Metal-zeolites

Catalysis by Metal Oxides and Zeolites. Metal oxides are common catalyst supports and catalysts. Some metal oxides alone are industrial catalysts an example is the y-Al202 used for ethanol dehydration to give ethylene. But these simple oxides are the exception mixed metal oxides are more... 

An important consideration in constructing certain types of geochemical models, especially those applied to environmental problems, is to account for the sorption of aqueous species onto sediment surfaces (e.g., Zhu and Anderson, 2002). Because of their large surface areas and high reactivities (e.g., Davis and Kent, 1990), many components of a sediment - especially clay minerals, zeolites, metal oxides and oxyhydroxides, and organic matter - can sorb considerable masses. 

Metal/zeolite, metal/mesoporous molecular sieves, and metal/mineral catalysts... 

The applications of IR spectroscopy in catalysis are many. For example, IR can be used to directly characterize the catalysts themselves. This is often done in the study of zeolites, metal oxides, and heteropolyacids, among other catalysts [77,78], To exemplify this type of application, Figure 1.11 displays transmission IR spectra for a number of Co Mo O (0 < x < 1) mixed metal oxides with various compositions [79]. In this study, a clear distinction could be made between pure Mo03, with its characteristic IR peaks at 993, 863, 820, and 563 cm-1, and the Mo04 tetrahedral units in the CoMo04 solid solutions formed upon Co304 incorporation, with its new bands at 946 and 662 cm-1. These properties could be correlated with the activity of the catalysts toward carburization and hy-drodenitrogenation reactions. 

In order to combine the catalytic activity of highly dispersed metal species and that of zeolites, metals can be deposited in the pores and on the external surface of zeolite particles. In this way, a catalyst is formed with both a metal functionality, e.g., redox or hydrogenation activity, and an acidic function. The metals can be deposited by different methods. Impregnation of a zeolite with a metal... 

Four different methods to store hydrogen are currently available compressed gas, liquid hydrogen, metal hydrides and sorption on different porous materials (carbon materials, zeolites, metal organic frameworks, etc).2-4... 

Work with the objective of comparing oxo-ions with oxide particles in order to test the validity of this reasoning has been reported by Chen et al. who used a catalyst that initially contains Fe oxo-ions, [HO-Fe-0-Fe-OH] +. These sites were first converted to Fc203 particies by a simpie chemical treatment. This was followed by another treatment, which redispersed these Fc203 particies back to oxo-ions. The change in particle size was monitored by a spectroscopic method based on the observation that in zeolites metal ions and oxo-ions, that are attached to the wall of a cage, give rise to a typical IR band caused by the perturbation of the vibrations of the zeolite lattice. 

Full catalyst formulations consist of zeolite, metal and a binder, which provides a matrix to contain the metal and zeolite, as well as allowing the composite to be shaped and have strength for handling. The catalyst particle shape, size and porosity can impact the diffusion properties. These can be important in facile reactions such as xylene isomerization, where diffusion of reactants and products may become rate-limiting. The binder properties and chemistry are also key features, as the binder may supply sites for metal clusters and affect coke formation during the process. The binders often used for these catalysts include alumina, silica and mixtures of other refractory oxides. 

Pd supported on acidic zeolite Metal-oxide-supported complexes of Cr, Ti or Zr... 

The important groups of dehydration catalysts are oxides, aluminosilicates (both amorphous and zeolitic), metal salts and cation exchange resins. Most work on mechanisms has been done with alumina. 

The same catalysts as for dehydration are suitable for the dehydrosulphidation, i.e. alumina, silica—alumina, zeolites, metal oxides and metal sulphides. (For a comparison of their activities, see ref. 247.)... 

For the past decade, the major thrust of one of the authors has been the elucidation of reaction mechanisms in heterogeneous catalysis on zeolites, metal oxides and other materials. The primary experimental tool has been in situ NMR spectroscopy, and this is increasingly coupled with theoretical calculations carried out by the other author. 

A more recent trend in polymer materials research is the hybridization of cellulosic polysaccharides with inorganic compounds natural and synthetic layered clays, silica, zeolites, metal oxides, and apatites are employable as nanoscale components. In addition, if mesoscopic assemblies such as liquid-crystalline ordering are used in the construction of new compositional systems, the variety of functionalized cellulosic materials will be further expanded. 

Current polymeric materials are inadequate to fully meet all requirements for the various different types of membranes (cf. Section 2.2) or to exploit the new opportunities for application of membranes. Mixed-matrix membranes, comprising inorganic materials (e.g., metal oxide, zeolite, metal or carbon particles) embedded in an organic polymer matrix, have been developed to improve the performance by synergistic combinations of the properties of both components. Such improvement is either with respect to separation performance (higher selectivity or permeability) or with respect to membrane stability (mechanical, thermal or chemical). 

Type I isotherms are characteristic of microporous solids having relatively small external surface area (activated carbons, molecular sieve zeolites, metal organic frameworks, etc.). They are usually obtained by most gases and vapors on activated carbons. 

Parnham ER, Morris RE. Ionothermal synthesis of zeolites, metal-organic frameworks, and inorganic-organic hybrids. Accounts of Chemical Research. 2007 40 1005-1013. 

The framework charge-compensating cations in a zeolite, which for synthetic zeolites are normally sodium ions, can be exchanged for other cations of different type and/or valency. However, care must be taken during ion exchange to avoid strongly acidic solutions which can lead to proton exchange with the zeolite metal cations or even structure collapse. For example, zeolites A, X, and Y decompose in 0.1 N HCI. The more silica-rich zeolites such as mordenite are, however, stable under such conditions. Acidity can be introduced into a zeolite in a number of different ways ... 

Process Licensor Zeolite Metal Oxide C1/A1203... 

Two sorts of catalyst have been widely applied in plastics pyrolysis [85], namely molecular sieve catalyst or reformed molecnlar sieve catalyst, such as Y-zeoUte and REY zeolite metal oxide catalyst, snch as silica-alumina, AI2O3, CuO, ZnO, Fe203, cerium oxide and Co-Mo oxide. 

The size of metal clusters and the number of atoms in the cluster can vary in a large range. The number of nuclei m can vary from 1 to thousands. In a zeolite, metal clusters can be located in different cages and defects. And the metal clusters in zeolites can be roughly classified as the following types (Figure 9.1) ... 

Zeolite Metals. Ion exchange. Insufficient data short term... 

Catalyst System HZSM-5 Zeolite Acid Modified Zeolite Metal Incorporated Zeolite... 

Catalytic behaviors of solid base catalysts for fine chemicals synthesis as well as the fundamental reactions are described. The reactions included are double bond isomerization of olefins, addition of hydrogen and amines to conjugated dienes, dehydration, dehydrogenation, reduction, alkylation, aldol addition and condensation, Wittig-Horner and Knoevenagel reactions, dehydrocyclodimerization, and ring transformation. The characteristic features of different types of solid base catalysts, zeolites, metal oxides, solid superbases and non metal-oxides, are summarized. 

I YWORDS Y zeolite, metal loading, hydrothermal aging, interaction mechanism, structure model... 

In the last section, we describe immobilization methods of Ti02 nanomaterials on different substrates which include glass, ceramic, stone, cement, zeolites, metallic and metal oxide materials and polymer substrates. 

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