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Activated Alumina: Aluminium Trihydrate Heated at 350 °C While Hot Air Carries the Steam Away (Derr, Alcoa, US 2,015,593)
Heating aluminium trihydrate drives out its water and leaves a porous alumina that soaks up moisture. Alcoa's Derr found it works much better when the steam is carried away at once, by a stream of hot air or by a vacuum, instead of lingering in the bed.
Result: activated alumina that takes up 14 % of its weight in water from air (8 % made the old way), up to 16 % if washed first in 3 % sulphuric acid.
Source: Derr, US 2,015,593 (Alcoa, 1935). Not given: times, bed depth, air rate, amounts. Picture drawn by Youblob.
Intermediate
1 day
Instructions
1
1
Wash the trihydrate in 3 % sulphuric acid
Wash the trihydrate in 3 % sulphuric acid
Before heating, wash the aluminium trihydrate in water containing about 3 % by weight of sulphuric acid. Derr calls this very desirable but not essential: it raises the capacity by about 1-2 %. Ours: stir in a beaker.
Materials for this step:
Aluminium Hydroxide1 as requiredTools needed:
Dilute Sulfuric Acid
Water
Borosilicate Beaker
Glass Stirring Rod2
2
Lay it in beds in a chamber
Lay it in beds in a chamber
Put the material in beds or layers in a chamber that gas can be drawn through. Ours: a tube furnace.
Tools needed:
Tube Furnace3
3
Draw air at 350 °C through the bed
Draw air at 350 °C through the bed
Draw air (or combustion gas) heated to about 350 °C through the bed and out of the chamber in a continuous flow, so the steam leaves at once. Temperature: 250-800 °C works, 350-400 °C is best; above 800 °C the alumina changes and loses capacity.
Tools needed:
Air Blower
Pyrometer4
4
Or heat it under a partial vacuum
Or heat it under a partial vacuum
Instead of hot air, close the chamber, keep a partial vacuum in it and heat above 250 °C and below 800 °C; 300-400 °C on a large scale. The steam passes quickly out of the chamber.
Tools needed:
Vacuum PumpPyrometer5
5
Keep it dry
Keep it dry
The product takes up about 14 % of its weight of water from air, 16 % if acid-washed. Ours: store it in an airtight container until use.
Tools needed:
Airtight Storage ContainersMaterials
1- 1 as requiredPlaceholder
Tools Required
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