Fluorous Biphasic Catalysis

6.15 Conclusions

The fluorous biphasic concept, which was first suggested by Horváth in 1994, has now been applied to a very wide range of catalytic reactions, in many cases with the recycling of the catalyst being demonstrated. In most cases there is a fall off of conversion with reuse and significant leaching of ligand and metal containing catalyst, although in some cases very good catalyst retention does appear to have been demonstrated by ICP analysis and by successive experiments. Two different types of continuous reactor have been developed for laboratory demonstration on a small scale, one with and one without the capacity for handling pressurised gases. Two reactions have been operated, both without gaseous reagents, continuously for up to three weeks with no noticeable loss in activity, suggesting that the technique should definitely be considered for scale-up. Preliminary costings using realistic price estimates suggest that losses of fluorous ligand and of fluorous solvent during the commercial hydroformylation of long chain alkenes would not greatly inflate the costs of the process, despite the high costs of these chemicals. The major renewable cost would still be from loss of rhodium.