Alumina dough

There are two main shapes of catalysts, cylindrical and spherical. The cylindrical catalysts are usually extruded alumina. The spherical catalysts may be formed through a dropping method or by rolling wet, soft alumina dough. In some instances, factors such as the resistance to flow or flow distribution concerns may cause one form to be chosen over the other. The density of the catalysts may vary from approximately 0.5-0.8 g/cm. The variability in density allows the refiner to load more pounds of catalyst in a unit should additional catalyst activity or stability be desired. 

Another interesting TLC method for the isolation and determination of bromate ion in flour dough and breads has been developed [59]. It involves extraction of BrOj from foodstuff, purification on alumina column, TLC separation on silica gel layer developed with water -1- -butanol + n-propanol (1 1 3), and quantification by densitometry. Bromate ion down to 0.1 pg in bread (1.0 g) was detected with tohdin-FIQ reagent. 

All the monolith composites were prepared at a 1 1 ratio between the magnesium silicate clay binder and the AC or alumina. After premixing of the dry powders by careful addition of water a dough was formed. This dough was extruded as honeycomb monolithic structures with parallel channels of square section at a cell density of 8 cells cm and a wall thickness of 0.9 mm using a Bonnot single screw extruder. 

To further process the washed and/or (spray-) dried alumina or silica-alumina precipitates, a dough is prepared by mixing the precipitate with water. 

The kneading of the alumina paste (dough) is monitored by the torque required. When boric acid is added the torque decreases drastically but increases again... 

Bulk Molding Compoimd, BMC, (Dough Molding Compound in Europe) is produced by first mixing pre-catalyzed liquid resin with fillers, mainly calcium carbonate and talc, in a heavy duty low speed sigma blade mixer. This is compression molded at 500 psi and 300 to 400°F. The resin most commonly used is unsaturated styrene-diluted polyester. Other BMC resins are alkyds, phenolics, urea, melamine, diallyl phthallate, silicones and epoxy. All are highly filled with calcium carbonate, talc, mica or alumina to improve mechanical properties and reduce shrinkage. 

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