A high-oxidation-resistance pseudo-boehmite-based solid amine carbon capture material and a preparation method thereof

Abstract

The application provides a high-oxidation-resistance pseudo-boehmite-based solid amine carbon capture material and a preparation method, and the material is a polyethyleneimine (PEI) loaded pseudo-boehmite composite material, and the chemical composition of the material is yPEI-AlOOH, wherein y is the mass fraction of polyethyleneimine in the material, and the value range of y is 30wt%-60wt%. The application utilizes the hydroxyl-rich surface characteristics of the pseudo-boehmite carrier, forms a stable hydrogen bond network through the hydroxyl and PEI, and effectively inhibits the oxidation-induced amine chain rupture and amine site inactivation. Experiments show that the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent still remains 1.20 after 3h oxidation aging at 80 DEG C under simulated air conditions, and still remains 1.32 after 3h oxidation under harsh 100%O2 conditions. In comparison, the sample prepared at a higher aging temperature has a reduced surface hydroxyl, and the adsorption capacity decreases by 29.2% after 3h oxidation.

Description

Technical Field

[0001] This invention belongs to the field of adsorption technology, specifically a highly antioxidant boehmite-based solid amine carbon capture material and its preparation method. Background Technology

[0002] Carbon dioxide is one of the main greenhouse gases contributing to global warming. Direct air capture (DAC) is a negative emission technology that can directly remove CO2 from the atmosphere, and it is of great significance for bridging the gap in carbon emission reduction from industrial sources and treating emissions from dispersed sources. With the advancement of global carbon neutrality goals, DAC technology has become one of the key pathways to achieving net-zero CO2 emissions.

[0003] However, due to the low partial pressure of CO2 in the air, the large mass transfer resistance, the high oxygen content (21%), and the large variation in humidity in different regions, higher requirements are placed on the antioxidant performance, resistance to water vapor co-adsorption, and high adsorption capacity of the adsorption materials.

[0004] Solid amine adsorbents exhibit high selectivity and adsorption capacity at low temperatures, while also possessing advantages such as low energy consumption and good renewability, making them a research hotspot in the DAC (Adsorption-Dependent Adsorption) field. Existing solid amine materials are mostly prepared by loading organic amines onto porous supports, and their performance depends on the support structure and the content and distribution of amine groups. However, current technologies still have the following shortcomings: On the one hand, O2-induced oxidative degradation leads to the irreversible loss of amine groups, reducing adsorption capacity. Studies have shown that additives with hydroxyl groups can improve adsorption-desorption performance and enhance oxidative stability. On the other hand, organic amines are prone to migration, aggregation, or loss during use, resulting in decreased adsorption performance and insufficient cycle stability. Furthermore, some preparation methods require template agents and high reaction temperatures, which are not conducive to large-scale applications.

[0005] Hydroxyl groups on the support surface can form a stable hydrogen bond network with organic amines, inhibiting oxidation-induced amine chain breakage and amine site deactivation, thereby improving the oxidative stability of the adsorbent in multiple dimensions. Therefore, introducing hydroxyl-rich supports is an effective strategy to overcome the bottleneck of oxidative stability in solid amine materials. However, how to achieve stable loading of amine groups and improve the antioxidant performance and cycle stability of the material while ensuring high CO2 adsorption capacity remains a pressing technical problem to be solved in the current DAC field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a highly antioxidant pseudoboehmite-based solid amine carbon capture material and its preparation method, thereby resolving the issues in the prior art.

[0007] A highly antioxidant boehmite-based solid amine carbon capture material and its preparation method are disclosed. The material is a boehmite composite material supported on polyethyleneimine, and its chemical composition is yPEI-AlOOH, wherein y is the mass fraction of polyethyleneimine in the material, and the value of y ranges from 30wt% to 60wt%.

[0008] Preferably, the material has the morphology of nanoparticles with a particle size of ~100 nm; and the hydroxyl content in the material is 55%.

[0009] Preferably, the value of y is 50wt%.

[0010] Preferably, a method for preparing a hydroxyl-rich solid amine material for direct air capture includes the following steps: Step (1) Dissolve the aluminum-containing precursor in deionized water to prepare a homogeneous aluminum source solution; Step (2) Under stirring conditions, the aluminum source solution is added to an alkaline solution to adjust the pH value of the system, a mixed solution is obtained, and an aging treatment is performed to form a pseudoboehmite precipitate. Step (3) The aged mixed solution is subjected to solid-liquid separation and repeatedly washed with deionized water until the pH value of the filtrate is close to neutral. The resulting precipitate is then dried to obtain the pseudoboehmite carrier material. Step (4) uses an impregnation method to load polyethyleneimine onto the pseudoboehmite carrier using an organic solvent, followed by vacuum drying to obtain the hydroxyl-rich yPEI-AlOOH solid amine material.

[0011] Preferably, the aluminum-containing precursor in step (1) is at least one selected from aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum acetate and sodium aluminate; and the solute in the alkaline solution is at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonia and urea.

[0012] Preferably, the pH value of the mixed solution in step (2) is controlled within the range of 6 to 8, the temperature of the aging treatment is 25 to 35°C, and the aging time is greater than 2 hours.

[0013] Preferably, the solid-liquid separation method in step (3) is vacuum filtration or centrifugation; the drying temperature is 60-100℃.

[0014] Preferably, the organic solvent in step (4) is at least one selected from anhydrous methanol, anhydrous ethanol and acetone.

[0015] Preferably, the specific process of the impregnation method in step (4) is as follows: polyethyleneimine is added to an organic solvent and stirred at room temperature to form a uniform solution; the pseudo-boehmite carrier material is added to the uniform solution and stirred at room temperature; the organic solvent in the mixed solution is removed by a rotary evaporator and the hydroxyl-rich yPEI-AlOOH solid amine material is obtained after vacuum drying.

[0016] Preferably, the stirring process in step (4) is carried out under air-isolated conditions.

[0017] Preferably, the hydroxyl-rich solid amine material prepared by the above method is used in direct air capture.

[0018] Preferably, the conditions for direct air capture include: a capture temperature of 0–40°C and a CO2 concentration of 400 ppm in the captured gas.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention utilizes the hydroxyl-rich characteristics of the boehmite support surface to effectively suppress oxidation-induced amine chain cleavage and amine site deactivation through the formation of a stable hydrogen bond network between hydroxyl groups and PEI. Experiments show that after oxidative aging at 80℃ for 3 hours under simulated air conditions (400ppmCO2, 21%O2, 3%H2O), the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent remains at 1.20. Even after oxidation under harsh conditions of 100% O2 for 3 hours, it still maintains a concentration of 1.32. In contrast, the adsorption capacity of the sample prepared at a higher aging temperature (80℃) decreased by 29.2% after 3 hours of oxidation due to the reduction of surface hydroxyl groups.

[0020] (2) The present invention demonstrates through dynamic breakthrough experiments that the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent under water vapor conditions (3 vol% H2O) is 3.74 ) relatively dry conditions (1.76) The adsorption rate increased by approximately 112%, indicating that water vapor significantly promotes CO2 adsorption, and the material has obvious advantages in practical air environment applications.

[0021] (3) This invention demonstrates that the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent reaches 1.76 under conditions of 25℃ and 400ppm CO2. Furthermore, its adsorption performance remains basically stable within a temperature range of 25–40℃, demonstrating good temperature adaptability.

[0022] (4) The performance loss of the 50PEI-AlOOH adsorbent in the present invention was only 5.56% in 5 adsorption-desorption cycles; while the performance loss of the 50TEPA-AlOOH adsorbent in the comparative example was as high as 55.74%, indicating that PEI has better thermal stability and recyclability than TEPA.

[0023] (5) The present invention can complete the synthesis of pseudoboehmite carrier and PEI loading under normal temperature conditions, without the need for high temperature reaction and template agent. It is simple to operate, low in cost, and has good prospects for large-scale application. Attached Figure Description

[0024] Figure 1 Antioxidant performance diagram of the 50PEI-AlOOH solid amine material prepared by this invention; Figure 2 Comparison of the direct air trapping performance of the 50PEI-AlOOH solid amine material prepared in this invention under simulated air humidity conditions; Figure 3 The CO2 adsorption capacity of yPEI-AlOOH solid amine materials with different PEI loadings (30-60 wt%) prepared in this invention; Figure 4 Adsorption-desorption cycle performance diagram of the 50PEI-AlOOH solid amine material prepared by this invention. Detailed Implementation

[0025] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0026] This invention provides a highly antioxidant boehmite-based solid amine carbon capture material and its preparation method. The solid amine material uses boehmite (AlOOH) as a carrier and polyethyleneimine (PEI) as the active component, with a chemical composition of yPEI-AlOOH, where y is the mass fraction of PEI in the material, ranging from 30wt% to 60wt%. The material has a nanoparticle morphology with a particle size of approximately 100nm. This material exhibits excellent antioxidant and water-resistant properties in direct air carbon capture, as well as excellent CO2 adsorption capacity and cycling stability.

[0027] In this invention, "hydroxyl-rich" refers to the presence of hydroxyl groups on the surface of the boehmite support. These groups can form a stable hydrogen bond network with polyethyleneimine, inhibiting oxidation-induced amine chain breakage and amine site deactivation, thereby enhancing the oxidative stability of the adsorbent in multiple dimensions. Preferably, when y is 50 wt%, the hydroxyl content in the material can reach 55%.

[0028] In this invention, the aluminum-containing precursor may be selected from at least one of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum acetate, and sodium aluminate, preferably aluminum nitrate. The alkaline precipitant may be selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonia, and urea, preferably sodium carbonate. The organic solvent may be selected from at least one of anhydrous methanol, anhydrous ethanol, and acetone, preferably anhydrous ethanol.

[0029] In this invention, the pH value of the mixed solution in step (2) is controlled within the range of 6 to 8, the aging temperature is 25 to 35°C, and the aging time is greater than 2 hours, preferably 12 hours. The drying temperature in step (3) is 60°C. The vacuum drying temperature in step (4) is 25 to 100°C, and the vacuum degree is -0.1 to 0 MPa; the water bath temperature of the rotary evaporator is set to 25 to 80°C, the rotation speed is 10 to 100 rpm, and the vacuum degree is -0.1 to 0 MPa.

[0030] In this invention, the specific process of the impregnation method in step (4) is as follows: a certain mass of PEI is added to an organic solvent and stirred thoroughly at room temperature to form a homogeneous solution; a certain mass of pseudoboehmite carrier material is weighed and added to the above solution, and vigorous stirring is continued at room temperature to ensure that PEI is fully impregnated on the carrier surface and in the pore structure; the organic solvent in the mixed solution is removed using a rotary evaporator, and the hydroxyl-rich yPEI-AlOOH solid amine material is obtained after vacuum drying. Preferably, the stirring process is carried out under air-isolated conditions.

[0031] The hydroxyl-rich yPEI-AlOOH solid amine adsorbent prepared by this invention is suitable for capturing low concentrations of CO2 (approximately 400 ppm) under conditions of 0–40°C, and has potential application value in the field of direct air capture.

[0032] Embodiments of the present invention Example 1: Preparation of 50PEI-AlOOH solid amine adsorbent 37.513 g of Al(NO3)3·9H2O was dissolved in 100 mL of deionized water, and 5.30 g of Na2CO3 was separately dissolved in 100 mL of deionized water, yielding clear and transparent solutions in both cases. Under room temperature and vigorous stirring, the Al(NO3)3·9H2O solution was added dropwise to the Na2CO3 solution, and the pH of the system was adjusted to approximately 7.0 using 4 mol / L NaOH solution. After the addition was complete, the resulting mixed solution was aged at room temperature for 12 hours.

[0033] After aging, the suspension was repeatedly washed with deionized water by vacuum filtration and dried to obtain a filter cake. The obtained filter cake was dried in a 60℃ drying oven for 12 hours and then ground into powder to obtain the AlOOH support.

[0034] 0.50 g of polyethyleneimine was dissolved in 30 mL of methanol and stirred thoroughly at room temperature for 0.5 h to form a homogeneous solution. 0.50 g of dried AlOOH powder was weighed and added to the solution, and the mixture was stirred continuously at room temperature for 3 h to ensure that the polyethyleneimine was fully impregnated on the carrier surface and in the pore structure. The resulting solution was placed in a 60 °C water bath, and the methanol solvent was removed using a rotary evaporator at -0.1 MPa. Then, it was dried in a 60 °C vacuum drying oven to obtain 50PEI-AlOOH adsorbent material.

[0035] Example 2: Antioxidant performance test of 50PEI-AlOOH adsorbent (1) Antioxidant performance test under simulated air conditions Approximately 10 mg of the 50PEI-AlOOH adsorbent prepared in Example 1 was weighed and aged under a mixed gas environment with a volume fraction of 400 ppm CO2, 21% O2, and 3% H2O. The oxidation temperature was 80°C, and the aging time was 1–3 h. After the aging treatment, the sample was removed, and the adsorption performance of the aged adsorbent was tested.

[0036] The CO2 adsorption performance test was conducted on a thermogravimetric analyzer, and the adsorption dose used was approximately 10 mg. At room temperature (25℃), a CO2 / N2 mixed gas with a volume fraction of 400 ppm was introduced for adsorption, and the adsorption time was 180 min. The CO2 adsorption capacity of the material was calculated from the mass difference between the sample before adsorption and after adsorption saturation.

[0037] The test results are shown in Table 1. Under simulated air conditions, the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent decreased after aging for 1–3 hours, but the adsorption capacity remained at 1.20 after 3 hours of oxidation under the same conditions. This indicates that the 50PEI-AlOOH adsorbent has good antioxidant stability under near-realistic air environment conditions.

[0038] Table 1. Antioxidant performance test of adsorbent under simulated air conditions.

[0039] Test conditions: The oxidation atmosphere was a mixture of 400 ppm CO2, 21% O2 and 3% H2O, the oxidation temperature was 80℃; the adsorption temperature was 25℃, the CO2 concentration was 400 ppm, and the adsorption time was 180 min.

[0040] (2) Antioxidant performance test under 100% oxygen conditions Using the above aging method, the sample was aged in a 100% O2 atmosphere at an oxidation temperature of 80℃ for 1–3 hours, and the adsorption performance of the aged adsorbent was tested.

[0041] The test results are shown in Table 2. After aging for 1–3 hours, the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent decreased to some extent, but it still retained a high adsorption capacity. After oxidation in 100% oxygen for 3 hours, the adsorption capacity remained at 1.32. This indicates that PEI-AlOOH still has a certain degree of stability under strong oxidizing conditions.

[0042] Table 2. Antioxidant performance test of the adsorbent under 100% oxygen conditions.

[0043] Test conditions: oxidation temperature 80℃; adsorption temperature 25℃; CO2 concentration 400ppm; adsorption time 180min.

[0044] Example 3: Effect of aging temperature on the anti-aging performance of 50PEI-AlOOH adsorbent The 50PEI-AlOOH adsorbent was prepared using the method described in Example 1, with the difference being that the resulting mixed solution was aged at 80°C for 12 hours. The antioxidant properties of the obtained material were then tested under simulated air conditions using the testing method described in Example 2.

[0045] The test results are shown in Table 3. Under simulated air conditions, the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent prepared at an aging temperature of 80℃ decreased significantly after aging for 1–3 hours, from 0.48 before aging. Decreased to 0.34 The oxidation stability was reduced by 29.2%. This indicates that samples prepared at higher aging temperatures have poorer antioxidant stability under near-realistic air conditions due to the reduced number of surface hydroxyl groups.

[0046] Table 3. Antioxidant performance test of 50PEI-AlOOH adsorbent prepared at 80℃ under simulated air conditions.

[0047] Example 4: Effect of water vapor on the adsorption performance of 50PEI-AlOOH adsorbent Approximately 100 mg of ground 50PEI-AlOOH adsorbent was weighed and placed into a sample tube, which was then placed in a reaction furnace for temperature control. Water vapor (approximately 3 vol% H2O) was introduced into the bubble flask to simulate the CO2 adsorption experiment at room temperature. The inlet gas flow rate was 40 mL / min, and the gas composition consisted of approximately 400 ppm CO2, 21% O2, and equilibrium N2 to simulate the actual air environment. The desorption process was carried out under a pure N2 atmosphere.

[0048] Dynamic breakthrough experiments were conducted on the adsorbent under both dry and water-containing atmospheres (3 vol% H₂O) at 25 °C and approximately 400 ppm CO₂ (volume fraction). The results showed that the adsorption capacity under dry and water-containing conditions was 1.76 g / mL. and 3.74 The results indicate that the presence of water vapor promotes the CO2 adsorption process. These findings demonstrate that, under actual air conditions (humid conditions), the 50PEI-AlOOH adsorbent exhibits superior CO2 capture performance and shows promising application prospects.

[0049] Example 5: Preparation and performance testing of yPEI-AlOOH adsorbents with different PEI loadings yPEI-AlOOH adsorbents with different PEI loadings (30–60 wt%) were prepared using the method described in Example 1: 30PEI-AlOOH adsorbent: The preparation method differs from that of the 50PEI-AlOOH adsorbent in Example 1 in that 0.21g of polyethyleneimine is dissolved in 30mL of methanol.

[0050] 40PEI-AlOOH adsorbent: The preparation method differs from that of the 50PEI-AlOOH adsorbent in Example 1 in that 0.33g of polyethyleneimine is dissolved in 30mL of methanol.

[0051] 60PEI-AlOOH adsorbent: The preparation method differs from that of 50PEI-AlOOH adsorbent in Example 1 in that 0.75g of polyethyleneimine is dissolved in 30mL of methanol.

[0052] Using the test method described in Example 2, the CO2 adsorption performance of PEI-AlOOH adsorbents with different PEI loadings (30–60 wt%) was tested under conditions of 400 ppm CO2 and room temperature. The test results are shown in Table 4.

[0053] Table 4. Effect of different PIE loading on CO2 adsorption capacity of yPEI-AlOOH adsorbent.

[0054] Test conditions: adsorption temperature 25℃, CO2 concentration 400ppm.

[0055] Table 4 shows that the PEI loading has a certain impact on the adsorption performance of the adsorbent under low CO2 concentration conditions. As the PEI loading increases from 30 wt% to 50 wt%, the CO2 adsorption capacity of the adsorbent increases from 1.35 wt%. Increased to 1.76 This indicates that a higher amine loading provides more effective adsorption sites, thereby improving the material's CO2 adsorption capacity under direct air capture conditions. When the PEI loading is further increased to 60 wt%, the adsorption capacity decreases to 1.55. This may be due to the accumulation of excess amine in the carrier pores, which obstructs some pore structures, thereby limiting the diffusion and mass transfer of CO2 molecules and reducing adsorption capacity.

[0056] Example 6: Effect of adsorption temperature on the adsorption performance of 50PEI-AlOOH adsorbent To systematically investigate the effect of adsorption temperature on the adsorption performance of the adsorbent, 50PEI-AlOOH adsorbent was selected as the research object. The CO2 adsorption capacity of the adsorbent was tested under different adsorption temperatures (25-40℃). The test conditions were a CO2 / N2 mixed gas with a volume fraction of 400ppm and an adsorption time of 180min. The results are shown in Table 5.

[0057] Table 5. Effect of adsorption temperature on the adsorption performance of 50PEI-AlOOH adsorbent.

[0058] Test conditions: CO2 concentration of 400 ppm, adsorption time of 180 min.

[0059] Table 5 shows that the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent varies little within the range of 400 ppm CO2 and 25–40 °C, and its adsorption performance remains basically stable at each temperature. This result indicates that temperature has a limited impact on the material's adsorption performance within a temperature range close to that of the actual environment, suggesting that the adsorbent has good near-ambient temperature adaptability under low CO2 concentration conditions.

[0060] Example 7: Adsorption-desorption cycle performance test of 50PEI-AlOOH adsorbent The CO2 adsorption-desorption cycle performance of the 50PEI-AlOOH adsorbent was tested using a thermogravimetric analyzer. Approximately 10 mg of adsorbent was used in the test. Adsorption was performed at room temperature (25°C) by introducing a CO2 / N2 mixed gas with a volume fraction of 400 ppm for 140 min. Subsequently, the atmosphere was switched to high-purity N2, and desorption was carried out at 120°C for 15 min, completing one adsorption-desorption cycle. This process was repeated five times.

[0061] The cyclic stability of the 50PEI-AlOOH adsorbent was evaluated using the CO2 adsorption capacity calculation method described in Example 2 and the aforementioned cyclic testing method. The test results are shown in Table 6.

[0062] Table 6. CO2 adsorption-desorption recycling performance of 50PEI-AlOOH adsorbent

[0063] As shown in Table 6, the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent remained relatively stable during the five adsorption-desorption cycles, with a loss rate of approximately 5.56%, indicating that the material has good stability for repeated use.

[0064] Comparative Example 1: Preparation and cycle performance test of TEPA-modified AlOOH adsorbent (50TEPA-AlOOH).

[0065] The preparation method of 50TEPA-AlOOH adsorbent differs from the preparation method of 50PEI-AlOOH material in Example 1 in that 0.5g of tetraethylenepentamine (TEPA) is placed in 30mL of methanol solution.

[0066] The recyclability of the 50TEPA-AlOOH adsorbent was determined using the adsorption-desorption cycle performance test method described in Example 7. The test results are shown in Table 7.

[0067] Table 7. Effects of organic amine type (PEI, TEPA) on the CO2 adsorption-desorption recycling performance of the adsorbent.

[0068] As shown in Table 7, although the comparative sample 50TEPA-AlOOH adsorbent exhibited a higher adsorption capacity (1.83%) in the first cycle, However, due to its low melting and boiling points and thermal stability, the adsorption capacity exhibits a rapid decline trend, decreasing to 0.81 by the fifth cycle. The adsorption capacity decayed by 55.74%. In comparison, the 50PEI-AlOOH adsorbent in Example 7 exhibited excellent recyclability in 5 adsorption-desorption cycles, with a performance loss of only 5.56%. The test results show that the 50PEI-AlOOH adsorbent prepared in this invention has long-term stability, which is beneficial for large-scale application.

[0069] Results Discussion Based on the above experimental results, the following conclusions can be drawn: (1) Antioxidant performance: The 50PEI-AlOOH adsorbent prepared in this invention exhibits good stability under simulated air conditions (400ppmCO2, 21%O2 and 3%H2O) and even more stringent oxidation conditions of 100%O2. Under simulated air conditions, after oxidative aging at 80℃ for 3 hours, its CO2 adsorption capacity still remains at 1.20. After aging under 100% O2 conditions for 3 hours, its CO2 adsorption capacity still remained at 1.32. This indicates that the high number of hydroxyl groups on the carrier surface of the PEI-AlOOH adsorbent prepared at room temperature in this invention can form a stable hydrogen bond network with PEI, inhibiting oxidation-induced amine chain cleavage and amine site deactivation, thus exhibiting high antioxidant stability.

[0070] (2) Effect of water vapor on adsorption performance: The 50PEI-AlOOH adsorbent prepared in this invention exhibits better dynamic CO2 penetration performance under a water-containing atmosphere (3 vol% H2O) than under dry conditions. Dynamic penetration experiments show that the CO2 penetration time and dynamic adsorption capacity are prolonged under humid conditions, indicating that the presence of water vapor promotes the reaction process between CO2 and amine groups and improves the mass transfer behavior of CO2 in the material. Therefore, the PEI-AlOOH adsorbent in this invention has superior CO2 capture performance and application potential in actual air environments.

[0071] (3) Effect of PEI loading: When y = 30–60 wt%, it exhibits good CO2 adsorption capacity under both room temperature (25–40 °C) and low CO2 concentration (approximately 400 ppm) conditions. Among these, when y is 50 wt%, the hydroxyl content in the adsorbent is 55%, exhibiting the best CO2 adsorption performance, reaching an adsorption capacity of 1.76 at 25 °C and 400 ppm CO2. As the PEI loading increased from 30 wt% to 50 wt%, the material's adsorption capacity increased from 1.35 wt%. Increased to 1.76 This indicates that a higher amine loading provides more effective adsorption sites, thereby improving the material's ability to capture low-concentration CO2; however, when the PEI loading is further increased to 60 wt%, the adsorption capacity decreases to 1.55. This indicates that excessive organic amines may accumulate on the surface or in the pore structure of the carrier, limiting the diffusion and mass transfer of CO2 molecules.

[0072] (4) Effect of adsorption temperature: The 50PEI-AlOOH adsorbent prepared in this invention maintains a stable CO2 adsorption capacity in the range of 25 to 40℃. Under the condition of 400ppmCO2, its adsorption capacity changes little, indicating that the adsorbent has good temperature adaptability in a range close to the actual ambient temperature fluctuation, and is suitable for direct air capture conditions.

[0073] (5) Cyclic Stability: The 50PEI-AlOOH adsorbent prepared in this invention exhibited good cyclic performance in five CO2 adsorption-desorption cycle tests. Under the cyclic adsorption-desorption test conditions, the CO2 adsorption capacity of the 50PEI-AlOOH adsorbent in the first cycle was approximately 1.80. It remained at approximately 1.70 after the 5th cycle. The performance loss was 5.56%. In contrast, the comparative sample 50TEPA-AlOOH adsorbent experienced a performance loss of 55.74% after 5 cycles, indicating that PEI has superior thermal and cycling stability compared to TEPA, making it more suitable as an active amine component for capturing low-concentration CO2.

[0074] (6) Advantages of the preparation method: Under normal temperature conditions, polyethyleneimine is loaded onto the surface of AlOOH support to obtain uniform nanoparticles (with a particle size of about 100 nm). The cost is low, and the prepared adsorbent has a high hydroxyl content, thus possessing good antioxidant stability and is suitable for the field of direct air capture.

[0075] The embodiments of the present invention are given for the purposes of illustration and description. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A highly antioxidant boehmite-based solid amine carbon capture material and its preparation method, characterized in that, The material includes a pseudoboehmite composite material supported on polyethyleneimine, with the chemical composition yPEI-AlOOH, where y is the mass fraction of polyethyleneimine in the material and the value of y ranges from 30wt% to 60wt%.

2. The high-antioxidant boehmite-based solid amine carbon capture material and its preparation method as described in claim 1, characterized in that: The material has the morphology of nanoparticles with a particle size of 100 nm; the hydroxyl content in the material is 55%.

3. The high-antioxidant boehmite-based solid amine carbon capture material and its preparation method as described in claim 1, characterized in that: The value of y is 50wt%.

4. A method for preparing a highly antioxidant boehmite-based solid amine carbon capture material, characterized in that, The method for preparing the hydroxyl-rich solid amine material according to any one of claims 1 to 3 comprises the following steps: Step (1) Dissolve the aluminum-containing precursor in deionized water to prepare a homogeneous aluminum source solution; Step (2) Under stirring conditions, the aluminum source solution is added to an alkaline solution to adjust the pH value of the system, a mixed solution is obtained, and an aging treatment is performed to form a pseudoboehmite precipitate. Step (3) The aged mixed solution is subjected to solid-liquid separation and repeatedly washed with deionized water until the pH value of the filtrate is close to neutral. The resulting precipitate is then dried to obtain the pseudoboehmite carrier material. Step (4) uses an impregnation method to load polyethyleneimine onto the pseudoboehmite carrier using an organic solvent, followed by vacuum drying to obtain the hydroxyl-rich yPEI-AlOOH solid amine material.

5. The preparation method of the high-antioxidant boehmite-based solid amine carbon capture material as described in claim 4, characterized in that: The aluminum-containing precursor in step (1) is selected from at least one of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum acetate and sodium aluminate; the solute in the alkaline solution is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonia and urea.

6. The preparation method of the high-antioxidant boehmite-based solid amine carbon capture material as described in claim 4, characterized in that: The pH value of the mixed solution in step (2) is controlled within the range of 6 to 8, the temperature of the aging treatment is 25 to 35°C, and the aging time is greater than 2 hours.

7. The preparation method of the high-antioxidant boehmite-based solid amine carbon capture material as described in claim 4, characterized in that: The solid-liquid separation method in step (3) is vacuum filtration or centrifugation; the drying temperature is 60-100℃.

8. The preparation method of the high-antioxidant boehmite-based solid amine carbon capture material as described in claim 4, characterized in that: The organic solvent in step (4) is at least one selected from anhydrous methanol, anhydrous ethanol and acetone; The stirring process in step (4) is carried out under conditions of air isolation.

9. The preparation method of the high-antioxidant boehmite-based solid amine carbon capture material as described in claim 4, characterized in that: The specific process of the impregnation method in step (4) is as follows: polyethyleneimine is added to an organic solvent and stirred at room temperature to form a uniform solution; the pseudo-boehmite carrier material is added to the uniform solution and stirred at room temperature; the organic solvent in the mixed solution is removed by a rotary evaporator and the hydroxyl-rich yPEI-AlOOH solid amine material is obtained after vacuum drying.

10. The application of the hydroxyl-rich solid amine material according to any one of claims 1 to 3 or the hydroxyl-rich solid amine material prepared by the preparation method according to any one of claims 4 to 10 in direct air capture.

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