processo para a trimerização e tetramerização simultânea de monômeros olefínicos

A process for the simultaneous trimerization and tetramerization of olefinic monomers, wherein the process comprises contacting at least one olefinic monomer with a catalyst system comprising: a) a source of chromium, molybdenum or tungsten; b) a ligand having the general formula (I); (R1)2P-X-P(R1)m(R2)n (I) wherein: X is a bridging group of the formula -N(R3)-; the R1 groups are independently selected from an optionally substituted aromatic group bearing a polar substituent on at least one of the ortho-positions; and the R2 groups are independently selected from hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl groups with the proviso that when the group is aromatic it does not contain a polar substituent at any of the ortho-positions; and c) a cocatalyst.