One-pot synthesis of MoO3-ZrO2 solid acid catalyst for solvent-free solketal production from glycerol

Abstract

Glycerol acetalization to solketal is a promising method of increasing the additional value of glycerol, which is a by-product in biodiesel industry. In this work, a series of mesoporous x-MoO3-ZrO2 (x = Mo/Zr) solid acid catalysts with controllable Mo contents were designed and synthesized for the acetalization of glycerol. As important influence factors of solid acid catalysts, the mesoporous structure and existential state of Mo species were systematically investigated. Results show that Mo species were introduced as planned and existed in a homogeneously dispersed state in MoO3-ZrO2 materials. The acidic properties of MoO3-ZrO2 were explored through NH3-TPD and pyridine-chemisorbed FT-IR spectroscopy, and the formation of Brønsted and Lewis acid sites was confirmed by density functional theory calculations. Given their excellent acidity, MoO3-ZrO2 catalysts were employed for the acetal reaction of glycerol. Among the tested catalysts, the 20 %-MoO3-ZrO2 catalyst exhibited the optimal catalytic performance and reusability, achieving a conversion of 89 % for glycerol and a selectivity of 97 % for solketal. Consequently, MoO3-ZrO2 is a green solid acid catalyst with promising applications in solvent-free solketal production from glycerol.