Mass transfer enhanced ethylbenzene adsorbent bed and its application

Abstract

This invention provides a mass transfer-enhanced ethylbenzene adsorbent bed and its application, belonging to the technical field of chemical engineering. The adsorbent bed of this invention comprises primary and secondary particles in a quantity ratio of 7:3 and a size ratio of (4-20):1. The primary adsorbent particle component contains a metal-modified low-silicon-to-alumina molecular sieve with a size of 20-100 nm. The adsorbent particles are modified with a surface modifier to improve adsorption sites. By contacting this high-density, mass transfer-enhanced adsorbent bed with a mixture of C8 aromatic hydrocarbon isomers, the selective separation of ethylbenzene from C8 aromatic hydrocarbons can be effectively achieved at relatively low temperatures.

Description

Technical Field

[0001] This invention belongs to the technical field of chemical engineering, specifically relating to a mass transfer enhanced ethylbenzene adsorbent bed and its application. Background Technology

[0002] Ethylbenzene is an important chemical intermediate, mainly used in the preparation of high-purity styrene, and further in the production of synthetic rubber and other products. Its applications are wide-ranging, resulting in a persistent supply shortage. Industrially, ethylbenzene is primarily produced through the alkylation reaction of benzene and ethylene, a single source that accounts for 50% of the total cost of styrene production, highlighting the urgent need to expand ethylbenzene sources. Cracked gasoline and reformed oil are major sources of mixed C8 aromatics, containing significant amounts of ethylbenzene. Adsorption and separation of ethylbenzene from mixed C8 aromatics would bring considerable economic value, while simultaneously ensuring that the feed to downstream xylene isomerization units is ethylbenzene-free. This would allow for a 20-30°C reduction in reaction temperature and hydrogen partial pressure compared to existing conditions, and an increase in isomerization reactor throughput of 20-50%.

[0003] Ethylbenzene can be separated from mixed C8 aromatic isomers using either preferential adsorption of xylene or preferential adsorption of ethylbenzene. Patent CN103373890A discloses a method for adsorbing and separating p-xylene and ethylbenzene from C8 aromatics. This method uses a first-stage adsorption separation device based on a simulated moving bed to obtain p-xylene product and raffinate containing ethylbenzene, m-xylene, and o-xylene. Then, a second-stage adsorption separation device based on gas-phase pressure swing adsorption is used to obtain the ethylbenzene product. The operating temperatures of the two stages are 130-230℃ and 170-300℃, respectively. This method requires two stages of adsorption separation to obtain the ethylbenzene product, and the material stream undergoes a gas-liquid transition, making the operation complex and energy-intensive. Patent CN114874065A discloses a method for separating p-xylene and ethylbenzene using a sequential simulated moving bed. This method also suffers from the problem of high operating temperatures in simulated moving beds, and with only 6-8 bed layers, the separation effect is poor, failing to simultaneously achieve the goals of high purity and high yield of ethylbenzene, thus failing to demonstrate the economic value of ethylbenzene separation. Therefore, the adsorption and separation of ethylbenzene from mixed C8 aromatics currently faces the following challenges: poor mass transfer kinetics at low temperatures, making it impossible for the device to simultaneously achieve high mass transfer rates and high adsorption capacity; the operating temperature of simulated moving beds is generally high, resulting in high energy consumption; and the traditional adsorption bed has high diffusion resistance and poor mass transfer kinetics, which severely restricts the device's processing capacity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a mass transfer-enhanced ethylbenzene adsorbent bed and its application. The purpose of this invention is to solve the problems of insufficient adsorption active sites and difficulty in achieving efficient ethylbenzene separation at low temperatures by loading shaped adsorbent particles of different sizes in a specific ratio and controlling the grain size of metal-modified nanomolecular sieves. A further objective of this invention is to address the problems of high surface diffusion resistance and poor selectivity of nanomolecular sieve adsorption sites by surface modification of the shaped adsorbent particles.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a mass transfer enhanced ethylbenzene adsorbent bed, wherein the shaped adsorbent particles include: primary particles and secondary particles, with a quantity ratio of 7:3 and a size ratio of (4-20):1; the size of the primary particles is 1-4 mm; the shaped adsorbent particles, by mass percentage, include the following components: 80-95% ultrafine molecular sieve nanocrystals and 5-20% binder; the ultrafine molecular sieve nanocrystals are one or more of metal-modified Beta and MOR molecular sieves, with a silicon-to-aluminum ratio of (1.5-40):1 and a size of 20-100 nm.

[0006] This invention uses pre-formed adsorbent particles of different sizes and fills them in a specific ratio, which can improve the throughput, product purity, and yield of the adsorption separation device. It effectively avoids the problem of traditional equal-size packing failing to achieve close packing. Through differential packing, fine particles can fill the gaps formed by larger particles, achieving close packing, improving packing efficiency, while ensuring low pressure drop and high mass transfer efficiency. Furthermore, by controlling the size of the first-stage and second-stage particles, it avoids excessively small particle sizes that would cause the porosity of the ethylbenzene adsorbent bed to approach a constant, thus failing to improve packing efficiency and even causing excessive pressure drop. This invention uses nano-molecular sieves with a larger external surface area as the main component of the pre-formed adsorbent particles. A larger proportion of the unit cells in each crystallite are exposed, effectively improving diffusion performance and the dynamic adsorption performance of the adsorbent, thereby allowing for operation at a lower temperature range. Simultaneously, the use of a lower silica-to-alumina ratio results in a considerable number of ions in the molecular sieve. Abundant ions increase the number of adsorption active sites, and the cations outside the framework reduce pore size, improving the separation selectivity of ethylbenzene.

[0007] Preferably, the modified metal of the ultrafine molecular sieve nanocrystals is Na. + K + 、Rb + One or more of these, with an ion exchange rate of 10-100%. Na + K + 、Rb +Alkali metal ions lack d-orbital electrons or have empty d-orbitals, resulting in weak catalytic ability. They do not react during adsorption. Furthermore, the molecular sieve after alkali metal exchange has strong basicity, enabling it to selectively adsorb ethylbenzene molecules with the lowest relative basicity in a mixture of C8 aromatic hydrocarbons.

[0008] Preferably, the shaped adsorbent particles use one or more of methyltrimethoxysilane, trimethylchlorosilane, and 3-aminopropyltriethoxysilane as the surface modifier. For nanoscale molecular sieves with a grain size of less than 100 nm, the surface adsorption effect has a significant impact on the entire diffusion process. Defects on the outer surface may become additional undesirable adsorption sites, causing a decrease in selectivity and mass transfer performance. Therefore, this invention employs surface modification, performing chemical liquid-phase deposition on the outer surface of the grains to reduce the diffusion resistance on the outer surface and weaken the influence of surface diffusion, thereby improving the separation performance of ethylbenzene. At the same time, the surface modification of the shaped particles in this invention can effectively avoid the processing of molecular sieve powder, simplify the process flow and reduce operating costs, which is beneficial for large-scale industrial production.

[0009] Preferably, the size of the Class I particles is 1-4 mm; the size of the Class II particles is 0.2-0.9 mm.

[0010] Preferably, the size of the Class I particles is 1-2 mm; the size of the Class II particles is 0.2-0.4 mm.

[0011] Preferably, the binder is one or more of silica sol, kaolin, and boehmite.

[0012] On the other hand, the present invention provides an application of the mass transfer enhanced ethylbenzene adsorbent bed described above, wherein the adsorbent bed is contacted with a mixture of C8 aromatic hydrocarbon isomers to selectively separate ethylbenzene; wherein the C8 aromatic hydrocarbon isomer mixture contains 3-90% ethylbenzene by mass percentage; and the selective separation temperature of ethylbenzene is 20-180°C.

[0013] Preferably, the selective separation temperature of the ethylbenzene is 20-120℃.

[0014] Preferably, the contact mode between the adsorbent bed and the C8 aromatic hydrocarbon isomer mixture is liquid-phase simulated moving bed adsorption, including the following steps: feeding the C8 aromatic hydrocarbon isomer mixture into an adsorption separation device containing an adsorbent bed, separating to obtain ethylbenzene-rich extract and ethylbenzene-lean raffinate, and removing the desorbent from the raffinate and extract by distillation to obtain high-purity ethylbenzene product and raffinate containing p-xylene, m-xylene, and o-xylene; the desorbent is one or more of n-heptane, n-octane, isooctane, toluene, p-diethylbenzene, propylbenzene, and isopropylbenzene.

[0015] Preferably, the contact mode between the adsorbent bed and the C8 aromatic isomer mixture is one of fixed bed adsorption, liquid phase simulated moving bed adsorption, and gas phase simulated moving bed adsorption.

[0016] Traditional C8 aromatic hydrocarbon simulated moving bed separation units, due to limitations in the mass transfer performance of the adsorbent, have to increase the operating temperature to 150-180°C or higher at the cost of sacrificing saturated adsorption capacity to increase the mass transfer rate of the adsorbent. However, the mass transfer-enhanced ethylbenzene adsorption bed structure can maintain a high mass transfer rate at low temperatures. Therefore, the application provided by this invention can maintain a high adsorption capacity of the adsorbent through low-temperature operation, making it suitable for a wider range of feed compositions and feed rates, thereby achieving high ethylbenzene yield and improving the economics of the process. In addition, the ethylbenzene content in mixed C8 aromatic hydrocarbons from different sources varies considerably. For example, by mass percentage, the ethylbenzene content in catalytic reforming units is relatively high, approximately 17.6%; the ethylbenzene content in ethylbenzene conversion isomerization units is moderate, approximately 9%; and the ethylbenzene content in toluene shape-selective disproportionation units is relatively low, approximately 3%. The ethylbenzene adsorption bed structure provided by this invention has higher mass transfer performance, and therefore can be applied to a wider range of feed compositions. The ethylbenzene content in the mixed C8 aromatic hydrocarbon isomer feed can be between 3% and 90% by mass percentage, making it suitable for a wide range of applications.

[0017] Preferably, the product obtained after selective separation of ethylbenzene has a purity of 99.8% or higher.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The mass transfer-enhanced ethylbenzene adsorbent bed structure provided by this invention achieves high packing density by proportionally loading two types of molded adsorbents of different sizes. Simultaneously, high mass transfer efficiency is achieved by controlling the adsorbent crystal size and surface modification. This mass transfer-enhanced ethylbenzene adsorbent bed can be applied to simulated moving beds operating at temperatures of 20-120℃, adaptable to a wide range of feed compositions, and suitable for diverse applications. It can produce high-purity ethylbenzene products with a mass concentration exceeding 99.7%. The ethylbenzene adsorption bed preparation method provided by this invention is simple, has a long service life, low energy consumption, and is suitable for industrial application. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0020] General Implementation Examples A mass transfer enhanced ethylbenzene adsorbent bed, wherein the shaped adsorbent particles comprise: primary particles and secondary particles in a quantity ratio of 7:3 and a size ratio of (4-20):1; the shaped adsorbent particles, by mass percentage, comprise the following components: 80-95% ultrafine molecular sieve nanocrystals and 5-20% binder; the ultrafine molecular sieve nanocrystals are one or more of metal-modified Beta and MOR molecular sieves, with a silicon-to-aluminum ratio of (1.5-40):1 and a size of 20-100 nm.

[0021] In some preferred embodiments of the present invention, the modified metal of the ultrafine molecular sieve nanocrystals is Na. + K + 、Rb + One or more of them, with an ion exchange degree of 10-100%.

[0022] In some preferred embodiments of the present invention, the preparation method of the ultrafine molecular sieve nanocrystals includes the following steps: mixing the molecular sieve with a modified metal salt solution, stirring for 2 hours at a temperature of 60-80°C and normal pressure, repeating 2-3 times, washing thoroughly with deionized water, and drying to obtain ultrafine molecular sieve nanocrystals.

[0023] In some more preferred embodiments of the present invention, the ion exchange degree of the ultrafine molecular sieve nanocrystals is 20-100%.

[0024] In some preferred embodiments of the present invention, the shaped adsorbent particles are surface modifiers selected from one or more of methyltrimethoxysilane, trimethylchlorosilane, and 3-aminopropyltriethoxysilane.

[0025] In some more preferred embodiments of the present invention, the method for preparing the shaped adsorbent particles includes the following steps: mixing ultrafine molecular sieve nanocrystals with a binder, placing them in a turntable and spraying water while rotating, so that the solid powder rolls into balls, then sieving out grade I and grade II particles, drying at 80°C for 10 hours, calcining at 500°C in an air stream for 4 hours, adding a surface modifier to the shaped particles, stirring at 25°C for 12 hours, distilling off the surface modifier in an oil bath at 90°C, and heating the residue to 550°C in a muffle furnace at a rate of 1°C / min, holding for 3 hours, and then naturally cooling. The surface modifier modification process is repeated 0-3 times to obtain the shaped adsorbent particles.

[0026] In some preferred embodiments of the present invention, the size of the Class I particles is 1-4 mm; the size of the Class II particles is 0.2-0.9 mm.

[0027] In some preferred embodiments of the present invention, the size of the Class I particles is 1-2 mm; the size of the Class II particles is 0.2-0.4 mm.

[0028] In some preferred embodiments of the present invention, the binder is one or more of silica sol, kaolin, and boehmite.

[0029] An application of the mass transfer-enhanced ethylbenzene adsorbent bed described above involves contacting the adsorbent bed with a mixture of C8 aromatic hydrocarbon isomers to selectively separate ethylbenzene; wherein the C8 aromatic hydrocarbon isomer mixture contains 3-90% ethylbenzene by mass percentage; and the selective separation temperature of ethylbenzene is 20-180℃.

[0030] In some preferred embodiments of the present invention, the selective separation temperature of the ethylbenzene is 20-120°C.

[0031] In some preferred embodiments of the present invention, the contact mode between the adsorbent bed and the C8 aromatic hydrocarbon isomer mixture is liquid-phase simulated moving bed adsorption, including the following steps: feeding the C8 aromatic hydrocarbon isomer mixture into an adsorption separation device containing an adsorbent bed, separating to obtain ethylbenzene-rich extract and ethylbenzene-lean raffinate, and removing the desorbent from the raffinate and extract by distillation to obtain high-purity ethylbenzene product and raffinate containing p-xylene, m-xylene, and o-xylene; the desorbent is one or more of n-heptane, n-octane, isooctane, toluene, p-diethylbenzene, propylbenzene, and isopropylbenzene.

[0032] In some preferred embodiments of the present invention, the contact mode between the adsorbent bed and the C8 aromatic isomer mixture is one of fixed bed adsorption, liquid-phase simulated moving bed adsorption, and gas-phase simulated moving bed adsorption.

[0033] In some preferred embodiments of the present invention, the ethylbenzene obtained after selective separation has a purity of 99.8% or higher. Example 1

[0034] A mass transfer enhanced ethylbenzene adsorbent bed and its application, comprising the following steps: S1: Preparation of ultrafine molecular sieve nanocrystals: Weigh 1 kg of Beta zeolite powder and 3 kg of potassium chloride solution; wherein the concentration of potassium chloride solution is 0.1 mol / L; mix Beta zeolite powder and potassium chloride solution, stir for 2 h at 60℃ and normal pressure, repeat 3 times, wash thoroughly with deionized water, and dry to obtain ultrafine molecular sieve nanocrystals of metal-modified Beta zeolite powder with a size of 20-30 nm and a potassium ion exchange rate of 89%; S2: Preparation of the shaped adsorbent particles: The components include 1 kg of ultrafine molecular sieve nanocrystals and 0.1 kg of boehmite. The ultrafine molecular sieve nanocrystals and boehmite are mixed and placed in a turntable. Water is sprayed in while the turntable is rotating. The amount of water sprayed during the rolling is 30% of the total mass of the solid powder, so that the solid powder rolls into balls. 0.4 mm diameter Class II particles and 2 mm diameter Class I particles are sieved out. After drying at 80℃ for 10 h and calcining at 500℃ in an air stream for 4 h, the shaped particles are weighed out. 1 kg of surface modifier 3-aminopropyltriethoxysilane solution and 5 kg of surface modifier 3-aminopropyltriethoxysilane solution were prepared. The mass concentration of the 3-aminopropyltriethoxysilane solution was 10%. The shaped spherical particles were added to the 3-aminopropyltriethoxysilane solution and stirred at 25°C for 12 h. The surface modifier was removed by distillation in an oil bath at 90°C. After evaporation, the residue was heated to 550°C in a muffle furnace at a rate of 1°C / min and held for 3 h. After natural cooling, the surface modifier modification process was repeated twice to obtain the shaped adsorbent particles. S3: The primary and secondary adsorbent particles are packed into a liquid-phase simulated moving bed separation device at a ratio of 7:3. The simulated moving bed consists of 16 adsorption columns and adopts a traditional four-zone structure. The C8 aromatic hydrocarbon isomer mixture includes, by mass percentage: 25% ethylbenzene, 25% p-xylene, 25% m-xylene, and 25% o-xylene. The desorbent includes: 25% toluene and 75% n-heptane. The operating temperature is set at 60℃, and a 3-4-6-3 zone configuration is adopted. After the temperature, pressure, and flow rate stabilize, the C8 aromatic hydrocarbon isomer mixture is introduced into the simulated moving bed through the feed inlet. The extract and residual liquid are distilled to obtain the target product, and the desorbent is recycled. Example 2

[0035] A mass transfer enhanced ethylbenzene adsorbent bed and its application, comprising the following steps: S1: Preparation of ultrafine molecular sieve nanocrystals: Weigh 1 kg of MOR zeolite powder and 5 kg of potassium chloride solution; wherein the concentration of potassium chloride solution is 0.2 mol / L; mix MOR zeolite powder and potassium chloride solution, stir for 2 h at 60℃ and normal pressure, repeat 3 times, wash thoroughly with deionized water, and dry to obtain ultrafine molecular sieve nanocrystals of metal-modified Beta zeolite powder with a size of 80-100 nm and a potassium ion exchange rate of 62%; S2: Preparation of the shaped adsorbent particles, weighing the following components: 1 kg of ultrafine molecular sieve nanocrystals, 0.1 kg of kaolin, and 5 kg of guar gum powder. g; Mix ultrafine molecular sieve nanocrystals, pseudoboehmite, and guar gum powder, place them in a turntable, and spray water while rotating. The amount of water sprayed during rolling is 30% of the total mass of the solid powder, so that the solid powder rolls into balls; sieve out Class II particles with a diameter of 0.2 mm and Class I particles with a diameter of 1 mm; dry at 80℃ for 10 h, and calcine at 500℃ in an air stream for 4 h; weigh out 1 kg of shaped small ball particles and 5 kg of surface modifier methyltrimethoxy solution; wherein, the mass concentration of methyltrimethoxy solution is 2%; add the shaped small ball particles to the methyltrimethoxy solution, stir at 25℃ for 12 h, and then distill off the surface modifier in an oil bath at 90℃. After evaporation, heat the residue in a muffle furnace at a rate of 1℃ / min to 550℃, hold for 3 h, and then cool naturally. Repeat the surface modifier modification process 3 times to obtain shaped adsorbent particles; S3: The primary and secondary adsorbent particles are packed into a liquid-phase simulated moving bed separation device at a ratio of 7:3. The simulated moving bed consists of 16 adsorption columns and adopts a traditional four-zone structure. The C8 aromatic isomer mixture includes, by mass percentage: ethylbenzene 9%, p-xylene 22%, m-xylene 47%, and o-xylene 22%. The desorbent includes: toluene 10% and n-heptane 90%. The operating temperature is set at 30℃, and a 2-3-9-2 zone configuration is adopted. After the temperature, pressure, and flow rate stabilize, the C8 aromatic isomer mixture is introduced into the simulated moving bed through the feed inlet. The extract and residual liquid are distilled to obtain the target product, and the desorbent is recycled. Example 3

[0036] A mass transfer enhanced ethylbenzene adsorbent bed and its application, comprising the following steps: S1: Preparation of ultrafine molecular sieve nanocrystals: Weigh 1 kg of Beta zeolite powder and 2 kg of sodium chloride solution; wherein the concentration of sodium chloride solution is 0.1 mol / L; mix Beta zeolite powder and sodium chloride solution, stir for 2 h at 80℃ and normal pressure, repeat 3 times, wash thoroughly with deionized water, and dry to obtain ultrafine molecular sieve nanocrystals of metal-modified Beta zeolite powder with a size of 30-60 nm and a sodium ion exchange rate of 85%. S2: Preparation of the shaped adsorbent particles: The components include 1 kg of ultrafine molecular sieve nanocrystals and 0.5 kg of silica sol, wherein the mass concentration of silica sol is 40%. The ultrafine molecular sieve nanocrystals and silica sol are mixed and placed in a turntable while water is sprayed in during rotation. The amount of water sprayed during rotation is 20% of the total mass of the solid powder, causing the solid powder to roll into balls. Second-grade particles with a diameter of 0.2 mm and first-grade particles with a diameter of 4 mm are sieved out. The particles are dried at 80℃ for 10 h and then baked in an air stream at 500℃. After calcination for 4 hours, 1 kg of shaped microspheres and 10 kg of trimethylchlorosilane solution as a surface modifier were weighed out; the mass concentration of the trimethylchlorosilane solution was 10%. The shaped microspheres were added to the trimethylchlorosilane solution and stirred at 25°C for 12 hours. The surface modifier was removed by distillation in an oil bath at 90°C. After evaporation to dryness, the residue was heated to 550°C in a muffle furnace at a rate of 1°C / min and held for 3 hours before being naturally cooled. The surface modifier modification process was repeated twice to obtain the shaped adsorbent particles. S3: The primary and secondary adsorbent particles are packed into a liquid-phase simulated moving bed separation device at a ratio of 7:3. The simulated moving bed consists of 16 adsorption columns and adopts a traditional four-zone structure. By mass percentage, the C8 aromatic hydrocarbon isomer mixture includes: 42% ethylbenzene, 11% p-xylene, 30% m-xylene, and 18% o-xylene. The desorbents include: 50% toluene and 50% n-heptane. The operating temperature is set at 120℃, and a 3-5-5-3 zone configuration is adopted. After the temperature, pressure, and flow rate stabilize, the C8 aromatic hydrocarbon isomer mixture is introduced into the simulated moving bed through the feed inlet. The evaporator and residual liquid are distilled to obtain the target product, and the desorbent is recycled. Example 4

[0037] A mass transfer enhanced ethylbenzene adsorbent bed and its application, comprising the following steps: S1: Preparation of ultrafine molecular sieve nanocrystals: Weigh 1 kg of Beta zeolite powder and 3 kg of rubidium chloride solution; wherein the concentration of rubidium chloride solution is 0.1 mol / L; mix Beta zeolite powder and rubidium chloride solution, stir for 2 h at 60℃ and normal pressure, repeat 3 times, wash thoroughly with deionized water, and dry to obtain ultrafine molecular sieve nanocrystals of metal-modified Beta zeolite powder crystals with a size of 20-30 nm and a rubidium ion exchange rate of 58%; S2: Preparation of the shaped adsorbent particles: The components include 1 kg of ultrafine molecular sieve nanocrystals, 0.05 kg of kaolin, and 3 g of guar gum powder. The ultrafine molecular sieve nanocrystals, kaolin, and guar gum powder are mixed and placed in a turntable. Water is sprayed in while the turntable rotates, with the amount of water sprayed being 20% ​​of the total mass of the solid powder, causing the solid powder to roll into balls. Grade II particles with a diameter of 0.9 mm and Grade I particles with a diameter of 4 mm are sieved out. The mixture is then dried at 80℃ for 10 hours in air. After calcining at 500℃ for 4 hours in the flow, 1 kg of shaped microspheres and 5 kg of methyltrimethoxy solution as surface modifier were weighed; wherein, the mass concentration of methyltrimethoxy solution was 5%; the shaped microspheres were added to the methyltrimethoxy solution, stirred at 25℃ for 12 hours, and the surface modifier was removed by distillation in an oil bath at 90℃. After evaporation to dryness, the residue was heated to 550℃ at a rate of 1℃ / min in a muffle furnace, held for 3 hours, and then naturally cooled to obtain shaped adsorbent particles; S3: The primary and secondary adsorbent particles are packed into a liquid-phase simulated moving bed separation device at a ratio of 7:3. The simulated moving bed consists of 16 adsorption columns and adopts a traditional four-zone structure. By mass percentage, the C8 aromatic hydrocarbon isomer mixture includes: 18% ethylbenzene, 19% p-xylene, 40% m-xylene, and 23% o-xylene. The desorbents include: 25% toluene and 75% n-heptane. The operating temperature is set at 150℃, and a 3-4-6-3 zone configuration is adopted. After the temperature, pressure, and flow rate stabilize, the C8 aromatic hydrocarbon isomer mixture is introduced into the simulated moving bed through the feed inlet. The extract and residual liquid are distilled to obtain the target product, and the desorbent is recycled. Example 5

[0038] A mass transfer enhanced ethylbenzene adsorbent bed and its application, comprising the following steps: S1: Preparation of ultrafine molecular sieve nanocrystals: Weigh 1 kg of Beta zeolite powder and 3 kg of sodium chloride solution; wherein the concentration of sodium chloride solution is 0.1 mol / L; mix Beta zeolite powder and sodium chloride solution, stir for 2 h at 60℃ and normal pressure, repeat 3 times, wash thoroughly with deionized water, and dry to obtain ultrafine molecular sieve nanocrystals of metal-modified Beta zeolite powder with a size of 60-100 nm and a sodium ion exchange rate of 80%. S2: Preparation of the shaped adsorbent particles: The components include 1 kg of ultrafine molecular sieve nanocrystals and 0.2 kg of pseudoboehmite. The ultrafine molecular sieve nanocrystals are mixed with silica sol and placed in a turntable. Water is sprayed in while the turntable is rotating. The amount of water sprayed during the rolling is 30% of the total mass of the solid powder, so that the solid powder rolls into balls. Second-grade particles with a diameter of 0.3 mm and first-grade particles with a diameter of 2 mm are sieved out. After drying at 80℃ for 10 h and calcining at 500℃ in an air stream for 4 h, the following are weighed: 1 kg of shaped microspheres and 3 kg of trimethylchlorosilane solution as a surface modifier were prepared; the mass concentration of the trimethylchlorosilane solution was 10%. The shaped microspheres were added to the trimethylchlorosilane solution and stirred at 25°C for 12 h. The surface modifier was then removed by distillation in an oil bath at 90°C. After evaporation to dryness, the residue was heated to 550°C in a muffle furnace at a rate of 1°C / min and held for 3 h before being naturally cooled. The surface modifier modification process was repeated twice to obtain the shaped adsorbent particles. S3: The primary and secondary adsorbent particles are packed into a liquid-phase simulated moving bed separation device at a ratio of 7:3. The simulated moving bed consists of 16 adsorption columns and adopts a traditional four-zone structure. By mass percentage, the C8 aromatic hydrocarbon isomer mixture includes: 13% ethylbenzene, 19% p-xylene, 47% m-xylene, and 21% o-xylene. The desorbents include: 20% toluene and 80% n-heptane. The operating temperature is set at 80℃, and a 3-4-6-3 zone configuration is adopted. After the temperature, pressure, and flow rate stabilize, the C8 aromatic hydrocarbon isomer mixture is introduced into the simulated moving bed through the feed inlet. The extract and residual liquid are distilled to obtain the target product, and the desorbent is recycled. Example 6

[0039] A mass transfer enhanced ethylbenzene adsorbent bed and its application, comprising the following steps: S1: Preparation of ultrafine molecular sieve nanocrystals: Weigh 1 kg of Beta zeolite powder and 3 kg of rubidium chloride solution; wherein the concentration of rubidium chloride solution is 0.1 mol / L; mix Beta zeolite powder and rubidium chloride solution, stir for 2 h at 60℃ and normal pressure, repeat twice, wash thoroughly with deionized water, and dry to obtain ultrafine molecular sieve nanocrystals of metal-modified Beta zeolite powder with a size of 20-30 nm and a rubidium ion exchange rate of 52%; S2: Preparation of the shaped adsorbent particles: The components include 1 kg of ultrafine molecular sieve nanocrystals, 0.05 kg of kaolin, and 3 g of guar gum powder. The ultrafine molecular sieve nanocrystals, kaolin, and guar gum powder are mixed and placed in a turntable while water is sprayed in. The amount of water sprayed during the rolling process is 20% of the total mass of the solid powder, causing the solid powder to roll into balls. 0.3 mm diameter Class II particles and 2 mm diameter Class I particles are sieved out. The particles are dried at 80℃ for 10 h and calcined at 500℃ in an air stream. After 4 hours, 1 kg of shaped microspheres and 3 kg of trimethylchlorosilane solution as a surface modifier were weighed out; the mass concentration of the trimethylchlorosilane solution was 10%. The shaped microspheres were added to the trimethylchlorosilane solution and stirred at 25°C for 12 hours. The surface modifier was removed by distillation in an oil bath at 90°C. After evaporation, the residue was heated to 550°C in a muffle furnace at a rate of 1°C / min and held for 3 hours before being naturally cooled. The surface modifier modification process was repeated twice to obtain the shaped adsorbent particles. S3: The first-stage and second-stage adsorbent particles are loaded into the gas-phase pressure swing adsorption separation device at a ratio of 7:3. The C8 aromatic hydrocarbon isomer mixture includes, by mass percentage: 3% ethylbenzene, 87% p-xylene, 8% m-xylene, and 2% o-xylene. The C8 aromatic hydrocarbon isomer mixture solution is heated into a gas phase under high pressure and introduced into the adsorption bed at an operating temperature of 180°C. Ethylbenzene is adsorbed, while other components are discharged from the adsorbent bed at an adsorption pressure of 1.5 MPa. The pressure of the adsorbent bed is reduced, and the adsorbed components are desorbed by purging with inert gas at a desorption pressure of 0.2 MPa. Example 7

[0040] A mass transfer enhanced ethylbenzene adsorbent bed and its application, comprising the following steps: S1: Preparation of ultrafine molecular sieve nanocrystals: Weigh 1 kg of Beta zeolite powder and 3 kg of potassium chloride solution; wherein the concentration of potassium chloride solution is 0.1 mol / L; mix Beta zeolite powder and potassium chloride solution, stir for 2 h at 60℃ and normal pressure, repeat 3 times, wash thoroughly with deionized water, and dry to obtain ultrafine molecular sieve nanocrystals of metal-modified Beta zeolite powder with a size of 20-30 nm and a potassium ion exchange rate of 89%; S2: Preparation of the shaped adsorbent particles: The components include 1 kg of ultrafine molecular sieve nanocrystals and 0.1 kg of boehmite. The ultrafine molecular sieve nanocrystals and boehmite are mixed and placed in a turntable. Water is sprayed in while the turntable is rotating. The amount of water sprayed during the rolling is 30% of the total mass of the solid powder, so that the solid powder rolls into balls. 0.4 mm diameter Class II particles and 2 mm diameter Class I particles are sieved out. After drying at 80℃ for 10 h and calcining at 500℃ in an air stream for 4 h, the shaped particles are weighed out. 1 kg of surface modifier 3-aminopropyltriethoxysilane solution and 5 kg of surface modifier 3-aminopropyltriethoxysilane solution were prepared. The mass concentration of the 3-aminopropyltriethoxysilane solution was 10%. The shaped spherical particles were added to the 3-aminopropyltriethoxysilane solution and stirred at 25°C for 12 h. The surface modifier was removed by distillation in an oil bath at 90°C. After evaporation, the residue was heated to 550°C in a muffle furnace at a rate of 1°C / min and held for 3 h. After natural cooling, the surface modifier modification process was repeated twice to obtain the shaped adsorbent particles. S3: The primary and secondary adsorbent particles are packed into a liquid-phase simulated moving bed separation device at a ratio of 7:3. The simulated moving bed consists of 16 adsorption columns and adopts a traditional four-zone structure. The C8 aromatic hydrocarbon isomer mixture includes, by mass percentage: 25% ethylbenzene, 25% p-xylene, 25% m-xylene, and 25% o-xylene. The desorbent includes: 25% toluene and 75% n-heptane. The operating temperature is set at 60℃, and a 3-4-6-3 zone configuration is adopted. After the temperature, pressure, and flow rate stabilize, the C8 aromatic hydrocarbon isomer mixture is introduced into the simulated moving bed through the feed inlet. The extract and residual liquid are distilled to obtain the target product, and the desorbent is recycled.

[0041] Comparative Example 1 The only difference between this comparative example and Example 1 is that in S3, the first-stage and second-stage particles of the shaped adsorbent granules are loaded into the liquid-phase simulated moving bed separation device in a quantity ratio of 5:5.

[0042] Comparative Example 2 The only difference between this comparative example and Example 1 is that in S3, the first-stage and second-stage particles of the shaped adsorbent granules are loaded into the liquid-phase simulated moving bed separation device in a quantity ratio of 3:7.

[0043] Comparative Example 3 The only difference between this comparative example and Example 2 is that it screens out Class II particles with a diameter of 0.9 mm and Class I particles with a diameter of 1 mm.

[0044] Comparative Example 4 The only difference between this comparative example and Example 3 is that it uses 0.2 mm diameter Class II particles and 6 mm diameter Class I particles for sieving.

[0045] Comparative Example 5 The only difference between this embodiment and Embodiment 1 is that in S2, the shaped microspheres do not use a surface modifier to obtain shaped adsorbent particles.

[0046] Table 1 The purity and yield of ethylbenzene obtained after processing Examples 1-7 and Comparative Examples 1-5 were tested, and the results are shown in Table 1.

[0047] According to the test results, the adsorbent bed of the present invention, with its high packing density and enhanced mass transfer, can effectively improve the purity and yield of ethylbenzene at lower operating temperatures when in contact with the C8 aromatic hydrocarbon isomer mixture. In Comparative Example 1, compared to Example 1, the number of Grade I and Grade II particles was the same; in Comparative Example 2, compared to Example 1, the number of Grade I particles was too small; neither could achieve a low pressure drop and high mass transfer efficiency. In Comparative Example 3, the size ratio of Grade I to Grade II particles was close to 1:1, resulting in low difference between them and a decrease in packing density and adsorption effect. In Comparative Example 4, the size ratio of Grade I to Grade II particles was 30:1, and the quantity ratio was 7:3. The smaller particle size and fewer particles of Grade II made it difficult to fill the voids, leading to a decrease in dynamic adsorption performance and a decrease in ethylbenzene selectivity. In Comparative Example 5, no surfactant was used to modify the shaped adsorbent particles, resulting in adsorption point defects on the surface of the shaped adsorbent particles, reducing the selectivity for ethylbenzene and weakening the separation performance.

[0048] The adsorbent bed structure of this invention achieves high packing density by proportionally loading two types of molded adsorbents of different sizes. Simultaneously, high mass transfer efficiency is achieved by controlling the adsorbent crystal size and surface modification. This invention uses metal-modified nanomolecular sieves with a larger external surface area and a lower silica-to-alumina ratio as the main component of the molded adsorbent particles, improving the dynamic adsorption performance of the adsorbent and increasing the number of adsorption active sites. This allows for the selective adsorption of ethylbenzene molecules with the lowest relative alkalinity at lower operating temperatures, achieving highly efficient ethylbenzene separation. To improve the surface adsorption sites of the nanomolecular sieves, this invention employs a surface modifier for chemical liquid-phase deposition on the outer surface of the crystals, reducing diffusion resistance and further enhancing the ethylbenzene separation performance.

Claims

1. A mass transfer enhanced ethylbenzene adsorbent bed, characterized in that, The molded adsorbent particles include: Grade I particles and Grade II particles, with a quantity ratio of 7:3 and a size ratio of (4-20):1; The molded adsorbent particles, by mass percentage, comprise the following components: 80-95% ultrafine molecular sieve nanocrystals and 5-20% binder; The ultrafine molecular sieve nanocrystals are one or more of metal-modified Beta and MOR molecular sieves, with a silicon-to-aluminum ratio of (1.5-40):1 and a size of 20-100 nm.

2. The mass transfer enhanced ethylbenzene adsorbent bed according to claim 1, characterized in that, The modified metal for the ultrafine molecular sieve nanocrystals is Na. + K + 、Rb + One or more of them, with an ion exchange degree of 10-100%.

3. A mass transfer enhanced ethylbenzene adsorbent bed according to claim 1 or 2, characterized in that, The shaped adsorbent particles are prepared using one or more of the following as surface modifiers: methyltrimethoxysilane, trimethylchlorosilane, and 3-aminopropyltriethoxysilane.

4. The mass transfer enhanced ethylbenzene adsorbent bed according to claim 1, characterized in that, The size of the Class I particles is 1-4 mm; the size of the Class II particles is 0.2-0.9 mm.

5. The mass transfer enhanced ethylbenzene adsorbent bed according to claim 3, characterized in that, The binder is one or more of silica sol, kaolin, and boehmite.

6. An application of the mass transfer enhanced ethylbenzene adsorbent bed according to any one of claims 1-5, characterized in that, Selective separation of ethylbenzene is achieved by contacting the adsorbent bed with a mixture of C8 aromatic isomers. In the mixture of C8 aromatic isomers, the ethylbenzene content is 3-90% by mass percentage; The selective separation temperature of the ethylbenzene is 20-180℃.

7. The application of the mass transfer enhanced ethylbenzene adsorbent bed according to claim 6, characterized in that, The selective separation temperature of the ethylbenzene is 20-120℃.

8. The application of a mass transfer-enhanced ethylbenzene adsorbent bed according to claim 6 or 7, characterized in that, The adsorbent bed is in contact with the C8 aromatic isomer mixture via liquid-phase simulated moving bed adsorption, and the desorbent is one or more of n-heptane, n-octane, isooctane, toluene, p-diethylbenzene, propylbenzene, and isopropylbenzene.

9. The application of a mass transfer-enhanced ethylbenzene adsorbent bed according to claim 6 or 7, characterized in that, The adsorbent bed is in contact with the C8 aromatic isomer mixture in one of the following ways: fixed bed adsorption, liquid-phase simulated moving bed adsorption, or gas-phase simulated moving bed adsorption.

10. The application of the mass transfer enhanced ethylbenzene adsorbent bed according to claim 9, characterized in that, The ethylbenzene obtained after selective separation has a purity of 99.8% or higher.

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