Recovery of acetic acid from an aqueous pyrolysis oil phase by reactive extraction using tri-n-octylamine

The application of reactive extraction to isolate organic acids, particularly acetic acid, from the aqueous stream of phase splitted pyrolysis oil using a long chain aliphatic tertiary amine is reported. Acetic acid recovery was optimized by selecting the proper amine and diluent combination and adjustment of the process conditions. The best results were obtained with tri-n-octylamine (TOA) in 2-ethyl-hexanol (40 wt%) with 84% acetic acid recovery at equilibrium conditions (room temperature). Other organic acids present in the feed (formic acid and glycolic acid) were also co-extracted (92% and 69% extraction efficiencies), as well as relatively non-polar compounds like substituted phenolics and ketones. The continuous reactive extraction process was successfully demonstrated in a centrifugal contactor separator (CCS) device, and acetic acid recoveries of 51% and 71% were obtained in a single CCS device and a two stage cross currently operated cascade, respectively.

► Reactive extraction as a method to isolate organic acids from pyrolysis oil. ► Long chain tertiary amines in combination with 2-ethylhexanol gave best results. ► Co-extraction of non-polar compounds (substituted phenolics and ketones) occurs. ► Continuous extraction in intensified contactor-separators (CCS) demonstrated ► The CCS was shown to operate in the kinetic regime.