Recovery of levulinic acid by reactive extraction using tri-n-octylamine in methyl isobutyl ketone: Equilibrium and thermodynamic studies and optimization using Taguchi multivariate approach

Abstract

Recovery of levulinic acid from an aqueous solution using a tertiary amine, tri-n-octylamine (TOA), as an extractant in methyl isobutyl ketone (MIBK) was studied at different temperatures (293-333 K). The physical equilibrium studies were performed using MIBK as a diluent. Partition (P) and dimerization (D) coefficients were found to decrease noticeably with increasing temperature. The coefficient of distribution was found to be very low in physical equilibrium. Chemical equilibrium studies were conducted using various concentrations of the extractant. The highest coefficient of distribution (K D ) and efficiency of extraction (%E) were found to be 58.0 and 98.0% respectively for 0.1 kmol m -3 of levulinic acid and 0.678 kmol m -3 of TOA at 293 K. Chemical equilibrium studies showed the formation of 2:1 complex as the main mechanism in the reactive extraction. Taguchi mixed design multivariate approach (L 18 ) was used to optimize the process variables. S/N ratio (larger-is-better) criterion was adopted to maximize the perfor mance parameters. The optimum combination of variables was found to include acid concentration (X 1 ) = 0.3 kmol m -3 , TOA concentration (X 2 ) = 0.678 kmol m -3 and temperature (X 3 ) = 293 K. A confirmation run was conducted using these parameters and K D and %E values from this run were determined to be 11.83 and of 92.2%, respectively, which were very close to the predicted values of K D = 12.78 and %E = 94%