Recoverable and Recyclable Catalysts for Multi-Step Reaction Networks
C.S. Gill, N.T.S. Phan, Z.J. Zhang and C.W. Jones
Georgia Institute of Technology, US
catalyst, nanoparticle, spinel, heterogeneous, cascade
Cascade reactions involve multiple catalysts promoting multiple reactions in a single vessel. However, these one-pot reactions generally yield a mixture of non-separable catalysts. Our research demonstrates a new approach in chemical catalysis through the use of multiple heterogeneous catalysts for one-pot cascade reactions, where the pure catalysts can be recovered after reaction by combining superparamagentic nanoparticles with tradition solid catalysts.
The one-pot deacetalization/Knoevenagel reaction of benzaldehyde dimethylacetal with malononitrile required both acid and base catalysts. Superparamagnetic cobalt spinel ferrite nanoparticles were functionalized with basic amine sites. A sulfonic acid polymer resin acted as the acid catalyst. Control reactions proved complete conversion was only observed when both acid and base catalysts were employed simultaneously. Upon reaction completion, the MNP were easily separated from the reaction mixture in the presence of an external magnetic field. The basic nanoparticle and acidic polymer catalysts were easily recovered in pure form as evidenced by elemental analysis. Recycle reactions displayed similar kinetic profiles, indicating no observable catalyst deactivation. This research highlights the importance of the magnetic nanoparticle catalyst as providing a means to utilize multiple, separable and recyclable heterogeneous catalysts for use in cascade reactions.
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Nanotech 2006 Conference Program Abstract