DE707152C - Process for the production of alkali hydroxide via alkali ferrite - Google Patents

Description

Process for the production of alkali hydroxide via alkali ferrite Es is known to produce caustic soda and caustic potash by using soda or potash reacts with iron oxide at high temperatures and the resulting alkali ferrite with Water leaches. This creates alkali and the iron oxide is recovered, that can be used again.

In addition to alkali carbonate, alkali nitrate has also been proposed for the same purpose. The use of alkali nitrate, however, is associated with the great disadvantage that nitrogen oxides are released during the reaction, which have to be regenerated at considerable expense.

It has now been found that alkali metal hydroxide can be prepared in a particularly advantageous manner via alkali metal ferrite by reacting alkali metal formate with iron oxide at temperatures above 650 ' and splitting the resulting alkali metal ferrite in a known manner with hot water into alkali metal hydroxide and iron oxide, which is reused.

The use of alkali formates has compared to your known process, which starts from alkali carbonates, the considerable advantage that AlkaJiformiate from the alkali sulphates in a much simpler way by treatment with lime and carbon dioxide can be obtained. The new method thus offers a particularly simple one Possibility of obtaining caustic alkalis from the corresponding alkali sulphates.

Since formates are known to have a reducing effect, it was to be feared that them when heated with Eisenoxvd this will reduce -. What the formation of ferrite would be a hindrance. Surprisingly, it was found that alkali metal formates with iron oxide at temperatures up to; 700 or 8oo 'and above can without a noticeable reduction of the iron oxide occurring.

In the practice of the invention, one can start from pure iron oxide. But you can also use the particularly cheap gravel burns. The reactivity of the iron oxide is relatively low in the first reaction. The formation of ferrite is slow when using fresh iron oxide. The alkali ferrites formed in the first reaction are also difficult to break down, so that the yields of Lange are poor in the first throughput. At the second throughput and the following. however, increasing yields of up to 3 % and above are achieved.

If you want the disadvantages of the first Ums s etming of the L isenoxyds, z. B. Avoid gravel burns with alkali formates, then the gravel burns can first glow with alkali carbonate or alkali metal hydroxide, leach out the glow product and only use the iron oxide obtained in this way for the actual reaction with alkafiformate.

. You can use the iron oxide or gravel burn-off with dry alkali metal formate erice. However, it is advisable to dry the greater part of the alkali metal oxide to add 1 / :; to '/, the required Alkaliformiatinenge but in the form of his hot saturated solution to use. This working method is also used for the pretreatment the gravel burn with alkali carbonate or hydroxide advantageous.

The mixture of iron oxide or gravel burn-off, dry alkali metal formate and hot, saturated alkali metal formate solution is heated to temperatures above 65 °. The most advantageous temperatures are different for each alkali formate. While the ferrite formation is already satisfactory at 700 ° when sodium formate is used, temperatures of 800 ° and above are expediently used for the conversion of potassium formate. About 95 % of the formate used is converted into ferrite, while the rest is converted into alkali carbonate.

The leaching of the alkali ferrite, which contains alkali carbonate, takes place in a known manner with hot water. It is useful to do this in several stages to work. The leaching is advantageously carried out in countercurrent, e.g. B. such that the resulting alkali ferrite with an alkali from previous leaching is treated, the product of this treatment is leached with a dilute alkali solution and the last leaching of the almost completely decomposed alkali ferrite with pure hot water is made. If necessary, the leaching can take place under pressure.

If one works in this way, one obtains an alkali carbonate one Alkali lye and, on evaporation, an alkali hydroxide containing alkali carbonate. this is irrelevant for the majority of the '#' purposes. However, one wants pure To produce allalihvdroxyd, one leaches (read AllJaliferrit with it before its cleavage hot water with cold water. Here only the alkali carbonate goes into solution, while the alkali ferrite remains almost unchanged.

The iron oxide produced during ferrite cleavage can be recovered many times be used.

The new approach offers special advantages for the production of potassium hydroxide, which is known, apart from its production by Clilork-alieleltrolysis, is much more difficult to manufacture than caustic soda.

Example i pyrite cinder is' tes mixed well with 2o0 / his weighting- of potassium carbonate. Then 1/4 of the potash amount already added becomes hot in the form of a. saturated solution was added, the mixture was dried with stirring and then heated to 8ooo for 1 hour. The mass obtained is then leached out. The residue is mixed with 250 ml of its weight of potassium formate, % of which is added in the form of its hot saturated solution. The gene is heated to 800 '# in a rotary kiln. The potassium ferrite obtained, which is only slightly baked together, is leached in known diffusion apparatus in countercurrent and the lye is evaporated.

Example 2 200 kg of linionite are mixed with 35 kg of anhydrous soda, the mixture is worked through briefly with about 151 water and, after drying for a short time, heated to 700 to 750 ° C. for one hour. The 'mass is then leached out and mixed with 35 kg of sodium formate while still moist. The mass is then placed in the rotary kiln; the annealing process and the leaching are carried out as in the example.

Claims (2)

PATENT CLAIMS: i. Process for the production of alkali hydroxide via Alkali ferrite, characterized in that one alkali formate with Iron oxide at temperatures above 65o 'and the resulting alkali ferrite in known Way with hot water splits into alkali hydroxide and iron oxide, which is reused will. 2. The method according to claim i, characterized in that iron oxide is used in the form of gravel burns. 3. The method according to claim 2, characterized in that the gravel burns are first annealed with alkali carbonate or hydroxide, the annealing product is leached and the iron oxide obtained is reacted with alkali metal formate. 4. Process according to claims i to 3, characterized in that 1/5 to 1/4 of the alkali metal used for the reaction with iron oxide or gravel burn or the alkali carbonate used for pretreatment of the gravel burn is added in the form of its hot, saturated solution. 5. Process according to Claims i to 4, characterized in that sodium formate is reacted with iron oxide at about 700 '. 6. Process according to Claims i to 4, characterized in that potassium formate is reacted with iron oxide at about 8oo '. 7. Process according to Claims i to 6, characterized in that the alkali ferrite is leached out with hot water in several stages, expediently in countercurrent, optionally under pressure. 8. The method according to claims i to 7, characterized in that the alkali metal carbonate formed in addition to alkali ferrite is leached from the ferrite with cold water before the cleavage thereof.