Catalyst systems for preparing 1-hexene and/or 1-octene from ethylene

1. A catalyst system for selective oligomerization of ethylene, comprising:

(i) a chromium compound;

(ii) a ligand represented by Chemical Formula 1 below; and

(iii) an activator:

wherein

X1 to X4 are each independently halogen;

R1 and R2 are each independently hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl, or substituted heterohydrocarbyl;

R3 to R18 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl, substituted heterohydrocarbyl or halogen.

2. The catalyst system of claim 1 , wherein the halogen is selected from the group consisting of fluorine (F), chlorine (Cl) and bromine (Br).

3. The catalyst system of claim 1 , wherein the R1 and R2 are each independently C1-C30 hydrocarbyl, substituted C1-C30 hydrocarbyl, C1-C30 heterohydrocarbyl, or substituted C1-C30 heterohydrocarbyl.

4. The catalyst system of claim 3 , wherein the R1 and R2 are each independently (C1-C10)alkyl.

5. The catalyst system of claim 3 , wherein the R1 and R2 are each independently methyl.

6. The catalyst system of claim 1 , wherein the R3, R7, R11 and R18 are each independently selected from the group consisting of hydrogen; halogen including fluorine (F), chlorine (Cl) or bromine (Br); and (C1-C3)alkyl.

7. The catalyst system of claim 6 , wherein the R3, R7, R11 and R18 are each independently hydrogen.

8. The catalyst system of claim 1 , wherein the R4 to R6, R8 to R10, and R12 to R17 are each independently hydrogen; C1-C30 hydrocarbyl or C1-C30 heterohydrocarbyl.

9. The catalyst system of claim 8 , wherein the R4 to R6, R8 to R10, and R12 to R17 are each independently hydrogen; (C1-C6)alkyl; (C1-C6)alkoxy; (C6-C12)aryl; or (C6-C12)aryloxy.

10. The catalyst system of claim 9 , wherein the R4 to R6, R8 to R10, and R12 to R17 are each independently hydrogen, methyl, ethyl, isopropyl, n-propyl, methoxy, ethoxy, phenyl, phenoxy or cyclohexyl.

11. The catalyst system of claim 1 , wherein the ligand is:

(S,S)- or (R,R)- or meso-(ortho-fluoro-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-fluoro-phenyl)2,

(S,S)- or (R,R) or meso-(ortho-fluoro-para-methoxy-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-fluoro-para-methoxy-phenyl)2,

(S,S)- or (R,R)- or meso-(ortho-fluoro-para-methyl-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-fluoro-para-methyl-phenyl)2,

(S,S)- or (R,R)- or meso-(ortho-fluoro-para-ethyl-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-fluoro-para-ethyl-phenyl)2,

(S,S)- or (R,R)- or meso-(ortho-chloro-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-chloro-phenyl)2,

(S,S)- or (R,R)- or meso-(ortho-chloro-para-methoxy-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-chloro-para-methoxy-phenyl)2,

(S,S)- or (R,R)- or meso-(ortho-chloro-para-methyl-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-chloro-para-methyl-phenyl)2, or

(S,S)- or (R,R)- or meso-(ortho-chloro-para-ethyl-phenyl)2P—CH(methyl)CH(methyl)-P(ortho-chloro-para-ethyl-phenyl)2.

12. The catalyst system of claim 1 , wherein the chromium compound is selected from the group consisting of chromium (III) acetylacetonate, tris(tetrahydrofuran)trichlorochromium, and chromium (III) 2-ethylhexanoate.

13. The catalyst system of claim 1 , wherein the activator is methylaluminoxane (MAO) or modified methylaluminoxane (MMAO).

14. The catalyst system of claim 1 , wherein the chromium compound and the ligand are provided in a form of a coordinated complex compound.

15. The catalyst system of claim 1 , wherein carbons in the P—C—C—P backbone structure of the ligand are chiral carbons, and have (R,R) or (S,S) configuration pairs.

16. A method of selectively preparing an ethylene oligomer, comprising bringing an ethylene monomer into contact with the catalyst system of claim 1 .

17. The method of claim 16 , wherein the ethylene oligomer is 1-hexene, 1-octene or a mixture thereof.

18. The method of claim 17 , wherein a total yield of 1-octene and 1-hexene is 50 mass % or more.

19. The method of claim 18 , wherein both selectivity of 1-octene and selectivity of 1-hexene are 70 wt % or more.

20. The method of claim 19 , wherein both the selectivity of 1-octene and the selectivity of 1-hexene are 90 wt % or more.