Natural sepiolite modification process suitable for medium-high temperature CO2 adsorption

Abstract

The invention discloses a chambering regulation and control process of natural sepiolite. The optimized sepiolite material is applied to a medium-high temperature CO2 adsorption process. Through the basic thought of a single-factor method and permutation and combination, different pairing modification processes are optimized to realize chambering treatment of the natural sepiolite. On the basis of a blank control method, the solid weight gain of CO2 adsorption of the material before and after modification under the medium-high temperature condition is compared, the optimal modification is preferably selected as a two-step chambering mode, calcination ending is the optimal optimization mode, the excellent medium-high temperature CO2 adsorption performance is 6.76 mmol / g, and compared with natural sepiolite, the adsorption capacity is remarkably improved by 104%. According to the method, the technological process is simple and easy to implement, the cost is low, the CO2 adsorption effect is excellent, and an efficient and feasible technical scheme is provided for practical application of sepiolite in the field of medium-high-temperature CO2 adsorption.

Description

Technical Field

[0001] The invention belongs to the field of adsorbent preparation, and in particular relates to a natural sepiolite modification process suitable for medium- and high-temperature CO2 adsorption. Technical Background

[0002] Against the backdrop of rapid global economic development, the large-scale use of fossil fuels has led to increasingly prominent carbon emissions. my country's coal-dominated energy structure faces severe carbon emission pressures. Excessive CO2 emissions, the most prominent greenhouse gas, are triggering a series of environmental problems, including global warming and frequent extreme weather events, posing a serious threat to ecological balance and the sustainable development of human society. Against this backdrop, the development of efficient CO2 emission reduction technologies has become a key initiative for addressing climate change and achieving sustainable development. Among existing emission reduction technology pathways, CO2 capture, utilization, and storage (CCUS) has attracted considerable attention due to its potential for large-scale application. As the core technology, the efficiency and economics of the carbon capture process directly determine the overall emission reduction effectiveness. Therefore, the development of efficient, low-cost, and environmentally friendly CO2 capture technologies is becoming increasingly important.

[0003] Existing CO2 capture technologies can be mainly divided into pre-combustion capture, oxygen-enriched combustion, and post-combustion capture. Among them, post-combustion capture technology has become the most widely used carbon capture solution in the current industrial field due to its mature process and low transformation cost. Post-combustion CO2 capture technologies mainly include absorption, adsorption, membrane separation, and low-temperature separation. Compared with other methods, adsorption has outstanding advantages such as low energy consumption, simple operation process, environmental friendliness, and low corrosion. The most critical issue in capturing CO2 based on adsorption is the selection of adsorbents. Among them, clay minerals have attracted much attention in CO2 capture material research due to their unique layered structure, high aspect ratio, abundant active sites, and excellent adsorption capacity. At the same time, the abundant reserves, low cost, and environmental friendliness of clay minerals also give them significant advantages in large-scale applications.

[0004] Sepiolite, a naturally occurring fibrous silicate mineral with abundant reserves and low cost in Xiangtan, Hunan, exhibits high specific surface area, excellent pore structure, and adsorption properties. It is widely used in adsorption and separation, as a catalyst support, in construction and building materials, and in agriculture. However, natural sepiolite suffers from high impurity content, narrow channels, limited specific surface area, and poor thermal stability, resulting in insufficient adsorption performance in direct applications. Improving the adsorption capacity of sepiolite through modification has been a research focus. A recent study (Separation and Purification Technology, 2023, 306: 122-627) developed a low-cost and highly efficient sepiolite-based solid amine adsorbent for post-combustion CO2 capture. By acid-treating sepiolite and loading it with pentaethylenehexamine (PEHA), the adsorbent exhibited a high adsorption capacity of 2.47 mmol / g at 50°C, with only a 9.8% decrease after 10 cycles. For example, a study (Chemical Engineering Journal, 2018, 353: 940-948) impregnated diethylenetriamine (DETA) onto an acid-activated sepiolite support. Experimental results showed that acid activation and amine loading significantly improved the adsorbent's CO2 adsorption performance. The optimal loading was 0.8 g DETA / g sepiolite, resulting in an adsorption capacity of 1.65 mmol / g at 35°C. After four adsorption-desorption cycles, 95.2% of the adsorption capacity was retained. However, most research on sepiolite modification has focused on environmental applications such as wastewater treatment and wastewater soil remediation. Research on waste gas treatment, particularly the adsorption of the greenhouse gas CO2, remains largely unexplored. Although some studies have explored sepiolite's CO2 adsorption performance at ambient temperatures, research on CO2 adsorption at medium and high temperatures is extremely scarce. Therefore, exploring the adsorption performance of sepiolite for CO2 at medium and high temperatures and its optimization methods can not only fill the gaps in existing research, but also provide new technical ideas for the development of new and efficient CO2 adsorption materials, thereby providing strong support for achieving greenhouse gas emission reduction goals.

[0005] The present invention combines the three commonly used processes for modifying sepiolite - water washing, acid modification, and calcination - and adopts a method combining single-factor experiments with permutation and combination to prepare sepiolite materials with different paired modification processes. Based on the synergistic effect of different modification processes, the pore structure of sepiolite is precisely controlled, and through systematic testing of CO2 adsorption performance under medium and high temperature conditions, the optimal process for optimizing sepiolite with a two-step sequence of acid modification followed by calcination is screened out. Single-factor experiments on calcination temperature and calcination time show that the optimized sepiolite material exhibits excellent CO2 adsorption performance, with a maximum adsorption capacity of 6.76 mmol / g, an increase of 104% compared to natural sepiolite. The process of the present invention is simple, low-cost, and has a significant adsorption effect, providing an efficient and feasible technical solution for the field of medium and high temperature CO2 adsorption. Summary of the Invention

[0006] Based on the above existing technologies, the present invention provides a process for modifying natural sepiolite suitable for medium- and high-temperature CO2 adsorption. This invention utilizes a permutation and combination approach to prepare sepiolite materials using different paired modification processes, resulting in simple operation and low cost. Compared to currently reported modified sepiolite CO2 adsorption processes, the sepiolite modification process described in this patent achieves even more significant medium- and high-temperature adsorption, bridging the gap in the transition from ambient-temperature to medium- and high-temperature CO2 adsorption for solid adsorbents and potentially offering a broader range of industrial applications.

[0007] The technical solution of the present invention is:

[0008] The timing of optimizing the hole expansion of natural sepiolite is carried out using the basic idea of permutation and combination:

[0009] Common impurity removal and pore expansion processes based on natural sepiolite, such as water washing, acid modification, and calcination, can remove impurities, alter the original composition, and expand pore size, respectively. The priority of each process and the sequence in which they are used significantly influence the CO2 adsorption performance of sepiolite under medium- and high-temperature conditions. This study experimentally discovered that the timing of the calcination treatment plays a key role in optimizing the structure of sepiolite. Specifically, the three basic modification processes were paired and combined using a permutation and combination approach, resulting in six different two-step pore expansion steps and six different three-step pore expansion steps. Optimized sepiolite samples obtained from these permutations were then tested and analyzed for CO2 adsorption performance using programmed temperature and solid weight loss. Using natural sepiolite as a blank control, the optimal pore expansion sequence was identified as acid modification followed by calcination. Calcination temperature and calcination duration were optimized using a single-factor approach, resulting in modified sepiolite materials with excellent CO2 adsorption performance under medium- and high-temperature conditions.

[0010] In the above preparation method, preferably, the optimized sequence of sepiolite is acidification followed by calcination.

[0011] In the above preparation method, preferably, the calcination temperature is 500°C.

[0012] In the above preparation method, preferably, the calcination time is 4 hours.

[0013] In the above preparation method, preferably, the calcination rate is 5°C / min.

[0014] In the above preparation method, preferably, the calcination time is 4 hours.

[0015] In the above preparation method, preferably, the temperature limit of the programmed temperature adsorption is 900°C.

[0016] In the above preparation method, preferably, the adsorption heating rate is 5°C / min.

[0017] In the above preparation method, preferably, the constant temperature adsorption time is 1 hour.

[0018] The above-mentioned sepiolite samples are used for the adsorption of CO2 at medium and high temperatures. The specific method is as follows:

[0019] Using a thermogravimetric analyzer, the program was set to start from an initial temperature of 30°C, gradually increase the temperature to 900°C at a heating rate of 5°C / min, and maintain a stable state at this temperature for 1 hour to obtain the adsorption capacity of CO2 by different paired sepiolite modified materials.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] (1) For the first time, the three basic modification processes of sepiolite - water washing, acid modification and calcination - were systematically studied using a combination of ideas, breaking through the limitations of the traditional single modification process. 15 modification sequences were comprehensively compared, and it was concluded that the process ending with calcination had the best adsorption effect. The blank control method was used to further optimize the optimal pore expansion sequence, which was acid modification followed by calcination.

[0022] (2) By optimizing the two-step pore expansion calcination process of sepiolite, namely acid modification and calcination, and regulating the calcination temperature and calcination time, the pore structure and surface active site distribution of sepiolite were optimized. The optimized modified sepiolite showed excellent CO2 adsorption capacity under medium and high temperature environments, which expanded the application range of sepiolite materials in the field of high-temperature gas treatment and provided an efficient and low-cost solution for the capture of heat-carrying CO2 in blast furnace exhaust gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Effect of different calcination temperatures on the CO2 adsorption properties of acid-modified sepiolite.

[0024] Figure 2 Effect of different calcination times on the CO2 adsorption properties of acid-modified sepiolite.

[0025] Figure 3 Graph showing the CO2 adsorption performance of natural sepiolite after one-step pore expansion treatment.

[0026] Figure 4 CO2 adsorption performance diagram of natural sepiolite after two-step pore expansion treatment.

[0027] Figure 5 CO2 adsorption performance of natural sepiolite after three-step pore expansion treatment. DETAILED DESCRIPTION

[0028] In order to more fully understand the technical content of the present invention, the technical solution of the present invention is further introduced and illustrated in conjunction with specific embodiments below.

[0029] Example 1:

[0030] (1) 4 g of natural sepiolite was mixed with 40 mL of 1% hydrochloric acid, stirred at 80 °C for 6 h, centrifuged, washed with ultrapure water until neutral, and then dried to obtain acid-modified sepiolite.

[0031] (2) The obtained acid-modified sepiolite was placed in a muffle furnace and calcined at 750°C for 4 hours at a heating rate of 5°C / min to obtain acid-modified-calcined sepiolite.

[0032] By setting the program of the thermogravimetric analyzer as follows: starting from an initial temperature of 30°C, gradually increasing the temperature to 900°C at a heating rate of 5°C / min, and maintaining a stable state at this temperature for 1 hour, the adsorption capacity of CO2 at medium and high temperatures was obtained to be 6.75 mmol / g.

[0033] Example 2: Effect of different calcination temperatures on the CO2 adsorption performance of acid-modified sepiolite. The specific experimental steps are as follows:

[0034] (1) 4 g of natural sepiolite was mixed with 1% hydrochloric acid, stirred at 80 °C for 6 h, centrifuged, washed with ultrapure water until neutral, and then dried to obtain acid-modified sepiolite.

[0035] (2) The acid-modified sepiolite was placed in a muffle furnace and calcined at 500°C, 600°C, 700°C, 750°C, and 800°C for 2 h at a heating rate of 5°C / min to obtain acid-modified-calcined sepiolite samples with different calcination temperatures.

[0036] (3) Using a thermogravimetric analyzer, the program of the thermogravimetric analyzer was set as follows: starting from an initial temperature of 30°C, gradually increasing the temperature to 900°C at a rate of 5°C / min, and maintaining a stable state at this temperature for 1 hour, the adsorption capacity of CO2 by sepiolite calcined at different temperatures and acid-modified-calcined was obtained. Related properties such as Figure 1As shown in the figure, the adsorption capacity first increases and then decreases with increasing calcination temperature, reaching a peak at 750°C. This is because moderately increasing the calcination temperature helps optimize the sample's pore structure, thereby enhancing adsorption performance; however, when the temperature is too high, the sample's structural stability is destroyed, resulting in a decrease in adsorption capacity.

[0037] Example 3: Effect of different calcination times on the CO2 adsorption performance of acid-modified sepiolite. The specific experimental steps are as follows:

[0038] (1) 4 g of natural sepiolite was mixed with 1% hydrochloric acid, stirred at 80 °C for 6 h, and then centrifuged. The mixture was washed with ultrapure water until neutral, and then dried to obtain acid-modified sepiolite.

[0039] (2) The acid-modified sepiolite was placed in a muffle furnace and calcined at 750 °C for 1 h, 2 h, 3 h, 4 h, and 5 h at a heating rate of 5 °C / min to obtain acid-modified-calcined sepiolite samples with different calcination times.

[0040] (3) Using a thermogravimetric analyzer, the program of the thermogravimetric analyzer was set as follows: starting from an initial temperature of 30°C, gradually increasing the temperature to 900°C at a heating rate of 5°C / min, and maintaining a stable state at this temperature for 1 hour, the adsorption capacity of CO2 by acid-modified-calcined sepiolite calcined at 750°C for different times was obtained. Related properties such as Figure 2 As shown in the figure, the adsorption amount first increases and then decreases with calcination time, reaching a peak at 4 hours. This is because appropriately extending the calcination time can optimize the sample's pore structure, increase the specific surface area and adsorption sites, and thus enhance the material's adsorption performance. However, excessive calcination time may damage the material's structure. Compared to calcination temperature, calcination time has a smaller effect on sepiolite's CO2 adsorption performance.

[0041] Comparative Example 1: Natural sepiolite was treated using three different one-step pore expansion methods. The specific experimental steps are as follows:

[0042] (1) Water washing and pore enlargement treatment: 10 g of natural sepiolite was mixed with 200 mL of ultrapure water and stirred at room temperature for 10 h. After standing for 24 h, the mixture was washed three times with ultrapure water and then dried to obtain water-washed sepiolite.

[0043] (2) Acid-modified pore expansion treatment: 4 g of natural sepiolite was mixed with 40 mL of 1% hydrochloric acid, stirred at 80 °C for 6 h, and then centrifuged. The mixture was washed with ultrapure water until neutral, and then dried to obtain acid-modified sepiolite.

[0044] (3) Calcination and pore expansion treatment: 4 g of natural sepiolite was placed in a muffle furnace and calcined at 500 °C for 2 h at a heating rate of 5 °C / min to obtain calcined sepiolite.

[0045] (4) By setting the thermogravimetric analyzer program to: starting from an initial temperature of 30 °C, gradually increasing the temperature to 900 °C at a heating rate of 5 °C / min, and maintaining a stable state at this temperature for 1 hour, the adsorption capacity of CO2 by washed sepiolite, acid-modified sepiolite, and calcined sepiolite was obtained respectively. Figure 3 From the perspective of one-step calcination and pore expansion, calcination is better because it optimizes the material structure and improves adsorption performance through high temperature. Although acid modification can remove some impurities and increase the specific surface area, the effect is slightly inferior to calcination. Water washing can only remove surface soluble impurities and has limited pore expansion effect, resulting in the lowest adsorption capacity.

[0046] Comparative Example 2: Two different one-step pore expansion methods for natural sepiolite were combined to form six different paired two-step pore expansion treatment methods (water washing-acid treatment, water washing-calcination treatment, acid treatment-water washing treatment, acid treatment-calcination treatment, calcination-water washing treatment, and calcination-acid treatment). Natural sepiolite was treated with these methods to obtain six different paired two-step pore expansion sepiolite samples. The thermogravimetric analyzer was programmed to start from an initial temperature of 30°C, gradually increase the temperature to 900°C at a heating rate of 5°C / min, and maintain a stable state at this temperature for 1 hour, and the CO2 adsorption capacity was obtained respectively. Related properties are as follows: Figure 4 From the perspective of two-step calcination pore expansion, acid modification-calcination treatment is better. This is because the acid modification treatment can effectively remove impurities in the pores of sepiolite and increase the specific surface area of the sample. The subsequent calcination treatment further optimizes the structural stability of the sample. The synergistic effect of the two significantly improves the adsorption capacity.

[0047] Comparative Example 3: Three different one-step pore expansion methods for natural sepiolite were combined to form 6 different paired three-step pore expansion treatment methods (water washing-acid modification-calcination treatment, water washing-calcination-acid modification treatment, acid modification-water washing-calcination treatment, acid modification-calcination-water washing treatment, calcination-water washing-acid modification treatment, and calcination-acid modification-water washing treatment). Natural sepiolite was treated to obtain 6 different paired three-step pore expansion sepiolite samples. The program of the thermogravimetric analyzer was set to: starting from an initial temperature of 30°C, gradually increasing the temperature to 900°C at a heating rate of 5°C / min, and maintaining a stable state at this temperature for 1 hour, and the adsorption capacity of CO2 was obtained respectively. Related properties are as follows: Figure 5 From the perspective of three-step calcination pore expansion, water washing-acid modification-calcination treatment is better. This is because water washing can initially remove soluble impurities in sepiolite, acid modification treatment further effectively removes residual impurities in the pores and increases the specific surface area. Finally, calcination treatment optimizes its pore structure and stability.

Claims

1. A natural sepiolite modification process suitable for medium and high temperature CO2 adsorption, characterized in that: The following steps are involved: Common impurity removal and pore expansion processes based on natural sepiolite, such as water washing, acid modification, and calcination, can remove impurities, alter the original composition, and expand pore size, respectively. The priority of each process and the sequence in which they are used significantly influence the CO2 adsorption performance of sepiolite under medium- and high-temperature conditions. This study experimentally discovered that the timing of the calcination treatment plays a key role in optimizing the structure of sepiolite. Specifically, the three basic modification processes were paired and combined using a permutation and combination approach, resulting in six different two-step pore expansion steps and six different three-step pore expansion steps. Optimized sepiolite samples obtained from these permutations were then tested and analyzed for CO2 adsorption performance using programmed temperature and solid weight loss. Using natural sepiolite as a blank control, the optimal pore expansion sequence was identified as acid modification followed by calcination. Calcination temperature and calcination duration were optimized using a single-factor approach, resulting in modified sepiolite materials with excellent CO2 adsorption performance under medium- and high-temperature conditions.

2. The natural sepiolite modification process for medium- and high-temperature CO2 adsorption according to claim 1, characterized in that: The calcination process is placed at the end of the sepiolite optimization process.

3. The natural sepiolite modification process for medium- and high-temperature CO2 adsorption according to claim 1, characterized in that: The calcination temperature is 500℃~800℃.

4. The natural sepiolite modification process for medium- and high-temperature CO2 adsorption according to claim 1, characterized in that: The calcination time is 1~4h.

5. The natural sepiolite modification process suitable for medium and high temperature CO2 adsorption according to claim 1, characterized in that: The calcination rate is 5℃ / min~20℃ / min.

6. The natural sepiolite modification process for medium- and high-temperature CO2 adsorption according to claim 1, characterized in that: Adsorption temperature range is 30℃~1000℃.

7. The process for modifying natural sepiolite suitable for medium- and high-temperature CO2 adsorption according to claim 1, characterized in that: Adsorption heating rate 5℃ / min~20℃ / min.

8. The natural sepiolite modification process suitable for medium- and high-temperature CO2 adsorption according to claim 1, characterized in that: The constant temperature adsorption time is 1h~4h.

Images