The formylation of 3-methoxypropylamine with hydrogen and “supercritical” carbon dioxide over Ru-based catalysts was studied. In this solventless process, carbon dioxide acts as both reactant and solvent. Interestingly, Ru/Al2O3 modified by the phosphine 1, 2-bis (diphenylphosphino) ethane (dppe) showed a high formylation activity at 100% selectivity, comparable to those of the homogeneous catalysts RuCl2 (dppe) 2 and RuCl2 (PPh3) 3. ...