On the Impact of the Preparation Method on the Surface Basicity of Mg–Zr Mixed Oxide Catalysts for Tributyrin Transesterification

• Main Authors: Abdallah I. M. Rabee, Jinesh C. Manayil, Mark A. Isaacs, Christopher M. A. Parlett, Lee J. Durndell, Mohamed I. Zaki, Adam F. Lee, Karen Wilson
• Format: Article
• Language: English
• Published: MDPI AG 2018-05-01
• Series: Catalysts
• Subjects: solid base; MgO; transesterification; mixed oxide; biodiesel
• Online Access: http://www.mdpi.com/2073-4344/8/6/228

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–ZrO2 mixed 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, N2 porosimetry, XRD, TEM, XPS, DRIFTS, and CO2-temperature-programmed desorption (TPD). MgO–ZrO2 catalysts 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.