Alkoxy magnesium carrier Ziegler-Natta catalyst and preparation method thereof

Abstract

According to the alkoxy magnesium carrier Ziegler-Natta catalyst and the preparation method thereof, alkoxy magnesium is activated and then loaded with titanium, fluorene diether is selected as an internal electron donor, the obtained catalyst is subjected to post-treatment, and finally the alkoxy magnesium carrier Ziegler-Natta catalyst with excellent performance is prepared. The raw material utilization rate is higher, the adding amount of required titanium tetrachloride is smaller, the steps are simpler, the preparation conditions are mild, the isotactic index of the prepared homo-polypropylene is higher, and the activity of the prepared catalyst is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of polymerization catalyst preparation, and particularly relates to an alkoxy magnesium carrier Ziegler-Natta catalyst suitable for industrial-scale polyolefin production and a preparation method thereof. Background Art

[0002] Ziegler-Natta (ZN) catalysts are widely used in the polyolefin industry and have evolved through five generations. Their preparation primarily involves chemically preparing a MgCl2 support. However, untreated MgCl2, due to its α-MgCl2 structure and its limited crystal structure defects, results in a low titanium loading and low activity in the resulting ZN catalyst. Therefore, activation is required before loading to obtain active MgCl2. Activation methods primarily include grinding and chemical reaction. Early activation methods primarily employed ball milling to remove surface defects in the MgCl2 crystals, facilitating the loading of TiCl4. Currently, chemical reaction is the predominant method, which disrupts the MgCl2 lattice in a way that physical methods cannot. In the chemical reaction method, the catalyst is prepared by reacting MgCl2 with anhydrous ethanol (EtOH) to form a magnesium chloride alcoholate (MgCl2·nEtOH). This is then impregnated with an excess of TiCl4 to form the titanium-loaded ZN catalyst. However, this method, particularly for spherical ZN catalysts, is complex and requires demanding preparation conditions. Summary of the Invention

[0003] (1) Technical issues to be solved

[0004] The present invention provides an alkoxymagnesium supported Ziegler-Natta catalyst and a preparation method thereof, in order to solve the technical problem of how to achieve a smaller amount of titanium tetrachloride added, higher catalyst activity, milder preparation conditions and simpler steps in the preparation.

[0005] (2) Technical solution

[0006] In order to solve the above technical problems, the present invention proposes a method for preparing an alkoxymagnesium supported Ziegler-Natta catalyst, which comprises the following steps:

[0007] S1. Under heating conditions, a mixture of carbon dioxide and sulfur dioxide is continuously introduced into the magnesium alkoxide to obtain a solid carboxysulfonic acid magnesium alkoxide after the reaction;

[0008] S2. An excess of an alcohol solution was added to the carboxysulfonic acid alkoxymagnesium to disperse the solution and stirred under an inert gas to obtain a suspension;

[0009] S3. The suspension was spray-dried under heating conditions to obtain a solid magnesium alkoxide after decarboxylation and desulfonation;

[0010] S4. The solid magnesium alkoxide is heated under an inert gas to obtain an active magnesium alkoxide, which is then slowly cooled to room temperature and stored for later use;

[0011] S5. TiCl4 is added to the active alkoxymagnesium and stirred. An internal electron donor is added after heating. After the reaction, a solid is obtained by filtration. The solid is heat-treated with a heated inert gas, then washed with a solvent, and vacuum-dried to obtain an alkoxymagnesium-supported Ziegler-Natta catalyst.

[0012] Furthermore, in step S1, the alkoxy magnesium is one or more of magnesium ethoxide, magnesium isopropoxide and magnesium tert-butoxide; the heating temperature is 50-80° C., the reaction time is 0.5-3 h; and the molar ratio of carbon dioxide to sulfur dioxide is 5:(1-3).

[0013] Furthermore, in step S2, the alcohol solution is one or more of ethanol, n-propanol, isopropanol and tert-butanol; the stirring speed is 300-700 rpm, and the stirring time is 0.5-3 h.

[0014] Furthermore, in step S3, the spray drying parameters are: inlet temperature of 60°C to 90°C, outlet temperature of 50°C to 80°C, centrifugal nozzle speed of 8000 to 12000 rpm, feed rate of 100 to 500 mL / h, and temperature control accuracy of ±1°C.

[0015] Furthermore, in step S4, the heating temperature is 100-150° C., and the heating reaction time is 1-3 hours.

[0016] Furthermore, in step S5, the mass ratio of TiCl4 to magnesium in the alkoxymagnesium support is (3-10):1; the temperature when adding TiCl4 is -20-5°C, the stirring speed is 200-500 rpm, and the stirring time after adding TiCl4 is continued for not less than 30 minutes.

[0017] Furthermore, in step S5, the internal electron donor is fluorene diether, and the ratio of the added amount to the mass of TiCl4 is 1:(80-100); the heating temperature is 80-110°C, and the reaction time is 1-3h.

[0018] Furthermore, in step S6, the temperature of the heated inert gas is 50-80° C., and the heat treatment time is 2 hours.

[0019] Furthermore, in step S7, the solvent is an alkane or benzene and its homologues, ethane, heptane, benzene and toluene solution; the vacuum drying temperature is 50-80°C, and the drying time is 2-6 hours.

[0020] In addition, the present invention also provides an alkoxy magnesium supported Ziegler-Natta catalyst, which is prepared by the above method.

[0021] (3) Beneficial effects

[0022] The present invention provides an alkoxymagnesium-supported Ziegler-Natta catalyst and a preparation method thereof. The catalyst comprises activating the alkoxymagnesium and then loading it with titanium. Fluorene diethers are selected as internal electron donors, and the resulting catalyst is post-treated to prepare an alkoxymagnesium-supported Ziegler-Natta catalyst with excellent performance. The present invention achieves higher raw material utilization, requires less titanium tetrachloride, simplifies the steps, operates under mild preparation conditions, and produces homopolypropylene with a higher isotactic index and higher catalyst activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart for preparing the alkoxy magnesium supported Ziegler-Natta catalyst of the present invention. DETAILED DESCRIPTION

[0024] 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.

[0025] Example 1

[0026] This embodiment provides a method for preparing an alkoxy magnesium supported Ziegler-Natta catalyst, the process of which is as follows: Figure 1 As shown, the specific steps include:

[0027] S1. At 60°C, a mixture of carbon dioxide and sulfur dioxide in a ratio of 5:1 was continuously introduced into magnesium ethoxide and the reaction was carried out at this temperature for 1.5h;

[0028] S2. The solid material obtained in step S1 was dispersed by adding an excess of ethanol solution and stirred at 400 rpm under nitrogen for 1.5 h;

[0029] S3. The suspension obtained in step S2 was spray dried at a certain temperature. Specific parameters were: inlet temperature 75°C, outlet temperature 60°C, centrifugal nozzle speed 8000rpm, feed rate 100mL / h, temperature control accuracy ±1°C;

[0030] S4. The solid obtained in step S3 was heated to 110 ° C under nitrogen protection, and reacted at this temperature for 2h to obtain an active magnesium alkoxide, which was then slowly cooled to room temperature and stored for use;

[0031] S5. Take a certain amount of the alkoxymagnesium obtained in step S4, add TiCl4 at a ratio of nMgCl2:TiCl4 = 1:3 at -5°C, maintain this temperature and stir the reaction for 30 minutes, then heat to 90°C, add fluorene dimethyl ether, the amount of fluorene dimethyl ether added is 1 / 80 of the mass of TiCl4, and react for 1.5 hours; blow with hot nitrogen at 60°C for 2 hours until dry, then wash with hexane 4 times, each time using 50 mL, and vacuum dry at 60°C for 2 hours to finally obtain an alkoxymagnesium supported Ziegler-Natta catalyst.

[0032] Propylene gas phase slurry polymerization: 800 mL of hexane was added to the reactor, and propylene gas was introduced into the reactor until the propylene was dissolved to saturation. 10 mg of the prepared alkoxymagnesium supported Ziegler-Natta catalyst was accurately weighed and dispersed with hexane. 14.7 mL of triethylaluminum was added, and the mixture was reacted at 70°C and 2 MPa for 2 h to obtain polypropylene.

[0033] Example 2

[0034] Steps S3, S6, S7, and S8 are the same as those in Example 1;

[0035] S1. At 60°C, a mixture of carbon dioxide and sulfur dioxide in a ratio of 5:2 was continuously introduced into magnesium ethoxide and the reaction was carried out at this temperature for 1.5h;

[0036] S2. The solid material obtained in step S1 was dispersed by adding an excess of isopropanol solution and stirred at 400 rpm under nitrogen for 1.5 h;

[0037] S4. The solid obtained in step S3 was heated to 130 ° C under nitrogen protection, and the reaction was carried out at this temperature for 1.5 h to obtain an active magnesium alkoxide, which was then slowly cooled to room temperature and stored for use;

[0038] S5. Take a certain amount of the alkoxymagnesium obtained in step S4, add TiCl4 at a ratio of nMgCl2:TiCl4 = 1:5 at -5°C, maintain this temperature and stir the reaction for 30 minutes, then heat to 100°C, add fluorene dimethyl ether, the amount of fluorene dimethyl ether added is 1 / 80 of the mass of TiCl4, and react for 1.5 hours; blow with hot nitrogen at 60°C for 2 hours until dry, then wash with hexane 4 times, each time using 50 mL, and dry in vacuo at 60°C for 2 hours to finally obtain an alkoxymagnesium supported Ziegler-Natta catalyst.

[0039] Example 3

[0040] Steps S3, S6, S7, and S8 are the same as those in Example 1;

[0041] S1. At 60°C, a mixture of carbon dioxide and sulfur dioxide in a ratio of 5:3 was continuously introduced into magnesium ethoxide and the reaction was carried out at this temperature for 1.5h;

[0042] S2. The solid material obtained in step S1 was dispersed by adding an excess of isopropanol solution and stirred at 400 rpm under nitrogen for 1.5 h;

[0043] S4. The solid obtained in step S3 was heated to 130 ° C under nitrogen protection, and the reaction was carried out at this temperature for 1.5 h to obtain an active magnesium alkoxide, which was then slowly cooled to room temperature and stored for use;

[0044] S5. Take a certain amount of the alkoxymagnesium obtained in step S4, add TiCl4 at a ratio of nMgCl2:TiCl4 = 1:7 at -5°C, maintain this temperature and stir the reaction for 30 minutes, then heat to 100°C, add fluorene dimethyl ether, the amount of fluorene dimethyl ether added is 1 / 80 of the mass of TiCl4, and react for 1.5 hours; blow with hot nitrogen at 60°C for 2 hours until dry, then wash with hexane 4 times, each time using 50 mL, and dry in vacuo at 60°C for 2 hours to finally obtain an alkoxymagnesium supported Ziegler-Natta catalyst.

[0045] The polypropylene obtained by polymerization in Examples 1 to 3 was tested. The isotactic index is shown in Table 1, and the melt index is shown in Table 2 (test conditions: temperature 230°C, load 2160g, sample pressure 0.2982MPa. Same below). The calculated catalyst activity is shown in Table 3.

[0046] Table 1 Isotactic index of polypropylene obtained by polymerization in Examples 1 to 3

[0047] unit Example 1 Example 2 Example 3 Test standards Isotactic index ％ 98.4 99.3 99.2 GB / T2412-2008

[0048] Table 2 Melt index of polypropylene obtained by polymerization in Examples 1 to 3

[0049] unit Example 1 Example 2 Example 3 Test standards Melt index g / 10min 38.9 40.1 39.6 GB / T3862.1-20118

[0050] Table 3 Activity of catalysts prepared in Examples 1 to 3

[0051] unit Example 1 Example 2 Example 3 Mass of polypropylene obtained by polymerization g 65.78 69.54 72.92 catalytic activity kgPP / gcat 65.78 69.54 72.92

[0052] 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 an alkoxy magnesium support Ziegler-Natta catalyst, characterized in that: The preparation method comprises the following steps: S1. Under heating conditions, a mixture of carbon dioxide and sulfur dioxide is continuously introduced into the magnesium alkoxide to obtain a solid carboxysulfonic acid magnesium alkoxide after the reaction; S2. An excess of an alcohol solution was added to the carboxysulfonic acid alkoxymagnesium to disperse the solution and stirred under an inert gas to obtain a suspension; S3. The suspension was spray-dried under heating conditions to obtain a solid magnesium alkoxide after decarboxylation and desulfonation; S4. The solid magnesium alkoxide is heated under an inert gas to obtain an active magnesium alkoxide, which is then slowly cooled to room temperature and stored for later use; S5. TiCl4 is added to the active alkoxymagnesium and stirred. An internal electron donor is added after heating. After the reaction, a solid is obtained by filtration. The solid is heat-treated with a heated inert gas, then washed with a solvent, and vacuum-dried to obtain an alkoxymagnesium-supported Ziegler-Natta catalyst.

2. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S1, the alkoxy magnesium is one or more of magnesium ethoxide, magnesium isopropoxide and magnesium tert-butoxide; the heating temperature is 50-80° C., the reaction time is 0.5-3 h; and the molar ratio of carbon dioxide to sulfur dioxide is 5:(1-3).

3. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S2, the alcohol solution is one or more of ethanol, n-propanol, isopropanol and tert-butanol; the stirring speed is 300-700 rpm, and the stirring time is 0.5-3 h.

4. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S3, the spray drying parameters are: inlet temperature of 60°C to 90°C, outlet temperature of 50°C to 80°C, centrifugal nozzle speed of 8000 to 12000 rpm, feed rate of 100 to 500 mL / h, and temperature control accuracy of ±1°C.

5. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S4, the heating temperature is 100-150° C., and the heating reaction time is 1-3 hours.

6. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S5, the mass ratio of TiCl4 to magnesium in the alkoxymagnesium support is (3-10):1; the temperature when adding TiCl4 is -20-5°C, the stirring speed is 200-500 rpm, and the stirring time after adding TiCl4 is continued for not less than 30 minutes.

7. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S5, the internal electron donor is fluorene diether, and the ratio of the added amount to the mass of TiCl4 is 1:(80-100); the heating temperature is 80-110°C, and the reaction time is 1-3h.

8. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S6, the temperature of the heated inert gas is 50-80° C., and the heat treatment time is 2 hours.

9. The method for preparing the alkoxy magnesium support Ziegler-Natta catalyst according to claim 1, wherein: In step S7, the solvent is an alkane or benzene and its homologues, ethane, heptane, benzene and toluene solution; the vacuum drying temperature is 50-80°C, and the drying time is 2-6 hours.

10. An alkoxymagnesium supported Ziegler-Natta catalyst, characterized in that The alkoxy magnesium support Ziegler-Natta catalyst is prepared by the method according to any one of claims 1 to 9.

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