Method and system for removing by-product polymer in ethylene oligomerization process

Abstract

The invention relates to the technical field of olefin polymerization, and particularly provides a method and a system for removing a byproduct polymer in an ethylene oligomerization process. The method for removing the by-product polymer in the ethylene oligomerization process comprises the following steps: continuously introducing ethylene, a catalyst, an adsorbent and a solvent into a reactor, carrying out an ethylene selective oligomerization reaction, feeding a reaction mixture into a separator, and carrying out separation, the first material flow contains the adsorbent and the by-product polymer and the second material flow contains the product, the first material flow is sent to a by-product polymer treatment unit to be treated, the second material flow is divided into two paths, the first path is sent to a product rectification separation unit to be separated to obtain alpha olefin, and the second path is cooled and then returns to the reactor as reflux liquid. The method and the system for removing the by-product polymer in the ethylene oligomerization process provided by the invention are used for removing the by-product polymer.

Description

Technical Field

[0001] This disclosure relates to the field of olefin polymerization technology, and more particularly to a method and system for removing by-product polymers in an ethylene oligomerization process. Background Technology

[0002] α Olefins (such as 1-hexene and 1-octene) are important linear terminal olefin products, mainly used as comonomers for high-end polyolefins such as polyolefin elastomers, and also used in fine chemicals such as lubricants and plasticizers.

[0003] Ethylene oligomerization is a production line for linear α The main process for olefins (such as 1-hexene and 1-octene) is the oligomerization of ethylene. However, it is difficult to avoid the generation of by-product macromolecular polymers (such as oligomers and polyethylene) during the oligomerization process. These by-products tend to adhere to the inner wall of the reactor, the agitator, and the pipelines. This not only affects mass and heat transfer but also encapsulates the catalyst, exacerbates side reactions, and causes system blockage. This forces the unit to be shut down frequently for cleaning, which seriously affects the long-term operation and economic efficiency of the unit.

[0004] Existing technologies have mitigated this problem through various means; however, the solutions adopted in existing technologies have problems such as complex processes, high equipment requirements, high operating costs, the need for shutdown for cleaning, and disruption to continuous production. Summary of the Invention

[0005] This disclosure is made in view of the above-mentioned problems. This disclosure provides a system and method for removing by-product polymers in an ethylene oligomerization process, which can efficiently remove by-product polymers in continuous production, reduce the risk of system blockage, extend the operating cycle of the unit, and improve reaction selectivity.

[0006] According to one aspect of this disclosure, a method for removing by-product polymers in an ethylene oligomerization process is provided, comprising the following steps: Ethylene, catalyst, adsorbent and solvent are continuously fed into a reactor to carry out a selective oligomerization reaction of ethylene, wherein the adsorbent is a solid particle or powder and the median particle size of the adsorbent is 10 μm to 1 mm. The reaction mixture is fed into a separator to separate the two streams, resulting in a first stream containing the adsorbent and the by-product polymer and a second stream containing the product. The first logistics is sent to the by-product polymer processing unit for processing. The second stream is divided into two streams. The first stream is sent to the product distillation and separation unit for separation to obtain α. The olefins, after being cooled, are returned to the reactor as reflux.

[0007] According to another aspect of this disclosure, a system for removing by-product polymers in an ethylene oligomerization process is provided, comprising: a reactor, a separator, a by-product polymer treatment unit, and a product distillation separation unit, wherein the outlet of the reactor is connected to the inlet of the separator, the separator has a first outlet and a second outlet, the first outlet being connected to the inlet of the by-product polymer treatment unit, the reactor having a reflux inlet, and the second outlet being divided into two paths, the first path being connected to the inlet of the product distillation separation unit, and the second path being connected to the reflux inlet of the reactor, wherein the reactor is used for carrying out a selective oligomerization reaction of ethylene in the presence of ethylene, a catalyst, a solvent, and a solid adsorbent.

[0008] Compared with existing technologies, the method and system for removing by-product polymers in the ethylene oligomerization process disclosed herein have the following advantages: In one or more technical solutions provided in this disclosure, firstly, by adding solid particles or powdered adsorbents with a median particle size of 10 μm to 1 mm to the reactor, the gas-liquid contact surface area of ​​the reaction system can be significantly increased, making the mixing of ethylene, catalyst, and solvent more uniform and significantly improving mass and heat transfer efficiency. This promotes the selective oligomerization of ethylene, effectively improving the selectivity of the formation of target α-olefins such as 1-hexene and 1-octene, and reducing the generation of by-product polymers. Moreover, the adsorbent can also adsorb the viscous macromolecular polymers generated in the reaction onto its surface and within its pores through its high specific surface area. At the same time, the adsorbent's aggregation effect allows the polymers to form easily separable aggregates, reducing the adhesion of polymers to the reactor inner wall, stirring paddle, and other internal components from the source, and avoiding the side reaction cycle exacerbated by polymer encapsulation of the catalyst.

[0009] Based on this, after the reaction mixture enters the separator for separation, the first stream containing the adsorbent and high concentration of by-product polymer can be sent separately to the by-product polymer treatment unit to recover the effective components, which is waste-free and environmentally friendly. The second stream containing the target product is processed in separate streams. One stream is distilled to obtain high-purity α-olefins, and the other stream is cooled and refluxed back to the reactor. This not only stably removes the heat of reaction to maintain the optimal reaction temperature, but also achieves efficient recycling of materials.

[0010] The method and system for removing by-product polymers in the ethylene oligomerization process disclosed herein effectively overcome the limitations of existing technologies in the selective oligomerization of ethylene to prepare α-polymers. This method overcomes the technical limitations of traditional olefin production processes, such as requiring shutdowns to clean byproduct polymers, adding flocculants, or installing complex packing materials. It achieves efficient and continuous removal of byproduct polymers. Furthermore, this method features a simple process flow, low equipment investment, and flexible operation, significantly improving overall process economy and production efficiency while resolving system blockage caused by byproduct polymers. Attached Figure Description

[0011] The above and other objects, features, and advantages of this disclosure will become more apparent from the more detailed description of the embodiments thereof in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0012] Figure 1 This is a process flow diagram of the system for removing by-product polymers in the ethylene oligomerization process of this disclosure embodiment; Figure 2 This is a flowchart illustrating the preparation process of a method for removing by-product polymers in the ethylene oligomerization process according to an embodiment of this disclosure.

[0013] Figure label: 110 - Reactor, 120 - Separator, 130 - By-product polymer processing unit, 140 - Product distillation and separation unit, 150 - Cooler, 160 - Circulation pump, a - First outlet, b - Second outlet, c - Reflux inlet. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this disclosure more apparent, exemplary embodiments according to this disclosure will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments of this disclosure. It should be understood that this disclosure is not limited to the exemplary embodiments described herein.

[0015] α Alkenes (such as 1) Hexene, 1 Octene is an important linear terminal olefin product, mainly used as a comonomer for high-end polyolefins, such as polyolefin elastomers, and also in fine chemicals such as lubricants and plasticizers. Ethylene oligomerization is the process for producing this type of linear α-olefin. The main industrial processes for olefins.

[0016] During the oligomerization of ethylene, it is unavoidable to generate by-product macromolecular polymers (such as oligomers and polyethylene). These polymers are highly viscous and easily adhere to the inner walls of the reactor, the agitator, and the inner surfaces of the pipes. This not only affects the mass and heat transfer efficiency of the system, but also encapsulates or adsorbs the catalyst, exacerbating side reactions and causing blockages in the reaction system and downstream equipment. This problem forces the unit to be shut down frequently for cleaning, which seriously restricts the long-term stable operation and economy of the unit.

[0017] Existing technologies typically alleviate polymer clogging problems by optimizing catalysts, employing flocculation and sedimentation, mechanical cleaning, or adding packing materials. However, these methods generally suffer from drawbacks such as complex processes, high equipment requirements, high operating costs, the need for shutdown operations, and disruption to continuous production.

[0018] To address the aforementioned issues, this disclosure provides a method and system for removing by-product polymers in an ethylene oligomerization process. This method can efficiently remove by-product polymers during continuous production, reduce the risk of system blockage, extend the operating cycle of the equipment, and improve reaction selectivity.

[0019] The method for removing by-product polymers in the ethylene oligomerization process provided in this disclosure is applied to the system for removing by-product polymers in the ethylene oligomerization process provided in this disclosure. Figure 1 A process flow diagram of a system for removing by-product polymers in the ethylene oligomerization process according to an embodiment of this disclosure is shown. Figure 1 As shown, the system for removing by-product polymers in the ethylene oligomerization process of this embodiment includes: a reactor 110, a separator 120, a by-product polymer processing unit 130, and a product distillation and separation unit 140. The outlet of the reactor 110 is connected to the inlet of the separator 120. The separator 120 has a first outlet a and a second outlet b. The first outlet a is connected to the inlet of the by-product polymer processing unit 130. The reactor 110 has a reflux inlet c. The second outlet b is divided into two paths: the first path is connected to the inlet of the product distillation and separation unit 140, and the second path is connected to the reflux inlet c of the reactor 110. The reactor 110 is used for selective oligomerization of ethylene in the presence of ethylene, a catalyst, a solvent, and a solid adsorbent.

[0020] The aforementioned separator 120 refers to a device that achieves phase separation by utilizing the density difference between the solid and liquid phases in a fluid, based on mechanisms such as centrifugal force, centripetal buoyancy, fluid drag, gravity, and concentration gradient. Specific forms include, but are not limited to, hydrocyclones, centrifuges, settling tanks, self-cleaning filters, cross-flow filtration separators, or membrane separators. In the implementation of this system, separator 120 is used to perform solid-liquid separation on the reaction mixture from reactor 110, obtaining a first stream (concentrated phase) containing adsorbent and by-product macromolecular polymers, and a second stream (dilute phase) containing the target product and solvent. The concentrated phase contains at least 99.0 wt% adsorbent and at least 95 wt% by-product polymers. This separation process achieves phase separation between the by-product polymer and α-polymer. Separation of olefin products.

[0021] It should be noted that the aforementioned reactor 110 includes, but is not limited to, a stirred tank reactor, a bubbling bed reactor, and a circulating fluidized bed reactor. The stirred tank reactor allows for stronger material turbulence of the adsorbent, further enhancing gas-liquid contact and mass and heat transfer. The bubbling bed reactor and the circulating fluidized bed reactor, through their fluid dynamic characteristics, ensure thorough mixing of the adsorbent and the reaction system, preventing localized adsorbent accumulation. The reactor 110 may also be equipped with external heat exchange structures, such as heat exchange jackets or heat exchange coils, for controlling the reaction temperature.

[0022] In actual operation, ethylene, catalyst, adsorbent, and solvent are introduced into reactor 110, and a selective oligomerization reaction of ethylene is carried out under stirred or flowing conditions. During the reaction, the adsorbent is uniformly dispersed in the system, and its surface can adsorb the by-product macromolecular polymer, while promoting gas-liquid mixing and mass and heat transfer. The reaction mixture is continuously led out through the outlet of reactor 110 and sent to separator 120, where separation is achieved by utilizing density differences, resulting in a first stream (concentrated phase) containing more than 99.0 wt% adsorbent and more than 95 wt% by-product polymer, and a second stream (dilute phase) containing the target product and solvent. The first stream is discharged from the first outlet a and enters the by-product polymer processing unit 130 for further processing to recover the adsorbent and solvent. The second stream is discharged from the second outlet b and splits into two paths. One path enters the product distillation separation unit 140, where high-purity α is obtained through distillation. The olefin product, after being cooled, is returned to reactor 110 through reflux inlet c to remove the heat of reaction and maintain the material balance of the system, thereby enabling the unit to efficiently remove by-product polymers and improve product selectivity under continuous operation.

[0023] In some examples, the by-product polymer processing unit 130 described above uses conventional methods in the art to perform heating, flash evaporation and / or distillation, devolatilization, filtration and separation on the mixed stream containing adsorbent and by-product polymer, so as to further concentrate and separate the by-product polymer and recover the entrained liquid products and solvents therein. The specific processing technology and configuration are known to those skilled in the art and will not be described in detail here.

[0024] In some examples, the aforementioned product distillation separation unit 140 also employs known conventional methods to process the dilute phase stream (containing α) from separator 120. The olefin and solvent are subjected to heating, flash evaporation and / or distillation, filtration and separation to finally obtain the target product 1. Hexene and / or 1 Octene. The specific equipment configuration and operating parameters of this unit are also conventional techniques in the art, and will not be described in detail in this disclosure. It should be understood that α-olefins refer to monoolefins with double bonds at the ends of the molecular chain. In the embodiments of this disclosure, α-olefins specifically refer to 1-octene and 1-hexene.

[0025] In one possible implementation, the system for removing by-product polymers in the ethylene oligomerization process of this disclosure further includes a cooler 150, a second path of the second outlet b being connected to the inlet of the cooler 150, and the outlet of the cooler 150 being connected to the reflux inlet c of the reactor 110.

[0026] It should be noted that the type of cooler 150 mentioned above includes, but is not limited to, shell-and-tube heat exchangers, coaxial heat exchangers, spiral heat exchangers, (spiral) plate heat exchangers, or air coolers. These heat exchange devices can be selected and configured according to actual process requirements and site conditions to ensure effective cooling and temperature control of the return material.

[0027] In practice, the second stream from the second outlet b can be first sent to the cooler for cooling, and then returned to the reactor through the reflux inlet c of the reactor 110. This removes the heat of reaction generated in the selective oligomerization of ethylene. Combined with the heat exchange jacket, heat exchange coil and other structures outside the reactor 110, the reaction system can be stabilized in the reaction temperature range of ethylene oligomerization, avoiding the decrease in catalyst activity or the surge in by-product polymers caused by temperature fluctuations.

[0028] In some examples, the system for removing by-product polymers in the ethylene oligomerization process of this disclosure further includes a circulation pump 160, with the outlet of the reactor 110 connected to the inlet of the circulation pump 160 and the outlet of the circulation pump 160 connected to the inlet of the separator 120.

[0029] It is understood that the above-mentioned circulating pump 160 includes, but is not limited to, centrifugal pumps, axial flow pumps, vortex pumps, screw pumps or gear pumps, and can be adapted and selected according to process flow rate, pressure, material characteristics and operational stability requirements.

[0030] In practice, the circulating pump 160 provides necessary pressurization to the discharge from the reactor 110, ensuring that the reaction mixture can overcome the resistance of the pipeline and separation equipment and be stably and continuously delivered to the separator 120 for separation. The operating pressure of this circulating pump can be adjusted according to actual process requirements, typically ensuring that its outlet pressure is slightly higher than the reactor operating pressure, for example, 0.5 MPaG to 1.5 MPaG higher, to form a stable material circulation and maintain system pressure balance. The circulating pump 160 not only ensures the continuous operation of the entire process but also helps maintain the uniformity of material composition and concentration within the reactor, further improving separation efficiency and system stability.

[0031] In one feasible embodiment, this disclosure also provides a method for removing by-product polymers in an ethylene oligomerization process, applied to the above-mentioned... Figure 1 A system for removing by-product polymers in the ethylene oligomerization process. Figure 2 A flowchart illustrating the preparation process of the method for removing by-product polymers in the ethylene oligomerization process according to embodiments of this disclosure is shown, as follows: Figure 2 As shown, the method for removing by-product polymers in the ethylene oligomerization process of this disclosure includes: Step 201: Ethylene, catalyst, adsorbent and solvent are continuously fed into the reactor to carry out selective oligomerization of ethylene. The adsorbent is a solid particle or powder with a median particle size of 10 μm to 1 mm, preferably 100 μm to 800 μm.

[0032] For example, ethylene, a catalyst, an adsorbent, and a solvent can be introduced into reactor 110 to carry out a selective oligomerization reaction of ethylene at a reaction temperature of 30℃~80℃ and a reaction pressure of 3.2MPaG~6.5MPaG for a reaction time of 15min~60min. During the reaction, by adding solid particles or powdered adsorbent with a median particle size of 10μm~1mm to the reactor, the gas-liquid contact surface area of ​​the reaction system can be significantly increased, allowing for more uniform mixing of ethylene, catalyst, and solvent, and significantly improving mass and heat transfer efficiency. This promotes the main reaction of selective oligomerization of ethylene, effectively improves the selectivity of the formation of target α-olefins such as 1-hexene and 1-octene, and reduces the generation of by-product polymers. Moreover, the adsorbent can adsorb the viscous byproduct macromolecular polymers generated in the reaction onto its surface and within its pores through its high specific surface area. At the same time, the adsorbent's aggregation effect enables the polymers to form easily separable aggregates, reducing the adhesion of polymers to the reactor wall, stirring paddle, and other internal components from the source, and avoiding the aggravated side reaction cycle caused by polymers encapsulating the catalyst.

[0033] Preferably, the reaction temperature is 40℃~60℃, the reaction pressure is 4.0MPaG~5.0MPaG, and the reaction time is 30min~45min.

[0034] In one example, the method further includes purifying the ethylene, adsorbent, and solvent separately before continuously feeding the ethylene, catalyst, adsorbent, and solvent into the reactor.

[0035] For example, the above purification process includes reducing the impurity content in ethylene, the adsorbent, and the solvent to within the allowable range of the process: for example, water content ≤ 5 ppmw, oxygen content ≤ 5 ppmw, sulfur ≤ 1 ppmw, phosphorus ≤ 1 ppmw, and arsenic ≤ 1 ppmw in the ethylene. The adsorbent may be dried to reduce its water content to ≤ 100 ppmw. The solvent may be dehydrated and deoxygenated to reduce its water content to ≤ 10 ppmw and its oxygen content to ≤ 5 ppmw.

[0036] In some examples, the method further includes mixing the adsorbent and solvent before continuously feeding ethylene, the catalyst, the adsorbent, and the solvent into the reactor. During mixing, the purified adsorbent is uniformly dispersed in the solvent to form a stable adsorbent. The solvent suspension system is then continuously fed into reactor 110 along with ethylene and the catalyst. This pretreatment step effectively avoids the poisoning of catalyst activity by impurities, ensures the dispersion stability and adsorption efficiency of the adsorbent, and thus improves the operating efficiency and product selectivity of the entire reaction system.

[0037] For example, the mass concentration of the adsorbent in the solvent is 0.01% to 10%, preferably 0.1% to 5%. Within this concentration range, the adsorbent can be fully dispersed in the reaction system, ensuring both its effective adsorption surface area and polymer capture capacity, while avoiding problems such as increased system viscosity, deteriorated mass transfer, or accelerated equipment wear caused by excessively high concentrations.

[0038] For the aforementioned adsorbents, the adsorbents can be selected from one or more of activated carbon, alumina, molecular sieves, reduced iron, and silica gel. These adsorbents possess high specific surface area, suitable pore structure, and good chemical stability, enabling them to maintain structural integrity and effectively adsorb by-product polymers under ethylene oligomerization reaction conditions.

[0039] For the solvents mentioned above, they can be selected from alkanes and / or alkenes with 5 to 9 carbon atoms. Examples include n-pentane, n-hexane, cyclohexane, n-heptane, n-octane, 1-hexene, 1-octene, or mixtures thereof. These solvents possess good ethylene solubility, suitable boiling point ranges, and compatibility with the reaction system, providing a homogeneous and stable liquid phase environment for the reaction, while also facilitating the separation and recovery of subsequent products.

[0040] The catalyst described above may include an active metal, a ligand, and a co-catalyst. The active metal is selected from one or more of chromium, titanium, and zirconium, and the co-catalyst is selected from alkyl aluminum compounds or modified methylaluminoxane.

[0041] Specifically, the active metal is preferably chromium, and the ligand can be selected from organic ligand systems containing electron-donating groups such as phosphorus and nitrogen, for example, PNP-type ligands. The co-catalyst can be triisobutylaluminum, triethylaluminum, or methylaluminoxane and their modified derivatives. This catalyst system can achieve highly efficient and selective oligomerization of ethylene under selected reaction conditions, promoting the polymerization of target α-elements such as 1-hexene and 1-octene. It promotes the formation of olefins while maintaining good catalytic stability.

[0042] Step 202: The reaction mixture is fed into a separator for separation to obtain a first stream containing the adsorbent and by-product polymer and a second stream containing the product.

[0043] For example, after the reaction in step 201 is completed, the mixture is pressurized to 4.2 MPaG~7.5 MPaG by circulating pump 160 and then transported to separator 120, utilizing the solid phase (adsorbent and by-product polymer) and the liquid phase (α) Separation is achieved through the density difference between the olefin product and the solvent, as well as the effects of centrifugal force and gravity, yielding a first stream (concentrated phase) containing the adsorbent and by-product polymers, and a second stream (dilute phase) containing the product. The first stream contains at least 99.0 wt% adsorbent and at least 95.0 wt% by-product polymers, while the second stream contains only a very small amount of by-product polymers, mainly including the target α-olefin. Olefin products and solvents. This separation process enables the efficient removal of by-product polymers, laying the foundation for subsequent product purification and polymer processing.

[0044] In a preferred embodiment, the outlet pressure of the circulation pump 160 is 1.0 MPaG higher than the operating pressure of the reactor 110, ensuring that the reaction mixture can stably overcome the resistance of the pipeline and separator, forming a continuous and uniform material circulation.

[0045] Step 203: Send the first material to the by-product polymer processing unit for processing.

[0046] In practice, the aforementioned first-phase material (dense phase) is transported via pipeline to the by-product polymer processing unit, where it is processed using conventional separation and recovery processes, including but not limited to heating, flash evaporation, distillation, devolatilization, or filtration. During the processing, entrained solvents and undeactivated adsorbents can be recovered, enabling partial recycling of the material. Simultaneously, the by-product polymer is concentrated and separated, facilitating subsequent disposal or resource utilization.

[0047] Step 204: The second stream is divided into two paths. The first path is sent to the product distillation and separation unit for separation to obtain α. The olefins, after being cooled, are returned to the reactor as reflux.

[0048] In practice, the aforementioned second stream (dilute phase) is diverted, with the first stream entering the product distillation and separation unit. Through conventional separation methods such as distillation and condensation, the α-phase is separated... Alkenes (such as 1) Hexene, 1 Octene is efficiently separated and purified from the solvent to obtain the target olefin that meets product specifications. The second stream, after being cooled to a suitable temperature (e.g., 30℃~54℃) by a cooler, is returned to the reaction system as reflux liquid through the reactor reflux port. This effectively removes the heat of reaction, maintaining a stable reaction temperature, replenishes the solvent and active components in the reaction system, maintains material balance, and further enhances system mixing and improves mass transfer efficiency through circulation. This reflux design achieves the removal of reaction heat and internal circulation of materials, ensuring reaction selectivity while supporting long-term continuous and stable operation of the system.

[0049] In some examples, the reaction system of this disclosure embodiment was stopped after running continuously for 2000 hours. Upon inspection of the inside of the reaction system, no by-product macromolecular polymer residues were found on the inner wall of the equipment, the surface of the internal components, and the inner wall of the pipes. The by-product polymer removal rate was ≥95.0 wt%. The by-product polymer removal rate refers to the ratio of the mass flow rate of the by-product polymer in the concentrated phase at the outlet of separator 120 to the mass flow rate of the by-product polymer in the separator feed, and is expressed as a mass percentage (wt%).

[0050] It should be noted that the by-product polymer in this embodiment refers to a macromolecular substance with a molecular weight (MW) ≥ 2000 g / mol, and the adsorbent removal rate refers to the ratio of the adsorbent mass flow rate in the concentrated phase at the outlet of separator 120 to the adsorbent mass flow rate in the feed 105 of separator, and is expressed as a mass percentage (wt%).

[0051] In summary, the method and system for removing by-product polymers in the ethylene oligomerization process of this disclosure effectively overcome the limitations of existing technologies in the selective oligomerization of ethylene to prepare α-polymers. This method overcomes the technical limitations of traditional olefin production processes, such as requiring shutdowns to clean byproduct polymers, adding flocculants, or installing complex packing materials. It achieves efficient and continuous removal of byproduct polymers. Furthermore, this method features a simple process flow, low equipment investment, and flexible operation, significantly improving overall process economy and production efficiency while resolving system blockage caused by byproduct polymers.

[0052] Example 1 In the first step, the raw materials ethylene, adsorbent, and solvent, after being purified, are continuously fed into reactor 110 at a flow rate of 300 kg / h for ethylene, 370 kg / h for solvent, 0.2 kg / h for catalyst, and 3.7 kg / h for adsorbent. The adsorbent is a granular Y-type molecular sieve with a median particle size of 200 μm, and its mass ratio to the solvent is 1:10. Under reaction conditions of 52℃ and 5.0 MPaG, ethylene dissolves in the solvent and undergoes selective oligomerization under the action of the catalyst, with a reaction residence time of 40 min.

[0053] In the second step, the reacted mixture is pumped by circulating pump 160 at a flow rate of 38,950 kg / h to separator 120 (concentrating hydrocyclone), where solid-liquid separation is performed at a flow rate of 8 m / s to 10 m / s. Two streams, a dense phase and a dilute phase, are obtained from the hydrocyclone outlet: the dense phase has a flow rate of 19 kg / h, with an adsorbent removal rate of 99.6 wt% and an adsorbent concentration of 19.4 wt%, and a by-product polymer removal rate of 95.2 wt% and a polymer concentration of 15.1 wt%; the dilute phase has a flow rate of 38,276 kg / h, mainly containing oligomers and solvent, with only trace amounts of by-product polymer.

[0054] In the third step, the dilute phase stream is further divided into two streams: one stream is discharged as the product, with a flow rate of 654.9 kg / h. The product is clear and transparent, with no polymer suspension or precipitation. After downstream processing, the total selectivity of (1-octene + 1-hexene) is measured to be 82.4%. The other stream is cooled to 48°C by a cooler and returned to reactor 110 to maintain the reaction temperature and constitute material reflux.

[0055] The fourth step involved stopping the reaction system after 2000 hours of continuous operation for inspection. No by-product macromolecular polymer residues were found on the reactor wall, stirring paddle, heat exchange surface, or inside the pipes. This indicates that the method can effectively inhibit polymer adhesion and accumulation during long-term operation, ensuring stable, continuous, and efficient system operation.

[0056] Example 2 In the first step, purified raw materials ethylene, reduced iron powder adsorbent, and solvent are continuously fed in at a flow rate of 300 kg / h for ethylene, 370 kg / h for solvent, 0.2 kg / h for catalyst, and 3.7 kg / h for adsorbent, with an adsorbent-to-solvent mass ratio of 1:10. The adsorbent used is reduced iron powder with a median particle size of 140 μm. The reaction conditions are a temperature of 52℃, a pressure of 5.0 MPaG, and a residence time of 40 min. Ethylene dissolves in the solvent and undergoes selective oligomerization under the action of the catalyst.

[0057] In the second step, the reaction mixture is pumped into a concentrator hydrocyclone at a flow rate of 38,870 kg / h via a circulating pump, with a flow velocity of 8 m / s to 10 m / s inside the hydrocyclone. After separation: the concentrated phase discharge flow rate is 14.5 kg / h, with an adsorbent removal rate of 99.8 wt% and an adsorbent concentration of 25.5 wt%, and a by-product polymer removal rate of 97.4 wt% and a polymer concentration of 20.2 wt%; the dilute phase discharge flow rate is 38,196 kg / h, mainly containing products and solvents, with only trace amounts of by-product polymers.

[0058] In the third step, a portion of the dilute phase stream is discharged as product at a flow rate of 659.9 kg / h. The product is clear and transparent, with no polymer suspension or precipitation. Downstream analysis showed a total selectivity of 84.1% for (1-octene + 1-hexene). The other portion is cooled to 48°C by a cooler and returned to the reactor to maintain the reaction temperature and material circulation.

[0059] The fourth step involved inspecting the reaction system after 2000 hours of continuous operation. No by-product polymer residues were found on the reactor wall, internal components, and pipes, indicating that the use of reduced iron powder adsorbent can also achieve efficient polymer removal and long-term stable operation of the system.

[0060] Example 3 In the first step, purified ethylene, adsorbent, and solvent are continuously fed into the reactor at a flow rate of 300 kg / h for ethylene, 370 kg / h for solvent, 0.2 kg / h for catalyst, and 3.7 kg / h for adsorbent, with a mass ratio of adsorbent to solvent of 1:10. The adsorbent is a granular Y-type molecular sieve with a median particle size of 200 μm. The reaction conditions are a temperature of 52℃, a pressure of 5.0 MPaG, and a residence time of 40 min. Ethylene dissolves in the solvent and undergoes selective oligomerization under the action of the catalyst.

[0061] In the second step, the reaction mixture was fed into a centrifuge via a circulating pump at a flow rate of 38,560 kg / h, with the centrifuge speed at 400 r / min. After separation, the following results were obtained: a concentrated phase with a flow rate of 8.2 kg / h, wherein the adsorbent removal rate was 99.9 wt% and the adsorbent concentration was 45.1 wt%, and the by-product polymer removal rate was 99.1 wt% and the polymer concentration was 36.3 wt%; and a dilute phase with a flow rate of 37,886 kg / h, which mainly contained oligomers and solvents, with only trace amounts of by-product polymers.

[0062] In the third step, a portion of the dilute phase stream is discharged as product at a flow rate of 665.7 kg / h. The product is clear and transparent, with no polymer suspension or precipitation. Downstream analysis showed a total selectivity of 85.3% for (1-octene + 1-hexene). The other portion is cooled to 48°C by a cooler and returned to the reactor to maintain the reaction temperature and material circulation.

[0063] The fourth step involved checking the system after 2000 hours of continuous operation. No by-product polymer residues were found on the reactor wall, internal components, and pipes, indicating that centrifugal separation can also efficiently remove polymers and ensure long-term stable operation of the system.

[0064] Example 4 In the first step, purified ethylene, adsorbent, and solvent are continuously fed into the reactor. The flow rates are: ethylene 300 kg / h, solvent 370 kg / h, catalyst 0.2 kg / h, and adsorbent 5.6 kg / h, with an adsorbent-to-solvent mass ratio of 1.5:10. A granular Y-type molecular sieve with a median particle size of 200 μm is selected as the adsorbent. The reaction conditions are: temperature 52℃, pressure 5.0 MPaG, and residence time 40 min. Ethylene dissolves in the solvent and undergoes selective oligomerization under the action of the catalyst.

[0065] In the second step, the reaction mixture was pumped into a concentrator hydrocyclone at a flow rate of 38,420 kg / h via a circulating pump, with a flow velocity of 8 m / s to 10 m / s inside the hydrocyclone. After separation, the following results were obtained: a dense phase with a flow rate of 17.1 kg / h, wherein the adsorbent removal rate was 99.7 wt% and the adsorbent concentration was 32.6 wt%, and the by-product polymer removal rate was 96.9 wt% and the polymer concentration was 17.0 wt%; and a dilute phase with a flow rate of 37,744 kg / h, which mainly contained oligomers and solvents, with only trace amounts of by-product polymers.

[0066] In the third step, a portion of the dilute phase stream is discharged as product at a flow rate of 658.7 kg / h. The product is clear and transparent, with no polymer suspension or precipitation. Downstream analysis showed a total selectivity of 83.2% for (1-octene + 1-hexene). The other portion is cooled to 48°C by a cooler and returned to the reactor to maintain the reaction temperature and material circulation.

[0067] The fourth step involved checking the system after 2000 hours of continuous operation. No by-product polymer residues were found on the reactor wall, internal components, and pipes, indicating that the system could still maintain efficient removal and stable operation even with a high adsorbent dosage (1.5:10).

[0068] Comparative Example 1 Comparative Example 1 did not contain any adsorbent or separator, and included the following steps: In the first step, purified ethylene and solvent were continuously fed into the reactor at a flow rate of 300 kg / h for ethylene, 370 kg / h for solvent, and 0.2 kg / h for catalyst. The reaction conditions were a temperature of 52°C, a pressure of 5.0 MPaG, and a residence time of 40 min. Ethylene dissolved in the solvent and underwent selective oligomerization under the action of the catalyst. No adsorbent was added in this comparative example.

[0069] In the second step, the reaction mixture is pumped out at a flow rate of 38330 kg / h and directly divided into two streams without passing through a separator: one stream, with a flow rate of 37660 kg / h, is cooled to 48°C by a cooler and returned to the reactor to maintain the reaction temperature; the other stream is discharged as the product at a flow rate of 670.2 kg / h. Observation revealed that the discharged stream was turbid and contained filamentous and flaky by-product polymers.

[0070] In the third step, downstream analysis showed that the overall selectivity of the target product (1-octene + 1-hexene) was only 76.4%. After 84 hours of system operation, equipment and pipeline blockages occurred. Upon shutdown and inspection, it was found that a large amount of blocky by-product polymers had accumulated on the inner walls of the reactor, internal components, and pipelines, making it impossible to continue operation.

[0071] Comparative Example 2 Comparative Example 2, without any adsorbent, contains a separator and includes the following steps: In the first step, purified ethylene and solvent were continuously fed into the reactor at a flow rate of 300 kg / h for ethylene, 370 kg / h for solvent, and 0.2 kg / h for catalyst. The reaction conditions were a temperature of 52°C, a pressure of 5.0 MPaG, and a residence time of 40 min. Ethylene dissolved in the solvent and underwent selective oligomerization under the action of the catalyst. No adsorbent was added in this comparative example.

[0072] In the second step, the reaction mixture was pumped into a hydrocyclone concentrator at a flow rate of 38260 kg / h, with a flow velocity of 8 m / s to 10 m / s inside the hydrocyclone. After separation, the following results were obtained: a dense phase with a flow rate of 20.3 kg / h, a by-product polymer removal rate of only 15.2 wt%, and a polymer concentration of 2.3 wt%; a dilute phase with a flow rate of 37590 kg / h, which was cooled to 48°C by a cooler and returned to the reactor; and a product with a flow rate of 649.9 kg / h, which was turbid and contained clearly visible filamentous and sheet-like polymers.

[0073] In the third step, downstream analysis showed that the total selectivity of the target product (1-octene + 1-hexene) was 80.6%. After 156 hours of system operation, equipment and pipeline blockage occurred. Inspection revealed that a large amount of blocky by-product polymers were attached to the inner wall of the reactor, internal components, and pipelines.

[0074] Table 1 shows a comparison of the removal of by-product polymers in the embodiments of this disclosure and the comparative examples.

[0075] Table 1:

[0076] As shown in Table 1 above, Examples 1 to 4, employing the adsorption, separation, and recycling process system of this disclosure, achieved a by-product polymer removal rate of 95.2% to 99.1%, with continuous system operation exceeding 2000 hours. No significant polymer residue was found on the reactor wall, internal components, or pipes. In Comparative Example 1 (no adsorbent added and no separator) and Comparative Example 2 (separator only, no adsorbent added), the by-product polymer removal rate was either unachievable or only 15.2%, and the systems shut down due to blockage after 84 and 156 hours, respectively. This demonstrates that the method of this disclosure effectively inhibits polymer adhesion and accumulation, ensuring long-term stable operation of the device. Simple separation equipment cannot effectively handle viscous polymers; the introduction of adsorbent and its synergistic effect with the separation process are necessary conditions for achieving efficient polymer removal.

[0077] Building upon this, in the embodiments, the polymer removal efficiency and product selectivity can be improved by adjusting the type of adsorbent (such as molecular sieves or reduced iron powder), increasing the amount of adsorbent (such as increasing the adsorbent-solvent ratio to 1.5:10 in Example 4), and changing the type of separation equipment (such as hydrocyclones or centrifuges). For example, using centrifuge separation (Example 3) can increase the polymer removal rate to 99.1% and the total product selectivity to 85.3%.

[0078] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0079] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0080] Additionally, as used herein, the "or" used in a list of items beginning with "at least one" indicates a separate list, such that a list of, for example, "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). Furthermore, the word "exemplary" does not imply that the described example is preferred or better than other examples.

[0081] It should also be noted that in the systems and methods of this disclosure, the components or steps can be decomposed and / or recombined. These decompositions and / or recombinations should be considered as equivalent solutions to this disclosure.

[0082] Various changes, substitutions, and modifications can be made to the technology described herein without departing from the teachings defined by the appended claims. Furthermore, the scope of the claims of this disclosure is not limited to the specific aspects of the processes, machines, manufactures, events, means, methods, and actions described above. Currently existing or later-developed processes, machines, manufactures, events, means, methods, or actions that perform substantially the same function or achieve substantially the same result as the corresponding aspects described herein can be utilized. Therefore, the appended claims include such processes, machines, manufactures, events, means, methods, or actions within their scope.

[0083] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0084] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for removing by-product polymers in an ethylene oligomerization process, characterized in that, Includes the following steps: Ethylene, catalyst, adsorbent and solvent are continuously fed into a reactor to carry out a selective oligomerization reaction of ethylene, wherein the adsorbent is a solid particle or powder and the median particle size of the adsorbent is 10 μm to 1 mm. The reaction mixture is fed into a separator to separate the two streams, resulting in a first stream containing the adsorbent and the by-product polymer and a second stream containing the product. The first logistics is sent to the by-product polymer processing unit for processing. The second stream is divided into two streams. The first stream is sent to the product distillation and separation unit for separation to obtain α. The olefins, after being cooled, are returned to the reactor as reflux.

2. The method for removing by-product polymers in the ethylene oligomerization process according to claim 1, characterized in that, Before continuously introducing ethylene, catalyst, adsorbent, and solvent into the reactor, the method further includes: The ethylene, adsorbent, and solvent are purified separately. The adsorbent and the solvent are mixed.

3. The method for removing by-product polymers in the ethylene oligomerization process according to claim 2, characterized in that, The adsorbent has a mass concentration of 0.01% to 10% in the solvent.

4. The method for removing by-product polymers in the ethylene oligomerization process according to claim 1, characterized in that, The adsorbent is selected from one or more of activated carbon, alumina, molecular sieve, reduced iron, and silica gel.

5. The method for removing by-product polymers in the ethylene oligomerization process according to claim 1, characterized in that, In the selective oligomerization reaction of ethylene, the reaction temperature is 30℃~80℃, the reaction pressure is 3.2MPaG~6.5MPaG, and the reaction time is 15min~60min.

6. The method for removing by-product polymers in the ethylene oligomerization process according to any one of claims 1 to 5, characterized in that, The solvent is selected from alkanes and / or alkenes with 5 to 9 carbon atoms.

7. The method for removing by-product polymers in the ethylene oligomerization process according to any one of claims 1 to 5, characterized in that, The catalyst comprises an active metal, a ligand, and a co-catalyst, wherein the active metal is selected from at least one of chromium, titanium, or zirconium, and the co-catalyst is selected from alkylaluminum compounds or modified methylaluminoxanes.

8. A system for removing by-product polymers in an ethylene oligomerization process, characterized in that, include: The reactor comprises a separator, a by-product polymer processing unit, and a product distillation and separation unit. The outlet of the reactor is connected to the inlet of the separator. The separator has a first outlet and a second outlet. The first outlet is connected to the inlet of the by-product polymer processing unit. The reactor has a reflux inlet. The second outlet is divided into two paths: the first path is connected to the inlet of the product distillation and separation unit, and the second path is connected to the reflux inlet of the reactor. The reactor is used for selective oligomerization of ethylene in the presence of ethylene, a catalyst, a solvent, and a solid adsorbent.

9. The system for removing by-product polymers in the ethylene oligomerization process according to claim 8, characterized in that, It also includes a cooler, with the second outlet connected to the inlet of the cooler and the outlet of the cooler connected to the reflux inlet of the reactor.

10. The system for removing by-product polymers in the ethylene oligomerization process according to claim 8, characterized in that, It also includes a circulating pump, with the outlet of the reactor connected to the inlet of the circulating pump, and the outlet of the circulating pump connected to the inlet of the separator.

Images