Interaction of CO with K-FER zeolite was investigated by a combination of variable-temperature IR spectroscopy and computational study. Calculations were performed using omega(CO)/r(CO) correlation method in combination with a periodic density functional theory model. On the basis of agreement between experimental and calculated results, the following carbonyl complexes were identified: (i) mono- and dicarbonyl C-down complexes on single K(+) sites characterized by IR absorption bands at 2163 and 2161 cm(-1), respectively; (ii) complexes formed by CO bridging two K(+) ions separated by about 7-8 A (dual sites) characterized by a band at 2148 cm(-1); and (iii) isocarbonyl (O-down) complexes characterized by a band at 2116 cm(-1). The bridged carbonyl complexes on dual K(+) sites are about 5 kJ/mol more stable than monodentate (monocarbonyl) CO complexes. The C-O stretching frequency of monocarbonyl species in K-FER depends on K(+) location in the zeolite, and not on K(+) coordination to the framework. A combination of theoretical calculations using a periodic density functional model and experimental results showed formation of two types of monocarbonyls. The most abundant type appears at 2163 cm(-1), and the less abundant one at 2172 cm(-1). These experimentally determined wavenumber values coincide, within +/-2 cm(-1), with those derived from theoretical calculations.

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A combination of variable-temperature Fourier transform infrared (FTIR) spectroscopy with calculations performed at the periodic density functional theory (DFT) level was used in the investigation of carbon monoxide adsorption on zeolites Na-ZSM-5 and K-ZSM-5. On the basis of a very good agreement between experimental and calculated frequencies and adsorption enthalpies, it is shown that the IR absorption band appearing in the intermediate frequency range for adsorbed CO (2155 and 2150 cm-1 for Na-ZSM-5 and K-ZSM-5, respectively) is due to the formation of linearly bridged CO adsorption complexes on dual-cation sites (M+···CO···M+, M = Na, K). The population of such adsorption complexes increases with increasing cation radius and with decreasing Si/Al ratio. Bridged adsorption complexes are slightly more stable than carbonyl complexes formed on isolated extraframework metal cations. Adsorption enthalpies and CO stretching frequencies of carbonyl complexes formed on isolated extraframework metal cations were found to depend on the metal cation coordination with the zeolite framework. This dependence is particularly apparent for Na-ZSM-5, where cations located on the intersection sites are coordinated to only two framework oxygen atoms and CO adsorption on these sites is up to 8 kJ/mol more stable than adsorption on the channel wall sites; CO stretching frequencies of carbonyls formed on intersection sites are up to 7 cm-1 higher than frequencies of carbonyls formed on channel wall sites.

Basic mixed oxides MgAl, ZnMgAl, and ZnAl were successfully prepared from hydrotalcite precursors synthesized by urea method. Materials with the same molar ratio (M2+/Al3+) = 2 were studied to describe the influence of Mg/Zn ratio on their physicochemical properties. Materials were tested as catalysts of the aldol condensation of furfural with acetone. For samples with similar particle sizes and surface BET areas, the varying catalytic activity was related to the different acidobasic properties. Higher furfural conversion and selectivity to longer carbon chain F2Ac product was observed for samples with higher total amount of basic sites. More specifically, it correlated with the population of Me2+–O2– pairs that represented dominant type of basic sites in all studied catalysts. At the same Al loading, Mg2Al mixed oxide exhibited higher specific surface area, higher total amount of basic sites and higher amount of acid sites than Zn2Al oxide.

Adsorption of CO 2 on alkali-metal exchanged (Li ? , Na ? , K ? ) FER zeolites was investigated by means of microcalorimetry and FTIR spectroscopy. The adsorption enthalpies strongly depend on coverage for all investigated materials and they are also influenced by concentration of Al in the framework. Especially, samples of Na-and K-FER with lower Si/Al ratio (8.6) exhibited substantially larger initial interaction energy than samples with Si/Al 27.5. Differences in zero-coverage adsorption energy of zeolites with different cation concentration (Si/Al ratio) are 9 and 7.2 kJ/mol for Na-and K-FER zeolites respectively. This phenomenon is attributed to formation of bridged CO 2 adsorption complexes formed between two cations, which are characterized by IR absorption band of m 3 stretching vibration mode at 2370 and 2357 cm -1 for Na-and K-FER respectively.

The interaction of CO with extraframework Li+ ions coordinated in ZSM-5 and FER zeolites with different compositions is investigated by FTIR spectroscopy, and the correlation between Li+ coordination, stability of CO adsorption complexes, and νCO frequencies is discussed in terms of the theoretical investigation of the stability and vibrational dynamics of CO adsorption complexes. Differences in IR spectra of adsorbed CO due to the following effects were considered:  (i) various Si/Al ratios, (ii) differences in zeolite topology, (iii) temperature, and (iv) the effect of a co-cation on relative stability and metal cation site preferences. The correlation between Li+ coordination and νCO frequencies of CO adsorption complexes discussed for Li zeolites is extrapolated to mesoporous Li−(Al)MCM-41 materials. The features in the IR spectra of CO/Li−(Al)MCM-41 are assigned to CO adsorption complexes formed on top of five- and six-membered rings on the surface of a channel wall. The spectra of CO/Li−ZSM-5 with different Si/Al ratios and various ion exchange levels bring evidence on the nonstatistical distribution of aluminum in the framework and on the preference of Li+ ions for channel-wall sites.

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