Eva alcoholysis reaction preparation of evo h fiber membrane reactor

Abstract

The utility model provides a kind of EVA alcoholysis reaction preparation EVOH's fibre membrane reactor, including shell, chamber is equipped in the shell, the chamber is from top to bottom and is divided into gas phase separation zone, main reaction zone and liquid phase separation zone, coaxially in the main reaction zone is equipped with whole bundle type fibre membrane cylinder, whole bundle type fibre membrane cylinder is filled with stainless steel fibre silk structure, the bottom of gas phase separation zone is equipped with mixed raw material feeding structure, and the mixed raw material feeding structure includes raw material inlet and feeding distribution pipe, the top of liquid phase separation zone is equipped with gas inlet structure, and the gas inlet structure includes gas inlet, inlet distribution pipe and porous plate type feeding distribution pipe, the top of gas phase separation zone is equipped with gas phase outlet, and the bottom of liquid phase separation zone is equipped with liquid phase outlet.

Description

Technical Field

[0001] This utility model relates to the field of chemical reactors, specifically to a fiber membrane reactor for the preparation of ethylene-vinyl acetate copolymer (EVOH) by the alcoholysis reaction of ethylene-vinyl acetate copolymer (EVA). Background Technology

[0002] Ethylene-vinyl alcohol copolymer (EVOH), as a high-performance, high-barrier resin, is widely used in high-end fields such as food packaging, automotive fuel systems, and pharmaceutical packaging due to its excellent oxygen and water barrier properties and good processability. Since vinyl alcohol monomers readily isomerize to acetaldehyde and cannot be directly copolymerized with ethylene, a two-step process is commonly used industrially to prepare EVOH. The alcoholysis reaction of ethylene-vinyl acetate copolymer (EVA) is the key step connecting the intermediate EVA with the final product EVOH. Its reaction efficiency, reaction uniformity, and by-product removal effect directly determine the degree of alcoholysis, molecular weight distribution, color, and overall barrier performance of the EVOH product, making it a core step in the EVOH production process.

[0003] EVA alcoholysis is a base-catalyzed transesterification reaction. Its core principle is as follows: the acetate group (–OAc) on the side chain of the EVA molecule undergoes transesterification with methanol under the action of a strong base catalyst (such as sodium hydroxide or sodium methoxide) to generate hydroxyl groups (–OH), thus producing EVOH. This is accompanied by the formation of methyl acetate as a byproduct. This reaction is reversible. To promote the reaction towards the formation of EVOH and ensure an alcoholysis degree of over 99% (≥99.5% for high-end EVOH), the byproduct methyl acetate generated during the reaction must be removed promptly to break the reaction equilibrium. Simultaneously, the reaction system must remain homogeneous and stable to avoid EVA chain breakage, product yellowing, and gelation caused by excessively high local catalyst concentrations or uneven mixing.

[0004] Currently, the reactors used in industrial EVA alcoholysis reactions are mainly traditional stirred tank reactors, with some processes supplemented by tower reactors for subsequent devolatilization. However, these reactors have many technical bottlenecks in practical applications and are difficult to adapt to the continuous production requirements of high-quality EVOH. For example, in the prior art, Chinese patent application number CN201710175007.0 discloses a vertical stirred tank for coating production. A first spiral section is set on the inner side wall of the stirred tank, and a second spiral section and a scraper are set on the stirring shaft. Combined with the rotation of the stirring blade, the material rotates and rises along the spiral section, ensuring uniform mixing of the bottom and upper materials and reducing production time.

[0005] In summary, the specific drawbacks of traditional stirred tank reactors are as follows: First, low mass transfer efficiency and slow reaction rate. The specific surface area of ​​a traditional stirred tank reactor is only tens of m² / m³. After the EVA methanol solution and catalyst solution are mixed, a homogeneous system is formed. As the alcoholysis reaction proceeds, the formation of EVOH causes a sharp increase in the viscosity of the system, leading to uneven mixing and an unbalanced distribution of the catalyst within the system, forming localized over-alkali regions. This not only reduces the mass transfer efficiency of the transesterification reaction and prolongs the reaction time (usually requiring 2–6 hours), but also easily triggers EVA molecular chain degradation, product yellowing, and affects the molecular weight and processing stability of EVOH.

[0006] Secondly, byproduct removal is difficult, and in-situ removal is challenging. Since alcoholysis is a reversible reaction, the accumulation of the byproduct methyl acetate significantly inhibits the forward reaction, limiting the degree of alcoholysis. Traditional stirred tank reactors cannot achieve in-situ removal of methyl acetate; the reaction solution must be transferred to a dedicated devolatilization device for separation, increasing process complexity, equipment investment, and energy consumption. Furthermore, during removal, some EVOH precipitates due to temperature fluctuations, leading to product loss and equipment blockage. The removal efficiency is also limited, making it difficult to meet the production requirements for high-degree-of-alcohol-removal EVOH.

[0007] Third, the reactor has poor adaptability and is not suitable for continuous production. Traditional stirred tank reactors are mostly batch or semi-continuous operations, with a wide distribution of material residence time, resulting in differences in the degree of alcoholysis and molecular weight distribution between different batches of products, and poor product uniformity. Moreover, the high-viscosity EVOH system is prone to dead zones during stirring, which aggravates local uneven reaction and further affects product quality. In addition, the production efficiency of batch operation is low, which is difficult to meet the needs of large-scale continuous industrial production, and frequent feeding and discharging operations will increase catalyst loss and waste. Utility Model Content

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a fiber membrane reactor for the alcoholysis reaction of ethylene-vinyl acetate copolymer (EVA) to prepare ethylene-vinyl alcohol copolymer (EVOH).

[0009] According to the present invention, a fiber membrane reactor for preparing EVOH by alcoholysis of EVA includes a shell, and a chamber is provided inside the shell. The chamber is divided into a gas phase separation zone, a main reaction zone, and a liquid phase separation zone from top to bottom. A bundle of stainless steel fibers is coaxially arranged in the main reaction zone. The bundle of stainless steel fibers includes multiple stainless steel filaments. A mixed raw material feeding structure is provided at the bottom of the gas phase separation zone. The mixed raw material feeding structure includes a raw material inlet, a feed distribution pipe, and a feed nozzle. The raw material inlet is located on the bottom side wall of the gas phase separation zone, and the feed distribution pipe passes through the raw material inlet and communicates with the feed nozzle located in the gas phase separation zone. An air inlet structure is provided at the top of the liquid phase separation zone. The air inlet structure includes an air inlet and an inlet distribution pipe. The perforated plate gas distributor has an inlet located on the top sidewall of the liquid phase separation zone. The inlet distribution pipe includes a connecting section and a distribution section. The connecting section connects the inlet to the distribution section, and the distribution section includes an annular pipe. The annular pipe is horizontally positioned below the perforated plate gas distributor. A connecting pipe is located inside the annular pipe and connects to the connecting section. The connecting pipe communicates with the internal space of the annular pipe. Multiple exhaust holes are provided on the walls of the annular pipe and the connecting pipe, so that the gas forms a uniform gas cushion layer below the perforated plate. The surface of the perforated plate gas distributor has multiple micropores with radially gradient pore sizes, increasing in a stepwise manner from the center to the edge. A gas phase outlet is located at the top of the gas phase separation zone, and a liquid phase outlet is located at the bottom of the liquid phase separation zone.

[0010] Preferably, the outer side of the shell is provided with a first jacket and a second jacket. The first jacket is located in the gas phase separation zone and the second jacket is located in the main reaction zone. The outer side of the first jacket is provided with a first jacket inlet and a first jacket outlet, and the outer side of the second jacket is provided with a second jacket inlet and a second jacket outlet.

[0011] Preferably, a spiral guide plate is provided on the inner side of the jacket.

[0012] Preferably, a wire mesh demister is provided in the gas phase separation zone. The wire mesh demister adopts a three-layer gradient aperture stainless steel wire mesh stacked structure. An anti-bubble device is provided at the liquid phase outlet. The anti-bubble device adopts an annular guide vane structure.

[0013] Preferably, the housing is provided with an upper liquid level gauge and a lower liquid level gauge, with the upper liquid level gauge located in the gas phase separation zone and the lower liquid level gauge located in the liquid phase separation zone.

[0014] Preferably, the housing is provided with an upper thermometer port, a middle thermometer port and a lower thermometer port. The upper thermometer port is located in the gas phase separation zone, the middle thermometer port is located in the reaction zone and the lower thermometer port is located in the liquid phase separation zone.

[0015] Preferably, the housing is provided with a concentration meter port, which is located in the liquid phase separation zone.

[0016] Preferably, the main reaction zone is also provided with multiple flushing fluid inlets, which are distributed in the upper, middle and lower sections of the main reaction zone.

[0017] Preferably, the shell is a separable structure, comprising an upper shell, a middle shell, and a lower shell. The inner cavity of the upper shell corresponds to the gas phase separation zone, the inner cavity of the middle shell corresponds to the main reaction zone, and the inner cavity of the lower shell corresponds to the liquid phase separation zone. The upper shell, the middle shell, and the lower shell are detachably connected by a flange structure.

[0018] Preferably, an upper cylindrical plate is provided between the flanges of the upper shell and the middle shell. The upper cylindrical plate has an annular plate structure and is connected to the flanges of the upper shell and the middle shell by multiple bolts. Multiple suspension beams are provided on the inner side of the upper cylindrical plate, and the bundled stainless steel fiber bundle is suspended in the middle shell through the multiple suspension beams on the upper cylindrical plate.

[0019] Compared with the prior art, the present invention has the following beneficial effects: In the synthesis of EVOH from EVA, a bundled fiber membrane reactor is employed, significantly increasing the reaction contact area. The specific surface area of ​​the fiber filaments is 1000~5000 m² / m³ (compared to only tens of m² / m³ in stirred tank reactors). The liquid forms a micron-sized thin liquid film on the fiber surface, increasing the mass transfer coefficient by 10~100 times. This leads to a significant acceleration of the reaction rate and a 30%~50% reduction in catalyst dosage. Simultaneously, the local alkali concentration is more uniform, reducing the likelihood of gelation, yellowing, and more uniform alcoholysis. Through precise temperature control, the gas interaction is enhanced, and the methyl acetate produced in the reaction is promptly removed, shifting the equilibrium towards higher conversion rates and thus stabilizing the degree of alcoholysis of EVOH. Furthermore, the fiber membrane structure is an open channel with low shear and no dead zones, allowing for stable and continuous flow even when EVOH becomes viscous, effectively avoiding the clogging and mass transfer deterioration problems caused by increased viscosity in traditional reactors. Real-time liquid level and temperature control work together to ensure stable residence time within a specific range, precisely controlling the degree of alcoholysis (saponification) of the product while suppressing molecular chain degradation caused by side reactions, ultimately yielding a narrow-distribution, high thermal stability EVOH product. Attached Figure Description

[0020] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a fiber membrane reactor for the preparation of EVOH by the alcoholysis reaction of EVA.

[0021] Figure 2 Schematic diagram of the upper cylinder plate structure; Figure 3 Schematic diagram showing the connection between the upper cylinder plate and the upper shell flange and the middle shell flange; Figure 4 Schematic diagram of a perforated plate gas distributor; Figure 5 Schematic diagram of the inlet distribution pipe structure; In the diagram, 1. Upper shell; 2. Middle shell; 3. Lower shell; 4. Bundled stainless steel fiber bundle; 5. Stainless steel fiber filament; 6. Upper cylinder plate; 7. Suspension beam; 8. Wire mesh demister; 9. Anti-fogging device; 10. Raw material inlet; 11. Air inlet; 12. Gas phase outlet; 13. Liquid phase outlet; 14. Second jacket; 141. Second jacket inlet; 142. Second jacket outlet; 15. First jacket; 151. First jacket inlet ; 152, First jacket outlet; 161, lower outlet of level gauge; 162, upper outlet of level gauge; 17, inlet distribution pipe; 18, feed distribution pipe; 19, flushing fluid inlet; 20, feed nozzle; 21, perforated plate gas distributor; 221, upper thermometer port; 222, middle thermometer port; 223, lower thermometer port; 23, concentration meter port; 24, bolt hole; 25, upper shell flange; 26, middle shell flange; 27, vent hole. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0023] For ease of understanding, the terms or concepts involved in this application are explained below: (1) Fiber membrane reactor: A fiber membrane reactor is a gas-liquid and liquid-liquid reactor with stainless steel fiber bundles with high specific surface area as the core mass transfer element. Its interior is filled with a large number of stainless steel fibers with hydrophilic, high elasticity and self-healing properties, forming a bundled fiber membrane cylindrical structure. The reactor uses an ultra-thin liquid film (usually 1-10 micrometers thick) formed on the surface of the fiber to replace the traditional bulk liquid phase mixing, which increases the interphase contact area from tens of m² / m³ in traditional reactors to 1000-5000 m² / m³, thereby greatly enhancing the mass transfer efficiency.

[0024] (2) Alcohololysis: an important type of reaction in organic chemistry, referring to the process by which compounds such as acyl halides, acid anhydrides, and esters decompose under the action of alcohols to generate new esters and other products.

[0025] (3) EVA alcoholysis reaction: This is a base-catalyzed transesterification reaction. The core reaction principle is that the acetate group (–OAc) on the side chain of the EVA molecule undergoes transesterification with methanol under the action of a strong base catalyst (such as sodium hydroxide or sodium methoxide) to generate hydroxyl groups (–OH), thereby obtaining EVOH. At the same time, the byproduct methyl acetate is generated. This reaction is reversible, and the reaction equation can be expressed as:

[0026] (4) Jacket: A common heat transfer structure in industrial equipment. Simply put, it is an "outer garment" for containers or pipes, which controls the temperature of internal materials by circulating hot and cold media in the jacket.

[0027] (5) Bundled stainless steel fiber bundle: A large number (usually thousands to tens of thousands) of highly elastic and corrosion-resistant stainless steel fibers are bundled together in a certain arrangement to form a stable fiber filament assembly with neat end faces. This bundled structure is suspended on the upper cylinder plate, with the middle part remaining free and loose, serving as the core mass transfer element of the fiber membrane reactor.

[0028] This embodiment provides a fiber membrane reactor for preparing EVOH by alcoholysis of EVA, including a shell with a chamber inside. The chamber is divided into a gas phase separation zone, a main reaction zone, and a liquid phase separation zone from top to bottom. The shell is a separable structure, including an upper shell 1, a middle shell 2, and a lower shell 3. The inner cavity of the upper shell 1 corresponds to the gas phase separation zone, the inner cavity of the middle shell 2 corresponds to the main reaction zone, and the inner cavity of the lower shell 3 corresponds to the liquid phase separation zone. The upper shell 1, the middle shell 2, and the lower shell 3 are detachably connected by a flange structure.

[0029] In this embodiment, the outer side of the shell is provided with a first jacket 15 and a second jacket 14. The first jacket 15 is located in the gas phase separation zone, and the second jacket 14 is located in the main reaction zone. The outer side of the first jacket 15 is provided with a first jacket inlet 151 and a first jacket outlet 152, and the outer side of the second jacket 14 is provided with a second jacket inlet 141 and a second jacket outlet 142. In this embodiment, the housing is provided with an upper thermometer port 221, a middle thermometer port 222 and a lower thermometer port 223. The upper thermometer port 221 is located in the gas phase separation zone, the middle thermometer port 222 is located in the reaction zone, and the lower thermometer port 223 is located in the liquid phase separation zone.

[0030] Based on the above scheme, the first jacket 15 works with the upper thermometer to precisely regulate the temperature of the upper gas-liquid separation zone through a temperature control medium, suppressing the condensation and reflux of stripping gas and methyl acetate, and ensuring stripping efficiency; ensuring that the upper region is always above the methyl acetate dew point temperature; the second jacket 14 works with the middle thermometer to precisely adjust the temperature range of the reaction zone through a temperature control medium, ensuring that the alcoholysis reaction rate and the narrowing of the EVOH molecular weight distribution are optimized simultaneously; providing stable thermal boundary conditions for the highly active base catalytic system. The jacket is equipped with a spiral guide plate to improve heat transfer uniformity, with temperature difference fluctuation ≤ ±0.5℃. In this embodiment, a bundle of stainless steel fiber 4 is coaxially arranged in the main reaction zone. The bundle of stainless steel fiber 4 includes several stainless steel fiber filaments 5. A mixed raw material feeding structure is provided at the bottom of the gas phase separation zone. The mixed raw material feeding structure includes a raw material inlet 10, a feed distribution pipe 18, and a feed nozzle 20. The raw material inlet 10 is located on the bottom side wall of the gas phase separation zone, and the feed distribution pipe 18 passes through the raw material inlet 10 and is connected to the feed nozzle 20 located in the gas phase separation zone.

[0031] Based on the above scheme, the mixture of EVA and NaOH / methanol catalyst enters the feed distribution pipe 18 through the feed inlet 10. Several feed nozzles 20 are set at the bottom of the feed distribution pipe 18 according to the required coverage area, so that the mixture is sprayed evenly on the upper surface of the bundled fiber membrane in an umbrella shape. The initial flow rate is controlled at 0.8–2 m / s to ensure that the fiber surface is fully wetted and there is no channeling, thus providing a homogenized feed basis for the subsequent highly selective alcoholysis reaction.

[0032] In this embodiment, an air intake structure is provided at the top of the liquid phase separation zone. The air intake structure includes an air inlet 11, an inlet distribution pipe 17, and a porous plate gas distributor 21. The air inlet 11 is located on the top side wall of the liquid phase separation zone. The inlet distribution pipe 17 includes a connecting section and a distribution section. The connecting section connects the air inlet 11 and the distribution section. The distribution section includes an annular pipe. The annular pipe is horizontally located below the porous plate gas distributor 21. A horizontal connecting pipe is provided inside the annular pipe. The lower center of the connecting pipe is connected to the connecting section, and the connecting pipe communicates with the internal space of the annular pipe. Multiple exhaust holes 27 are provided on the inner and outer pipe walls of the annular pipe and the connecting pipe at the horizontal or side lower level, so that the gas forms a uniform gas cushion layer below the porous plate gas distributor 21. Multiple micropores are distributed on the surface of the porous plate gas distributor 21. The pore size of the multiple micropores is radially gradient distributed, and the pore size increases stepwise from the center to the edge. The gas phase separation zone has a gas phase outlet 12 at the top and a liquid phase outlet 13 at the bottom. The gas and the methyl acetate it carries escape from here and enter the subsequent condensation and recovery system; the reaction products flow out from the liquid phase outlet 13.

[0033] Based on the above scheme, the inlet distribution pipe 17 and the porous plate gas distributor structure 21 allow inert gases such as methanol vapor and nitrogen to undergo primary distribution through the inlet distribution pipe 17, forming a uniform gas cushion layer. Then, the gas passes through the micropores of the porous plate for secondary cutting and is injected at a uniform speed into the bottom gaps of the bundled stainless steel fiber bundles 4, creating a counter-current stripping effect with the descending liquid film. During the upward process, the gas fully contacts the descending liquid film, accelerating the removal of methyl acetate and enhancing the interphase mass transfer driving force. It should be noted that the stainless steel fiber 5 possesses excellent mechanical strength and alkali corrosion resistance, and is characterized by hydrophilicity, high elasticity, and self-healing properties. EVA and the catalyst NaOH / methanol mixture react within this fiber bundle region. The fiber membrane wall provides a high specific surface area reaction interface, enhancing the contact efficiency between EVA molecular segments and alkaline active sites. Jacket temperature control precisely regulates the local concentration gradient and mass transfer rate in the reaction region, significantly suppressing side reactions. During the gas's ascent, it fully contacts the descending liquid film, accelerating methyl acetate removal, strengthening the interphase mass transfer driving force, achieving in-situ separation of the product methyl acetate, and promoting a positive shift in the alcoholysis equilibrium, thus stabilizing and increasing the hydroxylation degree of EVOH. This structural design simultaneously addresses three major pain points in traditional alcoholysis reactions: limited mass transfer, byproduct accumulation, and fluctuations in hydroxylation degree. The whole-bundle stainless steel fiber bundle 4 and the segmented jacket work together to achieve integrated "reaction-separation-temperature control," reducing energy consumption by 37% compared to the batch process.

[0034] In this embodiment, an upper cylindrical plate 6 is provided between the flanges of the upper shell 1 and the middle shell 2. The upper cylindrical plate is an annular plate structure. The upper cylindrical plate is connected to the flanges of the upper shell 1 and the middle shell 2 by multiple bolts. Multiple suspension beams 7 are provided on the inner side of the upper cylindrical plate. The bundled stainless steel fiber bundle 4 is suspended in the middle shell through the multiple suspension beams 7 on the upper cylindrical plate 6.

[0035] It is understandable that, such as Figure 2 As shown, multiple bolt holes 24 are distributed in a ring along the edge of the upper cylinder plate 6. Correspondingly, the surfaces of the upper shell flange 25 and the middle shell flange 26 are also provided with corresponding threaded holes. Bolts pass through the upper cylinder plate, the upper shell flange, and the middle shell flange to achieve a fixed connection. Figure 3 As shown.

[0036] It should be noted that the entire bundle of stainless steel fibers 4 is folded in half at the middle, and the folded and bent part is suspended on the suspension beam 7 located inside the upper cylinder plate 6. The suspension beam 7 has multiple positioning grooves evenly distributed along its length, and each fiber bundle is embedded in its corresponding positioning groove to prevent lateral slippage. The suspension beam is equipped with leveling adjustment devices at both ends, allowing independent adjustment of the height of the suspension beam ends to ensure that the vertical parallelism deviation of each fiber filament is ≤0.5°. The bottom of the entire fiber bundle hangs freely without mechanical constraints, forming a stable liquid film flow channel. Combined with the countercurrent stripping airflow, this significantly improves the removal efficiency and reaction selectivity of methyl acetate.

[0037] In this embodiment, the main reaction zone is also provided with multiple flushing fluid inlets 19, which are distributed in the upper, middle and lower sections of the main reaction zone.

[0038] In this embodiment, the lower housing is provided with a concentration meter port 23.

[0039] Based on the above scheme, the rinsing solution is connected and real-time concentration measurement is used as a backup method. It is turned on when the alcoholysis reaction is significantly weakened. The upper, middle and lower rinsing solutions are set up to rinse the surface residue of stainless steel fiber 5 online, so as to ensure the long-term stable operation of the continuous alcoholysis reaction.

[0040] In this embodiment, a wire mesh demister 8 is provided in the gas phase separation zone. The wire mesh demister 8 adopts a three-layer gradient aperture stainless steel wire mesh stacked structure, which effectively intercepts droplets with a particle size ≥5μm and achieves a separation efficiency of 99.97%, avoiding the alcoholysis liquid from being carried to the subsequent condensation system with the gas phase, causing blockage and cross-contamination. Its gradient aperture design takes into account both high throughput and high precision.

[0041] In this embodiment, the housing is provided with a liquid level gauge upper port 162 and a liquid level gauge lower port 161. The liquid level gauge upper port 162 is located in the gas phase separation zone, and the liquid level gauge lower port 161 is located in the liquid phase separation zone. This is used to monitor the liquid level height in the reactor in real time and ensure that the residence time of the reaction liquid in the reactor is accurate and controllable.

[0042] In this embodiment, an anti-cavitation device 9 is provided at the liquid phase outlet 13. The anti-cavitation device 9 adopts an annular guide vane structure, which effectively suppresses the formation of vortices and cavitation in the reaction liquid phase during the discharge process, and ensures that the EVOH product solution is discharged smoothly and continuously.

[0043] The synthesis of EVOH from EVA was carried out using both a conventional reactor and the fiber membrane reactor of this invention. Under the same feed rate (10 kg / h, 20% EVA methanol solution) and operating conditions within the range of 40–90 °C and 0.1–0.3 MPa, the reaction was carried out continuously for 200 hours after stabilization. The data shown in Table 1 are as follows:

[0044] Table 1 As shown in Table 1, under the same degree of alcoholysis, the fiber membrane reactor is superior to the batch reactor in many aspects, such as mass transfer efficiency, reaction residence time, by-product removal and catalyst usage.

[0045] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application 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 application.

[0046] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the substantive content of this utility model. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A fiber membrane reactor for the preparation of EVOH by alcoholysis of EVA, characterized in that, The device includes a housing, which contains a chamber. The chamber is divided into a gas phase separation zone, a main reaction zone, and a liquid phase separation zone from top to bottom. A bundle of stainless steel fibers (4) is coaxially arranged in the main reaction zone. The bundle of stainless steel fibers (4) includes multiple stainless steel fibers (5). A mixed raw material feeding structure is provided at the bottom of the gas phase separation zone. The mixed raw material feeding structure includes a raw material inlet (10), a feeding distribution pipe (18), and a feeding nozzle (20). The raw material inlet (10) is located on the bottom side wall of the gas phase separation zone. The feeding distribution pipe (18) passes through the raw material inlet (10) and communicates with the feeding nozzle (20) located in the gas phase separation zone. The top of the liquid phase separation zone is provided with an air intake structure, which includes an air inlet (11), an inlet distribution pipe (17), and a porous plate gas distributor (21). The air inlet (11) is located on the top side wall of the liquid phase separation zone. The inlet distribution pipe (17) includes a connecting section and a distribution section. The connecting section connects the air inlet (11) and the distribution section. The distribution section includes an annular pipe. The annular pipe is horizontally located below the porous plate gas distributor (21). A connecting pipe is provided inside the annular pipe. The connecting pipe is connected to the connecting section. The connecting pipe communicates with the internal space of the annular pipe. Multiple exhaust holes (27) are opened on the walls of the annular pipe and the connecting pipe. Multiple micropores are distributed on the surface of the porous plate gas distributor (21). The pore diameter of the multiple micropores is radially gradient distributed, and the pore diameter increases stepwise from the center to the edge. The gas phase separation zone is provided with a gas phase outlet (12) at the top and a liquid phase outlet (13) at the bottom.

2. The fiber membrane reactor for preparing EVOH by EVA alcoholysis according to claim 1, characterized in that, The outer side of the shell is provided with a first jacket (15) and a second jacket (14). The first jacket (15) is located in the gas phase separation zone, and the second jacket (14) is located in the main reaction zone. The outer side of the first jacket (15) is provided with a first jacket inlet (151) and a first jacket outlet (152), and the outer side of the second jacket (14) is provided with a second jacket inlet (141) and a second jacket outlet (142).

3. The fiber membrane reactor for preparing EVOH by EVA alcoholysis reaction according to claim 2, characterized in that, The inner side of the jacket is provided with a spiral guide plate.

4. The fiber membrane reactor for preparing EVOH by EVA alcoholysis reaction according to claim 1, characterized in that, The gas phase separation zone is equipped with a wire mesh demister (8), which adopts a three-layer gradient aperture stainless steel wire mesh stacked structure. The liquid phase outlet (13) is equipped with an anti-bubble device (9), which adopts an annular guide vane structure.

5. The fiber membrane reactor for preparing EVOH by alcoholysis of EVA according to claim 1, characterized in that, The housing is provided with a liquid level gauge upper port (162) and a liquid level gauge lower port (161). The liquid level gauge upper port (162) is located in the gas phase separation zone, and the liquid level gauge lower port (161) is located in the liquid phase separation zone.

6. The fiber membrane reactor for preparing EVOH by EVA alcoholysis according to claim 1, characterized in that, The housing is provided with an upper thermometer port (221), a middle thermometer port (222) and a lower thermometer port (223). The upper thermometer port (221) is located in the gas phase separation zone, the middle thermometer port (222) is located in the reaction zone, and the lower thermometer port (223) is located in the liquid phase separation zone.

7. The fiber membrane reactor for preparing EVOH by alcoholysis of EVA according to claim 1, characterized in that, The housing is provided with a concentration meter port (23), which is located in the liquid phase separation zone.

8. The fiber membrane reactor for preparing EVOH by alcoholysis of EVA according to claim 1, characterized in that, The main reaction zone is also provided with multiple flushing fluid inlets (19), which are distributed in the upper, middle and lower sections of the main reaction zone.

9. The fiber membrane reactor for preparing EVOH by alcoholysis of EVA according to claim 1, characterized in that, The shell is a detachable structure, comprising an upper shell (1), a middle shell (2) and a lower shell (3). The inner cavity of the upper shell (1) corresponds to the gas phase separation zone, the inner cavity of the middle shell (2) corresponds to the main reaction zone, and the inner cavity of the lower shell (3) corresponds to the liquid phase separation zone. The upper shell (1), the middle shell (2) and the lower shell (3) are detachably connected by a flange structure.

10. The fiber membrane reactor for preparing EVOH by alcoholysis of EVA according to claim 9, characterized in that, An upper cylinder plate (6) is provided between the flanges of the upper shell (1) and the middle shell (2). The upper cylinder plate is an annular plate structure. The upper cylinder plate is connected to the flanges of the upper shell (1) and the middle shell (2) by multiple bolts. Multiple suspension beams are provided on the inner side of the upper cylinder plate. The bundled stainless steel fiber bundle (4) is suspended in the middle shell by multiple suspension beams (7) on the upper cylinder plate (6).

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