Supported liquid phase hydroformylation catalysts containing rhodium and triphenylphosphine. Effects of additional solvents and kinetics

Abstract

Catalysts contaning hydridocarbonyltris(tripenylphosphine)rhodium (I), HRh(CO)(PPh 3) 3, and excess PPh 3 supported on silica show some modification in behaviour (hydroformylation of propene) if additional solvents are present. At high phosphine loadings the effect is to increase the overall rate of reaction and to reduce the regioselectivity for n-butanal production. At low phosphine loadings both the rate and regioselectivity are increased for small additions of other solvents (except Ph 3PO 4) but thereafter further increase in rate is accompanied by a fall in regioselectivity. It is believed that these result illustrate the distinction between chemical and physical roles played by the PPh 3 in these catalysts. The kinetics of hydroformylation can be reasonably described by a power rate law of the form r 1 = k 1 P G C 3 P b CD P c H 1 exp(− E 1/ RT) where r 1 is the overall rate of propene consumption. Analogous expressions for rates of production of n-butanal ( r 2) and isobutanal ( r 3 are presented. In all cases the values of the parameters typified by k 1, a, b, c and E 1 are given for the reaction conditions employed. The influences of phosphine loading on the kinetic parameters are discussed in terms of an increasing tendency of PPh 3 to become highly mobile at sufficiently high loadings. The choice of support (non-porous microspheroids or microporous gel) is largely without influence on the catalytic behaviour.