Adsorption of N2 and

DRIFT spectroscopy was used to determine Av0h shifts, induced by adsorption of N2 and hexane for zeolite H-ZSM-5 (ZSM-a and ZSM-b, Si/Al=15.5 and 26), H-mordenite (Mor-a and Mor-b, Si/AI— 6.8 and 10) and H-Y (Y-a and Y-b, Si/Al=2.5 and 10.4) samples. Catalysts were activated in 02 flow at 773 K in situ in the DRIFTS cell and contacted than with N2 at pressures up to 9 bar at 298 K or with 6.1% hexane/He mixture at 553 K, i.e., under reaction conditions. Catalytic activities of the solids were measured in a flow-through microreactor and kapp was obtained as slope of -ln(l-X0) vs. W/F plots. The concentration of Bronsted acid sites was determined by measuring the NH4+ ion-exchange capacity of the zeolite. The site specific apparent rate constant, TOFBapp, was obtained as the ratio of kapp and the concentration of Bronsted acid sites. 

Figure 9.14. Differential enthalpies of adsorption of N2 and Ar at 77 K on carbons Cl and C4 (same as in Figure 9.12) and on Spheron 1500 (Femandez-Colinas etal., 1989a).

The /-method of isotherm analysis adopted by Cases et al. (1992) is not entirely satisfactory and therefore the interpretation of the results is not altogether straightforward. However, the high BET C value is consistent with the conclusion that there was a small micropore filling contribution. To arrive at a more realistic quantitative assessment of the microporosity it would be desirable to obtain nitrogen isotherm data on a truly non-porous form of Na-montmorillonite. In practice, however, this may be difficult to accomplish and a more pragmatic approach would be to construct a series of comparison plots for the adsorption of N2 (and preferably also Ar) on pairs of samples of differing particle sizes and defect structures. In this way it should be possible to establish quantitative differences in the micropore capacities. 

For characterization we used IR and ESR spectroscopy. ESR spectra were recorded on a JE0L-FE-3X type spectrometer in the X-band using Mn in MgO matrix for field calibration. For IR studies KBr pellet and self-supporting wafer techniques were utilized. Adsorption of N2 and solid-gas (O2, H2) interactionE were investigated in a high vacuum equipment supplemented with MS gas analysis. 

Adsorption of N2 and CO (cf. also Sect. 5.5.2.2) on Cu-ZSM-5 was IR-spectro-scopically studied by Broclawik et al. [614] in the context of the catalytic activity of the adsorbent in NOx decomposition. The authors found three bands in the respective spectra originating from CU+N2 and Cu+CO adsorption complexes differing in bonding energies. The high frequency bands at 2297 (CU+N2) and 2157 cm (Cu+CO) indicated the strongest Cu adsorption sites. 

The density functional theory was employed by Neimark et al. [44,86,87] to study the adsorption of N2 and Ar on MCM-41 mesoporous silica and V catalysts supported on MCM-41. In another group of papers, Neimark et al. employed the density functional theory to study N2 and Ar adsorption MCM-48 mesoporous silica [28,29]. Their main goal was to characterize the pore size distribution of those mesoporous solids. According to the density functional approach it possible to calculate the adsorption isotherm on an individual pore. If a cylindrical symmetry is assumed for the pore, the adsorption... 

The adsorption of N2 and O2 on ion exchanged type X zeolite was studied, independently, by McKee (1964) and Habgood (1964). In both studies, the sorbents were commercial type X zeolite with Si/Al 1.25, and the zeolite was ion-exchanged with both alkali and alkaline earth metal ions. Li+ was one of the ions included in both studies. These studies were performed at 1 atm pressure. The highest N2/O2 selectivities were obtained for Ba + > Sr + > Li+ > Ni + (McKee, 1964). 

Pure gas isotherms for adsorption of N2 and O2 on five commercial zeolites (NaX, 5A, Na- Mordenite, CaX and CaLSX) at two different temperatures are reported. The isotherms can be described by the Langmuir model in the range of the data. Mixed gas Langmuir model is used to evaluate the relative N2 adsorption and desorption characteristics for these zeolites in connection with air separation application by the pressure swing adsorption (PSA) concepts. 

Adsorption of N2 and O2 on zeolite Kostrolith SX6 with small amounts of water permanently presorbed at 313 K for pressures (p < 0.12 MPa) Adsorption ofC02 on zeolite Nal3X with presorbed water ... 

High pressure adsorption of N2 and CO2 on activated carbon NORIT R1 EXTRA in the temperature range 298 K - 343 K for pressures up to 50 MPa. 

In order to reveal the intrinsic relation between the surface properties and textures with the hump-type activity curve, the specific surface area of both the ammonia synthesis fused iron catalyst with different iron oxides as precursors and their active components were measured by the means of low temperature physical adsorption of N2 and selective chemisorptions of CO, CO2 as shown in Table 3.17. 

A necessary way to compare the adsorptions of N2 and CO2 is to use the characteristic curves (temperature invariant) which should be the same for each carbon if the same mechanisms of adsorption occur. Such characteristic curves are shown in Figure 4.18(a-c) for the carbons D-19, D-52 and D-80, these illustrating the phenomena involved. The affinity coefficient p is not considered in these curves because of the similarity of nitrogen (0.33) and of carbon dioxide (0.35). In order to have a wide range of (A is the adsorption potential as... 

For another example, the adsorption of N2 and Ar on the 25 C outgassed thoria are presented in Table 27. The advantages for these data are presented under the Standard Thoria Plots in Chapter 5, which are the stability and uniformity of this powder with this treatment, but in addition to these, the advantage is that the measurements could be performed in a very accurate and controlled gravimetric system and many data points were collected. There is still, however, the question of range selection. The fewer the data points selected for the BET and DP fit, the better the statistics should be. (After all, if one were to select two data points one would obtain a perfect fit.) A best... 

The sample which was washed two days had excess chloride ions so, it had a small surface area. This could be because the Cl ions impede the adsorption of N2 and the diffusion of the pillaring agent toward the interior of the sheets. 

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