DE1567470C3 - Process for the production of basic chlorides of aluminum and / or iron - Google Patents

Description

35

The invention relates to a process for the production of basic chlorides of aluminum and iron by hydrolysis of the corresponding chlorides, which on the dry route to free-flowing powders leads.

The processes known since then for the production of basic chlorides of aluminum are mostly wet Process, according to which acidic aluminum chloride solutions with bases or with metallic Aluminum is neutralized or electrolyzed, using concentration solutions of 15 to 25% aluminum chloride is being worked on. For both reaction and door the evaporation of the proportionate large amounts of water after the reaction has ended, a considerable amount of energy is required because These large amounts of water need to be evaporated in order to door storage and transport a product in dry form.

These disadvantages can be avoided to a certain extent by another known process for producing a basic aluminum chloride by dry means, in that aluminum chloride hexahydrate (AlCl ₃ · 6H ₂ O) is heated at a temperature of 150 to 170 ° C. until the weight loss is approximately 60%, whereupon the heating is stopped. In this "dry process" a crystallized aluminum chloride in powder form is used as the starting material, which immediately results in the desired basic aluminum chloride in dry and ready-to-use powder form even if the water of crystallization and hydrogen chloride are only partially displaced.

However, a disadvantage of the latter process is that crystallized aluminum chloride only from its aqueous solution obtainable as hexahydrate by dissolving the metal or oxide in hydrochloric acid must be crystallized out by evaporation, with consequent still part of the energy expenditure of the wet process is required in this preliminary stage.

The invention was based on the task, a process for the production of basic chlorides of aluminum and / or iron by hydrolysis of the corresponding chlorides to indicate which at The production of basic chlorides from such starting materials is also possible with little energy consumption which arise as residues in industrial processes.

The characteristic of the invention is to be seen in the fact that anhydrous chlorides with water in high State of distribution to be treated at temperatures in the range of the boiling point of water, whereby partially hydrated, basic chlorides and hydrochloric acid can be obtained.

Anhydrous chlorides of aluminum and iron are available in large quantities as waste materials Available, e.g. B. Friedel-Crafts catalysts or chlorination residues, and often have to under financial Expenses associated with technical difficulties are annihilated as these connections react violently with water.

The method according to the invention consists of two sub-steps:

1. Partial hydration (water absorption) of the anhydrous salts at temperatures below 110 ° C and

2. Partial hydrolysis of the partially hydrated products at temperatures above 110 ° C.

The hydrolysis can also be carried out in one stage without previous partial hydration, but with the products have a greater tendency to sublimation and thus the yield is lower, provided that the sublimate is used is not returned to the reaction chamber.

The partial hydration of the anhydrous salts at temperatures below 110 ° C takes place with steam, preferably with superheated steam, or with finely atomized, liquid water. As the raw materials are very hygroscopic and have a strong tendency to clump, this process step becomes expediently carried out in a crushing device, for. B. in a ball mill, a Rotary barrel, which is equipped with scrapers. In the present process, the first stage is carried out Partial hydration of the anhydrous salts expediently at temperatures below 110 ° C., preferably at 70 to 80 ° C, since hydrolysis occurs when higher temperatures are used immediately occurs to a lesser extent, in addition, certain amounts of metal salts from the apparatus be carried out.

The second stage of the partial hydrolysis of those partially hydrated in the first stage at lower temperatures Products are then made at slightly higher temperatures above 110 ° C, preferably at 110 to 130 ° C. These working temperatures turned out to be compared to the temperatures of 150 to 170 ° C in the case of the above known dry processes as essential

: h cheaper, since otherwise larger amounts of metal salts are carried away from the apparatus, which contaminate the hydrochloric acid formed, which can be recovered according to known methods. Furthermore, with the present method it is possible to control water accumulation in terms of quantity in such a way that iß. the molar ratios AlCl ₃ : H ₂ O are about 1: 1.0 s 1: 2.5, whereby, in contrast to the known process, the hexahydrate is not formed and needs to be used for hydrolysis, but a lower one Hydration level is assumed.

By varying the amount of water given in, which is in a high state of dilution, as well as the duration and temperature of hydrolysis, basic chlorides of the most varied gross compositions can be obtained, as can be seen from Example 2 .

The two process steps can be carried out in one of the several reaction vessels. For a continuous mode of operation it proves to be expedient to treat the anhydrous salts in countercurrent with steam.
The process is not only applicable to pure chlorides, but also to chloride mixtures. So inside z. B. the residues resulting from the chlorination of iron-silicon alloys, which 1 essentially consist of an AlCl ₃ - FeCl ₃ mixture B. with a molar ratio of 2: 1, are treated by an on-the-fly method. -Ibei a mixture obtained basic chlorides of iron and aluminum is (s. Table, Experiment 7, wherein iron is in aluminum equivalents converted urde).

The basic chlorides obtained by the process are free-flowing powders that are after basicity with more or less heat development: let it dissolve safely in water. These Settings can be used for all purposes that have been customary since then, especially in the field the wastewater treatment, in which by adding them to the sewage due to the pH shift the Hydroxides are precipitated and causes a significant shortening of the drying time of the sewage sludge will.

example 1

In a ball mill, 200 g of anhydrous aluminum chloride are treated with 54 ml of water, which evaporates within an hour and the resulting steam is ^{superheated to about 150 ° C.} The reaction mixture is kept at a temperature of 70 to 80.degree. C. and then heated to above 110.degree. C. for 1.5 hours.

337 g (= 96.5% of theory) of free-flowing white powder are obtained which have an aluminum content of 23.2% and a chlorine content of 45.6%.

Example 2

Using the same procedure as in Example 1, varying the amount of water added, the hydrolysis time and temperature obtained the following basic chlorides:

Molar ratio hydrolysis Tempe Reaction pro 1 2.0 attempt AlCl ₃ : H ₂ O rature duct 1 1.6 No. duration ("C) Atomic ratio 1 1.5 130 Al: Cl 1 1.3 1: 1.0 (Hours.) 110 1 1.0 1 1: 2.0 1.5 110 1 1.5 2 1: 2.0 1.0 125 1 1.3 3 1: 1.5 1.5 150 4th 1: 2.0 1.5 120 5 1: 2.5 2.0 130 6 ¹ ) ² ) 1: 2.0 1.0 7 ¹ ) 1.0

') FeSi chlorination residue;

_{AlCl 3} : FeCl ₃ molar ratio = 2: 1.
² ) Without previous hydration.

Claims (5)

Patent claims: 1. Process for the production of basic chlorides of aluminum and / or iron by hydrolysis the corresponding chlorides, characterized in that the anhydrous chlorides in a first stage with steam or superheated steam or finely atomize Water can be partially hydrated at temperatures below 110 ° C, especially at about 70 to 80 ° C and then the further hydrolysis in a second stage at temperatures above 110 ° C, in particular at 120 to 130 ° C, made will. 2. The method according to claim 1, characterized in that the anhydrous chlorides are hydrated up to a molar ratio AlCl ₃ : H ₂ O of about 1: 1.0 to 1: 2.5. 3. Process according to Claims 1 and 2, characterized in that the partial hydration and / or the hydrolysis of the partially hydrated product in devices with a comminution effect is made. 4. Process according to claims 1 to 3, characterized in that the anhydrous chloride is treated in countercurrent with steam or with atomized water. 5. Process according to claims 1 to 4, characterized in that the partial hydration of the anhydrous chloride and the hydrolysis of the partially hydrated product in a rotary kiln with different temperature zones.