Co2 absorbent particles, methods of making, and chemical looping hydrogen production with co2 absorption

Abstract

The application provides a CO2 absorbent particle, a preparation method and a chemical chain hydrogen production and CO2 absorption method, wherein the preparation method for preparing the CO2 absorbent particle comprises the following steps: preparing K or Na doped Li4SiO4 powder, wherein the molar ratio of elements Li:Si:K or Na is 4.1:1:0.05-0.4, and the particle size of the powder is 0.1-10 microns; mixing the powder with a binder, a pore-forming agent and water to form a slurry; extruding the slurry in an extruder to obtain an extrudate, and rolling the extrudate in a roller to obtain spherical particles; and placing the dried spherical particles in a reaction container for calcination to obtain the CO2 absorbent particle. The application also provides a method for applying the CO2 absorbent particle to the chemical chain hydrogen production and CO2 absorption of methane, wherein the CO2 absorbent particle is used to absorb CO2 in the chemical chain hydrogen production of methane, so as to promote the balance to move forward and improve the hydrogen purity and the hydrogen production rate.

Description

Technical Field

[0001] This invention belongs to the technical field of chemical chain hydrogen production and CO2 absorbent particle preparation, and relates to a CO2 absorbent particle, a preparation method, and a chemical chain hydrogen production synergistic CO2 absorption method. More specifically, it relates to a method of applying CO2 absorbent particles to medium-temperature methane chemical chain hydrogen production synergistic CO2 absorption. Background Technology

[0002] Hydrogen is a clean and pollution-free ideal fuel and energy carrier. Methane steam reforming is one of the most mature hydrogen production processes currently available. However, purifying the effluent H2 requires downstream pressure swing adsorption (PSA) separation units, resulting in high energy consumption and large CO2 emissions. Developing low-CO2 emission H2 production technologies is crucial for the sustainable use of fossil fuels. Furthermore, most traditional chemical looping hydrogen production reactions require temperatures above 900°C, which not only necessitates high-temperature heat sources but also poses a significant challenge to reactor materials. Therefore, reducing the reaction temperature of methane chemical looping hydrogen production and capturing CO2 at the source are key considerations. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides CO2 absorbent particles, a preparation method, and a chemical looping hydrogen production-coordinated CO2 absorption method, aiming to at least partially solve the above-mentioned technical problems. The technical solution provided by this invention is as follows:

[0004] As a first aspect of the present invention, a method for preparing CO2 absorbent particles is provided, comprising:

[0005] Prepare K or Na-doped Li4SiO4 powder, wherein the molar ratio of Li:Si:K or Na is 4.1:1:0.05-0.4, and the particle size of the powder is 0.1-10 μm;

[0006] The powder is mixed with binder, pore-forming agent and water to form a slurry;

[0007] The slurry is placed in an extruder and extruded to obtain an extrudate. The extrudate is then placed in a rounding machine to round it into spherical particles.

[0008] After drying, the spherical particles are placed in a reaction vessel for calcination to obtain CO2 absorbent particles.

[0009] As a second aspect of the present invention, a CO2 absorbent particle prepared by the above method is provided, comprising:

[0010] The active component, and potassium or sodium elements modified on the active component, wherein the active component is Li4SiO4; wherein the molar ratio of Li:Si:K or Na in the CO2 absorbent particles is 4.1:1:0.05-0.4.

[0011] As a third aspect of the present invention, a method for using the above-mentioned CO2 absorbent particles for synergistic CO2 absorption in methane chemical chain hydrogen production is provided, comprising:

[0012] The bimetallic oxygen carrier and CO2 absorbent particles are filled into the reactor;

[0013] Methane and steam are introduced into the reactor to carry out a chemical chain reaction for hydrogen production from methane and an in-situ CO2 absorption reaction. The temperature for the chemical chain reaction for hydrogen production from methane and the in-situ CO2 capture reaction is 450-600℃. The chemical chain reaction for hydrogen production from methane includes a steam reforming reaction for hydrogen production from methane and a steam oxidation reaction. Steam is introduced in both the steam reforming reaction for hydrogen production from methane and the steam oxidation reaction.

[0014] In the process of hydrogen production by methane steam reforming, methane reacts with water vapor to generate hydrogen, CO and CO2 gas in the first stage, and the generated CO2 gas is absorbed in situ by CO2 absorbent particles.

[0015] In the water vapor oxidation reaction, water vapor is reduced to generate hydrogen gas in the second stage.

[0016] Based on the above technical solutions, the CO2 absorbent particles, preparation method, and chemical looping hydrogen production synergistic CO2 absorption method provided by the present invention have at least one of the following beneficial effects:

[0017] (1) In an embodiment of the present invention, K or Na-blended Li4SiO4 powder is mixed with a binder, a pore-forming agent, and water. The binder is used to tightly bind the potassium or sodium with the Li4SiO4 powder and the pore-forming agent to form a uniformly mixed slurry. This slurry is then subjected to an extrusion-spheronization process to obtain spherical particles, so that the particles can be stably transported and operated in subsequent applications. Subsequently, the spherical particles are dried and calcined to give them a porous structure and a certain mechanical strength, so that the CO2 absorbent particles have a high CO2 adsorption and desorption capacity during application, while reducing particle wear and giving them a long service life.

[0018] (2) In the embodiments of the present invention, K or Na elements are doped into lithium silicate. After calcination, the doped K or Na elements form defects on the surface of CO2 absorbent particles, which can promote the migration rate of CO2 and thus increase the absorption efficiency and absorption amount of CO2.

[0019] (3) In the embodiments of the present invention, by designing the synthesis process of CO2 absorbent particles, the doping metal, and the particle size of CO2 absorbent particles, CO2 absorbent particles that match the methane chemical chain hydrogen production reaction can be obtained. The bimetallic oxygen support and CO2 absorbent particles are simultaneously filled into the reactor for the methane chemical chain hydrogen production reaction. The CO2 absorbent particles absorb the CO2 generated during the hydrogen production reaction in situ, promoting the forward shift of the methane steam reforming reaction equilibrium, increasing the hydrogen production amount, hydrogen production rate, and hydrogen purity, and also helping to reduce the reaction temperature of the methane chemical chain hydrogen production reaction. Furthermore, the present invention introduces steam into both the methane steam reforming reaction and the steam oxidation reaction, achieving two-step hydrogen production and increasing the hydrogen production rate. In the first stage of hydrogen production, methane and steam are introduced into the methane steam reforming reaction. The introduced steam can suppress the carbon deposition on the surface of the oxygen carrier and improve the purity and yield of hydrogen in the methane chemical loop hydrogen production reaction. In the second stage of hydrogen production, steam is introduced into the steam oxidation reaction, which can remove the carbon deposition on the surface of the oxygen carrier and keep the oxygen carrier active. Attached Figure Description

[0020] Figure 1 The flowcharts show the different methods used to obtain CO2 absorbent particles in the embodiments of the present invention;

[0021] Figure 2 This is a schematic diagram illustrating the principle of methane chemical chain hydrogen production combined with CO2 absorbent particle absorption in an embodiment of the present invention;

[0022] Figure 3 This is a stability test diagram of the CO2 absorbent particles in Example 1 of the present invention in a thermogravimetric analyzer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0025] In the process of chemical looping hydrogen production from methane and source CO2 capture, oxygen carriers and CO2 absorbents are the core of the system, and therefore, the preparation and selection of oxygen carriers and CO2 absorbents are the decisive factors in chemical looping hydrogen production technology. Traditional methane chemical looping hydrogen production involves high reaction temperatures, generally above 900℃, requiring significant heat to drive the process and placing high demands on reactor materials. Furthermore, traditional CO2 absorption technologies often employ a reaction-then-separation approach, resulting in complex systems and high power consumption during CO2 separation. To address this, this invention provides a method for preparing CO2 absorbent particles. By designing the synthesis method, doping elements, and particle size of the CO2 absorbent particles, CO2 absorbent particles suitable for medium-temperature environments (450-600℃) and possessing high activity and long service life are obtained and applied to the methane chemical looping hydrogen production reaction. By designing reaction parameters such as CO2 concentration and oxygen carrier residence time during the methane chemical chain hydrogen production reaction, CO2 gas generated by the bimetallic oxygen carrier during the chemical chain hydrogen production reaction is captured in situ using CO2 absorbent particles. This achieves both medium-temperature methane chemical chain hydrogen production reaction and in-situ CO2 capture. Simultaneously, the capture of CO2 by the CO2 absorbent particles promotes the positive shift of the equilibrium of the methane chemical chain hydrogen production reaction, improves the purity and yield of hydrogen production, reduces the temperature of the methane chemical chain hydrogen production reaction, and reduces the energy consumption for CO2 capture. The system also has a simple structure.

[0026] Specifically, the present invention provides a method for preparing CO2 absorbent particles, comprising: preparing K or Na-doped Li4SiO4 powder, wherein the molar ratio of element Li:Si:K or Na is 4.1:1:0.05-0.4, and the particle size of the powder is 0.1-10 μm; mixing the powder with a binder, a pore-forming agent, and water to form a slurry; extruding the slurry in an extruder to obtain an extrudate; sphericalizing the extrudate in a spherical rolling mill to obtain spherical particles; and calcining the spherical particles in a reaction vessel after drying to obtain CO2 absorbent particles.

[0027] In embodiments of the present invention, K or Na-blended Li4SiO4 powder is mixed with a binder, a pore-forming agent, and water. The binder is used to tightly bind the potassium or sodium with the Li4SiO4 powder and the pore-forming agent to form a uniformly mixed slurry. The slurry is then solidified into spherical particles through an extrusion-spheronization process to ensure stable transport and smooth operation during subsequent reactor applications. Subsequently, the spherical particles are dried and calcined to give them a porous structure and a certain mechanical strength, enabling the CO2 absorbent particles to have high CO2 adsorption and desorption capabilities during application, while reducing particle wear and extending their service life.

[0028] Furthermore, the particle size of the prepared K or Na-doped Li4SiO4 powder is preferably 200 nm-500 nm. In the process of preparing CO2 absorbent particles, to obtain uniformly mixed K or Na-doped Li4SiO4 powder, the present invention employs mechanical solid-phase mixing, sol-gel-hydrothermal mixing, and impregnation mixing methods to obtain CO2 absorbent particles with uniform K or Na mixing and different particle sizes and specific surface areas. The specific process for preparing K or Na-doped Li4SiO4 powder is as follows.

[0029] Figure 1 The flowcharts show the different methods used to obtain CO2 absorbent particles in the embodiments of the present invention.

[0030] like Figure 1 As shown, the preparation of CO2 absorbent particles includes impregnation, hydrothermal and solid-phase reaction methods, and K or Na-doped Li4SiO4 powders prepared by different methods are used to prepare CO2 absorbent particles.

[0031] K or Na-doped Li4SiO4 powder was prepared by a solid-phase mixing method. The solid-phase mixing method included: mixing lithium salt, silica support, and potassium or sodium salt in a certain proportion, followed by ball milling to obtain K or Na-doped Li4SiO4 powder. The potassium salt was selected from either K2CO3 or KNO3; the lithium salt was selected from either Li2CO3 or LiNO3; the sodium salt was selected from either Na2CO3 or NaNO3; and the SiO2 support was SiO2 nanoparticles with a particle size of 50 nm-5 μm.

[0032] For example, weigh Li2CO3, SiO2 nanoparticles, and K2CO3 or Na2CO3 according to an elemental Li:Si:K or Na molar ratio of 4.1:1:0.2, put them into a ball mill and ball mill them at a speed of 100-800 r / min for 0.5-5 h. After grinding them into powder and mixing them evenly, K or Na mixed Li4SiO4 powder (i.e., mixed powder of Li2CO3, SiO2 nanoparticles and K2CO3 or Na2CO3) is obtained.

[0033] K or Na-doped Li4SiO4 powder was prepared using a sol-gel-hydrothermal method. The sol-gel-hydrothermal method includes: mixing lithium salt, silica support, and potassium or sodium salt with water in a specific ratio; stirring at a first stirring speed until homogeneous; adding a precipitant to form a suspension; transferring the suspension to a hydrothermal reactor for hydrothermal reaction; and washing, drying, and ball milling the obtained solid product to obtain K or Na-doped Li4SiO4 powder. The potassium salt is selected from K2CO3 and KNO3; the sodium salt is selected from Na2CO3 and NaNO3; the lithium salt is selected from Li2CO3, LiNO3, LiNO3·H2O, and LiOH·H2O; and the SiO2 support is SiO2 nanoparticles with a particle size of 50 nm-500 nm. The precipitant is selected from ammonia water, the concentration of which can be 28 wt.%, the pH of the resulting suspension is 8-10, the first stirring speed is 900-1300 r / min, the hydrothermal reaction temperature is 120-200℃, and the hydrothermal reaction time is 5-15 h.

[0034] For example, LiNO3, SiO2 nanoparticles, and K2CO3 or Na2CO3 are mixed with deionized water at an elemental Li:Si:K or Na molar ratio of 4.1:1:0.2. During mixing, the mixture is vigorously stirred at 1300 r / min to ensure uniform dispersion and adsorption of LiNO3 and K2CO3 or Na2CO3 onto the SiO2 nanoparticles, resulting in a mixed solution of nitrates containing K or Na, Si, and Li. Subsequently, a precipitant (e.g., 28 wt.% ammonia) is added to the mixed solution, and the pH is adjusted to 8 to obtain a suspension. The suspension is then transferred to a hydrothermal reactor and hydrothermally reacted at 120°C for 10 h to obtain a solid product containing K or Na-doped Li4SiO4. The obtained solid product containing K or Na doped Li4SiO4 was then washed multiple times with an ethanol-water solution (mixed solvent), dried, and ball-milled to obtain K or Na doped Li4SiO4 powder. The drying temperature was 80-100℃, the ball milling speed was 100-800 r / min, and the ball milling time was 0.5-1 h.

[0035] K or Na-doped Li₄SiO₄ powder was prepared by an impregnation method. The impregnation method included: mixing lithium salt, silica support, and potassium or sodium salt with water in a specific ratio, stirring until a homogeneous solution was obtained; the solution was then subjected to segmented drying, calcination, and ball milling to obtain K or Na-doped Li₄SiO₄ powder. The potassium salt was selected from K₂CO₃ and KNO₃; the sodium salt from Na₂CO₃ and NaNO₃; and the lithium salt from Li₂CO₃, LiNO₃, LiNO₃·H₂O, and LiOH·H₂O. The SiO₂ support consisted of SiO₂ nanoparticles with a particle size of 50 nm–5 μm. The segmented drying temperature was 40–80 °C, the calcination temperature was 450–600 °C, and the calcination time was 2–4 h.

[0036] For example, LiOH·H2O, SiO2 nanoparticles, and K2CO3 or Na2CO3 are mixed with deionized water in an elemental Li:Si:K or Na molar ratio of 4.1:1:0.2 and stirred for 1 hour. This allows the SiO2 nanoparticles to adsorb LiOH·H2O and K2CO3 or Na2CO3, forming a homogeneous mixed solution. Subsequently, the obtained mixed solution is dried in stages to remove moisture, and the dried solid powder is calcined in air at 500°C for 2 hours to remove moisture and impurities, such as nitrate, to obtain K or Na-doped Li4SiO4 powder.

[0037] According to an embodiment of the present invention, the active component in the CO2 absorbent powder prepared by impregnation method and sol-gel-hydrothermal method is Li4SiO4, which is mainly obtained by heating a mixture of Li2CO3 (or other lithium salts) and SiO2 nanoparticles. Potassium or sodium doping is also obtained by heating a mixture of K2CO3 or Na2CO3 (or other potassium or sodium salts).

[0038] According to an embodiment of the present invention, continuing as follows Figure 1 As shown, after preparing K or Na-doped Li4SiO4 powder using different methods, the powder is mixed with a binder, a pore-forming agent, and deionized water. The mixture is then extruded, sphericalized, dried, and calcined to obtain CO2 absorbent particles. The methods include: mixing the powder with a binder, a pore-forming agent, and water in a specific ratio to form a slurry; extruding the slurry in an extruder to obtain an extrudate; sphericalizing the extrudate in a sphericalization machine to obtain spherical particles; and calcining the dried spherical particles in a reaction vessel to obtain CO2 absorbent particles.

[0039] The mass ratio of K or Na-doped Li4SiO4 powder to binder, pore-forming agent, and water is 1:2-15%:2-15%:20-50%. The binder is selected from either kaolin or attapulgite, and the pore-forming agent is selected from either graphite or cellulose. Within this ratio range, the components of the obtained CO2 absorbent particles are firmly bonded, and the specific surface area and porosity are moderate.

[0040] After obtaining the slurry, it is placed in an extruder and extruded at a speed of 350–550 rpm, producing extrudates with a diameter of 1–5 mm. Within this extrusion parameter range, the resulting extrudates have suitable strength, specific surface area, and pore size. The extrudates are then placed in a spheroidizing machine and spheroidized at a speed of 500–1000 rpm, producing spherical particles with a diameter of 1–5 mm. Subsequently, the spherical particles are placed in a drying oven and dried at 80–150℃ for 4–20 hours to remove some of the moisture, preventing particle breakage due to excessive moisture loss during subsequent calcination. The dried spherical particles are then calcined in a muffle furnace, with the temperature increased from room temperature to 500–800℃ at a rate of 2–10℃ / min for 2–5 hours to obtain CO2 absorbent particles. Calcination removes impurities from the spherical particles and creates pores, increasing the mechanical strength of the CO2 absorbent particles.

[0041] For example, K or Na-blended Li4SiO4 powder is mixed with kaolin, cellulose, and deionized water in a mass ratio of 1:0.4:0.4:0.16 to obtain a viscous slurry with a certain moisture content. The slurry is then extruded in an extruder at a speed of 350-550 rpm to obtain columnar particles with an extrusion diameter of 1-5 mm. The extruded 1-5 mm columnar particles are then placed in a spherical roller, cooled with cold air, and sphericalized at a speed of 500-1000 rpm to form spherical particles with a diameter of 1-5 mm. These spherical particles are then placed on a square plate and placed in a drying oven. After drying at 80°C for a period of time, they are placed in a muffle furnace and heated to a calcination temperature of 500-800°C at a heating rate of 2°C / min, and calcined for 2-5 hours to obtain CO2 absorbent particles. By controlling different calcination temperatures and times, the physicochemical properties of the subsequently formed absorbent particles can be controlled, thereby affecting the effectiveness of subsequent methane chemical chain hydrogen production and in-situ CO2 gas capture.

[0042] In the embodiments of this invention, K or Na-doped Li4SiO4 powder prepared by the solid-phase method is calcined once to obtain CO2 absorbent particles. This effectively preserves the nano- or micro-structure of the powder and avoids agglomeration and particle growth during calcination, which would affect the performance in subsequent applications. If the K or Na-doped Li4SiO4 powder obtained by the solid-phase mixing method is extruded and spheroidized, and then calcined twice or more, the resulting CO2 absorbent particles may have problems such as agglomeration and particle growth. Although ball milling can break up the agglomerated particles to some extent, its improvement effect is not good (i.e., agglomeration still exists), and the specific surface area and porosity of the absorbent particles decrease after multiple calcinations, which has a significant impact on CO2 absorption and hydrogen production performance. The CO2 absorbent particles prepared by the solid-phase mixing method provided by this invention preferably have a particle size of 1.0±0.1 mm and a specific surface area of ​​1.4±0.1 μm. 2 / g. For the sol-gel-hydrothermal method and impregnation method, since the K or Na-doped Li4SiO4 powders prepared have nano- or micron-sized particles, the impact on the particle size of the CO2 absorbent particles is small after hydrothermal or calcination. The preferred particle size of the CO2 absorbent particles prepared by the sol-gel-hydrothermal method is 1.0±0.1 mm, and the specific surface area is 1.3±0.1 m². 2 / g. By combining the impregnation method and calcination process, the optimal particle size of the obtained CO2 absorbent particles is 1.0±0.1mm, and the specific surface area is 0.9±0.1m². 2 / g.

[0043] As a second aspect of the present invention, a CO2 absorbent particle prepared by the method in the above embodiments is also provided, comprising: an active component, and potassium or sodium elements modified on the active component, wherein the active component is Li4SiO4, and the molar ratio of Li:Si:K or Na in the CO2 absorbent particle is 4.1:1:0.05-0.4, preferably 4.1:1:0.2.

[0044] In embodiments of the present invention, K or Na elements are doped into lithium silicate. After calcination, the doped K or Na elements form defects on the surface of CO2 absorbent particles, which can promote the migration rate of CO2 and increase the absorption efficiency and absorption amount of CO2.

[0045] As a third aspect of the present invention, a method for using the CO2 absorbent particles in the above embodiments for co-CO2 absorption in methane chemical chain hydrogen production is also provided, comprising:

[0046] A bimetallic oxygen carrier and CO2 absorbent particles are filled into a reactor. Methane and water vapor are introduced into the reactor to carry out a methane chemical loop hydrogen production reaction and an in-situ CO2 absorption reaction. The temperature for the methane chemical loop hydrogen production reaction and the in-situ CO2 capture reaction is 450-600℃. The methane chemical loop hydrogen production reaction includes a methane steam reforming hydrogen production reaction and a water vapor oxidation reaction, and water vapor is introduced in both the methane steam reforming hydrogen production reaction and the water vapor oxidation reaction. In the methane steam reforming hydrogen production reaction, methane reacts with water vapor to generate hydrogen, CO and CO2 gas in the first stage, and the generated CO2 gas is absorbed in-situ by the CO2 absorbent particles. In the water vapor oxidation reaction, water vapor is reduced to generate hydrogen in the second stage.

[0047] In embodiments of the present invention, by designing the synthesis process, doping metal, and particle size of the CO2 absorbent particles, CO2 absorbent particles that match the methane chemical chain hydrogen production reaction can be obtained. The bimetallic oxygen support and CO2 absorbent particles are simultaneously filled into a reactor for the methane chemical chain hydrogen production reaction. The CO2 absorbent particles capture and absorb the CO2 generated during the hydrogen production reaction in situ, promoting a positive shift in the equilibrium of the methane steam reforming reaction, increasing the hydrogen production amount, hydrogen production rate, and hydrogen purity, and also helping to lower the reaction temperature of the methane chemical chain hydrogen production reaction. Furthermore, the present invention introduces steam into both the methane steam reforming reaction and the steam oxidation reaction, achieving two-step hydrogen production, thus improving the hydrogen production rate and yield.

[0048] According to an embodiment of the present invention, a method for using CO2 absorbent particles for co-absorption of CO2 in methane chemical loop hydrogen production further includes: introducing water vapor into a reactor to regenerate the CO2 absorbent particles that have adsorbed CO2 gas to obtain pure CO2 gas, while the regenerated CO2 absorbent particles are circulated in the reactor.

[0049] In embodiments of the present invention, the hydrogen production reaction and CO2 absorption reactor includes an oxidation reactor, a reforming reactor, and a regeneration reactor. CO2 absorbent particles that have absorbed CO2 gas enter the regeneration reactor. Water vapor is introduced into the regeneration reactor, and the water vapor desorbs the CO2 adsorbed on the CO2 absorbent particles, thus regenerating the CO2 absorbent particles. Specifically, the CO2 absorbent particles that absorbed CO2 become Li2CO3, which is then converted into Li2O after being purged and desorbed by water vapor.

[0050] Figure 2 This is a schematic diagram illustrating the principle of methane chemical chain hydrogen production combined with CO2 absorbent particle absorption in an embodiment of the present invention.

[0051] like Figure 2As shown, a bimetallic oxygen carrier and CO2 absorbent particles are filled into a reforming reactor, and methane and water vapor are introduced into the reactor. The methane and water vapor undergo a steam reforming reaction to produce hydrogen, CO, and CO2 gases in the first stage. The generated CO2 gas is captured in situ by the CO2 absorbent particles in the reforming reactor, thus obtaining relatively pure hydrogen. Simultaneously, the active metal oxide component in the bimetallic oxygen carrier is reduced to elemental metals within the reforming reactor. The CO2 absorbent particles (Li2CO3) that have absorbed CO2 gas enter a regeneration reactor, where water vapor is introduced. The water vapor desorbs the CO2 adsorbed on the CO2 absorbent particles, obtaining relatively pure CO2 gas, and simultaneously regenerating the CO2 absorbent particles. The regenerated CO2 absorbent particles (Li2O) are then reintroduced into the reforming reactor to absorb CO2 gas, and this cycle continues. Simultaneously, the reduced bimetallic oxide support (Me, i.e., elemental metal) enters the oxidation reactor. Water vapor is introduced into the oxidation reactor, and the water vapor reacts with the active elemental metal (Me) in the reduced bimetallic oxide support. The water vapor is reduced to hydrogen in the second stage, while the reduced bimetallic oxide support (Me) is oxidized to the oxidized bimetallic oxide support MeO. By introducing water vapor into both the methane steam reforming and water vapor oxidation reactions, a two-step hydrogen production process is achieved, increasing hydrogen yield. Furthermore, introducing water vapor during the methane steam reforming process inhibits carbon deposition on the surface of the bimetallic oxide support and increases hydrogen yield; and introducing water vapor during the oxidation reaction removes carbon deposits from the surface of the bimetallic oxide support. In addition, because the CO2 absorbent particles absorb CO2 in situ during the hydrogen production process, they promote the forward shift of the equilibrium of the methane vapor reforming reaction. This enables the reduction of the reaction temperature between the bimetallic oxygen carrier and methane at the same hydrogen production rate, thus achieving medium-temperature (450-600℃) methane chemical loop hydrogen production and CO2 capture.

[0052] According to embodiments of the present invention, the bimetallic oxygen support used in the hydrogen production reaction is an iron-nickel bimetallic oxygen support, wherein the active components in the iron-nickel bimetallic oxygen support are iron oxide and nickel oxide, and the inactive components are Al2O3 or SiO2; the reactor is a moving bed reactor or a fixed bed reactor. The iron-nickel bimetallic oxygen support is used for methane chemical looping hydrogen production, wherein the methane chemical looping hydrogen production reaction further includes: the reduction of iron oxide and nickel oxide in the bimetallic oxygen support to generate metallic iron and metallic nickel; and the steam oxidation reaction further includes: the oxidation of metallic iron and metallic nickel to generate iron oxide and nickel oxide.

[0053] In embodiments of the present invention, the nickel oxide active component in the iron-nickel bimetallic oxygen support can undergo a redox reaction with methane at a relatively low temperature, and the reduced nickel also has a certain ability to catalyze methane cracking. Therefore, the addition of nickel oxide lowers the reaction temperature between the iron-nickel bimetallic oxygen support and methane by approximately 50-100°C, achieving a medium-temperature methane chemical looping hydrogen production and CO2 capture reaction. Furthermore, the carbon dioxide absorption concentration of the CO2 absorbent particles during operation needs to match the carbon dioxide concentration produced in the reduction reaction of the methane chemical looping hydrogen production reaction. This helps to achieve effective carbon dioxide absorption and improve the hydrogen production rate and yield of the methane chemical looping hydrogen production reaction.

[0054] According to embodiments of the present invention, CO2 is captured by CO2 absorbent particles, which promotes the forward movement of the methane chemical chain hydrogen production reaction, thereby increasing the methane conversion rate, hydrogen production rate, and hydrogen purity.

[0055] The CO2 absorbent particles, preparation method, and chemical chain hydrogen production synergistic CO2 absorption method of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. It should be noted that the embodiments provided by the present invention are only illustrative and are not limited thereto.

[0056] Example

[0057] 15.44 kg of Li₂CO₃, 6.1245 kg of SiO₂, and 1.4088 kg of K₂CO₃ were weighed out, ground into powder using a ball mill, and then uniformly mixed to obtain K-doped Li₄SiO₄ powder. Subsequently, 10 kg of the K-doped Li₄SiO₄ powder was weighed out and then... CO2吸收剂 :m 高岭土 :m 纤维素 :m 去离子水 Weigh out 4 kg of kaolin, 4 kg of cellulose, and 2.25 L of deionized water in a ratio of 1:0.4:0.4:0.16, mix them into a wet mixture, and place it in an extruder. Extrude the mixture at 430 rpm to produce elongated strips with a diameter of 2 mm. Then, place the strips in a spherical mill, turn on the cold air cooling, and sphericalize them at 700 rpm to form spherical particles with a diameter of 1-2 mm. Finally, sieve the particles to obtain spherical particles with a diameter of 1.5 mm, place them in a square flat crucible in a muffle furnace, and calcine them at a heating rate of 2 °C / min to 700 °C for 4 hours.

[0058] Thirty sets of mechanical strength measurements were performed on the CO2 absorbent particles obtained in the above embodiments. The measured strength range of the absorbent particles was 35±5 N. The porosity and specific surface area of ​​the CO2 absorbent particles were also measured. The measured porosity of the CO2 absorbent particles was 40±5%, and the specific surface area was 1.4±0.2 m².2 / g.

[0059] Furthermore, the reaction performance of the molded particles was tested using a comprehensive thermogravimetric analyzer and a microreactor to obtain the cycle stability of the CO2 absorbent particles.

[0060] Figure 3 This is a stability test diagram of the CO2 absorbent particles in a thermogravimetric analyzer according to an embodiment of the present invention. During the stability test, nitrogen was used as the equilibrium gas, the absorption and regeneration temperatures of the CO2 absorbent particles were the same and maintained at 600°C, the carbon dioxide concentration in the absorption reaction was 10%, and the absorption time was 15 min. The regeneration reaction was performed by purging with 100% nitrogen gas for 15 min to regenerate the CO2 absorbent particles.

[0061] like Figure 3 As shown, after 200 cycles, the absorption performance of the CO2 absorbent particles remained consistent, indicating that it has good stability.

[0062] The rounded spherical particles were further cut into particles of different sizes (1mm-5mm) and then calcined to obtain CO2 absorbent particles of different sizes. The CO2 absorbent particles of different sizes were then applied to the methane chemical loop hydrogen production reaction to test the CO2 gas absorption performance. The test temperature was 600℃, the carbon dioxide concentration was 10%, and the absorption time was 10min. This study investigated the effect of CO2 absorbent particles of different sizes prepared by solid-phase mixing method on CO2 gas absorption. The specific test results are shown in Table 1.

[0063] Table 1

[0064]

[0065] As shown in Table 1, the absorption rate of CO2 absorbent particles gradually decreases with increasing particle size. This is because the specific surface area of ​​the CO2 absorbent particles gradually decreases, leading to a reduction in the number of exposed absorption sites on the absorbent surface. This makes the bulk diffusion reaction the main rate-limiting step, slowing down the reaction process. Therefore, when the particle size of the CO2 absorbent is 1 mm, it has a large specific surface area and a large number of pores, thus achieving a higher CO2 adsorption capacity.

[0066] Furthermore, the cyclic stability of CO2 absorbent particles with a particle size of 1.4 mm-1.6 mm prepared by solid-phase method in the chemical loop hydrogen production reaction of methane was tested, and the specific test results are shown in Table 2.

[0067] Table 2

[0068]

[0069] As shown in Table 2, the CO2 absorbent particles prepared by this invention have good adsorption and regeneration performance.

[0070] Furthermore, the physical properties of CO2 absorbent particles with a particle size of 1 mm prepared by solid-phase mixing, sol-gel method, and impregnation method were investigated, and their CO2 gas absorption performance in the methane chemical loop hydrogen production reaction was tested. The test temperature was 600℃, the carbon dioxide concentration was 10%, and the absorption time was 10 min. The specific test results are shown in Table 3.

[0071] Table 3

[0072]

[0073] Table 3 shows that potassium-doped CO2 absorbent particles exhibit a higher CO2 adsorption capacity compared to undoped particles. CO2 absorbent particles doped with 20 wt.% potassium carbonate achieve even higher CO2 absorption. Further increasing the potassium carbonate doping amount does not significantly improve the CO2 absorption effect; therefore, doping with 20 wt.% potassium carbonate is the preferred option from a cost perspective. Furthermore, CO2 absorbent particles prepared using solid-phase mixing, impregnation, and sol-gel-hydrothermal methods all demonstrate high CO2 adsorption efficiency. Sodium-doped CO2 absorbent particles exhibit the same CO2 adsorption performance as those prepared with potassium doping.

[0074] The effects of different mass ratios of CO2 absorbent particles and bimetallic oxygen carriers on methane chemical looping hydrogen production and CO2 adsorption performance were further investigated. The bimetallic oxygen carrier was an iron-nickel oxygen carrier, and the preparation process of the bimetallic oxygen carrier is as follows:

[0075] 1) Solid iron oxide and nickel oxide powders were placed separately into a reactor and pre-calcined at 500℃ for 2 hours. After calcination, they were ground and sieved to obtain active powders with a particle size of less than 50 μm. The micron-sized iron oxide and nickel oxide active powders and alumina carrier were mixed at a mass percentage ratio of 60%:40% for iron to aluminum and 30%:70% for nickel to aluminum. The mixture was continuously stirred to obtain a homogeneous powder. This powder was then placed in a ball mill and ball-milled at 500 r / min for 2 hours to obtain a mixed powder.

[0076] 2) Extrusion-Spheronization: A uniform, viscous slurry was obtained by simultaneously adding and stirring the mixed powder, binder (kaolin), pore-forming agent (cellulose), and deionized water at a mass ratio of 1:10%:8%:50%. This slurry was then placed in an extruder and extruded at 150 r / min to obtain an extrudate with a diameter of 1.5 ± 0.2 mm. Next, the extrudate was sheared and spheronized at 500 r / min to obtain spherical particles with a diameter of 1.5 ± 0.2 mm.

[0077] 3) Drying and calcination: The spherical particles are placed in a drying oven and dried at 80℃ for 6 hours. Then, they are placed in a muffle furnace for step-by-step calcination in an air atmosphere. The first stage of calcination is carried out by raising the temperature from room temperature to 700℃ for 5 hours. Finally, the calcination temperature is raised to 1200℃ for 2 hours to harden the powder and obtain the iron-nickel bimetallic oxygen carrier.

[0078] With the mass of the iron-nickel bimetallic oxygen carrier remaining constant, CO2 absorbent particles of different mass multiples of the iron-nickel bimetallic oxygen carrier were added to the reactor to carry out the methane chemical loop hydrogen production reaction. The methane conversion rate, hydrogen purity, CO2 capture rate and hydrogen production during the reaction process were tested. The test temperature was 600℃, the carbon dioxide concentration was 10%, and the absorption time was 10 min. The specific test results are shown in Table 4.

[0079] Table 4

[0080]

[0081] Table 4 shows that when CO2 absorbent particles are not used, both the methane conversion rate and hydrogen purity are low. When the mass of the bimetallic oxygen carrier (iron-nickel bimetallic oxygen carrier) remains constant, adjusting the mass of the CO2 absorbent particles to 0, 1, 3, and 5 times the mass of the bimetallic oxygen carrier, respectively, increases the CO2 capture rate, H2 purity, and CH4 conversion rate. This indicates that the CO2 absorbent particles in this invention can effectively absorb CO2 gas, improving the purity and yield of hydrogen production. Furthermore, when the mass ratio of CO2 absorbent particles to the bimetallic oxygen carrier is 5, the methane conversion rate can be increased by 10-15 percentage points, and the H2 concentration and CO2 capture rate can be increased to over 90%.

[0082] In summary, the CO2 absorbent particles provided by this invention are used in the absorption and enhancement of the methane chemical chain hydrogen production reaction. Through lithium orthosilicate, carbon dioxide is captured in situ, promoting the forward progress of the methane chemical chain hydrogen production reaction. At medium temperature, the methane conversion rate of the chemical chain reaction is greater than 90%, the hydrogen production purity and the source carbon dioxide capture are greater than 90%.

[0083] In embodiments of this invention, CO2 absorbent particles are applied to the methane chemical chain hydrogen production reaction, which needs to be compatible with the reaction. Firstly, traditional methane chemical chain hydrogen production reactions generally occur above 900°C, requiring high energy input and demanding reaction equipment. To address this, by designing the composition of the bimetallic oxide support, a bimetallic oxide support was obtained that can produce hydrogen at a medium temperature (450-650°C) with a high yield. However, the operating temperature of pure lithium silicate absorbent particles is generally 700-800°C, which does not match the operating temperature of the methane chemical chain hydrogen production reaction. Therefore, it is necessary to design a CO2 absorbent particle that can match the medium-temperature reaction environment of the methane chemical chain hydrogen production reaction. To solve the aforementioned problem of temperature mismatch, this invention obtains medium-temperature CO2 absorbent particles that can operate at 450-650°C by changing the synthesis method, the proportion of doped metals, the type of doped metals, and the particle size of the CO2 absorbent particles. Secondly, when applying CO2 absorbent particles to the methane chemical chain hydrogen production reaction, the concentration of CO2 gas absorbed by the CO2 absorbent particles needs to match the concentration of CO2 gas produced by the methane chemical chain hydrogen production reaction. Without absorbent, the concentration of CO2 gas produced in the reduction reaction of methane chemical chain hydrogen production is 10-30%. To obtain CO2 absorbent particles with better CO2 absorption performance, this invention uses the lowest CO2 concentration (10%) as the test condition to screen out the optimal CO2 absorbent particles and apply them to the methane chemical chain hydrogen production reaction. Furthermore, the residence time of the bimetallic oxygen carrier in the reduction reaction of methane chemical chain hydrogen production needs to be matched with the CO2 gas absorption time of the CO2 absorbent particles. Traditional lithium silicate absorbents suffer from a mismatch in absorption time (60-120 min), leading to a kinetic mismatch between methane chemical chain hydrogen production and CO2 absorption. Therefore, this invention limits the testing time to 10 min to obtain CO2 absorbent particles with good performance.

[0084] In embodiments of the present invention, the reactivity of integrated particles can be altered by controlling the synthesis method, doping ratio, particle size, and calcination temperature of K- or Na-doped Li4SiO4 powder. Appropriate synthesis methods, doping ratios, particle sizes, and calcination temperatures all affect the particle's reactivity, such as methane conversion, CO2 capture rate, and product selectivity. They also influence the particle's physical properties, such as specific surface area, porosity, mechanical strength, and cycle stability. For example, higher strength can improve the lifespan of CO2 absorbent particles, sphericity can adjust the flowability of CO2 absorbent particles in a moving bed reactor, and a larger specific surface area can improve the absorption activity of CO2 absorbent particles.

[0085] In embodiments of this invention, the preparation method of K or Na-doped Li4SiO4 powder can be interchanged between the sol-gel-hydrothermal method, mechanical mixing method, and impregnation method to achieve a simpler preparation process and better reaction performance. This invention, by utilizing fixed-bed and moving-bed reactors, can accurately measure the wear rate and reaction characteristics of integrated particles under long-term cold and hot conditions, providing technical support for the practical industrial application of high-performance, high-wear-resistance, and long-life particulate materials. Furthermore, this invention provides more comprehensive characterization methods for CO2 absorbent particles, from thermogravimetric cycle stability to methane conversion rate and product selectivity measured in microreactors, comprehensively demonstrating the reaction performance and physical properties of the particles.

[0086] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for using CO2 absorbent particles for methane chemical looping hydrogen production with CO2 absorption, comprising: filling a dual-metallic oxygen carrier and CO2 absorbent particles into a reactor; feeding methane and steam into the reactor to carry out a methane chemical looping hydrogen production reaction and an in-situ CO2 absorption reaction, wherein the temperature of the methane chemical looping hydrogen production reaction and the in-situ CO2 capture is 450-600℃, the methane chemical looping hydrogen production reaction comprises a steam methane reforming hydrogen production reaction and a steam oxidation reaction, and steam is fed into both the steam methane reforming hydrogen production reaction and the steam oxidation reaction; wherein, in the steam methane reforming hydrogen production reaction, methane reacts with steam to produce a first-stage hydrogen, CO and CO2 gas, and the produced CO2 gas is in-situ absorbed by the CO2 absorbent particles; in the steam oxidation reaction, steam is reduced to produce a second-stage hydrogen; wherein the CO2 absorbent particles comprise an active component Li4SiO4 and potassium or sodium elements modified on the active component, and the CO2 absorbent particles are prepared by a preparation method comprising: preparing K or Na-doped Li4SiO4 powder, wherein the molar ratio of elements Li:Si:K or Na is 4.1:1:0.05-0.4, and the particle size of the powder is 0.1-10 μm; mixing the powder with a binder, a pore-forming agent and water to form a slurry; extruding the slurry in an extruder to obtain an extrudate, and rolling the extrudate in a roller to obtain spherical particles; drying the spherical particles and placing them in a reaction container for calcination to obtain CO2 absorbent particles.

2. The method of claim 1, wherein, The K or Na-doped Li4SiO4 powder is prepared by a solid-phase mixing method, which comprises mixing lithium salt, silica carrier and potassium salt or sodium salt in a certain proportion, and obtaining K or Na-doped Li4SiO4 powder after ball milling.

3. The method of claim 1, wherein, The K or Na-doped Li4SiO4 powder is prepared by a hydrothermal method, which comprises mixing lithium salt, silica carrier and potassium salt or sodium salt with water in a certain proportion, stirring uniformly at a first stirring speed, adding a precipitant to form a suspension; transferring the suspension into a hydrothermal reactor for hydrothermal reaction, and obtaining a solid product which is washed, dried and ball milled to obtain K or Na-doped Li4SiO4 powder.

4. The method of claim 1, wherein, The K or Na-doped Li4SiO4 powder is prepared by an impregnation method, which comprises mixing lithium salt or LiOH·H2O, silica carrier and potassium salt or sodium salt with water in a certain proportion, stirring uniformly to obtain a mixed solution; the mixed solution is subjected to stepwise drying, calcination and ball milling to obtain K or Na-doped Li4SiO4 powder. 5.The method of claim 3, wherein: the precipitant is selected from ammonia water; the pH of the suspension is 8-10; the first stirring speed is 900-1300 r / min; the hydrothermal reaction temperature is 120-200℃, and the reaction time is 5-15 h; The obtained solid product is washed multiple times with a mixed solvent, wherein the mixed solvent is an ethanol aqueous solution.

6. The method of claim 4, wherein: the segment drying temperature is 40-80℃; the calcination temperature is 450-600℃, and the calcination time is 2-4h.

7. The method of any one of claims 2-4, wherein: the potassium salt is selected from any one of K2CO3, KNO3; the sodium salt is selected from any one of Na2CO3, NaNO3; the lithium salt is selected from any one of Li2CO3, LiNO3, LiNO3·H2O; the SiO2 carrier is SiO2 nano or micro particles with a particle size of 50nm-5μm.

8. The method of claim 1, wherein: the mass ratio of the K or Na doped Li4SiO4 powder to the binder, pore-forming agent, and water is 1:2-15%:2-15%:20-50%.

9. The method of claim 8, wherein: the binder is selected from any one of kaolin, attapulgite; the pore-forming agent is selected from any one of graphite, cellulose.

10. The method of claim 1, wherein: the rotation speed of the extruder is 350-550rpm, and the diameter of the extrudate is 1-5mm; the rotation speed of the spheroidizer is 500-1000rpm, and the diameter of the spherical particles is 1-5mm.

11. The method of claim 1, wherein: the drying temperature of the spherical particles is 80-150℃, and the drying time is 4-20h; the calcination of the dried spherical particles in the reactor comprises: increasing the temperature of the spherical particles from room temperature to 500-800℃ at a rate of 2-10℃ / min, and calcining for 2-5h to obtain CO2 absorbent particles.

12. The method of claim 1, wherein, the double metal oxide carrier is a Fe-Ni double metal oxide carrier, and the active components in the Fe-Ni double metal oxide carrier are iron oxide and nickel oxide.

13. The method of claim 1, further comprising: introducing water vapor into the reactor to regenerate the CO2 absorbent particles that have adsorbed CO2 gas, to obtain pure CO2 gas, while the regenerated CO2 absorbent particles are recycled in the reactor.

14. The method of claim 1, wherein: the non-active component in the double metal oxide carrier is Al2O3 or SiO2; the reactor is a moving bed reactor or a fixed bed reactor.

15. The method of claim 1, wherein: in the methane chemical looping hydrogen production reaction, the iron oxide and nickel oxide in the double metal oxide carrier are reduced to generate metallic iron and metallic nickel; in the water vapor oxidation reaction, the metallic iron and metallic nickel are oxidized to generate iron oxide and nickel oxide.

16. The method of claim 1, wherein, The capture of CO2 by the CO2 absorbent particles promotes the forward movement of the methane chemical looping hydrogen production reaction, and improves the methane conversion rate, hydrogen production rate, and hydrogen purity.

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