Hydroformylation in room temperature ionic liquids (RTILs): Catalyst and process developments

The ionic liquids have successfully been employed as alternative solvents for homogeneous biphasic catalysis caused by its very low vapor pressure and good thermal stability. The ionic liquids' stability has the possibility to tune its solubility and acidity-coordination properties by varying the nature of the anions and cations. This concept has been successfully employed in hydroformylation for reactions of short alkenes in the Ruhrchemie/Rhône-Poulenc Process (RCH/RP). Many of the important ligand development have been created for the biphasic hydroformylation reaction, and a great number of publications have shown improved potential of ionic liquids regarding product separation, catalyst recovery, improved catalyst stability, and selectivity. The engineered biphasic ionic liquid hydroformylation catalysts provide very effective catalyst immobilization and acquire optimized catalytic performance. However, the ionic liquids generally exhibit low syngas, making biphasic hydroformylation systems prone to mass transfer limitations. Addressing this issue, the ionic liquid-phase (SILP) catalyst systems and combined scCO2 catalysts systems can manage these transport problems through contact improvement between the ionic liquid catalyst phase and the syngas.