WOx/ZrO2 catalysts for the conversion of α-angelica lactone with butanol to butyl levulinates

WOx/ZrO2 catalysts with different tungsten loadings were prepared via wet impregnation, wherein the presence of WO3 appreciably altered the textural and structural properties. According to Raman spectroscopy, loadings as high as 15 wt% WO3 marked the onset of WO3-nanoparticle formation. Moreover, NH3-TPD and DRIFT spectroscopy with pyridine adsorption revealed that 15 wt% WO3/ZrO2 showed the highest total number of acid centres together with the largest population of Bronsted acid sites. This material was able to achieve full conversion of alpha-angelica lactone in n-butanol leading to the production of 43% n-butyl levulinate and 53% pseudo-butyl levulinate after 5 h at 75 degrees C. The catalytic performance and selectivity towards the esters were found to be strongly related to the concentration of Lewis and Bronsted acid species. [GRAPHICAL ABSTRACT]