CN1169851C - Titanium-nickel-salicylaldimine composite catalyst for ethylene polymerization and its preparation method - Google Patents

Abstract

The present invention relates to an ethylene polymerizing titanium-nickel-salicylaldehyde-imine composite catalyst and a preparation method thereof. A titanium compound-nickel compound-the salicylaldehyde-imine is loaded onto a MgCl2-SiO2 composite carrier to form a main catalyst, AlR3-Et2AlCl is used as a cocatalyst, an impregnating reaction method is adopted in the preparation method, and branched polyethylene with the advantages of good particle shape, high bulk density and different density can be prepared without using MAO to catalyze and polymerize single ethylene by an obtained spherical composite catalytic system; the present invention has the advantages of simple preparation method and easy use in production.

Description

Titanium-nickel-salicylaldimine composite catalyst for ethylene polymerization and preparation method thereof

Technical field

The invention relates to a titanium-nickel-salicylaldimine composite catalyst for preparing branched polyethylene with various densities with good particle shape and high bulk specific gravity from single ethylene and a preparation method thereof.

Background technique

For a long time, chemists have tried to research and develop a new type of branched polyethylene catalyst that can be used for the polymerization of single ethylene to prepare various densities with good particle shape and high bulk specific gravity. Recently, it has been reported in the literature that a variety of branched polyethylenes can be prepared from a single ethylene by using diimine complexes of late transition metals Ni, Pd, etc. and methylaluminoxane (MAO) or boron compounds as catalysts, which has attracted widespread attention (K. Johnson, C.M. Killian and M. Brookhart, J Am Chem Soc, 1995, 117:6414). The preparation of this kind of catalyst is relatively complicated, and expensive MAO or boron compound needs to be used as a cocatalyst. The resulting product has irregular shape and low bulk specific gravity, which is not conducive to popularization and use in production.

Contents of Invention

The invention provides a titanium-nickel-salicylaldimine composite catalyst for preparing branched polyethylene with good particle shape and high bulk specific gravity by polymerization of a single ethylene; it has a spherical particle shape and only needs cheap alkyl aluminum and _Et2AlCl as catalysts. The co-catalyst can catalyze the polymerization of single ethylene to produce branched polyethylene with various densities without using expensive MAO or boron compounds; the obtained polymer particles have good particle shape and high bulk specific gravity. The preparation method of the catalyst is simple and convenient, and is easy to be applied in production; thereby solving the problems existing in the prior art.

Catalyst of the present invention, its component comprises main catalyst and cocatalyst; With titanium compound, nickel compound and salicylaldimine loaded on MgCl2, _SiO2 composite carrier, constitute main catalyst, with alkylaluminum- _Et2AlCl as cocatalyst; The titanium compound is TiCl ₄ or TiCl ₄ and Ti(OR ₁ ) ₄ , the aluminum alkyl is AlR ₃ , where R ₁ is propyl or butyl, and R is C ₂ ~C ₈ alkyl; the nickel compound is NiX ₂ , where X is Cl or Br; salicylaldimine (S) is any compound shown in the following structural formula I (S ₁ to S ₃ ).

Salicylaldimine

where S ₁ : R ¹ =R ² =H;

S ₂ : R ¹ =CH ₃ ; R ² =H

S ₃ : R ¹ =H; R ² =CH ₃

The ratio of the above-mentioned components of the catalyst of the present invention is usually: MgCl ₂ : _{SiO 2} : TiCl ₄ = 1: (2-15): (0.5-3.0) calculated by weight ratio, and the rest of the components are calculated by the number of moles of TiCl ₄ , and its molar ratio is:

TiCl ₄ 1

Ti(OR ₁ ) ₄ 0～1.0

NiX ₂ 0.1～5

S 0.1～3

AlR ₃ 20～200

Et ₂ AlCl 15～150

Above-mentioned catalyst of the present invention can adopt impregnation-reaction method preparation, and concrete steps are as follows:

(1) Dissolve NiX ₂ in 95% ethanol, where the amount of ethanol is 1g NiX ₂ plus 15-20ml, add SiO ₂ , stir and react at 35-36°C for 1-2 hours, drain at 60-85°C, and Calcining micro-spherical SiO ₂ at 600°C for 4-6 hours under N2;

(2) Dissolve anhydrous MgCl ₂ in the mixture of alcohol and ether at 60-75°C, or add Ti(OR ₁ ) ₄ and stir for 2-3 hours to obtain a homogeneous mother liquor; the alcohol is ethanol, and the ether is THF (tetrahydrofuran), the amount used in molar ratio is MgCl ₂ : alcohol = 1: (1-5), MgCl _{2 :} THF = 1: (24-40);

(3) Under the protection of N ₂ , add the mother liquor obtained in (2) into pretreated SiO ₂ , then add the THF solution of S ligand (the weight concentration is 8-20%), and stir the reaction at 60-70°C for 2 Hours, heat and drain the liquid;

(4) Add alkanes and TiCl ₄ to the product obtained in (3), raise the temperature to 60-75°C and stir the reaction for 1-2 hours, filter, and wash with alkanes 2-3 times to obtain a solid catalyst; alkane, octane or decane, the dosage is 5-12ml per gram of SiO ₂ ;

(5) Add hexane and Et ₂ AlCl to the solid catalyst, heat up to 40-70°C to react for 0.5-1.5 hours under stirring, and filter; vacuum-dry the solvent at 60-80°C to obtain the main catalyst; The dosage is 5-12ml per gram of solid catalyst, and the molar ratio of Et ₂ AlCl to TiCl ₄ is TiCl ₄ : Et ₂ AlCl=1: (0.1-5); the main catalyst and the AlR ₃ -Et ₂ AlCl co-catalyst form ethylene The composite catalyst for polymerization has a molar ratio of TiCl ₄ :AlR ₃ :Et ₂ AlCl=1:(20-200):(10-150).

The present invention adopts titanium compound, nickel compound and salicylaldimine components, and the above-mentioned specific impregnation reaction preparation method to prepare the supported main catalyst, only needs general AlR ₃ -Et ₂ AlCl as catalyst, without MAO or boron compound; can catalyze Single ethylene polymerization can produce branched polyethylene of various densities with good particle shape and high bulk specific gravity. The preparation method of the catalyst of the invention is simple and convenient, has the above-mentioned excellent comprehensive performance, is easy to be applied in production, and has obvious advantages.

The catalyst of the present invention has a pressure of 106.7kPa, 30-70°C, ethylene slurry polymerization reaction for 1.5 hours, a catalytic efficiency of 2.0-4.8kg PE/g(Ti+Ni), and a density of 0.938-0.910g PE/cm ^3. Branched polyethylene with a branching degree of 2.0-18 (branching number/1000C). The heap specific gravity of the polymerization product is 0.35-0.40, which is significantly improved compared with the heap specific gravity of the polymerization product prepared by using the ZN titanium series catalyst under the same conditions as 0.25-0.30.

Detailed ways

Below by embodiment the present invention will be further described

Example one

1. Catalyst preparation

1-1 Dissolve 1.0g NiCl ₂ in 20ml 95% ethanol, add 3.0g SiO ₂ , stir and react at 35-40°C _for 1 hour, drain the solvent at 60-80°C to obtain solid powder, Heating and dehydration, raising the temperature to 600°C for 6 hours, then cooling, and discharging the material into a reaction bottle under the protection of _N2 .

1-2 Put 0.3g of anhydrous MgCl ₂ in another reaction flask, add 12ml of THF and 0.55ml of absolute ethanol, heat to 60-75°C and stir for 2 hours until completely dissolved to obtain mother liquor.

1-3 Under the protection of _N2 , add the pretreated _SiO2 prepared in 1-1 to the mother liquor prepared in 1-2, and then add 8ml THF solution containing 1.0g _S1 under stirring, at 65～70℃ The reaction was stirred for 2 hours, and the solvent was sucked dry at 65-80°C.

1-4 Add 20ml of hexane to the product of 1-3, add 0.25ml of TiCl ₄ under stirring, stir and react at 65-70°C for 2 hours, filter, add 15ml of hexane to wash and then drain, repeat this washing operation once.

1-5 Add 20ml of hexane, 0.7ml of Et ₂ AlCl, stir and react at 60-65°C for 0.5 hours, heat to 60-80°C and drain the liquid to obtain solid main catalyst, main catalyst and AlR ₃ -Et ₂ AlCl co-catalyst The composite catalyst system composed is used in the following polymerization method to prepare branched polyethylene with high bulk density and various densities from a single ethylene.

2. Preparation of high bulk density branched polyethylene by ethylene polymerization

Add 200ml of hexane or heptane and _Et2AlCl with a molar ratio of Al/Ti of 3:1 to the reaction flask that has been vacuum-dried at 120°C and replaced with _N2 for 3 times, then add a catalyst containing 0.5-1.5mg of titanium, and pump out After N ₂ , ethylene was maintained at 106.7kPa. After stirring and polymerizing at 30-40°C for 0.5 hours, Al(i-Bu) ₃ with an Al/Ti molar ratio of 80:1 was added, and the polymerization was continued at 50°C for 1 hour, and then stopped. Reaction, the reaction product was weighed to calculate the catalytic efficiency.

Under the above polymerization conditions, a branched polyethylene with a branching degree of 4.0, a density of 0.930, and a bulk specific gravity of 0.36 was obtained, and the catalytic efficiency was 3.2 kgPE/g(Ti+Ni).

Embodiment two

In embodiment one 1-3 step, add the 8ml THF solution that contains 1.0g S ₁ to adopt to contain 1.5g S 12ml THF solution instead, its condition and operation make catalyzer with embodiment _one , are identical by embodiment one Polymerization under conditions.

Under the above conditions, a branched polyethylene with a branching degree of 13.1, a density of 0.915, and a bulk specific gravity of 0.38 was obtained from a single ethylene polymerization, and the catalytic efficiency was 3.3kg PE/g(Ti+Ni).

Embodiment three

In embodiment one 1-3 step, add the 8ml THF solution containing 1.0g _S and change to adopt containing 2.0g _S3 The 12ml THF solution, all the other conditions and operation are obtained catalyst with embodiment one, are identical by embodiment one Polymerization under conditions.

Under the above conditions, a branched polyethylene with a branching degree of 6.0, a density of 0.925, and a bulk specific gravity of 0.37 was obtained from a single ethylene polymerization, and the catalytic efficiency was 2.6 kg PE/g (Ti+Ni).

Embodiment four

In Example 1, in the process of dissolving 0.3g of anhydrous MgCl ₂ in steps 1-2, add 0.2ml Ti(OBu) ₄ , and the rest of the conditions and operations are the same as in Example 1 to prepare the catalyst. Under the same conditions as in Example 1 Polymerization.

Under the above conditions, from a single ethylene polymerization, a branched polyethylene with a branching degree of 5.0, a density of 0.926, and a bulk specific gravity of 0.36 was obtained, with a catalytic efficiency of 2.8kg PE/g(Ti+Ni).

Embodiment five

In embodiment one step, 1.0g _NiCl is dissolved in 20ml 95% ethanol and is changed into 1.5g _NiBr Dissolved in 25ml ethanol, all the other conditions and operations are obtained catalyst with embodiment one, press embodiment one under the same condition Polymerization.

Under the above conditions, a branched polyethylene with a degree of branching of 4.7, a density of 0.928, and a bulk specific gravity of 0.37 was obtained from a single ethylene polymerization, with a catalytic efficiency of 3.5 kg PE/g(Ti+Ni).

Claims (3)

1. an ethylene polymerization titanium-nickel-salicylaldimine composite catalyst, its component comprises procatalyst and cocatalyst; It is characterized in that titanium compound, nickel compound and salicylaldimine are loaded on MgCl ₂ , SiO ₂ composite carrier, Constitute the main catalyst; use alkylaluminum-Et ₂ AlCl as the cocatalyst; the titanium compound is TiCl ₄ or TiCl ₄ and Ti(OR ₁ ) ₄ , the alkylaluminum is AlR ₃ , where R ₁ is propyl or butyl, R It is a C ₂ ~C ₈ alkyl group; the nickel compound is NiX ₂ , wherein X is Cl or Br; salicylaldimine S is any compound of S ₁ to S ₃ shown in the following structural formula I:

Wherein S ₁ : R ¹ =R ² =H; S ₂ : R ¹ =CH ₃ ; R ² =H S ₃ : R ¹ =H; R ² =CH ₃ 2. according to the described catalyst of claim 1, it is characterized in that the proportioning in each component is calculated as: MgCl ₂ : SiO ₂ : TiCl ₄ =1: (2～15): (0.5～3.0), the rest Each component is calculated with the number of moles of _TiCl4 , and its molar ratio is: TiCl ₄ 1 Ti(OR ₁ ) ₄ 0～1.0 NiX ₂ 0.1～5 S 0.1～3 AlR ₃ 20～200 Et ₂ AlCl 15-150. 3. the preparation method of the described catalyst of claim 1 or 2 is characterized in that adopting impregnation-reaction method, concrete steps are as follows: (1) Dissolve NiX ₂ in 95% ethanol, where the amount of ethanol is 1g NiX ₂ plus 15-20ml, add SiO ₂ , stir and react at 35-36°C for 1-2 hours, drain at 60-85°C, and Calcining micro-spherical SiO ₂ at 600°C for 4-6 hours under N2; (2) Dissolve anhydrous MgCl ₂ in the mixture of alcohol and ether at 60-75°C, or add Ti(OR ₁ ) ₄ and stir for 2-3 hours to obtain a homogeneous mother liquor; the alcohol is ethanol, and the ether is Tetrahydrofuran, the amount used in molar ratio is MgCl ₂ : alcohol = 1: (1-5), MgCl ₂ : tetrahydrofuran = 1: (24-40); (3) Under the protection of N ₂ , add the mother liquor obtained in (2) into pretreated SiO ₂ , then add the tetrahydrofuran solution of S ligand, the weight concentration is 8-20%, and stir the reaction at 60-70°C for 2 hours , heating and draining the liquid; (4) Add alkanes and TiCl ₄ to the product obtained in (3), raise the temperature to 60-75°C and stir the reaction for 1-2 hours, filter, and wash with alkanes 2-3 times to obtain a solid catalyst; alkane, octane or decane, the dosage is 5-12ml per gram of SiO ₂ ; (5) Add hexane and Et ₂ AlCl to the solid catalyst, heat up to 40-70°C to react for 0.5-1.5 hours under stirring, and filter; vacuum-dry the solvent at 60-80°C to obtain the main catalyst; The dosage is 5-12ml per gram of solid catalyst, and the molar ratio of _Et2AlCl to _TiCl4 is _TiCl4 : _Et2AlCl =1:(0.1-5); the main catalyst and _AlR3 - _Et2AlCl co-catalyst form ethylene The composite catalyst for polymerization has a molar ratio of TiCl ₄ :AlR ₃ :Et ₂ AlCl=1:(20-200):(15-150).