TECHNICAL FIELD

The present invention relates to a process for preparing a catalyst support comprising a reaction of magnesium (Mg) precursor with alcohol using halide compound as an activator, wherein a modifier is incorporated in said reaction; and also a catalyst support obtained from said process. The present invention further relates to a process for preparing an olefin polymerization catalyst comprising a transition metal compound of one of transition metal groups IV to VI in the Periodic Table of Element, di-isobutyl phthalate or dibutyl phthalate (DBP) and a catalyst support, wherein said catalyst support comprising Mg(OEt) ₂ and a modifier; and also an olefin polymerization catalyst prepared from mentioned process. Finally, a process for polymerizing olefin is preformed in the presence of the catalyst prepared by the specified process in this invention or the one having characteristic as specified in this invention.

BACKGROUND OF THE INVENTION

In olefin polymerization, a catalyst, specifically Ziegler-Natta catalyst, plays a major role in controlling, for example, morphology (including size and shape), stereo-regularity, bulk density, etc. of polymer products. The optimum particle size and shape of catalyst leads to a resultant polymer having controlled morphology. In addition, the shape of resultant polymers is the same as the shape of the catalysts. A spherical shape is preferred giving to its benefit to enhance flowability and avoid clogging in the polymerization system. Typically, Ziegler-Natta catalyst is a solid support based on titanium compound which is used in combination with co-catalyst organometallic compounds such as triethylalurninium. To increase an activity of catalysts, the controlled particle size, particle size distribution, shape and porosity of catalysts have been improved. There have been many attempts to develop a method or process for preparing solid supports having controlled particle size and shape to provide an optimum morphology of catalysts. One of classical methods for controlling particle size of catalysts disclosed in prior arts is grinding the solid support prior to a step of catalyst synthesis.

US 5,556,820 discloses a catalyst component for olefin polymerization having controlled particle size and particle size distribution. The catalyst component is obtained from the reaction of metallic magnesium, alcohol and a specific amount of halogen and/or halogen-containing compound, wherein the amount of halogen is much greater than being used as an initiator which is in a range from 0.019 to 0.06 gram-atom per one mole of metallic magnesium. The invention further discloses a catalyst composition consisting of the catalyst component obtained from above reaction, a titanium compound, and optional electron donor compound.

WO 2009/084799 Al discloses a method for preparing dialkoxy magnesium which is used as a catalyst support for olefin polymerization. The method comprises a step of reacting magnesium metal and alcohol in the presence of bromine as an initiator. The preferred alcohol of the invention is one or more selected from a group consisting of Ci-C aliphatic and aromatic alcohols.

It is noticeable that none of aforementioned preparation methods for magnesium-based catalyst support applies a modifier for controlling morphology or properties of the catalyst support as well as the catalyst obtained from the catalyst support as specified in this invention.

SUMMARY OF INVENTION

The present invention relates to a process for preparing a catalyst support comprising a reaction of magnesium (Mg) precursor with alcohol using halide compound as an activator, wherein a modifier is incorporated in said reaction; and also a catalyst support obtained from said process. The present invention further relates to a process for preparing an olefin polymerization catalyst comprising a transition metal compound of one of transition metal groups IV to VI in the Periodic Table of Element, di-isobutyl phthalate or dibutyl phthalate (DBP) and a catalyst support, wherein said catalyst support comprising Mg(OEt) ₂ and a modifier; and also an olefin polymerization catalyst prepared from mentioned process. Finally, a process for polymerizing olefin is preformed in the presence of the catalyst prepared by the specified process in this invention or the one having characteristic as specified in this invention.

The purpose of this invention is to prepare a porous spherical catalyst support comprising Mg(OEt) ₂ and the modifier; having relatively uniform dimension ranging from 3 to 120 μηι, preferably 35 to 65 μηι; having a pore volume range from 0.05 to 0.25 cc/g; and having a bulk density of 0.25 to 0.45 g/cc. This catalyst support is advantageous to a process of olefin polymerization catalyst since it generates a spherical catalyst with higher H response. This provides a decrease in H ₂ consumption during a termination reaction in the olefin polymerization, and also enhanced flowability of polymers and less blockage occurrence in the polymerization process. This support also provides the catalyst which could produce the lower xylene solubility (higher isotactic) polymer when increasing the Al compound co-catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.

Figure 1 shows SEM micrograph of catalyst supports prepared by the process according to this invention.

Figure 2 shows SEM micrograph of catalyst prepared by the process according to this invention.

DETAILED DESCRIPTION

In the first aspect, the present invention relates to a catalyst support comprising magnesium alkoxide and modifier, wherein the modifier is selected from a group consisting of organosilicon compounds, organophosphorus compounds, organoboron compounds, and a mixture thereof.

According to the present invention, organosilicon compounds can be selected from a group consisting of tetraethyl orthosilicate, orthosilicic acid, chlorosilanes, and silyl ether.

The organophosphorus compounds can be selected from a group consisting of tributyl phosphate, phosphatidylcholine, and triphenylphosphate.

The organoboron compounds can be selected from a group consisting of triethyl borate or other borate compounds wherein Ri, R ₂ , and R ₃ are saturated hydrocarbon containing from 1 to 5 carbon atoms, which may be the same or different.

In some embodiments, the modifier is selected from a group consisting of triethyl borate (TEB), tetraethyl orthosilicate (TEOS), tributyl phosphate (TBP), and a mixture thereof. Triethyl borate (TEB) is particularly preferred as the modifier in this invention. In some embodiments, the magnesium alkoxide is selected from magnesium ethoxide (Mg(OEt) ₂ ), magnesium propoxide (Mg(OPr) ₂ ) or magnesium butoxide (Mg(OBu) ₂ ). The preferred magnesium alkoxide is magnesium ethoxide (Mg(OEt) ₂ ).

In preferred embodiment, a molar ratio of modifier: Mg (of Mg(OEt) ₂ ) is in a range of 0.005: 1 to 1 : 1.

In preferred embodiment, a molar ratio of TEB: Mg (of Mg(OEt) ₂ ) is in a range of 0.05: 1 to 1 : 1.

In preferred embodiment, a molar ratio of TEOS: Mg (of Mg(OEt) ₂ ) is in a range of 0.02: 1 to 0.1 : 1.

In preferred embodiment, a molar ratio of TBP: Mg (of Mg(OEt) ₂ ) is in a range of

0.01 : 1 to 0.5: 1.

The obtained catalyst support is a porous particle, and in certain embodiment, the catalyst support has a pore volume ranging from 0.05 to 0.25 cc per gram of catalyst support. In some embodiment, the porous particles have spherical shape. The porous spherical catalyst support has a bulk density of 0.25 to 0.45 g/cc. The catalyst support has a particle size based on largest cross-sectional diameter ranging from 3 to 120 μηι, preferably ranging from 35 to 65 μηι. A span, describing a width of particle size distribution, is on average less than 2, regularly less than 1. The span is calculated from

span = (d ₉ o-dio)/d ₅ o

where djo, dso and d value obtained in measurement of the particle size distribution represent the particle size when the integrated value is 10%, 50% and 90%, respectively.

The catalyst support of this invention yields the technical results, for example, improved bulk density and pore volume of synthesized support and final catalyst, providing final catalyst with good hydrogen respond. Moreover, the catalyst produced using modified support produce polymer powder with lower xylene solubility than the one obtained from non-modified support. This implies that the modified support affects the stereo -regularity of the final catalyst.

It's apparent that an incorporation of modifier can control the particle size and porosity of the catalyst support, i.e. an increase in amount of modifier results in a decrease in particle size of catalyst support, conversely an increase in number of pores. This enhances a surface area of catalyst support, leading to greater active sites (i.e. higher reaction rate). In the second aspect, the present invention also relates to a process for preparing a catalyst support comprising a reaction of magnesium (Mg) precursor with alcohol by using halide compound as an activator, and a modifier wherein the modifier is selected from a group consisting of organosilicon compounds, organophosphor ^o us compounds, organoboron compounds, and a mixture thereof.

The specific examples of the modifier belong to the group of organosilicon, organophosphorus and organoboron compounds, which can be used in the catalyst support preparation process of this invention, are selected from a group consisting of triethyl borate (TEB), tetraethyl orthosilicate (TEOS), tributyl phosphate (TBP), and a mixture thereof. The preferred modifier is triethyl borate (TEB).

In some embodiments, a molar ratio of modifier: Mg (of magnesium precursor) is in a range of 0.01:1 to 0.06:1. In preferred embodiments, the molar ratio of TEB: Mg (of magnesium precursor) in the catalyst support is in a range of 0.01:1 to 0.03:1. In preferred embodiments, the molar ratio of TEOS: Mg (of magnesium precursor) in the catalyst support is in a range of 0.02:1 to 0.06:1. In preferred embodiments, the molar ratio of TBP: Mg (of magnesium precursor) in the catalyst support is in a range of 0.01 : 1 to 0.03 : 1.

According to the present invention, the specific molar ratio between magnesium precursor and each modifier as defined above can give benefits of improved bulk density, particle size, and pore volume of modified support. For example, increasing TEOS ratio results in an increase in bulk density of synthesized support. In case of TEB, increasing TEB results in an increase in pore volume but decreases of particle size.

In the present invention, alcohol is used as one of starting material and solvent in the magnesium alkoxide-based catalyst support. The alcohol having 2-4 carbon atoms is preferred.

In some embodiments, the alcohol is selected from ethanol, propanol, or butanol and a mixture thereof. The preferred alcohol is ethanol.

In some embodiments, the preferred molar ratio of ethanol: Mg (of magnesium precursor) in the catalyst support is in a range of 5:1 to 9:1. However, an excess amount of alcohol is applicable in this invention.

In some embodiments, the halide compound is I ₂ or MgCl ₂ .

In some embodiments, the molar ratio of activator: Mg (of magnesium precursor) in the catalyst support is in a range of 0.0045:1 to 0.0075:1. The process for preparing catalyst support in this invention comprises the following steps:

- adding Mg suspended in alcohol into activator dissolved in alcohol,

stirring a mixture using 90- 110 rpm speed and raising a temperature to 60-95°C, adding a modifier into the mixture and stirring for a certain time period,

- periodically adding more Mg suspended in alcohol into the mixture, preferably 3-4 times,

allowing the reaction to complete for certain time period,

- washing the obtained product , and finally

drying the final product

In the third aspect, the present invention relates to a catalyst for olefin polymerization obtained from a reaction of a transition metal compound of one of transition metal groups IV to VI in the Periodic Table of Element, di-isobutyl phthalate or dibutyl phthalate (DBP), and the catalyst support, where the catalyst support is prepared from the abovementioned process and has characteristic as described above. The catalyst according to the present invention comprises transition metal, Mg, CI, and modifier.

In preferred embodiments, the transition metal compound is titanium tetrachloride

(TiC ).

The prepared catalyst comprises Ti, Mg, CI, and di-isobutyl phthalate or dibutyl phthalate (DBP).

In preferred embodiment, the prepared catalyst comprise 3wt% of Ti based on the total weigh of catalyst. In preferred embodiments, a molar ratio of boron (B): titanium (Ti) in the catalyst is 0.01 :1 to 0.03:1. In preferred embodiments, a molar ratio of phosphorus (P): titanium (Ti) in the catalyst is 0.01 :1 to 0.03: 1. In preferred embodiments, a molar ratio of silicon (Si): titanium (Ti) in the catalyst is in a range of 0.03 : 1 to 0.07: 1.

In preferred embodiments, the catalyst comprises 0.0004 to 0.013 wt% of boron (B) based on the total weigh of catalyst. In preferred embodiments, the catalyst comprises 0.03 to 0.09 wt% of phosphorus (P) based on the total weigh of catalyst. In preferred embodiments, the catalyst comprises 0.03 to 0.07 wt% of silicon (Si) based on the total weigh of catalyst

The obtained olefin polymerization catalyst is a porous particle, and in certain embodiment, the catalyst has a pore volume ranging from 0.05 to 0.25 cc per gram of said catalyst. The porous spherical catalyst has a bulk density of 0.25 to 0.45 g/cc. The porous spherical catalyst has a particle size based on largest cross-sectional diameter ranging from 3 to 120 μιη, preferably ranging from 35 to 65 μηι.

According to the present invention, the catalyst yields good technical results in high catalytic activity. The high pore volume support results in high pore volume of final catalyst. Therefore, the high pore volume catalyst provides the active size for polymerization reaction, resulted in high catalytic activity of the final catalyst. The increasing bulk density and spherical morphology of support affect to the bulk density and also morphology of the final catalyst. Hence, the final catalyst produces high bulk density and increases flowability of polymer powder leading to increase of productivity. Moreover, the modifier effects to pore volume of support and final catalyst. Increasing of pore volume results in increase of co-monomer content that could produce high rubber polymer.

In the fourth aspect, the present invention relates to a process for preparing a catalyst for olefin polymerization comprising a transition metal compound of one of transition metal groups IV to VI in the Periodic Table of Element, di-isobutyl phthalate or dibutyl phthalate (DBP) and a catalyst support, wherein said catalyst support comprising Mg(OEt) ₂ and a modifier selected from a group consisting of organosilicon compounds, organophosphorus compounds, organoboron compounds, and a mixture thereof.

In some embodiment, the transition metal compound is preferably titanium tetrachloride (TiCL _t ).

Ιϊι preferred embodiment, the catalyst support used in the process for preparing olefin polymerization catalyst in this invention is prepared from the abovementioned process and has characteristic as described above.

In some embodiments, a molar ratio of Ti: Mg (of catalyst support) is in a range of 2:1 to 6:1. In preferred embodiment, a molar ratio of Ti: DBP in the catalyst is in a range of 30:1 to 40:1.

The process for preparing catalyst in this invention comprises the following steps:

slowly mixing transition metal compound with magnesium alkoxide in toluene solution at a temperature below 25 °C for certain time period,

- increasing the mixture's temperature until higher than 100°C,

adding di-isobutyl phthalate or dibutyl phthalate to the mixture,

allowing the reaction to proceed for few hours,

cooling down the temperature to 65-85°C, decanting and washing the obtained product with toluene,

adding the fresh toluene into obtained product,

adding the transition metal compound,

allowing the reaction to proceed at 80-100°C for few hours,

cooling down the temperature to 65-85 ^° C, and finally

- washing and drying the final product

In the fifth aspect, the present invention relates to a process for polymerization of olefin, in the gas phase, at a temperature in a range of 60 to 90°C and a pressure in a range of 25 to 45 bar, wherein the polymerization is performed in the presence of the catalyst prepared by the specified process in this invention or the one having characteristic as specified in this invention. In preferred embodiment, the catalyst is mixed with aluminum alkyl compound and optionally an external donor prior to polymerization step.

According to the present invention, aluminum alkyl compounds used in the olefin polymerization can be selected from a group consisting of triethylaluminium, ethylaluminum sesquichloride, diethylaluminum chloride, ethylaluminum dichloride, and triisobutylaluminum. The preferred aluminum alkyl compounds for this invention is triethylaluminum (TEA).

In some embodiments, the external donor is mixed with the catalyst for polymerizing olefin such as ethylene, propylene. The external donor may be silane compound, for example, cyclohexylmethyldimethoxysilane, dicyclopentyldimethoxysilane, diisopropyldimethoxyilane, and n-propyldimethoxysilane.

The catalyst manufactured using this catalyst support have higher H ₂ response, hence; this would reduce ¾ consumption during a termination reaction in the olefin polymerization. Moreover, using spherical catalyst support would produce the spherical catalyst, offering better fiowability of polymers and less blockage occurrence in the polymerization process. As commonly known, the fiowability is of great importance for olefin polymerization since this reflects to the production time. Consequently, high polymerization activity is exhibited providing a high catalyst product yield. Other features of the invention will become apparent in the course of the following description of exemplary embodiments which are given for illustration of the invention and are not intended to be limiting thereof. Example

Example 1

Preparation of Catalyst Support

Mg(OEt) ₂ was prepared in 1 L round bottom flask reactor equipped with mechanical stirrer and reflux condenser. After sufficient N ₂ replacement, 1.0 g of I ₂ used as an initiator and 40 ml of dehydrated ethanol were introduced, and then started stirring at 90 rpm. Next, the reaction temperature was raised to the desired temperature of 70°C. After dissolution of I ₂ at 70°C, 2.5 g of Mg suspended in 32 ml of ethanol and 1.75 ml of TEB as modifier were introduced into the reactor, and allowed 30 minutes reaction. Thereafter, 2.5 g of Mg suspended in 32 ml of ethanol was added repeatedly for 4 times every 30 minute. After completing addition of the mixture of Mg metal and ethanol, the temperature and stirring speed of the reactor were still maintained at refluxing state for 2 hours (aging). After completing aging step, the reaction mixture was cooled-down to room temperature, and the product was then washed for 3 times with 200 ml of hexane for each washing. Finally, the resulting product was dried to obtain Mg(OEt) ₂ as a solid white powder. The physical properties of obtained Mg(OEt) ₂ such as bulk density, average particle size and particle size distribution were analyzed.

Preparation of Solid Catalyst

Mg(OEt) ₂ based Ziegle-Natta catalyst was prepared in 1 L glass reactor equipped with agitator rotating at 150 rpm under N ₂ atmosphere. 250 ml of toluene and 40 g of Mg(OEt) ₂ were added under N ₂ atmosphere. Then, 80 ml of TiCLt was slowly dropped for approximately 2 hours, while the temperature of suspension was kept within 0-5°C. Thereafter, the temperature of mixture was gradually increased to 90°C and 10.80 ml of DBP was added. The mixture was then heated to 110°C and continuously stirred for 2 hours. Subsequently, the reaction product was washed with 150 ml of toluene for 3 times at 75°C. The resulting product was then added 250 ml of toluene and 80 ml TiC was introduced into the reactor, and the mixture was reacted for another 2 hours at 90°C. After completion of the reaction, the reaction product was washed with 150 ml of toluene for 3 times at 75°C, subsequent by 150 ml of hexane for 7 times at 40°C to obtain a solid catalyst component.

Polymerization testing

Catalyst performance was tested under gas phase polymerization condition in 10 L stainless steel reactor equipped with mechanical stirrer. Liquid propylene was vaporized by passing through evaporator unit before feeding into the reactor. Under N ₂ atmosphere, 100 g of polymer seeding (polypropylene) was added into the reactor. Then, the temperature was raised up to 45°C and the reactor was pressurized and purged with 5 bar of propylene gas for 3 times. The pressure was released, then, 10 mmol of TEA and 1 mmol of cyclohexyl-methyl- dimethoxysilane were subsequently added. Thereafter, 100 mg of prepared solid catalyst was loaded into the reactor. Around 0.5 bar of H ₂ was added at once and the temperature was raised to 70°C. The polymerization started by feeding propylene gas into the reactor and the total pressure was kept constant at 28 bar by controlling propylene feeding rate. After 1 hour of polymerization, the solid polypropylene polymer was collected. The properties of polymer such as melt flow index, bulk density, xylene soluble and molecular weight distribution were determined. The results are summarized in Table I.

Example 2

The experiment procedure of Example 1 was followed, except that 2.80 ml of TBP as modifier was used instead of TEB in the preparation of catalyst support procedure. The results are shown in Table 1.

Example 3

The experiment procedure of Example 1 was followed, except that 2.41 ml of TEOS as modifier was used instead of TEB in the preparation of catalyst support procedure. The results are shown in Table 1. Comparative Example

Preparation of Catalyst Support

Mg(OEt) ₂ was prepared in 1 L round bottom flask reactor equipped with mechanical stirrer and reflux condenser. After sufficient N ₂ replacement, 1.0 g of I ₂ used as an initiator and 40 ml of dehydrated ethanol were introduced, and then started stirring at 90 rpm. Next, the reaction temperature was raised to the desired of 70°C. After dissolution of I ₂ at 70°C, 2.5 g of Mg suspended in 32 ml of ethanol was introduced into reactor, and allowed 30 minutes reaction. Thereafter, 2.5 g of Mg suspended in 32 ml of ethanol was added repeatedly for 4 times every 30 minute. After completing addition of the mixture of Mg metal and ethanol, the temperature and stirring speed of the reactor were still maintained at refluxing state for 2 hours (aging). After completing aging step, the reaction mixture was cooled-down to room temperature, and the product was then washed for 3 times with 200 ml of hexane for each washing. Finally, the resulting product was dried to obtain Mg(OEt) ₂ as a solid white powder. The physical properties of obtained Mg(OEt) ₂ such as bulk density, average particle size and particle size distribution were analyzed.

Preparation of Solid Catalyst and Polymerization testing

The procedure of solid catalyst preparation and polymerization of Example 1 was followed. The results are shown in Table I.

Table I

Example Comp.

Example

Unit 1 2 3

Support Modifier : Mg mole 0.02 0.02 0.02 -

Bulk density g/cm ³ 0.3984 0.3344 0.2804 0.3004

Average Particle size μιη 47.83 46.40 63.62 56.58

Particle size 1.53 1.72 0.92 1.4 distribution

Solid Catalyst Ti content wt.% n.d n.d n.d. 2.55

Remained modifier mg/kg 85.58 603.79 - -

Polymerization Activity g PP/g cat 23,700 22,110 - 21,685

Melt flow index g/10 min 17.86 15.50 - 11.58

Bulk density g/cc 0.47 0.47 - 0.45

Xylene soluble wt.% 1.13 2.37 - 1.97

MWD - 4.22 7.36 - 6.92