Non‐Hydrothermal Synthesis of MCM‐41‐Type Catalysts Modified With Zirconia and Tungsten Oxide for the Esterification of Levulinic Acid With Ethanol

ABSTRACT In the present study, ordered mesoporous silica of the MCM‐41 type was synthesized via a non‐hydrothermal route at room temperature and with reduced reaction time. The material was grafted with 10 wt% ZrO 2 and WO 3, aiming to obtain heterogeneous acidic catalysts for the esterification of levulinic acid with ethanol. The catalysts were characterized by X‐ray diffraction (XRD), N 2 adsorption–desorption, thermogravimetric analysis (TG/DTG), infrared spectroscopy (FTIR) and temperature‐programmed desorption of ammonia (TPD‐NH 3 ). All catalysts retained the well‐ordered hexagonal mesoporous structure characteristic of MCM‐41. Although the incorporation of zirconium and tungsten resulted in reduced specific surface area and pore volume, the materials presented excellent textural properties and thermal stability. Moreover, the presence of moderate and strong acid sites evidenced that the metal insertion promoted the acidity of the synthesized solids, being more pronounced in the tungsten‐modified material. Consequently, 10% W/MCM‐41 was more active than 10%Zr/MCM‐41, with ester conversions of 69% and 61%, respectively. All catalysts proved stable and active for five consecutive cycles in the esterification reaction at 120°C for 3 h.