Claims:WE CLAIM:
1. A catalyst composition for olefin oligomerization, said catalyst composition comprising:
i. a chromium salt in an amount in the range of 0.05 to 0.5 wt%;
ii. an electron donor in an amount in the range of 0.1 to 1.0 wt%;
iii. a modifier in an amount in the range of 0.05 to 1.0 wt%;
iv. a co-catalyst in an amount in the range of 1.0 to 5.0 wt%; and
v. a fluid medium in an amount in the range of 95.0 to 97.0 wt%.
2. The catalyst composition as claimed in claim 1, wherein said chromium salt is at least one selected from the group consisting of chromium trichloride-tris-tetrahydrofuran complex, chromium tris(2-ethylhexanoate), chromium(III)octanoate, and chromium(III)acetylacetonate.
3. The catalyst composition as claimed in claim 1, wherein said electron donor is at least one selected from the group consisting of 2,5-dimethylpyrrole, tris(4-methoxyphenyl) phosphine, 2,5-dimethylthiophene, cis-2,6-dimethylpiperidine, tetrahydrofuran, 2,5-dimethyl tetrahydrofuran, 2-tert butylfuran, N,N-bis(diphenylphosphino) (isopropyl)amine, and 2,6-Bis[bis(diphenylphosphino)amino]pyridine.
4. The catalyst composition as claimed in claim 1, wherein said modifier is represented as
(Ar)2P-N(R)-P(Ar)2
wherein, Ar is an ortho-substituted phenyl, and R is an alkyl group.
5. The catalyst composition as claimed in claim 4, wherein said modifier is at least one selected from the group consisting of (phenyl)2P-N(i-propyl)-P(phenyl)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2.
6. The catalyst composition as claimed in claim 1, wherein said co-catalyst is at least one selected from the group consisting of methylalumoxane (MAO), polymethylalumoxane (P-MAO), and triethylaluminum (TEAL).
7. The catalyst composition as claimed in claim 1, wherein said fluid medium is at least one selected from the group consisting of hexane, cyclohexane, and heptane.
8. The catalyst composition as claimed in claim 1, wherein the molar ratio of said chromium salt to said electron donor is in the range of 1:5 to 1:25, preferably 1: 20 to 1:25.
9. The catalyst composition as claimed in claim 1, wherein the molar ratio of said chromium salt to said modifier is in the range of 1:0.5 to 1:1.0.
10. The catalyst composition as claimed in claim 1, wherein the molar ratio of said chromium salt to said co-catalyst is in the range of 1: 20 to 1:180, preferably 1: 80 to 1: 180.
11. The catalyst composition as claimed in claim 1 comprises
i. chromium (III) 2-ethylhexnoate;
ii. the electron donor selected from 2,5-dimethyl tetrahydrofuran, 2,5-dimethylpyrrole and 2,5-dimethylthiophene;
iii. the modifier selected from (phenyl)2P-N(i-propyl)-P(phenyl)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2;
iv. the co-catalyst selected from methylaluminoxane (MAO), poly- methylaluminoxane (PMAO) and triethylaluminum (TEAL); and
v. heptane.
12. The catalyst composition as claimed in claim 1 comprises
i. chromium (III) 2-ethylhexnoate;
ii. 2,5-dimethyl tetrahydrofuran;
iii. (phenyl)2P-N(i-propyl)-P(phenyl)2;
iv. combination of methylaluminoxane (MAO) and triethylaluminum (TEAL), wherein molar ratio of methylaluminoxane to triethylaluminum is 1:1; and
v. heptane.
13. A process for preparing a catalyst composition for olefin oligomerization, the process comprising
mixing in oxygen free atmosphere, a predetermined quantity of chromium salt, an electron donor, and a modifier in a fluid medium to obtain a mixture; and adding to the mixture a co-catalyst followed by stirring at a speed in the range of 300 rpm to 700 rpm, preferably 500-600 rpm to obtain the catalyst composition.
14. A process for olefin oligomerization, said process comprising:
oligomerizing olefin under oxygen free atmosphere in the presence of a catalyst composition comprising a chromium salt, an electron donor, a modifier, a co-catalyst and a fluid medium under stirring at a speed in the range of 200 to 600 rpm, at a temperature in the range of 40 °C to 100 °C and at a pressure in the range of 10 kg /cm2 to 50 kg/ cm2 to obtain an oligomer.
15. The process as claimed in claim 14, wherein said olefin is ethylene and said oligomer is at least one selected from 1-hexene and 1-octene.
, Description:FIELD
The present disclosure relates to a catalyst composition for olefin oligomerization and a process for preparing the same.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Alpha-olefins represent important petro-chemical materials. The alpha olefins find applications as co-monomers, plasticizers, synthetic lubricants and detergent alcohols. The selective oligomerization of ethylene to 1-hexene and 1-octene is of great interest due to the great demand for these compounds.
Selective oligomerization of olefin using transition metal catalyst is known and some of the conventional systems are based on the chromium catalysts. However, the conventional olefin oligomerization techniques are associated with drawbacks such as low selectivity towards desired products such as 1-hexene and 1-octene. The selectivity of the desired product is limited alpha-olefins are produced via a Schulz-Flory type of distribution. On the other hand the selective formation of hexene (ethylene trimer) and octene (ethylene tetramer) involves a metalacyclic mechanism involving a seven membered or nine membered active catalytic intermediates leading to the selective formation of hexene and octene. Most of the known catalyst systems for ethylene trimerization or tetramerization generate by-product such as internal olefins and polyethylene which is difficult to separate. Formation of the byproducts reduces the overall catalyst productivity and affects the economics of commercial production.
Therefore, there is felt a need to provide a catalyst composition for selective oligomerization of olefin to eliminate completely or at least further reduce the undesired polymer formation and internal olefins and to improve selectivity of desired oligomers.
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 for selective olefin oligomerization.
Another object of the present disclosure is to provide a process for the preparation of the catalyst composition for selective olefin oligomerization.
Yet another object of the present disclosure is to provide a process for selective oligomerization of ethylene.
Still another object of the present disclosure is to provide a process for selective oligomerization of ethylene to eliminate completely or at least reduce the formation of undesired polymer and to improve selectivity of desired olefins.
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
In one aspect, the present disclosure provides a catalyst composition for olefin oligomerization. The catalyst composition comprises a chromium salt in an amount in the range of 0.05 to 0.5 wt%; an electron donor in an amount in the range of 0.1 to 1.0 wt%; a modifier in an amount in the range of 0.05 to 1.0 wt%; a co-catalyst in an amount in the range of 1.0 to 5.0 wt% and a fluid medium in an amount in the range of 95.0 to 97.0 wt%.
The chromium salt is at least one selected from the group consisting of chromium trichloride tris tetrahydrofuran complex, chromium tris(2-ethylhexanoate), chromium(III)octanoate, and chromium(III)acetylacetonate.
The electron donor is at least one selected from the group consisting of 2,5-dimethylpyrrole, tris(4-methoxyphenyl) phosphine, 2,5-dimethylthiophene, cis-2,6-dimethylpiperidine, tetrahydrofuran, 2,5-dimethyl tetrahydrofuran, 2-tert butylfuran, N,N-bis(diphenylphosphino)-(isopropyl)amine and 2,6-Bis[bis(diphenylphosphino)amino]pyridine. The molar ratio of the chromium salt to the electron donor is in the range of 1:5 to 1:25, preferably 1: 20 to 1: 25.
The modifier is represented as
(Ar)2P-N(R)-P(Ar)2
wherein, Ar is an ortho-substituted phenyl, and R is an alkyl group. The molar ratio of the chromium salt to the modifier is in the range of 1:0.5 to 1:1.0.
The co-catalyst is at least one selected from the group consisting of methylalumoxane (MAO), polymethylalumoxane (P-MAO), and triethylaluminum (TEAL). The molar ratio of the chromium salt to the co-catalyst is in the range of 1: 20 to 1:180, preferably 1: 80 to 1: 180.
The fluid medium is at least one selected from the group consisting of hexane, cyclohexane and heptane.
In second aspect, the present disclosure provides a process for preparing a catalyst composition for olefin oligomerization. The process comprises mixing in oxygen free atmosphere, a predetermined quantity of chromium salt, an electron donor, and a modifier in a fluid medium to obtain a mixture; and adding to the mixture a co-catalyst followed by stirring at a speed in the range of 300 rpm to 700 rpm, preferably 500-600 rpm to obtain the catalyst composition.
Typically, the step of admixing a co-catalyst with the mixture is carried out under stirring at a speed in the range of 300 rpm to 700 rpm.
In third aspect, the present disclosure provides a process for olefin oligomerization using a catalyst composition comprising a chromium salt, an electron donor, a modifier, a co-catalyst and a fluid medium.
The process comprises oligomerizing ethylene under oxygen free atmosphere in the presence of the catalyst composition under stirring at a speed in the range of 200 to 600 rpm, at a temperature in the range of 40 °C to 100 °C and a pressure in the range of 10 kg/cm2 to 50 kg/cm2 to obtain an oligomer.
The olefin is ethylene and the oligomer is at least one selected from 1-hexene and 1- octene.
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 oligomerization of olefin is of great interest. However, the conventional olefin oligomerization techniques are associated with drawbacks such as low selectivity towards desired products, due to formation of by-products. Formation of the byproducts reduces the overall catalyst productivity and affects the economics of the commercial production.
To overcome the drawbacks of the conventional processes, the present disclosure envisages a catalyst composition for selective olefin oligomerization and a process for preparing the same.
In one aspect, the present disclosure provides a catalyst composition for olefin oligomerization. The catalyst composition comprises a chromium salt in an amount in the range of 0.05 to 0.5 wt%; an electron donor in an amount in the range of 0.1 to 1.0 wt%; a modifier in an amount in the range of 0.05 to 1.0 wt%; a co-catalyst in an amount in the range of 1.0 to 5.0 wt% and a fluid medium in an amount in the range of 95.0 to 97.0 wt%.
In accordance with the process of the present disclosure, the chromium salt is at least one selected from the group consisting of chromium trichloride tris tetrahydrofuran complex, chromium tris(2-ethylhexanoate), chromium(III)octanoate, and chromium(III)acetylacetonate. In accordance with one embodiment of the present disclosure, the chromium salt is chromium tris(2-ethylhexanoate).
In accordance with the process of the present disclosure, the electron donor is at least one selected from the group consisting of 2,5-dimethylpyrrole, tris(4-methoxyphenyl) phosphine, 2,5-dimethylthiophene, cis-2,6-dimethylpiperidine, tetrahydrofuran, 2,5-dimethyl tetrahydrofuran, 2-tert butylfuran, N,N-bis(diphenylphosphino) (isopropyl)amine, and 2,6-Bis[bis(diphenylphosphino)amino]pyridine.
In accordance with the process of the present disclosure, the molar ratio of the chromium salt to the electron donor is in the range of 1: 5 to 1: 25. In accordance with the embodiments of the present disclosure, the molar ratio of the chromium salt to the electron donor is in the range of 1: 20 to 1: 25.
In accordance with the process of the present disclosure, the modifier is represented as
(Ar)2P-N(R)-P(Ar)2
wherein, Ar is an ortho-substituted phenyl, and R is an alkyl group.
In accordance with the process of the present disclosure, the modifier is at least one selected from the group consisting of (phenyl)2P-N(i-propyl)-P(phenyl)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2.
In accordance with the process of the present disclosure, the molar ratio of the chromium salt to the modifier is in the range of 1:0.5 to 1:1.0. In accordance with the embodiments of the present disclosure, the molar ratio of the chromium salt to the modifier is in the range of 1:0.8 to 1:1.0.
In accordance with the process of the present disclosure, the co-catalyst is at least one selected from the group consisting of methylalumoxane (MAO), polymethylalumoxane (P-MAO) and triethylaluminum (TEAL).
In accordance with one embodiment of the present disclosure, the co-catalyst is methylalumoxane (MAO).
In accordance with another embodiment of the present disclosure, the co-catalyst is a combination of polymethylalumoxane (P-MAO), and triethylaluminum (TEAL).
In accordance with the process of the present disclosure, the molar ratio of the chromium salt to the co-catalyst is in the range of 1: 20 to 1:180, preferably 1: 80 to 1: 180.
In accordance with the process of the present disclosure, the fluid medium is at least one selected from the group consisting of hexane, cyclohexane, and heptane.
In accordance with the present disclosure, the selectivity of oligomerization reaction is enhanced by carrying out the reaction in an aliphatic organic solvent contrary to the teachings in the conventional processes, wherein aromatic solvent is used for oligomerization reaction. Though aromatic solvents as taught in the conventional techniques give higher yields, but it lead to significantly higher polyethylene formation which is a by-product and not desired.
In accordance with one embodiment of the present disclosure, the catalyst composition comprises a chromium salt; an electron donor; a modifier; a co-catalyst and a fluid medium, wherein the molar ratio of the chromium salt to the electron donor is in the range of 1: 5 to 1: 25.
In accordance with another embodiment of the present disclosure, the catalyst composition comprises a chromium salt; an electron donor; a modifier; a co-catalyst and a fluid medium, wherein the molar ratio of the chromium salt to the modifier is in the range of 1: 0.5 to 1: 1.0.
In accordance with still another embodiment of the present disclosure, the catalyst composition comprises a chromium salt; an electron donor; a modifier; a co-catalyst and a fluid medium, wherein the molar ratio of the chromium salt to the co-catalyst is in the range of 1: 20 to 1: 180.
In accordance with the exemplary embodiments of the present disclosure, the catalyst composition comprises chromium (III) 2-ethylhexnoate; an electron donor selected from 2,5-dimethyl tetrahydrofuran, 2,5-dimethylpyrrole and 2,5-dimethylthiophene; a modifier selected from (phenyl)2P-N(i-propyl)-P(phenyl)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2, (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2; a co-catalyst selected from methylaluminoxane (MAO), poly- methylaluminoxane (PMAO) and triethylaluminum (TEAL); and heptane.
In accordance with one exemplary embodiment of the present disclosure, the catalyst composition comprises chromium (III) 2-ethylhexnoate; 2,5-dimethyl tetrahydrofuran; (phenyl)2P-N(i-propyl)-P(phenyl)2; combination of methylaluminoxane (MAO) and triethylaluminum (TEAL), wherein molar ratio of methylaluminoxane to triethylaluminum is 1:1; and heptane.
In second aspect, the present disclosure provides a process for preparing a catalyst composition for olefin oligomerization. The process comprises mixing in oxygen free atmosphere, a predetermined quantity of chromium salt, an electron donor, and a modifier in a fluid medium to obtain a mixture; and adding to the mixture a co-catalyst followed by stirring at a speed in the range of 300 rpm to 700 rpm, preferably 500-600 rpm to obtain the catalyst composition.
In accordance with the embodiments of the present disclosure, the step of ad-mixing a co-catalyst with the mixture is carried out under stirring at a speed in the range of 300 rpm to 700 rpm.
In third aspect, a process for olefin oligomerization using the catalyst composition of the present disclosure is disclosed, wherein the oligomer selectivity is more than 96%.
The process comprises oligomerizing olefin under oxygen free atmosphere in the presence of a catalyst composition comprising a chromium salt, an electron donor, and a modifier, a co-catalyst and a fluid medium to obtain a reaction mixture. The reaction mixture is stirred at a speed in the range of 200 to 600 rpm, at a temperature in the range of 40 °C to 100 °C and a pressure in the range of 10 kg/cm2 to 50 kg/cm2 to obtain an oligomer.
In accordance with the process of the present disclosure, a chain terminating agent is used to terminate the oligomerization reaction. The chain terminating agent is selected from the group consisting of methanol, ethanol, hexanol and octanol.
In accordance with one embodiment of the present disclosure, the olefin is ethylene and the oligomer is at least one selected from 1-hexene and 1- octene.
Ligand / donor molecules coordinate with the metal center and affect both the electron density and space around the metal center. The formation of by-products can be minimized by controlling the electron density and steric effect around the metal center. In order to achieve the object, the catalyst composition of the present disclosure comprises mixed donor i.e. an electron donor and a modifier. The catalyst composition of the present disclosure can readily reduce the coproduction of internal or isomerized olefins to less than 4 wt%. Moreover, the catalyst composition of the present disclosure provides the desired oligomers with as high purity as 98% to 99%, thereby obviating the trouble and expense of the further purification.
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
Example 1: Preparation of the catalyst composition for olefin oligomerization in accordance with the present disclosure
Experiment 1:
Initially, chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 104 mg, 0.215 mmol) was dissolved in toluene (5 mL) under nitrogen atmosphere. 2,5-dimethyltetrahydrofuran (400 mg, 4.0 mmol) and (phenyl)2P-N(i-propyl)-P(phenyl)2 ligand (51 mg, 1.2 mmol) were added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 600 mL reactor containing dry heptane (150 mL). 10% solution of methyl alumoxane in toluene (18 mL) was then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition of the present disclosure. The molar proportion of Cr: modifier: donor: MAO was 1: 0.8: 25: 180.
Experiment 2:
Chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 124 mg, 0.184 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. 2,5-dimethyltetrahydrofuran (415 mg,4.1 mmol) and (phenyl)2P-N(i-propyl)-P(phenyl)2 ligand (74 mg, 1.73 mmol) were added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 600 mL reactor containing dry heptane (150 mL). 10% solution of methylaluminoxane in toluene (15 mL) was then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition of the present disclosure. The molar proportion of Cr: modifier: donor: MAO was 1: 1.0: 23: 125.
Experiment 3:
Chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 144 mg, 0.209 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. 2,5-dimethyltetrahydrofuran donor (446 mg, 4.4 mmol) and (phenyl)2P-N(i-propyl)-P(phenyl)2 ligand (75 mg, 1.75 mmol) were added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 600 mL reactor containing dry heptane (150 mL). Polymethylalumoxane in toluene (3.5 mL) and triethylaluminum (1.2 mL) were then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition of the present disclosure. The molar proportion of Cr: modifier: donor: PMAO: TEAL was 1: 0.8: 20: 40: 40.
Experiment 4:
Chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 196 mg, 0.280 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. 2,5-dimethyltetrahydrofuran (606 mg, 6.0mmol) and (phenyl)2P-N(i-propyl)-P(phenyl)2 ligand (107 mg, 2.5 mmol) were added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 600 mL reactor containing dry heptane (150 mL). Triethylaluminium (2 mL) was then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition. The molar proportion of Cr: modifier: donor: TEAL was 1: 0.9: 22: 50.
Experiment 5:
Chromium (III) 2-ethylhexnoate ((70 % in mineral spirit; 137 mg, 0.20 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. 2,5-dimethylthiophene (68 mg, 6.0mmol) and (phenyl)2P-N(i-propyl)-P(phenyl)2 ligand (45 mg, 1.0 mmol) were added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 600 mL reactor containing dry heptane (150 mL). 10 % methyl alumoxane in toluene (11 mL) was then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition. The molar proportion of Cr: modifier: donor: MAO was 1: 0.5: 3: 80.
Experiment 6:
Chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 173 mg, 0.25 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. 2,5-dimethylpyrole (110 mg, 1.1 mmol) and (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2 ligand (108 mg, 1.2 mmol) were added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 600 mL reactor containing dry heptane (150 mL). Polymethyl alumoxane in toluene (0.5 mL, 1.1 mmol) and triethylaluminum (1 mL, 7.3 mmol) were then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition. The molar proportion of Cr: modifier: donor: PMAO: TEAL was 1: 0.5: 4.5: 5: 30.
Experiment 7:
Chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 139 mg, 0.20 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. 2,5-dimethylpyrole donor (97 mg,1.0 mmol) and (Ph2P)2-N(6)-Pyridine(N)-(2)N-(PPh2)2 ligand (75 mg, 0.9 mmol) were added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 600 mL reactor containing dry heptane (150 mL). Polymethyl alumoxane in toluene (0.6 mL, 1.4 mmol) and triethylaluminum (1.8 mL, 1.3 mmol) were then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition. The molar proportion of Cr: modifier: donor: PMAO: TEAL was 1: 0.5: 5: 7: 65.
Experiment 8 (Control example, without mixed donor):
Chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 150 mg, 0.215 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. Cis-2,6-dimethylpiperidine donor (138 mg, 1.2 mmol) was added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 300 mL reactor containing dry toluene (100 mL). Triethylaluminum (1.2 mL) was then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition. The molar proportion of Cr: donor: TEAL was 1: 5.5: 40.
Experiment 9 (Control example, without mixed donor):
Chromium (III) 2-ethylhexnoate (70 % in mineral spirit; 160 mg, 0.230 mmol) was dissolved in toluene (5mL) under nitrogen atmosphere. 3,5-dimethylpyrazole (74 mg, 7.7 mmol) was added, followed by stirring for 5 min to obtain a mixture.
The so obtained mixture was transferred using a Schlenk addition funnel to a 300 mL reactor containing dry toluene (200 mL). Triethylaluminum (1.2 mL) was then charged into the reactor under nitrogen atmosphere and stirred at a speed of 500 rpm to obtain the catalyst composition. The molar proportion of Cr: donor: TEAL was 1: 3.3: 60.
Example 2: Ethylene Oligomerization using the catalyst composition of the present disclosure
General procedure:
Ethylene was fed into the reactor containing catalyst composition of the present application at a pressure of 28 kg/cm2 continuously while the reactor temperature was maintained at specific predetermined temperature. Onset of the oligomerization reaction was indicated by an exotherm that was monitored and controlled by cooling the reactor by a circulating bath containing chilled water. After 1 hour, the reaction was stopped by disconnecting the ethylene feed. The contents in the reactor were cooled to 18 °C and thereafter degassed carefully to vent out excess ethylene. The liquid mixture in the reactor was quenched by injecting 5% acidic methanol.
Experiments 10-18:
Experiments 10-18 were carried out by following the general procedure described herein above. The results for the oligomerization reactions are provided in Table 1 given below.
Table 1: Oligomerization of ethylene
Ex.
No. Catalyst used Reaction temperature
(°C) Yield
(gm) Ethylene Conversion 1-Octene selectivity (%) 1-hexene selectivity (%) Polyethylene recovered (%) Productivity of the catalyst
Kg/g of Cr
1 Ex. 1 50 22.1 44 99 96 1.3 3.8
2 Ex. 2 60 25 43 99 95 19 3.7
3 Ex. 3 50 81.0 71 99 94 6 10
4 Ex. 4 80 7.0 19 99 97.5 79 0.62
5 Ex. 5 50 3.5 10 99 97 24 0.3
6 Ex. 6 50 21.0 36 1.0 51 3.8 2.2
7 Ex. 7 50 10.2 20 2.4 29 10 2.6
8
(Control) Ex. 8 50 7.0 13 - 97.5 60 0.3
9
(Control) Ex. 9 90 1.7 5 - 97 15 0.25

It is evident from the above examples that the catalyst composition according to the present disclosure exhibited remarkably improved selectivity to alpha-olefin (1-hexene and 1-octene) and produced a very small amount of solid by-products (such as PE).
In particular, the use of the catalyst composition of the present disclosure enables both 1-hexene selectivity and 1-octene selectivity to be more than 90 wt%, which is much higher than that of control examples 8 and 9. Therefore, further purification of the products becomes simplified and cost effective which leads to reduced commercialization cost.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
? a catalyst composition for selective oligomerization of olefin;
? a process for the preparation of the catalyst composition for selective oligomerization of olefin; and
? a process for selective oligomerization of olefin to eliminate completely or at least further reduces the undesired internal or isomerized olefins or polymeric by-products and thereby improves selectivity of desired olefins.
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.
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.
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.
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.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments 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.