A method for preparing powdered activated carbon for food processing

Abstract

The present invention relates to a method for preparing powdered activated carbon for food processing, and belongs to the technical field of activated carbon. The present invention is based on the fact that the starting raw materials for preparing activated carbon used in the field of food processing are mostly biomass materials with high cellulose, hemicellulose and lignin content, and the raw materials are creatively crushed, washed and dried in sequence, and then deionized water, hydrogen peroxide, 1-ethyl-3-methylimidazole acetate and polyethylene glycol in a certain weight ratio are used as reaction media, coupled with ultrasound, and hydrothermal reaction is carried out in a nitrogen atmosphere, thereby preparing an activated carbon precursor, and finally carbon dioxide is used as an activator, and physical activation is carried out within a certain temperature and time range, and an activated carbon is obtained by naturally cooling to room temperature, which not only has a high specific surface area and excellent adsorption capacity, but also is very suitable for application in the field of food processing, and no large amount of acid and alkali reagents need to be added in the entire preparation process of the activated carbon, and the corrosion to the production equipment is small.

Description

Technical Field

[0001] The invention belongs to the technical field of activated carbon, and in particular relates to a method for preparing powdered activated carbon for food processing. Background Art

[0002] Activated carbon, as a carbon-based material with high specific surface area and high porosity structure, is widely used in energy storage, catalysis, food processing and other fields. Among them, activated carbon used in the field of food processing mostly chooses biomass materials with less impurities and no toxicity as the starting raw materials in the actual preparation process due to safety and other factors, and then carbonizes and activates them in sequence. However, the activation methods of activated carbon are generally divided into physical activation and chemical activation. Physical activation refers to activation with oxidizing gas as an activator, while chemical activation refers to activation with inorganic compounds such as potassium hydroxide, sodium hydroxide, phosphoric acid, etc. as activators. Relatively speaking, physical activation has the advantages of being greener and more environmentally friendly, without the need for a large amount of corrosive reagents such as acids and alkalis, and with less damage to production equipment. It is more suitable for the preparation of activated carbon for the field of food processing. However, a large number of studies have shown that the specific surface area of ​​activated carbon prepared only by physical activation is often not high, which seriously limits its own adsorption capacity. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing powdered activated carbon for food processing. Based on the fact that the starting raw materials for preparing activated carbon used in the field of food processing are mostly biomass materials with high cellulose, hemicellulose and lignin content, the present invention creatively first performs crushing, washing and drying treatments in sequence, and then uses deionized water, hydrogen peroxide, 1-ethyl-3-methylimidazole acetate and polyethylene glycol in a certain weight ratio as reaction media, couples ultrasound, and performs hydrothermal reaction in a nitrogen atmosphere to prepare an activated carbon precursor, and finally uses carbon dioxide as an activator to perform physical activation within a certain temperature and time range, and obtains an activated carbon by naturally cooling to room temperature. The activated carbon not only has a high specific surface area and excellent adsorption capacity, but is also very suitable for use in the field of food processing, and does not require a large amount of acid and alkali reagents to be added during the entire preparation process of the activated carbon, and has low corrosion to production equipment.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for preparing powdered activated carbon for food processing, the method comprising the following steps:

[0006] (1) The biomass material is crushed, then washed with deionized water, and finally vacuum dried until constant weight is obtained to obtain component A;

[0007] (2) adding hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate, polyethylene glycol and component A to deionized water, and then hydrothermally reacting the mixture under ultrasound in a nitrogen atmosphere, cooling the mixture naturally to room temperature, filtering the mixture, removing the filtrate, washing the mixture with deionized water, and finally vacuum drying the mixture until a constant weight is obtained to obtain component B;

[0008] (3) Activate the component B in a carbon dioxide atmosphere and cool it naturally to room temperature. The preparation is completed.

[0009] As a preferred technical solution of the present invention, the biomass material in step (1) is at least one of corn cobs, peanut shells, rice husks and coconut shells.

[0010] As a preferred technical solution of the present invention, the pulverizing in step (1) refers to pulverizing until it can pass through a 50-60 mesh sieve.

[0011] As a preferred technical solution of the present invention, the vacuum drying until constant weight in step (1) refers to vacuum drying at 50-70° C. until constant weight.

[0012] As a preferred technical solution of the present invention, in step (2), the mass ratio of the deionized water, the hydrogen peroxide, the 1-ethyl-3-methylimidazole acetate, the polyethylene glycol and the component A is 240-250:35-40:15-20:3-4:40-50.

[0013] As a preferred technical solution of the present invention, the polyethylene glycol in step (2) is at least one of polyethylene glycol 600 and polyethylene glycol 800.

[0014] As a preferred technical solution of the present invention, the ultrasonic power of the ultrasound in step (2) is 400-500W.

[0015] As a preferred technical solution of the present invention, the reaction conditions of the hydrothermal reaction in step (2) are to heat the mixture to 160-170°C at a heating rate of 4-5°C / min under a pressure of 18-20 MPa and then keep the temperature for 4-6 hours.

[0016] As a preferred technical solution of the present invention, the vacuum drying until constant weight in step (2) refers to vacuum drying at 50-70° C. until constant weight.

[0017] As a preferred technical solution of the present invention, the activation under carbon dioxide atmosphere in step (3) refers to introducing carbon dioxide gas at a flow rate of 150-200 mL / min per gram of component B and simultaneously heating the mixture to 850-900°C at a heating rate of 4-6°C / min and then keeping the temperature for 2-3 hours.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention is based on the fact that the starting raw materials for the preparation of activated carbon used in the food processing field are mostly biomass materials with high cellulose, hemicellulose and lignin content. The raw materials are creatively crushed, washed and dried in sequence, and then deionized water, hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate and polyethylene glycol in a certain weight ratio are used as reaction media, coupled with ultrasound, and hydrothermal reaction is carried out in a nitrogen atmosphere to prepare an activated carbon precursor. Finally, carbon dioxide is used as an activator to carry out physical activation within a certain temperature and time range, and an activated carbon is obtained after natural cooling to room temperature. The activated carbon not only has a high specific surface area and excellent adsorption capacity, but is also very suitable for use in the food processing field. In addition, in the entire activated carbon preparation process, no large amount of acid and alkali reagents need to be added, and the corrosion to the production equipment is low.

[0020] (2) The present invention is based on the fact that biomass materials are mainly composed of "three elements" namely cellulose, hemicellulose and lignin, and creatively conducts hydrothermal reaction coupled with ultrasonic treatment to prepare activated carbon precursor. In the reaction medium of the hydrothermal reaction, hydrogen peroxide mainly plays a strong oxidizing role, improves the reaction activity and surface oxygen-containing groups, and promotes adsorption capacity. 1-Ethyl-3-methylimidazolium acetate is widely used as an ionic liquid to dissolve cellulose and other components. However, due to the presence of deionized water in the reaction medium of the present invention, its actual dissolving effect is negligible. It mainly realizes hydrolysis, decomposition and other reactions through the π-π stacking of imidazole groups. It should be able to be carried out better. Polyethylene glycol contains multiple ether bond repeating units, which can form hydrogen bonds with the hydroxyl groups of components such as cellulose, weakening the stable spatial structure formed by the "three elements" themselves, and the cavitation effect of ultrasound accelerates the transmission efficiency between the media. Finally, the activated carbon precursor is physically activated in a carbon dioxide atmosphere to obtain an activated carbon. It not only has a high specific surface area and excellent adsorption capacity, but also does not require a large amount of acid and alkali reagents during the entire preparation process, and has little corrosion and damage to production equipment. At the same time, the reaction medium can be deeply removed by subsequent deionized water washing and physical activation high-temperature decomposition without residue, which is very suitable for the field of food processing.

[0021] (3) Compared with the prior art, the present invention creatively adds a certain weight ratio of hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate and polyethylene glycol to deionized water, so as to couple ultrasound to carry out hydrothermal reaction on biomass materials, thereby achieving more excellent technical effects. Even if no subsequent chemical activation is performed, activated carbon with high specific area and good adsorption capacity can still be obtained. DETAILED DESCRIPTION

[0022] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0023] Example 1

[0024] A method for preparing powdered activated carbon for food processing, the method comprising the following steps:

[0025] (1) The biomass material is crushed, then washed with deionized water, and finally vacuum dried until constant weight is obtained to obtain component A;

[0026] (2) adding hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate, polyethylene glycol and component A to deionized water, and then hydrothermally reacting the mixture under ultrasound in a nitrogen atmosphere, cooling the mixture naturally to room temperature, filtering the mixture, removing the filtrate, washing the mixture with deionized water, and finally vacuum drying the mixture until a constant weight is obtained to obtain component B;

[0027] (3) Activate the component B in a carbon dioxide atmosphere and cool it naturally to room temperature. The preparation is completed.

[0028] The biomass material in step (1) is coconut shell.

[0029] The pulverizing in step (1) refers to pulverizing until it can pass through a 50-mesh sieve.

[0030] The vacuum drying until constant weight in step (1) refers to vacuum drying at 50° C. until constant weight.

[0031] In step (2), the mass ratio of the deionized water, the hydrogen peroxide, the 1-ethyl-3-methylimidazole acetate, the polyethylene glycol and the component A is 240:35:15:3:40.

[0032] The polyethylene glycol in step (2) is polyethylene glycol 600.

[0033] The ultrasonic power of the ultrasound in step (2) is 400W.

[0034] The reaction conditions of the hydrothermal reaction in step (2) are to heat the mixture to 160° C. at a heating rate of 4° C. / min under a pressure of 18 MPa and then keep the temperature for 4 h.

[0035] The vacuum drying until constant weight in step (2) refers to vacuum drying at 50° C. until constant weight.

[0036] The activation under carbon dioxide atmosphere in step (3) refers to introducing carbon dioxide gas at a flow rate of 150 mL / min per gram of component B and simultaneously raising the temperature to 850° C. at a heating rate of 4° C. / min and then keeping the temperature for 2 hours.

[0037] Example 2

[0038] A method for preparing powdered activated carbon for food processing, the method comprising the following steps:

[0039] (1) The biomass material is crushed, then washed with deionized water, and finally vacuum dried until constant weight is obtained to obtain component A;

[0040] (2) adding hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate, polyethylene glycol and component A to deionized water, and then hydrothermally reacting the mixture under ultrasound in a nitrogen atmosphere, cooling the mixture naturally to room temperature, filtering the mixture, removing the filtrate, washing the mixture with deionized water, and finally vacuum drying the mixture until a constant weight is obtained to obtain component B;

[0041] (3) Activate the component B in a carbon dioxide atmosphere and cool it naturally to room temperature. The preparation is completed.

[0042] The biomass material in step (1) is coconut shell.

[0043] The pulverizing in step (1) refers to pulverizing until the product can pass through a 60-mesh sieve.

[0044] The vacuum drying until constant weight in step (1) refers to vacuum drying at 70° C. until constant weight.

[0045] In step (2), the mass ratio of the deionized water, the hydrogen peroxide, the 1-ethyl-3-methylimidazole acetate, the polyethylene glycol and the component A is 250:40:20:4:50.

[0046] The polyethylene glycol in step (2) is polyethylene glycol 800.

[0047] The ultrasonic power of the ultrasound in step (2) is 500W.

[0048] The reaction conditions of the hydrothermal reaction in step (2) are to heat the mixture to 170° C. at a heating rate of 5° C. / min under a pressure of 20 MPa and then keep the temperature for 6 h.

[0049] The vacuum drying until constant weight in step (2) refers to vacuum drying at 70° C. until constant weight.

[0050] The activation under carbon dioxide atmosphere in step (3) refers to introducing carbon dioxide gas at a flow rate of 200 mL / min per gram of component B and simultaneously raising the temperature to 900° C. at a heating rate of 6° C. / min and then keeping the temperature for 3 hours.

[0051] Example 3

[0052] A method for preparing powdered activated carbon for food processing, the method comprising the following steps:

[0053] (1) The biomass material is crushed, then washed with deionized water, and finally vacuum dried until constant weight is obtained to obtain component A;

[0054] (2) adding hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate, polyethylene glycol and component A to deionized water, and then hydrothermally reacting the mixture under ultrasound in a nitrogen atmosphere, cooling the mixture naturally to room temperature, filtering the mixture, removing the filtrate, washing the mixture with deionized water, and finally vacuum drying the mixture until a constant weight is obtained to obtain component B;

[0055] (3) Activate the component B in a carbon dioxide atmosphere and cool it naturally to room temperature. The preparation is completed.

[0056] The biomass material in step (1) is coconut shell.

[0057] The pulverizing in step (1) refers to pulverizing until the particles can pass through a 55-mesh sieve.

[0058] The vacuum drying until constant weight in step (1) refers to vacuum drying at 60° C. until constant weight.

[0059] In step (2), the mass ratio of the deionized water, the hydrogen peroxide, the 1-ethyl-3-methylimidazole acetate, the polyethylene glycol and the component A is 245:38:18:3.5:45.

[0060] The polyethylene glycol in step (2) is polyethylene glycol 600.

[0061] The ultrasonic power of the ultrasound in step (2) is 450W.

[0062] The reaction conditions of the hydrothermal reaction in step (2) are to heat the mixture to 165° C. at a heating rate of 4° C. / min under a pressure of 19 MPa and then keep the temperature for 5 h.

[0063] The vacuum drying until constant weight in step (2) refers to vacuum drying at 60° C. until constant weight.

[0064] The activation under carbon dioxide atmosphere in step (3) means that, based on each gram of component B, carbon dioxide gas is introduced at a flow rate of 180 mL / min and the temperature is simultaneously raised to 880° C. at a heating rate of 5° C. / min and then kept at this temperature for 2.5 h.

[0065] Example 4

[0066] A method for preparing powdered activated carbon for food processing, the method comprising the following steps:

[0067] (1) The biomass material is crushed, then washed with deionized water, and finally vacuum dried until constant weight is obtained to obtain component A;

[0068] (2) adding hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate, polyethylene glycol and component A to deionized water, and then hydrothermally reacting the mixture under ultrasound in a nitrogen atmosphere, cooling the mixture naturally to room temperature, filtering the mixture, removing the filtrate, washing the mixture with deionized water, and finally vacuum drying the mixture until a constant weight is obtained to obtain component B;

[0069] (3) Activate the component B in a carbon dioxide atmosphere and cool it naturally to room temperature. The preparation is completed.

[0070] The biomass material in step (1) is coconut shell.

[0071] The pulverizing in step (1) refers to pulverizing until it can pass through a 50-mesh sieve.

[0072] The vacuum drying until constant weight in step (1) refers to vacuum drying at 55° C. until constant weight.

[0073] In step (2), the mass ratio of the deionized water, the hydrogen peroxide, the 1-ethyl-3-methylimidazole acetate, the polyethylene glycol and the component A is 240:40:17:4:45.

[0074] The polyethylene glycol in step (2) is polyethylene glycol 600.

[0075] The ultrasonic power of the ultrasound in step (2) is 500W.

[0076] The reaction conditions of the hydrothermal reaction in step (2) are to heat the mixture to 165° C. at a heating rate of 5° C. / min under a pressure of 20 MPa and then keep the temperature for 6 h.

[0077] The vacuum drying until constant weight in step (2) refers to vacuum drying at 60° C. until constant weight.

[0078] The activation under carbon dioxide atmosphere in step (3) means that, based on each gram of component B, carbon dioxide gas is introduced at a flow rate of 170 mL / min and the temperature is simultaneously raised to 850° C. at a heating rate of 4° C. / min and then kept at this temperature for 3 h.

[0079] Comparative Example 1

[0080] Based on Example 1, ultrasound is not performed in step (2), and the rest remain unchanged.

[0081] Comparative Example 2

[0082] Based on Example 1, hydrogen peroxide was replaced by an equal weight of 1-ethyl-3-methylimidazolium acetate, and the rest remained unchanged.

[0083] Comparative Example 3

[0084] On the basis of Example 1, 1-ethyl-3-methylimidazole acetate was replaced with an equal weight of polyethylene glycol 600, and the rest remained unchanged.

[0085] Comparative Example 4

[0086] Based on Example 1, polyethylene glycol 600 was replaced by an equal weight of hydrogen peroxide, and the rest remained unchanged.

[0087] Comparative Example 5

[0088] On the basis of Example 1, hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate and polyethylene glycol 600 were replaced by deionized water of equal weight, and the rest remained unchanged.

[0089] Test Example 1

[0090] BET Test:

[0091] The powdered activated carbons prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to BET tests respectively. The testing instrument was a fully automatic specific surface area analyzer produced by Micromeritics Instruments, Inc., USA, model number ASAP2420-4MP.

[0092] Table 1. BET test results

[0093]

[0094] Test Example 2

[0095] Iodine adsorption value test:

[0096] The powdered activated carbons prepared in Examples 1-4 and Comparative Examples 1-5 were respectively subjected to iodine adsorption value tests according to standard GB / T 12496.8-2015 to illustrate the adsorption capacity.

[0097] Table 2. Iodine adsorption test results

[0098]

[0099] From Test Examples 1-2, as shown in Table 1 and Table 2, it can be seen from the comparison between Example 1 and Comparative Examples 1-5 that the powdered activated carbon prepared by the present invention has a high specific surface area and excellent adsorption capacity. At the same time, no large amount of acid and alkali reagents are required in the entire preparation process of the powdered activated carbon, and the corrosion to the production equipment is small, which is very suitable for application in the field of food processing.

[0100] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing powdered activated carbon for food processing, characterized in that: The preparation method comprises the following steps: (1) The biomass material is crushed, then washed with deionized water, and finally vacuum dried until constant weight is obtained to obtain component A; (2) adding hydrogen peroxide, 1-ethyl-3-methylimidazolium acetate, polyethylene glycol and component A to deionized water, and then hydrothermally reacting the mixture under ultrasound in a nitrogen atmosphere, cooling the mixture naturally to room temperature, filtering the mixture, removing the filtrate, washing the mixture with deionized water, and finally vacuum drying the mixture until a constant weight is obtained to obtain component B; (3) activating the component B in a carbon dioxide atmosphere and naturally cooling it to room temperature, thereby completing the preparation; In step (2), the mass ratio of the deionized water, the hydrogen peroxide, the 1-ethyl-3-methylimidazolium acetate, the polyethylene glycol and the component A is 240-250:35-40:15-20:3-4:40-50; The polyethylene glycol in step (2) is at least one of polyethylene glycol 600 and polyethylene glycol 800; The reaction conditions of the hydrothermal reaction in step (2) are to heat the mixture to 160-170° C. at a heating rate of 4-5° C. / min under a pressure of 18-20 MPa and then keep the temperature for 4-6 hours.

2. The method for preparing powdered activated carbon for food processing according to claim 1, characterized in that: The biomass material in step (1) is at least one of corn cobs, peanut shells, rice husks and coconut shells.

3. The method for preparing powdered activated carbon for food processing according to claim 1, characterized in that: The pulverizing in step (1) refers to pulverizing until the product can pass through a 50-60 mesh sieve.

4. The method for preparing powdered activated carbon for food processing according to claim 1, characterized in that: The vacuum drying until constant weight in step (1) refers to vacuum drying at 50-70° C. until constant weight.

5. The method for preparing powdered activated carbon for food processing according to claim 1, characterized in that: The ultrasonic power of the ultrasound in step (2) is 400-500W.

6. The method for preparing powdered activated carbon for food processing according to claim 1, characterized in that: The vacuum drying until constant weight in step (2) refers to vacuum drying at 50-70° C. until constant weight.

7. The method for preparing powdered activated carbon for food processing according to claim 1, characterized in that: The activation under carbon dioxide atmosphere in step (3) refers to introducing carbon dioxide gas at a flow rate of 150-200 mL / min per gram of component B and simultaneously heating the mixture to 850-900°C at a heating rate of 4-6°C / min and then keeping the temperature for 2-3 hours.

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