The dimerisation of 1-butene using (cod)Ni(hfacac)(1) under bar as catalyst has been investigated in different chloroaluminate ionic liquids. Systems prepared by buffering an acidic ionic liquid with weak organic bases proved to be very suitable solvents for the reaction. The reaction takes place in biphasic reaction mode with facile catalyst separation and catalyst recycling. The high intrinsic dimer linearity of catalyst (1) under bar is maintained, but with significant enhancement of catalyst activity and of the selectivity to the dimer product over that observed in toluene solvent. For further investigation, a continuous reactor was designed. Our results in continuous mode show the general technical applicability of the selective Ni-catalysed dimerisation in chloroaluminate ionic liquids using a loop reactor concept.