Catalyst carrier as well as preparation method and application thereof
By mixing silicon halide with silica gel under low temperature conditions, silanol and hydrogen halide are generated, surface moisture is consumed, hydroxyl content is reduced, and the temperature increase rate is controlled to expand the silica gel pores, the problem of poor morphology and high cost in polymer production is solved, and the loading and dispersion of the catalyst is significantly improved, and the polymerization activity is improved.
Patent Information
- Application Number
- CN202510318343.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-18
- Publication Date
- 2025-06-17
AI Technical Summary
The existing metallocene catalysts have problems of poor particle morphology and difficult to control in polymer production, and require a large amount of methylaluminoxane, which is costly and difficult to handle, and requires granulation processes, which limits its industrial applications.
By mixing silicon halide with silica gel under low temperature conditions, the reaction is to generate silanol and hydrogen halide, consume surface moisture and reduce hydroxyl content, control the heating rate to expand the silicone pores, improve the specific surface area and pore volume, and optimize the loading and dispersion of the metallocene catalyst.
The loading and dispersion of the metallocene catalyst is significantly improved, the polymerization activity is improved, the stability and selectivity of the catalyst is improved, the dependence on methylaluminoxane is reduced, and the process flow is simplified.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of polymers, and particularly relates to a catalyst carrier, a preparation method thereof, and an application thereof. Background Art
[0002] Metallocene catalysts are the third generation of olefin polymerization catalysts after Ziegler catalysts and Ziegler-Natta catalysts. The basic composition of metallocene catalysts is an organometallic complex catalyst formed by cyclopentadienyl and its derivatives and transition metals. Homogeneous metallocene catalysts have many advantages, but some problems occur when using existing devices to produce polyolefin products. For example, the particle morphology of the polymer is not good and difficult to control; a large amount of methylaluminoxane (MAO) needs to be used, which has high costs, is easy to stick to the reactor, and is difficult to handle in subsequent processes. Moreover, a granulation process is required, which limits its further industrial application.
[0003] Currently, the commonly used method is to load metallocene catalysts. Silica gel is a porous medium material with a high specific surface area and pore size distribution, and its structure can be regulated. Using silica gel as a carrier can increase the dispersion and stability of metallocene catalysts, and improve the catalytic activity and selectivity of the catalysts. In addition, silica gel also has good heat resistance and chemical stability, and still has good performance under high temperature and strong acid-base conditions. The vast majority of researchers believe that silica gel mainly relies on the free hydroxyl groups on its surface to load metallocene catalysts. However, silica gel generally cannot be directly used as a carrier for metallocene catalysts. Excessive amounts of free water, vicinal hydroxyl groups, geminal hydroxyl groups, and free hydroxyl groups on its surface will cause catalyst poisoning. Therefore, it is very necessary to develop a preparation method for silica gel carriers that is easy to operate and applicable to loading metallocene catalysts for olefin polymerization. Summary of the Invention
[0004] In view of this, the present invention provides a catalyst carrier, a preparation method thereof, and an application thereof.
[0005] To solve the above technical problems, the technical solution provided by the present invention is:
[0006] A preparation method of a catalyst carrier, comprising the following steps:
[0007] Step 1: Add silica gel to a benzene solvent to obtain a silica gel-benzene solvent mixture;
[0008] Step 2: At -15°C to -10°C, add silicon halide to the silica gel-benzene solvent mixture, then carry out a reaction, heat up the reactants, and keep the temperature at 90°C to 110°C to obtain a catalyst carrier;
[0009] In Step 2, the conditions for temperature increase are as follows: increasing the temperature at a rate of 0.3°C / min to 0.4°C / min to -1°C to 1°C; increasing the temperature at a rate of 0.4°C / min to 0.6°C / min to 39°C to 41°C; increasing the temperature at a rate of 0.9°C / min to 1.1°C / min to 90°C to 110°C.
[0010] When a silica support is loaded with a metallocene catalyst, the metallocene catalyst is usually fixed on the silica surface through hydroxyl groups. However, the surface of untreated silica usually adsorbs a large amount of moisture, which can poison the catalyst; and the ionic radius of Si 4+ is 0.41 nm, which is smaller than the active center ion of the metallocene catalyst (for example, the ionic radius of Ti 3+ is 0.68 nm). Since Si 4 + has a smaller ionic radius, this also means that Si 4+ is arranged more closely, and thus the hydroxyl groups are arranged closely, making it difficult to load the metallocene catalyst. As a result, the hydroxyl density on the silica surface is much higher than the active center density of the metallocene catalyst, thereby affecting the dispersion and stability of the metallocene catalyst loaded on the silica.
[0011] Even though the prior art discloses thermal activation of silica before use to remove free water and hydroxyl groups, however, through a large number of studies, the inventor found that simply removing the free water and hydroxyl groups on the silica surface does not significantly improve the polymerization activity of the catalyst when the metallocene catalyst is loaded on the silica support surface.
[0012] Compared with the prior art, the present invention mixes silicon halide and silica under specific low-temperature conditions, enabling the silicon halide and silica to fully react. On the one hand, the silicon halide can react with the free water on the silica surface and in the pores, thereby generating silanol and hydrogen halide, consuming a large amount of moisture in the catalyst support, and the hydrogen halide can also leave voids in the silica during the overflow process, increasing the pore volume; on the other hand, the silicon halide also reacts with the hydroxyl groups in the silica, to a certain extent reducing the hydroxyl content on the silica surface and in the pores. The present invention also controls the temperature during the reaction and selects the silicon halide as the reaction substrate, which can remove the free water and some hydroxyl groups in the silica pores and on the surface, avoid excessive removal of hydroxyl groups and damage to the silica structure, and to a certain extent improve the specific surface area, pore volume and pore diameter of the silica as a catalyst support. It not only increases the loading amount of the metallocene catalyst, but also adjusts the hydroxyl concentration on the silica surface and in the silica pores, enabling the metallocene catalyst to be loaded on the silica catalyst support to achieve the optimal active center density and improve the polymerization activity of the catalyst during olefin polymerization.
[0013] Furthermore, the present invention defines a three-stage heating rate. A specific heating rate will cause the chemical bonds in the silica particles to break and recombine, changing the charge distribution and chemical activity within the silica pores, thereby causing a structural change in the void structure within the silica pores. By expanding the pores, the pore volume and pore diameter of the silica are increased, and further, the specific surface area of the catalyst support is increased. To a certain extent, not only the loading amount of the metallocene catalyst is increased, but also the metallocene catalyst can be better dispersed on the silica surface and within the pores. By increasing the number and dispersion of the effective active centers of the catalyst, the polymerization activity of the catalyst is improved; the specific heating rate can also form some new active sites or functional groups on the silica surface and within the pores, enabling the catalyst to be more stably fixed in the silica catalyst support, thereby improving the polymerization activity of the metallocene catalyst.
[0014] Preferably, in step 1, the mass-volume ratio of the silica to the benzene solvent is 1 g : (10 - 20) mL.
[0015] Preferably, in step 1, the benzene solvent is toluene.
[0016] Preferably, in step 2, the silicon halide is silicon tetrachloride.
[0017] The preferred silicon halide is beneficial for further removing the free water in the catalyst support and improving the hydroxyl density on the surface and in the pores of the catalyst support, enabling the metallocene catalyst to have the optimal active center density when loaded on the catalyst support and improving the polymerization activity of the catalyst.
[0018] Preferably, the mass ratio of the silica to the silicon halide is 1 : (1 - 5).
[0019] The preferred dosage of the silicon halide can not only meet the removal of the free water in the catalyst support, but also improve the hydroxyl density on the surface and in the pores of the catalyst.
[0020] Preferably, in step 2, the silicon halide is added dropwise, and the dropping time is 50 min - 60 min.
[0021] The specific addition method is beneficial for the full reaction between the silicon halide and the silica, to remove the free water in the silica pores to the greatest extent and improve the density of the hydroxyl groups in the silica pores.
[0022] Preferably, in step 2, the reaction time is 120 min - 130 min.
[0023] It should be further noted that stirring treatment is also required during the reaction, and the stirring rate is 235 rpm - 245 rpm.
[0024] Preferably, during the heating in step 2, stirring is also required.
[0025] Further preferably, in step 2, the stirring rate is 235 rpm to 245 rpm.
[0026] Preferably, in step 2, the heat preservation time is 1 h to 10 h.
[0027] Preferably, in step 2, the mixture after heat preservation is cooled and precipitated to obtain the catalyst support.
[0028] As a preferred embodiment, the mixture after heat preservation is cooled and precipitated, solid-liquid separated, washed, solid-liquid separated, and dried to obtain the catalyst support.
[0029] Preferably, the washing is carried out using an inert solvent, and the inert solvent is a liquid aromatic hydrocarbon compound, an alkane compound or a mixture in any proportion.
[0030] The aromatic compound is at least one of benzene, toluene, xylene, ethylbenzene, propylbenzene, trimethylbenzene, chlorobenzene or dichlorobenzene.
[0031] The alkane is at least one of hexane, heptane or decane.
[0032] The second aspect of the present invention provides a catalyst support prepared by the preparation method of the above catalyst support.
[0033] The third aspect of the present invention provides the application of the above catalyst support in the preparation of metallocene catalysts.
[0034] The catalyst support prepared by the preparation method of the catalyst support provided by the present invention, when applied to load metallocene catalysts, can significantly improve the polymerization activity during olefin polymerization. Detailed Embodiments
[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.
[0036] To better illustrate the present invention, further illustrative examples are given below through embodiments.
[0037] Example 1
[0038] This example provides a preparation method of a catalyst support, including the following steps:
[0039] Step 1: Add 30 g of silica gel to 300 mL of toluene to obtain a silica gel-toluene mixture;
[0040] Step 2: Add 33 g of silicon tetrachloride dropwise to the silica-toluene mixture at -15°C, control the dropping time to be 50 min, then react for 120 min. During the reaction process, stir at a rate of 240 rpm. Heat up the reactants, and during the heating process, also stir at a rate of 235 rpm. Keep the temperature at 90°C for 1 h. Cool down and precipitate the mixture after the heat preservation, filter, wash with benzene, filter again, and dry to obtain the catalyst support.
[0041] In Step 2, the conditions for heating up are as follows: Heat up to -1°C at a heating rate of 0.4°C / min; heat up to 39°C at a heating rate of 0.6°C / min; heat up to 90°C at a heating rate of 0.9°C / min.
[0042] Example 2
[0043] This example provides a method for preparing a catalyst support, which includes the following steps:
[0044] Step 1: Add 30 g of silica to 600 mL of toluene to obtain a silica-toluene mixture.
[0045] Step 2: Add 150 g of silicon tetrachloride dropwise to the silica-toluene mixture at -10°C, control the dropping time to be 60 min, then react for 130 min. During the reaction process, stir at a rate of 240 rpm. Heat up the reactants, and during the heating process, also stir at a rate of 245 rpm. Keep the temperature at 100°C for 10 h. Cool down and precipitate the mixture after the heat preservation, filter, wash with benzene, filter again, and dry to obtain the catalyst support.
[0046] In Step 2, the conditions for heating up are as follows: Heat up to 1°C at a heating rate of 0.3°C / min; heat up to 41°C at a heating rate of 0.4°C / min; heat up to 100°C at a heating rate of 1.1°C / min.
[0047] Example 3
[0048] This example provides a method for preparing a catalyst support, which includes the following steps:
[0049] Step 1: Add 30 g of silica to 360 mL of toluene to obtain a silica-toluene mixture.
[0050] Step 2: At -15°C, add 30 g of silicon tetrachloride dropwise to the silica-toluene mixture, control the dropping time to 55 min, then react for 125 min. During the reaction process, it is necessary to stir at a rate of 240 rpm. Heat up the reactants, and during the heating process, it is also necessary to stir at a rate of 245 rpm. Keep the temperature at 110°C for 2 h. Cool down and precipitate the mixture after the heat preservation, filter, wash with benzene, filter, and dry to obtain the catalyst support;
[0051] In Step 2, the conditions for heating up are as follows: Heat up to 0°C at a heating rate of 0.33°C / min; heat up to 40°C at a heating rate of 0.5°C / min; heat up to 110°C at a heating rate of 1°C / min.
[0052] Example 4
[0053] This example provides a preparation method of a catalyst support. Compared with Example 1, the difference is that
[0054] Silicon tetrachloride is replaced with an equal amount of silicon tetrafluoride;
[0055] Other raw materials are the same as those in Example 1.
[0056] Comparative Example 1
[0057] This comparative example provides a preparation method of a catalyst support. Compared with Example 1, the difference is that the reaction temperature in Step 2 is reduced, specifically as follows:
[0058] Step 2: At -30°C, add 30 g of silicon tetrachloride dropwise to the silica-toluene mixture, control the dropping time to 50 min, then react for 120 min. During the reaction process, it is necessary to stir at a rate of 240 rpm. Heat up the reactants, and during the heating process, it is also necessary to stir at a rate of 235 rpm. Keep the temperature at 110°C for 1 h. Cool down and precipitate the mixture after the heat preservation, filter, wash with benzene, filter, and dry to obtain the catalyst support;
[0059] Other raw materials are the same as those in Example 1.
[0060] Comparative Example 2
[0061] This comparative example provides a preparation method of a catalyst support. The difference is that the heat preservation temperature in Step 2 is reduced, specifically as follows:
[0062] Step 2: At -15°C, add 30 g of silicon tetrachloride dropwise to the silica-toluene mixture, control the dropping time to 50 min, then react for 120 min. During the reaction process, stir at a rate of 240 rpm. Heat up the reactants, and during the heating process, also stir at a rate of 235 rpm. Keep the temperature at 80°C for 1 h. Cool down and precipitate the mixture after the heat preservation, filter, wash with benzene, filter again, and dry to obtain the catalyst support;
[0063] In Step 2, the conditions for heating up are as follows: Heat up to -1°C at a heating rate of 0.4°C / min; heat up to 39°C at a heating rate of 0.6°C / min; heat up to 80°C at a heating rate of 0.9°C / min;
[0064] Other raw materials are the same as those in Example 1.
[0065] Comparative Example 3
[0066] This comparative example provides a method for preparing a catalyst support, which is different in that the heating conditions in the first stage are changed, specifically as follows:
[0067] In Step 2, the conditions for heating up are as follows: Heat up to -1°C at a heating rate of 1°C / min; heat up to 39°C at a heating rate of 0.6°C / min; heat up to 90°C at a heating rate of 0.9°C / min;
[0068] Other raw materials are the same as those in Example 1.
[0069] Comparative Example 4
[0070] This comparative example provides a method for preparing a catalyst support, which is different in that the heating conditions in the second stage are changed, specifically as follows:
[0071] In Step 2, the conditions for heating up are as follows: Heat up to -1°C at a heating rate of 0.4°C / min; heat up to 39°C at a heating rate of 1°C / min; heat up to 90°C at a heating rate of 0.9°C / min;
[0072] Other raw materials are the same as those in Example 1.
[0073] Comparative Example 5
[0074] This comparative example provides a method for preparing a catalyst support, which is different in that the heating conditions are different, specifically as follows:
[0075] In Step 2, the conditions for heating up are as follows: Heat up to -1°C at a heating rate of 0.4°C / min; heat up to 90°C at a heating rate of 0.9°C / min;
[0076] Other raw materials are the same as those in Example 1.
[0077] Application Example
[0078] A method for preparing a metallocene catalyst specifically includes the following steps:
[0079] Under a nitrogen atmosphere, 1 g of the silica catalyst carriers prepared in Examples 1-3 and Comparative Examples 1-7 were respectively placed in an oven at 110 °C and dried for 4 hours, then added to a reaction flask protected by dry nitrogen. 5 mmol of methylaluminoxane (MAO) and 30 mL of toluene were added to the reaction flask, stirred evenly at 50 °C, and the obtained solid was washed with 15 mL of toluene after filtration. The washing was repeated at least 3 times to obtain the MAO-loaded silica support; the obtained MAO-loaded silica support and 0.05 g of the metallocene complex dimethylsilyl(tetramethylcyclopentadienyl)(2-methyl-4-tert-butylphenylindenyl)zirconium dichloride were added to 30 mL of toluene and stirred at 50 °C for 2 h. After filtration, the obtained solid was washed with 15 mL of toluene, the washing was repeated at least 3 times, and the obtained solid was dried in vacuo, namely the metallocene catalyst for olefin polymerization.
[0080] A synthesis method for olefin polymerization includes the following steps:
[0081] After a 5 L high-pressure reactor was purged with nitrogen and purified with triethylaluminum, propylene was introduced at 35 °C until the pressure reached 1.0 MPa, and then 0.2 g of the metallocene catalysts prepared in Examples 1-3 and Comparative Examples 1-7 were respectively added. Propylene was introduced again until the pressure in the reactor reached 2.0 MPa, and polymerization was carried out at 60 °C for 1 hour.
[0082] The specific surface area, pore volume, pore diameter of the catalyst carriers prepared in Examples 1-3 and Comparative Examples 1-7, and the polymerization activity of the silica-supported metallocene catalysts prepared in Examples 1-3 and Comparative Examples 1-7 during olefin polymerization were detected;
[0083] Among them, the morphological characterization method of the catalyst carrier:
[0084] Analysis was carried out using a Quantachrome NOVA 4200e fully automatic specific surface area and pore size distribution analyzer. The degassing temperature for sample pretreatment was 300 °C, the degassing time was 3 hours. After cooling to room temperature, the mass of the degassed sample was accurately weighed, and then the sample was subjected to isothermal adsorption and desorption analysis under the condition of 77K;
[0085] Polymerization activity: It is the mass ratio of polypropylene to the catalyst;
[0086] The specific detection results are shown in Table 1:
[0087] Table 1
[0088]
[0089]
[0090] As can be seen from Table 1, compared with Comparative Examples 1-5, the catalyst carriers provided in Examples 1-3 of the present invention have a larger specific surface area, pore diameter and pore volume, and the metallocene catalysts prepared using the catalyst carriers provided in Examples 1-3 of the present invention can reach a polymerization activity of 7000 gPP / gCat when catalyzing olefin polymerization, which is significantly better than the polymerization activity of the metallocene catalysts prepared in the comparative examples of the present invention.
[0091] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a catalyst carrier, characterized in that: The steps include: Step 1, adding silica gel to a benzene solvent to obtain a silica gel-benzene solvent mixture; Step 2, adding silicon halide to the silica gel benzene solvent mixture at -15°C to -10°C, then reacting, heating the reactants, and keeping the temperature at 90°C to 110°C to obtain a catalyst carrier; In step 2, the heating conditions are: heating to -1°C to 1°C at a heating rate of 0.3°C / min to 0.4°C / min; heating to 39°C to 41°C at a heating rate of 0.4°C / min to 0.6°C / min; heating to 90°C to 110°C at a heating rate of 0.9°C / min to 1.1°C / min.
2. The method for preparing a catalyst carrier according to claim 1, characterized in that: In step 1, the mass volume ratio of the silica gel and the benzene solvent is 1 g: (10-20) mL.
3. The method for preparing a catalyst carrier according to claim 1, characterized in that: In step 1, the benzene solvent is toluene; and / or In step 2, the silicon halide is silicon tetrachloride.
4. The method for preparing a catalyst carrier according to claim 1, characterized in that: The mass ratio of the silica gel to the silicon halide is 1:(1-5).
5. The method for preparing a catalyst carrier according to claim 1, characterized in that: In step 2, the silicon halide is added dropwise for 50 to 60 minutes.
6. The method for preparing a catalyst carrier according to claim 1, characterized in that: In step 2, the reaction time is 120 min to 130 min.
7. The method for preparing a catalyst carrier according to claim 1, characterized in that: In step 2, the insulation time is 1 h to 10 h.
8. The method for preparing a catalyst carrier according to claim 1, characterized in that: In step 2, the mixture after the insulation is completed is cooled and precipitated to obtain the catalyst carrier.
9. A catalyst carrier, characterized in that: The catalyst carrier is prepared by the method for preparing the catalyst carrier according to any one of claims 1 to 8.
10. Use of a catalyst support prepared by the method for preparing a catalyst support according to any one of claims 1 to 8 or a catalyst support according to claim 9 in preparing a metallocene catalyst.