Recovery of Enlarged Olefin Metathesis Catalysts by Nanofiltration in an Eco-Friendly Solvent

This study was aimed at integrating a green separation process without phase change, namely nanofiltration, with olefin metathesis to recover the homogeneous catalyst. As the commercially available Hoveyda II catalyst was not sufficiently retained by the membrane, a set of homogeneous ruthenium-based catalysts were prepared to enhance the recovery, of the catalyst by solvent-resistant commercial membranes made of polyimide (Star-mem 228). The molecular weights of the catalysts were gradually increased from 627 to 2195 g mol(-1), and recovery was found to increase from around 70% to 90% both in toluene and dimethyl carbonate. The most retained catalyst was then engaged in a series of model ring-closing metathesis reactions associated to a final nanofiltration step to recover and recycle the catalyst. Up to five cycles could be performed before a deterioration in the performance of the process was observed.