Oligomerisation in the presence of both a tetramerisation catalyst and a further oligomerisation catalyst

An oligomerisation process comprising contacting at least one olefinic compound in the form of an olefin or a compound including an olefinic moiety with at least two different catalysts, including a tetramerisation catalyst and a further oligomerisation catalyst to produce an oligomeric product, which includes a mixture of at least one tetramer olefin and at least one other oligomer, wherein the tetramerisation catalyst comprises a combination of

• i) a source of a transition metal which transition metal is Cr;
• and
• ii) a ligating compound of the formula
• (R1)mX1(Y)X2(R2)n
• wherein:
• X1 and X2 are independently selected from the group consisting of N, P, As, Sb, Bi, O, S and Se;
• Y is a linking group between X1 and X2;
• provided Y excludes (CH2)xZ(CH2)y, where Z is —P(R8)—, —N(R8)—, —As(R8)—, —Sb(R8)— or —S—, and x and y are individually 1-15, and wherein R8 is hydrogen or a halogen or a nitro group or a hydrocarbyl or a substituted hydrocarbyl group;
• m and n are independently 0, 1 or a larger integer;
• and R1 and R2 are independently hydrogen, a hydrocarbyl group, or a heterohydrocarbyl group, and R1 is the same or different when m>1, and R2 is the same or different when n>1, provided that:
• (a) if two or more of R1 and R2 are aromatic with a ring atom of the aromatic ring structure bound to either X1 of X2, not more than two of said aromatic R1 and R2 have a substituent as a non-ring atom bound to a ring atom of the aromatic ring structure adjacent to the ring atom bound to X1 or X2;
• and
• (b) none of R1 and R2 are aromatic with a ring atom of the aromatic ring structure bound to either X1 and X2 and with a polar substituent as a non-ring atom bound to a ring atom of the aromatic ring structure adjacent to the ring atom bound to X1 or X2;
• and wherein the further oligomerisation catalyst is a catalyst comprising the combination of
• iii) a source of transition metal;
• and
• iv) a ligating compound of the formula
• (R1)n′A-B—C(R″)m′
• wherein:
• A and C are independently selected from the group consisting of N, P, As, Sb, Bi, O, S and Se;
• B is a linking group between A and C;
• m′ and n′ are independently 0, 1 or larger integer;
• R′ and R″ are independently hydrogen, a hydrocarbyl group or a heterohydrocarbyl group;
• and R′ is the same or different when n′>1, and R″ is the same or different when m′>1and
• wherein the oligomeric product of the process contains from 9.5 wt % to 52.8 wt % of the tetramer olefin.