external circulation heating. The condenser is connected to the outlet of the top section of the reactive distillation column for condensing the gas phase. The condenser is also connected to the reflux port of the top section of the reactive distillation column to allow some of the condensate to flow back into the reactive distillation column.

2. The copolymer alcoholysis system according to claim 1, characterized in that, The blowing pipe is a long blowing nitrogen pipe connected to the nitrogen source.

3. The copolymer alcoholysis system according to claim 1, characterized in that, The reactive distillation column is also equipped with a demister located at the top of the column, which is situated above the oil collection tank.

4. The copolymer alcoholysis system according to claim 1, characterized in that, The copolymer alcoholysis system further includes a first delivery pump, which is connected to the heating circulation pipeline between the heating device and the reactive distillation column. The first delivery pump is used to discharge the reaction products from the bottom section of the reactive distillation column or to return products that have not reached the degree of alcoholysis to the oil collection tank after being heated by the heating device.

5. The copolymer alcoholysis system according to any one of claims 1 to 4, characterized in that, The copolymer alcoholysis system further includes a second transfer pump, which is connected to the reflux pipe between the liquid outlet of the condenser and the reflux port of the condenser. The second transfer pump is used to discharge the condensate from the condenser to the outside or reflux it back to the condenser and the reactive distillation column.

6. The copolymer alcoholysis system according to claim 5, characterized in that, The copolymer alcoholysis system also satisfies at least one of the following conditions: (1) The condenser is provided with a first nozzle that communicates with the return port of the condenser; (2) The top section of the reactive distillation column is provided with a second nozzle that communicates with the reflux port of the top section.

7. The copolymer alcoholysis system according to any one of claims 1 to 4, 6, characterized in that, The copolymer alcoholysis system also satisfies at least one of the following conditions: (1) The number of oil collection tanks is one or more, and the residence time of the oil collection tanks is set to 0.1hr~3hr; (2) A downcomer is provided in the oil collection tank, and the downcomer is also connected to the separation element. The liquid in the oil collection tank overflows to the separation element through the downcomer. (3) The temperature inside the oil collection tank can be adjusted by the heating device; (4) The oil collection tank has an annular groove structure; (5) The inlet of the feed pipe and the outlet of the downcomer in the oil collection tank are in relative positions.

8. The copolymer alcoholysis system according to any one of claims 1 to 4, 6, characterized in that, The copolymer alcoholysis system also satisfies at least one of the following conditions: (1) The separation element includes packing and / or trays; (2) The top section of the reactive distillation column is connected to a gas phase pipe that communicates with the condenser. The gas phase pipe is inclined upward and the angle between the gas phase pipe and the horizontal plane is greater than 30°.

9. The copolymer alcoholysis system according to any one of claims 1 to 4, 6, characterized in that, The bottom section of the reactive distillation column is provided with a first baffle and a second baffle. The first baffle is connected to the inner wall of the reactive distillation column and extends toward the bottom surface of the bottom section, with a gap between them. The second baffle is connected to the bottom surface of the bottom section and extends toward the middle section of the column. There is a gap between the first baffle and the second baffle, and this gap forms the overflow channel. The first baffle and the second baffle divide the bottom section of the reactive distillation column into an independent constant liquid level space and an external discharge space. The constant liquid level space is connected to the separation unit, and the external discharge space is connected to the outlet of the bottom section.

10. A method for alcoholysis of copolymers, characterized in that, The copolymer alcoholysis system according to any one of claims 1 to 9 comprises the following steps: The copolymer to be hydrolyzed is controlled to enter the top section of the reactive distillation column through the feed pipe, and the hydrolysis gas is controlled to enter the bottom section of the reactive distillation column through the inlet pipe. The heating device is controlled to heat the reactive distillation column, driving the reaction raw materials in the reactive distillation column to circulate. The hydrolysis gas and the copolymer to be hydrolyzed undergo an ester exchange reaction. The reaction products are separated by a separation element. The gas phase containing the hydrolysis gas and ester products enters the condenser for condensation, while the alcohol copolymer is discharged from the outlet of the bottom section of the reactive distillation column. The product that has not reached the degree of hydrolysis is controlled to be heated by the heating device and then returned to the oil collection tank.

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