Structure adsorptivity

TTigh silica zeolites attract great attention since they are characterized by relatively high thermal stability and considerable acid resistance. Physicochemical properties of high silica zeolites, despite a number of investigations, have not been sufficiently studied. The same is true for L- and clinoptilolite zeolite. The data on synthesis, structure, adsorption properties, decationization, dealuminization, adsorption heats, and other properties of the above-mentioned zeolites have been given (1-15). Results of studies of physicochemical properties of L zeolites and of natural and modified clinoptilolite are given here. 

Following this line, Zheligovskaya et al. [55] compared the adsorption properties of copolymers with special adsorption-tuned primary structures (adsorption-tuned copolymers, ATCs) with those of truly random copoly-... 

SYNTHESIS AND STRUCTURAL/ADSORPTION CHARACTERISTICS OF UNMODIFIED AND MODIFIED HYBRID CARBON/MINERAL ADSORBENTS... 

Potential modulation causes alterations in the electrode surface that, measured as a function of incident light frequency, permits conclusions to be taken in relation to electronic structure, adsorption, film formation, etc. The type of curve obtained is shown in Fig. 12.3. 

The observations illustrate that inelastic and thermally activated tunnel channels may apply to metalloproteins and large transition metal complexes. The channels hold perspectives for mapping protein structure, adsorption and electronic function at metallic surfaces. One observation regarding the latter is, for example that the two electrode potentials can be varied in parallel, relative to a common reference electrode potential, at fixed bias potential. This is equivalent to taking the local redox level up or down relative to the Fermi levels (Fig. 5.6a). If both electrode potentials are shifted negatively, and the redox level is empty (oxidized), then the current at first rises. It reaches a maximum, convoluted with the bias potential between the two Fermi levels, and then drops as further potential variation takes the redox level below the Fermi level of the positively biased electrode. The relation between such current-voltage patterns and other three-level processes, such as molecular resonance Raman scattering [76], has been discussed [38]. 

Model 3. Polarized adsorbent-hard sphere adsorbate ( structural adsorption ). ... 

The important advances in adsorption technology made possible by the BET theory (S, 4) clearly justify Model 1 in many applications. But one of the Models 2, 3, or 4 is apparently required for first-layer adsorption in a Type II isotherm. That an important condensation potential at the solid-gas interface is the Lennard-Jones 3-9 potential now seems well established (3, 7, 9, 10, 15). Equally clear is the fact that this potential is not solely responsible for physical adsorption the type of surface polarization predicted by the theory of structural adsorption (10) has been demonstrated by observed changes due to adsorption in linear... 

Following the detailed balancing methods of Brunauer, Emmett, and Teller (BET) (3, 4), the equations for adsorption of gaseous adsorbates on solid adsorbents may be presented in a sufficiently general form to take into account van der Waals, structural adsorption, and other adsorption potentials (7, 9, 10) as follows ... 

The evidence for structural adsorption (or surface polarization in first-layer physical adsorption) (5, 12, 18, 26) may be augmented by various considerations... 

In accord with predictions of Trapnell(24), there were shown to be really two types of surface sites in the adsorption of C02 on thoria, both of which exhibited the linear variation of adsorption potential with coverage. Thus, plots of AF (0) [= pC02 (1 — 0)/0] against 0 gave two series of straight lines in which for temperatures above 150°C. one type of site only was active but below 150°C. both were active. The observed adsorption constants are shown in Table II. Both the b values and the AF0 s varied nearly linearly with 0. This perhaps reflects the influence of temperature on the magnitude of structural adsorption in which increased temperature appears to diminish surface strain as anticipated by the theory of structural adsorption. 

While Cook and Oblad showed that structural adsorption causes AF for activated adsorption to increase linearly with 0 and thereby accounts for the equation for the rate of activated adsorption (Equation 9), Pitt and Wadsworth demonstrated that desorption of C02 from thoria followed the equation of Becker (2) for desorption—namely,... 

Pack, D. H., Theory of Physical and Structural Adsorption, Ph.D. thesis, University of Utah, 1950. 

One of the most intriguing aspects of surface diffusion is the strong dependence of the diffusivity on sorbate concentration. The dependence of surface diffusivities on pressure, temperature and composition is much more complicated than those of the molecular and Knudsen diffusivities, because of all the complexities of porous medium geometry, surface structure, adsorption equilibrium, mobility of adsorbed molecules, etc. 

Interfacial Aspects of Phase Transformations, Nato Advanced Studies, Institute Series. Series C, Vol. 87 (1982), B. Mutaftchiev, Ed., D. Reidel Publ. Cy. (Dordrecht, the Netherlands). (Surface structure, adsorption and heterogeneous nucleation.)... 

Sample Proportion Na Al P Sn Si T Template Crystallization temp. Structure Adsorption... 

The preparation, atomic and electronic structure, adsorption and reaction properties of metal nanoparticles supported on AljOj/NiAlCllO) were thoroughly explored by Freund and coworkers [11, 43, 52], Most studies were carried out under UHV, including CO dissociation on Rh nanoparticles [39], alkene hydrogenation [53], and CO and methanol oxidation [52],... 

Rollman recently described some interesting work on coke formation in several zeolites, which suggests that coking and aging rates are intrinsic properties of the zeolite pore structure. Adsorption measurements and the catalytic conversion of five hydrocarbons were used to compare zeolite performance. 

Adsorption is a physical process in which a substance, in this case a gas, is attracted to and held on the surface of another material. Neither material is changed in the process, and it can be easily separated again under the right conditions. In the VS A cycle, adsorption takes place on both the outer and inner surfaces of each structure. Adsorption is a temperature- and pressure-sensitive phenomenon. Both of these variables must be kept in an ideal range for ef cient oxygen production to occur. 

The structures of typical aluminophosphates, namely A1P04-11[6] and VPl-5[7] were generated from the reported crystal structures, adsorption of probe molecules such as water and ammonia, as well as the template organic molecules and larger molecules were... 

Wendland, M., Heinbuch, U., and Fischer,. (1989). Adsorption of simple gas mixtures on a plane waU Born-Green-Yvon for structure, adsorption isotherms and selectivity. Fluid Phase Equii, 48, 259-77. 

---