CN107141383A - Wide molecular weight polypropylene catalyst, preparation method and method for preparing polypropylene by using wide molecular weight polypropylene catalyst - Google Patents

Abstract

The invention aims to provide a broad molecular weight polypropylene catalyst which comprises, by weight, 10-25% of magnesium, 1-15% of titanium, 40-60% of halogen and 1% -20% of an internal electron donor, and is characterized in that the internal electron donor is selected from the group consisting of those with molecular frameworks shown in a general formula (I)A 7-oxabicyclo [2.2.1 ]]Hept-5-ene-2, 3-dicarboximide compounds:

Description

A kind of wide molecular weight polypropylene catalyst, preparation method and method for preparing polypropylene with it method

technical field

The invention relates to the field of polypropylene catalysts, in particular to a wide molecular weight polypropylene catalyst, a preparation method thereof and a method for preparing polypropylene using the catalyst as a catalyst.

Background technique

Polypropylene is one of the fastest growing polyolefin materials, and its output is second only to polyethylene in the world. In 1954, Natta invented TiCl ₃ /AlR ₃ polypropylene Ziegler-Natta (ZN) catalyst, but at that time the catalyst had low orientation ability and low activity. By the middle and late 1960s, certain Lewis bases (called internal electron donors) were mixed into titanium trichloride crystals by mechanical grinding or chemical methods, so that the surface area of the catalyst was greatly increased, and the obtained polypropylene isotacticity reached 90-96%. People have gradually found that the electron donor introduced in the catalyst plays a key role in improving the performance of the catalyst. The electron donor can not only improve the activity and orientation ability of the catalyst, but more importantly, it can change the molecular structure of the polymer and improve the performance of polypropylene. the quality of. So far, the main energy of research on polypropylene ZN catalysts has turned to finding electron donor compounds with better overall performance or special performance. The renewal of the electron donor compound has also become the main factor to promote the replacement of the catalyst.

The application of the diether electron donor compound significantly improves the catalytic activity of the catalyst and the isotacticity of the polymer. Technologists have applied for many patents on Ziegler-Natta olefin polymerization catalysts prepared from diether electron donor compounds, such as: US6395670, EP0728724, US4971973, CN1066723, CN99125566, etc.

In terms of improving the polymerization activity of Ziegler-Natta olefin polymerization catalysts, as well as improving their hydrogen tuning performance and stereoselectivity, some diether compounds with special structures are considered to be the best known electron donors. For example, in the 1,3-diether compound disclosed in patent EP 0728724, the carbon atom at the 2-position is on a special ring (5-7 membered ring), and the ring contains two to three unsaturated double bonds. The catalyst prepared by the compound as an electron donor has high activity and stereoselectivity. In the patent EP 0361494, a 1,3-diether compound whose 2-position carbon atom is an acyclic structure is disclosed as an electron donor. It is generally believed that when the hydrogen on the 2-carbon atom in the 1,3-diether structure is replaced by a sterically hindered substituent, the catalyst prepared with it has better catalytic performance. The possible reason is that such The 1,3-diether compound has a relatively fixed spatial conformation, which to a certain extent determines the coordination direction of MgCl ₂ and TiCl ₄ , thereby affecting the performance of the catalyst, especially the stereoselectivity of the catalyst, as reported in EP 0728769 The 1,3-diether compounds can be used not only as internal electron donors of Ziegler-Natta olefin polymerization catalysts, but also as external electron donors.

Succinic acid amides are used as electron donors, and their unique electronic effects and steric effects make the catalysts have excellent overall performance. When used in propylene homopolymerization and copolymerization, the catalysts have high polymerization activity and high stereospecificity. The sensitivity is also very good, and the molecular weight distribution of the obtained polymer is wide, which is beneficial to the development of different polypropylene grades.有关专利有：CN200710105094.9，CN200910090467.9，CN200810222179.X，CN200810222180.2，CN200810238970.X，CN200910079175.5，CN200910235560.4，CN201010199059.X，CN201010199066.X，CN01803744.5等。 In order to obtain higher polymer stereoregularity, it is still of positive significance and technical prospect to continuously develop new structures based on the molecular skeleton of electron donor compounds.

The present invention adopts 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide compounds as internal electron donors, and the synthesized spherical When the catalyst is used for olefin polymerization, especially propylene polymerization, it not only maintains the ultra-high polymerization activity of amide catalysts, but also significantly improves its molecular weight distribution.

Contents of the invention

The object of the present invention is to provide a catalyst for polypropylene, which contains electron-donating compounds of specific structure, endowing polypropylene with higher activity and molecular weight distribution. Another object of the present invention is to provide a preparation method of the catalyst.

The polypropylene catalyst provided by the present invention is mainly composed of 10%-25% magnesium, 1%-15% titanium, 40%-60% halogen and 1%-20% internal electron donor in terms of weight percentage. The body is a compound containing 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide in the molecular skeleton, which specifically meets the structural formula (I):

(I) In the formula, the substituents R ₁ and R ₆ are the same or different, selected from H, C ₁ to C ₁₀ straight chain or branched chain alkyl; R ₂ , R ₃ , R ₄ , R ₅ are the same or different, selected from From H, halogen, C ₁ to C ₁₀ straight or branched chain alkyl, C ₃ to C ₁₀ cycloalkyl or aryl; R ₇ is selected from H, C ₁ to C ₁₀ straight or branched chain alkane group, C ₃ -C ₁₀ cycloalkyl or aryl group.

In the internal electron donor compound described in the present invention, contain imide structure and ether structure in the molecular skeleton, amide bond and ether bond in its structure, and MgCl _on the carrier surface ^Mg chelation easily forms stable Chelates, which facilitate the adsorption of electron donors on the surface of the _MgCl2 carrier, form multiple active centers, and polypropylene exhibits a higher molecular weight distribution. Specifically, the internal electron donor can be selected from any of the following compounds:

7-Oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

1-Methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

1-Pentyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

1-Chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

2-Methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

2-Octyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

1-isobutyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

2-Hexyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

2-Chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

5-Chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

1-Phenyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

5-Phenyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-isobutyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Phenyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Methyl-1-ethyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Ethyl-2-propyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Hexyl-1,2-dimethyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Methyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Methyl-1-ethyl-4-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Methyl-1-ethyl-5-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Butyl-1-ethyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Butyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Ethyl-1-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

N-Methyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

The electron donor compound in the general formula (I) can be synthesized by reacting any furan compound and any maleimide in the next step of heating and reflux.

The magnesium in the catalyst is provided by a magnesium halide alcoholate with a particle size distribution of 50-250 μm and a general structural formula of Mg(OR')mX ₍₂ -m)·n(R ₂ OH). In the general formula, R' is an alkyl, aralkyl or aryl group of C ₁ to C ₂₀ ; X is a halogen; m is an integer of 0≦m<2; n is a decimal or integer of 0<n<5; R ₂ It is a C1-C20 alkyl group, aralkyl group or aryl group. The magnesium halide in the magnesium halide alcoholate is selected from one of magnesium chloride, magnesium bromide, chloromethoxymagnesium or chloroethoxymagnesium, preferably magnesium chloride. The alcohol used is selected from methanol, ethanol, propanol, isopropanol, butanol or isobutanol, preferably ethanol.

Magnesium halide alcoholate is obtained by heating and dissolving magnesium halide and alcohol together, spraying at high pressure or stirring at high speed, and solidifying into microsphere particles in a cooling medium. For specific steps, refer to patent publication number CN1110281 (application number CN94103454.2, patent Name: Relevant description in olefin polymerization carrier catalyst system and preparation method).

The catalytic component titanium is provided by titanium halide with the general formula Ti(OR) _p X _(4-p) , where R is an alkyl, aryl or aralkyl group of C ₁ to C ₂₀ ; X is a halogen; p is An integer of 0≦p<4. Specifically selected from tetraethoxytitanium, tetrabutoxytitanium, chlorotrialkoxytitanium, dichlorodialkoxytitanium, trichloroalkoxytitanium, titanium tetrachloride or titanium tetrabromide species, preferably titanium tetrachloride.

The present invention further proposes the preparation method of supported catalyst, and concrete process comprises:

(1) Add spherical magnesium halide alcoholate particles into the titanium halide liquid at -50-20°C, preferably -30-0°C, and react for 10 minutes to 5 hours, preferably 1 to 4 hours. The molar ratio to titanium is 1:5~1:100, preferably 1:10~1:50;

(2) Heat up to 0-80°C, preferably 30-60°C, add internal electron donor compound, the molar ratio of magnesium to internal electron donor compound is 2:1-20:1, preferably 2:1 ~12:1;

(3) heat up to 100-150°C, preferably 110-130°C, and react for 1-6 hours, preferably 1-4 hours;

(4) Add titanium halide liquid after filtration, react at 110-130°C for 1-4 hours, preferably 1-2 hours, then filter, wash and dry to obtain the catalyst.

When the above-mentioned supported catalyst catalyzes the polymerization of propylene, an alkylaluminum compound and an alkoxysilane compound are also added as required.

Wherein the alkylaluminum compound is selected from one of trimethylaluminum, triethylaluminum, triisobutylaluminum, monochlorodiethylaluminum or monochlorodiisobutylaluminum, preferably triethylaluminum or triisobutylaluminum.

The alkoxysilane compound is selected from dimethoxydimethylsilane, diethoxydimethylsilane or dimethoxydiphenylsilane, preferably dimethoxydiphenylsilane.

When the catalyst is used for polymerization, the molar ratio of titanium to aluminum is 1:1 to 1:2000, preferably 1:1 to 1:500; the molar ratio of titanium to silicon is 1:1 to 1:50, preferably 1:1～1:20.

Various methods in the prior art can be used for the catalyst to catalyze the polymerization of propylene without any particular limitation. Here, taking the bulk polymerization of propylene as an example, the basic process of using the catalyst is briefly explained: In a reactor that has been vacuum-dried and fully replaced with nitrogen and propylene, add the supported catalyst, aluminum alkyl and alkoxy Silane, the polymerization temperature is 0-80°C, preferably 20-70°C, and the remaining propylene is vented after 1 hour of polymerization reaction to obtain a dry polymer.

Compared with the prior art, the present invention has an amide structure and an ether structure in the molecular skeleton of the internal electron donor compound, and the amide bond and ether bond in the structure are easily complexed with Mg ²⁺ on the surface of the MgCl ₂ carrier to form a stable The complex is beneficial to the adsorption of electrons on the surface of MgCl ₂ carrier, reducing the formation of random active centers, the catalyst has high catalytic activity and stereoregularity, and the internal electron donor is easily prepared by one-step reaction, reflecting The application advantages of this compound as an internal electron donor are presented. When the catalyst is used for olefin polymerization, especially propylene polymerization, it not only maintains the ultra-high polymerization activity of ether catalysts, but also significantly improves the molecular weight distribution of polypropylene.

the term:

The electron donor in the present invention is also called Lewis base. According to different adding methods, it can be divided into internal electron donor and external electron donor. The internal electron donor is added during the preparation of the solid catalyst, and the external electron donor is added during the olefin polymerization process. In the description of the composition and preparation method of the catalyst of the present invention, the meaning of the electron donor and the internal electron body is the same, while in the description of the alkyl aluminum compound and the alkoxysilane compound in the catalytic propylene polymerization, the electron donor has the same meaning as the inner electron body. The outer electron body has the same meaning.

detailed description

Embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only for illustrating the present invention, and should not be regarded as limiting the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products.

Part of the preparation method of the internal electron donor

(1) 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

Add 6.8g (0.1mol) of furan and 9.7g (0.1mol) of maleimide into a 100ml round bottom flask, 50mL of solvent toluene, install a reflux condenser, and heat to reflux for 6 hours under magnetic stirring. Pure crystallization after completion of the reaction, the product obtained is a white solid with a yield of 72%. ¹ H NMR (400MHz, CDCl ₃ ) δ: 3.07(2H), 4.64(2H), 5.78(2H), 4.33(1H), MS(EI) m/z: 165(M+).

(2) N-ethyl-1-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

In a 100ml round bottom flask, add 8.2g (0.1mol) 1-methylfuran and 12.5g (0.1mol) N-ethylmaleimide, 50mL solvent toluene, install a reflux condenser, and heat under magnetic stirring The reaction was refluxed for 6 hours. Pure crystallization after completion of the reaction, the product obtained is a white solid with a yield of 61%. ¹ H NMR (400MHz, CDCl ₃ ) δ: 1.20(3H), 1.41(3H), 3.06(1H), 3.07(1H), 3.52(2H), 4.64(1H), 5.78(2H), MS(EI) m/z: 207 (M+).

(3) N-methyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide

In a 100ml round bottom flask, add 10.25g (0.1mol) 1-chlorofuran and 11.3g (0.1mol) N-methylmaleimide, 50mL solvent toluene, install a reflux condenser, and heat to reflux under magnetic stirring React for 6 hours. Pure crystallization after completion of the reaction, the product obtained is a white solid with a yield of 67%. ¹ H NMR (400MHz, CDCl ₃ ) δ: 3.16(3H), 3.07(1H), 3.38(1H), 4.64(1H), 5.78(2H), MS(EI) m/z: 213(M+).

(4) The synthesis method of 2-phenylfuran-3,4-(N,N,N',N'-tetraethyl)diamide comes from CN101671408 (CN200810222179.X, composed of propylene polymerization solid catalyst).

(5) The synthesis method of N, N, N', N'-tetramethyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-diamide comes from CN101628951 (CN200910090467.9, Solid catalytic components and catalysts for olefin polymerization).

Two catalyst preparation

Example 1

Under anhydrous and oxygen-free conditions, 5.0 grams of microspherical magnesium chloride alcoholate particles, the average particle size is 50 μm, the specific surface is 150-300m ² /g, the molar ratio of alcohol to magnesium chloride content is 2.76:1, molecular formula: MgCl ₂ 2.76CH ₃ CH ₂ OH, added to 30 ml of titanium tetrachloride liquid at -20°C, reacted for 1 hour, then gradually heated to 60°C; added 0.75g 7-oxabicyclo[2.2.1]heptane- 5-ene-2,3-dicarboximide was gradually heated to 120°C, reacted for 2 hours, and filtered; then added 30 ml of titanium tetrachloride, reacted at 120°C for 1 hour, and filtered. Wash with 20 ml of hexane at 60° C. for 5 times, wash once with 10 ml of hexane at room temperature, and dry in vacuum to obtain a magnesium chloride-supported catalyst.

The content of each component in the catalyst is shown in Table 1.

Comparative example 1

The preparation method of the catalyst is the same as in Example 1, except that 2-phenylfuran-3,4-(N, N, N', N'-tetraethyl) diamide is used to replace 7-oxabicyclo in the catalyst preparation process [2.2.1] Hept-5-ene-2,3-dicarboximide.

The content of each component in the catalyst is shown in Table 1.

Comparative example 2

The preparation method of the catalyst is the same as in Example 1, except that N, N, N', N'-tetramethyl-7-oxabicyclo[2.2.1]hept-5-ene-2 ,3-diamide instead of 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide.

The content of each component in the catalyst is shown in Table 1.

Embodiment 2-9

Preparation of supported catalyst: In addition to the internal electron donor compound, N-ethyl-1-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide was used , N-methyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, 1-pentyl-7-oxabicyclo[2.2 .1]hept-5-ene-2,3-dicarboximide, 1-phenyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide , N-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-butyl-1-ethyl-7-oxabicyclo[ 2.2.1] Hept-5-ene-2,3-dicarboximide, N-butyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3- Dicarboximide, N-methyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, and the rest are the same as in Example 1. The content of each component in the catalyst is shown in Table 1.

The content of each component in the catalyst of table 1

Three Catalyst Catalyzed Polymerization

Bulk polymerization: in 10 liters of reactors that have been vacuum-dried and fully replaced with nitrogen and propylene, first add 0.5 kg of propylene, add 50 mg of the supported catalysts of Comparative Examples 1, 2 and Examples 1-9, and add 5 milliliters of three Ethyl aluminum, add dimethoxydiphenylsilane, the molar ratio of titanium to silicon is 1:6. Then continue to add 1.5kg of propylene. The temperature of the reactor was raised to 70° C., the polymerization was carried out for 1 hour, and the unreacted propylene was vented to obtain a polymer.

Measure and calculate the M _η and the molecular weight distribution of catalyst activity and product polymer according to routine method, the results are shown in Table 2.

The polymerization result of table 2 embodiment 1～9 and comparative example 1～2

As can be seen from Table 2, the activity of the catalysts of Examples 1-9 is significantly higher than that of Comparative Examples 1-2. The molecular weight distribution of polypropylene prepared with the catalysts of Examples 1-9 is obviously larger than that of Comparative Example 1-2.

Although specific embodiments of the present invention have been described in detail, those skilled in the art will understand. Based on all the teachings that have been disclosed, various modifications and substitutions can be made to those details, and these changes are all within the scope of the invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

Claims (10)

1. A wide molecular weight polypropylene catalyst, by weight percent, comprising 10-25% magnesium, 1-15% titanium, 40-60% halogen and 1%-20% internal electron donor, its characteristics In that, the internal electron donor is selected from a 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide compound whose molecular skeleton is a general formula (I) : Among them, the substituents R ₁ and R ₆ are the same or different, and are selected from H, C ₁ to C ₁₀ linear or branched chain alkyl groups; R ₂ , R ₃ , R ₄ , and R ₅ are the same or different, and are selected from H, Halogen, straight chain or branched alkyl of C ₁ to C ₁₀ , cycloalkyl or aryl of C ₃ to C ₁₀ ; R ₇ is selected from H, straight or branched alkyl of C ₁ to C ₁₀ , C ₃ -C ₁₀ cycloalkyl or aryl. 2. wide molecular weight polypropylene catalyst as claimed in claim 1, is characterized in that, described interior electron donor is selected from following any compound: 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-ethyl-1-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-methyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, 1-pentyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, 1-phenyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-butyl-1-ethyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-butyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-methyl-1-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide. 3. The broad molecular weight polypropylene catalyst according to claim 1, wherein the magnesium has a particle size distribution of 50 to 250 μm and a general structural formula of Mg(OR')mX _(2-m) n(R ₂ OH) magnesium halide alcoholates; in the general formula, R' is an alkyl, aralkyl or aryl group of C ₁ to C ₂₀ ; X is a halogen; m is an integer of 0≦m<2; n is 0< Decimals or integers of n<₅; R2 is an alkyl group, aralkyl group or aryl group of C1～C20; the magnesium halide in the magnesium halide alcoholate is selected from magnesium chloride, magnesium bromide, and chloromethoxymagnesium Or one of chloroethoxymagnesium; the alcohol is selected from one of methanol, ethanol, propanol, isopropanol, butanol or isobutanol. 4. The wide molecular weight polypropylene catalyst according to claim 3, wherein the magnesium halide in the magnesium halide alcoholate is magnesium chloride, and the alcohol is ethanol. 5. The wide molecular weight polypropylene catalyst according to claim 1, wherein the titanium is provided by a titanium halide having the general formula Ti(OR) _p X _(4-p) , wherein R is C ₁ -C ₂₀ alkyl, aryl or aralkyl; X is halogen; p is an integer of 0≦p<4; the titanium provider is selected from tetraethoxytitanium, tetrabutoxytitanium, chlorotrialkoxy One of base titanium, dichlorodialkoxytitanium, trichloroalkoxytitanium, titanium tetrachloride or titanium tetrabromide. 6. The broad molecular weight polypropylene catalyst of claim 5, wherein the titanium donor is titanium tetrachloride. 7. a preparation method as described in any one of claim 1-6 wide molecular weight polypropylene catalyst, is characterized in that, comprises the following steps: (1) Add the spherical magnesium halide alcoholate particles into the titanium halide liquid at -50-20°C, and react for 10 minutes to 5 hours. The molar ratio of magnesium to titanium is 1:5-1:100; (2) Heat up to 0-80°C, add internal electron donor compound, the molar ratio of magnesium to internal electron donor compound is 2:1-20:1; (3) heating up to 100～150℃ again, and reacting for 1～6 hours; (4) Add titanium halide liquid after filtration, react at 110-130° C. for 1-4 hours, then filter, wash and dry to obtain the catalyst. 8. wide molecular weight polypropylene catalyst preparation method as claimed in claim 7, is characterized in that, comprises the following steps: (1) Add spherical magnesium halide alcoholate particles into the titanium halide liquid at -30-0°C, react for 1-4 hours, and the molar ratio of magnesium to titanium is 1:10-1:50; (2) Heat up to 30-60°C, add internal electron donor compound, the molar ratio of magnesium to internal electron donor compound is 2:1-12:1; (3) heating up to 110～130°C again, and reacting for 1～4 hours; (4) Add titanium halide liquid after filtration, react at 110-130° C. for 1-2 hours, then filter, wash and dry to obtain the catalyst. 9. A method for preparing polypropylene with a broad molecular weight polypropylene catalyst as claimed in any one of claims 1-6, characterized in that, comprising the following steps: In a reactor that has been vacuum-dried and fully replaced with nitrogen and propylene gas, add a supported catalyst, an alkylaluminum compound and an alkoxysilane compound, carry out a polymerization reaction at a certain temperature, and then vent the remaining propylene to obtain a dry polymerization thing; The alkylaluminum compound is selected from one of trimethylaluminum, triethylaluminum, triisobutylaluminum, monochlorodiethylaluminum or monochlorodiisobutylaluminum; The alkoxysilane compound is selected from dimethoxydimethylsilane, diethoxydimethylsilane or dimethoxydiphenylsilane; The molar ratio of titanium to aluminum is 1:1 to 1:2000; the molar ratio of titanium to silicon is 1:1 to 1:50. 10. the method for preparing polypropylene by wide molecular weight polypropylene catalyst as claimed in claim 9, is characterized in that, described alkylaluminum compound is triethylaluminum or triisobutylaluminum; Described alkoxysilane compound It is dimethoxydiphenylsilane; the molar ratio of titanium to aluminum is 1:1~1:500; the molar ratio of titanium to silicon is 1:1~1:20.