Improvements in the Manufacture of Hydrate of Alumina from Silicates of Alumina or Clay.
Year: 1890

page_text: Date of Application, 8th Sept., 1890
Complete Specification Left, 16'h Apr., 1891-Accepted, 5th Sept., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Hydrate of Alumina from
Silicates of Alumina or Clay.
1, Exxo MEYER, Doctor of Philosophy and Chemist, of No. 10 Tieckstrasse,
Berlin, Prussia, do hereby declare the nature of this invention to be as follows:-
This invention relates to the manufacture of hydrate of alumina and concerns a
process which enables this product to be directly obtained from silicates of alumina
(combined or not with iron or ferro-silicates) or clay.
The process is based on the heretofore unknown property possessed by super
heated steam of exerting a decomposing action upon silicates of alumina (inclusive
of those combined with iron or ferro-silicates) or clay in such a manner that the
metallic oxides (such as alumina, oxide of iron, lime and alkalies) which they
contain, become converted with separation of the silicic acid into water-soluble
hydrates. The superheated steam acts upon the materials which must be in a
state of division with equal effect whether the said materials are in a dry or in a
wet condition.
The new process consists in bringing steam which has been superheated, pre-
ferably by means of red-hot iron surfaces into intimate contact with finely divided
silicate of alumina (combined or not with iron or ferro silicates) or clay, dissolving
the hydrates formed and obtaining the hydrate of alumina therefrom by precipi-
tation. When the materials have been suspended in water before being acted
upon the dissolution readily takes place and may be accelerated by adding a small
quantity of pure hydrochloric acid. When the materials have been heated in a
dry condition (in which case they must have been spread out so as to expose a
large surface for instance by spreading them in thin layers, mixing them with
inert materials, or moulding them in porous blocks the decomposed mass must be
leached with water. In both cases the silicic acid remains undissolved. After
separating the solution from the residue and acidulating with hydrochloric acid the
hydrate of alumina is precipitated in the known manner by means of ammonia and
then washed and dried. When iron is present in the materials the precipitation of
the iron from the solution obtained is prevented by the addition of suitable
reducing agents before proceeding with the precipitation of the alumina hydrate.
By operating as hercinbefore described an almost quantative yield of very pure
hydrate of alumina is obtained.
Dated the 8th den of Santamber 1800
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Hydrate of Alumina from
Silicates of Alumina or Clay.
I, ENNO MEYER, Doctor of Philosophy and Chemist, of No. 10, Tieck-strasse,
Berlin, Prussia, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
My invention relates to the manufacture of hydrate of alumina, and it consists
in a process for producing this substance directly from silicates of alumina or from

page_text: compounds or mixtures thereof with other silicates and with oxides of metal, for
instance from clay.
The new process is based on the property heretofore unknown, which is possessed
by superheated steam, that, when it is caused to act on silicates of alumina, it
decomposes them into silicic acid and oxide of aluminium, while simultaneously the
latter is converted into a hydrate soluble in water. This reaction of the superheated
steam also takes place if the silicate of alumina is mixed or combined with other
silicates and with metallic oxides, as is the case in clay, the said other silicates
being decomposed in the same manner, and the oxides resulting from this decom-
position or present in free state, such as oxide of iron and lime, being likewise
transformed into soluble hydrates, while the silicic acid remains insoluble. The
materials, which must be in a state of division, are acted upon by the superheated
steam with equal effect whether they are in wet or in dry condition. If they are to
be treated in wet condition, the mole of proceeding is as follows.
The silicate of alumina or the compound silicate is ground or otherwise divided
iuto fine powder; or, as may be done with clay, the finely divided portion is
separated out by washing. The substance thus obtained is distributed in a suitable
vessel in water which is, with advantage, kept hot during the whole operation.
Thereupon steam is passed through red-hot pipes, preferably of iron, and the
superheated steam this produced, is conducted to the bottom of the said vessel,
for instance through a perforated flat serpentine arranged therein.
The steam bubbling up through the mixture of water and silicates speedily
decomposes the latter and brings about the formation of soluble hydrates, which
dissolve in the water. The process may be promoted by the addition of a small
quantity of purified hydrochloric acid, say 5 cubic centimeters of the acid to
100 grammes of clay. The solution obtained is decanted from the silicic acid,
which remains undissolved, and is filtered. The filtrate, which if desired, may ho
concentrated by evaporation, is thereupon treated in known manner by acidulating
with hydrochloric acid (provided the same does not already contain such acid) and
adding ammonia, in view of precipitating the hydrate of alumina, which is then
filtered repeatedly washed and dried. If the raw material contains iron, the
precipitation of the same is prevented as known, by the addition of suitable
reducing agents, such as sulphuretted hydrogen or sulphurous acid, before pro-
ceeding with the precipitation of the alumina hydrate. Almost the whole amount
of hydrate of alumina contained in the raw material is thus obtained in nearly
pure state.
Its chemical constitution corresponds to the formula Al (OH)³,
For the purpose of producing highly concentrated solutions, the solution obtained
by the first decomposing process may be used instead of water for distributing
another quantity of raw material therein, and so on, until the desired degree of
concentration has been attained.
If the pulverized material is to be decomposed while being in dry state, this
may be done as follows. The material is brought into a vessel, preferably of iron
and adapted to be heated to a red heat. It is spread out therein in thin layers, or
it is previously mixed with inert materials or formed into porous blocks, so that the
steam may have free access to all portions of the saine, the said vessel being by
preference so arranged and the material placed therein in such position that a free
space remains, into which the steam is admitted and where its superheating may
take place. After the vessel has been raised to the temperature required, the
steam is introduced, which then becomes superheated in contact with the hot walls
of the vessel and operates to bring about the desired decomposition and conversion
of the oxides into hydrates. The latter are subsequently extracted by means of
water, the silicic acid remaining behind, and from the solution obtained the hydrate
of alumina is produced as in the first case.
1 prefer, however, to employ the first-described method, because the same has
the advantage that a greater surface of contact of the materials with the steam is
attained, and that the apparatus required is more simple and convenient.

page_text: Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what I
claim is :-
;-
The process which consists in exposing silicates of alumina to the action of
superheated steam for the purpose of decomposing the same and producing soluble
hydrate of alumina, substantially as described.
בד
1
P
11081
J. H. JOHNSON & Co.,
Agents.