(602b) Methyl Ketone Oxidative Scission over ?-Al2O3 Supported Vanadium Oxides: An Interpretation of Roles of Lattice Oxygen and Molecular Oxygen from Spectroscopic Insight
AIChE Annual Meeting
Thursday, November 11, 2021 - 12:48pm to 1:06pm
Oxidative scission does not occur over Î³-Al2O3 under He, which is consistent with its non-reducible lattice; however, we do observe oxidative scission products over Î³-Al2O3 under aerobic environments. This indicates that dioxygen can facilitate ketone oxidation through Eley-Rideal or Langmuir-Hinshelwood type pathways. In contrast, oxidative scission is observed over VOX/Î³-Al2O3 under both anaerobic and aerobic environments, which indicates that lattice oxygen of VOX can facilitate the oxidative scission of 3M2B. During transient kinetic experiments over Î³-Al2O3 and VOX/Î³-Al2O3 under aerobic conditions, we observe that both materials produce the oxidative scission product acetone; however, its stoichiometric co-product acetic acid is only observed over VOX/Î³-Al2O3. Further, Î³-Al2O3 becomes inactive for oxidative scission after completing roughly 1 turnover, whereas VOx/Î³-Al2O3 approaches a steady state turnover rate after roughly 60 minutes on stream. FTIR spectra obtained under identical conditions reveal that surfaces are dominated by carboxylates; consequently, we conclude that strong binding of acetate fragments on Î³-Al2O3 render it inactive, whereas lattice reducibility at VOX centers facilitates acetate desorption, resulting in an active material. Since both molecular and lattice oxygen plays significant roles in the oxidative scission of 3-methyl-2-butanone, we conclude that the oxidative scission of ketones on vanadium oxide surfaces has elements of Eley-Rideal and Mars-van Krevelen pathways.