(360d) Efficient Immobilization and Recycling of Homogeneous Catalysts Via Supported Ionic Liquid Phase (SILP) Technology

Supported Ionic Liquid Phase (SILP) catalysts are new materials consisting of an ionic liquid, a metal catalyst and a porous support.[1] The principle of SILP technology involves surface modification of a highly porous solid material by a thin film of ionic liquid, which is confined on the surface of the solid via e.g. physisorption, tethering, or covalent anchoring of ionic liquid fragments. By dissolving homogeneous transition metal complexes in the ionic liquid film, the SILP concept allows tailor making of solid materials with definite properties and a controlled chemical reactivity.[2] Since the ionic liquid is dispersed on the inner surface of the support, a dry solid material is obtained that can be handled like a classical heterogeneous catalyst and can be applied in established fixed-bed reaction engineering, thus making these novel materials highly attractive for large scale applications.[3] Due to the extremely low vapor pressure of ionic liquids, the SILP concept is especially suited for conti-nuous gas-phase reactions. No leaching of ionic liquid and catalyst can occur via the gas-phase and the SILP catalyst remains intact under steady state conditions for more than 1000 hours time on stream. Since the catalyst is retained inside the reac-tor, only products and non-converted substrates leave the reactor, thus simplifying the downstream processing significantly. In this contribution we highlight the latest developments from our research with SILP catalyst materials in gas-phase hydroformylation, asymmetric hydrogenation, and water-gas shift reaction. In continuous gas-phase hydroformylation of propene and 1-butene the rhodium based SILP catalyst exhibited excellent selectivity towards the desired product of more than 98 %. In a technical scenario only one small distillation column would then be required for product purification compared to e.g. a decanter unit and two distillation columns in the industrial RCH/RP process. We therefore anticipate increased applications of SILP technology in homogeneously catalyzed reactions in the future. References: [1] A. Riisager, R. Fehrmann, S. Flicker, R. van Hal, M. Haumann, P. Wasserscheid, Angew. Chem. Int. Ed. 2005, 44, 185. [2] www.silp-technology.de [3] A. Riisager, R. Fehrmann, M. Haumann, P. Wasserscheid, Eur. J. Inorg. Chem. 2006, 695.