caa a22 4500 475843657 CHVBK 20180406123907.0 cr unu---uuuuu 170329e20000401xx s 000 0 eng 10.1023/A:1027269629785 doi (NATIONALLICENCE)springer-10.1023/A:1027269629785 Analysis of oxidation states of vanadium in vanadia-titania catalysts by the IR spectra of adsorbed NO [Elektronische Daten] [Konstantin Hadjiivanov, Patricia Concepción, Helmut Knözinger] Adsorption of NO on vanadia-titania samples pre-subjected to different reduction treatments has been studied by FTIR spectroscopy. When the NO adsorption is performed at 85 K on oxidized samples, antisymmetric NONO species, typical for V5+ sites, are detected and characterized by bands at 1779 and 1686 cm−1. At ambient temperature, however, adsorption is negligible and only with time reactive adsorption occurs producing NO+ (2120 cm−1), nitro/nitrato species (bands in the 1650-1100 cm−1 region) and weakly adsorbed NO (broad band at 1915 cm−1). Adsorption of NO at ambient temperature on reduced samples results in the formation of two types of species: (i) V4+(NO)2 dinitrosyls characterized by νs(NO) and νas(NO) at 1903-1880 and 1769-1753 cm−1, respectively, and (ii) V3+(NO)2 complexes, which give rise to νs(NO) at 1834-1822 cm−1 and νas(NO) at 1697-1685 cm−1. At low temperature the dinitrosyls are transformed into species in which more than one (NO)2 dimer is attached to one cationic site. Addition of O2 to NO, preadsorbed on reduced vanadia-titania samples, results in a fast oxidation of the V3+(NO)2 species, whereas the V4+(NO)2 complexes are more stable and do not disappear completely in the presence of oxygen. The results obtained suggest that NO is a convenient probe molecule for the analysis of the oxidation state of vanadium in vanadia-titania catalysts. To prevent oxidation of reduced vanadium sites, low equilibrium pressures of NO and registration of the IR spectrum soon after the NO admission are recommended. Kluwer Academic Publishers, 2000 vanadia nationallicence VOx/TiO2 nationallicence oxidation states nationallicence nitric oxide adsorption nationallicence FTIR spectroscopy nationallicence Hadjiivanov Konstantin Institut für Physikalische Chemie, Universität München, Butenandtstrasse 5-11 (Haus E), 81377, München, Germany aut Concepción Patricia Institut für Physikalische Chemie, Universität München, Butenandtstrasse 5-11 (Haus E), 81377, München, Germany aut Knözinger Helmut Institut für Physikalische Chemie, Universität München, Butenandtstrasse 5-11 (Haus E), 81377, München, Germany aut Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 11-12/1-4(2000-04-01), 123-130 1022-5528 11-12:1-4<123 2000 11-12 11244 https://doi.org/10.1023/A:1027269629785 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1027269629785 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Hadjiivanov Konstantin Institut für Physikalische Chemie, Universität München, Butenandtstrasse 5-11 (Haus E), 81377, München, Germany aut NATIONALLICENCE 700 1- Concepción Patricia Institut für Physikalische Chemie, Universität München, Butenandtstrasse 5-11 (Haus E), 81377, München, Germany aut NATIONALLICENCE 700 1- Knözinger Helmut Institut für Physikalische Chemie, Universität München, Butenandtstrasse 5-11 (Haus E), 81377, München, Germany aut NATIONALLICENCE 773 0- Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 11-12/1-4(2000-04-01), 123-130 1022-5528 11-12:1-4<123 2000 11-12 11244 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer