Abstract: A process for producing an olefin oligomer by the polymerization of an olefin in the presence of boron trifluoride as a catalyst, and further in the co-presence of water and/or an alcohol and a carboxylic acid anhydride as a co-catalyst. The process has advantages that (i) olefin oligomers having a low viscosity can be produced at high yields, (ii) the production efficiency can be improved by decreasing the time required for the reaction, (iii) the amount of the co-catalyst required can be decreased, and (iv) the viscosity of an olefin oligomer to be obtained can be freely controlled by changing the amounts of the olefin, the catalyst, the co-catalyst, etc.

Abstract: A process for the manufacture of an olefin oligomer, comprising the steps of polymerizing an olefin monomer in the presence of boron trifluoride and a boron trifluoride-alcohol complex as catalysts, to prepare a first oligomerization product, and then carrying out one of following steps (a) to (c): (a) removing boron trifluoride from the above first product by (i) placing the product under a reduced pressure, (ii) blowing an inert gas into the product, or (iii) heating the product at a relatively low temperature, to thereby prepare a second oligomerization product, and then subjecting the second product to a precipitation treatment to separate the boron trifluoride-alcohol complex therefrom, (b) heating the above first product at a relatively elevated temperature to recover boron trifluoride, or (c) centrifuging the above first product to recover the boron trifluoride-alcohol complex. These steps allow the catalysts to be recovered while maintaining the activity thereof at a desired level.