Method for preparing a catalyst composition for oligomerization of ethylene and respective catalyst composition pre-formation unit

A method for preparing a catalyst composition for the oligomerization of ethylene comprising the steps:

• a) reacting in a first solvent, a co-catalyst and a modifier, wherein the co-catalyst is triethylaluminum, and wherein the modifier is tetraphenylphosphonium chloride to form a reaction product;
• b) adding a chromium compound and a ligand to the first solution of the reaction product obtained in step a) to obtain a second solution;
• and
• c) mixing the second solution obtained in step b) for 10 seconds to 5 hours by pressurizing with ethylene at a pressure of 30 bar and at a temperature of 50° C.;
• wherein the first solvent is toluene;
• wherein the second solvent is an aromatic or aliphatic solvent or mixtures thereof;
• wherein the chromium compound is selected from organic or inorganic salts, coordination complexes and organometallic complexes of Cr(II) or Cr(III);
• wherein the molar ligand/Cr ratio is from 0.5 to 50;
• and
• wherein the ligand has the general structure R1R2P—N(R3)—P(R4)—N(R5)—H, wherein R1, R2, R3, R4 and R5 are independently selected from halogen, amino, trimethylsilyl, C1-C10-alkyl, substituted C1-C10 alkyl, aryl and substituted aryl;
• wherein the reaction product is a liquid clathrate having the formula
• [PPh4]Cl+2Al(CH2CH3)3+13C7H8→[PPh4][Al2(CH2CH3)6Cl]*(C7H8)13.