| AVS 55th International Symposium & Exhibition | |
| In Situ Microscopy and Spectroscopy: Interfacial and Nanoscale Science Topical Conference | Wednesday Sessions |
| Session IS+NS+TR-WeA |
| Session: | In Situ Microscopy and Spectroscopy – Interfacial Science and Catalysis |
| Presenter: | M.A. Bañares, Catalytic Spectroscopy Laboratory, CSIC, Spain |
| Authors: | M.A. Bañares, Catalytic Spectroscopy Laboratory, CSIC, Spain S.J. Khatib, Catalytic Spectroscopy Laboratory, CSIC, Spain O. Guerrero-Pérez, Catalytic Spectroscopy Laboratory, CSIC, Spain M.V. Martínez-Huerta, Catalytic Spectroscopy Laboratory, CSIC, Spain A.E. Lewandowska, Catalytic Spectroscopy Laboratory, CSIC, Spain |
| Correspondent: | Click to Email |
Catalysts with large surfaces are much more complex than the model single crystals. To single out the active site under real working conditions of the catalyst is an enormous task. It requires a combination of techniques and the development or adaptation of techniques, which allow measurements under catalytic conditions (high temperatures and high pressures). This is the field of in situ spectroscopy. We have recently developed a new methodology that combines the determination of catalyst activity/selectivity and its molecular structure in a single experiment.1,2 We have named this methodology “operando” (Latin for “working”). The presentation will cover Raman studies to assess structure-activity relationships on supported oxides (namely V, Cr, Mo) during alkane and ammonia activation (ammoxidation). In addition, a combination of in situ Raman, XANES, and EPR spectroscopies is used to study the nature of the interaction between V and oxides supports. On most oxide supports, the redox cycle involves reversible reduction of supported vanadia sites. Ceria support behaves differently, though. Surface V5+ species strongly interact with ceria support promoting a reduction of surface Ce4+ to Ce3+. Upon heating or during reaction surface vanadia reacts with ceria support forming a CeVO4 phase. The active site appears to be V5+–O–Ce3+ for both systems. The redox cycle for oxidative dehydrogenation appears to be associated with Ce, rather than with V sites.3
ACKNOWLEDGMENT. The support of the Spanish Ministry of Education and Science (CTQ2005-02802/PPQ)
1 “Operando Raman study of alumina-supported Sb-V-O catalyst during propane ammoxidation to acrylonitrile with on line activity measurement”, M. O. Guerrero-Pérez and M. A. Bañares, Chem. Commun. 12, 1292 (2002).
2Miguel A. Bañares, Catal. Today 100, 71 (2005) (SPECIAL ISSUE NUMBER 100)
3M.V. Martínez-Huerta, J. M. Coronado, M. Fernandez-García, A. Iglesias-Juez, G. Deo, J.L.G. Fierro, M.A. Bañares, J. Catal. 225 (2004) 240-248