Recycling of a thermoresponsive “catalyst pill”: separation of a molecular catalyst in solid ethylene carbonate in various reactions

Abstract

One approach to recycle homogeneous catalysts is through multiphase catalysis. Multiphase catalysis is not only limited to liquid–liquid multiphase systems but also includes for example solid and liquid phases. In this work, we present a catalyst recycling system based on the crystallization of the entire catalyst phase after the reaction at ambient temperature. Using the green and polar solvent ethylene carbonate, the polar Rh/sulfoXantphos catalyst is trapped in the crystallized ethylene carbonate phase. The product can be decanted under air as the catalyst is stabilized in the solid phase and the entire solid phase including the solvent is recycled. Several reactions such as the hydroformylation of hexene, octene and decene, and the hydrogenation of C₁₄ aldol products were conducted with this system. A TTON of 8627 could be achieved in the hydroformylation of 1-octene with initial turnover frequencies up to 1460 h⁻¹. In addition, the catalyst “pill” was switched between different reactions to show the flexibility of the system.