Extractive recovery of aqueous diamines for bio-based plastics production

Background This paper reports an extractant screening study for the recovery of putrescine (butylene-1,4-diamine, BDA) and cadaverine (pentylene-1,5-diamine, PDA) from aqueous solutions (e.g. fermentation broths) by liquid–liquid extraction. Several extractants were studied, including 4-nonylphenol, 3,4-bis((2-ethylhexyl)oxy)phenol, di-2-ethylhexyl phosphoric acid (D2EHPA), Versatic acid 1019, di-nonyl-naphthalene-sulfonic acid (DNNSA), and 4-octylbenzaldehyde. 1-Octanol, 2-octyl-1-dodecanol and heptane were used as diluents, and temperatures of 25 °C and 65 °C. Results The most promising solvent is 4-nonylphenol, hardly leaching into the aqueous raffinate (19 ppm), and showing BDA distribution coefficients very strongly dependent on the extractant concentration, ranging from very low distribution ( D ∼ 1 at <20 wt% 4-nonylphenol in 1-octanol at 25 °C) to high distribution (D > 100) for pure 4-nonylphenol at 25 °C. The strong dependency of the distribution on extract phase composition was applied to efficiently back-extract up to 90% BDA in a single step. To achieve this, the pure 4-nonylphenol used in extraction was diluted to a 20 wt% dilution in 1-octanol. The use of 4-nonylphenol as extractant was also examined for PDA, and higher distributions were observed than for BDA, which can be attributed to the longer hydrocarbon chain of PDA. Conclusions Recovery of diamines from aqueous medium can be accomplished in an effective way using 4-nonylphenol as extractant. These results may be used to develop a bio-based butylene-1,4-diamine production route