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Adsorbents zeolitic

To run adsorption storage systems efficiently the appropriate adsorbent has to be used. The right choice is possible on the basis of the measured adsorption equilibrium. The adsorption equilibrium of water vapor and different adsorbents (zeolites and silica gels) was experimentally found [3,4], The differential heat of adsorption (AHd) was calculated from the equilibrium data. [Pg.400]

Concerning the application of these adsorbents as thermal energy storages the amount of water, which can be adsorbed is the most important property. Figure 238 shows the maximum water uptake of some commercially available adsorbents. Zeolite A can reach 25% and Zeolite 13X up to 32% of its dry weight. Narrow pore Silicagel can adsorb 38% water. Two special adsorbents Sizeo, which is a mixture of Zeolite and Silicagel, and SWS, which is a wide... [Pg.401]

The rate of adsorption from dilute aqueous solutions by solid adsorbents (zeolites) is a highly significant factor for applications of this process for water quality control. [Pg.21]

Surface alkoxy species Chemical shift (ppm) Adsorbate Zeolite References... [Pg.173]

At the time of their inception, cluster calculations of adsorbate-zeolite systems were largely treated by using a semiempirical method. In the mid-... [Pg.85]

Qynthetic and natural zeolites are becoming increasingly important as catalysts, carriers of catalysts, and adsorbents. Zeolites are especially suited to these purposes because their properties can be modified by cation exchange. The literature describes several studies which show characteristic changes in physicochemical properties resulting from cation exchange— e.g., catalytic activity (1,2), acidic properties (3), adsorption behavior (4), structure of solid (5,6), and thermal stability (7,8). [Pg.251]

To achieve a significant adsorptive capacity an adsorbent must have a high specific area, which implies a highly porous structure with very small micropores. Such microporous solids can be produced in several different ways. Adsorbents such as silica gel and activated alumina are made by precipitation of colloidal particles, followed by dehydration. Carbon adsorbents are prepared by controlled burn-out of carbonaceous materials such as coal, lignite, and coconut shells. The crystalline adsorbents (zeolite and zeolite analogues are different in that the dimensions of the micropores are determined by the crystal structure and there is therefore virtually no distribution of micropore size. Although structurally very different from the crystalline adsorbents, carbon molecular sieves also have a very narrow distribution of pore size. The adsorptive properties depend on the pore size and the pore size distribution as well as on the nature of the solid surface. [Pg.36]

MOF-177 has been demonstrated to act like a super sponge in capturing vast quantities of carbon dioxide at room temperature. At moderate pressure (about 35 bar), its voluminous pores result in a gravimetric CO2 uptake capacity of 33.5 mmol/g, which far exceeds those of the benchmark adsorbents zeolite 13X (7.4 mmol/g at 32 bar) and activated carbon MAXSORB (25 mmol/g at 35 bar). In terms of volume capacity, a container filled with MOF-177 can hold about twice the amount of CO2 versus the benchmark materials, and 9 times the amount of CO2 stored in an empty container under the same conditions of temperature and pressure. [Pg.802]

The transport and adsorption properties of hydrocarbons on microporous zeolites have been of practical interest due to the important properties of zeolites as shape-selective adsorbents and catalysts. The system of benzene adsorbed on synthetic faujasite-type zeolites has been thoroughly studied because benzene is an ideal probe molecule and the related role of aromatics in zeolitic catalysts for alkylation and cracking reactions. For instance, its mobility and thermodynamic properties have been studied by conventional diffusion 1-6) and adsorption 7-9) techniques. Moreover, the adsorbate-zeolite interactions and related motion and location of the adsorbate molecules within the zeolite cavities have been investigated by theoretical calculations 10-15) and by various spectroscopic methods such as UV (16, 17), IR 17-23), neutron 24-27), Raman 28), and NMR 29-39). [Pg.273]

The strength of adsorption of unsaturated hydrocarbons by a polar adsorbent (zeolite) is much greater than for saturated hydrocarbons, and increases with increasing carbon number (Fig. 3) (5). This observation maybe understood as a consequence of the increasing polarizability of molecules with increasing numbers of bonds and the presence of dipole and stronger quadrupole moments in the unsaturated hydrocarbons compared to the saturated hydrocarbons. [Pg.271]

The examples cited in this review show that all stages of the development of the molecular theory of adsorption mentioned above have been studied to a limited extent for the adsorbate-zeolite system. The examples also show, however, that in order to determine experimentally the stable constants and to establish their dependence on the details of the zeolite structure and the structure of the adsorbate molecule, more systematic investigations will be needed. [Pg.54]

A. V. Kiselev Zeolites are porous crystals. This means that we can find the molecular field distribution in their channels. The advantage of describing the adsorption on zeolites using the molecular theory consists in obtaining the constants which have a definite physical meaning (for example, the Henry constant and second virial coefficient). Further development of the theory needs a further improvement of the model based on the investigation of the adsorbate-zeolite systems by the use of modern physical methods. [Pg.68]

Zeolites. The weak Raman signals arising from the aluminosilicate zeolite framework allow for the detection of vibrational bands of adsorbates, especially below 1200 cm which are not readily accessible to infrared absorption techniques. Raman spectroscopy is an extremely effective characterization method when two or more colored species coexist on the surface, since the spectrum of one of the species may be enhanced selectively by a careful choice of the exciting line. A wide range of adsorbate/zeolite systems have been examined by Raman spectroscopy and include SO2, NO2, acety-lene/polyacetylene, dimethylacetylene, benzene, pyridine, pyrazine, cyclopropane, and halogens. Extensive discussions of these absorbate/zeolite studies are found in a review article by Bartlett and Cooney. ... [Pg.146]

The basic concept of a H2 PSA process is relatively simple. The impurities from the H2-containing feed gas mixture are selectively adsorbed on a micro- and meso-porous solid adsorbent (zeolites, activated carbons, silica and alumina gels) at a relatively high pressure by contacting the feed gas with the solid in a packed column of... [Pg.414]

The elementary rate constant for proton activation is weakly dependent on the micropore size as long as steric constraints do not affect the transition state. Because of the zwitterionic nature of the transition state, dielectric screening by the oxygen atoms of the micropore tends to decrease the cluster-calculated transition state energies to 10 to 30% of the activation energies. Steric constraints on the transition state may substantially increase the cluster-computed activation energies by similar amounts. These steric constraints can be computed from periodical DFT calculations or from transition-state model structures using Monte Carlo adsorbate-zeolite pore interaction calculations. [Pg.430]

The hydrophobic nature of the activated carbons is best suited for the solvent vapor recovery applications because most industrial waste gas streams containing organic solvents are saturated with water vapor. Activated carbons can retain a large fraction of their dry adsorption capacities for organic compounds in presence of high humidity. Table 22.3 shows a few examples of this behawor [22]. Most polar adsorbents (zeolites, alumina, and silica gels) will not be effective for this appHcation. [Pg.572]

Zeolite shells on polystyrene beads were prepared by a combination of layer-by-layer (LbL) and hydrothermal synthesis techniques. The negatively charged polystyrene beads were surface modified in order to adsorb zeolite Beta nanocrystals. Such particles were then adsorbed on the surface of the beads and induced to grow into a continuous film of intergrown crystals of zeolite Beta. The effect of the preliminary treatment on the formation of the zeolite film was studied. Finally the polystyrene beads used as macro-templates were removed by calcination in air, yielding hollow spheres of zeolite Beta. The zeolite Beta/polystyrene composites and the corresponding hollow zeolite spheres were characterized by XRD, SEM, TG/DTA and BET surface area measurements. [Pg.298]

The advantages of IR and Raman spectroscopy and INS lie in the fact that they provide information about microporous materials on a molecular level. However, the utilization of vibrational spectroscopic techniques necessitates the reliable assignment of vibrational transitions to particular forms of normal modes in relation to a given structure. Already in the case of medium-sized molecules studied purely on an empirical basis, this leads to unbridgeable difficulties. Force field and quantum mechanical methods can significantly contribute to obtain this information about the dynamic behavior and allow a more sophisticated interpretation of the experimental data. Thus, besides the development achieved over the last years in the field of experimental techniques, substantial progress in describing vibrational spectra of zeolites and adsorbate/zeolite systems on a theoretical basis has been made. [Pg.12]


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Acidity zeolitic adsorbents

Adsorbates in zeolites

Adsorbents aluminum-rich zeolites

Adsorbents molecular sieve zeolites

Adsorbents zeolite adsorbent

Adsorbents zeolite-based

Adsorbents, zeolite

Applications of zeolite adsorbents

Benzene, adsorbed on zeolites

Cluster model adsorbate-zeolite systems

Composite zeolite adsorbent

Finishing Post-Forming Manufacturing of Zeolite Catalysts and Adsorbents

Industrial adsorbents zeolites

NH3 Adsorbed on All-Silica MFI Zeolites (Silicalite)

Of molecules adsorbed on zeolites

Zeolite 13C-labelled adsorbates

Zeolite adsorbate acetone

Zeolite adsorbate aniline

Zeolite adsorbate aromatics

Zeolite adsorbate nitriles

Zeolite adsorbate olefins

Zeolite adsorbate phenol

Zeolite adsorbate/framework interaction

Zeolite, adsorbed molecules

Zeolite/adsorbate systems

Zeolite/adsorbate systems organic compounds

Zeolites interactions with adsorbed species

Zeolites normal paraffin separation adsorbents

Zeolites, as adsorbents

Zeolitic adsorbents, post-forming

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