The dimerization of propene in the presence of homogeneous nickel catalysts in acidic chloroaluminate ionic liquids has been investigated The solubility of both substrate and products has been carefully determined in order to interpret kinetic findings. Detailed kinetic studies have indicated strong mass transport limitation of the overall reaction rate. The diffusion coefficient of propene in the ionic liquid has been determined from gas solubility measurements. This established method allowed the calculation of the Hatta number to be 4 9, indicating the severe mass transport limitation For such fast biphasic reactions a loop reactor design is Suggested. (C) 2009 Published by Elsevier B.V.