Patent Application
20240116771
This application claims priority from the Chinese patent application 2022112199792 filed Oct. 8, 2022, the content of which is incorporated herein in the entirety by reference.
The present disclosure belongs to the technical field of chemical-looping oxygen carriers, and particularly relates to a perovskite oxygen carrier for hydrogen production by chemical-looping reforming of methane and a preparation method thereof.
In order to solve increasingly serious environmental problems, countries around the world have reached a consensus of developing low-carbon economies and developing renewable energy. In recent years, despite the rapid development of therenewable energy, the renewable energy still hardly replaces fossil energy as main energy resource in a short term. Hydrogen is an attractive energy carrier due to its high energy density (143 MJ/kg), clean, free of pollution (combustion products are water), and can be used for transportation stationary power generation and ammonia synthesis for energy storage. Thus, it is of great significance for developing a novel economic and pollution-free technology for hydrogen production economic, and studies on hydrogen production in many countries are also correspondingly increasing rapidly. Existing hydrogen production technologies may be divided into hydrogen production from fossil fuel and hydrogen production from renewable resources, in which hydrogen production from fossil fuel is currently the main hydrogen production manner. Hydrogen production from fossil fuel includes natural gas steam reforming, partial oxidation, auto thermal reforming, plasma reforming, aqueous-phase reforming, high-temperature deposition and other methods. Methane steam reforming (reaction 4) is the most widely used hydrogen production technology in the industry at present. However, the main reaction is a strong endothermic process (reaction 1), which is high in energy consumption. Heat is supplied by combusting natural gas outside pipes (reaction 3), and generated CO2 and air are mixed, leading to high CO2 capture costs. In addition, such a process has many product purifications (reaction 2) and separation operation units, resulting in high energy consumption and low product separation integration level.
Steam reforming: CH4+H2O=CO+3H2, ΔH(T=800° C.)=225 kJ (1)
Water-gas shift: CO+H2O=H2+CO2, ΔH(T=800° C.)=−34 kJ (2)
Combustion heat supply: CH4+O2=CO2+2H2O, ΔH(T=800° C.)=−802 kJ (3)
Overall reaction: xCH4+yH2O+(x−0.5y)O2→(2x+y)H2+xCO2, ΔH(T=800° C.)=0 kJ (4)
In order to solve the above problems, improve energy conversion efficiency and reduce production costs, researchers are constantly researching and developing novel thermal-chemical hydrogen production processes. Reaction paths are designed again based on a chemical-looping concept, the overall reaction is decomposed into two or more sub-reactions performed in different spaces or time, substances and energy are transferred in a system by cyclically utilizing oxidation and reduction processes of a solid oxygen carrier (usually metal oxide), separate conversion of raw materials and in-situ separation of products are achieved, and therefore the problems of heat supply, separation and carbon capture are integrally solved. Due to inherent advantages of system simplification and/or carbon capture, hydrogen can be produced from the system at high process efficiency, and carbon dioxide can be captured. Thus, the technology for hydrogen production by chemical-looping reforming of methane has attracted extensive attention and research.
The technology for hydrogen production by chemical-looping reforming of methane couples the preparation of syngas by partial oxidation of methane by lattice oxygen and hydrogen production by thermal pyrolysis of water. As shown in
As a medium for oxygen atoms and heat transfer, the oxygen carrier circulates between different reactors, which is a key to the whole process of hydrogen production by chemical-looping reforming of methane. Selecting the oxygen carrier is very important in hydrogen production by chemical-looping reforming of methane, and the oxygen carrier needs to have high oxygen storage capacity, sufficient oxygen migration capacity and high reaction activity. In alternate oxidation and reduction reactions, perovskite materials have good structural reversibility and stable reaction properties, which are excellent oxygen carrier materials. Wherein, an ABO3 perovskite oxygen carrier is one of the most widely studied oxygen carrier materials as it has good electron and oxygen ion migration properties, and sites A and sites B can be replaced with multiple cations. When radii of doping ions at the sites A and the sites B meet a certain condition, AA′BB′O6 double perovskite can be formed. Compared with ABO3 perovskite, the AA′BB′O6 double perovskite usually has higher oxygen vacancy concentration due to two B-site transition metal ions with different valence alternation capacities in a structure. Thus, the double perovskite shows higher electron and oxygen ion migration capacity than that of the ABO3 perovskite, which is widely studied in fields such as oxygen ion permeable membranes, fuel cells and electrocatalysis, and has also been used for a chemical-looping field in recent years (CN102441396A and CN102441396B). However, a double perovskite oxygen carrier has problems such as unsatisfied syngas selectivity in methane reduction step and low hydrogen yield in steam re-oxidation step caused by too high activity of lattice oxygen, or carbon deposition at a methane reduction stage and low hydrogen purity at a steam re-oxidation stage caused by too low activity of the lattice oxygen. Thus, an ion doping manner is usually used for further adjusting and controlling properties of the lattice oxygen of the double perovskite oxygen carrier, so as to improve the syngas selectivity and the hydrogen yield. However, a crystalline phase structure of the perovskite is easily damaged when the concentration of the doping ions is high, affecting cycling stability of the oxygen carrier. An A3B′B″B′″O9 medium-entropy perovskite oxygen carrier is established by selecting proper doping ions, and an entropy of the structure is increased to improve chaos of atoms in the structure, thereby reducing enthalpy of formation of the oxygen carrier and improving cycling stability of the structure of the oxygen carrier. However, pure perovskite phases are hardly prepared as the medium-entropy perovskite oxygen carrier contains four or more metal ions at the same time. Preparation of the perovskite oxygen carrier mainly includes a coprecipitation method, a high-temperature solid-phase reaction method, a sol-gel method, a wet chemistry method and other methods. Application and popularization of the oxygen carrier are limited as the existing preparation methods have the defect that pure-phase perovskite cannot be prepared, or that the preparation methods are complex, high in preparation cost and not beneficial to scaled-up production.
The present disclosure provides a medium-entropy perovskite oxygen carrier and a preparation method and application thereof to solve the technical problems that an ABO3 perovskite oxygen carrier has low methane reaction activity or low syngas selectivity, which is common in an existing partial chemical-looping methane partial oxidation reaction, leading to nonideal syngas yield and nonideal cycling stability of a structure of an AA′BB′O6 double perovskite oxygen carrier, and that a preparation method of A3B′B″B′″O9 medium-entropy perovskite is complex, which is not conducive to scale-up preparation or hardly prepares pure-phase perovskite. In the present disclosure, an aqueous solution is prepared from metallic nitrate serving as a raw material by a simple coprecipitation method; a coprecipitation reaction is performed with aqueous ammonia solution, a sodium hydroxide aqueous solution or a sodium carbonate aqueous solution as a precipitant by adjusting a pH value of the solution, to obtain a hydroxide precursor; and a La3CoMnAlO9 medium-entropy perovskite oxygen carrier is obtained after stirring, standing, washing, drying and calcining. The oxygen carrier is used for a system of hydrogen production by chemical-looping reforming of methane in a fluidized bed, so that methane is efficiently converted at a methane reduction stage and hydrogen at high purity is prepared at a steam re-oxidation stage.
To solve the above technical problems, the present disclosure is achieved by the following technical solutions:
According to one aspect of the present disclosure, a preparation method of a medium-entropy perovskite oxygen carrier is provided, including the following steps:
Furthermore, the metallic nitrate is La(NO3)3·6H2O, Co(NO3)3·6H2O, a Mn(NO3)2 aqueous solution and Al(NO3)3·9H2O. An ionic molar ratio of La to Co to Mn to Al is 3:1:1:1.
Furthermore, a mixing manner of the precipitant and the metallic nitrate solution is one of forward dropwise adding, cocurrent or reverse dropwise adding.
According to another aspect of the present disclosure, a medium-entropy perovskite oxygen carrier for hydrogen production by chemical-looping reforming of methane is provided, which is prepared by the above preparation method.
According to yet another aspect of the present disclosure, application of the above medium-entropy perovskite oxygen carrier in a reaction of chemical-looping reforming of methane to hydrogen in a fluidized bed is provided. At a reduction stage, the oxygen carrier reacts with the methane under an oxygen-free condition, the methane is partially oxidized by lattice oxygen in the oxygen carrier to generate syngas, and meanwhile the oxygen carrier is reduced. At an oxidation stage, the oxygen carrier reacts with steam, to obtain part of the lattice oxygen, and meanwhile hydrogen is generated. At an air combustion stage, the oxygen carrier is further oxidized by air to be cyclically regenerated, so that the oxygen carrier restores to a structure before reacting with the methane.
Furthermore, reaction temperatures of the reduction stage and the oxidation stage are 700° C. to 1100° C.
Furthermore, mixed gas of methane and nitrogen is introduced at the reduction stage, wherein a volume percentage of the methane is 5% to 100%, and with benchmarking against methane, a volume space velocity of the reaction is controlled to be 120 h−1 to 12000 h−1.
Furthermore, mixed gas of steam and nitrogen is firstly introduced at the oxidation stage, wherein a volume percentage of the steam is 5% to 100%, and with benchmarking against steam, a volume space velocity of the reaction is controlled to be 120 h−1 to 12000 h−1.
The present disclosure has the following beneficial effects:
The present disclosure is further described in detail below through specific embodiments, and the following embodiments can allow those skilled in the art to understand the present disclosure more comprehensively, instead of limiting it in any manner.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, aqueous ammonia solution was dropwise added into the nitrate solution with stirring by a forward dropwise adding method, to obtain a hydroxide precursor, an addition amount of the aqueous ammonia solution was adjusted, and a final pH value of a mixed solution was controlled at 10; stirring continued for 0.5 hour; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours, to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9;
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 meshes to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, a 2 mol/L sodium hydroxide aqueous solution was dropwise added into the nitrate solution with stirring by a forward dropwise adding method, to obtain a sodium hydroxide precursor, an addition amount of the sodium hydroxide aqueous solution was adjusted, and a final pH value of a mixed solution was controlled at 10; stirring continued for 0.5 hour; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionised water, to obtain a nitrate solution;
step 2, a 2 mol/L sodium carbonate aqueous solution was dropwise added into the nitrate solution with stirring by a forward dropwise adding method to obtain a hydroxide precursor, an additional amount of the sodium carbonate aqueous solution was adjusted, and a final pH value of a mixed solution was controlled at 10; stirring continued for 0.5 hours; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, a mixed solution (a 2 mol/L NaOH aqueous solution and aqueous ammonia solution were mixed at an equal volume) of the sodium hydroxide aqueous solution and the aqueous ammonia solution was dropwise added into the nitrate solution with stirring by a forward dropwise adding method, to obtain a hydroxide precursor, an additional amount of the sodium hydroxide aqueous solution was adjusted, and a final pH value of a mixed solution was controlled at 10; stirring continued for 0.5 hours; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, a 2 mol/L mixed solution (wherein concentrations of sodium hydroxide and sodium carbonate were 1 mol/L respectively) of the sodium hydroxide and the sodium carbonate was dropwise added into the nitrate solution with stirring by a forward dropwise adding method to obtain a hydroxide precursor, an additional amount of the sodium hydroxide aqueous solution was adjusted, and a final pH value of a mixed solution was controlled at 10; stirring continued for 0.5 hours; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, a mixed solution (a 2 mol/L sodium carbonate aqueous solution and aqueous ammonia solution were mixed at an equal volume) of the sodium carbonate aqueous solution and the aqueous ammonia solution was dropwise added into the nitrate solution with stirring by a forward dropwise adding method, to obtain a hydroxide precursor, an additional amount of the sodium hydroxide aqueous solution was adjusted, and a final pH value of a mixed solution was controlled at 10; stirring continued for 0.5 hours; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, the nitrate solution was slowly dropwise added into 80 mL of a 2 mol/L mixed solution (wherein concentrations of sodium hydroxide and sodium carbonate were 1 mol/L respectively) of the sodium hydroxide and the sodium carbonate with stirring by a reverse dropwise adding method, to obtain a hydroxide precursor, finally, an additional amount of the mixed solution of the sodium hydroxide and the sodium carbonate was adjusted, and a final pH value of a mixed solution was controlled at 10; stirring continued for 0.5 hours; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, a 2 mol/L mixed solution (wherein concentrations of sodium hydroxide and sodium carbonate were 1 mol/L respectively) of the sodium hydroxide and the sodium carbonate was dropwise added into the nitrate solution with stirring by a forward dropwise adding method to obtain a hydroxide precursor, an additional amount of the sodium hydroxide aqueous solution was adjusted, and a final pH value of a mixed solution was controlled at 9.5; stirring continued for 0.5 hours; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at a constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
Step 1, 12.9900 parts by mass of La(NO3)3·6H2O, 2.9105 parts by mass of Co(NO3)3·6H2O, 3.5790 parts by mass of an Mn(NO3)2 aqueous solution (mass fraction is 50%) and 3.7513 parts by mass of Al(NO3)3·9H2O were weighed and dissolved in deionized water, to obtain a nitrate solution;
step 2, a 2 mol/L mixed solution (wherein concentrations of sodium hydroxide and sodium carbonate were 1 mol/L respectively) of the sodium hydroxide and the sodium carbonate was dropwise added into the nitrate solution with stirring by a forward dropwise adding method to obtain a hydroxide precursor, an additional amount of the sodium hydroxide aqueous solution was adjusted, and a final pH value of a mixed solution was controlled at 10.5; stirring continued for 0.5 hours; and then standing at room temperature was performed for 2 hours;
step 3, the obtained mixed solution was filtered and washed, and dried at constant temperature of 80° C. for 12 hours; and precursor powder was roasted in an air atmosphere at 1300° C. for 4 hours to obtain a medium-entropy perovskite oxygen carrier, wherein a molecular formula of the oxygen carrier was La3CoMnAlO9; and
step 4, La3CoMnAlO9 solid powder was sieved, and a granular oxygen carrier of 200 to 140 meshes was taken.
10.5 mL of the La3CoMnAlO9 medium-entropy perovskite oxygen carrier prepared in Embodiment 5 was weighed and added to a monotube micro fluidized bed reactor with an internal diameter of a reaction tube of 20 mm. An experiment was performed at 700° C. and constant pressure. After temperature rose to 700° C. in an N2 atmosphere, (1) mixed gas (120 mL/min 20% CH4/He-300 mL/min N2) of methane and nitrogen with total flow of 400 m/min was introduced for 10 minutes, a volume of the methane was 5% of a total volume of the mixed gas, tail gas within 20 minutes (methane stage for 10 minutes+nitrogen purging for 20 minutes) was collected by a gas bag, and an average composition of the tail gas was analyzed; (2) nitrogen at 300 mL/min continued to be used for purging for 5 minutes; (3) mixed gas (21 mL/min H2O(g)-399 mL/min N2) of steam and nitrogen with total flow of 420 mL/min was introduced for 15 minutes, a volume of the steam was 5% of the total volume of the gas, tail gas within 25 minutes (steam stage for 15 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and a composition of the tail gas was analyzed by gas chromatography; (4) nitrogen at 399 mL/min continued to be used for purging for 5 minutes; (5) air at 420 mL/min was used for oxidation for 10 minutes; and (6) nitrogen at 300 mL/min was used for continuous purging for 15 minutes. Reaction activities of the oxygen carriers in the above embodiment are all an average activity of a corresponding reaction stage; a volume space velocity of the reaction is 120 h−1 with benchmarking against a reactant, namely the methane, and the volume space velocity of the response is 120 h−1 with benchmarking against the steam.
2.4 mL of the La3CoMnAlO9 medium-entropy perovskite oxygen carrier prepared in Embodiment 5 was weighed and added to a monotube micro fluidized bed reactor with an internal diameter of a reaction tube of 20 mm. An experiment was performed at 850° C. and constant pressure. After temperature rose to 850° C. in an N2 atmosphere, (1) mixed gas (180 mL/min 20% CH4/Ar-180 mL/min N2) of methane and nitrogen with total flow of 360 m/min was introduced for 5 minutes, a volume of the methane was 10% of a total volume of the mixed gas, tail gas within 15 minutes (methane stage for 5 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and an average composition of the tail gas was analyzed; (2) nitrogen at 180 mL/min continued to be used for purging for 5 minutes; (3) mixed gas (36 mL/min H2O(g)-324 mL/min N2) of steam and nitrogen with total flow of 360 mL/min was introduced for 10 minutes, a volume of the steam was 10% of the total volume of the gas, tail gas within 20 minutes (steam oxidation stage for 10 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and a composition of the tail gas was analyzed by gas chromatography; (4) nitrogen at 324 mL/min continued to be used for purging for 5 minutes; (5) air at 360 mL/min was used for oxidation for 10 minutes; and (6) nitrogen at 180 mL/min was used for continuous purging for 10 minutes. Reaction activities of the oxygen carriers in the above embodiment are all an average activity of a corresponding reaction stage; a volume space velocity of the reaction is 900 h−1 with benchmarking against a reactant, namely the methane, and the volume space velocity of the response is 900 h−1 with benchmarking against the steam.
1.5 mL of the La3CoMnAlO9 medium-entropy perovskite oxygen carrier prepared in Embodiment 5 was weighed and added to a monotube micro fluidized bed reactor with an internal diameter of a reaction tube of 20 mm, and an experiment was performed at 1100° C. and constant pressure. After temperature rose to 1100° C. in an N2 atmosphere, (1) pure methane with total flow of 300 mL/min was introduced for 2 minutes, tail gas within 12 minutes (methane stage for 2 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and an average composition of the tail gas was analyzed; (2) nitrogen at 300 mL/min was used for purging for 5 minutes; (3) pure steam with flow of 300 mL/min was introduced for 3 minutes, tail gas within 13 minutes (steam stage for 3 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and a composition of the tail gas was analyzed by gas chromatography; (4) nitrogen at 300 mL/min was used for continuous purging for 5 minutes; (5) air at 300 mL/min was used for oxidation for 10 minutes; and (6) nitrogen at 300 mL/min was used for continuous purging for 5 minutes. Reaction activities of the oxygen carriers in the above embodiment are all an average activity of a corresponding reaction stage, a volume space velocity of the reaction is 12000 h−1 with benchmarking against a reactant, namely the methane, and the volume space velocity of the reaction is 12000 h−1 with benchmarking against the steam.
2.4 mL of the La3CoMnAlO9 medium-entropy perovskite oxygen carrier prepared in Embodiment 5 was weighed and added to a monotube micro fluidized bed reactor with an internal diameter of a reaction tube of 20 mm, and an experiment was performed at 850° C. and constant pressure. After temperature rose to 850° C. in an N2 atmosphere, (1) mixed gas (180 mL/min 20% CH4/Ar-180 mL/min N2) of methane and nitrogen with total flow of 360 m/min was introduced for 5 minutes, a volume of the methane was 10% of a total volume of the mixed gas, tail gas within 15 minutes (methane stage for 5 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and an average composition of the tail gas was analyzed; (2) nitrogen at 180 mL/min continued to be used for purging for 5 minutes; (3) mixed gas (36 mL/min H2O(g)-324 mL/min N2) of steam and nitrogen with total flow of 360 mL/min was introduced for 10 minutes, a volume of the steam was 10% of the total volume of the gas, tail gas within 20 minutes (steam stage for 10 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and a composition of the tail gas was analyzed by gas chromatography; (4) nitrogen at 324 mL/min continued to be used for purging for 5 minutes; (5) air at 360 mL/min was used for oxidation for 10 minutes; and (6) nitrogen at 180 mL/min was used for continuous purging for 10 minutes. One complete cycle was completed by the above steps (1) to (6), and the test was performed for 50 consecutive cycles. Reaction activities of the oxygen carriers in the above embodiment are all an average activity of a corresponding reaction stage, a volume space velocity of the reaction is 900 h−1 with benchmarking against a reactant, namely the methane, and the volume space velocity of the reaction is 900 h−1 with benchmarking against the steam.
2.4 mL of the La3CoMnAlO9 medium-entropy perovskite oxygen carrier prepared in Embodiment 5 was weighed and added to a fixed bed reactor with an internal diameter of a reaction tube of 20 mm, and an experiment was performed at 850° C. and constant pressure. After temperature rose to 850° C. in an N2 atmosphere, (1) mixed gas (180 mL/min 20% CH4/Ar-180 mL/min N2) of methane and nitrogen with total flow of 360 mL/min was introduced for 5 minutes, a volume of the methane was 10% of a total volume of the mixed gas, tail gas within 15 minutes (methane stage for 5 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and an average composition of the tail gas was analyzed; (2) nitrogen at 180 mL/min continued to be used for purging for 5 minutes; (3) mixed gas (36 mL/min H2O(g)-324 mL/min N2) of steam and nitrogen with total flow of 360 mL/min was introduced for 10 minutes, a volume of the steam was 10% of the total volume of the gas, tail gas within 20 minutes (steam stage for 10 minutes+nitrogen purging for 10 minutes) was collected by a gas bag, and a composition of the tail gas was analyzed by gas chromatography; (4) nitrogen at 324 mL/min continued to be used for purging for 5 minutes; (5) air at 360 mL/min was used for oxidation for 10 minutes; and (6) nitrogen at 180 mL/min was used for continuous purging for 10 minutes. Reaction activities of the oxygen carriers in the above embodiment are all an average activity of a corresponding reaction stage, a volume space velocity of the reaction is 900 h−1 with benchmarking against a reactant, namely the methane, and the volume space velocity of the reaction is 900 h−1 with benchmarking against the steam.
Results of the above embodiments were discussed as follows:
Table 1 Properties of chemical-looping reforming reaction of methane to hydrogen of La3CoMnAlO9 medium-entropy perovskite oxygen carriers at different reaction temperatures and space velocities
Although the preferred embodiments of the present disclosure are described above with reference to the drawings, the present disclosure is not limited to the above specific implementations, and the above specific implementations are only schematic instead of restrictive. Those ordinarily skilled in the art may also make many forms of specific transformations without departing from the purpose of the present disclosure and the scope protected by the claims under the inspiration of the present disclosure, and these transformations all belong to the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022112199792 | Oct 2022 | CN | national |
