RU2502560C1 - Method of obtaining vanadium-magnesium catalyst of ethylene polymerisation and copolymerisation of ethylene with alpha-olefins - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to field of catalyst. Described is method of obtaining catalyst for ethylene polymerization and copolimerisation of ethylene with alpha-olefins, containing vanadium compound on magnesium-containing carrier, which is obtained by interaction of solution of magnesium-organic compound with composition Mg(C₆H₅)₂nMgCl₂mR₂O, where; n=0.37-0.7, m=2, R₂O is ether with R=i-Am, n-Bu with chlorinating agent phenyltrichloromethane PhCCl₃ with mole ratio PhCCl₃/MgR₂≥1.0, with further processing of carrier with alkylaluminium chloride and application of vanadium compound, with alkylaromatic ether being preliminarily introduced into magnesium organic compound at temperature 20-40°C with molar ratio alkylaromatic ether/Mg=0.05-0.2.

EFFECT: obtained catalyst makes it possible to obtain polymers with wide molecular-weight distribution, increased bulk density and high output.

1 tbl, 5 ex

Description

The invention relates to a method for producing catalysts for the polymerization of ethylene and copolymerization of ethylene with α-olefins, and more particularly, to supported Ziegler-type catalysts containing a transition metal compound on a magnesium-containing support.

Various methods are known for preparing supported Ziegler-type catalysts. However, only some of these methods allow you to control the morphology of the particles of the carrier and, accordingly, of the catalyst (particle size, shape and density, particle size distribution). In the case of suspension and gas phase polymerization, the morphology of the catalyst particles determines the morphology of the polymer particles formed on them. Obtaining a polymer powder with a certain average particle size, with a narrow particle size distribution, with an increased bulk density is an important condition for the technology of the polymerization process, and for this it is necessary to obtain catalysts having a narrow particle size distribution and improved morphology. Moreover, for various polymerization technologies and various applications of polymers, catalysts with different average particle sizes are required. Catalysts with a particle size of 5-20 microns are used in the case of suspension polymerization of ethylene. Catalysts with a particle size of 25-50 microns are used for gas phase polymerization.

A catalyst with a narrow particle size distribution containing magnesium chloride as a carrier can be prepared by reacting a solution of the compound MgCl ₂ · 3i-C ₈ H ₁₇ OH in a carbohydrate diluent with TiCl ₄ in the presence of an electron-donor compound (ethyl benzoate, ethylanisate and others) [JP 59-53511, B01J 31/32, 1986]. The catalyst obtained in this way is characterized by a particle size of 5-15 μm, has a sufficiently high activity (up to 35 kg / g PE g Ti h atm C ₂ H ₄ ) and allows the production of polyethylene powder with narrow granulometry and high bulk density. The disadvantage of this method of producing a catalyst is the use of low temperatures (up to -20 ° C), the use of large quantities of liquid TiCl ₄ as a reaction medium, and the release of a significant amount of hydrogen chloride during the synthesis of the catalyst.

A known method of producing a supported catalyst for the polymerization of ethylene and copolymerization of ethylene with alpha-olefins, containing a transition metal compound (TiCl ₄ , VOCl ₃ , VCl ₄ ) on a carrier composition MgCl ₂ · mR ₂ O, by applying a transition metal compound to a carrier [RU 2064836 , B01J 31/38, 08/10/96]. In this case, the carrier is prepared by reacting an organomagnesium compound (MOS) with the composition Mg (C ₆ H ₅ ) ₂ · nMgCl ₂ · mR ₂ O (n = 0.37-0.7, m = 2, R ₂ O is an ether with R = i-Am, n-Bu) with carbon tetrachloride. The catalyst prepared by this method allows one to obtain polymers with a narrow, controlled particle size distribution and increased bulk density while maintaining high activity in the processes of suspension and gas-phase polymerization of ethylene and copolymerization of ethylene with α-olefins.

The main disadvantage of this method is the use of carbon tetrachloride as a chlorinating agent: the reaction of carbon tetrachloride with an organomagnesium compound proceeds very intensively, with high heat generation and is difficult to control, especially when preparing catalysts in large quantities.

The closest solution to the problem posed in this application is a method for producing a catalyst, according to which a supported catalyst containing titanium tetrachloride or vanadium tetrachloride (oxytrichloride) on a magnesium-containing support is prepared by reacting a solution of an organomagnesium compound (MOS) of the composition MgPh ₂ · nMgCl ₂ · mR ₂ O, where : Ph = phenyl, R ₂ O = ether with R = butyl or i-amyl, n = 0.37-0.7, m = 1-2. with phenyltrichloromethane (PhCCl ₃ / Mg≥1 (mol.)), followed by treatment of the obtained magnesium-containing support with a transition metal compound. This method allows the synthesis of highly active vanadium-magnesium catalysts with an adjustable particle size in the region of 40 to 7.5 μm with a narrow particle size distribution (SPAN <0.9), which allows to obtain polyethylene with a wide molecular weight distribution (MMP) [WO 2005/097322, B01J 31 / 36, 2005.10.20].

The main disadvantages of the catalyst prepared by the above method in a suspension process in the production of polyethylene are:

(1) The use of low temperatures (less than 10 ° C) to obtain catalysts for suspension polymerization of ethylene with a particle size of less than 10 microns. which makes it difficult to control the temperature, especially when preparing the catalyst in large quantities.

(2) Catalysts with a large average particle size, obtained at high chlorination temperatures (more than 20 ° C), especially vanadium magnesium. have a low activity at polymerization temperatures of ethylene less than 90 ° C.

(3) Polymers prepared using catalysts prepared according to the method described above have a bulk density of less than 350 g / l.

The basis of the claimed invention is the task of developing a method for producing vanadium-magnesium catalysts for suspension polymerization of ethylene and copolymerization of ethylene with α-olefins, which allows to obtain a magnesium chloride-containing carrier with a controlled particle size in the region of 5-20 μm by chlorination of MOC (phenyl magnesium chloride) with phenyl trichloromethane (PhCCl ₃ ) at a temperature ≥ 20 ° C. In this case, the catalyst prepared using this support should provide polymers with a wide molecular weight distribution (IR ^21.6 / IR ⁵ ≥18), with an increased bulk density (more than 350 g / l) and a high yield (≥250 kg / g V) with a narrow distribution of particle size in the processes of suspension polymerization of ethylene and copolymerization of ethylene with α-olefins at polymerization temperatures of 70-90 ° C.

This problem is solved in that in the process of obtaining a magnesium-containing support for these catalysts, a modifying additive alkaromatic ether (D) is used in an amount of 0.05-0.2 mol / mol Mg, which is added to the MOC composition Mg (C ₆ H ₅ ) ₂ nMgCl ₂ mR ₂ O (C ₆ H ₅ -phenyl, n = 0.37-0.7, m = 2. R ₂ O - ether). The modified organomagnesium compound is chlorinated with phenyltrichloromethane at a temperature of ≥20 ° С PhCCl ₃ / MgR ₂ ≥1.0 followed by treatment of the support with alkylaluminum chloride and deposition of a vanadium compound.

Thus, the main distinguishing feature of the proposed method is the use of alkylaromatic ether at a molar ratio of D / Mg = 0.05-0.2 to modify the MOC composition of Mg (C ₆ H ₅ ) ₂ nMgCl ₂ mR ₂ O in the synthesis of a magnesium-containing support by chlorination with phenyltrichloromethane C ₆ H ₅ CCl ₃ at temperatures of 20-60 ° C.

The carrier obtained by this method has an average particle size in the region of 5 to 20 μm and a narrow particle size distribution. The required particle size of the carrier and, accordingly, the catalyst in this area is determined by the ratio of alkyl aromatic ether / MOS and the conditions for the process of interaction of MOS with C ₆ H ₅ CCl ₃ . Before applying the transition metal compound, the magnesium-containing support is treated with a chlorine-containing organoaluminum compound (for example, DEAC) to remove by-product electron-donating organic carrier synthesis products from the surface of the support. The catalyst is prepared by subsequent treatment of the support with a solution of vanadium chloride (VCl ₄ , VOCl ₃ ) in a hydrocarbon solvent.

The proposed method provides for the production of highly active vanadium-magnesium catalysts for suspension polymerization of ethylene with an average particle size of 5-20 μm when using the technological temperature range (≥20 ° C) for chlorination of MOC with phenyltrichloromethane.

During the polymerization of ethylene, polyethylene with a high bulk density (more than 0.35 g / cm) and a narrow particle size distribution is formed on this catalyst. The activity of the obtained catalysts reaches 250 kg PE / g V. The polyethylene obtained on the vanadium-magnesium catalyst synthesized by the proposed method has a wide molecular weight distribution.

The catalysts are used for the polymerization of ethylene or the copolymerization of ethylene with α-olefins in combination with a cocatalyst - aluminum trialkyl (mainly triisobutylaluminum or triethylaluminum). The polymerization is carried out in suspension mode at temperatures of 50-100 ° C in a hydrocarbon solvent (for example, hexane, heptane) pressures of 2-40 atm. As a regulator of the molecular weight of the polymer using hydrogen in an amount of 5-50 vol.%. In the copolymerization of ethylene with α-olefins, propylene, butene-1, hexene-1, 4-methyl-pentene-1 and other higher α-olefins are used.

The invention is illustrated by the following examples.

Example 1

(BUT). Preparation of a solution of an organomagnesium compound (MOS).

29.2 g of powdered magnesium (1.2 mol) in 450 ml of chlorobenzene (4.4 mol), 203 ml of dibutyl ether (1.2 mol) and an activating agent, which is a solution of 0.05 g of iodine, are loaded into a 1 L glass reactor equipped with a stirrer and a thermostatic device. 3 ml of butyl chloride. The reaction is carried out in an inert gas atmosphere (nitrogen, argon) at a temperature of from 80 to 100 ° C for 10 hours. At the end of the reaction, the resulting reaction mixture is settled and the liquid phase is separated from the precipitate. The liquid phase is a solution in chlorobenzene of an organomagnesium compound with the composition MgPh ₂ · 0.49MgCl ₂ · 2 (C ₄ H ₉ ) ₂ O with a concentration of 1.0 mol Mg / L.

(B) The synthesis of the media.

200 ml of the obtained MOC solution (0.2 mol Mg) was loaded into the reactor with a stirrer and at a temperature of 25 ° С for 15 min. dose 0.01 mol of ethyl benzoate (EB) (1.1 ml of EB and 3 ml of heptane), EB / Mg = 0.05 (mol.). The mixture is kept for 15 minutes, then a solution of 26 ml (0.32 mol) of phenyltrichloromethane (PhCCl ₃ ) in 30 ml of heptane is metered into the reactor for 35 minutes (PhCCl _{3 /} Mg = 1.0 (mol)). Then the reaction mixture is heated to 60 ° C for 30 minutes and kept at this temperature for 1 hour. The mother liquor is removed and the precipitate formed is washed with heptane 4 times in 250 ml each at a temperature of 20 ° C. Obtain 33 g of powdered magnesium-containing media in the form of a suspension in heptane.

After that, 204 ml of a solution of diethylaluminium chloride with a concentration of 1.6 mol / L at a molar ratio of AlEt ₂ Cl / Mg = 1.2 is added to the suspension of the carrier in the course of 20 minutes. at room temperature and then the reaction mixture was kept for 1 h at 45 ° C. After this, the carrier is washed 5 times with 200 ml of heptane.

(B) A catalyst is obtained by treating a suspension of a carrier in heptane with a solution of vanadium tetrachloride in carbon tetrachloride (24 ml with a vanadium concentration of 0.035 g / ml) at a temperature of 50 ° C for 1 h and then washing it with 1 time 200 ml of heptane. The catalyst contains 2.5 wt.% Vanadium and has an average particle size of 18 microns.

Ethylene is polymerized in a 0.8 L steel reactor equipped with a stirrer and a thermostatic jacket. Heptane (250 ml) and Al (i-Bu) ₃ cocatalyst with a concentration of 4.8 mmol / L are used as a solvent for polymerization. The polymerization is carried out at a temperature of 80 ° C, an ethylene pressure of 7.4 bar, a hydrogen pressure of 0.5 bar, for 2 hours

For the experiment, 0.0083 g of catalyst is used, 54 g of polymer are obtained with a yield of 6.5 kg / g of catalyst or 250 kg / g V. The bulk density of PE powder is 360 g / l, and the average particle size of PE according to sieve analysis is 336 μm. PE powder has a narrow particle size distribution, which is characterized by the value of SPAN = (d ₉₀ -d ₁₀ ) / d ₅₀ , where d ₉₀ , d ₁₀ and d ₅₀ are the sizes of PE particles corresponding to the integral content of particles in the amount of 90, 50 and 10 wt.%, respectively. The SPAN value for this example is 0.7. The PE obtained on this catalyst has a wide molecular weight distribution (the ratio of melt indices at a load of 21.6 and 5 kg (MIR (21.6 / 5)) = 19.2).

The polymerization results are shown in the table.

Example 2

The catalyst was prepared under the conditions of Example 1, except that in the synthesis of the magnesium-containing support, the ratio EB / Mg = 0.2 (mol.) Was used. The catalyst contains 3.1 wt.% Vanadium and has an average particle size of 7 μm. The polymerization of ethylene is carried out under the conditions of example 1.

The polymerization results are shown in the table.

Example 3

The catalyst was prepared under the conditions of Example 1, except that dibutyl phthalate (DBP) was used in the synthesis of the magnesium-containing support at a ratio of DBP / Mg = 0.1 (mol.) Instead of ethyl benzoate. Chlorination of MOC with phenyltrichloromethane is carried out at a temperature of 20 ° C. The catalyst contains 2.6 wt.% Vanadium and has a particle size of 6 μm. The polymerization of ethylene is carried out under the conditions of example 1.

The polymerization results are shown in the table.

Example 4

The catalyst obtained in example 3 is used in the copolymerization of ethylene with hexene-1. The copolymerization is carried out under the conditions of Example 1, except that in the beginning, hexene-1 with a concentration of hexene-1 of 0.16 mol / L is used as a comonomer, then after every 20 g of polymer is produced, hexene-1 is calculated at the rate of 0.064 mol / L. A copolymer containing 2.1 mol% of butyl branches is obtained.

The polymerization results are shown in the table.

Example 5 (comparative).

The catalyst was prepared under the conditions of Example 1, except that in accordance with the prototype [WO 2005/097322], alkyl aromatic ether was not used for the reaction of PhCCl ₃ with an organomagnesium compound to obtain a carrier. MOC chlorinates PhCCl ₃ at a temperature of 35 ° C. The catalyst contains 3.2 wt.% Vanadium and has an average particle size of 30 μm. The polymerization of ethylene is carried out under the conditions of example 1, except that the ethylene pressure is 9 bar. The polymerization results are shown in the table.

It can be seen from the presented examples and the table that the use of phenyl trichloromethane for the synthesis of a carrier in combination with an alkyl aromatic ether for chlorination of an organomagnesium compound allows one to obtain highly active vanadium-magnesium catalysts for suspension polymerization of ethylene with an average particle size of 5-20 μm when using the technological temperature range for chlorination of MOS (≥20 ° C). During the polymerization of ethylene, polyethylene with a high bulk density (more than 0.35 g / cm ³ ) and a narrow particle size distribution is formed on this catalyst. The activity of the obtained catalysts exceeds 250 kg PE / g V. PE has a wide MMP (MFR (21.6 / 5) = 18-21).

Using for preparation of a magnesium-containing carrier only phenyltrichloromethane in accordance with the prototype (WO 2005/097322) (comparative example 5) does not allow to achieve the task.

Table Polymerization conditions: heptane, [TIBA] = 4.8 mmol / l, hydrogen pressure 0.5 bar, 80 ° C, 2 h Example No. Alkyl aromatic ether (AAE) (AAE) /
Mg (mol.) T ₁ ¹⁾ , ° C The content of V, wt.% d cf. ²⁾ Microns RS ₂ H ₄ , Exit IR (5) ³⁾ , g / 10 min MFR ⁴⁾ (21.6 / 5) NP ⁵⁾ g / l Span kg PE / g cat

$$\frac{\mathrm{TO}gPE}{gV}$$

one ethyl benzoate 0.05 25 2.5 eighteen 7.4 6.5 250 1.0 19.2 360 0.7 2 ethyl benzoate 0.2 25 3.1 7.0 7.4 7.8 252 1.4 18.0 345 0.9 3 dibutyl phthalate 0.1 twenty 2.6 6.0 7.4 8.5 327 0.3 19.6 392 0.6 4 ⁶⁾ dibutyl phthalate 0.1 twenty 2.6 6.0 7.4 9.0 345 1.0 18.0 438 0.5 5 ⁷⁾ - - 35 3.2 thirty 9.0 4.6 144 0.05 - 280 - ¹⁾ the chlorination temperature of the organomagnesium compound PhCCl ₃ ^{2) the} average particle size of the catalyst ³⁾ PE melt index at a load of 5 kg (190 ° C) ^{4) the} ratio of the melt indices at loads of 21.6 and 5 kg ⁵⁾ bulk density of polymer powder ⁶⁾ copolymerization of ethylene with hexene-1 (concentration of hexene-1 = 0.16 M), containing 2.1 mol.% Butyl branches ⁷⁾ comparative example

Claims (1)

A method of producing a catalyst for the polymerization of ethylene and copolymerization of ethylene with alpha-olefins containing a vanadium compound on a magnesium-containing support, which is obtained by reacting a solution of an organomagnesium compound of the composition Mg (C ₆ H ₅ ) ₂ nMgCl ₂ mR ₂ O, where: n = 0.37- 0,7, m = 2, R ₂ O - ether with R = i-Am, n-Bu with a chlorinating agent phenyltrichloromethane PhCCl ₃ with a molar ratio PhCCl ₃ / MgR ₂ ≥1,0, followed by treatment of the support with alkylaluminum chloride and deposition vanadium compounds, characterized in that the organomagnesium compound is preceded the alkyl aromatic ether is carefully introduced at a temperature of 20-40 ° C with a molar ratio of alkyl aromatic ether / Mg = 0.05-0.2.