Separation of different metathesis Grubbs-type catalysts using organic solvent nanofiltration

In this paper, the challenge of separating and re-using homogeneous catalysts from their post-reaction mixture in the field of metathesis is addressed using organic solvent nanofiltration (OSN). A coupled reaction–separation process was applied for the metathesis reaction of 1-octene to 7-tetradecene and ethene. Five different Grubbs-type catalysts and the STARMEM™ series of OSN membranes were used. It was found that the STARMEM™ 228 membrane successfully separates the different catalysts from their post-reaction mixtures to below 9 ppm. The coupled reaction–separation and recycling process also increased the turnover number from 1400 for a single pass reaction to 5500 for the overall consecutive reaction–separation steps of four cycles. The OSN process was further characterized for mixtures of 1-octene, 1-tetradecene and 7-tetradecene by varying operating pressures and solvent concentration.