Activated Alumina Pellets With Improved Catalytic Activity

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Activated alumina is a widely used adsorbent in water treatment and catalytic process applications for a variety of reactions. It is also used as a desiccant to dry out air. Unlike traditional activated alumina that is made by dehydrating aluminatrihydrate to a combined water content of 8 to 10 per cent and then pilling and calcining, alumina pellets are manufactured in a new process that produces a much more highly porous material with improved properties and increased catalytic activity.

In one embodiment, partially dehydrated alumina trihydrate received from the Aluminum Company of America was heated in a gas-fired rotary kiln under conditions controlled to produce a material that, when ignited to constant weight at about 2200 F., undergoes a weight loss of between 20 and 26 per cent. The partial dehydration procedure may vary in specific embodiments, but the chief control criterion is that the material retains at least 20 per cent of the combined water upon ignition.

Pelleting and Calcining

In a preferred embodiment, the partially dehydrated material is ground to a size of 40 to 100 mesh. It is then sprayed with an organic compound or lubricant and compressed into pellets of the usual size and shape.

The pellets are then calcined under conditions such that the residual combined water is removed. The temperature used is preferably 900 to 1200 F., but in exceptional cases a higher temperature may be employed.

As a result of the improved catalytic properties of pelleted alumina prepared in accordance with the principles of this invention, it is possible to employ the material as a catalyst support or ingredient with improved results. As a catalyst support, the material can be admixed with any catalytic material such as chromic oxide and/or magnesia or other promoters which form upon calcination.