title: Catalyst recycling via specific non-covalent adsorption on modified silicas.
abstract: This article describes a new strategy for the recycling of a homogeneous hydroformylation catalyst, by selective adsorption of the catalyst to tailor-made supports after a batchwise reaction. The separation of the catalyst from the product mixture is based on selective non-covalent supramolecular interactions between a ligand and the support. Changing the solvent releases the active catalyst back into the reactor and allows a subsequent batch reaction with the recycled active catalyst. For this purpose, the bidentate NixantPhos ligand has been equipped with a pyridine group. The corresponding rhodium pre-catalyst [Rh(Nix-py)(acac)] (acac = acetylacetonate) forms a very selective, active and highly stable catalyst, and able to reach a turnover number (TON) of 170 000 in a single run (reaction performed in nearly neat 1-octene, S/C ratio of 200 000, at 140 °C, 20 bars syngas pressure). Various commercially available supports have been explored in binding studies and recycling experiments. The end-capped silica-alumina performs the best so far with respect to ligand-adsorbing properties for the current purpose. Although this system has not been fully optimized, four recycling runs could be performed successfully.
authors.affiliation: InCatT B.V. Science Park 904, 1098 XH Amsterdam, The Netherlands. sander.kluwer@incatt.nl
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Kluwer
authors.forename: Chretien
authors.initials: C
authors.lastname: Simons
authors.forename: Quinten
authors.initials: Q
authors.lastname: Knijnenburg
authors.forename: Jarl Ivar
authors.initials: JI
authors.lastname: van der Vlugt
authors.forename: Bas
authors.initials: B
authors.lastname: de Bruin
authors.forename: Joost N H
authors.initials: JN
authors.lastname: Reek