Metals Oxides, acidic

Cure Agent Metal oxide acid acceptor Comments... 

Metallic oxide + acid salt + water Cr is a spectator ion. 

Sulphur and oxygen are interchangeable in sulphides and oxides. Metal oxides (basic) and non-metal oxides (acidic) combine to form salts. Likewise metal sulphides may combine with sulphides of weakly metallic or non-metallic elements to form salts, the so-called thio-salts, or sulpho-salts. Thio-salts of a few of the elements, notably tin, are very well defined. Stannous sulphide does not form a thio-salt but addition of sulphur converts it to stannic sulphide which does form a soluble thio-salt with the sulphide of an alkali metal. 

An impressive number of papers and books has been published and numerous patents have been registered on the aq lation of aromatic compounds over solid catalysts. Recently Sartori and Maggi [1] have written an excellent review with 267 references on the use of solid catalysts in Friedel-Crafts acylation. In one section of this review, namely acylation of aromatic ethers or thioethers, the authors report work on acylation by solid catalysts such as zeolites, clays, metal oxides, acid-treated metal oxides, heteropolyacids or Nafion. When examining in details these results, it appeared very difficult for us to build upon these experimental results as the reaction conditions differ drastically from one paper to the next. This prompted us to reinvestigate the scope and limitations of the Friedel-Crafts acylation using heterogeneous solids as catalysts, trying as much as we could to rationalize the observed effects. 

Ingo, G.M., Riccucci, C., and Chiozzini, G., Origin of gas porosity in gold-based alloys cast in calcium sulfate-bonded investment and influence of metal oxide acid-base properties on calcium sulfate thermal stabihty, J. Am. Ceram. Soc., 84, 1839, 2001. 

Incompatibilities and Reactivities Oxidizers, hydrogen peroxide, nitric acid, metallic oxides, acids... 

III. Binary Oxides (Salts of Metal-Oxide Acids f ... 

As described above, mesoporous materials can be used as supports for metals, oxides, acids, and bases. However, perhaps the most intriguing and exciting application is in catalysis involving large active molecules such as organometallics and transition metal complexes immobilized within the pores, as illustrated in Fig. 12. The large surface areas of mesoporous materials makes the materials very attractive as supports for such active phases. 

The metal oxide catalysts used for hydrogenation reactions are reduced to an active form of the metal before use. Apart from metallic platinum and silver, which are used to oxidize ammonia and methanol, respectively, oxidation catalysts are usually transition metal oxides. Acidic oxides, such as alumina, sihca alumina, and zeolites are used in cracking, isomerization, and dehydrogenation reactions. These are only a few examples of the catalysts now being widely used. A more detailed list is given in Table 1.4. 

Functional Groups Metal/Oxide acid pnetreatment tofefm-OOOH -NHj... 

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