Tobias Hamerla

Hydroformylation of 1-Dodecene with Water-Soluble Rhodium Catalysts with Bidentate Ligands in Multiphase Systems

A hydrophilic metal–ligand complex formed from the precursor [dicarbonyl(acetylacetonato)rhodium(I)] {[Rh(acac)(CO)2]} and the bidentate ligand [2,7‐bis(SO3Na)‐4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene] (SulfoXantPhos), was found to be a suitable candidate as a catalyst complex for the hydroformylation of 1‐dodecene in multiphase systems formulated from water, 1‐dodecene, and a nonionic surfactant. To improve the solubilization of the olefin in the aqueous phase, surfactants were added. The multiphase system acted as a tunable solvent, through which not only the interfacial area was increased during the reaction but also the phase separation behavior could be manipulated through temperature changes, thus allowing an easy separation of the expensive rhodium complex from the organic phase after the reaction. The influence of different process parameters such as the type of surfactant, type of ligand, and the metal/ligand ratio was investigated and discussed. Also the influence of the phase state on the reaction was determined. Under optimized reaction conditions, turnover frequencies of >300 h−1 and selectivities of 98:2 towards the linear product could be achieved.

Comparison of phase transfer agents in the aqueous biphasic hydroformylation of higher alkenes

The Rh-catalyzed aqueous biphasic hydroformylation with the bidentate ligand SulfoXantPhos was investigated for different phase transfer agents (PTA). As such, polymer latices and microemulsions formed by non-ionic surfactants were used. In general, a higher PTA concentration enhances the reaction progress. The feasibility of catalyst recycling by simple phase separation is shown in principle. The Rh losses are low in the surfactant system and promising for a technical approach.

Rhodium catalyzed hydrogenation reactions in aqueous micellar systems as green solvents

The hydrogenation of itaconic acid and dimethyl itaconate is transferred from methanol to aqueous micellar solutions of several surfactants, e.g., SDS and Triton X-100, in order to facilitate the recovery of the catalyst. The reaction rate and selectivity strongly depends on the chosen surfactant and in some cases also on the surfactant concentration. In the best case the selectivity is the same as in methanol but the reaction rate is still lower because of a lower hydrogen solubility in water. Repetitive semi-batch experiments are chosen to demonstrate that high turn-over-numbers (>1000) can be reached in aqueous micellar solutions. No notable catalyst deactivation is observed in these experiments. The performance of micellar reaction systems is controlled by the partition coefficient of the substrates between the micelles and the continuous aqueous phase which can be predicted using the Conductor-like Screening Model for Real Solvents (COSMO-RS).