Preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon

Abstract

The application discloses a preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon, and the wet-process phosphoric acid used for activating sawdust is preheated, and then the preheated wet-process phosphoric acid is used for preparing the activated carbon from the sawdust. The activated carbon treated by the method has the characteristics of low ash content and high quality. In addition, the method has the characteristics of short time consumption, small acid consumption and low cost, and is suitable for industrial promotion.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of activated carbon, in particular, a preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon. BACKGROUND

[0002] The wet-process phosphoric acid activated carbon is a kind of activated carbon obtained by activating wood chips with wet-process phosphoric acid as an activator, and its conventional preparation process is to mix wet-process phosphoric acid with biomass raw materials such as wood chips, then heat and activate, and finally acid wash and dry.

[0003] In order to obtain high-quality wet-process phosphoric acid activated carbon, the current wet-process phosphoric acid process generally needs to increase the activation temperature to above 550℃ (the actual activation temperature of some activated carbon processing enterprises may be higher), so as to obtain activated carbon with larger iodine adsorption value and methylene blue adsorption value. However, the activation at a high temperature will cause the wet-process phosphoric acid to be excessively dehydrated to generate insoluble pyrophosphoric acid and polyphosphoric acid, and even polyphosphoric acid, and with the increase of the polymerization degree of phosphoric acid, the polyphosphoric acid and the metal ions in the wood chips will form more insoluble polyphosphates. The generation of these polyphosphoric acid and polyphosphates not only further reduces the content of orthophosphoric acid in the wet-process phosphoric acid, thereby reducing the activation effect, and these insoluble pyrophosphoric acid, polyphosphoric acid, polyphosphoric acid and polyphosphates will also form ash residues in the activated carbon, thereby causing the activated carbon to have a high ash content.

[0004] That is, high-temperature activation not only further reduces the content of orthophosphoric acid in the wet-process phosphoric acid, but also causes ash residues to be retained in the activated carbon, ultimately resulting in a decrease in the quality of the wet-process phosphoric acid activated carbon.

[0005] However, if the activation treatment is performed at a lower activation temperature, although it can avoid the generation of a larger amount of polyphosphoric acid and polyphosphates, due to the unsatisfactory low-temperature activation effect, the quality of the activated carbon is low, and few activated carbon production enterprises will adopt this method.

[0006] In addition, since the wet-process phosphoric acid itself contains a large amount of polyphosphoric acid and polyphosphoric acid, the wet-process phosphoric acid has a large viscosity and poor flowability at a low temperature, so it is difficult for the orthophosphoric acid, which plays a role in activation, to enter the inside of the wood chips. When the temperature is increased, although the viscosity of the wet-process phosphoric acid gradually decreases and its flowability also increases, the aforementioned phenomenon that the polyphosphoric acid will continuously increase with the increase of the temperature will occur, thereby further reducing the concentration of the orthophosphoric acid and the activation effect.

[0007] Although some enterprises currently adopt the methods of prolonging the impregnation time, increasing the phosphoric acid content and adding additives to overcome the aforementioned problems to some extent, the defects that follow are long time consumption (generally 6-10h) and production cost increase, which are not friendly to enterprises.

[0008] Therefore, how to shorten the process time, reduce the phosphoric acid dosage and lower the activation temperature under the premise of improving the quality of activated carbon is the focus of the current research in this field. SUMMARY

[0009] The purpose of the present application is to provide a preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon. The activated carbon treated by the process of the present application has the characteristics of low ash content and high quality. In addition, the process of the present application has the characteristics of short time consumption, small amount of acid used and low cost, and is suitable for industrial promotion.

[0010] The technical solution of the present application is a preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon, which preheats the wet-process phosphoric acid used for activation of sawdust, and then uses the preheated wet-process phosphoric acid to prepare activated carbon from sawdust.

[0011] The aforementioned preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon comprises the following steps:

[0012] (1) The sawdust is first dried, then crushed and sieved to obtain wood powder;

[0013] (2) The wet-process phosphoric acid is taken and preheated to obtain hot wet-process phosphoric acid;

[0014] (3) The wood powder is added to the hot wet-process phosphoric acid while hot and stirred uniformly, and then heated under the protection of inert gas for activation for 1-3h to obtain activated material;

[0015] (4) The activated material is taken out and cooled, then acid washed with phosphoric acid solution, then washed with deionized water until neutral, and finally dried to obtain activated carbon.

[0016] The aforementioned preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon comprises the following steps:

[0017] (1) The sawdust is first dried at 70-90℃, then crushed and sieved to 20-60 mesh to obtain wood powder;

[0018] (2) The wet-process phosphoric acid is taken and preheated at 50-90℃ for 5-20min to obtain hot wet-process phosphoric acid;

[0019] (3) The wood powder is added to the hot wet-process phosphoric acid while hot and stirred uniformly, and then heated under the protection of inert gas to 400-500℃ for activation for 1-3h to obtain activated material;

[0020] (4) The activated material is taken out and cooled, and then is subjected to acid washing with a phosphoric acid solution, and then is washed with deionized water until neutral, and finally is dried to obtain the activated carbon.

[0021] The aforementioned preparation method of the high-quality and low-cost wet-process phosphoric acid activated carbon, the drying temperature in step (1) is 80℃.

[0022] The aforementioned preparation method of the high-quality and low-cost wet-process phosphoric acid activated carbon, the concentration of the wet-process phosphoric acid in step (2) is 40-50Be.

[0023] The aforementioned preparation method of the high-quality and low-cost wet-process phosphoric acid activated carbon, the preheating temperature in step (2) is 70℃, and the time is 10min.

[0024] The aforementioned preparation method of the high-quality and low-cost wet-process phosphoric acid activated carbon, the mass ratio of the heated wet-process phosphoric acid to the wood powder in step (3) is 2-3:1.

[0025] The aforementioned preparation method of the high-quality and low-cost wet-process phosphoric acid activated carbon, the heating rate in step (3) is 10℃ / min, and the final activation temperature is 450℃.

[0026] The aforementioned preparation method of the high-quality and low-cost wet-process phosphoric acid activated carbon, the activated material in step (4) is cooled to room temperature.

[0027] The aforementioned preparation method of the high-quality and low-cost wet-process phosphoric acid activated carbon, the concentration of the phosphoric acid solution in step (4) is 10Be, and the temperature is 80℃.

[0028] Advantages of the present application

[0029] The present application can promote the hydrolysis of polyphosphoric acid in the wet-process phosphoric acid to form orthophosphoric acid at low-temperature preheating, thereby improving the flowability of the wet-process phosphoric acid and the content of orthophosphoric acid, especially when the preheating treatment is at about 70℃, the orthophosphoric acid content is the highest, when the preheated wet-process phosphoric acid is mixed with wood chips, a large amount of orthophosphoric acid in it can quickly enter the inside of the wood chips, thereby improving the subsequent activation effect; and the extra orthophosphoric acid is generated by the hydrolysis of the polyphosphoric acid of the wet-process phosphoric acid itself, and no additional phosphoric acid is needed, so the amount of phosphoric acid is also reduced.

[0030] Meanwhile, since a large amount of orthophosphoric acid is activated in the inside of the sawdust in advance, the process of the present application does not need additional prolonged impregnation time; and the activation temperature can be lowered on the basis of the original activation temperature of 550 DEG C or above, and the present applicant has found that the process of the present application can obtain good activation effect when the activation is carried out at about 450 DEG C; in addition, the generation amount of polyphosphoric acid and polyphosphate is relatively small at this temperature, and the content of polyphosphoric acid is also reduced due to the decomposition of polyphosphoric acid during preheating, so that the ash content of the activated carbon is further reduced, and the iodine value and methylene blue value are improved.

[0031] In summary, the activated carbon treated by the process of the present application has the advantages of low ash content and high quality, and the process of the present application has the advantages of short time consumption, small amount of acid used and low cost, and is suitable for industrial promotion. BRIEF DESCRIPTION OF DRAWINGS

[0032] ATTACHMENT Figure 1 Performance of activated carbon prepared by phosphoric acid with different polymerization degrees;

[0033] ATTACHMENT Figure 2 Phosphoric acid content in wet-process phosphoric acid with different polymerization degrees; Figure 2 It can be seen that the higher the polymerization degree of phosphoric acid is, the lower the phosphoric acid content is;

[0034] ATTACHMENT Figure 3 Orthophosphoric acid content in wet-process phosphoric acid treated for 10 min at different preheating temperatures. DETAILED DESCRIPTION

[0035] The present application will be further described below in conjunction with examples, but is not limited to the basis of the present application.

[0036] Embodiments of the present application

[0037] Example 1

[0038] A preparation method of high-quality and low-cost wet-process phosphoric acid activated carbon, the specific steps are as follows:

[0039] (1) 5g sawdust is first dried at 80 DEG C, then crushed and sieved to 20-60 meshes to obtain wood powder;

[0040] (2) 10g of wet-process phosphoric acid with a concentration of 45Be is preheated at 70 DEG C for 10 min to obtain hot wet-process phosphoric acid;

[0041] (3) The hot wet-process phosphoric acid is heated to 450 DEG C at a rate of 10 DEG C / min under the protection of inert gas to activate for 2h to obtain activated material;

[0042] (4) The activated material is taken out and cooled to room temperature, then washed with a phosphoric acid solution with a concentration of 10Be, then washed with deionized water until neutral, and finally dried at 120°C to obtain activated carbon.

[0043] Example 2

[0044] A high-quality and low-cost preparation method of wet-process phosphoric acid activated carbon, the specific steps are as follows:

[0045] (1) 5g sawdust is first dried at 70°C, then crushed and sieved to 20-60 mesh to obtain wood powder;

[0046] (2) 12g wet-process phosphoric acid with a concentration of 50Be is preheated at 50°C for 20min to obtain hot wet-process phosphoric acid;

[0047] (3) The wood powder is added to the hot wet-process phosphoric acid while hot and stirred uniformly, then heated to 400°C at a rate of 10°C / min under the protection of inert gas for activation for 3h to obtain activated material;

[0048] (4) The activated material is taken out and cooled to room temperature, then washed with a phosphoric acid solution with a concentration of 10Be, then washed with deionized water until neutral, and finally dried at 120°C to obtain activated carbon.

[0049] Example 3

[0050] A high-quality and low-cost preparation method of wet-process phosphoric acid activated carbon, the specific steps are as follows:

[0051] (1) 5g sawdust is first dried at 90°C, then crushed and sieved to 20-60 mesh to obtain wood powder;

[0052] (2) 15g wet-process phosphoric acid with a concentration of 40Be is preheated at 90°C for 5min to obtain hot wet-process phosphoric acid;

[0053] (3) The wood powder is added to the hot wet-process phosphoric acid while hot and stirred uniformly, then heated to 500°C at a rate of 10°C / min under the protection of inert gas for activation for 1h to obtain activated material;

[0054] (4) The activated material is taken out and cooled to room temperature, then washed with a phosphoric acid solution with a concentration of 10Be, then washed with deionized water until neutral, and finally dried at 120°C to obtain activated carbon.

[0055] Example 4

[0056] The applicant selects three different polymeric phosphoric acids, orthophosphoric acid, pyrophosphoric acid and metapolyphosphoric acid, and activates the sawdust according to the process of Example 1 to prepare activated carbon, and the performance of the obtained activated carbon is as shown in Table 1. Figure 1 FromFigure 1 It can be seen that the ash content, iodine value and methylene blue value of the activated carbon activated by orthophosphoric acid are higher than those of the activated carbon activated by pyrophosphoric acid and meta-phosphoric acid, especially the activated carbon activated by meta-phosphoric acid, the ash content, iodine value and methylene blue value of which are far lower than those of the activated carbon activated by orthophosphoric acid. Therefore, the higher the content of orthophosphoric acid contained in the wet-process phosphoric acid, the better the activation effect, and the increase of the content of polyphosphoric acid and polyphosphoric acid salt will cause the performance of the activated carbon to decrease obviously.

[0057] Example 5

[0058] The applicant detected the content of orthophosphoric acid in the wet-process phosphoric acid after preheating treatment for 10 min at different temperatures, and the results are shown in Table 2. Figure 3 Figure 3 It can be seen that when the wet-process phosphoric acid is preheated, the content of orthophosphoric acid increases first and then decreases, and the content of orthophosphoric acid is the highest when the preheating treatment is performed at about 70°C for 10 min.

[0059] Example 6

[0060] The applicant also conducted a quality comparison experiment of activated carbon treated by different preheating temperatures and processes. Specifically, 6 batches of wet-process phosphoric acid were taken, 2 batches of which were not preheated, one batch of which was activated according to the other steps of Example 1 without preheating, and the obtained activated carbon was recorded as AC-no, and the other batch was also activated according to the other steps of Example 1 without preheating, but the wood powder was immersed for 12 h before the activation treatment, and the obtained activated carbon was recorded as AC-(immersed for 12 h); and the other 4 batches were activated according to the process of Example 1, the difference being that the preheating temperatures were 30°C, 50°C, 70°C and 90°C in turn, and the obtained activated carbon was recorded as AC-30, AC-50, AC-70 and AC-90 in turn. Then the activated carbon recorded as AC-no, AC-30, AC-50, AC-70, AC-90 and AC-(immersed for 12 h) was detected, and the detection results are shown in Table 1.

[0061] Table 1 Quality comparison of activated carbon treated by different preheating temperatures and processes

[0062]

[0063] As can be seen from Table 1, when the preheating temperature is 70°C, the ash content of the prepared activated carbon is the lowest, the iodine value is the largest, and the methylene blue value is the highest, which is consistent with our previous conclusion, because at 70°C, the hydrolysis degree of polyphosphoric acid in the wet-process phosphoric acid is the highest, that is, the content of orthophosphoric acid is the highest (as shown in Table 2). Figure 3 ​), second, preheating phosphoric acid, to some extent, can promote the phosphoric acid solution into the biomass sawdust inside, so that the activation is more sufficient. Therefore, the wet method of phosphoric acid is taken in the way of preheating, which can increase the quality of activated carbon, and reduce the production cost.

[0064] The above is only a preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art, according to the technical solution and the inventive concept of the present application, should be covered within the protection scope of the present application.

Claims

1. A method for preparing high quality low cost wet-process phosphoric acid activated carbon, characterized by, The method comprises the following steps: (1) drying sawdust first, then crushing and screening to obtain wood powder; (2) taking wet-process phosphoric acid, preheating it at 50-90℃ for 5-20 min to obtain hot wet-process phosphoric acid; (3) adding wood powder into the hot wet-process phosphoric acid while hot and stirring uniformly, then continuing to heat to 400-500℃ under the protection of inert gas for 1-3 h to obtain activated material; (4) taking out the activated material to cool, then acid washing with phosphoric acid solution first, then washing with deionized water until neutral, and finally drying to obtain activated carbon.

2. The preparation method of high quality and low cost wet-process phosphoric acid activated carbon according to claim 1, characterized in that, The method comprises the following steps: (1) drying sawdust first at 70-90℃, then crushing and screening to 20-60 mesh to obtain wood powder; (2) taking wet-process phosphoric acid, preheating it at 50-90℃ for 5-20 min to obtain hot wet-process phosphoric acid; (3) adding wood powder into the hot wet-process phosphoric acid while hot and stirring uniformly, then continuing to heat to 400-500℃ under the protection of inert gas for 1-3 h to obtain activated material; (4) taking out the activated material to cool, then acid washing with phosphoric acid solution first, then washing with deionized water until neutral, and finally drying to obtain activated carbon.

3. The process for the preparation of high quality low cost wet process phosphoric acid activated carbon as claimed in claim 2 wherein: The drying temperature in step (1) is 80℃.

4. The process for the preparation of high quality low cost wet process phosphoric acid activated carbon as claimed in claim 2 wherein: The concentration of the wet-process phosphoric acid in step (2) is 40-50 Baume.

5. The process for the preparation of high quality low cost wet process phosphoric acid activated carbon as claimed in claim 2 wherein: The preheating temperature in step (2) is 70℃, and the time is 10 min.

6. The process for the preparation of high quality low cost wet process phosphoric acid activated carbon as claimed in claim 2 wherein: The mass ratio of the hot wet-process phosphoric acid to wood powder in step (3) is 2-3:

1.

7. The process for the preparation of high quality low cost wet process phosphoric acid activated carbon as claimed in claim 2 wherein: The heating rate in step (3) is 10℃ / min, and the final activation temperature is 450℃.

8. The process for the preparation of high quality low cost wet process phosphoric acid activated carbon as claimed in claim 2 wherein: The activated material in step (4) is cooled to room temperature.

9. The process for the preparation of high quality low cost wet process phosphoric acid activated carbon as claimed in claim 2 wherein: The concentration of the phosphoric acid solution in step (4) is 10 Baume, and the temperature is 80℃.

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