Esterification of levulinic acid over tetravalent metal phosphates: An efficient route to fuel additives

Layered materials, including tetravalent metal phosphates and phosphonates, have been widely investigated in several fields acting as good, selective catalysts in a great number of reactions. In the present work, α- and γ-zirconium phosphates (α- and γ-ZrP) were prepared and evaluated as catalysts in the esterification reactions of levulinic acid (LA) with ethanol (EtOH) or methanol (MeOH) using the conventional reflux method (CV) or the microwave assisted method (MW). The best selectivities for ethyl and methyl levulinates and conversions of LA were achieved with γ-ZrP using the MW method and are strongly related with the properties and structure of this catalyst and the method used. Two intermediates, the 5-ethoxy-5-methyldihydrofuran-2-one also designated by pseudo-ethyl levulinate (pseudo-EL) or the 5-methoxy-5-methyldihydrofuran-2-one also designated by pseudo-methyl levulinate (pseudo-ML) were also formed. [Display omitted] •Levulinic acid and levulinate esters: biomass-based green platform compounds.•Levulinic acid esterification: microwave versus conventional reflux method.•Solid acid heterogeneous catalysts: α- and γ-zirconium phosphates.