Abstract
Ethylene glycol (EG) is a common impurity in bio-derived 1,2-propylene glycol (PG). EG was isolated from PG via selective adsorption on basic ion-exchange resin. A small amount of moisture improved the porosity of resin, thereby reinforcing the intraparticle diffusion and adsorption performance. The adsorption equilibrium could be reached within 1 min, indicating that EG can be instantly removed. The real adsorption capacity for PG was much lower than that for EG, and the selectivity was up to 5.5 at 60 °C due to the susceptibility of PG adsorption to temperature. The PG content was increased from 90 to 95.7 wt% in a continuous-flow process with low bed pressure drop. The EG adsorption process agreed with the Langmuir isotherm model, and the apparent EG adsorption capacity reached 250.6 mg/g at 60 °C, while real PG adsorption capacity was negligible. The different interactions between diols and OH− ions were proven by UV and surface-tension measurements, and the stronger acidity of hydroxyl group in EG contributed to its stronger acid-base interaction with basic materials. The resin adsorbent could be reused and completely regenerated without leaching via elution with 20 wt% NaOH. Based on the acidity of EG, this work presents an unprecedented cost-effective strategy to separate diols.
Published Version
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