IT8368104A1 - MANUFACTURING PROCESS OF BASIC ALUMINUM CHLOROSULPHATES - Google Patents

Description

DOCUMENTATION

BOUND

The present invention relates to a process for the preparation of basic aluminum salts corresponding to the general formula:

?I??n (OH)3n-m.-2?p cim (SO4)p ?jz

where the basicity of aluminum chlorosulfate, defined

3n-m-2p

from the ratio ? -- , and between 40 and 70?.

3n

These products are generally aqueous solutions

having a concentration of 1 to 35 moles of alumina per liter,

but they can also appear in a more or less solid form

hydrated, containing more than 30% by weight of soluble alumina.

These basic aluminum chlorosulfates find

application particularly for water purification.

It has been proposed to prepare chlorosulfates

aluminum bases, operating as follows: 1'hydrargillite

It is attacked by a mixture of hydrochloric acid

and sulfuric acid and neutral chlorosulfate is brought to the desired basicity by partial neutralization.

and consolidated by means of carbonate, hydroxide or alkaline bicarbonate (FR 2.036.685); this type of process

It actually allows you to prepare the most suitable compounds, but it has the drawback of giving as a by-product

a non-negligible quantity of alkaline earth sulfate,

for example calcium, which raises pollution problems

chin.

There are other variations of the above procedure, in which the chloride ion is provided by calcium chloride.

and not in the form of hydrochloric acid (FR 2.281.895): the

the effluent problem is still amplified.

For this reason, an attempt has been made to overcome this drawback of the prior art by performing the

basification stage in a different way: chlorosulfate

or aluminum chloride is treated with metallic aluminum powder. This process, in addition to the disadvantage

economical from the use of aluminum powder,

does not allow to obtain basic salts having the structure

polymer required for water treatment.

Finally, a process has been proposed which carries out the basification by bringing under pressure and at a

temperature of 170?C a mixture of aluminum chloride,

of aluminum hydroxide and sulfuric acid, recycling

possibly the excess products that have not reacted & JACOBACCITANI CASET PERA -(FR 2.125.337). This way of proceeding is close to the

already known basification technique, consisting in attacking an excess of hydrargillite with hydrochloric acid, this reaction being carried out equally

under pressure to accelerate its kinetics (FR 2.174.114).

This way of proceeding requires the addition of acid

sulfuric before the basification phase, to obtain

a basic chlorosulfate with better efficacy in water treatment than a similar salt, basified in the absence of sulfuric acid.

Now, quite unexpectedly, it has been found

in the Applicant's laboratories which is possible to prepare

a basic aluminum chlorosulfate having characteristics

equally good for water treatment, carrying out the basification stage under pressure in the absence

of sulfuric acid, contrary to what they left

assume the prior art data.

It was surprising to find that after having

dissolved aluminum hydroxide in a concentrated solution of aluminum chloride under pressure,

can the reaction mixture be stabilized, i.e. maintained

in solution basic aluminum chloride, by adding a more dilute solution of aluminum sulfate

slightly basic; to carry out this stabilization,

we proceed in the following way: after having brought the solution JCAOBCCI & PENIA CSETTRAAA - supersaturated with basic aluminium chloride - back to its boiling point at atmospheric pressure, we add

a freshly prepared solution of aluminum sulfate

basic obtained by attacking an excess of hydroxide

of aluminum with sulfuric acid at atmospheric pressure, eoo

fjr

this last solution being at a temperature equal to * te ' L

(ti ?-as close as possible to that of the basic chloride.

The present invention therefore provides a process for the manufacture of basic aluminum chlorosulfate corresponding to the general formula:

DO YOU (DH)? (I)

L n 3n-m-2 ?p ci m (so 4 ) p?j z

in which:

3n^m-2p

- - and between 0.4 and 0.7,

3n

- p ? between 0.4 and 0.25 n and

- m/p ? between 8 and 35, z being ^ 1

which consists in reacting basic aluminum chloride

with basic aluminum sulphate, previously brought

a. cd j hot, at a temperature between 80 and 120*0. The

?:* reaction ? rapid: the duration of the reaction ? usually c?*

5* G

between a few minutes and an hour. or 8<t The relative proportions of the constituents are determined in such a way as to obtain a product having the above-mentioned

formula (I).

The basic aluminum chloride can be used according to

The present invention can be achieved by any suitable means. It can be achieved, in particular, in the following known manner: reacting

hydrochloric acid with alumina in proportions such as to obtain, after reaction, a solution of vici aluminum chloride

to supersaturation, this solution is then made to react

with aluminum hydroxide in excess of 10 to 150? compared

to the theoretical quantity necessary for the desired basicity,

in a stirred medium, for a maximum duration of 5 hours, at a

temperature of 140-165?C under a pressure of 0.5 to 3

bar..

Basic aluminum sulfate can be used according to

The present invention may be prepared by any suitable means. In particular, it may be prepared in the following manner known to itself: to a solution

of sulfuric acid aluminum hydroxide is added in

10 to 100% excess over the stoichiometry of neutral sulfate, the resulting suspension is heated and kept at boiling point for 15 to 30 minutes.

? In more detail, the execution of the

process, which can be continuous or discontinuous, can

take place as follows: in a stirred reactor

introduces hydrochloric acid having a weight concentration equal to or greater than 30%, and preferably 33%, as well as

aluminum hydroxide (e.g. hydrargillite) in proportions such as to obtain, after reaction, a solution of

aluminum chloride which is close to saturation; yes

then transfers the solution, which may contain hydroxide

of aluminum in suspension if the previous reaction is?

was carried out with an excess of this reagent, in

a pressure-resistant reactor, into which aluminum hydroxide is also introduced so as to have

an excess of 10 to 150% and preferably 70 to 120% over the theoretical amount required for the desired basicity.

The reaction medium, subjected to stirring, is brought to a maximum period of 5 hours, but preferably 2

3 hours depending on the fineness of the hydroxide used,

a temperature of 140-165?C and under a pressure of 0.5

at 3 bar; these operating conditions allow to obtain

the maximum dissolution of aluminum hydroxide.

The reaction mixture is then brought back to pressure

atmospheric, the temperature then being 120-125?C depending on the initial chloride concentrations, the degree of dissolution of the hydroxide and the water content of the latter. LU CO

a Simultaneously with the basification of the QCJ 8 aluminium chloride, the synthesis of aluminium sulphate is carried out.

basic nium, intended to stabilize the basic chloride.

Hydroxide is added to a solution of sulfuric acid

of aluminum in excess of 10 to 100% and preferably 30

at 70% of the stoichiometry of neutral sulfate and

the resulting suspension is heated, then kept at boiling point for 15 to 30 minutes; this duration varies, depending on the fineness of the hydroxide used. After

dilution with water to thin the reaction medium,

this slightly basic aluminum sulfate, whose

temperature? then between 70 and 100?C, it is poured

s.

in basic aluminum chloride whose temperature is?

120-125?C, in proportions such that the chlorosulfate obtained

corresponds to the general formula:

At the CI

n (OH)3n-m-2p m '?.',1 i

in which n, m, p have the above meanings and z

? 1.

In order to ensure maximum dissolution

of aluminum hydroxide in chloride solution

of aluminum, it is necessary to add an excess of approximately

100%, in one or more times, the smaller granules

at 30 microns, contributing preferentially, by dissolving, to basify the reaction medium. The unreacted aluminum hydroxide is recovered at the time of

filtration, which provides the final solution of basic chlorosulfate; depending on the excess used, its quantity

It may be sufficient to prepare a new solution & PE JARNIC0BACC1 CATASETA -

of aluminum chloride, the complement being assured

from^ new hydroxide. This solution is then made basic by adding new hydroxide in excess, in a

or more times.

This excess amount can vary between .10 and

150% and preferably 70 and 120%, depending on the reactivity and

the humidity of the hydroxide. In fact, a very humid hydroxide *9*

fo?IH? added in too large excess leads to a dilution of the aluminum chloride solution and a reduction

of its boiling point, therefore of attack,

which must then be compensated for by increasing the pressure of the agitated autoclave.

After stabilization of the basic chloride by

the sulfate solution, the basic chlorosulfate is diluted, cooled, filtered to remove the hydroxide in

excess according to procedures known to the technician.

The aluminum hydroxide used in the process

according to the invention it can have different origins, it can

be a freshly prepared hydroxide, but will it be used?

preferably, for economic reasons, hydrargillite from the Bayer alumina extraction process

starting from bauxite, in the wet state (water content

of the order of 35?) or in the dry state. According to the tenors

acceptable levels of impurities, it is also possible to use an alumina mineral, such as bauxite, directly or after prior calcination.

The following examples illustrate the invention, without

limit it.

EXAMPLE 1

550 g of acid are poured into a stirred reactor

40% hydrochloric acid (density 1.190) on 162 g of alumina

wet hydrate containing 62.3% Al^O^. After braking

The reaction is conducted using a suitable heating-cooling device to maintain the temperature at 40-60°C. The mixture is gradually heated to 105°C, then 324 g of moist hydrated alumina are added. Continuing heating, the mixture reaches boiling point at 123°C at atmospheric pressure. The reactor is then placed under an air pressure of 1.2 bar, and boiling is reestablished when the reactor temperature reaches 147°C. The heating is moderated to maintain the initial boiling point for 3 hours. Despite the excess hydrated alumina used, the suspension does not thicken, which would be due to precipitation of basic chloride. The heating is stopped, the pressure is slowly reduced to atmospheric pressure, and a hot (about 30-90°C) basic sulfate solution is poured in, stirring. The solution is prepared as follows: 91 g of 70% sulfuric acid is poured into 55 g of hydrated alumina. Bring to a boil for 15 minutes, stirring constantly. 30 g of cold water is added, followed by 220 g of hot water for dilution.

The contents of the 1-liter reactor are transferred to a 2-liter vessel and stirred. 700 g of water at 40°C is then poured in, stirred for 15 minutes to cool to 40°C, and the suspension is filtered. In less than 12 minutes, 1895 g of solution with a density of 1.225 at 20°C is collected, which is diluted with 136 g of water to bring the density back to 1.206. The solid residue weighs 207 g, contains 57% Al 0 and 2.0% chlorine ion. It is essentially composed of

2 3

of excess alumina and soaking solution.

The solution of density 1.206 contains 10.0% of

gold ion, 10.5% alumina and 3.0% total sulfate ion.

EXAMPLE 2

In 550 g of 40% hydrochloric acid, pour

184 g of the previous residue to make the solution

of aluminum chloride, then basify as previously with 324 g of moist hydrated alumina, maintaining for 3

hours to boiling at 146?C under 1.2 bar.

On the other hand, basic sulfate is prepared

with the remaining residue to which 43 g of

hydrated alumina. After boiling, dilute with 30 g.

of cold water and 220 g of water brought to 90?C, pour

this suspension in the basic chloride solution, which

It is then diluted with 830 g of water at 40?C. The filtration

produces 200 g of residue containing 57.7% Al^O^ with JCOBCI CS & PAETTAERANIACA -1.93% chlorine ion and 2050 g of solution of density 1.213,

which is brought back to a density equal to 1.206 with 58

g of water. The 2108 g of final solution contains 9.95%

of chlorine ion, 10.6% of Al 0 and 3.0% of SO? ion.

2 3 4

As can be seen, we are reaching a point of consumption

complete with alumina while producing basic aluminum chlorosulfate solutions, while in certain processes

neutralization with lime or calcium carbonate, the unattached portion at 105?C in an acid medium

hydrochloric sulfuric acid is lost together with the residue

bulky plaster cast.

c<r E

?5

<r

1. Process for the manufacture of chlorosulfate

aluminum base corresponding to the general formula:

iA1 (OH) CI

Jn-m-2p u] (SO ) T

4 PJ 2 ( I )

in which:

? between 0.4 and 0.7

3n

- p ? between 0.04 and 0.25 n and

- m/p ? between 8 and 35, z being ^ 1

which consists in reacting basic aluminium chloride S o. with basic aluminium sulphate, previously brought to a temperature of between 80 and 120?C, the

relative proportions of the constituents being chosen in 2 or CJ < so as to obtain a product corresponding to the following

formula (I).

2. Process according to claim 1, wherein

said basic aluminum chloride is obtained by reacting hydrochloric acid with alumina in such proportions

to obtain, after reaction, a chloride solution

substantially supersaturated aluminum, followed by the reaction

of this solution of aluminum chloride with hydroxide

of aluminum which is found in excess of 10 to 150% of the

to the theoretical quantity necessary for the desired basicity,

in a stirred medium, for a maximum duration of 5 hours, at a

Claims (1)

temperature of 140 to 165?C under a pressure of 0.5 to 3 bar. 3. Process according to one of claims 1 or 2, wherein said basic aluminum sulfate is obtained by reacting sulfuric acid with aluminum hydroxide in excess of 10 to 100% with respect to the stoichiometry of the neutral sulfate, the solution being heated and then kept at boiling point for 15 to 30 minutes. f (H>?> ?(./> Iti J. Giuseppe QUINTERNO I (On his own for the olirli fe??r (?