Swing processes for solvent regeneration in liquid-liquid extraction of succinic acid

Abstract

Solvent regeneration processes for liquid-liquid extraction of succinic acid (HSuc) from aqueous streams were investigated. Tri-n-octyl amine (TOA) and tri-n-octyl phosphine oxide (TOPO) in methyl isobutyl ketone (MIBK) showed good extraction. For 20 wt% TOA in MIBK, addition of pentane at anti-solvent-to-solvent ratio of 1 (vol/vol) decreased KD from 10.2 to 0.46, applying ethane at 30 bar decreased KD to 0.45 and increasing the temperature to 60 °C decreased KD to 1.6. Evaporation of MIBK from a solvent of 40 wt% TOA in MIBK decreased KD from 10.2 to 4.0. For these processes, capital investments and energy requirements were calculated for 10 kiloton per year at a concentration factor of 5. Costs of all processes to obtain the product at maximum solubility are less than evaporation (2600 kJ/kg product at maximum solubility). A combination of a swing in diluent and temperature results in higher product concentrations after back-extraction, and reduced the energy input to obtain the pure HSuc to 19 MJ/kg. The ethane-based process is most effective with 13 MJ/kg to obtain the pure HSuc product. Although additional capital investments for compressors and pumps are required, only 110 days of production are required for return on investments.