Viscosity chemical equilibria pressure effects

In order to increase the sustainability of chemical processes, environmentally friendly solvents such as supercritical fluids (SCFs) are widely investigated. Han and coworkers studied the ethenolysis of ethyl oleate in SC C02 in relation with the phase behavior of the reaction mixture [62]. They carried out the ethenolysis reaction at 35°C in the absence of C02 and in the presence of C02 at three different pressures (50, 82, and 120 bar). The reaction in the absence of C02 reached equilibrium in 1 h at 80% conversion. The reaction rate in the presence of 50 bar of C02 was higher than without C02 and, at 82 bar, again increased with respect to 50 bar. However, when the pressure was increased to 120 bar, the reaction rate decreased. This effect was explained according to the variations on the phase behavior with the pressure an increase in the C02 pressure carried an increase of solubility of reactants, products, and C02, which produced a decrease of the viscosity of the reaction mixture. This positive effect was enhanced at 82 bar and was accompanied by an increase of selective solubility of the products in the vapor phase that further increased both reaction rate and conversion. The decrease of efficiency at 120 bar was related to an increase of the solubility of the reactants in the C02 phase. 

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