RU2185881C1 - Method of preparing catalyst for stereospecific polymerization of propylene - Google Patents

Abstract

FIELD: polymerization catalysts. SUBSTANCE: catalyst is prepared by reducing titanium tetrachloride by diethylaluminum chloride in presence of electronodonor compounds, in particular by reaction of complex TiCl₄•nD•mD₂ with complex Al(C₂H₅)₂Cl•kD₂, where D₁ represents diisoamyl ether, D₂ dibutyl ether, n = 0.1-0.4, m ≤ 0.2, and k = 0.7-2.2. Use of catalyst results in formation of polypropylene with lower content of side atactic fraction and polypropylene powder has higher apparent density and contains less dust-like fraction. EFFECT: increased catalytic activity and stereospecificity. 8 ex

Description

 The invention relates to methods for producing a stereospecific polymerization catalyst based on titanium trichloride.

A known method of producing a catalyst based on titanium trichloride / USSR Patent 504496, cl. C 08 F 10/14, 1972 / in three stages:
reduction of TiCl _{4 with an} organoaluminum compound at low temperature;
treating the resulting brown modification of TiCl ₃ with ether,
heat treatment of the obtained product in the presence of TiCl ₄ .

This method made it possible to obtain a catalyst with high activity, high stereospecificity and good powder morphology of the obtained polymer. The disadvantages of this method are:
long duration of the synthesis process;
low thermal stability of the catalyst during storage.

 Later, numerous patents appeared describing simpler methods for preparing such catalysts in two or one stage.

A known method of producing a catalyst / US Patent 4235745, class. C 08 F 4/64, 1980 / by reduction of TiCl _{4 with an} organoaluminum compound in the presence of an aliphatic ester and a haloaromatic compound. This method allows by varying the content of halogenated compounds to adjust the particle size of the catalyst over a wide range. The disadvantage of this method is the low bulk density of the obtained polymer 0.24-0.32 g / cm ³ .

A known method for producing titanium trichloride by reduction of TiCl _{4 with an} organoaluminum compound in the presence of ether in an aliphatic hydrocarbon medium / US Patent 4,199,474, class. C 08 F 4/64, 1980 /. In this method, the regulation of the average particle size of the catalyst from 10 to 43 microns is carried out by changing the ether content in the system and redistributing the ether content in mixtures with TiCl ₄ and AlEt ₂ Cl. The catalysts obtained by this method have high activity and high stereospecificity. The disadvantage of this method is that when the average particle size is reduced, the bulk density of the obtained polymer is greatly reduced.

 The closest in technical essence to the present invention is a method for producing a catalyst by reacting complexes of titanium tetrachloride with ether and diethylaluminium chloride with diisoamyl ether in a hydrocarbon solvent / RF Patent 2053841, cl. B 01 J 37/00, 1993 /. This catalyst has a sufficiently high activity, high stereospecificity and provides a high bulk density of the resulting polymer. This catalyst is used in the industrial production of polypropylene.

 The invention solves the problem of improving the performance of a catalyst based on titanium trichloride, in particular activity and particle size distribution. Another objective of the present invention is the replacement of expensive and inaccessible diisoamyl ether to a cheaper and more affordable dibutyl ether.

Preliminary experiments conducted by us showed that with the complete replacement of diisoamyl ether with dibutyl ether in the preparation of titanium trichloride by the prototype method, a sharp deterioration in the morphology of the obtained polymer is observed. However, in the future we found that when using complexes of TiCl ₄ and diethylaluminium chloride with dibutyl and diisoamyl ethers, taken in certain proportions, namely, a complex of the composition TiCl ₄ • nD ₁ • mD ₂ and a complex of the composition AlEt ₂ Cl • kD ₂ , where D ₁ - diisoamyl ether, D ₂ - dibutyl ether, n = 0.1-0.4, m≤0.2, k = 0.7-2.2, more efficient catalysts can be obtained compared to the prototype. In particular, the catalyst, obtained when using complexes of composition TiCl ₄ • nD ₁ • mD ₂ and AlEt ₂ Cl • kD ₂ , has a higher activity, higher stereo specificity and contains less dust fraction.

Distinctive features of this catalyst preparation method are the use of complexes of TiCl ₄ • nD ₁ • mD ₂ and Al (C ₂ H ₅ ) ₂ Cl • kD ₂ composition, where D ₁ is diisoamyl ether, D ₂ is dibutyl ether, when reducing titanium tetrachloride with diethylaluminium chloride n = 0.1-0.4, m≤0.2 and k = 0.7-2.2.

The catalyst according to the invention is prepared as follows. A solution of a complex of titanium tetrachloride with dibutyl and diisoamyl ethers in a hydrocarbon solvent is prepared in the reactor and thermostatted at a temperature of 25-40 ^o С, at this temperature a solution of a diethylaluminium chloride complex with dibutyl ether in a hydrocarbon solvent is dosed for 3-10 hours. At the end of dosing, the reaction mixture is kept at a dosing temperature for 0-1 hours, then the temperature is raised to 80-110 ^o C for 2-4 hours and kept at this temperature for 2-3 hours. After precipitation of the solid precipitate, the mother liquor is decanted and the resulting catalyst is washed several times with a hydrocarbon solvent.

 The catalyst obtained according to the invention has a high activity of 170-200 g PP / (g cat • h • atm) and a low content of dust fraction in the polymer. In addition, in comparison with the prototype, the catalyst provides a higher bulk density of the PP and a lower content of the soluble polymer fraction — atactic polypropylene (APP).

 The invention is illustrated by the following laboratory and pilot examples.

 Example 1

In a 1-liter glass reactor, a solution of a complex of titanium tetrachloride with diisoamyl ether (DIAE) is prepared by sequentially loading 30 ml of heptane, 30 ml of cyclohexane, 48.2 ml of TiCl ₄ (0.438 mol) and 7.6 ml of DIAE (0.0377 praying). The molar ratio of DIAE / Ti = 0.09. A solution of a complex of 15.5 ml of diethylaluminium chloride (DEAC, 0.125 mol) with 45.5 ml of dibutyl ether (DBE, 0.269 mol, molar ratio of DBE / Al = 2.2) is metered into this solution at 35 ^° C and stirring for 4 hours. in 90 ml of heptane. At the end of dosage, the reaction mixture is stirred at 35 ^o C for 1 hour, then heated to 90 ^o C for 3 hours and maintained at this temperature for 2 hours. The solid product is settled, the liquid phase is decanted, and the solid product is washed 5 times with 150 ml heptane and get the finished catalyst.

The catalyst test is carried out as follows. 250 ml of hexane, 0.24 g of DEAC, 100 ml of hydrogen, 0.045 g of the obtained catalyst are introduced into a 1 liter autoclave. The propylene pressure is raised to 6 ati, and the temperature to 70 ^o C. After 2 hours, the contents of the autoclave are unloaded and filtered. Obtain 105.3 g of polypropylene powder (PP) with a bulk density of 490 g / l. After evaporation of hexane, a soluble fraction of the polymer is isolated in the amount of 1.6 g (atactic PP-APP). Sieve analysis determines the content of the dust fraction in the polymer powder with a size of less than 0.063 mm The activity of the catalyst is 198 g PP / (g cat • h • atm).

 Example 2 (comparative).

In a glass reactor, a solution of the TiCl ₄ complex with DIAE is prepared, sequentially loading 30 ml of heptane, 30 ml of cyclohexane, 48.2 ml of TiCl ₄ (0.438 mol) and 17.3 ml of DIAE (0.0855 mol). To this solution, at 35 ^{° C.} with constant stirring for 4 hours, a solution of the complex is dosed with 15.5 ml of DEAC (0.125 mol) with 44.7 ml of DIAE (0.221 mol) in 90 ml of heptane. At the end of dosing, the preparation of the catalyst and its testing is carried out analogously to example 1.

 Example 3

The catalyst is prepared analogously to example 1, but using a solution of the TiCl ₄ complex (0.438 mol) with 15.2 ml of DIAE (0.075 mol) and 12.7 ml of DBE (0.075 mol) in 60 ml of heptane and the DEAC complex with 25.4 ml of DBE ( 0.15 mol). The molar ratio of the components in these complexes is: DIAE / Ti = 0.17, DBE / Ti = 0.17; RHEED / Al = 1.2.

 Example 4

The catalyst is prepared analogously to example 3, but using the complex TiCl ₄ with 26.6 ml of DIAE (0.131 mol) and 3.7 ml of DBE (0.0219 mol) and a complex of DEAC with 26 ml of DBE (0.153 mol). The molar ratio of the components in these complexes is: DIAE / Ti = 0.3, DBE / Ti = 0.05; RHEED / Al = 1.23.

 Example 5

256 l of TiCl ₄ (2.33 kmol), 43 l of diisoamyl ether (0.213 kmol) and 360 l of heptane fraction containing about 5% toluene are charged into a 3.2 m ³ industrial reactor in a nitrogen atmosphere. The resulting solution was heated to 35 ^{° C.} and at this temperature a solution of a diethylaluminium chloride-dibutyl ether complex was metered into it, obtained by mixing 72 kg of DEAC (0.597 kmole), 200 L of DBE (1.18 kmol) and 200 L of the above heptane fraction in an apparatus with a stirrer . The molar ratio of the components in these complexes is: DIAE / Ti = 0,092; RHEED / Ti = 0; RHEED / Al = 1.98. At the end of the dosage, the reaction mixture is stirred at 35 ^° C for 1 hour, then heated to 90 ^° C for 3 hours and maintained at this temperature for 2 hours. The solid product is settled, the liquid phase is decanted and the solid product is washed 5 times with 600 l each. heptane and get the finished catalyst.

 Example 6

The catalyst is prepared analogously to example 5, but using a solution of a complex of 240 l of TiCl ₄ (2.18 kmol) with 180 l of DIAE (0.885 kmol) in 360 l of heptane fraction and a complex of 72 kg of DEAC with 70 l of DBE (0.414 kmol) in 300 l of heptane fractions. The molar ratio of the components in these complexes is: DIAE / Ti = 0.40; RHEED / Ti = 0, RHEED / Al = 0.69.

 Example 7

The catalyst is prepared analogously to example 5, but using a solution of a complex of 240 l of TiCl ₄ with 160 l of DIAE (0.791 kmole) and 20 l of RHEED (0.118 kmol) in 360 l of heptane fraction and a complex of 72 kg of DEAH with 70 l of RHEED in 300 l of heptane fraction. The molar ratio of the components in these complexes is: DIAE / Ti = 0.36; RHEED / Ti = 0.05; RHEED / Al = 0.69.

 Example 8 (comparative).

The catalyst is prepared analogously to example 5, but using a solution of a complex of 240 l of TiCl ₄ with 180 l of DIAE (0.885 kmole) in 360 l of heptane fraction and a complex of 72 kg of DEAC with 70 l of DIAE (0.346 kmol) in 300 l of heptane fraction. The molar ratio of the components in these complexes is: DIAE / Ti = 0.40; RHEED / Ti = 0; DIAE / Al = 0.58.

 As can be seen from the presented examples, the catalysts prepared by the proposed method (examples 1, 3-7), compared with the catalysts prepared according to the prototype (examples 2, 8), have higher activity and lead to the formation of polypropylene with a lower content of side atactic fraction; the resulting polypropylene powder has a higher bulk density and contains less dust fraction.

Claims (1)

A method of producing a catalyst for stereospecific polymerization of propylene by reduction of titanium tetrachloride with diethylaluminium chloride in the presence of electron-donating compounds, characterized in that titanium tetrachloride is reduced by reacting a complex of composition TiCl ₄ • nD ₁ • mD ₂ with a complex composition Al (C ₂ H ₅ ) ₂ Cl • kD ₂ where D ₁ is diisoamyl ether; D ₂ is dibutyl ether; n = 0.1-0.4; m≤0.2; k = 0.7-2.2.