Heterogeneous hydroformylation of propene over surface rhodium coordinated by immobilized multi-N ligands.

Olefin hydroformylation is an extremely important reaction for producing bulk oxygen-containing organic functional molecules and homogeneous rhodium catalysts with organic phosphorous ligands are most commonly used. We report here a highly active heterogeneous catalyst for propene hydroformylation with Rh immobilized by alumina bonded 3-trimethoxysilylpropyl-diethyle-netriamine, of which ligand is more readily available, inexpensive, low toxic and no loss in reaction. The catalyst Rh-NQ62/Al2O3 shows a TOF value as high as 710 h-1 for propene conversion to C4 oxygenates in selectivity higher than 99% in a fixed-bed reactor and sustains stable for at least 1000 h without any deactivation. Characterization and theoretical calculation reveal that the atomically dispersed Rh species in surface-bound configurations by the multi-N ligand effectively promotes the heterolytic cleavage of H2 at the Rh-N site and enhances the overall propene hydroformylation. We envisage the work establishes a blueprint for development of better catalysts using multi-N ligands for heterogeneous hydroformylations.