Heat management in ethylene oligomerization

A method for mitigating the formation of by-product polyethylene that is produced in a solution process for the selective tetramerization of ethylene, said method comprising

• a) contacting ethylene and a solvent with hydrogen;
• and
• b) contacting said ethylene, solvent and hydrogen with
• i) an oligomerization catalyst comprising
• 1.1) a source of chromium that is soluble in said solvent;
• and
• 1.2) a ligand defined by the formula (R1)(R2)—P1-bridge-P2(R3)(R4)
• wherein R1, R2, R3 and R4 are independently selected from the group consisting of unsubstituted phenyl and phenyl having only a single ortho-fluoro-substituent and said bridge is bonded to both phosphorus atoms and defined by the formula —N(R5)— wherein R5 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, aryloxy, substituted aryloxy, halogen, alkoxycarbonyl, carbonyloxy, alkoxy, aminocarbonyl, dialkylamino and silyl groups
• ii) an activator comprising an aluminoxane;
• said process being conducted under oligomerization conditions at a temperature of from 10° C. to 100° C. and at a pressure of from 5 to 100 atmospheres in an oligomerization reactor system, characterized in that said process is conducted with process equipment that includes:
• 1) a first heat exchanger that is used to provide heat to said process;
• and
• 2) a second heat exchanger that is used to remove heat from said oligomerization reactor system;
• wherein said oligomerization of ethylene process provides a liquid product comprising 20 to 80 weight % octene, wherein less than 5 weight % of the octenes are internal olefins, further characterized in that the formation of polymer during the oligomerization of ethylene process is reduced compared to the same oligomerization of ethylene process where ethylene and solvent are not contacted with hydrogen.