Identification of recovery pathway for glycolic acid from aqueous phase of bio-crude oil via computer-aided molecular design

Bio-crude oil obtained from hydrothermal liquefaction of biomass, comprising aqueous and organic fractions contains several value-added chemicals. In this study, hydrothermal liquefaction of palm empty fruit bunch fibers was conducted at different temperatures (225 – 275 °C) and water to biomass ratios (10:1 to 20:1) to find their effect on the concentration of organic acids in aqueous phase. The models developed fit the experimental responses well. Recycling of the aqueous phase was found to increase the concentration of organic acids significantly. One of the main component of aqueous phase was glycolic acid, which is worth extracting in its pure form to improve the sustainability of the process. This study adopted a methodological framework which develop a separation scheme integrated with solvent design using Computer-Aided Molecular Design (CAMD) to economically extract and recover glycolic acid. Solvent design for extraction involved a novel CAMD approach, which include the integration of Hansen Solubility Parameters (HSP), solvent power, selectivity and solvent loss. Further purification methods were then evaluated for the purification of glycolic acid. An optimisation model was developed to identify the optimal solvent ratio, that directly impacts the economic viability of the process by minimising the solvent cost as well as glycolic acid and solvent losses via fixing the solvent added. The results suggested that the developed design strategy can efficiently and economically extract pure glycolic acid from the aqueous phase of bio-crude oil produced via hydrothermal liquefaction, where isobutene glycol was selected as the most efficient solvent for the extraction.