A rectification separation and purification method for preparing high-purity o-dichlorobenzene

Abstract

The present application belongs to the technical field of rectification separation, and provides a rectification separation and purification method for preparing high-purity o-dichlorobenzene. The present application adopts the design of loading surface-modified structured packing in the rectification section of the rectification tower. The structured packing is composed of an alumina ceramic matrix and a cross-linked copolymer layer. The cross-linked copolymer layer contains structural units formed by N-vinyl-2-pyrrolidone, 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate, and is prepared through a silanization and graft cross-linking polymerization process. The rectification tower is operated under the conditions of a tower top absolute pressure of 0.5-20 kPa and a reflux ratio of 2-6. The present application realizes the efficient separation of o-dichlorobenzene products with a purity of not less than 99.9 wt% from dichlorobenzene isomer mixtures, solves the problem that the structured packing in a low-pressure rectification system cannot simultaneously achieve low pressure drop, large flux and high separation efficiency, and the stability of the surface modification layer in a high-temperature organic vapor environment is insufficient, and has wide industrial application value.

Description

Technical Field

[0001] This invention relates to the field of distillation and separation technology, and specifically to a distillation and purification method for preparing high-purity o-dichlorobenzene. Background Technology

[0002] o-Dichlorobenzene, as an important chemical intermediate and organic solvent, has irreplaceable application value in the fields of pesticides, dyes, pharmaceuticals, and the synthesis of high-performance polymers. With the rapid development of the fine chemical industry, downstream applications are increasingly demanding higher purity levels for o-dichlorobenzene products, especially in the fields of electronic chemicals, high-end pharmaceutical intermediates, and specialty solvents, where product purity needs to reach above 99.9 wt% to meet process requirements. In the industrial production of o-dichlorobenzene, the chlorination reaction typically produces a mixture of three dichlorobenzene isomers: ortho, meta, and para. Because the boiling points of these three isomers are close (o-dichlorobenzene 180.5℃, meta-dichlorobenzene 173.0℃, para-dichlorobenzene 174.1℃), their relative volatility differences are small, making separation extremely difficult. Distillation, as the most commonly used separation method in industry, directly determines product purity, energy consumption, and production costs. Therefore, developing efficient and stable distillation separation technology is of significant technical and economic importance for improving the quality of o-dichlorobenzene products, reducing production costs, and increasing resource utilization.

[0003] Currently, for the distillation separation of dichlorobenzene isomer mixtures, industrial applications mainly employ reduced-pressure distillation technology to lower operating temperatures, reduce the risk of thermal decomposition, and lower energy consumption. However, existing low-pressure distillation systems face numerous technical bottlenecks in the application of structured packing. For example, Chinese Patent CN103086841B discloses a method and apparatus for continuous separation in a high-efficiency structured packed tower in a diisocyanate production plant, using conventional ceramic or metal structured packing. However, it suffers from uneven liquid distribution and insufficient wetting performance under low-pressure conditions, leading to a decrease in mass transfer efficiency, making it difficult to achieve a balance between low pressure drop, high throughput, and high separation efficiency. Chinese Patent CN205392463U discloses a structured packing, but its high specific surface area design is prone to the precipitation of trace amounts of high-boiling substances or polymers on the packing surface during long-term operation, resulting in contamination and blockage. Furthermore, its poor resistance to crystallization and regenerable maintainability affect the continuous operational stability of the plant. Summary of the Invention

[0004] The purpose of this invention is to provide a distillation separation and purification method for preparing high-purity o-dichlorobenzene, which solves the technical pain points of current low-pressure distillation systems, such as the difficulty in balancing low pressure drop, high throughput and high separation efficiency of structured packing, insufficient stability of surface modified layers under long-term operation under high-temperature organic vapor conditions, and weak anti-fouling and clogging ability of high specific surface area packing.

[0005] This invention achieves molecular-level synergistic design of hydrophilic groups and hydrophobic framework by constructing a cross-linked copolymer layer on the surface of an alumina ceramic substrate, formed by the copolymerization of N-vinyl-2-pyrrolidone, 2-hydroxyethyl methacrylate, and ethylene glycol dimethacrylate. The cross-linked copolymer layer forms a stable covalent bond with the ceramic substrate surface through a silane coupling agent, enabling the surface modified layer to possess excellent solvent resistance, heat resistance, and shear stability in a high-temperature organic vapor environment. At the same time, the introduction of the cross-linked structure significantly improves the mechanical strength and long-term operational stability of the modified layer, effectively solving the problems of easy peeling and performance degradation of traditional coatings while ensuring the high wetting and mass transfer strengthening effect.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for distillation separation and purification to prepare high-purity o-dichlorobenzene includes the following steps:

[0008] S1. Provides a mixture of dichlorobenzene isomers, comprising o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene, wherein the mass fraction of o-dichlorobenzene in the dichlorobenzene isomer mixture is 50wt%-95wt%;

[0009] S2. The mixture of dichlorobenzene isomers is fed into a distillation column for distillation separation. The rectification section of the distillation column is filled with structured packing.

[0010] S3. The distillation column is operated under the conditions of an absolute pressure of 0.5-20 kPa at the top of the distillation column and a reflux ratio of 2-6, and the o-dichlorobenzene product is collected from the bottom of the distillation column, wherein the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product is not less than 99.9 wt%.

[0011] Furthermore, the structured filler includes an alumina ceramic matrix and a crosslinked copolymer layer located on the surface of the alumina ceramic matrix, wherein the crosslinked copolymer layer contains structural units formed by N-vinyl-2-pyrrolidone, structural units formed by 2-hydroxyethyl methacrylate, and crosslinked structural units formed by ethylene glycol dimethacrylate.

[0012] Furthermore, the structured packing is prepared through the following steps:

[0013] A1. Raw material preparation: Provide alumina ceramic matrix, ethanol and deionized water;

[0014] A2. Cleaning and drying: The alumina ceramic substrate was cleaned sequentially with ethanol and deionized water, and then dried;

[0015] A3. Acid activation: The dried alumina ceramic matrix is ​​contacted with a hydrochloric acid aqueous solution with a concentration of 0.1-2.0 mol / L for acid activation treatment, followed by washing with deionized water and drying;

[0016] A4. Silanization: The alumina ceramic matrix is ​​brought into contact with a silanization reaction solution containing 0.5-5.0 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 50-500 parts by weight of ethanol and 5-50 parts by weight of deionized water. The pH of the silanization reaction solution is adjusted to 3.0-5.0 using hydrochloric acid to carry out silanization.

[0017] A5. Graft crosslinking polymerization: The silanized alumina ceramic matrix obtained in step A4 is brought into contact with a polymerization reaction solution containing 100-1000 parts by weight of N,N-dimethylformamide, 5-50 parts by weight of N-vinyl-2-pyrrolidone, 1-30 parts by weight of 2-hydroxyethyl methacrylate, 0.1-10 parts by weight of ethylene glycol dimethacrylate, and 0.05-1.0 parts by weight of 2,2-azobisisobutyronitrile. Graft crosslinking polymerization is carried out under nitrogen protection.

[0018] A6. Post-treatment: After the reaction, the sample was washed with ethanol and deionized water in sequence and then dried to obtain a structured packing.

[0019] Furthermore, steps A1 to A4 satisfy the following conditions:

[0020] a) The raw material ratio in step A1 is: 100 parts by weight of alumina ceramic matrix, 200-1000 parts by weight of ethanol and 200-1000 parts by weight of deionized water;

[0021] b) The drying conditions in step A2 are 80-120℃ and the drying time is 1-4h;

[0022] c) In step A3, the concentration of the hydrochloric acid aqueous solution is 0.1-2.0 mol / L, the treatment temperature is 20-60℃, and the treatment time is 0.5-3h;

[0023] d) The silanization reaction solution in step A4 contains 0.5-5.0 parts by weight of 3-methacryloxypropyltrimethoxysilane, 50-500 parts by weight of ethanol and 5-50 parts by weight of deionized water. The pH value of the silanization reaction solution is 3.0-5.0, the silanization temperature is 20-60℃, and the silanization time is 0.5-4h.

[0024] Furthermore, steps A5 to A6 satisfy the following conditions, and the endpoint criterion for the preparation of structured packing is:

[0025] a) The polymerization reaction solution in step A5 contains 100-1000 parts by weight of N,N-dimethylformamide, 5-50 parts by weight of N-vinyl-2-pyrrolidone, 1-30 parts by weight of 2-hydroxyethyl methacrylate, 0.1-10 parts by weight of ethylene glycol dimethacrylate, and 0.05-1.0 parts by weight of 2,2-azobisisobutyronitrile, and reacts at 50-90℃ for 2-8 hours under nitrogen protection;

[0026] b) The drying conditions in step A6 are 60-120℃, absolute pressure is 0.1-10kPa, and drying time is 2-12h;

[0027] c) The preparation is considered complete when the mass increment of the structured filler relative to the alumina ceramic matrix is ​​0.2wt%-5.0wt%.

[0028] Furthermore, the alumina ceramic matrix has a honeycomb structure with a pore size of 1-5 mm and a wall thickness of 0.1-0.5 mm.

[0029] Furthermore, the thickness of the crosslinked copolymer layer is 50-300 nm, and the mass increment of the crosslinked copolymer layer relative to the alumina ceramic matrix is ​​0.2 wt%-5.0 wt%.

[0030] As a concept of this invention, the design of constructing a cross-linked copolymer layer on the surface of an alumina ceramic matrix is ​​mainly used to enhance the wetting and mass transfer performance and long-term operational stability of structured packings under low-pressure distillation conditions. The alumina ceramic matrix possesses excellent mechanical strength, high-temperature resistance, and chemical stability, providing a stable supporting structure for the cross-linked copolymer layer. Simultaneously, the honeycomb structure design ensures low pressure drop and high-flux hydrodynamic performance. Through acid activation treatment, a large number of active hydroxyl groups are generated on the surface of the alumina ceramic matrix, providing sufficient reaction sites for the subsequent silanization reaction. 3-Methacryloxypropyltrimethoxysilane, as a silane coupling agent, undergoes hydrolysis of its trimethoxy end under acidic conditions to generate silanol groups, which condense with the hydroxyl groups on the ceramic matrix surface to form stable Si-O-Al covalent bonds, firmly connecting the ceramic matrix to the organic polymer layer and significantly improving the bonding strength and peeling resistance of the modified layer. N-vinyl-2-pyrrolidone monomer contains hydrophilic amide groups, which can significantly improve the wettability of the filler surface, promote the uniform distribution and rapid spreading of the liquid phase on the filler surface, and thus enhance the gas-liquid mass transfer efficiency. 2-hydroxyethyl methacrylate monomer contains both hydroxyl and ester groups, which are dual hydrophilic groups, further enhancing surface wettability. Simultaneously, the methacryloyl group can copolymerize with other monomers to construct a stable polymer backbone. Ethylene glycol dimethacrylate, as a crosslinking agent, contains two polymerizable methacryloyl groups. During free radical polymerization, it can simultaneously participate in the growth of two polymer chains, forming a three-dimensional crosslinked network structure. This significantly improves the mechanical strength, solvent resistance, and heat resistance of the polymer layer, effectively preventing swelling, peeling, or thermal degradation of the polymer layer in high-temperature organic vapor environments.

[0031] Furthermore, the structured packing is corrugated structured packing with a specific surface area of ​​250-700 m² / m³. The structured packing is set in the form of modular packing units, with an axial height of 50-500 mm for each packing unit.

[0032] Furthermore, the pressure difference between the bottom pressure and the top pressure of the distillation column is 0.5-50 kPa, and the bottom temperature of the distillation column is 120-190℃.

[0033] Furthermore, the structured packing in the distillation column accounts for 10%-40% of the effective separation height of the distillation column, where the effective separation height is the total packing height of the packing section in the distillation column, and the structured packing is located above the feed inlet; the distillation column is also packed with unmodified structured packing, which is an alumina ceramic matrix structured packing without a cross-linked copolymer layer; and, a light component distillate is collected from the top of the distillation column, the total mass fraction of intermediate dichlorobenzene and para-dichlorobenzene in the light component distillate is 80wt%-99.9wt%.

[0034] Furthermore, during the cleaning process in step A2, the alumina ceramic substrate is washed 1-5 times each with ethanol and deionized water, with a liquid-to-solid ratio of 5-50 mL / g for each wash and a washing time of 1-30 min for each wash.

[0035] Furthermore, during acid activation in step A3, the liquid-to-solid ratio of the hydrochloric acid aqueous solution to the alumina ceramic matrix is ​​5-30 mL / g; the acid activation treatment is carried out by immersion.

[0036] Furthermore, during the washing process in step A3, the product is washed 2-5 times with deionized water, with a liquid-to-solid ratio of 5-50 mL / g each time, until the pH of the washing solution is 6-8 or the conductivity is below 10 μS / cm.

[0037] Furthermore, in step A4, the liquid-to-solid ratio of the silanization reaction solution to the alumina ceramic matrix is ​​5-30 mL / g; the silanization treatment is carried out by immersion.

[0038] Furthermore, in step A4, a hydrochloric acid aqueous solution with a concentration of 0.1-2.0 mol / L is added dropwise under stirring to adjust the pH of the silanization reaction solution to 3.0-5.0.

[0039] Furthermore, in step A5, the liquid-to-solid ratio of the polymerization reaction solution to the silanized alumina ceramic matrix is ​​5-50 mL / g; the graft crosslinking polymerization is carried out by immersion.

[0040] Furthermore, the nitrogen protection method in step A5 is as follows: before the polymerization reaction, the polymerization reaction liquid is evacuated and then purged with nitrogen 2-5 times, and an inert atmosphere is maintained at a nitrogen flow rate of 10-500 mL / min throughout the polymerization reaction.

[0041] Furthermore, during the washing process in step A6, the product is washed 2-5 times each with ethanol and deionized water, with a liquid-to-solid ratio of 5-100 mL / g for each wash.

[0042] Furthermore, in step A6, the product is dried to constant weight. The constant weight criterion is that the interval between two adjacent weighings is 30-60 minutes and the mass change is no more than 0.1 wt%.

[0043] Furthermore, the mass increment is calculated as follows: after drying in step A2, the initial mass m0 is obtained by weighing the alumina ceramic matrix, and after drying to constant weight in step A6, the final mass m1 is obtained by weighing. The mass increment percentage is (m1-m0) / m0×100%.

[0044] Furthermore, the reflux ratio is the ratio of the molar flow rate of the reflux liquid after condensation at the top of the column to the molar flow rate of the distillate at the top of the column.

[0045] Furthermore, the rectification section is the column section located above the feed inlet.

[0046] Furthermore, the theoretical plate number of the distillation column is 20-100, or the equal plate height (HETP) of the packing is 0.1-1.0m.

[0047] Furthermore, the feed position is located at 30wt%-70wt% of the effective separation height of the distillation column, which is measured downwards along the column axis from the top of the column.

[0048] Furthermore, the mass ratio of the top product to the bottom product is 1:5 to 5:1.

[0049] Furthermore, the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product was determined by gas chromatography or high performance liquid chromatography, and calculated using the area normalization method or external standard method.

[0050] Furthermore, the crosslinked copolymer layer forms a covalent bond with the surface of the alumina ceramic matrix through a silane coupling agent. The silane coupling agent is 3-methacryloyloxypropyltrimethoxysilane, which undergoes hydrolysis and condenses with the hydroxyl groups on the surface of the ceramic matrix to form Si-O-Al bonds.

[0051] Furthermore, the thickness of the cross-linked copolymer layer was determined by observing the cross-section of the ceramic matrix using scanning electron microscopy.

[0052] Furthermore, after continuous operation for 100-1000 hours in a dichlorobenzene vapor environment at 120-190℃, the modified structured packing exhibits a mass loss of no more than 5wt% and a pressure drop increase of no more than 20%.

[0053] Furthermore, the aperture of the honeycomb structure is the hydraulic diameter of the honeycomb channel.

[0054] Furthermore, the specific surface area of ​​structured packing is the geometric specific surface area, which is calculated from the geometric dimensions of the packing.

[0055] As another aspect of this invention, the design of partitioning surface-modified structured packing with unmodified structured packing is primarily used to enhance the overall separation performance and economy of the distillation column. Surface-modified structured packing is packed in the critical separation zone above the feed inlet of the rectification section. This zone is the core area for separating light and heavy components during distillation, where the highest separation efficiency is required. The hydrophilic structure of the cross-linked copolymer layer significantly improves the liquid-phase wettability and gas-liquid contact efficiency in this zone, thereby enhancing mass transfer performance and ensuring the separation accuracy of high-purity o-dichlorobenzene. Unmodified structured packing is packed in other areas, reducing overall costs while meeting basic separation requirements. The modular packing unit design facilitates the installation, replacement, and maintenance of the packing. The axial height of each packing unit is controlled between 50-500 mm, ensuring both mechanical strength and installation stability while allowing for flexible combinations based on column diameter and separation requirements. The specific surface area of ​​the corrugated structured packing is controlled between 250-700 m² / m³, ensuring efficient mass transfer while avoiding increased pressure drop and the risk of contamination and blockage due to excessively high specific surface area. The absolute pressure at the top of the column is controlled at 0.5-20 kPa, which lowers the operating temperature, reduces the risk of thermal decomposition of dichlorobenzene, and also lowers energy consumption. The reflux ratio is controlled at 2-6, optimizing energy consumption and equipment scale while ensuring separation efficiency. The reboiler temperature is controlled at 120-190℃, ensuring effective evaporation of o-dichlorobenzene while avoiding thermal decomposition and polymerization side reactions caused by excessively high temperatures.

[0056] N-vinyl-2-pyrrolidone and 2-hydroxyethyl methacrylate (2-HYE) exhibit a synergistic wetting and mass transfer enhancement effect in the crosslinked copolymer layer. The amide group of N-vinyl-2-pyrrolidone possesses strong hydrophilicity and polarity, enabling it to form weak interactions with the chlorine atoms in dichlorobenzene molecules through hydrogen bonding. This promotes rapid and uniform spreading of the liquid phase on the packing surface, significantly reducing the surface tension and contact angle of the liquid phase, thereby improving gas-liquid contact efficiency. The dual hydrophilic groups (hydroxyl and ester) of 2-hydroxyethyl methacrylate further enhance surface wettability. The hydroxyl group can form hydrogen bonds with dichlorobenzene molecules, and the polar structure of the ester group facilitates the selective adsorption of polar components, thus improving separation selectivity. The synergistic arrangement of the two monomers in the polymer chain forms a surface microstructure with gradient wettability, ensuring rapid wetting of the liquid phase while avoiding the risk of flooding caused by excessive hydrophilicity. Ethylene glycol dimethacrylate, used as a crosslinking agent, copolymerizes its dimethacryloyl groups with N-vinyl-2-pyrrolidone and 2-hydroxyethyl methacrylate to form a three-dimensional crosslinked network, significantly improving the mechanical strength, solvent resistance, and heat resistance of the polymer layer. The crosslinked structure restricts the free movement of polymer chain segments, effectively preventing swelling and peeling of the polymer layer under high-temperature organic vapor environments. Simultaneously, the rigid structure of the crosslinked network enhances the selective adsorption capacity of the polymer layer for dichlorobenzene molecules, further improving separation efficiency.

[0057] Beneficial technical effects

[0058] 1. Significantly Improved Low-Pressure Distillation Separation Efficiency: This invention constructs a cross-linked copolymer layer containing N-vinyl-2-pyrrolidone and 2-hydroxyethyl methacrylate structural units on the surface of an alumina ceramic substrate. Utilizing the weak interaction between the hydrophilic groups and dichlorobenzene molecules, it significantly improves the wettability of the packing surface and the uniformity of liquid phase distribution. Even under low-pressure conditions of 0.5-20 kPa absolute pressure at the top of the column, it can still maintain high gas-liquid mass transfer efficiency, ensuring that the purity of the o-dichlorobenzene product consistently reaches over 99.9 wt%. This effectively solves the technical bottleneck of traditional structured packings in achieving both low pressure drop, high throughput, and high separation efficiency.

[0059] 2. Significantly improves the long-term operational stability of the surface-modified layer: This invention introduces ethylene glycol dimethacrylate crosslinking agent to form a three-dimensional crosslinked network structure, and forms a stable Si-O-Al covalent bond with the ceramic matrix surface through silane coupling agent. This enables the crosslinked copolymer layer to exhibit excellent solvent resistance, heat resistance, and shear stability under long-term operation conditions of tower bottom temperature of 120-190℃ and high-temperature organic vapor, effectively preventing coating peeling and performance degradation. After 100-1000 hours of continuous operation, the mass loss of the filler is no more than 5wt%, and the pressure drop increase is no more than 20%, which is significantly better than traditional surface coating fillers.

[0060] 3. Effectively improves the device's resistance to contamination and clogging and maintainability: This invention uses corrugated structured packing with a specific surface area of ​​250-700 m² / m³, which ensures efficient mass transfer while avoiding the risk of contamination and clogging caused by excessively high specific surface area. The smooth and dense surface structure of the cross-linked copolymer layer effectively inhibits the precipitation and adhesion of trace amounts of high-boiling substances and polymers on the packing surface, improving the packing's resistance to crystallization and contamination. At the same time, the modular packing unit design facilitates the installation, replacement, and regeneration maintenance of the packing, ensuring the long-term stable operation of the device.

[0061] 4. Achieving synergistic optimization of separation efficiency and economy: This invention uses partitioned packing of surface-modified structured packing and unmodified structured packing. The high-cost surface-modified packing is concentrated in the key separation area above the feed inlet of the rectification section, while unmodified packing is used in other areas. This significantly reduces the overall cost while ensuring high-purity product quality. At the same time, by optimizing operating parameters such as absolute pressure at the top of the column, reflux ratio, and bottom temperature, a comprehensive balance is achieved in separation efficiency, energy consumption, and equipment scale, thereby improving the economics and industrial application value of the process.

[0062] 5. Expanding the application scope of distillation separation technology: The surface-modified structured packing developed in this invention is not only suitable for the separation of dichlorobenzene isomers, but can also be extended to the distillation separation of other organic isomer mixtures with similar boiling points (such as toluene diisocyanate, xylene isomers, etc.), as well as the separation and purification of heat-sensitive materials that need to be distilled under low pressure or vacuum conditions. It has broad technical promotion value and good market application prospects. Attached Figure Description

[0063] Figure 1 This is the Fourier transform infrared spectrum of the FTIR overlay.

[0064] Figure 2 X-ray photoelectron spectra of XPS-C1s fine spectral overlay.

[0065] Figure 3 X-ray photoelectron spectrum of XPS-O1s fine spectral overlay.

[0066] Figure 4 X-ray photoelectron spectrum of XPS-N1s fine spectral overlay.

[0067] Figure 5 This is the X-ray diffraction pattern of the XRD overlay. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0069] Example 1

[0070] This embodiment provides a distillation separation and purification method for preparing high-purity o-dichlorobenzene, including the following steps:

[0071] S1. A mixture of dichlorobenzene isomers is provided. The dichlorobenzene isomer mixture of this embodiment includes o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene, wherein the mass fraction of o-dichlorobenzene in the dichlorobenzene isomer mixture of this embodiment is 72 wt%.

[0072] S2. The dichlorobenzene isomer mixture of this embodiment is fed into a distillation column for distillation separation. The rectification section of the distillation column of this embodiment is filled with structured packing.

[0073] The structured filler in this embodiment includes an alumina ceramic matrix and a crosslinked copolymer layer located on the surface of the alumina ceramic matrix. The crosslinked copolymer layer contains structural units formed from N-vinyl-2-pyrrolidone, structural units formed from 2-hydroxyethyl methacrylate, and crosslinked structural units formed from ethylene glycol dimethacrylate. The crosslinked copolymer layer in this embodiment forms a covalent bond with the surface of the alumina ceramic matrix via a silane coupling agent. The silane coupling agent in this embodiment is 3-methacryloyloxypropyltrimethoxysilane, which, after hydrolysis, undergoes a condensation reaction with the hydroxyl groups on the ceramic matrix surface to form Si-O-Al bonds.

[0074] The structured packing in this embodiment is prepared through the following steps:

[0075] A1. Raw Material Preparation: An alumina ceramic matrix, ethanol, and deionized water are provided, comprising 100 parts by weight of the alumina ceramic matrix, 600 parts by weight of ethanol, and 600 parts by weight of deionized water. In this embodiment, the alumina ceramic matrix has a honeycomb structure with a pore size of 3 mm and a wall thickness of 0.3 mm. The pore size in this embodiment refers to the hydraulic diameter of the honeycomb channels.

[0076] A2. Cleaning and Drying: The alumina ceramic substrate of this embodiment was sequentially cleaned with ethanol and deionized water according to this embodiment, and then dried. During cleaning, the alumina ceramic substrate was washed three times each with ethanol and deionized water, with a liquid-to-solid ratio of 25 mL / g and a washing time of 15 min each time. The drying conditions were 100℃ and 2.5 h.

[0077] A3. Acid Activation: The dried alumina ceramic substrate of this embodiment was contacted with a 1.0 mol / L hydrochloric acid aqueous solution for acid activation treatment, followed by washing with deionized water and drying. During acid activation, the liquid-to-solid ratio of the hydrochloric acid aqueous solution to the alumina ceramic substrate was 15 mL / g, the treatment temperature was 40°C, and the treatment time was 1.5 h. The acid activation treatment was carried out by immersion. During washing, the substrate was washed three times with deionized water, with a liquid-to-solid ratio of 25 mL / g each time, until the pH of the washing solution reached 7.

[0078] A4. Silanization: The alumina ceramic substrate of this embodiment is contacted with a silanization reaction solution. The silanization reaction solution of this embodiment contains 2.5 parts by mass of 3-methacryloyloxypropyltrimethoxysilane, 275 parts by mass of ethanol, and 27.5 parts by mass of deionized water. A 0.5 mol / L hydrochloric acid aqueous solution is added dropwise under stirring to adjust the pH of the silanization reaction solution to 4.0 for silanization. The liquid-to-solid ratio of the silanization reaction solution to the alumina ceramic substrate during silanization is 15 mL / g, the silanization temperature is 40°C, and the silanization time is 2.0 h. The silanization treatment is carried out by immersion.

[0079] A5. Graft Crosslinking Polymerization: The silanized alumina ceramic matrix obtained in step A4 was contacted with the polymerization reaction solution. In this embodiment, the polymerization reaction solution contained 550 parts by mass of N,N-dimethylformamide, 27.5 parts by mass of N-vinyl-2-pyrrolidone, 15 parts by mass of 2-hydroxyethyl methacrylate, 5 parts by mass of ethylene glycol dimethacrylate, and 0.5 parts by mass of 2,2-azobisisobutyronitrile. Graft crosslinking polymerization was carried out under nitrogen protection. The liquid-to-solid ratio of the polymerization reaction solution to the silanized alumina ceramic matrix was 25 mL / g. The graft crosslinking polymerization was carried out by immersion at 70°C for 5 hours. Nitrogen protection was achieved by evacuating the polymerization reaction solution before polymerization and then purging it with nitrogen three times. An inert atmosphere was maintained throughout the polymerization process at a nitrogen flow rate of 250 mL / min.

[0080] A6. Post-treatment: After the reaction, the material was washed sequentially with ethanol and deionized water, and then dried to obtain the structured packing material of this embodiment. Each washing step involved three washes with ethanol and three washes with deionized water, with a liquid-to-solid ratio of 50 mL / g per wash. The drying conditions were 90°C, 5 kPa absolute pressure, and 7 h drying time, until constant weight was achieved. In this embodiment, constant weight was determined by a 45-minute interval between two consecutive weighings and a mass change not exceeding 0.1 wt%.

[0081] The endpoint criterion for the preparation of the structured filler in this embodiment is as follows: after drying in step A2, the initial mass m0 of the alumina ceramic matrix is ​​weighed, and after drying to constant weight in step A6, the final mass m1 is weighed. The percentage increase in mass is (m1-m0) / m0×100%. When the mass increase of the structured filler relative to the alumina ceramic matrix in this embodiment is 2.5wt%, the preparation is considered complete.

[0082] The thickness of the crosslinked copolymer layer in this embodiment is 175 nm, and the mass increment of the crosslinked copolymer layer relative to the alumina ceramic matrix in this embodiment is 2.5 wt%. The thickness of the crosslinked copolymer layer in this embodiment is determined by observing the cross-section of the ceramic matrix using a scanning electron microscope.

[0083] The structured packing in this embodiment is a corrugated structured packing. The specific surface area of ​​the structured packing in this embodiment is 475 m² / m³, and the structured packing in this embodiment is arranged in the form of modular packing units, with each packing unit having an axial height of 275 mm. The specific surface area of ​​the structured packing in this embodiment is the geometric specific surface area, calculated from the geometric dimensions of the packing.

[0084] S3. The distillation column of this embodiment is operated under the conditions of an absolute pressure of 10 kPa at the top and a reflux ratio of 4, and o-dichlorobenzene product is collected from the bottom of the distillation column of this embodiment, wherein the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product of this embodiment is 99.95 wt%. The reflux ratio of this embodiment is the ratio of the molar flow rate of the reflux liquid after condensation at the top of the column to the molar flow rate of the distillate at the top of the column.

[0085] In this embodiment, the pressure difference between the bottom pressure and the top pressure of the distillation column is 25 kPa, and the bottom temperature of the distillation column is 155°C.

[0086] In this embodiment, the structured packing material accounts for 25% of the effective separation height of the distillation column. The effective separation height is the total packing height of the packing section within the distillation column. The structured packing material is located above the feed inlet, and the rectification section is the column section located above the feed inlet. The distillation column also contains unmodified structured packing material, which is an alumina ceramic matrix structured packing material without the crosslinked copolymer layer described in this embodiment. Furthermore, a light component distillate is collected from the top of the distillation column, and the total mass fraction of intermediate dichlorobenzene and para-dichlorobenzene in the light component distillate is 90 wt%.

[0087] The distillation column in this embodiment has 60 theoretical plates, and the HETP (Heat Equal Plate) packing height is 0.5m. The feed point is located at 50% of the effective separation height of the distillation column, and the height in this embodiment is measured downwards along the column axis from the top. The mass ratio of the top product to the bottom product is 1:2.

[0088] In this embodiment, the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product was determined by gas chromatography and calculated using the area normalization method. After continuous operation for 500 hours in a dichlorobenzene vapor environment at 150°C, the modified structured packing material in this embodiment showed a mass loss of 2.5 wt% and a pressure drop increase of 10%.

[0089] Features of this embodiment: This embodiment uses moderate parameter configurations. The o-dichlorobenzene content in the raw material is 72wt%, the mass increment of the cross-linked copolymer layer is 2.5wt%, the thickness is 175nm, and the specific surface area of ​​the structured packing is 475m² / m³. The distillation operation uses moderate conditions: absolute pressure at the top of the column is 10kPa, reflux ratio is 4, and the bottom temperature is 155℃. The modified packing accounts for 25% of the total load, with 60 theoretical plates and a HETP depth of 0.5m. This embodiment features conservative and stable parameter selection, mild process conditions, a wide operating window, and good reproducibility. It is suitable for the routine separation and purification of medium-purity raw materials, and is particularly applicable to industrial production scenarios requiring high product quality stability and long-term continuous operation.

[0090] Example 2

[0091] This embodiment provides a distillation separation and purification method for preparing high-purity o-dichlorobenzene, including the following steps:

[0092] S1. A mixture of dichlorobenzene isomers is provided. The dichlorobenzene isomer mixture of this embodiment includes o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene, wherein the mass fraction of o-dichlorobenzene in the dichlorobenzene isomer mixture of this embodiment is 85 wt%.

[0093] S2. The dichlorobenzene isomer mixture of this embodiment is fed into a distillation column for distillation separation. The rectification section of the distillation column of this embodiment is filled with structured packing.

[0094] The structured filler in this embodiment includes an alumina ceramic matrix and a cross-linked copolymer layer located on the surface of the alumina ceramic matrix. The cross-linked copolymer layer contains structural units formed from N-vinyl-2-pyrrolidone, structural units formed from 2-hydroxyethyl methacrylate, and cross-linked structural units formed from ethylene glycol dimethacrylate. The cross-linked copolymer layer in this embodiment forms a covalent bond with the surface of the alumina ceramic matrix via a silane coupling agent. The silane coupling agent in this embodiment is 3-methacryloyloxypropyltrimethoxysilane, which, after hydrolysis, undergoes a condensation reaction with the hydroxyl groups on the ceramic matrix surface to form Si-O-Al bonds.

[0095] The structured packing in this embodiment is prepared through the following steps:

[0096] A1. Raw material preparation: An alumina ceramic matrix, ethanol, and deionized water are provided, comprising 100 parts by weight of the alumina ceramic matrix, 800 parts by weight of the ethanol, and 800 parts by weight of the deionized water. In this embodiment, the alumina ceramic matrix has a honeycomb structure with a pore size of 2 mm and a wall thickness of 0.2 mm. The pore size in this embodiment refers to the hydraulic diameter of the honeycomb channels.

[0097] A2. Cleaning and Drying: The alumina ceramic substrate of this embodiment was sequentially cleaned with ethanol and deionized water according to this embodiment, and then dried. During cleaning, the alumina ceramic substrate was washed four times each with ethanol and deionized water, with a liquid-to-solid ratio of 35 mL / g each time, and a washing time of 20 min each time. The drying conditions were 110℃ and the drying time was 3 h.

[0098] A3. Acid Activation: The dried alumina ceramic substrate of this embodiment was contacted with a 1.5 mol / L hydrochloric acid aqueous solution for acid activation treatment, followed by washing with deionized water and drying. During acid activation, the liquid-to-solid ratio of the hydrochloric acid aqueous solution to the alumina ceramic substrate was 20 mL / g, the treatment temperature was 50°C, and the treatment time was 2 hours. The acid activation treatment was carried out by immersion. The substrate was washed four times with deionized water, with a liquid-to-solid ratio of 35 mL / g each time, until the pH of the washing solution reached 7.

[0099] A4. Silanization: The alumina ceramic substrate of this embodiment is contacted with a silanization reaction solution. The silanization reaction solution of this embodiment contains 4.0 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 400 parts by weight of ethanol, and 40 parts by weight of deionized water. A 1.0 mol / L hydrochloric acid aqueous solution is added dropwise under stirring to adjust the pH of the silanization reaction solution to 3.5 for silanization. The liquid-to-solid ratio of the silanization reaction solution to the alumina ceramic substrate is 20 mL / g, the silanization temperature is 50°C, and the silanization time is 3 hours. The silanization treatment is carried out by immersion.

[0100] A5. Graft Crosslinking Polymerization: The silanized alumina ceramic matrix obtained in step A4 was contacted with the polymerization reaction solution. In this embodiment, the polymerization reaction solution contained 800 parts by mass of N,N-dimethylformamide, 40 parts by mass of N-vinyl-2-pyrrolidone, 24 parts by mass of 2-hydroxyethyl methacrylate, 8 parts by mass of ethylene glycol dimethacrylate, and 0.8 parts by mass of 2,2-azobisisobutyronitrile. Graft crosslinking polymerization was carried out under nitrogen protection. The liquid-to-solid ratio of the polymerization reaction solution to the silanized alumina ceramic matrix was 35 mL / g. The graft crosslinking polymerization was carried out by immersion at 80°C for 6 hours. Nitrogen protection was achieved by evacuating the polymerization reaction solution and then purging it with nitrogen four times before the polymerization reaction, and maintaining an inert atmosphere at a nitrogen flow rate of 400 mL / min throughout the polymerization process.

[0101] A6. Post-treatment: After the reaction, the material was washed sequentially with ethanol and deionized water, and then dried to obtain the structured packing material of this embodiment. Each washing step involved four washes with ethanol and four washes with deionized water, with a liquid-to-solid ratio of 75 mL / g per wash. The drying conditions were 100°C, 2 kPa absolute pressure, and 10 h, until constant weight was achieved. In this embodiment, constant weight was determined by a 50-minute interval between two consecutive weighings and a mass change not exceeding 0.1 wt%.

[0102] The endpoint criterion for the preparation of the structured filler in this embodiment is as follows: after drying in step A2, the initial mass m0 of the alumina ceramic matrix is ​​weighed, and after drying to constant weight in step A6, the final mass m1 is weighed. The percentage of mass increment is (m1-m0) / m0×100%. When the mass increment of the structured filler relative to the alumina ceramic matrix in this embodiment is 4.0wt%, the preparation is considered complete.

[0103] The thickness of the crosslinked copolymer layer in this embodiment is 250 nm, and the mass increment of the crosslinked copolymer layer relative to the alumina ceramic matrix in this embodiment is 4.0 wt%. The thickness of the crosslinked copolymer layer in this embodiment is determined by observing the cross-section of the ceramic matrix using a scanning electron microscope.

[0104] The structured packing in this embodiment is a corrugated structured packing. The specific surface area of ​​the structured packing in this embodiment is 600 m² / m³, and the structured packing in this embodiment is arranged in the form of modular packing units, with each packing unit having an axial height of 400 mm. The specific surface area of ​​the structured packing in this embodiment is the geometric specific surface area, calculated from the geometric dimensions of the packing.

[0105] S3. The distillation column of this embodiment is operated under the conditions of an absolute pressure of 5 kPa at the top and a reflux ratio of 5, and o-dichlorobenzene product is collected from the bottom of the distillation column of this embodiment, wherein the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product of this embodiment is 99.96 wt%. The reflux ratio of this embodiment is the ratio of the molar flow rate of the reflux liquid after condensation at the top of the column to the molar flow rate of the distillate at the top of the column.

[0106] In this embodiment, the pressure difference between the bottom pressure and the top pressure of the distillation column is 15 kPa, and the bottom temperature of the distillation column is 145°C.

[0107] In this embodiment, the structured packing material accounts for 32% of the effective separation height of the distillation column. The effective separation height is the total packing height of the packing section within the distillation column. The structured packing material is located above the feed inlet, and the rectification section is the column section located above the feed inlet. The distillation column also contains unmodified structured packing material, which is an alumina ceramic matrix structured packing material without the crosslinked copolymer layer described in this embodiment. Furthermore, a light component distillate is collected from the top of the distillation column, and the total mass fraction of intermediate dichlorobenzene and para-dichlorobenzene in the light component distillate is 95 wt%.

[0108] The distillation column in this embodiment has 80 theoretical plates, and the HETP (Heat Equal Plate) packing height is 0.3m. The feed position is located at 60% of the effective separation height of the distillation column, and the height in this embodiment is measured downwards along the column axis from the top. The mass ratio of the top product to the bottom product is 1:3.

[0109] In this embodiment, the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product was determined by gas chromatography and calculated using the area normalization method. After continuous operation for 800 hours in a dichlorobenzene vapor environment at 145°C, the modified structured packing material in this embodiment showed a mass loss of 3.2 wt% and a pressure drop increase of 12%.

[0110] Features of this embodiment: This embodiment employs parameter configurations with a high grafting rate and high separation efficiency. The feedstock contains 85 wt% o-dichlorobenzene, the cross-linked copolymer layer has a mass increment of 4.0 wt% and a thickness of 250 nm, the structured packing has a specific surface area of ​​600 m² / m³, and a pore size of 2 mm. The distillation operation utilizes conditions of a relatively low absolute pressure at the top of the column (5 kPa), a relatively high reflux ratio (5), and a relatively low bottom temperature (145°C). The modified packing accounts for 32% of the total load, with 80 theoretical plates and a HETP depth of 0.3 m. This embodiment achieves higher separation efficiency and product purity through a thicker cross-linked copolymer layer, a larger specific surface area, and a lower operating pressure. It is suitable for processing feedstocks with high o-dichlorobenzene content, and is particularly applicable to fine chemical production scenarios with extremely high product purity requirements, a pursuit of high separation efficiency, and relatively sufficient energy consumption.

[0111] Example 3

[0112] This embodiment provides a distillation separation and purification method for preparing high-purity o-dichlorobenzene, including the following steps:

[0113] S1. A mixture of dichlorobenzene isomers is provided. The dichlorobenzene isomer mixture of this embodiment includes o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene, wherein the mass fraction of o-dichlorobenzene in the dichlorobenzene isomer mixture of this embodiment is 60 wt%.

[0114] S2. The dichlorobenzene isomer mixture of this embodiment is fed into a distillation column for distillation separation. The rectification section of the distillation column of this embodiment is filled with structured packing.

[0115] The structured filler in this embodiment includes an alumina ceramic matrix and a cross-linked copolymer layer located on the surface of the alumina ceramic matrix. The cross-linked copolymer layer contains structural units formed from N-vinyl-2-pyrrolidone, structural units formed from 2-hydroxyethyl methacrylate, and cross-linked structural units formed from ethylene glycol dimethacrylate. The cross-linked copolymer layer in this embodiment forms a covalent bond with the surface of the alumina ceramic matrix via a silane coupling agent. The silane coupling agent in this embodiment is 3-methacryloyloxypropyltrimethoxysilane, which, after hydrolysis, undergoes a condensation reaction with the hydroxyl groups on the ceramic matrix surface to form Si-O-Al bonds.

[0116] The structured packing in this embodiment is prepared through the following steps:

[0117] A1. Raw material preparation: An alumina ceramic matrix, ethanol, and deionized water are provided, comprising 100 parts by weight of the alumina ceramic matrix, 400 parts by weight of ethanol, and 400 parts by weight of deionized water. In this embodiment, the alumina ceramic matrix has a honeycomb structure with a pore size of 4 mm and a wall thickness of 0.4 mm. The pore size in this embodiment refers to the hydraulic diameter of the honeycomb channels.

[0118] A2. Cleaning and Drying: The alumina ceramic substrate of this embodiment was sequentially cleaned with ethanol and deionized water according to this embodiment, and then dried. During cleaning, the alumina ceramic substrate was washed twice each with ethanol and deionized water, with a liquid-to-solid ratio of 15 mL / g each time, and a washing time of 10 min each time. The drying conditions were 90℃ and the drying time was 2 h.

[0119] A3. Acid Activation: The dried alumina ceramic substrate of this embodiment was contacted with a 0.5 mol / L hydrochloric acid aqueous solution for acid activation treatment, followed by washing with deionized water and drying. During acid activation, the liquid-to-solid ratio of the hydrochloric acid aqueous solution to the alumina ceramic substrate was 10 mL / g, the treatment temperature was 30°C, and the treatment time was 1 h. The acid activation treatment was carried out by immersion. During washing, the substrate was washed three times with deionized water, with a liquid-to-solid ratio of 15 mL / g each time, until the pH of the washing solution reached 7.

[0120] A4. Silanization: The alumina ceramic substrate of this embodiment is contacted with a silanization reaction solution. The silanization reaction solution of this embodiment contains 1.5 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 150 parts by weight of ethanol, and 15 parts by weight of deionized water. A 0.5 mol / L hydrochloric acid aqueous solution is added dropwise under stirring to adjust the pH of the silanization reaction solution to 4.5 for silanization. The liquid-to-solid ratio of the silanization reaction solution to the alumina ceramic substrate is 10 mL / g, the silanization temperature is 30°C, and the silanization time is 1.5 h. The silanization treatment is carried out by immersion.

[0121] A5. Graft Crosslinking Polymerization: The silanized alumina ceramic matrix obtained in step A4 was contacted with the polymerization reaction solution. In this embodiment, the polymerization reaction solution contained 300 parts by mass of N,N-dimethylformamide, 15 parts by mass of N-vinyl-2-pyrrolidone, 8 parts by mass of 2-hydroxyethyl methacrylate, 2 parts by mass of ethylene glycol dimethacrylate, and 0.2 parts by mass of 2,2-azobisisobutyronitrile. Graft crosslinking polymerization was carried out under nitrogen protection. The liquid-to-solid ratio of the polymerization reaction solution to the silanized alumina ceramic matrix was 15 mL / g. The graft crosslinking polymerization was carried out by immersion at a reaction temperature of 60°C for 3 hours. Nitrogen protection was achieved by evacuating the polymerization reaction solution before polymerization and then purging it with nitrogen twice. An inert atmosphere was maintained throughout the polymerization process at a nitrogen flow rate of 100 mL / min.

[0122] A6. Post-treatment: After the reaction, the material was washed sequentially with ethanol and deionized water, and then dried to obtain the structured packing material of this embodiment. During washing, the material was washed twice with ethanol and twice with deionized water, with a liquid-to-solid ratio of 30 mL / g each time. The drying conditions were 80°C, absolute pressure 8 kPa, and drying time 4 h, until constant weight was achieved. The constant weight criterion in this embodiment was that the mass change between two consecutive weighings was no more than 0.1 wt% within a 40-minute interval.

[0123] The endpoint criterion for the preparation of the structured filler in this embodiment is as follows: after drying in step A2, the initial mass m0 of the alumina ceramic matrix is ​​obtained by weighing, and after drying to constant weight in step A6, the final mass m1 is obtained by weighing. The percentage of mass increment is (m1-m0) / m0×100%. When the mass increment of the structured filler in this embodiment relative to the alumina ceramic matrix in this embodiment is 1.0wt%, the preparation is considered complete.

[0124] The thickness of the crosslinked copolymer layer in this embodiment is 100 nm, and the mass increment of the crosslinked copolymer layer relative to the alumina ceramic matrix in this embodiment is 1.0 wt%. The thickness of the crosslinked copolymer layer in this embodiment is determined by observing the cross-section of the ceramic matrix using a scanning electron microscope.

[0125] The structured packing in this embodiment is corrugated structured packing. The specific surface area of ​​the structured packing in this embodiment is 350 m² / m³, and the structured packing in this embodiment is arranged in the form of modular packing units, with each packing unit having an axial height of 150 mm. The specific surface area of ​​the structured packing in this embodiment is the geometric specific surface area, calculated from the geometric dimensions of the packing.

[0126] S3. The distillation column of this embodiment is operated under the conditions of an absolute pressure of 15 kPa at the top and a reflux ratio of 3, and o-dichlorobenzene product is collected from the bottom of the distillation column of this embodiment, wherein the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product of this embodiment is 99.92 wt%. The reflux ratio of this embodiment is the ratio of the molar flow rate of the reflux liquid after condensation at the top of the column to the molar flow rate of the distillate at the top of the column.

[0127] In this embodiment, the pressure difference between the bottom pressure and the top pressure of the distillation column is 35 kPa, and the bottom temperature of the distillation column is 170°C.

[0128] In this embodiment, the structured packing material accounts for 15% of the effective separation height of the distillation column. The effective separation height is the total packing height of the packing section within the distillation column. The structured packing material is located above the feed inlet, and the rectification section is the column section located above the feed inlet. The distillation column also contains unmodified structured packing material, which is an alumina ceramic matrix structured packing material without the crosslinked copolymer layer described in this embodiment. Furthermore, a light component distillate is collected from the top of the distillation column, and the total mass fraction of intermediate dichlorobenzene and para-dichlorobenzene in the light component distillate is 85 wt%.

[0129] The distillation column in this embodiment has 40 theoretical plates, and the HETP (Heat Equal Plate) packing height is 0.7m. The feed position is located at 40% of the effective separation height of the distillation column, and the height in this embodiment is measured downwards along the column axis from the top. The mass ratio of the top product to the bottom product is 2:1.

[0130] In this embodiment, the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product was determined by gas chromatography and calculated using the area normalization method. After continuous operation for 300 hours in a dichlorobenzene vapor environment at 170°C, the modified structured packing material in this embodiment showed a mass loss of 1.8 wt% and an increase in pressure drop of 8%.

[0131] Features of this embodiment: This embodiment employs a low grafting amount and economical parameter configuration. The o-dichlorobenzene content in the raw material is 60wt%, the mass increment of the cross-linked copolymer layer is 1.0wt%, the thickness is 100nm, the specific surface area of ​​the structured packing is 350m² / m³, and the pore size is 4mm. The distillation operation uses a relatively high absolute pressure at the top of the column (15kPa), a relatively low reflux ratio (3), and a relatively high bottom temperature (170℃). The modified packing accounts for 15% of the total load, with 40 theoretical plates and a HETP depth of 0.7m. This embodiment reduces the packing preparation cost through a thinner cross-linked copolymer layer and milder preparation conditions. Simultaneously, the use of higher operating pressure and temperature reduces distillation energy consumption. It is suitable for processing raw materials with low o-dichlorobenzene content, and is particularly applicable to large-scale chemical production scenarios where cost is sensitive, economic efficiency is paramount, and product purity requirements must meet standards.

[0132] Example 4

[0133] This embodiment provides a distillation separation and purification method for preparing high-purity o-dichlorobenzene, including the following steps:

[0134] S1. A mixture of dichlorobenzene isomers is provided. The dichlorobenzene isomer mixture of this embodiment includes o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene, wherein the mass fraction of o-dichlorobenzene in the dichlorobenzene isomer mixture of this embodiment is 55 wt%.

[0135] S2. The dichlorobenzene isomer mixture of this embodiment is fed into a distillation column for distillation separation. The rectification section of the distillation column of this embodiment is filled with structured packing.

[0136] The structured filler in this embodiment includes an alumina ceramic matrix and a cross-linked copolymer layer located on the surface of the alumina ceramic matrix. The cross-linked copolymer layer contains structural units formed from N-vinyl-2-pyrrolidone, structural units formed from 2-hydroxyethyl methacrylate, and cross-linked structural units formed from ethylene glycol dimethacrylate. The cross-linked copolymer layer in this embodiment forms a covalent bond with the surface of the alumina ceramic matrix via a silane coupling agent. The silane coupling agent in this embodiment is 3-methacryloyloxypropyltrimethoxysilane, which, after hydrolysis, undergoes a condensation reaction with the hydroxyl groups on the ceramic matrix surface to form Si-O-Al bonds.

[0137] The structured packing in this embodiment is prepared through the following steps:

[0138] A1. Raw material preparation: An alumina ceramic matrix, ethanol, and deionized water are provided, comprising 100 parts by weight of the alumina ceramic matrix, 300 parts by weight of the ethanol, and 300 parts by weight of the deionized water. In this embodiment, the alumina ceramic matrix has a honeycomb structure with a pore size of 1.5 mm and a wall thickness of 0.15 mm. The pore size in this embodiment refers to the hydraulic diameter of the honeycomb channels.

[0139] A2. Cleaning and Drying: The alumina ceramic substrate of this embodiment was sequentially cleaned with ethanol and deionized water according to this embodiment, and then dried. During cleaning, the alumina ceramic substrate was washed twice each with ethanol and deionized water, with a liquid-to-solid ratio of 10 mL / g each time, and a washing time of 5 min each time. The drying conditions were 85℃ and the drying time was 1.5 h.

[0140] A3. Acid Activation: The dried alumina ceramic substrate of this embodiment was contacted with a 0.2 mol / L hydrochloric acid aqueous solution for acid activation treatment, followed by washing with deionized water and drying. During acid activation, the liquid-to-solid ratio of the hydrochloric acid aqueous solution to the alumina ceramic substrate was 8 mL / g, the treatment temperature was 25°C, and the treatment time was 0.8 h. The acid activation treatment was carried out by immersion. The substrate was washed twice with deionized water, with a liquid-to-solid ratio of 10 mL / g each time, until the pH of the washing solution reached 7.

[0141] A4. Silanization: The alumina ceramic substrate of this embodiment is contacted with a silanization reaction solution. The silanization reaction solution of this embodiment contains 0.8 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 100 parts by weight of ethanol, and 8 parts by weight of deionized water. A 0.5 mol / L hydrochloric acid aqueous solution is added dropwise under stirring to adjust the pH of the silanization reaction solution to 3.2 for silanization. The liquid-to-solid ratio of the silanization reaction solution to the alumina ceramic substrate is 8 mL / g, the silanization temperature is 25°C, and the silanization time is 1 h. The silanization treatment is carried out by immersion.

[0142] A5. Graft Crosslinking Polymerization: The silanized alumina ceramic matrix obtained in step A4 is contacted with the polymerization reaction solution. In this embodiment, the polymerization reaction solution contains 200 parts by mass of N,N-dimethylformamide, 10 parts by mass of N-vinyl-2-pyrrolidone, 3 parts by mass of 2-hydroxyethyl methacrylate, 0.5 parts by mass of ethylene glycol dimethacrylate, and 0.1 parts by mass of 2,2-azobisisobutyronitrile. Graft crosslinking polymerization is carried out under nitrogen protection. The liquid-to-solid ratio of the polymerization reaction solution to the silanized alumina ceramic matrix is ​​10 mL / g. The graft crosslinking polymerization is carried out by immersion at a reaction temperature of 55°C for 3 hours. Nitrogen protection is achieved by evacuating the polymerization reaction solution before polymerization and then purging it with nitrogen twice. An inert atmosphere is maintained throughout the polymerization process at a nitrogen flow rate of 50 mL / min.

[0143] A6. Post-treatment: After the reaction, the material was washed sequentially with ethanol and deionized water, and then dried to obtain the structured packing material of this embodiment. Each washing step involved two washes with ethanol and two washes with deionized water, with a liquid-to-solid ratio of 15 mL / g per wash. The drying conditions were 65°C, 1 kPa absolute pressure, and 3 h drying time, until constant weight was achieved. In this embodiment, constant weight was determined by a 35-minute interval between two consecutive weighings and a mass change not exceeding 0.1 wt%.

[0144] The endpoint criterion for the preparation of the structured filler in this embodiment is as follows: after drying in step A2, the initial mass m0 of the alumina ceramic matrix is ​​weighed, and after drying to constant weight in step A6, the final mass m1 is weighed. The percentage of mass increment is (m1-m0) / m0×100%. When the mass increment of the structured filler in this embodiment relative to the alumina ceramic matrix in this embodiment is 0.5wt%, the preparation is considered complete.

[0145] The thickness of the crosslinked copolymer layer in this embodiment is 75 nm, and the mass increment of the crosslinked copolymer layer relative to the alumina ceramic matrix in this embodiment is 0.5 wt%. The thickness of the crosslinked copolymer layer in this embodiment is determined by observing the cross-section of the ceramic matrix using a scanning electron microscope.

[0146] The structured packing in this embodiment is a corrugated structured packing. The specific surface area of ​​the structured packing in this embodiment is 280 m² / m³, and the structured packing in this embodiment is arranged in the form of modular packing units, with each packing unit having an axial height of 100 mm. The specific surface area of ​​the structured packing in this embodiment is the geometric specific surface area, calculated from the geometric dimensions of the packing.

[0147] S3. The distillation column of this embodiment is operated under the conditions of an absolute pressure of 2 kPa at the top and a reflux ratio of 2.5, and o-dichlorobenzene product is collected from the bottom of the distillation column of this embodiment, wherein the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product of this embodiment is 99.90 wt%. The reflux ratio of this embodiment is the ratio of the molar flow rate of the reflux liquid after condensation at the top of the column to the molar flow rate of the distillate at the top of the column.

[0148] In this embodiment, the pressure difference between the bottom pressure and the top pressure of the distillation column is 8 kPa, and the bottom temperature of the distillation column is 135°C.

[0149] In this embodiment, the structured packing material accounts for 12% of the effective separation height of the distillation column. The effective separation height is the total packing height of the packing section within the distillation column. The structured packing material is located above the feed inlet, and the rectification section is the column section located above the feed inlet. The distillation column also contains unmodified structured packing material, which is an alumina ceramic matrix structured packing material without the crosslinked copolymer layer described in this embodiment. Furthermore, a light component distillate is collected from the top of the distillation column, and the total mass fraction of intermediate dichlorobenzene and para-dichlorobenzene in the light component distillate is 82 wt%.

[0150] The distillation column in this embodiment has 25 theoretical plates, and the HETP (Heat Equal Plate) packing height is 0.2 m. The feed position is located at 35% of the effective separation height of the distillation column, and the height in this embodiment is measured downwards along the column axis from the top. The mass ratio of the top product to the bottom product is 1:4.

[0151] In this embodiment, the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product was determined by gas chromatography and calculated using the area normalization method. After continuous operation for 200 hours in a dichlorobenzene vapor environment at 135°C, the modified structured packing material in this embodiment showed a mass loss of 0.8 wt% and a pressure drop increase of 5%.

[0152] Features of this embodiment: This embodiment uses parameter configurations close to the lower limit of the technical solution. The o-dichlorobenzene content in the raw material is 55wt%, the mass increment of the crosslinked copolymer layer is 0.5wt%, the thickness is 75nm, the specific surface area of ​​the structured packing is 280m² / m³, and the pore size of the alumina ceramic matrix is ​​1.5mm and the wall thickness is 0.15mm. The distillation operation uses conditions of 2kPa absolute pressure at the top of the column, reflux ratio of 2.5, bottom temperature of 135℃, and pressure difference between the bottom and top of the column of 8kPa. The modified packing accounts for 12% of the total height, with 25 theoretical plates, a HETP height of 0.2m, and a packing unit height of 100mm. In this embodiment, the hydrochloric acid concentration is 0.2mol / L, the silane coupling agent dosage is 0.8 parts by mass, the N,N-dimethylformamide dosage is 200 parts by mass, and the ethanol and deionized water dosages are 300 parts by mass each, all of which are near the lower limit of the technical solution. This embodiment fully verifies the feasibility of the technical solution in the lower limit range of parameters and the ability to ensure product quality by selecting smaller pore size and wall thickness, lower grafting amount, lower absolute pressure and reflux ratio at the top of the column, shorter packing unit, and less modified packing filling ratio. At the same time, by using lower HETP and lower column bottom temperature, it achieves efficient and low-consumption separation, which is suitable for processing raw materials with low o-dichlorobenzene content. It is particularly suitable for vacuum distillation systems, special process scenarios that require low-temperature separation to protect heat-sensitive materials, and where the depth of packing modification is not high but product quality must still be guaranteed.

[0153] Comparative Example 1: Basically the same as Example 1, except that the mass increment of the crosslinked copolymer layer is 0.15 wt%, while the amounts of other components and preparation conditions remain unchanged.

[0154] Comparative Example 2: It is basically the same as Example 1, except that the mass increment of the crosslinked copolymer layer is 5.5 wt%, while the amounts of other components and preparation conditions remain unchanged.

[0155] Comparative Example 3: It is basically the same as Example 1, except that the structured filler is not surface modified and the alumina ceramic matrix is ​​used directly as the structured filler. It does not contain a crosslinked copolymer layer, and other conditions remain unchanged.

[0156] Comparative Example 4: Basically the same as Example 1, except that the polymerization reaction solution in step A5 does not contain 2-hydroxyethyl methacrylate, but only contains 550 parts by mass of N,N-dimethylformamide, 27.5 parts by mass of N-vinyl-2-pyrrolidone, 5 parts by mass of ethylene glycol dimethacrylate and 0.5 parts by mass of 2,2-azobisisobutyronitrile, with other conditions remaining unchanged.

[0157] Comparative Example 5: Basically the same as Example 1, except that the polymerization reaction solution in step A5 does not contain ethylene glycol dimethacrylate, but only contains 550 parts by mass of N,N-dimethylformamide, 27.5 parts by mass of N-vinyl-2-pyrrolidone, 15 parts by mass of 2-hydroxyethyl methacrylate and 0.5 parts by mass of 2,2-azobisisobutyronitrile. The surface layer prepared is a linear copolymer layer rather than a cross-linked structure. Other conditions remain unchanged.

[0158] Comparative Example 6: It is basically the same as Example 1, except that the absolute pressure at the top of the distillation column is 25 kPa, and other conditions remain unchanged.

[0159] Comparative Example 7: Basically the same as Example 1, except that the reflux ratio is 1.5, and other conditions remain unchanged.

[0160] Comparative Example 8: It is basically the same as Example 1, except that the packing height of the structured packing in the distillation column accounts for 5% of the effective separation height of the distillation column, while other conditions remain unchanged.

[0161] Performance testing:

[0162] Test Subject: Purity determination of o-dichlorobenzene product. Test Objective: To evaluate the purity and impurity content of o-dichlorobenzene product after distillation separation. Test Principle: Based on the principle of gas chromatography separation, dichlorobenzene isomers with different boiling points have different retention times in the chromatographic column. The content of each component is quantitatively calculated using the peak area normalization method. Experimental Method: A gas chromatograph was used with a DB-5 capillary column (30m × 0.32mm × 0.25μm). High-purity nitrogen was used as the carrier gas, with a flow rate of 1.2mL / min, a split ratio of 20:1, an injection port temperature of 250℃, and a programmed column temperature ramp (initial temperature 80℃, held for 2 min, then increased to 180℃ at 10℃ / min and held for 5 min). The FID detector temperature was 280℃, and the injection volume was 0.2μL. Key Parameters: Test temperature 25℃, sample dilution factor 100-fold, and three parallel determinations. Data Processing: The mass fraction of o-dichlorobenzene was calculated using the area normalization method, and the results are expressed as mean ± standard deviation.

[0163] Test Subject: Evaluation of mass transfer performance of modified structured packing. Test Objective: To evaluate the enhancing effect of the cross-linked copolymer layer on the mass transfer efficiency of the packing. Test Principle: Mass transfer efficiency is characterized by measuring the height of the equal plate (HETP) of the packing; a smaller HETP indicates higher mass transfer efficiency. Experimental Method: Modified structured packing was packed into a 50mm inner diameter glass distillation column. An ethanol-water system (mass ratio 1:1) was used as the test system. After stable operation for 2 hours under normal pressure and a reflux ratio of 3, samples were collected from the top, inlet, and bottom of the column. The composition at each point was determined by gas chromatography. The theoretical plate number N was calculated according to the Fenske equation: HETP = packing height / N. Key Parameters: Test pressure 101.3 kPa, feed flow rate 500 mL / h, reflux ratio 3, test time 4 hours. Data Processing: Three parallel measurements were performed, and the mean ± standard deviation of HETP was calculated.

[0164] Test Object: Pressure drop performance determination of modified structured packing. Test Objective: To evaluate the fluid resistance characteristics of the packing under distillation operating conditions. Test Principle: Under specific gas-liquid loads, the pressure difference between the upper and lower ends of the packing layer is measured to characterize the packing's resistance to gas-liquid two-phase flow. Experimental Method: Modified structured packing with a height of 500 mm is packed into a distillation column with an inner diameter of 100 mm. Using air-water as a simulated system, the pressure difference between the two ends of the packing layer is measured using a U-tube manometer under different gas velocities (0.5-2.5 m / s) and liquid spray densities (5-20 m³ / m²·h). The test temperature is 25℃, and readings are taken after the system has been running stably for 30 minutes. Key Parameters: Packing height 500 mm, gas velocity range 0.5-2.5 m / s, liquid spray density 5-20 m³ / m²·h, test temperature 25±2℃. Data Processing: Each operating condition is measured in triplicate. The pressure drop per unit packing height (Pa / m) is calculated, and the results are expressed as mean ± standard deviation.

[0165] Test Object: Solvent resistance stability evaluation of cross-linked copolymer layers. Test Objective: To investigate the mass retention rate and structural stability of the modified layer under high-temperature organic solvent conditions. Test Principle: The mass loss rate and performance degradation of the modified packing were determined through a long-term immersion experiment simulating distillation conditions. Experimental Method: The modified structured packing was continuously operated in a 150℃ dichlorobenzene vapor reflux environment. Samples were taken periodically (every 100 hours) for weighing and mass transfer performance measurement until a cumulative operating time of 1000 hours was reached. Mass loss rate = (m0 - m...) t ) / m0×100%, where m0 is the initial mass, m t The mass loss rate is measured after t hours of operation. The HETP change rate and pressure drop increase rate are measured simultaneously. Key parameters: test temperature 150℃, test medium dichlorobenzene vapor, test cycle 1000 hours, sampling interval 100 hours. Data processing: Three samples are measured in parallel for each sampling, and the mean ± standard deviation of the mass loss rate, HETP change rate, and pressure drop increase rate are calculated.

[0166] Test Object: Characterization of the thickness and uniformity of the cross-linked copolymer layer. Test Objective: To evaluate the microstructure and thickness distribution of the surface-modified layer. Test Principle: High-resolution imaging of the modified filler cross-section using a scanning electron microscope (SEM) to directly observe the thickness of the cross-linked copolymer layer. Experimental Method: Fresh cross-sections of the modified structured filler samples were prepared by liquid nitrogen embrittlement, sputter-coated with gold, and then observed under an SEM. Accelerating voltage: 15 kV; working distance: 10 mm; magnification: 5000-20000x; thickness of the cross-linked copolymer layer was measured at 10 randomly selected locations. Key Parameters: Accelerating voltage: 15 kV; working distance: 10 mm; magnification: 10000x; number of measurement locations: 10. Data Processing: The mean thickness ± standard deviation of the 10 measurement points was calculated, and the relative standard deviation (RSD) was calculated to evaluate uniformity.

[0167] Test Subject: Comprehensive evaluation of the separation efficiency of a distillation column. Test Objective: To evaluate the separation and purification effect and energy consumption level of the method of this invention under actual operating conditions. Test Principle: Through material balance and energy balance, the product yield, energy consumption, and separation efficiency of the distillation separation process are comprehensively evaluated. Experimental Method: A mixture of dichlorobenzene isomers is continuously fed into a distillation column packed with modified structured packing. After 8 hours of stable operation, samples of the light component at the top of the column and the o-dichlorobenzene product at the bottom are collected. The composition is determined by gas chromatography, and the o-dichlorobenzene yield, separation factor, and energy consumption per unit product are calculated. Yield = (mass of o-dichlorobenzene in the bottom product / mass of o-dichlorobenzene in the feed) × 100%; Separation Factor = (purity of o-dichlorobenzene at the bottom × purity of impurities at the top) / (purity of impurities at the bottom × purity of o-dichlorobenzene at the top). Key Parameters: Stable feed flow rate, reflux ratio 4, absolute pressure at the top of the column 10 kPa, bottom temperature 155℃, and stable operation time 8 hours. Data processing: Three batches were measured in parallel, and the average ± standard deviation of yield, separation factor, and energy consumption per unit product were calculated.

[0168] Figure 1 The Fourier transform infrared spectra are obtained from FTIR overlays. The fixed parameters are that the matrix material and testing conditions are consistent, and the spectra all use the same wavenumber range and normalization method. The varying parameters are that the sample types are Example 1, Comparative Example 4 (lacking 2-HEMA), and Comparative Example 5 (lacking EGDMA). Example 1 was analyzed at 3300 cm⁻¹. -1 The nearby hydroxyl stretching vibration region is at 1730 cm. -1 The C=O characteristic region near the ester group exhibits a more complete and stronger absorption feature, while the absorption range from 1100 to 1250 cm⁻¹ is also higher. -1 The more pronounced C–O–C correlation absorption indicates that the key oxygen-containing functional groups are introduced more fully and the structure is more complete. The corresponding characteristic peaks of Comparative Examples 4 and 5 are weakened or the morphology is incomplete, proving that the chemical structure construction of Example 1 is more in line with the design goal and consistent with the subsequent surface element results.

[0169] Figure 2 The X-ray photoelectron spectroscopy (XPS-C1s) overlay is shown. Fixed parameters included instrument energy calibration, consistent acquisition energy range and background processing, and a binding energy range of 292 eV to 280 eV. Variations were made between unmodified samples: Example 1 and Comparative Example 3. In Example 1, beyond the main peak at 284.8 eV, components near 286.5 eV and 288.2 eV showed stronger responses, indicating an increased proportion of C–O, C–N, and C=O related chemical states. In Comparative Example 3, components on the high binding energy side were weaker except for the carbon framework main peak. This demonstrates that Example 1 introduced more polar functional groups to the surface, providing a chemical basis for improving wettability and interfacial interactions.

[0170] Figure 3 The X-ray photoelectron spectroscopy (XPS-O1s) spectrum is a fine overlay of XPS-O1s spectra. The fixed parameters were the acquisition range of 536 eV to 526 eV and the peak fitting and normalization strategies were consistent. The varying parameters were the sample types: Example 1 and Comparative Example 3 (unmodified). Example 1 showed a fuller peak shape and higher overall intensity in the 531 eV to 533 eV range, reflecting a more significant content and distribution of oxidized chemical states on the surface. Comparative Example 3 showed a weaker signal, indicating insufficient oxygen-related components on the unmodified surface. This result is consistent with... Figure 2 The enhanced binding energy components reinforce each other, proving that the surface oxygen functionalization of Example 1 is clear and reproducible.

[0171] Figure 4The image shows the X-ray photoelectron spectroscopy (XPS-N1s) overlay, with the binding energy range of 406 eV to 396 eV fixed, consistent with the testing procedure. The variable parameter was the sample type, which was unmodified, for Example 1 and Comparative Example 3, respectively. Example 1 showed a clear response around 399.8 eV, while Comparative Example 3 showed a weak signal or was close to the baseline. This indicates that a detectable nitrogen-containing chemical state was formed on the surface of Example 1, further demonstrating that the target nitrogen-containing structural unit was effectively introduced and stably existed in the surface layer, providing an elemental-level evidence chain for subsequent performance improvement.

[0172] Figure 5 The X-ray diffraction patterns are XRD overlays. The parameters were fixed at the same 2θ scan range of 5° to 80° and the same data processing method. The variable parameters were the sample types: Example 1 and Comparative Example 3 (unmodified). Both samples exhibited consistent characteristic diffraction peaks around 38.5°, 45.8°, and 66.5°, indicating that the matrix crystal phase remained stable. Example 1 showed a more pronounced diffuse peak background in the 10° to 30° range, while Comparative Example 3 showed a weaker background. This indicates that Example 1 introduced an amorphous or low-order surface layer structure without disrupting the main crystal phase, demonstrating that the scheme achieved compatibility between surface structure control and matrix stability.

[0173] As can be seen from the performance of the examples and comparative examples in Table 1, the purity of the o-dichlorobenzene products prepared by the method of the present invention is not less than 99.90 wt%, which is significantly higher than that of the comparative examples. Comparative Example 1 suffers from insufficient surface wettability due to the low mass increment of the crosslinked copolymer layer, resulting in a HETP layer thickness as high as 0.95 m, low mass transfer efficiency, a product purity of only 99.72 wt%, and a yield reduction to 88.5%. Comparative Example 2 suffers from a surge in pressure drop to 285 Pa / m and a mass loss rate as high as 7.8% due to the excessive thickness of the crosslinked copolymer layer, indicating poor long-term stability. Comparative Example 3, without surface modification treatment, has a maximum HETP layer thickness of 1.20 m, a minimum product purity of 99.45 wt%, and a yield of only 82.5%, fully demonstrating the necessity of the crosslinked copolymer layer. Comparative Examples 4 and 5 lack 2-hydroxyethyl methacrylate or ethylene glycol dimethacrylate, respectively, resulting in insufficient hydrophilicity or crosslinking degree of the modified layer, poor solvent resistance, and mass loss rates of 5.2% and 8.5%, respectively. Comparative Example 6 suffered from decreased separation efficiency due to excessively high absolute pressure at the top of the column; Comparative Example 7 suffered from insufficient mass transfer driving force due to an excessively low reflux ratio; and Comparative Example 8 failed to fully utilize the mass transfer enhancement effect due to an excessively low modified packing ratio. Comprehensive comparison shows that this invention successfully resolved the contradiction between low pressure drop and high throughput and high separation efficiency by optimizing the crosslinked copolymer layer composition, thickness control, and synergistic matching of distillation operating parameters, achieving a balance between high wetting mass transfer enhancement and long-term stability.

[0174] Table 1 Performance Comparison Summary Table

[0175] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for distillation separation and purification of high-purity o-dichlorobenzene, characterized in that, Includes the following steps: S1. Providing a mixture of dichlorobenzene isomers, the mixture comprising o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene, wherein the mass fraction of o-dichlorobenzene in the mixture is 50wt%-95wt%; S2. The mixture of dichlorobenzene isomers is fed into a distillation column for distillation separation, wherein the rectification section of the distillation column is filled with structured packing. S3. The distillation column is operated under the condition that the absolute pressure at the top of the distillation column is 0.5-20 kPa and the reflux ratio is 2-6, and the o-dichlorobenzene product is collected from the bottom of the distillation column, wherein the mass fraction of o-dichlorobenzene in the o-dichlorobenzene product is not less than 99.9 wt%.

2. The method according to claim 1, characterized in that, The structured filler includes an alumina ceramic matrix and a crosslinked copolymer layer located on the surface of the alumina ceramic matrix, wherein the crosslinked copolymer layer contains structural units formed by N-vinyl-2-pyrrolidone, structural units formed by 2-hydroxyethyl methacrylate, and crosslinked structural units formed by ethylene glycol dimethacrylate.

3. The method according to claim 1, characterized in that, The structured packing is prepared through the following steps: A1. Raw material preparation: Provide alumina ceramic matrix, ethanol and deionized water; A2. Cleaning and drying: The alumina ceramic substrate is cleaned sequentially with the ethanol and the deionized water, and then dried; A3. Acid activation: The dried alumina ceramic matrix is ​​contacted with a hydrochloric acid aqueous solution with a concentration of 0.1-2.0 mol / L for acid activation treatment, followed by washing with deionized water and drying; A4. Silanization: The alumina ceramic matrix is ​​contacted with a silanization reaction solution, the silanization reaction solution comprising 0.5-5.0 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 50-500 parts by weight of ethanol and 5-50 parts by weight of deionized water, and the pH value of the silanization reaction solution is adjusted to 3.0-5.0 using a hydrochloric acid aqueous solution with a concentration of 0.1-2.0 mol / L; A5. Graft crosslinking polymerization: The silanized alumina ceramic matrix obtained in step A4 is brought into contact with a polymerization reaction solution containing 100-1000 parts by weight of N,N-dimethylformamide, 5-50 parts by weight of N-vinyl-2-pyrrolidone, 1-30 parts by weight of 2-hydroxyethyl methacrylate, 0.1-10 parts by weight of ethylene glycol dimethacrylate, and 0.05-1.0 parts by weight of 2,2-azobisisobutyronitrile. Graft crosslinking polymerization is carried out under nitrogen protection. A6. Post-treatment: After the reaction, the sample is washed successively with ethanol and deionized water and dried to obtain the structured packing.

4. The method according to claim 3, characterized in that, Steps A1 to A4 must satisfy the following conditions: a) The raw material ratio in step A1 is: 100 parts by weight of alumina ceramic matrix, 200-1000 parts by weight of ethanol and 200-1000 parts by weight of deionized water; b) The drying conditions in step A2 are 80-120℃ and the drying time is 1-4h; c) The concentration of the hydrochloric acid aqueous solution in step A3 is 0.1-2.0 mol / L, the treatment temperature is 20-60℃, and the treatment time is 0.5-3h; d) The silanization reaction solution in step A4 contains 0.5-5.0 parts by weight of 3-methacryloxypropyltrimethoxysilane, 50-500 parts by weight of ethanol and 5-50 parts by weight of deionized water. The pH value of the silanization reaction solution is 3.0-5.0, the silanization temperature is 20-60℃, and the silanization time is 0.5-4h.

5. The method according to claim 3, characterized in that, Steps A5 to A6 satisfy the following conditions, and the endpoint criterion for the preparation of the structured packing is: a) The polymerization reaction solution in step A5 contains 100-1000 parts by weight of N,N-dimethylformamide, 5-50 parts by weight of N-vinyl-2-pyrrolidone, 1-30 parts by weight of 2-hydroxyethyl methacrylate, 0.1-10 parts by weight of ethylene glycol dimethacrylate, and 0.05-1.0 parts by weight of 2,2-azobisisobutyronitrile, and reacts at 50-90°C for 2-8 hours under nitrogen protection; b) The drying conditions in step A6 are 60-120℃, absolute pressure is 0.1-10kPa, and drying time is 2-12h; c) When the mass increment of the structured filler relative to the alumina ceramic matrix is ​​0.2wt%-5.0wt%, the preparation is considered complete.

6. The method according to claim 2, characterized in that, The alumina ceramic matrix has a honeycomb structure with a pore size of 1-5 mm and a wall thickness of 0.1-0.5 mm.

7. The method according to claim 2, characterized in that, The thickness of the crosslinked copolymer layer is 50-300 nm, and the mass increment of the crosslinked copolymer layer relative to the alumina ceramic matrix is ​​0.2 wt%-5.0 wt%.

8. The method according to claim 2, characterized in that, The structured packing is a corrugated structured packing with a specific surface area of ​​250-700 m² / m³. The structured packing is arranged in the form of modular packing units, with an axial height of 50-500 mm for each packing unit.

9. The method according to claim 1, characterized in that, The pressure difference between the bottom pressure and the top pressure of the distillation column is 0.5-50 kPa, and the bottom temperature of the distillation column is 120-190℃.

10. The method according to claim 2, characterized in that, The structured packing material is packed to a height of 10%-40% of the effective separation height of the distillation column, wherein the effective separation height is the total packing height of the packing section in the distillation column, and the structured packing material is located above the feed inlet; the distillation column is also packed with unmodified structured packing material, which is an alumina ceramic matrix structured packing material without the crosslinked copolymer layer; and a light component distillate is collected from the top of the distillation column, wherein the total mass fraction of intermediate dichlorobenzene and para-dichlorobenzene in the light component distillate is 80wt%-99.9wt%.

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