HU212974B - Process for the preparation of a catalyst and for producing olefins - Google Patents

Description

The present invention relates to a process for the preparation of a Ziegler-Natta catalyst. The present invention also relates to an olefin polymerization process using a catalyst prepared by the process.

French Patent Nos. 2,116,698 and 2,099,331 disclose the preparation of ZieglerNatta catalysts for use in the polymerization of olefins, in particular ethylene. According to French Patent No. 2,116,698, the catalyst is prepared by reaction of a metal magnesium, a monohalogenated hydrocarbon, an ether and a derivative of a transition metal having at least 4 valencies. According to French Patent No. 2,099,331, the catalyst is prepared by reacting activated magnesium with a monohalogenated hydrocarbon and a derivative of a transition metal having a valence of at least 4.

Further, GB 2 103 226 and HU 196 437 describe a solution in which Ti and alcohol are used, as well as condensed magnesium vapor, for the preparation of a catalyst component.

In EPA 452,156, the catalyst component is prepared using a magnesium compound.

These catalysts are effective, but their catalytic activity is greatly enhanced by increasing the temperature of the polymerization, especially within the temperature range commonly used in olefin polymerization reactions. It is a common experience with the use of such catalysts that small changes in the reaction temperature may result in relatively large changes in the activity of the catalyst and, as a result, the rate of polymerization may vary significantly. This phenomenon can be particularly disturbing in the case of polymerization reactions which may result in unexpected temperature changes. Unexpected changes in the rate of polymerization can result in the formation of polymer agglomerates, particularly in gas phase polymerization processes, for example in the implementation of a fluidized bed polymerization process.

The present invention relates to a process for the preparation of polymerization catalysts which overcome or at least mitigate the difficulties associated with known catalysts. The catalysts produced by the process of the present invention have relatively constant activity in the desired temperature range, i.e. a slight change in temperature does not cause a large change in the catalytic activity. The constant activity also allows the use of the catalyst in large-scale industrial reactors.

The present invention therefore relates to a process for the preparation of a Ziegler-Natta catalyst, characterized in that a halogen atom, a magnesium atom and a IV, V or VI compound of a periodic table of the elements are formed. The solid component containing the transition metal atoms of Group II is contacted with an electron donor compound.

The solid component used in the process of the invention is preferably characterized by the following general formula:

Mg _m Me _n M (0R ') _p (R ² ) _g X _r D _s

In the general formula

Me represents aluminum and / or zinc;

M is a periodic system of elements

IV, V or VI transition metal, preferably titanium and / or vanadium;

R ¹ is C 1 -C 14 alkyl;

R ² is C 1 -C 12 alkyl;

X is chlorine and / or bromine;

D is an electron donor compound which preferably contains oxygen, sulfur, nitrogen or phosphorus; and m is from 1.5 to 50, preferably from 2 to 10;

n is 0-2, preferably 0-1;

p is 0-4, preferably 0-3;

q is 0 to 1, preferably 0 to 0.5;

r is 4 to 110, preferably 5 to 27; and s is from 0 to 0.5, preferably from 0 to 0.2.

Particularly useful in the process of the present invention are solid components which comprise the production of metallic magnesium with at least one monohalogenated hydrocarbon and at least one of IV, V or VI of the Periodic Table of the Elements. is optionally in the presence of an electron donor compound. Preferably, the solid component is prepared according to the process described in French Patent Nos. 2,099,311 and 2,116,698. The solid component prepared according to those patents generally consists of particles of irregular shape.

The IV, V or VI of the Periodic Table of the Elements used in the preparation of the solid component. transition metal, preferably titanium and / or vanadium. The titanium compounds used are preferably those of the tetravalent titanium having the following general formula:

TiX ₄ , (OR ³ ),

In the general formula

X is halogen, generally chlorine or bromine;

R ³ is C 2 -C 8 alkyl; and t is an integer from 0 to 4, for example an integer or fraction from 0 to 3, preferably 2 or close to 2.

Representative examples of titanium compounds as defined above include titanium tetrachloride,

Ti (OR ³ ) ₄ alkyl tetratitanates - wherein

R ³ is as defined above for group 2

EN 212 974 Β or a mixture of titanium tetrachloride and an alkyl tetratitanate.

The magnesium used in the preparation of the solid component is preferably magnesium in the metallic state. The metal is typically used in the form of magnesium powder or magnesium turnings. Magnesium is preferably of very high purity. In order to avoid a long period of induction, magnesium is preferably used in an active form, that is, in a form that is completely free of contaminants such as contamination from the oxidation of the metal. The preactivation of magnesium can be accomplished, for example, by grinding the metal in an inert atmosphere or in an inert liquid such as an aliphatic solvent. Preferably, the activation can also be effected by treating the magnesium with iodine vapor. However, it is even more convenient to carry out the magnesium activation in the reaction medium, for example by introducing a small amount of material such as iodine into the periodic table system LA, HA. or ΠΙΑ. an alcoholate of an metal of Group II, an alkyl titanate, an ether oxide or an alcohol such as isobutanol. These materials are used in an amount of less than 10% by weight, preferably less than 5% by weight, based on the magnesium used.

The monohalogenated hydrocarbon compound is preferably selected from the group consisting of chlorinated or brominated saturated aliphatic hydrocarbon derivatives. These compounds are

R ⁴ -Z are represented by the general formula wherein

Z is bromine or chlorine, and

R ⁴ is C 1-10 alkyl.

Typical examples of monohalogenated hydrocarbons are ethyl chloride, propyl chloride, butyl chloride and pentyl chloride.

The reaction for preparing the solid component can be carried out in various ways. Alternatively, each reactant may be introduced into an inert solvent at a temperature sufficiently low to prevent the reaction from starting. Subsequently, the reaction mixture is heated, if necessary, at a temperature between -20 'C and 150' C, preferably 40 'C and 100' C, for a few minutes to 30 hours, after administration of a magnesium activating agent such as iodine crystals. No crushing operation is required during the reaction.

At the end of the preparation, the solid component is preferably washed with a liquid hydrocarbon and then dried at a temperature between 10 'C and 50' C, preferably near 20 'C. In a preferred embodiment, the solid product is not heated to a temperature above 100 ° C, preferably above 90 ° C.

In the preparation of the solid component from the point of view of the active catalyst, it is advantageous to react the reactants in such proportions that the molar ratio of monohalogenated hydrocarbon to magnesium is 0.5 to 10, preferably 1 to 4, while the molar ratio of transition metal to magnesium is lower. should be less than 1, preferably less than 0.5.

In the process of the invention, the solid component is contacted with an electron donor compound. The latter is an organic compound. Preferably, this compound does not contain a mobile hydrogen atom. Electron donor compounds useful in the process of the present invention include, for example, aliphatic ethers, tertiary phosphines, tertiary amines, secondary amides, and organosilicon compounds. Preferably, dimethylformamide or hexamethylphosphoric triamide is used. The amount of this reactant is selected such that the molar ratio of the electron donor compound to the amount of transition metal present in the solid component is 0.01 to 0.1, preferably 0.02 to 0.07.

The contacting step between the solid component and the electron donor compound is carried out in a stirred hydrocarbon. This is done under conditions that allow the maximum amount of electron donor compound to be bound to the solid component. The liquid hydrocarbon can be, for example, a C 4 -C 10 alkane or cycloalkane, or a C 6 -C 14 aromatic hydrocarbon. In most cases, the contacting operation is carried out at a temperature in the range of about 20 'C to 100' C, preferably between 40 'C and 90' C. There are several ways to perform this operation. For example, the electron donor compound may be added to a suspension of the solid component in the liquid hydrocarbon. In order to achieve homogeneous binding of the electron donor compound, the addition is preferably carried out slowly. The addition time may be, for example, from 10 to 600 minutes; in most cases, this is between 15 and 30 minutes. After the addition, the resulting suspension is stirred for 30 minutes to 5 hours. Generally, no co-catalyst is used in the contacting operation; the operation is carried out by the removal of organoaluminum compounds and olefins.

At the end of the contacting step, the electron-donor compound in free liquid hydrocarbon is not retained or may be present in very small amounts. However, it is preferable to wash the resulting solid product to completely remove impurities in the liquid hydrocarbon.

The solid catalyst prepared using the process of the invention has a stable activity within the temperature range used in practice. This range is generally from 85 'C to 95' C.

The catalyst prepared by the process of the present invention is used in the presence of a co-catalyst in the polymerization of C2-C8 olefins. Preferably, the catalyst is polymerized by ethylene, optionally mixed with an alpha-olefin such as 1-butene

EN 212 974 Β with the aim of producing high density or linear, low density or very low density polyethylene. Such polyethylene has a density in the range of 0.890 to 0.965. The temperature of the polymerization is preferably selected within the temperature range in which the catalyst activity is stable. The polymerization temperature is generally between 70 'C and 100' C, preferably between 70 and 90 'C for the production of linear low density polyethylene, and preferably between 8595 C for the production of high density polyethylene.

The olefin polymerization can be carried out in a liquid olefin containing the catalyst in a dispersed state or in a saturated aliphatic hydrocarbon.

The olefin polymerization can also be carried out in a known manner in a gas phase in a gas phase polymerization reactor, for example a fluidized or mechanically stirred bed reactor as described in French Patent No. 2,207,145 or 2,335,526. In the case of gas phase polymerizations, the catalyst is preferably used in the form of a prepolymer. The prepolymer is prepared in advance by contacting the catalyst with ethylene in the presence of a co-catalyst and optionally hydrogen, optionally mixed with one or more olefins.

Surprisingly, it has been found that the prepolymer obtained with the catalyst of the present invention contains relatively small amounts of fine particles. This amount is less than that obtained under the same prepolymerization conditions but using a catalyst prepared without an electron donor compound.

The co-catalyst was introduced in Part II of the Periodic Table of the Elements. or III. is selected from the group consisting of organometallic compounds of the group of metals; examples of such derivatives are organoaluminium, organomagnesium or organocin compounds. Typically, a trialkylaluminum is used as the cocatalyst. The cocatalyst may be introduced in a prepolymer or in a separate form into the polymerization reactor.

The following examples illustrate the invention.

Figure 1 is a schematic representation of the fluidized bed reactor used in Examples 1 and 2; the reactor consists essentially of a vertical cylinder and a separation chamber located above it.

Figure 2 shows the temperature dependence of the activity of two different catalysts: the lower curve is for a catalyst according to the invention and the upper curve is for a comparative catalyst.

The fluidized bed reactor shown schematically in Figure 1 consists of the following main parts: a vertical cylinder 2, above which is a separating chamber 3, and a fluidizing grid 4 in the lower part of the vertical cylinder 2; the top of the separation chamber 3 is connected by a recirculation line 5 to the lower part of the reactor underneath the fluidizing grid 4 which comprises a recycle line 5 with a heat exchanger 6, a compressor 7 and an ethylene feed line 9, comonomer feeder 9 10 are provided with a chain transfer agent, such as a hydrogen feed line. The reactor is also equipped with a catalyst feed line 11 and a polymer outlet pipe 12.

Example 7

(a) Preparation of a catalyst

A 10 m ³ reactor equipped with a mechanical stirrer with 100 rpm mechanical stirring was charged with 4.6 m ^{3 of} n-hexane, 5.5 kg of iodine, 3160 moles of magnesium, 29 moles of isobutanol, 60 moles of n-propyl titanate and 60 moles of n-hexane. butyl chloride. The reactor was then heated to 85 ° C until the reaction started, and the temperature was maintained at 80 ° C. At this temperature, 340 moles of n-propyltitanate, 400 moles of titanium tetrachloride, and 4,700 moles of n-butyl chloride were introduced into the reactor over 240 minutes. The resulting mixture was then stirred at 80 ° C for 2 hours. After two hours, 44 moles of dimethylformamide electron donor were introduced into the reactor over 20 minutes. Stirring was continued for another 60 minutes. The reactor was cooled to room temperature and n-hexane containing unreacted n-butyl chloride was replaced with pure n-hexane. Thus, the catalyst was obtained as a slurry in hexane.

b) Preparation of a prepolymer

Under a nitrogen atmosphere, 500 liters of n-hexane, 2 moles of tri (n-octyl) aluminum, and 2.5 moles of titanium were prepared in a catalyst.

It was charged into a 1.5 m ³ stainless steel reactor. The reactor agitator was operated at 150 rpm while the temperature was raised to 70 ° C. Hydrogen was then introduced into the reactor until a partial pressure of 1 kPa was reached, followed by ethylene at a constant flow rate of 15 kg / h for 6 h 40 min. At the end of the addition time, the reactor was degassed and the contents of the reactor transferred to a mechanically stirred evaporator. N-hexane was removed by circulating nitrogen heated to 70 ° C in the evaporator. 100 kg of ready-to-use prepolymer containing 40 g of polyethylene per 1 mol of titanium were obtained.

c) Production of a high density polyethylene

The operation was carried out in the gas phase polymerization reactor shown in schematic form in Figure 1. The reactor has two vertical cylinders with a diameter of 90 cm and a height of 6 m.

The reactor contained a fluidized bed of particles of ethylene polymer formed. The bed was 2 m high and the bed was fluidized by the upstream reaction gas mixture. The gas mixture moved upward at 50 cm / sec. The total pressure was 1.7 MPa and the temperature at the outlet of the separation chamber was 90 'C.

The reaction gas mixture was 30% by volume ethylene, 1.6% by volume

The 212,974% tooth contained 1-butene, 21% by volume hydrogen and 47.4 volumes by volume of nitrogen.

The above prepolymer was fed to the reactor at a rate of 600 g / h. Separately, triethylaluminum was also fed in an amount which resulted in a molar ratio of aluminum to 1.2 based on the titanium content of the prepolymer.

Under the conditions described above, a polymer was aspirated at a rate of 70 kg / h. This polymer had a relative density of 0.960 and a titanium content of 10 ppm, while the polymer contained approximately 1% by weight of 1-butene.

Example 2

a) Preparation of a solid component

The solid component was prepared in the same manner as in the catalyst of Example 1 (a) except that dimethylformamide was not used in this case.

b) Preparation of a prepolymer

Under a nitrogen atmosphere, 500 liters of n-hexane, 0.125 mol of dimethylformamide and 2.5 mol of titanium were prepared in an

It was charged into a 1.5 m ³ stainless steel reactor. The reactor agitator was operated at 150 rpm while the temperature was raised to 50 ° C. The resulting mixture was stirred for 30 minutes at 50 ° C and then 2 mol of tri (n-octyl) aluminum was added to the reactor. The resulting mixture was stirred for another 30 minutes at 50 ° C. Hydrogen was then introduced into the reactor until a partial pressure of 1 kPa was reached, followed by ethylene at a constant flow rate of 15 kg / h for 6 h 40 min. During the polymerization reaction, the reactor temperature was maintained at 70 ° C. At the end of the reaction, the reactor was degassed and the reactor contents transferred to a mechanically stirred evaporator. N-hexane was removed by circulating nitrogen heated to 70 ° C in the evaporator. 100 kg of ready-to-use prepolymer was obtained, containing 40 g of polyethylene per 1 mmol of titanium.

c) Production of a linear low density polyethylene

The process was carried out in the gas phase reactor described in Example 1, step c).

The bed was 2 m high and the bed was fluidized by the upstream reaction gas mixture. The gas mixture moved upward at 50 cm / sec. The total pressure was 1.7 MPa and the temperature at the outlet of the separation chamber was 80 ° C.

The reaction gas mixture contained 30% ethylene, 13.5% 1-butene, 6% hydrogen and 50.5% nitrogen.

The above prepolymer was fed to the reactor at a rate of 600 g / h. Separately, triethylaluminum was also fed in an amount which resulted in a molar ratio of aluminum to 1.2 based on the titanium content of the prepolymer.

Under the conditions described above, a polymer was aspirated at a rate of 70 kg / h. This polymer had a relative density of 0.918 and a titanium content of 10 ppm, while the polymer contained approximately 8% by weight of 1-butene.

Example 3

Measurement of catalyst activity

Two series of gas phase polymerization reactions were performed. In both cases, the reaction was carried out in a 2.5 liter stainless steel reactor with a 300 rpm mixing system and a temperature control system. The first reaction sequence was carried out using a prepolymer prepared using the catalyst of Example 1 in which the molar ratio of aluminum to titanium was 1.5, and the prepolymer contained 40 g of polyethylene per millimole of titanium. The second reaction sequence was carried out using a prepolymer prepared on the catalyst of Example 1, except that dimethylformamide was not used in the preparation of the catalyst. The molar ratio of aluminum to titanium in the prepolymer was 1.2 and the prepolymer contained 40 g of polyethylene per millimole of titanium.

In both series, a large number of polymerization reactions were performed at different temperatures. In each reaction, 200 g of polyethylene, 0.5 mmol of titanium prepolymer, hydrogen of 0.1 MPa partial pressure and ethylene of 0.4 MPa total pressure were introduced as a powder pack. In each reaction, the activity of the catalyst was measured, i.e., the amount of titanium produced in grams of polyethylene produced and the amount of titanium present in the reactor for 1 hour [g polyethylene (PE) / mmol Ti / hour],

Figure 2 is a graph of the catalyst activity values for both catalysts. The lower curve belongs to the catalyst of the invention, while the upper curve is based on the values obtained for the comparative catalyst.

The lower curve shows that the activity of the catalyst according to the invention has practically stabilized above 85 ° C, while the activity of the comparative catalyst is constantly increasing.

Claims (6)

1. Procedure Mg _m Me _n M (OR ¹ ) p (R ² ) q X _r D _{s for} producing a solid Ziegler-Natta catalyst of the formula wherein Me is aluminum and / or zinc; HU 212,974 Β M represents an IV, V or VI of the periodic table of the elements. transition metal, preferably titanium and / or vanadium; R ¹ is C 1 -C 14 alkyl; R ² is C 1 -C 12 alkyl; X is chlorine and / or bromine; D is an electron donor compound which preferably contains oxygen, sulfur, nitrogen or phosphorus; and m is from 1.5 to 50, preferably from 2 to 10; n is 0-2, preferably 0-1; p is 0-4, preferably 0-3; q is 0 to 1, preferably 0 to 0.5; r is from 4 to 110, preferably from 5 to 27; and s is from 0 to 0.5, preferably from 0 to 0.2, characterized in that it is a solid metallic magnesium in powder or shavings, at least one monohalogenated hydrocarbon, chlorinated or brominated derivative of a saturated aliphatic hydrocarbon, and the elements IV, V or VI of the periodic table. is a known derivative which does not contain mobile hydrogen and is selected from aliphatic ethers, tertiary phosphors, tertiary amines, secondary amides and organosilicon compounds. The process of claim 1, wherein the amount of electron donor compound used is such that the molar ratio of the electron donor compound to the amount of transition metal present in the solid component is 0.01 to 0.1. The process according to claim 1 or 2, wherein the electron donor compound is dimethylformamide or hexamethylphosphoric triamide. 4. An olefin polymerization process comprising the steps of 1-3. Use of a catalyst according to any one of claims 1 to 5. Process according to claim 4, characterized in that the polymerization is carried out in a gas phase. Process according to claim 4 or 5, characterized in that the polymerization is carried out at a temperature of 85-95 ° C.