The influence of phase behavior on reactions at supercritical conditions: The hydrogenation of alpha-pinene

In this paper, results on the hydrogenation of a-pinene, a liquid reactant, in supercritical (SC) CO2 are presented. Visual observation of phase equil ibria under the conditions of the reaction experiments was also performed. Much faster reaction rates were obtained when a two-phase system was presen t in the reactor than when a homogeneous, one-phase situation occurred. Thi s phenomenon is attributed to the fact that SC CO2 can dissolve extensively in the liquid reactant, leading to the formation of an "expanded liquid", which can dissolve large quantities of hydrogen. This seems to be the first time that this type of behavior is reported in the literature.