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US Patent, US 9480978 B1 (2016)

Surface bonded Rh-bis(diarylphosphine) on magnetic nanoparticles as a recyclable catalyst for hydroformylation of olefins


Shaikh, M.N., Yamani, Z. H. A 

Filing date Jan. 6, 2016     Publication date Nov 1, 2016

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Catalysis plays a central role in the production of essential chemicals in our daily lives such as medicines, fine chemicals, polymer, fibers, and fuel. Homogeneous catalysis plays a dominating role in this area as catalysts react in the same phase with the reactant and thereby all sites are accessible and easy to tune by organic functional groups inter-conversion.

However, the limitation of separating catalyst from the desired product after the reaction hinders scale up in many commercial processes.  For Examples, the separation of catalyst from the products by column chromatography, centrifugation or filtration reduces the yield substantially.

Significant efforts have been devoted to developing alternatives to minimize the separation cost and to maximize product purity. Heterogeneous catalysis draws chemists' attention as it is easy to separate, recycle and is often more environmentally friendly. 

Superparamagnetic Iron oxide nanoparticles (SPIONs) as solid supported catalyst becomes the obvious choice, which opened up a promising research strategy to develop surface coated recyclable catalyst by anchoring homogeneous organic species (ligand or metal complexes) and mimicking the homogeneous catalysis.

Furthermore, SPIONS provide recyclable catalysts due to their insolubility in organic solvents and their distinct magnetic nature, rendering their separation from the heterogeneous reaction system virtually effortless.

In this invention, the newly prepared organic ligand has been coated on the ultrasmall magnetic nanoparticles (5-7 nm).  These nanomaterials exhibited high catalytic activity toward the conversion of alkenes to aldehydes; the reactions reached the maximum (>99%) with a low syngas pressure. The recyclability was tested with the catalyst on styrene as the substrate, and it was found that even after seven cycles, without the addition of further Rh(I), the catalyst was persistently active.

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