Zeigler-natta catalyst having particle size distribution with a span of less than one

Abstract

The present disclosure relates to a process for obtaining a Zeigler Natta catalyst having a particle size distribution with a span difference of less than one. The process is simple and there is no requirement for stringent control on raw material or catalyst synthesis process. The obtained catalyst fractions are used in different polymerization technology and hence there is no generation of waste.

Description

[0001] ZEIGLER-NATTA CATALYST HAVING PARTICLE SIZE DISTRIBUTION WITH A SPAN OF LESS THAN ONE

[0002] FIELD

[0003] BACKGROUND

[0004] The background information herein below relates to the present disclosure but is not necessarily prior art.

[0005] Ziegler-Natta catalyst is used for the polymerization of propylene as well as ethylene. Different polymerization processes such as gas phase fluidized bed polymerization, stirred gas phase polymerization, slurry phase polymerization, bulk phase polymerization and solution phase polymerization are used in the production of these polymers. A uniquely designed catalyst is required for such polymerization processes and the key differentiator is particle size of the catalyst. For example, gas phase fluidized bed technology requires a catalyst with an average particle size of 22 to 25p and a catalyst smaller than lOp is not desired. It is because a smaller size catalyst gives smaller size polymer resins (fines) in the polymerization process. Bigger size catalyst particles also tend to fragment and create fines in polymerization process, which is not desirable. Thus it is required to have catalyst with narrow particle size distribution.

[0006] For various polymerization reactions, different grades of catalysts are produced to fulfill such requirements. For instance, slurry phase polypropylene requires catalyst having 12 to I 5p average particle size; catalyst particles smaller than 8p and bigger than 18p are not desired. Slurry phase polyethylene technology requires catalyst having 7 to I Op average particle size, catalyst bigger than 16p is not desired.

[0007] Conventional methods address this challenge by refining the catalyst having varied particle size into desired fractions, to achieve required narrow particle size catalysts for different polymerization processes. However, preparing such desired particle size needs a precisely controlled process, a precursor with specific particle size, and different operating conditions for different grades of catalysts. This leads to complex, energy intensive and costly catalyst production processes. Therefore, there is felt a need to provide a process for obtaining a Zeigler Natta catalyst having a predetermined particle size distribution that mitigates the drawbacks mentioned herein above or at least provides a suitable alternative.

[0008] OBJECTS

[0009] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

[0010] It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.

[0011] Another object of the present disclosure is to provide a process for obtaining a Zeigler Natta catalyst having a predetermined size distribution with a span difference of less than 1.

[0012] Still another object of the present disclosure is to provide a process for obtaining Zeigler Natta catalyst having a predetermined size distribution with a span difference of less than 1, without specific requirement of a precursor particle size.

[0013] Another object of the present disclosure is to provide catalyst particles having desired particle size distribution which provide good control over polymerization process.

[0014] 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.

[0015] SUMMARY

[0016] In an aspect the present disclosure relates to a process for obtaining a Zeigler Natta catalyst having a predetermined particle size distribution with a span difference of less than one, the process comprises the steps of mixing Zeigler Natta catalyst in a first fluid medium to obtain a catalyst slurry (14a). An apparatus (10) having a column (12) is arranged. A second fluid medium is continuously fed (16a) from an operative bottom (16) of the column (12) at a first predetermined velocity to obtain a fluidized bed in the column (12), the column (12) having a first opening (14) at an operative top to receive a first discharge (14b) from the column (12). The catalyst slurry (14a) is fed to the column (12) to blend with the fluidized bed. The velocity of the second fluid medium is increased to a second predetermined velocity to enable the catalyst slurry to be entrained in the first discharge (14b), and receiving the first discharge in a cyclone separator (22) configured with a first outlet (24) and a second outlet (26). Catalyst particles are separated from the first discharge to obtain a second discharge (16b) and a settled catalyst fraction comprising Ziegler Natta catalyst particles having a predetermined mean particle size distribution with a span difference of less than one. The settled catalyst fraction comprising the Ziegler Natta catalyst particles is collected through the first outlet (24) into a collection tank (34). The second discharge (16b) is obtained through the second outlet (26) and fed to a buffer tank (28) for recirculating the second discharge to the column (12).

[0017] In an embodiment of the present disclosure, the mean particle size distribution of the Zeigler Natta catalyst particles in the settled fraction is in the range of 10 pm to 30 pm.

[0018] In an embodiment of the present disclosure, the span difference is in the range of 0.6 to 0.7.

[0019] In an embodiment of the present disclosure, the first fluid medium is a mineral oil having carbon number in the range of C22-C35.

[0020] In an embodiment of the present disclosure, the second fluid medium (16a) is selected from the group consisting of pentane, hexane, heptane, decane and a combination thereof.

[0021] In an embodiment of the present disclosure, the first discharge is a mixture of the first fluid medium, the second fluid medium and Zeigler Natta catalyst particles.

[0022] In an embodiment of the present disclosure, the second discharge is a mixture of the first fluid medium and the second fluid medium.

[0023] In an embodiment of the present disclosure, the first predetermined velocity is in the range of 0.07 cm / s to 0.075 cm / s.

[0024] In an embodiment of the present disclosure, the second predetermined velocity is in the range of 0.08 cm / s to 0. 18 cm / s.

[0025] In an embodiment of the present disclosure, the Ziegler Natta catalyst comprises magnesium alkoxide as a support, at least one titanium halide, at least one internal donor in at least one hydrocarbon medium.

[0026] In an embodiment of the present disclosure, the second fluid medium is supplied from a fluid tank (32) for any losses in the second discharge. In another aspect, the present disclosure relates to an apparatus for obtaining a Zeigler Natta catalyst having a predetermined particle size distribution with a span difference of less than one, the apparatus comprising:

[0027] A. a column (12) having a height (H) and a diameter (D) such that the ratio H / D is equal to or greater than 4; wherein the column comprising:

[0028] • a first opening (14) at an operative top of the column for receiving a catalyst slurry (14a) comprising a mixture of Zeigler Natta Catalyst and a first fluid medium and / or discharging a first discharge (14b) from the column; and

[0029] • a second opening (16) at an operative bottom of the column for receiving a second fluid medium (16a) and generating a fluidized bed;

[0030] B. a cyclone separator (22) in fluid communication with the column for receiving the first discharge (14b) through an inlet port (20), the cyclone separator is configured with a first outlet (24) to discharge a settled catalyst fraction comprising the Ziegler Natta catalyst particles having a predetermined particle size distribution with a span difference of less than one and a second outlet (26) to discharge a second discharge (16b);

[0031] C. a buffer tank (28) in fluid communication with the cyclone separator (22) for receiving the second discharge (16b) and recirculating the received second discharge to the column; and

[0032] D. a fluid tank (32) configured downstream the column (12) for providing the second fluid medium to the column.

[0033] In an embodiment of the present disclosure, the cyclone separator (22) includes means to keep the cyclone separator under inert atmosphere; wherein the inert atmosphere includes blanketing with nitrogen or argon.

[0034] In an embodiment of the present disclosure, the apparatus includes means for altering the flow rate of the second fluid medium (16a) into the column (12).

[0035] In an embodiment of the present disclosure, the column (12) comprises a bottom distributor plate (18) and a mesh to pass the second fluid medium (16a) into the column (12).

[0036] In an embodiment of the present disclosure, a collection tank (34) is configured downstream of the cyclone separator (22) to collect the settled catalyst fraction comprising the Ziegler Natta catalyst particles having a predetermined particle size distribution with a span difference of less than one.

[0037] In an embodiment of the present disclosure, a pump (30) is configured downstream of the buffer tank (28) for recirculating the second discharge (16b) to the column through the second opening.

[0038] In still another aspect, the present disclosure relates to a Zeigler-Natta catalyst having particle size distribution with a span difference of less than one obtained from the process of the present disclosure.

[0039] BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

[0040] The present disclosure will now be described with the help of the accompanying drawing, in which:

[0041] Figure 1 illustrates an apparatus for the obtaining a Zeigler Natta catalyst having a predetermined particle size distribution with a span difference of less than one, in accordance with the present disclosure.

[0042] LIST OF REFERENCE NUMERALS

[0043] 10: Apparatus

[0044] 12: Column

[0045] 14: First Opening

[0046] 14a: Catalyst slurry

[0047] 14b: First discharge

[0048] 16: Second Opening

[0049] 16a: Second Fluid Medium

[0050] 16b: Second Discharge

[0051] 18: Bottom Distributor Plate

[0052] 20: Inlet port IT. Cyclone Separator

[0053] 24: First Outlet

[0054] 26: Second Outlet

[0055] 28: Buffer Tank

[0056] 30: Pump

[0057] 32: Fluid tank

[0058] 34: Collection Tank

[0059] DETAILED DESCRIPTION

[0060] The present disclosure relates to a process for obtaining a Zeigler Natta catalyst. Particularly, the present disclosure relates to a process for obtaining a Zeigler Natta catalyst having a particle size distribution with a span of less than one.

[0061] Embodiments of the present disclosure will now be described with reference to the accompanying drawings.

[0062] Embodiments, of the present disclosure, will now be described herein. Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

[0063] The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and / or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

[0064] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0065] The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

[0066] Ziegler-Natta catalyst is used for the polymerization of propylene as well as ethylene. Different polymerization processes such as gas phase fluidized bed polymerization, stirred gas phase polymerization, slurry phase polymerization, bulk phase polymerization and solution phase polymerization are used in the production of these polymers. A uniquely designed catalyst is required for such polymerization processes and the key differentiator is particle size of the catalyst. For example, gas phase fluidized bed technology requires a catalyst with an average particle size of 22 to 25p and a catalyst smaller than lOp is not desired. It is because a smaller size catalyst gives smaller size polymer resins (fines) in the polymerization process. Bigger size catalyst particles also tend to fragment and create fines in polymerization process, which is not desirable. Thus it is required to have catalyst with narrow particle size distribution.

[0067] For various polymerization reactions, different grades of catalysts are produced to fulfill such requirements. For instance, slurry phase polypropylene requires catalyst having 12 to I 5p average particle size; catalyst particles smaller than 8p and bigger than 18p are not desired. Slurry phase polyethylene technology requires catalyst having 7 to I Op average particle size, catalyst bigger than 16p is not desired.

[0068] Conventional methods address this challenge by refining the catalyst having varied particle size into the desired fractions, to achieve required narrow particle size catalysts for different polymerization processes However, preparing such designed particle sizes need a precisely controlled process, a precursor with specific particle size, and different operating conditions for different grades of catalysts. This leads to complex, energy intensive and costly catalyst production processes.

[0069] In an aspect the present disclosure provides a process for obtaining a Zeigler Natta catalyst. Particularly, the process provides a Zeigler Natta catalyst having particles particle size distribution with a span difference of less than one.

[0070] The process is described in detail.

[0071] In a first step, Zeigler Natta catalyst is mixed in a first fluid medium to obtain a catalyst slurry (14a).

[0072] In an embodiment of the present disclosure, the first fluid medium is a mineral oil having carbon number in the range of C22-C35.

[0073] In a second step, an apparatus (10) having a column (12) is arranged.

[0074] In a third step, a second fluid medium (16a) is continuously fed from an operative bottom (16) of the column (12) at a first predetermined velocity to obtain a fluidized bed in the column (12), the column (12) having a first opening (14) at an operative top to receive a first discharge (14b) from the column (12).

[0075] In an embodiment of the present disclosure, the second fluid medium (16a) is selected from the group consisting of pentane, hexane, heptane, decane and a combination thereof. In an exemplary embodiment, the second fluid medium is hexane.

[0076] In an embodiment of the present disclosure, the first predetermined velocity is in the range of 0.07 cm / s to 0.075 cm / s.

[0077] In an embodiment of the present disclosure, the first predetermined velocity is minimum fluidization velocity and terminal settling velocity of the second fluid medium. In an exemplary embodiment, the first predetermined velocity is 0.0731 cm / s.

[0078] In a fourth step, the velocity of the second fluid medium is increased to a second predetermined velocity to enable the catalyst slurry to be entrained in the first discharge (14b), and receiving the first discharge in a cyclone separator (22) configured with a first outlet (24) and a second outlet (26). In an embodiment of the present disclosure, the second predetermined velocity is in the range of 0.08 cm / s to 0. 18 cm / s. In an exemplary embodiment, the second predetermined velocity is 0.0882 cm / s. In another exemplary embodiment, the second predetermined velocity is 0.1336 cm / s. In still another exemplary embodiment, the second predetermined velocity is 0.1487 cm / s. In yet another exemplary embodiment, the second predetermined velocity is 0.1790 cm / s.

[0079] In an embodiment of the present disclosure, the first discharge is a mixture of the first fluid medium, the second fluid medium and Zeigler Natta catalyst particles. In an exemplary embodiment, the first discharge is a mixture of hexane, mineral oil, and Zeigler Natta catalyst particles.

[0080] In a fifth step, the catalyst particles are separated from the first discharge to obtain a second discharge (16b) and a settled catalyst fraction comprising Ziegler Natta catalyst particles having a predetermined mean particle size distribution with a span difference of less than one.

[0081] In an embodiment of the present disclosure, the second discharge is a mixture of the first fluid medium and the second fluid medium. In an exemplary embodiment, the second discharge is a mixture of hexane and mineral oil.

[0082] In an embodiment of the present disclosure, the mean particle size of the Zeigler Natta catalyst particles in the settled fraction is in the range of 10 pm to 30 pm. In an exemplary embodiment, the mean particle size of the Zeigler Natta catalyst particles in the settled fraction is 23 pm. In another exemplary embodiment, the mean particle size of the Zeigler Natta catalyst particles in the settled fraction is 23.8 pm. In another exemplary embodiment, the mean particle size of the Zeigler Natta catalyst particles in the settled fraction is 23.6. In another exemplary embodiment, the mean particle size of the Zeigler Natta catalyst particles in the settled fraction is 23.7 pm. In another exemplary embodiment, the mean particle size of the Zeigler Natta catalyst particles in the settled fraction is 26.4 pm. In another exemplary embodiment, the mean particle size of the Zeigler Natta catalyst particles in the settled fraction is 29.7 pm.

[0083] In an embodiment of the present disclosure, a D10 particle size lies in the range of 10 pm to 22 pm. In an exemplary embodiment, the catalyst is having a D10 particle size of 15.5 pm. In another exemplary embodiment, the catalyst is having a DIO particle size of 16.7 pm. In still another exemplary embodiment, the catalyst is having a DIO particle size of 16.6 pm. In yet another exemplary embodiment, the catalyst is having a DIO particle size of 19 pm. In another exemplary embodiment, the catalyst is having a DIO particle size of 21.3 pm.

[0084] In an embodiment of the present disclosure, a D50 particle size of the Ziegler Natta catalyst lies in the range of 20 pm to 30 pm. In an exemplary embodiment, D50 particle size of the catalyst is 22.9 pm. In another exemplary embodiment, D50 particle size of the catalyst is 22.9 pm. In another exemplary embodiment, D50 particle size of the catalyst is 22.6 pm. In another exemplary embodiment, D50 particle size of the catalyst is 22.8 pm. In another exemplary embodiment, D50 particle size of the catalyst is 25.6 pm. In another exemplary embodiment, D50 particle size of the catalyst is 28.7 pm.

[0085] In an embodiment of the present disclosure, a D90 particle size of the Ziegler Natta catalyst lies in the range of 30 pm to 40 pm. In an exemplary embodiment, D90 particle size of the catalyst is 31.7 pm. In another exemplary embodiment, D90 particle size of the catalyst is 32.2 pm. In yet another exemplary embodiment, D90 particle size of the catalyst is 32.0 pm. In still another exemplary embodiment, D90 particle size of the catalyst is 34.8 pm. In another exemplary embodiment, D90 particle size of the catalyst is 39.4 pm.

[0086] In a sixth step, the settled catalyst fraction comprising the Ziegler Natta catalyst particles is collected through the first outlet (24) into a collection tank (34).

[0087] In a seventh step, the second discharge (16b) is obtained through the second outlet (26) and fed to a buffer tank (28) for recirculating the second discharge to the column (12).

[0088] In an embodiment of the present disclosure, the mean particle size distribution of said Zeigler Natta catalyst particles in the settled fraction is in the range of 10 pm to 30 pm.

[0089] In an embodiment of the present disclosure, the span difference is in the range of 0.6 to 0.7. In an exemplary embodiment, the span difference is 0.6. In another exemplary embodiment, the span difference is 0.7.

[0090] The formula to calculate the span difference is as follows:

[0091] Span Difference = (D90-D10) / D50 In an embodiment of the present disclosure, the Ziegler Natta catalyst comprises magnesium alkoxide as a support, at least one titanium halide, and at least one internal donor in at least one hydrocarbon medium.

[0092] In an embodiment of the present disclosure, magnesium alkoxide is selected from a group consisting of magnesium methoxide, magnesium ethoxide or magnesium propoxide. In an embodiment, the magnesium alkoxide is a mixture of magnesium methoxide and magnesium ethoxide. In an exemplary embodiment, the magnesium alkoxide contains 2% to 10% magnesium methoxide and 90% to 98% magnesium ethoxide.

[0093] In an embodiment of the present disclosure, the second fluid medium is supplied from a fluid tank (32) for any losses in the second discharge.

[0094] The present disclosure provides a unique process, which produces a catalyst with desired size fractions required for different polymerization processes. The catalyst of different sizes are obtained by a semi continuous process. The catalyst bed is expanded by passing a hydrocarbon solvent and allowed to form a stable expanded bed at lower velocity. Gradually the velocity of the solvent is increased and desired size catalyst fractions are taken out from a settling tank. Solvent is circulated throughout the system continuously.

[0095] The process of the present disclosure addresses multiple challenges in polyolefin catalyst manufacturing such as getting rid of undesired smaller catalyst particles, using the undesired fraction of the process as a feed for another polymerization process. The process of the present disclosure also provides sustainable solution for olefin polymerization catalyst manufacturing, as the process does not require multiple separation columns or any additional hardware for getting desired size fraction catalyst. The process of the present disclosure provides Ziegler Natta catalyst without the use of specific requirement of particle size of the precursors, and / or any stringent control in catalyst production process. According to the process of the present disclosure, the segregation of the catalyst is a two-step process i.e., the development of the expanded bed, followed by elutriation at enhanced fluid velocity. In a first step, the entire catalyst mass is kept in expanded bed mode (i.e., stable fluidized bed), by passing a solvent through bottom of the distributor plate. The catalyst particles attain their position in column according to individual particle’s terminal settings velocity. The catalyst particles having particle size distribution with a span difference of less than one is achieved by gradual increase in velocity of circulation mode through changing flow-rate. The obtained catalyst particles can be used for various polymerization processes such as gas, bulk and slurry technology.

[0096] In another aspect, the present disclosure relates to an apparatus for obtaining a Zeigler Natta catalyst having a predetermined particle size distribution with a span difference of less than one.

[0097] The apparatus comprises a column (12) having a height (H) and a diameter (D) such that the ratio H / D is equal to or greater than 4. The column is configured with a first opening (14) at an operative top of the column for receiving a catalyst slurry (14a) comprising a mixture of Zeigler Natta Catalyst and a first fluid medium and / or discharging a first discharge (14b) from the column and a second opening (16) at an operative bottom of the column for receiving a second fluid medium (16a) and generating a fluidized bed.

[0098] In an embodiment of the present disclosure, the ratio of H / D is equal to or greater than 4. In an exemplary embodiment, the ratio of H / D is 10.

[0099] The column (12) has a bottom distributor plate (18) and a mesh to pass the second fluid medium (16a) into the column (12).

[0100] A fluid tank (32) is configured downstream of the column (12) for providing the second fluid medium to the column. The fluid tank is used as a source of second fluid medium in case of any loss in the second discharge coming into the column. The loss in second fluid medium entering into the column through the second opening (16) is indicated by the indicators and sensors configured in the column.

[0101] A cyclone separator (22) is in fluid communication with the column for receiving the first discharge (14b) through an inlet port (20), the cyclone separator is configured with a first outlet (24) to discharge a settled catalyst fraction comprising the Ziegler Natta catalyst particles having a predetermined particle size distribution with a span difference of less than one and a second outlet (26) to discharge a second discharge (16b).

[0102] The cyclone separator (22) includes means to keep the cyclone separator under inert atmosphere. The inert atmosphere includes blanketing with nitrogen or argon.

[0103] A buffer tank (28) is in fluid communication with the cyclone separator (22) for receiving the second discharge (16b) and recirculating the received second discharge to the column. The buffer tank can store excess of the second discharge received from the cyclone separator. A collection tank (34) is configured downstream of the cyclone separator (22) to collect the settled catalyst fraction comprising the Ziegler Natta catalyst particles having a predetermined particle size distribution with a span difference of less than one. The collection tank can store the obtained Ziegler Natta catalyst particles.

[0104] A pump (30) is configured downstream of the buffer tank (28) for recirculating the second discharge (16b) to the column through the second opening.

[0105] In an embodiment of the present disclosure, the apparatus includes means for altering the flow rate of the second fluid medium (16a) into the column (12).

[0106] In another aspect, the present disclosure provides a Zeigler-Natta catalyst having particle size distribution with a span difference of less than one obtained from the process of the present disclosure.

[0107] The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.

[0108] 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. The following experiments are scalable to industrial / commercial process.

[0109] EXPERIMENTAL DETAILS

[0110] Experiment 1: Preparation of Zeigler-Natta Catalyst in accordance with the present disclosure

[0111] Preparation of Zeigler-Natta Catalyst

[0112] A mixture of magnesium methoxide and magnesium ethoxide (2.2 Kmole) was treated with 12 Kmoles of TiC’h diluted in equivalent volume of chlorobenzene at 105 °C. The process step of treatment was repeated thrice. Di-iso butyl phthalate internal donor (0.23 Kmoles) was added in the first step whereas 0.1 Kmoles benzoyl chloride was added in the last step. After three stages of treatment, a solid pro-catalyst component was obtained, which was filtered and washed four times with equivalent volume of iso-pentane. Subsequently, the procatalyst component was dried at 60 °C under stream of nitrogen for getting a resultant catalyst. The resultant catalyst was slurried to have 30% solids concentration. This catalyst slurry was then fed to a fluidization column, having a cyclone separator.

[0113] Example 1: Process for obtaining Zeigler Natta catalyst having a predetermined particle size distribution with a span difference of less than one in accordance with the present disclosure

[0114] 15 grams of the Zeigler Natta catalyst obtained in Example 1 was mixed with 30 grams of mineral oil to obtain a catalyst slurry (14a). An apparatus having a column (12) was arranged. The column had an internal diameter of 20 mm and height of 550 mm with a distributor plate and mesh for passage of hexane. Hexane (16a) was continuously fed from the second opening (16) of the column at a velocity of 0.0731 cm / s to obtain a stable catalyst bed in the column (12). 45 grams of the catalyst slurry was then fed to the column comprising hexane from the first opening of the column to blend with the catalyst bed. The velocity of hexane was gradually increased to 0.0882 cm / s to enable the catalyst slurry to be entrained in the first discharge (14b). The first discharge was then allowed to pass into a cyclone separator (22). The catalyst particles were separated from the first discharge to obtain a settled fraction and a second discharge (16b). The settled fraction was collected after 290 minutes through the first outlet into a collection tank (34). The cyclone separator included means to maintain an inert atmosphere with nitrogen. A buffer tank (28) was positioned to receive the second discharge from the cyclone separator. The second discharge was re-circulated from the cyclone separator to the column by a pump (30) through the second opening of the column. The settled fraction was analysed in a particle size analyser. By the controlled flow rate of hexane, the Zeigler Natta catalyst particles having a particle size distribution with a span difference of less than one with a mean particle size of 23 pm were obtained.

[0115] Examples 2 to 9

[0116] Examples 2 to 9 were carried out by using similar procedure provided in Example 1 except by varying the velocity of the second fluid medium. The settled fractions were collected as per the time indicated in Table 1. Table 1: The experimental conditions and Zeigler Natta catalyst fractions collected and their particle size distribution for various separated catalyst fractions. From Table-1, it is clear that smaller size catalyst particles were eluted in initial fractions and later fractions had catalyst particles having relatively larger particle size. On gradual increase in solvent feed velocity, the particles with relatively higher size (DIO, D50, D90) were eluted and were collected in different fractions. Since, the smaller size particles were eluted earlier, the resultant later fractions had narrower particle size distribution. It is observed to have span less than ‘ 1’ in case of Table- 1. On increasing the velocity of hexane to more than 0.179 cm / s, the Zeigler Natta catalyst with mean particle size greater than 30 pm was obtained.

[0117] The process of the present disclosure provided catalysts with desired size fractions (preferably average particle size in the range of less than 20 pm, 20-30 pm and greater than 30p) required for different polymerization processes.

[0118] TECHNICAL ADVANCEMENT

[0119] The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of the process for obtaining a Zeigler Natta catalyst having particle size distribution with a span difference of less than one, that:

[0120] • is simple since no stringent control on raw material or synthesis process is required; • provides good control over polymerization process due to availability of desired size of catalyst;

[0121] • segregates catalyst particles having narrow particle size distribution range;

[0122] • provides catalyst segregation according to the desired particle size distribution, hence all the fractions can be used in different polymerization technology; and

[0123] • provides segregated catalyst particles that can be used in different polymerization processes such as gas phase polypropylene, slurry phase polypropylene, and slurry phase polyethylene process.

[0124] The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following 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.

[0125] The foregoing description of the specific embodiments 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 have 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.

[0126] 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 example 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.

[0127] Any discussion of documents, acts, materials, devices, articles or 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.

[0128] 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.

[0129] 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

CLAIMS:

1. A process for obtaining a Zeigler Natta catalyst having a predetermined particle size distribution with a span difference of less than one, said process comprising the following steps: a. mixing Zeigler Natta catalyst in a first fluid medium to obtain a catalyst slurry (14a); b. arranging an apparatus (10) having a column (12); c. continuously feeding a second fluid medium (16a) from an operative bottom (16) of said column (12) at a first predetermined velocity to obtain a fluidized bed in said column (12), said column (12) having a first opening (14) at an operative top to receive a first discharge (14b) from said column (12); d. feeding said catalyst slurry (14a) to said column (12) to blend with said fluidized bed; e. increasing the velocity of said second fluid medium to a second predetermined velocity to enable said catalyst slurry to be entrained in said first discharge (14b), and receiving said first discharge in a cyclone separator (22) configured with a first outlet (24) and a second outlet (26); f. separating catalyst particles from said first discharge to obtain a second discharge (16b) and a settled catalyst fraction comprising Ziegler Natta catalyst particles having a predetermined mean particle size distribution with a span difference of less than one; g. collecting said settled catalyst fraction comprising said Ziegler Natta catalyst particles through said first outlet (24) into a collection tank (34); and h. obtaining said second discharge (16b) through said second outlet (26) and feeding to a buffer tank (28) for recirculating said second discharge to said column (12).

2. The process as claimed in claim 1, wherein said mean particle size distribution of said Zeigler Natta catalyst particles in said settled fraction is in the range of 10 pm to 30 pm.

3. The process as claimed in claim 1, wherein said span difference is in the range of 0.6 to 0.7.

4. The process as claimed in claim 1, wherein said first fluid medium is a mineral oil having carbon number in the range of C22-C35.

5. The process as claimed in claim 1, wherein said second fluid medium (16a) is selected from the group consisting of pentane, hexane, heptane, decane and a combination thereof.

6. The process as claimed in claim 1, wherein said first discharge is a mixture of said first fluid medium, said second fluid medium and Zeigler Natta catalyst particles.

7. The process as claimed in claim 1, wherein said second discharge is a mixture of said first fluid medium and said second fluid medium.

8. The process as claimed in claim 1, wherein said first predetermined velocity is in the range of 0.07 cm / s to 0.075 cm / s.

9. The process as claimed in claim 1, wherein said second predetermined velocity is in the range of 0.08 cm / s to 0.18 cm / s.

10. The process as claimed in claim 1, wherein said Ziegler Natta catalyst comprises magnesium alkoxide as a support, at least one titanium halide, and at least one internal donor in at least one hydrocarbon medium.

11. The process as claimed in claim 1, wherein said second fluid medium is supplied from a fluid tank (32) for any losses in said second discharge.

12. An apparatus for obtaining a Zeigler Natta catalyst having a predetermined particle size distribution with a span difference of less than one, said apparatus comprising:A. a column (12) having a height (H) and a diameter (D) such that the ratio H / D is equal to or greater than 4; wherein said column comprising:• a first opening (14) at an operative top of said column for receiving a catalyst slurry (14a) comprising a mixture of Zeigler Natta Catalyst and a first fluid medium and / or discharging a first discharge (14b) from said column; and• a second opening (16) at an operative bottom of said column for receiving a second fluid medium (16a) and generating a fluidized bed;B. a cyclone separator (22) in fluid communication with said column for receiving said first discharge (14b) through an inlet port (20), said cyclone separator is configured with a first outlet (24) to discharge a settled catalyst fraction comprising said Ziegler Natta catalyst particles having apredetermined particle size distribution with a span difference of less than one and a second outlet (26) to discharge a second discharge (16b);C. a buffer tank (28) in fluid communication with said cyclone separator (22) for receiving said second discharge (16b) and recirculating said received second discharge to said column; andD. a fluid tank (32) configured downstream said column (12) for providing said second fluid medium to said column.

13. The apparatus as claimed in claim 12, wherein said cyclone separator (22) includes means to keep said cyclone separator under inert atmosphere; wherein said inert atmosphere includes blanketing with nitrogen or argon.

14. The apparatus as claimed in claim 12, wherein said apparatus includes means for altering the flow rate of said second fluid medium (16a) into said column (12).

15. The apparatus as claimed in claim 12, wherein said column (12) comprises a bottom distributor plate (18) and a mesh to pass said second fluid medium (16a) into said column (12).

16. The apparatus as claimed in claim 12, wherein a collection tank (34) is configured downstream of said cyclone separator (22) to collect said settled catalyst fraction comprising said Ziegler Natta catalyst particles having a predetermined particle size distribution with a span difference of less than one.

17. The apparatus as claimed in claim 12, wherein a pump (30) is configured downstream of said buffer tank (28) for recirculating said second discharge (16b) to said column through said second opening.

18. Zeigler-Natta catalyst having particle size distribution with a span difference of less than one, obtained from the process as claimed in claim 1.

Images