Valorization of glycerol via continuous etherification with ethanol: Thermodynamic modeling and process optimization.

The valorization of glycerol into value-added chemicals is essential for improving the sustainability of biodiesel and biorefinery systems. This study integrates a thermodynamic vapor-liquid equilibrium model with experimental etherification data to optimize superheated vapor-phase conversion of glycerol using ethanol. Phase behavior of the ethanol-glycerol system was predicted using the Peng-Robinson equation of state with classical van der Waals mixing rules. Experimental investigations evaluated the effects of temperature (210-370°C), catalyst loading (0-0.95 g), ethanol-to-glycerol molar ratio (4:1-30:1), and pressure (7-103 MPa) over a β-zeolite catalyst. Under optimized conditions, a maximum ether yield of 50% and glycerol conversion of 83% were achieved, showing competitive performance compared with existing glycerol upgrading technologies, particularly under continuous fixed-bed operation. Maintaining the reaction system in a single-phase superheated vapor state at moderate pressure (7.9 MPa) and elevated temperature (319°C) effectively reduced mass-transfer limitations typical of biphasic systems. The results demonstrate the potential of superheated vapor-phase processing as an efficient route for glycerol waste valorization and provide guidance for process optimization and scale-up toward sustainable chemical production.