Method for producing polyethylene by means of operation using reactor completely filled with slurry

Abstract

A method for producing polyethylene by means of an operation using a reactor completely filled with a slurry. The method comprises: introducing an alkane solvent into a polymerization reactor until the polymerization reactor is in a completely-filled state; introducing ethylene into the polymerization reactor in a completely-filled state until the concentration of ethylene in the polymerization reactor is 12-100%; introducing hydrogen into the polymerization reactor until the molar ratio of hydrogen to ethylene in the polymerization reactor is 0.00001-0.0025; introducing comonomers into the polymerization reactor until the molar ratio of the comonomers to ethylene in the polymerization reactor is 0.001-0.1; synchronously adding a metallocene catalyst and a co-catalyst to the polymerization reactor; and establishing a polymerization reaction, and then continuously introducing ethylene and the comonomers into the polymerization reactor to perform a polymerization reaction, so as to obtain a target polyethylene product. The method achieves the strengthening of the polymerization reaction process by controlling various process conditions; moreover, the process of the polymerization reaction is stable, the time for process adjustments is relatively short, and the consumption of materials and energy and the amount of transition materials are low.

Description

A method for producing polyethylene using a slurry-filled reactor.

[0001] This application claims priority to Chinese Patent Application No. 202411534535.7, filed on October 30, 2024, entitled "A Method for Producing Polyethylene by Full-Bottle Operation with Slurry", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to a method for producing polyethylene using a slurry-filled reactor, belonging to the field of olefin polymerization technology, particularly the field of controlling the ethylene polymerization process. Background Technology

[0003] High-density polyethylene (HDPE) production methods include gas-phase, solution-phase, and slurry processes. Among these, the batch slurry process has a higher market share and is capable of producing high-performance polyethylene resins. It has become a crucial process for HDPE production, with typical examples being Mitsui's CX process and LyondellBasell's Hostalen / ACP process. The slurry process typically uses solvents such as hexane, isobutane, or mixed alkanes to dissolve ethylene monomers, comonomers, and the molecular weight regulator hydrogen. After contacting a catalyst, the polymerized polyethylene particles are suspended in the solvent medium to form a slurry. Currently, existing technologies (e.g., US9790303B2, US20150259446A1, WO2012 / 028591A1, and EP 2336200 A1) typically produce bimodal polyethylene in two or more cascaded batch reactors. The process of producing bimodal polyethylene in a cascaded reactor requires individual control of polymerization conditions in each reactor. The operating conditions are quite demanding, and the material needs a considerable amount of time to reach steady-state operation during the polymerization reaction. It is necessary to control the solids concentration in the target reactor while ensuring sufficient residence time for the polyethylene product to achieve the desired productivity.

[0004] CN106146713A discloses a single-reactor slurry polyethylene process with an ethylene feed rate of 100 kg / h. In this method, a mixture of hexane, triethylaluminum co-catalyst, and titanium tetrachloride main catalyst is added to the reactor from the bottom. Hydrogen and vaporized propylene or butene-1 are added to the ethylene pipeline and mixed with the ethylene before entering the reactor through a bottom pipe for polymerization. The reactor level is controlled at 50-85%, and the comonomers propylene and butene-1 account for 0-8% of the ethylene by weight. The polymerization slurry is a hexane suspension containing 10-30% polyethylene by weight. This process is compatible with both the Hostalen process from Basell (Germany) and the CX process from Mitsui Chemicals (Japan). However, this process, with an ethylene feed rate of 100 kg / h, does not provide operating conditions for maintaining stable reactor pressure. If the reactor becomes overpressured, significant ethylene loss occurs through venting, resulting in high energy consumption.

[0005] CN116410372A discloses a method for producing bimodal polyethylene resin by homopolymerization or copolymerization with α-olefins in a single slurry polymerization reactor. This method adjusts the melt flow rate of bimodal polyethylene by controlling the hydrogen concentration based on the hydrogen sensitivity of the catalyst's active center. By leveraging the differences in copolymerization performance of the active centers, comonomers can be effectively inserted into the high molecular weight fraction, which helps improve the long-term mechanical properties of the bimodal polyethylene product. However, this method, relying solely on catalyst performance to control the properties of high-density polyethylene products, cannot accurately guide industrial-scale pilot production.

[0006] CN105669883A discloses a method for in-situ copolymerization to prepare broad / bimodal polyethylene. This method selects a suitable NNN tridentate cobalt complex catalyst and reaction conditions, using ethylene as the monomer in a single reactor to obtain broad / bimodal polyethylene. The selectivity of C6-C12 in the α-olefin of the oligomer is 40%-60%, and a slurry process can be used to produce high-value-added broad / bimodal polyethylene. However, this method, by changing the catalyst ligand structure and adjusting the catalyst performance, only controls the performance of the high-density polyethylene product through a single catalyst variable, and cannot accurately guide industrial-scale pilot production.

[0007] Furthermore, the catalyst systems currently used in the slurry polymerization of polyethylene are typically titanium-based or chromium-based. This is because these slurry polymerization processes do not operate at full capacity; the gas phase space within the reactor allows for a very wide range of adjustments to the amount of hydrogen used as a chain transfer agent, resulting in polyethylene with a broad molecular weight distribution. However, when metallocene catalysts are used in slurry polymerization of ethylene, the amount of hydrogen is usually controlled at the ppm level, and within this range, the amount of hydrogen must be controllable. Therefore, this is quite demanding for metallocene catalysts with narrow molecular weight distributions.

[0008] Therefore, providing a novel method for producing polyethylene using a full-boiler operation with slurry has become a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0009] To address the aforementioned shortcomings and deficiencies, the present invention aims to provide a method for producing polyethylene using a full-boiler slurry process. This method enhances the polymerization reaction by controlling various process operating conditions, resulting in a stable polymerization process, shorter process setup time, higher equipment load, and lower material, energy, and transition material consumption.

[0010] To achieve the above objectives, in one aspect, the present invention provides a method for producing polyethylene using a slurry-filled reactor, wherein the method includes:

[0011] Step (1): Introduce alkane solvents into the polymerization reactor until the reactor is full;

[0012] Step (2): Introduce ethylene into the full-capacity polymerization reactor until the ethylene concentration in the polymerization reactor is 12-100 v% (based on the total volume of the polymerization reactor), then stop the ethylene feed;

[0013] Step (3): After the ethylene feed is completed, hydrogen is introduced into the polymerization reactor until the hydrogen / ethylene molar ratio in the polymerization reactor is 0.00001-0.0025, and then the hydrogen feed is stopped;

[0014] Step (4): After the hydrogen feed is completed, the comonomer is introduced into the polymerization reactor until the comonomer / ethylene molar ratio in the polymerization reactor is 0.001-0.1, and then the comonomer feed is stopped;

[0015] Step (5): After the comonomer feed is completed, metallocene catalyst and co-catalyst are simultaneously added to the polymerization reactor;

[0016] Step (6): Establish a polymerization reaction, and then continuously introduce ethylene and comonomers into the polymerization reactor to carry out the polymerization reaction and obtain the target polyethylene product.

[0017] In step (1) of the method described above, the full state refers to controlling the liquid level in the polymerization reactor to 100%.

[0018] As a specific embodiment of the method described above in this invention, in step (1), the alkane solvent includes one or a combination of several of the following: propane, butane, isobutane, pentane, isopentane, and hexane.

[0019] In the method described above in this invention, the ethylene concentration in the polymerization reactor is maintained at a target ethylene concentration, i.e., 12-100%, by adjusting the ethylene flow rate entering the polymerization reactor. As a specific embodiment of the method described above in this invention, in step (2), the ethylene feed flow rate is 10-100 kg / h.

[0020] In the method described above in this invention, the hydrogen flow rate entering the polymerization reactor is adjusted to maintain the hydrogen / ethylene molar ratio at a target range of 0.00001-0.0025. This invention does not impose specific requirements on the hydrogen flow rate; it can be adjusted as needed, as long as it ensures that the hydrogen flow rate in the polymerization reactor maintains the hydrogen / ethylene molar ratio at the target range of 0.00001-0.0025.

[0021] In the method described above in this invention, the comonomer flow rate entering the polymerization reactor is adjusted to maintain the comonomer / ethylene molar ratio at a target range, i.e., 0.001-0.1. This invention does not impose specific requirements on the comonomer flow rate; it can be adjusted as needed, as long as the comonomer / ethylene molar ratio in the polymerization reactor is maintained at the target range, i.e., 0.001-0.1. The ethylene flow rate, hydrogen flow rate, and comonomer flow rate in this invention can be measured using a mass flow meter.

[0022] As a specific embodiment of the method described above in this invention, in steps (4) and (6), the comonomer is an α-olefin, including one or a combination of several of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene and 4-methyl-1-pentene.

[0023] As a specific embodiment of the method described above in this invention, in step (5), the support for the metallocene catalyst includes an inorganic support, an organic support, or an inorganic-organic composite support.

[0024] As a specific embodiment of the method described above in this invention, the inorganic carrier includes SiO2, Al2O3, AlF3, Al(OHx)y, MgCl2, MgO, MgF2, molecular sieve, clay or zeolite, etc., and the organic carrier includes polystyrene, polymethyl methacrylate or polysiloxane, etc.

[0025] As a specific embodiment of the method described above in this invention, the co-catalyst includes organoboron compounds, alkylaluminum compounds, or alkylaluminoxanes, etc.

[0026] As a specific embodiment of the method described above in this invention, the alkylaluminum compound includes a trialkylaluminum compound, the alkylaluminoxane includes methylaluminoxane (MAO), ethylaluminoxane (EAO), or butylaluminoxane (BAO), etc., and the organoboron compound includes [HCB]. 11 H n X (11-n) ]-Anions, etc., where X is F, Cl, Br or I.

[0027] As a specific embodiment of the method described above in this invention, the trialkylaluminum compound includes trimethylaluminum (TMA), triethylaluminum (TEAL), triisobutylaluminum (TIBAL), or tri-n-hexylaluminum (TNHAL), etc.

[0028] As a specific embodiment of the method described above in this invention, in step (6), the establishment of the polymerization reaction includes starting the stirring and raising the temperature of the polymerization reactor to the reaction temperature of the polymerization reaction to establish the polymerization reaction.

[0029] As a specific embodiment of the method described above in this invention, in step (6), the temperature of the polymerization reaction is 30-110°C, preferably 60-110°C, and the pressure is 0.1-2 MPa, preferably 0.15-2 MPa.

[0030] As a specific embodiment of the method described above in this invention, step (6) further includes: during the polymerization reaction, based on the sampling analysis data, while keeping the ethylene feed rate and the metallocene catalyst feed rate constant, adjusting the hydrogen / ethylene molar ratio and the comonomer / ethylene molar ratio within the range of 0.00001-0.0025 and the comonomer / ethylene molar ratio within the range of 0.001-0.1 respectively, to ensure that the polymerization reaction is carried out under constant temperature and pressure conditions in the polymerization reactor, thereby obtaining the target polyethylene product.

[0031] As a specific embodiment of the method described above in this invention, in step (6), during the polymerization reaction, the concentration of polyethylene is 10-50% based on the total weight of the slurry (suspension) as 100%.

[0032] In the method described above in this invention, the temperature of the material entering the polymerization reactor can be controlled by adjusting the temperature of the temperature-controlled water used in the heat exchanger. For example, in some embodiments of this invention, the temperature of the temperature-controlled water can be set to 20-110°C.

[0033] In the method described above in this invention, liquid chromatography is used to analyze the composition, and the analytical objects include ethylene, hydrogen, alkane solvents and comonomers.

[0034] The method for producing polyethylene using the slurry-filled reactor operation of the present invention can obtain high-density polyethylene with a density of 0.942-0.970 g / cm³. 3 The molecular weight distribution (MWD) is 2.0-3.44.

[0035] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0036] The method provided by this invention utilizes a metallocene catalyst in a slurry-filled reactor to produce high-density polyethylene. This full-reactor operation allows for adjustable hydrogen concentrations at the ppm level. Under controllable conditions of the comonomer / ethylene molar ratio, hydrogen / ethylene molar ratio, catalyst feed, and ethylene feed rate, and while maintaining constant metallocene catalyst and ethylene feed rates, adjusting the comonomer / ethylene and hydrogen / ethylene molar ratios ensures constant pressure and temperature within the reactor, thereby obtaining the final target product. Furthermore, this method enables rapid polymerization, achieving polyethylene product specifications within 1-3 hours. The process is energy-efficient, has low production costs, high safety, and minimal venting, providing crucial technical support for polyolefin production and accurately guiding the industrial-scale pilot production of metallocene polyethylene using the slurry method. Detailed Implementation

[0037] It should be noted that the term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0038] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0039] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0040] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0041] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0042] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the appendices and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0044] In the following embodiments, the methods for characterizing the structure and properties of polyethylene include:

[0045] (1) Analytical criteria:

[0046] MI (Melt Flow Index): GB / T 3682-2018;

[0047] Density: GB / T 1033-2008.

[0048] (2) Detection frequency:

[0049] Aggregation and Adjustment Phase:

[0050] MI: 1 time / 1 hour;

[0051] Density: 1 time / 1 hour;

[0052] Production stage:

[0053] MI: 1 time / 2 hours;

[0054] Density: 1 time / 2 hours.

[0055] Example 1

[0056] This embodiment provides a method for producing polyethylene using a full-boiler operation with slurry, wherein the method includes the following specific steps:

[0057] Step (1): Replace the batch polymerization reactor with purified nitrogen. When the water content in the batch polymerization reactor is ≤3ppm, start feeding hexane. After the hexane feeding is completed, heat the batch polymerization reactor to 150℃ and boil for 4 hours. Analyze the oxygen value of the water using a trace water analyzer. When the oxygen value is ≤1ppm, it is considered qualified. Discharge the hexane from the batch polymerization reactor and start full-boil feeding with hexane again until the batch polymerization reactor is full, that is, the liquid level in the batch polymerization reactor is 100%.

[0058] Step (2): After the hexane full-boiler feed is completed, start the ethylene feed at 30 kg / h to establish the ethylene component concentration. Observe the ethylene concentration shown by liquid chromatography until the ethylene concentration in the batch polymerization reactor is 40%. At this time, the pressure of the batch polymerization reactor is 0.3 MPa.

[0059] Step (3): After the ethylene feed is completed, start the hydrogen feed, observe the liquid chromatography and obtain the hydrogen / ethylene molar ratio. Stop the hydrogen feed when the hydrogen / ethylene molar ratio in the batch polymerization reactor is 0.001.

[0060] Step (4): After the hydrogen feed is completed, start the 1-butene comonomer feed at 0.005 kg / h, observe the liquid chromatography and obtain the 1-butene / ethylene molar ratio, and stop the 1-butene feed when the 1-butene / ethylene molar ratio in the batch polymerization reactor is 0.01.

[0061] Step (5): After the 1-butene feed is completed, a metallocene catalyst and a co-catalyst MAO are added simultaneously, wherein the MAO is added according to an Al / Ti molar ratio of 10 with the metallocene catalyst.

[0062] Step (6): Start stirring and raise the temperature of the batch polymerization reactor to 75°C. After establishing the polymerization reaction, start feeding 50 kg of ethylene and 2.5 kg of 1-butene at a feed temperature of 35°C. Control the pressure of the batch polymerization reactor at 0.8 ± 0.05 MPa. Based on the sampling analysis data, with the ethylene feed rate and metallocene catalyst feed rate constant, adjust the 1-butene / ethylene molar ratio and hydrogen / ethylene molar ratio to achieve the target working conditions for the polymerization reaction. In each adjustment process, the slurry concentration is controlled at 36 ± 0.05 wt% to obtain the target polyethylene product.

[0063] In this embodiment, the 1-butene / ethylene molar ratio, hydrogen / ethylene molar ratio data, and the performance parameters of the obtained polyethylene product are shown in Table 1 below.

[0064] Table 1. 1-Butene / ethylene molar ratio, hydrogen / ethylene molar ratio, and performance parameters of the obtained polyethylene product in Example 1.

[0065] Comparative Example 1

[0066] This comparative example provides a method for producing polyethylene using a slurry-filled reactor, which differs from Example 1 only in that the adjusted hydrogen / ethylene molar ratio in step (6) is different and not within the range of 0.00001-0.0025.

[0067] The data for the 1-butene / ethylene molar ratio, hydrogen / ethylene molar ratio, and the performance parameters of the resulting polyethylene product in this comparative example are shown in Table 2 below.

[0068] Table 2 shows the 1-butene / ethylene molar ratio, hydrogen / ethylene molar ratio, and performance parameters of the obtained polyethylene product in Comparative Example 1.

[0069] Example 2

[0070] This embodiment provides a method for producing polyethylene using a full-boiler operation with slurry, wherein the method includes the following specific steps:

[0071] Step (1): Replace the batch polymerization reactor with purified nitrogen. When the water content in the batch polymerization reactor is ≤3ppm, start feeding hexane. After the hexane feeding is completed, heat the batch polymerization reactor to 150℃ and boil for 4 hours. Analyze the oxygen value of the water using a trace water analyzer. When the oxygen value is ≤1ppm, it is considered qualified. Discharge the hexane from the batch polymerization reactor and start full-boil feeding with hexane again until the batch polymerization reactor is full, that is, the liquid level in the batch polymerization reactor is 100%.

[0072] Step (2): After the hexane full-boiler feed is completed, start the ethylene feed at 50 kg / h to establish the ethylene component concentration. Observe the ethylene concentration shown by liquid chromatography until the ethylene concentration in the batch polymerization reactor is 50%. At this time, the pressure of the batch polymerization reactor is 0.8 MPa.

[0073] Step (3): After the ethylene feed is completed, start the hydrogen feed, observe the liquid chromatography and obtain the hydrogen / ethylene molar ratio. Stop the hydrogen feed when the hydrogen / ethylene molar ratio in the batch polymerization reactor is 0.0001.

[0074] Step (4): After the hydrogen feed is completed, start feeding 1 kg / h of the comonomer 1-butene, observe the liquid chromatography and obtain the 1-butene / ethylene molar ratio, and stop feeding 1-butene when the 1-butene / ethylene molar ratio in the batch polymerization reactor is 0.1.

[0075] Step (5): After the 1-butene feed is completed, a metallocene catalyst and a co-catalyst MAO are added simultaneously, wherein the MAO is added at an Al / Ti molar ratio of 20 with the metallocene catalyst.

[0076] Step (6): Start stirring and raise the temperature of the batch polymerization reactor to 80℃. After establishing the polymerization reaction, start feeding 70kg of ethylene and 5.0kg of 1-butene at a feed temperature of 35℃. Control the pressure of the batch polymerization reactor at 1.0±0.05MPa. Based on the sampling analysis data, with the ethylene feed rate and the metallocene catalyst feed rate constant, adjust the 1-butene / ethylene molar ratio and the hydrogen / ethylene molar ratio to achieve the target working conditions for the polymerization reaction. In each adjustment process, the slurry concentration is controlled at 40±0.05wt% to obtain the target polyethylene product.

[0077] The data on the 1-butene / ethylene molar ratio, hydrogen / ethylene molar ratio, and the performance parameters of the resulting polyethylene product in this embodiment are shown in Table 3 below.

[0078] Table 3. Performance parameters of 1-butene / ethylene molar ratio, hydrogen / ethylene molar ratio, and the resulting polyethylene product in Example 2.

[0079] Example 3

[0080] This embodiment provides a method for producing polyethylene using a full-boiler operation with slurry, wherein the method includes the following specific steps:

[0081] Step (1): Replace the batch polymerization reactor with purified nitrogen. When the water content in the batch polymerization reactor is ≤3ppm, start feeding hexane. After the hexane feeding is completed, heat the batch polymerization reactor to 150℃ and boil for 4 hours. Analyze the oxygen value of the water using a trace water analyzer. When the oxygen value is ≤1ppm, it is considered qualified. Discharge the hexane from the batch polymerization reactor and start full-boil feeding with hexane again until the batch polymerization reactor is full, that is, the liquid level in the batch polymerization reactor is 100%.

[0082] Step (2): After the hexane full-boiler feed is completed, start the ethylene feed at 10 kg / h to establish the ethylene component concentration. Observe the ethylene concentration shown by liquid chromatography until the ethylene concentration in the batch polymerization reactor is 60%. At this time, the pressure of the batch polymerization reactor is 0.5 MPa.

[0083] Step (3): After the ethylene feed is completed, start the hydrogen feed, observe the liquid chromatography and obtain the hydrogen / ethylene molar ratio. Stop the hydrogen feed when the hydrogen / ethylene molar ratio in the batch polymerization reactor is 0.00002.

[0084] Step (4): After the hydrogen feed is completed, start the 1-butene comonomer feed at 0.1 kg / h, observe the liquid chromatography and obtain the 1-butene / ethylene molar ratio. After the 1-butene / ethylene molar ratio in the batch polymerization reactor is 0.001, stop the butene-1 feed.

[0085] Step (5): After the 1-butene feed is completed, a metallocene catalyst and a co-catalyst MAO are added simultaneously, wherein the MAO is added at an Al / Ti molar ratio of 30 with the metallocene catalyst.

[0086] Step (6): Start stirring and raise the temperature of the batch polymerization reactor to 100℃. After establishing the polymerization reaction, start feeding 20kg of ethylene and 0.1kg of 1-butene. The feed temperature of both is 35℃. The pressure of the batch polymerization reactor is controlled at 1.0±0.05MPa. Based on the sampling analysis data, on the basis of keeping the ethylene feed rate and the metallocene catalyst feed rate constant, the polymerization reaction parameters are adjusted by adjusting the 1-butene / ethylene molar ratio and the hydrogen / ethylene molar ratio to achieve the target working conditions. In each adjustment process, the slurry concentration is controlled at 42±0.05wt% to obtain the target polyethylene product.

[0087] The data on the 1-butene / ethylene molar ratio, hydrogen / ethylene molar ratio, and the performance parameters of the resulting polyethylene product in this embodiment are shown in Table 4 below.

[0088] Table 4. 1-Butene / ethylene molar ratio, hydrogen / ethylene molar ratio, and performance parameters of the resulting polyethylene product in Example 3.

[0089] The experimental data from Examples 1-3 show that hydrogen is an effective chain transfer agent in the ethylene polymerization reaction under a metallocene catalyst system. In the presence of hydrogen, the transfer of active chains to hydrogen is the main chain transfer reaction. Therefore, the use of a metallocene catalyst and full-boiler operation in this invention can effectively control the hydrogen addition amount within the ppm range, thereby regulating the relative molecular mass and distribution of polyethylene and the degree of branching of the branches. Simultaneously, the amount of hydrogen also has a significant impact on the index, apparent density, and particle size distribution of the polyethylene product, as detailed in the experimental data obtained in Example 1 and Comparative Example 1.

[0090] The method provided in this invention utilizes online liquid chromatography connected to a batch polymerization reactor to analyze the liquid phase composition within the reactor, thereby effectively controlling the concentrations of various components in the ethylene slurry polymerization process, such as alkane solvents, ethylene, hydrogen, and α-olefin comonomers. Specifically, by using data from online liquid chromatography analysis connected to the batch reactor, the ethylene concentration is precisely adjusted, thereby controlling the comonomer / ethylene concentration ratio, the hydrogen / ethylene concentration ratio, and the catalyst feed rate. This effectively controls the structure, composition, molecular weight, and molecular weight distribution of the polyethylene product, improving its quality and optimizing its performance to obtain the final target product.

[0091] In summary, the method provided in this invention is simple and easy to implement, requires a short reaction time, and uses energy-saving and consumption-reducing equipment, making it an ideal slurry stirred tank reactor method for homopolymerization or copolymerization of ethylene. This method has guiding significance for catalyst evaluation systems in polyolefin industries, pilot-scale or small-scale plants.

[0092] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A method for producing polyethylene using a slurry-filled reactor, wherein, The method for producing polyethylene using a full-boiler operation with slurry includes: Step (1): Introduce alkane solvents into the polymerization reactor until the reactor is full; Step (2): Introduce ethylene into the full-capacity polymerization reactor until the ethylene concentration in the polymerization reactor is 12-100 v%, then stop feeding ethylene. Step (3): After the ethylene feed is completed, hydrogen is introduced into the polymerization reactor until the hydrogen / ethylene molar ratio in the polymerization reactor is 0.00001-0.0025, and then the hydrogen feed is stopped; Step (4): After the hydrogen feed is completed, the comonomer is introduced into the polymerization reactor until the comonomer / ethylene molar ratio in the polymerization reactor is 0.001-0.1, and then the comonomer feed is stopped; Step (5): After the comonomer feed is completed, metallocene catalyst and co-catalyst are simultaneously added to the polymerization reactor; Step (6): Establish a polymerization reaction, and then continuously introduce ethylene and comonomers into the polymerization reactor to carry out the polymerization reaction and obtain the target polyethylene product.

2. The method according to claim 1, wherein, In step (1), the alkane solvent includes one or a combination of several of propane, butane, isobutane, pentane, isopentane and hexane.

3. The method according to claim 1 or 2, wherein, In step (2), the feed flow rate of ethylene is 10-100 kg / h.

4. The method according to claim 1 or 2, wherein, In steps (4) and (6), the comonomer is C3-C. 10 α-olefins, including one or a combination of several of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene and 4-methyl-1-pentene.

5. The method according to claim 1, wherein, In step (5), the support for the metallocene catalyst includes an inorganic support, an organic support, or an inorganic-organic composite support.

6. The method according to claim 5, wherein, The inorganic carrier includes SiO2, Al2O3, AlF3, Al(OHx)y, MgCl2, MgO, MgF2, molecular sieve, clay or zeolite, and the organic carrier includes polystyrene, polymethyl methacrylate or polysiloxane.

7. The method according to any one of claims 1, 5-6, wherein, The cocatalyst includes alkylaluminum compounds or alkylaluminoxanes.

8. The method according to claim 7, wherein, The alkylaluminum compound includes a trialkylaluminum compound, and the alkylaluminoxane includes methylaluminoxane, ethylaluminoxane, or butylaluminoxane.

9. The method according to claim 1, wherein, In step (6), establishing the polymerization reaction includes starting the stirring and raising the temperature of the polymerization reactor to the reaction temperature of the polymerization reaction to establish the polymerization reaction.

10. The method according to claim 1 or 9, wherein, In step (6), the polymerization reaction is carried out at a temperature of 30-110°C and a pressure of 0.1-2 MPa.

11. The method according to claim 1 or 9, wherein, Step (6) further includes: during the polymerization reaction, based on the sampling analysis data, while keeping the ethylene feed rate and the metallocene catalyst feed rate constant, adjusting the hydrogen / ethylene molar ratio and the comonomer / ethylene molar ratio within the range of 0.00001-0.0025 and the comonomer / ethylene molar ratio within the range of 0.001-0.1 respectively, to ensure that the polymerization reaction is carried out under constant temperature and pressure conditions in the polymerization reactor, and to obtain the target polyethylene product.

12. The method according to claim 1 or 9, wherein, In step (6), during the polymerization reaction, the concentration of polyethylene is 10-50% based on the total weight of the slurry as 100%.

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