A type of AlO2 - Intercalated hydrotalcite-derived oxygen carriers, their preparation and application

Abstract

This invention discloses an AlO 2‑ Intercalated hydrotalcite-derived oxygen carriers, their preparation, and applications. This invention prepares hydrotalcite-like materials that can be assembled at the molecular level via a co-precipitation method, integrating AlO2 through interlayer insertion. 2‑ By introducing a layer of hydrotalcite-like interlayer and undergoing thermal conversion, a spinel-type oxygen carrier with higher purity can be obtained. The oxygen carrier prepared by this method avoids high-temperature thermal conversion and reduces interference from divalent metal oxides. At the same time, the suitable oxygen release capacity and catalytic activity of spinel enable the oxygen carrier to have good fuel conversion rate, syngas selectivity, and anti-carbon deposition ability at medium and low temperatures, which is beneficial for industrial Fischer-Tropsch synthesis and hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of oxygen carrier technology, specifically relating to an AlO2 for chemical loop steam reforming. - Oxygen carriers derived from intercalated Ni-Fe-Al hydrotalcite, their preparation methods, and applications. Background Technology

[0002] Chemically recycled steam methane reforming (CL-SMR) offers a feasible solution to this problem by recycling oxygen carriers (OCs) in fuel reactors and steam reactors to produce syngas and hydrogen separately, thereby reducing production costs and energy consumption. As a key factor in CL-SMR, the OC should possess good lattice oxygen migration capability, product selectivity, and stability; however, achieving all three simultaneously in reality is often challenging.

[0003] Layered double hydroxides (LDHs) are layered composite hydroxides with uniformly dispersed metal cations at the molecular level. They can be assembled at the molecular level by controlling the types and amounts of metal ions and anions, avoiding the high-temperature calcination (>1100℃) required for conventional spinel formation. They can be transformed into spinels with good oxygen release and catalytic abilities at moderate temperatures (500–800℃). However, the molar ratio of divalent to trivalent metals in LDHs ranges from 2 to 4. Calcination produces excess divalent metal oxides, which limit the lattice oxygen release capacity of the oxygen carrier. Therefore, it is of great significance to avoid the formation of excess divalent metal oxides after calcination of LDHs and to improve the lattice oxygen release capacity of the oxygen carrier. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide an AlO2... - A method for preparing oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0005] Another object of the present invention is to provide an AlO2 prepared by the above-described preparation method. - Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0006] Another object of the present invention is to provide the above-mentioned AlO2 - Applications of oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A type of AlO2 - A method for preparing an oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite includes the following steps:

[0009] (1) Under an inert atmosphere, a mixed aqueous solution of nickel nitrate, ferric nitrate, and aluminum nitrate, along with a mixed solution of sodium aluminate and sodium hydroxide, are simultaneously added dropwise to a sodium aluminate solution. After stirring at 60–120 °C, the mixture is aged, filtered, washed, and dried to obtain AlO2. - Intercalated Ni-Fe-Al type hydrotalcite precursor;

[0010] (2) AlO2 - Intercalated Ni-Fe-Al type hydrotalcite precursors were calcined at 400–900℃ for 4–8 hours to obtain AlO2. - Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite;

[0011] The molar ratio of Ni to Al is 2–3:1, and the molar ratio of aluminum nitrate to sodium aluminate is 1–3:8.

[0012] Preferably, the nickel nitrate in step (1) is nickel nitrate hexahydrate; the aluminum nitrate is aluminum nitrate hexahydrate; and the ferric nitrate is ferric nitrate hexahydrate.

[0013] Preferably, the molar ratio of nickel nitrate and ferric nitrate in step (1) is 2 to 3:1.

[0014] Preferably, the molar ratio of aluminate ions in the mixed solution of sodium aluminate and sodium hydroxide and the sodium aluminate solution in step (1) is 3:3 to 5.

[0015] Preferably, the molar ratio of the cations in the mixed aqueous solution of nickel nitrate, ferric nitrate, and aluminum nitrate in step (1) to the cations in the mixed solution of sodium aluminate and sodium hydroxide is 0.72 to 1:1.

[0016] Preferably, in the mixed aqueous solution of nickel nitrate, ferric nitrate and aluminum nitrate in step (1), the total concentration of cations is 0.1 to 1 mol / L.

[0017] Preferably, in the mixed solution of sodium aluminate and sodium hydroxide in step (1), the total concentration of cations is 0.1 to 1.5 mol / L.

[0018] Preferably, the concentration of the sodium aluminate solution in step (1) is 0.1 to 1.5 mol / L.

[0019] Preferably, the stirring speed in step (1) is 500-800 r / min.

[0020] Preferably, the stirring time in step (1) is 10 to 25 minutes.

[0021] Preferably, the aging temperature in step (1) is room temperature, and the time is 12 to 24 hours.

[0022] Preferably, the washing in step (1) refers to washing with water, and the number of washing cycles is 1 to 6.

[0023] Preferably, the drying temperature in step (1) is 70-120°C and the drying time is 15-24 hours.

[0024] Preferably, the calcination temperature in step (2) is 500-900°C and the time is 2-6 hours; more preferably, the calcination is performed at 500°C for 2 hours and then at 900°C for 4 hours.

[0025] Preferably, the calcination in step (2) is carried out in an air atmosphere.

[0026] Preferably, the heating rate of the calcination in step (2) is 2 to 15 °C / min; more preferably, it is 10 °C / min.

[0027] Preferably, after the hydrotalcite precursor described in step (2) is calcined, it needs to be ground and sieved; more preferably, the sieving refers to passing through an 80-mesh sieve.

[0028] An AlO2 prepared by the above method - Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0029] The above-mentioned AlO2 - Application of intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carriers in chemically looped steam generation of syngas and pure hydrogen.

[0030] Preferably, the application specifically involves: using the above-mentioned AlO2 - An oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite is added to a fuel reactor. First, an inert gas is introduced to purge the air from the fuel reactor. Then, the fuel reactor is heated to the reaction temperature. Once the temperature of the fuel reactor stabilizes, gaseous fuel, liquid fuel, or solid fuel is introduced to produce syngas (a mixture of H2 and CO). After the reaction is complete, an inert gas is introduced to purge the syngas from the reactor. After the steam reactor stabilizes, steam and inert gas are introduced to perform steam reforming to produce hydrogen.

[0031] More preferably, the gaseous fuel is an alkane fuel diluted with an inert gas to a volume percentage of 5-25%; the liquid fuel is an alcohol or bio-oil fuel; and the solid fuel is biomass or organic solid waste fuel.

[0032] More preferably, the gaseous fuel is methane diluted with an inert gas to a volume percentage of 5-25%.

[0033] More preferably, the flow rate of the inert gas is 90-100 ml / min, and the introduction time (inert gas scavenging) is 5-10 min.

[0034] More preferably, the flow rate of the gaseous fuel is 50-150 ml / min, and the introduction time is 20-180 min.

[0035] More preferably, the gaseous fuel, liquid fuel, or solid fuel is mixed with AlO2. - The lattice oxygen molar ratio of the oxygen carrier derived from intercalated Ni-Fe-Al type hydrotalcite is 1.2 to 0.8:1.

[0036] More preferably, the water vapor and AlO2 - The molar ratio of lattice oxygen in the oxygen carrier derived from intercalated Ni-Fe-Al type hydrotalcite is 0.82 to 8.2:1.

[0037] More preferably, the flow rate of the inert gas in the steam reforming stage is 50-100 ml / min.

[0038] More preferably, the reaction temperature is 500–900°C.

[0039] This invention introduces gaseous fuels such as alkanes, liquid fuels such as alcohols and bio-oils, and solid fuels such as biomass and organic solid waste into a fuel reactor separately, while water vapor is introduced into a steam reactor. The process utilizes AlO2, which possesses excellent lattice oxygen transport and activation capabilities. - Syngas and hydrogen are produced through oxidation and reduction reactions under the action of oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] (1) This invention prepares a hydrotalcite-like material that can be assembled at the molecular level via coprecipitation, and incorporates AlO2 through interlayer insertion. - By introducing a layer similar to hydrotalcite and then thermally converting it, a spinel-type oxygen carrier with higher purity can be obtained. The oxygen carrier prepared by this method reduces the interference of divalent metal oxides. At the same time, the suitable oxygen release capacity and catalytic activity of spinel enable the oxygen carrier to have good fuel conversion rate, syngas selectivity and anti-carbon deposition ability at medium and low temperatures.

[0042] (2) The present invention prepares a spinel oxygen carrier with higher purity by means of medium-temperature thermal conversion (<900℃) similar to hydrotalcite, avoiding the high-temperature calcination method (>1100℃) in the preparation of traditional spinel oxygen carriers, and reducing the energy consumption in the preparation of oxygen carriers.

[0043] (3) This invention regulates AlO2 -The amount of intercalation between layers of hydrotalcite can be adjusted at the molecular level to regulate the spinel composition and reaction microenvironment, thereby controlling the reaction exposure of the oxygen carrier crystal facets and the oxygen migration rate, enhancing the oxygen carrier's ability to release oxygen at medium and low temperatures and its ability to activate and convert fuels, which is beneficial for the medium and low temperature conversion of fuels.

[0044] (4) The oxygen carrier prepared by the present invention has good porosity and specific surface area, and has good cycling ability in a wide temperature range. It can maintain high H2 and CO selectivity under high conversion rate, and at the same time has good anti-sintering and anti-carbon deposition ability.

[0045] (5) The oxygen carrier preparation conditions in this invention are simple and easy to control, inexpensive, and can achieve high stability and high reactivity, which is beneficial for large-scale application in chemical chain steam reforming. Compared with existing oxygen carrier preparation methods, AlO2 is used. - The method of intercalation-type hydrotalcite avoids high-temperature conversion to obtain an oxygen carrier with high specific surface area and spinel purity, giving the oxygen carrier good lattice oxygen transport capability and catalytic activity. Attached Figure Description

[0046] Figure 1 AlO2 obtained in Example 1 - X-ray diffraction patterns of intercalated Ni-Fe-Al hydrotalcite and Ni-Fe-Al hydrotalcite obtained in Comparative Example 3.

[0047] Figure 2 AlO2 obtained in Example 1 - X-ray diffraction patterns of the oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite and the oxygen carrier derived from Ni-Fe-Al hydrotalcite obtained in Comparative Example 3.

[0048] Figure 3 AlO2 obtained in Example 1 - The effect of intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carrier on methane reforming.

[0049] Figure 4 AlO2 obtained in Example 2 - The effect of intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carrier on methane reforming.

[0050] Figure 5 AlO2 obtained in Example 3 - The effect of intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carrier on methane reforming.

[0051] Figure 6 AlO2 obtained for Comparative Example 1 -The effect of intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carrier on methane reforming.

[0052] Figure 7 AlO2 obtained for Comparative Example 2 - The effect of intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carrier on methane reforming.

[0053] Figure 8 The image shows the effect of the Ni-Fe-Al type hydrotalcite-derived oxygen carrier obtained in Comparative Example 3 on the reforming of methane. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0055] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0056] Example 1

[0057] (1) AlO2 in raw materials with an Al(NO3)3:NaAlO2 ratio of 3:8 - Preparation of oxygen carrier derived from intercalated Ni-Fe-Al type hydrotalcite: 0.05 mol nickel nitrate hexahydrate, 0.025 mol ferric nitrate nonahydrate, and 0.0068 mol aluminum nitrate were dissolved in 100 ml of deionized water to prepare a mixed metal solution with a metal ion concentration of 0.8180 mol / L; 0.1 mol sodium hydroxide and 0.0068 mol sodium aluminate were dissolved in 100 ml of water to obtain a mixed alkali solution with a concentration of 1.0680 mol / L; 0.0113 mol sodium aluminate was dissolved in 100 ml of water to prepare a sodium aluminate solution with a concentration of 0.1130 mol / L. Under a nitrogen atmosphere of 100 ml / min, the metal solution and the mixed alkali solution were simultaneously added dropwise to the sodium aluminate solution. At the same time, the mixture was stirred at a constant temperature of 80℃ and 600 r / min for 20 min to obtain a precipitate. After aging at room temperature for 24 hours, the precipitate was filtered, washed with deionized water until neutral, and then dried in an oven at 70°C for 24 hours to obtain a hydrotalcite-like precursor. The hydrotalcite-like precursor was then calcined in a muffle furnace under air atmosphere at stages of 500°C for 2 hours and 900°C for 4 hours (heating rate 10°C / min). After cooling, it was ground through an 80-mesh sieve to obtain AlO2 with an Al(NO3)3:NaAlO2 ratio of 3:8. - Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0058] (2) Evaluation of oxygen carrier reaction characteristics: The reaction for the chemical chaining of methane to syngas was carried out in a small fixed bed. 1.45g of oxygen carrier was placed in the center of a quartz tube, and quartz wool was plugged at both ends to fix the oxygen carrier. Nitrogen gas was introduced for 10 minutes to purge the air. After the atmosphere furnace was heated to 750℃, the quartz tube was placed in the atmosphere furnace and the temperature was allowed to stabilize. Then, the gas was switched to 100ml / min of methane (10% CH4 / 90% N2). The reaction time for this stage was 27 minutes. The syngas obtained from the reaction was collected in a gas bag and its composition was analyzed by gas chromatography. The analysis showed that the methane conversion rate was as high as 92.66%, the hydrogen selectivity was as high as 95.30%, and the carbon monoxide selectivity was as high as 85.20%. The steam reforming stage was followed by the methane stage, after which nitrogen gas was introduced for 10 min at a flow rate of 90 ml / min. Then, H₂O was injected into the quartz tube at a flow rate of 0.1 ml / min for 27 min under a nitrogen flow rate of 90 ml / min. The resulting gas was collected using a gas bag and its composition was analyzed. The analysis showed that the hydrogen yield was 8.03 mol·h⁻¹. -1 ·kg -1 The purity is 100.00%.

[0059] Example 2

[0060] AlO2 with an Al(NO3)3:NaAlO2 ratio of 2:8 in the raw materials was prepared according to the method in Example 1. - The oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite differs in that in step (1), 0.0500 mol nickel nitrate hexahydrate, 0.0250 mol ferric nitrate nonahydrate, and 0.0068 mol aluminum nitrate are dissolved in 100 ml of deionized water to prepare a metal mixed solution with a metal ion concentration of 0.8180 mol / L; 0.15 mol sodium hydroxide and 0.0204 mol sodium aluminate are dissolved in 150 ml of water to obtain an alkaline mixed solution with a concentration of 1.0680 mol / L; 0.017 mol sodium aluminate is dissolved in 150.4 ml of water to prepare a sodium aluminate solution with a concentration of 0.1130 mol / L. Under a nitrogen atmosphere of 100 ml / min, the metal solution and the alkaline mixed solution are simultaneously added dropwise to the sodium aluminate solution. At the same time, the mixture is stirred at a constant temperature of 80℃ and 600 r / min for 20 min to obtain a precipitate. After aging at room temperature for 24 hours, the precipitate was filtered, washed with deionized water until neutral, and then dried in an oven at 70°C for 24 hours to obtain a hydrotalcite-like precursor. The hydrotalcite-like precursor was then calcined in a muffle furnace under air atmosphere at stages of 500°C for 2 hours and 900°C for 4 hours (heating rate 10°C / min). After cooling, it was ground through an 80-mesh sieve to obtain AlO2 with an Al(NO3)3:NaAlO2 ratio of 2:8. - Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0061] (3) Evaluation of oxygen carrier reaction characteristics: The reaction for the chemical chaining of methane to syngas was carried out in a small fixed bed. 1.45g of oxygen carrier was placed in the center of a quartz tube, and quartz wool was plugged at both ends to fix the oxygen carrier. Nitrogen gas was introduced for 10 minutes to purge the air. After the atmosphere furnace was heated to 900℃, the quartz tube was placed in the atmosphere furnace and the temperature was allowed to stabilize. Then, the gas was switched to 100ml / min of methane (10% CH4 / 90% N2). The reaction time for this stage was 27 minutes. The syngas obtained from the reaction was collected in a gas bag and its composition was analyzed by gas chromatography. The analysis showed that the methane conversion rate was as high as 92.66%, the hydrogen selectivity was as high as 82.09%, and the carbon monoxide selectivity was as high as 84.46%. The steam reforming stage was followed by the methane stage, after which nitrogen gas was introduced for 10 min at a flow rate of 90 ml / min. Then, H₂O was injected into the quartz tube at a flow rate of 0.1 ml / min for 27 min under a nitrogen flow rate of 90 ml / min. The resulting gas was collected using a gas bag and its composition was analyzed. The analysis showed that the hydrogen yield was 7.73 mol·h⁻¹. -1 ·kg -1 It has a purity of 100%.

[0062] Example 3

[0063] AlO2 with an Al(NO3)3:NaAlO2 ratio of 1:8 in the raw materials was prepared according to the method in Example 1. - The oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite differs in that in step (1), 0.05 mol nickel nitrate hexahydrate, 0.025 mol ferric nitrate nonahydrate, and 0.0068 mol aluminum nitrate are dissolved in 100 ml of deionized water to prepare a metal mixed solution with a metal ion concentration of 0.8180 mol / L; 0.3 mol sodium hydroxide and 0.0204 mol sodium aluminate are dissolved in 300 ml of water to obtain an alkaline mixed solution with a concentration of 1.0680 mol / L; 0.034 mol sodium aluminate is dissolved in 300.8 ml of water to prepare a sodium aluminate solution with a concentration of 0.1130 mol / L. Under a nitrogen atmosphere of 100 ml / min, the metal solution and the alkaline mixed solution are simultaneously added dropwise to the sodium aluminate solution. At the same time, the mixture is stirred at a constant temperature of 80℃ and 600 r / min for 20 min to obtain a precipitate. After aging at room temperature for 24 hours, the precipitate was filtered, washed with deionized water until neutral, and then dried in an oven at 70°C for 24 hours to obtain a hydrotalcite-like precursor. The hydrotalcite-like precursor was then calcined in a muffle furnace under air atmosphere at stages of 500°C for 2 hours and 900°C for 4 hours (heating rate 10°C / min). After cooling, it was ground through an 80-mesh sieve to obtain AlO2 with an Al(NO3)3:NaAlO2 ratio of 1:8. -Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0064] (3) Evaluation of oxygen carrier reaction characteristics: The reaction for the chemical chaining of methane to syngas was carried out in a small fixed bed. 1.45g of oxygen carrier was placed in the center of a quartz tube, and quartz wool was plugged at both ends to fix the oxygen carrier. Nitrogen gas was introduced for 10 minutes to purge the air. After the atmosphere furnace was heated to 900℃, the quartz tube was placed in the atmosphere furnace and the temperature was allowed to stabilize. Then, the gas was switched to 100ml / min of methane (10% CH4 / 90% N2). The reaction time for this stage was 27 minutes. The syngas obtained from the reaction was collected in a gas bag and its composition was analyzed by gas chromatography. The analysis showed that the methane conversion rate was as high as 88.24%, the hydrogen selectivity was as high as 78.18%, and the carbon monoxide selectivity was as high as 83.89%. The steam reforming stage was followed by the methane stage, after which nitrogen gas was introduced for 10 min at a flow rate of 90 ml / min. Then, H₂O was injected into the quartz tube at a flow rate of 0.1 ml / min for 27 min under a nitrogen flow rate of 90 ml / min. The resulting gas was collected in a gas bag and its composition was analyzed. The hydrogen yield was found to be 10.20 mol·h⁻¹. -1 ·kg -1 It has a purity of 100%.

[0065] Comparative Example 1

[0066] AlO2 with an Al(NO3)3:NaAlO2 ratio of 4:8 in the raw materials was prepared according to the method in Example 1. - The oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite differs in that in step (1), 0.05 mol nickel nitrate hexahydrate, 0.025 mol ferric nitrate nonahydrate, and 0.0068 mol aluminum nitrate are dissolved in 100 ml of deionized water to prepare a metal mixed solution with a metal ion concentration of 0.8180 mol / L; 0.075 mol sodium hydroxide and 0.0051 mol sodium aluminate are dissolved in 75 ml of water to obtain an alkaline mixed solution with a concentration of 1.0680 mol / L; 0.0085 mol sodium aluminate is dissolved in 75 ml of water to prepare a sodium aluminate solution with a concentration of 0.1130 mol / L; under a nitrogen atmosphere of 100 ml / min, the metal solution and the alkaline mixed solution are simultaneously added dropwise to the sodium aluminate solution, while maintaining a constant temperature of 80℃ and 600 r / min for 20 min to obtain a precipitate. After aging at room temperature for 24 hours, the precipitate was filtered, washed with deionized water until neutral, and then dried in an oven at 70°C for 24 hours to obtain a hydrotalcite-like precursor. The hydrotalcite-like precursor was then calcined in a muffle furnace under air atmosphere at stages of 500°C for 2 hours and 900°C for 4 hours (heating rate 10°C / min). After cooling, it was ground through an 80-mesh sieve to obtain AlO2 with an Al(NO3)3:NaAlO2 ratio of 4:8.- Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0067] (3) Evaluation of oxygen carrier reaction characteristics: The reaction for the chemical chaining of methane to syngas was carried out in a small fixed bed. 1.45g of oxygen carrier was placed in the center of a quartz tube, and quartz wool was plugged at both ends to fix the oxygen carrier. Nitrogen gas was introduced for 10 minutes to purge the air. After the atmosphere furnace was heated to 900℃, the quartz tube was placed in the atmosphere furnace and the temperature was allowed to stabilize. Then, the gas was switched to 100ml / min of methane (10% CH4 / 90% N2). The reaction time for this stage was 27 minutes. The syngas obtained from the reaction was collected in a gas bag and its composition was analyzed by gas chromatography. The analysis showed that the methane conversion rate was as high as 86.43%, the hydrogen selectivity was 72.51%, and the carbon monoxide selectivity was 77.90%. The steam reforming stage was followed by the methane stage, after which nitrogen gas was introduced for 10 min at a flow rate of 90 ml / min. Then, H₂O was injected into the quartz tube at a flow rate of 0.1 ml / min for 27 min under a nitrogen flow rate of 90 ml / min. The resulting gas was collected in a gas bag and its composition was analyzed. The hydrogen yield was found to be 9.83 mol·h⁻¹. -1 ·kg -1 It has a purity of 100%.

[0068] Comparative Example 2

[0069] AlO2 with an Al(NO3)3:NaAlO2 ratio of 0:8 in the raw materials was prepared according to the method in Example 1. - The oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite differs in that in step (1), 0.05 mol nickel nitrate hexahydrate and 0.025 mol ferric nitrate nonahydrate are dissolved in 100 ml of deionized water to prepare a mixed metal solution; 0.1 mol sodium hydroxide and 0.0068 mol sodium aluminate are dissolved in 100 ml of water to obtain a mixed alkali solution with a concentration of 1.0680 mol / L; 0.0113 mol sodium aluminate is dissolved in 100 ml of water to prepare a sodium aluminate solution with a concentration of 0.1130 mol / L. Under a nitrogen atmosphere of 100 ml / min, the metal solution and the mixed alkali solution are simultaneously added dropwise to the sodium aluminate solution. At the same time, the mixture is stirred at a constant temperature of 80℃ and 600 r / min for 20 min to obtain a precipitate. After aging at room temperature for 24 h, the precipitate is filtered and washed with deionized water until neutral, and then dried in an oven at 70℃ for 24 h to obtain the hydrotalcite precursor. The hydrotalcite-like precursor was calcined in a muffle furnace under air atmosphere at a staged heating rate of 10℃ / min (500℃ for 2 hours, 900℃ for 4 hours). After cooling, it was ground through an 80-mesh sieve to obtain AlO2 with an Al(NO3)3:NaAlO2 ratio of 0:8. -Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0070] (3) Evaluation of oxygen carrier reaction characteristics: The reaction for the chemical chaining of methane to syngas was carried out in a small fixed bed. 1.45g of oxygen carrier was placed in the center of a quartz tube, and quartz wool was plugged at both ends to fix the oxygen carrier. Nitrogen gas was introduced for 10 minutes to purge the air. After the atmosphere furnace was heated to 900℃, the quartz tube was placed in the atmosphere furnace and the temperature was allowed to stabilize. Then, the gas was switched to 100ml / min of methane (10% CH4 / 90% N2). The reaction time for this stage was 27 minutes. The syngas obtained from the reaction was collected in a gas bag, and its composition was analyzed by gas chromatography. The analysis showed that the methane conversion rate was as high as 85.06%, the hydrogen selectivity was as high as 73.41%, and the carbon monoxide selectivity was as high as 76.83%. The steam reforming stage was followed by the methane stage, after which nitrogen gas was introduced for 10 min at a flow rate of 90 ml / min. Then, H₂O was injected into the quartz tube at a flow rate of 0.1 ml / min for 27 min under a nitrogen flow rate of 90 ml / min. The resulting gas was collected in a gas bag and its composition was analyzed. The hydrogen yield was found to be 9.70 mol·h⁻¹. -1 ·kg -1 It has a purity of 100%.

[0071] Comparative Example 3

[0072] Prepare conventional AlO2-free products using the method described in Example 1 - The oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite differs in that in step (1), 0.05 mol nickel nitrate hexahydrate, 0.025 mol ferric nitrate nonahydrate, and 0.025 mol aluminum nitrate are dissolved in 100 ml of deionized water to prepare a metal mixed solution; 0.132 mol sodium hydroxide and 0.066 mol anhydrous sodium carbonate are dissolved in 200 ml of water to obtain an alkaline mixed solution. The metal solution is rapidly poured into the alkaline mixed solution at 500 r / min to obtain a precipitate. After aging at room temperature for 24 h, the precipitate is filtered and washed with deionized water until neutral, and then dried in an oven at 70 °C for 24 h to obtain a hydrotalcite precursor. The hydrotalcite precursor is placed in a muffle furnace and calcined in an air atmosphere at 500 °C for 2 h and 900 °C for 4 h in stages (heating rate 10 °C / min). After cooling, it is ground through an 80-mesh sieve to obtain a product without AlO2. - Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite.

[0073] (3) Evaluation of oxygen carrier reaction characteristics: The reaction for the chemical chain conversion of methane to syngas was carried out in a small fixed bed. 1.45g of oxygen carrier was placed in the center of a quartz tube, and quartz wool was plugged at both ends to fix the oxygen carrier. Nitrogen gas was introduced for 10 minutes to purge the air. After the atmosphere furnace was heated to 900℃, the quartz tube was placed in the atmosphere furnace and the temperature was allowed to stabilize. Then, the gas was switched to 100ml / min of methane (10% CH4 / 90% N2). The reaction time for this stage was 27 minutes. The syngas obtained from the reaction was collected in a gas bag and its composition was analyzed by gas chromatography. The analysis showed that the methane conversion rate was 53.68%, the hydrogen selectivity was as high as 31.10%, and the carbon monoxide selectivity was as high as 68.89%. The steam reforming stage was followed by the methane stage, after which nitrogen gas was introduced for 10 min at a flow rate of 90 ml / min. Then, H₂O was injected into the quartz tube at a flow rate of 0.1 ml / min for 27 min under a nitrogen flow rate of 90 ml / min. The resulting gas was collected in a gas bag and its composition was analyzed. The hydrogen yield was found to be 8.88 mol·h⁻¹. -1 ·kg -1 Its purity is only 70.03%.

[0074] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An AlO2 - The application of intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carriers in the chemical chaining of methane to syngas is characterized by, The AlO2 - The preparation method of the oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite includes the following steps: (1) Under an inert atmosphere, a mixed aqueous solution of nickel nitrate, ferric nitrate, and aluminum nitrate, along with a mixed solution of sodium aluminate and sodium hydroxide, are simultaneously added dropwise to a sodium aluminate solution. After stirring at 60–120 °C, the solution is aged, filtered, washed, and dried to obtain AlO2. - Intercalated Ni-Fe-Al type hydrotalcite precursor; (2) AlO2 - Intercalated Ni-Fe-Al type hydrotalcite precursors were calcined in air at 400–900℃ for 4–8 hours to obtain AlO2. - Oxygen carriers derived from intercalated Ni-Fe-Al type hydrotalcite; The molar ratio of Ni to Al is (2-3):1, and the molar ratio of aluminum nitrate to sodium aluminate is (1-3):

8.

2. The application according to claim 1, characterized in that, The molar ratio of nickel nitrate and ferric nitrate in step (1) is (2-3):1; In step (1), the molar ratio of aluminate ions in the mixed solution of sodium aluminate and sodium hydroxide and the sodium aluminate solution is 3:(3-5).

3. The application according to claim 1, characterized in that, The aging process in step (1) is carried out at room temperature for 12 to 24 hours. The calcination temperature in step (2) is 500–900℃, and the time is 2–6 hours; The heating rate of calcination in step (2) is 2 to 15 °C / min.

4. The application according to claim 1, characterized in that, The molar ratio of cations in the mixed aqueous solution of nickel nitrate, ferric nitrate, and aluminum nitrate in step (1) to cations in the mixed solution of sodium aluminate and sodium hydroxide is (0.72~1):1; In step (1), the total concentration of cations in the mixed aqueous solution of nickel nitrate, ferric nitrate, and aluminum nitrate is 0.1–1 mol / L. In step (1), the total concentration of cations in the mixed solution of sodium aluminate and sodium hydroxide is 0.1–1.5 mol / L. The concentration of the sodium aluminate solution in step (1) is 0.1 to 1.5 mol / L.

5. The application according to claim 1, characterized in that, The stirring speed in step (1) is 500-800 r / min; The stirring time in step (1) is 10 to 25 minutes.

6. The application according to claim 1, characterized in that, After the hydrotalcite precursor described in step (2) is calcined, it still needs to be ground and sieved.

7. The application according to claim 1, characterized in that, The AlO2 - An oxygen carrier derived from intercalated Ni-Fe-Al hydrotalcite is added to a fuel reactor. First, an inert gas is introduced to purge the air from the fuel reactor. Then, the fuel reactor is heated to the reaction temperature. Once the temperature of the fuel reactor stabilizes, gaseous fuel is introduced to react and produce syngas.

8. The application according to claim 7, characterized in that, The gaseous fuel is methane diluted with an inert gas to a volume percentage of 5-25%. The flow rate of the gaseous fuel is 50-150 ml / min, and the introduction time is 20-180 min; The gaseous fuel and AlO2 - The lattice oxygen molar ratio of the intercalated Ni-Fe-Al type hydrotalcite-derived oxygen carrier is (1.2~0.8):1.

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