Hydroformylation of ethene with triphenylphosphine modified rhodium catalyst: kinetic and mechanistic studies

The kinetics of ethene hydroformylation with triphenylphosphine modified rh odium catalyst has been investigated. The reaction is first order in rhodiu m. The kinetic order for ethene is also one for most of the reaction condit ions investigated, however, the combination of low phosphine and high olefi n concentration leads to a saturation in ethene. The kinetic effects of CO and triphenylphosphine are also a function of their concentrations: both in hibit the reaction above a threshold value, while below the threshold a pos itive kinetic response can be observed. Hydrogen concentration has little e ffect on the rate of hydroformylation. The olefin hydrogenation selectivity is generally low and can be described as a linear function of the H-2/CO p artial pressure ratio. Hydrogenation of the product propionaldehyde cannot be detected by GC, Based on a refined Wilkinson mechanism [C.A. Tolman, J.W . Faller, Mechanistic studies of catalytic reactions using spectroscopic an d kinetic techniques, in: L.H. Pignolet (Ed.), Homogeneous Catalysis with M etal Phosphine Complexes, Plenum Press, New York, 1983.], a kinetic model h as been developed which fits all experimental observations and can be used to predict reaction rates and selectivities over a wide range of reaction c onditions. (C) 1999 Elsevier Science B.V. All rights reserved.