Extraction performance evaluation of amide-based deep eutectic solvents for carboxylic acid: Molecular dynamics simulations and a mini-pilot study

Carboxylic acids are important precursors of chemical raw materials produced from the bioconversion of renewable feedstocks. In these processes, the separation of carboxylic acid products from fermentation broth is of great significance and challenge. In this research, the extraction performance of carboxylic acid using novel hydrophobic deep eutectic solvents (DESs) composed of amides and geraniol was studied. Molecular dynamics (MD) simulations have also been adopted to understand the extraction mechanism. Radial and combined distribution functions analysis shows that hydrogen bond-induced geraniol-carboxylic acid and amide-carboxylic acid multi-molecular assembly drives the separation of carboxylic acids from fermentation broth. Thermodynamics and mean square displacement calculations show that increasing temperature breaks the hydrogen bond networks, and the hydrophobic DESs can be recycled. Finally, a mini-pilot experiment for lactic acid recovery from fermentation broth verified the effectiveness of the amide-based DESs and their application to practice. These findings provide references for industrial-scale production of carboxylic acid separation.