On the impact of the preparation method on the surface basicity of Mg-Zr mixed oxide catalysts for tributyrin transesterification

Mixed metal oxides are promising heterogeneous catalysts for biofuel production from lipids via alcoholysis, however, the impact of solid acidity and/or basicity on reactivity is comparatively poorly understood. Two systematically related families of MgO-ZrO2mixed oxide catalysts were therefore prepared by different synthetic routes to elucidate the impact of surface acid-base properties on catalytic performance in the transesterification of tributyrin with methanol. The resulting materials were characterized by TGA-MS, ICP-OES, N2porosimetry, XRD, TEM, XPS, DRIFTS, and CO2-temperature-programmed desorption (TPD). MgO-ZrO2catalysts prepared by both non-aqueous impregnation and citric acid-mediated sol-gel routes exhibit excellent activity and stability. The citrate routes favor highly dispersed MgO and concomitant Lewis acid-base pair formation at the interface with zirconia. However, for both the citrate and impregnation routes, tributyrin transesterification occurs over a common, strongly basic MgO active site.