(556c) Continuous Homogeneous Hydroformylation Using Nanofiltration Membrane for Catalyst Containment

Hydroformylation of higher olefins with rhodium (Rh) based catalyst in carbon dioxide expanded liquids (CXLs) provides higher turnover frequency at lower temperatures and pressures than cobalt based catalyst¹. However, for this process to be economically viable, the Rh recovery rate per pass has to be greater than 99.8%². Bulky polymer bound phosphorus ligands that are soluble in the hydroformylation mixture were synthesized to facilitate the retention of Rh catalyst in the membrane reactor³. This talk will present the first detailed experimental measurements of H₂/CO ratio in CO₂-expanded hydroformylation reaction mixtures. At identical total pressures, it is shown that the H₂/CO ratio in CXLs is more tunable than with syngas alone. The implications of increased H₂/CO ratio in CXLs on the enhanced activity and regioselectivity (n/i) will be discussed. In addition, a CXL-based continuous stirred tank reactor equipped with a nanofiltration membrane was constructed and demonstrated to effectively retain the polymer bound Rh complex while providing steady activity and n/i selectivity. Rh leakage in the permeate was on the order of tens of ppb at steady state, which exceeds the economic viability criterion. The effects of pressure, temperature and space velocity on extended catalyst activity and membrane stability will be presented.