Single alumina

Figure 14.3 TEM micrographs of y-A Os supports (a) homogeneous support prepared from a single alumina precursor and (b) heterogeneous support prepared by combining two alumina precursors of different densities embedded in a peptizable alumina matrix...

Kaolinite is a clay mineral with the chemical formula Al2(0H)4Si205 [5] or (OH)8Si4Al40io [6]. The basic unit of kaolinite consists of a single silica tetrahedral sheet and a single alumina octahedral sheet such that the oxygen atoms at the tips of the silica tetrahedrons and one of the oxygen atoms of the alumina octahedral sheet form a common layer. 

Figure 2.4. Guinier transmission scans (Co K a-radiation) of a set of differently promoted catalysts prepared from the same iron oxide. Catalyst 3 is nominally doubly promoted, containing extra calcium and silicon, catalyst 6 is singly potassium promoted, and catalyst 7 is singly alumina promoted. Both single promoted samples contain also calcium impurities.

Bare S R, Strongin D R and Somoqai G A 1986 Ammonia synthesis over iron single crystal catalysts—the effects of alumina and potassium J. Phys. Chem. 90 4726... 

Ruby Laser. Ruby (essentially alumina) owes its well-known color to the presence of very small proportions of chromium ions (Cr +) distributed through it. Ruby lasers do not use natural rubies because of the imperfections they contain. Instead, synthetic single crystals of chromium... 

Gainum (HI) Ga203 is the single gallium oxide that is stable under normal conditions. Like alumina, it exists iu several crystalline forms. The... 

Catalytic processes frequently require more than a single chemical function, and these bifunctional or polyfunctional materials innst be prepared in away to assure effective communication among the various constitnents. For example, naphtha reforming requires both an acidic function for isomerization and alkylation and a hydrogenation function for aromati-zation and saturation. The acidic function is often a promoted porous metal oxide (e.g., alumina) with a noble metal (e.g., platinum) deposited on its surface to provide the hydrogenation sites. To avoid separation problems, it is not unusual to attach homogeneous catalysts and even enzymes to solid surfaces for use in flow reactors. Although this technique works well in some environmental catalytic systems, such attachment sometimes modifies the catalytic specifici-... 

Properties of the deposits Almost any material which can be melted is suitable for plasma spraying, giving a vast range of possible coatings of single or mixed metallic or non-metallic substances. It is often possible to produce types of coatings which are not obtainable in any other way. Typical of the materials which are plasma sprayed are copper, nickel, tantalum, molybdenum. Stellites, alumina, zirconia, tungsten and boron carbides, and stainless steels. 

Figure 7. Ionic conductivities for various monovalent (a) and multivalent (b) ions in f) and / " -alumina single crystals in the direction of the conduction plane [4, 19J.

Note The principal reinforcement, with respect to quantity, is glass fibers, but many other types are used (cotton, rayon, polyester/TP, nylon, aluminum, etc.). Of very limited use because of their cost and processing difficulty are whishers (single crystals of alumina, silicon carbide, copper, or others), which have superior mechanical properties. 

An alternative preparation of benzofurans was carried out via a microwave-assisted Mannich condensation of paraformaldehyde and a secondary amine followed by cyclization with an alkynyl phenol 185 mediated by alumina doped with Cul (Scheme 67). The reaction can be carried out in a single-step... 

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