Continuous flow homogeneous catalysis using supercritical fluids

Following our successful development of the first continuous flow homogeneous catalytic system in which the products are of relatively low volatility, which involves supercritical fluid - ionic liquid biphasic systems, we have developed a process which can operate under milder conditions (especially lower pressure. In this process we have replaced the ionic liquid as the solvent for the catalyst by the reaction products. This allows the reactions to be carried out at lower overall pressure because the product is no longer required to be extracted from the ionic liquid, in which it is soluble. It also removes the ionic liquid, over which there are some residual environmental concerns. The new system does not necessarily require an ionic catalyst, so that the process could allow a wider range of catalysts to be employed. was ensured by using ionic species, but high molecular mass, low volatiity compounds should also be possible.
The new system has been developed and optimised using the hydroformylation of long chain alkenes as a test reaction, but has also been used in the oxidation of alcohols to sldehydes for which product separation is an issue.
Because we have used continuous flow operation, the separation of the products from the catalyst is intrinsic to the process, thus overcoming a hurdle which has hindered the commercialisation of several otherwise very attractive homogeneous catalytic processes.