Metallic oxide activators

A large variety of catalysts, both homogeneous and heterogeneous, has been found active for dehydrohalogenation. The catalysts include a number of Br nsted and Lewis acids (liquid or soluble, as well as solid), metal oxides, active carbon, carbides, nitrides and some metals. However, in the latter case, the actual catalysts are most probably surface metal halides... 

Peroxidic cure systems are applicable only to fluorocarbon elastomers with cure sites that can generate new stable bonds. Although peroxide-cured fluorocarbon elastomers have inferior heat resistance and compression set, compared with bisphenol cured types they develop excellent physical properties with little or no postcuring. Peroxide cured fluoroelastomers also provide superior resistance to steam, acids, and other aqueous solvents because they do not require metal oxide activators used in bisphenol cure systems. Their difficult processing was an obstacle to their wider use for years, but recent improvements in chemistry and polymerization are offering more opportunities for this class of elastomers [42]. 

The lEPs obtained in [2969] probably represent metal oxide-dextrin precipitates rather than pure metal oxides. Activated carbons studied in [2970] had very high ash content. Water treatment residual was studied in [2971]. The material studied in [2972] was impure. Other examples of surface charging studies carried out in complex, ill-defined materials can be found in [2722,2834,2973-2978]. 

Many synthetic routes for preparing transition metal oxide catalysts produce a supported metal oxide structure consisting of an active metal oxide phase (the surface oxide) dispersed on a second, high surface area oxide (the support oxide) [1-3]. A key metric in characterizing SMOs is surface density. International Union of Pure and Applied Chemistry (lUPAC) defines surface density as mass per unit area [4]. For supported metal oxides, this is vaguely interpreted as the amount of supported metal oxide active phase per surface area of the underlying oxide support. This broad definition allows considerable latitude in whether total or exposed surface oxide content is considered and whether the surface area is of the uncovered support or final catalyst. Furthermore, absence of standardized methods to measure these parameters introduces additional variability into the determination of surface density. 

Trofimov, B.A., L.N. Sobenina, Z.V. Stepanova et al. 2008. Reactions of 2-phenylpyrrole with bromobenzoylacetylene on metal oxides active surfaces. Tetrahedron 64 5541-5544. 

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