A magnesium oxide-based carbon dioxide adsorbent and a method for preparing the same

Abstract

The application belongs to the technical field of carbon dioxide adsorbents, and provides a magnesium oxide-based carbon dioxide adsorbent and a preparation method thereof. Basic magnesium carbonate is calcined to obtain magnesium oxide powder; the magnesium oxide powder is immersed in an alkali metal salt solution and then dried to obtain magnesium oxide powder loaded with alkali metal; the magnesium oxide powder loaded with alkali metal is immersed in a calcium nitrate solution and then sequentially subjected to drying, calcination and refinement treatment to obtain the magnesium oxide-based carbon dioxide adsorbent. The adsorbent of the application effectively improves the carbon dioxide adsorption capacity and cycle stability of the adsorbent through the mutual synergistic effect of magnesium oxide, sodium ions, potassium ions, manganese ions and calcium oxide and by controlling the proportion of each component and the process parameters, has high carbon dioxide removal rate, and has excellent cycle regeneration performance; the immersion of magnesium oxide in the alkali metal salt solution can further increase the pores of the adsorbent, which is conducive to the diffusion of carbon dioxide in the interior of the adsorbent.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide adsorbent technology, and in particular to a magnesium oxide-based carbon dioxide adsorbent and its preparation method. Background Technology

[0002] Increased CO2 concentrations can lead to environmental problems such as global warming, sea-level rise, and glacial melting, making the development of CO2 capture technologies imperative. CO2 capture methods mainly include absorption, membrane separation, and solid adsorption. Currently, amine-based chemical absorption is a relatively mature method for capturing CO2 from industrial waste gas. This technology is suitable for capturing CO2 from combustion flue gas, but its high cost and strong corrosiveness limit its application. Compared to chemical absorption, solid adsorbents, such as activated carbon, magnesium oxide (MgO), and calcium oxide (CaO), exhibit physical or chemical interactions with CO2, thus offering advantages in CO2 capture such as a wide adsorption temperature range, simple operation, and lower post-treatment complexity.

[0003] Magnesium oxide (MgO) is a competitive CO2 adsorbent due to its low cost and suitable alkaline adsorption sites. Although MgO-based adsorbents have a high theoretical adsorption capacity, the reaction of pure MgO with CO2 forms a dense MgCO3 layer, hindering CO2 diffusion into the product layer and leading to incomplete reaction. Furthermore, caking easily occurs during adsorption, resulting in a significant decrease in adsorption performance after multiple adsorption-desorption cycles. The carbonation conversion rate of MgO-based adsorbents decreases rapidly with increasing calcination temperature and carbonation cycle number, necessitating the addition of new MgO-based adsorbent to the reaction system, significantly increasing the cost of CO2 capture.

[0004] Therefore, improving the carbon dioxide capture capacity and cycle stability of magnesium oxide-based adsorbents in multi-cycle carbonation and calcination reactions is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a magnesium oxide-based carbon dioxide adsorbent and its preparation method, addressing the shortcomings of existing technologies.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a magnesium oxide-based carbon dioxide adsorbent, comprising the following steps:

[0008] 1) Calcine basic magnesium carbonate to obtain magnesium oxide powder;

[0009] 2) Magnesium oxide powder is impregnated in an alkali metal salt solution and then dried to obtain magnesium oxide powder loaded with alkali metal;

[0010] 3) After impregnating magnesium oxide powder loaded with alkali metals in calcium nitrate solution, the powder is successively dried, calcined, and refined to obtain magnesium oxide-based carbon dioxide adsorbent.

[0011] Preferably, the calcination temperature in step 1) is 550–650°C, and the calcination time is 25–45 min.

[0012] Preferably, the alkali metal salt solution in step 2) is a mixed solution of potassium permanganate and sodium carbonate; in the alkali metal salt solution, the mass fraction of potassium permanganate is 15-25%, and the mass ratio of potassium permanganate to sodium carbonate is 15-25:20-30.

[0013] Preferably, in step 2), the mass ratio of magnesium oxide powder to potassium permanganate is 50-80:1.

[0014] Preferably, the immersion temperature in step 2) is 30–50°C and the immersion time is 3–10 h; the drying temperature is 80–130°C and the drying time is 1–4 h.

[0015] Preferably, in step 3), the mass ratio of the magnesium oxide powder loaded with alkali metal to the calcium nitrate solution is 10-20:1, and the mass fraction of the calcium nitrate solution is 10-15%.

[0016] Preferably, the immersion temperature in step 3) is 30–50°C and the immersion time is 2–7 h; the drying temperature is 100–120°C and the drying time is 1–3 h.

[0017] Preferably, the calcination temperature in step 3) is 550–650°C, and the calcination time is 0.5–1.5 h.

[0018] The present invention also provides a magnesium oxide-based carbon dioxide adsorbent prepared by the above preparation method, wherein the particle size of the magnesium oxide-based carbon dioxide adsorbent is 50-150 μm.

[0019] The beneficial effects of this invention include the following:

[0020] 1) This invention uses an impregnation method to impregnate the manganese and potassium ions of potassium permanganate and the sodium ions of sodium carbonate solution into the pores of magnesium oxide powder. The potassium and sodium ions can improve the reactivity of the adsorbent, and the manganese ions can improve the cyclic reaction stability of the adsorbent. Impregnation of magnesium oxide in alkali metal salt solution can further increase the porosity of the adsorbent, which is beneficial to the diffusion of carbon dioxide inside the adsorbent.

[0021] 2) The adsorbent of the present invention effectively improves the adsorption capacity and cycle stability of carbon dioxide by means of the synergistic effect of magnesium oxide, sodium ions, potassium ions, manganese ions and calcium oxide, and by controlling the proportion of each component and process parameters. It has a high carbon dioxide removal rate and excellent regeneration performance. Detailed Implementation

[0022] This invention provides a method for preparing a magnesium oxide-based carbon dioxide adsorbent, comprising the following steps:

[0023] 1) Calcine basic magnesium carbonate to obtain magnesium oxide powder;

[0024] 2) Magnesium oxide powder is impregnated in an alkali metal salt solution and then dried to obtain magnesium oxide powder loaded with alkali metal;

[0025] 3) After impregnating magnesium oxide powder loaded with alkali metals in calcium nitrate solution, the powder is successively dried, calcined, and refined to obtain magnesium oxide-based carbon dioxide adsorbent.

[0026] In this invention, the calcination temperature in step 1) is preferably 550–650°C, more preferably 580–620°C, and even more preferably 600–610°C; the calcination time is preferably 25–45 min, more preferably 28–42 min, and even more preferably 32–35°C.

[0027] In this invention, the alkali metal salt solution in step 2) is preferably a mixed solution of potassium permanganate and sodium carbonate; the mass fraction of potassium permanganate in the alkali metal salt solution is preferably 15-25%, more preferably 17-23%, and even more preferably 19-20%; the mass ratio of potassium permanganate to sodium carbonate is preferably 15-25:20-30, more preferably 17-23:22-28, and even more preferably 19-20:24-25.

[0028] Alkali metal carbonates have the advantages of high adsorption performance, low adsorption temperature and low cost. The adsorption performance of carbon dioxide can be improved by dispersing sodium carbonate and potassium permanganate on a porous magnesium oxide support.

[0029] In step 2) of the present invention, the mass ratio of magnesium oxide powder to potassium permanganate is preferably 50-80:1, more preferably 55-75:1, and even more preferably 60-70:1.

[0030] In this invention, the soaking temperature in step 2) is preferably 30-50°C, more preferably 35-45°C, and even more preferably 38-40°C; the soaking time is preferably 3-10 hours, more preferably 4-9 hours, and even more preferably 5-8 hours; the drying temperature is preferably 80-130°C, more preferably 90-120°C, and even more preferably 100-110°C; and the drying time is preferably 1-4 hours, and even more preferably 2-3 hours.

[0031] In this invention, the mass ratio of magnesium oxide powder loaded with alkali metal and calcium nitrate solution in step 3) is preferably 10-20:1, more preferably 12-18:1, and even more preferably 15-16:1; the mass fraction of calcium nitrate solution is preferably 10-15%, more preferably 11-14%, and even more preferably 12-13%.

[0032] In this invention, the soaking temperature in step 3) is preferably 30-50°C, more preferably 35-45°C, and even more preferably 38-40°C; the soaking time is preferably 2-7 hours, more preferably 3-6 hours, and even more preferably 4-5 hours; the drying temperature is preferably 100-120°C, more preferably 105-115°C, and even more preferably 110°C; the drying time is preferably 1-3 hours, more preferably 1.5-2.5 hours, and even more preferably 2 hours.

[0033] In this invention, the calcination temperature in step 3) is preferably 550–650°C, more preferably 570–620°C, and even more preferably 590–600°C; the calcination time is preferably 0.5–1.5 h, and even more preferably 1 h.

[0034] Metal-doped (magnesium, sodium, potassium, manganese) magnesium oxide-based adsorbents can effectively suppress the decline in CO2 adsorption capacity during adsorption / regeneration cycles. Manganese doping helps the adsorbent form abundant micropores and mesopores, promoting CO2 diffusion and O2 regeneration. 2- The migration of magnesium oxide and alkali metals helps to inhibit calcium oxide sintering and improve the cycle stability of the adsorbent.

[0035] Magnesium oxide is abundant and possesses advantages such as strong theoretical adsorption capacity, non-toxicity, and low cost. The adsorption performance of magnesium oxide-based adsorbents is closely related to the adsorption active sites. By doping with alkali metal ions and calcium oxide, and rationally controlling the proportion of each metal element, more adsorption active sites can be exposed, thereby improving the adsorption performance for carbon dioxide.

[0036] The present invention also provides a magnesium oxide-based carbon dioxide adsorbent prepared by the aforementioned preparation method.

[0037] In this invention, the particle size of the magnesium oxide-based carbon dioxide adsorbent is preferably 50-150 μm, and more preferably 80-130 μm.

[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0039] Example 1

[0040] Basic magnesium carbonate was calcined at 580℃ for 42 min to obtain magnesium oxide powder. The magnesium oxide powder was completely immersed in a mixed solution of potassium permanganate and sodium carbonate (the mass fraction of potassium permanganate in the mixed solution was 17%, the mass ratio of potassium permanganate to sodium carbonate was 17:28, and the mass ratio of magnesium oxide powder to potassium permanganate was 55:1) and impregnated at 35℃ for 8 h, and then dried at 90℃ for 4 h to obtain alkali metal-loaded magnesium oxide powder.

[0041] Magnesium oxide powder loaded with alkali metal was completely immersed in a 10% calcium nitrate solution (the mass ratio of magnesium oxide powder loaded with alkali metal to calcium nitrate solution was 12:1), immersed at 35°C for 6 hours, dried at 100°C for 3 hours, calcined at 570°C for 1.5 hours, and then ground to obtain a magnesium oxide-based carbon dioxide adsorbent with a particle size of 50 μm.

[0042] Example 2

[0043] Basic magnesium carbonate was calcined at 620℃ for 28 min to obtain magnesium oxide powder. The magnesium oxide powder was completely immersed in a mixed solution of potassium permanganate and sodium carbonate (the mass fraction of potassium permanganate in the mixed solution was 23%, the mass ratio of potassium permanganate to sodium carbonate was 23:22, and the mass ratio of magnesium oxide powder to potassium permanganate was 70:1) and impregnated at 45℃ for 4 h, and then dried at 120℃ for 1 h to obtain alkali metal-loaded magnesium oxide powder.

[0044] Magnesium oxide powder loaded with alkali metal was completely immersed in a 15% calcium nitrate solution (the mass ratio of magnesium oxide powder loaded with alkali metal to calcium nitrate solution was 18:1), immersed at 45℃ for 3 h, dried at 120℃ for 1.5 h, calcined at 620℃ for 0.5 h, and then ground to obtain a magnesium oxide-based carbon dioxide adsorbent with a particle size of 130 μm.

[0045] Example 3

[0046] Basic magnesium carbonate was calcined at 600℃ for 35 min to obtain magnesium oxide powder. The magnesium oxide powder was completely immersed in a mixed solution of potassium permanganate and sodium carbonate (the mass fraction of potassium permanganate in the mixed solution was 20%, the mass ratio of potassium permanganate to sodium carbonate was 20:25, and the mass ratio of magnesium oxide powder to potassium permanganate was 65:1) and impregnated at 40℃ for 6 h, and then dried at 100℃ for 3 h to obtain alkali metal-loaded magnesium oxide powder.

[0047] Magnesium oxide powder loaded with alkali metal was completely immersed in a 13% calcium nitrate solution (the mass ratio of magnesium oxide powder loaded with alkali metal to calcium nitrate solution was 15:1), immersed at 40℃ for 4 h, dried at 110℃ for 2 h, calcined at 600℃ for 1 h, and then ground to obtain a magnesium oxide-based carbon dioxide adsorbent with a particle size of 80 μm.

[0048] Comparative Example 1

[0049] Instead of potassium permanganate as in Example 3, magnesium oxide powder was directly immersed in sodium carbonate solution at a mass ratio of 100:1, with other conditions the same as in Example 3.

[0050] Comparative Example 2

[0051] Instead of sodium carbonate in Example 3, magnesium oxide powder was directly immersed in potassium permanganate solution, with the mass fraction of potassium permanganate changed to 30%, and other conditions were the same as in Example 3.

[0052] Comparative Example 3

[0053] The steps of impregnating the alkali metal-loaded magnesium oxide powder in calcium nitrate solution, followed by drying and calcination, as in Example 3 are omitted. All other conditions are the same as in Example 3, and the alkali metal-loaded magnesium oxide powder is used as the final magnesium oxide-based carbon dioxide adsorbent.

[0054] The adsorbents of Examples 1-3 and Comparative Examples 1-3 were subjected to CO2 adsorption tests. Adsorption conditions: the temperature was increased to 340℃ at a rate of 5℃ / min, and CO2 was adsorbed at a constant temperature and pressure under pure CO2 gas conditions at 0.1 MPa for 1 h. The CO2 adsorption capacities of the adsorbents of Examples 1-3 were 19.45 mmol / g, 19.91 mmol / g, and 20.15 mmol / g, respectively; the CO2 adsorption capacities of the adsorbents of Comparative Examples 1-3 were 14.15 mmol / g, 14.26 mmol / g, and 13.05 mmol / g, respectively.

[0055] The CO2 adsorption-regeneration cycle performance of the adsorbents in Examples 1-3 was tested. Adsorption conditions: temperature increased to 340℃ at a rate of 5℃ / min, CO2 adsorbed under constant temperature and pressure at 0.1 MPa and pure CO2 gas for 1 h. After adsorption, the adsorbent was regenerated under the following conditions: 400℃ and 100% N2 for 20 min. The adsorbents underwent 60 adsorption-regeneration cycles. The CO2 adsorption capacity results for the 1st, 10th, 30th, and 60th cycles are shown in Table 1.

[0056] Table 1. Cyclic test results of the adsorption capacity of the adsorbents for CO2 in different embodiments.

[0057]

[0058] As shown in Table 1, the adsorbent of the present invention has a large adsorption capacity for CO2, and still has a high adsorption capacity for CO2 after 60 cycles of testing. The adsorbent of the present invention has excellent CO2 adsorption stability.

[0059] The adsorbent of this invention effectively improves the adsorption capacity and cycle stability of carbon dioxide by the synergistic effect of magnesium oxide, sodium ions, potassium ions, manganese ions and calcium oxide, and by controlling the proportion of each component and process parameters. It has a high carbon dioxide removal rate and excellent regeneration performance.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a magnesium oxide-based carbon dioxide adsorbent, characterized by, The method comprises the following steps: 1) calcining basic magnesium carbonate to obtain magnesium oxide powder; 2) impregnating the magnesium oxide powder in an alkali metal salt solution and then drying to obtain alkali metal loaded magnesium oxide powder; 3) impregnating the alkali metal loaded magnesium oxide powder in a calcium nitrate solution and then sequentially performing drying, calcining and refining treatment to obtain a magnesium oxide based carbon dioxide adsorbent; In step 2), the alkali metal salt solution is a mixed solution of potassium permanganate and sodium carbonate; in the alkali metal salt solution, the mass fraction of potassium permanganate is 15-25%, and the mass ratio of potassium permanganate to sodium carbonate is 15-25:20-30. In step 2), the mass ratio of magnesium oxide powder to potassium permanganate is 50-80:

1.

2. The production method according to claim 1, characterized by, In step 1), the calcining temperature is 550-650°C, and the calcining time is 25-45 min.

3. The preparation method according to claim 2, characterized in that, In step 2), the impregnating temperature is 30-50°C, the impregnating time is 3-10 h, the drying temperature is 80-130°C, and the drying time is 1-4 h.

4. The production method according to claim 3, characterized by, In step 3), the mass ratio of alkali metal loaded magnesium oxide powder to calcium nitrate solution is 10-20:1, and the mass fraction of calcium nitrate solution is 10-15%.

5. The production method according to claim 3 or 4, characterized by, In step 3), the impregnating temperature is 30-50°C, the impregnating time is 2-7 h, the drying temperature is 100-120°C, and the drying time is 1-3 h.

6. The production method according to claim 5, wherein In step 3), the calcining temperature is 550-650°C, and the calcining time is 0.5-1.5 h.

7. The magnesium oxide-based carbon dioxide adsorbent produced by the production method according to any one of claims 1 to 6, characterized by, The particle size of the magnesium oxide based carbon dioxide adsorbent is 50-150 μm.

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