Screening and modifying method of coal-based activated carbon suitable for supergravity device

Abstract

The invention aims to provide a method for screening and modifying coal-based activated carbon suitable for a supergravity device, and belongs to the technical field of activated carbon catalyst preparation. Wear rates of different activated carbon in the supergravity device are compared through experiments, and the stability of the different activated carbon in the supergravity device is compared; different activated carbon is subjected to load modification, and the catalytic activity of different activated carbon catalysts after modification is compared; the active carbon carrier screened by the invention has higher mechanical strength and wear resistance, and the prepared catalyst has higher catalytic activity and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of activated carbon catalysts, and particularly relates to a method for screening and modifying coal-based activated carbon applicable to a rotating packed bed device. Background Art

[0002] Coal is the main energy source in China, and its content accounts for a relatively high proportion in fossil energy resources, making it the most stable energy source in terms of economic stability and self-guarantee ability. However, with the increasing maturity of modern coal chemical technologies, the problem of homogenization of coal-based end products has become prominent, leading to a continuous decline in the prices of coal-based end products. Therefore, the high-value utilization of coal is realized through the development of high-end carbon materials.

[0003] Coal-based activated carbon has a high specific surface area and a controllable pore structure, and is widely used in the fields of adsorption and catalysis. The main types of activated carbon are spherical activated carbon, columnar activated carbon, and amorphous activated carbon, and these three types of activated carbon are widely used as adsorbents and catalyst carriers in the field of wastewater treatment.

[0004] The invention patent with the publication number CN109382107A prepares an ozone catalyst with activated carbon loaded with metal oxides by the method of equal-volume impregnation and high-temperature calcination. When used for the ozone catalytic oxidation of industrial sewage, it can efficiently remove nbsCOD in the sewage. After 60 minutes of ozone catalytic oxidation, the removal rate of nbsCOD can reach as high as 80%, which is more than 50% higher than the COD removal rate of ozone contact oxidation. However, the time for preparing the activated carbon catalyst by this equal-volume impregnation method is relatively long and the dispersion of the metal active components is poor, which will greatly affect the catalytic performance of the activated carbon catalyst; the patent with the publication number CN115007148A loads α-FeOOH on the surface of activated carbon by the co-precipitation method. The process of the catalyst prepared by this method is relatively complex and the activity of the catalyst is low; the invention patent with the publication number CN114308113A uses the powdered activated carbon modified by alkali as the carrier and molecular sieve as the additive, and realizes the loading of the active components by the methods of magnetic stirring and calcination to prepare the catalyst, and applies it to the advanced treatment of low-concentration and difficult-to-degrade chemical wastewater. After treatment, the effluent quality of low-concentration and difficult-to-degrade organic chemical wastewater (COD = 80-100 mg / L) can reach the level of COD ≤ 50 mg / L. However, due to the small particle size of this activated carbon catalyst, it is not conducive to recycling and reuse, which greatly limits its wide application; The method of preparing catalysts by the traditional method is relatively basic. Usually, it requires complex processes and a long time. The preparation process is cumbersome and the catalytic activity is poor. This is because the fluidity of the impregnation solution in the traditional method is poor, resulting in a slow diffusion rate and poor dispersion of the active components on the surface of the carrier. The method of preparing catalysts by the high-gravity method can improve this defect. The principle is that the high-speed rotation of the high-gravity rotating packing bed cuts the incoming precursor solution into fine liquid filaments, droplets, and liquid films, improving the fluidity of the precursor solution, enhancing the renewal rate of the liquid on the surface of the carrier, increasing the interfacial contact area, and thus greatly improving the mass transfer rate between the solid and liquid phases. The catalysts prepared by this method have a higher and more uniform loading of active components.

[0005] The invention patent with the publication number CN116328762A selects the ZSM-5 catalyst carrier as the packing of the rotating packing bed, prepares an impregnation solution with nitrates of Mn and Fe, prepares a supported Mn-based catalyst, and uses it in the experiment of degrading nitrobenzene. The invention patent with the publication number CN116328762A dissolves and disperses the carbon material in water and / or alcohol solvents to obtain a carbon material dispersion liquid, transports the carbon material dispersion liquid and the metal complex suspension to the high-gravity rotating packing bed, and after circulating and reacting in the high-gravity rotating packing bed for 5-10 minutes, a carbon material suspension loaded with active metal complexes can be obtained. After drying, the precursor of the carbon-based metal catalyst is obtained, and the precursor of the carbon-based metal catalyst is calcined and reduced at high temperature under nitrogen protection to obtain the carbon-based metal catalyst. The activated carbon catalyst prepared by this invention by the high-gravity method has high activity and high dispersion of active components, but the catalyst particle size is small, which is not conducive to recycling; due to considering the special reaction environment of the high-gravity rotating packing bed, with the continuous progress of the reaction, the loss of the catalyst will be relatively serious. Therefore, screening out an activated carbon carrier suitable for the high-gravity device is the key to improving the activity and reusability of the activated carbon catalyst. Summary of the Invention

[0006] The purpose of the present invention is to provide a screening and modification method for coal-based activated carbon suitable for a high-gravity device. The present invention first tests various performance parameters of different activated carbons, screens out the coal-based activated carbon suitable for the high-gravity device, and then modifies the selected activated carbon by loading to further prepare an activated carbon catalyst with high activity and high stability in the high-gravity device.

[0007] The present invention adopts the following technical solutions: A screening and modification method for coal-based activated carbon suitable for a high-gravity device, by testing the strength and catalytic activity of different coal-based activated carbons, screening out a type of activated carbon with the lowest wear rate and the strongest catalytic activity in the high-gravity field, and modifying it by loading to prepare an activated carbon catalyst with high stability and high activity, specifically including the following steps: S1. After cleaning, pre-treating, drying, and cooling six different types of coal-based activated carbon with deionized water, use different types of activated carbon as the packing material of the high-gravity rotating packed bed, use water as the impregnating solution, react under the high-gravity factor, measure the loss rate of different types of activated carbon, and screen out suitable activated carbon to ensure strong stability of the activated carbon catalyst; S2. After cleaning, pre-treating, drying, and cooling six different types of coal-based activated carbon with deionized water respectively, impregnate them in a 0.1 mol / L cobalt salt impregnating solution for loading modification, and make the activated carbon catalyst by high-temperature calcination to load it on the surface of the activated carbon. Then explore the catalytic performance of different activated carbon catalysts in the aeration device and screen out the activated carbon catalyst with higher catalytic activity; S3. Use the screened activated carbon as the packing material of the high-gravity rotating packed bed. Prepare a precursor solution with a total concentration of 0.1 mol / L and a cobalt-manganese ratio of 3:1 as the impregnating solution and place it in the liquid storage tank. The impregnating solution in the liquid storage tank is transported into the inner cavity of the high-gravity rotating packed bed by a circulating pump, and then evenly sprayed on the inner edge of the activated carbon carrier bed layer by a liquid distributor. Under the action of high-speed centrifugal force, the impregnating solution contacts and impregnates the activated carbon carrier in the form of a spray along the radial direction. The impregnating solution returns to the liquid storage tank from the lower outlet of the bed layer for circulating impregnation; after reacting for a period of time, dry it, and then realize the loading of the active components by high-temperature calcination.

[0008] Further, the six different types of coal-based activated carbon include 2 mm spherical activated carbon, 4 mm spherical activated carbon, 5 mm spherical activated carbon, 7 mm spherical activated carbon, 5 mm columnar activated carbon, and 5 - 30 mesh amorphous activated carbon.

[0009] Further, the high-gravity factor in S1 is 0 - 50.

[0010] Further, the high-temperature calcination in S2 and S3 is to control the heating rate at 5°C / min, heat up to 500°C, and calcine for 5 h.

[0011] Further, the parameters of the high-gravity rotating packed bed are: inner diameter of the rotor: outer diameter: height = 1:3:2.

[0012] The loss rate of different activated carbon in the high-gravity environment is calculated based on the change in the mass of the activated carbon before and after the reaction.

[0013] Cobalt salt is selected as the active component of the activated carbon catalyst, and the loading of different activities and catalytic activities are preliminarily judged by the loading of cobalt salt.

[0014] Since the wear degrees of activated carbons with different shapes and particle sizes in a rotating packed bed may vary, mainly depending on the frictional force during rotation and the hardness of the activated carbon, considering the wear rate of the activated carbon is a prerequisite for ensuring the stability and high activity of the activated carbon catalyst.

[0015] Different types of activated carbons exhibit different adsorption and catalytic properties because different types of activated carbons have different pore structure characteristics, including pore size, pore volume, and pore distribution, etc. These pore structure characteristics will affect the dispersion of active components on the surface of the activated carbon, and thus affect the activity of the activated carbon catalyst.

[0016] The preparation of the activated carbon catalyst essentially relies on the adsorption of the activated carbon on the active components, and the active components are fixed on the surface of the activated carbon by high-temperature calcination. The traditional method for preparing the activated carbon catalyst mainly utilizes the adsorption of the activated carbon. However, due to the poor fluidity of the impregnating solution, the preparation time of the activated carbon catalyst is long and the dispersion of the active components is poor. While in the preparation of the activated carbon catalyst by the high gravity method, the rotating packing can shear the impregnating solution into extremely thin liquid films and tiny liquid mists and droplets, which can accelerate the renewal rate of the liquid on the surface of the activated carbon, increase the interfacial contact area, strengthen the solid-liquid mass transfer, and thus reach the adsorption equilibrium faster, realize the uniform loading of the active components, and complete the preparation of the catalyst.

[0017] The beneficial effects of the present invention are as follows: The present invention has screened out a coal-based activated carbon suitable for a high gravity device and provided a preparation method for an activated carbon catalyst. The appropriate type of activated carbon can not only meet the high strength requirements in the high gravity environment but also achieve the uniform loading of the active components and has strong catalytic activity. At the same time, the preparation of the activated carbon catalyst by the high gravity method has the advantages of simple preparation, short preparation time, high catalyst activity, and easy promotion. Description of the Drawings

[0018] Figure 1 It is a flow chart of the high gravity reaction device adopted by the present invention; Figure 2 It is a physical diagram of different types of coal-based activated carbons; Figure 3 It is a comparison of the loss rates of different coal-based activated carbons in a high gravity environment. The abscissa is the type of activated carbon, and the ordinate is the loss rate of the activated carbon; Figure 4 It is a reaction device diagram for detecting the catalytic activity of different activated carbon catalysts; Figure 5 It is a comparison of the catalytic properties of different modified coal-based activated carbons. The abscissa is the type of modified activated carbon, and the ordinate is the mineralization rate of phenol. The catalytic activity of the catalyst is reflected by the mineralization rate of phenol; Figure 6Comparison of the catalytic activities of the catalysts prepared by the hypergravity method and the traditional method; Figure 7 Comparison of the uniformity of the catalysts prepared by the hypergravity method and the traditional method; Figure 8 Comparison of the reusability of the catalysts prepared by the hypergravity method and the traditional method; Wherein: 1 - motor; 2 - rotating packed bed; 3 - rotameter; 4 - water pump; 5 - liquid storage tank; 6 - oxygen cylinder; 7 - ozone generator; 8 - gas flowmeter; 9 - ozone concentration detector; 10 - aeration reaction device; 11 - catalyst; 12 - tail gas absorption device. Detailed implementation manners

[0019] To make the design scheme and idea of the present invention clearer, the present invention will be further described below in combination with cases. At the same time, the described embodiments are partial embodiments of the present invention, rather than all embodiments; based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Example 1 As Figure 1 shown is the process flow chart for detecting the loss rate of different coal-based activated carbons in a hypergravity environment in the present invention. Different types of activated carbons are used as the packing of the hypergravity rotating packed bed, and water is used as the impregnating solution. After reacting for several hours, the loss rate of different activated carbons is calculated by the change in the mass of different activated carbons before and after the reaction.

[0021] The specific detection method is as follows: First, six different types of coal-based activated carbons (2 mm spherical activated carbon, 4 mm spherical activated carbon, 5 mm spherical activated carbon, 7 mm spherical activated carbon, 5 mm columnar activated carbon, and 5 - 30 mesh irregular activated carbon) (numbered AC1, AC2, AC3, AC4, AC5, and AC6 respectively) were pre-treated by washing with deionized water to remove the residual impurities and dust on the surface of the activated carbon. After repeated treatment five times, the washed activated carbon was placed in an oven at 110 °C and dried for 12 h. After cooling, it was sealed and stored for later use. Then, a certain mass of the pre-treated activated carbon was weighed and loaded into a rotating packed bed to act as the packing. Water was filled into the liquid storage tank, and the motor was adjusted to make the supergravity factor of the packing 50. The liquid in the liquid storage tank was pumped into the rotating packed bed through a water pump, and the liquid flow rate was 100 L / h. The water was sprayed onto the packing and then thrown onto the inner wall under the action of centrifugal force, flowed down along the inner wall to the lower outlet, and finally flowed back to the liquid storage tank to form a circulating system. After reacting for 2 h, the activated carbon was taken out, placed in an oven at 110 °C and dried for 12 h. After it cooled, its mass was weighed and compared with the mass before the reaction to calculate the loss rate of the activated carbon.

[0022] Example 2 To judge the catalytic performance of different activated carbon catalysts, six different activated carbons will be loaded and modified and used in the experiment of catalytic ozonation degradation of phenol. The catalytic activity of the catalyst is reflected by the mineralization rate of phenol, and then the catalytic performance of different activated carbon catalysts can be obtained.

[0023] The specific experimental method is as follows: First, six different types of coal-based activated carbons (2 mm spherical activated carbon, 4 mm spherical activated carbon, 5 mm spherical activated carbon, 7 mm spherical activated carbon, 5 mm columnar activated carbon, and 5 - 30 mesh irregular activated carbon) were pre-treated by washing with deionized water to remove the residual impurities and dust on the surface of the activated carbon. After repeated treatment five times, the washed activated carbon was placed in an oven at 110 °C and dried for 6 h. After cooling, it was sealed and stored for later use. A cobalt salt impregnation solution with a concentration of 0.1 mol / L was prepared and added to a conical flask. Then, a certain mass of different activated carbons was weighed and added to the conical flask. After impregnation for a period of time, the impregnated activated carbon particles were placed in an oven at 110 °C and dried for 12 h. Then, the dried activated carbon was put into a tubular furnace with nitrogen flowing through it and calcined. After it cooled, different activated carbon catalysts C1, C2, C3, C4, C5, and C6 were obtained.

[0024] The device for detecting the catalytic performance of the activated carbon catalyst is as follows Figure 3, the prepared catalyst was used in the experiment of catalytic ozonation of phenol to explore its catalytic activity. The reaction was carried out in a 500 mL aeration reactor. An aeration head was installed at the bottom of the graduated cylinder, and ozone generated continuous bubbles through the aeration head. 500 mL of phenol-simulated wastewater with a concentration of 100 mg / L and 2 g / L of activated carbon catalyst were added to the reactor. The inlet ozone concentration was 40 mg / L, the reaction time was 30 min, and the ozone after the reaction was absorbed by KI solution.

[0025] Example 3 As follows Figure 1 The following is the process flow chart of preparing activated carbon catalyst by the high-gravity method. The selected activated carbon was further subjected to loading modification treatment to prepare a highly active and stable activated carbon catalyst.

[0026] The specific experimental method is as follows: First, the selected activated carbon was pre-treated by washing with deionized water to remove the residual impurities and dust on the surface of the activated carbon. After repeated treatment five times, the washed activated carbon was placed in an oven at 110 °C and dried for 6 h. After cooling, it was sealed and stored for later use. Weigh a certain amount of granular activated carbon (GAC) as the packing of the rotating packed bed. Add a metal salt solution with a total concentration of 0.1 mol / L and a cobalt-manganese ratio of 3:1 to the liquid storage tank. The solution was sprayed into the entire packing through the liquid distributor at a liquid inlet rate of 80 L / h to ensure full contact with the carrier. The reaction device is as follows Figure 1 . The solution after the reaction flowed back to the liquid storage tank for recycling. After treatment for 40 min, it was dried in an oven and calcined in a tubular furnace under the same method and conditions as above. After cooling, the activated carbon catalyst C7 prepared by the high-gravity method rotating packed bed was obtained.

[0027] Comparative Example 1 In order to compare the catalytic activity and stability of the activated carbon catalyst prepared by the high-gravity method, an activated carbon catalyst was further prepared by the traditional impregnation method.

[0028] The specific experimental method is as follows: First, the selected activated carbon was pre-treated by washing with deionized water to remove the residual impurities and dust on the surface of the activated carbon. After repeated treatment five times, the washed activated carbon was placed in an oven at 110 °C and dried for 6 h. After cooling, it was sealed and stored for later use. Prepare a metal salt solution with a total concentration of 0.1 mol / L and a cobalt-manganese ratio of 3:1, add it to a conical flask, and then weigh a certain mass of activated carbon and add it to the conical flask. After impregnation for a period of time, the impregnated activated carbon particles were placed in an oven at 110 °C and dried for 12 h. Then the dried activated carbon was put into a tubular furnace with nitrogen flowing through and calcined. After cooling, the activated carbon catalyst C8 was obtained.

[0029] Table 1 Physical properties of different coal-based activated carbons Combined with the physical property parameters of each activated carbon in the above table and Figure 3 the abrasion rates of different activated carbons in it, it can be seen that spherical activated carbon has a lower abrasion rate and higher mechanical strength; at the same time, combined with Figure 5 it can be known that spherical activated carbon catalysts with diameters of 4 mm, 5 mm, and 7 mm have lower abrasion rates, but their catalytic activities are lower; for amorphous activated carbon catalysts, the TOC removal rate can reach 71% when the reaction lasts for 30 min, and the catalytic activity is also relatively high, but its abrasion rate is high and the stability is poor; while the 2-mm spherical activated carbon catalyst has a lower abrasion rate and higher catalytic activity, and the TOC removal rate can reach 74.3% when the reaction lasts for 30 min. Therefore, considering the stability and catalytic activity of activated carbon comprehensively, 2-mm spherical activated carbon is selected as the most suitable type of coal-based activated carbon for the rotating packed bed device.

[0030] Table 2 Preparation time, loading amount, dissolution rate and catalytic activity of catalysts prepared by different methods Two different catalysts were prepared by the rotating packed bed method and the traditional impregnation method, namely Co-MnO X / GAC (RPB) and Co-MnO X / GAC (TIM). The time for preparing the catalyst by the rotating packed bed method is shortened by 98% compared with the traditional method, the catalytic activity is 6.62% higher, and at the same time, the loading amount is more, and less active components are lost during the reaction process. It can be seen that the catalyst prepared by the rotating packed bed method is more stable, has a higher recycling rate, and stronger catalytic activity, showing significant advantages.

[0031] In this paper, 3 examples and 1 comparative example are used to elaborate the implementation schemes and ideas of the present invention. The above content is only used to help understand the core scheme and core idea of the present invention. The above is the preferred implementation mode of the present invention. It should be noted that for those skilled in the art, various changes and modifications can be made to the present invention.

[0032] Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention, or the direct application of the concept and technical solution of the invention to other occasions without improvement, shall be regarded as the protection scope of the present invention.

Claims

1. A method for screening and modifying coal-based activated carbon suitable for supergravity devices, characterized in that: By testing the strength and catalytic activity of different coal-based activated carbons, a type of activated carbon with the lowest wear rate and the strongest catalytic activity in a hypergravity field was screened out, and loaded and modified to prepare a highly stable and highly active activated carbon catalyst, which specifically includes the following steps: S1. After six different types of coal-based activated carbon were washed, pretreated, dried and cooled with deionized water, different types of activated carbon were used as fillers of the high-gravity rotating packed bed, water was used as the impregnation liquid, and the reaction was carried out under the high-gravity factor. The loss rate of different types of activated carbon was measured, and suitable activated carbon was screened to ensure that the activated carbon catalyst had strong stability; S2. Six different types of coal-based activated carbon were washed with deionized water, pretreated, dried and cooled, and then immersed in 0.1 mol / L cobalt salt impregnation solution for loading modification. The activated carbon was loaded on the surface of the activated carbon by high-temperature calcination to obtain an activated carbon catalyst. The catalytic performance of different activated carbon catalysts was investigated in an aeration device to screen out activated carbon catalysts with higher catalytic activity. S3. Use the selected activated carbon as the filler of the supergravity rotating packed bed, prepare a precursor solution with a total concentration of 0.1 mol / L and a cobalt-manganese ratio of 3:1 as the impregnation liquid and place it in a liquid storage tank, transport the impregnation liquid in the liquid storage tank into the inner cavity of the supergravity rotating packed bed through a circulating pump, and then spray it evenly on the inner edge of the activated carbon carrier bed layer by a liquid distributor. Under the action of high-speed centrifugal force, the impregnation liquid fully contacts and impregnates the activated carbon carrier in the form of a spray in the radial direction, and the impregnation liquid returns to the liquid storage tank from the lower end outlet of the bed layer for cyclic impregnation; dry it after reacting for a period of time, and then realize the loading of active components by high-temperature calcination.

2. The method for screening and modifying coal-based activated carbon suitable for a supergravity device according to claim 1, characterized in that: The six different types of coal-based activated carbon include 2 mm spherical activated carbon, 4 mm spherical activated carbon, 5 mm spherical activated carbon, 7 mm spherical activated carbon, 5 mm columnar activated carbon and 5-30 mesh amorphous activated carbon.

3. The method for screening and modifying coal-based activated carbon suitable for a supergravity device according to claim 1, characterized in that: The hypergravity factor described in S1 is 0-50.

4. The method for screening and modifying coal-based activated carbon suitable for a supergravity device according to claim 1, characterized in that: The high temperature calcinations in S2 and S3 are both carried out by controlling the temperature rise gradient to 5°C / min, raising the temperature to 500°C, and calcining for 5h.

5. The method for screening and modifying coal-based activated carbon suitable for supergravity device according to claim 1, characterized in that: The parameters of the ultra-gravity rotating packed bed are: rotor inner diameter: outer diameter: height is 1:3:2.

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