WO 3 -Modified KIT-6 Catalysts Synthesized via Non-Hydrolytic Sol-Gel for Glycerol Dehydration to Acrolein

Abstract

The expansion of biodiesel production has generated a surplus of glycerol. Valorization of this renewable byproduct into value-added chemicals is therefore of growing interest. This study presents a systematic investigation of WO₃/KIT-6 catalysts synthesized via a non-hydrolytic sol-gel (NHSG) method for glycerol dehydration to acrolein. The NHSG method provides improved tungsten dispersion and enhanced surface acidity compared to conventional preparation routes. Catalysts with 5-35 wt.% WO₃ were prepared and systematically characterized. XRD confirmed the formation of monoclinic WO₃ in all samples. The 25 wt.% WO₃/KIT-6 catalyst exhibited the highest medium acid site density (204 µmol NH₃ g⁻¹), intrinsic acidity (0.56 µmol NH₃ m⁻²), and a Brønsted/(Brønsted+Lewis) ratio of 0.67. It delivered 83% glycerol conversion and 43% acrolein selectivity. XPS analysis confirmed the presence of W⁶⁺/W⁵⁺ surface species associated with acid site formation. Correlation analysis demonstrates that an optimal balance between medium-strength acidity and mesostructural properties governs acrolein selectivity and catalyst stability, while excessive total acidity promotes coke formation.