Krypton sorption

Krypton Sorption. Volumetric adsorption using gases with low saturated vapor pressure has been found to be an effective technique to gain detailed structural information for small quantities of porous materials, especially using krypton (Kr).27 The substitution of nitrogen by Kr reduces significantly the amount of unadsorbed molecules in the dead volume, allows for the characterization of small surface areas, and is thus ideal for mesoporous... 

Figure 5 shows data for catalytic activity, CO adsorption at 23°, surface area by the B.E.T. method using krypton at —196°, and the fast hydrogen adsorption at —196° plotted against the temperature at which the various films were sintered. All quantities were taken as unity for films sintered at 23°C. These experiments clearly indicate that the previously observed slow adsorption of hydrogen on nickel catalysts is not adsorption but is sorption consisting of adsorption and... 

The virial isotherm equation, which can represent experimental isotherm contours well, gives Henry s law at low pressures and provides a basis for obtaining the fundamental constants of sorption equilibria. A further step is to employ statistical and quantum mechanical procedures to calculate equilibrium constants and standard energies and entropies for comparison with those measured. In this direction moderate success has already been achieved in other systems, such as the gas hydrates 25, 26) and several gas-zeolite systems 14, 17, 18, 27). In the present work AS6 for krypton has been interpreted in terms of statistical thermodynamic models. 

In this paper we report experimental and theoretical results on the sorption of methane and krypton on 5A zeolite. The sorption of methane in the 5A cavity is reported to be non-localized (9.), whereas that of krypton is localized at a cavity site and window site (10). The multicomponent form of the isotherm of Schirmer et al. is used to interpret the experimental data and to predict mixture equilibria at other concentrations. 

The system methane-krypton 5A was selected for study because previous pure component studies for each of these sorbates on Linde 5A zeolite indicate that the sorption mechanisms are significantly different. 

Pure component experimental data for sorption of methane and krypton on 5A zeolite at 238, 255. and 271K, and in the pressure range of 0 to 97.36 kPa were also obtained during this work (shown in Figures 3 and U). Further sorption data for methane on 5A zeolite (10, 13, 1 0, and for krypton on 5A zeolite (10. 15) are also plotted for other temperatures, all of which appear to be consistent. These experimental data were used to derive the energy and entropy parameters in equation U for the isotherm model of Schirmer et al. by a minimization of a sum of squares optimization procedure. 

The resulting optimized parameters and for sorption of methane and krypton on 5A zeolite are shown in Figure 5 and are presented in Table 1. The calculated energy parameters -22000 Joules/mole for methane and - 16,725-0 Joules/mole for krypton were independent of the amount adsorbed and agree with... 

As the two sorbates methane and krypton on 5A appeared to have different mechanistic behaviour, further theoretical study appeared warranted. Two hypothetical gases P and Q whose properties are tabulated in Table 1 were used for comparison with the behaviour of methane and krypton. Hypothetical gas P was designed to have a Henry constant equal to methane, but to be a localized sorbate having entropy of sorption values decreasing incrementally as for krypton. Conversely, hypothetical gas Q had a Henry constant equal to that of krypton, but entropy of sorption values non-localized and decreasing incrementally as for methane. 

Wacker J. F. (1989) Laboratory simulation of meteoritic noble gases III. Sorption of neon, argon, krypton, and xenon on carbon elemental fractionation. Geochim. Cosmochim. Acta 53, 1421-1433. 

Here we present the first systematic study on the pore size- and temperature dependence of the sorption- and phase behavior of argon, krypton and nitrogen in the well defined, three-dimensional pore network of pristine mesoporous MCM-48 silica and MCM-48 silica/iron(III) oxide host-guest compounds. 

Results of systematic sorption studies of Nitrogen, Argon and Krypton at 77 K and 87 K on different pristine MCM-48 silica materials... 

The results for nitrogen, argon and krypton adsorption on pristine MCM-48 materials can be summarized as follows (i) Argon sorption isotherms at 87 K (T/Tc = 0.58, where Tc is the critical temperature of the bulk fluid) reveal for all MCM-48 silica phases used in this study pore condensation but no hysteresis at relative pressures p/po < 0.4. With increasing pore size... 

A systematic study of the sorption and pore condensation behavior of nitrogen, argon and krypton in various silica materials (MCM-48, MCM-41 and Controlled Pore Glass (CPG)) at 87 and 77 K is presented. A detailed characterization with respect to surface area, pore volume and pore size distribution together with a comparison of sorption hysteresis in MCM-48 and MCM-41 silica materials of nearly equal pore size has been performed. In addition we focus on the sorption and phase behavior of argon and krypton below the bulk triple-point temperature. 

Table 7. Permeability, diffusion and sorption coefficients for krypton and xenon in...

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