Abstract: A method of producing an ?-olefin low polymer, wherein an ?-olefin is subjected to low polymerization in a solvent in the presence of a chromium catalyst and at least one inert gas. The proportion of the inert gas is maintained from 0.010 to 50.00% by volume in a gas phase part of a reactor, such that inert gas is discharged from the reactor and/or circulation piping when the proportion exceeds 50.00%. The chromium catalyst contains a chromium compound, at least one nitrogen-containing compound, an aluminum-containing compound, and optionally a halogen-containing compound. Unreacted ?-olefin and solvent separated from a reaction liquid are circulated back into the reactor.

Abstract: The object of the present invention is to provide a production method of an ?-olefin low polymer, wherein a low polymer of an ?-olefin is obtained in high yield. The present invention relates to that when an inert gas is allowed to exist in a gas phase part of a reactor 10 in the proportion of from 0.010 to 50.00% by volume, and an ?-olefin is subjected to low polymerization reaction in a solvent in the presence of a chromium series catalyst comprising a chromium compound (a), at lest one nitrogen-containing compound (b) selected from the group consisting of an amine, an amide and an imide, and an aluminum-containing compound (c), an unreacted ?-olefin and the solvent separated from a reaction liquid are circulated into the reactor 10, and where the proportion of the inert gas in the gas phase exceeds 50.00% by volume, the inert gas is discharged outside the reaction system from a gas phase part of the reactor 10 and/or a circulation piping 21 of an unreacted ?-olefin.