General Properties of Supercritical Media

In the research on a supercritical hydroformylation process, all the important dynamic and equilibrium steps in the catalytic system had to be measured for comparisons with conventional media. The hydrogenation of dicobaltocta-carbonyl 

This process would interconvert the Co signals without affecting the signals and is believed to be responsible for the observations. An activation barrier of (15.3 0.4)kcal/mol was determined for the process by using NMR line-shape analysis [38]. 

In a related activity, thermodynamics were determined for the hydrogenation of dimanganese decacarbonyl [39]. 

5 Rate and Selectivity Measurements Associated with Propylene Hydroformylation in CO2 

HCo(CO)4 is held below its equilibrium value for the reaction in eq (3.2-1), which is only achieved after the alkene is fully consumed. The results for propylene hydroformylation in supercritical CO2 have been compared [53] with those of Mirbach [55] for the reaction of 1-octene in methylcyclohexane solution. Under comparable conditions, the steady-state concentrations of the intermediates do not differ greatly (i.e. by little more than a factor of three), and the overall hydroformylation rates are quite similar, d[aldehyde]/dt = 1.2 x 10 M s and 0.77 x 10 M s , for the methylcyclohexane and CO2 systems, respectively. Although different alkenes were used in the two studies, the comparisons are believed to be meaningful, as Wender et al. [56] have shown that hydroformylation rates for a wide range of straight-chain terminal alkenes vary only slightly with chain length for cobalt catalysts. 

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