SE439775B - PROCEDURE FOR POLYMERIZATION OF A 1-ALKEN WITH 2-8 COLATOMES USING SILICON Dioxide AS CATALYSTS - Google Patents

Description

Dutch patent application 76.05535 was filed 20 20 25 30 35 78079h8-0.

The chromium compounds of the above formula are chromium complexes of 1,3-diketo compounds of the general formula R 2 I * Hime OHO in which R 1, R 2 and R 3 are as defined above, and are acetyl acetone, hexane-2,4-dione, heptane-2 , 4-dione, octane-2,4-dione, octane-3,5-dione and homologues of these compounds, in which R 2 instead of a hydrogen atone represents an alkyl group having 1 to 20 carbon atoms, preferably the diketo compound is acetylacetone and the associated chromium compound is chromium. (III) acetylacetonate.

Such a chromium-1,3-diketo compound, preferably chromium (III) acetylacetonate, is reacted by means of an organometallic compound of a metal in Group II or III of the Periodic Table, such as beryllium, magnesium, boron, aluminum or gallium.

The hydrocarbyl groups in these compounds are preferably alkyl groups having 1 to 20 carbon atoms.

Suitable metal compounds are especially aluminum trialkyls and magnesium dialkyls. The alkyl groups contained in the magnesium dialkyls preferably have 4 to 12 carbon atoms and especially 4 to 8 carbon atoms. Suitable organomagnesium compounds are diethylmagnesium, dipropylmagnesium, diisopropylmagnesium, dibutyl- and diisobutylmagnesium, diamylmagnesium, dihexy-magnesium, dioctylmagnesium, didecylmagnesium and didodecylmagnesium, but also dicycloalkylmagnesium with the same or different cycloalkyl groups having 3 to 12 carbon atoms and preferably having 5 or 6 carbon atoms. An alkyl and a cycloalkyl group may also be attached to magnesium. Although alkyl or cycloalkylmagnesium compounds are preferred, magnesium aryls can also be used, especially diphenylmagnesium, but also ditothyl and dixylylmagnesium.

The diarylmagnesium compounds are not soluble or poorly soluble in aliphatic hydrocarbons and are therefore dissolved in aromatic hydrocarbons. The organomagnesium compounds can be prepared in a manner known per se (see, for example, GE Coates, MLH Green and K. Wade "Organo-Metallic Compounds", Vol. 1, and F. Runge n * 'Jfr- ¿_, "1 e___, i In particular, solutions of magnesium alkyls, which are prepared according to the process described in Dutch Patent Specification 139 98L, are used.

Suitable aluminum compounds are aluminum trialkyls and organoaluminum compounds of the general formula (R 4) 2 AlX, in which R 4 is an alkyl group having 1 to 10 carbon atoms and X is hydrogen or a halogen. Aluminum compounds which contain one or more residues, derived from a diene, and which are known from the 1 183 084, 136 113 186 633 can also be used. The reaction of chromium diketo- several German Offices I 956 353, and in the compound, in particular chromium (III) acetylacetonate, with an organomagnesium or organoaluminum compound must take place in a solvent which is inert in relation to these compounds.

Preferably, this reaction of the chromium compound with the organometallic compound is carried out in a hydrocarbon solvent, in particular in one or more aliphatic hydrocarbons such as hexane, heptane or a light gasoline which preferably consists of hexanes and / or heptanes. Lighter and heavier hydrocarbons, such as butanes and pentanes and petroleum fractions, such as petrol, kerosene and gas oil are also useful. Other suitable solvents, such as halogenated hydrocarbons, can also be used.

The chromium-1,3-diketo compounds, and in particular chromium (IIl) -acetylacetonate, are more readily soluble in aromatic hydrocarbons than in aliphatic hydrocarbons, and can be readily reacted with magnesium diaryls, soluble in aromatic hydrocarbons. the cost price of hydrocarbon solvents, and in particular because of their toxicity, they are preferably not used if the process can be adequately designed in aliphatic and / or cycloaliphatic solvents. Chromium (III) acetylacetonate is sparingly soluble in aliphatic and / or cycloaliphatic / hydrocarbons, and is partially dispersed therein. If an organomagnesium or organoaluminum compound is now added, the chromium (III) acetyl acetonate, probably with the simultaneous formation of a complex compound with the organomagnesium or organoaluminum compound, is at least partially in solution. This process benefits from a slight heating to temperatures around 40 to 100 ° C, resp. at low boiling point solvent to the boiling point of the solvent.

Chromium (III) acetylacetonate in light petrol colors the latter violet, as a small amount goes into solution. With the organo- - ~ -._ __ išlšéä QUifâLITY (II 10 15 20 25 78079148-0 magnesium or organoaluminum compound a dark colored solution is formed. In this solution the atomic ratio Mg: Cr or Al: Cr is preferably between 0.5: 1 and 10: 1 and especially between 1: 1 and 3: 1.

Such a solution is brought into contact with a non-organic carrier, for example by adding the solution to a carrier and with constant stirring to a carrier suspended in a solvent. The chromium compound can be precipitated on the support by evaporation, insofar as it does not directly deposit from the solution on the support, in whole or in part. When the chromium compound falls out of the solution on the support, this is clearly seen, since the solution is completely or largely discolored and the support is stained.

The support and chromium compound are separated from the dispersant by decantation, filtration or evaporation, and are thus heated in a non-reducing atmosphere to a temperature between 120 DEG C. and 120 DEG C.

It has been found that the activity of such catalysts can vary considerably. It has been established that the activity is affected by the method of manufacturing the chromium component and the choice of starting compound for this component and the temperature to which the support with the chromium component is heated, as well as the duration of this heating. Experimentally, the most favorable conditions can be determined and then applied during manufacture. If the catalyst is now produced under otherwise similar conditions, it turns out that the activity is still highly variable if different supports are used. The applicant has now determined the requirements which must be imposed on a support in order for catalysts to be produced on such a support, with very high activity for the polymerization of alkonur.

It has now been found that it is possible to polymerize an alkene having 2 to 8 carbon atoms, optionally with minor amounts of at most mol% of one or more other 1-alkenes having 2 to 8 carbon atoms, especially ethylene, if desired with a maximum of 2 moles of propylene and / or butene, in high yield in the presence of a catalyst, which is obtained by leaving a chromium-1,6-diketo compound of the formula Cr (OCR1CR2CR30) 3, in which R2 and R3 are the same or different and each represents an alkyl group having 1 to 10 carbon atoms, while R 2 may additionally represent a P1, hydrogen atom, reacting with an organometallic compound of a metal of the Periodic Table Group II or III, in which hydrocarbyl groups having 1 to 20 carbon atoms are bonded via a carbon atom to the metals in question, whereupon this reaction product is brought into contact with an inert inorganic support, whereupon the reaction product precipitated on the support of the chromium compound heated in a non-reducing atmosphere to a temperature between 200 and 1200 ° C, and finally the product thus obtained combines with an organometallic compound of an element of group II or III of the periodic table, wherein - and this is the hallmark of the present invention - a silica having a pore volume of not less than 1.5 cm3 / g and a sodium content not exceeding 200 ppm.

Silica support for catalyst supports, in particular silica xerogels, is prepared by first preparing a hydrogel starting from a sodium silicate solution and an acid, generally sulfuric acid. The gels, which contain a lot of sodium, must therefore be washed thoroughly. See, for example, German Publication Nos. 2,411,734 and 2,411,735, Canadian Patent 967,936 and U.S. Patents 2,700,061, 2,763,533, 2,785,051, 3,041,140, 3,081,154, 3,428,425, 3,453. 077, 3,652,214, 3,794,713 and 3,819,811.

However, small amounts of sodium remain. It turns out that these, when calcining the catalyst on the support, can exert an adverse influence on the later activity of the catalyst.

If the amount of sodium is considerable, for example 500 ppm or more, when heating a silica gel to the most common temperatures of calcination 800-950 ° C, a certain concentration occurs, whereby the pore volume decreases sharply; such silica gels are unsuitable as carriers for catalysts according to the invention. At lower sodium contents, a sharp reduction of the pore volume often occurs, for example, to 950 ° C, to a few 0.1 cm 3 / g, but many times the pore volume decreases quite slightly, whereby this volume can still amount to at least 1.5 after calcination. cm3 / g. If the sodium content is more than 200 ppm, active catalysts with such carriers can not be obtained, not even if the pore volume only decreases insignificantly on the holding. The reason for this relationship is not entirely clear, but it is assumed, although this may not be seen as a binding statement by the applicant, that the silica gel crystallizes on heating, and that this crystallization is unfavorable to the formation of an active catalyst on such a catalyst.

If the sodium content is less than 200 ppm, the pur volume on heating, for example to 90 DEG C., may decrease by some 0.1 cm 3 / g, but with such silica gels active catalysts can still be produced if the pore volume of the original gel is at least 1.5 cm 3 / g. Preferably the sodium content is at most 150 ppm. Silica can come in many forms. Silica xerogels are best suited for the preparation of catalysts according to the invention. It has been found that it is favorable to dry the silica to be used as a catalyst support, for example by heating in dry air before precipitating the complex chromium compound. The drying should be carried out in such a way that the carrier preferably no longer contains any physically bound water.

The amount of complex chromium compound, described above, which is precipitated on the support can be varied within wide limits, but generally amounts to 0.01 to 10% by weight, calculated as chromium on the support. Larger or smaller quantities are possible, but offer no benefits. Preferably, so much complex chromium compound is applied to the support that the chromium content of the whole amounts to 0.02 to 2% by weight, and in particular 0.05 to 1% by weight. After the complex chromium compound in a dispersant is brought into contact with the carrier, the carrier and chromium compound are separated from the dispersant by evaporation, decantation or filtration. If the chromium compound does not settle to a significant degree on the support, as evidenced by the absence or slight discoloration of the dispersant, the dispersant is evaporated. The non-reducing atmosphere in which the support is heated with the chromium component may consist of oxygen, air, nitrogen, carbon dioxide or a noble gas.

Preferably, the atmosphere in which the heating is carried out is oxidizing, for example oxygen or air, whereby of course also air with increased or reduced oxygen content constitutes an oxidizing atmosphere.

The support with the chromium compound is preferably heated to 400 to 1200 ° C and especially to 500 to 100 ° C. The heating time can vary between a few seconds and several tens of hours or longer. At temperatures between 500 and 100 ° C, the heating time can generally be from 30 minutes to 6 hours. The optimum heating time can be easily determined experimentally by the person skilled in the art, by manufacturing catalysts of equal composition under constant conditions and varying the heating time at a certain heating temperature and thus in this connection examining the properties of the catalyst thus obtained.

Preferably, the support with the catalyst component after cooling is placed in a hydrocarbon solvent, which preferably consists of the polymerizing agent. These can be aliphatic or cyclic hydrocarbons, such as butane, isobutane, normal or branched pentanes, hexanes, heptanes, octanes, etc., cyclopentane, cyclohexane, cycloheptane, cyclooctane, etc., as well as mixtures, in particular directly or indirectly from petroleum-derived fractions. , such as light petrol, petrol, kerosene or gas oil, which may contain aromatics, but preferably consist of aliphatics and / or cycloaliphates. From a technical point of view, aromatic hydrocarbons such as benzene, toluene, xylenes or halogenated hydrocarbons are also useful, but for practical reasons, namely due to the cost price and toxicity of these compounds, aliphatic hydrocarbons or petroleum fractions are generally preferred.

To the chromium component applied to the support, which is dispersed in a dispersant, is added an organometallic compound of a Group II or III element of the Periodic Table, such as beryllium, magnesium, boron aluminum or gallium.

The molar ratio between the organometallic compound and the chromium component applied to the support can vary within wide limits, for example between 0, 1: 1 and 200:]. Preferably this ratio is between 5: 1 and 40: 1.

Polymerization of 1-alkenes with catalysts according to the invention preferably takes place in a dispersant under such conditions that a suspension of polymer occurs in the dispersant. For polymerization of ethylene, this means that the polymerization temperature is generally chosen below 110 ° C and preferably below 100 ° C and in particular amounts to at most QOOC. In nwcket volatile solvents, suspen-, r) _ _ _ siunspolymorhuujon dovk is possible annu vnlllü (o «h | n> nn. ~ Ud u) m å 'fl l u -tc = Ü få” W * M_. Polymerization can also be carried out at higher temperatures, for example at 150 to 100 DEG C., whereby a solution of polyethylene in general is generally obtained at 150 DEG-70 DEG. The dispersant, which can be worked up in a manner known per se, It is also possible to carry out polymerization as so-called gas-phase polymerization, embodiments of which are known, inter alia, from the English patent specification 1,373,982.

Polymerization of propylene and higher olefins can also be carried out in liquid monomers. To achieve a good polymerization rate, polymerization is generally carried out at elevated temperature, 50 ° C and higher, and preferably at least 70 ° C. Polymerization can be carried out at atmospheric pressure but also under elevated pressure, which is required when using low-boiling dispersants such as butane, isobutane and pentane. If polymerization is carried out under elevated pressure, higher yields can be achieved, which is why one generally works under elevated pressure up to, for example, 100 kp / cmg. Higher pressures up to, for example, values as high as 2000 kp / cmz and more are possible, but are not used for practical reasons. Preferably, polymerization is carried out at pressures between 6 kp / cm 2 and 80 kp / cm 2, especially between 12 and 50 kp / cm 2.

The amount of catalyst is generally selected so that 0.001 to 10 mmol of chromium is present in each liter of dispersant, and preferably 0.01 to 1 mmol / liter.

The suspensions or solutions which result from polymerization in a solvent can be worked up in a manner known per se.

In connection with the method according to the invention, per se known modifications are possible. For example, one can regulate the molecular weight by adding hydrogen or other modifiers. The polymerization can also be carried out in one or more parallel or series-connected steps, possibly working with different catalyst compositions, temperatures, residence times, pressures, hydrogen concentrations, etc. For example, products with a broad molecular weight distribution can be prepared by selecting the conditions in one step so that a high molecular weight polymer is formed, while selecting these conditions in a second step so that a relatively low molecular weight polymer is formed. The present invention is explained in more detail with reference to the following examples, without, however, implying any limitation of the invention.

Comparative Example A a. Preparation of the catalyst In a 1-liter flask equipped with a stirrer, reflux condenser and inlet, 20.78 g of chromium (III) acetylacetonate (59.5 mmol) are suspended in 400 ml of dry light gasoline (boiling range 65-85 ° C).

This suspension is heated with continuous stirring until the petrol boils, after which 45 ml of pure triisobutylaluminum (TIBA) are added dropwise. A dark, brown-green solution, which contains only traces of solids, is now formed. After filtration, 15.5 ml of the solution thus obtained are added dropwise to a suspension of 20 g of Ketjen F ~ 5 in 250 ml of dry petrol. The F-5 chain had been pre-dried for 4 hours in 20006 in air, after which the air was displaced with dry nitrogen.

Ketjen F-5 is a silica gel marketed by Ketjen with a pore volume of 1.25 cm 3 / g and a sodium content of 220 ppm.

After a short time, the dark colored solution has decolorized, while the silica gel carrier material has taken on color. The silica gel carrier with precipitated chromium compound is now separated from the dispersant by evaporation of the light gasoline, after which the powder thus obtained is dried under vacuum for 16 hours at 5 ° C. In connection with this, the powder is heated in a rotary kiln under a dry air stream to 900 ° C. The heating time is about 1 hour and the powder is then kept for 6 hours at 900 ° C.

After cooling, the catalyst powder is suspended in so much petrol that the concentration amounts to 10 g of catalyst on a support per 100 ml of petrol.

A small amount of the catalyst powder calcined at 90 DEG C. is analyzed; it contains 0.53% by weight of chromium and 0.83% by weight of aluminum. b. Polymerization of ethylene Into an autoclave equipped with a stirrer (3.2 liters) is introduced 1500 ml of dry petrol, to which is added 5 ml of catalyst suspension. Then 0.4 ml of a 10 M M TIBA solution in petrol is added, after which the reactor is closed and pressurized with ethylene with 5% hydrogen. The contents of the autoclave are heated to 8500, and polymerization is carried out at a total pressure of 4 atm. for 90 minutes.

Only 5 g of polyethylene is produced, which corresponds to an activity of 30 g of polyethylene per mmol of chromium per atm. otwn and hour.

The pore volume of the support chain K-F-5 is determined after it has been heated to 900 ° C in the same way as the supported catalyst. The pore volume amounts to only 0.16 cm3 / g.

Example 1a. Preparation of the catalyst The procedure described for the comparative example is repeated, this time adding 15.5 ml of the complex chromium compound solution dropwise to a suspension of 15 g of washed Ketjenïß fl in 250 ml of dry petrol.

Ketjen F-7 is a silica gel marketed by Ketjen with a pore volume of 2.0 cm3 / g and a sodium content of 300 ppm. For this experiment, Chain F-7 was used, the sodium content of which was reduced to 5 ppm by additional washing of the gel. The pore volume now amounts to 1.6 cm3 / G. After 6 hours of heating this silica gel at 900 ° C, the pore volume is unchanged.

After a short time, the dark colored solution has decolorized and the silica gel carrier material has taken on color. The silica gel carrier with the precipitated chromium compound is now separated by evaporation of the light gasoline from the dispersant, after which the powder thus obtained is dried under vacuum for 16 hours at 50 ° C. In connection with this, the powder is heated in a rotary kiln under a dry air stream to 900oC.

The heating time is approximately 1 hour, and the powder is kept for 6 hours at 90,000. After cooling, the catalyst powder is suspended in such a large amount of petrol that the concentration amounts to 0.0048 mmol of chromium per liter of petrol. A small amount of the catalyst powder calcined at 900 ° C is analyzed; it contains 0.50% by weight of chromium and 0.78% by weight of aluminum. ___, ._. ~ «---. ' 'Pos-li. fiïftffï; .šf "% w'5 _ * s - 10 15 7807948-0 u b. Polymerization of ethylene In an autoclave equipped with a stirrer (3.2 Liters), 1500 ml of dry petrol are introduced, to which 10 ml of catalyst suspension is added. Then 0.3 ml of a 1 M TIBA solution in petrol is added, the reactor is closed and pressurized with ethylene with 10% hydrogen, the contents of the autoclave are heated to 85 DEG C. and polymerization is carried out at a total pressure of 7 atm. for 90 minutes 195 g of polyethylene are obtained, which corresponds to an activity of 575 g of polyethylene per mmol of chromium per atm of ethylene and hour.

Example 2 Example 1 is repeated, this time introducing such a large amount of catalyst suspension into the autoclave that the chromium concentration amounts to 0.016 mmol / liter. In connection with this, 0.3 ml of a 1 M TIBA solution is added. The yield this time amounts to 101 g, which corresponds to an activity of 595.

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Claims (3)

7807948-0 THE PATENT REQUIREMENTS 1. Process for the polymerization of a 1-alkene having 2 to 8 carbon atoms and optionally smaller amounts, not more than 10 mol% of one or more other 1-alkenes having 2 to 8 carbon atoms, in particular ethylene, if desired with not more than 2 mol-10 propylene and / or butene, in the presence of a catalyst obtained by a chromium-1β-diketo compound of the formula Cr (OCR 1 CR 2 CR 3 O) 3, in which R 1, R 2 and R; are the same or different and each represents an alkyl group having 1-10 l <013t0m9b VafVíd RzDess may also denote a hydrogen atom, has reacted with an organometallic compound of a metal in the Periodic Table Group II or III, in which hydrocarbyl groups having 1-20 carbon atoms are bonded to the metal in question via a carbon atom, after which the reaction product has been contacted with an inert inorganic support, the reaction product deposited on the support of the chromium compound has been heated in a non-reducing atmosphere to a temperature between 200 ° C and 1200 ° C and then finally The product thus obtained has been combined with an organometallic compound of an element of Group II or III of the Periodic Table, characterized in that, as catalyst support, a silica having a pore volume of at least 1.5 cm 2 / g and a sodium content of not more than 200 ppm. Process according to Claim 1, characterized in that a silica gel is used as silica gel. 3. Process according to any one of claims 1-2, characterized in that a silica with a sodium content of at most 150 ppm is used.