Origin of the Activity Trend in the Oxidative Dehydrogenation of Ethanol over VO_x/CeO₂**

Abstract

Supported vanadia (VO x ) is a versatile catalyst for various redox processes where ceria-supported VO x have shown to be particularly active in the oxidative dehydrogenation (ODH) of alcohols. In this work, we clarify the origin of the volcano-shaped ethanol ODH activity trend for VO x /CeO x catalysts using operando quick V K-and Ce L 3 -edge XAS experiments performed under transient conditions. We quantitatively demonstrate that both vanadium and cerium are synergistically involved in alcohol ODH. The concentration of reversible Ce 4 + /Ce 3 + species was identified as the main descriptor of the alcohol ODH activity. The activity drop in the volcano plot, observed at above ca. 3 V nm À 2 surface loading (ca. 30 % of VO x monolayer coverage), is related to the formation of spectator V 4 + and Ce 3 + species, which were identified here for the first time. These results might prove to be helpful for the rational optimization of VO x /CeO 2 catalysts and the refinement of the theoretical models.

Aerobic Oxidation of Methyl Glycolate by α-Fe2O3 for the Eco-Friendly Synthesis of Methyl Glyoxylate

“…In the MvK process, generally, the oxidation of the substrate by lattice oxygen is considered to be the rate-controlling step. , So, the reactivity of the lattice oxygen in the α-Fe 2 O 3 catalysts should be in line with their catalytic activity. The H 2 -TPR, as a useful tool for exploring the lattice oxygen reactivity, was employed to study the α-Fe 2 O 3 catalysts with varied surface OH content.…”

“…For comparison, the transition metal oxides (TMOs) with the outstanding low-temperature activity as well as the lower cost have been studied extensively. Typically, the FeMoO x has been practically applied in the gas-phase oxidation of methanol to formaldehyde process under much lower operating temperatures (300–400 °C) than that for the Ag-based catalysts (600–700 °C). , Moreover, the TMOs (such as V 2 O 5 , , MnO 2 , , Fe 2 O 3 , and their mixed oxides , ) are widely reported to show outstanding activity in the partial oxidation of alcohols such as benzyl alcohol, glycerin, and methyl lactate.…”