Oligomerisation of olefinic compounds with reduced polymer formation

1. A process for producing an oligomeric product by oligomerisation of at least one olefinic compound, the process including:

a) providing an activated oligomerisation catalyst by combining, in any order,

i) a source of chromium;

ii) a ligating compound of the formula I

(R 1 ) m X 1 (Y)X 2 (R 2 ) n   I

wherein: X 1 and X 2 are independently an atom selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulphur and selenium or said atom oxidized by S, Se, N or O where the valence of X 1 and/or X 2 allows for such oxidation;

Y is a linking group between X 1 and X 2 ;

m and n are independently 0, 1 or a larger integer; and

R 1 and R 2 are independently hydrogen, a hydrocarbyl group, an organoheteryl group or a heterohydrocarbyl group, and R being the same or different when m>1, and R 2 being the same or different when n>1;

iii) a catalyst activator or combination of catalyst activators;

b) providing a zinc compound; and

c) contacting the at least one clef irk compound with a composition containing the activated oligomerisation catalyst and the zinc compound, the zinc compound being present in a sufficient quantity such that the ratio of the molar amount of zinc in the zinc compound to the molar amount of chromium in the source of chromium is from 10 to 1000.

2. A process for activating an oligomerisation catalyst to be used to produce an oligomeric product from at least one olefinic compound, the process comprising the combination, in any order, of

i) a source of chromium;

ii) a ligating compound of the formula I

(R 1 ) m X 1 (Y)X 2 (R 2 ) n   I

wherein: X 1 and X 2 are independently an atom selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulphur and selenium or said atom oxidized by S, Se, N or O where the valence of X 1 and/or X 2 allows for such oxidation;

Y is a linking group between X 1 and X 2 ;

m and n are independently 0, 1 or a larger integer; and

R 1 and R 2 are independently hydrogen, a hydrocarbyl group an organoheteryl group or a heterohydrocarbyl group, and R 1 being the same or different when m>1 and R 2 being the same or different when n>1;

iii) a catalyst activator or combination of catalyst activators;

iv) a zinc compound, the zinc compound being present in a sufficient quantity such that the ratio of the molar amount of zinc in the zinc compound to the molar amount of chromium in the source of chromium is from 10 to 1000.

3. The process of claim 1 or claim 2 wherein the zinc compound is present in a sufficient quantity such that the ratio of the molar amount of zinc in the zinc compound to the molar amount of chromium in the source of chromium is from 50 to 450.

4. The process of claim 1 or claim 2 wherein the process includes the use of a solvent.

5. The process of claim 1 or claim 2 wherein the oligomerisation catalyst is a trimerisation catalyst or a tetramerisation catalyst.

6. The process of claim 1 or claim 2 wherein X 1 and X 2 are independently phosphorus or phosphorus oxidised by S or Se or N or O.

7. The process of claim 1 or claim 2 wherein the ligating compound is of the formula II

wherein Y is a linking group between X 1 and X 2 , X 1 and X2 are independently selected from the group consisting of nitrogen, phosphorus, arsenic, antimony and bismuth and R 3 to R 6 are each independently a hydrocarbyl group or a heterohydrocarbyl group.

8. The process of claim 1 or claim 2 wherein Y is selected from the group consisting of an organic linking group comprising a hydrocarbylene, substituted hydrocarbylene, heterohydrocarbylene and a substituted heterohydrocarbylene; an inorganic linking group comprising either a single- or two-atom linker spacer; and a group comprising methylene; dimethylmethylene; ethylene; ethene-1,2-diyl; propane-1,2-diyl, propane-1,3-diyl; cyclopropane-1,1-diyl; cyclopropane-1,2-diyl; cyclobutane-1,2-diyl, cyclopentane-1,2-diyl, cyclohexane-1,2-diyl, cyclohexane-1,1-diyl; 1,2-phenylene; naphthalene-1,8-diyl; phenanthrene-9,10-diyl, phenanthrene-4,5-diyl, 1,2-catecholate, 1,2-diarylhydrazine-1,2-diyl (—N(Ar)—N(Ar)-) where Ar is an aryl group; 1,2-dialkylhydrazine-1,2-diyl (—N(Alk)-N(Alk)-) where Alk is an alkyl group; —B(R 7 )—, —Si(R 7 ) 2 —, —P(R 7 )— and —N(R 7 )— where R 7 is hydrogen, a hydrocarbyl or heterocarbyl or halogen.

9. The process of claim 7 wherein the ligating compound is of the formula III

wherein R 3 to R 7 are each independently a hydrocarbyl group or a heterohydrocarbyl group.

10. The process of claim 9 wherein each of R 3 to R 6 is an alkyl selected from the group consisting of methyl, ethyl and isopropyl or an aromatic selected from the group consisting of phenyl and substituted phenyl.

11. The process of claim 1 or claim 2 wherein the activator is selected from the group of organoboron compound, alumoxanes including modified aluminoxanes, aluminum alkyls, other metal or main group alkyl or aryl compounds, ionizing activators which are neutral or ionic, Lewis acids, reducing acids oxidising agents and combinations thereof.

12. The process of claim 1 or claim 2 wherein the process includes a reagent selected from a Group 13 reagent, a divalent metal reagent or an alkali metal reagent.

13. The process of claim 1 or claim 2 wherein the zinc compound is selected from zinc, activated zinc, and zinc-containing compounds selected from the group comprising zinc halides, zinc alkyls, zinc oxygenates including zinc acetate, zinc acetylacetonates and zinc carboxylates, and zinc porphyrin.

14. The process of claim 13 wherein the zinc-containing compound is a zinc dialkyl.

15. The process of claim 14 , wherein the in dialkyl is dimethyl zinc or diethyl zinc.