Natural gas adsorption and storage activated carbon with high specific surface area and preparation method thereof

Abstract

The invention discloses natural gas adsorption and storage activated carbon with a high specific surface area and a preparation method thereof, and relates to the technical field of natural gas adsorption and storage, the preparation method comprises the following steps: (1) crushing coconut shells, soaking the crushed coconut shells in a hydrochloric acid solution, filtering, washing and drying to obtain fine coconut shells; (2) adding the fine coconut shells into a ferric chloride solution for soaking, then adding a hydrogen peroxide solution for stirring reaction, performing freeze drying after filtration, and then performing carbonization to obtain coconut shell charcoal; and (3) mixing the coconut shell charcoal with sodium hydroxide powder, adding deionized water, stirring into mud, sintering, washing and drying to obtain the natural gas adsorption and storage activated carbon with high specific surface area. The activated carbon has a large specific surface area and a rich pore structure, shows very high adsorption capacity for natural gas, and has relatively high physical and chemical stability and mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of natural gas adsorption storage technology, and particularly relates to a high specific surface area natural gas adsorption storage activated carbon and a preparation method thereof. BACKGROUND

[0002] The rapid development of society has led to an increasing demand for industrial gas. Currently, acetylene and propane commonly used on the market can meet the basic demand, but their intrinsic problems limit their further application. First, the high reactivity of acetylene and the high liquefaction pressure of propane impose strict requirements on the storage and transportation conditions. In addition, the inhalation of acetylene and propane is harmful to the human body, which requires strict protection from workers to the construction environment. Therefore, from the economic and safety perspectives, a more suitable substitute should be sought. Compared with acetylene and propane, natural gas as a clean energy has lower cost, higher stability, higher safety, more extensive application scenarios, and is more environmentally friendly. In addition, it can be compressed at a lower pressure and can be liquefied by a simple method, which greatly reduces the cost of transportation and storage. Therefore, natural gas is considered to be a gas fuel with more extensive application potential.

[0003] At present, in addition to natural gas pipeline transportation, gas cylinder storage and transportation dominate in small-scale application scenarios, and the main methods are compressed natural gas (CNG) and liquefied natural gas (LNG). Moreover, for vehicle natural gas, the CNG and LNG natural gas storage methods are also the current first choice. However, the storage method of CNG leads to high internal pressure, which brings certain safety hazards to the transportation and use process. In addition, the storage container must have the characteristics of high pressure resistance, which also makes the overall manufacturing cost high. The storage method of LNG requires low-temperature refrigeration, and the process is complex, the energy consumption is high, and the equipment maintenance cost is high, which also makes the overall operating cost high. In order to meet the natural gas storage capacity while ensuring safety and reducing the use cost, it is of great significance to develop a new natural gas storage method. In recent years, the international community has begun to use the adsorption natural gas (ANG) storage method. This technology fills the adsorbent with high specific surface area in the gas cylinder, and uses its rich microporous structure to realize the efficient adsorption storage of natural gas at room temperature through medium pressure (usually 3.5-5.0 MPa), which is much lower than the high pressure of 20 MPa required by CNG, effectively reducing the risk of storing and transporting natural gas. When natural gas is needed, the internal gas can be desorbed by reducing the internal pressure of the gas cylinder.

[0004] The adsorbent cyclically adsorbs and desorbs natural gas is the core of the ANG cylinder to repeatedly charge and discharge natural gas, and therefore, designing and preparing high-performance adsorbents is the most critical link in the overall design of the ANG cylinder. In order to meet the use requirements, the ANG adsorbent must have a high specific surface area and a rich microporous structure to achieve a high adsorption capacity. At the same time, the internal micropores must be mainly based on physical adsorption and as little chemical adsorption as possible, so as to ensure a very high desorption ratio, which is the key to ensuring that the natural gas charging and discharging capacity is close to and the ANG cylinder can be repeatedly used. In addition, the ANG adsorbent should also have high stability, certain mechanical strength, low cost, environmental friendliness and other characteristics to ensure the durability and economy of the ANG cylinder. However, whether it is activated carbon, molecular sieve, silica gel, metal organic framework or covalent organic framework, there is still no high-efficiency adsorbent on the market that can truly meet the use requirements of the ANG cylinder, which is also an important reason for the stagnation of the development of the domestic ANG storage method. Therefore, it is of great practical significance to design and prepare adsorbents that are economical, usable and safe. SUMMARY

[0005] In order to solve the above technical problems, the purpose of the present application is to provide a high specific surface area natural gas adsorption and storage activated carbon and a preparation method thereof, which has a large specific surface area and a rich pore structure, exhibits a high adsorption capacity for natural gas, and has high physical and chemical stability and mechanical strength.

[0006] The technical solution of the present application to solve the above technical problems is as follows: a preparation method of a high specific surface area natural gas adsorption and storage activated carbon is provided, which comprises the following steps: (1) The coconut shell is crushed, then soaked in a hydrochloric acid solution, filtered, washed and dried to obtain fine-grained coconut shell; (2) The fine-grained coconut shell obtained in step (1) is added to a ferric chloride solution and soaked, then a hydrogen peroxide solution is added and stirred to react, filtered, freeze-dried, and then carbonized to obtain coconut shell carbon; (3) The coconut shell carbon obtained in step (2) is mixed with sodium hydroxide powder, deionized water is added and stirred into a mud, then sintered, washed and dried to obtain a high specific surface area natural gas adsorption and storage activated carbon.

[0007] Further, in step (1), the coconut shell is crushed to a particle size of 200-500 μm; the concentration of the hydrochloric acid solution is 0.0.5-0.2 mol / L.

[0008] The beneficial effect of the further technical solution is that: because the hardness of the coconut shell is high and the carbon content during sintering is high, the coconut shell is processed into fine particles with a particle size of 200-500 μm, which can ensure that the particle size of the activated carbon adsorbent prepared finally is in the range of 150-450 μm, and the volume loss is small. Limiting the particle size of the activated carbon particles in this range not only effectively increases the exposed specific surface area and adsorption pore volume to improve the adsorption and desorption capacity of natural gas, but also meets the demand for the mechanical properties of the adsorbent.

[0009] Further, in step (1), the soaking is 0.5-2 h.

[0010] The beneficial effect of the further technical solution is that: the surface impurities are removed by soaking in dilute hydrochloric acid.

[0011] Further, in steps (1) and (3), the drying is carried out at a temperature of 80-120℃ for 12-36 h.

[0012] Further, in step (2), the mass-volume ratio of the fine particle coconut shell, the ferric chloride solution and the hydrogen peroxide solution is 20 g:30-60 mL:10-30 mL; the concentration of the ferric chloride solution is 0.2-0.4 mol / L; and the concentration of the hydrogen peroxide solution is 2-10wt%.

[0013] Further, in step (2), the carbonization is carried out at 400-600℃ for 1-3 h under a nitrogen atmosphere.

[0014] Further, in step (2), the soaking is carried out under stirring for 5-15 h; and the stirring reaction is carried out for 5-15 h.

[0015] Further, in step (3), the mass ratio of the coconut shell carbon to sodium hydroxide is 1:2-4.

[0016] Further, in step (3), the sintering is carried out at 700-800℃ for 1-3 h under a nitrogen atmosphere.

[0017] Further, in step (3), the washing is carried out with a hydrochloric acid solution and deionized water.

[0018] The application also provides the high specific surface area natural gas adsorption and storage activated carbon prepared by the preparation method of the high specific surface area natural gas adsorption and storage activated carbon.

[0019] The application has the following beneficial effects: 1、The method of the present application uses a secondary activation method to prepare activated carbon from coconut shells. First, the Fenton reaction of iron ions and hydrogen peroxide can produce hydroxyl radicals with strong oxidizing ability, which react with lignin and cellulose on the surface of the coconut shell, thereby producing a large number of microporous structures. Then, by freeze-drying to remove the water in the immersed coconut shell, the internal void volume is increased, achieving the effect of reducing the natural bulk density, and then sintering and carbonizing to achieve the first effective pore-forming activation. Finally, the coconut shell carbon is activated again using sodium hydroxide, not only producing new micropores, but also expanding the original micropores to some extent, thereby further improving the performance of the activated carbon.

[0020] 2、The activated carbon of the present application has a large specific surface area and rich pore structure, and exhibits a high adsorption capacity for natural gas, while having high physical and chemical stability and mechanical strength.

[0021] 3、The natural bulk density of the activated carbon of the present application is low, meeting the requirements of ANG cylinder filling.

[0022] 4、The activated carbon prepared by the method of the present application can achieve a natural gas adsorption capacity of 4 m 3 in a steel cylinder with a full volume of 52.3 L and a weight of 40 kg, and the residual amount after pressure reduction is maintained in the range of 0.1-0.2 m 3 , and the adsorption and desorption capacity is stable in repeated cycle adsorption and desorption tests. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Nitrogen adsorption and desorption curves and pore size distribution graphs of the activated carbon prepared in Example 1; Figure 2 Nitrogen adsorption and desorption curves and pore size distribution graphs of the activated carbon prepared in Comparative Example 1; Figure 3 Raman spectrum of the activated carbon prepared in Example 1; Figure 4 Scanning electron microscope graph of the activated carbon prepared in Example 1 before filling; Figure 5 Scanning electron microscope graph of the activated carbon prepared in Example 1 after three times of filling and releasing. DETAILED DESCRIPTION

[0024] The principles and features of the present application are described below, and the examples are used only to explain the present application and are not intended to limit the scope of the present application. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagents or instruments is specified, it is a conventional product that can be purchased on the market.

[0025] Example 1 A high specific surface area natural gas adsorption storage activated carbon, a preparation method thereof comprises the following steps: (1) The coconut shell is crushed to a particle size of 200-500 μm, then soaked in 0.1 mol / L hydrochloric acid solution for 1 h, washed with deionized water after filtration, and dried at a temperature of 100°C for 24 h to obtain fine particle coconut shell; (2) 20 g of the fine particle coconut shell obtained in step (1) is added into 40 mL of 0.3 mol / L iron chloride solution, soaked for 10 h under stirring, then 20 mL of 5 wt% hydrogen peroxide solution is added and stirred for 10 h, filtered, then freeze-dried, and carbonized at 500°C for 2 h under nitrogen atmosphere to obtain coconut shell carbon; (3) The coconut shell carbon obtained in step (2) is mixed with sodium hydroxide powder at a mass ratio of 1:3, stirred into mud with the addition of deionized water, then sintered at 750°C for 2 h under nitrogen atmosphere, repeatedly washed with 0.1 mol / L dilute hydrochloric acid and deionized water, and dried at a temperature of 100°C for 24 h to obtain a high specific surface area natural gas adsorption storage activated carbon.

[0026] Example 2 A high specific surface area natural gas adsorption storage activated carbon, a preparation method thereof comprises the following steps: (1) The coconut shell is crushed to a particle size of 200-500 μm, then soaked in 0.0.5 mol / L hydrochloric acid solution for 0.5 h, washed with deionized water after filtration, and dried at a temperature of 80°C for 12 h to obtain fine particle coconut shell; (2) 20 g of the fine particle coconut shell obtained in step (1) is added into 30 mL of 0.2 mol / L iron chloride solution, soaked for 5 h under stirring, then 10 mL of 2 wt% hydrogen peroxide solution is added and stirred for 5 h, filtered, then freeze-dried, and carbonized at 400°C for 1 h under nitrogen atmosphere to obtain coconut shell carbon; (3) The coconut shell carbon obtained in step (2) is mixed with sodium hydroxide powder at a mass ratio of 1:2, stirred into mud with the addition of deionized water, then sintered at 700°C for 1 h under nitrogen atmosphere, repeatedly washed with 0.1 mol / L dilute hydrochloric acid and deionized water, and dried at a temperature of 80°C for 12 h to obtain a high specific surface area natural gas adsorption storage activated carbon.

[0027] Example 3 A high specific surface area natural gas adsorption storage activated carbon, a preparation method thereof comprises the following steps: (1) The coconut shell is crushed to a particle size of 200-500 μm, then soaked in 0.2 mol / L hydrochloric acid solution for 2 h, washed with deionized water after filtration, and dried at a temperature of 120°C for 36 h to obtain fine particle coconut shell; (2) 20 g of the fine particle coconut shell obtained in step (1) was added into 60 mL of a 0.4 mol / L ferric chloride solution and soaked under stirring for 15 h, then 30 mL of a 10 wt% hydrogen peroxide solution was added and stirred for 15 h, after filtration, freeze drying was performed, and then carbonization was performed at 600°C under a nitrogen atmosphere for 3 h to obtain coconut shell carbon; (3) The coconut shell carbon obtained in step (2) was mixed with sodium hydroxide powder at a mass ratio of 1:4, deionized water was added and stirred to form a paste, then sintering was performed at 700-800°C under a nitrogen atmosphere for 3 h, and then repeated washing was performed with 0.1 mol / L dilute hydrochloric acid and deionized water, and drying was performed at 120°C for 36 h to obtain a high specific surface area natural gas adsorption and storage activated carbon.

[0028] Comparative Example 1 An activated carbon, a preparation method thereof comprising the following steps: (1) Coconut shell was crushed to a particle size of 200-500 μm, then soaked in a 0.1 mol / L hydrochloric acid solution for 1 h, after filtration, washed with deionized water, and dried at 100°C for 24 h to obtain fine particle coconut shell; (2) The fine particle coconut shell obtained in step (1) was carbonized at 500°C under a nitrogen atmosphere for 2 h to obtain coconut shell carbon; (3) The coconut shell carbon obtained in step (2) was mixed with sodium hydroxide powder at a mass ratio of 1:3, deionized water was added and stirred to form a paste, then sintering was performed at 750°C under a nitrogen atmosphere for 2 h, and then repeated washing was performed with 0.1 mol / L dilute hydrochloric acid and deionized water, and drying was performed at 100°C for 24 h to obtain an activated carbon.

[0029] Test Example 1 (1) The nitrogen adsorption-desorption curve and pore size distribution test results of the activated carbons prepared in Example 1 and Comparative Example 1 are shown in Figure 1 and Figure 2 respectively.

[0030] As can be seen from Figure 1 and Figure 2 , the BET specific surface area of the high specific surface area natural gas adsorption and storage activated carbon prepared in Example 1 was as high as 1800.4916 m 2 / g, the BJH adsorption pore volume was 0.574523 cm 3 / g, the BJH desorption pore volume was 0.572408 cm 3 / g, and the BJH average adsorption pore diameter was 3.7601 nm; the BET specific surface area of the activated carbon prepared in Comparative Example 1 was only 1136.9206 m 2 / g, the BJH adsorption pore volume was 0.141558 cm 3cm / g, BJH desorption pore volume is 0.127903 cm 3 / g, BJH average adsorption pore size is 2.4733 nm; it can be known that the Fenton reaction and freeze drying pretreatment in the preparation method are very beneficial to subsequent high-efficiency pore-forming activation.

[0031] (2) The Raman spectrum result of the high specific surface area natural gas adsorption and storage activated carbon prepared in Example 1 is shown in Figure 3 .

[0032] As shown in Figure 3 , the D band peak area of the batch of activated carbon is obviously higher than the G band peak area, which indicates that the internal amorphous structure is dominant, and meets the demand of activated carbon adsorbent.

[0033] In addition, due to the construction of a large number of micropores inside, the natural bulk density is as low as 0.37 g / cm 3 , which effectively ensures that the overall mass is lower after the ANG cylinder is filled with activated carbon, thereby reducing the transportation cost and adsorbent material cost.

[0034] Test Example 2 In order to directly reflect the adsorption and desorption effect of the prepared activated carbon on natural gas, a steel cylinder with a mass of 40 kg and a volume of 52.3 L is filled with the high specific surface area natural gas adsorption and storage activated carbon prepared in Example 1. By comparing the mass before and after filling, it is calculated that the mass of the filled activated carbon is 16.496 kg. The ANG cylinder is filled with gas, and the filling is stopped when the gas pressure reaches 5 MPa. It is measured that the filled natural gas is 3.882 m 3 . When the gas is discharged to near atmospheric pressure, the gas valve is removed to connect the inside and outside of the ANG cylinder, and the residual natural gas is measured to be 0.197 m 3 by weighing and converting with the density of natural gas. Subsequently, the filling and discharging of natural gas are repeated twice, and the filling amount and the residual amount of each time are similar to the first time, which proves that the activated carbon adsorbent of Example 1 has excellent natural gas cyclic adsorption and desorption performance.

[0035] In addition, the scanning electron microscope images of the activated carbon before and after filling and discharging are shown in Figure 4 and Figure 5 . The results show that the activated carbon of Example 1 does not break down obviously during the natural gas adsorption and desorption process, and better maintains the original micro-morphology, which indicates that the activated carbon has high physical and chemical stability and mechanical strength.

[0036] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high specific surface area natural gas adsorptive storage activated carbon, characterized by, The method comprises the following steps: (1) crushing the coconut shell, then soaking it in a hydrochloric acid solution, filtering, washing and drying to obtain fine-grained coconut shell; (2) soaking the fine-grained coconut shell obtained in step (1) in a ferric chloride solution, then adding a hydrogen peroxide solution and stirring to react, filtering, freeze-drying, carbonizing to obtain coconut shell carbon; (3) mixing the coconut shell carbon obtained in step (2) with sodium hydroxide powder, adding deionized water and stirring to form a mud, then sintering, washing and drying to obtain natural gas adsorption and storage activated carbon with high specific surface area.

2. The method for preparing high specific surface area activated carbon for natural gas adsorption and storage as described in claim 1, characterized in that, In step (1), the coconut shell is crushed to a particle size of 200-500 μm; the concentration of the hydrochloric acid solution is 0.0.5-0.2 mol / L.

3. The method for preparing high specific surface area activated carbon for natural gas adsorption and storage as described in claim 1, characterized in that, In steps (1) and (3), drying is carried out at a temperature of 80-120℃ for 12-36 h.

4. The method of claim 1, wherein the high surface area activated carbon is a natural gas adsorbent storage activated carbon. In step (2), the mass-volume ratio of the fine-grained coconut shell, the ferric chloride solution and the hydrogen peroxide solution is 20 g:30-60 mL:10-30 mL; the concentration of the ferric chloride solution is 0.2-0.4 mol / L; the concentration of the hydrogen peroxide solution is 2-10 wt%.

5. The method for preparing high specific surface area activated carbon for natural gas adsorption and storage as described in claim 1, characterized in that, In step (2), carbonization is carried out at 400-600℃ under a nitrogen atmosphere for 1-3 h.

6. The method of claim 1, wherein the high surface area activated carbon is a natural gas adsorbent storage activated carbon. In step (2), soaking is carried out under stirring for 5-15 h; stirring reaction is carried out for 5-15 h.

7. The method for preparing high specific surface area activated carbon for natural gas adsorption and storage as described in claim 1, characterized in that, In step (3), the mass ratio of the coconut shell carbon to sodium hydroxide is 1:2-4.

8. The method of claim 1, wherein the high surface area activated carbon is a natural gas adsorbent storage activated carbon. In step (3), sintering is carried out at 700-800℃ under a nitrogen atmosphere for 1-3 h.

9. The method of claim 1, wherein the high surface area activated carbon is a natural gas adsorbent storage activated carbon. In step (3), washing is carried out with a hydrochloric acid solution and deionized water.

10. Natural gas adsorption and storage activated carbon with high specific surface area prepared by the method of any one of claims 1-9.

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