Abstract:
Nowadays, the production of biodiesel has been increased. The conversion of glycerol derived from biodiesel production into high value product has therefore become a big challenge. As a precursor for polyester production, 1,3-propanediol (1,3-PDO) is one of the most interesting high value chemicals produced from glycerol. Its production can be achieved either by a chemical or biological process, however the environmental friendly biological process is more preferable. For the separation of 1,3-PDO from fermentation broth, high separation factor and easy operation are the key issues, and this study therefore focuses on investigation of adsorption of 1,3-PDO in model mixture of fermentation broth onto non-ionic polymeric resins (hydrophilic XAD-7 and hydrophobic XAD-16). First, the adsorption equilibrium isotherm of 1,3-PDO on both XAD-7 and XAD-16 resins in binary system (303 K) were investigated. The results indicated that the amount of 1,3-PDO adsorbed increased with the increase in initial concentration of 1,3-PDO. In this study, the maximum adsorption was achieved at the initial concentration of 1,3-PDO at 160 g/L. The Freundlich type model gave a reasonable fit to the experimental adsorption isotherms for both resins, and the parametric constants for adsorption on XAD-7 were much higher than that for XAD-16. In the tertiary system, the presence of glycerol promoted 1,3-PDO adsorption for XAD-16 at 160 g/L initial concentration of 1,3-PDO. However, XAD-16 also adsorbed higher amount of glycerol caused lower the selectivity. In multiple component system, the presence of acetic acid and butyric acid in aqueous solution promoted 1,3-PDO adsorption and selectivity for both resins. In addition, the study of desorption with ethanol solution showed that the desorption yield increased with increasing the ethanol content. The mass fraction of 1,3-PDO in desorbed solution from XAD-7 (0.321) was higher than that for XAD-16 (0.294) while the mass fraction of butyric acid in desorbed solution of XAD-7 (0.087) was lower than that XAD-16 resin (0.131). Based on these results, XAD-7 was concluded to be appropriate, giving higher amount of 1,3-PDO adsorbed (1335.7 mg/g) and higher selectivity (4.46) compared to the adsorbs obtained by XAD-16 resins.
