Continuous Gas-Phase Hydroformylation of Propene with CO2 Using SILP Catalysts

Hydroformylation is an important process for the synthesis of aldehydes and alcohols in the chemical industry. Although this process uses toxic CO as one of the reactants, some types of Ru complex catalysts have been known to replace CO with CO2 as a reactant in hydroformylation. Herein, we report the continuous hydroformylation of propene with CO2, heterogeneously catalyzed by supported Ru complexes on silica using ionic liquids [i.e., supported ionic liquid-phase (SILP) catalysts] in a flow reactor. When the reaction was carried out at 170 degrees C, 8.6 MPa, and gas hourly space velocity (GHSV) of 1.13 x 10(3) h(-1) using the SILP catalyst prepared from Ru-3(CO)(12), 1-ethyl-3-methylimidazolium chloride, and silica, the conversion of propene was 81.6% and the selectivity of hydroformylation was 66.1%. Kinetic analysis showed that the reaction rates of CO formation and hydroformylation were near-identical at 170 degrees C, indicating that the CO formed by the reverse water-gas shift reaction was readily used for the subsequent hydroformylation reaction. ESI-MS analysis of the ionic liquid phase showed the formation of trinuclear and mononuclear Ru complexes, and a plausible reaction mechanism was proposed based on these findings.