abstracts - Институт катализа им. Г.К. Борескова

OP-III-11which corresponds to ΔS° about -12 J/mol*K. Using this value, from the position of theinterception point with vertical axis ( -0.75 [3]) we find ε HF /ε LF = 0.45. Our measurementsgive for NaY the ε HF value of 2.1 . 10 6 cm/mol, then for LF band we find ε LF =4.7 . 10 6 cm/mol,well above the εCO value for free molecules of gas (2.6 . 10 6 cm/mol).These values, together with other ourexperimental results for integral absorptioncoefficient of adsorbed CO are plotted in the figureagainst the electrostatic field of surface sites,obtained from the frequency shifts of COmolecules on adsorption, considered as a result ofthe vibrational Stark effect. Two curves show atheoretical dependence of εCO and CO stretchingfrequency in the axial electric field [1].In a fair agreement with the theoretical predictions, these results demonstrate the decreaseof εCO values for C-bonded molecules adsorbed on Lewis acid sites and its increase formolecules attached to the cations via oxygen atom.Thus, variable temperature spectroscopy of adsorbed species combined with pressuremeasurements provides data for enthalpy and entropy of adsorption and reorientation energyfor bistable complexes of CO with the cations. Low entropy values for the bands of CO“physisorbed” on CsX zeolite and silica testify for the rotational mobility of molecules inside-on complexes with surface oxygen. Analysis of experimental data shows that the integralabsorption coefficient of adsorbed CO decreases for molecules C-bonded to the cations andincreases for O-bonded species, in agreement with the electrostatic model.Literature1 Storozhev P.Yu., Yanko V.S., Tsyganenko A.A. et al. Appl. Surface Sci., 238 (2004) 390.2 Soltanov R.I., Paukshtis E.A., Yurchenko E.N. Kinet. and Catalysis, 23 (1982) 164.3 Tsyganenko A.A., Escalona Platero E., Otero Arean C., et al. Catal. Lett., 61 (1999) 187.334