Standard calcined aluminas

All of the systems described are now available with an incorporated differential thermal analyzer. DTA has been described in Section 16.2, so a few examples of the advantages of combining these systems will be presented. The incorporation of a DTA with one of the optical analyzers described requires the use of two thermocouples to measure the temperature difference between the sample and a reference standard (calcined kaolin or alumina). As noted, the optical noncontact instruments described are particularly useful in the glass and ceramics industries, so examples of evaluating raw materials from these industries will be described (from Paganelli and Venturelli). 

Alumina produced by the Bayer process is precipitated and then calcined [Krawczyk, Ceramic Forum International, 67(7-8), 342-8 (1990)]. Aggregates are typically 20 to 70 [Lm, and have to be reduced. The standard product is typically made in continuous dry ball or vibra-toiy mills to give a product d o size of 3-7 [Lm, 98 percent finer than 45 [Lm. The mills are lined with wear-resistant alumina blocks, and balls or cylinders are used with an alumina content of 80-92 percent. The products containing up to 96 percent AI9O3 are used for bricks, kiln furniture, grinding balls and liners, high voltage insulators, catalyst carriers, etc. 

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Somewhat similar to the Phillips catalyst is the Standard Oil of Indiana catalyst, which was the first olefin polymerisation coordination catalyst to be discovered [239], It typically consists of M0O3 supported on alumina or silica and calcined in air at high temperature. Unlike the Phillips catalyst, it is necessary to reduce the catalyst precursor thus obtained with hydrogen at elevated temperature before using it for polymerisation. Despite extensive studies, Standard Oil of Indiana catalysts have not been widely commercialised [43],... 

A standard membrane as prepared by de Lange [45] consisted of a die-pressed a-alumina support, fired at 1360°C with a pore diameter of 160 nm on which a y-alumina membrane was coated with a home-prepared boehmite sol. The coated y-alumina layer was calcined at 600°C, had a thickness of 7 pm with a pore diameter of 5 nm. On top of this mesoporous membrane,... 

Apparatus. The Attrition Index Analyzer (AIA) is shown in Figure 1. The instrument, a modification of the Forsythe and Hertwig design (16). was developed at Alcoa Laboratories to improve and standardize, within Alcoa, the measurement of attrition resistance for calcined and hydrate aluminas. The instrument and test... 

In an attempt to upgrade the siliceous bauxites and other aluminous materials, such as clay where the alumina usually is in the form of complex silicates, Skow and Conley (Si 9) considered the removal of the silica by caustic digestion. Prior to leaching, the aluminuous materials were calcined at 970°C, resulting in an optimal removal of silica with little loss in alumina content in the subsequent leaching step. The desilication step is necessary prior to using the raw materials as feed to the standard Bayer process (E3). The pilot plant operation to extract alumina from an anorthosite ore has been reported by St. Clair et al. (S24). 

A last complication results from the measurement of the thickness of supported layers. This can easily be done with SEM for calcined layers. Wet lyogel, or even dry xerogel, layers cannot be measured in this way. Reproducible thickness measurements on wet lyogel films could not be obtained with other easy-to-perform methods. Consequently layer thicknesses were measured after calcination. Estimates of the shrinkage in the thickness direction were made for supported alumina (boehmite) membranes dried at 40°C and 60% RH made with a standard precursor solution of 1 mol AlOOH/1 stabilised at pH = 4 by... 

The thermal stability of aluminas in the presence and absence of dopants was then examined. Samples were calcined at 1000 C for 2 h and at 1200°C for 4 h, the latter treatment being a standard washcoat test. The results, summarised in Table 1, show that thermally stable alumina can be produced from the sulphate in the presence of additives. At least in the presence of baria, the formation of Ba0.Al203 and BaO.bAlOs was detected by X-ray diffraction [6]. 

The multitude of refractory aggregates (for example, calcined clay, flint clay, andalusite, mulhte, bauxite, fused white or brown alumina, sintered alumina, etc.) and the different grain sizes of these materials—in addition to the big variety of bonding agents, additives, and mixing liquids—enable endless combination possibihties in development work on unshaped refractory products. Therefore, a qualitative standardization is not really possible as it is the case for refractory bricks. As a result of the ENV 1402-1 standard, which now provides a more precise definition of the products, there will probably be adjustments on the market in the long run. If also considering economic aspects, suitable products will obviously be developed on the basis of all the available constituents. 

Retention of nickel surface area of standard reduced alpha alumina supported catalyst and the novel catalyst after Just reduction rotary calcination calcination of a monolayer on gauze calcination in an Erlen-Meyer flask heating up in moist N2 P ior- to reduction, respectively. 

ReCenCion of BET surface area of the alpha alumina supported catalyst and the bare carrier after standard reduction conditions reduction followed by Ik extra treatment in moist hydrogen at reduction temperature calcination in an Erlen-heyer flask prior to reduction, respectively. 

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