An adsorbent applicable to the pressure swing adsorption carbon dioxide removal process

Abstract

The present invention discloses an adsorbent applicable to the pressure swing adsorption decarbonization process, belonging to the technical fields of adsorbent preparation and carbon dioxide separation. The method comprises the following steps: activated carbon is treated with a nitric acid solution to obtain oxidized activated carbon; the oxidized activated carbon is completely immersed in a sodium silicate solution, and then placed in a hydrochloric acid solution for heat treatment to obtain silica gel-oxidized activated carbon, and the silica gel-oxidized activated carbon is treated with a hydrofluoric acid solution to obtain acid-treated silica gel-oxidized activated carbon; the acid-treated silica gel-oxidized activated carbon is treated with an amino-hydroxybenzene ring derivative solution, and then taken out and dried to obtain the adsorbent. In the present invention, sodium silicate is acid-deposited on the surface of oxidized activated carbon to obtain silica gel-oxidized activated carbon, which is then treated with hydrofluoric acid to obtain acid-treated silica gel-oxidized activated carbon, and finally condensed with an amino-hydroxybenzene ring derivative to obtain the adsorbent, improving the adsorption stability of the silica gel-based adsorbent in pressure swing adsorption.

Description

Technical Field

[0001] The present invention belongs to the technical fields of adsorbent preparation and carbon dioxide separation, and particularly relates to an adsorbent suitable for a pressure swing adsorption decarbonization process. Background Art

[0002] Carbon dioxide (CO2) is a major greenhouse gas in the Earth's atmosphere. Although its concentration in the atmosphere is relatively low, its impact on global climate change is significant. With the acceleration of industrialization and the increase in human activities, the emissions of carbon dioxide have risen substantially, leading to more serious phenomena of global warming and climate anomalies. Although the sources of carbon dioxide are diverse, including the consumption of oxygen by plants and animals through respiration, the decomposition of organic matter, and industrial emissions, the main source of carbon dioxide is still industrial emissions (such as the combustion of fossil fuels and vehicle exhaust emissions). At present, the dependence of humans on fossil fuels, as well as the slow development and application of new energy, means that fossil fuels will still be the main energy source for humans. As the main product of fossil fuel combustion, effective capture of carbon dioxide is a necessary condition for humans to reduce carbon emissions and control climate change while using large amounts of fossil fuels. Carbon dioxide is a colorless and odorless gas at normal temperature and pressure, safe and non-toxic, and can be liquefied or solidified by pressurization at normal temperature. In the industrial field, carbon dioxide can be used for fertilizer production, liquid fuel preparation, and driving the improvement of crude oil extraction efficiency, etc.; in daily life, with the improvement of people's living standards, carbon dioxide is increasingly used in the refrigeration, preservation of food, and the air-conditioning storage and transportation of fruits and vegetables, and carbon dioxide has extremely wide applications in the production of carbonated beverages. Therefore, from the perspectives of the environment and the economy, captured carbon dioxide can not only reduce its impact on the environment but also achieve relatively high economic value (such as oil extraction, metallurgy, fertilizers, gas fertilizers, food, etc.).

[0003] Pressure swing adsorption (PSA) is a technology used for gas separation and purification, widely applied in the production and separation processes of industrial gases. Its basic principle is to utilize the adsorption characteristics of different gases on solid adsorbents to separate gases under different pressures. The pressure swing adsorption process generally includes the following steps: (1) Adsorption stage: Under high pressure, the gas mixture to be separated is introduced into the adsorption tower (filled with adsorbent), and certain gas components are preferentially adsorbed by the adsorbent while other components are discharged, thus achieving the preliminary separation of gases; (2) Residence stage: After the adsorption stage, the pressure in the adsorption tower is maintained stable for a period of time to ensure that the adsorbent fully adsorbs the target gas; (3) Desorption stage: By reducing the pressure, the adsorbed gas on the adsorbent is desorbed. This process causes the adsorbent to release the previously adsorbed gas components, enabling it to be reused; (3) Regeneration stage: After desorption, the adsorbent can be regenerated through gas flow or other means to return to its initial state and be ready for the next round of adsorption process. The advantages of pressure swing adsorption include (1) High efficiency: It can efficiently separate and purify the target gas; (2) Simple operation: The equipment is relatively simple, easy to operate and maintain; (3) Cost advantage: Compared with other separation technologies (such as membrane separation or cryogenic distillation), PSA is usually more cost-effective in terms of energy consumption and equipment investment; (4) Environmentally friendly: No harmful chemicals are required during the operation process, and it has less impact on the environment. In pressure swing adsorption, one of the cores lies in the use of adsorbents. Commonly used adsorbents include activated alumina, molecular sieves, activated carbon, and silica gel, etc.

[0004] Patent CN115672264A discloses a preparation method of a pressure swing adsorption adsorbent. In this invention, 5A molecular sieve raw powder, clay, and additives are first mixed evenly and then formed and calcined. Then, the formed adsorbent is placed in an aqueous urea solution, and by raising the temperature, urea hydrolysis occurs to form an alkaline solution, which dissolves the clay blocking between the molecular sieve adsorbents, achieving unobstructed pores of the adsorbent.

[0005] Patent CN114682236A discloses a preparation method of a molecular sieve adsorbent for pressure swing adsorption. In this invention, starch is added in the form of an aqueous solution and formed at a certain temperature to promote the stretching of the coiled structure in the starch, which is beneficial to generating more mesoporous structures with better connectivity to micropores during the high-temperature calcination stage. Therefore, the obtained molecular sieve has better mass transfer performance and good adsorption effect.

[0006] Patent CN114682234A discloses a preparation method of a pressure swing adsorption molecular sieve adsorbent. In this invention, an azeotrope of water is added during the molecular sieve treatment process to form an azeotrope with a lower boiling point with water, making it easier to remove the water in the shaped molecular sieve. Thus, most of the water in the molecular sieve can be removed in the low-temperature drying stage. By this method, not only can the damage to the strength of the molecular sieve caused by the rapid evaporation of water be prevented, but also the damage to the crystal structure of the molecular sieve by water vapor can be reduced, obtaining a molecular sieve adsorbent with high crystallinity, high strength, and high yield.

[0007] Silica gel adsorbents are amorphous active adsorption materials, which are processed by processes such as gelling, washing, and drying from sodium silicate solution and inorganic acid. Although silica gel adsorbents can achieve the capture and treatment of carbon dioxide through physical adsorption and chemical reaction adsorption generated by van der Waals forces and pore structures, due to the strong water absorption of silica gel, the adsorption capacity is greatly affected by water vapor, indirectly resulting in a shorter industrial application life. In addition, silica gel has low mechanical strength and is prone to powdering after encountering water and cannot be used for a long time. All these factors lead to less application of silica gel adsorbents in the field of pressure swing adsorption of carbon dioxide.

[0008] Therefore, how to improve the adsorption stability of silica gel adsorbents in pressure swing adsorption is of great significance. Summary of the Invention

[0009] In view of the deficiencies of the prior art, in this invention, sodium silicate is deposited on the surface of oxidized activated carbon through acid to obtain silica gel - oxidized activated carbon, which is then treated with hydrofluoric acid to obtain acid-treated silica gel - oxidized activated carbon, and finally condensed with amino-hydroxybenzene ring derivatives to obtain the adsorbent, solving the technical problems raised in the background art. Specifically, the technical solution of this invention includes the following content:

[0010] An adsorbent suitable for the pressure swing adsorption decarbonization process, the preparation of the adsorbent includes the following steps:

[0011] The activated carbon is treated with a nitric acid solution to obtain oxidized activated carbon;

[0012] After the oxidized activated carbon is completely immersed in the sodium silicate solution for 40 min to 60 min, it is then placed in a hydrochloric acid solution for heat treatment for 30 min to 40 min to obtain silica gel - oxidized activated carbon, and the silica gel - oxidized activated carbon is treated with a hydrofluoric acid solution for 5 min to 10 min to obtain acid-treated silica gel - oxidized activated carbon;

[0013] The acid-treated silica gel - oxidized activated carbon is immersed in the amino-hydroxybenzene ring derivative solution for treatment for 60 min to 80 min, and then taken out and placed in an oven at 110°C to 120°C for drying for 1 h to 2 h to obtain the adsorbent.

[0014] Further, the specific surface area of the activated carbon > 1000 m 2 / g. If the specific surface area of the activated carbon is low, there are few adsorption sites, which is not conducive to the deposition and distribution of silica gel.

[0015] Further, the mass percentage concentration of the nitric acid solution is 30% - 40%.

[0016] Further, the conditions for treating the activated carbon with the nitric acid solution include a treatment temperature of 90°C - 100°C and a treatment time of 30 min - 80 min.

[0017] Further, the mass percentage concentration of the sodium silicate solution is 10% - 15%.

[0018] Further, the pH of the hydrochloric acid solution is 4.5 - 5.0.

[0019] Further, the temperature of the heat treatment is 30°C - 40°C.

[0020] Further, the mass percentage concentration of the hydrofluoric acid solution is 3% - 5%.

[0021] Further, the preparation of the amino-hydroxy benzene ring derivative solution includes the following steps:

[0022] A benzene ring derivative, a dihydroxy amino compound, and dimethyl sulfoxide are mixed to form a reaction bottom liquid. Sodium hydroxide is added to the reaction bottom liquid and heated to 120°C - 140°C for reaction for 2 h - 3 h to obtain a mixed liquid. The mixed liquid is extracted with ethyl acetate to obtain the amino-hydroxy benzene ring derivative solution.

[0023] Further, the benzene ring derivative includes benzoic acid or 3-amino-4-hydroxybenzoic acid. The benzene ring derivative needs to include a carboxyl group for connecting the dihydroxy amino compound through an esterification reaction.

[0024] Further, the dihydroxy amino compound includes diethanolamine or 2-amino-2-methyl-1,3-propanediol. The role of the dihydroxy amino compound is to provide a flexible carbon chain, thereby cooperating with the benzene ring to improve the mechanical properties and hydrophobicity of silica gel.

[0025] Further, the weight part ratio of the benzene ring derivative : dihydroxy amino compound : sodium hydroxide is 1 : 1 - 2 : 1.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention uses activated carbon as a substrate. Through oxidation treatment of the activated carbon, oxygen-containing groups such as hydroxyl groups are loaded on the surface of the activated carbon to obtain oxidized activated carbon. Then, the oxidized activated carbon is immersed in a sodium silicate solution for adsorption treatment, and then taken out and impregnated in an acidic solution. Under acidic conditions, sodium silicate forms silica gel and is chemically cross-linked and deposited on the surface of the oxidized activated carbon to obtain silica gel-oxidized activated carbon. The large specific surface area and mechanical stability of the activated carbon are used to improve the adsorption stability of the silica gel. Due to the deposition effect, the pores of the silica gel-oxidized activated carbon will be blocked. At this time, the silica gel-oxidized activated carbon is soaked in a hydrofluoric acid solution for a short time to obtain acid-treated silica gel-oxidized activated carbon. On the one hand, the pores of the silica gel-oxidized activated carbon are increased to improve the adsorption capacity. On the other hand, the Si-O-Si bonds on the silica gel on the surface of the silica gel-oxidized activated carbon are broken to obtain silanol groups. The acid-treated silica gel-oxidized activated carbon combines an amino-hydroxybenzene ring derivative with a rigid benzene ring and a flexible long carbon chain to the surface of the acid-treated silica gel-oxidized activated carbon through the condensation reaction of silanol groups and hydroxyl groups to obtain an adsorbent. The amino group can react with carbon dioxide to form a salt to further improve the adsorption of carbon dioxide. The benzene ring with rigid and non-polar characteristics and the flexible long carbon chain can adjust the mechanical properties and hydrophobicity of the silica gel, so that the mechanical strength of the silica gel is improved and the water absorption performance of the silica gel is reduced. Detailed Embodiments

[0028] The technical solutions of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0029] Unless otherwise specified, the raw materials and reagents used in the present invention below are all commercially available products or can be prepared by known methods.

[0030] The activated carbon was purchased from Henan Zhongju Purification Materials Co., Ltd., and the specific surface area was greater than 1000m 2 / g.

[0031] Preparation Example 1:

[0032] The preparation of the amino-hydroxybenzene ring derivative solution specifically includes the following process:

[0033] Dimethyl sulfoxide was dehydrated and dehumidified with anhydrous magnesium sulfate, and then anhydrous magnesium sulfate was removed by filtration to obtain dried dimethyl sulfoxide. 5 parts by weight of the dried dimethyl sulfoxide was weighed and added to a reactor, and then 1 part by weight of benzoic acid and 1 part by weight of 2-amino-2-methyl-1,3-propanediol were added and stirred evenly to form a reaction bottom liquid. 1 part by weight of sodium hydroxide was added to the reaction bottom liquid and stirred at a speed of 200 r / min, and then the temperature was raised to 120 °C and reacted for 2 h. After the reaction was completed, deionized water was added to the mixture to neutralize sodium hydroxide, and then ethyl acetate was added and stirred and extracted to collect the organic layer. After the organic layer was rinsed with deionized water until the rinsing water was neutral, anhydrous magnesium sulfate was used to remove water to obtain an amino-hydroxy benzene ring derivative solution.

[0034] Preparation Example 2:

[0035] The preparation of the amino-hydroxy benzene ring derivative solution specifically includes the following process:

[0036] Dimethyl sulfoxide was dehydrated and dehumidified with anhydrous magnesium sulfate, and then anhydrous magnesium sulfate was removed by filtration to obtain dried dimethyl sulfoxide. 5 parts by weight of the dried dimethyl sulfoxide was weighed and added to a reactor, and then 1 part by weight of benzoic acid and 1.5 parts by weight of diethanolamine were added and stirred evenly to form a reaction bottom liquid. 1 part by weight of sodium hydroxide was added to the reaction bottom liquid and stirred at a speed of 250 r / min, and then the temperature was raised to 130 °C and reacted for 2.5 h. After the reaction was completed, deionized water was added to the mixture to neutralize sodium hydroxide, and then ethyl acetate was added and stirred and extracted to collect the organic layer. After the organic layer was rinsed with deionized water until the rinsing water was neutral, anhydrous magnesium sulfate was used to remove water to obtain an amino-hydroxy benzene ring derivative solution.

[0037] Preparation Example 3:

[0038] The preparation of the amino-hydroxy benzene ring derivative solution specifically includes the following process:

[0039] Dimethyl sulfoxide was dehydrated and dehumidified with anhydrous magnesium sulfate, and then anhydrous magnesium sulfate was removed by filtration to obtain dried dimethyl sulfoxide. 6 parts by weight of the dried dimethyl sulfoxide was weighed and added to a reactor, and then 1 part by weight of 3-amino-4-hydroxybenzoic acid and 2 parts by weight of diethanolamine were added and stirred evenly to form a reaction bottom liquid. 1 part by weight of sodium hydroxide was added to the reaction bottom liquid and stirred at a speed of 300 r / min, and then the temperature was raised to 140 °C and reacted for 3 h. After the reaction was completed, deionized water was added to the mixture to neutralize sodium hydroxide, and then ethyl acetate was added and stirred and extracted to collect the organic layer. After the organic layer was rinsed with deionized water until the rinsing water was neutral, anhydrous magnesium sulfate was used to remove water to obtain an amino-hydroxy benzene ring derivative solution.

[0040] Example 1:

[0041] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following processes:

[0042] Wash the activated carbon with water to remove surface impurities and dry it. Then, completely immerse the dried activated carbon in a nitric acid solution with a mass percentage concentration of 30%, and heat it to 90 °C in a constant temperature oil bath for reflux oxidation treatment for 30 min. After the reaction ends, take out the activated carbon and wash it with water until the rinsing water is neutral, and then dry it to a constant weight to obtain oxidized activated carbon;

[0043] Completely immerse the oxidized activated carbon in a sodium silicate solution with a mass percentage concentration of 10% for 40 min. After the treatment ends, take out the oxidized activated carbon and immerse it in a hydrochloric acid solution with a pH of 4.5, then heat it to 30 °C for reaction treatment for 30 min. After the treatment ends, take out and wash the silica-oxidized activated carbon with deionized water. Then, wash the silica-oxidized activated carbon with a hydrofluoric acid solution with a mass percentage concentration of 3% for 5 min at room temperature, and then quickly wash the surface residual hydrofluoric acid solution of the silica-oxidized activated carbon with a large amount of deionized water until the rinsing water is neutral, and then dry it to a constant weight to obtain acid-treated silica-oxidized activated carbon;

[0044] Completely immerse the acid-treated silica-oxidized activated carbon in the amino-hydroxy benzene ring derivative solution obtained in Preparation Example 1 for adsorption treatment for 60 min, and then take it out and place it in an oven at 110 °C for drying for 1 h to obtain the adsorbent.

[0045] Example 2:

[0046] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following processes:

[0047] Wash the activated carbon with water to remove surface impurities and dry it. Then, completely immerse the dried activated carbon in a nitric acid solution with a mass percentage concentration of 32%, and heat it to 90 °C in a constant temperature oil bath for reflux oxidation treatment for 40 min. After the reaction ends, take out the activated carbon and wash it with water until the rinsing water is neutral, and then dry it to a constant weight to obtain oxidized activated carbon;

[0048] Completely immerse the oxidized activated carbon in a sodium silicate solution with a mass percentage concentration of 11% for 40 min. After the treatment ends, take out the oxidized activated carbon and immerse it in a hydrochloric acid solution with a pH of 4.5, then heat it to 30 °C for reaction treatment for 30 min. After the treatment ends, take out and wash the silica-oxidized activated carbon with deionized water. Then, wash the silica-oxidized activated carbon with a hydrofluoric acid solution with a mass percentage concentration of 3% for 6 min at room temperature, and then quickly wash the surface residual hydrofluoric acid solution of the silica-oxidized activated carbon with a large amount of deionized water until the rinsing water is neutral, and then dry it to a constant weight to obtain acid-treated silica-oxidized activated carbon;

[0049] The acid-treated silica-oxidized activated carbon was completely immersed in the solution of the amino-hydroxy benzene ring derivative obtained in Preparation Example 1 for adsorption treatment for 60 min, and then taken out and placed in an oven at 110 °C for drying for 1 h to obtain the adsorbent.

[0050] Example 3:

[0051] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following process:

[0052] The activated carbon was rinsed with water to remove surface impurities and dried, and then the dried activated carbon was completely immersed in a nitric acid solution with a mass percentage concentration of 34%, and heated to 95 °C in a constant temperature oil bath for reflux oxidation treatment for 50 min. After the reaction ended, the activated carbon was taken out and rinsed with water until the rinsing water was neutral, and then dried to a constant weight to obtain oxidized activated carbon;

[0053] The oxidized activated carbon was completely immersed in a sodium silicate solution with a mass percentage concentration of 12% for treatment for 50 min. After the treatment ended, the oxidized activated carbon was taken out and immersed in a hydrochloric acid solution with a pH of 4.5, and then heated to 30 °C for reaction treatment for 35 min. After the treatment ended, the silica-oxidized activated carbon was taken out and rinsed with deionized water. Then, the silica-oxidized activated carbon was rinsed with a hydrofluoric acid solution with a mass percentage concentration of 4% at room temperature for 7 min, and then quickly rinsed with a large amount of deionized water to remove the residual hydrofluoric acid solution on the surface of the silica-oxidized activated carbon until the rinsing water was neutral, and then dried to a constant weight to obtain acid-treated silica-oxidized activated carbon;

[0054] The acid-treated silica-oxidized activated carbon was completely immersed in the solution of the amino-hydroxy benzene ring derivative obtained in Preparation Example 2 for adsorption treatment for 70 min, and then taken out and placed in an oven at 115 °C for drying for 1.5 h to obtain the adsorbent.

[0055] Example 4:

[0056] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following process:

[0057] The activated carbon was rinsed with water to remove surface impurities and dried, and then the dried activated carbon was completely immersed in a nitric acid solution with a mass percentage concentration of 36%, and heated to 95 °C in a constant temperature oil bath for reflux oxidation treatment for 60 min. After the reaction ended, the activated carbon was taken out and rinsed with water until the rinsing water was neutral, and then dried to a constant weight to obtain oxidized activated carbon;

[0058] The oxidized activated carbon is completely immersed in a sodium silicate solution with a mass percentage concentration of 13% for 50 min. After the treatment, the oxidized activated carbon is taken out and immersed in a hydrochloric acid solution with a pH of 5.0, and then heated to 40 °C for reaction treatment for 35 min. After the treatment, the silica-oxidized activated carbon is taken out and rinsed with deionized water. Then, the silica-oxidized activated carbon is rinsed with a hydrofluoric acid solution with a mass percentage concentration of 4% for 8 min at room temperature. Then, the residual hydrofluoric acid solution on the surface of the silica-oxidized activated carbon is quickly rinsed with a large amount of deionized water until the rinsing water is neutral, and then dried to a constant weight to obtain the acid-treated silica-oxidized activated carbon;

[0059] The acid-treated silica-oxidized activated carbon is completely immersed in the amino-hydroxy benzene ring derivative solution obtained in Preparation Example 2 for adsorption treatment for 70 min, and then taken out and placed in an oven at 115 °C for drying for 1.5 h to obtain the adsorbent.

[0060] Example 5:

[0061] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following process:

[0062] The activated carbon is rinsed with water to remove surface impurities and dried, and then the dried activated carbon is completely immersed in a nitric acid solution with a mass percentage concentration of 38%, and heated to 100 °C in a constant temperature oil bath for reflux oxidation treatment for 70 min. After the reaction, the activated carbon is taken out and rinsed with water until the rinsing water is neutral, and then dried to a constant weight to obtain the oxidized activated carbon;

[0063] The oxidized activated carbon is completely immersed in a sodium silicate solution with a mass percentage concentration of 14% for 60 min. After the treatment, the oxidized activated carbon is taken out and immersed in a hydrochloric acid solution with a pH of 5.0, and then heated to 40 °C for reaction treatment for 40 min. After the treatment, the silica-oxidized activated carbon is taken out and rinsed with deionized water. Then, the silica-oxidized activated carbon is rinsed with a hydrofluoric acid solution with a mass percentage concentration of 5% for 9 min at room temperature. Then, the residual hydrofluoric acid solution on the surface of the silica-oxidized activated carbon is quickly rinsed with a large amount of deionized water until the rinsing water is neutral, and then dried to a constant weight to obtain the acid-treated silica-oxidized activated carbon;

[0064] The acid-treated silica-oxidized activated carbon is completely immersed in the amino-hydroxy benzene ring derivative solution obtained in Preparation Example 3 for adsorption treatment for 80 min, and then taken out and placed in an oven at 120 °C for drying for 2 h to obtain the adsorbent.

[0065] Example 6:

[0066] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following process:

[0067] The activated carbon was rinsed with water to remove surface impurities and then dried. Subsequently, the dried activated carbon was completely immersed in a nitric acid solution with a mass percentage concentration of 40%, and refluxed and oxidized at 100 °C for 80 min in a thermostatic oil bath. After the reaction ended, the activated carbon was taken out, rinsed with water until the rinsing water was neutral, and then dried to a constant weight to obtain oxidized activated carbon;

[0068] The oxidized activated carbon was completely immersed in a sodium silicate solution with a mass percentage concentration of 15% for 60 min. After the treatment ended, the oxidized activated carbon was taken out and immersed in a hydrochloric acid solution with a pH of 5.0, and then heated to 40 °C for reaction treatment for 40 min. After the treatment ended, the silica-oxidized activated carbon was taken out and rinsed with deionized water. Then, the silica-oxidized activated carbon was rinsed with a hydrofluoric acid solution with a mass percentage concentration of 5% for 10 min at room temperature. Then, the residual hydrofluoric acid solution on the surface of the silica-oxidized activated carbon was quickly rinsed with a large amount of deionized water until the rinsing water was neutral, and then dried to a constant weight to obtain acid-treated silica-oxidized activated carbon;

[0069] The acid-treated silica-oxidized activated carbon was completely immersed in the amino-hydroxy benzene ring derivative solution obtained in Preparation Example 3 for adsorption treatment for 80 min, and then taken out and placed in an oven at 120 °C for drying for 2 h to obtain the adsorbent.

[0070] Comparative Example 1:

[0071] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following process:

[0072] The activated carbon in Example 6 was replaced with activated carbon having a specific surface area of 600 - 900 m 2 / g, and the remaining conditions were the same as those in Example 6.

[0073] Comparative Example 2:

[0074] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following process:

[0075] The concentration of the nitric acid solution in Example 6 was increased to 50%, and the reflux oxidation treatment time was increased to 100 min, and the remaining conditions were the same as those in Example 6.

[0076] Comparative Example 3:

[0077] An adsorbent applicable to the pressure swing adsorption decarbonization process, and the specific preparation includes the following process:

[0078] The concentration of the sodium silicate solution in Example 6 was increased to 30%, and the remaining conditions were the same as those in Example 6.

[0079] Comparative Example 4:

[0080] An adsorbent applicable to the pressure swing adsorption carbon dioxide removal process, and its specific preparation includes the following process:

[0081] Remove the process of treating with hydrofluoric acid solution in Example 6, and keep the other conditions the same as those in Example 6.

[0082] Comparative Example 5:

[0083] An adsorbent applicable to the pressure swing adsorption carbon dioxide removal process, and its specific preparation includes the following process:

[0084] Replace the amino-hydroxy benzene ring derivative solution in Example 6 with 3-amino-4-hydroxybenzoic acid solution, and keep the other conditions the same as those in Example 6.

[0085] Comparative Example 6:

[0086] An adsorbent applicable to the pressure swing adsorption carbon dioxide removal process, and its specific preparation includes the following process:

[0087] Treat the sodium silicate solution with a mass percentage concentration of 15% with hydrochloric acid solution with a pH of 4.5, then heat to 40 °C and react with stirring until precipitation occurs, then let it stand until the solution is stratified, collect the silica gel precipitate by centrifugal filtration, rinse the silica gel precipitate with hydrofluoric acid solution with a mass percentage concentration of 5% for 10 min, and then quickly rinse the surface of the silica gel precipitate with a large amount of deionized water until the rinsing water is neutral, and dry to constant weight to obtain the acid-treated silica gel precipitate;

[0088] Completely immerse the acid-treated silica gel precipitate in the amino-hydroxy benzene ring derivative solution obtained in Preparation Example 3 for adsorption treatment for 80 min, and then take it out and dry it in an oven at 120 °C for 2 h to obtain the adsorbent.

[0089] Use a specific surface area analyzer to measure the specific surface area of the adsorbents obtained in Examples 1-6 and Comparative Examples 1-6, and the results are shown in Table 1.

[0090] Table 1 Specific surface area of adsorbents

[0091]

[0092] Pack the adsorbents obtained in Examples 1-6 and Comparative Examples 1-6 into the adsorption column for fixation, and then use the self-prepared raw material gas (the volume content of carbon dioxide is 14%, and the rest is nitrogen) as the test gas, control the temperature at 25 ± 2 °C, humidify it to the test gas humidity of 70 ± 1% through an atomizer, control the flow rate of the test gas at 200 mL / min, adjust the adsorption pressure to 0.9 MPa, and when the concentration of the outlet gas is the same as that of the inlet gas, complete the adsorption. The dynamic adsorption capacity results are shown in Table 2 below. After adsorption, evacuate to desorb it, then take out the adsorbent and dry it to constant weight, and observe whether the silica gel on the surface of the adsorbent is damaged. The results are shown in Table 2.

[0093] Table 2 Dynamic adsorption capacity values and apparent states of adsorbents

[0094]

[0095] The following conclusions can be drawn from the above Table 1 and Table 2:

[0096] (1) It can be found from Examples 1 to 6 that in the present invention, sodium silicate is deposited on the surface of oxidized activated carbon by acid to obtain silica gel - oxidized activated carbon, then treated with hydrofluoric acid to obtain acid - treated silica gel - oxidized activated carbon, and finally condensed with an amino - hydroxy benzene ring derivative to obtain an adsorbent. This adsorbent not only has good carbon dioxide adsorption performance, but also the deposited silica gel has good mechanical properties and no serious cracking and pulverization and shedding phenomena occur.

[0097] (2) It can be found from Comparative Example 1 that although the deposition of silica gel on the surface of activated carbon can also be achieved in this comparative example, due to the small specific surface area of the activated carbon in this comparative example, the deposited silica gel after acid - adjusted treatment of sodium silicate is unevenly distributed, which may block the fine pores on the surface of the activated carbon, resulting in a decrease in the specific surface area. Even after treatment with the hydrofluoric acid solution under the conditions of this comparative example, the adsorption efficiency of the obtained adsorbent when adsorbing carbon dioxide is relatively low. Therefore, increasing the specific surface area of the used activated carbon helps to improve the dispersibility of the silica gel deposited on the surface of the activated carbon, thereby promoting the adsorption of carbon dioxide.

[0098] (3) It can be found from Comparative Example 2 that although nitric acid oxidation is beneficial to increasing oxygen - containing groups such as hydroxyl groups on the surface of activated carbon, excessive concentration and too long oxidation time will damage the surface structure of the activated carbon, resulting in a decrease in the specific surface area, thus affecting the deposition of silica gel on the surface of oxidized activated carbon, and further leading to a relatively low adsorption efficiency of the obtained adsorbent when adsorbing carbon dioxide.

[0099] (4) It can be found from Comparative Example 3 that although the increase in the concentration of sodium silicate solution helps to increase the deposition amount of silica gel on the surface of oxidized activated carbon, due to the small pore size of the activated carbon, too much deposition of silica gel by too much sodium silicate solution is likely to exacerbate the blockage of the surface of oxidized activated carbon, and the effect of relieving the blockage by treatment with hydrofluoric acid in this comparative example system may be poor, resulting in a relatively low adsorption efficiency of the obtained adsorbent when adsorbing carbon dioxide.

[0100] (5) It can be found from Comparative Example 4 that the purpose of the hydrofluoric acid solution treatment is, on the one hand, to reduce the blockage of the activated carbon pores by the deposited silica gel, so that the adsorption capacity of the activated carbon can form a synergistic cooperation with the silica gel and improve the adsorption of carbon dioxide. On the other hand, after the hydrofluoric acid solution treatment, part of the Si-O-Si is broken to form Si-OH, and the silicon hydroxyl group can dehydrate and condense with the hydroxyl group on the aminohydroxybenzene ring derivative at high temperature to introduce more amino sites with carbon dioxide adsorption, further improving the adsorption of carbon dioxide. In addition, the introduction of the aminohydroxybenzene ring derivative can improve the mechanical properties and hydrophobicity of the silica gel deposited on the surface of the oxidized activated carbon. If the hydrofluoric acid solution treatment is not used, it is not conducive to the exposure of the pore size of the activated carbon surface and reduces the adsorption of carbon dioxide. In addition, the deposited silica gel is only supported and protected by the large skeleton structure of the activated carbon, and the mechanical properties are poor and the silica gel is fragile.

[0101] (6) It can be found from Comparative Example 5 that although the 3-amino-4-hydroxybenzoic acid solution can also undergo dehydration condensation with the acid-treated silica gel-oxidized activated carbon, the rigidity of the benzene ring structure in 3-amino-4-hydroxybenzoic acid easily causes the deposited silica gel to break during pressure swing adsorption, affecting the adsorption of carbon dioxide. Therefore, the introduction of a dihydroxyamino compound with a flexible carbon chain structure can alleviate the adverse effect of silica gel breakage caused by the excessive rigidity of the benzene ring.

[0102] (7) It can be found from Comparative Example 6 that although the aminohydroxybenzene ring derivative with a rigid benzene ring and a flexible long carbon chain can improve the mechanical properties of silica gel, it loses the mechanical protection of the activated carbon skeleton, the mechanical properties are poorly improved, and the effect of adsorbing carbon dioxide is also slightly poor.

[0103] The above-described embodiments provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected.

Claims

1. An adsorbent applicable to the pressure swing adsorption decarbonization process, characterized in that, The preparation of the adsorbent comprises the following steps: Activated carbon is treated with a nitric acid solution to obtain oxidized activated carbon; After the oxidized activated carbon is completely immersed in a sodium silicate solution for 40 min to 60 min, it is then placed in a hydrochloric acid solution and heated for 30 min to 40 min to obtain silica-oxidized activated carbon, and the silica-oxidized activated carbon is treated with a hydrofluoric acid solution for 5 min to 10 min to obtain acid-treated silica-oxidized activated carbon; The acid-treated silica-oxidized activated carbon is immersed in an amino-hydroxy benzene ring derivative solution for 60 min to 80 min, and then taken out and placed in an oven at 110°C to 120°C for drying for 1 h to 2 h to obtain the adsorbent; The preparation of the amino-hydroxy benzene ring derivative solution comprises the following steps: A benzene ring derivative, a dihydroxy amino compound and dimethyl sulfoxide are mixed to form a reaction bottom liquid, sodium hydroxide is added to the reaction bottom liquid and heated to 120°C to 140°C for reaction for 2 h to 3 h to obtain a mixed liquid, and the mixed liquid is extracted with ethyl acetate to obtain the amino-hydroxy benzene ring derivative solution; The benzene ring derivative includes benzoic acid or 3-amino-4-hydroxybenzoic acid; The dihydroxy amino compound includes diethanolamine or 2-amino-2-methyl-1,3-propanediol.

2. The adsorbent applicable to the pressure swing adsorption decarbonization process according to claim 1, characterized in that, The mass concentration of the nitric acid solution is 30% to 40%.

3. The adsorbent applicable to the pressure swing adsorption decarbonization process according to claim 1, characterized in that, The conditions for treating the activated carbon with the nitric acid solution include a treatment temperature of 90°C to 100°C and a treatment time of 30 min to 80 min.

4. The adsorbent applicable to the pressure swing adsorption decarbonization process according to claim 1, wherein, The mass concentration of the sodium silicate solution is 10% to 15%.

5. The adsorbent applicable to the pressure swing adsorption decarbonization process according to claim 1, characterized in that, The pH of the hydrochloric acid solution is 4.5 to 5.

0.

6. The adsorbent applicable to the pressure swing adsorption decarbonization process according to claim 1, characterized in that, The mass concentration of the hydrofluoric acid solution is 3% to 5%.

7. The adsorbent applicable to the pressure swing adsorption decarbonization process according to claim 1, wherein, The weight ratio of the benzene ring derivative: dihydroxy amino compound: sodium hydroxide is 1:1 to 2:1.

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