Browsing by Subject "FTIR of adsorbed CO"

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    FTIR characterization of Ru/SiO2 catalyst for ammonia synthesis
    (Elsevier, 1999-05-04) Sayan, Ş.; Kantcheva, M.; Süzer, Şefik; Uner, D. O.
    Carbon monoxide adsorption on a Ru/SiO2 catalyst was followed by IR spectroscopy to investigate the active sites. Using this catalyst, ammonia synthesis was achieved at 3508C in an N2/H2 gas mixture (N2/H2 < 3 : 1) for different reaction times. In addition to NH3 other NHx (x 1,2) species were also observed. CO adsorption after NH3 production was also performed to investigate the change in nature of the active sites. Based on the experimental evidence participation of Ru0 sites in ammonia synthesis was confirmed and a partial oxidation of the reduced Ru sites during the synthesis was observed. q 1999 Elsevier Science B.V. All rights reserved.
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    Spectroscopic investigation of species arising from CO chemisorption on titania-supported manganese
    (Academic Press, 2000) Kantcheva, M.; Kucukkal, M. U.; Süzer, Şefik
    The nature of manganese species on the surface of TiO2(anatase) has been investigated by means of XPS, visible absorption spectroscopy, and FTIR spectroscopy of adsorbed CO. The catalysts were prepared by ion-exchange from aqueous manganese(II) chloride solution and impregnation. The application of ion-exchange results in a loading of manganese oxide phase corresponding to a monolayer coverage. On the surface of the ion-exchanged sample two kinds of Mn3+ ions are stabilized, differing in their coordinative saturation and localization. The Mn3+ ions form two kinds of linear carbonyls characterized by absorption at 2194 and 2187 cm−1, respectively. The impregnated catalyst contains a mixture of Mn3+ and Mn2+species. The latter ions produce a carbonyl band at 2114 cm−1. The adsorption of CO at room temperature on the catalysts studied results in formation of formate, carbonate, and hydrogen carbonate structures as well. It is found that the formation of formate species is associated with the Mn3+ ions and the possible mechanism is discussed. The stabilization of the hydrogen carbonates is favored by Mn2+ions. The reduction of the catalyst studied with hydrogen strongly suppresses the adsorption of CO and is indicative of the occurrence of a strong metal–support interaction.
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    XPS and FTIR characterization of manganese ions deposited on alumina
    (Elsevier, 1999-05-25) Kantcheva, M.; Kucukkal, M. U.; Süzer, Şefik
    By application of XPS and FTIR spectroscopy of adsorbed CO the effect of preparation conditions on the state and localization of manganese ions deposited on h-Al2O3 is studied. Both Mn21 and Mn31 ions are observed on the impregnated sample. The sample obtained by ion exchange contains only Mn31 ions. The adsorbed CO species are identified. q 1999 Elsevier Science B.V. All rights reserved.