Continuous Nanofiltration and Recycle of a Metathesis Catalyst in a Microflow System

Continuous-flow nanofiltration and recycle of a metathesis catalyst is demonstrated in a small-scale continuous-flow system using less than 2mg of catalyst in 50h of operation. This length of time corresponds to an average of approximately 70recycle experiments, where catalyst is partially removed and replaced during each cycle. The small-scale (2.9mL total system volume) continuous-flow catalyst recycle system includes the first fully functional microfluidic organic solvent nanofiltration module using polyimide membranes, a stirred holding tank (<1mL volume) with a liquid-level control system to respond to membrane-flux decline, a membrane reactor using Teflon AF for permeation of the ethylene byproduct, and automated sampling. A turnover number of 935 is obtained for the Hoveyda-Grubbs catalyst. Ruthenium contamination in the product remains less than 1ppm throughout each experimental run.