| Base Catalysis |
Solid bases are heterogeneous catalysts that have not been as broadly exploited as solid acids. Our previous work with cesium compounds located inside the cages of zeolite supports and on the surfaces of metal oxides revealed intriguing surface properties and chemical reactivities for a variety of probe molecules and base-catalyzed transformations. One recent area of investigation involves layered double hydroxides known as hydrotalcites and Mg-Al mixed oxides formed by decomposition of hydrotalcites. Thermal decomposition of hydrotalcites followed by controlled rehydration creates an active Brønsted base catalyst that can be used for transesterification. We have also studied the intercalation of ions into layered materials to improve or change their thermal and chemical stability. Additionally, recent work has focused on the promotional effect that zirconia has on magnesia in the catalytic transesterification of tributyrin. Solid bases are also being employed in the synthesis of butanol from ethanol via the Guerbet Reaction. A major goal of this study is to elucidate fundamental structure/property relationships that can be used to improve the activity and selectivity of base catalysts for the alcohol coupling reaction. A combination of materials synthesis (sol-gel, co-precipitation), electron microscopy, spectroscopic materials characterization (EXAFS, IR, Raman, ESR), analysis of adsorbed species (IR, TPD, microcalorimetry) and kinetic measurements (steady state, isotopic transient) is being utilized in the work.
Recent Publications
Yuanzhou Xi and Robert J. Davis, “Influence of Water on the Activity and Stability of Activated Mg-Al Hydrotalcites for the Transesterification of Tributyrin with Methanol” J. Catal. 254 (2008) 190-197.
Yuanzhou Xi, Robert J. Davis, “Influence of Textural Properties and Trace Water on the Reactivity and Deactivation of Reconstructed Layered Hydroxide Catalysts for Transesterification of Tributyrin with Methanol”, Journal of Catalysis, 268 (2009) 307–317.
Yuanzhou Xi, Robert J. Davis, Intercalation of Ethylene Glycol into Yttrium Hydroxide Layered Materials, Inorganic Chemistry, 49 (2010) 3888–3895.
Yuanzhou Xi, Robert J. Davis, Glycerol-Intercalated Mg-Al Hydrotalcite as a Potential Solid Base Catalyst for Transesterification, Clays and Clay Minerals, Vol. 58 No. 4 (2010) 475–485.
Joseph T. Kozlowski, Matthew T. Aronson, Robert J. Davis, Transesterification of Tributyrin with Methanol over Basic Mg:Zr Mixed Oxide Catalysts, Applied Catalysis B: Environmental, 96 (2010) 508–515.
Y. Xi and R.J. Davis, “Nanocrystalline MgO Catalysts for the Henry Reaction of Benzaldehyde and Nitromethane,” J. Mol. Cat. A: Chem. 341 (2011) 22-27.