Synthesis of Porous Clay Heterostructures Modified with SiO2–ZrO2 Nanoparticles for the Valorization of Furfural in One-Pot Process

Abstract

The layered structure of two smectites (montmorillonite and saponite) are modified by the insertion of SiO2–ZrO2 nanoparticles, with a Si/Zr molar ratio of 5, to form porous clay heterostructures (PCHs). These PCHs exhibit a clear improvement of the textural and acid properties in comparison to the starting clays, due to the formation of a pillared structure and the presence of Zr species, which provide an increase in the amount of Lewis acid sites. These materials are studied in one-pot catalytic processes to transform furfural into valuable products, such as furfuryl alcohol, alkyl furfuryl ethers, alkyl levulinates or γ-valerolactone, depending on the experimental conditions. Thus, the use of milder reaction temperature (110 °C) favors the formation of furfuryl alcohol and alkyl furfuryl ethers, while higher temperatures (170 °C) promote the formation of alkyl levulinate and γ-valerolactone, as well as an increase in nondetected products associated to the formation of humins due to the polymerization of furfural and/or furfuryl alcohol.