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Mesoporous S,N-TiO(2) nanocomposite was prepared by a one-pot template free homogeneous coprecipitation technique using titanium oxysulfate sulfuric acid complex hydrate, thiourea, ethanol, and water. Nano gold deposition on mesoporous S,N-TiO(2) was preformed by a borohydrate reduction method. To evaluate the structural and electronic properties, these catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), UV-vis DRS, photoluminescent (PL) spectra, Fourier transform infrared (FTIR), and TPO/TPD. CO adsorption and CO + O(2) interaction over these catalysts were investigated by in situ FTIR. Sulfur and nitrogen doping enhances the catalytic activity of Au/TiO(2.) Higher catalytic activity of Au/S,N-TiO(2) compared to Au/TiO(2) was attributed to the presence of oxygen vacancy and creation of new adsorption sites at Au/TiO(2) interfaces for the adsorption and activation of O(2) molecules.

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Occlusion of benzene in NaZSM-5 zeolite is investigated using in situ FTIR spectroscopy as a function of substitution of Na+ with group IIA cations. At least four pairs of overlapping vibrational bands were observed in the region of out-of-plane C−H bending vibrations (2000−1800 cm-1) on adsorption of benzene in NaZSM-5 at room temperature. Whereas two pairs of these bands, e.g., one pair at around 2007 and 1986 cm-1 and the other at 1969 and 1956 cm-1, correspond to the 1960 cm-1 band of liquid benzene, the other two pairs, e.g., at 1874 and 1852 cm-1 and 1831 and 1810 cm-1, appear in place of the 1815 cm-1 band of liquid benzene in this region. No measurable difference was observed in the frequencies of these bands for adsorption in cation-exchanged samples, suggesting that any specific interaction between cations and benzene molecules is small compared to the effect of benzene−benzene interaction. These multiple bands are therefore attributed to the existence of at least two distinct clustered states of benzene, localized at intersections and in the straight channels of NaZSM-5, respectively. While the frequency of these bands remained unchanged, the intensity of the lower frequency side pair (i.e., 1969, 1956 cm-1 and 1831 and 1810 cm-1) was found to be very sensitive to the nature of the charge-balancing cation and followed a trend NaZSM5 < CaZSM5 > SrZSM5 > BaZSM5, similar to that followed by the pore volume of exchanged samples. These two pairs of bands are therefore identified with the benzene clusters encapsulated in straight zeolitic channels where most of the balancing cations are located. Dose-dependent measurements have shown that such benzene clusters may form at loading as low as ∼1.6 molecules/uc; when a larger fraction is located at intersection sites and at the same time a small fraction also exists in the straight or sinusoidal channels. The concentration in the later locations grows with the increasing benzene loading. Considering these results and in view of the fact that no frequency shift or band splitting was observed in the in-plane C−H/C−C and fundamental ν19 stretching vibrations of adsorbed benzene, we infer that the benzene molecules are packed side by side with their planes parallel to the zeolite channel, the intermolecular interaction occurring through π-electron cloud.

Adsorption of CO at ambient temperature on NaX zeolite produces four distinct infrared absorption bands at around 2207, 2192, 2178 and 2165 cm-'. The relative intensities of these bands depend on sample crystallinity and vary considerably when sodium is exchanged with other Group 1 or Group 2 cations. These bands are ascribed to weakly held (CO), molecular clusters trapped in supercages and stabilized under cation fields. In addition, two pairs of bands are also observed in the 1200-1800 cm-' region, the frequencies and the relative intensities of which depend on the cation, CO exposure temperature and the sample crystallinity. These bands are stable under ambient-temperature evacuation and show a uniform isotopic shift corresponding to a frequency ratio V ( ' ~C / ' ~C ) of ca. 0.973 on using 13C0 as adsorbate. The possible origins of these bands are discussed in detail.The catalytic properties of synthetic zeolites are closely related to their capacity to adsorb a variety of molecular species into structural cages and in the inter-connecting channels. The adsorption characteristics are in turn influenced by framework composition and the nature of charge-balancing cations.'-4 A number of studies have been devoted, particularly using probe molecules such as CO, CO,, CH, and C6H6, to understand the mode of adsorption in zeolitic cages.'-' ' In the previous thermal desorption spectroscopy studies on X-type zeolites, we have demonstrated the existence of multiple C O binding states which were found to be modified by charge balancing cation^.'^"^ C O at some of these sites was found to convert to CO, during adsorption as well as on subsequent heat treatment. The Fourier-transform infrared (FTIR) spectroscopy studies reported here were undertaken to investigate further the identity of various CO adsorption modes on cationexchanged X-zeolites and to identify the multiple sites if possible. The effect of temperature on the species formed in the C O interaction was investigated in detail for this purpose. Parallel studies were also performed on NaY zeolite, alumina and silica for comparative evaluation. 3C isotope substitution experiments were also carried out to examine the isotopic shifts. The results of these studies are presented and discussed below. ExperimentalThe high-temperature, high-pressure stainless steel cell used in these transmission mode IR studies has been described earlier." The cell having a pathlength of ca. 6 cm was fitted with water-cooled CaF, windows. It had a provision for in situ evacuation (10-3-10-4 Torrt) and for pretreatment of the sample under inert or reactive gas media at temperatures in the range 300-625 K.The zeolite-X sample, NaX (Si : A1 = 1.25, from Union Carbide, USA), was washed repeatedly with hot water and then dried under vacuum for several hours before use. The representative samples of cation-exchanged zeolites were prepared by substituting H', K', Li+, Mg2+ and Ca2' for sodium, using conventional ion-exchange procedures as reported earlier.17 HX, LiX, KX, MgX and CaX were ex...

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