CLIAMS:1. A process for preparing a catalyst for olefin polymerization; said process comprising the following steps:
a. reacting at least one magnesium alkoxide with at least one metal halide in the presence of at least one fluid medium to obtain an intermediate compound;
b. adding at least one aromatic alcohol to said intermediate compound to obtain a pro-catalyst; and
c. alkylating said pro-catalyst using an alkylating agent to obtain the catalyst.

2. The process as claimed in claim 1, wherein said magnesium alkoxide comprises 20 to 22% magnesium metal, 70 to 76% ethoxy and 4 to 8% methoxy.

3. The process as claimed in claim 1, wherein said metal halide is titanium tetrachloride.

4. The process as claimed in claim 1, wherein said fluid medium is chlorobenzene.

5. The process as claimed in claim 1, wherein said aromatic alcohol is phenol.

6. The process as claimed in claim 1, wherein said alkylating agent is triethyl aluminium. ,TagSPECI:FIELD
The present disclosure relates to a process for preparing a catalyst that can be used for polymerizing olefins.

BACKGROUND
Polyolefins particularly, polyethylene and polypropylene are commonly known as commodity plastic due to their use in high volume and wide range of applications. These polyolefins are in high demand for their characteristics such as low cost, chemical inertness, mechanical properties, processability and absence of potential toxicity. Polyethylene and polypropylene have many industrial applications including films, packaging, machinery parts, electrical insulators, inks, petroleum additives and hot melt adhesives.
Ziegler catalysts have helped to improve the productivity and product quality in olefin polymerization reaction by eliminating deactivation of catalyst, use of different solvents and polymer purification steps. It has been observed that immobilizing a pre-catalyst based on titanium compounds (also vanadium-based) onto a magnesium chloride supporting material results in improved productivity. Various other supports such as silica, alumina, MCM 40 and organic materials have also been studied for achieving enhanced productivity.
US7456126 suggests a process for preparing Ziegler–Natta catalyst by reacting a transition metal compound (in which the transition metal has an oxidation number of 4 or more and is selected from Groups IV, V or VI of the Periodic table and two or more aryloxy ligands are bound to the transition metal) with an organomagnesium compound to convert the transition metal compound to aryloxy ligand based catalyst. However, the process of US7456126 uses multiple steps to synthesize the catalyst.

Therefore, there is felt a need for a simple and economic process for the preparation of a catalyst by bounding aryloxy ligand to the transition metal for olefin polymerization.

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 provide a process for preparing a catalyst for olefin polymerization.
It is another object of the present disclosure to provide a process for preparing a catalyst for olefin polymerization by using aromatic alcohol (organic modifier).
It is yet another object of the present disclosure to provide a simple and economical process for preparing a catalyst for olefin polymerization.
It is still another object of the present disclosure to provide an olefin polymerization catalyst having enhanced productivity.
Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.

SUMMARY
The present disclosure provides a process for preparing an aryloxy ligand based catalyst system, the process involving the step of reacting at least one magnesium alkoxide and at least one metal halide in the presence of at least one fluid medium to obtain an intermediate. The so obtained intermediate is further treated with at least one aromatic alcohol to obtain an aryloxy metal pro-catalyst. The aryloxy metal pro-catalyst is further alkylated with at least one alkylating agent to obtain aryloxy ligand based catalyst system.
The aryloxy ligand based catalyst system obtained from the process of the present disclosure has higher activity and can be used in olefin polymerization.

DETAILED DESCRIPTION
Ziegler catalysts are used to achieve improved productivity and product quality during olefin polymerization. There are many routes to increase the productivity of the catalyst system; out of which two important routes are a) by introducing organo electron donor with the catalyst system during catalyst preparation leading to increased productivity and b) bonding organic groups to the active site (pre-catalyst) which will improve the activity or comonomer incorporation rate of the catalysts.
Various processes for preparation of supported alkoxy titanium catalyst exist, where alkoxy titanium complexes are first prepared and are supported on a support. However, there is still scope to improve the catalyst system to enhance performance of the catalyst system by one pot synthesis.
The inventors of the present disclosure provide a one pot synthesis for preparing catalyst which can be employed in olefin polymerization. The reaction is carried out in a glass reactor equipped with a stirrer, temperature and pressure indicator and nitrogen gas.
The process for preparing the catalyst used for preparing polyolefins, involves the following steps:
In the first step of the present disclosure, the reaction mixture comprising at least one magnesium alkoxide and at least one metal halide in the presence of at least one fluid medium is stirred at a speed ranging from 300 to 500 rpm at room temperature for 30 to 90 minutes to obtain an intermediate product.
In an exemplary embodiment, a titanium compound comprising at least a titanium-halogen bond is contacted with the solid support of magnesium alkoxide to obtain an intermediate in the form of Magnesium dichloride (MgCl2) support.
Magnesium alkoxide used in the present disclosure comprises C1-C5 carbon containing alcohols. In one embodiment, magnesium alkoxide is at least one selected from the group consisting of magnesium methoxide, magnesium ethoxide, magnesium propoxide, magnesium butaoxide and mixtures thereof. In a preferred embodiment of the present disclosure, the magnesium alkoxide is at least one selected from the group consisting of magnesium methoxide, magnesium ethoxide and mixtures thereof.
The metal halide used in the process of the present disclosure is at least one selected from the group consisting of titanium tetrachloride (TiCl4), triethoxy titanium chloride (Ti(OC2H5)3Cl), tripropoxy titanium chloride (Ti(OC3H7)3Cl) and titanium butoxy trichloride ( Ti(OC4H9)Cl3).
In one embodiment of the present disclosure the metal halide (Metal tetrachloride) is dissolved in a fluid medium to carry out the reaction. The fluid medium in accordance with the present disclosure includes, but is not limited to, chlorobenzene, bromobenzene, iodobenzene, dichlorobenzene, trichlorobenzene, dibromobenzene, tribromobenzene hexane, heptane and decane.
In an exemplary embodiment of the present disclosure, the ratio of metal halide to the magnesium alkoxide ranges from 6 to 1.
In the second step of the reaction of the present disclosure, the intermediate product obtained in the first step is treated with at least one aromatic alcohol (organic modifier) at room temperature and is stirred at a speed ranging from 300 to 500 rpm. The reaction mixture is then heated at a temperature ranging from 85-90 oC for 1 hour to obtain a pro-catalyst.
The aromatic alcohol (organic modifier) used in the process of the present disclosure is at least one selected from the group consisting of phenol, hydroquinone, 4-allyl-2-methoxyphenol, bisphenol and 2,2-methylenebis(4-tert-butyl-6-methylphenol). Typically, phenol is used as organic modifier for preparing an aryloxy ligand base catalyst. In one embodiment the organic modifier is the aromatic alcohol and the amount of aromatic alcohol used in the process of the present disclosure ranges from 5 to 25 g.
The interaction of organic ligand with the active site changes the steric and electronic environment around active Ti thereby, enhancing chain propagation/termination reaction i.e. leading to increased productivity.
In the third step of the present disclosure, the pro-catalyst system obtained in the second step is reacted with at least one alkylating agent in the temperature range of from 30 to 90 oC to form the reaction mixture of the catalyst system. The process of alkylation is required to activate the pro-catalyst. After addition of the alkylating agent, the reaction mixture is stirred at room temperature for 5 minutes and then heated in the temperature range of 25-80 oC. The reaction mixture is allowed to stirr for one hour. In one embodiment the alkylating agent is dissolved in a dry solvent and added dropwise into the reaction mixture.
In an exemplary embodiment of the present disclosure the alkylating agent is alkyl aluminium. The alkyl aluminium is selected from the group consisting of triethyl aluminium, tridecyl aluminium, tri-n-butyl aluminium, tri-isopropyl aluminium, tri-isoprenyl aluminium, tri-isobutyl aluminium, ethyl aluminium sesquichloride, diethyl aluminium chloride, di-isobutyl aluminium chloride, triphenylaluminium, tri-n-octylaluminium and tri-n-decylaluminium.
The solvent used for dissolving the alkylating agent is selected from the group consisting of decane, pentane, hexane, heptane and chlorobenzene.
After 1 hour of stirring, the stirring of the reaction mixture is stopped and the reactor is depressurized. Due to this, the temperature of the reaction/reaction mixture drops to 30oC. The reaction mixture is allowed to cool and settle. The liquid phase of the cooled reaction mixture is decanted and the residue is washed with 300 ml anhydrous hexane for 3-4 times. Anhydrous hexane is removed by decantation followed by drying under vacuum oven at 40 oC to obtain a dry solid catalyst.
The reaction of the present disclosure for preparing catalyst is a one pot synthesis of magnesium supported aryloxy titanium complexes by the in-situ generation of an intermediate (magnesium dichloride) by reacting magnesium alkoxide with metal halide followed by incorporating aryloxy ligand on active site (titanium) of the support. The catalyst system prepared by optimum concentration of organic compound shows better productivity in comparison to catalyst system that are not modified by an organic compound.
In the present process, the aforestated reactants are used in predetermined quantities and proportions with respect to each other.
In another aspect of the present disclosure, the process for the polymerization of olefin is provided. The process involves polymerization of olefin in presence of an aryloxy ligand base catalyst. The polymer obtained in presence of the aryloxy ligand base catalyst of the present disclosure is observed to exhibit higher productivity.
The present disclosure is further illustrated herein below with the help of following examples. The examples used herein are intended merely to facilitate an understanding of 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 examples should not be construed as limiting the scope of embodiments herein. The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale.
Experimental Details:
Example 1 below describes a process for the preparation of an aryloxy ligand based catalyst. A comparative study was carried out without the use of an organic modifier (phenol).
Example 2 below describes the polymerization performance of the aryloxy ligand base catalyst system in accordance with the present disclosure
Example 1:
Preparation of Mg-Supported Ziegler catalyst containing aryloxy ligands:
In a 500 ml round bottom flask, 3.05 g of magnesium alkoxide support was added. Magnesium alkoxide support contains 22% of Mg, 7% of methoxy and 71% ethoxy. 100 ml of chlorobenzene was added to the magnesium alkoxide support and stirred under nitrogen atmosphere.
Calculated amount of pure TiCl4 was added slowly to the reaction mixture (Magneisum alkoxide support and chlorobenzene) under stirring at room temperature. After completion of TiCl4 addition, predetermined amount of phenol (organic modifier) was added slowly to the above reaction mixture. After complete addition of phenol, the temperature of reaction was raised from room temperature to 90oC and the stirring was maintained for 1 hour. After one hour, the stirring was stopped and allowed to settle at 30 oC temperature. When the reaction mixture was cooled to 30 oC, the liquid phase was decanted and the residue was washed with 300 ml of anhydrous hexane. The residue was washed three times using 300 ml of anhydrous hexane each time. The residue was vacuum dried at 50 oC.
Four kinds of Magnesium supported aryloxy ligand containing titanium catalyst were synthesized by the reaction of organic modifier and TiCl4 with and without magnesium alkoxide as a support precursor. The organic modifier in the present disclosure is aromatic alcohol.
Catalyst 1 was prepared without use of magnesium alkoxide. Catalyst 2, 3 and 4 were prepared with the use of magnesium alkoxide as magnesium support.
The comparative catalyst was prepared without use of organic modifier (phenol) using the same reaction procedure and reaction condition and results are given in table 1.
Table 1: Catalyst composition by one-pot reaction of titanium compound and organic modifier:
Sr. No. Catalyst Magnesium alkoxide (g) TiCl4 (ml) Phenol (g) Ti
(wt%) Mg (wt%)
1 Catalyst 1 -- 8.9 7.5 6.4 ----
2 Catalyst 2 3.05 8.9 7.5 2.4 19.5
3 Catalyst 3 3.05 17.89 7.5 7.1 16.5
4 Catalyst 4 3.05 8.9 15 10.6 12.5
5 Comparative catalyst 7.5 23 - 7.7 12

From table 1, it is observed that after supporting aryloxy ligand base titanium active site, the titanium content into the catalyst significantly reduced. However, with increasing TiCl4 quantity during catalyst preparation, the weight percent of Ti into the catalyst increases. The same phenomenon is also observed when the amount of organic compound is increased during catalyst preparation.

Example 2: Ethylene polymerization
Ethylene polymerization was carried out in a 1 liter glass reactor equipped with a stirrer, temperature and pressure indicator, feeding line for catalyst, ethylene and nitrogen. The triethyl aluminium was served as co-catalyst for this catalyst system.
In a 100 ml three neck round bottom flask, 50 ml of anhydrous decane, calculated amount of triethylaluminium (TEA (Al/Ti=250)) in decane solution and 20 mg of the synthesized catalyst were taken. The reactants were mixed together and stirred at room temperature for 5 min and thereafter introduced to the magnesium support through the catalyst feeding line by using nitrogen pressure.
Under continuous stirring, the ethylene pressure was maintained at 2 bar for a one hour. At the end of one hour the reactor was depressurized and the temperature was dropped to 30 oC to obtain a polymer. The recovered polymer was dried in vacuum oven at 40 oC.

Table 2: Ethylene polymerization catalyzed by different catalysts
Sr. No. Catalyst Temperature Deg C Ethylene pressure (Bar) Time (hour) Productivity (Kg of PE/gm catalyst) Bulk density (Untapped) Bulk density
(Tapped)
1 Catalyst 1 80 2 1 0.1 0.14 0.16
2 Catalyst 2 80 2 1 0.26 0.26 0.28
3 Catalyst 3 80 2 1 0.7 0.15 0.18
4 Catalyst 4 80 2 1 0.08 0.14 0.17
5 Comparative Catalyst 80 2 1 0.3 0.08 0.09

The catalytic activities of catalyst 1 to 4 and the product properties are summarized in table 2. From the table 2, it is observed that after immobilization of the catalyst onto the magnesium support, the catalytic activity increases. With the increase of TiCl4 quantity during catalyst preparation, catalyst activity dramatically improved (Catalyst 3) as compared to comparative catalyst .
However, there is a negative impact on catalytic productivity after increasing phenol quantity (Catalyst 4). Significant improvement of bulk density of the synthesized polymer is observed in case of catalyst 2.

TECHNICAL ADVANCES
? A process for preparing a catalyst that has higher activity.
? A process for preparing a catalyst that is simple and cost effective.
? A process for preparing a catalyst increases the purity of the polymerized product when used in olefin polymerization.
? A process for preparing a catalyst that is one pot reaction.

The exemplary embodiments herein quantifies the benefits arising out of this disclosure and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of 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 examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein has been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments 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.