H2O adsorption

Temperature programmed reaction spectra depicting the reaction of H2O and OH groups with oxygen on Pd(lOO) are shown in fig. 3. Curve (a) was obtained for H2O adsorption on the clean surface and contains two peaks, the state at 167 K of multilayer H2O, and the <>2 state at 182 K due to H2O bound directly to the surface /7/. An additional state at 255 K, labelled y, is observed following coadsorption of 1 0 and 0 (fig. 3b). This state represents the reaction of OH groups III... 

Figures 6a-c report the effect of H2O adsorption on Ti(IV) sites on the Raman features of TS-1 using three different excitation sources. As far as the asymmetric modes of the [Ti(OSi)4] units are concerned, we observed a blue shift of the 960 cm band whichever laser was used in the experiment [48,52,64]. More interesting are the consequences that water adsorption has on the to-...

TABLE 4.1 Metal-Dependent Vapor Phase Binding Energy for H2O Adsorption to Gronp VIII and IB... 

For the same reason, Ru(OOOl) modihcation by Pt monolayer islands results in a pronounced promotion of the CO oxidation reaction at potentials above 0.55 V, which on unmodified Ru(OOOl) electrodes proceeds only with very low reaction rates. The onset potential for the CO oxidation reaction, however, is not measurably affected by the presence of the Pt islands, indicating that they do not modify the inherent reactivity of the O/OH adlayer on the Ru sites adjacent to the Pt islands. At potentials between the onset potential and a bending point in the j-E curves, COad oxidation proceeds mainly by dissociative H2O formation/ OHad formation at the interface between the Ru(OOOl) substrate and Pt islands, and subsequent reaction between OHad and COad- The Pt islands promote homo-lytic H2O dissociation, and thus accelerate the reaction. At potentials anodic of the bending point, where the current increases steeply, H2O adsorption/OHad formation and COad oxidation are proposed to proceed on the Pt monolayer islands. The lower onset potential for CO oxidation in the presence of second-layer Pt islands compared with monolayer island-modified Ru(OOOl) is assigned to the stronger bonding of a double-layer Pt film (more facile OHad formation). 

Fiaure5. Proposed structure for Br / H2O adsorption on Ag 110 which is compatible with LEED, and TDS measurements/12/. 

The H2O adsorption isotherms for AIPO1.-5, -11, -17, and -20 are shown in Figure 17. For comparison, the hydrophilic NaX and the hydrophobic silicalite are included. The isotherm shape for A1P0 -11 and A1P0 -17, like that of NaX and silicalite, is Type I, typical of micropore filling. The isotherm shape of the AlPOi.-20... 

Poschl, U., Letzel, T., et al. (2001) Interaction of ozone and water vapor with spark discharge soot aerosol particles coated with benzo[a]pyrene and H2O adsorption, benzo[a]pyrene degrada-... 

Table I. Micropore volumes deduced from N2, CO2 and H2O adsorption...

Figure 2 represents the H2O adsorption isotherms of the adsorbent-impregnated ceramic sheets. The aluminum silicate and titanium silicate-impregnated ceramic sheets showed better adsorption behavior than the pure silica-impregnated ceramic sheets, as like to the results for the dehumidification efficiencies obtained by the simple weight increment test. 

Fig. 2. H2O adsorption isotherms of silica, aluminum silicate and titanium silicate-impregnated ceramic sheets.

Figure 4. Characteristic curve of H2O adsorption on NaX temperature range from 293° to 523°K (A, cal/mole)...

Similar results have been obtained for H2O adsorption. No interaction between hydroxyls and small quantities of H2O occurs. By contrast when a H2O pressure is introduced the structure is destroyed. 

Further study showed that adsorption isotherms of BAC-n by using H20, hexane, and cyclohexane as plug gauge molecules were all of the I type. To illustrate these results, H2O adsorption isotherms of BAC-5, -3, and -10 compared with those of NaX, AIPO4-I7, and silicalite-1 are shown in Figure 4.2. 

The fiuorinated ACF was prepared by reaction between a gaseous fluorine of 101.3 kPa and ACF at 373 K after drying the ACF sample. The chemical composition of the fluori-nated ACF was C].4F by the weight change. The -plots of the N2 adsorption isotherm indicated that the micropores are preserved after fluorination. Fig. 7(A) shows the adsorption isotherms of H2O on the fiuorinated ACF and pristine ACF at 303 K. The ordinate is expressed by the amount of adsorption per unit pore volume. The H2O adsorption isotherm of ACF is of type V and has a marked hysteresis. This ACF, therefore, is hydro-... 

The H2O adsorption on superhigh surface area carbon was studied by the in situ X-ray diffraction technique [36]. The surface area, micropore volume, and pore width of superhigh surface area carbon were 2670 m /g, 0.97 ml/g, and 1.3 nm, respectively. The H2O adsorption isotherm determined at 303 K was of typical type V. The H2O molecules were not adsorbed below P/Po = 0.6 and then they were abundantly adsorbed above P/Pq = 0.6. Fig. 8 shows the X-ray diffraction patterns of adsorbed H2O as a function of... 

Thus, in situ X-ray diffraction examination shows explicitly that H2O adsorption in graphitic micropores is accompanied by formation of the ordered molecular assembly. The surface oxidation of activated carbon accelerates the cluster formation on the surface and thereby H2O adsorption isotherm has an uptake in the low relative pressure. 

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