Matrix composition effects metal activity

The most cost-efficient way to improve operational characteristics is to modify the existing polymeric matrixes therefore, currently the group of polymeric materials modified with NS is of special interest. The NS are able to influence the supermolecular stmcture, stimulate self-organization processes in polymeric matrixes in supersmall quantities, and thus contributing to the efficient formation of a new phase medium modified - nanocomposite and qualitative improvement of the characteristics of final product - PCM. This effect is especially visible when NS activity increases which directly depends on the size of specific surface, shape of the particle, and its ultimate composition [22]. Metal ions in the NS used in this work also contribute to the activity increase as they stimulate the formation of new bonds. 

For heterogeneous systems, the solid-state matrix can influence the activity by altering both electronic and structural features about the active site. We can distinguish two types of solid-state matrix effects. The first involves the embedding of the active site within the catalytically active particle and the indirect changes that arise from the interaction of the active particle and the support. Examples of the direct effects include the overall size, shape and morphology of the metal particle and the composition and the sp>ecific atomic arrangements in alloy particles. 

To show the effect of having zeolite present in the contaminated particles, a REY commercial cracking catalyst with a matrix surface area of ca. 85 m /g was also contaminated with nickel and vanadium, and steamed (1450 F, 4 hrs, 90% steam, 10% air) to age the metals. Its select vities were compared to the non-zeolitic additive having the same surface area and chemical composition blended with sufficient metals-free active cracking component to give the same conversion. 

The supramolecular bis-aniline cross-linked metallic NPs/enzyme composite does not only act as a conducting matrix that electrically contacts the redox center with the electrode, but the NPs may also provide catalytic sites that enhance the biocatalytic transformations at the enzyme active site. This has been demonstrated by the effective... 

Chapter 10 deals with composite films synthesized by the physical vapor deposition method. These films consist of dielectric matrix containing metal or semiconductor (M/SC) nanoparticles. The film structure is considered and discussed in relation to the mechanism of their formation. Some models of nucleation and growth of M/SC nanoparticles in dielectric matrix are presented. The properties of films including dark and photo-induced conductivity, conductometric sensor properties, dielectric characteristics, and catalytic activity as well as their dependence on film structure are discussed. There is special focus on the physical and chemical effects caused by the interaction of M/SC nanoparticles with the environment and charge transfer between nanoparticles in the matrix. 

Thus, the size effects for catalytic reactions of metal atom clusters in a gas phase are manifested only in very small, essentially quantum clusters, which are in essence nonmetal particles. Another situation takes place in films, containing a set of nanoparticles immobilized at a surface or inside of a dielectric matrix. In this case the influence of M nanoparticle size on catalytic activity and structure of products formed is observed for considerably larger already classical particles of sizes from 2 ( 150 atoms) to 20-30 nm ( 105 atoms) [113, 114]. It is necessary to note that catalytic properties of M nanoparticles in composite systems are determined substantially by their interaction with a matrix, which depends on the size of particles. 

The key parameters in the preparation of active and stable catalysts for N2O decomposition under conditions of industrial interest were examined using mixed oxides obtained form hydrotalcite-type (HT) precursors. The relationship between activity and composition of the catalysts was studied, with attention focused on the nature and amount of metal ions present in the HT precursor (Rh/Mg/Al or Rh/Co/Al). An activation procedure was developed which makes it possible to prepare catalysts, active and stable even under the severe reaction conditions of industrial interest. The relationship between active phase and composition of the bulk matrix was also investigated. Moreover, the flexible structure of the HT precursor made it possible to investigate the use of other active elements (Pd or La) to develop synergetic effects, without any interactions due to side phase segregation, or lack of homogeneity. 

Coordination, localization and stabilization of transition metal ions in zeolitic materials, apart from activation conditions, depend on the structure and composition of the zeolite matrix. To evaluate the extent of such a matrix effect Cu +ions are used as a metal ion probe in this work, and copper ion-matrix interaction in different zeolites and oxides has been studied by EPR and TPR. ... 

Recently, ultrafine metai particles have attracted much interest because of their unique properties which differ from those of buiK metals, e.g., quantum size effect, such as low melting point, plasmon resonance absorption and so an It is well known that ultrafine metal particles are quite active because of their large surface area and that they are liable to aggregate and grow in size. Thus, it is necessary to maintain them in stable form in a matrix for size control and tor narrow size distribution. Ultrafine metal partides-polymer composites, which are prepared by embedding ntetal particles in a polymer, can be used as electrical, magnetic, optical or chemically useful materials. The techniques to prepare ultrafine metal partides-polymer composites have been explored end reported by many researchers. Many of these involve co-evaporation or co-sputtering of a metal and polymer . In the case of thesb methods, however, metal-polymer composites have to be prepared at a rate below ca. 10 nm/min so that ultrafine metal particles will not... 

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