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Cover Picture: (ChemCatChem 5/2012)
Publication year - 2012
Publication title -
chemcatchem
Language(s) - English
Resource type - Reports
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201290012
Subject(s) - electron paramagnetic resonance , cover (algebra) , dehydrogenation , spin (aerodynamics) , paramagnetism , chemistry , vanadium , spectroscopy , propane , nuclear magnetic resonance spectroscopy , computer science , catalysis , nuclear magnetic resonance , physics , condensed matter physics , inorganic chemistry , quantum mechanics , organic chemistry , thermodynamics , mechanical engineering , engineering
Qualification and Quantification of Reduced Sites Quantification of spin concentration by electron paramagnetic resonance (EPR) is a complicated issue, in particular if overlapping contributions of different paramagnetic centers exist. This problem can be overcome by using high‐frequency EPR, by which contributions with different g values can be disentangled. This approach is similar to the use of ever increasing magnetic fields in NMR spectroscopy. Double integration of the EPR spectrum results in step‐like features, familiar to those seen in NMR spectroscopy, which permits a direct readout of relative spin concentrations. Invoking an external or internal spin standard like Mn 2+ , it is also possible to determine the absolute spin concentration. This method was applied for the qualification and quantification of reduced sites on supported vanadium oxide catalysts used for sample reactions, such as the oxidative dehydrogenation of propane or deep reduction with propane or hydrogen. The data show the important influence of the support material on the type of potentially active sites and the degree of reduction obtained.