Aluminosilicate support

A ground mixture of iron(III) nitrate and HZSM-5 zeolite, termed zeofen , has also been used both, in dichloromethane solution and in solid state under MW irradiation conditions [101]. It has been suggested that the zeolite aids the reproducibility of the reaction but any other aluminosilicate support would probably be equally effective. Recent studies point out attractive alternatives that do not employ any of the solid supports in such oxidations with nitrate salts [102]. 

Hirai T, Bando Y (2005) Immobilization of CdS nanoparticles formed in reverse micelles onto aluminosilicate supports and their photocatalytic properties. J Colloid Interface Sci 288 513-516... 

Zeolites (crystalline aluminosilicates) supporting oxidizing metals (Fe or Cu) have been introduced by Garcia and co-workers [106]. In particular, they showed that FeMCM-41 affords binaphthol from 2-naphthol as virtually the only product. Unfortunately, this compound is trapped in the zeolite pores and the isolated yields are lower than expected. 

The standard enthalpies of adsorption (Table 15) of these molecules on the thermally treated aluminosilicate support the former explanation. So the adsorption of benzene on H-473 is the most exothermic due to the specific interaction with the silanol groups. When the thermal treatment progresses, the process becomes less and less exothermic due to i) the partial dehydroxylation of the surface (H-673), ii) the change in the chemical surface groups (siloxane groups on H-873 and H-1073) and iii) the destruction of the chemical surface groups (H-1273). As a consequence of the latter process the standard enthalpy of adsorption of benzene on H-1273 is very similar to the heat of liquefaction. 

In another approach, an oxime carbapalladacycle ionic liquid catalyst was attached to an aluminosilicate support (Al/MCM-41, Si/Al 13) via electrostatic interaction by... 

Sodium alumiaate is widely used in the preparation of alumina-based catalysts. Aluminosilicate [1327-36-2] can be prepared by impregnating siHca gel with alumiaa obtained from sodium alumiaate and aluminum sulfate (41,42). Reaction of sodium alumiaate with siHca or siHcates has produced porous crystalline alumiaosiHcates which are useful as adsorbents and catalyst support materials, ie, molecular sieves (qv) (43,44). 

X-ray photoelectron spectra, V3f Alumina-supported metals, multitechnique characterization, 37V-83 Aluminosilicates, Intercalates of, role In heterogeneous catalysis, V72-83 Alumlmin... 

In this chapter, we demonstrate the potential of such agents as catalysts/promoters in key steps for the derivatization of sugars. The most significant catalytic approaches in carbohydrate chemistry that use aluminosilicate porous materials, namely zeolites and montmorillonite clays, are reviewed and discussed. Silica gel is a porous solid silicate that has also been used for heterogeneous catalysis of organic reactions in general. We include here its usefulness as promoter and reagent support for the reactions under consideration. 

The immobilization of catalysts on a solid support is a well-known approach to render a system recycleable, and this has been performed recently by the immobilization of rhodium-MonoPhos 29 a on aluminosilicate A1TUD-1. The resultant system showed high efficiency in water, and could be recycled [80]. 

The EDX spectrum (Fig. 11.8) shows the main surface scale impurity peaks of silica, aluminium, sodium, chloride and iron. If this EDX is compared to that of a new, clean membrane surface (Fig. 11.9), the clean surface shows sulphur, carbon and oxygen, which is typical of a porous polysulphone support. It was concluded that the scale is amorphous, composed of aluminosilicate and silicate. These compounds are normally found in trace amounts in brine solutions. Analysis showed that the surface could be cleaned with hydrochloric acid and analysis of the dissolved scale was similar to the EDX spectrum analysis. Review of the plant operation determined that the precipitation was the result of high pH in combination with high silica concentrations in the brine. 

The surface modification of an inorganic support with organophosphorus coupling agents (OPCA) is an extremely versatile route to hybrid materials. This route has been applied to a variety of supports, including metal oxides, metals, aluminosilicates, silica, metal hydroxides, and carbonates. 

Alumina, silica, and the aluminosilicates, whether amorphous or crystalline in the form of zeolites, play an important role in catalysis because they are used as supports in a large number of industrial catalysts. In addition to its role in dispersing the catalyst, the support is known to play a significant part in the chemistry of the surface reactions and this is illustrated by the electron transfer mechanism described earlier (Fig. 16). For these reasons, it is important to study the adsorption of oxygen on the support itself. 

Most of the adsorbents used in the adsorption process are also useful to catalysis, because they can act as solid catalysts or their supports. The basic function of catalyst supports, usually porous adsorbents, is to keep the catalytically active phase in a highly dispersed state. It is obvious that the methods of preparation and characterization of adsorbents and catalysts are very similar or identical. The physical structure of catalysts is investigated by means of both adsorption methods and various instrumental techniques derived for estimating their porosity and surface area. Factors such as surface area, distribution of pore volumes, pore sizes, stability, and mechanical properties of materials used are also very important in both processes—adsorption and catalysis. Activated carbons, silica, and alumina species as well as natural amorphous aluminosilicates and zeolites are widely used as either catalyst supports or heterogeneous catalysts. From the above, the following conclusions can be easily drawn (Dabrowski, 2001) ... 

Aluminum (properly called aluminium, but the former name prevails in North America) is found in combination with Si and 0 as aluminosilicates in rocks, and as its ore, bauxite. The metal finds use in vehicles, aircraft, packaging, cookware, construction materials, etc., while aluminum salts are used in baking powders, water treatment, and dyeing of textiles. Aluminum oxide is widely used as a refractory and as a support for catalysts. Aluminosilicate catalysts such as zeolites are of key importance in the chemical and petroleum industries. 

That Al3+ is the main toxic agent in many acidified lakes is supported by observations of improved fish survival rates when the silica content of the water is increased, as dissolved silica can form either soluble or insoluble aluminosilicates (see Section 7.6). Mobilized aluminum has also been linked to forest damage, since, in sufficient concentration, it is directly toxic to roots of spruce trees and many other plants. 

The synthesis and characterization of the structural defects within aluminosilicate mesoporous materials were provided. We further discussed the fascinating adsorption-desorption hysteresis behaviors and the influencing factors in the formation of the structural defects. However, mesoporous MCM-41 can act as catalyst support for many catalytic reactions, especially involve bulk oiganic molecules, due to its large surface area and pore size. The ability to synthetically control the connectivity of the mesoporous materials may have important applications in catalysis. 

---