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AT THE INSTITUTE of Catalysis & Petrochemistry at the Spanish Council for Scientific Research, in Madrid, Miguel A. Baņares also takes advantage of the operando approach--a term that he coined--to relate information about a catalyst's changing surface structure to its activity and selectivity. In Baņares' experimental setup, Raman spectra and GC data are measured simultaneously. In one study, Baņares examined propane ammoxidation to acrylonitrile using alumina-supported Sb-V-O catalysts. Based on analysis of Raman spectral features, he reported that oxides of antimony and vanadium interact on the catalyst surface, forming SbVO4 and Sb2O4. The data indicate that both phases of the catalyst are directly involved in the reaction's rate-determining step, he noted. In contrast, vanadia species on alumina are not involved in the ammoxidation reaction [Chem. Commun., 2002, 1292]. In related work carried out with chemical engineers at Delft University of Technology, in the Netherlands, Baņares investigated oxidative dehydrogenation of propane on vanadium oxide catalysts supported on alumina. Using Raman spectroscopy and GC in tandem, Baņares observed that under steady-state conditions, the catalyst remains in an oxidized state that's free of carbonaceous deposits. But in the absence of oxygen, propane reacts with the catalyst to form two types of cokelike deposits: a graphitic form and a more aliphatic form. |
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