Selectivity of rhodium-catalyzed hydroformylation of 1-octene during batch and semi-batch reaction using trifluoromethyl-substituted ligands

The regioselectivity of catalysts generated in situ from dicarbonyl rhodium(I)(2,4-pentanedione) and trifluoromethyl-substituted triphenylphosphine ligands has been evaluated during the hydroformylation of 1-octene. The influence of batch or semi-batch operation, the solvent, and the number of trifluoromethyl substituents has been investigated. During batch operation in a supercritical carbon dioxide (CO2)-rich system the differential n:iso ratio increases from approximately 4 to a value of 12-16 at about 90-95 % conversion for the catalyst based on bis[3,5-bis(trifluoromethyl)phenyl]phenylphosphine. For semi-batch conditions using hexane a constant n:iso ratio is obtained over a broad conversion range. Batch hydroformylation in neat 1-octene is faster than in a supercritical CO2-rich, one-phase system, with a similar overall selectivity as observed in the supercritical case. The results provide further directions for the development of ligands that are especially designed for the separation of homogeneous catalysts in continuously operated hydroformylation in scCO2