Transesterification of tributyrin with methanol over basic Mg:Zr mixed oxide catalysts

Two series of Mg:Zr mixed oxides, prepared by either co-precipitation or sol–gel synthesis, were characterized and evaluated in the base catalyzed transesterification of tributyrin with methanol. A co-precipitated Mg-rich mixed oxide catalyst with Mg:Zr 11:1 was approximately 300% more active than MgO on a surface area basis, whereas pure ZrO2 was inactive for the reaction. To explore the nature of the activity enhancement, samples were characterized by X-ray diffraction, N2 adsorption, CO2 adsorption microcalorimetry and DRIFTS of adsorbed CO2 and CH3OH. Although the sol–gel synthesis method provided better atomic level mixing of Mg and Zr, the resulting catalysts were not as effective as mixed oxides prepared by co-precipitation. The most active mixed oxide (Mg:Zr 11:1) exhibited a high initial heat of CO2 adsorption and modified modes of methanol adsorption compared to MgO. However, the CO2 adsorption capacity did not correlate to catalyst activity.