Inorganic oxides reactivity

Surface organometallic chemistry with rare-earth metals (or lanthanides) on various inorganic oxides has advanced considerably during the past decade but is still in its infancy. A major drawback has been the difficult access and handling of pure (homoleptic) Ln alkyl precursors with reactive Ln-C(alkyl) bonds [101]... 

Prior to the reaction, the inorganic oxide support is thermally pretreated to remove physisorbed water and thus avoid spurious reactions which would not lead to anchoring/grafting. The support can be also dchy-droxylated to various extents to control the amount and dispersion of the anchored/graftcd species. Different types of hydroxy groups with different reactivities are present on supports. The structure of support surfaces and their reactivity have been extensively described in several reviews ([12-18] and references therein). 

Industrial catalysis is an old practice. Catalysts have always been used in the production of wine and beer. Among the first industrial catalytic processes are a few inorganic oxidation processes, viz. the Deacon process (oxidation of HC1 into CI2) and the production of sulphuric acid. These processes were developed before a scientific basis of chemical reactivity was established. Only after the formulation of the theory of chemical equilibria by van t Hoff did a framework for catalyst development become available. This had a major impact on the development of a process for the synthesis of ammonia at the beginning of the twentieth century, allowing a systematic, scientifically based search for a good catalyst to be performed. It also initiated the development of chemical process engineering as we know it today. 

The extremely low weight loss rate observed with silicone rubber is due to the change of chemical structure of polymer by chemical reaction of the reactive oxygen. The oxidation of Si forms nonvolatile oxides, whereas the oxidation of C leads to volatile oxides. Consequently, Si in the organic polymer is converted to inorganic oxides, which are stable in the luminous gas phase in vacuum. 

Inorganic oxides may present several different types of reactive functional groups, among them several kinds hydroxyl groups, strained rings, oxo groups, and Lewis-acidic vacant sites. The occurrence and relative abundance of these different sites depend primarily on the identity of the oxide (silica, alumina, niobia, etc.), the synthesis and conditioning of the oxide, and the eventual calcination and other thermal treatment of the solid immediately before use. 

Support (carrier, matrix) - the solid matter, the participant of chemical modification. Support might be both mono or polycrystalline, amorphous, more or less dispersed and pelicular. There are inherent (structural) functional groups on the surface of support. The latter are responsible for the reactivity of surface. Normally, inorganic oxides or metals covered with oxide films are used as supports. Not less than 90% of studies in this field is performed on a silica surface. This comes from the following facts. Firstly, silica has soft surface hydroxyls secondly, silica is commercially available in a wide range of pore, particle sizes and specific surface areas. 

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