Silicon-magnesium composite Ziegler-Natta catalyst precursor and preparation method thereof
The precursor of silicon-magnesium composite Ziegler-Natta catalyst was prepared by hydrothermal amplification and high-temperature activation of silica gel, combined with magnesium salt impregnation, which solved the problem of uneven morphology and particle size in the prior art and improved the performance of the catalyst.
Patent Information
- Application Number
- CN202510505286.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-22
- Publication Date
- 2025-08-15
AI Technical Summary
In the existing preparation technology, the morphological perfection and particle size uniformity of the Ziegler-Natta catalyst are insufficient, which limits the development of the polyolefin industry toward high activity, high orientation and product series.
The silica gel was amplified and activated at high temperature by hydrothermal method to prepare silica microspheres with good morphology and pore structure, and then impregnated with soluble magnesium salt and supported by magnesium source to finally obtain a silicon-magnesium composite Ziegler-Natta catalyst precursor.
The prepared catalyst precursor has a more perfect morphology, a more uniform particle size, and a better magnesium loading effect, which improves the performance of the catalyst.
Smart Images
Figure CN120484162A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a hydrothermal silicon-magnesium composite Ziegler-Natta catalyst precursor and a preparation method thereof, which is suitable for industrial-scale polypropylene catalyst production. Background Art
[0002] In the polyolefin catalysis industry, a major breakthrough in the development of Ziegler-Natta catalysts has been the ability to load the active component (Ti compound) onto a support surface, dispersing it at high density across the surface of the catalyst precursor to maximize its activity. To date, the most effective supports for Ziegler-Natta catalysts have primarily included SiO2 and Mg compounds, such as MgCl2, Mg(OH)Cl, Mg(OEt)2, and MgR2 (where R is an alkyl group). To date, the most widely used and industrially applicable polypropylene catalyst precursor is still a MgCl2-supported catalyst precursor. However, due to limitations in preparation methods, the resulting precursors remain suboptimal in terms of morphology, particle size distribution, and titanium attachment points. This presents a significant obstacle to the polyolefin industry's shift from prioritizing high activity and specificity to focusing on product serialization, high performance, precise control of polymer structure, and the production of specialized products, ultimately increasing value-added products. Summary of the Invention
[0003] (1) Technical issues to be solved
[0004] The present invention proposes a silicon-magnesium composite Ziegler-Natta catalyst precursor and a preparation method thereof to solve the technical problems of insufficient morphology perfection and particle size uniformity in existing preparation technologies. The prepared catalyst precursor has a more perfect morphology, a more uniform particle size, and a better magnesium loading effect.
[0005] (2) Technical solution
[0006] In order to solve the above technical problems, the present invention provides a method for preparing a silicon-magnesium composite Ziegler-Natta catalyst precursor, which comprises the following steps:
[0007] S1. Hydrothermal silica gel pore expansion: The silica gel is placed in a high-pressure hydrothermal synthesis reactor, ultrapure water is added, and the reactor is kept sealed and heated to react. After the reaction is completed, heating is stopped and the mixture in the reactor is slowly cooled to room temperature. The silica gel is washed for pore expansion;
[0008] S2. Silica gel thermal activation: The expanded silica gel obtained in step S1 is placed in a suspension furnace, the silica gel is heated to decompose the silica gel into silica and water, and then cooled to room temperature to obtain activated silica microspheres;
[0009] S3. Loading magnesium source: The silica microspheres obtained in step S2 were placed in a single-necked flask, an aqueous solution of a soluble magnesium salt was added to the flask, magnetically stirred at room temperature, and the solution was evaporated using a rotary evaporator in a nitrogen stream until the water was completely evaporated to obtain silica microspheres loaded with a magnesium source;
[0010] S4. Preparation of a catalyst precursor: The magnesium-loaded silica microspheres obtained in step S3 are placed in a suspension furnace, the nitrogen flow rate is controlled to keep the silica microspheres in a suspended state in the quartz tube, and the magnesium-loaded silica microspheres are heated to remove free water and bound water contained in the magnesium-loaded silica microspheres, while converting the magnesium source into magnesium oxide, thereby finally obtaining a silicon-magnesium composite Ziegler-Natta catalyst precursor.
[0011] Furthermore, in step S1, the silica gel is 955 silica gel; the mass ratio of silica gel to ultrapure water is 1:(4-10); the heating temperature is 100-200° C., and the reaction time is 0.5-3 h.
[0012] Furthermore, in step S1, the pore-expanding silica gel is washed multiple times with ultrapure water using a point-mixing method.
[0013] Furthermore, in step S2, the suspension furnace is a vertically placed quartz tube, the device for holding silica gel is a crucible with a sand core at the bottom, and the upper and lower ends of the quartz tube are provided with gas guide valves and gas turbulence devices. The air inlet valve is adjusted so that nitrogen enters the quartz tube from the lower opening at a flow rate of 200 to 700 mL / min, so that the silica gel is in a boiling state in the quartz tube, ensuring the fluidization effect and uniform heat distribution; the silica gel in the quartz tube is heated by setting a programmed temperature rise, and then cooled to room temperature. The entire process is always in a high-purity nitrogen atmosphere.
[0014] Furthermore, in step S2, the heating process of the silica gel in the quartz tube is as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for 1 hour, and the temperature is maintained for 1 hour, and then the temperature is further raised to 300°C for 0.5 hours, and the temperature is maintained at 300°C for 1 hour. The heating is stopped and the silica gel in the quartz tube is allowed to cool naturally to room temperature. The nitrogen flow rate remains unchanged during the entire process to ensure that the silica gel in the quartz tube is always in a boiling state.
[0015] Furthermore, in step S3, the magnesium salt is one or more of magnesium acetate, magnesium citrate and magnesium chloride; the concentration of the magnesium salt aqueous solution is 0.25-1M, and n(Mg):n(Si)=5%-15%.
[0016] Furthermore, in step S3, the stirring time at room temperature is 4 to 8 hours; and the rotary evaporation heating temperature is 100°C.
[0017] Furthermore, in step S4, the nitrogen flow rate is 200 to 700 mL / min.
[0018] Furthermore, in step S4, the heating process of the silica microspheres loaded with a magnesium source in the quartz tube is as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for a heating time of 1 hour, and the temperature is maintained for 2 hours, and then the temperature is continued to be raised to 300°C for a heating time of 0.5 hours. After the temperature reaches 300°C, the gas is switched from high-purity nitrogen to dry air, and the temperature is maintained for 30 minutes, and then the temperature is continued to be raised to 450°C for a heating time of 1 hour, and the temperature is maintained for 2.5 hours. The temperature is continued to be raised to 600°C for a heating time of 30 minutes, and the temperature is maintained for 1 hour and then the heating is stopped. After the quartz tube is cooled to 450°C, the dry air is changed to high-purity nitrogen, and it is naturally cooled to room temperature. The nitrogen flow rate remains unchanged during the entire process to ensure that the silica microspheres loaded with a magnesium source in the quartz tube are always in a boiling state.
[0019] In addition, the present invention also provides a silicon-magnesium composite Ziegler-Natta catalyst precursor, which is prepared by the above method.
[0020] (3) Beneficial effects
[0021] This invention proposes a silicon-magnesium composite Ziegler-Natta catalyst precursor and its preparation method. The precursor uses a hydrothermal method to expand the pores of silica gel, followed by high-temperature activation to produce silica microspheres with a well-defined morphology and pore structure. These microspheres are then impregnated with a soluble magnesium salt to load the magnesium source, ultimately yielding a silicon-magnesium composite Ziegler-Natta catalyst precursor. This method successfully addresses the shortcomings of existing preparation technologies in terms of morphological perfection and particle size uniformity. The precursor prepared by the invention has a more perfect morphology, a more uniform particle size, and better magnesium loading. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1a to Figure 1c These are TEM images of the silicon-magnesium composite Ziegler-Natta catalyst precursors prepared in Examples 1 to 3, respectively. DETAILED DESCRIPTION
[0023] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings and examples.
[0024] Example 1
[0025] S1. Take 5g of 955 silica gel produced by Grace Company in the United States and place it in a 50mL high-pressure hydrothermal synthesis reactor. Add 25g of ultrapure water. Keep the reactor sealed and raise the temperature to 100°C. Keep the reaction at this temperature for 2h. After that, stop heating and allow the mixture in the reactor to slowly cool to room temperature. Use the point-to-point mixing method to wash the expanded silica gel three times with ultrapure water.
[0026] S2. Place the expanded silica gel obtained in step S1 in a suspension furnace, adjust the air inlet valve to allow nitrogen to enter the quartz tube from the lower port at a certain gas velocity, and make the silica gel highly boiling in the tube to ensure the fluidization effect and uniform distribution of heat. Adjust the gas velocity to 500mL / min, first raise the temperature in the quartz tube from room temperature to 200℃ for 1h, keep heating at this temperature for 1h, then continue to heat it to 300℃ for 0.5h, maintain the reaction at 300℃ for 1h, stop heating, and allow the silica gel in the quartz tube to cool naturally to room temperature. The nitrogen flow rate remains unchanged during the whole process to ensure that the silica gel in the quartz tube is always in a boiling state; obtain activated silica microspheres, and place the activated silica microspheres in a glove box under nitrogen protection for standby use;
[0027] S3. A certain amount of silica microspheres obtained in step S2 was placed in a single-necked flask. A 1 M aqueous solution of magnesium acetate (n(Mg):n(Si)) was added to the flask. The mixture was magnetically stirred at room temperature for 6 h. The mixture was then rotary evaporated at 100°C in a nitrogen stream until the water was completely evaporated to obtain magnesium-loaded silica microspheres. The silica microspheres were then placed in a glove box for later use.
[0028] S4. the silica microspheres of the load magnesium source obtained in step S3 are placed in a suspension furnace and reacted, first the temperature in the quartz tube is raised to 200 ℃ from room temperature, and the heating time is 1h, after keeping the temperature heated for 2h, the temperature is continuously raised to 300 ℃, and the heating time is 0.5h, after the temperature is raised to 300 ℃, gas is switched to dry air by high-purity nitrogen, and after keeping the temperature heated for 30min, the temperature is continuously raised to 450 ℃, and the heating time is 1h, and the temperature reaction is kept for 2.5h, and the temperature is continuously raised to 600 ℃, and the heating time is 30min, and heating is stopped after keeping the temperature heated for 1h, and after making the quartz tube be cooled to 450 ℃, dry air is changed to high-purity nitrogen, and naturally cool to room temperature, whole process nitrogen gas flow rate keeps 500mL / min constant, and it is always ensured that the silica microspheres in the load magnesium source in the quartz tube are in a boiling state, and finally obtain silicon-magnesium composite Ziegler-Natta catalyst precursor.
[0029] The properties of the silica microspheres obtained in step S2 are shown in Table 1. The TEM image of the silicon-magnesium composite Ziegler-Natta catalyst precursor obtained in step S4 is shown in Table 1. Figure 1a shown.
[0030] Example 2
[0031] Steps S2 and S4 are the same as in Example 1;
[0032] S1. Take 5g of 955 silica gel produced by Grace Company in the United States and place it in a 50mL high-pressure hydrothermal synthesis reactor. Add 35g of ultrapure water. Keep the reactor sealed and raise the temperature to 140°C. Keep the reaction at this temperature for 2h. After that, stop heating and allow the mixture in the reactor to slowly cool to room temperature. Use the point-to-point mixing method to wash the expanded silica gel three times with ultrapure water.
[0033] S3. A certain amount of silica microspheres obtained in step S2 was placed in a single-necked flask. A 1 M magnesium citrate aqueous solution with a ratio of n(Mg):n(Si) = 10% was added to the flask. The mixture was magnetically stirred at room temperature for 6 h. The mixture was then rotary evaporated at 100°C in a nitrogen stream until the water was completely evaporated to obtain magnesium-loaded silica microspheres. The silica microspheres were then placed in a glove box for later use.
[0034] The properties of the silica microspheres obtained in step S2 are shown in Table 1. The TEM image of the silicon-magnesium composite Ziegler-Natta catalyst precursor obtained in step S4 is shown in Table 1. Figure 1b shown.
[0035] Example 3
[0036] Steps S2 and S4 are the same as in Example 1;
[0037] S1. Take 5g of 955 silica gel produced by Grace Company in the United States and place it in a 50mL high-pressure hydrothermal synthesis reactor. Add 50g of ultrapure water. Keep the reactor sealed and raise the temperature to 190°C. Keep the reaction at this temperature for 2h. After that, stop heating and allow the mixture in the reactor to slowly cool to room temperature. Use the point-to-point mixing method to wash the expanded silica gel three times with ultrapure water.
[0038] S3. A certain amount of silica microspheres obtained in step S2 was placed in a single-necked flask. A 1 M magnesium citrate aqueous solution with a ratio of n(Mg):n(Si) = 14% was added to the flask. The mixture was magnetically stirred at room temperature for 6 h. The mixture was then rotary evaporated at 100°C in a nitrogen stream until the water was completely evaporated to obtain magnesium-loaded silica microspheres. The silica microspheres were then placed in a glove box for later use.
[0039] The properties of the silica microspheres obtained in step S2 are shown in Table 1. The TEM image of the silicon-magnesium composite Ziegler-Natta catalyst precursor obtained in step S4 is shown in Table 1. Figure 1c shown.
[0040] Comparative Example
[0041] S1. Take 5g of 955 silica gel produced by Grace Company in the United States and place it in a 50mL high-pressure hydrothermal synthesis reactor. Keep the reactor sealed and raise the reactor temperature to 100°C. Keep the reaction at this temperature for 2h and then stop heating. Allow the mixture in the reactor to slowly cool to room temperature. Then, use the point-to-point mixing method to wash the resulting expanded silica gel three times with ultrapure water.
[0042] S2. Place the expanded silica gel obtained in step S1 in a suspension furnace, adjust the air inlet valve so that nitrogen enters the quartz tube from the lower port at a certain gas velocity, so that the silica gel is highly boiled in the tube to ensure the fluidization effect and uniform distribution of heat. Adjust the gas velocity to 500mL / min, first raise the temperature in the quartz tube from room temperature to 200°C, the heating time is 1h, keep the temperature heated for 1h, then continue to heat to 300°C, the heating time is 0.5h, maintain 300°C for 1h, stop heating, and allow the silica gel in the quartz tube to cool naturally to room temperature. The nitrogen flow rate remains unchanged throughout the process, and the silica in the quartz tube is always ensured to be in a boiling state, and finally obtain activated silica microspheres.
[0043] The properties of the silica microspheres obtained in step S2 are shown in Table 1.
[0044] Table 1 Properties of silica microspheres obtained in Examples 1 to 3
[0045] Calcination temperature / ℃ Aperture / mesh m(Silica gel / water) Relative pore volume Relative aperture Example 1 100 100 1:5 1.17 1.38 Example 2 140 100 1:7 1.29 1.47 Example 3 190 100 1:10 1.32 1.42 Comparative Example 100 100 Anhydrous 1.00 1.00
[0046] As can be seen from Table 1, the silica microspheres prepared by the present invention as a precursor skeleton have controllable pore structure and good mechanical strength. Figures 1a to 1c It can be seen that the silicon-magnesium composite Ziegler-Natta catalyst precursor prepared by the present invention has uniform particle size and good sphericity.
[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing a silicon-magnesium composite Ziegler-Natta catalyst precursor, characterized in that: The preparation method comprises the following steps: S1. Hydrothermal silica gel pore expansion: The silica gel is placed in a high-pressure hydrothermal synthesis reactor, ultrapure water is added, and the reactor is kept sealed and heated to react. After the reaction is completed, heating is stopped and the mixture in the reactor is slowly cooled to room temperature. The silica gel is washed for pore expansion; S2. Silica gel thermal activation: The expanded silica gel obtained in step S1 is placed in a suspension furnace, the silica gel is heated to decompose the silica gel into silica and water, and then cooled to room temperature to obtain activated silica microspheres; S3. Loading magnesium source: The silica microspheres obtained in step S2 were placed in a single-necked flask, an aqueous solution of a soluble magnesium salt was added to the flask, magnetically stirred at room temperature, and the solution was evaporated using a rotary evaporator in a nitrogen stream until the water was completely evaporated to obtain silica microspheres loaded with a magnesium source; S4. Preparation of a catalyst precursor: The magnesium-loaded silica microspheres obtained in step S3 are placed in a suspension furnace, the nitrogen flow rate is controlled to keep the silica microspheres in a suspended state in the quartz tube, and the magnesium-loaded silica microspheres are heated to remove free water and bound water contained in the magnesium-loaded silica microspheres, while converting the magnesium source into magnesium oxide, thereby finally obtaining a silicon-magnesium composite Ziegler-Natta catalyst precursor.
2. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 1, characterized in that In step S1, the silica gel is 955 silica gel; the mass ratio of silica gel to ultrapure water is 1:(4-10); the heating temperature is 100-200° C., and the reaction time is 0.5-3 h.
3. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 1, characterized in that In step S1, the pore-enlarging silica gel is washed multiple times with ultrapure water using a point-to-point mixing method.
4. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 1, characterized in that In step S2, the suspension furnace is a vertically placed quartz tube, the device for holding silica gel is a crucible with a sand core at the bottom, and the upper and lower ends of the quartz tube are equipped with gas guide valves and gas turbulence devices. The air inlet valve is adjusted to allow nitrogen to enter the quartz tube from the lower opening at a flow rate of 200 to 700 mL / min, so that the silica gel is in a boiling state in the quartz tube, ensuring the fluidization effect and uniform heat distribution; the silica gel in the quartz tube is heated by setting a programmed temperature rise, and then cooled to room temperature. The entire process is always in a high-purity nitrogen atmosphere.
5. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 4, characterized in that In step S2, the heating process of the silica gel in the quartz tube is as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for 1 hour, and the temperature is maintained at this temperature for 1 hour, and then the temperature is further raised to 300°C for 0.5 hours, and the temperature is maintained at 300°C for 1 hour. The heating is stopped and the silica gel in the quartz tube is allowed to cool naturally to room temperature. The nitrogen flow rate remains unchanged during the entire process to ensure that the silica gel in the quartz tube is always in a boiling state.
6. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 1, characterized in that: In step S3, the magnesium salt is one or more of magnesium acetate, magnesium citrate and magnesium chloride; the concentration of the magnesium salt aqueous solution is 0.25-1M, and n(Mg):n(Si)=5%-15%.
7. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 1, characterized in that: In step S3, the stirring time at room temperature is 4 to 8 hours; and the rotary evaporation heating temperature is 100°C.
8. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 1, characterized in that In step S4, the nitrogen flow rate is 200-700 mL / min.
9. The silicon-magnesium composite Ziegler-Natta catalyst precursor according to claim 1, characterized in that: In step S4, the heating process of the silica microspheres loaded with a magnesium source in the quartz tube is as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for a heating time of 1 hour, the temperature is maintained for 2 hours, and then the temperature is continued to be raised to 300°C for a heating time of 0.5 hours. After the temperature reaches 300°C, the gas is switched from high-purity nitrogen to dry air, and the temperature is maintained for 30 minutes, and then the temperature is continued to be raised to 450°C for a heating time of 1 hour, and the temperature is maintained for 2.5 hours. The temperature is continued to be raised to 600°C for a heating time of 30 minutes, and the temperature is maintained for 1 hour. After heating, the heating is stopped, and after the quartz tube is cooled to 450°C, the dry air is changed to high-purity nitrogen, and naturally cooled to room temperature. The nitrogen flow rate remains unchanged during the whole process to ensure that the silica microspheres loaded with a magnesium source in the quartz tube are always in a boiling state.
10. A silicon-magnesium composite Ziegler-Natta catalyst precursor, characterized in that: The silicon-magnesium composite Ziegler-Natta catalyst precursor is prepared by the method according to any one of claims 1 to 9.