DD141013A5 - PROCESS FOR PREPARING SODIUM PERCARBONATE FROM A SODA SOLUTION OR SUSPENSION - Google Patents

Description

Scope of the invention

The invention relates to sodium percarbonate production from sodium carbonate. Sodium percarbonate should be obtained as a coarse-grained, abrasion-resistant product with good transport and storage properties, which has a uniform composition and is therefore suitable for use as an oxygen supplier for predictable and repeatable oxygen delivery.

Known technical solutions

It is known sodium percarbonate by reacting a soda solution or suspension with aqueous hydrogen peroxide solutions of the formula

GO ₃ + 1.5 H ₂ O ₂ - * Na ₂ CO ₃ . 1.5

while reducing the solubility of the percarbonate formed by the addition of inert salts - such as sodium chloride - (CH-PS 90 295).

BR-PS 568 754 discloses the continuous production of sodium percarbonate from hydrogen peroxide and sodium

carbonate, in which the necessary quantities of hydrogen peroxide and sodium carbonate are added only in small amounts to the reaction solution.

At the same time, reference is made to the use of active oxygen stabilizers, such as, for example, magnesium compounds, and to the beneficial effect of hexametaphosphate on the granular structure of the percarbonate.

The disadvantage of the method is that - as I said, the soda and hydrogen peroxide addition takes place only in small proportions, with between the additions reaction times are turned on.

During the feed, the temperature rises from 15 ° to 22 ⁰ and is held at this temperature until the end of the reaction. This procedure results in a fine, spiky percarbonate

Perne-r according to DE-OS 2,328,803 an abrasion-resistant coarse percarbonate by reacting a soda solution or suspension containing 2 - 8 g sodium hexametaphosphate p. Liter of solution, with a hydrogen peroxide solution containing 3-10 S magnesium ions p. Liter of solution, if appropriate in the presence of common salt. ,

Great emphasis is placed on the exact observance of the quantities of sodium hexametaphosphate and magnesium ions. Otherwise, fine or non-resistant particles would be produced.

The disadvantage of the only discontinuous process is that when reusing the mother liquor

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at the higher soda solution temperature of 24 ⁰ G, the hydrogen peroxide yield is greatly reduced by active oxygen degradation, which is enhanced by the impurities which accumulate in the mother liquor using technical soda.

By this active oxygen decomposition, which continues during the hydrogen peroxide feeding, the sodium percarbonate crystallization conditions can not be kept constant

The. Soda / sodium percarbonate ratio shifts in favor of the soda, which in turn exerts additional pressure on the still-dissolved sodium percarbonate as a more easily soluble component.

The result is a too rapid crystallization, it is obtained a fine-grained product.

Furthermore, as described in DE-PS (P26 44 147.4-4-1), when using an ITatriunicarbonat saturated solution certain amounts of Hatriumhexametaphosphat required «

If the amount of sodium TO ₀ great, too stable to oversaturation of forming Uatriumpercarbonats is built up which does not degrade or only partly.

If the amount of Uatriumhexametaphosphat too small _S is constructed is too low PercarbonatüberSättigung and the percarbonate obtained is too fine.

It is therefore important that at a given

Zenden soda amount at constant concentration of the remaining solution components and the reaction temperature a certain ratio of Sodaumsatz to dissolved Natriumhexametaphosphatmenge is selected.

'This was possible by the method of DE-PS (P 26 44 14-7.4-41) only to the soda solubility.

Z iel the invention .

The aim of the invention is therefore a still technically simpler implementation of the method according to DE-PS (P 26 44 14-7.4-41), which already led to an absolutely safe reproducibility of the coarse compact grain at 10 - 20 ⁰ G and also an increase in the Sodaumsatzes.

Essence of the invention

The invention is based on the object, by influencing the proportions of the reactants, on temperature and time to the o. G. to get the desired end product.

It has now been found that the object and the object in the reaction of sodium carbonate with hydrogen peroxide, starting from a Natriumcarbonate-containing and sodium percarbonate saturated solution in the presence of 100 - 200 g of sodium chloride p ", liter solution, known active material Stabilizers and sodium hexametaphosphate at 10 - 20 ⁰ C, if in such a solution containing per liter 0.1 - 1.9 g of sodium hexametaphosphate, a ratio of soda to Natriumhexametaphosphat of 65 J 1 to ^ 00: 1 set

-s-209130

is then added to the soda-use solution or suspension thus prepared with an amount of hydrogen peroxide, which is dissolved and suspended in the starting solution

Sodium carbonate is practically equivalent while maintaining about one and the same temperature during the entire precipitation process, before and after completion of * hydrogen peroxide addition up to 60 minutes after this addition, the resulting supersaturation of dissolved sodium percarbonate degraded by precipitation of the sodium percarbonate, the salt obtained by known Separated process and dried and the resulting mother liquor if necessary. Is returned back to the working stage for the soda feed solution. -

To keep the active oxygen loss as low as possible, the process is not carried out at temperatures above 2o C. Preferably, the temperature is -lh - 16 ° C.

Among the soda used is calcined soda, soda p.a. as well as technical soda.

It would be found that at a constant concentration of components dissolved in addition to soda and at a constant reaction temperature a certain ratio of Sodaumsatzes to dissolved Natriumhexametaphosphatmenge must be respected for during and after the Hydrogen peroxdadabe targeted formation and degradation of Natriumpercarbonatübersättigung, and dami.t ultimately for a coarse, compact product.

To determine the correct ratio of sodium phosphate to sodium hexametaphosphate proceed as follows: After determining the reaction temperature to a value between + 1o C and + 2o C of the saline in solution to an amount between 100 g / l and 2oo g / l about constant levels about 4.5 g Mg SO. , 7 HO / l and ca, o, 1 g of sodium hexametaphosphate / l, this solution is approximately saturated by dissolving 51 g of sodium carbonate and adding 30 ml of hydrogen peroxide (70 Gew ->), with ca, 75 S sodium percarbonate p. Liters are formed.

In this percarbonate mother liquor, the correct ratio of soda ash to sodium hexametaphosphate is now through a series of preliminary tests, in which a coarse, compact product is obtained by a specific assembly and disassembly of the sodium percarbonate supersaturation. ,

For example, at + Io C in a saturated sodium percarbonate solution in the presence of 2oo g of common salt / l, h _t 5 ~ g of Mg SO. , 7 HO / l and o, 1 g sodium hexametaphosphate / a ratio of Na _? CO ^: (Na P0 ~) <5 ° o: 1 to obtain a coarse, compact percarbonate.

At + 2o C in a saturated solution of sodium percarbonate in the presence of 1 000 g of common salt / l, 4.5 g of MgSO 4. J HO / l and 1.9 S sodium hexametaphosphate / l had to be the ratio of Na ₂ CO ι (Na ^PO O) g 11o: 1 to obtain a coarse, compact product eu.

To avoid active oxygen losses, the entire precipitation process is carried out below 2o C at about the same temperature, i. at + ^ 1 C with respect to the selected temperature performed.

The amounts of hydrogen peroxide to be added should - as stated - be approximately equivalent to the amount of sodium carbonate present, s. Formula on page 1. Here, "approximately equivalent" means a ratio of active oxygen to sodium of o, 6 to o, 9 * 1.

Hydrogen peroxide solutions are particularly suitable for aqueous solutions of weight; however, higher percent commercial aqueous hydrogen peroxide solutions can also be used.

Even less concentrated solutions than 70% are operational; However, with decreasing concentration of hydrogen peroxide more water is introduced into the system, whereby on the one hand, the crystallization pressure for percarbonate decreases and on the other hand, the excess of mother liquor increases.

In the method, the usual active oxygen stabilizers are used, such as magnesium salts, alkali metal salts, preferably magnesium sulfate.

The stabilizers are added to the aqueous hydrogen peroxide solution. .. - ·

At the beginning of the process according to the invention, the mother liquor, consisting of - based on 1 liter of solution - ho to 1oo g of sodium percarbonate, o. 1 to 1.9 g Natriumhexametaphos- phat, 1oo, to 2oo g of sodium chloride and saturated with basic magnesium carbonate and Magnesiumsilikät synthetically produced as an aqueous solution,

This synthetic mother liquor is used to prepare the soda solution BEZW. -suspension. This solution can be used also with the obtained after separating the sodium percarbonate formed mother liquor also ko to 1oo g Sodium p. Contains liters.

-a

209 1

However, this mother liquor must still be brought to the specified in the description of the invention concentrations of sodium hexamate / taphosphate and saline.

It is advantageous, when using water glass and reuse of saturated sodium percarbonate mother liquor, which still contains a portion of the stabilizers of the previous batch, before inserting the calcined soda, the mother liquor to separate the precipitated Magnesiumeilikats to filter. ·

At the same time, the magnesium concentration is reduced, which therefore varies only slightly in this solution.

The assembly and disassembly of the supersaturation takes place with stirring. It is known that the nucleation rate depends on the stirring speed. With rapid stirring occurs too rapid degradation of supersaturation, and it falls out too fine a product. By too slow stirring, however, the degradation is incomplete? If now the mother liquor from such a batch is used in the preparation of the soda-use solution, sodium percarbonate already crystallizes out during the preparation of this starting solution, since the more easily soluble soda pushes out the less soluble sodium percarbonate from the solution.

This sodium percarbonate then coincides with the impurities. cleaning and is lost.

To determine the optimum stirring speed, immediately after the addition of the hydrogen peroxide, the supersaturation of sodium percarbonate which has occurred is determined and its degradation determined. ,

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The rate of stirring to be chosen is ultimately determined by the salt quality obtained, i. the coarse compact grain, set.

If the supersaturation has been too rapid, the stirring rate must be lowered and vice versa until the desired rate of degradation has been reached.

The same applies to the metering rate of hydrogen peroxide solution in the soda solution. This dosing rate can be determined for operation in the laboratory experiment.

Optimal dosing speeds of Io - 2o minutes for the amounts required for the reaction.

The precipitated sodium percarbonate is filtered off in a known manner and dried. The process can easily be carried out in conventional systems for the production of sodium perborate.

The technical progress of the process lies in the reuse of the mother liquor while the crystallization parameters are largely constant, such as the composition of the soda feed solution, an approximately constant degree of impurity and the temperature and the very simple technical implementation. ^ä: - ..: '- »

Thus, after each conversion, a qualitatively uniform, i. coarse, compact product. The invention is illustrated by the following example:

It means; NaPc - sodium percarbonate

Hexa - sodium hexametaphosphate

^Oa - active oxygen g-At / 1 _ gram atom / l

example

In a V4A container (0 - 1530 mm, H = 1420 mm) 1 m NaPc-liquor of 15 ° C, the per liter 200 g NaCl, 72.2 g Na ₂ CO ₃ * 1.5 H ₂ O ₂ , 4.5 g of MgSO ₄ * 7 H ₂ O and 0.15 g of hexa, under stirring (Rührpropellerdurchmesser = 500 mm, stirring speed = 220 rpm) presented

 This template dissolves 1.35 kg of hexa. Then under constant temperature (15 C) and stirring within 25 minutes via an AEG metering 105 kg techn. calc. Soda 496%) dosed in the above template.

Immediately after completion of the addition of soda within 15 minutes at 15 ° C 76 liters of H ^ solution (23.7 mol / l), which per liter 52.6 g MgSO ₄ . 7 H ₂ O and 65, S g NaCl, added via rotameter.

After the addition of the HpO 4 solution, 142 g of NaPc / 1 were in solution, which were degraded within 45 minutes to 71.4 g / l.

Post-reaction time min. Ka g at / i Alkalis OA g AtA Analysis Oa / Na Verh. NaPc dissolved g / i to H _? O ₂ train. 0 1.81 1.43 0.79 142.0 45 0.91 0.79 0.87 71.4

The salt slurry was separated from the mother liquor via a continuous centrifuge and the salt was dried in a fluid bed dryer.

Were obtained. 150 kg finished product with the following analysis data:

Active oxygen: , 94 % Bulk weight: g / i Sieve Analysis at 0.8 ram s % to 0.5 mm: % to 0.4 mm j % at 0, 2 now: % to 0.1 mm: % Rest! % : 13 : 941 ; 6 29 15 : 38 12 t 0

Claims (2)

-W- ErfindungsansOrüche 209 130 A process for the production of a compact, coarse sodium percarbonate obtained by reacting hydrogen peroxide with sodium carbonate at 10 -20 ⁰ C, starting from a sodium carbonate-containing and sodium percarbonate saturated solution in the presence of-100 - 200 g of sodium chloride per liter of solution, known active oxygen stabilizers and sodium hexametaphosphate, characterized in that in this solution containing 0.1 to 1.9 g of sodium hexametaphosphate per liter of solution, a. Ratio of soda to sodium hexametaphosphate from 65 to 1 to 500 to 1 is adjusted, and then the soda feed solution or suspension thus prepared is mixed with an amount of hydrogen peroxide, which is practically equivalent to the solution dissolved and / or suspended in the sodium carbonate, while maintaining about a and at the same temperature throughout the IP precipitation process, whereupon during and after completion of hydrogen peroxide addition up to 60 minutes after this addition, the resulting supersaturated sodium percarbonate supernatant is degraded by precipitation of the sodium percarbonate, the resulting salt separated and dried by known methods, and the resulting mother liquor possibly returned to the working stage for the soda insert solution · 2 · Method according to item 1, characterized in that the selected precipitation temperature is + 1 ⁰ C ί steps during the process. selected precipitation temperature exceeded by + + 1 ° 0