Oligomer preparation method and oligomer preparation apparatus

An apparatus for preparing an oligomer, the device comprising:

• a reactor oligomerizing a feed stream containing a monomer, feeding a first discharge stream to a first separation device, and feeding a second discharge stream to a second separation device;
• the first separation device receiving the first discharge stream of the reactor;
• the second separation device receiving the second discharge stream of the reactor and feeding a lower discharge stream to a third separation device;
• the a third separation device receiving the lower discharge stream of the second separation device and feeding an upper discharge stream containing the monomer to a monomer dissolution device;
• and
• the monomer dissolution device dissolving the fed upper discharge stream of the third separation device in a separately fed solvent and feeding a discharge stream to the reactor.