Hydrogenation of itaconic acid in micellar solutions: catalyst recycling with cloud point extraction?

The biggest problem in homogeneous catalysis is how to devise efficient recycling of the catalyst in its active form. In this contribution, cloud point extraction (CPE), a methodology already known from different applications, is adapted for the recycling of homogeneous catalysts from micellar solutions. About 96% of a homogeneously dissolved Rh/BPPM catalyst complex is recycled by CPE from aqueous micellar solutions of the nonionic surfactant NP8 and reused in subsequent reactions. The hydrogenation of itaconic acid is studied as a benchmark reaction to prove this alternative concept showing that it is feasible for catalyst recycling. However, severe catalyst deactivation takes place for substrates with carboxylic acid groups, which needs consideration during substrate selection.