MOFs (Metal-Organic Frameworks) derived oxygen decoupling oxygen carrier as well as preparation method and application thereof

Abstract

The invention provides an MOFs (Metal-Organic Frameworks) derived oxygen decoupling oxygen carrier as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The general formula of the MOFs derived oxygen decoupling oxygen carrier is AaOb / Fe-MgMOF, A comprises Cu, Co or Mn, a ranges from 0.5 to 2, and b ranges from 1 to 3. The MOFs-derived oxygen decoupling oxygen carrier is prepared by taking Fe-MgMOFs as a carrier and metal oxides (CuO, CoO and Mn2O3) with oxygen decoupling capability as a loading substance and adopting a two-step catalysis method of carrying out an impregnation method after a hydrothermal method, and the preparation method disclosed by the invention has the advantages that active components in the oxygen carrier are highly dispersed, and the oxygen decoupling performance of the catalyst is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to a MOFs-derived oxygen uncoupling oxygen carrier and its preparation method and application. Background Art

[0002] Hydrogen energy has the advantages of large reserves, pollution-free, high unit energy, wide application scenarios, etc. However, the current hydrogen production industry faces problems such as relying on fossil energy technologies and serious carbon emissions. Therefore, the development of green hydrogen production technologies is a current research hotspot, and bioethanol has attracted much attention due to its unique raw material advantages. The methods for applying ethanol reforming to produce hydrogen include steam reforming, partial oxidation reforming, autothermal reforming, dry reforming, plasma reforming, chemical looping reforming, and aqueous phase reforming. Among them, chemical looping reforming has an autothermal function under normal pressure and has broad application prospects due to its advantages such as simple operation, high efficiency, good durability, and environmental friendliness. However, this technology has relatively high requirements for oxygen carriers. Developing and optimizing oxygen carriers is an urgent problem to be solved for realizing the chemical looping steam reforming of bioethanol to produce hydrogen.

[0003] For the chemical looping reforming technology, its oxygen-carrying capacity and reaction activity are difficult to meet the requirements. After multiple cycles, some oxygen carriers have a decrease in oxygen-carrying capacity and reaction activity due to structural changes and loss of active sites, affecting the efficiency and stability of the chemical loop.

[0004] Currently, metal-organic framework (MOFs) derivatives, as a class of emerging materials, inherit the advantages of MOFs due to their adjustable structures and various functions and show great potential in various catalytic reactions. Metal-organic frameworks are a class of crystalline porous materials with a periodic network structure formed by the self-assembly of metal ions or metal clusters and organic ligands. Due to their characteristics of rich metal active sites, high specific surface area, and high porosity, they provide an ideal precursor for preparing high-performance oxygen carriers. However, the performance of single-metal MOFs is mainly determined by the properties of a single metal, and its active centers may not be able to meet the needs of complex reactions.

[0005] In bimetallic metal-organic frameworks (MOFs), synergistic effects such as electronic effects and lattice effects can occur between the two metals, which can provide more active sites, change the reaction path and rate, and improve the catalytic efficiency. However, bimetallic MOFs are sensitive to temperature, humidity, and chemical environment. Some bimetallic MOFs are prone to decomposition of organic ligands at high temperatures, thus destroying the entire framework structure. Bimetallic MOF-derived oxides are products obtained after pyrolysis, calcination, and other treatments. In this process, the organic ligands are decomposed and removed, leaving only the oxide structure composed of metals. Their structure is usually nanoscale metal oxide particles, and these particles may retain some structural characteristics of the MOF precursor, such as a certain degree of porosity. Compared with transition metal oxides obtained by the sol-gel method and impregnation method, MOF derivatives obtained by pyrolysis or calcination have a highly porous structure, so they may provide additional catalytic active sites on the internal pore surface and can even be used as advanced multifunctional materials to decompose ethanol for hydrogen production. Although bimetallic MOF-derived oxides have certain advantages, their oxygen-carrying capacity and reaction activity are still difficult to meet the requirements of chemical looping. After multiple cycles, some oxygen carriers show a decrease in oxygen-carrying capacity and reaction activity due to structural changes and loss of active sites, affecting the efficiency and stability of chemical looping.

[0006] Therefore, it is very important to provide a bimetallic MOF-derived oxygen-decoupled oxygen carrier with high activity and high oxygen-carrying capacity. Summary of the Invention

[0007] The purpose of the present invention is to provide a MOF-derived oxygen-decoupled oxygen carrier, its preparation method and application, to solve the technical problems in the prior art that the oxygen-carrying capacity of the oxygen carrier decreases and the reaction activity decreases, thereby affecting the efficiency and stability of chemical looping.

[0008] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0009] The present invention provides a MOF-derived oxygen-decoupled oxygen carrier, and the general formula of the MOF-derived oxygen-decoupled oxygen carrier is: A a O b / Fe-Mg MOF, where A includes Cu, Co or Mn, a is 0.5 - 2, and b is 1 - 3;

[0010] The A a O b and the mass ratio of the Fe-Mg MOF carrier is 29 - 43:51 - 68.

[0011] The present invention provides a preparation method of the above-mentioned MOF-derived oxygen-decoupled oxygen carrier, including the following steps:

[0012] 1) Mix the water-soluble Fe salt precursor, Mg salt precursor, terephthalic acid ligand, and N,N-dimethylformamide solution, then carry out a hydrothermal reaction, centrifuge and dry to obtain the Fe-Mg MOFs support;

[0013] 2) Dissolve the Fe-Mg MOFs support in a metal salt solution with oxygen decoupling ability to obtain a mixed solution, then add the NaBH4 solution and mix, and then centrifuge and dry to obtain the oxygen carrier precursor;

[0014] 3) Calcinate the oxygen carrier precursor to obtain the MOFs-derived oxygen decoupling oxygen carrier.

[0015] Further, the Fe salt precursor is Fe(NO3)3·9H2O, and the Mg salt precursor is Mg(NO3)2·6H2O;

[0016] The terephthalic acid ligand is C8H6O4.

[0017] Further, the dosage ratio of the Fe salt precursor, Mg salt precursor, terephthalic acid ligand, and N,N-dimethylformamide solution is 16-20 mmol: 16-20 mmol: 16-20 mmol: 180 mL;

[0018] The mass concentration of the N,N-dimethylformamide solution ≥ 99%;

[0019] The dosage ratio of the Fe-Mg MOFs support, the metal salt solution with oxygen decoupling ability, and the NaBH4 solution is 5-15 g: 200 mL: 200 mL;

[0020] The metal in the metal salt solution with oxygen decoupling ability includes Cu, Co, or Mn, and the concentration of the metal salt solution with oxygen decoupling ability is 20-30 mmol / L;

[0021] The mass concentration of the NaBH4 solution is 1-2%.

[0022] Further, in step 1), the mixing is carried out under stirring, the mixing temperature is 15-40 °C, and the mixing time is 10-50 min;

[0023] The temperature of the hydrothermal reaction is 140-180 °C, and the time of the hydrothermal reaction is 6-10 h.

[0024] Further, in step 2), the mixing is carried out under stirring, the stirring time is 30-120 min, and the stirring temperature is 20-40 °C.

[0025] Further, in the steps 1) and 2), the rotation speed of centrifugation is independently 8000 - 12000 r / min, and the time of centrifugation is independently 3 - 7 min.

[0026] Further, in the steps 1) and 2), the drying temperature is independently 90 - 120 °C, and the drying time is independently 10 - 14 h.

[0027] Further, in the step 3), the calcination temperature is 800 - 1000 °C; the calcination time is 1 - 3 h.

[0028] The present invention also provides an application of the MOFs-derived oxygen-carrying carrier in the chemical-looping oxygen-uncoupling steam reforming of bioethanol to produce hydrogen.

[0029] Advantages of the present invention:

[0030] 1) The present invention uses Fe-Mg MOFs as the carrier and metal oxides (CuO, CoO, Mn2O3) with oxygen-uncoupling ability as the loaded substances, and prepares the MOFs-derived oxygen-carrying carrier by a two-step catalytic method of hydrothermal method followed by impregnation method. The preparation method of the present invention highly disperses the active components in the oxygen-carrying carrier. Among them, the existence form of Cu in the oxygen-carrying carrier is CuO, the existence form of Co in the oxygen-carrying carrier is CoO, and the existence form of Mn in the oxygen-carrying carrier is Mn2O3, which improves the oxygen-uncoupling performance of the catalyst. Moreover, the preparation method provided by the present invention is relatively simple, and the raw material usage cost is low;

[0031] 2) The MOFs-derived oxygen-carrying carrier of the present invention can be used for the chemical-looping oxygen-uncoupling steam reforming of bioethanol to produce hydrogen. Description of the drawings

[0032] Figures 1 - 2 It is the transmission electron microscope image of the CuO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 1 of the present invention;

[0033] Figures 3 - 4 It is the transmission electron microscope - elemental surface scan image of the CuO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 1 of the present invention;

[0034] Figure 5 It is the Fe element distribution map of the CuO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 1 of the present invention;

[0035] Figure 6 It is the Mg element distribution map of the CuO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 1 of the present invention;

[0036] Figure 7Cu element distribution map of the CuO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 1 of the present invention;

[0037] Figure 8 X-ray diffraction pattern of the CuO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 1 of the present invention;

[0038] Figures 9 - 10 Transmission electron microscopy image of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 2 of the present invention;

[0039] Figures 11 - 12 Transmission electron microscopy - elemental mapping image of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 2 of the present invention;

[0040] Figure 13 Fe element distribution map of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 2 of the present invention;

[0041] Figure 14 Mg element distribution map of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 2 of the present invention;

[0042] Figure 15 Co element distribution map of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 2 of the present invention;

[0043] Figure 16 X-ray diffraction pattern of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 2 of the present invention;

[0044] Figures 17 - 18 Transmission electron microscopy image of the Mn2O3 / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 3 of the present invention;

[0045] Figures 19 - 20 Transmission electron microscopy - elemental mapping image of the Mn2O3 / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 3 of the present invention;

[0046] Figure 21 Fe element distribution map of the Mn2O3 / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 3 of the present invention;

[0047] Figure 22 Mg element distribution map of the Mn2O3 / Fe-Mg MOF-derived oxygen-carrying carrier prepared in Example 3 of the present invention;

[0048] Figure 23Element distribution map of Mn in the Mn2O3 / Fe-Mg MOF-derived oxygen carrier for oxygen decoupling prepared in Example 3 of the present invention;

[0049] Figure 24 X-ray diffraction pattern of the Mn2O3 / Fe-Mg MOF-derived oxygen carrier for oxygen decoupling prepared in Example 3 of the present invention;

[0050] Figure 25 Volume distribution diagrams of H2, CO2, CO, and CH4 mixed gases of the MOF-derived oxygen carriers for oxygen decoupling prepared in Examples 1 to 3 at different temperatures;

[0051] Figure 26 Thermogravimetric cycling test curve of the MOF-derived oxygen carriers for oxygen decoupling prepared in Examples 1 to 3. Detailed implementation mode

[0052] The present invention provides a MOF-derived oxygen carrier for oxygen decoupling, and the general formula of the MOF-derived oxygen carrier for oxygen decoupling is: A a O b / Fe-Mg MOF, where A includes Cu, Co, or Mn, a is 0.5 to 2, preferably 0.6 to 1.8, and more preferably 0.8 to 1.5; b is 1 to 3, preferably 1.2 to 2.8, and more preferably 1.5 to 2.5;

[0053] The a O b and the mass ratio of the Fe-Mg MOF carrier is 29 to 43:51 to 68, preferably 30 to 41:52 to 66, and more preferably 32 to 40:55 to 65.

[0054] In the present invention, when A a O b / Fe-Mg MOF is CuO / Fe-Mg MOF, the mass ratio of CuO to the Fe-Mg MOF carrier is preferably 31 to 32:67 to 68; when A a O b / Fe-Mg MOF is CoO / Fe-Mg MOF, the mass ratio of CoO to the Fe-Mg MOF carrier is preferably 42 to 43:56 to 57; when A a O b / Fe-Mg MOF is Mn2O3 / Fe-Mg MOF, the mass ratio of Mn2O3 to the Fe-Mg MOF carrier is preferably 38 to 39:60 to 61.

[0055] The present invention provides a preparation method of the MOF-derived oxygen carrier for oxygen decoupling, including the following steps:

[0056] 1) Mix a water-soluble Fe salt precursor, a Mg salt precursor, a terephthalic acid ligand, and an N,N-dimethylformamide solution, then conduct a hydrothermal reaction, centrifuge, and dry to obtain an Fe-Mg MOFs support;

[0057] 2) Dissolve the Fe-Mg MOFs support in a metal salt solution with oxygen decoupling ability to obtain a mixed solution, then add a NaBH4 solution and mix, and then centrifuge and dry to obtain an oxygen carrier precursor;

[0058] 3) Calcinate the oxygen carrier precursor to obtain a MOFs-derived oxygen decoupling oxygen carrier.

[0059] In the present invention, the Fe salt precursor is preferably Fe(NO3)3·9H2O, and the Mg salt precursor is preferably Mg(NO3)2·6H2O;

[0060] The terephthalic acid ligand is preferably C8H6O.

[0061] In the present invention, the dosage ratio of the Fe salt precursor, the Mg salt precursor, the terephthalic acid ligand, and the N,N-dimethylformamide solution is 16-20 mmol: 16-20 mmol: 16-20 mmol: 180 mL, preferably 17-19 mmol: 17-19 mmol: 17-19 mmol: 180 mL, and more preferably 18 mmol: 18 mmol: 18 mmol: 180 mL;

[0062] The mass concentration of the N,N-dimethylformamide solution is ≥99%, preferably ≥99.3%, and more preferably ≥99.5%;

[0063] The dosage ratio of the Fe-Mg MOFs support, the metal salt solution with oxygen decoupling ability, and the NaBH4 solution is 5-15 g: 200 mL: 200 mL, preferably 7-12 g: 200 mL: 200 mL, and more preferably 10 g: 200 mL: 200 mL;

[0064] The metal in the metal salt solution with oxygen decoupling ability includes Cu, Co, or Mn, preferably Cu or Co, and more preferably Cu;

[0065] The concentration of the metal salt solution with oxygen decoupling ability is 20-30 mmol / L, preferably 22-28 mmol / L, and more preferably 24-26 mmol / L;

[0066] The mass concentration of the NaBH4 solution is 1-2%, preferably 1.2-1.8%, and more preferably 1.4-1.6%.

[0067] In the present invention, in step 1), the mixing is carried out with stirring. The mixing temperature is 15 to 40 °C, preferably 20 to 35 °C, and more preferably 25 to 30 °C; the mixing time is 10 to 50 min, preferably 15 to 45 min, and more preferably 20 to 40 min.

[0068] The temperature of the hydrothermal reaction is 140 to 180 °C, preferably 145 to 175 °C, and more preferably 150 to 170 °C; the time of the hydrothermal reaction is 6 to 10 h, preferably 7 to 9 h, and more preferably 8 h.

[0069] In the present invention, in step 2), the mixing is carried out with stirring. The stirring time is 30 to 120 min, preferably 35 to 110 min, and more preferably 40 to 100 min; the stirring temperature is 20 to 40 °C, preferably 25 to 35 °C, and more preferably 30 °C.

[0070] In the present invention, in steps 1) and 2), the centrifugation speed is independently 8000 to 12000 r / min, preferably 8500 to 11500 r / min, and more preferably 9000 to 11000 r / min; the centrifugation time is independently 3 to 7 min, preferably 4 to 6 min, and more preferably 5 min.

[0071] In the present invention, in steps 1) and 2), the drying temperature is independently 90 to 120 °C, preferably 95 to 115 °C, and more preferably 100 to 110 °C; the drying time is independently 10 to 14 h, preferably 11 to 13 h, and more preferably 12 h.

[0072] In the present invention, in step 3), the calcination temperature is 800 to 1000 °C, preferably 850 to 950 °C, and more preferably 900 °C; the calcination time is 1 to 3 h, preferably 1.5 to 2.5 h, and more preferably 2 h.

[0073] The present invention also provides an application of the MOFs-derived oxygen-carrying carrier in the chemical-looping oxygen-uncoupling steam reforming of bioethanol for hydrogen production.

[0074] In the present invention, the chemical-looping reforming hydrogen production technology is mainly based on the principle of chemical-looping combustion, and the production of hydrogen is realized through the alternating operation of two reactors. In the fuel reactor, the solid oxygen carrier releases lattice oxygen to react with the fuel, oxidizing the fuel into syngas; at the same time, the oxygen carrier is reduced to a metal oxide or metal in a lower valence state, and the reduced oxygen carrier is transported to the air reactor to be oxidized and regenerated in contact with air. The oxygen in the air oxidizes the oxygen carrier in the lower valence state into a higher valence state, restoring its lattice oxygen content to prepare for the next cycle. For chemical-looping oxygen decoupling steam reforming hydrogen production, the solid oxygen carrier can release molecular oxygen as a gasifying agent to reduce the cost required for the gasification reaction; at the same time, the metal ions of the oxygen carrier play a catalytic role in the gasification process, accelerating the reaction process. Therefore, the research and development of the oxygen carrier is the key to chemical-looping reforming hydrogen production.

[0075] In the present invention, copper oxide, cobalt oxide, and manganese oxide have the ability of oxygen decoupling at a certain temperature. Applying these three oxides to the oxygen carrier can achieve chemical-looping oxygen decoupling reforming hydrogen production. The uniform pore shape and size in MOFs allow substrate molecules of specific shapes and sizes to enter, thus realizing the selectivity of the reaction; the pores in MOFs enable the reaction to occur not only on the material surface but also at the internal active sites; therefore, loading elements with oxygen decoupling ability onto MOFs can achieve chemical-looping steam reforming hydrogen production of bioethanol.

[0076] In the present invention, the specific steps for the application of the above-mentioned MOF-derived oxygen decoupling oxygen carrier in chemical-looping oxygen decoupling steam reforming hydrogen production of bioethanol include: putting a certain amount of oxygen carrier into the fixed-bed reactor bed layer, introducing N2 to exclude the air in the bed layer, and maintaining an inert atmosphere in the bed layer; setting the reaction temperature at 500 - 900 °C, introducing a mixture of ethanol and water. The ethanol and water mixture is first gasified in a preheater and then mixed with N2 and enters the reactor to react with the oxygen carrier. After cooling, a mixed gas such as H2, CO2, CO, and CH4 is obtained.

[0077] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0078] Cu(NO3)2·xH2O, Fe(NO3)3·9H2O, Mg(NO3)2·6H2O, Co(NO3)2·6H2O, Mn(NO3)2·4H2O, terephthalic acid ligand C8H6O4, ethanol, deionized water, and N,N-dimethylformamide used in the embodiments of the present invention are all of analytical purity.

[0079] Example 1

[0080] 18 mmol of Fe(NO3)3·9H2O, 18 mmol of Mg(NO3)2·6H2O and 18 mmol of terephthalic acid C8H6O4 were poured into a beaker, 180 mL of N,N-dimethylformamide solution was added, and the mixture was stirred evenly with a glass rod. Then it was placed on a magnetic stirrer and stirred at 20 °C for 15 min to dissolve the organic ligand, thus preparing an Fe-Mg mixed solution. Subsequently, the Fe-Mg mixed solution was poured into a polytetrafluoroethylene liner and then placed in a hydrothermal reaction chamber, and hydrothermal reaction was carried out under the conditions of 160 °C and 8 h. After the reaction, a solid-liquid mixture was obtained. The solid-liquid mixture was centrifuged at a rotation speed of 10,000 r / / min for 5 min. After removing the supernatant, the solid product was placed in a blast drying oven at 100 °C for drying for 12 h to obtain an Fe-Mg MOFs support;

[0081] Cu(NO3)2·xH2O was configured into a copper salt solution with a concentration of 25 mmol / L. Then the Fe-Mg MOFs support was dissolved in the copper salt solution and stirred at room temperature for 30 min to obtain a mixed solution. Subsequently, a NaBH4 solution with a mass concentration of 1.23% was added to the mixed solution and continuously stirred for 2 h to obtain a solid-liquid mixture. Among them, the dosage ratio of the Fe-Mg MOFs support, the metal salt solution with oxygen decoupling ability and the NaBH4 solution was 10 g: 200 mL: 200 mL. The solid-liquid mixture was centrifuged at a rotation speed of 10,000 r / / min for 5 min. After removing the supernatant, the solid product was placed in a blast drying oven at 100 °C for drying for 12 h to obtain a CuO / Fe-Mg MOF oxygen carrier precursor;

[0082] The oxygen carrier precursor was heated to 1000 °C at a rate of 10 °C / min for high-temperature calcination for 2 h. After the calcination, a CuO / Fe-Mg MOF-derived oxygen decoupling oxygen carrier was obtained.

[0083] The MOF-derived oxygen decoupling oxygen carrier prepared in Example 1 was tested, and the test results are as Figures 1 - 8 shown. From Figures 1 - 2 it can be seen that a large number of rod-like substances are stacked together; from Figures 3 - 4 it can be seen that the oxygen carrier is in a rod-like structure; from Figures 5 - 7 it can be seen that Fe, Mg, Cu, and O elements are evenly distributed on the rod-like structure; Figure 8 it can be seen that the phases of the CuO / Fe-Mg MOF-derived oxygen decoupling oxygen carrier are CuFe2O4 and MgFe2O4 respectively, and sharp diffraction peaks appear at 2θ = 18.32, 30.17, 35.53, 43.17, 57.09, 62.68 °, showing high crystallinity.

[0084] Example 2

[0085] Compared with Example 1, the difference is that in Example 2, Co(NO3)2·6H2O is configured into a cobalt salt solution with a concentration of 25 mmol / L, and the temperature for calcining the oxygen carrier precursor is 800 °C;

[0086] The preparation method is the same as that of Example 1 to obtain a CoO / Fe-Mg MOF-derived oxygen decoupling oxygen carrier.

[0087] The MOF-derived oxygen decoupling oxygen carrier prepared in Example 2 was tested, and the test results are as Figures 9 - 16 shown. It can be seen from Figures 9 - 10 that a large number of rod-like substances are stacked together; it can be seen from Figures 11 - 12 that the oxygen carrier is in a rod-like structure; it can be seen from Figures 13 - 15 that Fe, Mg, Co, and O elements are evenly distributed on the rod-like structure; it can be seen from Figure 16 that the phases of the CoO / Fe-Mg MOF-derived oxygen decoupling oxygen carrier are CoFe2O4 and MgFe2O4 respectively, and medium-intensity diffraction peaks appear at 2θ = 30.06, 37.16, 43.17, 53.58, 62.68°, and the crystallinity is relatively low.

[0088] Example 3

[0089] Compared with Example 1, the difference is that in Example 3, Mn(NO3)2·4H2O is configured into a manganese salt solution with a concentration of 25 mmol / L, and the temperature for calcining the oxygen carrier precursor is 900 °C;

[0090] The preparation method is the same as that of Example 1 to obtain a Mn2O3 / Fe-Mg MOF-derived oxygen decoupling oxygen carrier.

[0091] The MOF-derived oxygen decoupling oxygen carrier prepared in Example 3 was tested, and the test results are as Figures 17 - 24 shown. It can be seen from Figures 17 - 18 that a large number of rod-like substances are stacked together; it can be seen from Figures 19 - 20 that the oxygen carrier is in a rod-like structure; it can be seen from Figures 21 - 23 that Fe, Mg, and O elements are evenly distributed on the rod-like structure, and the distribution of Mn elements is relatively loose; it can be seen from Figure 24 that the phases of the MnO / Fe-Mg MOF-derived oxygen decoupling oxygen carrier are (Mn 0.983 Fe 0.017 )2O3 and MgFe2O4 respectively, and sharp diffraction peaks appear at 2θ = 23.13, 32.93, 35.66, 49.31, 53.25, 64.04°, and it has a high crystallinity.

[0092] The MOF-derived oxygen-carrying carriers prepared in Examples 1 to 3 were used for chemical-looping oxygen uncoupling steam reforming of bioethanol to produce hydrogen. The specific method includes: 0.3 g of CuO / Fe-Mg MOF-derived oxygen-carrying carrier, CoO / Fe-Mg MOF-derived oxygen-carrying carrier, and Mn2O3 / Fe-Mg MOF-derived oxygen-carrying carrier were respectively placed in the fixed-bed reactor bed for reaction. Before the reaction, N2 was introduced to remove the air in the bed and maintain an inert atmosphere in the bed. The reaction temperatures were set at 500-900 °C. A mixture of ethanol and water was introduced. The ethanol and water mixture was first vaporized in a preheater and then mixed with N2 and introduced into the reactor to react with the oxygen-carrying carrier. After cooling, a mixed gas of H2, CO2, CO, and CH4 was obtained. The test results are as Figures 25 - 26 shown. As Figure 25 can be seen, with the increase in temperature, the hydrogen volume increased significantly. Among the three oxygen-carrying carriers, the CuO / Fe-Mg MOF-derived oxygen-carrying carrier showed the best hydrogen production effect at 900 °C. The optimal hydrogen production temperature of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier was also 900 °C, and the optimal hydrogen production temperature of the Mn2O3 / Fe-Mg MOF-derived oxygen-carrying carrier was 800 °C. As Figure 26 can be seen, the oxygen release temperature of the CuO / Fe-Mg MOF-derived oxygen-carrying carrier was 800-1000 °C, the oxygen release temperature of the CoO / Fe-Mg MOF-derived oxygen-carrying carrier was 800-1000 °C, and the oxygen release temperature of the Mn2O3 / Fe-Mg MOF-derived oxygen-carrying carrier was 700-1000 °C, further indicating that the prepared MOF-derived oxygen-carrying carrier can produce more hydrogen at the oxygen release temperature.

[0093] As can be seen from the above examples, the present invention provides a MOFs-derived oxygen-carrying carrier, its preparation method and application. The general formula of the MOFs-derived oxygen-carrying carrier is: A a O b / Fe-MgMOF, where A includes Cu, Co or Mn, a is 0.5-2, and b is 1-3. The present invention uses Fe-MgMOFs as the carrier and metal oxides (CuO, CoO, Mn2O3) with oxygen uncoupling ability as the loading substances, and prepares the MOFs-derived oxygen-carrying carrier by a two-step catalytic method of hydrothermal method followed by impregnation method. The preparation method of the present invention highly disperses the active components in the oxygen-carrying carrier and improves the oxygen uncoupling performance of the catalyst.

[0094] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A MOFs-derived oxygen-decoupling oxygen carrier, characterized in that, The general formula of the MOF-derived oxygen decoupling oxygen carrier is: A a O b / Fe-Mg MOF, where A includes Cu, Co or Mn, a is 0.5 to 2, and b is 1 to 3; The said A a O b and the mass ratio of the Fe-Mg MOF support is 29 to 43:51 to 68.

2. The preparation method of the MOFs-derived oxygen decoupling oxygen carrier according to claim 1, characterized in that, It includes the following steps: 1) Mix a water-soluble Fe salt precursor, a Mg salt precursor, a terephthalic acid ligand, and an N,N-dimethylformamide solution, then carry out a hydrothermal reaction, centrifuge, and dry to obtain an Fe-Mg MOFs support; 2) Dissolve the Fe-Mg MOFs support in a metal salt solution with oxygen decoupling ability to obtain a mixed solution, then add a NaBH4 solution and mix, and then centrifuge and dry to obtain an oxygen carrier precursor; 3) Calcinate the oxygen carrier precursor to obtain a MOFs-derived oxygen decoupling oxygen carrier.

3. The preparation method of the MOFs-derived oxygen-carrying oxygen-decoupling carrier according to claim 2, wherein The Fe salt precursor is Fe(NO3)3·9H2O, and the Mg salt precursor is Mg(NO3)2·6H2O; The terephthalic acid ligand is C8H6O4.

4. The preparation method of the MOF-derived oxygen-decoupled oxygen carrier according to claim 2 or 3, characterized in that, The dosage ratio of the Fe salt precursor, the Mg salt precursor, the terephthalic acid ligand, and the N,N-dimethylformamide solution is 16-20 mmol: 16-20 mmol: 16-20 mmol: 180 mL; The mass concentration of the N,N-dimethylformamide solution ≥99%; The dosage ratio of the Fe-Mg MOFs support, the metal salt solution with oxygen decoupling ability, and the NaBH4 solution is 5-15 g: 200 mL: 200 mL; The metal in the metal salt solution with oxygen decoupling ability includes Cu, Co, or Mn, and the concentration of the metal salt solution with oxygen decoupling ability is 20-30 mmol / L; The mass concentration of the NaBH4 solution is 1-2%.

5. The preparation method of the MOFs-derived oxygen-decoupling oxygen carrier according to claim 4, characterized in that, In the step 1), the mixing is carried out with stirring, the mixing temperature is 15-40 °C, and the mixing time is 10-50 min; The temperature of the hydrothermal reaction is 140-180 °C, and the time of the hydrothermal reaction is 6-10 h.

6. The preparation method of the MOFs-derived oxygen decoupling oxygen carrier according to claim 5, characterized in that, In the step 2), the mixing is carried out with stirring, the stirring time is 30-120 min, and the stirring temperature is 20-40 °C.

7. The preparation method of the MOFs-derived oxygen-carrier with oxygen decoupling according to claim 6, characterized in that, In the steps 1) and 2), the centrifugation speed is independently 8000-12000 r / min, and the centrifugation time is independently 3-7 min.

8. The preparation method of the MOFs-derived oxygen-decoupled oxygen carrier according to claim 7, characterized in that, In the steps 1) and 2), the drying temperature is independently 90-120 °C, and the drying time is independently 10-14 h.

9. The preparation method of the MOFs-derived oxygen-decoupling oxygen carrier according to claim 8, wherein, In the step 3), the calcination temperature is 800-1000 °C; the calcination time is 1-3 h.

10. Application of the MOFs-derived oxygen decoupling oxygen carrier according to claim 1 in the chemical-looping oxygen decoupling steam reforming of bioethanol for hydrogen production.

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