A system and method for online detection of the prepolymerization factor of olefin polymerization catalysts

Abstract

This invention relates to a system and method for online detection of the prepolymerization factor of olefin polymerization catalysts, belonging to the field of olefin polymerization catalyst technology. The method of this invention enables stable real-time detection of the prepolymerization factor of the catalyst, thereby achieving the goals of stable product production, ensuring product quality, and quantitatively controlling parameters. The system of this invention includes a separation tank, a buffer tank, a measuring device, and a control device connected in sequence. By online collection of the prepolymerization slurry, the particle size and particle size distribution of the catalyst and olefin prepolymer are measured. Through the corresponding standard curve, the prepolymerization factor of the catalyst can be accurately determined, thereby achieving the goal of ensuring catalyst activity and product quality.

Description

Technical Field

[0001] This invention relates to the field of olefin polymerization catalysts, and more particularly to a system and method for online detection of the prepolymerization ratio of catalysts in olefin polymerization, which is especially applicable to propylene polymerization and ethylene polymerization plants with prepolymerization processes. Background Technology

[0002] In the industrial production of polyolefins, prepolymerization technology of catalysts is often used to optimize production, improve catalyst activity, and enhance product quality. For example, in the BP-Amoco process for producing polyethylene, the catalyst typically undergoes prepolymerization before entering the main polymerization reactor, forming a prepolymer catalyst with olefin oligomers coated on the surface of the catalyst particles. This prepolymer catalyst is then added to the main reactor for ethylene polymerization. By adopting this approach, the catalyst can better adapt to the requirements of fluidized beds in terms of activity, particle size, and distribution, enhancing mass and heat transfer within the reactor and improving the quality of the polymerization reaction. Another example is the production of polypropylene using Sinopec's third-generation loop reactor. The catalyst first undergoes prepolymerization with a small amount of propylene monomer in a prepolymerization reactor, forming a prepolymer catalyst with a certain propylene polymerization ratio. This increases the strength of the catalyst particles, avoids violent collisions, transport, and friction of materials in the reactor, reduces catalyst breakage and fine powder generated in the industrial process, and thus significantly improves the safety, stability, cycle life, and product quality of the plant operation.

[0003] Currently, in all olefin polymerization industrial plants with prepolymerization process flow fields, the detection and judgment of catalyst prepolymerization ratio is usually estimated empirically based on the reaction temperature of the prepolymerization reactor, the residence time of reactants, and the feed rate and consumption of reactants such as propylene. If prepolymerization-related parameters need to be adjusted, adjustments need to be made according to the degree of the main polymerization reaction and the subsequent output. Often, the material needs to go through the entire process route before the impact and results of the initial prepolymerization reaction adjustment can be observed, which causes great inconvenience to long-term production and product quality stability. Summary of the Invention

[0004] To address the aforementioned problems in the prior art and enable those skilled in the art to effectively obtain the prepolymerization degree related to the catalyst in real time, i.e., the prepolymerization multiple of the catalyst, this invention proposes a system and method for online detection of the prepolymerization multiple of the catalyst in olefin polymerization.

[0005] This method is applicable to the determination of the prepolymerization ratio of catalyst in "catalyst + olefin" prepolymers under any circumstances. It is particularly useful in continuous polyolefin production processes with prepolymerization units, where the prepolymerization catalyst, as an intermediate product, is not easy to separate, has high activity but is easily quenched, and the feedback from process parameter adjustments is prone to lag. The method described in this invention has significant advantages in determining the prepolymerization ratio.

[0006] This invention employs an online detection system to achieve stable real-time online detection of the prepolymerization ratio of the catalyst after prepolymerization. By collecting the prepolymerized slurry online, the particle size and particle size distribution of the catalyst and olefin prepolymer are measured. Through the corresponding standard curve, the prepolymerization ratio of the catalyst can be accurately determined, thereby achieving the purpose of ensuring catalyst activity, stabilizing product production, ensuring product quality, and quantitatively controlling parameters.

[0007] A first aspect of the present invention provides a method for online detection of the prepolymerization factor of an olefin polymerization catalyst, comprising:

[0008] S01, a catalyst of mass m is subjected to a prepolymerization reaction with an olefin monomer. After the reaction is completed, the catalyst is diluted, washed, and dried to obtain a solid prepolymer catalyst. The mass m' of the solid prepolymer catalyst is weighed, and the prepolymerization factor n is obtained by the ratio of m' to m, i.e., n = m' / m.

[0009] S02, measure the average particle size d50 of the prepolymerized catalyst solid described in S01;

[0010] S03, repeat steps S01 and S02 multiple times to obtain multiple prepolymer catalyst solids with different prepolymerization multiples n and average particle size d50;

[0011] S04, using the cube of the average particle size d50 as the independent variable and the pre-aggregation factor n as the dependent variable, performs linear fitting to obtain the linear fitting curve equation Y.

[0012] Optionally, the method further includes:

[0013] S05, obtain the average particle size d50 of the sample to be tested, substitute it into the linear fitting curve equation Y, and calculate the prepolymerization factor n of the sample to be tested.

[0014] Optionally, the dilution and washing includes, after the pressure of the container carrying the prepolymer catalyst slurry has been balanced, introducing an inert organic reagent to rinse the inner wall of the container while diluting the prepolymer catalyst slurry.

[0015] A second aspect of the present invention provides a system for online detection of the prepolymerization multiple of an olefin polymerization catalyst, comprising a separation tank, a buffer tank, and a measuring device connected in sequence;

[0016] The separation tank is used to separate olefins from the prepolymer catalyst slurry;

[0017] The buffer tank is used to receive non-gas phase materials introduced from the buffer tank to obtain the sample to be tested;

[0018] The measuring equipment includes particle size analysis equipment and data processing equipment;

[0019] The particle size analysis device is used to measure the particle size and particle size distribution of the sample to be tested and obtain the average particle size d50; the data processing device is used to obtain the pre-polymerization factor n, and includes a data receiving port, a data processing system and a data display device.

[0020] In this invention, the prepolymer catalyst slurry refers to a solution obtained after the catalyst undergoes a prepolymerization reaction with a small amount of olefin monomer.

[0021] The system for online detection of the prepolymerization multiple of olefin polymerization catalysts described in this invention is located downstream of the prepolymerization process section and upstream of the main polymerization reaction section. It serves as a branch or bypass, directly connected to the pipeline connecting the prepolymerization reactor and the main reactor, positioned before the feed inlets for the main polymerization process feedstocks (such as propylene) and other auxiliaries (such as alkylaluminum and external electron donors). This design does not affect the normal polymerization reaction process.

[0022] Optionally, the system further includes a control device, which includes an equipment control system or controller involved in the process of sample collection, analysis, and post-processing.

[0023] Optionally, the separation tank is a flash tank.

[0024] Optionally, the flash tank is equipped with a temperature sensor and a pressure sensor.

[0025] Optionally, the flash tank is equipped with a jacket for auxiliary heating.

[0026] Optionally, the buffer tank is equipped with a stirring or ultrasonic vibration device to prepare a uniform and stable test sample.

[0027] Optionally, the particle size analysis device is a Malvern laser particle size analyzer.

[0028] Optionally, the data processing system is Matlab, Origin, or Excel.

[0029] Optionally, both the separation tank and the buffer tank are located under inert gas protection.

[0030] Optionally, the separation tank and the buffer tank are respectively connected to a three-waste temporary storage tank for recycling and treating wastewater, waste gas and solid waste.

[0031] In this invention, various valves, such as pressure reducing valves, solenoid valves, ball valves, and manual valves, can be installed on the pipelines connecting the various devices; flow meters or flow monitoring devices can also be installed on the pipelines to display the material conveying.

[0032] In this invention, the first valve of the separator is opened, and a small amount of prepolymer catalyst slurry is introduced into the separator through a pressure reducing valve or related pipeline. The first valve of the separator is then closed. After the prepolymer catalyst slurry is introduced into the separator through a pipeline branch, olefins, such as propylene, are removed by flash evaporation. Subsequently, after the pressure in the separator is balanced, a certain amount of inert organic solvent, such as hexane, is added to flush the separator walls and dilute the prepolymer catalyst slurry.

[0033] The buffer tank is used to receive non-gaseous materials introduced from the separation tank and to store the sample to be tested. It can be filled with the same or different organic solvents as the organic solvent used for flash evaporation to prepare the sample solution to be tested.

[0034] In the actual particle size measurement process of this invention, the probe of the Malvern laser particle size analyzer can be inserted into the buffer tank, or the sample to be measured can be taken out from the buffer tank.

[0035] In this invention, d50 indicates that 50% of all measured particles have a volume smaller than this value.

[0036] The beneficial effects of this invention include:

[0037] (1) An online detection system is used to realize the real-time online detection of the catalyst prepolymerization ratio;

[0038] (2) Real-time feedback on the impact of prepolymerization parameter adjustments on the prepolymerization factor;

[0039] (3) It does not affect the polymerization process;

[0040] (4) The equipment modification is simple, and the number of controllers, valves, pipelines, instruments and equipment is very small;

[0041] (5) It achieves a high degree of automation control, which can effectively reduce manual operation, avoid measurement errors, and reduce labor intensity. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a system for online detection of the prepolymerization multiple of olefin polymerization catalysts, where I-flash tank, II-buffer tank, III-measuring equipment, and IV-control equipment.

[0043] Figure 2 This is a schematic diagram of the linear fitting curve equation Y. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention. It should be noted that the present invention focuses on providing a relatively comprehensive and detailed description of the design scheme or model, principle, and method, and is not intended to limit the present invention. At the same time, the present invention is inspiring for any subsequent devices or products based on the principles, designs, methods, or models of the present invention.

[0045] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0046] In the accompanying drawings of this invention, it should be understood that the positional relationships indicated by terms such as "center", "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" are based on the positions or relationships shown in the drawings and are only for the convenience of describing this application and simplifying the description. They are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0048] Standard curve determination

[0049] 5g of Ziegler-Natta type polypropylene catalyst (BCND-II type catalyst provided by Sinopec Catalyst Company Aoda Branch) was placed in a reactor thoroughly purged with nitrogen. 500mL of hexane was added as solvent, along with 5mL of 0.1M triethylaluminum. Propylene gas was introduced simultaneously, and the propylene pressure was controlled at 0.15 MPa. The reaction temperature was 20℃, and prepolymerization was carried out for 10 minutes. After the reaction, hexane was added to wash the catalyst, and the solvent was removed by filtration. After the solid was dried, 13.6g of prepolymer catalyst was obtained by weighing. The calculated prepolymerization factor was 2.7. Using a Malvern laser particle size analyzer 3000, the d50 of the sample with a polymerization factor of 2.7 was predicted to be 32.170 μm.

[0050] By changing different experimental conditions, such as prepolymerization temperature, prepolymerization time, alkyl aluminum dosage, and propylene polymerization pressure, and using the same post-treatment method, the particle size and particle size distribution corresponding to different prepolymerization ratios can be obtained, as shown in the table below.

[0051]

[0052] Using the data in Table 1, the relationship between the prepolymerization factor n and the cubic value of d50 was fitted using Origin to obtain the linear fitting curve equation Y, as shown below. Figure 2 As shown, Y = 3.2 + (6.6 × 10) -5 )×(d50) 3 .

[0053] like Figure 1 As shown, in a loop-type polypropylene unit with prepolymerization, by employing the system and method described in this invention, under nitrogen protection, during the propylene polymerization reaction, a prepolymerization catalyst sample with the same catalyst is obtained through a flash tank, and the flash tank is rinsed with anhydrous hexane; after transferring the liquid in the flash tank to a buffer tank, a small amount of hexane is added to bring the volume to 50 mL.

[0054] According to the present invention, this suspension can typically be used to measure the particle size and particle size distribution of the prepolymer catalyst. By reading the d50 data and performing corresponding calculations using a computer, the real-time prepolymerization multiple can be obtained. However, in this experiment, to illustrate the technical effect of the present invention, the inventors shook the 50 mL suspension until it was homogenized and, after thorough stirring, divided it into two portions of 25 mL each.

[0055] One sample was used to determine the particle size and particle size distribution of the prepolymer catalyst using a Malvern 3000 laser particle size analyzer. The prepolymerization factor of the sample was determined using a computer and Origin software and the corresponding fitting curve. This sample was labeled as Example 1.

[0056] Another suspension was filtered to remove the organic solvent under nitrogen protection. The prepolymerization factor was calculated by weighing the dried solid and labeled as Comparative Example 1.

[0057] By changing the prepolymerization temperature and residence time of the loop process, the system and method described in this invention were used under different process parameter conditions to obtain Examples 2-6 and Comparative Examples 2-6.

[0058] The relevant results are summarized in the table below: The data differences represent the deviations between the examples and the corresponding comparative examples, calculated as follows:

[0059] Difference = (Prepolymerization factor of the example - Prepolymerization factor of the comparative example) / Prepolymerization factor of the comparative example × 100%

[0060]

[0061] The above data shows that the method involved in this invention is stable and reliable. In particular, for continuous polyolefin production processes with prepolymerization devices, where catalysts are not easy to separate, the system and method described in this invention can quickly and accurately determine the prepolymerization factor. Compared with the current method of estimating the prepolymerization factor based entirely on personal experience according to the prepolymerization reaction conditions, this method has obvious advantages.

[0062] The design and method of this invention are also applicable to the determination of the prepolymerization factor of the catalyst in the "catalyst + olefin" prepolymer under any circumstances, including when it is necessary to determine the prepolymerization factor in certain "offline" situations, including but not limited to, when it is necessary to estimate the prepolymerization factor when producing large batches of prepolymer catalysts; or when the prepolymerization factor is controlled to calibrate the factory standard of the prepolymer catalyst product; or when the prepolymer catalyst is dissolved in solvents such as white oil and silicone oil and is difficult to dry or remove.

[0063] Based on the above-described preferred embodiments according to this application, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification, but must be determined according to the scope of the claims.

[0064] Furthermore, it should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to exemplary embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from its scope and spirit. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications having the same function.

Claims

1. A method for online detection of the prepolymerization factor of an olefin polymerization catalyst, characterized in that, include: S01, a catalyst of mass m is subjected to a prepolymerization reaction with an olefin monomer. After the reaction is completed, the catalyst is diluted, washed, and dried to obtain a solid prepolymer catalyst. The mass m' of the solid prepolymer catalyst is weighed, and the prepolymerization factor n is obtained by the ratio of m' to m, i.e., n = m' / m. S02, measure the average particle size d50 of the prepolymerized catalyst solid described in S01; S03, repeat steps S01 and S02 multiple times to obtain multiple prepolymer catalyst solids with different prepolymerization multiples n and average particle size d50; S04, taking the cube of the average particle size d50 as the independent variable and the pre-aggregation factor n as the dependent variable, performs linear fitting to obtain the linear fitting curve equation Y; S05, obtain the average particle size d50 of the sample to be tested, substitute it into the linear fitting curve equation Y, and calculate the prepolymerization factor n of the sample to be tested.

2. The method according to claim 1, characterized in that, The dilution and washing process includes, after the pressure of the container containing the prepolymer catalyst slurry has been balanced, introducing an inert organic reagent to rinse the inner wall of the container while simultaneously diluting the prepolymer catalyst slurry.

3. A system for online detection of the prepolymerization multiple of an olefin polymerization catalyst, characterized in that, It includes a separation tank, a buffer tank, and measuring equipment connected in sequence; The separation tank is used to separate olefins from the prepolymer catalyst slurry; The buffer tank is used to receive non-gas phase materials introduced from the separation tank to obtain the sample to be tested; The measuring equipment includes particle size analysis equipment and data processing equipment; The particle size analysis device is used to measure the particle size and particle size distribution of the sample to be tested and obtain the average particle size d50; the data processing device is used to read the average particle size d50 of the sample to be tested and substitute it into the linear fitting curve equation Y to obtain the pre-polymerization factor n, including a data receiving port, a data processing system and a data display device; The linear fitting curve equation Y is obtained through the following steps: S01, a catalyst of mass m is subjected to a prepolymerization reaction with an olefin monomer. After the reaction is completed, the catalyst is diluted, washed, and dried to obtain a solid prepolymer catalyst. The mass m' of the solid prepolymer catalyst is weighed, and the prepolymerization factor n is obtained by the ratio of m' to m, i.e., n = m' / m. S02, measure the average particle size d50 of the prepolymerized catalyst solid described in S01; S03, repeat steps S01 and S02 multiple times to obtain multiple prepolymer catalyst solids with different prepolymerization multiples n and average particle size d50; S04, using the cube of the average particle size d50 as the independent variable and the pre-aggregation factor n as the dependent variable, performs linear fitting to obtain the linear fitting curve equation Y.

4. The system according to claim 3, characterized in that, The system also includes control equipment, which includes equipment control systems or controllers involved in the collection, analysis, and post-processing of the sample to be tested.

5. The system according to claim 3, characterized in that, The separation tank is a flash tank.

6. The system according to claim 5, characterized in that, The flash tank is equipped with a temperature sensor and a pressure sensor, and / or the flash tank is equipped with a jacket for auxiliary heating.

7. The system according to any one of claims 3 to 6, characterized in that, The buffer tank is equipped with a stirring or ultrasonic vibration device for preparing the sample to be tested.

8. The system according to any one of claims 3 to 6, characterized in that, The particle size analysis equipment is a Malvern laser particle size analyzer.

9. The system according to any one of claims 3 to 6, characterized in that, The data processing system is Matlab, Origin, or Excel.

10. The system according to any one of claims 3 to 6, characterized in that, Both the separation tank and the buffer tank are under inert gas protection; and / or, the separation tank and the buffer tank are respectively connected to a three-waste temporary storage tank for recycling and treating wastewater, waste gas and solid waste.

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