Homogeneously catalyzed propylene hydroformylation in supercritical carbon
dioxide (SCCO2) using Co-2(CO)(8) pre-catalyst was studied in batch reactor
s. The experiments were carried out at temperatures of 66 to 108 degrees C,
and pressures of 90.6 to 194.1 bar. The phase behavior of the reaction mix
ture was monitored in a cell with a sight glass to ensure that the reaction
s were carried out in the single phase region. The product selectivity was
determined at different reaction conditions. At a fixed temperature, the se
lectivity increased with pressure and at a fixed pressure it decreased with
temperature. By chemical equilibrium calculations it was shown that the ch
anges in selectivity were not chemical equilibrium controlled. The partial
molar volumes of two isomers of the product were determined experimentally
and after fitting the interaction parameters for the Peng-Robinson equation
of state from partial molar volume data, the partial molar enthalpies were
predicted from the same equation. It is shown that the selectivity increas
e with pressure at constant temperature can be explained in terms of the di
fference of the partial molar volumes of the isomers and the selectivity de
crease with temperature at constant pressure can be explained in terms of t
he difference of the partial molar enthalpies of the two isomers. (C) 1999
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