A carbon deposition-resistant perovskite oxygen carrier for methane chemical chaining to synthesis gas, and its preparation method and application

Abstract

The present invention discloses a carbon-deposition-resistant perovskite oxygen carrier for methane chemical chaining to produce synthesis gas, as well as its preparation method and application. The preparation method of the carbon-deposition-resistant perovskite oxygen carrier comprises the following steps: (1) dissolving lanthanum nitrate and ferric nitrate in water, adding glycine as a sol-gelling agent, and adjusting the pH value of the solution to 1.4-1.85 to obtain a precursor solution; (2) heating and stirring the precursor solution to evaporate the water to form an oily wet gel, and drying and activating it to obtain an activated precursor; (3) calcining the activated precursor at 500-900°C for 2-6 hours to obtain a LaFeO3 oxygen carrier, namely the carbon-deposition-resistant perovskite oxygen carrier for methane chemical chaining to produce synthesis gas. The method of the present invention can increase the specific surface area, oxygen carrying capacity and catalytic properties of the oxygen carrier, can convert methane into H2 and CO, and reduce carbon deposition.

Description

Technical Field

[0001] The present invention belongs to the technical field of oxygen carriers, and in particular relates to a carbon deposition-resistant perovskite oxygen carrier for producing synthesis gas from methane chemical chaining, and a preparation method and application thereof. Background Art

[0002] Methane chemical looping gasification (CLG) is a new gasification technology based on chemical looping combustion (CLC). The development of CLG technology has provided a broader application platform for CLC. During the chemical looping gasification process, methane reacts with lattice oxygen, an oxygen carrier, in the fuel reactor (FR) to produce CO and H2 in a 2:1 volume ratio. This upgrades CLC technology, originally limited to carbon capture, to an industrialized process capable of producing syngas and cascading its application. Compared to traditional technologies, this eliminates the need for expensive air separation units, significantly reducing costs and improving fuel conversion rates.

[0003] To improve energy efficiency, the air reactor (AR) portion of methane chemical looping gasification technology has been optimized. The resulting methane chemical looping steam reforming (CL-SMR) and methane chemical looping dry reforming (CL-DMR) technologies aim to replace air with steam or carbon dioxide as the oxygen source in the air reactor, cracking it to produce hydrogen or carbon monoxide. These two technologies increase the yield of combustible gas during the reaction and overcome the problems encountered in traditional steam reforming or dry reforming. However, due to their low oxidizing properties, steam and carbon dioxide cannot completely regenerate the oxygen carrier, resulting in lower reaction efficiency in the later stages of the AR reactor. Furthermore, the lower reaction efficiency in the AR reactor results in lower gas production than in the FR process, meaning that the AR process can only be performed as an auxiliary reaction. Finally, carbon deposits are generated due to methane cracking in the FR process, resulting in high levels of hydrogen or carbon monoxide impurities in the AR reactor, which incurs additional costs for gas purification.

[0004] The current reaction temperature of the FR stage of the methane chemical chain is generally between 750°C and 950°C. As an exothermic reaction, methane cracking is more likely to occur at higher temperatures. The resulting carbon deposition is one of the key issues in the methane chemical chain. Therefore, suppressing the formation of carbon deposition in the methane chemical chain can achieve the following goals: (1) generating an ideal synthesis gas with a volume ratio of H2 / CO of 2; (2) protecting the active sites of the oxygen carrier; and (3) preventing the oxygen carrier from being separated from the active metal and the carrier metal due to carbon deposition growth. At the same time, suppressing the formation of carbon deposition in the FR stage will help promote the development of technologies such as CL-SMR and CL-DRM that use AR reactors to promote the value-added utilization of chemical chains. To address this issue, methane CLG technology is currently focusing on improving reaction performance while overcoming carbon deposition resistance.

[0005] The sol-gel method for preparing oxygen carriers is currently the mainstream preparation method, and its preparation technology has many advantages, including uniform distribution of components and small particle size. In the preparation process of multi-metal oxygen carriers, the sol-gel method can achieve uniformity and high thermal stability. In addition, during the preparation of oxygen carriers, active metals can be melt-bonded with inert carriers to form new alloy oxide phases, thereby strengthening the interaction between metal carriers. This feature means that the sol-gel method can help oxygen carriers provide a wide range of possibilities in catalytic cooperative oxidation. However, the boundaries of controlling the ratio of precursors and pH in the sol-gel method on the promotion and inhibition of oxygen carriers are currently unclear. Summary of the Invention

[0006] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a method for preparing a carbon deposition-resistant perovskite oxygen carrier for use in methane chemical chaining to produce synthesis gas.

[0007] Another object of the present invention is to provide a carbon deposition-resistant perovskite oxygen carrier prepared by the method for producing synthesis gas from methane chemical chaining.

[0008] Another object of the present invention is to provide an application of the carbon deposition resistant perovskite oxygen carrier for producing synthesis gas from methane chemical chaining.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing a carbon deposition-resistant perovskite oxygen carrier for methane chemical chaining to synthesis gas comprises the following steps:

[0011] (1) dissolving lanthanum nitrate and ferric nitrate in water, then adding glycine as a sol-gelling agent, and adjusting the pH value of the solution to 1.4-1.85 to obtain a precursor solution; wherein the molar ratio of glycine to the metal cation in the precursor solution is (1-2):1;

[0012] (2) placing the precursor solution obtained in step (1) at 80±5°C and stirring to evaporate the water to form an oily wet gel, and further drying to obtain a dry gel; then placing the dry gel at 200±5°C for activation to obtain an activated precursor;

[0013] (3) calcining the activated precursor obtained in step (1) at 500-900° C. for 2-6 hours, cooling, grinding and sieving to obtain a LaFeO3 oxygen carrier, i.e., the carbon deposition-resistant perovskite oxygen carrier for methane chemical chaining to synthesis gas.

[0014] The molar ratio of lanthanum nitrate to ferric nitrate in step (1) is preferably 1:1.

[0015] In step (1), the lanthanum nitrate is preferably ferric nitrate nonahydrate (Fe(NO3)3·9H2O), and the lanthanum nitrate is preferably lanthanum nitrate hexahydrate (La(NO3)3·6H2O).

[0016] The amount of water used in step (1) is preferably calculated based on a ratio of 0.0025 mol of ferric nitrate per milliliter of water.

[0017] The water described in step (1) is preferably deionized water or distilled water.

[0018] The glycine in step (1) reacts with the metal cations (Fe 3+ and La 3+ ) is preferably in a molar ratio of 1.5:1.

[0019] The pH value described in step (1) is preferably 1.5.

[0020] The evaporation in step (2) is preferably carried out in an oil bath.

[0021] The stirring time in step (2) is 10 to 12 hours, preferably 10 hours.

[0022] The drying conditions described in step (2) are: drying in an oven at 105° C. for 24 h.

[0023] The activation time in step (2) is 10 to 30 minutes, preferably 20 minutes.

[0024] In step (3), the heating rate during calcination is 10°C / min.

[0025] The calcination in step (3) is preferably carried out at 500° C. for 2 h and then at 900° C. for 4 h.

[0026] The sieving in step (3) is preferably through a 60-mesh sieve.

[0027] A carbon deposition-resistant perovskite oxygen carrier for methane chemical chaining to produce synthesis gas is prepared by any of the methods described above.

[0028] Application of the carbon deposition resistant perovskite oxygen carrier for methane chemical looping to produce synthesis gas in methane chemical looping to produce synthesis gas.

[0029] The application of the carbon-resistant perovskite oxygen carrier for methane chemical chain synthesis gas production in methane chemical chain synthesis gas production is to pass diluted methane into a fuel reactor, pass air into an air reactor, and then use the above-mentioned carbon-resistant perovskite oxygen carrier to carry out oxidation and reduction reactions to produce synthesis gas (H2 and CO); preferably, it is achieved by the following steps: adding the above-mentioned carbon-resistant perovskite oxygen carrier to the fuel reactor, first passing nitrogen to purge the air in the fuel reactor, and then heating the fuel reactor to 750℃~950℃ (preferably 900℃), after the temperature of the fuel reactor stabilizes, passing diluted methane, and then carrying out oxidation-reduction reaction. After the reaction is completed, nitrogen is passed to purge the methane in the reactor, and air is passed after the temperature of the air reactor stabilizes, to produce synthesis gas H2 and CO.

[0030] The flow rate of the nitrogen is preferably 100 ml / min, and the introduction time (nitrogen purge) is preferably 10 min.

[0031] The diluted methane is methane diluted with nitrogen to a volume percentage of 10%.

[0032] The flow rate of the diluted methane is preferably 100 ml / min, and the introduction time is preferably 45 min.

[0033] The molar ratio of methane to the active metal in the anti-carbon deposition perovskite oxygen carrier is 0.4-0.8:1.

[0034] The air introduction time is 45 minutes.

[0035] The present invention introduces diluted methane into a fuel reactor alone, introduces air into the reactor, and prepares synthesis gas through oxidation and reduction reactions under the action of a lanthanum iron perovskite oxygen carrier with a high specific surface area and a porous structure.

[0036] The present invention has the following advantages and effects compared to the prior art:

[0037] (1) The present invention adopts a sol-gel method to prepare a lanthanum iron perovskite oxygen carrier material (general formula: LaFeO3) with a high specific surface area and porous self-supporting structure: glycine is used as a sol-gel agent, and active metal iron and inert metal lanthanum are introduced as metal precursors. The obtained oxygen carrier is a perovskite-type oxygen carrier with a lanthanum iron ratio of 1. The oxygen carrier prepared by this preparation method has the characteristics of high specific surface area and low grain size. At the same time, the oxygen carrier has good oxygen transmission capacity, synthesis gas selectivity and anti-carbon deposition ability.

[0038] (2) The lanthanum iron perovskite type oxygen carrier material in the present invention is modified by introducing glycine to improve the specific surface area, oxygen carrying capacity and catalytic properties of the oxygen carrier, and can realize the conversion of methane into H2 and CO and reduce the formation of carbon deposits under certain reaction conditions. By regulating the reaction conditions, the H2 / CO ratio in the synthesis gas can be regulated to about 2.0 to 3.0, which is conducive to the preparation of synthesis gas according to actual needs.

[0039] (3) The present invention is based on the glycine sol-gel method. By regulating the ratio of the sol-gel precursors and the pH of the precursors to regulate the active metal sites and the cation migration rate, it can increase the specific surface area of ​​the oxygen carrier and reduce the grain size under certain conditions, and improve the conversion efficiency and selectivity, thereby achieving the purpose of controlling the reaction performance and inhibiting the formation of carbon deposits.

[0040] (4) The oxygen carrier prepared by the present invention has a strong anti-carbon deposition performance and can maintain high selectivity (94.90%) of H2 and high selectivity of CO at a high conversion rate.

[0041] (5) The oxygen carrier in the present invention is prepared by a two-step method. The preparation conditions are simple and easy to control, the cost is low, and it can achieve the effects of high specific surface area and high reaction activity, which is conducive to large-scale application in methane chemical loop gasification. Compared with the existing lanthanum iron perovskite oxygen carrier and preparation method, the dry gel activation process is added, so that it has a higher specific surface area and better metal particle dispersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a graph showing the conversion efficiency of the oxygen carrier prepared when the glycine ratio in Example 1 is 1 for methane chemical chaining to produce synthesis gas.

[0043] Figure 2 1. The X-ray diffraction patterns of the oxygen carrier prepared when the glycine ratio is 1.5 in Example 2 before and after the reaction.

[0044] Figure 3 This is a graph showing the conversion efficiency of methane chemical looping to synthesis gas using the oxygen carrier obtained when the glycine ratio in Example 2 is 1.5.

[0045] Figure 4 This is a graph showing the conversion efficiency of the oxygen carrier prepared when the glycine ratio in Comparative Example 1 is 0.5 for methane chemical chaining to synthesis gas. DETAILED DESCRIPTION

[0046] The present invention will be described in further detail below in conjunction with the examples, but embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. The test methods in the following examples where specific experimental conditions are not specified are generally based on conventional experimental conditions. Unless otherwise specified, the reagents and raw materials used in the present invention can be obtained commercially.

[0047] Experimental steps in the present invention:

[0048] (1) The CLG reaction is carried out in a fixed bed reaction, which includes gas cylinders (nitrogen, methane, air), a gas conversion device, a gas mass flow meter, a tubular atmosphere furnace, a quartz tube, and a gas collection bag.

[0049] (2) Fuel reactor stage: 2 g of oxygen carrier was placed in the quartz tube and fixed to the middle of the tube with quartz wool. Before starting the reaction, 100 ml / min of nitrogen (99.999%) was first introduced into the quartz tube and maintained for 10 minutes to exhaust the impurity gas in the quartz tube. The quartz tube was then placed in a tubular atmosphere furnace that had been preheated to the specified temperature. The nitrogen gas was maintained stable before the furnace body temperature was re-regulated to the specified temperature. After the furnace temperature was stabilized, the gas was replaced with methane (10% CH4) reaction gas and gas collection began. The gas collection bag was replaced every 3 minutes, and the reaction time was 45 minutes. After the reaction was completed, the quartz tube was removed and the gas was replaced with nitrogen until it cooled down. Finally, the FR reaction gas bag was transferred to a gas chromatograph for measurement, i.e., an Agilent 6820 gas chromatograph (GC) produced by Agilent was used for gas composition and content analysis, using an HP-PLOT / Q column and N2 (99.999%) carrier gas.

[0050] (3) Air reactor stage: After the tube furnace is evacuated under nitrogen atmosphere, the tube furnace is placed in the air reactor. After the furnace temperature is constant, the gas is replaced with air and maintained for 45 minutes. After the reaction is completed, the quartz tube is removed and the gas is replaced with nitrogen until the temperature is cooled down.

[0051] Example 1

[0052] (1) Prepare the precursor solution: Dissolve 0.05 mol of iron nitrate nine hydrate Fe(NO3)3·9H2O and 0.05 mol of lanthanum nitrate hexahydrate La(NO3)3·6H2O in a 500 ml beaker filled with 200 ml of distilled water. After complete dissolution, add the metal cations (Fe 3+ 、La 3+ ) glycine was added in an equimolar ratio, and its pH was 1.85.

[0053] (2) Preparing a precursor: The precursor solution prepared in step (1) is then placed in an 80°C oil bath and stirred for 10 hours to evaporate the water into an oily state, thereby forming a wet gel; the precursor is then dried in a 105°C forced air drying oven for 24 hours to form a dry gel precursor, and then placed in a 200°C forced air drying oven for 20 minutes to activate the precursor.

[0054] (3) Preparation of oxygen carrier: The solid mixture of the above precursors was poured into a crucible and calcined at 500°C for 2 h and 900°C for 4 h (heating rate 10°C / min). After cooling, the mixture was ground through a 60-mesh sieve to obtain a LaFeO3 oxygen carrier with a particle size of less than 300 μm.

[0055] (4) Evaluation of the reaction characteristics of the oxygen carrier: The methane chemical chaining reaction to syngas was carried out on a small fixed bed apparatus. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2 g of LaFeO3 oxygen carrier was weighed and placed in the center of a quartz tube. Quartz wool was plugged at both ends of the oxygen carrier to fix it. Nitrogen was introduced into the quartz tube at a gas flow rate of 100 ml / min for 10 minutes. After the tube furnace was heated to 900°C, the quartz tube was placed in it and the temperature was allowed to stabilize. Then, the gas was switched to methane (10% (v / v) CH4, 100 ml / min) (CH4 was diluted to 10% (v / v) with nitrogen, the same below). In one chemical chaining cycle, the reaction time of the fuel reactor stage was 45 minutes. The syngas obtained by the reaction was collected by a gas collection bag after cooling, and its composition was analyzed by gas chromatography. After analysis, the methane conversion efficiency in the synthesis gas reached 93.72%, the hydrogen selectivity reached 94.90%, and the carbon monoxide selectivity reached 82.60%. At this time, the carbon deposit ratio was 26.10% ( Figure 1 ), where the carbon deposit ratio is calculated using the following formula (X C , %):

[0056]

[0057] Where n CH4,in represents the molar amount of methane gas introduced into the tube furnace, n CH4,out represents the molar amount of methane gas after the reaction, n CO,out represents the molar amount of carbon monoxide gas after the reaction, n CO2,out Represents the molar amount of carbon dioxide gas after the reaction.

[0058] Example 2

[0059] The LaFeO3 oxygen carrier was prepared by the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nine hydrate, Fe(NO3)3·9H2O, and 0.05 mol of lanthanum nitrate hexahydrate, La(NO3)3·6H2O, were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 1.50:1, and the pH was 1.5. The specific surface area analysis results of the prepared oxygen carrier are shown in Table 1, and the X-ray diffraction patterns of the oxygen carrier before and after the reaction are shown in Table 1. Figure 2 shown.

[0060] Evaluation of oxygen carrier reaction characteristics: The methane chemical chain reaction to synthesis gas is carried out on a small fixed bed device. First, the oxygen carrier is ground and passed through a 60-mesh sieve. Then, 2g of LaFeO3 oxygen carrier is weighed in the center of the quartz tube, and quartz wool is plugged at both ends of the oxygen carrier to fix it. Nitrogen is introduced into the quartz tube at a gas flow rate of 100ml / min for 10 minutes. When the tubular furnace is heated to 900°C, the quartz tube is placed in it and the temperature is waited for to stabilize. Then the gas is switched to methane (10% (v / v) CH4, 100ml / min). In a chemical chain cycle, the reaction time of the fuel reactor stage is 45min. The synthesis gas obtained by the reaction is collected by a gas collection bag after cooling, and its composition is analyzed by gas chromatography. After analysis, the methane conversion efficiency in the synthesis gas reached 95.79%, the hydrogen selectivity reached 94.90%, and the carbon monoxide selectivity reached 82.60%. At this time, the carbon deposit ratio was 20.10% ( Figure 3 ).

[0061] Table 1 Specific surface area analysis of oxygen carriers prepared at a glycine ratio of 1.5

[0062]

[0063] Example 3

[0064] The LaFeO3 oxygen carrier was prepared according to the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O and 0.05 mol of lanthanum nitrate hexahydrate La(NO3)3·6H2O were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 2.00:1, and its pH was 1.4.

[0065] Evaluation of oxygen carrier reaction characteristics: The methane chemical looping reaction to syngas was conducted in a small fixed-bed apparatus. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2g of LaFeO3 oxygen carrier was weighed and placed in the center of a quartz tube. Quartz wool was inserted at both ends to secure the oxygen carrier. Nitrogen gas was introduced into the quartz tube at a flow rate of 100ml / min for 10 minutes. After the tube furnace was heated to 900°C, the quartz tube was placed inside and allowed to stabilize. The gas flow was then switched to methane (10% CH4, 100ml / min). The reaction time in the fuel reactor stage of a chemical loop was 45 minutes. After cooling, the resulting syngas was collected in a gas collection bag and analyzed for composition by gas chromatography. Analysis revealed a methane conversion efficiency of 85.83%, a hydrogen selectivity of 85.95%, and a carbon monoxide selectivity of 71.20%. The carbon deposit fraction was 39.95%.

[0066] Comparative Example 1

[0067] (1) Preparation of precursor solution:

[0068] The LaFeO3 oxygen carrier was prepared according to the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O and 0.05 mol of lanthanum nitrate hexahydrate La(NO3)3·6H2O were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 0.50:1, and its pH was 2.0.

[0069] (2) Evaluation of oxygen carrier reaction characteristics: The methane chemical chaining reaction to syngas was carried out on a small fixed bed device. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2 g of LaFeO3 oxygen carrier was weighed in the center of the quartz tube and quartz wool was plugged at both ends of the oxygen carrier to fix it. Nitrogen was introduced into the quartz tube at a gas flow rate of 100 ml / min for 10 minutes. After the tube furnace was heated to 900 ° C, the quartz tube was placed in it and the temperature was waited for to stabilize. Then the gas was switched to methane (10% CH4, 100 ml / min). In one chemical chaining cycle, the reaction time of the fuel reactor stage was 45 minutes. The syngas obtained by the reaction was collected by a gas collection bag after cooling, and its composition was analyzed by gas chromatography. After analysis, the methane conversion efficiency in the syngas was 50.37%, the hydrogen selectivity was 78.33%, the carbon monoxide selectivity was 61.22%, and the carbon deposit ratio at this time was 50.10% ( Figure 4 ).

[0070] Comparative Example 2

[0071] The LaFeO3 oxygen carrier was prepared according to the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O and 0.05 mol of lanthanum nitrate hexahydrate La(NO3)3·6H2O were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 2.50:1, and its pH was 1.3.

[0072] Evaluation of oxygen carrier reaction characteristics: The methane chemical looping reaction to syngas was conducted in a small fixed-bed apparatus. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2g of LaFeO3 oxygen carrier was weighed and placed in the center of a quartz tube. Quartz wool was inserted at both ends to secure the oxygen carrier. Nitrogen gas was introduced into the quartz tube at a flow rate of 100ml / min for 10 minutes. After the tube furnace was heated to 900°C, the quartz tube was placed inside and allowed to stabilize. The gas flow was then switched to methane (10% CH4, 100ml / min). The reaction time in the fuel reactor stage of a chemical looping cycle was 45 minutes. After cooling, the resulting syngas was collected in a gas collection bag and analyzed for composition by gas chromatography. Analysis revealed a methane conversion efficiency of 88.24%, a hydrogen selectivity of 84.17%, and a carbon monoxide selectivity of 60.76%. The carbon deposit fraction was 48.62%.

[0073] Comparative Example 3

[0074] The LaFeO3 oxygen carrier was prepared according to the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O and 0.05 mol of lanthanum nitrate hexahydrate La(NO3)3·6H2O were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 1.50:1, and then ammonium carbonate was added to adjust the pH of the precursor solution to 3.5.

[0075] Evaluation of oxygen carrier reaction characteristics: The methane chemical looping reaction to syngas was conducted in a small fixed-bed apparatus. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2g of LaFeO3 oxygen carrier was weighed and placed in the center of a quartz tube. Quartz wool was inserted at both ends to secure the oxygen carrier. Nitrogen gas was introduced into the quartz tube at a flow rate of 100ml / min for 10 minutes. After the tube furnace was heated to 900°C, the quartz tube was placed inside and the temperature stabilized. The gas flow was then switched to methane (10% CH4, 100ml / min). The reaction time in the fuel reactor stage of a chemical looping cycle was 45 minutes. After cooling, the resulting syngas was collected in a gas collection bag and analyzed for composition by gas chromatography. Analysis revealed a methane conversion efficiency of 90.00%, a hydrogen selectivity of 89.93%, and a carbon monoxide selectivity of 64.81%. The carbon deposit fraction was 42.59%.

[0076] Comparative Example 4

[0077] The LaFeO3 oxygen carrier was prepared according to the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nonahydrate Fe(NO3)3·9H2O and 0.05 mol of lanthanum nitrate hexahydrate La(NO3)3·6H2O were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 1.50:1, and then ammonium carbonate was added to adjust the pH of the precursor solution to 5.5.

[0078] Evaluation of oxygen carrier reaction characteristics: The methane chemical looping reaction to syngas was conducted in a small fixed-bed apparatus. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2g of LaFeO3 oxygen carrier was weighed and placed in the center of a quartz tube. Quartz wool was inserted at both ends to secure the oxygen carrier. Nitrogen gas was introduced into the quartz tube at a flow rate of 100ml / min for 10 minutes. After the tube furnace was heated to 900°C, the quartz tube was placed inside and the temperature stabilized. The gas flow was then switched to methane (10% CH4, 100ml / min). The reaction time in the fuel reactor stage of a chemical looping cycle was 45 minutes. After cooling, the resulting syngas was collected in a gas collection bag and analyzed for composition by gas chromatography. Analysis revealed a methane conversion efficiency of 64.59%, a hydrogen selectivity of 82.91%, and a carbon monoxide selectivity of 46.41%. The carbon deposit fraction was 44.88%.

[0079] Comparative Example 5

[0080] The LaFeO3 oxygen carrier was prepared according to the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nine hydrate, Fe(NO3)3·9H2O, and 0.05 mol of lanthanum nitrate hexahydrate, La(NO3)3·6H2O, were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 1.50:1, and then ammonium carbonate was added to adjust the pH of the precursor solution to 7.5.

[0081] Evaluation of oxygen carrier reaction characteristics: The methane chemical looping reaction to syngas was conducted in a small fixed-bed apparatus. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2g of LaFeO3 oxygen carrier was weighed and placed in the center of a quartz tube. Quartz wool was inserted at both ends to secure the oxygen carrier. Nitrogen gas was introduced into the quartz tube at a flow rate of 100ml / min for 10 minutes. After the tube furnace was heated to 900°C, the quartz tube was placed inside and the temperature stabilized. The gas flow was then switched to methane (10% CH4, 100ml / min). The reaction time in the fuel reactor stage of a chemical loop was 45 minutes. After cooling, the resulting syngas was collected in a gas collection bag and analyzed for composition by gas chromatography. Analysis revealed a methane conversion efficiency of 64.21%, a hydrogen selectivity of 82.67%, and a carbon monoxide selectivity of 58.40%. The carbon deposit fraction was 49.10%.

[0082] Comparative Example 6

[0083] The LaFeO3 oxygen carrier was prepared according to the method of Example 1, with the only difference being that in step (1), 0.05 mol of ferric nitrate nine hydrate, Fe(NO3)3·9H2O, and 0.05 mol of lanthanum nitrate hexahydrate, La(NO3)3·6H2O, were dissolved in a 500 ml beaker containing 200 ml of distilled water. After complete dissolution, glycine was added at a molar ratio of glycine to metal cation of 1.50:1, and then ammonium carbonate was added to adjust the pH of the precursor solution to 9.5.

[0084] Evaluation of oxygen carrier reaction characteristics: The methane chemical looping reaction to syngas was conducted in a small fixed-bed apparatus. First, the oxygen carrier was ground and passed through a 60-mesh sieve. Then, 2g of LaFeO3 oxygen carrier was weighed and placed in the center of a quartz tube. Quartz wool was inserted at both ends to secure the oxygen carrier. Nitrogen gas was introduced into the quartz tube at a flow rate of 100ml / min for 10 minutes. After the tube furnace was heated to 900°C, the quartz tube was placed inside and allowed to stabilize. The gas flow was then switched to methane (10% CH4, 100ml / min). The reaction time in the fuel reactor stage of a chemical looping cycle was 45 minutes. After cooling, the resulting syngas was collected in a gas collection bag and analyzed for composition by gas chromatography. Analysis revealed a methane conversion efficiency of 54.31%, a hydrogen selectivity of 84.88%, and a carbon monoxide selectivity of 53.70%. The carbon deposit fraction was 55.01%.

[0085] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a carbon deposition-resistant perovskite oxygen carrier for methane chemical chaining to synthesis gas, characterized in that: The steps include: (1) Dissolving lanthanum nitrate and ferric nitrate in water, then adding glycine as a sol-gelling agent, and adjusting the pH value of the solution to 1.4-1.85 to obtain a precursor solution; wherein the molar ratio of glycine to the metal cation in the precursor solution is 1.5:1; (2) The precursor solution obtained in step (1) is placed at 80±5°C and stirred to evaporate the water to form an oily wet gel, and then dried to obtain a dry gel; the dry gel is then placed at 200±5°C for activation for 10 to 30 minutes to obtain an activated precursor; (3) The activated precursor obtained in step (1) is first calcined at 500°C for 2 h, then calcined at 900°C for 4 h, cooled, ground and sieved to obtain a LaFeO3 oxygen carrier, i.e., the carbon deposition-resistant perovskite oxygen carrier for methane chemical chaining to synthesis gas; The molar ratio of lanthanum nitrate to ferric nitrate in step (1) is 1:

1.

2. The method according to claim 1, wherein: The pH value described in step (1) is 1.

5.

3. The method according to claim 1, wherein: The stirring time in step (2) is 10 to 12 hours; The drying conditions described in step (2) are: drying in an oven at 105°C for 24 hours; The sieving in step (3) is through a 60-mesh sieve.

4. A carbon deposition-resistant perovskite oxygen carrier for methane chemical chaining to synthesis gas, characterized by: It is prepared by the method according to any one of claims 1 to 3.

5. Use of the carbon deposition resistant perovskite oxygen carrier for methane chemical looping to produce synthesis gas according to claim 4 in methane chemical looping to produce synthesis gas.

6. The use according to claim 5, characterized in that: The diluted methane is introduced into the fuel reactor, and the air is introduced into the air reactor, and then the anti-carbon deposition perovskite oxygen carrier is used to perform oxidation and reduction reactions to produce synthesis gas H2 and CO.

7. The use according to claim 6, characterized in that: The application is achieved through the following steps: adding an anti-carbon deposition perovskite oxygen carrier to a fuel reactor, first introducing nitrogen to purge the air in the fuel reactor, then heating the fuel reactor to 750°C to 950°C, and after the temperature of the fuel reactor stabilizes, introducing diluted methane to carry out an oxidation-reduction reaction. After the reaction is completed, introducing nitrogen to purge the methane in the reactor, and introducing air after the temperature of the air reactor stabilizes to produce synthesis gas H2 and CO.

8. The use according to claim 6 or 7, characterized in that: The diluted methane is methane diluted with nitrogen to a volume percentage of 10%; The molar ratio of the diluted methane to the active metal in the anti-carbon deposition perovskite oxygen carrier is 0.4-0.8:

1.

9. The use according to claim 7, characterized in that: The flow rate of the diluted methane is 100 ml / min, and the introduction time is 45 min; The air introduction time is 45 minutes; The flow rate of the nitrogen gas is 100 ml / min, and the introduction time is 10 min.

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