Reactive separation of dilute ethylene by hydroformylation using slurried rhodium catalysts on phosphinated resins and silica

A series of slurried rhodium catalysts on phosphinated resins and silica were tested for the reactive separation of dilute ethylene by hydroformylation to propanal. The amount of rhodium leaching was determined for most of the systems investigated. Leaching ranged from <2 to 11% for catalytic runs for resin supported systems, but was found to be much more significant for the phosphinated silica system studied, 19%. The level of rhodium leaching correlated well with the loss in rate of propanal formation between repeated experiments using recycled catalysts for the resin based systems, but the loss in rate was much more significant for the silica based system. This level of leaching is very high for a commercial process for basic chemical synthesis, for which leaching is typically at the ppb level. Rates of propanal formation for resin supported catalyst systems correlated well with the cone angle of the free phosphine, with rates as high as 0.35 mol/l/h. However, while smaller cone angles were found to be directly proportional to rate, supported systems were less active than homogeneous counterparts.