Process catalyst carrier drying

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. 

Such tailoring of properties is feasible for many catalyst-carrier formulations, bnt drying processes, for instance, may be restricted by other considerations. Fluidization of difficult materials can be maintained by mechanical or ultrasonic vibration of the vessel, or pulsation of the supply of the fluid, or mechanical agitation of the contents of the vessel, or by addition of fluidization aids such as fine foreign solids. 

Catalyst carriers are often manufactured in a two-step process. In the first step, the solid material, e.g., silica or alumina, is precipitated from a solution and filtered. Then the wet powder is brought into the desired shape, as grains or pellets of a certain size, e.g., by spray drying, pressing or extrusion. The resulting particles are then dried and sintered at elevated temperatures. The more active catalytic material may be formed by co-precipitation. At elevated temperatures oxides are usually formed, that may be reduced to obtain a pure metal. Sometimes oxides or sulfides are the active species. 

Aromatic aldehydes are prepared by passing carbon monoxide and dry hydrogen chloride through an ether or nitrobenzene solution of an aromatic hydrocarbon in the presence of a catalyst, commonly aluminum chloride with cuprous chloride as a carrier. The process is illustrated by the synthesis of p-tolualdehyde (51%). A convenient procedure for obtaining an equimolar mixture of anhydrous hydrogen chloride and carbon monoxide consists in dropping chlorosulfonic acid on formic acid, viz.,... 

In some processes coated catalysts are employed. They are made by coating massive solid grains with a thin and very i rous layer of carrier powder with the catalytic material. These are then dried and sintered, subjected to reduction, etc. Catalyst pellets result with a thin porous outer layer that is catalytically active. Coated catalysts are particularly attractive when the catalytic material is both expensive and very active (e.g., noble metal catalysts). 

Hydrated iron group metal salts supported on porous carriers after drying acid calcination modified with organoaluminum compounds are used as catalysts in Huels-UCP- Hexall and Octol processes for propylene oligomerization and propylene-butene co-oligomerization [622-624]. 

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