Claims:WE CLAIM:
1. A catalyst composition comprising:
a) a pro-catalyst;
b) a co-catalyst;
c) a donor free Grignard reagent.
2. The catalyst composition as claimed in claim 1, wherein the weight ratio of said co-catalyst to said pro-catalyst is in the range of 10 to 15.
3. The catalyst composition as claimed in claim 1, wherein the weight ratio of said donor free Grignard reagent to said pro-catalyst is in the range of 1 to 3.
4. The catalyst composition as claimed in claim 1, wherein said pro-catalyst is at least one selected from MgCl2 supported metal compound and silica supported metal compound.
5. The catalyst composition as claimed in claim 4, wherein said metal compound is at least one selected from the group consisting of TiCl3, TiCl4, and VCl4.
6. The catalyst composition as claimed in claim 1, wherein said co-catalyst is dialkylmagnesium.
7. The catalyst composition as claimed in claim 6, wherein the dialkylmagnesium is selected from butylethylmagnesium and di-dodecylmagnesium and combinations thereof.
8. The catalyst composition as claimed in claim 6, wherein the dialkylmagnesium is di-dodecylmagnesium.
9. The catalyst composition as claimed in claim 1, wherein said donor free Grignard reagent is at least one selected from the group consisting of dodecyl magnesium chloride, dodecyl magnesium bromide, decyl magnesium bromide, and decyl magnesium chloride.
10. The catalyst composition as claimed in claim 9, wherein said donor free Grignard reagent is dodecyl magnesium bromide.
11. A process for preparing the catalyst composition, said process comprising the following steps:
a. mixing a predetermined amount of a co-catalyst and a donor free Grignard reagent at a first pre-determined temperature under a first pre-determined stirring speed to obtain a mixture; and
b. adding a predetermined amount of a pro-catalyst to said mixture at a second pre-determined temperature under a second pre-determined stirring speed to obtain the catalyst composition.
12. The process as claimed in claim 11, wherein said pro-catalyst catalyst is at least one selected from the group consisting of MgCl2 supported titanium compound and silica supported titanium compound.
13. The process as claimed in claim 12, wherein said titanium compound is selected from TiCl3 and TiCl4.
14. The process as claimed in claim 11, wherein said co-catalyst is at least one selected from butylethylmagnesium and di-dodecylmagnesium.
15. The process as claimed in claim 11, wherein said donor free Grignard reagent is at least one selected from the group consisting of dodecyl magnesium chloride, dodecyl magnesium bromide, decyl magnesium bromide, and decyl magnesium chloride.
16. The process as claimed in any one of the preceding claims, wherein the ratio of the amount of Mg in the mixture of said co-catalyst and said donor free Grignard reagent, to the amount of Ti in said pro-catalyst is in the range of 45 to 55.
17. The process as claimed in claim 11, wherein said donor free Grignard reagent is obtained by reacting a magnesium powder, iodine crystals and a halodecane in a donor free solvent in an inert atmosphere at a temperature in the range of 80 oC to 130 oC, for the time period in the range of 60 to 70 hours.
18. The process as claimed in claim 17, wherein said donor free solvent is toluene.
19. The process as claimed in claim 11, wherein the molar ratio of said donor free Grignard reagent to said co-catalyst is in the range of 0.01 to 1.
20. Polymer particles obtained by using the catalyst composition as claimed in claim 1, are characterized by having a particle size in the range of 1-4 mm.
, Description:FIELD
The present disclosure relates to a catalyst composition and a process for its preparation.
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 indicates otherwise.
Ziegler Natta catalyst: is a catalyst which contains the complex of titanium/vanadium halide with organo-aluminum/organo-magnesium compound, and is typically used in the polymerization reaction. Typically, the complex is made by reacting TiCl4 with tri-ethyl-aluminum.
Grignard reagent: is an organometallic compound with generic formula R-Mg-X (X is halogen and R is alkyl or aryl group) which are typically stabilized by solvent such as tetrahydrofuran and di-ethyl-ether containing electron donating groups.
Donor free Grignard reagent: is an organometallic compound with generic formula R-Mg-X where X is halogen and, R is alkyl, wherein the chain length of the alkyl group is equal to or > 12 carbon atoms in a suitable solvent. The reagent does not contain any stabilizing components such as tetrahydrofuran or some other di-ethyl-ether containing electron donating groups.

BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Conventionally, polyethylene is largely produced by polymerizing ethylene in homo- and co-polymerization conditions. A variety of polymerization processes are known, wherein the most widely used catalyst system is the Ziegler-Natta catalyst system. The most common version of the Ziegler-Natta catalyst consists of an MgCl2 as a carrier upon which TiCl4 is deposited. The MgCl2 support material has to be in an active crystal form in order to enhance the activity of the catalyst.
Further, the precipitation method is the most common way of producing an active MgCl2 crystal structure. However, the precipitation technique has the disadvantage that, the synthesized active carrier often possessess a powder-like morphology, which when used for the manufacturing the Ziegler-Natta catalyst, results in the catalyst having powder-like morphology. Still further, when the catalyst with powder like morphology is used in a polymerization process, the produced polymer also possesses a powder-like morphology. The powder-like structure of the polymer material is often undesirable because of the low bulk density, stocking problems, transportation problems and even a risk for dust explosions.
Therefore, there is, felt a need to develop a catalyst composition that mitigates the drawbacks mentioned hereinabove.
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 catalyst composition.
Another object of the present disclosure is to provide a simple process for the preparation of the catalyst composition.
Yet another object of the present disclosure is to provide a catalyst composition that is used in the polymerization reaction to obtain polymer particles with comparatively higher size.
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 relates to a catalyst composition comprising a pro-catalyst; at least one co-catalyst; and a donor free Grignard reagent.
The present disclosure further relates to a process for preparation of the catalyst composition. The process comprises mixing a predetermined amount of a co-catalyst and a donor free Grignard reagent at a first pre-determined temperature under a first pre-determined stirring speed to obtain a mixture. A predetermined amount of pro-catalyst is added to the so obtained mixture at a second pre-determined temperature under a second pre-determined stirring speed to obtain the catalyst composition.
The present disclosure still further relates to the polymer particles obtained by using the catalyst composition. The polymer particles are characterized by having a particle size in the range of 1-4 mm.
DETAILED DESCRIPTION
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.
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.
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.
Conventionally, in the Ziegler Natta catalyst system, the MgCl2 support material is prepared by a precipitation method that often possesses a powder-like morphology, which when employed in preparing a Ziegler-Natta catalyst that results in the catalyst composition of the similar morphology. When the powdered catalyst composition is used in the process of polymerization, the resultant polymer material also carries the powder-like morphology which is undesirable because of the disadvantages such low bulk density, stocking problems, transport problems and even a risk for dust explosions.
The drawbacks of the polymer particles with fine powder-like morphology are more prominent during the two-step polymerization process which is particularly employed for the production of materials for various applications. In the first step of two-step polymerization process, a low molecular weight polyethylene homo-polymer is produced which is very crystalline, brittle and has a fine powder like morphology. When finely divided polyethylene powder is transferred in a gas phase reactor at the second step, problem of instability of the bed arises as finely divided polyethylene material will escape with the fluidizing monomer stream.
The present disclosure provides a catalyst composition which solves above mentioned problems.
In an aspect, the present disclosure provides a catalyst composition comprising a pro-catalyst; a co-catalyst and a donor free Grignard reagent.
In accordance with the present disclosure, the weight ratio of the co-catalyst to the pro-catalyst is in the range of 10 to 15. In an exemplary embodiment, the weight ratio is 13.68.
The weight ratio of the donor free Grignard reagent to the pro-catalyst is in the range of 1 to 3. In an exemplary embodiment, the weight ratio is 1.7.
The pro-catalyst is at least one selected from MgCl2 supported metal compound or silica supported metal compound. The metal compound is at least one selected from the group of TiCl3, TiCl4, and VCl4. In an exemplary embodiment, the pro-catalyst is MgCl2 supported TiCl4. In another exemplary embodiment, the pro-catalyst is silica supported TiCl4.
In accordance with the present disclosure, the co-catalyst is dialkylmagnesium (DAM). Typically, dialkylmagnesium is selected from butylethylmagnesium and di-dodecylmagnesium. In an exemplary embodiment, the dialkylmagnesium is di-dodecylmagnesium.
The donor free Grignard reagent is at least one selected from the group consisting of dodecyl magnesium chloride, dodecyl magnesium bromide, decyl magnesium bromide, and decyl magnesium chloride. In an exemplary embodiment, the donor free Grignard reagent is dodecyl magnesium bromide.
Conventional Grignard reagent contains substantial amounts of donor compounds like tetrahydrofurane or diethylether to stabilize the RMgX complex. However, the donor compounds inhibit the activity of typical Ziegler Natta catalysts. This is the reason, why Grignard reagents are normally not used as co-catalysts for Ziegler Natta catalyst systems.
The present disclosure provides a process to obtain a stable donor free Grignard reagent which is included in the catalyst composition of the present disclosure. The chemical equation for the reaction to prepare donor free Grignard reagent is as follows:
C12H25-Br + Mg + I2 + C6H5-CH3 ? C12H25-Mg-Br in C6H5-CH3
In accordance with the present disclosure, the donor free Grignard reagent is obtained by reacting a magnesium powder, iodine crystals and a halo-decane in a donor free solvent in an inert atmosphere at a temperature in the range of 80 oC to 130 oC, for a time period in the range of 60-70 hours. In an exemplary embodiment, halo-decane is 1- bromodecane, the donor free solvent is toluene and the inert atmosphere is maintained by using argon gas. In a further embodiment, donor free Grignard reagent is obtained by reacting a magnesium powder, iodine crystals and a 1-bromodecane in toluene in an inert atmosphere maintained by the use of argon gas, at a temperature in the range of 90 oC to 125 oC for time period of 66 hours.
In accordance with the present disclosure, the ratio of the amount of Mg in the mixture of the co-catalyst and the donor free Grignard reagent to the amount of Ti in pro-catalyst is in the range of 45 to 55. In an exemplary embodiment, the ratio is 50.
In another aspect of the present disclosure, there is provided a process for preparing a catalyst composition for the polymerization. The process is described herein below:
Initially, the co-catalyst and the donor free Grignard reagent are mixed at the first pre-determined temperature under the first pre-determined stirring speed to obtain a mixture. In an exemplary embodiment, the co-catalyst di-dodecylmagnesium is mixed with the donor free Grignard reagent dodecyl magnesium bromide at the temperature of 60°C under the stirring speed of 50 rpm.
In a further step, the pro-catalyst is added to the mixture at the second pre-determined temperature under the second pre-determined stirring speed to obtain a catalyst composition. In an exemplary embodiment, MgCl2 supported TiCl4 is added to the mixture containing di-dodecylmagnesium (co-catalyst) and dodecyl magnesium bromide (donor free Grignard reagent) at the temperature of 50°C under the stirring speed of 100 rpm.
In accordance to the present disclosure, the donor free Grignard reagent is first mixed with the co-catalyst in a mole ratio in the range of 0.01 to 1. In an exemplary embodiment, the mole ratio is 0.125.
In accordance to the embodiments of the present disclosure, the polymer particles obtained by using the catalyst composition of the present disclosure are characterized by having a particle size in the range of 1-4 mm.
The present disclosure provides a technical advancement in terms of providing a stable donor free Grignard reagent and a process of obtaining the same. Unlike the typical Grignard reagent stabilized by the donor compounds, the donor free Grignard reagent of the present disclosure can be included in the catalyst composition used in the polymerization. The polymer obtained by employing the catalyst composition of the present disclosure, have bigger particle size than the polymer particles obtained by the catalyst composition without the donor free Gignard reagent.
The foregoing description of the embodiments has been provided for purposes of illustration and 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.
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 can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS:
Experiment:
Example 1: Synthesis of donor free Grignard reagent.
Oven dried Mg-powder (1.337 g; 55 mmol) was weighted into a 3-necked 100 ml round-bottomed flask. The flask was connected to an argon gas line, a dropping funnel and a reflux condenser. The reflux condenser was further connected to a mercury-trap, which eliminated the possibility of a gas flow from room atmosphere into the reactor. 8 mg of iodine was added into the magnesium powder. The whole reactor system was flushed with a stream of argon in order to create totally inert conditions. The Mg/I2 mixture was heated with a heat-gun until the iodine started to evaporate as a violet gas. 1-bromododecane (3.6 ml; 15 mmol, 98-99 % solution) was then introduced from the dropping funnel into the reactor. The mixture was heated for a 3 min with the heat-gun to start the reaction.
50 ml of dry and degassed toluene was then introduced in inert conditions into the dropping funnel together with 8.4 mL of 1-bromododecane (35 mmol). This solution was added drop-wise into the reactor. Temperature was maintained at 90°C. After the addition, the temperature was increased to the reflux temperature of toluene i. e. 125°C. The reaction was allowed to continue for 66 h. A clear liquid resulted with a layer of dull-gray un-reacted magnesium in the bottom. The clear liquid was analyzed and the concentration of the Grignard reagent was found it be 0.25 mol/l.
Example 2: Ethylene polymerization using catalyst composition comprising MgCl2 supported TiCl4, (pro-catalyst) di-dodecyl-magnesium (co-catalyst) and dodecyl magnesium bromide (donor free Grignard reagent):
200 mL of toluene and ethylene gas at the pressure of 3 bar was introduced into the reactor as in example 1 and the temperature of the reactor was increased to 50°C giving the total pressure inside the reactor 4 bar. 1.08 mL of 0.7 molar solution of di-dodecyl-magnesium in toluene was mixed with a solution of 0.5 mL of dodecyl-Mg-bromide at 60oC at 50 rpm. Then 20 mg MgCl2 supported TiCl4 pro-catalyst was added to the mixture of di-dodecyl-magnesium and dodecyl-Mg-bromide in toluene at 50oC at 100 rpm, to obtain a catalyst composition of the present disclosure. Considering the amount of di-dodecyl-magnesium, dodecyl-Mg-bromide and MgCl2 supported TiCl4 pro-catalyst, the Mg/Ti molar ratio was 50:1.
5.0 mL of the above catalyst composition was introduced into the reactor at 50oC and 100 rpm. Polymerization was maintained for 54 minutes. Results are summarized in Table 1.
The resulting polyethylene material consisted of a coarse granular like material with polymer particles having a particle size between 1 - 4 mm.
Example 3 - Ethylene polymerization using catalyst composition comprising MgCl2 supported TiCl4, (pro-catalyst), dodecyl magnesium bromide (donor free Grignard reagent):
The autoclave was loaded with 200 mL of toluene as polymerization medium. 3.0 bar of ethylene monomer gas was introduced into the reactor. Temperature was set to 50°C giving a total pressure of 4 bar. After this, 1.0 mL of the dodecyl magnesium bromide as synthesized in example 4 was mixed with 30 mg MgCl2 supported TiCl4 pro-catalyst and the slurry was injected into the autoclave. Results are summarized in Table 1.
No polymerization occurred. The reason for the inactivity was that donor free Grignard reagent is not capable of forming the active polymerizing species on titanium that could bring the polymerization forward.
Example 4 - Ethylene polymerization using activated catalyst comprising MgCl2 supported TiCl4, (pro-catalyst) Triethylaluminum (co-catalyst):
200 mL of toluene and ethylene gas at the pressure of 3 bar was introduced into the reactor and the temperature in the reactor was increased to 50°C which led to the increase in the total pressure in the reactor to 4 bar. Then 20 mg MgCl2 supported TiCl4 pro-catalyst was mixed with 1.5 mL of the 25% solution of triethylaluminum in toluene to obtain an activated catalyst. The Mg/Ti molar ratio was 50.
5.0 mL of the activated catalyst was introduced into the reactor. Polymerization was carried out for 18 minutes. Results are summarized in Table 1.
The resulting polyethylene material consisted of a fine powder-like material and size of the polymer particles was below 1 mm.
Example 5 - Ethylene polymerization using catalyst composition comprising MgCl2 supported TiCl4, (pro-catalyst) di-dodecyl-magnesium (co-catalyst):
200 mL of toluene and ethylene gas at the pressure of 3 bar ethylene was introduced into the reactor as in example 1 and the temperature of the reactor was increased to 50°C which led the increase in the pressure inside the reactor to 4 bar. Then 20 mg MgCl2 supported TiCl4 pro-catalyst was mixed with 1.08 mL of the 0.7 molar solution of di-dodecyl-magnesium in toluene was used to obtain an activated catalyst. Considering the amount of the di-dodecyl-magnesium and the MgCl2 supported TiCl4, the Mg/Ti molar ratio was 50. 5.0 mL of an activated catalyst was introduced into the reactor. Polymerization was maintained for 10 minutes. The results are summarized in the table 1.
The resulting polyethylene material consisted of a fine powder-like material and size of the polymer particles was below 1mm.
Example 6 - Ethylene polymerization using catalyst composition comprising MgCl2 supported TiCl4, (pro-catalyst) di-dodecyl-magnesium (co-catalyst):
200 mL of toluene and ethylene gas at the pressure of 3 bar was introduced into the reactor as in example 1 and the temperature of the reactor was increased to 50°C which led to the increase in the total pressure inside the reactor to 4 bar. Then 20 mg MgCl2 supported TiCl4 pro-catalyst was mixed with 1.0 mL of the 0.7 molar solution of di-dodecyl-magnesium in toluene. Considering the amount of the di-dodecyl-magnesium and the TiCl4, the Mg/Ti molar ratio was 50.
5.0 mL of the above activated catalyst was introduced into the reactor. Polymerization was maintained for 41 minutes. The results are summarized in the table 1.
The resulting polyethylene material consisted of a fine powder-like material and size of the polymer particles was below 1 mm.
Table 1: Comparison of the polymer properties:
Exp.No Catalyst composition Yield of polymerization
(g) Reaction Time (min) Relative activityof catalyst Mw of polymer
(kg/
mol) MWD of polymer MP of polymer
(°C) Crystallinity of polymer
(%) Particle size
(mm)
2 Pro-catalyst +
co-catalyst (DAM)
+
donor free GR 12.9 54 238 280 - 133.3 49.6 1 – 4
3 Pro-catalyst
+
donor free GR 0 15 0 - - - - -
4 Pro-catalyst
+
co-catalyst (Triethyl-aluminium) 10.1 18 1093 840 11.0 134.1 63.1 < 1
5 Pro-catalyst
+
co-catalyst (DAM) 2.6 10 259 1519 11.8 - - < 1
6 Pro-catalyst
+
co-catalyst (DAM) 8.7 41 213 1131 9.4 133.5 50.1 < 1

Table 1 shows that the polyethylene produced with both tri-alkyl amine or with dialkyl magnesium (experiments 3, 4 and 5) as co-catalyst showed a powder-like morphology with polymer particles that all had a particle size below 1 mm. Experiment 3 showed that a donor free Grignard solution consisting of dodecylmagnesium bromide cannot by itself act as a co-catalyst to activate a typical Ziegler-Natta catalyst for homopolymerization of ethyelene in order to produce polyethylene. Example 2 showed surprisingly that, if a donor free Grignard reagent solution was added with the dialkyl magnesium co-catalyst, there was a significant change in the morphology of the produced granular polyethylene material showing a particle size that was between 1 – 4 mm. No particles were below 1 mm.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of
- a stable catalyst composition;
-a simple process for the preparation of catalyst composition; and
- polymer particles having the size in the range of 1-4 mm.
The embodiments as described herein above, and various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description.
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 disclosure to achieve one or more of the desired objects or results.
The foregoing description of 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 of 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. Further, 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.
Having described and illustrated the principles of the present disclosure with reference to the described embodiments, it will be recognized that the described embodiments can be modified in arrangement and detail without departing from the scope of such principles.
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 embodiment 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.