JP2014533649A - Ion exchange method - Google Patents

Abstract

The present invention relates to an improved method for exchanging alkali metal or alkaline earth metal ions of a zeolite for ammonium ions. For this exchange, aqueous solutions of ammonium salts such as ammonium sulfate, ammonium nitrate or ammonium chloride are currently used. The resulting “ammonia zeolite” is calcined for modification, releasing ammonia and becoming an H-type zeolite suitable for the catalyst. According to the present invention, ammonium carbonate is used in place of the ammonium compound. Excess ammonium carbonate can be reused in the form of carbon dioxide and ammonia, as opposed to nitrates, sulfates and chlorides, and significantly reduces the amount of salt to be discharged. [Selection] Figure 1

Description

  The present invention relates to an improved process for exchanging alkali metal or alkaline earth metal ions in zeolites for ammonium ions. For this exchange, aqueous solutions of ammonium salts such as ammonium sulfate, ammonium nitrate or ammonium chloride are currently used. The resulting “ammonium zeolite” is calcined to release ammonia and converted to zeolite H form suitable for the catalyst.

  According to the invention, it is proposed to use ammonium carbonate instead of the ammonium compound described above. Excess ammonium carbonate, in contrast to nitrates, sulfates or chlorides, can be reused in the form of carbon dioxide and ammonia, so that the amount of salt to be discharged can be significantly reduced.

  The high demand in the petrochemical field for lower hydrocarbons such as saturated and unsaturated aliphatic, alicyclic or aromatic hydrocarbons is met by modification methods such as catalytic cracking, hydrocracking, thermal cracking. The feedstock used is crude oil or a relatively high boiling crude oil distillate fraction.

  In catalytic cracking, a method using a fluidized bed made of zeolite (FCC method) is considered preferable. Zeolites are used in the H form, which can be produced by heating the corresponding zeolite containing ammonium ions to about 400 ° C. (Hans-Jürgen Alpe, Industrial Organic Chemie [Industrial Organic Chemistry], 6th edition, 2007, Wiley-VCH Publishing, pp. 64-65).

For example, US Pat. No. 3,966,882 discloses the exchange of Na ions and NH ₄ ions, but does not disclose ammonium carbonate.

  U.S. Pat. No. 28,629 and U.S. Pat. No. 4,346,067 disclose methods of using ammonium chloride, ammonium nitrate or ammonium sulfate for ion exchange. U.S. Pat. No. 4,346,067 also discloses the presence of urea apart from the ammonium compound. Tables I and II of Example 1C show that the original amount of Na 9.18-8.17% = 0.61% is still replaced by urea water in the absence of ammonium compound. This can be explained by hydrolysis of urea to ammonium carbonate followed by ion exchange.

  Chinese Patent Application No. 106233650 discloses the use of ammonium carbonate for ion exchange.

  The exchange between an alkali metal or alkaline earth metal ion such as sodium Y zeolite and an ammonium salt such as ammonium nitrate constitutes an equilibrium reaction.

  In order to sufficiently exchange sodium ions to ammonium ions, the zeolite is preferably treated multiple times with excess aqueous ammonium nitrate for sodium ions, preferably at a temperature of 70 ° C. to 100 ° C., and in some cases 200 ° C. or less. There is a need to. After the ion exchange step, the salt solution is usually separated from the zeolite. In order to remove the salt, the solid zeolite is then washed with water. After each ion exchange step, the zeolite is calcined at 200 ° C or higher and 600 ° C or lower. During this time, the release of ammonia forms the desired H-type zeolite (Ullman's Encyclopedia of Industrial Chemistry, 6th edition, 39, 2003, published by Wiley-VCH, pages 638-640).

  As a result of ion exchange and calcination, an H-type Y zeolite and an aqueous salt solution containing a mixture of sodium nitrate and unconverted ammonium nitrate are obtained. Since the replacement of sodium ions by ammonium ions is insufficient, the ammonium compounds are present in the mother liquor along with the sodium compounds.

  The heat release of ammonia and carbon dioxide from an aqueous ammonium carbonate solution is disclosed in WO 2009/036145. For example, FIG. 1 shows that ammonia and water are first released from an ammonium bicarbonate / sodium carbonate mixture, and the remaining sodium bicarbonate is converted to sodium carbonate as the carbon dioxide is released.

  According to Holman-Wieberg, Textbook on Inorganic Chemistry, 102nd edition (2007) Walter de Greater, 671, “Ammonium carbonate”, carbon dioxide by introducing it into aqueous ammonia. It is known that ammonium can be produced.

  An example of the disadvantages of prior art methods are, for example, when ammonium nitrate, ammonium sulfate or ammonium chloride is used for ion exchange of zeolite containing sodium ions, sodium nitrate and ammonium nitrate aqueous solution, sodium sulfate and ammonium sulfate aqueous solution, or A large amount of sodium chloride and ammonium chloride aqueous solution is produced.

US Pat. No. 3,966,882 US Patent Reissue Publication No. 28,629 US Pat. No. 4,346,067 Chinese Patent Application No. 102623650 International Publication No. 2009/036145 Specification

Hans-Jurgen Alpe, Industriale Organic Chemie, 6th edition, 2007, Wiley-VCH Publishing, pp. 64-65 (Ullman's Encyclopedia of Industrial Chemistry, 6th edition, 39, 2003, Wiley-VCH Publishing, 638-640). Holman-Wieberg, Textbook on Inorganic Chemistry, 102nd edition (2007), Walter de Greater, 671

  The salt solution can basically be used for the production of fertilizers. However, this means that the added value is very low. Moreover, the economics of use as a fertilizer depends on the location.

  Ammonia bound in the ammonium salt is released by the addition of at least an equimolar amount of sodium hydroxide solution, removed by stripping or distillation, and reused for the production of the ammonium salt. However, the added value decreases with consumption of sodium hydroxide solution. A large amount of each sodium salt aqueous solution remains there. Without further use, they can only be discarded. The known methods required a high circulation rate with considerable energy requirements, which resulted in economic disadvantages.

  Accordingly, it is an object of the present invention to provide a method that does not suffer from the above disadvantages.

  In particular, the object of the present invention is to regenerate the ammonia present in the salt solution obtained by ion exchange, and optionally additional corresponding counter ions, to increase the economic value.

  According to the present invention, the above object is achieved by a method of exchanging sodium ions in a sodium-containing zeolite with ammonium ions, which has the following steps.

a) treating the sodium-containing zeolite with a solution containing water and ammonium carbonate;
b) separating the zeolite from the solution (mother liquor) containing aqueous sodium carbonate and ammonium carbonate; and
c) heat treating the mother liquor to release ammonia and carbon dioxide.

FIG. 2 shows a preferred embodiment of the method according to the invention.

<Ion exchange>
For ion exchange, natural or synthetic crystalline zeolites containing alkali metal or alkaline earth metal ions are preferred. Sodium, potassium, calcium and magnesium ions are preferred, and sodium ions are particularly preferred.

  In principle, all zeolites containing alkali metal and alkaline earth metal ions are preferred. Preferred zeolites are ZSM type, in particular ZSM-5, and X, Y, A and L zeolites. Other choices are naturally occurring zeolites such as faujasite, chabazite, erionite, mordenite, and offretite (US Pat. No. 4, 346,067, column 1, lines 43-57). In particular, sodium-type Y zeolite is preferred.

  In order to obtain an effective catalytic cracking catalyst, the alkali metal content of the zeolite should be reduced by ion exchange to less than 10% by weight, preferably less than 5% by weight, more preferably less than 1% by weight.

  The solution containing water and ammonium carbonate is preferably made from water and ammonium carbonate, optionally further compounds.

  Further compounds are preferably those which produce ammonium carbonate under the reaction conditions of ion exchange with water.

  Of the further compounds, urea, ammonium carbamate, a mixture of carbon dioxide and ammonia, and mixtures thereof are preferred. In a further form of the invention, these further compounds are used instead of ammonium carbonate.

Ammonium carbonate is used for ion exchange as an aqueous solution having a concentration from 0.1% by mass to the solubility limit, preferably 5% by mass to 35% by mass, more preferably 10% by mass to 25% by mass. It is. Ammonium carbonate is considered to mean (NH ₄ ) ₂ CO ₃ , NH ₄ HCO ₃ and mixtures thereof.

  Instead of ammonium carbonate or a mixture with ammonium carbonate, a compound that forms ammonium carbonate in an aqueous solution under reaction conditions can also be used for ion exchange. Examples are urea and ammonium carbamate.

  Carbon dioxide and ammonia can be dissolved in water, for example in a molar ratio of 1: 2, and they can be reacted with the suspended zeolite.

  For example, the reaction of urea and / or ammonium carbamate with water can occur in a separate reaction step prior to ion exchange. However, it is also possible to carry out the reaction of urea and / or ammonium carbamate and the ion exchange in the same processing step.

In the ion exchange, the temperature is 0 ° C. or higher and 200 ° C. or lower, preferably 20 ° C. or higher and 100 ° C. or lower, more preferably 50 ° C. or higher and 80 ° C. or lower, and the total pressure is 1 × 10 ⁵ Pa or higher and 3 × 10 ⁷ Pa or lower. 300 bar), preferably 1 × 10 ⁵ Pa to 5 × 10 ⁶ Pa (1 to 50 bar), more preferably 1 × 10 ⁵ Pa to 1 × 10 ⁶ Pa (1 to 10 bar).

  The ion exchange can be performed batchwise or continuously.

  The zeolite can be suspended in a stirred aqueous ammonium carbonate solution. However, the zeolite is placed in a fixed bed form, for example in a cylindrical reactor, and the aqueous ammonium carbonate solution is sucked onto the zeolite in the liquid phase or trickle mode and the ammonium carbonate solution is circulated or It can also flow in a straight path.

  In a further preferred embodiment, the zeolite and ammonium carbonate solution is passed through the tube, particularly preferably the solution is made to flow countercurrent to the zeolite.

  In a preferred embodiment, ion exchange is performed with one or more belt filters. The mother liquor from the downstream filter is recycled in countercurrent toward the previous filter.

  In a particularly preferred embodiment, the ion exchange is carried out continuously in countercurrent with a combination of one or more stirred tanks or one or more flow tubes and one or more belt filters.

  The reaction time required for ion exchange is 0.1 second to 10 hours, preferably 1 second to 2 hours, and more preferably 1 second to 1 hour.

<Zeolite removal and calcination>
The zeolite suspended in the aqueous ammonium carbonate solution can be removed, for example, by filtration or centrifugation.

  In order to remove the salt adsorbed on the zeolite, it is washed with water once or more, preferably 1 to 3 times. The amount of water is 1-1000 g / g zeolite.

  Wash water can be combined with the salt solution removed from the zeolite. The calcined zeolite can optionally be advanced to a second ion exchange stage a).

  The cycle sequence of ion exchange, zeolite removal and calcination is optionally repeated until the sodium content of the zeolite drops to the desired value. Usually 1 to 3 cycles, especially 1 to 2 cycles are required for this purpose.

<Heat release of ammonia and carbon dioxide from excess ammonium carbonate aqueous solution (mother liquor)>
The excess ammonium carbonate solution removed from the zeolite after ion exchange further contains sodium carbonate. If the zeolite is washed with water, this solution can also be combined with the wash water.

  The mixture of ammonium carbonate solution, sodium carbonate solution and water is heated to a temperature above 50 ° C, preferably above 60 ° C. In principle, there is no upper limit to the temperature, but a temperature exceeding 100 ° C. requires boosting. Heating can be performed batchwise or continuously. As part of the liquid evaporates, carbon dioxide and possibly ammonia are released.

  In a particularly preferred variant, the mixture is fed continuously to the distillation column. The liquid at the bottom of the column is heated and partially evaporated by the introduction of heat or water vapor. Ammonium carbonate decomposes along the column plate and the ammonia and carbon dioxide formed are extracted from the liquid by the rising vapor (back-extracted, stripped out). At the bottom, a solution is obtained from which the ammonium carbonate has been removed. More preferably, the bottom ammonium carbonate is trace or zero.

  Desirably, heat release occurs with the addition of a base. Preferred bases are alkali metal hydroxides and / or alkaline earth metal hydroxides. These can be added in solid form or as a solution, preferably as an aqueous solution.

  When the base is added as an aqueous solution, a concentration of 0.1% by mass to 50% by mass is preferable, and a concentration of 10% by mass to 50% by mass is particularly preferable. Particularly preferred is an aqueous solution of sodium hydroxide (sodium hydroxide solution) having a concentration of 0.1% by mass or more and 50% by mass or less. In a particularly preferred embodiment, an aqueous sodium hydroxide solution (sodium hydroxide solution) having a concentration of 10% by mass to 50% by mass is used.

<Reuse of ammonia and carbon dioxide>
Carbon dioxide and ammonia obtained as low-boiling substances from the heat treatment can be recombined by cooling for recovery. They are preferably recombined in an aqueous solution. Particular preference is given to concentrating (condensing) and recovering the liquid stream used for the absorption of gaseous carbon dioxide and ammonia by cooling.

  The aqueous ammonium carbonate solution can be reused for ion exchange.

  However, it is also possible to introduce ammonia and carbon dioxide directly into an aqueous ammonium carbonate solution used for ion exchange.

<Discharge of sodium carbonate solution>
The bottom product obtained by the heat treatment is an aqueous sodium carbonate solution discharged in the treatment step (process).

  Sodium carbonate (soda) is one of the most important products in the large-scale chemical industry and is optionally used in place of NaOH. Annual global production is 50 megatons (Holeman-Wieberg, Textbook on Inorganic Chemistry, 102nd edition (2007) Walter de Greater, 1291).

  Thus, the choice of using an aqueous sodium carbonate solution is highly preferred compared to an ammonium nitrate / sodium nitrate, ammonium sulfate / sodium sulfate, or ammonium chloride / sodium chloride aqueous solution.

  FIG. 1 shows a preferred embodiment of the method according to the invention. Sodium-type zeolite is treated with aqueous ammonium carbonate in the ion exchange stage. Thereafter, the treated zeolite and mother liquor are separated by a preferred method such as filtration and dried by any method. The zeolite pretreated in this way is calcined in a furnace to release ammonia. These steps can be performed twice or more continuously. The mother liquor from the removal stage is fed to a column with a stripping section and heated at the bottom by direct addition of an evaporator or steam. The increase in temperature causes ammonia and carbon dioxide to be exhausted in the form of steam, involving water. The vapor-like mixture is condensed in a direct or indirect condenser and ammonia and carbon dioxide combine with water to produce aqueous ammonium carbonate. The ammonium carbonate solution thus obtained is reused in the ion exchange stage. The aqueous sodium carbonate solution is discharged through the bottom of the column. Ammonia from the calcination furnace can optionally be routed along with supplemental ammonia and carbon dioxide upstream of the condenser column.

  The present invention will be described in detail by the following examples and comparative examples, but is not limited thereto.

  The following examples illustrate the sodium exchange of the present invention in zeolite Y using ammonium carbonate. The used zeolite Y has a sodium content of 7.3% by mass and is purchased from Zeolist under the product name CBV100. For Example 9 and Comparative Example 12, USY (X6503, Engelhardt) having a sodium content of 3.1% by mass was used. Chemical analysis of the ammonium carbonate or nitrate used (before zeolite treatment) showed a sodium content of less than 0.01% by weight. Hereinafter, the specified total sodium content was determined in an analog manner by chemical analysis. Prior to the experiment, the zeolite used in each case was calcined at 500 ° C. for 5 hours. XRD analysis of selected samples after completion of treatment showed that the zeolite structure was not impaired after ion exchange.

  The sodium content was determined by flame atomic absorption spectrometry, and the ammonium content was according to the Kjeldahl method. Inorganic carbon was measured as carbon dioxide by a thermal conductivity measurement method after burning the sample with an oxygen stream.

<Ion exchange>
Example 1
100 g of ammonium carbonate was dissolved in 1000 g of water and heated to 80 ° C. 100 g of zeolite was suspended in the solution and heated with stirring for 2 hours. Thereafter, the suspension was filtered. The sodium content of the filtrate increased to 0.4% by weight. The filtered zeolite was reprocessed for 2 hours in an ammonium carbonate solution containing 100 g ammonium carbonate and 1000 g water and heated to 80 ° C. Subsequently, filtration and zeolite washing using 1800 g of water were performed. The subsequent filtrate had a sodium content of 0.1% by mass. The filter cake was dried at 120 ° C. for 4 hours and then calcined at 500 ° C. for 5 hours. The sodium content of the zeolite after calcination was 2.7% by mass.

(Example 2)
The procedure was the same as in Example 1, but the zeolite treatment with ammonium carbonate solution was extended from 2 hours to 14 hours in both rounds. The sodium content of the subsequent zeolite was 2.5% by mass.

Example 3
The procedure was the same as in Example 1, but the zeolite treatment with ammonium carbonate solution was brought to 60 ° C instead of 80 ° C in both rounds. The sodium content of the subsequent zeolite was 2.5% by mass.

(Comparative Example 4)
The procedure was the same as in Examples 1 to 3 except that the zeolite treatment was performed with an ammonium nitrate solution.

  The sodium content of the ammonium nitrate solution after the zeolite treatment was in all cases comparable to the sodium content of the ammonium carbonate solution. The sodium content of the zeolite after treatment with ammonium nitrate was 2.3 to 2.6% by mass.

(Example 5)
50 g of ammonium carbonate was dissolved in 500 g of water and heated to 60 ° C. 50 g of zeolite was suspended in the solution and heated for 2 hours. Thereafter, the suspension was filtered. The sodium content of the filtrate increased from 0.5 to 0.6% by weight. The filtered zeolite was retreated in an ammonium carbonate solution containing 50 g ammonium carbonate and 500 g water and heated to 60 ° C. for 2 hours. This was followed by filtration and washing of the zeolite with 1500 g of water. The subsequent filtrate had a sodium content of 0.1% by mass. The filter cake was dried at 120 ° C. for 4 hours and then calcined at 500 ° C. for 5 hours. The sodium content of the zeolite after calcination was 2.3 to 2.6% by mass.

(Example 6)
The procedure was the same as in Example 5 except that ammonium oxalate was used for the zeolite treatment. The sodium content of the zeolite after calcination was 2.6% by mass.

(Comparative Example 7)
The procedure was the same as Example 5 except that ammonium nitrate was used for the zeolite treatment. The sodium content of the filtrate was 0.5% by mass and 0.1% by mass, respectively. The sodium content of the zeolite after calcination was 2.3% by mass.

(Example 8)
50 g of ammonium carbonate was dissolved in 500 g of water and heated to 60 ° C. 50 g of zeolite was suspended in the solution and heated for 2 hours. Thereafter, the suspension was filtered and washed with 1500 g of water. The sodium content of the filtrate was increased to 0.4% by mass. The filter cake was dried at 120 ° C. for 4 hours and then calcined at 500 ° C. for 5 hours. The calcined powder was reprocessed for 2 hours in an ammonium carbonate solution containing 50 g of ammonium carbonate and 500 g of water and heated to 60 ° C. This was followed by filtration and washing of the zeolite with 1500 g of water. The subsequent filtrate had a sodium content of 0.1% by mass. The filter cake was dried at 120 ° C. for 4 hours and then calcined at 500 ° C. for 5 hours. The sodium content of the zeolite at the end of the treatment was 1.9% by mass.

Example 9
The procedure was the same as in Example 8, but USY (X6503, Engelhardt, sodium content 3.1 mass%) was used. The sodium content of the zeolite after calcination was 1.0% by mass.

(Example 10)
Procedure similar to Example 8, but the zeolite treatment was performed with ammonium oxalate. The sodium content of the filtrate was 0.4% by mass and 0.1% by mass, respectively. The sodium content of the zeolite after calcination was 2.0% by mass.

(Comparative Example 11)
The procedure was similar to Example 8, but the zeolite treatment was performed with ammonium nitrate. The sodium content of the filtrate was 0.4% by mass and 0.1% by mass, respectively. The sodium content of the zeolite at the end of the treatment was 1.4% by mass.

(Comparative Example 12)
USY (X6503, Engelhardt, sodium content 3.1 mass%) was used in the same procedure as Comparative Example 11. The sodium content of the zeolite after calcination was 0.8% by mass.

(Example 13)
15 g of zeolite was suspended in 165 g of ammonia solution (7%). Carbon dioxide 5 × 10 ⁵ Pa (5 bar) was then injected and the mixture was stirred at 60 ° C. for 2 hours. Subsequently, after filtration, it was washed with 1000 ml of water. The sodium content of the filtrate increased to 0.3% by weight. The filter cake was dried at 120 ° C. for 4 hours and then calcined at 500 ° C. for 5 hours. The sodium content of the zeolite after calcination was 3.4 to 3.6% by mass. The calcined powder was suspended again in 165 g of an ammonia solution (7%) and stirred at 60 ° C. for 2 hours with 5 × 10 ⁵ Pa (5 bar) of carbon dioxide. This was followed by filtration, drying and firing as described above. The sodium content of the second filtrate was 0.1% by mass, and the sodium content of the zeolite at the end of the treatment was 2.3% by mass.

(Example 14)
The procedure was the same as Example 13 except that a 7% ammonia solution and 2 × 10 ⁵ Pa (2 bar) carbon dioxide were used. The sodium content of the first filtrate was 0.2 to 0.3% by mass. The sodium content of the zeolite after the first calcination was 3.4 to 3.8% by mass. The sodium content of the second filtrate was 0.1% by mass. The sodium content of the zeolite at the end of the treatment was 2.6% by mass.

(Example 15)
The procedure was the same as Example 13 except that 3% ammonia solution and 5 × 10 ⁵ Pa (5 bar) carbon dioxide were used. The sodium content of the first filtrate was 0.3% by mass. The sodium content of the zeolite after the first calcination was 3.6% by mass. The sodium content of the second filtrate was 0.1% by mass. The sodium content of the zeolite at the end of the treatment was 2.5% by mass.

(Example 16)
The procedure was the same as Example 13 except that 3% ammonia solution and 2 × 10 ⁵ Pa (2 bar) carbon dioxide were used. The sodium content of the first filtrate was 0.2% by mass. The sodium content of the zeolite after the first calcination was 4.0% by mass. The sodium content of the second filtrate was 0.1% by mass. The sodium content of the zeolite at the end of the treatment was 2.1% by mass.

(Example 17)
The same method as in Example 13 was performed, except that the zeolite treatment was performed with a 3% ammonia solution and 1 × 10 ⁵ Pa (1 bar) carbon dioxide. The sodium contents of the two kinds of filtrates were 0.2% by mass and 0.1% by mass, respectively. The sodium content of the zeolite at the end of the treatment was 3.4% by mass.

(Example 18)
The procedure was the same as Example 13 except that the zeolite treatment was performed with 1% ammonia solution and 1 × 10 ⁵ Pa (1 bar) carbon dioxide. The sodium contents of the two kinds of filtrates were 0.2% by mass and 0.1% by mass, respectively. The sodium content of the zeolite at the end of the treatment was 3.2% by mass.

<Heat release of carbon dioxide and ammonia from excess ammonium carbonate aqueous solution (mother liquor)>
(Example 19)
First, 50 g of ammonium carbonate was added to 500 g of water and heated to 60 ° C. 50 g of USY (X6503, Engelhardt, sodium content 3.1 wt%) was suspended in the solution and heated with stirring for 2 hours. Thereafter, the suspension was filtered. The sodium content of the filtrate increased to 0.3% by weight. The mixture was heated at 100 ° C. with stirring for several hours. Samples were taken after 1, 3 and 24 hours and the amounts of ammonium ions and inorganic carbon were measured (see table). A decrease in the two values indicates thermal decomposition of the ammonium carbonate used to ammonia and carbon dioxide.

Claims (14)

A method for exchanging sodium ions in sodium-containing zeolite with ammonium ions,
a) treating the sodium-containing zeolite with a solution containing water and ammonium carbonate;
b) separating the zeolite from the solution (mother liquor) containing aqueous sodium carbonate and ammonium carbonate;
c) heat treating the mother liquor to release ammonia and carbon dioxide;
An ion exchange method comprising:   The ion exchange method according to claim 1, wherein the removal in the step c) is performed by back extraction.   The ion exchange method according to claim 1, wherein the removed ammonia and carbon dioxide are recombined to produce ammonium carbonate.   The ion exchange method according to claim 3, wherein the produced ammonium carbonate is reused in step a).   The ion exchange method according to any one of claims 1 to 4, wherein the treated zeolite is calcined before ion exchange.   6. The ion exchange method according to claim 5, wherein carbon dioxide is added to the produced ammonia to convert it to ammonium carbonate, which is reused in step a).   7. The ion exchange method according to claim 1, wherein the aqueous sodium carbonate solution obtained in step c) is discharged from the process.   The ion exchange method according to any one of claims 1 to 7, wherein the zeolite separated in the treatment step b) is washed with water.   9. The ion exchange method according to claim 8, wherein the washing water obtained is separated from the zeolite and added to the mother liquor before the processing step c).   10. The process according to claim 1, wherein, in process step a), the solution containing water and ammonium carbonate is made from water and ammonium carbonate, and further further compounds can be used in the solution. The ion exchange method according to item.   11. The ion exchange method according to claim 10, wherein the further compound is urea and / or ammonium carbamate and / or a mixture of carbon dioxide and ammonia.   12. In process step a), the solution containing water and ammonia is made with water and urea and / or ammonium carbamate and / or a mixture of carbon dioxide and ammonia. Ion exchange method.   The ion exchange method according to any one of claims 1 to 12, wherein in the treatment step c), a heat is released by adding a base.   The ion exchange method according to claim 13, wherein the base is an aqueous solution of sodium hydroxide (sodium hydroxide solution).

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