Membrane-supported rhodium hydroformylation catalysts

Abstract

Films prepared from THF solutions containing cellulose acetate, [HRh(CO)(PPh 3) 3] and PPh 3 were tested for catalytic activity in the vapor phase hydroformylation of ethylene and propylene: RCH=CH 2+CO+H 2→RCH 2CH 2CHO. The reaction proceeded smoothly at 800 ton- and 80 °C. Turnover rates were about 25 mol propanai per mol Rh per h. No loss of PPh 3 or Rh from the film was observed even after long periods of reaction. The excess PPh 3 seemed to stabilize the catalytic activity of the film but concentrations beyond 10 molar produced no further improvement. The turnover rate with the films was equal to or even slightly higher than that obtained under similar conditions using a homogeneous solution of [HRh(CO)PPh 3] in 2-methylmaphthalene solvent. The turnover rate for propylene to C-4 aldehydes was about an order of magnitude smaller than that for ethylene to propanal. Films prepared from poly(phenylsulfone) were also active catalysts. The ratio of n/iso C-4 aldehydes with this support was about 20. In the absence of oxygen the catalyst system retained its activity for more than 13 days but no attempt was made to test for longer lifetimes. The use of polymeric films or membranes as a support for the rhodium catalysis of the hydroformylation reaction thus appears to hold considerable promise.