Process for preparing linear -olefins

Process for preparing linear α-olefins by oligomerization of ethylene (1, 1a) in the presence of an organic solvent and a liquid catalyst homogeneous in a reactor (2), introducing ethylene (1a, 12) in the reactor (2) liquid state at least partially, wherein the ethylene leaving the reactor (2) in gaseous form condenses only partially, resulting in a biphasic mixture which is separated in a separator (4), returning the liquid phase directly to the reactor ( 2), while the gas phase is returned in gaseous form to the reactor (2) after compression.