Irina R. Subbotina
Russian Academy of Sciences
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Featured researches published by Irina R. Subbotina.
Journal of Physical Chemistry A | 2009
Irina R. Subbotina; V.B. Kazansky; Jutta Kröhnert; Friederike C. Jentoft
An attempt to measure absolute intensities of IR C-H stretching bands of ethane specifically adsorbed by Na+, Ca2+, or Mg2+ cations in Y zeolite was carried out via simultaneous transmission IR and volumetric measurements at very low pressures using self-supporting wafers. For wafers with a thickness of 7-9 mg/cm2 quantitative measurements of absorption coefficients of C-H stretching bands were possible. More pronounced shifts of C-H bands toward lower frequencies indicated that the perturbation of the corresponding bonds in ethane upon adsorption by the bivalent Ca2+ or Mg2+ ions was much stronger than by the monovalent Na+ ions. In addition, the integral extinction coefficient of the C-H stretching bands of ethane adsorbed by Na+ ions was only about 53% of that of gas-phase ethane. For adsorption on the bivalent Ca2+ or Mg2+ ions the coefficients exceeded those of the free ethane molecule, indicating strong polarization of the C-H bonds during the vibration. Bands representing the fully symmetric C-H stretching vibrations, which are IR inactive for free ethane, were perturbed most strongly upon adsorption. Their intensities reached up to 60% of the total intensity in the C-H stretching region. In contrast, the intensities of the other C-H bands were several times lower than for free ethane. These trends indicate anisotropy in the polarizability of the adsorbed molecules. In addition, the absorption coefficients indicate a weaker adsorption and polarization of ethane by Mg2+ than by Ca2+ ions in Y zeolite. Because of their smaller ionic radius, the Mg2+ cations are more strongly shielded by the surrounding oxygen atoms of the zeolite framework than the Ca2+ cations, and therefore, their polarizing ability is decreased.
Kinetics and Catalysis | 2013
A. N. Subbotin; G. M. Zhidomirov; Irina R. Subbotina; V.B. Kazansky
Interest in water adsorption on cation-substituted zeolites is due to the possibility of the Mn+ (H2O) + [Si-O-Al]−1 → MOH(n − 1)+ + Si-O(H)-Al (M = metal, n = 1–3) reaction taking place. As a result of this reaction, the cation-substituted zeolite can exhibit Brønsted acid activity. The molecular adsorption of water on Zn/ZSM-5 zeolite at room temperature and the subsequent heterolytic dissociation of adsorbed water under heating have been investigated by diffuse-reflectance IR spectroscopy. For theoretical simulation of these processes, three different fragments of the ZSM-5 lattice corresponding to possible variants of the structure of the ionic site of the substituting cation have been examined. Calculations on the molecular and dissociative adsorption of water molecules on substituting Zn2+ cations have been performed by the DFT method. Two pathways of the dissociation of adsorbed H2O molecules-endothermic and exothermic ones-have been discovered, and it has been demonstrated that the spatial separation of two lattice Al ions at the Zn2+ cation site significantly affects the adsorption energy.
Studies in Surface Science and Catalysis | 2008
Irina R. Subbotina; V.B. Kazansky; Friederike C. Jentoft; Robert Schlögl
Abstract An attempt to measure integral molar extinction coefficients (IMEC) of C-H and C=C stretching bands of propene specifically adsorbed by Na + , Ca 2+ and Mg 2+ cations in Y zeolite was carried out via parallel IR spectroscopic and volumetric measurements. Propene was adsorbed at low pressures ( 2+ and Mg 2+ cations the IMEC values exceeded those for free propene. Simultaneously, the IMEC of the C-H stretching band decreased relative to that of the C=C band. These observations indicate that the C=C bond is more strongly polarized and thus more activated during interaction with bivalent than with monovalent cations. This conclusion is confirmed by oligomerization of propene on ZnY zeolite, which proceeds at room temperature. Intensities of IR bands thus provide a sensitive criterion for the activation of double bonds arising from their polarization by cations.
Journal of Physical Chemistry B | 2006
V.B. Kazansky; Irina R. Subbotina; Andrey A. Pronin; Robert Schlögl; Friederike C. Jentoft
Journal of Catalysis | 2006
V.B. Kazansky; Irina R. Subbotina; Friederike C. Jentoft
Langmuir | 2005
Barbara S. Klose; Friederike C. Jentoft; Robert Schlögl; Irina R. Subbotina; V.B. Kazansky
Journal of Physical Chemistry B | 2006
V.B. Kazansky; Irina R. Subbotina; Friederike C. Jentoft; Robert Schlögl
Catalysis Today | 2006
Barbara S. Klose; Friederike C. Jentoft; Pradnya Joshi; Annette Trunschke; Robert Schlögl; Irina R. Subbotina; V.B. Kazansky
Journal of Physical Chemistry C | 2013
Friederike C. Jentoft; Jutta Kröhnert; Irina R. Subbotina; V.B. Kazansky
Journal of Photochemistry and Photobiology A-chemistry | 2016
Denis V. Barsukov; Aleksey N. Pershin; Irina R. Subbotina