One pot synthesis of WOx/mesoporous-ZrO2 catalysts for the production of levulinic-acid esters

• One pot synthesis of WOx/ZrO2via evaporation induced self-assembly.
• WO3 loadings and calcination temperatures affect the resulted WOx/ZrO2 properties.
• Affirmed correlation between the catalytic activity and Brønsted acid sites.

WOx/mesoporous-ZrO2 (WmZr) has been successfully prepared by one-pot evaporation induced self-assembly. The resulting textural properties are highly affected by the additions of WO3 and calcination temperatures. XRD and Raman spectroscopy were used to investigate the crystalline structures and surface states of the materials. Surface acidity was studied employing NH3-TPD and DRIFT spectroscopy with pyridine adsorption. Catalysts loaded with 20–25 wt.% WO3 and calcined at 800 °C exhibited the highest surface acidity with the greatest amount of Brønsted acid sites. The catalysts were tested in the esterification of levulinic acid (LA) with 1-butanol (1-BuOH). Pseudo- (p-BL) and normal-butyl levulinate (n-BL) were observed as the only products. The highest conversion of LA (64–67%) as well as a selectivity of n-BL of up to 97% could be achieved applying a catalyst with 20 wt.% WO3 loading calcined at 800 °C. A clear correlation between catalyst activity and the relative ratio of Brønsted and Lewis acid sites could be confirmed.

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