Alumina-silica Chemical decomposition

Lavoisier published a list of elemental substances in 1789. He prepared his list after conducting careful chemical decomposition and recombination reactions. This list of 23 elements is considered by many as the first list of elements. But, he included lime, alumina and silica - stable chemical compounds - and light and heat in his list of elements... 

Tabun may be removed from cleaning organic solvents by adsorbing over Fuller s earth, activated carbon, activated alumina, or silica gel (Fowler and Mcllvaine 1989). Incineration and molten metal reduction (Schultz 1987) are efficient thermal processes. Chemical decomposition can be achieved by oxidation with 7/,7/ -dihalo-2-imidazolidinone in tetrachloroethylene (Worley 1989). It may be fully decomposed by bleaching powder. One of the products, however, is cyanogen chloride, which is toxic and undesirable. Tabun may be hydrolyzed by alkalies, forming less toxic substances. 

It is fruitless to attempt detailed study of a phenomenon whose products are not well identified. It is unfortunately frequently noted in the literature, especially in cases of column chromatography, that fractions are only identified as to the chemical operations which brought them to light. Fractions are identified, for example, only by the solvent used. Speculations as to the composition of the radioactive solutes in such solutions can seldom be really reliable, and the presence of an unexpected radioactive species is in such cases undetectable. It is also important in reading the literature to watch out for cases in which the chemical yields of the carriers have not been measured. Extensive decomposition can often occur on silica gel and alumina columns, especially when photosensitive or moisture sensitive compounds are used. For these reasons much of the information now existing in the literature must be regarded as only exploratory, awaiting the development of better analytical methods for separation, purification, identification and determination of the products —known or expected. 

Before going further, however, two remarks should be made. First the importance of certain structural modifications of the surface of the irradiated catalysts should be stressed. Among these modifications we cite the sometimes considerable transformations of the physical texture of the solid (modifications of the pore spectrum, etc.) ( 4, 7 S) due to sintering, as well as the modifications of the chemical nature of the surface (decomposition of oxides, of silanol groups,. . . ) (74). These structural modifications may have a particularly important influence in the case of large surface solids such as the silica and alumina used in our experiments. 

Cobo, S., Heidkamp, J., Jacques, P. A., Fize, J., Fourmond, V., Guetaz, L., et al. (2012). A Janus cobalt-based catalytic material for electro-splitting of v/ater. Nature Materials, 11, 802—807. Consul, J. M. D., Peralta, C. A., Benvenutti, E. V., Ruiz, J. A. C., Pastore, H. O., Baibich, I. M. (2006). Direct decomposition of nitric oxide on alumina-modified amorphous and mesoporous silica-supported palladium catalysts. Journal of Molecular Catalysis A Chemical, 246, 33—38. 

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