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

WO x /ZrO 2 catalysts with different tungsten loadings were prepared via wet impregnation, wherein the presence of WO 3 appreciably altered the textural and structural properties. According to Raman spectroscopy, loadings as high as 15 wt% WO 3 marked the onset of WO 3 -nanoparticle formation. Moreover, NH 3 -TPD and DRIFT spectroscopy with pyridine adsorption revealed that 15 wt% WO 3 /ZrO 2 showed the highest total number of acid centres together with the largest population of Brønsted acid sites. This material was able to achieve full conversion of α-angelica lactone in n -butanol leading to the production of 43% n -butyl levulinate and 53% pseudo -butyl levulinate after 5 h at 75 °C. The catalytic performance and selectivity towards the esters were found to be strongly related to the concentration of Lewis and Brønsted acid species. Graphical abstract