Alumina sources

The choice of selected raw materials is very wide, but they must provide calcium oxide (lime), iron oxide [1309-37-1/, siHca, and aluminum oxide (alumina). Examples of the calcereous (calcium oxide) sources are calcium carbonate minerals (aragonite [14791-73-2] calcite [13397-26-7] limestone [1317-65-3] or mad), seasheUs, or shale. Examples of argillaceous (siHca and alumina) sources are clays, fly ash, mad, shale, and sand. The iron oxide commonly comes from iron ore, clays, or mill scale. Some raw matedals supply more than one ingredient, and the mixture of raw matedals is a function of their chemical composition, as deterrnined by cost and availabiHty. 

Figure 4.12 Histogram from automated SEM-EDS particle analysis of 362 zeolite precursor particles. Particles were reacted from silica and alumina sources slowly combined and aged at (a) room temperature and (b) 75°C.

A sodium aluminate solution (2.00 moles Al203/liter, 3.40 moles Na20/ liter, density 1.36 grams/ml) produced from hydrargillite was used as the alumina source in each series of tests. Silica was used as sodium silicate solution (5.98 moles Si02/liter, 1.77 moles Na20/liter, density 1.36 grams/ ml) and as solid amorphous silica with different surface areas (Table I). 

Preparing mixture solution A Distilled H20, NaOH and surfactant (cetyltrimethylammonium chloride, CTAC) were mixed together with stirring, then adding alumina source (if synthesis of Zr (Ti)-Si-Al material, here adding alumina source + Zr (Ti)... 

An alumina source (e.g., pseudo-boehmlte or aluminum 1sopropoxlde) Is mixed with dilute orthophosphor 1c acid, then combined with an aqueous solution containing the metal salt. Finally the template, an amine or quaternary ammonium hydroxide, Is added. 

The alumina source Is combined with an aqueous solution of the metal salt first, then dilute orthophosphor 1c acid Is added, and finally the template. 

The typical A1P0 synthesis gel contains four components an alumina source, a phosphate source, water, and an organic amine or quaternary ammonium salt. The relative concentrations and, of course, the individual characteristics of these reactants are important factors in the preparation of A1P0<, molecular sieves. One factor is particularly evident, namely, without the organic no A1P0<, molecular sieves are formed. The concept of a template in molecular sieve synthesis is not new. A template is a spec-... 

Alcoa s rehydratable CP alumina powders can be used effectively to improve a viable FCC catalyst formulation. Well-formed microspheres which have superior attrition resistance can be fabricated by controlling the pH and viscosity of the FCC slurry. At this time, the preferred formulation uses CP-2 as the free alumina source and a silica sol which has aged at conditions conducive to the formation of chains of polysilicic acid aggregates. The addition of the rehydratable alumina can also have a beneficial effect on the cracking activity of the catalyst. The conversion and selectivity of a CP-2 formulated sample were comparable to a commercial grade catalyst and an experimental reference, which was alumina-free. After heavy metals poisoning, the CP-2 material had activity which was superior to the reference formulation. 

Compositions of the initial mixtures, alumina sources and results of the syntheses of MWW zeolite without and with ball milling pretreatment (XRD-1 and XRD-2) are represented in the Table 1,... 

Na20/Si02 NaF/SiOz Si02/Ab03 Alumina source XRD-1 XRD-2... 

In both cases two chemical factors were considered variable (A and B), while the crystallization time was considered as a third factor (C). The other factors were maintained constant temperature (70 °C), sihca (water-glass, Merck) and alumina source (sodium aluminate. Carlo Erba) and the preparation mode of the hydrogel. The crystaUization runs were performed in polypropylene bottles in static conditions. 

Identification of such eflFects is made difficult, however, by the complexity of a crystallization experiment. Crystallization typically occurs from a molecularly inhomogeneous, aqueous gel, prepared by combination of a silica and an alumina source together with varying amounts of hydroxide ion. Since the product obtained is often nucleation-controlled, variables in an experiment can include not only the silica source (gel, sol, sodium silicate) and the alumina source (sodium aluminate, aluminum sulfate) but also the detailed mixing and crystallizing procedures (temperatures, aging, stirring rate, etc.). 

Sic whisker-reinforced alumina Source Thompson et al., 1997b. 

Everitt, G.F. 1988. Stabilized aluminum acetate used for an alumina source in ceramic fibers. Pp. 463-476 in Ultrastructure Processing of Advanced Ceramics, J.D. Mackenzie and D.R. Ulrich (eds). New York John Wiley and Sons. 

The aluminum-chelated alkoxide can also be used unhydrolyzed, in a mixture with prehydrolyzed TEOS [51]. This mixture is concentrated under reduced pressure and the fibers are dry [49] [51] or wet spun [48]. Mullite fibers were prepared from a single phase precursor [52], whereby the alumina source was a viscous solution of aluminum formoacetate. After concentration, the dope was dry spun, yielding fibers which contained orthorhombic mullite after firing at 1250°C. Mullite fibers can also be prepared from another single phase liquid precursor, a mixture of an alkoxysilane, such as tetramethoxysilane or ethyl silicate, and an aluminum chlorohydrate polyol complex, such as the 1,2- dihydroxypropane complex, Al2(0H)5CI-H20-CH3CH(0H)CH20H[46]. 

Depending on the backward integration of the individual zeolite production process, the alumina source may be aluminum hydroxide as well as sodium aluminate [20,103,114,116,117,123, 124,129,130,132-136,139,141,152,158,160-165]. Usually, the synthesis starts with the dissolution of aluminum hydroxide in caustic soda solution at temperatnres above 80°C and filtration (see Equation 22.4) [15,20,99,104,110,126,128,166],... 

The production of zeolites is frequently performed in batch reactors. Gel precipitation and crystallization are then carried out stepwise. A sodium aluminate solution is prepared first by mixing an alumina source with caustic soda. The silica-containing solution is then dosed to the alkaline alumina-containing solution [140]. 

Typically, the synthesis of AIPO4 involves the use of an aqueous reaction mixture containing an alumina source, a phosphate source, and an amine or/and a quaternary ammonium salt. The aluminum source is usually aluminum isopropoxide or pseudoboehmite, whereas orthophosphoric acid is most frequently the source of the phosphorus component. In the synthesis of SAPO, MeAPO, and MeAPSO materials, silica sol and/or a solution of the Me salt (usually acetate or sulfate) are introduced in the reactive mixture. Typical reaction mixtures have the molar compositions as follows (where R is an amine or/and a quaternary ammonium salt) ... 

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