Method for preparing high-performance activated carbon from coconut shell by gasification and activation and application thereof

Abstract

The application relates to a method for preparing high-performance coconut shell activated carbon and application, and relates to a method for preparing high-performance coconut shell activated carbon. The application aims to solve the problems of high energy consumption, long activation time and high cost of additional reagents in the prior art. The method comprises the following steps: 1, crushing coconut shells; 2, ball milling the crushed coconut shells and coconut bran; 3, controlling temperature for calcination in sections; and 4, activating the reaction product by passing into hot steam to obtain high-performance coconut shell activated carbon. The method improves the performance of the activated carbon from two microcosmic aspects of atomic composition and atomic configuration, improves the graphitization degree of carbon atoms on one hand, and introduces nitrogen / sulfur / phosphorus heteroatoms to simultaneously affect the spin effect, charge effect and ligand effect of carbon atoms in the crystal lattice and further strengthen the adsorption of organic matters on the other hand. The whole process does not need additional chemical reagents, the technological process is simple, and the method is beneficial to industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing high-performance coconut shell activated carbon. BACKGROUND

[0002] Global warming is an environmental problem that mankind is facing together, and the global greenhouse effect is gradually intensifying due to the emission of a large amount of carbon dioxide. In addition to taking measures to limit industrial carbon emissions, it is also important to fix and store CO2 in the atmosphere. Crops play an indispensable role in carbon sequestration, as they fix carbon dioxide in the air into their own organic carbohydrates through photosynthesis. Coconut shell is a common agricultural by-product, and the global annual production of coconut shell waste is as high as 3 million tons, and our country produces about 270,000 tons of coconut shell waste every year, that is, an average of 740 tons of coconut shell is discarded every day. However, in many places, coconut shells are still regarded as garbage and are usually discarded or burned in the open air, which not only limits the resource utilization of coconut shells, but also harms human health and exacerbates environmental pollution and the greenhouse effect.

[0003] As a biomass rich in lignin and cellulose, coconut shell, under the action of biomass gasification, on the one hand, will produce synthesis gas such as CO, CO2, H2, CH4, which can be directly used as an internal combustion engine fuel, or can be further processed and utilized, such as power generation, hydrogen production, liquid fuel production, etc., thereby reducing the consumption of fossil energy; on the other hand, it will produce solid by-product biomass charcoal, which can be converted into activated carbon with high added value after further physical activation or chemical activation. Due to the high specific surface area and porous structure, activated carbon shows superior adsorption capacity, and at the same time, activated carbon has high chemical stability, not only can withstand high temperature and high pressure, but also can be used in a wide pH range. At present, activated carbon has been widely used in water pollution treatment, development of catalysts and catalyst carriers, etc.

[0004] The existing method for preparing activated carbon from coconut shells mainly uses physical activation and chemical activation. Traditional physical activation usually uses single CO2 to activate the biomass raw material, which not only requires high temperature and long reaction time, but also cannot effectively utilize waste heat, often resulting in high energy consumption; in addition, the activators used in the existing chemical activation method can be divided into alkaline (such as KOH, NaOH) and acidic (such as H3PO4) activators, which not only usually have high cost, but also have certain corrosiveness to production equipment, and the prepared activated carbon also needs to be post-treated, so it is not suitable for large-scale production. SUMMARY

[0005] The purpose of the present application is to solve the problems of high energy consumption, long activation time and high cost of additional reagents in the prior art, and to provide a method for preparing high-performance coconut shell activated carbon by gasification activation and application.

[0006] The application discloses a method for preparing high-performance coconut shell activated carbon through gasification and activation, and specifically is completed through the following steps.

[0007] I. Taking coconut shells as raw materials, the coconut shells are crushed in a crusher, sieved and dried to obtain crushed coconut shells;

[0008] II. The crushed coconut shells, coconut bran and corundum balls are put into a planetary polytetrafluoroethylene ball mill tank, and then the ball mill tank is placed in a planetary ball mill to perform ball milling, so as to obtain mixed biomass;

[0009] III. The mixed biomass is put into a tube furnace to be calcined in a segmented temperature control mode, so as to obtain a reaction product;

[0010] IV. The reaction product is introduced into hot steam for activation, so as to obtain high-performance coconut shell activated carbon.

[0011] Principles of the application:

[0012] The application takes coconut shells as raw materials, adopts coconut bran for doping modification, the coconut bran contains nitrogen, sulfur and phosphorus heteroatoms, and high-performance activated carbon is prepared through gasification and activation, so that the coconut shells achieve a comprehensive utilization method. The method can scientifically and reasonably prepare high-performance activated carbon in an efficient and environmentally friendly manner, and obtain combustible gases such as CO, CH4 and H2. The combustible gas generated in the biomass gasification process can be used as clean energy instead of coal, and the combustion waste heat can be used for heating; meanwhile, the coconut shell activated carbon has a high specific surface area and rich pore structure, and has a certain degree of graphitization, and can effectively adsorb emerging pollutants bisphenol A (BPA) and heavy metal copper ions; the application can effectively realize waste resource utilization, energy saving and emission reduction and water pollution treatment, and does not need to add chemical reagents in the whole process, and the process flow is simple, which is beneficial to industrial production.

[0013] Compared with the prior art, the application has the following beneficial effects:

[0014] I. The application takes coconut shells as raw materials, and the coconut bran is doped and modified, and all raw materials come from a coconut processing industry chain;

[0015] II. The application improves the performance of activated carbon from two microcosmic aspects of atomic composition and atomic configuration, improves the graphitization degree of carbon atoms on one hand, and introduces nitrogen / sulfur / phosphorus heteroatoms to simultaneously affect the spin effect, charge effect and ligand effect of carbon atoms in the crystal lattice on the other hand, and further strengthens the adsorption of the activated carbon on organic matters;

[0016] Thirdly, the method of the present application adopts gasification and activation in combination, realizes gasification and activation in combination by controlling temperature in stages, and produces active carbon and clean combustible gas at the same time; the combustible components in the coconut shell generate clean gas fuel such as CO, H2 and CH4 through drying, pyrolysis, oxidation and reduction processes at high temperature; the solid product of gasification, biochar, is further prepared into active carbon through steam activation; the large amount of heat released in the oxidation stage can be used for drying, pyrolysis and reduction stages through heat conduction, thereby realizing comprehensive utilization of gas, solid and heat in the gasification preparation; meanwhile, no additional chemical reagent is needed in the whole process, the process flow is simple, and it is conducive to industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Adsorption kinetics diagram of BPA by the active carbon HC prepared in Example 1 and H5P1-C prepared in Example 2;

[0018] Figure 2 Adsorption kinetics diagram of metal divalent copper (Cu 2+ ) by the active carbon HC prepared in Example 1 and H5P1-C prepared in Example 2;

[0019] Figure 3 Adsorption determination results of the coconut shell active carbon HC prepared in Example 1, H5P1-C prepared in Example 2 and H3P3-C prepared in Example 3. DETAILED DESCRIPTION

[0020] Specific embodiment one: the method of the present embodiment for preparing high-performance coconut shell active carbon through gasification and activation is completed according to the following steps:

[0021] I. Taking coconut shell as raw material, the coconut shell is crushed in a crusher, sieved and dried to obtain crushed coconut shell;

[0022] II. The crushed coconut shell, coconut bran and corundum balls are put into a planetary polytetrafluoroethylene ball mill jar, and then the ball mill jar is placed in a planetary ball mill for ball milling to obtain mixed biomass;

[0023] III. The mixed biomass is put into a tube furnace for calcination by controlling temperature in stages to obtain reaction products;

[0024] IV. The reaction products are introduced into hot steam for activation to obtain a high-performance coconut shell active carbon.

[0025] Specific embodiment two: the difference between the present embodiment and specific embodiment one is that the temperature of drying in step I is 180-200℃, and the time of drying is 2-3h. The other steps are the same as those in specific embodiment one.

[0026] Specific embodiment three: the difference between this embodiment and one or two of the specific embodiments is that in step one, the coconut shell is crushed in a crusher and then passed through a 100-200 mesh sieve. The other steps are the same as in one or two of the specific embodiments.

[0027] Specific embodiment four: the difference between this embodiment and one to three of the specific embodiments is that in step two, the mass ratio of the crushed coconut shell to the coconut bran is (3-6):(0-3). The other steps are the same as in one to three of the specific embodiments.

[0028] Specific embodiment five: the difference between this embodiment and one to four of the specific embodiments is that in step two, the mass ratio of the total mass of the crushed coconut shell and coconut bran to the corundum balls is 6:100. The other steps are the same as in one to four of the specific embodiments.

[0029] Specific embodiment six: the difference between this embodiment and one to five of the specific embodiments is that in step two, the speed of the ball mill is 650 r / min-750 / min, and the ball milling time is 1.5 h-2 h. The other steps are the same as in one to five of the specific embodiments.

[0030] Specific embodiment seven: the difference between this embodiment and one to six of the specific embodiments is that in step three, the specific process of the segmented temperature control calcination is as follows: under the protection of a nitrogen atmosphere, heating at a rate of 5°C / min-10°C / min to 200°C-600°C, heating for 2 h-3 h, then heating at a rate of 5°C / min-10°C / min to 600°C-800°C, heating for 2 h-3 h, and finally cooling at a rate of 5°C / min-10°C / min to 650°C-600°C, and maintaining the temperature at 650°C-600°C for 1.5 h-2 h. The other steps are the same as in one to six of the specific embodiments.

[0031] Specific embodiment eight: the difference between this embodiment and one to seven of the specific embodiments is that in step four, the specific process of the hot steam activation is as follows: the temperature of the tube furnace is raised to 800°C-950°C, water vapor is introduced into the tube furnace, and the hot steam activation time is 2 h-3 h, obtaining coconut shell activated carbon. The other steps are the same as in one to seven of the specific embodiments.

[0032] Specific embodiment nine: this embodiment is a high-performance coconut shell activated carbon for adsorbing organic pollutants and heavy metal ions. The other steps are the same as in one to eight of the specific embodiments.

[0033] Specific embodiment ten: the difference between this embodiment and nine of the specific embodiments is that the organic pollutants are bisphenol A, and the heavy metal ions are copper ions. The other steps are the same as in nine of the specific embodiments.

[0034] The beneficial effects of the present application are verified by the following examples:

[0035] Example 1: A method for preparing high-performance coconut shell activated carbon by gasification activation is completed according to the following steps:

[0036] I. Taking coconut shell as raw material, the coconut shell is crushed in a crusher and sieved through a 200-mesh sieve, and then dried at 200℃ for 2h to obtain crushed coconut shell;

[0037] II. The crushed coconut shell, coconut bran and corundum balls are put into a planetary polytetrafluoroethylene ball mill jar, and then the ball mill jar is placed in a planetary ball mill for ball milling to obtain mixed biomass;

[0038] The mass ratio of the crushed coconut shell to the coconut bran in step II is 6:0;

[0039] The mass ratio of the total mass of the crushed coconut shell and the coconut bran to the mass of the corundum balls in step II is 6:100;

[0040] The speed of ball milling in step II is 700rpm, and the ball milling time is 2h;

[0041] III. The mixed biomass is put into a tube furnace for staged temperature control calcination to obtain a reaction product;

[0042] The specific process of the staged temperature control calcination in step III is: heating to 600℃ at a heating rate of 10℃ / min under the protection of nitrogen atmosphere, heating for 2h, then heating to 800℃ at a heating rate of 10℃ / min, heating for 2h, and finally cooling to 600℃ at a cooling rate of 10℃ / min, and keeping the temperature at 600℃ for 2h;

[0043] IV. The reaction product is subjected to hot steam activation to obtain a high-performance coconut shell activated carbon.

[0044] The specific process of the hot steam activation in step IV is: the temperature of the tube furnace is raised to 800℃, water vapor is introduced into the tube furnace, and the hot steam activation time is 2h to obtain coconut shell activated carbon (HC).

[0045] Example 2: The difference between this example and Example 1 is that the mass ratio of the crushed coconut shell to the coconut bran in step II is 5:1; and step IV obtains a high-performance coconut shell activated carbon doped with nitrogen in situ (H5P1-C). The other steps and parameters are the same as those in Example 1.

[0046] Example 3: The difference between this example and Example 1 is that the mass ratio of the crushed coconut shell to the coconut bran in step II is 3:3; and step IV obtains a high-performance coconut shell activated carbon doped with nitrogen in situ (H3P3-C). The other steps and parameters are the same as those in Example 1.

[0047] The embodiments of the present invention use bisphenol A (BPA) and divalent copper (Cu) 2+ This wastewater is a typical example of recalcitrant organic wastewater. It contains BPA and divalent copper (Cu). 2+ Wastewater is difficult to biodegrade, severely damaging aquatic ecosystems and posing a serious threat to human health. Therefore, phenolic substances were selected as the target pollutants in this example. The above samples were used for adsorption evaluation of bisphenol A (BPA), an emerging pollutant in water treatment, and copper ions. The specific operating method is as follows:

[0048] The prepared 5 g / L BPA standard stock solution was diluted with deionized water to concentrations of 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, and 300 mg / L, respectively. Activated carbon (HC) and H5P1-C were added at 0.5 g / L to prepare a 100 mL reaction system. The system was placed on a 25°C constant-temperature magnetic stirrer and stirred at 300 rpm for 12 hours. Samples were then taken to determine the BPA concentration.

[0049] Divalent copper (Cu) 2+ The solution concentration gradient was set to 30 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, and 300 mg / L. The remaining operations were the same as those for the determination of BPA.

[0050] This invention utilizes a combination of heteroatom doping modification and gasification activation techniques to prepare high-performance activated carbon (H5P1-C), with a maximum adsorption capacity of 161.29 mg / g for BPA and [missing information - likely referring to adsorption capacity for divalent copper (Cu)]. 2+ The maximum adsorption capacity was 6.45 mg / g, representing increases of 62.10% and 24.28% respectively compared to the unmodified form.

[0051] Figure 1 The adsorption kinetics of BPA by activated carbon HC and H5P1-C are shown in the figure.

[0052] Figure 2 The activated carbon HC and H5P1-C are used to react with divalent copper (Cu) 2+ Adsorption kinetics diagram;

[0053] Figure 3 The adsorption results of coconut shell activated carbon HC, in-situ nitrogen-doped activated carbon H5P1-C, and in-situ nitrogen-doped activated carbon H3P3-C are as follows:

[0054] Depend on Figure 3 It can be seen that when coconut shell powder and coconut bran powder are in situ doped at a ratio of 5:1, the adsorption saturation capacity is the highest, and this is particularly effective in water treatment for the adsorption of bisphenol A (BPA) and divalent copper (Cu). 2+ The adsorption effect is the best.

Claims

1. A method for preparing high-performance coconut shell activated carbon by gasification activation, characterized in that... This method is specifically completed in the following steps:

1. Using coconut shells as raw material, the coconut shells are crushed in a crusher, sieved, and dried to obtain crushed coconut shells; 2. Place the crushed coconut shells, coconut bran and corundum balls into a planetary polytetrafluoroethylene ball mill jar, and then place the ball mill jar in a planetary ball mill for ball milling to obtain the mixed biomass; The mass ratio of the crushed coconut shell to coconut bran mentioned in step two is 5:1; 3. The mixed biomass is placed in a tube furnace and calcined in stages under controlled temperature to obtain the reaction products; The specific process of segmented temperature-controlled calcination described in step three is as follows: under nitrogen atmosphere protection, heat to 200℃~600℃ at a heating rate of 5℃ / min~10℃ / min, heat for 2h~3h, then heat to 600℃~800℃ at a heating rate of 5℃ / min~10℃ / min, heat for 2h~3h, and finally cool down to 650℃~600℃ at a cooling rate of 5℃ / min~10℃ / min, and hold at 650℃~600℃ for 1.5h~2h. IV. The reaction product is activated by passing hot steam to obtain a high-performance coconut shell activated carbon. The specific process of hot steam activation in step four is as follows: the temperature of the tubular furnace is raised to 800℃~950℃, water vapor is introduced into the tubular furnace, and the reheat steam activation time is 2h~3h to obtain coconut shell activated carbon.

2. The method for preparing high-performance coconut shell activated carbon by gasification activation according to claim 1, characterized in that... The drying temperature in step one is 180℃~200℃, and the drying time is 2h~3h.

3. The method for preparing high-performance coconut shell activated carbon by gasification activation according to claim 1, characterized in that... In step one, the coconut shell is crushed in a crusher and then passed through a 100-200 mesh sieve.

4. The method for preparing high-performance coconut shell activated carbon by gasification activation according to claim 1, characterized in that... The total mass ratio of the crushed coconut shells and coconut bran to the corundum balls in step two is 6:

100.

5. The method for preparing high-performance coconut shell activated carbon by gasification activation according to claim 1, characterized in that... The ball milling speed in step two is 650 r / min to 750 r / min, and the ball milling time is 1.5 h to 2 h.

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