Ligands for production of 1-hexene in chromium assisted ethylene oligomerization process
Catalyst compositions and processes for the oligomerization of ethylene to 1-hexene are described. The catalyst composition includes a triamino bisphospino (NPNPN) ligand system with specific phosphorous and nitrogen ligands. The terminal nitrogen atoms include linear alkyl hydrocarbons that differ in the number of carbon atoms by 3.
1. A catalyst composition for the oligomerization of ethylene to 1-hexene, the catalyst composition comprising:
a chromium (III) species; and
a ligand having the formula of:
where R 1 and R 2 are the same or different and are selected from the group consisting of (i) C 3 to C 4 non-cyclic aliphatic groups, (ii) C 5 to C 7 aliphatic groups which may be cyclic or non-cyclic, linear or branched, substituted or unsubstituted, and (iii) any combination thereof; and,
wherein n is 0 or 1, and m=n+3.
2. The catalyst composition of claim 1 , wherein R 1 and R 2 are each independently a cyclic hydrocarbon group, a substituted cyclic hydrocarbon group, a linear hydrocarbon group or a branched hydrocarbon group having 1 to 10 carbon atoms.
3. The catalyst composition of claim 2 , wherein R 1 and R 2 are each a cyclohexyl group.
4. The catalyst composition of claim 3 , wherein n is 0, and the ligand has the structure of:
5. The catalyst composition of claim 3 , wherein n is land the ligand has the structure of:
6. The catalyst composition of claim 1 , wherein the composition further comprises an activator or co-catalyst.
7. The catalyst composition of claim 6 , wherein the activator or co-catalyst is a methylaluminoxane compound.
8. The catalyst composition of claim 6 , wherein the activator or co-catalyst is a methyl iso-butyl aluminum oxide compound.
9. The catalyst composition of claim 1 , wherein the chromium (III) species is selected from the group consisting of chromium (III) acetylacetonate, Cr(2,2,6,6,-tetramethyl-3,5-heptadionate) 3 , chromium(III)2-ethylhexanoate, chromium trichloride; tris-tetrahydrofuran, (benzene)tricarbonyl chromium, chromium (III) octanoate and chromium (III) naphthenate.
10. The catalyst composition of claim 1 , wherein one or both of R 1 and R 2 are selected from the group consisting of iso-propyl and tert-butyl.
11. A process to produce 1-hexene from ethylene, the process comprising contacting a reactant stream comprising an olefin source with a solution comprising the catalyst composition of claim 1 to produce a oligomer composition comprising 1-hexene.
12. The process of claim 11 , wherein the solution comprises a solvent.
13. The process of claim 12 , wherein the solvent is a saturated hydrocarbon.
14. The process of claim 13 , wherein the solvent is n-hexane, methylcyclohexane, or a mixture thereof.
15. The process of claim 11 , wherein the oligomer product further comprises 1-octene and a selectivity for 1-hexene is greater than 99%, and a weight ratio of 1-octene to 1-hexene is less than 0.15.
16. The process of claim 15 , wherein the ligand comprises:
17. The process of claim 15 , wherein the solution further comprises an activator or co-catalyst.
18. The process of claim 11 , wherein the catalyst composition comprises the chromium (III) species, an activator or co-catalyst and the ligand has the structure of:
19. The process of claim 11 , wherein the contacting comprises a temperature of 15° C. to 100° C.
20. The process of claim 11 , wherein the contacting comprises a pressure of at least 2 MPa or 2 to 20 MPa.