Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to products which are entirely or largely
made up of hydroxychlorides of aluminium obtained from active alumina.
. Basic inorganic salts of trivalent metals, and more particularly
hydroxychlorides of aluminium of the general formula A12 ~OH)xCl6 X~ are
known to have various applications, especially in the fields of cosmetics, the
treatment of water and mud, and the manufacture of catalyst carriers.
The various previously described methods of preparing aluminium
hydroxychlorides comprise either making hydrochloric acid or aluminium chloride
react with aluminium, or hydrolysing aluminium chloride, or dissolving hydrates
or gels of alumina in aluminium chloride or hydrochloric acid.
Some of these methods have obvious economic drawbacks where metal-
v~ lic aluminium is used, while most of the other methods have technical draw-
, backs. These are due to the variation in the reactivity of the compounds used
as the source of aluminium, which may lead to difficulties in reacting on the
substance and to inconsistency in the properties of the products obtained.
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According to the invention, there is provided a method for pre-
,, paring products consisting essentially of aluminium hydroxychlorides in homo-
r geneous solution in which the aluminium hydroxychlorides have the general for-
mula A12 (OH)xCl6 X~ in which X is a value of 3 to more than 5 but less than
6, comprising reacting activated alumina with an aqueous solution of a com-
pound selected from the group consisting of aluminium chloride, hydrochloric
','~r acid and mixtures thereof at a temperature of 60F to reflux temperature with
vigorous agitation to provide said aluminium hydroxychloride in homogeneous
..~.
~' solution, the activated alumina consisting of the product of the partial de-
hydration of hydrates of alumina in a stream of hot gases to less than 2
. moles combined water and a specific surface area of at least 200 m2/g.
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complex products consisting chiefly of aluminium hydrochlorides
may be obtained by adding, to the partially dehydrated alumina,
compounds which will provide other anionic, e.g. polyvalent
radicals and various other metals, such as alkali and/or alka-
line earth metals. Moreover, these more complex products can
also be obtained by adding the desired compounds to previously ~-
prepared aluminium hydroxychlorides.
Products obtained by partially dehydrating hydrates
of alumina, and commonly réferred to as active aluminas, are
known to be used very widelyO particularly in adsorption and
in catalysis. It has now been found that this activity, due to
the specific sur~ace area which may be several hundreds of m2/g,
enables the aluminas to be dissolved gradually and evenly in
solutions of hydrochloric acid and/or aluminium chloride without
the same disadvantages as are encountered with hydrates of alum-
ina, even if freshly prepared; these drawbacks often consist of
the fact that gelled products are obtained, and clear solutions
of hydroxychlorides can be separated from them only with diffi-
culty.
The previously used term "aluminium chloride" naturally
covers various soluble compositions containing chlorine and
aluminium, where the ratio of aluminium to chlorine can thus be
varied by reaction on the active alumina; the term "aluminium
chloride" particularly includes hydroxychlorides of aluminium
already obtained from active aluminas.
Active aluminas, according to the invention, may have
a specific surface area which varies within broad limits but
which must preferably be fairly high if fairly large X values
are desired. ~oreover, the aluminas may be used as appropriate,
3 either in powder form or in the form of agglomerated granulaF
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substancesO The use of the latter may e.g. make the aluminas
easier to react on by improving the circulation o~ liquids be-
tween the granules; this is particularly important for large
scale manufacture by continuous processes.
Active aluminas, which are particularly suitable, can
be ob~ained by partially dehydrating hydrargillite, particularly
:,,
by dehydrating the hydrargillite obtained in large quantities by
the Bayer process, and by dehydrating various alumina gels The
æpecific surface areas of the active aluminas thus obtained may
vary widely, ~ut for the method of the invention should prefer-
ably be over 200 to 250 m2/g and even over 350 m2/g when the
active aluminas are made from gels. Such aluminas are in powder
form and can be used in the method of the invention either with-
out further treatment or after being crushed to adjust the dis-
tribution of grain sizes, or in the form of agglomerated sub-
stances, particularly pellets obtained from a rotary granulator.
~, The reactivity of the active aluminas is such that the
;~ temperature of the reaction medium may rise spontaneously and
-i' will then encourage the aluminas to dissolve in the solutions
of hydrochloric acid and/or aluminium chloride. However, it is
sometimes advisable to heat the solutions somewhat, e.g. to
` temperatures of about 60 to 90C, and under these conditions,
the temperature may rise to over 100C when the alumina has been
added.
The temperature rise is also particularly helpful in
dissolving preliminary compounds which provide other anionic
radicals and other metals, when the intention is to obtain more
complex products than hydroxychlorides of aluminium. In such
cases it may be more advantageous to carry out the reactions in
3 an autoclave, which will further facilitate the dissolving of
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the various substances. The dissolving process is not completed in one
operation, and the non-dissolved pOTtiOn of the active alumina may be
brought back into contact with a reacting solution with fresh active
alumina added to it, and so on until all the alumina involved has been
dissolved.
,~ According to the various operating conditions, it is possible
to obtain aluminium hydroxychlorides in which X has variable values, which
may more particularly be from 3 to 4, when the aim is to obtain products
particularly designed for treating water and mud. Higher X values, which
. 10 may be over 5, are suitable for products designed for the manufacture of
catalyst carriers. -
Finally, the products obtained according to the invention,
which owing to the method of manufacture usually consist initially of solu-
tions of various concentrations containing from 100 to 250 grams of alumina
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" A1203 per litre, may equally be put into the form of solid, powdered or
granular products, obtained by known methods such as spraying.
Non-restrictive examples will now be given of the preparation
of aluminium hydroxychlorides of various compositions, using active alu-
; minas obtained from hydrargillite and from gel treated in streams of hot
gases, the aluminas having various specific surface areas and being in
powder form. An example is also given in which S04 ions are added to the
` reacting solution and finally, by way of comparison, an experiment is de-
- scribed in which aluminium hydroxychloride is prepared by hydrochloric re-
action on non-activated alumina gel.
EXAMPLE 1
Hydrargillite obtain by the BAYER process is partially de-
hydrated in a stream of hot gases, to give an active
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alumina with a specific surface area of 312 m2/g. The alumina
is in the form of a powder with the following distribution of
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graln slzes:
grains < 90~ 84% by weight
grains < 58~ 50% by weight
grains < 29,u 16% by weight
430 g of the alumina is stirred into a solution,
heated to 85C, of 420 ml of 36% hydrochloric acid in 800 ml of
water, the addition of the alumina taking thirty minutes. The
temperature rises spontaneously to 103C. Agitation of the sus-
pension ana reflux are maintained at this temperature for 16
hours. Then heating and agitation are terminated, the excess
alumina is decanted and the liquid above it drawn off and cen-
trifugedO This gives 0.80 litre of a 10186 dense solution of
aluminium hydroxychloride with an X value of 3.93.
The excess alumina is put back into suspension in 800
ml of water and heated to 85C. 420 ml of 36% hydrochloric acid
is added and the temperature rises to 103C. Reflux is main-
tained for 2 hours at this temperature. 225 g of the same ac-
~ 20 tive alumina is stirred in, in the course of 5 minutes, and
- agitation and reflux are continued at this temperature for 22
hours. In the same way as before~ the excess alumina is s9par-
ated from the liquid, which has a volume of 1.05 litre and a
density of 1.18. The value of X is 3.53.
EX~MPLE 2
A powdered active alumina is again prepared from hydrar-
gillite emanating from the BAyER process, by partial dehydration
in a stream of hot gases but under less severe thermal conditions
than those used to obtain the active alumina in the previous
3 example. m is alumina has a specific surface area of 285 m2/g
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and the following distribution of grain sizes:
grains ~ 90~ 84% by weight
grains < 60~ 50% by weight
grains < 25,u 16% by weight
248 kg of the alumina is stirred at 60 kg/h into a -
reactor which is heated to 80C and which contains a solution
made up of 300 litres of water and 300 kg of 36% hydrochloric
acid. m e temperature rises spontaneously to 105C. Reflux `
and agitation are maintained for 10 hours at that temperature.
400 litres of a solution of aluminium hydroxychloride is separ-
ated from the remaining alumina in the same way as in the pre-
vious examples. m e solution has a density of 1.303 and an X
value of 3,5~.
e undissolved alumina, thus recovered, is put back
into suspension in 300 litres of water and heated to 85C, and
250 litres of 36% hydrochloric acid is added. The temperature
rises to 104C. After the reflux action has been maintained
for 2 hours, 120 kg of the same active alumina is added in the
course of 2 hours. Agitation and reflux are maintained at that
temperature for 15 hours, after which the undissolved alumina
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is separated from 530 litres of a solution of aluminium hydroxy-
- chloride with a density of 1.270 and an X value of 3.54.
EXAMPLE 3
Active alumina with a specific surface area of about
-25 300 m2/g, obtained as indicated in example 1, is calcined to
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' reduce that area to 101 m2/g.
430 g of the alumina is introduced with agitation in
the course of 10 minutes into a solution comprising 700 ml of
water and 420 ml of 36% hydrochloric acid, heated to 90C.
3 The temperature rises spontaneously to 103C. Reflux and
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agitation are maintained at that temperature for 22 hours. In
the same way as in the previous examples, the undissolved
alumina is then separated from 0.7 litre of a solution of
aluminium hydroxychloride with a density of 1.150 and an X
; 5 value of 1.58.
If the results of these first three examples are com-
pared one can see the effect of the specific surface area of
the active aluminas used on the X values of the solutions of
aluminium hydroxychloride obtained. In addition, examples 1
and 2 show that the aluminas can be totally dissolved by re-
using the insoluble portions in a fresh orieration, and that this
does not appreciably affect the value of X.
EXAMPLE 4
This example concerns the dissolving of active alumina
; 15 in aluminium chloride. 126 g of the same active alumina as was
used in example 2 is stirred, in the course of 60 minutes, into
a reactor heated to 80C and containing a solution of 216 g of
anhydrous aluminium chloride AlC13 in 800 ml of water. The
temperature rises to 103C. Heating under reflux is maintaine~
for 15 hours. By the same method as before, 0~8 litre of a
solution of aluminium hydroxychloride is separated from the
undissolved alumina. The solution has a density of 1.235 with an
X value of 3.15. This example shows the great reactivity of
; active aluminas, even in relation to aluminium chloride in solu-
tion, and the possibility of thus obtaining aluminium hydroxy-
chlorides with large X values.
EXAMPLE 5
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is example concerns a method of obtaining complex
products by reaction with a mixture of HCl and H2SO4.
The reacting ll~uor is made up of 1526 ml of water,
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14 ml of concentrated sulphuric acid and 374 ml of 36% hydro- -
chloric acid. This solution is heated to 75C and 414 g of the
alumina of example 1 is introduced with stirring over 40 minutes.
m e temperature rises to 102C. ~gitation, heating and reflux
'~ 5 are maintained for 20 hours, then the undissolved alumina is
separated, as indicated above, from 0.58 litre of a solution
of aluminium hydroxychloride. The solution has a density of
1.270, contains 10.1 g/litre of SO4 and has an X value of 3.51.
EX~MPLE 6
i
A substantially amorphous alumina gel is obtained by
neutralising sodium aluminate with nitric acid at pH 8.5, while
keeping the temperature below 35C. The freshly precipitated
gel is agitated for 2 hoursO It is then filtered, washed and
sprayed to reduce it to finely divided form and dried while keep-
ing it in an amorphous state. It is activated by treatment in a
stream of hot gases. The resulting alumina is in the form of a
white powder with a specific surface area of 374 m2/g; it loses
10% by weight when heated to 1200C. Its x-ray diffraction
diagram indicates an amorphous appearance with some traces of
pseudoboehmite.
m e following are placed in an agitated 2 litre glass
reactor:
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-0.333 litre of a 36% solution of HCl
-0.500 litre of purified water (eau permutée).
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m is is all brought to reflux and 430 g of the alumina
$; obtained as indicated abo~e is added in the course of 30 minutes.
After reacting for 7 hours at boiling point (100-101C) the reac-
tion medium is cooled and a solution of the following formula is
decanted:
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A1203 : 376g/1
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Cl 2 : 131 . 3 g/l
d : 1.40
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pH : 2.7
m e empirical formula of the aluminium hydroxychlor-
icle obtained is A12 (OH)5 Cl.
EX~MPLE 7
900 litres of a solution of basic aluminium chloride
of the formula A12 (OH)2 88Cl30l2~ previously obtained by
dissolving active alumina in hydrochloric acid, diluted with
1000 litres of purified water is placed in an agitated reactor
~ and brought to boiling point. m e reactor is made of glazed
i steel with a capacity of 3 m3 and is equipped with a total
reflux condensor. 700 kg of active alumina, having a specific
surface area of 290 m2/g, obtained by partial dehydration of
hydrargillite in a stream of hot gases, is added to the reflux.
All the ingredients are left to react for 18 hours at boiling
temperature. After cooling and decanting, 1500 litres of a
solution of density 1.22 and pH 4.0 is recovered. Each litre
of the solution contains 205 g of alumina A1203 and 74.5 of
chlorine; this substantially corresponds to the formula A12
(OH) 5 ~ 05 Clo 0 95 -
; EX~MPLE 8
' This is a comparative example and concerns the dis-
solving of an alumina gel in aluminium chloride. An alumina
gel is prepared by precipitating a solution of sodium aluminate,
containing 230 g/litre of alumina A12`03, with 58% nitric acid
at pH 8~5 and a temperature of 57Co m e gel obtained is
`` washed, drained and filtered, then left to developO This gives
a product which contains 12~55% by weight of alumina A1203.
1000 ml of a solution containing 167 g of aluminium chloride
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is heated to boiling point in a reactor and 1 ~g of the pre-
viously prepared gel is gradually stirred in, The heating and
reflux action are maintained for 15 hours, after which the
liquid obtained is separated as before. It has a density of
1.25 and an X value of 2.74. However, if one tries to continue
the reaction instead of separating the liquid, the alumina swells
and absorbs the liquid and it becomes impossible to separate the
liquid by filtration or centrifuging.
This is an example of the specificity of the behaviour -
of active aluminas, which enable a seriPs of reactions to be
carried out until they are completely dissolved, while at the
same time reaching high X values.
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