Heterogenized rhodium catalysts for hydroformylation of olefins

  • 05/06/2023

In the context of the project MACBETH (Membranes And Catalysts Beyond Economic and Technological Hurdles) one essential building block is the catalyst system. Hydroformylation, one of the world´s most relevant reaction and show case within the MACBETH project, usually uses a Rhodium based homogeneous catalyst to transform olefins into aldehydes via a syngas reaction. Homogeneous catalysts in combination with appropriate ligand systems are very active and selective, can be operated at mild conditions but suffer from high separation efforts. On the contrary, heterogeneous catalysts are easy to separate. Within the MACBETH project the advantages of both systems were combined using a heterogenized homogeneous catalyst: To do so, a supported liquid phase (SLP) approach was chosen by immobilizing the Rh-based homogeneous catalyst system containing the metal precursor, the ligand and a stabilizer in a monolithic porous ceramic support structure (SiC). Figure 1 shows the principle of a SLP system and its components used.

Worth to note, the essential part of the catalytic system is the ligand and the stabilizer. The latter provides the ability to keep the catalyst immobilized in the given pore structure whereas the former coordinates to the active species of the catalysts to achieve the desired selectivity of the n/iso aldehyde formation. The BIPHEPHOS ligand used in the present system is an organophosphorus compound and can be purchased from Evonik Operations GmbH under the trademark OXOPHOS® 17.  The careful combination of the given pore structure in combination with the homogeneous catalyst system makes the developed catalytic system superior to other existing systems for the hydroformylation of olefins.