caa a22 4500 475843436 CHVBK 20180406123907.0 cr unu---uuuuu 170329e20000401xx s 000 0 eng 10.1023/A:1027275225668 doi (NATIONALLICENCE)springer-10.1023/A:1027275225668 In situ IR, Raman, and UV-Vis DRS spectroscopy of supported vanadium oxide catalysts during methanol oxidation [Elektronische Daten] [Loyd Burcham, Goutam Deo, Xingtao Gao, Israel Wachs] The application of in situ Raman, IR, and UV-Vis DRS spectroscopies during steady-state methanol oxidation has demonstrated that the molecular structures of surface vanadium oxide species supported on metal oxides are very sensitive to the coordination and H-bonding effects of adsorbed methoxy surface species. Specifically, a decrease in the intensity of spectral bands associated with the fully oxidized surface (V5+) vanadia active phase occurred in all three studied spectroscopies during methanol oxidation. The terminal V = O (∼1030 cm−1) and bridging V-O-V (∼900-940 cm−1) vibrational bands also shifted toward lower frequency, while the in situ UV-Vis DRS spectra exhibited shifts in the surface V5+ LMCT band (>25,000 cm−1) to higher edge energies. The magnitude of these distortions correlates with the concentration of adsorbed methoxy intermediates and is most severe at lower temperatures and higher methanol partial pressures, where the surface methoxy concentrations are greatest. Conversely, spectral changes caused by actual reductions in surface vanadia (V5+) species to reduced phases (V3+/V4+) would have been more severe at higher temperatures. Moreover, the catalyst (vanadia/silica) exhibiting the greatest shift in UV-Vis DRS edge energy did not exhibit any bands from reduced V3+/V4+ phases in the d-d transition region (10,000-30,000 cm−1), even though d-d transitions were detected in vanadia/alumina and vanadia/zirconia catalysts. Therefore, V5+ spectral signals are generally not representative of the percent vanadia reduction during the methanol oxidation redox cycle, although estimates made from the high temperature, low methoxy surface coverage IR spectra suggest that the catalyst surfaces remain mostly oxidized during steady-state methanol oxidation (15-25% vanadia reduction). Finally, adsorbed surface methoxy intermediate species were easily detected with in situ IR spectroscopy during methanol oxidation in the C-H stretching region (2800-3000 cm−1) for all studied catalysts, the vibrations occurring at different frequencies depending on the specific metal oxide upon which they chemisorb. However, methoxy bands were only found in a few cases using in situ Raman spectroscopy due to the sensitivity of the Raman scattering cross-sections to the specific substrate onto which the surface methoxy species are adsorbed. Kluwer Academic Publishers, 2000 in situ spectroscopy nationallicence methanol oxidation nationallicence oxide catalysts nationallicence vanadia nationallicence Raman nationallicence infrared, UV-Vis nationallicence Burcham Loyd Zettlemoyer Center for Surface Studies and Department of Chemical Engineering, Lehigh University, Bethlehem, 18015, PA, USA aut Deo Goutam Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208-016, UP, India aut Gao Xingtao Zettlemoyer Center for Surface Studies and Department of Chemical Engineering, Lehigh University, Bethlehem, 18015, PA, USA aut Wachs Israel Zettlemoyer Center for Surface Studies and Department of Chemical Engineering, Lehigh University, Bethlehem, 18015, PA, USA aut Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 11-12/1-4(2000-04-01), 85-100 1022-5528 11-12:1-4<85 2000 11-12 11244 https://doi.org/10.1023/A:1027275225668 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1027275225668 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Burcham Loyd Zettlemoyer Center for Surface Studies and Department of Chemical Engineering, Lehigh University, Bethlehem, 18015, PA, USA aut NATIONALLICENCE 700 1- Deo Goutam Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208-016, UP, India aut NATIONALLICENCE 700 1- Gao Xingtao Zettlemoyer Center for Surface Studies and Department of Chemical Engineering, Lehigh University, Bethlehem, 18015, PA, USA aut NATIONALLICENCE 700 1- Wachs Israel Zettlemoyer Center for Surface Studies and Department of Chemical Engineering, Lehigh University, Bethlehem, 18015, PA, USA aut NATIONALLICENCE 773 0- Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 11-12/1-4(2000-04-01), 85-100 1022-5528 11-12:1-4<85 2000 11-12 11244 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer