CO2-expanded liquids (CXLs) represent a continuum of reaction media that combine the reaction benefits provided by organic solvents and the environmental benefits provided by supercritical CO2 (scCO(2)) in an optimal manner. Homogeneous hydroformylation of I-octene using an unmodified rhodium catalyst (Rh(acac)(CO)2) was successfully demonstrated employing CXLs as reaction media [Jin, H., Subramaniam, B., 2004. Homogeneous catalytic hydroformylation of I-octene in CO2-expanded solvent media. Chemical Engineering Science 59, 4887-4893]. The reported experimental study, however, showed a long induction period of nearly 2h, following which reaction occurs. A detailed reactor model incorporating reaction kinetics, mass transfer rates and phase equilibrium is presented to systematically investigate the effects of mass transfer and catalyst activation on induction period in I-octene hydroformylation in CXL. Complementary experiments performed in stirred autoclave reactors equipped with an in situ ReactIR probe validate the cause of the induction period predicted by the model. (c) 2007 Elsevier Ltd. All rights reserved.