Tautomeric reaction equilibrium of ethyl acetoacetate in CO2–n-pentane and CO2–ethanol mixed solvents in the critical region

The tautomeric equilibrium constant KC of ethyl acetoacetate (EAA) in CO2–n-pentane and CO2–ethanol was studied by UV–VIS spectroscopy at 308.2 K over the pressure range from 6.5 to 9.0 MPa. This work focuses on how the tautomeric equilibrium changes with pressure and composition of the mixed solvents in the near critical region. The results showed that the effect of pressure on KC was very limited at pressures much higher than the phase separation pressures. However, the KC increased sharply as the pressure approached the critical point or the bubble point of the mixed solvents.