A microtubular monolithic oxygen carrier, its preparation method and application

Abstract

This invention provides a method for preparing a microtube monolithic oxygen carrier, comprising the following steps: First, a metal oxide is uniformly mixed with a binder, solvent, and dispersant to obtain a slurry; second, the slurry and a first curing agent are simultaneously added to a porous mold and extruded to obtain a first product; the first product is placed in a second curing agent to complete a phase transformation process, and then dried and shaped to obtain a second product; finally, the second product undergoes preliminary calcination and high-temperature calcination to obtain the microtube monolithic oxygen carrier. The monolithic oxygen carrier prepared by this invention has abundant axial and radial hierarchical pore structures, enabling simultaneous achievement of low bed pressure drop and low heat and mass transfer resistance. The oxygen carrier exhibits high reactivity, strong resistance to sintering and carbon deposition, and can be used in processes such as chemical looping combustion, reforming, or hydrogen production of gaseous fuels in fixed-bed reactors. The oxygen carrier structure is adjustable, has wide applicability to raw materials, and a simple preparation process, allowing for large-scale preparation and possessing broad prospects for promotion and application.

Description

Technical Field

[0001] This invention belongs to the field of energy and chemical engineering, specifically relating to an integral oxygen carrier with a microtubular structure and its preparation method, as well as the application of the aforementioned integral oxygen carrier with a microtubular structure. Background Technology

[0002] Chemical looping redox technology decouples the oxygen release and oxygen gain processes of the oxygen carrier, and features internal product separation. It is widely used in CO2 separation and capture, fuel reforming and hydrogen production.

[0003] Oxygen carriers and reactors are crucial for ensuring the efficient and stable operation of chemical looping processes, and therefore have attracted much attention. Currently, the high cost associated with efficient and stable oxygen carriers is a key factor limiting the commercialization of chemical looping processes; oxygen carrier wear increases both raw material and operating costs. Fixed-bed reactors, due to the absence of wear on the oxygen carrier particles and their simple structure and ease of operation and control, hold great commercial potential. However, fixed-bed reactors face a conflict between pressure drop and heat and mass transfer: large-diameter particles can achieve low bed pressure drop in fixed-bed reactors, but this increases the internal heat and mass transfer resistance of the particles; reducing the particle diameter can improve the heat and mass transfer performance of the particles, but this leads to an increase in the reactor bed pressure drop.

[0004] In view of this, some scholars have designed monolithic oxygen carriers, which are made into monolithic structures with "honeycomb" or other porous shapes to improve gas transport in fixed-bed reactors. At present, the preparation processes of monolithic oxygen carriers include coating method (such as patent CN202110853975.9, paper Ce-Fe-Zr-O / MgO coated monolithic oxygencarriers for chemical looping reforming of methane to co-produce syngas and H2. Chemical Engineering Journal, 388(2020)124190), mechanical extrusion method (such as patent CN202010987910.9), and 3D printing method (such as patents CN202111452454.9, CN202111446993.1). It should be noted that monolithic oxygen carriers prepared by coating methods have disadvantages such as low effective component content and easy coating peeling; monolithic oxygen carriers prepared by mechanical extrusion methods usually have thick pore walls to ensure sufficient mechanical strength, thereby increasing axial heat and mass transfer resistance; monolithic oxygen carriers prepared by 3D printing provide additional radial channels, promoting radial diffusion and increasing the reaction area. However, 3D printing has high requirements for the properties of raw materials, and due to the limitation of the printer's build chamber volume, it is not suitable for printing materials with large volumes, which is not conducive to the large-scale preparation of monolithic oxygen carriers.

[0005] Based on this, a novel monolithic oxygen carrier and its preparation method are provided to overcome the shortcomings of existing monolithic oxygen carrier preparation processes, such as low oxygen carrier reactivity, poor resistance to sintering and carbon deposition, and unsuitability for large-scale production. This is a technical problem that urgently needs to be solved to meet the application requirements of low bed pressure drop and low heat and mass transfer resistance in fixed-bed reactors. Summary of the Invention

[0006] One of the objectives of this invention is to provide a method for preparing a microtube monolithic oxygen carrier that has high reactivity, strong resistance to sintering and carbon deposition, and is suitable for large-scale production.

[0007] The second objective of this invention is to provide a microtube monolithic oxygen carrier with high reactivity, strong resistance to sintering and carbon deposition, and suitable for large-scale production.

[0008] The third objective of this invention is to provide an application of a microtube monolithic oxygen carrier in a fixed-bed reactor.

[0009] One of the technical solutions adopted to achieve the objective of this invention is: to provide a method for preparing a microtubular monolithic oxygen carrier, comprising the following steps:

[0010] S1. Mix the metal oxide with binder, solvent and dispersant evenly to obtain a slurry;

[0011] S2. The slurry and the first curing agent are simultaneously added to a porous mold at a certain flow rate ratio and extruded to obtain the first product; the first product is placed in the second curing agent to complete the phase transformation process, and then dried and shaped to obtain the second product;

[0012] S3. The second product is initially calcined to remove organic components, and then calcined at high temperature to obtain a microtubule-based monolithic oxygen carrier.

[0013] The overall concept of the preparation method of the microtube monolithic oxygen carrier provided by this invention is as follows: To achieve both low bed pressure drop and low heat and mass transfer resistance in the monolithic oxygen carrier, while ensuring its large-scale preparation, this invention provides a method for preparing microtube monolithic oxygen carriers through a "phase inversion-assisted extrusion method". In this method, the oxygen carrier raw material and a first curing agent are simultaneously added to a porous mold at a certain flow rate ratio and extruded. The mixture then enters a second curing agent to complete the phase inversion process, obtaining a monolithic oxygen carrier precursor. After drying and stepwise calcination, a monolithic oxygen carrier with a microtube structure is obtained. The monolithic oxygen carrier prepared by this invention has abundant axial and radial hierarchical pore structures, achieving both low bed pressure drop and low heat and mass transfer resistance. It exhibits high reactivity, strong resistance to sintering and carbon deposition, and can be used in processes such as chemical looping combustion, reforming, or hydrogen production of gaseous fuels in fixed-bed reactors. Monolithic oxygen carriers with different microtube numbers can be manufactured according to application requirements. The oxygen carrier structure is adjustable, the raw material applicability is wide, the preparation process is simple, and large-scale preparation is easily achieved.

[0014] Further, in step S1, the metal oxide is composed of 50% to 80% active metal oxide and 20% to 50% inert metal oxide by weight percentage.

[0015] Further, in step S1, the active metal oxide includes one or more combinations of Fe2O3, Co2O3, MnO2, CrO2, CuO, and NiO; the inert metal oxide includes one or more combinations of Al2O3, TiO2, ZrO2, ZnO, alkaline earth metal oxides, and rare earth metal oxides.

[0016] Preferably, the particle size of the metal oxide is 5 to 50 μm, which helps to obtain a more uniformly mixed slurry and makes the surface of the prepared tubular oxygen carrier smoother.

[0017] Further, in step S1, the weight ratio of metal oxide to binder is 6:1 to 3:1; the weight ratio of solvent to the total weight of metal oxide and binder is 1:1 to 1:3; and the amount of dispersant accounts for 0.5% to 2% of the total weight of the slurry. By controlling the proportions of the above raw materials within a suitable range, the viscosity of the slurry can be adjusted, enabling the slurry to have flow properties that match the subsequent extrusion and curing processes.

[0018] Preferably, the solvent is selected from one or more combinations of N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and dihydro-L-glucanone.

[0019] Preferably, the dispersant is selected from one or more combinations of Arlacel P135 (polyoxyethylene (30) dihydroxystearate), dihydroxystearate, polyethylene glycol monolaurate, polyethylene glycol dilaurate, glycerol monolaurate, N,N-dimethylhexamethylene amide, polyglycerol fatty acid ester, diglycerol monolaurate, sorbitol monolaurate, Span 80, and polyether.

[0020] Preferably, the adhesive is selected from one or more combinations of polyethersulfone, polymethyl methacrylate, polyamide, polycarbonate, dimethyl phthalate, and dibutyl phthalate.

[0021] Furthermore, in step S2, the extrusion pressure is 5-20 MPa, the extrusion operation can be carried out using a high-pressure injection device, and the number of orifices in the mold can be 1, 3, 4, 7 or other numbers, specifically, it can be flexibly adjusted according to the actual application.

[0022] Furthermore, in step S2, the flow rate ratio of the slurry to the first curing agent needs to be controlled. An excessively high flow rate ratio will hinder the formation of pores within the microtubes; while an excessively low flow rate ratio will lead to channel merging, making it impossible to obtain the microtube-based monolithic oxygen carrier with the expected number of channels. Preferably, the flow rate ratio of the slurry to the first curing agent is 1:1 to 1:2.

[0023] Further, in step S2, the first curing agent is selected from one or more combinations of polyvinyl alcohol aqueous solution, polyethylene glycol aqueous solution, and water-ethanol mixture; preferably, the mass concentration of the first curing agent is 5% to 10%. The second curing agent is water.

[0024] Furthermore, in step S2, the time interval between the formation of the first product and its entry into the second curing agent is controlled to be 1 to 5 seconds. This operation enables the first product to complete the phase transformation process as quickly as possible, avoiding prolonged contact with air and premature drying and setting.

[0025] In the preparation method of the present invention, by optimizing and controlling factors such as the distribution ratio of each component of the slurry, the flow rate ratio of the curing agent to the slurry, and the interval between the first product entering the second curing agent, it is beneficial to improve the application performance of the integral oxygen carrier, giving it the dual advantages of low bed pressure drop and low heat and mass transfer resistance.

[0026] Furthermore, in step S2, the drying and setting temperature is 10–40°C, and the time is 24–72 hours. This invention uses room temperature conditions for drying and setting, which ensures that the setting stage is carried out under mild and stable conditions, avoiding deformation or cracking of the oxygen carrier caused by high-temperature drying.

[0027] Furthermore, in step S3 of this invention, a stepwise calcination method is used to obtain the monolithic oxygen carrier. In the first stage, if the initial calcination temperature is too low, the removal of organic components cannot be achieved; simultaneously, the heating rate during the initial calcination should not be too high, otherwise the microtube monolithic oxygen carrier will crack due to significant thermal stress. In the second stage of high-temperature calcination, if the calcination temperature is too low, the mechanical strength of the oxygen carrier will be low, affecting its application performance; while if the calcination temperature is too high, the oxygen carrier will sinter, reducing its reactivity.

[0028] Preferably, in step S3, the initial calcination temperature is 400–600°C, the heating rate is 1–3°C / min, and the holding time is 2–4 hours. Specifically, the initial calcination temperature is mainly determined by the decomposition temperature of the binder in step S1, and is preferably 500–600°C.

[0029] Preferably, in step S3, the high-temperature calcination temperature is 1000-1200℃, more preferably 1100-1200℃, the heating rate is 5-10℃ / min, and the holding time is 3-5h.

[0030] The second objective of this invention is to provide a microtubule-based integral oxygen carrier, which is prepared by the preparation method described in one of the objectives of this invention.

[0031] The monolithic oxygen carrier prepared by this invention has a rich axial and radial multi-level pore structure. The axial pores are circular or elliptical with a diameter of 0.5–10 mm, and the radial pores have a diameter of 2–10 μm. The axial and radial pore diameters can be adjusted by changing the slurry formulation and extrusion parameters. The wall thickness of the axial pores on the periphery and the wall thickness of the internal pores of the monolithic oxygen carrier are 0.1–2 mm, which can be adjusted by the extrusion process (including extrusion pressure, the flow rate ratio of slurry and the first curing agent, the die channel size, etc.) to ensure the mechanical strength and mass transfer performance of the monolithic oxygen carrier.

[0032] The third objective of this invention is to provide an application of the microtube monolithic oxygen carrier described in the second objective of this invention in a fixed-bed reactor.

[0033] Specifically, the microtube monolithic oxygen carrier can be used in fixed-bed reactions, chemical looping combustion of gaseous fuels, reforming, and hydrogen production processes.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) This invention provides a method for preparing a microtube monolithic oxygen carrier. The microtube monolithic oxygen carrier is prepared by "phase inversion assisted extrusion". Compared with the monolithic oxygen carrier prepared by coating method, the microtube monolithic oxygen carrier prepared by this invention has an inert carrier and active components as an integral structure, which are tightly bound and not easy to separate.

[0036] (2) Compared with the monolithic oxygen carrier prepared by mechanical extrusion, the microtube monolithic oxygen carrier prepared by this invention has abundant axial and radial multi-level microchannels, which can simultaneously achieve low bed pressure drop and low heat and mass transfer resistance, high reactivity, and strong resistance to sintering and carbon deposition. Compared with the monolithic oxygen carrier prepared by 3D printing, the microtube monolithic oxygen carrier prepared by this invention has a wide range of applicable raw materials, simple preparation process, low cost, and can achieve large-scale preparation.

[0037] (3) The microtube integral oxygen carrier provided by the present invention can be used in the chemical looping combustion, reforming or hydrogen production of gaseous fuels in fixed bed reactors, and has broad prospects for promotion and application. Attached Figure Description

[0038] Figure 1 This is a cross-sectional view of the microtube monolithic oxygen carrier obtained in Embodiment 1 of the present invention;

[0039] Figure 2 This is a tail gas distribution diagram of the microtube monolithic oxygen carrier prepared in Example 1 of the present invention, used in the chemical loop combustion of biomass gasification syngas and chemical loop hydrogen production.

[0040] Figure 3 This is a tail gas distribution diagram of the microtube monolithic oxygen carrier prepared in Example 2 of the present invention, used for the temperature-programmed reduction of methane. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0043] This invention provides a method for preparing a microtubule-based monolithic oxygen carrier, comprising the following steps:

[0044] Step 1: Mix the metal oxide with the binder, solvent, and dispersant evenly to obtain a slurry; the composition of the metal oxide, by weight percentage, consists of 50%–80% active metal oxide and 20%–50% inert metal oxide; in the slurry, the weight ratio of metal oxide to binder is 6:1–3:1; the weight ratio of solvent to the total weight of metal oxide and binder is 1:1–1:3; the amount of dispersant accounts for 0.5%–2% of the total weight of the slurry.

[0045] The active metal oxide includes one or more combinations of Fe2O3, Co2O3, MnO2, CrO2, CuO, and NiO; the inert metal oxide includes one or more combinations of Al2O3, TiO2, ZrO2, ZnO, alkaline earth metal oxides, and rare earth metal oxides.

[0046] The solvent is selected from one or more combinations of N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and dihydro-L-glucanone;

[0047] The dispersant is selected from one or more combinations of Arlacel P135, dihydroxystearate, polyethylene glycol monolaurate, polyethylene glycol dilaurate, glycerol monolaurate, N,N-dimethylhexamethylene amide, polyglycerol fatty acid ester, diglycerol monolaurate, sorbitol monolaurate, Span 80, and polyether.

[0048] The adhesive is selected from one or more combinations of polyethersulfone, polymethyl methacrylate, polyamide, polycarbonate, dimethyl phthalate, and dibutyl phthalate.

[0049] Step 2: The slurry and the first curing agent are simultaneously added to a porous mold at a flow rate ratio of 1:1 to 1:2. The extrusion pressure is controlled at 5 to 20 MPa, and the extrusion operation is carried out to obtain the first product. The first product is quickly (within 1 to 5 seconds) transferred to the second curing agent to complete the phase transformation process, and then dried at 10 to 40°C for 24 to 72 hours to obtain the second product.

[0050] The first curing agent is selected from one or more of the following: polyvinyl alcohol aqueous solution, polyethylene glycol aqueous solution, and water-ethanol mixture, and the mass concentration of the first curing agent is 5% to 10%; the second curing agent is water.

[0051] Step 3: The second product is subjected to preliminary calcination to remove organic components. In the preliminary calcination, the temperature is 400-600℃, the heating rate is 1-3℃ / min, and the holding time is 2-4h. Then, it is subjected to high-temperature calcination at a temperature of 1000-1200℃, a heating rate of 5-10℃ / min, and a holding time of 3-5h to obtain the microtube monolithic oxygen carrier.

[0052] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0053] Example 1

[0054] This embodiment provides a method for preparing a microtubule-based monolithic oxygen carrier, including the following steps:

[0055] Step 1: Weigh 60g Al2O3, 100g Fe2O3, 5g CuO, 5g NiO, 30g polymethyl methacrylate, 75g N-methyl-2-pyrrolidone and 2g Arlacel P135 into a mixing tank and mechanically mix for 24 hours to obtain a slurry;

[0056] Step 2: Pour the uniformly mixed slurry into high-pressure injector #1, and simultaneously pour polyvinyl alcohol solution into high-pressure injector #2. Set the output volume flow ratio of high-pressure injectors #1 and #2 to 1:1, and control the extrusion pressure to 5 MPa. After extruding the two materials together through a 7-channel die, the resulting monolithic oxygen carrier is placed in a tap water bath for hardening and shaping. Fix the hardened monolithic oxygen carrier in a slot and dry it at room temperature for 24 hours.

[0057] Step 3: Place the shaped monolithic oxygen carrier in a muffle furnace and calcine it in air. The muffle furnace heating program is as follows: room temperature → 500℃, heating rate 1℃ / min, hold at 500℃ for 2 hours; 500℃ → 1200℃, heating rate 5℃ / min, hold at 1200℃ for 2 hours; then allow it to cool naturally to room temperature and remove it to obtain the final monolithic oxygen carrier, denoted as MOC1. See the attached diagram for the appearance and cross-sectional morphology of the monolithic oxygen carrier. Figure 1 .

[0058] Example 2

[0059] This embodiment provides a method for preparing a microtubule-based monolithic oxygen carrier, including the following steps:

[0060] Step 1: Weigh 50g Al2O3, 120g Fe2O3, 7g CuO, 7g NiO, 40g polymethyl methacrylate, 75g N-methyl-2-pyrrolidone and 2g Arlacel P135 into a mixing tank and mechanically mix for 24 hours to obtain a slurry;

[0061] Step 2: Pour the uniformly mixed slurry into high-pressure injector #1, and simultaneously pour polyvinyl alcohol solution into high-pressure injector #2. Set the output volume flow ratio of high-pressure injectors #1 and #2 to 1:1.3, and control the extrusion pressure to 8 MPa. After extruding the two materials together through a 7-channel die, the resulting monolithic oxygen carrier is placed in a tap water bath for hardening and shaping. Fix the hardened monolithic oxygen carrier in a slot and dry it at room temperature for 24 hours.

[0062] Step 3: Place the shaped monolithic oxygen carrier in a muffle furnace and calcine it in an air atmosphere. The muffle furnace heating program is as follows: room temperature → 600℃, heating rate 1℃ / min, hold at 600℃ for 2 hours; 600℃ → 1200℃, heating rate 5℃ / min, hold at 1200℃ for 5 hours; then let it cool naturally to room temperature and remove it to obtain the final monolithic oxygen carrier, denoted as MOC2.

[0063] Example 3

[0064] This embodiment provides a method for preparing a microtubule-based monolithic oxygen carrier, including the following steps:

[0065] Step 1: Weigh 60g Al2O3, 120g Fe2O3, 7g CuO, 7g NiO, 50g polycarbonate, 100g N-methyl-2-pyrrolidone and 2g glycerol monosilicone into a mixing tank and mechanically mix for 24 hours to obtain a slurry;

[0066] Step 2: Pour the uniformly mixed slurry into high-pressure injector #1, and simultaneously pour polyethylene glycol solution into high-pressure injector #2. Set the output volume flow ratio of high-pressure injectors #1 and #2 to 1:1.2, and control the extrusion pressure to 10 MPa. After extruding the two materials together through a 4-channel mold, the resulting monolithic oxygen carrier is placed in a tap water bath for hardening and shaping. Then, the prepared monolithic oxygen carrier is taken out and fixed in a slot for drying and shaping at 40°C for 24 hours.

[0067] Step 3: Place the shaped monolithic oxygen carrier in a muffle furnace and calcine it in an air atmosphere. The muffle furnace heating program is as follows: room temperature → 500℃, heating rate 2℃ / min, hold at 500℃ for 4 hours; 500℃ → 1100℃, heating rate 5℃ / min, hold at 1100℃ for 5 hours; then let it cool naturally to room temperature and remove it to obtain the final monolithic oxygen carrier, denoted as MOC3.

[0068] Example 4

[0069] This embodiment provides a method for preparing a microtubule-based monolithic oxygen carrier, including the following steps:

[0070] Step 1: Weigh 30g ZrO2, 120g Fe2O3, 25g polymethyl methacrylate, 80g N-methyl-2-pyrrolidone and 1.5g Arlacel P135 into a mixing tank and mechanically mix for 24 hours to obtain a slurry;

[0071] Step 2: Pour the uniformly mixed slurry into high-pressure injector #1, and simultaneously pour polyvinyl alcohol solution into high-pressure injector #2. Set the output volume flow ratio of high-pressure injectors #1 and #2 to 1:1, and control the extrusion pressure to 5 MPa. After extruding the two materials together through a 4-channel mold, the resulting monolithic oxygen carrier is placed in a tap water bath for hardening and shaping. Then, the prepared monolithic oxygen carrier is taken out and fixed in a slot to dry and shape at room temperature for 24 hours.

[0072] Step 3: Place the shaped monolithic oxygen carrier in a muffle furnace and calcine it in an air atmosphere. The muffle furnace heating program is as follows: room temperature → 600℃, heating rate 1℃ / min, hold at 600℃ for 2 hours; 600℃ → 1200℃, heating rate 5℃ / min, hold at 1200℃ for 3 hours; then let it cool naturally to room temperature and remove it to obtain the final monolithic oxygen carrier, denoted as MOC4.

[0073] Example 5

[0074] This embodiment provides a method for preparing a microtubule-based monolithic oxygen carrier, including the following steps:

[0075] Step 1: Weigh 60g Al2O3, 120g CuO, 35g polymethyl methacrylate, 100g N-methyl-2-pyrrolidone and 2g Arlacel P135 into a mixing tank and mechanically mix for 24 hours to obtain a slurry;

[0076] Step 2: Pour the uniformly mixed slurry into high-pressure injector #1, and simultaneously pour polyvinyl alcohol solution into high-pressure injector #2. Set the output volume flow ratio of high-pressure injectors #1 and #2 to 1:1, and control the extrusion pressure to 5 MPa. After extruding the two materials together through a single-channel mold, the resulting monolithic oxygen carrier is placed in a tap water bath for hardening and shaping. Then, the prepared monolithic oxygen carrier is taken out and fixed in a slot for drying and shaping at 30°C for 24 hours.

[0077] Step 3: Place the shaped monolithic oxygen carrier in a muffle furnace and calcine it in an air atmosphere. The muffle furnace heating program is as follows: room temperature → 500℃, heating rate 1℃ / min, hold at 500℃ for 5 hours; 600℃ → 1100℃, heating rate 10℃ / min, hold at 1100℃ for 5 hours; then let it cool naturally to room temperature and remove it to obtain the final monolithic oxygen carrier, denoted as MOC5.

[0078] Application Example 1

[0079] MOC1 prepared in Example 1 was loaded into a fixed-bed reactor with an empty bed volume of 10 mL. The reactor temperature was set to 850 °C. Before fuel was introduced, the reactor was purged with nitrogen at 100 mL / min to remove air. Then, syngas (25% CO, 10% CO2, 10% H2, 5% CH4, and the remainder N2) was introduced at 150 mL / min until the CO concentration at the reactor outlet exceeded 0.5%. The syngas supply was then stopped, and the reactor was purged with nitrogen at 100 mL / min for about 10 min to remove residual gas. Then, water vapor was introduced at 0.25 g / min, and the gases produced in this process were purged with nitrogen at 200 mL / min as the carrier gas. Throughout the process, the tail gas (CO2, CO, H2, CH4, and O2) from the reactor was monitored and recorded in real time using a gas analyzer. The final results are shown in the attached figure. Figure 2 As shown.

[0080] From the appendix Figure 2 It is evident that only CO2 was present in the tail gas of Stage I, indicating that the prepared monolithic oxygen carrier can achieve complete combustion of biomass gasification syngas. In Stage II, the Steam-iron reaction mainly occurs, generating a large amount of hydrogen, with virtually no CO or CO2 generated, and the hydrogen purity exceeds 99%.

[0081] Application Example 2

[0082] 0.5 g of MOC2 prepared in Example 2 was placed in a fixed-bed reactor, and then 5% CH4 / N2 mixed gas was introduced. The reactor was heated from room temperature to 950°C at a rate of 5°C / min. The distribution of tail gas flow rate over time was detected and recorded using a gas analyzer. The results are shown in the attached figure. Figure 3 As shown, it can be observed that when the temperature rises to 743℃, the amount of CO2 produced decreases, and CO and H2 begin to flow out. Furthermore, until 855℃, the H2 / CO ratio remains around 2 throughout the entire range, indicating that CH4 only undergoes a partial oxidation reaction and no carbon deposits are formed.

[0083] In summary, the microtube monolithic oxygen carrier provided by this invention has a tubular channel structure, which can bring about a low bed pressure drop effect. At the same time, the microtube monolithic oxygen carrier has a small wall thickness and an axial microporous structure within the wall (such as... Figure 1As shown in the figure, the microtube monolithic oxygen carrier has the advantage of low heat and mass transfer resistance. Application examples show that the microtube monolithic oxygen carrier provided by this invention is suitable for chemical looping combustion of biomass gasification syngas and hydrogen production in fixed-bed reactors, as well as chemical looping reforming of natural gas, exhibiting advantages of high reactivity and strong resistance to carbon deposition.

[0084] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for preparing a microtubular monolithic oxygen carrier, characterized in that, Includes the following steps: S1. The metal oxide is mixed evenly with the binder, solvent and dispersant to obtain a slurry; in the slurry, the weight ratio of the metal oxide to the binder is 6:1 to 3:1; the weight ratio of the solvent to the total weight of the metal oxide and binder is 1:1 to 1:3; the amount of dispersant accounts for 0.5% to 2% of the total weight of the slurry; the solvent is selected from one or more combinations of N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and dihydro-L-glucanone; S2. The slurry and the first curing agent are simultaneously added to a porous mold at a flow rate ratio of 1:1 to 1:2 and extruded to obtain the first product; The first product is placed in the second curing agent to complete the phase inversion process, and then dried and shaped to obtain the second product; the time interval between the formation of the first product and its entry into the second curing agent is 1~5s; the first curing agent is selected from one or more combinations of polyvinyl alcohol aqueous solution, polyethylene glycol aqueous solution, and water-ethanol mixture; the second curing agent is water; S3. The second product is subjected to preliminary calcination to remove organic components, and then subjected to high-temperature calcination to obtain a microtube monolithic oxygen carrier. The microtube monolithic oxygen carrier has an axial and radial multi-level pore structure. The axial pores are circular or elliptical with a diameter of 0.5~10mm, and the radial pores have a diameter of 2~10μm.

2. The preparation method according to claim 1, characterized in that, In step S1, the metal oxide is composed of 50% to 80% active metal oxide and 20% to 50% inert metal oxide by weight percentage.

3. The preparation method according to claim 2, characterized in that, In step S1, the active metal oxide includes one or more combinations of Fe2O3, Co2O3, MnO2, CrO2, CuO, and NiO; the inert metal oxide includes one or more combinations of Al2O3, TiO2, ZrO2, ZnO, alkaline earth metal oxides, and rare earth metal oxides.

4. The preparation method according to claim 1, characterized in that, In step S2, the extrusion pressure is 5~20MPa.

5. The preparation method according to claim 1, characterized in that, In step S3, the initial calcination temperature is 400~600℃, the heating rate is 1~3℃ / min, and the holding time is 2~4h.

6. The preparation method according to claim 1, characterized in that, In step S3, the high-temperature calcination temperature is 1000~1200℃, the heating rate is 5~10℃ / min, and the holding time is 3~5h.

7. A microtubular monolithic oxygen carrier, characterized in that, It is prepared by the method according to any one of claims 1-6.

8. The application of the microtube monolithic oxygen carrier according to claim 7 in a fixed-bed reactor.

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