A green process for continuous dry preparation of potassium percarbonate

Abstract

The invention discloses a green process for preparing potassium percarbonate by a continuous dry process, and it adds coating agent polyethylene glycol PEG, and reaction promoter nano-SiO to potassium carbonate, stirring is uniform to obtain mixed raw material, and then it is fed into a twin-screw extrusion reactor simultaneously with hydrogen peroxide to react, and to prevent hydrogen peroxide from decomposing, the reaction temperature is controlled below 35 DEG C, and the residence time of the control material in the reactor is maintained at 20 30 minutes; Extrudate is granulated, dried, sieved, and white granular potassium percarbonate product is obtained. The present invention is by reacting mechanochemical activation, and adding reaction promoter nano-SiO and coating agent polyethylene glycol PEG in the reaction system, reaction yield, H2O2 utilization rate and product stability etc. are well improved, and solvent-free, low-energy consumption, high-purity continuous production are realized, and its application scene in multiple fields is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic peroxide preparation, and particularly relates to a green process for preparing potassium percarbonate by a continuous dry process. Background Art

[0002] Percarbonate production methods are mainly divided into dry and wet methods. The core principle is to react carbonate with hydrogen peroxide to form percarbonate. The compound molecule contains carbonate and hydrogen peroxide, which are bound together by hydrogen bonds. This method has a high active oxygen content and stability, and is widely used in detergents, disinfectants and other fields.

[0003] 1. Dry preparation

[0004] Taking the preparation of sodium percarbonate as an example, the process flow is as follows:

[0005] ① Place anhydrous sodium carbonate on a fluidized bed and continuously spray a 30% hydrogen peroxide solution under high temperature conditions (usually 100-150°C).

[0006] ②The heat generated during the reaction is removed through the fluidized bed, and finally a dry sodium percarbonate product is obtained.

[0007] The advantages of the existing dry preparation technology are simple process and short flow, but the equipment requirements are high, and high temperature can easily lead to loss of active oxygen, affecting product quality.

[0008] 2. Wet preparation

[0009] Traditional percarbonate preparation generally adopts a wet process, which is usually carried out in a kettle reactor. Potassium carbonate is dissolved in water and 50% ethanol is used as a base in the reactor. Potassium carbonate slurry and hydrogen peroxide are added simultaneously to react. After precipitation, particles are centrifuged. The wet process produces waste liquid and requires recycling of ethanol, which is a relatively complicated process. The wet process of the existing technology has the following disadvantages:

[0010] ① Dependence on solvents: A large amount of water or organic solvent is required as a medium, and subsequent crystallization and drying consumes a lot of energy and has a high risk factor.

[0011] ② The purity of the product is low: the wet method easily introduces impurity ions, affecting the decomposition efficiency.

[0012] ③H2O2 is easily decomposed in liquid phase reactions, and the actual utilization rate is less than 70%.

[0013] Potassium percarbonate, a potassium salt derivative, has a higher solubility (25 g / 100 mL at 25°C) and is adaptable to alkaline environments, but its preparation is relatively understudied. Existing wet processes for preparing potassium percarbonate require strict control of low temperatures (<2°C) and pH (10-11), and the product easily absorbs moisture and agglomerates. This invention, through dry mechanochemical activation technology, overcomes these limitations of traditional processes, achieving efficient, low-cost, and scalable production. Summary of the Invention

[0014] In response to the above-mentioned technical problems existing in the prior art, the object of the present invention is to provide a green process for the continuous dry preparation of potassium percarbonate. The present invention combines a mechanochemical activation reaction with a modular temperature control system to achieve solvent-free, low-energy consumption, high-purity continuous production and expand its application scenarios in multiple fields.

[0015] The technical solution adopted in the present invention is as follows:

[0016] A green process for preparing potassium percarbonate by a continuous dry process comprises the following steps:

[0017] S1. Raw material pretreatment: adding polyethylene glycol (PEG), a coating agent, and nano-SiO2, a reaction accelerator, to potassium carbonate, stirring evenly to obtain a mixed raw material; wherein the mass of PEG is 0.5-1.5% of the mass of potassium carbonate, and the mass of nano-SiO2 is 0.3-0.9% of the mass of potassium carbonate;

[0018] S2 Extrusion reaction: The potassium carbonate material mixed in step S1 and hydrogen peroxide are simultaneously fed into a twin-screw extrusion reactor for reaction. To prevent decomposition of hydrogen peroxide, the reaction temperature is controlled below 35°C and the residence time of the materials in the reactor is controlled to be maintained at 20-30 minutes;

[0019] S3 product post-processing: the extrudate is granulated, dried and sieved to obtain a white granular potassium percarbonate product.

[0020] Furthermore, in step S1, the mass of PEG is 0.8-1.0% of the mass of potassium carbonate.

[0021] Furthermore, in step S1, the mass of nano-SiO2 is 0.5-0.7% of the mass of potassium carbonate.

[0022] Furthermore, in step S2, the feed molar ratio of potassium carbonate to hydrogen peroxide is 1:1.2-1.5.

[0023] Furthermore, in step S2, the reaction temperature is controlled at 20-35°C.

[0024] Furthermore, in step S2, the rotation speed of the twin-screw extruder reactor is 100-300 rpm, and the extrusion pressure is 0.4-1 MPa.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The present method utilizes a twin-screw extruder reactor to continuously feed potassium carbonate (K2CO3) and hydrogen peroxide in a proportional amount. Under mechanical shear and temperature control, they directly react to produce potassium percarbonate. The reaction temperature is controlled between 20 and 35°C, the pressure is 0.4-1 MPa, and the residence time is 20-30 minutes. This continuous feeding and discharging process allows for the continuous production of potassium percarbonate. To enhance the stability of the potassium percarbonate product and the utilization rate of hydrogen peroxide, a trace amount of nano-silica is added as a reaction accelerator. This surface hydroxyl group enhances the interfacial contact efficiency between K2CO3 and H2O2, resulting in an H2O2 utilization rate of ≥95%. Furthermore, the simultaneous introduction of a coating agent, polyethylene glycol (PEG), forms a protective film on the product surface, inhibiting H2O2 decomposition and improving product stability.

[0027] 2) The product potassium percarbonate prepared by the method of the present invention has the advantages of high active oxygen content, low hygroscopicity, long half-life of active oxygen release after dissolution in water, and high stability.

[0028] 3) The process of the present invention does not require solvent addition, utilizes mechanical energy to replace chemical solvents, reduces wastewater discharge by more than 90%, and significantly improves H2O2 utilization. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0030] The active oxygen content of potassium percarbonate in the examples of the present invention was determined by iodine titration according to GB 7489-87.

[0031] The stability test of the product in the embodiment of the present invention refers to the stability data after storage in an 80°C oven for one day, and its stability = the active oxygen content data after storage in an 80°C oven for one day / the active oxygen content data of the fresh product * 100%.

[0032] PEG400 is used in the examples of the present invention.

[0033] Example 1: A green process for preparing potassium percarbonate by a continuous dry process, comprising the following steps:

[0034] S1. Raw material pretreatment: adding polyethylene glycol (PEG), a coating agent, and nano-SiO2, a reaction accelerator, to potassium carbonate, stirring evenly to obtain a mixed raw material; wherein the mass of nano-SiO2 is 0.3% of the mass of potassium carbonate, and the mass of PEG is 0.5% of the mass of potassium carbonate;

[0035] S2 Extrusion reaction: The potassium carbonate material mixed in step S1 and hydrogen peroxide with a mass concentration of 35% are simultaneously fed into a twin-screw extrusion reactor for reaction. The feed molar ratio of potassium carbonate to hydrogen peroxide is controlled at 1:1.2. To prevent decomposition of hydrogen peroxide, the temperature in the reactor is controlled at around 25°C, and the feed rate is controlled so that the residence time of the material in the reactor is maintained at about 25 minutes. The speed of the twin-screw extrusion reactor is 200 rpm, and the extrusion pressure is 0.5 MPa.

[0036] Post-processing of S3 product: The extrudate was granulated, dried, and sieved (20-60 mesh) to obtain white granular potassium percarbonate. The active oxygen content was measured to be 13.0%, the stability was 95.3%, and the product yield was 93.1%.

[0037] Example 2. The experimental steps of Example 2 are repeated in Example 1, except that "in step S1, the mass of nano-SiO2 is 0.5% of the mass of potassium carbonate", and the other conditions remain unchanged. The final experimental results are: white granular potassium percarbonate is obtained, the active oxygen content is measured to be 13.15%, the stability is 95.4%, and the product yield is 95.4%.

[0038] Example 3. The experimental steps of Example 3 are repeated in Example 1, except that "in step S1, the mass of nano-SiO2 is 0.7% of the mass of potassium carbonate", and the other conditions remain unchanged. The final experimental results are: white granular potassium percarbonate, the measured active oxygen content is 13.42%, the stability is 95.2%, and the product yield is 95.8%.

[0039] Example 4. The experimental steps of Example 4 are repeated in Example 1, except that "in step S1, the mass of nano-SiO2 is 0.9% of the mass of potassium carbonate", and the other conditions remain unchanged. The final experimental results are: white granular potassium percarbonate, the measured active oxygen content is 13.26%, the stability is 95.8%, and the product yield is 96.2%.

[0040] Example 5. The experimental steps of Example 5 were repeated in Example 1, with the only difference being that "in step S1, the mass of PEG was 0.8% of the mass of potassium carbonate." The other conditions remained unchanged. The final experimental results were: white granular potassium percarbonate was obtained, with a measured active oxygen content of 13.22%, a stability of 96.0%, and a product yield of 95.6%.

[0041] Example 6. The experimental steps of Example 6 were repeated in Example 1, with the only difference being that "in step S1, the mass of PEG was 1.0% of the mass of potassium carbonate." The other conditions remained unchanged. The final experimental results were: white granular potassium percarbonate was obtained, with a measured active oxygen content of 13.29%, a stability of 97.9%, and a product yield of 95.7%.

[0042] The stability of potassium percarbonate in Example 6 of the present invention reaches 97.9% after being stored in an oven at 80°C for one day, the half-life of active oxygen release after being dissolved in water reaches 45 minutes, and the weight gain rate is <2% when stored in an environment of 25°C / RH 60% for 30 days.

[0043] Example 7. The experimental steps of Example 7 were repeated in Example 1, with the only difference being that "in step S1, the mass of PEG was 1.2% of the mass of potassium carbonate." The other conditions remained unchanged. The final experimental results were: white granular potassium percarbonate was obtained, with a measured active oxygen content of 13.37%, a stability of 96.1%, and a product yield of 95.5%.

[0044] In Example 7, compared with Example 6, the amount of PEG was further increased, but the stability of the product decreased. This is because too much additive introduced relatively more impurities to a certain extent, which in turn affected the stability of potassium percarbonate.

[0045] Example 8. The experimental steps of Example 8 were repeated as in Example 1, except that "in step S2, the feed molar ratio of potassium carbonate to hydrogen peroxide was controlled at 1:1.3", and the other conditions remained unchanged. The final experimental results were: white granular potassium percarbonate was obtained, with a measured active oxygen content of 13.24%, a stability of 96.3%, and a product yield of 96.5%.

[0046] Example 9. The experimental steps of Example 9 were repeated as in Example 1, except that in step S2, the feed molar ratio of potassium carbonate to hydrogen peroxide was controlled at 1:1.4. The other conditions remained unchanged. The final experimental results were as follows: white granular potassium percarbonate was obtained, with a measured active oxygen content of 13.20%, a stability of 96.1%, and a product yield of 97.6%.

[0047] Example 10. The experimental steps of Example 10 were repeated as in Example 1, except that "in step S2, the feed molar ratio of potassium carbonate to hydrogen peroxide was controlled at 1:1.5", and the other conditions remained unchanged. The final experimental results were: white granular potassium percarbonate was obtained, with a measured active oxygen content of 13.27%, a stability of 96.2%, and a product yield of 98.5%.

[0048] It can be seen from Examples 1-10 that when the addition amount of nano-SiO2 is 0.7%, the addition amount of ethylene glycol-PEG is 1%, and the molar ratio of potassium carbonate material to hydrogen peroxide is 1:1.5, the stability, content and product yield of the material are all optimal.

[0049] Comparative Example 1: The experimental steps of Comparative Example 1 were repeated in Example 5, with the only difference being that "in step S1, the amount of nano-SiO2 added was 0", and the other conditions remained unchanged. The final experimental results were: white granular potassium percarbonate was obtained, with a measured active oxygen content of 12.58%, a stability of 96.0%, and a product yield of 95.5%.

[0050] From the comparison between Example 5 and Comparative Example 1, it can be seen that silicon dioxide has a more obvious promoting effect on the reaction and can increase the utilization rate of hydrogen peroxide to a certain extent.

[0051] Comparative Example 2: The experimental steps of Comparative Example 2 were repeated in Example 2, except that "in step S1, the amount of PEG added was 0", and the other conditions remained unchanged. The final experimental results were: white granular potassium percarbonate was obtained, the active oxygen content was measured to be 13.51%, the stability was 88.6%, and the product yield was 96.5%.

[0052] The product of Comparative Example 2 was stored at 25°C / RH 60% for 30 days, and the weight gain rate was 6.2%.

[0053] From the comparison between Example 2 and Comparative Example 2, it can be seen that the coating agent polyethylene glycol (PEG) can greatly improve the stability of the product. Due to the PEG coating, the half-life of active oxygen release of the product of the present invention after dissolution in water is relatively longer.

[0054] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.

Claims

1. A green process for preparing potassium percarbonate by continuous dry process, characterized in that The following steps are involved: S1. Raw material pretreatment: adding polyethylene glycol (PEG), a coating agent, and nano-SiO2, a reaction accelerator, to potassium carbonate, stirring evenly to obtain a mixed raw material; wherein the mass of PEG is 0.5-1.5% of the mass of potassium carbonate, and the mass of nano-SiO2 is 0.3-0.9% of the mass of potassium carbonate; S2 Extrusion reaction: The potassium carbonate material mixed in step S1 and hydrogen peroxide are simultaneously fed into a twin-screw extrusion reactor for reaction. To prevent decomposition of hydrogen peroxide, the reaction temperature is controlled below 35°C and the residence time of the materials in the reactor is controlled to be maintained at 20-30 minutes; S3 product post-processing: the extrudate is granulated, dried and sieved to obtain a white granular potassium percarbonate product.

2. a green process for preparing potassium percarbonate by continuous dry method as claimed in claim 1, characterized in that In step S1, the mass of PEG is 0.8-1.0% of the mass of potassium carbonate.

3. a green process for preparing potassium percarbonate by continuous dry method as claimed in claim 1, characterized in that The mass of nano-SiO2 is 0.5-0.7% of the mass of potassium carbonate.

4. a green process for preparing potassium percarbonate by continuous dry method as claimed in claim 1, characterized in that In step S2, the feed molar ratio of potassium carbonate to hydrogen peroxide is 1:1.2-1.

5.

5. a green process for preparing potassium percarbonate by continuous dry method as claimed in claim 1, characterized in that In step S2, the reaction temperature is controlled at 20-35°C.

6. A green process for preparing potassium percarbonate by continuous dry method as claimed in claim 1, characterized in that In step S2, the rotation speed of the twin-screw extruder reactor is 100-300 rpm, and the extrusion pressure is 0.4-1 MPa.