A low-cost Na2ZrO3-based CO2 adsorbent and its preparation method

Abstract

This invention discloses a low-cost Na2ZrO3-based CO2 adsorbent and its preparation method. The method of this invention includes: (1) adding zirconium silicate powder and heated high-concentration sodium hydroxide solution into a reaction vessel; (2) placing the sealed reaction vessel into a muffle furnace for heating reaction; (3) removing the reaction vessel, rapidly cooling it with water, separating the product into solid and liquid phases, collecting the filter cake, washing and drying it; (4) mixing the dried solid with sodium carbonate powder and calcining it to obtain the target product. This invention uses low-cost zirconium silicate as the zirconium source, and achieves low-energy and effective separation of Zr and Si in zircon sand through the alkali fusion method, and synthesizes a Na2ZrO3-based CO2 adsorbent, which effectively reduces the preparation cost of the adsorbent and provides a technical basis for the subsequent resource utilization of the separated products. In addition, the prepared adsorbent has extremely strong CO2 adsorption performance at high temperature, providing a new technical idea for its industrial application.

Description

Technical Field

[0001] This invention belongs to the field of adsorbent preparation technology, and more specifically, relates to a low-cost Na2ZrO3-based CO2 adsorbent and its preparation method. Background Technology

[0002] With rapid industrialization and increasing human dependence on fossil fuels, atmospheric CO2 concentrations have continued to rise, leading to a growing problem of global warming. The most feasible solution to this problem is to develop low-cost, environmentally friendly large-scale carbon capture, utilization, and storage (CCUS) technologies.

[0003] Carbon capture, utilization, and storage (CCUS) technology is a comprehensive environmental engineering technology that integrates three key stages: carbon capture, carbon utilization, and carbon sequestration. Carbon capture, the first step in CCUS technology, primarily involves capturing CO2 from emission sources, including pre-combustion capture, in-combustion capture, and post-combustion capture. Carbon utilization, another crucial stage of CCUS, involves converting captured CO2 into useful resources or energy, primarily through the production of chemical raw materials and the conversion into clean energy. Carbon sequestration, another important stage of CCUS, involves the long-term storage of CO2 underground or in the ocean to prevent its release into the atmosphere, primarily through geological sequestration and marine sequestration. Therefore, the effective development of carbon capture technology plays a key role in the development of CCUS technology; hence, the development of highly efficient CO2 adsorbents is of great significance.

[0004] In recent years, post-combustion capture technology based on high-temperature solid adsorption has attracted widespread attention worldwide due to its high carbon capture efficiency and low application cost, demonstrating strong industrial adaptability. Among various high-temperature solid adsorbent materials, calcium-based adsorbents have large adsorption capacity and low material cost, but poor cycle stability, making them less economically viable in the long run. Lithium-based adsorbents have low regeneration energy consumption and high cycle stability, but their lithium source cost is high, making them uneconomical for large-scale application. Sodium-based adsorbents, represented by Na2ZrO3, have been proven to possess both excellent cycle stability and a wider adsorption temperature window, making them a high-potential high-temperature solid CO2 adsorbent material. However, although the material cost of sodium-based adsorbents is generally lower than that of lithium-based adsorbents, zirconium, an element in Na2ZrO3, is a transition metal, and its limited natural reserves result in relatively high costs for its raw materials (such as ZrO2 and Zr(NO3)4), which significantly increases the difficulty of applying Na2ZrO3-based adsorbents. Therefore, developing a process route for preparing Na2ZrO3-based adsorbents based on low-cost zirconium sources has significant economic benefits and practical significance.

[0005] Zircon sand is an important industrial mineral for zirconium, primarily found in granite, alkaline rocks, and related pegmatites or post-magmatic deposits. Statistics show that nearly 80% of the world's zircon sand is directly used in the foundry industry and refractory material manufacturing, with smaller quantities used in alloys, paints, and the nuclear industry. In recent years, with the continuous development of the zirconium industry, zirconium-containing industrial waste has been continuously generated and accumulated, greatly promoting the iterative updates and technological breakthroughs in zirconium recycling processes. Furthermore, the in-depth development of the zirconium-containing industrial waste recycling industry provides a new approach to achieving diversified supply, cost reduction, lower production costs for zirconium products, improved ecological environment, and a sustainable industrial model.

[0006] Since zircon sand is directly used as the zirconium source in most zirconium product industries, a large amount of unreacted zircon sand inevitably exists in the final zirconium-containing waste. Its main component is zirconium silicate (molecular formula ZrSiO4), with a theoretical composition of 67.21 wt.% ZrO2 and 32.79 wt.% SiO2. ZrSiO4 is the only and most stable compound in the ZrO2-SiO2 phase diagram, exhibiting high resistance to thermal and acid decomposition and being difficult to wet by molten metal. At extremely high temperatures (>2000℃), ZrSiO4 can decompose into ZrO2 and SiO2. Therefore, ZrSiO4 can serve as a relatively inexpensive zirconium source for the preparation of Na2ZrO3, achieving a win-win situation for environmental, social, and economic benefits. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, the present invention aims to provide a low-cost Na2ZrO3-based CO2 adsorbent and its preparation method. This invention utilizes inexpensive zirconium silicate as a zirconium source and achieves efficient, low-energy separation of Zr and Si from zirconium silicate via an alkali fusion method, synthesizing a Na2ZrO3-based CO2 adsorbent. This effectively reduces the preparation cost of the adsorbent and provides a technical foundation for the subsequent resource utilization of the separated products. Furthermore, the prepared Na2ZrO3 exhibits extremely strong CO2 adsorption performance, providing a new technical approach for the industrial application of Na2ZrO3-based adsorbents. This invention combines alkali fusion and calcination methods to prepare the Na2ZrO3-based CO2 adsorbent, resulting in lower reaction temperatures, energy savings, and inexpensive raw materials, thereby reducing the application cost of the adsorbent and improving its economic viability.

[0008] To achieve the above objectives, this invention provides a method for preparing a low-cost Na2ZrO3-based CO2 adsorbent, comprising the following steps:

[0009] (1) Add ZrSiO4 powder and heated high-concentration sodium hydroxide solution to the reaction vessel;

[0010] (2) The sealed reaction vessel is placed in a muffle furnace for heating and reaction;

[0011] (3) After the reaction vessel is heated, it is quickly cooled down by water and the product is separated into solid and liquid. The filter cake is collected, washed and dried in sequence.

[0012] (4) Mix the dried solid with Na2CO3 powder evenly, and then calcine it in a muffle furnace to obtain the target product.

[0013] In this invention, in step (1), the concentration of the sodium hydroxide solution is 70wt.%-77wt.%, and the sodium hydroxide solution is heated to above 97°C; the mass ratio of ZrSiO4 powder to heated high-concentration sodium hydroxide is 1:25-1:15.

[0014] In this invention, in step (1), the concentration of the sodium hydroxide solution is 75wt.%-77wt.%, and the mass ratio of ZrSiO4 powder to heated high-concentration sodium hydroxide solution is 18:1-22:1.

[0015] In this invention, in step (2), the heating temperature is 230-250℃ and the heating time is 10-30h.

[0016] In this invention, in step (3), the product is separated into solid and liquid while hot by a vacuum filtration device; the filter cake is washed with water and dried at a temperature of 100-110℃ for 6-20 hours.

[0017] In this invention, in step (4), the dried solid is ZrO2, and the molar ratio of the dried solid to Na2CO3 powder is 1:1.1 to 1:1.2; the calcination temperature is 850-900℃, and the calcination time is 5h-8h.

[0018] The present invention also provides a low-cost Na2ZrO3-based CO2 adsorbent prepared by the above-described preparation method.

[0019] Furthermore, this invention provides an application of a low-cost Na2ZrO3-based CO2 adsorbent in removing CO2 from industrial flue gas.

[0020] The principle of this invention is as follows: low-cost ZrSiO4 undergoes an alkaline fusion reaction with a high-concentration sodium hydroxide solution in a high-pressure reactor at a certain temperature, causing ZrSiO4 to decompose into ZrO2 and Na2SiO3. Subsequently, zirconium and silicon elements in ZrSiO4 are separated by filtration, and the filter cake is the obtained ZrO2. Finally, the obtained ZrO2 is recovered and mixed with Na2CO3 in a certain molar ratio, and then calcined under high temperature conditions to obtain a Na2ZrO3-based CO2 adsorbent.

[0021] In summary, the above-described technical solutions conceived by this invention have the following application advantages:

[0022] 1. ZrSiO4 has a lower price than ZrO2 and Zr(NO3)4 and is widely found in various industrial zirconium-containing wastes. Therefore, zirconium-containing wastes can be preliminarily purified and immediately used for the preparation of adsorbents, which reduces application costs and makes full use of resources.

[0023] 2. Verification has shown that the Na2ZrO3-based CO2 adsorbent prepared by this process route has excellent high-temperature CO2 adsorption performance and can meet the CO2 removal requirements of industrial flue gas. Attached Figure Description

[0024] Figure 1 These are the X-ray diffraction patterns of the solids after drying in Examples 1-5.

[0025] Figure 2 X-ray diffraction pattern of the Na2ZrO3-based CO2 adsorbent finally prepared in Example 1.

[0026] Figure 3 This is the temperature-varying CO2 adsorption curve of the Na2ZrO3-based CO2 adsorbent finally prepared in Example 1.

[0027] Figures 4a-4f These are the isothermal CO2 adsorption curves of the Na2ZrO3-based CO2 adsorbent finally prepared in Example 1, with adsorption temperatures of 600℃, 650℃, 700℃, 750℃, 800℃, and 850℃.

[0028] Figures 5a-5c The image shows the isothermal desorption curve of the Na2ZrO3-based CO2 adsorbent finally prepared in Example 1. The sample was first saturated in a pure CO2 gas stream at 850°C, and then desorbed in pure N2 gas streams at 850°C, 900°C, and 950°C, respectively. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] This invention provides a method for preparing a low-cost Na2ZrO3-based CO2 adsorbent, comprising the following steps:

[0031] (1) Add ZrSiO4 powder and sodium hydroxide solution of a certain mass fraction to the reaction vessel according to a certain solid-liquid mass ratio;

[0032] (2) Place the reactor in a muffle furnace and heat for a period of time;

[0033] (3) After the reaction vessel is heated, it is quickly cooled down by water. The product is then separated into solid and liquid by a vacuum filter. The filter cake is collected and washed with deionized water. The filter cake is then placed in an oven for heating and drying.

[0034] (4) The dried solid and Na2CO3 powder are mixed evenly according to a certain mass ratio, and then placed in a muffle furnace for calcination to obtain the target product.

[0035] In step (1), the solubility of sodium hydroxide in water increases with increasing temperature, so it is necessary to control the temperature of the solution to achieve the desired mass fraction of solution.

[0036] In step (2), the inner liner of the reactor is made of polytetrafluoroethylene to meet the temperature requirements of the alkali fusion reaction.

[0037] In step (3), after the reactor is taken out of the muffle furnace, it needs to be cooled down quickly with water. Then, the filter cake is collected while it is still hot and washed several times with deionized water. The timing of filtration directly affects the effect of zirconium-silicon separation.

[0038] The main component of the dried solid in step (4) is ZrO2. Therefore, the mixing molar ratio of ZrO2 and Na2CO3 is set, and Na2CO3 needs to be added at least 10 wt.% more to reduce the impact of sodium sublimation at high temperature on the purity of the reaction product.

[0039] Example 1

[0040] (1) Prepare a 77 wt.% sodium hydroxide solution in a constant temperature water bath (keeping the temperature above 97°C until the solution is saturated);

[0041] (2) Subsequently, ZrSiO4 powder and sodium hydroxide solution were mixed in the inner liner of the reactor at a solid-liquid mass ratio of 20:1.

[0042] (3) After sealing the reactor, place it in a muffle furnace and heat it at a temperature of 240°C for 24 hours.

[0043] (4) After heating is complete, take out the reactor and quickly rinse it with 20°C cold water to cool it down so that the metal shell can be cooled down quickly. Then open the metal shell of the reactor. At this time, the temperature of the inner liner is still high, still above 90°C. Separate the solid and liquid products in the inner liner through a vacuum filter.

[0044] (5) During the filtration process, deionized water was added and washed 5 times. Then the filter cake was collected and dried in an oven at 105°C for 12 hours.

[0045] (6) The dried solid and Na2CO3 powder were mixed evenly at a mass ratio of 41:38.8, and then placed in a muffle furnace for calcination at a temperature of 900℃ for 5 hours.

[0046] Furthermore, the parameters for Examples 2-5 are shown in Table 1. Parameters not listed in the table are the same as those for Example 1.

[0047] Table 1

[0048]

[0049]

[0050] Experimental Results Analysis

[0051] Phase composition analysis of the dried solids in Examples 1-5 was performed by X-ray diffraction (XRD), and the results are as follows: Figure 1 As shown, the mass fraction of sodium hydroxide significantly affects the phase composition of the alkali fusion product. Specifically, when the mass fraction of sodium hydroxide is 32.43 wt.%, the alkali fusion reaction hardly occurs. As the alkali concentration gradually increases, the diffraction peaks of ZrSiO4 gradually weaken, while the diffraction peaks of Na2ZrSiO5 become more prominent. When the mass fraction of sodium hydroxide exceeds 60 wt.%, the diffraction peaks of ZrSiO4 are almost invisible, which can be considered as ZrSiO4 being completely converted into Na2ZrSiO5. When the mass fraction of sodium hydroxide exceeds 75 wt.%, the diffraction peaks of Na2ZrSiO5 disappear, and the main component of the product is ZrO2. At this point, zirconium and silicon in ZrSiO4 are completely separated.

[0052] X-ray fluorescence spectrometry (XRF) was used to analyze the elemental composition of the sample in Example 1 before and after alkali fusion, and the results are shown in Table 2. It can be found that after the alkali fusion reaction, the Si content of the solid product decreased from 13.09% to 8.13%, while the Na content increased from 0.02% to 8.52%.

[0053] Table 2

[0054]

[0055] The phase composition of the Na2ZrO3-based CO2 adsorbent finally prepared in Example 1 was analyzed by X-ray diffraction (XRD), and the results are as follows: Figure 2As shown, a strong diffraction peak of Na2ZrO3 was detected in the final sample, which further indicates that the solid product after alkali fusion recovery is ZrO2 with high purity.

[0056] The temperature-dependent CO2 adsorption performance of the Na2ZrO3-based CO2 adsorbent prepared in Example 1 was tested using a thermogravimetric analyzer (STD-Q600). Corresponding temperature-dependent adsorption curves are shown below. Figure 3 As shown, when the temperature slowly rises to 300℃, the sample mass growth rate first increases and then decreases, showing a peak at 300℃. As the temperature continues to rise, the mass continues to increase, and when the temperature rises to around 800℃, the mass growth rate surges to 900℃. This indicates that 800-900℃ is the optimal CO2 adsorption temperature range for the adsorbent. As the temperature continues to rise, the sample mass growth gradually slows down, reaching its maximum at around 1000℃. Subsequently, the mass begins to decrease continuously, indicating the start of the CO2 desorption stage.

[0057] The isothermal CO2 adsorption performance of the Na2ZrO3-based CO2 adsorbent prepared in Example 1 was tested using a thermogravimetric analyzer (STD-Q600). Isothermal adsorption tests were conducted at six temperatures within the range of 600-850℃ under a pure CO2 gas flow. The corresponding isothermal adsorption curves are shown below. Figures 4a-4f As shown, the entire adsorption process can be divided into three stages. The first stage is very short, during which the adsorbent mass increases at an accelerating rate. The second stage is longer than the first, with the adsorbent mass increasing at a steady rate, the growth rate remaining almost constant. The third stage is the longest, during which the adsorbent mass continues to rise, but the growth rate gradually decreases. Notably, when the adsorption temperature is 850℃, the third stage accounts for almost the entire process, at which point the final mass almost stops increasing, indicating that there is a threshold for CO2 adsorption.

[0058] The isothermal CO2 desorption performance of the Na2ZrO3-based CO2 adsorbent prepared in Example 1 was tested using a thermogravimetric analyzer (STD-Q600). Isothermal adsorption tests were conducted at three temperatures within the range of 850-950℃ under a pure N2 gas flow. The corresponding isothermal adsorption curves are shown below. Figures 5a-5c As shown in the figure. By comparison, it can be found that the higher the desorption temperature, the shorter the time required for complete desorption and regeneration of the adsorbent. Moreover, at temperatures above 850℃, the adsorbent can be completely regenerated within 25 minutes.

Claims

1. A method for preparing a low-cost Na2ZrO3-based CO2 adsorbent, characterized in that, Includes the following steps: (1) Add ZrSiO4 powder and heated high-concentration sodium hydroxide solution to the reaction vessel; (2) Place the sealed reactor into a muffle furnace for heating and reaction; (3) After the reaction vessel is heated, it is quickly cooled down with water and the product is separated into solid and liquid. The filter cake is collected, washed and dried in sequence. (4) The dried solid is mixed evenly with Na2CO3 powder, and then calcined in a muffle furnace to obtain the target product; wherein: In step (1), the concentration of the sodium hydroxide solution is 75 wt.%-77 wt.%, and the sodium hydroxide solution is heated to above 97°C; the mass ratio of ZrSiO4 powder to the heated high-concentration sodium hydroxide solution is 1:22-1:

18. In step (2), the heating temperature is 230-250℃ and the heating time is 10-30 h; In step (4), the dried solid is ZrO2.

2. The preparation method according to claim 1, characterized in that, In step (3), the product is separated into solid and liquid while hot by a vacuum filtration device; the filter cake is washed with water and dried at a temperature of 100-110℃ for 6-20 h.

3. The preparation method according to claim 1, characterized in that, In step (4), the molar ratio of the dried solid to Na2CO3 powder is 1:1.1 to 1:1.2; the calcination temperature is 850-900℃ and the calcination time is 5h-8h.

4. The application of a low-cost Na2ZrO3-based CO2 adsorbent prepared by the preparation method according to any one of claims 1 to 3 in the removal of CO2 from industrial flue gas.

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