GB2028347A

GB2028347A - Mixed catalyst supports

Info

Publication number: GB2028347A
Application number: GB7927607A
Authority: GB
Original assignee: Euteco SpA
Current assignee: Euteco SpA
Priority date: 1978-08-08
Filing date: 1979-08-08
Publication date: 1980-03-05
Also published as: IN152359B; ES483218A1; GB2028347B; BR7905083A; IT1098011B; IT7826566A0

Abstract

In order to achieve high catalytic activity during the homopolymerisation or copolymerisation of olefins by the Ziegler method, the active catalyst components - a compound of a metal of Group IVB to VIB of the Periodic System and an organometallic compound of a metal of Group IA to IIIA of the Periodic System - are supported on a mixed catalyst support comprising a substantially inert inorganic or organic first component and magnesium chloride which has been deposited thereon from a solution in a usually alcohol solvent which has evaporated off. Suitable first components include gamma-alumina, silica-alumina and styrene/divinyl benzene copolymer.

Description

SPECIFICATION Catalyst supports for the homo- or copolymerisation of a-olefins This invention relates to modified catalyst supports, to catalyst compositions comprising such supports and to the use of the catalysts for the polymerisation and the copolymerisation of a-olefins, for example at low pressure, i.e. at less than about 50 kg/cm2.

It is usual to employ a catalyst system constituted by a Ziegler catalyst, for example a transition metal halide, and an organometallic compound in polymerisation of er-olefins under reduced pressure.

The transition metal can be carried on a support, for example Awl203, an alumino-silicate, SiO2, MgO, MgCO3 or Mg(OH)2. Polymerisation processes of this type generally enable the average molecular weight of the polymer product to be readily regulated. However, because of the relatively low specific activity of the catalysts, relatively large amounts have to be used and it is thus necessary to subject the polymers to a final washing to remove harmful catalyst residues.

It has hitherto been found that the halogenation of the support when formed for example of Awl203, SiO2, MgO or SiO2.AI203 enables a notable increase in the activity of the catalyst system to be obtained, thereby enabling small amountsofcatalystto be used and hence the elimination of costly final washing operations for the polymers. The use of such modified supports is described for example in British patent specifications Nos. 1,315,785 and 1,315,770.

Such catalysts do not however allow easy regulation of the main molecular weight of the polymers and the products obtained are usually difficult to work with, having in general very high molecular weights and low melt index values.

According to one aspect of the present invention, there is provided a mixed catalyst support for supporting a Ziegler catalyst for the homo- or copolymerisation of olefins, which catalyst support comprises a substantially inert, inorganic or organic first component (A) and magnesium chloride deposited thereon from a solution in a solvent which has subsequently been substantially eliminated by vapourisation as component (B).

By using a catalyst support of this type, it is possible to obtain a catalyst composition which allows the following advantages to be obtained when producing olefin polymers, namely: a) high catalytic activity during the polymerisa tion so that the problem or washing off catalyst residues from the polymers obtained is obvi ated; b) easy regulability of the average molecular weight of the polymers.

Thus according to a second aspect of the invention, there is provided a catalyst composition for the homo- or copolymerisation of olefins, which comprises a compound of a metal of Groups IV B to VI B of the Periodic System of the Elements and an organometallic compound of a metal of groups I A two Ill A of the Periodic System of the Elements supported on a mixed catalyst support according to the first aspect of the invention.

When producing a modified catalyst support according to the invention, the following operations will be carried out: a) Use of a first component which will be substan tially inert and which preferably has a particle size of from 2 to 100 microns.

Examples of such supports are forms of alumina, alumino-silicates, SiO2, MgO, MgCO3, Mg(OH)2, silica-aluminas, zeolites and porous organic supports such as styrene-divinyl ben zene resins. This support A can be rendered inert before use by means of calcination.

b) Impregnation of support component A with a solution of MgCI2 in quantities such that the treated support A adsorbs from 5% to 75% of MgCI2 based on its weight. The solvent used is preferably an alcohol.

The type of alcohol used as solvent for MgCI2 is not important. However, the use of ethyl and methyl alcohols is preferred. The impregnation can be carried out by various presently avail able techniques which allow the best possible distribution (as to homogeneity and maximum diffusion) of the MgCI2 on the support compo nent A, so as to exploit, in the best way, the active centres of the MgCI2 molecules which react with the transition metals of the Ziegler catalyst constituents subsequently to be car ried on the modified catalyst support. The MgCl2 can be transferred to support compo nent A by impregnation carried out, for exam ple: 1) In the liquid phase; 2) In a fluidised bed or in rotating container.

c) Vapourisation of the solvent for the MgCI2 is then carried out to obtain the final mixed sup port. Substantially all of the solvent should be removed. Nevertheless, it has been found that the presence in the final mixed support of a quantity of alcohol of up to 2% by weight and preferably less than 0.5% by weight is not harmful.

A catalytic system according to the second aspect of the present invention can be prepared by reaction of the aforesaid mixed support with a compound of a metal of Groups IV B to Vi B of the Periodic System of the Elements. Activation of the catalyst composition thus formed is effected by treatment with an organometallic compound of a metal of Groups I A two Ill A of the Periodic System of the Elements. When reference is made herein to the Periodic System of the Elements, this should be taken to indicate the system as set out in the table on the front flyleaf of the "CRC Handbook of Chemistry and Physics", CRC Press, 59th Edition.

The Group IV B to VI B metal compounds which have been found to be particularly useful are the halides, the oxyhalides or the alkoxy halides. The metals of Groups IV B to VI B which are preferred are titanium, vanadium and chromium. Preferred Group IV B to VI B metal compounds are then for example: TIC4, TiBr4, VCI4, LOCI3, VOBr3, CrO2Cl2, Ti(OC2HE)3CI and Ti(OisoC4Hg)2Ci2. The best results are obtained moreover with TiCI4.

The conditions employed for the reaction between the modifed support and the Group IV B to VI B metal compound can be varied considerably. For example, the reaction temperature may lie anywhere in the range from OTto 300 C; and the duration of the reaction may be from 1 to 4 hours. The Group IV B to VI B compound can be used in pure state or in mixture with an anhydrous organic solvent.

The organometallic compounds used as catalyst activators may be, for example, metal alkyls, halides or hydrides of metal alkyls, or Grignard compounds.

Preferred metals of Groups I Ato ill Aforthis purpose are Al, Zn, Mg, Na and Li. Examples of specific organometallic catalysts activators which can be used are trimethyl aluminium, monochlorodiethyl aluminium, aluminium diisobutyl hydride, (C2H5)MgBr and ethyl aluminium sesquichloride. The best results have been found to be obtained in general with the aluminium alkyls and the aluminium alkyl halides; in particular aluminium triethyl and aluminium triisobutyl have been found to be best.

The quantity of organometallic activator compound used is not critical; nevertheless such compounds are preferably present in molar excess with respect to the Group IV B to Vl B metal contained on the support.

According to a third aspect of the invention, there is provided a process for the homo- or copolymerisation of olefins containing from 2 to 10 carbon atoms per molecule, wherein polymerisation is carried out by the Ziegler method using a catalyst composition according to the second aspect of the invention, preferably under a pressure of less than 50 kg/cm2, more preferably less than 10 kg/cm2.

The catalyst system of the present invention may be used for the homo- of copolymerisation of a-olefins; for example: ethylene, propylene, butene-1, pentene-1, hexene-1 and 4-methylpentene-1. It is of particular value when used for the preparation of homo-or copolymers of ethylene. The homo- or copolymerisation of olefins can be carried out in accordance with any one of the usual techniques, whether in the gaseous phase or in solution. In the latter case inert solvents such as aliphatic or cycloal iphatic hydrocarbons are preferably used.

The regulation of the average molecular weight of the polymers which it is desired to obtain and which may be achieved by the choice of a suitable catalyst composition according to this invention, may also be obtained by the addition of one or more of the usual chain terminating agents: hydrogen, alcohols, CO2, Zn-alkyls or Cd-alkyls may be used for this purpose.

The density of the polymer products obtained can be regulated by addition to the polymerisation reaction mixture of an alkoxide of a metal of Group IV B to V B of the PeriodicSystem,-in particular an alkoxide of titanium or vanadium, for example Ti(O isobutyl)4 The following Examples illustrate this invention.

EXAMPLE 1 5.7 g of gamma-alumina in microspheroidal form, with an average particle size of 20 microns, having a surface area of 250 m2!g and a pore volume of 1.5 cc/g were calcined at a temperature of 900"C in a stream of dry nitrogen (dew point = 70"C) for 12 hours. The alumina underwent a loss in weight of about 30%.

At the end of the calcination, the alumina was cooled to ambient temperature and was transferred, always being kept under an atmosphere of dry nitrogen, into an impregnator constituted by a glass flask heatable by means of an electric element and furnished with a stirrer, a dropping funnel containing an alcoholic solution of MgCI2 (150 g/l in ethanol) and a Liebig condenser. The flask and the dropping funnel were fed with anhydrous nitrogen.

10 cc of the MgCI2 solution were added drop by drop to the alumina which was subjected to stirring, taking care at all times that lumps did not form and that the ethanolicsolution became completely absorbed by the alumina. Finally, the contents of the flask were heated to distil off the excess alcohol. 1.5 g of MgCl2 remained in the alumina.

This operation was repeated in identical manner another two times in order to introduce into the alumina, in all, 4.5 g of MgCI2. The impregnated alumina was finally dried for 2 hours at a temperature of 1300C. The modifed catalyst support which was obtained contained 0.2% of ethanol.

29 of this support were contacted with 20 cc of anhydrous n-heptane containing 0.4 cc of TiCI4 for 4 hours at ambient temperature. The suspension produced was then filtered and dried at 136 C for 1 hour.

A catalyst component containing 2.45% of titanium was obtained.

15 mg of this catalyst component were suspended in 2 litres of anhydrous n-heptane containing 0.2 cc of triethyl aluminium and polymerisation of ethylene using the catalyst composition thus produced was then carried out in a 4 litre autoclave furnished with a stirrer. The polymerisation was carried out under a total pressure of 5 kg/cm2 and with a partial pressure of H2 of a kg/cm2 at a temperature of 90"C over a period of 30 minutes.

480 g of polyethylene having a melt index of 0.3 and a crystallinity of 72% were obtained. The productivity of the catalyst system amounted to 4800 g of polyethylenelg of catalystlhourlatmosphere of ethylene.

The specific activity of the catalyst system amounted to 196 kg of polyethylenelg of titaniumlhourlatmosphere of ethylene.

The polyethylene obtained contained 3.1 ppm of titanium and did not require washing or purification of any type.

EXAMPLE 2 {Comparative) 10 g of anhydrous magnesium chloride were dissolved in ethanol and the solution was evaporated to dryness under a stream of anhydrous nitrogen, taking care to ensure that the residual alcohol amount was the same as that of the catalyst support produced in Example 1.

The sample obtained was ground while being kept under anhydrous nitrogen until a maximum particle size of 50 microns was obtained and it was then tre ated with TiCI4 is the manner indicated in Example 1.

A catalyst component containing 2.80/0 by weight of titanium was obtained. 30 mg of this component were used in the polymerisation, carried out as indicated in Example 1 after activation with triethylaluminium as set out in claim 1. 120 g of polyethylene were obtained.

The productivity of the catalyst system amounted to 2000 g of polyethylene/g of catalyst/houqatmos- phere of ethylene.

The specific activity of the catalyst system amounted to 71.4 kg of polyethylene/g of tita ni u m/hou r/atmosphere of ethylene.

EXAMPLE3 The procedure of Example 1 was repeated to produce a series of catalysts having MgCI2 adsorbed on the alumina in different amounts.

Again operating under conditions set out in Example 1,the catalysts were used in the polymerisation of ethylene. The results obtained are set out in Table 1.

It was found that the productivity increased as the percentage of MgCI2 supported on the alumina decreased until it began to decrease when the amount of MgCI2 dropped 5% by weight and dropped sharply when lower quantities of MAC12 were used, as in Tests 4 and 5.

In the range 50 to 10% by weight of MgCI2 (molar ratioAl2O3/MgCI2 of 1:1 to 9:1) a ceiling ofsubstan- tially constant highest productivity values is obtained.

Moreover, it may be noted that the amount of titanium bound to the support became less as the amount of deposited MgCl2 decreased. The specific activity of the catalyst composition stayed at very high levels and practically constant in the range of MgCI2 concentrations extending from 50% to 5%.

TABLE 1

Number Molar ratio I Ti boundlProductivitg pecific of test 81203/IgC12 to the (+) rctivitg support (++) 1 0.5 : 1 3.60 2200 61 2 3 : 1 2.10 4500 214 3 9 : 1 2.30 5150 224 4 19 : l 1.50 3100 207 5 49 : 1 1.05 800 76 (+) expressed as g polyethylene/g eatalyst/h/atmospheres of ethylene (++) expressed as Kg polyethylenelg titanium/h/atmosphere of ethylene EXAMPLE4 25 g of silica-alumina containing 25% by weight of alumina and having microspheroidal form with a maximum diameter of 25 microns were calcined at 750"C for 16 hours until no further elimination of water occurred. The silica-alumina was then cooled to ambient temperature under a stream of anhydrous nitrogen. 18 g of the calcined product were obtained.

The calcined product was then transferred to a heated container and maintained under an atmosphere of anhydrous nitrogen. This was sprayed from above with a solution of 10% by weight MgCI2 in ethanol, maintaining the contents of the container at a temperature of 1 00 C. The alcoholic solvent was thus eliminated to an extent of 98%. The modified support obtained contained 25% of MgCI2.

20 g of this modified support were transferred to a 500 cc reactor provided with heater, stirrer, reflux condenser, liquid supply system and a filter. 50 cc of TiCI4 diluted in 200 cc of n-heptane were added and heating under refluxwas effected for4 hours. Atthe end of this time, the contents of the reactor were filtered while hot and washed with 200 cc of n-heptane at ambient temperature. The catalyst component produced (which contained 3% of Ti) was then placed in suspension in n-heptane to form a 20% suspension (weight pew volume of suspension).

0.2 cc of this suspension (containing 40 mg of catalyst components) were used for carrying out the polymerisation procedure set out after activation with triethylaluminium as set out in Example 1. In 30 minutes, 390 g of polyethylene were obtained.

The productivity of the catalyst system amounted to 4875 g of polyethylene/g of catalyst/h/atmosphere of ethylene. The specific activity of the catalyst system amounted to 162.5 kg of polyethylene/g of titanium/h/atmosphere of ethylene.

EXAMPLE 5 10 g of a styrene-divinyl benzene resin (containing 4% by weight divinyl benzene) with a minimum particle size of 30 microns were placed in a tubular reactor having a diameter of 25 mm surrounded by an electric mantle and having on its base a porous septum and in an upper part a dropping funnel. The resin was dried for 24 hours, dry nitrogen being passed through the porous eptum at a speed of 5 cc per second and at a temperature of 120"C for this purpose. A solution of 10 cc of MgCI2 in methanol maintained always at a temperature of 1 20 C was then supplied dropwise onto the fluidised resin from the feeding funnel. Thus 3.0 g of MgCI2 were added to the resin.

The modified catalyst support thus obtained was then treated with TiCI4 in the manner indicated in Example 1: a catalyst component containing 2.2% by weight of titanium was obtained.

Polymerisation of ethylene was carried out using this catalyst component after activation in the man nerset out in Example 1,the polymerisation being effected in the manner set out in Example 1.

The productivity of the catalyst system used was 4400 g of polyethylene/g of catalyst/h/atmosphere of ethylene. The specific activity of the catalyst system was 200 kg of polyethylene/g of titaniu m/h/atmosphere of ethylene.

The polyethylene thus obtained had a melt index of 0.2 and a crystallinity of 70%.

Claims

1. A mixed catalyst support for supporting a Ziegler catalyst for the homo- or copolymerisation of olefins, which catalyst support comprises a substantially inert, inorganic or organic first component (A) and magnesium chloride, deposited thereon from a solution in a solvent which has subsequently been substantially eliminated by vapourisation, as component (B).

2. A catalyst support as claimed in claim 1, wherein said solvent is an alcohol and the catalyst contains up to 2% by weight residual alcohol.

3. A catalyst support as claimed in claim 2, wherein the alcohol is methanol or ethanol.

4. A catalyst support as claimed in any one of the preceding claims, wherein the amount of adsorbed magnesium chloride is from 5 to 75% by weight of component (A).

5. A catalyst support as claimed in any one of the preceding claims, wherein component (A) is alumina, silicon-alumina, a zeolite or a porous organic support.

6. A catalyst support as claimed in claim 5, wherein the porous organic support is a styrene divinylbenzene resin.

7. A catalyst support as claimed in any one of the preceding claims, wherein component (A) has been rendered inert, prior to deposition of the magnesium chloride, by calcination.

8. A catalyst support as claimed in any one of the preceding claims, wherein component (A) has a particle size of from 2 to 100 microns.

9. A mixed catalyst support, substantially as described in any one of the foregoing Examples 1 and 3 to 5.

10. Amethodforthe production of a mixed catalyst support for supporting a Ziegler catalyst for the homo- or copolymerisation of olefins, which comprises impregnating a substantially inert inorganic or organic first component (A) with a solution of magnesium chloride in a solvent and substantially eliminating the solvent by vapourisation.

11. A method as claimed in claim 10, wherein the impregnation is carried out in the liquid phase, in a fluidised bed or a rotating container.

12. A method as claimed in claim 10 or 11, wherein the magnesium chloride is employed in solution in an alcohol.

13. A method as claimed in claim 12, wherein the impregnation and the vapourisation are carried out to such an extent that the mixed catalyst support contains magnesium chloride in an amount from 5 to 75% by weight of the first component and has a residual alcohol content of not more than 2% by weight.

14. A method as claimed in any one of claims 10 to 13 wherein component (A) is as defined in any one of claims 5 to 9.

15. A method for the production of a mixed catalyst support, substantially as described in any one of the foregoing Examples 1 and 3 to 5.

16. A mixed catalystsupportwhenever produced by the method claimed in any one of claims 10 to 15.

17. A catalyst composition for the homo- or copolymerisation of olefins, which comprises a component of a metal of Groups IVB to VIB of the Periodic System of the elements and an organometallic compound of a metal of Groups lAto lIlA of the Periodic System of the Elements supported on a mixed catalyst support as claimed in any one of claims 1 to 9 and 16.

18. A composition as claimed in claim 17, wherein the metal of Groups IVB to VIB is titanium vanadium or chromium.

19. Acomposition as claimed in claim 18, wherein the compound of a metal of Groups IVB to VIB is a halide, an oxyhalide or an alkoxyhalide.

20. A composition as claimed in claim 19, wherein said component is titanium tetrachloride.

21. A composition as claimed in any one of claims 17 to 20, wherein the organometallic compound is a compound of Al, Zn, Mg, Na or Li.

22. A composition as claimed in claim 21, wherein the organometallic compound is an aluminium alkyl oran aluminium alkyl halide.

23. A composition as claimed in claim 22, wherein the organometallic compound is aluminium triethyl or aluminium triisobutyl.

24. A catalyst composition of the homo- orco- polymerisation of olefins, substantially as described in any one of the foregoing Examples 1 and 3 to 5.

25. A process for the homo- or copolymerisation of olefins containing from 2 to 10 carbon atoms per molecule, wherein polymerisation is carried out by the Ziegler method using a catalyst composition as claimed in any one of claims 17 to 24.

26. A process as claimed in claim 25, wherein ethylene is homopolymerised.

27. A process as claimed in claim 25 or 26, wherein the density of the polymer product obtained is regulated by inclusion in the polymerisation system of an alkoxideofa metal of Groups IVB to VIB of the Periodic System.

28. A polymerisation process, substantially as described in any one of the foregoing Examples 1 and 3 to 5.

29. An olefin homo- or copolymer which has been produced by the process claimed in any one of claims 25 to 28.