PURAL and CATAPAL are the trade names given to Sasol’s innovative high-purity alumina hydrate products for use in the chemicals sector.
PURAL and CATAPAL are available as white, free-fl owing powders whose unique combination of purity and controllable physical properties make them excellent starting materials for many products.
This family of alumina hydrates (boehmite, AlOOH, and bayerite, Al(OH)3) has historically been chosen as supports or binders for catalysts in refi nery and chemical processes.
Recent developments in many other applications have demonstrated these unique aluminas have applications in areas far beyond catalysts.
Advantages of PURAL and CATAPAL Alumina Hydrates
Sasol pioneered processes to convert aluminium metal to synthetic alumina hydrates of high-purity.
Unlike other alumina manufacturing processes that start with bauxite derivatives, our processes yield aluminas with significantly lower levels of common impurities such as iron, sodium and silica.
Additionally, our 50 years of alumina manufacturing experience allows us to control and adjust physical properties such as surface area and porosity, particle size, crystal size and shape and peptisation behavior so that our customers are not limited in their thinking for possible uses for the aluminas.
Ultra-high-purity grades (PURAL UHPA) are available upon request.
Processing of PURAL and CATAPAL
The unique ability to adjust the physical properties of the boehmites makes them perfect for a variety of different end use applications requiring different types of processing.
Extrusion behaviour
Extrusion is a key use for these types of alumina hydrates due to their ability to form excellent extruded supports. This application takes advantage of the ability to peptise in the presence of organic / inorganic acids.
A wide variety of extrudate properties can be obtained by using different grades of PURAL and CATAPAL and by controlling the formulation and extrusion variables.
Optimum formulations depend on the exact choice of mixer, extruder and powder properties. General extrusion guidelines can be recommended by our technical staff.
Our unique ability to adjust the peptisation behaviour means that the gelling behaviour of PURAL and CATAPAL can be modified to supply a product optimised for our customers’ own unique set of processing conditions.
Nitric acid gelation time (NAG) is a valuable tool for selecting the right material for your processing conditions.
NAG is the time required for a concentrated dispersion of boehmite to reach a certain viscosity by peptisation.
Calcination
The final crystalline phase and physical properties of calcined aluminas depend on the initial crystalline properties of the starting alumina hydrate as well as the calcination temperature.
Physical properties such as crystalline phase, surface area and porosity can be altered significantly by varying the calcining time and temperature.
Applied temperatures are typically between 600°C and 1,000°C. This process results in the loss of physisorbed and crystal water.
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