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.

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التعليمات

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.

المواد لهذه الخطوة:

هيدروكسيد الألومنيوم1 as required

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حمض الكبريتيك المخفّف

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كأس زجاج بوروسيليكاتي

قضيب تحريك زجاجي

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.

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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.

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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.

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