Green and Sustainable Bamboo Leaf Ash Derived WO 3 Impregnated Mesoporous KIT-6 Catalyst for Acetalization of Glycerol to Biofuel Additives: Activation Energy Calculation

Abstract

Utilizing surplus glycerol from biodiesel production for dioxolane synthesis, a significant fuel enhancer, is pivotal. We developed mesoporous spherical KIT-6 supported WO₃ using sodium silicate derived from bamboo leaf ash (BLA) and ammonium tungstate hydrate. Characterization via XRD, N₂ adsorption-desorption, SEM, TEM, NH₃-TPD, and XPS confirmed KIT-6's phase purity. WO₃ impregnation on BLA-KIT-6 notably improved glycerol conversion and dioxolane selectivity compared to amorphous KIT-6 from tetraethyl orthosilicate (TEOS), primarily due to its advantageous spherical morphology. Spherical structures typically offer higher surface areas, facilitating more active sites for acid catalysis and thereby enhancing acidity. Additionally, glycerol conversion and dioxolane selectivity over the WO₃/BLA-KIT-6 catalyst were higher with p-nitrobenzaldehyde due to its -M effect, while long chain aldehydes exhibited reduced conversion due to their + I effect. Conversely, cyclic ketones displayed heightened reactivity in glycerol acetalization over WO₃/BLA-KIT-6 catalyst. Catalyst recyclability and hot-filtration tests verified its stability and heterogeneity. The Arrhenius plot yielded an apparent activation energy of 37.098 kJ/mol for the WO₃/BLA-KIT-6 catalyst.