System and method for on-line detection of prepolymerization multiple of catalyst in olefin polymerization

Abstract

The invention relates to a system and a method for online detection of the prepolymerization multiple of an olefin polymerization catalyst, and belongs to the technical field of olefin polymerization catalysts. The method provided by the invention can realize stable real-time detection of the prepolymerization multiple of the catalyst, thereby achieving the purposes of stabilizing product production, ensuring product quality and quantitatively regulating and controlling parameters. The system comprises a separation tank, a buffer tank, measuring equipment and control equipment which are connected in sequence, the prepolymerization multiple of the catalyst can be accurately determined by collecting the prepolymerization slurry on line, determining the particle sizes and particle size distribution of the catalyst and the olefin prepolymer in the prepolymerization slurry and determining the prepolymerization multiple of the catalyst through the corresponding standard curve, so that the aim of guaranteeing the activity of the catalyst and the product quality is fulfilled.

Description

Technical Field

[0001] The invention relates to the field of olefin polymerization catalysts, and in particular to a system and method for online detection of catalyst prepolymerization multiples in olefin polymerization, which is particularly suitable for propylene polymerization and ethylene polymerization devices with prepolymerization processes. Background Art

[0002] In the industrial production of polyolefins, catalyst prepolymerization technology is usually used to achieve the purpose of optimizing production, improving catalyst activity, and improving product quality. For example, in the process of producing polyethylene products using the BP-Amoco process, the catalyst usually undergoes a prepolymerization reaction before entering the main polymerization reactor to form a prepolymerization catalyst with olefin oligomers coated on the surface of the catalyst particles, and then the prepolymerization catalyst is added to the main reactor for ethylene polymerization; by adopting this form, the catalyst can better adapt to the requirements of the fluidized bed for activity, particle size and distribution, enhance mass transfer and heat transfer in the kettle, and improve the quality of the polymerization reaction. For another example, in the process of producing polypropylene using Sinopec's third-generation loop process, the catalyst will first pass through the prepolymerization reactor and prepolymerize with a small amount of propylene monomer to form a prepolymerization catalyst with a certain propylene polymerization multiple, so as to improve the strength of the catalyst particles, avoid the violent collision, transportation and friction of the materials in the reactor, and reduce the fine powder generated by the catalyst breakage in the industry, thereby greatly improving the safety, stability, long cycle and product quality of the device operation.

[0003] At present, in all olefin polymerization industrial units with prepolymerization process flow fields, the detection and judgment of the catalyst prepolymerization multiple is usually estimated through experience based on the reaction temperature of the prepolymerization reactor, the residence time of the reactants, the feed amount and consumption of reactants such as propylene; if the prepolymerization related parameters need to be adjusted, it is necessary to make relevant adjustments based on the degree of the main polymerization reaction and the subsequent discharge conditions. It is often necessary for the material to go through the entire process route before the impact and results of the initial prepolymerization reaction adjustment can be observed, which has caused great inconvenience to long-term production and product quality stability. Summary of the invention

[0004] In order to solve the above problems in the prior art and enable those skilled in the art to effectively and in real time obtain the catalyst-related prepolymerization degree, i.e., the catalyst prepolymerization multiple, the present invention proposes a system and method for online detection of the catalyst prepolymerization multiple in olefin polymerization.

[0005] The method is applicable to the determination of the prepolymerization multiple of the catalyst in the "catalyst + olefin" prepolymer under any circumstances, especially in the continuous polyolefin production process with a prepolymerization device, where the prepolymerized catalyst, as an intermediate product, is not easy to separate, is easily quenched due to its high activity, and the feedback of process parameter adjustment tends to show hysteresis. The method of the present invention is used to determine the prepolymerization multiple, which has obvious advantages.

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

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

[0008] S01, a catalyst of mass m is subjected to a prepolymerization reaction with an olefin monomer, and after the reaction is completed, the catalyst is diluted, washed, and dried to obtain a prepolymerized catalyst solid, and the mass m' of the prepolymerized catalyst solid is weighed, and the prepolymerization multiple n is obtained by the ratio of m' to m, that is, n = m' / m;

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

[0010] S03, repeating step S01 and step S02 for multiple times to obtain multiple prepolymerization catalyst solids with different prepolymerization multiples n and average particle sizes d50;

[0011] S04, taking the cube of the average particle size d50 as the independent variable and the prepolymerization multiple n as the dependent variable, linear fitting is performed to obtain the linear fitting curve equation Y.

[0012] Optionally, the method further comprises:

[0013] S05, obtaining the average particle size d50 of the sample to be tested, substituting it into the linear fitting curve equation Y, and calculating the pre-polymerization multiple n of the sample to be tested.

[0014] Optionally, the dilution washing comprises, after the pressure of the container carrying the prepolymerization catalyst slurry is balanced, introducing an inert organic reagent to wash the inner wall of the container and dilute the prepolymerization catalyst slurry at the same time.

[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 prepolymerization catalyst slurry;

[0017] The buffer tank is used to receive the non-gaseous material introduced from the buffer tank to obtain a sample to be tested;

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

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

[0020] In the present invention, the prepolymerized catalyst slurry refers to a solution obtained by prepolymerizing a catalyst with a small amount of olefin monomer.

[0021] The system for online detection of the prepolymerization multiple of olefin polymerization catalyst of the present invention is located in the rear section of the prepolymerization process section and the front section of the main polymerization reaction process section; as a branch or bypass, it is directly connected to the pipeline connecting the prepolymerization reactor and the main reactor, and is located before the feed port of the main polymerization reaction process raw materials (such as propylene) and other auxiliary agents (such as alkyl aluminum, external electron donor). This design does not affect the normal polymerization reaction process.

[0022] Optionally, the system further comprises a control device, wherein the control device comprises a device control system or controller involved in the process of collecting, analyzing, post-processing, etc. of the sample to be tested.

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

[0024] Optionally, the flash tank is provided 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 sample to be tested.

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

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

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

[0030] Optionally, the separation tank and the buffer tank are respectively connected to three waste temporary storage tanks for recycling and treating waste water, waste gas and waste solids.

[0031] In the present invention, various valves, such as pressure reducing valves, solenoid valves, ball valves, hand valves, etc., may be provided on the pipelines connecting the various devices; the pipelines may also be provided with flow meters or flow monitoring equipment to display material transportation.

[0032] In the present invention, the valve at the front end of the separation tank is opened, a small amount of prepolymerized catalyst slurry is introduced into the separation tank through the pressure reducing valve or the relevant pipeline, and the valve at the front end of the separation tank is closed; after the separation tank introduces the prepolymerized catalyst slurry from the pipeline branch, olefins such as propylene are removed by flash evaporation; then, after the pressure of the separation tank is balanced, a certain amount of inert organic solvent such as hexane is added to wash the wall of the separation tank flushing device and dilute the prepolymerized catalyst slurry.

[0033] The buffer tank is used to receive the non-gaseous material introduced from the separation tank and to store the sample to be tested. An organic solvent that is the same as or different from the organic solvent used for flash evaporation can be added to prepare the sample solution to be tested.

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

[0035] In the present invention, d50 means that among all measured particles, the proportion of particles whose volume is smaller than this value is 50%.

[0036] The beneficial effects of the present invention include:

[0037] (1) Using an online detection system to achieve real-time online detection of the catalyst prepolymerization multiple;

[0038] (2) Real-time feedback on the impact of pre-aggregation parameter adjustment on the pre-aggregation multiple;

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

[0040] (4) Equipment modification is simple, with very few controllers, valves, pipelines, instruments and equipment;

[0041] (5) A high degree of automated control can effectively reduce manual operations, avoid measurement errors, and reduce labor intensity. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0043] Figure 2 Schematic diagram of the linear fitting curve equation Y. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with specific embodiments, but does not constitute any limitation to the present invention. It should be noted that the present invention focuses on a more comprehensive and detailed description of the design scheme or model, principle, and method, and does not limit the present invention. At the same time, the present invention is inspiring for any subsequent equipment or products based on the principle, design, method, or model of the present invention.

[0045] In the absence of conflict, the embodiments in this application and the features in the embodiments may be combined with each other.

[0046] In the illustrations of the present invention, it is necessary to understand that the orientations or positional relationships indicated by positional relationships such as “center”, “longitudinal”, “lateral”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside” and “outside” in the figures are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application.

[0047] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0048] Standard curve determination

[0049] 5g of Ziegler-Natta polypropylene catalyst (BCND-II catalyst provided by Sinopec Catalyst Company Aoda Branch) was placed in a reactor fully purged with nitrogen, 500mL of hexane was added as solvent, 5mL of triethylaluminum with a concentration of 0.1M was added, and propylene gas was introduced at the same time. The propylene pressure was controlled to be 0.15MPa, and the reaction temperature was 20°C. Prepolymerization was carried out for 10 minutes. After the reaction was completed, hexane was added to wash the catalyst, and the solvent was removed by suction filtration. After the solid was drained, 13.6g of prepolymerized catalyst was weighed. After calculation, the prepolymerization multiple was 2.7. Using Malvern Laser Particle Size Analyzer 3000, the sample with a polymerization multiple of 2.7 was predicted, and the d50 was 32.170um.

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

[0051]

[0052]

[0053] Using the data in Table 1, the relationship between the prepolymerization multiple n and the cubic value of d50 was fitted using origin to obtain the linear fitting curve equation Y, as shown in Figure 2 As shown, Y = 3.2 + (6.6 × 10 -5 )×(d50) 3 .

[0054] like Figure 1 As shown, on a loop process polypropylene device with prepolymerization, by adopting the system and method of the present invention, under the protection of nitrogen, during the propylene polymerization reaction, a prepolymerization catalyst sample of the same catalyst is obtained through a flash tank, and the flash tank is flushed with anhydrous hexane; after the liquid in the flash tank is transferred to a buffer tank, a small amount of hexane is added to 50mL.

[0055] According to the present invention, the suspension can be used to measure the particle size and particle size distribution of the prepolymerization catalyst, and the real-time prepolymerization multiple can be obtained by reading the d50 data and converting it accordingly by a computer. However, in order to illustrate the technical effect of the present invention, the inventors shake the 50mL suspension evenly in the experiment, and divide it into two portions, each 25mL, under sufficient stirring.

[0056] In one of the samples, the particle size and particle size distribution of the prepolymerized catalyst were measured using a Malvern 3000 laser particle size analyzer, and the prepolymerization multiple of the sample was measured using a computer, Origin software and a corresponding fitting curve, which is marked as Example 1.

[0057] In another suspension, the organic solvent was extracted by filtration under the protection of nitrogen, and the solid after drying was weighed to calculate the prepolymerization multiple, which was marked as Comparative Example 1.

[0058] By changing the prepolymerization temperature, residence time, etc. of the loop process, the system and method of the present invention were used under different process parameter conditions to obtain Examples 2 to 6 and Comparative Examples 2 to 6.

[0059] The relevant results are summarized in the following table: The data difference is the deviation between the embodiment and the corresponding comparative example, and the calculation method is:

[0060] Phase difference = (prepolymerization multiple of the embodiment - prepolymerization multiple of the comparative example) / prepolymerization multiple of the comparative example × 100%

[0061] Pre-polymerization multiple difference Comparative Example 1 5.8 - Example 1 6.1 5％ Comparative Example 2 45.7 - Example 2 51.3 12％ Comparative Example 3 88.9 - Example 3 80.4 -10％ Comparative Example 4 108.3 - Example 4 115.8 7％ Comparative Example 5 166.7 - Example 5 180.1 8％ Comparative Example 6 234.5 - Example 6 266.4 14％

[0062] The above data show that the method involved in the present invention is stable and reliable, especially for a continuous polyolefin production process with a prepolymerization device, in which the catalyst is not easy to separate. The system and method of the present invention can determine the prepolymerization multiple more quickly and accurately, which has obvious advantages compared to the current device that estimates the prepolymerization multiple based on the prepolymerization reaction conditions and relies entirely on personal experience.

[0063] The design and method of the present invention are of course also applicable to the determination of the prepolymerization multiple of the catalyst in the "catalyst + olefin" prepolymer under any circumstances, including certain "offline" situations where the prepolymerization multiple needs to be determined, including but not limited to, when a large number of prepolymerized catalysts need to be estimated; or when the prepolymerization multiple is controlled to calibrate the factory standard of the prepolymerized catalyst product; or when the prepolymerized catalyst is dissolved in solvents such as white oil and silicone oil and is not easy to be drained or removed.

[0064] Based on the above ideal embodiments of this application, the relevant staff can make various changes and modifications without departing from the technical concept of this application through the above description. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

[0065] Furthermore, it should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for online detection of the prepolymerization multiple 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, and after the reaction is completed, the catalyst is diluted, washed, and dried to obtain a prepolymerized catalyst solid, and the mass m' of the prepolymerized catalyst solid is weighed, and the prepolymerization multiple n is obtained by the ratio of m' to m, that is, n = m' / m; S02, measuring the average particle size d50 of the prepolymerized catalyst solid described in S01; S03, repeating step S01 and step S02 for multiple times to obtain multiple prepolymerization catalyst solids with different prepolymerization multiples n and average particle sizes d50; S04, taking the cube of the average particle size d50 as the independent variable and the prepolymerization multiple n as the dependent variable, linear fitting is performed to obtain the linear fitting curve equation Y.

2. The method according to claim 1, characterized in that The method comprises: S05, obtaining the average particle size d50 of the sample to be tested, substituting it into the linear fitting curve equation Y, and calculating the pre-polymerization multiple n of the sample to be tested.

3. The method according to claim 1 or 2, characterized in that: The dilution washing includes, after the pressure of the container carrying the prepolymerization catalyst slurry is balanced, introducing an inert organic reagent to wash the inner wall of the container and dilute the prepolymerization catalyst slurry at the same time.

4. A system for online detection of the prepolymerization multiple of olefin polymerization catalyst, characterized in that: It includes a separation tank, a buffer tank and a measuring device connected in sequence; The separation tank is used to separate olefins from the prepolymerization catalyst slurry; The buffer tank is used to receive the non-gaseous material introduced from the separation tank to obtain the sample to be tested; The measuring equipment includes a particle size analysis device and a data processing device; The particle size analysis device is used to measure the particle size and particle size distribution of the sample to be tested to obtain the average particle size d50; the data processing device is used to obtain the pre-polymerization multiple n, and includes a data receiving port, a data processing system and a data display device.

5. The system according to claim 4, characterized in that The system also includes a control device, which includes a device control system or controller involved in the collection, analysis, and post-processing of the sample to be tested.

6. The system according to claim 4 or 5, characterized in that: The separation tank is a flash tank; Preferably, the flash tank is provided 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 4 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 4 to 7, characterized in that: The particle size analysis equipment is a Malvern laser particle size analyzer.

9. The system according to any one of claims 4 to 8, characterized in that: The data processing system is Matlab, Origin or Excel.

10. The system according to any one of claims 4 to 9, characterized in that: The separation tank and the buffer tank are both located under the protection of inert gas; and / or, the separation tank and the buffer tank are respectively connected to three waste temporary storage tanks for recycling and treating waste water, waste gas and waste solids.

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