Kinetic and Spectroscopic Investigations of Alcohol Conversions over Metal Oxide Catalysts

The next advancement in the field of catalysis is to move from catalyst discovery to catalyst design. For this to be realized, we must meet one of the grand challenges in science identified in the 2007 Basic Research Needs Workshop report on Catalysis for Energy, which is to “Understand reaction mechanisms and dynamics of catalyst transformations.” One cannot draw reaction mechanism without quantitative and qualitative characteristic of the chemical composition/intermediate as well as the orientation at the catalyst surface. Therefore, monitoring these interactions in situ is necessary to understand different reaction steps and what transient intermediates/structures are present during the reaction.

In situ and operando vibrational spectroscopies have proven to be valuable tools to probe the chemical transformation as they occur in real time during heterogeneous catalysis. Here, we show how sum-frequency generation (SFG) spectroscopy can be used to probe surface-specific interactions that lead to a better understanding of reaction pathways of isopropyl alcohol (IPA) on the (100) surface of two metal oxides, cerium oxide and strontium titanate. Inelastic neutron scattering (INS), a complimentary vibrational technique, which offers unparalleled sensitivity towards monitoring hydrogenous materials on a variety of surfaces, was used to characterize and compare the reactivity of both synthesized and commercially-available samples. We use these two in-situ vibrational techniques to spectroscopically characterize catalyst samples during the reaction process. In addition, we correlate these spectroscopic observations with reaction kinetic studies to gain insights of the reaction mechanisms that govern the activity and selectivity.