Enhanced Hydrothermal Stability and Catalytic Activity of LaxZryOz Mixed Oxides for the Ketonization of Acetic Acid in the Aqueous Condensed Phase

Abstract

Common ketonization catalysts such as ZrO2-, CeO2-, and TiO2-based catalysts have been reported to lose surface area, undergo phase transformation, and lose catalytic activity when they are utilized in the condensed aqueous phase. In this work, we synthesized a series of LaxZryOz mixed-metal oxides with different La:Zr atomic ratios with the goal of enhancing the catalytic activity and stability for the ketonization of acetic acid in condensed aqueous media at 568 K. We synthesized a hydrothermally stable LaxZryOz mixed-metal oxide catalyst with ketonization activity 265 and 45 times more active than La2O3 and ZrO2, respectively. Catalyst characterization techniques suggest that the enhanced stability of the LaxZryOz catalysts is observed with the formation of a phase isomorphic with tetragonal ZrO2. DRIFTS spectroscopy measurements indicated the enhanced catalytic activity of LaxZryOz catalysts correlated with greater acetic acid surface population in the presence of H2O versus pure ZrO2.