(754a) Raman Spectrokinetics to Gain Insights into the Redox Properties of Supported Vanadium Oxide Catalysts: Surface Structure, Support, and Synergistic Effects

Establishing structure-reactivity/selectivity/stability relationships while using supported metal oxide catalysts for the selective oxidation of light hydrocarbons continues to be difficult to achieve, which limits the discovery of new catalysts with unprecedented catalytic performance. Supported ternary (VO_x)_m-(M₂O_y)_n/support (M₂= Ti, Zr, Nb, Ta) catalysts have shown promising reactivity and selectivity in various reactions depending on V and M₂ relative amounts and coverage, the V:M₂ ratio, the V and M₂ structures, and the kind of support used. In this study, by combining operando Raman spectroscopy with conventional time-resolved reaction kinetics, we measure the redox rates of surface species directly from the Raman spectra. This approach, coined Raman spectrokinetic, exceeds one major limitation of measuring kinetics by mass spectrometry (MS) and gas chromatography (GC). It allows us to observe reaction rates at a specific catalytic site while conventional MS and GC analysis only provide overall reaction rates (average rates from the entire sample’s sites). This study is a continuation of an earlier study which explored the oxidation of (VO_x)_m/(NbO_y)_n/SiO₂ catalysts. Herein, we aim to quantitively determine the redox rates of supported: i) two-dimensional (VO₄ and VO_x) and three-dimensional V₂O₅ nanoparticles, ii) V and M₂ on different supports, and iii) (VO_x)_m-(M₂O_y)_m synergistic effects using our Ramanspectrokinetics approach. It is known that TOF remains constant as a function of coverage, and we are observing the same trend via Raman spectrokinetics. We expect that this study will launch the use of the Raman spectrokinetcis approach to study the the vast library of supported metal oxides used in various important catalytic reactions. These insights will further our goal of preparing supported metal oxide catalysts with rational design choices in order to achieve unprecedented catalytic performances in terms of reactivity, selectivity, and stability.