Modeling vapour-liquid phase equilibrium for the aqueous solutions of formaldehyde and electrolyte

Modeling of vapor - liquid equilibrium for the aqueous solutions of formaldehyde and electrolyte is required for the extractive distillation of formaldehyde-containing multicomponent mixtures using salt as entrainers. Here a revised physicochemical model, which integrates the advantages of the physicochemical model for the vapor - liquid and the chemical equilibria in aqueous formaldehyde solution and the LIFAC model for the phase behavior in mixed-solvent electrolyte systems, has been proposed. The new vapor - liquid equilibrium data in (HCHO – H 2 O – salt) were systematically measured and utilized to determine newly-introduced model parameters. Comparisons of model calculated and experimental measured values proved that the model presented here provides a reliable method for correlating the vapor - liquid equilibria data in (HCHO – H 2 O – salt) system. Furthermore, the model established in this work was used to study salts effect on vapor - liquid equilibria. Both the model calculations and the VLE experiments uncover that Zn(NO 3 ) 2 is the most promising among all of the entrainers investigated.