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| - In-Situ UV/vis and Transient Isotopic Analysis of the Role of Oxidizing Agent in theOxidative Dehydrogenation of Propane over Silica-Supported Vanadia Catalysts
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| - In-situ UV/vis spectroscopy in combination with transient isotopic analysis was applied for elucidating thegoverning factors, which determine the superior performance of N2O as compared to O2 in the oxidativedehydrogenation of propane (ODP) over VOx/MCM-41, VOx/MCM-48, and VOx/SiO2 catalytic materials.Characterization studies applying in-situ steady-state UV/vis spectroscopy evidenced higher reduction degreeof surface VOx species at 773 K in a C3H8−N2O (C3H8/N2O = 1/1) feed than in a C3H8−O2 (C3H8/O2 = 2/1)flow at controlled conversions of propane (<5%) and oxidizing agent (<10%). The in-situ UV/vis method ina transient mode enabled to distinguish the ability of O2 and N2O for reoxidation of reduced VOx species;N2O reoxidizes reduced VOx species slower than O2. This property of N2O is very essential for suppressingnonselective consecutive propene oxidation to COx (mainly to CO). Additionally, the results of transientisotopic experiments in the temporal analysis of products reactor revealed that adsorbed (nonlattice) oxygenspecies are formed upon O2 activation over reduced VOx species and participate in CO2 and CO formation.It is suggested that these nonselective species do not originate from N2O.
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