Method for cyclic capture and in-situ conversion of CO2

Abstract

The invention provides a method for cyclic capture and in-situ conversion of CO2, and belongs to the technical field of CO2 capture and conversion. According to the method, the metal oxide is prepared by refining the carbonate through hydrogen reduction, the pyrolysis temperature of the carbonate is reduced by introducing the hydrogen, and compared with the metal oxide refined in an air atmosphere, the energy consumption is greatly reduced; the carbonate is calcined and reduced under the hydrogen atmosphere, so that the sintering of the metal oxide can be prevented, and the obtained metal oxide CO2 trapping agent has a high-density oxygen vacancy defect, has high activity during CO2 trapping, and has a relatively high application value in the field of CO2 trapping. The carbonate is calcined and reduced in the hydrogen atmosphere, so that the capture temperature of CO2 capture can be reduced, the captured CO2 is converted into a value-added chemical CO in situ, the reduction of production energy consumption and the realization of a dual-carbon target are facilitated, and the obtained regenerated metal oxide CO2 capture agent has good cycle stability and conforms to the concept of sustainable development.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 capture and conversion, and particularly relates to a method for cyclic capture and in-situ conversion of CO2. Background Art

[0002] In recent years, in pursuit of green, low-carbon environmental protection, people have reduced carbon emissions through various means. Using the carbonation reaction of metal oxides (such as calcium oxide, magnesium oxide, etc.) to "reduce carbon" is a capture method that does not require enrichment and purification of CO2, and can be used for the absorption and storage of low-concentration CO2 in air or flue gas. Metal oxides have the ability to absorb CO2 again, providing a basis for establishing an industrial cycle of CO2 absorption and conversion. Metal oxides are economical and efficient CO2 capture materials, which have the advantages of low cost, large adsorption capacity, and a wide range of operating temperatures.

[0003] Currently, most of the preparation methods of metal oxide CO2 capture agents are high-temperature calcination, that is, the decarboxylation reaction of carbonates in a high-temperature and air atmosphere generates metal oxides while releasing CO2. However, the high temperature of 1000-1600 °C required for pyrolysis will bring extremely high energy consumption. In addition, the metal oxides obtained by calcination in an air atmosphere still have deficiencies in the adsorption activity and cycle stability for CO2.

[0004] The prior art improves the cycle stability of metal oxides by changing the particle size and pore structure of metal oxides, adding inert dopants, etc., such as Lai Xiaoling, Zhou Wei, Zang Jiazhong, etc. Research progress on low-temperature cyclic absorption of carbon dioxide by calcium oxide-based absorbents [J]. Inorganic Chemicals Industry, 2023, 55(5): 16-23. DOI: 10.19964 / j.issn.1006-4990.2022-0419. However, the temperatures for capturing CO2 and regenerating metal oxides in the above methods are relatively high, which is not conducive to reducing production energy consumption. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for cyclic capture and in-situ conversion of CO2. The method for cyclic capture and in-situ conversion of CO2 provided by the present invention can achieve efficient capture, conversion, and utilization of CO2, and has the advantage of low energy consumption. The carbonate produced after capturing CO2 has a relatively low regeneration temperature and good cycle stability.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a method for cyclic capture and in-situ conversion of CO2, comprising the following steps:

[0008] (1) Calcinate carbonates and / or carbonate-containing minerals in a hydrogen atmosphere to obtain a metal oxide CO2 sorbent;

[0009] (2) Use the metal oxide CO2 sorbent to capture CO2 to obtain regenerated carbonate;

[0010] (3) Calcinate the regenerated carbonate in a hydrogen atmosphere, and perform an in-situ conversion reaction of CO2 during the calcination to obtain a regenerated metal oxide CO2 sorbent and by-product CO;

[0011] (4) Recycle the regenerated metal oxide CO2 sorbent through the processes of capturing CO2 and calcining in a hydrogen atmosphere.

[0012] Preferably, the carbonate includes calcium carbonate and / or magnesium carbonate;

[0013] The carbonate-containing minerals include one or more of limestone, dolomite, magnesite, and calcite.

[0014] Preferably, the particle size of the carbonate and / or carbonate-containing minerals is 20 nm to 500 μm.

[0015] Preferably, in steps (1), (3), and (4), the volume concentration of hydrogen in the hydrogen atmosphere is 5 to 100%.

[0016] Preferably, in steps (1), (3), and (4), the calcination temperature in the hydrogen atmosphere is independently 600 to 900 °C, and the holding time is 5 to 30 min;

[0017] The heating rate to the calcination temperature is 2 to 20 °C / min.

[0018] Preferably, the flow rate of hydrogen in the hydrogen atmosphere is 0.1 to 10 mL / (min·mg).

[0019] Preferably, in steps (1) and (4), when capturing CO2, the volume fraction of CO2 in the gas is 1 to 100%.

[0020] Preferably, in steps (1) and (4), the temperature for capturing CO2 is independently 600 to 700 °C, and the time is independently 5 to 90 min.

[0021] Preferably, the number of cycles in step (4) is 6 to 100 times.

[0022] The present invention provides the application of a metal oxide CO2 sorbent obtained by calcining carbonates and / or carbonate-containing minerals in a hydrogen atmosphere in capturing CO2.

[0023] The present invention provides a method for cyclic capture and in-situ conversion of CO2, comprising the following steps: (1) calcining carbonate and / or carbonate-containing minerals in a hydrogen atmosphere to obtain a metal oxide CO2 capture agent; (2) using the metal oxide CO2 capture agent to capture CO2 to obtain regenerated carbonate; (3) calcining the regenerated carbonate in a hydrogen atmosphere, and performing an in-situ conversion reaction of CO2 during the calcination to obtain a regenerated metal oxide CO2 capture agent and an additional product CO; (4) cyclically performing the processes of capturing CO2 and calcining in a hydrogen atmosphere on the regenerated metal oxide CO2 capture agent. The present invention uses hydrogen to reduce and refine carbonate to prepare metal oxide, and reduces the pyrolysis temperature of carbonate by introducing hydrogen. On the one hand, calcining and reducing carbonate in a hydrogen atmosphere can reduce the pyrolysis temperature of carbonate to 600-900 °C, which greatly reduces the energy consumption compared with metal oxides usually refined in an air atmosphere; on the other hand, compared with metal oxides usually refined in an air atmosphere, calcining and reducing carbonate in a hydrogen atmosphere can prevent the sintering of metal oxides, and the obtained metal oxide CO2 capture agent has high-density oxygen vacancy defects and has high activity in capturing CO2, realizing the efficient capture of CO2 and having high application value in the field of CO2 capture. The present invention can reduce the capture temperature of CO2 capture by calcining and reducing carbonate in a hydrogen atmosphere, and in-situ convert the captured CO2 into value-added chemical CO to obtain syngas, bringing economic benefits. The present invention helps to reduce production energy consumption and achieve the "dual carbon" goal, and the obtained regenerated metal oxide CO2 capture agent has good cycle stability, meeting the concept of sustainable development. In addition, there is no additional doping of metal in the metal oxide CO2 capture agent of the present invention, avoiding the adverse effects of excessive doping, thereby maintaining the high-efficiency capture performance of the CO2 capture agent under low-temperature cycle conditions.

[0024] The method for cyclic capture and in-situ conversion of CO2 provided by the present invention is non-toxic and low-cost, and is suitable for industrial promotion and application. Brief Description of the Drawings

[0025] Figure 1 It is a schematic flow chart of cyclic capture and in-situ conversion of CO2 of the present invention;

[0026] Figure 2 It is a thermogravimetric analysis diagram of calcium carbonate in 10% hydrogen in Example 1;

[0027] Figure 3 It is a mass spectrometry analysis diagram of gas products of calcium carbonate varying with the calcination temperature in Example 1;

[0028] Figure 4 It is an analysis diagram of the gas product composition of calcined CaCO3 at different temperatures in Example 1;

[0029] Figure 5XRD pattern of the calcined product obtained by calcining CaCO3 at 800 °C in Example 1;

[0030] Figure 6 N2 adsorption - desorption isotherms and pore size distribution curves of calcium carbonate, calcium oxide obtained by calcining with pure hydrogen at 800 °C, calcium oxide obtained by calcining with pure hydrogen at 700 °C, and calcium oxide obtained by calcining with air at 800 °C in Example 1;

[0031] Figure 7 Adsorption capacity diagram of the CO2 sorbent obtained from dolomite under different calcination atmospheres in Example 2;

[0032] Figure 8 XRD patterns of highly active CaO obtained in Example 3 after absorbing CO2 at different temperatures;

[0033] Figure 9 Adsorption capacity diagram of highly active CaO obtained in Example 3 at different adsorption temperatures;

[0034] Figure 10 Adsorption capacity diagram of highly active CaO obtained in Example 4 at different calcination temperatures;

[0035] Figure 11 Adsorption capacity diagram of CaO obtained in Example 5 under different calcination atmospheres;

[0036] Figure 12 Adsorption capacity curve diagram of six - cycle calcination - CO2 adsorption under different calcination atmospheres in Example 6;

[0037] Figure 13 Gas product analysis diagram of hydrogen - refining CaCO3 with different cycle numbers in Example 7. Detailed implementation mode

[0038] The present invention provides a method for cyclic capture and in - situ conversion of CO2, comprising the following steps:

[0039] (1) Calcining a carbonate and / or a carbonate - containing mineral in a hydrogen atmosphere to obtain a metal oxide CO2 sorbent;

[0040] (2) Using the metal oxide CO2 sorbent to capture CO2 to obtain a regenerated carbonate;

[0041] (3) Calcining the regenerated carbonate in a hydrogen atmosphere, and simultaneously performing an in - situ conversion reaction of CO2 during the calcination to obtain a regenerated metal oxide CO2 sorbent and a by - product CO;

[0042] (4) Cyclically performing the processes of capturing CO2 and calcining in a hydrogen atmosphere with the regenerated metal oxide CO2 sorbent.

[0043] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0044] In the present invention, carbonates and / or carbonate-containing minerals are calcined in a hydrogen atmosphere to obtain a metal oxide CO2 capture agent. In the present invention, the carbonate preferably includes calcium carbonate and / or magnesium carbonate; the carbonate-containing mineral preferably includes one or more of limestone, dolomite, magnesite, and calcite. In the present invention, the particle size of the carbonate and / or carbonate-containing mineral is preferably 20 nm to 500 μm, specifically 20 nm, 100 nm, 500 nm, 1 μm, 10 μm, 100 μm, 300 μm, or 500 μm.

[0045] In the present invention, the hydrogen atmosphere is preferably pure hydrogen or a mixed gas of hydrogen and argon, and the volume concentration of hydrogen in the hydrogen atmosphere is preferably 5 to 100%, specifically 5%, 10%, 20%, 50%, 80%, or 100%.

[0046] In the present invention, the flow rate of hydrogen in the hydrogen atmosphere is preferably 0.1 to 10 mL / (min·mg), specifically 0.1 mL / (min·mg), 0.5 mL / (min·mg), 1 mL / (min·mg), 5 mL / (min·mg), or 10 mL / (min·mg), where mg represents the mass of the carbonate and / or carbonate-containing mineral. In the present invention, the calcination temperature is preferably 600 to 900 °C, more preferably 650 to 750 °C, and even more preferably 700 °C; as a specific embodiment of the present invention, the calcination temperature can be 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, or 900 °C. In the present invention, the holding time of the calcination is preferably 5 to 30 min, more preferably 10 to 20 min, and even more preferably 15 min. In the present invention, the heating rate to the calcination temperature is preferably 2 to 20 °C / min, more preferably 5 to 10 °C / min. In the present invention, the heating time from room temperature to the calcination temperature is preferably 68 to 156 min, more preferably 78 to 146 min, and even more preferably 136 min.

[0047] After obtaining the metal oxide CO2 capture agent, the present invention uses the metal oxide CO2 capture agent to capture CO2, obtaining a regenerated carbonate. In the present invention, the gas to be captured is preferably air, flue gas, industrial waste gas, natural gas treatment gas, biomass combustion gas or biogas fermentation process gas. In the present invention, the volume fraction of CO2 in the gas is preferably 1-100%, more preferably 20-80%, and even more preferably 50%. In the present invention, the temperature for capturing CO2 is preferably 600-700 °C, specifically it can be 600 °C, 650 °C or 700 °C. In the present invention, the time for capturing CO2 is preferably 5-90 min, more preferably 20-80 min, and even more preferably 45 min; as a specific embodiment of the present invention, the time for capturing CO2 can be 5, 10, 20, 30, 40, 45, 50, 60, 70, 80 or 90 min. In the present invention, during the process of capturing CO2, CO2 reacts with the metal oxide CO2 capture agent to obtain a regenerated carbonate.

[0048] After obtaining the regenerated carbonate, the present invention calcines the regenerated carbonate in a hydrogen atmosphere, and an in-situ conversion reaction of CO2 is carried out during the calcination, obtaining a regenerated metal oxide CO2 capture agent and by-product CO. In the present invention, the hydrogen atmosphere is preferably pure hydrogen or a mixed gas of hydrogen and argon, and the volume concentration of hydrogen in the hydrogen atmosphere is preferably 5-100%, specifically it can be 5%, 10%, 20%, 50%, 80% or 100%.

[0049] In the present invention, the flow rate of hydrogen in the hydrogen atmosphere is preferably 0.1-10 mL / (min·mg), specifically it can be 0.1 mL / (min·mg), 0.5 mL / (min·mg), 1 mL / (min·mg), 5 mL / (min·mg) or 10 mL / (min·mg). In the present invention, the temperature for the calcination is preferably 600-900 °C, more preferably 650-750 °C, and even more preferably 700 °C; as a specific embodiment of the present invention, the temperature for the calcination can be 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C or 900 °C. In the present invention, the heat preservation time for the calcination is preferably 5-30 min, more preferably 10-20 min, and even more preferably 15 min. In the present invention, the heating rate for rising to the calcination temperature is preferably 2-20 °C / min, and more preferably 5-10 °C / min. In the present invention, the heating time for rising from room temperature to the calcination temperature is preferably 68-156 min, more preferably 78-146 min, and even more preferably 136 min.

[0050] In the present invention, during the calcination, CO2 is in-situ converted into CO, obtaining a mixture gas of H2 and CO, namely synthesis gas. Synthesis gas is an important chemical raw material and is widely used in industrial applications, especially in chemical synthesis and energy production.

[0051] After obtaining the regenerated metal oxide CO2 sorbent, the present invention circulates the regenerated metal oxide CO2 sorbent through the processes of CO2 capture and calcination in a hydrogen atmosphere. In the present invention, the optional ranges of the conditions for CO2 capture and calcination in a hydrogen atmosphere are the same as those described above and will not be elaborated herein.

[0052] In the present invention, the number of cycles is preferably 6 to 100 times, more preferably 6 to 50 times, and further preferably 6 to 12 times.

[0053] The schematic flow chart of the cyclic capture and in-situ conversion of CO2 in the present invention is as Figure 1 shown.

[0054] The present invention provides the application of a metal oxide CO2 sorbent obtained by calcining a carbonate and / or a carbonate-containing mineral in a hydrogen atmosphere in CO2 capture. In the present invention, the optional types of the carbonate and / or the carbonate-containing mineral are preferably the same as those described above and will not be elaborated herein. The conditions for calcination in a hydrogen atmosphere are preferably the same as those described above and will not be elaborated herein.

[0055] The following examples are used to elaborate in detail the method for cyclic capture and in-situ conversion of CO2 provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0056] In the following examples, the volume concentration of hydrogen in a 10% hydrogen atmosphere is 10%, and the remaining components are argon.

[0057] Example 1

[0058] Take 300 mg of calcium carbonate and place it in a quartz tube. Calcinate it under different atmospheres (10% hydrogen, pure hydrogen or air, with a flow rate of 100 mL / min), control the heating rate of the tube furnace to be 5 °C / min, and heat it to 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C and 800 °C respectively. Keep it at each temperature for 15 min and then cool it naturally to obtain the calcination products at 500 - 800 °C. Evaluate the gas products using gas chromatography and mass spectrometry.

[0059] The thermogravimetric analysis diagram of calcium carbonate in 10% hydrogen is as Figure 2 shown. It can be seen from Figure 2 that calcium carbonate starts to decompose at approximately 660 °C in 10% hydrogen and reaches the decomposition peak at approximately 750 °C.

[0060] In a pure hydrogen atmosphere, the mass spectrometry analysis diagram of the gas products of calcium carbonate with the change of calcination temperature is as follows Figure 3 shown. From Figure 3 it can be seen that calcium carbonate begins to decompose at 475 °C in pure hydrogen and reaches the decomposition peak at 680 °C.

[0061] In a pure hydrogen atmosphere, the analysis diagram of the gas product composition of CaCO3 calcined at different temperatures is as follows Figure 4 shown. From Figure 4 it can be seen that CO appears at 500 and 550 °C with a selectivity of 100%, CO2 appears at 600 °C and its proportion increases with the increase of temperature, and CaCO3 is completely decomposed at 750 and 800 °C.

[0062] In a pure hydrogen atmosphere, the XRD diagram of the calcined product obtained by calcining CaCO3 at 800 °C is as follows Figure 5 shown. From Figure 5 it can be seen that after calcination of calcium carbonate in a pure hydrogen atmosphere, the characteristic diffraction peaks of its X-ray diffraction pattern are completely consistent with the diffraction peak positions and relative intensities in the calcium oxide standard card, indicating that calcium carbonate has been completely converted into calcium oxide after calcination under pure hydrogen conditions.

[0063] The nitrogen adsorption-desorption curves and pore size distribution diagrams of calcium carbonate (a), calcium oxide obtained by calcining in pure hydrogen at 800 °C (b), calcium oxide obtained by calcining in pure hydrogen at 700 °C (c), and calcium oxide obtained by calcining in air at 800 °C (d) are as follows Figure 6 shown. The specific surface area, pore volume, and pore diameter of the calcium oxide samples treated at different temperatures are shown in Table 1. From Figure 6 and Table 1, it can be seen that the highly active calcium oxide obtained by calcination in a hydrogen atmosphere has a significantly higher specific surface area and pore volume than the calcium oxide obtained by calcination in an air atmosphere. In addition, in a hydrogen atmosphere, the calcium oxide prepared by calcination at 700 °C has a better specific surface area and pore volume than the calcium oxide obtained by calcination at 800 °C in the same atmosphere, thus indicating that the combination of an appropriate calcination temperature and a hydrogen atmosphere can significantly improve the specific surface area and pore volume of calcium oxide.

[0064] Table 1 Specific surface area, pore volume, and pore diameter of calcium oxide samples treated at different temperatures

[0065]

[0066]

[0067] Example 2

[0068] Take 10 mg of dolomite and place it in a thermal analyzer. Calcinate it by passing 10% hydrogen (flow rate of 100 mL / min) and air (flow rate of 100 mL / min) respectively. Control the heating rate of the thermal analyzer to be 10 °C / min, heat up to 700 °C and hold for 45 min to obtain a CO2 capture agent. Control the cooling rate of the thermal analyzer to be 10 °C / min and cool down to the adsorption temperature of 650 °C. Then pass 50% CO2 for CO2 adsorption for 45 min. Repeat this cycle 2 times.

[0069] The adsorption capacity diagrams of the CO2 capture agents obtained from dolomite under different calcination atmospheres are as Figure 7 shown. In the reaction control stage, after 10 min of adsorption, at the same adsorption temperature, the adsorption capacity in the hydrogen atmosphere is much higher than that in the air atmosphere. During the whole adsorption process, the adsorption capacity of the CO2 capture agent obtained by calcination in the hydrogen atmosphere is better than that in the air atmosphere.

[0070] Example 3

[0071] Take 10 mg of calcium carbonate and place it in a thermal analyzer. Pass 10% hydrogen (100 mL / min) for calcination. Control the heating rate to be 10 °C / min, heat up to 800 °C and hold for 15 min to obtain highly active calcium oxide, i.e., the CO2 capture agent. Control the cooling rate of the thermal analyzer to be 10 °C / min and cool down to different adsorption temperatures (550 °C, 600 °C, 650 °C, 700 °C). Then pass 50% CO2 for CO2 capture for 20 min.

[0072] The XRD diagrams of the obtained highly active CaO after absorbing CO2 at different temperatures are as Figure 8 shown, as Figure 8 can be seen, characteristic diffraction peaks of calcium carbonate appear in the X-ray diffraction patterns of the highly active CaO after absorbing CO2 at different temperatures. This indicates that calcium oxide is converted into calcium carbonate after adsorbing carbon dioxide, thus confirming the adsorption of carbon dioxide by calcium oxide and the process of forming calcium carbonate.

[0073] The adsorption capacity diagrams of the obtained highly active CaO at different adsorption temperatures are as Figure 9 shown. In the reaction control stage, after 10 min of adsorption, the adsorption capacity has reached 0.6 g CO2 / g CaO; in the diffusion control stage, it increases to 0.68 g CO2 / g CaO after 20 min of adsorption. During the whole adsorption process, the adsorption effect is the best at the adsorption temperature of 650 °C.

[0074] Example 4

[0075] Put 10 mg of calcium carbonate into a thermal analyzer, introduce 10% hydrogen (flow rate of 100 mL / min) for calcination, with a heating rate of 10 °C / min. Heat to 700, 750, and 800 °C respectively and hold for 15 min to obtain highly active calcium oxide, i.e., the CO2 capture agent. Cool to the adsorption temperature of 650 °C. Then introduce 50% CO2 for CO2 adsorption for 20 min.

[0076] The adsorption capacity diagrams of the obtained highly active CaO at different calcination temperatures are as Figure 10 shown. In the reaction control stage, after 10 min of adsorption, the adsorption capacity has reached 0.6 g CO2 / g CaO; in the diffusion control stage, it increases to 0.68 g CO2 / g CaO after 20 min of adsorption. During the whole adsorption process, the adsorption effect is the best at the calcination temperature of 800 °C.

[0077] Example 5

[0078] Put about 10 mg of calcium carbonate into a thermal analyzer, introduce 10% hydrogen (flow rate of 100 mL / min) and air (flow rate of 100 mL / min) respectively for calcination, control the heating rate of the thermal analyzer to be 10 °C / min, heat to 800 °C and hold for 15 min to obtain calcium oxide, i.e., the CO2 capture agent. Control the cooling rate of the thermal analyzer to be 10 °C / min and cool to the adsorption temperatures of 600 and 650 °C. Then introduce 50% CO2 for CO2 adsorption for 20 min.

[0079] The adsorption capacity diagrams of the obtained CaO under different calcination atmospheres are as Figure 11 shown. In the reaction control stage, after 10 min of adsorption, at the same adsorption temperature, the adsorption capacity in the hydrogen atmosphere is much higher than that in the air atmosphere; the adsorption capacity in the hydrogen atmosphere has reached 0.6 g CO2 / g CaO; in the diffusion control stage, it only increases to 0.61 g CO2 / g CaO in the air atmosphere after 20 min of adsorption, while it has reached 0.68 g CO2 / g CaO in the hydrogen atmosphere. During the whole adsorption process, the calcium oxide adsorbed in the hydrogen atmosphere has a better adsorption capacity than that in the air atmosphere.

[0080] Example 6

[0081] The advantage of the metal oxide-based sorbent is that the sorbent can be regenerated and recycled through the process of heating and cooling. Therefore, stability is an important indicator for evaluating the performance of the sorbent. Six cyclic calcination-CO2 adsorption experiments were carried out under different calcination atmospheres. The conditions for the cyclic experiments were as follows: 10 mg of calcium carbonate was placed in a thermal analyzer, and calcined in 10% hydrogen or air (flow rate 100 mL / min). The heating rate of the thermal analyzer was controlled at 10 °C / min, heated to 700 °C and held for 15 min to obtain the CO2 sorbent. The cooling rate of the thermal analyzer was controlled at 10 °C / min, cooled to the adsorption temperature of 650 °C. Then 50% CO2 was introduced for CO2 adsorption for 90 min, and this cycle was repeated. The adsorption capacity curves for different numbers of cycles are as Figure 12 shown. After 6 adsorption / desorption cycles, the adsorption performance decreased from the initial 0.70 g CO2 / g CaO to about 0.64 g CO2 / g CaO. It was detected by the thermal analyzer that the adsorption effect of the calcium oxide sorbent calcined in a hydrogen atmosphere after adsorption treatment was better than that calcined in an air atmosphere. After 6 adsorption / desorption cycles, the adsorption capacity was still about 0.64 g CO2 / g CaO (theoretical adsorption capacity 0.786 g CO2 / g CaO), indicating that the metal oxide CO2 sorbent of the present invention has good cyclic stability.

[0082] Example 7

[0083] 300 mg of calcium carbonate was placed in a quartz tube with a diameter of 10 mm and calcined in pure hydrogen (flow rate 100 mL / min). The heating rate of the tube furnace was controlled at 5 °C / min, heated to 700 °C and held for 15 min to obtain highly active calcium oxide. The cooling rate of the thermal analyzer was controlled at 10 °C / min, cooled to 650 °C, and then 50% CO2 (flow rate 100 mL / min) was introduced for CO2 capture for 20 min. Gas products were evaluated using gas chromatography and mass spectrometry. The analysis diagrams of gas products obtained by hydrogen refining of CaCO3 for different numbers of cycles are as Figure 13 shown. It can be seen from the chromatogram that the CaO sorbent has good stability.

[0084] In summary, through the synergistic effect of carbonate and hydrogen atmosphere, controlling the gas flow rate, concentration, and calcination temperature of the carbonate, the present invention significantly improves the adsorption capacity and cyclic stability of the metal oxide sorbent for CO2. At the same time, the sorbent exhibits excellent cyclic regeneration and CO2 conversion and utilization performance.

[0085] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for cyclic capture and in-situ conversion of CO2, comprising the following steps: (1) calcining carbonate and / or carbonate-containing minerals in a hydrogen atmosphere to obtain a metal oxide CO2 capture agent; (2) using the metal oxide CO2 capture agent to capture CO2 to obtain regenerated carbonate; (3) calcining the regenerated carbonate in a hydrogen atmosphere, and simultaneously carrying out an in-situ conversion reaction of CO2 to obtain a regenerated metal oxide CO2 capture agent and an additional product CO; (4) The regenerated metal oxide CO2 capture agent is circulated to capture CO2 and calcine in a hydrogen atmosphere.

2. The method according to claim 1, characterized in that The carbonate includes calcium carbonate and / or magnesium carbonate; The carbonate-containing minerals include one or more of limestone, dolomite, magnesite and calcite.

3. The method according to claim 1 or 2, characterized in that: The particle size of the carbonate and / or carbonate-containing mineral is 20 nm to 500 μm.

4. The method according to claim 1, characterized in that: In the steps (1), (3) and (4), the volume concentration of hydrogen in the hydrogen atmosphere is 5 to 100%.

5. The method according to claim 1 or 4, characterized in that: The calcination temperatures in step (1), step (3) and step (4) in a hydrogen atmosphere are independently 600-900° C., and the holding time is 5-30 min; the heating rate to the calcination temperature is 2-20° C. / min.

6. The method according to claim 1 or 4, characterized in that: The flow rate of hydrogen in the hydrogen atmosphere is 0.1 to 10 mL / (min·mg).

7. The method according to claim 1, characterized in that In the steps (1) and (4), when capturing CO2, the volume fraction of CO2 in the gas is 1 to 100%.

8. The method according to claim 1 or 7, characterized in that: In the steps (1) and (4), the temperature for capturing CO2 is independently 600 to 700°C, and the time is independently 5 to 90 minutes.

9. The method according to claim 1, characterized in that: The number of cycles in step (4) is 6 to 100.

10. Use of metal oxide CO2 capture agents obtained by calcining carbonates and / or carbonate-containing minerals in a hydrogen atmosphere in capturing CO2.

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