Description:FIELD
The present disclosure relates to a catalyst composition for olefin oligomerization and a process for its preparation. Particularly, the present disclosure relates to a catalyst composition for olefin oligomerization comprising aquated chromium salts.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
The preparation of 1-hexene by trimerization of ethylene produces by-products such as polyethylene, internal olefins and higher alpha olefin oligomers. The formation of the by-products reduces overall catalyst productivity for the preparation of 1-hexene and affects the economics of commercial production. Further, the formation of by-product polyethylene poses serious complications in the plant operations. The polyethylene deposits on the reactor walls, pumps, heat exchanger and the like and deteriorates their performance.
In the conventional processes of olefin trimerization, the catalyst is prepared by mixing Cr (EH)3 (EH = 2-ethylhexanoate), 2, 5-dimethylpyrrole, Et3Al, and Et2AlCl in a 1:3:11:8 mole ratio in toluene. On generation of the catalyst, the precipitate is formed in the catalyst solution in the conventional process which needs to be separated from the catalyst solution for the excellent activity of the catalyst and low polyethylene formation. The separation of the precipitate from the catalyst solution is a tedious job and requires air free equipments. The precipitate free catalyst solution is the ideal catalyst because it avoids the filtration process and makes the process safe and cost effective. The formation of precipitate is dependent on the composition of metal precursor i.e. chromium (III) 2-ethylhexanoate. The composition of chromium (III) 2-ethylhexanoate depends on its method of preparation. The presence of chromium oligomers in aquated chromium (III) 2-ethylhexanoate produces solids in the catalyst solution which affects the catalyst selectivity in terms of high polymer formation. Further, batch-to-batch variations in the quality of commercial chromium (III) 2-ethylhexanoate samples can have major influence upon the productivity and selectivity of ethylene trimerization catalyst system.
There is, therefore, felt a need to provide a catalyst composition and a process for its preparation that mitigates the aforementioned drawbacks or at least provides a useful alternative.
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 background or to at least provide a useful alternative.
An object of the present disclosure is to provide a catalyst composition for olefin oligomerization.
Another object of the present disclosure is to provide a catalyst composition comprising aquated chromium salts.
Still another object of the present disclosure is to provide a catalyst composition having high productivity for oligomerization of ethylene to 1-hexene.
Yet another object of the present disclosure is to provide a catalyst composition which can provide high selectivity for 1-hexene.
Still another object of the present disclosure is to provide a process for the preparation of aquated chromium salts.
Yet another object of the present disclosure is to provide a process for the preparation of a catalyst composition comprising the aquated chromium salts.
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 for olefin oligomerization. The catalyst composition comprises an aquated chromium salt; at least one organic ligand; a first co-catalyst; a second co-catalyst; and at least one fluid medium, wherein the aquated chromium salt is a reaction product of a chromium precursor and a carboxylic acid, wherein a molar ratio of the chromium precursor to the carboxylic acid is in the range of 1:4 to 1:9; and wherein a molar ratio of the aquated chromium salt to the organic ligand is in the range of 1:1 to 1:8; a molar ratio of the aquated chromium salt to the first co-catalyst is in the range of 1:8 to 1:15; and a molar ratio of the aquated chromium salt to the second co-catalyst is in the range of 1:5 to 1:15.
The present disclosure further relates to a process for the preparation of an aquated chromium salt. The process comprises dissolving a predetermined amount of inorganic salt in water to obtain a salt solution. A predetermined amount of a carboxylic acid is added to the salt solution under stirring to obtain a salt of carboxylic acid. Separately, a predetermined amount of a chromium precursor is dissolved in water to obtain a chromium precursor solution. The chromium precursor solution is slowly added to the salt of carboxylic acid over a first predetermined time period under stirring to obtain a slurry. A predetermined amount of a first fluid medium is added to the slurry and stirred at a first predetermined temperature for a second predetermined time period to obtain a biphasic mixture comprising an organic layer and an aqueous layer. The biphasic mixture is cooled to a second predetermined temperature followed by separating an organic layer to obtain a separated organic layer. The separated organic layer is added to a second fluid medium to obtain a granular solid and filtering the granular solid and air drying to obtain the aquated chromium salt.
Furthermore, the present disclosure relates to a process for the preparation of a catalyst composition. The process comprises mixing predetermined amounts of an aquated chromium salt, an organic ligand and a third fluid medium to obtain a first mixture, wherein the aquated chromium salt is a reaction product of a chromium precursor and a carboxylic acid, wherein a molar ratio of the chromium precursor to the carboxylic acid is in the range of 1:4 to 1:9; and wherein a molar ratio of the aquated chromium salt to the organic ligand is in the range of 1:1 to 1:8. Separately, predetermined amounts of at least one first co-catalyst, at least one second co-catalyst and a third fluid medium are mixed to obtain a second mixture. The first mixture is admixed with the second mixture at a third predetermined temperature to obtain the catalyst composition. A molar ratio of aquated chromium salt to the first co-catalyst is in the range of 1:8 to 1:15; and a molar ratio of the aquated chromium salt to the second co-catalyst is in the range of 1:5 to 1:15.
DETAILED DESCRIPTION
The present disclosure relates to a catalyst composition for olefin oligomerization and a process for its preparation. Particularly, the present disclosure relates to a catalyst composition for olefin oligomerization comprising aquated chromium salts.
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.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
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.
The preparation of 1-hexene by trimerization of ethylene produces by-products such as polyethylene, internal olefins and higher alpha olefin oligomers. The formation of the byproducts reduces overall catalyst productivity for the preparation of 1-hexene and affects the economics of commercial production. Further, the formation of byproduct polyethylene poses serious complications in the plant operations. The polyethylene deposits on the reactor walls, pumps, heat exchanger and the like and deteriorates their performance.
In the conventional processes of olefin trimerization, the catalyst is prepared by mixing Cr (EH) 3 (EH = 2-ethylhexanoate), 2, 5-dimethylpyrrole, Et3Al, and Et2AlCl in a 1:3:11:8 mole ratio in toluene. On generation of the catalyst the precipitate is formed in the catalyst solution in the conventional process which needs to be separated from the catalyst solution for the excellent activity of the catalyst and low polyethylene formation. The separation of the precipitate from the catalyst solution is a tedious job and requires air free equipments. The precipitate free catalyst solution is the ideal catalyst because it avoids the filtration process and makes the process safe and cost effective. The formation of precipitate is dependent on the composition of metal precursor i.e. chromium (III) 2-ethylhexanoate. The composition of chromium (III) 2-ethylhexanoate depends on its method of preparation. The presence of chromium oligomers in aquated chromium (III) 2-ethylhexanoate produces solids in the catalyst solution which affects the catalyst selectivity in terms of high polymer formation. Further, batch-to-batch variations in the quality of commercial chromium (III) 2-ethylhexanoate samples can have major influence upon the productivity and selectivity of ethylene trimerization catalyst system.
The present disclosure provides a catalyst composition for olefin oligomerization comprising aquated chromium salts and a process of preparation thereof.
In a first aspect, the present disclosure provides a catalyst composition for olefin oligomerization. The catalyst composition comprises:
i. an aquated chromium salt;
ii. at least one organic ligand;
iii. a first co-catalyst;
iv. a second co-catalyst; and
v. at least one fluid medium,
wherein the aquated chromium salt is a reaction product of a chromium precursor and a carboxylic acid, wherein a molar ratio of the chromium precursor to the carboxylic acid is in the range of 1:4 to 1:9.
In an exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:4. In another exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:5. In yet another exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:6. In still another exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:8.
The aquated chromium salt can be selected from the group consisting of Cr (2-ethylhexanoate)3.nH2O, wherein ‘n’ is in the range of 1 to 6, chromium butyrate, chromium pentanoate, chromium hexanoate, chromium decanoate, chromium oleate, chromium stearate, chromium toluate, chromium cresylate, chromium benzoate, chromium alkylbenzoate, and chromium naphthenate. In an exemplary embodiment of the present disclosure the aquated chromium salt is chromium (2-ethyl hexanoate)3.3 H2O.
The aquated chromium salt possesses carbon content in an amount in the range of 55% to 60%. In an embodiment of the present disclosure, the carbon content is 55.96%.
The chromium precursor can be selected from the group consisting of chromium nitrate nonahydrate, chromium chloride hexahydrate, chromium sulphate, chromium bromide and chromium fluoride. In an exemplary embodiment of the present disclosure, the chromium precursor is chromium nitrate nonahydrate.
The carboxylic acid can be selected from the group consisting of 2-ethylhexanoic acid, benzoic acid, acetic acid, formic acid, octanoic acid, salicylic acid, dodecanoic acid, oleic acid, 2-methoxypropionic acid, toluic acid, ascorbic acid, linoleic acid, linolenic acid, acrylic acid, methacrylic acid, naphthoic acid, chloroacetic acid, lactic acid, ricinoleic acid, stearic acid, butyric acid, cyclohexane carboxylic acid, picolinic acid and furan carboxylic acid. In an exemplary embodiment of the present disclosure the carboxylic acid is 2-ethylhexanoic acid.
The organic ligand can be at least one selected from the group consisting of 2, 5 dimethylpyrrole, tris(4-methoxyphenyl) phosphine, 2,5-dimethylthiophene and cis-2,6-dimethylpiperidine. In an exemplary embodiment of the present disclosure, the organic ligand is 2, 5 dimethylpyrrole.
The first co-catalyst can be at least one selected from the group consisting of triethylaluminium (TEAL), tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, triisoprenylaluminum, tri-isobutylaluminum, triphenylaluminum and tri-n-octylaluminum. In an exemplary embodiment of the present disclosure, the first co-catalyst is triethylaluminium (TEAL).
The second co-catalyst can be at least one selected from the group consisting of diethyl aluminium chloride (DEAC), di-isobutyl aluminum chloride and ethyl aluminum dichloride. In an exemplary embodiment of the present disclosure, the second co-catalyst is diethyl aluminium chloride (DEAC).
The fluid medium can be at least one selected from the group consisting of toluene, hexane, cyclohexane, ethylbenzene, heptane, benzene, mesitylene, diethylbenzene and xylenes. In an exemplary embodiment of the present disclosure, the fluid medium is toluene.
A molar ratio of the aquated chromium salt to the organic ligand is in the range of 1:1 to 1:8. In an exemplary embodiment of the present disclosure, the molar ratio of the aquated chromium salt to the organic ligand is 1:4.
A molar ratio of the aquated chromium salt to the first co-catalyst is in the range of 1:8 to 1:15. In an exemplary embodiment of the present disclosure, the molar ratio of the aquated chromium salt to the first co-catalyst is 1:11.
A molar ratio of the aquated chromium salt to the second co-catalyst is in the range of 1:5 to 1:15. In an exemplary embodiment of the present disclosure, the molar ratio of the aquated chromium salt to the second co-catalyst is 1:8.
In a second aspect, the present disclosure provides a process for the preparation of an aquated chromium salt.
The process for the preparation of an aquated chromium salt comprises the following steps:
i. dissolving a predetermined amount of inorganic salt in water to obtain a salt solution;
ii. adding a predetermined amount of a carboxylic acid under stirring to the salt solution to obtain a salt of carboxylic acid;
iii. separately, dissolving a predetermined amount of chromium precursor in water to obtain a chromium precursor solution;
iv. slowly, adding the chromium precursor solution to the salt of carboxylic acid over a first predetermined time period under stirring to obtain a slurry;
v. adding a predetermined amount of a first fluid medium to the slurry and stirring at a first predetermined temperature for a second predetermined time period to obtain a biphasic mixture comprising an organic layer and an aqueous layer;
vi. cooling the biphasic mixture to a second predetermined temperature followed by separating an organic layer to obtain a separated organic layer ;
vii. adding the separated organic layer to a second fluid medium to obtain a granular solid followed by filtering the granular solid and air drying to obtain the aquated chromium salt.
The process for the preparation of an aquated chromium salt is described in detail herein below.
In a first step, a predetermined amount of an inorganic salt is dissolved in water to obtain a salt solution.
The inorganic salt can be at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide. In an exemplary embodiment of the present disclosure, the inorganic salt is sodium hydroxide.
In a second step, a predetermined amount of a carboxylic acid is then added under stirring to the salt solution to obtain a salt of carboxylic acid.
The carboxylic acid can be at least one selected from the group consisting of 2-ethylhexanoic acid, benzoic acid, acetic acid, formic acid, octanoic acid, salicylic acid, dodecanoic acid, oleic acid, 2-methoxypropionic acid, toluic acid, ascorbic acid, linoleic acid, linolenic acid, acrylic acid, methacrylic acid, naphthoic acid, chloroacetic acid, lactic acid, ricinoleic acid, stearic acid, butyric acid, cyclohexane carboxylic acid, picolinic acid and furan carboxylic acid. In an exemplary embodiment of the present disclosure, the carboxylic acid is 2-ethyl hexanoic acid.
A molar ratio of the carboxylic acid to the inorganic salt is in the range of 1:0.5 to 1:1.5. In an exemplary embodiment of the present disclosure, the molar ratio of the carboxylic acid to the inorganic salt is 1:0.99.
In a third step, separately, a predetermined amount of chromium precursor is dissolved in water to obtain a chromium precursor solution.
The chromium precursor can be selected from the group consisting of chromium nitrate nonahydrate, chromium chloride hexahydrate, chromium sulphate and chromium bromide. In an exemplary embodiment of the present disclosure the chromium precursor is chromium nitrate nonahydrate.
A molar ratio of the carboxylic acid to the chromium precursor is in the range of 1:0.05 to 1:0.5. In an exemplary embodiment of the present disclosure, the molar ratio of the carboxylic acid to the chromium precursor is 1: 0.12.
In a fourth step, the chromium precursor solution is slowly added to the salt of carboxylic acid over a first predetermined time period under stirring to obtain a slurry.
The salt of the carboxylic acid can be selected from the group consisting of sodium salt of carboxylic acid, potassium salt of carboxylic acid and calcium salt of carboxylic acid. In an exemplary embodiment of the present disclosure, the salt of carboxylic acid is sodium salt of carboxylic acid.
The first predetermined time period is in the range of 10 minutes to 60 minutes. In an exemplary embodiment of the present disclosure the first predetermined time period is 15 minutes.
In a fifth step, a predetermined amount of a first fluid medium is added to the slurry and stirred at a first predetermined temperature for a second predetermined time period to obtain a biphasic mixture comprising an organic layer and an aqueous layer.
The first fluid medium can be at least one selected from the group consisting of toluene, hexane, cyclohexane, ethylbenzene, heptane, benzene, mesitylene, diethylbenzene and xylenes. In an exemplary embodiment of the present disclosure the first fluid medium is toluene.
A mass ratio of the carboxylic acid to the first fluid medium is in the range of 1:0.5 to 1:1.5. In an exemplary embodiment of the present disclosure, the mass ratio of the carboxylic acid to the first fluid medium is 1:0.74.
The first predetermined temperature is in the range of 70 °C to 110 °C. In an exemplary embodiment of the present disclosure, the first predetermined temperature is 85 °C.
The second predetermined time period is in the range of 1 hour to 4 hours. In an exemplary embodiment of the present disclosure the second predetermined time period is 2 hours.
In a sixth step, the biphasic mixture is cooled to a second predetermined temperature followed by separating an organic layer to obtain a separated organic layer.
The second predetermined temperature is in the range of 20 °C to 35 °C. In an exemplary embodiment of the present disclosure, the second predetermined temperature is 25 °C.
In a seventh step, the separated organic layer is added to a second fluid medium to obtain a granular solid followed by filtration of the granular solid and air drying to obtain the aquated chromium salt.
The aquated chromium salt in accordance with present disclosure possesses carbon content in an amount in the range of 55% to 60%. In an embodiment of the present disclosure, the carbon content is 55.96%.
In a third aspect, the present disclosure provides a process for the preparation of a catalyst composition for olefin oligomerization.
The process for the preparation of the catalyst composition for olefin oligomerization comprises the following steps:
a. mixing predetermined amounts of an aquated chromium salt, an organic ligand, and a third fluid medium to obtain a first mixture;
b. separately, mixing predetermined amounts of at least one first co-catalyst, at least one second co-catalyst and the third fluid medium to obtain a second mixture; and
c. admixing the first mixture and the second mixture at a third predetermined temperature to obtain the catalyst composition.
The aquated chromium salt is a reaction product of a chromium precursor and a carboxylic acid.
The aquated chromium salt is selected from the group consisting of Cr (2-ethylhexanoate)3.nH2O, wherein ‘n’ is in the range of 1 to 6, chromium butyrate, chromium pentanoate, chromium hexanoate, chromium decanoate, chromium oleate, chromium stearate, chromium toluate, chromium cresylate, chromium benzoate, chromium alkylbenzoate, and chromium naphthenate. In an exemplary embodiment of the present disclosure the aquated chromium salt is chromium (2-ethyl hexanoate)3.3H2O.
The chromium precursor can be selected from the group consisting of chromium nitrate nonahydrate, chromium chloride hexahydrate, chromium sulphate, chromium bromide and chromium fluoride. In an exemplary embodiment of the present disclosure, the chromium precursor is chromium nitrate nonahydrate.
The carboxylic acid can be at least one selected from the group consisting of 2-ethylhexanoic acid, benzoic acid, acetic acid, formic acid, octanoic acid, salicylic acid, dodecanoic acid, oleic acid, 2-methoxypropionic acid, toluic acid, ascorbic acid, linoleic acid, linolenic acid, acrylic acid, methacrylic acid, naphthoic acid, chloroacetic acid, lactic acid, ricinoleic acid, stearic acid, butyric acid, cyclohexane carboxylic acid, picolinic acid and furan carboxylic acid. In an exemplary embodiment of the present disclosure the carboxylic acid is 2-ethylhexanoic acid.
The organic ligand can be at least one selected from the group consisting of 2, 5 dimethylpyrrole, tris(4-methoxyphenyl) phosphine, 2,5-dimethylthiophene and cis-2,6-dimethylpiperidine. In an exemplary embodiment of the present disclosure, the organic ligand is 2, 5 dimethylpyrrole.
The third fluid medium can be at least one selected from the group consisting of toluene, hexane, cyclohexane, ethylbenzene, heptane, benzene, mesitylene, diethylbenzene and xylenes. In an exemplary embodiment of the present disclosure, the third fluid medium is toluene.
A molar ratio of the chromium precursor to the carboxylic acid is in the range of 1:4 to 1:9. In an exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:4. In another exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:5. In yet another exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:6. In still another exemplary embodiment of the present disclosure the molar ratio of the chromium precursor to the carboxylic acid is 1:8.
The molar ratio of the aquated chromium salt to the organic ligand is in the range of 1:1 to 1:8. In an exemplary embodiment of the present disclosure, the molar ratio of the aquated chromium salt to the organic ligand is 1:4.
The first co-catalyst can be at least one selected from the group consisting of triethylaluminum (TEAL), tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, triisoprenylaluminum, tri-isobutylaluminum, triphenylaluminum and tri-noctylaluminum. In an exemplary embodiment of the present disclosure, the first co-catalyst is triethylaluminum (TEAL).
The second co-catalyst can be at least one selected from the group consisting of diethyl aluminium chloride (DEAC), di-isobutyl aluminium chloride and ethyl aluminium dichloride. In an exemplary embodiment of the present disclosure, the second co-catalyst is diethyl aluminium chloride (DEAC).
A molar ratio of the aquated chromium salt to the first co-catalyst is in the range of 1:8 to 1:15. In an exemplary embodiment of the present disclosure, the molar ratio of the aquated chromium salt to the first co-catalyst is 1:11.
A molar ratio of the aquated chromium salt to the second co-catalyst is in the range of 1:5 to 1:15. In an exemplary embodiment of the present disclosure, the molar ratio of the aquated chromium salt to the second co-catalyst is 1:8.
The third predetermined temperature is in the range of 20°C to 30°C. In an exemplary embodiment of the present disclosure, the first predetermined temperature is 25°C.
In a fourth aspect, the present disclosure provides a process for olefin oligomerization by using the catalyst composition. The process comprises the following steps:
a. mixing the catalyst composition of the present disclosure in a fourth fluid medium at a fourth predetermined temperature to obtain a third mixture;
b. ageing the third mixture at a third predetermined time period to obtain an aged catalyst composition;
c. oligomerizing an olefin in the presence of the aged catalyst composition under stirring at a predetermined stirring speed at a fifth predetermined temperature and at a predetermined pressure for a fourth predetermined time period to obtain a slurry comprising oligomers;
d. cooling the slurry at a sixth predetermined temperature followed by adding a terminating agent to obtain a product mixture comprising oligomers; and
e. separating the oligomers from the product mixture and drying to obtain oligomerized olefin.
The fourth fluid medium can be at least one selected from the group consisting of cyclohexane, methyl cyclohexane, n-hexane and n-heptane. In an exemplary embodiment of the present disclosure, the third fluid medium is cyclohexane.
The olefin is at least one selected from the group consisting of ethylene and propylene. In an exemplary embodiment of the present disclosure, the olefin is ethylene.
The fourth predetermined temperature is in the range of 45°C to 55°C. In an exemplary embodiment of the present disclosure, the fourth predetermined temperature is 50°C.
The third predetermined time period is in the range of 20 hours to 30 hours. In an exemplary embodiment of the present disclosure, the third predetermined time period is 24 hours.
The predetermined stirring speed is in the range of 350 rpm to 450 rpm. In an exemplary embodiment of the present disclosure, the predetermined stirring speed is 400 rpm.
The fifth predetermined temperature is in the range of 80°C to 100°C. In an exemplary embodiment of the present disclosure, the fifth predetermined temperature is 90°C.
The predetermined pressure is in the range of 20 kg/cm2 to 40 kg/cm2. In an exemplary embodiment of the present disclosure, the predetermined pressure is 30 kg/cm2.
The fourth predetermined time period is in the range of 30 minutes to 90 minutes. In an exemplary embodiment of the present disclosure, the fourth predetermined time period is 60 minutes.
The sixth predetermined temperature is in the range of 5°C to 15°C. In an exemplary embodiment of the present disclosure, the sixth predetermined temperature is 10°C.
The terminating agent is at least one selected from the group consisting of methanol, ethanol, propanol, butanol and 2-ethyl hexanol. In an exemplary embodiment of the present disclosure, the terminating agent is 2-ethyl hexanol.
The oligomer is 1-hexene.
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.
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 the industrial scale.
EXPERIMENTAL DETAILS
Experiment 1: Process for the preparation of the aquated chromium 2- ethylhexanoate in accordance with the present disclosure
Example 1: 16 g of sodium hydroxide was dissolved in 50 ml of distilled water to obtain a sodium hydroxide solution. 58.4 g (405 mmol) of 2-Ethylhexanoic acid was added under stirring to the sodium hydroxide solution to obtain a solution of sodium salt of 2-ethylhexanoic acid. Separately, 20 g (50 mmol) of chromium nitrate nonahydrate was dissolved in 50 ml of distilled water to obtain a chromium nitrate solution. The chromium nitrate solution was slowly added to the solution of sodium salt of 2-ethylhexanoic acid for 15 minutes under stirring to obtain a slurry. 50 ml of toluene was added to the slurry and heated to 85 °C under stirring for 2 hours to obtain a biphasic mixture comprising an organic layer (toluene layer) and an aqueous layer. The so obtained biphasic mixture was cooled to 25 °C to obtain a cooled biphasic mixture comprising an organic layer (toluene layer) and an aqueous layer. The organic layer (toluene layer) was separated from the cooled biphasic mixture to obtain a separated toluene layer. The separated toluene layer was added to 50 ml methanol to obtain granular solids. The granular solids were filtered and air dried to obtain 20.1 g (75%) of the aquated chromium (III) 2-ethylhexanoate.
Examples 2 to 5: The aquated chromium (III) 2-ethylhexanoate samples were prepared by using the same procedure of Example 1 except the molar ratio of chromium nitrate to 2-ethylhexanoic acid were varied in the range of 1:3 to 1:8.
Experiment 2: CHNS analysis of the aquated chromium (III) 2-ethylhexanoate samples
CHNS analysis was done for the characterization and measurement of the ligand content in chromium 2-ethylhexanoate samples prepared in Examples 1-5.The results are summarized in Table 1.
Table 1: CHNS analysis of aquated chromium (III) 2-ethyl hexanoate samples
Example Molar Ratio of Cr:EH
(Chromium:
2-ethyl hexanoic acid) C % H %
Replicates Average Replicates Average
1. 1:8 56.03 55.96 9.80 9.81
1:8 55.90 9.83
2. 1:6 54.98 55.00 9.93 9.80
1:6 55.03 9.68
3. 1:5 54.08 53.96 9.37 9.22
1:5 53.84 9.07
4. 1:4 53.29 53.20 8.77 8.97
1:4 53.12 9.17
5. 1:3 51.95 51.95 8.12 8.10
1:3 51.96 8.08
From table 1, it can be seen that as the molar ratio of Chromium: 2-ethyl hexanoic acid increases from 1:3 to 1:8, the % of carbon content in the sample increases.
In accordance with the present disclosure, the aquated chromium 2- ethylhexanoate was prepared by mixing one equivalent of chromium nitrate and eight equivalents of 2-ethylhexanoate acid in water medium. The prepared aquated chromium carboxylate of the present disclosure is extracted into the hydrocarbon medium. The weight percentage of carbon content in the samples with 1:8 weight ratio of Chromium: 2-ethyl hexanoic acid are found to be 56.03 wt%. Whereas wt% of carbon content, prepared by mixing one equivalent of chromium nitrate and three equivalents of 2-ethylhexanoic acid, is found to be less than 52 wt%. This value is in close agreement with values measured for conventional aquated chromium 2-ethylhexanoate.
The conventional chromium 2-ethylhexanoate comprises chromium oligomers and polymer species. The chromium oligomers and polymers in chromium 2-ethylhexanoate sample decrease the content of ligand in the sample. In other words, chromium metal is less crowded with ligands in chromium oligomers and polymer species. The presence of chromium oligomers in aquated chromium (III) 2-ethylhexanoate produces solids in catalyst solution which affects the catalyst selectivity in terms of high polymer formation.
During the preparation of the aquated chromium (III) 2-ethylhexanoate, the neutral aqua ligands are replaced by 2-ethylhexanoic acid or sodium 2-ethylhexanoate. The addition of excess 2-ethylhexanoic acid eases the replacement of water molecules from the aquated chromium (III) 2-ethylhexanoate. The replacement of water molecules by 2-ethylhexanoic acid increases the ligand content around chromium metal centre thereby increasing the carbon content. In the conventional processes, replacement of water molecules by 2-ethylhexanoic acid is carried out by heating the aquated chromium (III) 2-ethylhexanoate in the presence of excess of 2-ethylhexanoic acid at high temperature (above 140 °C) in a multistep reaction. The additional step increases the overall cost of manufacture of chromium (III) 2-ethylhexanoate.
However, the process of the present disclosure for the preparation of the aquated chromium 2- ethylhexanoate is devoid of any additional step, thereby, making the process convenient and economic.
Experiment 3: Process for the preparation of the catalyst composition comprising the aquated chromium 2- ethylhexanoate in accordance with the present disclosure
Examples I to III: The catalyst compositions I to III were prepared by using the aquated chromium (III) 2-ethylhexanoate samples of examples 1, 2 and 5 of Experiment 1 respectively.
0.53 g aquated chromium (III) 2-ethylhexanoate was mixed with 0.38 g 2,5-dimethylpyrrole in 10 mL toluene in a first vessel to obtain a first mixture. Separately 7.9 ml triethylaluminum (20 wt% in toluene) and 5.4 ml diethylaluminum chloride (20 wt% in toluene) were mixed in a second vessel to obtain a second mixture. The first mixture and the second mixture were admixed at 25 °C to obtain the catalyst composition. The molar proportion of the aquated chromium (III) 2-ethylhexanoate: DMP: TEAL: DEAC was 1: 4: 11: 8.
All the catalyst systems (catalyst I to catalyst III) were tested for their activity and polymer formation in ethylene oligomerization reaction.
Experiment 4: Process of ethylene oligomerization using the catalyst compositions prepared in Experiment 3
The catalyst compositions I to III prepared by using the aquated chromium (III) 2-ethylhexanoate samples of Examples 1, 2 and 5 of Experiment 1 are tested for ethylene oligomerization.
The catalyst composition obtained in Experiment 3 was mixed with 400 ml cyclohexane at 50 °C to obtain a third mixture. The obtained third mixture was aged for 24 hours to obtain an aged catalyst composition. The aged catalyst composition was thoroughly mixed by using a paddle type stirrer at a speed of 400 rpm in a reactor. Ethylene gas was fed to the reactor till a pressure of 30 kg/cm2 was attained, while the reactor temperature was increased to 90 °C. The oligomerization reaction was monitored by an exotherm and the exothermicity of the reaction was controlled by cooling the reactor by a circulating bath containing chilled water. Stirring was continued for 1 hour to obtain a slurry comprising ethylene. Thereafter ethylene feed was disconnected. The obtained slurry in the reactor was cooled to 10 °C and degassed carefully by venting out excess ethylene. The contents of the reactor were quenched by injecting 2-ethyl hexanol, which is used as a terminating agent to obtain a product mixture comprising 1-hexene. The product 1-hexene was collected and weighed separately.
The liquid product is obtained along with some gaseous products. The composition of the gas and the liquid samples were analysed by Gas chromatography using an Agilent 123-1033: DB-1 30 m * 320 µm * 1 µm GC column and flame ionization detector respectively.
The performance of the catalyst compositions comprising the aquated chromium (III) 2-ethylhexanoate in olefin oligomerization is summarized in table 2.
Table 2: Performance of the catalyst composition comprising the aquated chromium (III) 2-ethylhexanoate
catalyst Molar Ratio of Cr:EH
(Chromium:
2-ethyl hexanoic acid) Activity (Kg hexene /g Cr/h) Selectivity of hexene Selectivity of 1-hexene PE (Wt%)
Catalyst I 1:8 26.0 91.0 99.51 0.016
Catalyst II 1:6 25.0 91.1 99.50 0.015
Catalyst III 1:3 22.1 92.0 99.62 0.115
Table 2 shows that as carbon content (%) increases in the catalyst composition containing the aquated chromium 2-ethylhexanoate samples from catalyst III to catalyst I, the activity of catalyst increases and formation of polyethylene decreases in the ethylene oilgomerization reaction.
However, it was observed that further increasing the carbon content by increasing the molar ratio of chromium to 2-ethyl hexanoic acid (i.e. beyond 1:8), does not affect much the activity of the catalyst and reduction of polyethylene in the ethylene oilgomerization reaction. Thus, the molar ratio of chromium to 2-ethyl hexanoic acid in the range of 1:4 to 1:9 is the optimized ratio as the catalyst is found to give the best results in this optimized range of 1:4 to 1:9.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of;
? a catalyst composition for olefin oligomerization that:
• provides 1-hexene with high purity (> 99% alpha purity) and selectivity;
• forms lower by-product polyethylene; and
• is economical;
and
? a process for the preparation of the aquated chromium salts that:
• is convenient and economical; and
• provides high carbon content to the aquated chromium salts.
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 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.
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.
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 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.
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:WE CLAIM:
1. A catalyst composition for olefin oligomerization, said catalyst composition comprising:
i. an aquated chromium salt;
ii. at least one organic ligand;
iii. a first co-catalyst;
iv. a second co-catalyst; and
v. at least one fluid medium,
wherein said aquated chromium salt is a reaction product of a chromium precursor and a carboxylic acid, wherein a molar ratio of said chromium precursor to said carboxylic acid is in the range of 1:4 to 1:9; and
wherein a molar ratio of;
? said aquated chromium salt to said organic ligand is in the range of 1:1 to 1:8;
? said aquated chromium salt to said first co-catalyst is in the range of 1:8 to 1:15; and
? said aquated chromium salt to said second co-catalyst is in the range of 1:5 to 1:15.
2. The catalyst composition as claimed in claim 1, wherein said chromium precursor is selected from the group consisting of chromium nitrate nonahydrate, chromium chloride hexahydrate, chromium sulphate, chromium bromide and chromium fluoride.
3. The catalyst composition as claimed in claim 1, wherein said carboxylic acid is selected from the group consisting of 2-ethylhexanoic acid, benzoic acid, acetic acid, formic acid, octanoic acid, salicylic acid, dodecanoic acid, oleic acid, 2-methoxypropionic acid, toluic acid, ascorbic acid, linoleic acid, linolenic acid, acrylic acid, methacrylic acid, naphthoic acid, chloroacetic acid, lactic acid, ricinoleic acid, stearic acid, butyric acid, cyclohexane carboxylic acid, picolinic acid and furan carboxylic acid.
4. The catalyst composition as claimed in claim 1, wherein said organic ligand is at least one selected from the group consisting of 2, 5 dimethylpyrrole, tris(4-methoxyphenyl) phosphine, 2,5-dimethylthiophene and cis-2,6-dimethylpiperidine.
5. The catalyst composition as claimed in claim 1, wherein said first co-catalyst is at least one selected from the group consisting of triethylaluminium (TEAL), tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, triisoprenylaluminum, tri-isobutylaluminum, triphenylaluminum and tri-n-octylaluminum.
6. The catalyst composition as claimed in claim 1, wherein said second co-catalyst is at least one selected from the group consisting of diethyl aluminium chloride (DEAC), di-isobutyl aluminium chloride and ethyl aluminium dichloride.
7. The catalyst composition as claimed in claim 1, wherein said fluid medium is at least one selected from the group consisting of toluene, hexane, cyclohexane, ethylbenzene, heptane, benzene, mesitylene, diethylbenzene and xylenes.
8. The catalyst composition as claimed in claim 1, wherein said aquated chromium salt is selected from the group consisting of Cr (2-ethylhexanoate)3.nH2O, wherein ‘n’ is in the range of 1 to 6, chromium butyrate, chromium pentanoate, chromium hexanoate, chromium decanoate, chromium oleate, chromium stearate, chromium toluate, chromium cresylate, chromium benzoate, chromium alkylbenzoate, and chromium naphthenate.
9. The catalyst composition as claimed in claim 1, wherein said aquated chromium salt possesses carbon content in an amount in the range of 55% to 60%.
10. A process for the preparation of an aquated chromium salt, said process comprising the following steps:
i. dissolving a predetermined amount of an inorganic salt in water to obtain a salt solution;
ii. adding a predetermined amount of a carboxylic acid under stirring to said salt solution to obtain a salt of carboxylic acid;
iii. separately, dissolving a predetermined amount of chromium precursor in water to obtain a chromium precursor solution;
iv. slowly, adding said chromium precursor solution to said salt of carboxylic acid over a first predetermined time period under stirring to obtain a slurry;
v. adding a predetermined amount of a first fluid medium to said slurry and stirring at a first predetermined temperature for a second predetermined time period to obtain a biphasic mixture comprising an organic layer and an aqueous layer;
vi. cooling said biphasic mixture to a second predetermined temperature followed by separating an organic layer to obtain a separated organic layer;
vii. adding said separated organic layer to a second fluid medium to obtain a granular solid and filtering said granular solid followed by air drying to obtain said aquated chromium salt.
11. The process as claimed in claim 10, wherein
? said inorganic salt is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide and calcium hydroxide;
? said carboxylic acid is at least one selected from the group consisting of 2-ethylhexanoic acid, benzoic acid, acetic acid, formic acid, octanoic acid, salicylic acid, dodecanoic acid, oleic acid, 2-methoxypropionic acid, toluic acid, ascorbic acid, linoleic acid, linolenic acid, acrylic acid, methacrylic acid, naphthoic acid, chloroacetic acid, lactic acid, ricinoleic acid, stearic acid, butyric acid, cyclohexane carboxylic acid, picolinic acid and furan carboxylic acid;
? said chromium precursor is selected from the group consisting of chromium nitrate nonahydrate, chromium chloride hexahydrate, chromium sulphate, chromium bromide and chromium fluoride.
12. The process as claimed in claim 10, wherein said first fluid medium is at least one selected from the group consisting of toluene, hexane, cyclohexane, ethylbenzene, heptane, benzene, mesitylene, diethylbenzene and xylenes; and said second fluid medium is at least one selected from the group consisting of methanol, ethanol, propanol, butanol, 2-ethyl hexanoyl and acetone.
13. The process as claimed in claim 10, wherein a molar ratio of said carboxylic acid to said inorganic salt is in the range of 1:0.5 to 1:1.5; wherein a molar ratio of said carboxylic acid to said chromium precursor is in the range of 1:0.05 to 1:0.5; wherein a mass ratio of said carboxylic acid to said first fluid medium is in the range of 1:0.5 to 1:1.
14. The process as claimed in claim 10, wherein said first predetermined temperature is in the range of 70 °C to 110 °C; said second predetermined temperature is in the range of 20 °C to 35 °C; said first predetermined time period is in the range of 10 minutes to 60 minutes; and said second predetermined time period is in the range of 1 hour to 4 hours.
15. A process for the preparation of a catalyst composition, said process comprising the following steps:
a. mixing predetermined amounts of an aquated chromium salt, an organic ligand, and a third fluid medium to obtain a first mixture;
b. separately, mixing predetermined amounts of at least one first co-catalyst, at least one second co-catalyst and said third fluid medium to obtain a second mixture; and
c. admixing said first mixture and said second mixture at a third predetermined temperature to obtain said catalyst composition.
wherein said aquated chromium salt is a reaction product of a chromium precursor and a carboxylic acid, wherein a molar ratio of said chromium precursor to said carboxylic acid is in the range of 1:4 to 1:9; and
wherein a molar ratio of;
? said aquated chromium salt to said organic ligand is in the range of 1:1 to 1:8;
? said aquated chromium salt to said first co-catalyst is in the range of 1:8 to 1:15; and
? said aquated chromium salt to said second co-catalyst is in the range of 1:5 to 1:15.
16. The process as claimed in claim 15, wherein
? said aquated chromium salt is selected from the group consisting of Cr (2-ethylhexanoate)3.nH2O, wherein ‘n’ is in the range of 1 to 6, chromium butyrate, chromium pentanoate, chromium hexanoate, chromium decanoate, chromium oleate, chromium stearate, chromium toluate, chromium cresylate, chromium benzoate, chromium alkylbenzoate, and chromium naphthenate;
? said organic ligand is at least one selected from the group consisting of 2, 5 dimethylpyrrole, tris(4-methoxyphenyl) phosphine, 2,5-dimethylthiophene and cis-2,6-dimethylpiperidine;
? said third fluid medium is at least one selected from the group consisting of toluene, hexane, cyclohexane, ethylbenzene, heptane, benzene, mesitylene, diethylbenzene and xylenes;
? said first co-catalyst is at least one selected from the group consisting of triethylaluminium (TEAL), tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, triisoprenylaluminum, tri-isobutylaluminum, triphenylaluminum and tri-n-octylaluminum;
? said second co-catalyst is at least one selected from the group consisting of diethyl aluminium chloride (DEAC), di-isobutyl aluminum chloride and ethyl aluminum dichloride.
17. The process as claimed in claim 15, wherein a molar ratio of said aquated chromium salt to said organic ligand is in the range of 1:1 to 1:8; wherein a molar ratio of said aquated chromium salt to said first co-catalyst is in the range of 1:8 to 1:15; wherein a molar ratio of said aquated chromium salt to said second co-catalyst is in the range of 1:5 to 1:15.
18. The process as claimed in claim 15, wherein said third predetermined temperature is in the range of 20°C to 30°C.
19. A process for olefin oligomerization by using a catalyst composition as claimed in claim 1, said process comprising the following steps:
a. mixing said catalyst composition in a fourth fluid medium at a fourth predetermined temperature to obtain a third mixture;
b. ageing said third mixture at a third predetermined time period to obtain an aged catalyst composition;
c. oligomerizing an olefin in the presence of said aged catalyst composition under stirring at a predetermined stirring speed at a fifth predetermined temperature and at a predetermined pressure for a fourth predetermined time period to obtain a slurry comprising oligomers;
d. cooling said slurry at a sixth predetermined temperature followed by adding a terminating agent to obtain a product mixture comprising oligomers; and
e. separating said oligomers from said product mixture and drying to obtain oligomerized olefin.
20. The process as claimed in claim 19, wherein
? said fourth fluid medium is at least one selected from the group consisting of cyclohexane, methyl cyclohexane, n-hexane and n-heptane;
? said olefin is at least one selected from the group consisting of ethylene, and propylene; and
? said terminating agent is at least one selected from the group consisting of methanol, ethanol, propanol and 2-ethylhexanol.
21. The process as claimed in claim 19, wherein said fourth predetermined temperature is in the range of 45°C to 55°C; wherein said fifth predetermined temperature is in the range of 80°C to 100°C; and wherein said sixth predetermined temperature is in the range of 5°C to 15°C.
22. The process as claimed in claim 19, wherein said third predetermined time period is in the range of 20 hours to 30 hours; and wherein said fourth predetermined time period is in the range of 30 minutes to 90 minutes.
23. The process as claimed in claim 19, wherein said predetermined stirring speed is in the range of 350 rpm to 450 rpm; and wherein said predetermined pressure is in the range of 20 kg/cm2 to 40 kg/cm2.
Dated this 05th day of May, 2023

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI