Method of recovering unreacted ethylene in ethylene oligomerization process

A method of recovering unreacted ethylene in an ethylene oligomerization process, the method comprising:

• in the ethylene oligomerization process,
• mixing a first recovery stream comprising the unreacted ethylene and a low boiling point reaction product separated in a second separation device in a latter stage of a reactor with a solvent introduced to a reaction raw material;
• transferring the mixture to a first separation device, wherein an oligomerization catalyst introduced to a reaction raw material is introduced to the first separation device;
• separating the mixture into a first upper effluent comprising the low boiling point reaction product and a first lower effluent comprising the ethylene and the solvent in the first separation device;
• transferring the first lower effluent in the first separation device to the reactor and performing an ethylene oligomerization reaction;
• and
• transferring a first reactant reacted in the reactor to the second separation device and recovering the first recovery stream comprising the unreacted ethylene and the low boiling point reaction product as a second upper effluent and separating a reactant comprising C4 or higher olefin oligomers and the solvent as a second lower effluent.