Catalyst composition and process for oligomerization of ethylene

1. A catalyst composition comprising:

(a) a chromium compound;

(b) a ligand of the general structure

R 1 R 2 P—N(R 3 )—P(R 4 )—N 5 R 6

wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are independently C 1 -C 10 -alkyl, C 6 -C 20 -aryl, C 3 -C 10 -cycloalkyl, aralkyl, alkylaryl, or trialkylsilyl; and

(c) an activator or co-catalyst.

2. The catalyst composition according to claim 1 , wherein the chromium compound is an organic salt, an inorganic salt, a coordination complex, an organometallic complexes of Cr(II), or Cr(III), or a combination comprising at least one of the foregoing.

3. The catalyst composition according to claim 2 , wherein the chromium compound is CrCl 3 (THF) 3 , Cr(III)acetylacetonate, Cr(III)octanoate, chromium hexacarbonyl, Cr(III)-2-ethylhexanoate, (benzene)tricarbonyl-chromium, or a combination comprising at least one of the foregoing.

4. The catalyst composition according to claim 1 , wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, phenyl, benzyl, tolyl, or xylyl.

5. The catalyst composition according to claim 1 , wherein the activator or co-catalyst is trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, ethylaluminumsesquichloride, diethylaluminum chloride, ethylaluminumdichloride, methylaluminoxane (MAO), modified methylaminoxane (MMAO), or a combination comprising at least one of the foregoing.

6. The catalyst composition according to claim 1 , wherein the ligand is Ph 2 PN(i-Pr)P(Ph)NMe 2 , Ph 2 P—N(i-Pr)—P(Ph)—N(i-Pr)Ph, Ph 2 P—N(i-Pr)—P(Ph) —N(Me)C 6 H 11 , or a combination comprising at least one of the foregoing.

7. The catalyst composition according to claim 1 , additionally comprising a solvent, wherein the solvent is one of aromatic hydrocarbons, straight-chain aliphatic hydrocarbons, cyclic aliphatic hydrocarbons, straight-chain olefins, ethers, toluene, benzene, ethylbenzene, cumene, xylenes, mesitylene, hexane, octane, cyclohexane, methylcyclohexane, hexene, heptene, octene, diethylether, tetrahydrofuran, chlorobenzene, or a combination comprising at least one of the foregoing.

8. The catalyst composition according to claim 7 , wherein the concentration of the chromium compound is from 0.01 to 100 mmol/l.

9. The catalyst composition according to claim 1 , wherein the ligand/Cr molar ratio is from 0.5 to 50.

10. The catalyst composition according to claim 5 , wherein the Al/Cr molar ratio is from 1:1 to 1000:1.

11. A catalyst composition, obtainable by combining at least:

(a) a chromium compound;

(b) a ligand of the general structure

R 1 R 2 P—N(R 3 )—P(R 4 )—N 5 R 6 ,

Wherein

R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are independently C 1 -C 10 -alkyl, C 6 -C 20 -aryl, C 3 -C 10 -cycloalkyl, aralkyl, alkylaryl, or trialkylsilyl; and

(c) an activator or co-catalyst.

12. A process for tri- and/or tetramerization of ethylene, comprising subjecting the catalyst composition according to claim 1 to a gas phase of ethylene in a reactor and conducting an oligomerization.

13. The process according to claim 12 , wherein the oligomerization is carried out at a pressure of 1 to 200 bar.

14. The process according to claim 13 , wherein the oligomerization is carried out at a temperature of from 10 to 200° C.

15. The process according to claim 14 , wherein the mean residence time is from 10 minutes to 20 hours.

16. The process according to claim 13 , wherein the pressure is 10 to 50 bar.

17. The process according to claim 14 , wherein the temperature is from 20 to 100° C.

18. The process according to claim 15 , wherein the mean residence time is from 1 to 4 hours.