for hydrogen molecules to enter (diffuse) into the cavities so that the lower the temperature, the longer the time to attain the pressure equilibrium between the inside and outside of the cavity. Since all the temperature-dependent experimental data were obtained by taking 15 min of encapsulation time? we cannot exclude the possibility of incomplete hydrogen encapsulations at the low temperatures. According to the time-dependent hydrogen encapsulation study in Cs2,,-zeolite A done by Heo et the time required for the pressure equilibrium at the low temperatures is at least 180 min. However, at higher temperatures, the hydrogen encapsulation, which decreases with increasing temperature, can be found both in theory and in experiment. However, if we assume that our formalism is correct, the hydrogen encapsulation would increase exponentially with decreasing temperature (see Figure 4).One additional remark here is that in both pressure-and temperature-dependent studies, the theoretically calculated values always underestimated the experimental data (except for the first four low-temperaturedependent data). We believe that this may be due largely to the neglect of attractive interactions between guest hydrogen and the host Cs2,5-zeolite A molecules in our theoretical model. Nevertheless, we have been able to successfully functionalize the hydrogen encapsulation process without including any interaction between the host and the guest molecules at least with respect to pressure. This suggests that the major physical process responsible for the hydrogen encapsulation at high temperatures seems to be the molecular diffusion.We feel that experiments covering wider ranges of pressures and temperatures are needed to gain a more detailed understanding of this phenomenon. Such experiments are in preparation.The infrared spectra of the hydroxyl region and that of surface chemisorbed C02 species for Re207/A1203, Cr03/A1203, M&3/,4@,V20s/A1203, Ti02/A1203, and Nb05/A1203 catalytic systems have been investigated. A sequential consumption of the alumina OH groups upon deposition of the supported metal oxide has been found for all the investigated catalytic systems. A possible relationship between Bronsted acidity and a new low-frequency band in the hydroxyl region observed at high loadings of the supported metal oxide systems is postulated. The various chemisorbed C02 surface species formed on the uncovered parts of the exposed surface of alumina are identified. Furthermore, the applicability of the infrared C02 chemisorption technique as a general method to determine the monolayer coverage for alumina-supported metal oxides has been confirmed because CO2 adsorption is suppressed as monolayer coverage is approached. Infrared pyridine chemisorption data for selected alumina-supported metal oxide catalysts are quantified, and a simple model for the Bransted acid site is proposed. Comparison with the molecular structures of the surface metal oxide overlayer, determined by Raman spectroscopy, reveals that there is no correlation betwe...

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