Adsorbent support

Electrocatalyst see also specific catalysts adsorbate-support interactions, 30 273-279 adsorption, 30 240-264 isotherms, 30 241-243 bimetallic activity, 30 275... 

It was not until recently that Chen and Goodman probed the influence of the oxide support material on the intrinsic properties at the metal surface. By covering a titania support with one or two flat atomic layers of gold they eliminated, direct adsorbate-support interactions as well as particle size and shape effects. Their results definitively showed that the electronic properties at the metal surface changed due to charge transfer between the support and the metal. Furthermore, their comparison of one- and two-layer films highlighted the dependence of these effects on the thickness of the metal slab. 

PLOT Columns. Porous-layer open tubular columns wherein the internal wall is coated with a layer of adsorbent support. If the support is then coated with a liquid phase it is referred to as a SCOT Column (i.e., support-coated open tubular column). 

Marvillet, L., Tranchant, M. Analysis of permanent gases using a gas liquid precolumn having an adsorbent support. Method. Phys. Anal. 1965, 37. — Chem. Abstr. 

The -vk contribution to / in Eq. (26) from the desorbing water molecules can be roughly estimated by assuming that the potential varies linearly with the distance x in the compact layer enclosed between the electrode surface plane x = 0 and the outer Helmholtz plane x = d. In the presence of a strong excess of a nonspecifically adsorbed supporting electrolyte or upon correction for the potential difference across the diffuse layer, the electric potential in the bulk... 

In view of this need, we discuss here a variety of electrocatalytic topics, ranging from basic and microscopic concepts to phenomenological principles. Thus, the origin of electrodic reactions, electrosorption, and electrode kinetics are introduced briefly for the benefit of the nonelectrochemist. Since electrocatalytic reactions take place at the electrode surface, attention is given to recent efforts to link catalyst activity with microscopic surface properties. These include surface crystallographic orientation, crystallite size and distribution, adsorbate-adsorbent-support synergism, multiple adsorption states, identification of surface intermediates, and electrocatalytic surface reaction mechanisms. 

Conventional heterogeneous catalysis and empiricism could provide a starting point in the selection of electrocatalysts for new unexplored processes for chemical production, energy generation or conservation, and environmental control. However, a fundamental understanding of adsorption characteristics, electrode kinetics, mechanisms, adsorbate-support interactions, and deactivation processes are needed for improved electrocatalyst... 

Hybrid photocatalysts consisting of Ti02 and an adsorbent such as activated carbon were used in the photoinduced mineralization of bromoform and propy-zamide dissolved in water. In the first step, the target substrates were adsorbed onto the adsorbent support. Next, due to the presence of Ti02, they were photodestructed [64, 65]. 

Thin-layer chromatography (TLC) is a planar form of chromatography useful for wide-scale qualitative analysis screening and can also be used for quantitative analysis. The stationary phase is a thin layer of finely divided adsorbent supported on a glass or aluminum plate, or plastic strip. Any of the solids used in column liquid chromatography can be used, provided a suitable binder can be found for good adherence to the plate. 

Fig. 8. Expanded-bed feed arrangements. (A) Feed passes through adsorbent support, (B) Feed enters above adsorbent support screen.

Adsorption chromatographic separation can be carried out either in closed columns or open films the latter usually consists of a rectangular film of adsorbent supported on a glass plate. Chromatography on open films is referred to as thin-layer chromatography when the adsorbent particles adhere to each other and to the plate, and as loose-layer chromatography when the adsorbent particles are nonadherent. The combination... 

The adsorbent support makes a high concentration environment to target organic substances around the loaded Ti02 particles by adsorption. Therefore, the rate of photooxidation is enhanced. 

Since the adsorbed substances on the adsorbent supports are finally oxidized to give CO2, the high adsorbed ability of the hybrid photocatalysts for organic substances is maintained for a long time. The amount of Ti02 as catalyst may play a significant role upon the photo-efficiency of hybrid catalysts. 

The structured packing for column and ceramic monoliths has been in use for several decades. The latter is used in catalytic converters for automobile exhausts for the in-line conversion of CO and oxides of nitrogen into harmless oxides. It is also used for catalyst and adsorbent supports in process industries. They offer higher specific surface area and low pressure drop. A comprehensive review of monolith reactors as alternatives to trickle-bed, slurry, and slurry bubble column reactors is available in Roy et al. [65]. The monolith reactor... 

FI. An adsorbent gas drier has been sized to contain 2580 cubic feet of adsorbent. The drier will be an horizontal cylindrical vessel that has a circular cross-section and flow from top to bottom of the vessel (across the circular cross-section). The adsorbent will be supported above the bottom of the vessel. The area (width x length) of the adsorbent layer at the adsorbent support should be 860 ft. Determine the vessel dimensions that will minimize the weight of the vessel (minimum weight will be minimum cost) subject to the constraints that the vessel is designed for an operating pressure of 6 atm, a maximum temperature of 500°C, a maximum diameter of 16 feet, and a maximum length of 60 feet. 

Uptake of water and polar solvents by the column From mixed mobile phases, polar solvent(s) are preferentially adsorbed on the surface of polar adsorbents, sometimes giving rise to multilayer solvent adsorption on the adsorbent support. In such a case, the retention is contributed to by a liquid-liquid partition mechanism between the adsorbed liquid layer and the bulk mobile phase, in addition to the adsorption. Such a mixed-mode mechanism can be intentionally utilized for separation of strongly polar or even ionic compounds. 

The SEA method can be extended to the synthesis of bimetallics and may represent a simpler, more versatile alternative to surface redox reactions. The syntheses of bimetallics are the same as described in the previous section, only that the adsorbing supported oxide, like the CO3O4 depicted in Figure 13.13, is itself reducible and, after reduction, forms a bimetallic particle in intimate contact with the second metal precursor that had adsorbed directly onto it. This process can be conducted at ambient conditions, with an intermediate calcination in air to create the first metal oxide from a deposited or adsorbed precursor. The first metal might itself be deposited by SEA in well-dispersed form by precursors such as cationic cobalt hexa-ammine on silica. Thus, there is the potential to create homogeneous bimetallic particles with very high dispersion, using simple methods with common metal precursors. 

Wattraint, O., Warschawski, D.E., and Sarazin, C. 2005b. Tethered or adsorbed supported hpid bilayers in nanotubes characterized by deuterium magic angle spinning NMR spectroscopy. Langmuir 21 3226-3228. 

This equation corresponds only to the simplified model of the sorbent where a thin film of the SLP covers the entire surface of a solid adsorbent (support). 

Coating a metal or oxide species on the surface of adsorbent supports have been traditionally accomplished by the solid dispersion method [68] and wet-impregnation method [65, 69]. The first method is done by mixing physically the support body and solid active specie followed by heat-treatment to disperse the active species on the internal pore surface of the support. In the second method, the support body is brought in contact with a liquid solution containing the precursor of the active species. The precursor is transported into the pores of the support by capillary force. Solvent is removed by drying. The adsorbent is then calcined under specific atmosphere to convert the precursor to the desired active species. 

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