DESC:FIELD
The present disclosure relates to a supported hybrid catalyst for olefin polymerization and a process for preparation thereof.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
Metallocene: A metallocene is a compound typically consisting of two cyclopentadienyl anions (Cp, which is C5H5-) bound to a metal center (M) in the oxidation state II, with the resulting general formula (C5H5)2M.
Hybrid catalyst: The hybrid catalyst of the present disclosure comprised of the magnesium supported titanium catalyst, which catalyzes propylene polymerization and the metallocene compound that catalyzes com-polymerization.
Pro-catalyst: The pro-catalyst is a species that can be converted to an olefin polymerization catalyst by contacting it with a co-catalyst and optionally an internal electron donor.
Stereo-rigid compound: Stereorigid compounds of the present disclosure are the metallocene compounds having indenyl ligands.
Nonstereo-rigid compound: Nonstereorigid compounds of the present disclosure are the metallocene compounds having substituted or un-substituted cyclopentadienyl ligands.
BACKGROUND
Polypropylene is produced using a magnesium supported titanium catalyst system based on monoester/diester/diether internal donors. The obtained polypropylene products have excellent properties like high isotacticity, superior morphology and broad molecular weight distribution (MWD). The broad molecular weight distribution (MWD) is due to the presence of multiple active sites. The molecular weight distribution influences the mechanical and rheological properties of polypropylene, which in turn are responsible for the performance and the applications of the polypropylene.
A magnesium supported titanium catalyst system consists of a pro-catalyst, an organoaluminum co-catalyst and an external electron donor or selectivity control agent.
US patent 8633124 discloses a process for the synthesis of spheroidal and morphologically controlled magnesium alkoxide based catalyst precursors. Spheroidal magnesium alkoxide precursors are treated with TiCl4 to produce spherical and morphologically controlled in-situ generated MgCl2 supported titanium based Zeigler-Natta pro-catalysts in the presence of monoester/diester type internal donors. The polypropylene resin produced using this pro-catalyst is spheroidal in nature.
Advances in magnesium supported titanium catalysts are achieved through the development of hybrid catalyst systems containing titanium chloride and a metallocene compound. WO 1994028034 mention a hybrid catalyst containing a titanium compound and a metallocene compound. The resulting catalyst system is used to control the molecular weight distribution between the magnesium supported titanium pro-catalyst and the metallocene based system.
US Patent 5,648,422 suggests a multistage process for the production of olefin polymer compositions using different catalytic systems at various stages. The processes combine the advantages of different catalysts; however, it is difficult to employ it for industrial practice due to the complexity of the process. There is, therefore, still a need for a catalyst system for the production of high rubber content polypropylene grades.
US patent 2009/0062466 discloses a masking agent covering styrene and its derivatives to synthesize a copolymer of propylene and ethylene in two stages using a single hybrid catalyst system. The hybrid catalyst consists of a mixture of Ziegler Natta and metallocene catalyst which remains catalytically active at different stages during the olefinic polymerization process. The Zeigler-Natta catalyst produces a polypropylene matrix in the presence of styrene and its derivatives as a masking agent to mask the metallocene in the first stage. The reactivation of the metallocene active species in the second stage due to the presence of ethylene results in the formation of a polypropylene copolymer. However, the system employs a non-morphological Zeigler-Natta diester/diether catalyst system.
In the known system the reactivity of the supported hybrid metallocene catalyst is low in polymerization because lower content and amount of metallocene in the catalyst.
In the known system hydrogen is not used as chain terminating agent to control the molecular weight.
There is, therefore, felt a need to provide a supported hybrid metallocene catalyst having metallocene content.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for the preparation of a supported hybrid metallocene catalyst.
Another object of the present disclosure is to provide a process for the preparation of a supported hybrid metallocene catalyst for olefin polymerization;
Still another object of the present disclosure is to provide a process of olefin polymerization in the presence of a supported hybrid metallocene catalyst; and
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a process for the preparation of a supported hybrid metallocene catalyst, the process comprises charging a predetermined amount of a pro-catalyst, and a predetermined amount of a first fluid medium into a reactor to obtain a first slurry. This is followed by addition of a predetermined amount of a borate based binder of formula (I), and a metallocene compound to the first slurry to obtain a first mixture,

Formula (I)
wherein R1, R2 and R3 are at least one independently selected from a C1 to C8 linear or branched alkyl and arylalkyl groups.
The first mixture is stirred at a temperature in the range of 40 °C to 80 °C for a time period in the range of 1 hour to 5 hours to obtain a second mixture, which is followed by separation of solid from the second mixture. The solid is washed with a second fluid medium to remove the unreacted species and dried to obtain the supported hybrid metallocene catalyst.
The pro-catalyst of the present disclosure comprises at least one magnesium compound selected from the group consisting of magnesium dichloride, magnesium methoxide, magnesium ethoxide and magnesium isopropoxide, at least one titanium component selected from the group consisting of elemental titanium, TiCl4, Ti(OC2H5)3Cl, Ti(OC3H7)3Cl and Ti(OC4H9)Cl3; and an internal electron donor.
The borate based binder of the present disclosure is at least one selected from a group consisting of trimethyl borate, triethyl borate, tri-isopropyl borate, tributyl borate and triphenyl borate. The metallocene compound is a stereo-rigid or non-stereo-rigid metallocene compound comprising at least one metal selected from the group consisting of Zr, Hf and Ti as a central metal atom. The internal electron donor is di-isobutyl phthalate. The first fluid medium and the second fluid medium are at least one independently selected from the group consisting of hexane, decane, isopentane and toluene.
The present disclosure also provides a process of polymerization of at least one olefin using the supported hybrid metallocene catalyst, the process comprises introducing a predetermined amount of the supported hybrid metallocene catalyst in a reactor containing a predetermined amount of a third fluid medium, which is followed by adding to the reactor, a predetermined amounts of a masking compound, an organoaluminum co-catalyst and an external electron donor to obtain a second slurry. The ratio of elemental aluminum to elemental titanium is in the range of 230:1 to 270:1 and the ratio of the external electron donor and elemental titanium of the titanium component is in the range of 1:1 to 5:1. Further, at least one olefin to is introduced into the reactor containing the second slurry and is subjected to polymerization in the presence of the supported hybrid metallocene catalyst at a temperature in the range of 60 °C to 100 °C and a pressure of olefin in the range of 1 bar to 6 bar to obtain a polyolefin.
The masking compound is at least one selected from a group consisting of 4-vinyl cyclohexene, 9-vinyl carbazole and styrene. The organo-aluminum co-catalyst is at least one selected from the group consisting of triethylaluminum, tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, tri-isoprenylaluminum, tri-isobutylaluminum, ethyl aluminum sesquichloride, diethylaluminum chloride, di-isobutyl aluminum chloride, triphenylaluminum, tri-n-octylaluminum and tri-n-decylaluminum. The external electron donor is at least one selected from a group consisting of organosilane compounds, typically the external electron donor is dicyclopentyldimethoxysilane.
A supported hybrid metallocene catalyst for olefin polymerization of the present disclosure comprises:
a. a pro-catalyst comprising a magnesium compound and a titanium component, wherein the pro-catalyst is magnesium chloride supported titanium catalyst;
b. a borate based binder of formula I

Formula (I)

wherein R1, R2 and R3 are at least one independently selected from a C1 to C8 linear or branched alkyl and arylalkyl groups; and
c. a metallocene compound.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The process of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 is a graph, which illustrates the content in terms of percentage of the supported hybrid metallocene catalyst prepared using different borate binders, wherein 1 denotes titanium, 2 denotes magnesium and 3 denotes chlorine.
Figure 2 is a graph, which illustrates the effect of a particular binder (tributyl borate) concentration on the productivity of polymerization.
DETAILED DESCRIPTION
The present disclosure provides a process for preparing a supported hybrid metallocene catalyst for olefin polymerization. The supported hybrid metallocene catalyst of the present disclosure comprises a pro-catalyst, a borate based binder and a metallocene compound. The borate based binderfacilitate mixing of the pro-catalyst and a metallocene compound, which results in high metallocene content.
In accordance with one aspect of the present disclosure, there is provided a process for the preparation of the supported hybrid metallocene catalyst. The process is discussed herein further:
A reactor is charged with a predetermined amount of a pro-catalyst, and a first fluid medium to obtain a first slurry. The pro-catalyst of the present disclosure comprises a magnesium compound, a titanium component, and an internal electron donor. Further, a predetermined amount of a borate based binder of formula (I) and a predetermined amount of a metallocene compound are added to the first slurry to obtain a first mixture.

Formula (I)
wherein R1, R2 and R3 are at least one independently selected from C1 to C8 linear or branched alkyl and arylalkyl groups.
The first mixture is stirred at a temperature in the range of 40 °C to 80 °C, for a time period in the range of 1 hour to 5 hours to obtain a second mixture containing a solid supported hybrid metallocene catalyst. The solid is separated from the second mixture. The separated solid is then washed with a second fluid medium to remove unreacted species, followed by drying to obtain the supported hybrid metallocene catalyst.
In accordance with one embodiment of the present disclosure, the drying step was carried out at room temperature.
The borate based binder is at least one selected from the group consisting of trimethyl borate, triethyl borate, tri isopropyl borate, tributyl borate and triphenyl borate.
In accordance with the present disclosure, the metallocene compound is a stereo-rigid or non-stereo-rigid metallocene compound comprising at least one metal selected from the group consisting of Zr, Hf and Ti as a central metal. In accordance with an exemplary embodiment of the present disclosure, the metallocene compound is a stereo-rigid rac-dimethyl silylbis(1-indenyl) zirconium dichloride.
The magnesium compound of the present disclosure is at least one selected from the group consisting of magnesium dichloride, magnesium methoxide, magnesium ethoxide, magnesium isopropoxide and mixtures thereof.
In accordance with the present disclosure, the titanium component is at least one selected from the group consisting of TiCl4, Ti(OC2H5)3Cl, Ti(OC3H7)3Cl and Ti(OC4H9)Cl3.
In accordance with one embodiment of the present disclosure, the internal electron donor is di-isobutyl phthalate.
In accordance with an exemplary embodiment of the present disclosure, the first mixture is stirred at 60 °C.
In accordance with one embodiment of the present disclosure, the first mixture is stirred for 3 hours.
The first fluid medium and the second fluid medium are at least one independently selected from the group consisting of hexane, decane, isopentane and toluene.
Metallocene content in the catalyst allows more dispersion of the ethylene moiety in polypropylene products during the co-polymerization of propylene and ethylene. Use of a borate based binder allows metallocene content in the supported hybrid metallocene catalyst.
It is observed by using Inductively Coupled Plasma (ICP) Mass Spectrometry that the zirconium content was found to be higher in case of butyl borate based supported hybrid metallocene catalyst. It is observed that the long chain alkyl borates facilitate metallocene content.
The molar ratio of the amount of the magnesium compound to the amount of the titanium component is in the range of 0.05 to 0.25. Further, the molar ratio of the magnesium compound to the amount of the internal electron donor is in the range of 3 to 10. The molar ratio of the magnesium compound to borate based binder is in the range of 5 to 15
In accordance with the present disclosure, the temperature at which drying of the washed solid is carried out is in the range of 25 to 30°C
In accordance with another aspect of the present disclosure, there is provided a process for olefin polymerization in the presence of the supported hybrid metallocene catalyst.
The supported hybrid metallocene catalyst is introduced in a reactor containing a third fluid medium. A masking compound, an organoaluminum co-catalyst and an external electron donor are added to the reactor containing the supported hybrid metallocene catalyst to obtain a slurry. At least one olefin is charged into the reactor containing the slurry. The olefin in the reactor is subjected to polymerization in the presence of the supported hybrid metallocene catalyst at a temperature in the range of 60 °C to 100 °C and an olefin pressure in the range of 1 bar to 6 bar to obtain polyolefin. The reaction is terminated using hydrogen as a terminating agent.
The masking compound is at least one selected from a group consisting of 4-vinyl cyclohexene, 9-vinyl carbazole and styrene.
In accordance with the present disclosure, the organo-aluminum co-catalyst is at least one selected from the group consisting of triethylaluminum, tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, tri-isoprenylaluminum, tri-isobutylaluminum, ethyl aluminum sesquichloride, diethylaluminum chloride, di-isobutyl aluminum chloride, triphenylaluminum, tri-n-octylaluminum and tri-n-decylaluminum.
In accordance with the present disclosure, the molar ratio of the elemental aluminum to the elemental titanium is in the range of 230:1 to 270:1.
The external electron donor of the present disclosure is an organosilane compound. In accordance with an exemplary embodiment of the present disclosure, the external electron donor is dicyclopentyldimethoxysilane. The molar ratio of the external electron donor to titanium of the titanium component is in the range of 1:1 to 5:1;
In accordance with the present disclosure, the terminating agent used is hydrogen, which is used to terminate the polymerization.
The co-polymerization reaction of the present disclosure takes place in a step wise manner. Initially, the magnesium supported titanium catalyst based pro-catalyst catalyzes the propylene polymerization reaction, thereby producing polypropylene. Later, co-polymerization is catalyzed by the metallocene compound, thereby producing a composite polymer of previously formed polypropylene and a co-polymer of propylene and ethylene.
The metallocene compound has a poisoning effect on propylene polymerization. The magnesium supported titanium catalyst produces a polypropylene matrix in the presence of a masking agent, which masks the metallocene during homo-polymerization of propylene.
It is observed that long chain alkyl borates facilitate metallocene content. Steric and electronic effect of borates moiety facilitates metallocene content.
The polymer material obtained by the process of the present disclosure exhibit improved characteristics.
In accordance with still another aspect of the present disclosure, there is provided a supported hybrid metallocene catalyst for olefin polymerization, the catalyst comprising:
a. a pro-catalyst comprising a magnesium compound and a titanium component, wherein the pro-catalyst is a magnesium supported titanium pro-catalyst;
b. a borate based binder of formula I

Formula (I)

wherein R1, R2 and R3 are independently selected from a C1 to C8 linear or branched alkyl and arylalkyl groups; and
c. a metallocene compound.
In accordance with an exemplary embodiment of the present disclosure, the metallocene compound is stereo-rigid rac-dimethyl silylbis(1-indenyl) zirconium dichloride.
In accordance with an exemplary embodiment of the present disclosure, the borate based binder is at least one compound selected from a group consisting of trimethyl borate, triethyl borate, triisopropyl borate, tributyl borate and triphenyl borate.
In accordance with one embodiment of the present disclosure, the magnesium compound is at least one selected from the group consisting of magnesium dichloride, magnesium methoxide, magnesium ethoxide, magnesium isopropoxide and mixtures thereof.
In accordance with one embodiment of the present disclosure, the titanium component is at least one selected from the group consisting of TiCl4, Ti(OC2H5)3Cl, Ti(OC3H7)3Cl and Ti(OC4H9)Cl3.
The present disclosure will now be described with experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of the embodiments herein. These laboratory experiments can be scaled to commercial scale.
Experiment 1: Preparation of spherical magnesium alkoxide precursor (E1)
55 g magnesium powder was added to 1250 mL mixture of ethanol and methanol in the presence of 0.150 g of iodine as an initiator at 40°C under continuous stirring. The reaction is exothermic and the reaction temperature is controlled using external temperature control. The reaction was conducted in a step-wise manner. In the first step, the reaction temperature was maintained at 40° C for a period of 2 hours followed by increasing it further to 65°C, which was maintained for 1 hour and finally to 80°C that was maintained for a period of 7 hours. The vapors of the mixture produced during the reaction were condensed in an overhead condenser. Hydrogen gas produced during the reaction was vented off and the mixture of alcohols left after the reaction was removed by filtration. The filtrate was reused for further synthesis. A wet cake was obtained after removal of the filtrate. The wet cake was dried to obtain 250 g of white free flowing powder.
Table 1: Characteristics of spheroidal particles of magnesium alkoxide:
S. No. Components Values
1. Methoxy content (wt %) 8.0
2. Ethoxy content (wt %) 70

The composition of the magnesium alkoxide contains 8 wt% of methoxy and 60 wt% of ethoxy content. The particles of the magnesium alkoxide with given composition have a spherical shape. The magnesium alkoxide obtained is further used for the preparation of the magnesium supported titanium pro-catalyst.

Experiment 2: Preparation of magnesium supported titanium pro-catalyst (E2)
50 g 10 g of the magnesium alkoxide from Experiment 1 was treated with an equal volume mixture of 115 mL of TiCl4 and chlorobenzene at 100 °C. 5.5 g Di-isobutyl phthalate was added as an internal electron donor. After the reaction was completed, the solid was filtered and given four washes with 1000 mL of isopentane each, and then the solid was dried at 50 °C under nitrogen atmosphere. 15 g of the yellow colored supported titanium pro-catalyst was obtained, and was stored in mineral oil.

Table 2. Characterization of magnesium alkoxide supported titanium catalyst
Elements Value
Magnesium (wt %) 18.6
Titanium (wt %) 2.6
Chlorine (wt %) 60.7
Ethoxy (wt %) 0.32
Mean Particle size (micron) 23
Surface Area (m2/g) 260

The synthesized magnesium supported titanium pro-catalyst possessed 2.6 wt% of titanium and 18.6 wt% of magnesium. The synthesized pro-catalyst had a surface area 260 m2/g.

Experiment 3: Slurry polymerization of propylene using supported titanium catalyst (E3)
0.08 g solid pro-catalyst obtained in Experiment 2 was mixed with 1.2 g triethyl aluminum as a co-catalyst and 0.05 g dicyclopentyldimethoxysilane as an external electron donor. The components were mixed in such proportions that the aluminum to titanium ratio was maintained as 250±5:1. The mole ratio of the selectivity control agent i.e. organosilane (dicyclopentyldimethoxysilane) to titanium was kept 3.2:1. The synthesized catalyst was employed to polymerize propylene in a slurry phase with hexane as the diluent under a constant propylene pressure of 5 kg/cm2 for 2 hours at 70 °C, followed by addition of 50 mmole of hydrogen to terminate the polymerization.

Table 3. Results of the homo-polymerization process using supported titanium catalyst
Productivity (kg PP/g catalyst) 8.5
MFI (g/10 min) 2.5
Bulk density (g/ml) 0.49
Xylene soluble (wt%) 1.4

The productivity of the polymerization reaction was found to be 8.5 Kg/ g catalyst, with MFI of 2.5 g/10 min, and 0.49 g/mL of bulk density.

Experiments 4-8: Supported hybrid metallocene catalyst synthesis using different borate binders (E4 to E8)

Experimental procedure: 9 g slurry of supported titanium catalyst obtained in Experiment 2 containing 30 wt % of solid content was washed with hexane to remove the mineral oil. The dry powder obtained after washing was suspended in 100 mL of hexane. 4 mL of borate based binder, as provided in Table 4 was added to the supported titanium catalyst slurry. Further, 250 mg of rac-dimethyl silylbis (1-indenyl) zirconium dichloride was added and the whole reaction mixture was stirred at 60 °C for 3 hours. After the reaction was completed, the mixture was cooled to room temperature and the liquid was decanted. The residue was washed and decanted five times with toluene/hexane mixture to remove the unreacted species to obtain the supported hybrid metallocene catalyst. The dried powder of the supported hybrid metallocene catalyst was collected for determining its composition.

Composition of the supported hybrid metallocene catalyst obtained in different experiments performed using different borate based binders is presented in Table 4.

Table 4: Composition of the supported hybrid metallocene catalyst obtained in different experiments performed using different borate based binders
ExperimentComposition Borate based binder Magnesium (wt%) Titanium (wt%) Zirconium (wt%) Chlorine (wt%)
E4 Trimethyl borate 16.2 2.2 0.2 52.3
E5 Triethyl borate 17.0 2.1 0.3 54.2
E6 Triisopropyl borate 17.0 1.9 0.3 51.7
E7 Tributyl borate 16.7 1.9 0.6 51.4
E8 Triphenyl borate 16.5 1.8 0.45 50.5

From Table 4 it is evident that, the zirconium content was found to be higher in-case of catalyst containing tributyl borate as a binder as compared to other borate compounds.
Borate based activator helped to maximize metallocene content in the hybrid catalyst. The amount of metallocene content depends on the structure of borate moiety. It was noticed that long chain alkyl borates has metallocene content. Steric and electronic effect of borates moiety play important role in metallocene content. In case of tributyl borate more than 90% metallocene content was achieved.
Figure 1 is a graph, which illustrates the content in terms of percentage of the supported hybrid metallocene catalyst prepared using different borates, wherein ‘1’ denotes titanium, ‘2’ denotes magnesium and ‘3’ denotes chlorine.

Propylene slurry polymerization using supported hybrid metallocene catalysts of Experiments 4 to 8.
The polymerization procedure was followed as given in Experiments 3 by replacing the supported titanium catalyst with the supported hybrid metallocene catalysts.

Table 5: The polymerization process results for catalysts prepared in experiments 4 to 8

Experimentparameter Productivity (kg PP/ g catalyst) MFI (g/ 10minutes) Bulk Density Xylene soluble (wt%)
E4 1.3 1.4 0.49 1.5
E5 3.9 1.7 0.49 1.0
E6 1.2 0.9 0.47 1.0
E7 6.4 2.8 0.5 1.4
E8 5.2 1.4 0.5 1.7

The supported hybrid metallocene catalysts prepared in experiments 4 to 8 were used for homo-polymerization of propylene. The productivity of the catalysts of E4 to E8 was found to be in the range of 1.2 to 6.4 kg PP/ g catalyst. Table 5 reveals that the productivity for polymerization reactions is highest when tributyl borate is used as binder. MFI was found to range between 0.9 to 2.8 g/10 minutes. The highest MFI 2.8 g/10 minutes was recorded for the catalyst prepared using tributyl borate.

Experiments 9-12: Synthesis of supported hybrid metallocene catalysts using different concentration of metallocene compound (E9 to E12)
Experimental procedure: 4 ml tributyl borate, used as a binder was added to 9 g slurry of supported titanium catalyst obtained in Experiment 2 containing 30 wt % of solid content, followed by addition of rac-dimethylsilylbis (1-indenyl) zirconium dichloride in varying amount as provided in Table 6, to obtain a reaction mixture. The reaction mixture was agitated at a speed of 400 rpm for 2 hours at 60 °C. After the reaction was completed, the supernatant liquid was decanted and the catalyst was washed 5 times with toluene and decanted to remove any unreacted component. The hybrid catalyst formed was stored in hexane under nitrogen atmosphere. The composition of the supported hybrid metallocene catalyst, synthesized as above is given in Table 6.

Table 6: Composition of the supported hybrid metallocene catalyst obtained in different experiments performed using different metallocene compound concentration
ExperimentComposition Weight of metallocene compound (mg) Magnesium (wt%) Titanium (wt%) Zirconium (wt%) Chlorine (wt%)
E9 75 16.3 2.2 0.2 52.2
E10 250 16.7 1.9 0.6 51.4
E11 350 16.4 1.8 0.9 53.4
E12 500 15.7 1.6 1.2 51.7
The composition of the catalysts of experiments 9 to 12 had magnesium content in the range of 15.7 to 16.7 wt%, titanium content was found to be in the range of 1.6 to 2.2 wt%. The highest zirconium content was achieved in E12, wherein high amount of metallocene compound was used.
Experiment 13 and 14: Effect of masking compound on slurry polymerization of propylene using supported titanium catalyst

4-vinyl cyclohexene 9-vinyl carbazole
Slurry Polymerization: Polymerization reaction was performed using different masking compounds. Experiment 5 was repeated using 4-vinyl cyclohexene as a masking compound. Experiment 6 was repeated using 9-vinyl carbazole as a masking compound.
The masking compound was added to 2 liter hexane slurry containing supported titanium catalyst of Experiment 2 in the slurry polymerization reactor. The ratio of masking compound to titanium was varied as 0, 1500, 3000 and 6000 (mmole/mmole).
The polymerization process was followed as given in Experiment 3.

Table 7: The polymerization process results using 4-vinyl cyclohexene as a masking compound (E13)

S. No 4-Vinyl Cyclohexene/Ti
ratio Productivity (kg PP/g cat) MFI (g/10 min) Bulk Density (g/ml) Xylene soluble (%) Melting temp (°C)
1 0 10.5 1.1 0.50 1.3 162
2 1500.0 10.3 1.0 0.50 1.2 161
3 3000.0 9.4 0.99 0.5 1.4 162
4 6000.0 9.1 0.92 0.51 1.1 160

From Table 7 , it is evident that the productivity, and MFI of homo polymerization of propylene did not reduce significantly on increasing the concentration of masking agent. Bulk density of the polypropylene and isotacticity remains same in all cases even at higher concentration of masking compounds.

Table 8: The polymerization process results using 9-vinyl carbazole as a masking compound (E14)

S. No 9-Vinyl carbazole/Ti
ratio
Productivity (Kg PP/g cat) MFI (g/10 min) Bulk Density (g/ml) Xylene soluble (wt %)
1 0 8.5 2.5 0.5 1.3
2 1500.0 4.5 1.8 0.45 2.5
3 3000.0 4.1 2.3 0.43 2.3
4 6000.0 3.6 1.7 0.43 2.2

The productivity for the polymerization performed using 9-vinyl carbazole as a masking compound was found to be in the range of 3.6 to 4.5 kg pp/g catalyst. MFI ranges between 1.7 to 2.3 g/10 minutes.

Experiments 15-17 (E15 to E17): Supported hybrid metallocene catalyst synthesis by varying the concentration of tributyl borate
The experimental procedure was followed as given in experiments 9 to 12 by varying concentration of tributyl borate. The weight of metallocene compound was kept constant at 250 mg.

Table 9: Composition of Supported hybrid metallocene catalyst synthesized by varying the concentration of tributyl borate content
ExperimentComposition Volume of tributyl as a binder (mL) Magnesium (wt%) Titanium (wt%) Zirconium (wt%) Chlorine (wt%)
E15 2 16.3 1.7 0.2 50.0
E16 4 16.7 1.9 0.6 51.4
E17 8 15.7 1.6 0.6 50.6

The composition of the catalysts of experiment 15 to 17 were found to have magnesium content in the range of 15.7 to 16.7 wt%, and the titanium content was found to be in the range of 1.6 to 1.9 wt%.

Propylene slurry polymerization for supported hybrid metallocene catalyst
The polymerization procedure was followed as given in Experiment 3 by replacing supported titanium catalyst with supported hybrid metallocene catalyst.
Table 10: Polymerization process results for Supported hybrid metallocene catalyst synthesized by varying tributyl borate content

Experimentparameter Binder compound concentration (mmole) Productivity (g PP/ g catalyst) MFI (g/ 10minutes) Bulk Density Xylene soluble (wt%)
E15 8.7 1500 1.0 0.47 1.5
E16 17.4 6400 2.8 0.5 1.4
E17 34.8 1200 2.0 0.48 1.7
Figure 2 is a graph of productivity (of the polymerization) vs binder compound concentration Highest productivity was achieved for 17.4 mmole of tributyl borate as given in Figure 2. Decreasing the concentration of tributyl borate or increasing the concentration of tributyl borate significantly varies the productivity of propylene polymerization.
Experiment 18, 19 and 20 (E18, E19, E20): Stereo-rigid hybrid catalyst (rac-Dimethylsilylbis(1-indenyl)zirconium dichloride) and Non-stereo-rigid hybrid catalyst (ethyl bis(cyclopentadienyl) zirconium chloride) using borates as activator for C3 homo polymerization in slurry phase with vinyl cyclohexene as masking agent and its product characterization

The polymerization reaction in Experiment 18 was performed using a stereo-rigid hybrid catalyst, while the polymerization reaction in Experiment 19 was performed using a Non stereo-rigid hybrid catalyst.
The polymerization reaction was performed using vinyl cyclohexene as a masking agent for Experiment 18 and 19, while Experiment 20 was performed using stereo-rigid hybrid catalyst and styrene as a masking compound.
0.1 g supported titanium catalyst was mixed with triethyl aluminum co-catalyst, external donor and vinyl cyclohexene. The components were mixed in such proportions that the aluminum to titanium ratio was maintained at 250±5:1. The mole ratio of aluminum to external donor was maintained tot 3.0 ±0.2:1. The catalyst was employed to polymerize propylene in gas phase reactor under a constant propylene pressure of 5 kg/cm2 for 1 hour at 70 °C, followed by addition of 50 mmole of hydrogen to terminate the polymerization.
The results of the polymerization reaction are tabulated in Table 11.
Table 11: Polymerization results for experiment 18 and 19
Experimentparameter Masking compound: Ti ratio (mmole/mmole) Productivity (g PP/ g catalyst) MFI (g/ 10 minutes) Bulk Density Xylene soluble (wt%)
E18 1500 3570 1.1 0.48 1.7
E19 1500 1970 2.2 0.47 1.8
E20 1500 3250 1.3 0.48 2.6

It is observed that the productivity reduced significantly when borate based binder was used for non-stereorigid metallocene (1970 g PP/g cat) as compared to stereorigid metallocene (3250 g PP/g cat).

Experiment 21(E21): Gas phase propylene homo-polymerization and ethylene with propylene copolymerization with supported titanium catalyst using vinyl cyclohexene as masking compound
Supported titanium catalyst synthesis was performed as given in Experiment 2.
Gas Phase propylene homo-polymerization with magnesium supported titanium catalyst with:
Polypropylene resin was used as a seedbed in the gas phase reactor as a fluidization media. Masking compound Vinyl cyclohexene was used and masking compound/Ti ratio was 1500.
0.1 g supported titanium catalyst was mixed with triethyl aluminum co-catalyst, external electron donor and vinyl cyclohexene. The components were mixed in such proportions that the aluminum to titanium ratio was maintained at 250±5:1. The mole ratio of aluminum to external donor was 3.0 ± 0.2:1. The catalyst was employed to polymerize propylene in gas phase reactor under a constant propylene pressure of 7 kg/cm2 for 1 hour at 70°C followed by addition of 50 mmole of hydrogen to terminate the polymerization.
Table 11: Polymerization process results for Experiment 21
Without masking compound With masking compound
Productivity (Kg PP/ g catalyst) 2.1
1.8
MFI (g/ 10 min) 4.9 4.2
Bulk density (g/ml) 0.43 0.43
Xylene soluble (wt %) 1.4 1.9
From Table 11, it is evident that the use of masking compound during polymerization in experiment 21 does not alter the productivity much i.e. use of masking compound does not have adverse effect on homo-polymerization.
Copolymerization of ethylene with propylene: After 1 hour of homo polymerization, the polymerization was stopped and the reactor was cooled to 45 °C and the excess propylene was vented off. Modified triethyl aluminum and some amount of hydrogen were added and co-polymerization with ethylene-propylene mixture was started at 55°C to 80°C keeping C2/ (C2+C3) ratio of 0.35. The co-polymerization reaction was carried for a period of 20 minutes. The reactor was cooled to room temperature and the co-polymer was dried overnight.
Table 12: Co-polymerization performance and Product characteristics
Productivity (kg PP/g cat) Et (%) Ec (%) Rc (%)
1. Supported titanium catalyst without masking compound 2.1 16.91 69.70 24.26
2. Supported titanium catalyst with masking compound 1.9 17.30 57.50 24.10

The productivity of co-polymer produced using supported titanium catalyst does not change much on using supported titanium catalyst in combination with a masking compound. It is observed that the total ethylene content increased from 16.91% to 17.3%, while ethylene percentage in co-polymer decreased from 69.7% to 57.5% on using the supported titanium catalyst in combination with the masking compound.

Experiment-22 (E22): Gas phase propylene homo-polymerization and ethylene-propylene copolymerization for supported hybrid metallocene catalyst using vinyl cyclohexene masking compound

Supported hybrid catalyst Synthesis: In 9 g supported titanium catalyst (30%) slurry, 4 ml tributyl borate binder was added followed by addition of 250 mg rac-dimethylsilyl bis (1-indenyl) zirconium dichloride metallocene. The reaction was carried out at 60°C for 2-3 hours and agitator speed was maintained at 400 rpm. After the reaction was completed, the supernatant liquid was decanted and the catalyst was washed 5-6 times with toluene and decanted to remove any unreacted component. The hybrid catalyst formed was stored in hexane slurry in nitrogen atmosphere.
Table 13: Composition of the catalyst of Experiment 22
Elements Value
Magnesium (% wt) 16.7
Titanium (% wt) 1.9
Zirconium (% wt) 0.6
Chlorine (% wt) 51.4
Gas Phase homo-polymerization of supported hybrid metallocene catalyst with propylene: Polypropylene resin was used as a seedbed in the gas phase reactor as a fluidization media. Masking compound Vinyl cyclohexene was used and masking compound/Ti ratio was kept about 1500.
Supported hybrid metallocene catalyst (0.1 g) was mixed with triethyl aluminum co-catalyst and external donor and Vinyl cyclohexene. The components were mixed in such proportions that the aluminum to titanium ratio is maintained at 250±5:1. The mole ratio of aluminum to external electron donor kept at 3.0 ±0.2 :1. The catalyst was employed to polymerize propylene in a gas phase reactor under a constant propylene pressure of 7 kg/cm2 for 1 hour at 70°C followed by addition of 50 mmole of hydrogen to terminate the polymerization.

Table 14: Polymerization process results
Parameters Without masking compound With masking compound
Productivity (Kg PP/ g catalyst) 0.45 1.6
MFI (g/ 10 min) 4.2 4.9
Bulk density (g/ml) 0.45 0.43
Xylene soluble (wt %) 0.3 0.4
The productivity of the polymer increased from 0.45 kg/ g cat to 1.6 kg/g cat, MFI increased from 4.2 to 4.9 g/10 minutes on using the supported hybrid metallocene catalyst with masking compound.
Copolymerization of ethylene with propylene: After 1 hour of homo polymerization, the polymerization was stopped and the reactor was cooled to 45 °C and the excess propylene was vented. Triethyl aluminum and 200 mL hydrogen were added and co-polymerization with ethylene-propylene mixture was started at 55 to 80 °C keeping C2/ (C2+C3) ratio about 0.35. The co-polymerization reaction was carried for a period of 10 to 30 min. The reactor was cooled to room temperature and the co-polymer was dried overnight.

Table 15: Co-polymerization performance and Product characteristics
Parameters Productivity (Kg PP/g cat) Et (%) Ec (%) Rc (%)
1. Supported hybrid catalyst without masking compound 0.9 11.9 78.6 15.1
2. Supported hybrid catalyst with masking compound 1.6 26.70 53.20 50.20

It is observed that the productivity of the co-polymer produced using supported hybrid metallocene catalyst increased on use of supported hybrid metallocene catalyst in combination with the masking compound. The total ethylene content increased from 11.9% to 26.7%, while ethylene percentage in co-polymer decreased from 78.6% to 53.2% on using the supported titanium catalyst in combination with the masking compound. Rc determines dispersed rubber content in the copolymer. Supported hybrid catalyst in presence of masking compound gives increased rubber content i.e. 50.20%. Ec is ethylene content in wt % in the dispersed phase and Et is weight of ethylene. It was observed that the rubber content has considerably changed from 15.1% to 50.20%.

TECHNICAL ADVANCEMENT AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a supported hybrid metallocene catalyst that can be
• used for olefin polymerization;
• used for improved metallocene content in the hybrid catalyst comprising a magnesium supported titanium pro-catalyst and a metallocene compound;
• used for the process of polymerization, which is helpful in controlling the composition of the copolymer of propylene obtained; and
• used for obtaining polypropylene, which exhibit improved characteristics as compared to the polypropylene obtained through conventional polymerization process.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of experiment only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:1. A process for the preparation of a supported hybrid metallocene catalyst, said process comprising the following steps:
a. charging a predetermined amount of a pro-catalyst comprising
i. at least one magnesium compound selected from the group consisting of magnesium dichloride, magnesium methoxide, magnesium ethoxide and magnesium isopropoxide,
ii. at least one titanium component selected from the group consisting of elemental titanium, TiCl4, Ti(OC2H5)3Cl, Ti(OC3H7)3Cl and Ti(OC4H9)Cl3; and
iii. an internal electron donor;
and a predetermined amount of a first fluid medium into a reactor to obtain a first slurry,
wherein, said pro-catalyst is magnesium chloride supported titanium catalyst;
b. adding a predetermined amount of a borate based binder of formula (I), and a metallocene compound to said first slurry to obtain a first mixture,

Formula (I)
wherein R1, R2 and R3 are at least one independently selected from a C1 to C8 linear or branched alkyl and arylalkyl groups;
c. stirring said first mixture at a temperature in the range of 40 °C to 80 °C for a time period in the range of 1 hour to 5 hours to obtain a second mixture;
d. separating solid from said second mixture;
e. washing said solid, with a second fluid medium to remove the unreacted species; and
f. drying said washed solid to obtain the supported hybrid metallocene catalyst.
2. The process as claimed in claim 1, wherein said borate based binder is at least one selected from a group consisting of trimethyl borate, triethyl borate, tri-isopropyl borate, tributyl borate and triphenyl borate.
3. The process as claimed in claim 1, wherein said metallocene compound is a stereo-rigid or non-stereo-rigid metallocene compound comprising at least one metal selected from the group consisting of Zr, Hf and Ti as a central metal atom.
4. The process as claimed in claim 1, wherein said metallocene compound is stereo-rigid rac-dimethyl silylbis(1-indenyl) zirconium dichloride.
5. The process as claimed in claim 1, wherein said internal electron donor is di-isobutyl phthalate.
6. The process as claimed in claim 1, wherein said first fluid medium and second fluid medium are at least one independently selected from the group consisting of hexane, decane, isopentane and toluene.
7. The process as claimed in claim 1, wherein the molar ratio of the amount of said magnesium compound and the amount of said titanium component is in the range of 0.05 to 0.25.
8. The process as claimed in claim 1, wherein the molar ratio of the amount of said magnesium compound and the amount of said internal electron donor is in the range of 3 to 10.
9. The process as claimed in claim 1, wherein the molar ratio of the amount of said magnesium compound and the amount of said borate based binder is in the range of 5 to 15.
10. The process as claimed in claim 1, wherein the molar ratio of the amount of said magnesium compound and the amount of said metallocene compound is in the range of 15:1 to 100:1.
11. A process of polymerization of at least one olefin using the supported hybrid metallocene catalyst as claimed in claim 1, said process comprising the following steps:
a. introducing a predetermined amount of said supported hybrid metallocene catalyst in a reactor containing a predetermined amount of a third fluid medium;
b. adding to said reactor, predetermined amounts of a masking compound, an organoaluminum co-catalyst and an external electron donor to obtain a second slurry; wherein the ratio of elemental aluminum to elemental titanium is in the range of 230:1 to 270:1 and the ratio of said external electron donor and elemental titanium of said titanium component is in the range of 1:1 to 5:1;
c. charging at least one olefin to said reactor containing said second slurry; and
d. subjecting said at least one olefin to polymerization in the presence of said supported hybrid metallocene catalyst contained in said second slurry at a temperature in the range of 60 °C to 100 °C and a pressure of olefin in the range of 1 bar to 6 bar to obtain a polyolefin.
12. The process as claimed in claim 11, wherein said masking compound is at least one selected from the group consisting of 4-vinyl cyclohexene, 9-vinyl carbazole and styrene.
13. The process as claimed in claim 11, wherein said organo-aluminum co-catalyst is at least one selected from the group consisting of triethylaluminum, tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, tri-isoprenylaluminum, tri-isobutylaluminum, ethyl aluminum sesquichloride, diethylaluminum chloride, di-isobutyl aluminum chloride, triphenylaluminum, tri-n-octylaluminum and tri-n-decylaluminum.
14. The process as claimed in claim 11, wherein said external electron donor is at least one selected from the group consisting of organosilane compounds, typically said external electron donor is dicyclopentyldimethoxysilane.
15. The process as claimed in claim 11, wherein the molar ratio of the amount of said pro-catalyst and the amount of said masking agent is in the range of 0.05 to 0.25.
16. A supported hybrid metallocene catalyst for olefin polymerization, said supported hybrid metallocene catalyst comprising:
a. a pro-catalyst comprising a magnesium compound and a titanium component, wherein said pro-catalyst is magnesium chloride supported titanium catalyst;
b. a borate based binder of formula I

Formula (I)

wherein, R1, R2 and R3 are at least one independently selected from a C1 to C8 linear or branched alkyl and arylalkyl groups; and
c. a metallocene compound.
17. The catalyst as claimed in claim 16, wherein said borate based binder is at least one selected from a group consisting of trimethyl borate, triethyl borate, tributyl borate, tri isopropyl borate, tributyl borate and triphenyl borate.
18. The catalyst as claimed in claim 16, wherein said metallocene compound is a stereo-rigid rac-dimethyl silylbis(1-indenyl) zirconium dichloride.
19. The catalyst as claimed in claim 16, wherein said internal electron donor is di-isobutyl phthalate.
20. The catalyst as claimed in claim 16, wherein the molar amount of said pro-catalyst and the amount of said masking agent of the amount of said magnesium compound and the amount of said titanium component is in the range of 0.05 to 0.25.
21. The catalyst as claimed in claim 16, wherein the molar ratio of the amount of said magnesium compound and the amount of said internal electron donor is in the range of 3 to 10.
22. The catalyst as claimed in claim 16, wherein the molar ratio of the amount of said magnesium compound and the amount of said borate based binder is in the range of 5 to 15.
23. The catalyst as claimed in claim 16, wherein the molar ratio of the amount of said magnesium compound and the amount of said metallocene compound is in the range of 15:1 to 100:1