BIPHASNANOCAT

Catalytic transformations are at the heart of the chemical industry. Catalyst recovery and recycling is one very important aspect of the application of catalytic technology, with a strong impact on energy efficiency, industrial economy, and the environment (waste production). Homogeneous catalysis provides clear benefits in terms of activity and selectivity but the catalyst recovery and recycling is often problematic. Methods for the efficient catalyst confinement in a different and easily separable phase are of continuous interest. The current project proposes a new approach for efficient biphasic catalysis using water to confine the catalyst, based on the catalyst covalent linking to the hydrophobic core of well defined amphiphilic nanosized core-shell polymers. Like in micellar catalysis, these objects will function as nanoreactors where the core insures an environment compatible with the reactant/product phase, whereas the hydrophilic shell insures solubility and total confinement in the aqueous phase. This strategy provides the advantages of micellar catalysis without the associated problems of micelle stability, formation of stable emulsions, and surfactant/catalyst loss into the product phase. Being an innovative approach, the character of the research project is fundamental. We propose to prepare and characterize tailored polymers and the corresponding supported catalysts and to elucidate the mass transport limitations of the system under a broad range of conditions. We shall then apply this new tool, in order to provide proof of principle, to one family of industrially important catalytic transformations - the Rh-catalyzed hydroformylation reaction - that we believe would most benefit from this approach. This industrial process has severe limitations, in many cases, in terms of catalyst recovery/recycling and pollution generation, especially for the large number of industrial plants that are still running with cobalt-based catalysts. The project will consists of a robust anchoring of the catalytic Rh complex to the polymer core through suitably modified ligands that also insure a suitable coordination environment for high catalytic activity and appropriate selectivity. The polymers will be assembled by controlled radical polymerization methods. One stepwise approach allows the assembly of individual arms and of a hydrophobic nanogel core, on which the polar hydrophilic shell can later be added. A second approach, in a single step, consists in the sequential polymerization of hydrophilic, then hydrophobic and finally crosslinking monomers, carried out in aqueous dispersed media. Comparative catalytic studies will be carried out with the polymer-supported catalyst under aqueous biphasic conditions and on soluble model compounds under homogeneous conditions and will also include mass transport investigations with a chemical engineering approach, providing feedback for optimization of the polymer architecture. In perspective, we anticipate that it will be possible to apply this approach to all industrial processes where hydrophobic reagents are transformed into hydrophobic products without the generation of water-soluble by-products. Thus, the results of this project are expected to raise wide industrial interest and to have a tremendous impact on the application of homogeneous catalytic technology at the industrial level, and then constitute a very important step for sustainable development.