Recovery of propylene glycol from dilute aqueous solutions by complexation with organoboronates in ion-pair extractants
- Lawrence Berkeley Lab., CA (United States). Dept. of Chemical Engineering
Recovery of propylene glycol (1,2-PD) from aqueous solution was studied in batch experiments using extractants consisting of ion pairs of Aliquat 336 and phenylboronate in 2-ethylhexanol, toluene, o-xylene, or diisobutyl ketone. The heterogeneous complexation constant {beta}{sub 11} calculated from the results of 25 C was highest in 2-ethylhexanol (49--100 (mol/L){sup {minus}1}). The equilibrium water concentration in the extractants was 8--12 wt% and decreased with increasing uptake of 1,2-PD. Nearly all extractant/diluent systems exhibited stoichiometric overloading. Evidence for aggregation of the ion-pair extractant in the organic phase was found from water solubilization studies and {sup 1}H NMR spectroscopy studies. The complexation constant decreased with increasing temperature. Up to 80% of the extracted 1,2-PD was back extracted into water after acidification with CO{sub 2}. The extractant could then be regenerated by stripping CO{sub 2} from solution at temperatures exceeding 110 C. However, at these temperatures the color of the extractant changes, and the extraction capacity is reduced to about 60% of its original value. Regeneration by contacting with aqueous solutions of Na{sub 2}CO{sub 3} did not cause extractant degradation; regeneration effectiveness increased with increasing pH.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 238037
- Journal Information:
- Industrial and Engineering Chemistry Research, Vol. 35, Issue 4; Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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