Catalyst systems suitable for the tetramerization of ethylene and methods of using the same
Catalyst systems suitable for tetramerizing ethylene to form 1-octene may include a catalyst including a chromium compound coordinated with a ligand and a co-catalyst including an organoaluminum compound. The ligand may have a chemical structure according to Formula (1), wherein R 1 is a (C 3 -C 20 ) substituted or unsubstituted hydrocarbyl group; R 2 , R 3 , R 4 , and R 5 are independently chosen from (C 1 -C 50 ) hydrocarbyl groups; and R 1 and N are in a cis configuration.
1. A catalyst system suitable for tetramerizing ethylene to form 1-octene, the catalyst system comprising:
a catalyst comprising a chromium compound coordinated with a ligand; and
a co-catalyst comprising an organoaluminum compound,
wherein:
the ligand has the chemical structure:
R 1 is a (C 3 -C 20 ) substituted or unsubstituted hydrocarbyl group;
R 2 , R 3 , R 4 , and R 5 are independently chosen from (C 1 -C 50 ) hydrocarbyl groups; and
R 1 and N are in a cis configuration.
2. The catalyst system of claim 1 , wherein R 1 is a (C 3 -C 20 ) unsubstituted hydrocarbyl group.
3. The catalyst system of claim 1 , wherein R 1 is a (C 3 -C 20 ) alkyl group.
4. The catalyst system of claim 1 , wherein R 1 is a (C 3 -C 20 ) substituted hydrocarbyl group comprising one or more heteroatoms.
5. The catalyst system of claim 4 , wherein the one or more heteroatoms are chosen from boron, nitrogen, oxygen, fluorine, phosphorous, silicon, sulfur, chlorine, and combinations thereof.
6. The catalyst system of claim 1 , wherein R 2 , R 3 , R 4 , and R 5 are independently chosen from (C 1 -C 50 ) cyclohydrocarbyl groups.
7. The catalyst system of claim 1 , wherein R 2 , R 3 , R 4 , and R 5 are independently chosen from (C 4 -C 50 ) aryl groups.
8. The catalyst system of claim 1 , wherein each of R 2 , R 3 , R 4 , and R 5 are phenyl groups.
9. The catalyst system of claim 1 , wherein the ligand is chosen from cis-1-bis(diphenylphosphino)amino-4-butylcyclohexane, or cis-1-bis(diphenylphosphino)amino-4-isopropylcyclohexane, or cis-1-bis(diphenylphosphino)amino-4-dodecylcyclohexane.
10. The catalyst system of claim 1 , wherein the catalyst system further comprises an aliphatic solvent.
11. The catalyst system of claim 10 , wherein the aliphatic solvent comprises one or more of alkanes and cycloalkanes.
12. The catalyst system of claim 1 , wherein the chromium compound comprises one or more of an organic chromium salt, an inorganic chromium salt, a chromium coordination, and a chromium organometallic complex.
13. The catalyst system of claim 1 , wherein the chromium compound is chosen from one or more of chromium trichloride tris-tetrahydrofuran complex, (benzene)tricarbonyl chromium, chromium (III) octanoate, chromium (III) acetylacetonoate, chromium hexacarbonyl, tris(2,2,6,6-tetramethyl-3,5-heptanedionato) chromium (III), and chromium (III) 2-ethylhexanoate.
14. The catalyst system of claim 1 , wherein a molar ratio of the ligand to the chromium compound is from 1.0 to 2.0.
15. The catalyst system of claim 1 , wherein the organoaluminum compound has a structure:
wherein R 6 , R 7 , and R 8 are each selected from the group consisting of a hydrogen atom and an unsubstituted (C 1 -C 20 ) linear or branched alkyl group.
16. The catalyst system of claim 1 , wherein the organoaluminum compound is chosen from one or more of trimethylaluminium, triethylaluminum, tripropylaluminum, tri-iso-butylaluminum, diisobutylaluminium hydride, trihexylaluminum, tri-n-octylaluminium, methylaluminium dichloride, ethylaluminium dichloride, dimethylaluminium chloride, diethylaluminium chloride, aluminium isopropoxide, ethylaluminiumsesquichloride, methylaluminiumsesquichloride, methylaluminoxane, ethylaluminoxane, and modified methylaluminoxane.
17. The catalyst system of claim 1 , wherein a molar ratio of the organoaluminum compound to the chromium compound is from 100 to 5000.
18. A method for tetramerizing ethylene to form 1-octene, the method comprising contacting ethylene with a catalyst system to form a product comprising 1-octene, wherein the catalyst system is the catalyst system of claim 1 .
19. The method of claim 18 , wherein the 1-octene is formed at a pressure of from 5 bar to 120 bar.
20. The method of claim 18 , wherein the 1-octene is formed at a temperature of from 20° C. to 130° C.