Carborundum , silver

Carborundum, silver on, 27 10-12 3-Carboxy - 2,2,5,5,- tetramethylpyrrolidin-1-oxy m-nitrophenyl ester, enantiomeric specificity in reactions of cyclohexaamy-lose and cycloheptaamylose on, 23 233 Carboxylate ions, 32 117-118 Carboxybc acids a, 3-unsaturated, 25 109 hydrogenation of, 25 107-115 ketonization of, 24 35-37 Lewis base-promoted ruthenium catalysis, 32 389, 400... 

A very clear-cut example for the influence of the electronic factor in supported catalysts, again involving a thin-layer metal type, is represented in Fig. 2. Here the carriers are commercially available samples of doped carborundum (SiC) which by itself is catalytically entirely inactive. In the abscissa of Fig. 2 we have arranged these samples in the order of their conductivity as stated by their manufacturers. The concentration of positive holes increases towards the right and that of the quasi-free electrons towards the left. Grains of these supports approximately 1 mm in size were covered with a thin layer of silver by the usual mirror produc-... 

Fusion of silicides Metallic silicides and carborundum are rarely encountered in routine qualitative analysis. They are best brought into solution by fusion with sodium or potassium hydroxide in a silver crucible (CAUTION) ... 

All present industrial catalyst systems are based on silver deposited on a slightly porous solid. The most widely used support is x-alumina, but silica-alumina and carborundum can also be employed. The specific surface area of the support, its porosity, and the pore size exert a considerable influence on the metal distribution at the surface, and consequently on catalytic activity. Several techniques are also available for fixing the silver, either by impregnation from a solution, or by deposition from a suspension. An initiator, usually consisting of alkaline earth or alkaline metals, can be added to the catalyst, but other metallic additions have also been recommended. Certain halogenated organic derivatives, such as dichloropropane, may increase selectivity in trace amounts (10 ppm in the feed), by reducing combustion side reactions. 

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