WO2004002885A1

WO2004002885A1 - A process for making sodium percarbonate

Info

Publication number: WO2004002885A1
Application number: PCT/CN2003/000415
Authority: WO
Inventors: Zhigang Zhu
Original assignee: Zhejiang Jinke Chemistry Co.,Ltd
Priority date: 2002-06-27
Filing date: 2003-05-30
Publication date: 2004-01-08
Also published as: AU2003234900A1; AU2003234899A1; CN1463913A; WO2004002942A1; CN1330561C

Abstract

The invention discloses a process for making sodium percarbonate, which pertains to the field of preparing the oxygen-containing bleaching agents. The said process includes a reaction between a suspension of hydrated sodium carbonate, which is obtained by emulsifing and hydrating a sodium carbonate solution, and a 25%-70% aqueous solution of H2O2,, followed by crystallization. During the reaction, sodium chloride or sodium sulfate is added as the salting-out agent, and sodium silicate, organo-phosphoric acid, and ethylenediamine tetraacetic acid and the sodium salt thereof are used as crystallization promoter. The hydration and emusification of the aqueous solution of sodium carbonate substantially accelerate the crystallization of the remaining hydrogen peroxide, while decreasing the content of sodium carbonate present in the mother solution as well. The sodium percarbonate products prepared according to this invention have high yield with low consumption of the starting materials. The sodium percarbonate products prepared according to this invention have advantages in higher content of activated oxygen, bigger particle size, and higher hydrothermal stability in comparison with the products obtained from the common wet process. The practice of this invention affords good economic benefits and environmental benefits.

Description

Preparation method of sodium percarbonate

Technical field

The invention relates to a method for preparing sodium percarbonate, and belongs to the technical field of preparation of oxygen-containing bleach. Background technique

Sodium percarbonate, also known as sodium peroxycarbonate, has a molecular formula of Na ₂ C0 _3. L. 5HA, sodium carbonate peroxyhydrate, and the common name of sodium percarbonate in the industry is PCS. The most widespread use of PCS is as a bleaching agent for detergent compositions, especially as a bleaching agent for concentrated and ultra-concentrated compositions. Sodium percarbonate is usually prepared by the reaction of hydrogen peroxide and sodium carbonate aqueous solution, commonly known as wet crystallization processing method. The wet reaction includes the generation of an aqueous sodium carbonate solution and the reaction with an aqueous hydrogen peroxide solution. The reaction conditions include the selection of sodium carbonate and hydrogen peroxide concentration, temperature, reaction time, and selected auxiliary agents. Crystals formed in solution. In order to reduce the solubility of sodium percarbonate in water, salting out agents such as sodium chloride and sodium sulfate are usually added to increase the yield and reduce the cost. The addition of a salting-out agent moves the reaction further to completion, which converts a larger portion of the reactant into the desired product. Synthetic reactions need to stabilize the active oxygen in sodium percarbonate, so it is also necessary to add an active oxygen stabilizer, called a crystallization aid. Chinese patents CN1240407A and CN1156738 A disclose commonly used stabilizers.

The active oxygen content of crystalline sodium percarbonate obtained by the traditional wet method is generally 13-13.5%, and the bulk density is also large. However, due to the above-mentioned preparation method, the synthesis reaction is fast, resulting in insufficient reaction, and the crystalline product obtained by the reaction has poor wet stability. At the same time, the consumption of sodium carbonate in the reaction is also high, and the waste liquid is discharged with some water pollution. Summary of the Invention

The object of the present invention is to provide a method for preparing sodium percarbonate, which can make sodium percarbonate have a high active oxygen content, good wet heat stability, and low raw material consumption. The task of the present invention is achieved by the following technical solutions.

The sodium percarbonate is prepared by reacting a sodium carbonate solution with an aqueous hydrogen peroxide solution, which is characterized by the following steps:

In a further step, an anhydrous sodium carbonate is added to an aqueous solution or a circulating mother liquor, and an aqueous sodium carbonate suspension is obtained through an emulsification and hydration reaction;

(2) In the second step, the hydrated sodium carbonate suspension and the hydrogen peroxide aqueous solution are introduced into the reaction kettle to react at a certain acceleration rate, and the sodium percarbonate crystal product is obtained by the reaction; The third step is the solid-liquid separation of the crystals, the filtrate is recycled, and the crystals are post-processed into products; the molar ratio of the reaction between sodium carbonate and hydrogen peroxide is 1: 1. 3-1. 5;

A sodium-containing salting-out agent and a crystallization aid are added to the reaction.

The hydrated sodium carbonate suspension is prepared by adding anhydrous sodium carbonate to the circulating mother liquor, the amount of which is 20-5 OU'L hydration reaction temperature is 20-45 ° C_ emulsification hydration reaction time 5- 60 minutes;

The compound crystallization reaction temperature is 16-30 ° C, and the reaction time is 30-50 minutes.

The sodium percarbonate crystals are separated by filtration or centrifugation. The crystals are dried at a temperature of 80-95 ° C, and then sieved to obtain a finished product.

The sodium-containing salting-out agent is one of sodium chloride and sodium sulfate, and the input amount is to maintain its concentration in the mother liquor of 17-22%;

The crystallization aid is selected from one or several mixtures of sodium silicate, organic phosphonic acid, magnesium sulfate, ethylenediaminetetraacetic acid or its sodium salt, and polypropionamide, and the input amount is 0.5 to the amount of sodium carbonate. 3%;

The hydrated sodium carbonate has a projecting acceleration of 800-1600 ml / h, and a hydrogen peroxide aqueous solution has a feeding rate of 210-660 ml / h.

In the present invention, the one-step reaction of the wet process is changed to a two-step reaction, and in particular, the reaction for preparing sodium carbonate hydrate is designed separately. When an anhydrous sodium carbonate is used to prepare an aqueous solution, or when anhydrous sodium carbonate is added to a circulating mother liquor, Using a high-speed emulsification shearer and agitator, the anhydrous sodium carbonate is hydrated with the water in the solution to form a hydrated sodium carbonate suspension. The amount of anhydrous sodium carbonate used in the hydration reaction is the amount of mother liquor 20- 50 ° / », preferably 30-40 ° /», the hydration reaction time is 5- 50 minutes, preferably 10-30 minutes, and the hydration reaction temperature is 20-6 (TC , 25-45 ° C is preferred. The degree of hydration of sodium carbonate in the 7-synthesis reaction is achieved by the temperature control of the suspension. When the temperature of the suspension is 32-35 ° C, sodium carbonate heptahydrate is formed, which is higher or lower than this. At temperature, sodium carbonate monohydrate or decahydrate will be formed, respectively.

In the second step of the reaction, the hydrated sodium carbonate suspension is mixed with a 25-70% hydrogen peroxide aqueous solution or added dropwise to the reactor at the same time to carry out the compounding reaction to form sodium percarbonate crystals. Since the sodium carbonate solution can fully react with hydrogen peroxide after emulsification and hydration, the amount of sodium carbonate dissolved in hydrogen peroxide water is greatly reduced, and the sodium carbonate content in the circulating fluid is reduced. During the preparation process, part of the circulating liquid is discharged, and the decrease of the content will reduce the loss of sodium carbonate, which will help reduce water pollution.

Another technical effect of the present invention is to utilize the characteristics of the hydration reaction as an exothermic reaction. The temperature control of the emulsification hydration reaction only requires conventional water cooling, which will greatly reduce the heat of the second step reaction. The result is that during the crystallization reaction, only a small amount of frozen brine is needed to control the reaction temperature, thereby reducing the amount of frozen brine required.

In the reaction process of the present invention, the addition of a sodium-containing salting-out agent is indispensable. The addition of sodium chloride or sodium sulfate can improve the yield of sodium percarbonate. At the same time, because sodium in the salting-out agent does not participate in the reaction, Therefore, the addition of the salting-out agent can also reduce the sodium carbonate content in the mother liquor. The salting-out agent is added to maintain its concentration in the circulating mother liquor of 15-22%, preferably Π- ²⁰ %.

The crystallization aid to be added in the present invention has the function of stabilizing active oxygen, such as sodium silicate, organic phosphonic acid, ethylenediaminetetraacetic acid and its sodium salt, a mixture of one or more kinds of polyacryl, etc. 5-3%。 The amount of sodium carbonate in the reaction solution was added in an amount of 0.5-3%. The addition of crystallization aids makes the sodium percarbonate crystal particles have higher uniformity and purity, so that the product has better wet and thermal stability. The thermal stability of the sodium percarbonate prepared by the invention is> 92% (105 ° C for 2 hours), and the wet stability is> 50%. The product is very suitable for use in solid bleaching agents and phosphorus-free detergents.

Test method for wet stability: 10 g of sodium percarbonate particles are mixed with 10 g of 4A zeolite, placed in an open culture subculture, and stored at 32 ° C and 80% relative humidity for 48 hours to calculate the sample active oxygen The remaining rate.

The following are the results of a comparative measurement of the performance of sodium percarbonate prepared by the method of the present invention and sodium percarbonate prepared by a general wet process:

Term active oxygen water bulk density average particle size thermal stability wet stability

(%) (%) (G / L) (ra) Qualitative (%) Qualitative (%) Note Example 1 14. 2 0. 82 957 512 95. 1 53. 3 Example 2 14. 5 0. 57 1072 762 94. 7 56. 1 Example 3 14. 3 0. 66 1032 432 95. 5 51. 7 Example 4 14. 2 0. 92 981 561 96. 3 52. 4 Example 5 13. 9 0. 43 760 523 96. 5 51. 6 Example 6 14. 2 0. 83 983 462 96. 6 53. 8 Example 7 14. 4 0. 55 940 625 95. 5 55. 4 Example 8 14. 6 0. 88 1060 912 94. 4 60. 2 Comparative test 13. 6 0. 92 810 430 92. 3 23. 6 According to the comparative analysis of the above test results, the active oxygen content of the sodium percarbonate prepared by the present invention is over 14%, the product moisture content is reduced, the average particle size is increased, and especially the wet stability is greatly improved, and the effect is very significant. .

The implementation of the present invention can also reduce the consumption of sodium carbonate, reduce the process energy consumption, is beneficial to environmental protection, and is a preparation process with good economic and environmental benefits. detailed description

Example one

Take 840 grams of mother liquor into the pulping kettle, start the shear emulsifier, add 280 grams of light anhydrous sodium carbonate, 8 G grams of sodium chloride and 3 grams of sodium silicate; shear emulsification reaction for 20 minutes to produce sodium carbonate monohydrate Suspension, the temperature of the suspension is controlled at 38-43 ° C; this reaction solution contains 6.0% sodium carbonate mother liquor 840 g, sodium carbonate 280 g, sodium chloride 80 g and 3 g sodium silicate. 440 g of a 27.5% hydrogen peroxide solution was introduced into the hydrogen peroxide tank, and 4 g of aminotrimethylene phosphonic acid (ATMP), 1 g of disodium ethylenediamine tetraacetate, and 2 g of magnesium sulfate were added. At the same time, another 250 grams of mother liquor was taken, and 3 grams of sodium percarbonate with an average particle size of 100 μm was added as seeds.

Then, a hydrated sodium carbonate suspension was introduced at a total speed of 1200 ml per hour, while a concentration of 27.5% hydrogen peroxide solution was introduced at a total speed of 675 ML per hour, and the hydrogen peroxide in the mother liquor of the reactor was maintained at> 0.7%. During the reaction, the temperature is maintained at 22-23 ° C, the process lasts about 40 minutes, and the feeding is completed. The crystallization reaction product in the reaction kettle is separated from the mother liquor by a centrifuge, and the filtrate is recycled into the mother liquor tank for reuse. Dry in a fluidized bed at about 90 ° C for 30 minutes to obtain 409 g of finished product. Example two

The method steps are the same as in Example 1. The different process conditions are as follows: In the first step, 840 g of mother liquor with 5% sodium carbonate content, 280 g of anhydrous sodium carbonate, 80 g of sodium chloride, reaction time 25 minutes, and reaction temperature ²⁵ -3 (TC, to generate sodium carbonate decahydrate suspension; in the second step reaction, 450 g of 27.5% hydrogen peroxide solution, 1 g of seed crystals, hydrogen peroxide solution feed rate 430ml / h, sodium carbonate hydrate The suspension was fed at a speed of 800ml / h, the reaction time was 60 minutes, and the reaction temperature was 22-23 ° C. 410 g of sodium percarbonate was obtained. Example three

The method steps are the same as in Example 1, and the different process conditions are as follows: The first step is a reaction, containing 840 g of sodium carbonate 7% mother liquor, adding 280 g of anhydrous sodium carbonate, 60 g of sodium chloride, 7 minutes of reaction time 25 minutes, hydration the reaction temperature of 25- 30 ° C, a suspension of sodium carbonate decahydrate generated; the second reaction, a concentration of ³⁵ percent aqueous hydrogen peroxide 330 g seed 5 g, sodium carbonate hydrate suspension feed rate 960ml / h, The hydrogen peroxide solution was fed at a speed of 400 ml / h, and the reaction time for crystallization was 50 minutes, and the reaction temperature was 22-23 ° C. 395 g of sodium percarbonate was obtained. Example 4

The method steps are the same as in Example 1, and the different process conditions are as follows: The first step is a reaction, containing 840 g of sodium carbonate 7.2% mother liquor, adding 280 g of anhydrous sodium carbonate, 60 g of sodium chloride, and a hydration reaction time of 20 minutes. The hydration reaction temperature is 32-35 ° C, and a sodium carbonate heptahydrate suspension is formed. In the second step, 325 g of a 35% hydrogen peroxide aqueous solution, 3 g of seed crystals, and a hydrated sodium carbonate suspension feed rate of 1200 ml / h, The hydrogen peroxide aqueous solution was fed at a rate of 500 ml / h, and the reaction time for crystallization was 40 minutes, and the reaction temperature was 22-23 ° C. 391 g of sodium percarbonate was obtained. Example 5

The method steps are the same as in Example 1, and the different process conditions are as follows: The first step is reaction, 840 g of mother liquor containing 8% sodium carbonate, 280 g of anhydrous sodium carbonate, 68 g of sodium chloride, hydration reaction time 15 minutes, hydration reaction At a temperature of 38-43 ° C, a sodium carbonate monohydrate suspension is formed; in the second step reaction, 320 g of a 35% hydrogen peroxide aqueous solution, 8 grams of seed crystals, and a hydrated sodium carbonate suspension feed rate of 1600 ml / h _; peroxidation The hydrogen hydrogen solution was fed at a speed of 660 ml / h, the reaction time was 30 minutes, and the reaction temperature was 24-25 ° C. 394 g of sodium percarbonate crystals were obtained. Example Six

The method steps are the same as in Example 1. The different process conditions are as follows: The first step is reaction, 840 g of mother liquor containing 2% sodium carbonate, 280 g of anhydrous sodium carbonate, 32 g of sodium chloride, hydration reaction time 20 minutes, hydration reaction temperature 2 ⁵ - 3 (TC, generates a suspension of sodium carbonate decahydrate; the second reaction, a concentration of over 235 g of 50% aqueous hydrogen peroxide solution, the seed crystal 5 grams of sodium carbonate hydrate suspension feed rate 1070ml / h, over Feeding rate of hydrogen oxide solution is 300ml / h, and the reaction time of feeding crystallization is 45 minutes, The reaction temperature was 22-23 ° C, and 415 g of sodium percarbonate was obtained. Example Seven

The method steps are the same as in Example 1. The different process conditions are as follows: In the first step, 840 g of mother liquor containing 12% sodium carbonate, 280 g of anhydrous sodium carbonate, 16 g of sodium chloride, hydration reaction time 20 minutes, and hydration reaction At a temperature of 25-30 ° C, a suspension of sodium carbonate decahydrate is formed; in the second reaction step, 180 g of a 70% hydrogen peroxide aqueous solution, 2 g of seed crystals, a sodium hydrate feed rate of 107 Oml / h, and hydrogen peroxide The feed rate of the aqueous solution was 210 ml / h, the reaction time of the crystallization was 45 minutes, and the reaction temperature was 22-23 ° C. 423 g of sodium percarbonate was obtained. Example eight

The method steps are the same as in Example 1, and the different process conditions are as follows: The first step is a reaction, containing 840 g of sodium carbonate 12.3% mother liquor, adding 280 g of anhydrous sodium carbonate, 16 g of sodium chloride, and a reaction time of 20 minutes. 5 克。, Hydration reaction temperature of 32-35 ° C, to generate a sodium carbonate heptahydrate suspension; the second step of the reaction, a concentration of 70% hydrogen peroxide aqueous solution 188 grams, seed 0. 5 grams. The feed rate of 7J sodium carbonate suspension is 1070ml / h, the feed rate of aqueous hydrogen peroxide solution is 210ml / h, the reaction time of crystallization is 90 minutes, and the reaction temperature is 22-23 ° C. 394 g of sodium percarbonate is obtained.

Claims

Claim

1. A method for preparing sodium percarbonate, which is obtained by reacting an aqueous solution of sodium carbonate and an aqueous solution of hydrogen peroxide, and is characterized in that the following steps are performed:

In the first step, a hydrated sodium carbonate suspension is prepared through the emulsification and hydration reaction when anhydrous sodium carbonate is added to an aqueous solution or a circulating mother liquor;

In the second step, a hydrated sodium carbonate suspension and an aqueous hydrogen peroxide solution are added to the reaction kettle to react, and a sodium percarbonate crystal is obtained by the reaction;

The third step is the solid-liquid separation of the sodium percarbonate crystals, and the filtrate is recycled, and the crystals are post-processed into products;

Molar ratio of sodium carbonate to hydrogen peroxide reaction 1: 1. 3-1. 5;

2. The method for preparing sodium percarbonate according to claim 1, characterized in that the amount of anhydrous sodium carbonate added is 25-50% of the amount of the mother liquor;

Emulsion hydration reaction temperature is 20-45, emulsification hydration reaction time is 5-60 minutes; crystallization reaction temperature is 16-30 ° C, reaction time is 30-50 minutes.

3. The method for preparing sodium percarbonate according to claim 1 and 2, characterized in that the crystallized product is separated by filtration or centrifugation, the crystallized substance is dried at a temperature of 80-95 ° C, and sieved to obtain a finished product.

4. The method for preparing sodium percarbonate according to claim 1, characterized in that the sodium-containing salting-out agent is one of sodium chloride or sodium sulfate, and the input amount is to maintain a concentration of 17-22% in its mother liquor;

5. The method for preparing sodium percarbonate according to claim 1, wherein the crystallization aid is selected from sodium silicate, organic phosphonic acid, magnesium sulfate, ethylenediaminetetraacetic acid or its sodium salt, and polyacrylamide. 5-3 ° /。 One or several mixtures, the amount of 0.5-3 ° /. .