Preparation method and application of structural defect MOF pyrolysis derived zirconia supported nanometal catalyst

Abstract

The application relates to a preparation method and application of a structural defect MOF pyrolysis derived zirconia supported nanometal catalyst, belonging to the technical field of catalytic reforming. A structural defect UiO-66-X is used as a precursor, a CO x atmosphere is used for pyrolysis, and then air calcination is carried out in a derived approach, a multistage pore zirconia carrier is used for supporting an active nanometal catalyst, and a preparation method of the catalyst is provided. Through the regulation of the defect structure, quantity and pyrolysis atmosphere of the precursor, the crystal phase, morphology and oxygen defect site of the surface microenvironment of the dry reforming catalyst carrier ZrO2 are optimized, and a supported catalyst is prepared, which is used for preparing synthesis gas / hydrogen by methane carbon dioxide reforming.

Description

Technical Field

[0001] This invention belongs to the field of MOF pyrolysis derivatization preparation of metal oxide supports and catalysts, specifically involving a method using UiO-66-X with different structural defects as a precursor and employing CO... x A derivative route of atmospheric pyrolysis followed by air calcination was developed, and a method for preparing catalysts with hierarchical porous zirconia supports and supported active nano-metals was proposed. By controlling the defect structure and number of precursors and the pyrolysis atmosphere, the surface microenvironment of the dry reforming catalyst support ZrO2, including its crystal phase, morphology, and oxygen-containing defect sites, was optimized. Supported catalysts were then prepared and used for the reforming of methane and carbon dioxide to produce syngas / hydrogen. Background Technology

[0002] With the accelerating pace of global warming, emission reduction and control of greenhouse gases such as carbon dioxide and methane have become a crucial issue of global concern. The dry reforming of methane (CH4 + CO2 → 2CO + 2H2, DRM) can simultaneously convert two greenhouse gases into syngas, representing a typical low-carbon process within the framework of carbon capture, utilization, and storage (CCUS). However, the DRM reaction is a strongly endothermic process, typically requiring reaction temperatures above 700°C. o Temperatures below 600°C result in significant energy consumption and environmental pollution. Therefore, the development of DRM technology under mild conditions is receiving increasing attention. However, when the reaction temperature is below 600°C... o At C, methane cracking and CO disproportionation reactions occur more readily, leading to catalyst deactivation due to carbon deposition. Therefore, developing catalysts with high activity, selectivity, and stability under mild conditions remains a significant challenge.

[0003] Numerous studies have shown that transition metal catalysts, especially nickel-based catalysts, have high activity and anti-coking properties, and are inexpensive, making them the most promising catalysts for industrial applications. Among non-precious metal catalysts, the dissociation activation performance of metallic Ni for methane is comparable to that of precious metals, but nickel-based catalysts also suffer from the problem of easy coking or sintering and deactivation. The methods to improve the anti-coking ability of nickel-based catalysts are mainly from the following three perspectives: (1) Strengthening the adsorption and activation of CO2, providing surface active oxygen, and inhibiting coking, such as using alkaline supports and oxygen supports, such as ZrO2 and CeO2; (2) Modifying the surface of Ni particles to destroy or cover active sites that are prone to coking, such as step sites and sharp corners; (3) Improving the dispersion of Ni active components and reducing the size of Ni particles. ZrO2 is considered an ideal catalyst support for methane dry reforming due to its high thermal stability, good surface properties such as easy generation of oxygen vacancies, high oxygen mobility, Lewis acid-base properties, and redox properties. Current research on the preparation of zirconia supports primarily employs traditional methods such as co-precipitation, sol-gel, and hydrothermal methods. These methods involve modifying the support preparation conditions, calcination atmosphere, calcination temperature, reduction temperature, and loading method of the active component to control the structure of the support, including oxygen vacancies, crystal phase, crystal face exposure, and the strength of the interaction between the support and the active component. Preliminary results indicate that compared to monoclinic / tetragonal mixed-phase and monoclinic zirconia, tetragonal zirconia exhibits higher oxygen vacancy density, more basic active sites, and stronger metal-support interactions, forming partially reduced Zr species and demonstrating better reactivity and resistance to carbon deposition. The lower pore volume and specific surface area of ​​monoclinic zirconia result in very low Ni particle dispersion, which is the main reason for the low activity of this type of catalyst in methane dry reforming. Simultaneously, by controlling the calcination atmosphere to alter the distribution and quantity of oxygen vacancies on the support surface, a hydrogen atmosphere, compared to nitrogen or oxygen, maximizes the basicity and oxygen vacancy of the zirconia support, resulting in the most stable catalyst that can promote carbon deposition removal. However, materials synthesized using these methods generally have a small specific surface area, involve complex processes, and have fewer active sites on the support surface.

[0004] Metal-organic framework (MOF)-derived materials have attracted widespread attention due to their preserved morphology, large specific surface area, and functionality. Using MOFs as precursors and preparing metal oxides via pyrolysis has become a potential route (Material Letters 341(2023)134221, Chemical Engineering Journal 466(2023)143242). UIO-66, with its ultra-large specific surface area, excellent pore structure, and flexible tunability, shows great promise for applications in catalysis, functional materials, and adsorption. Zhang Junfeng et al. used a hydrothermal method with Zr-MOF as a template to investigate the effect of different nickel loading stages on the catalytic performance of Ni / ZrO2 catalysts derived from Zr-MOF after calcination at 800℃ for 5 h on the dry reforming reaction of methane. The results showed that at a reaction temperature of 750℃, the Ni / ZrO2 catalyst derived by co-calcining Zr-MOF with active metal Ni could achieve a methane conversion rate of 76%, a syngas H2 / CO ratio greater than 0.8, and the prepared Ni / ZrO2 catalyst had the largest specific surface area of ​​12.93 m². 2 / g, with a particle size of 20~30 nm (Molecular Catalysis 558(2024)114028). Currently, there are few literature reports on the use of MOFs, especially Zr-MOF-derived zirconium oxide supports to support nano-metal catalysts. Patent publication number CN116459823A proposes a two-step calcination strategy to pyrolyze MOFs at high temperature (150~1000 ℃) in an inert atmosphere (nitrogen or argon) and then calcinate them in air (150~1000 ℃), or to use a one-step method to directly calcine MOFs at high temperature (150~1000 ℃) in an oxidizing atmosphere (air) to obtain ordered mesoporous cerium zirconium composite oxides with a pore size of 2~15 nm, and use them for carbon dioxide cyclization reaction, with a conversion rate and selectivity of up to 99%. Patent publication number CN117599852A discloses a method for preparing a Zr-MOF pyrolysis-derived Cu-based catalyst. The method involves wet impregnation of active metal Cu and Ga salts onto a high specific surface area Zr-MOF, followed by high-temperature pyrolysis in air, argon, and nitrogen atmospheres at 300–600 °C for 3–5 h. Finally, reduction yields CuGaZrO. xThree-way catalysts can be used in the hydrogenation of carbon dioxide. However, most current MOF derivatization processes employ a one-step method (direct calcination in air) or a two-step method (pyrolysis in an inert atmosphere followed by calcination in air) for material structure control. Excessively high pyrolysis temperatures can cause varying degrees of precursor structure collapse, resulting in derivative materials with disordered pore structures, small specific surface areas, and few surface active sites, leading to less than ideal catalytic performance. In particular, research on Zr-MOF pyrolysis-derived Ni / ZrO2 catalysts has yielded few reports on the qualitative control mechanisms of precursor defects and pyrolysis conditions such as different calcination atmospheres (CO2 and mixed atmospheres) and staged pyrolysis on the structure of derived metal oxides, as well as how to improve catalyst structural stability, activity, and anti-carbon deposition performance. Summary of the Invention

[0005] This invention develops a method for preparing ZrO2-supported active nano-metal catalysts suitable for methane dry reforming to syngas / hydrogen. Its unique MOF-derived pyrolysis method facilitates the preparation of defect-rich metal oxide supports with hierarchical porous structures and large specific surface areas, enabling high dispersion of active species such as Ni and achieving high catalyst activity and stability during the methane dry reforming process. This method is simple to operate, easy to control, and provides a novel approach to preparing high-performance metal oxide-supported nano-metal catalysts by controlling the types and concentrations of defects in the MOF precursor itself, the composition of active components, the loading method and amount, and pyrolysis process parameters (including pyrolysis temperature, pyrolysis rate, raw material composition and properties, and pyrolysis atmosphere).

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a high-performance mesoporous zirconia-supported nano-metal catalyst based on the pyrolysis of UiO-66-X with different structural defects is disclosed. This catalyst is prepared by further optimizing the hydrothermal crystallization conditions of UiO-66-X through the addition of a defect structure modifier, thereby preparing UiO-66-X with a specific defect structure. This UiO-66-X is used as a precursor. By controlling the pyrolysis process parameters, active component composition, loading mode and loading amount, the catalyst precursor is obtained. Finally, the catalyst is reduced by high-temperature hydrogen to obtain the high-performance zirconia-supported nano-metal catalyst.

[0008] A method for preparing a structurally defective MOF pyrolysis-derived zirconium oxide supported nano-metal catalyst, characterized by comprising the following steps:

[0009] (1) After fully dissolving and mixing the MOF precursor metal salt, organic solvent, carboxyl ligand and defect structure modifier, UiO-66-X with a certain defect structure was prepared by hydrothermal method after cooling, centrifugation, washing and drying.

[0010] (2) Preparation of M / ZrO2: ZrO2 support is prepared by pyrolysis derivatization of catalyst precursor UiO-66-X. During the preparation of ZrO2 support or on the prepared ZrO2 support, the supported catalyst precursor MO is prepared by impregnation or vapor deposition. X / ZrO2; finally, it is reduced by high temperature hydrogen to obtain the high-performance catalyst M / ZrO2 supported on zirconium oxide nano-metal; M is the active metal component.

[0011] In step (1), the MOF precursor metal salt is one or more of zirconium chloride, zirconium nitrate, and zirconium oxychloride containing Zr. The carboxyl ligand includes one or more of terephthalic acid, aminoterephthalic acid, hydroxyterephthalic acid, trimesic acid, 2,5-dinitroterephthalic acid and their derivatives. The organic solvent includes one or more of N,N-dimethylformamide, acetonitrile, N-methylimidazolium, pyridine, N-methylpyrrolidone, dimethyl sulfoxide, diethylformamide, and trichlorobenzene. The regulator is a protic acid, including one or more of nitric acid, hydrochloric acid, citric acid, lactic acid, p-toluenesulfonic acid, formic acid, acetic acid, and benzoic acid.

[0012] In further step (1), the molar ratio of the zirconium source and the organic carboxyl ligand is 0.1-80; the molar ratio of the protonic acid modifier and the zirconium source is 0.1-100; the molar ratio of the organic solvent and the zirconium source is 60-2500; and the hydrothermal conditions are 80-200℃ for 12-72 h.

[0013] The preferred embodiment is that the molar ratio of zirconium source to organic carboxyl ligand is 0.5-1.5; the molar ratio of protonic acid modifier to zirconium source is 0.2-15; and the molar ratio of organic solvent to zirconium source is 100-2000.

[0014] The pyrolysis described in step (2) is a two-step strategy, in which the UiO-66-X precursor is subjected to high-temperature pyrolysis to obtain the derived hierarchical porous ZrO2 support. In the two-step strategy, the precursor is first pyrolyzed in another atmosphere and then calcined in air. The other atmosphere is one or more of nitrogen, argon, carbon dioxide, carbon monoxide or water vapor. The pyrolysis temperature is 300~1000℃, the pyrolysis time is 0.5~10 h, the heating rate is 2~50 ℃ / min, and the carrier gas flow rate per gram of catalyst is 10 ml / min~300 ml / min. The calcination in air is carried out at a temperature of 300~1000℃ for 0.5~10 h with a heating rate of 2~50 ℃ / min.

[0015] Alternatively, the pyrolysis described in step (2) can be a one-step strategy, in which the UiO-66-X precursor is calcined in air to obtain the corresponding multi-level porous ZrO2 support. The calcination temperature is 300~900℃ and the calcination time is 0.5~10 h.

[0016] The preferred solution is a two-step strategy, with other atmospheres preferably containing one or more of carbon dioxide or carbon monoxide, pyrolysis temperature of 400~800℃, pyrolysis time of 0.5~3.5 h, and heating rate of 2~20 ℃ / min.

[0017] The active component M mentioned in step (2) is one or more of transition metals such as Ni, Co, Fe, Cu, and Mn. The content of the active component accounts for 0.1 to 25 wt.% of the total weight of the catalyst. The active component is loaded by impregnation or vapor deposition. When two active components are used, the molar ratio of the active components is 1:5 to 5:1.

[0018] Preparation of MO X When using ZrO2, the metal, metal oxide, and / or metal salt corresponding to the active component can be loaded onto the UiO-66-X preparation, or onto the intermediate product after pyrolysis in other atmospheres during the two-step pyrolysis strategy described above; or the metal and metal oxide corresponding to the active component can be loaded onto the ZrO2 support obtained by the two-step or one-step pyrolysis strategy. The active component metal salt precursor can be one or more of nitrates, chlorides, acetates, and sulfates.

[0019] The preferred embodiment is that the active component is one or two of Ni, Co, and Fe active components, with a loading of 0.1% to 15%.

[0020] Step (2) High-temperature hydrogen reduction refers to reduction at 300~800℃ for 0.1-5 h in a mixed atmosphere of hydrogen, hydrogen and argon, or hydrogen and nitrogen; the preferred reduction temperature is 500~700℃ and the reduction time is 1.5 h~3.5 h.

[0021] The catalyst M / ZrO2 obtained in this invention exhibits hierarchical porosity, including a micro-mesoporous composite material containing both micropores and mesopores, and a hierarchical mesoporous material with multiple mesopore size distribution ranges. The micropores have a diameter no greater than 2 nm; the mesopores have diameters of approximately 2–8 nm and 12–25 nm, and a specific surface area greater than 70 m². 2 / g.

[0022] Another object of the present invention is to provide an application of the above-mentioned zirconium oxide-supported nano-metal catalyst, wherein the catalyst is used in a methane dry reforming reaction; the reaction pressure is atmospheric pressure, the reaction temperature is 400~900℃, and the reaction space velocity is 6,000~60,000 mLh. -1 gcat -1 The volume ratio of the raw material gas, methane, to carbon dioxide is 1:5 to 5:1.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] In this invention, the M / ZrO2 catalyst obtained by pyrolysis derivatization of UiO-66-X exhibits hierarchical porous characteristics, including a micro-mesoporous composite material containing both micropores and mesopores, and a hierarchical mesoporous material with multiple mesopore size distribution ranges. The micropores have a pore size of no more than 2 nm; the mesopores have pore sizes of approximately 2~8 nm and 12~25 nm, respectively, and a relatively large specific surface area (~70 m²). 2 It contains a certain amount of surface defects and excellent dispersion characteristics of active components (g and above), and has a certain surface defects.

[0025] The M / ZrO2 catalyst provided by this invention not only exhibits high activity and product selectivity but also high stability. The Ni / ZrO2 catalyst prepared by this invention was evaluated for stability in a low-methane dry reforming reaction system over 8 hours. The results showed that at a reaction temperature of 600℃, the initial methane conversion rate of the catalyst was above 50%, and the initial carbon dioxide conversion rate was above 50%. After 8 hours of reaction, the methane conversion rate was above 40%, the carbon dioxide conversion rate remained at around 45%, and the H2 / CO ratio remained consistently between 0.7 and 0.8. This indicates that the catalyst possesses excellent stability and good syngas selectivity.

[0026] This invention provides a method for optimizing the microstructure of the catalyst and improving its catalytic performance by controlling the defect composition and structure of the UIO-66-X precursor and the operating conditions such as the reaction atmosphere and pyrolysis temperature during the pyrolysis process. This provides a new preparation approach for metal oxide supported catalysts and has good potential for industrial and large-scale application. Attached Figure Description

[0027] Figure 1 SEM images of MOF pyrolysis-derived ZrO2 supports for Example 1 and Comparative Example 5;

[0028] (a) Pyrolysis-derived ZrO2 support in Example 1 (b) Pyrolysis-derived ZrO2 support in Comparative Example 5

[0029] Figure 2The XRD patterns of the 5% Ni / ZrO2 catalysts derived from MOF pyrolysis in Example 1 and Comparative Example 5 are shown below.

[0030] (a) Catalyst prepared in Example 1 (b) Catalyst prepared in Comparative Example 5.

[0031] Figure 3 The pore size distribution diagrams are shown for the BJH model of the MOF pyrolysis-derived 5% Ni / ZrO2 catalysts of Example 1 and Comparative Example 5.

[0032] Figure 4 The nitrogen adsorption-desorption curves of pyrolysis-derived 5% Ni / ZrO2 catalysts in Examples 1, 3, and 5 are shown. Detailed Implementation

[0033] The present invention will be described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions and conditions described in the manual, or according to the manufacturer's recommendations. The general equipment, materials, reagents, etc. used are commercially available unless otherwise specified. The raw materials required in the following embodiments and comparative examples are all commercially available.

[0034] CO X Atmosphere-derived catalyst preparation

[0035] Example 1

[0036] Benzoic acid (3.0195 g, 0.024725 mol), ZrCl4 (0.396 g, 0.001699 mol), and terephthalic acid (0.2739 g, 0.001699 mol) were dissolved in 33 g of N,N-dimethylformamide. The resulting suspension was sonicated until the mixture was completely clear, then transferred to a 50 mL polytetrafluoroethylene-lined autogenous pressure reactor and placed in a preheated oven at 120 °C for 24 hours. After cooling to room temperature, the white product was centrifuged, washed several times with a mixture of DMF and methanol, and dried at 100 °C for 12 hours to obtain UiO-66 powder with certain defects.

[0037] The UiO-66 (1 g) with certain defects prepared above was pyrolyzed at 700 °C for 3.5 h under a CO2 atmosphere at a flow rate of 60 ml / min to obtain ZrO2 / C. 5wt% Ni active metal was loaded onto the ZrO2 / C support using an impregnation method. The specific steps are as follows: a certain amount of nickel nitrate was dissolved in ethanol, and after complete dissolution, it was mixed with the pyrolyzed ZrO2 / C material. The mixture was ultrasonicated for 30 min and then continuously stirred for 24 h. After stirring, ultrasonication was continued for another 30 min, followed by drying to complete the loading. Then, it was calcined in a muffle furnace at 500 °C for 180 min to obtain the oxidized catalyst. Finally, it was reduced at 500 °C for 2 h to obtain the Ni / ZrO2 catalyst.

[0038] Example 2

[0039] Concentrated hydrochloric acid (0.6 g, 0.005941 mol), zirconium oxychloride (0.3320 g, 0.001864 mol), and 2,5-dinitroterephthalic acid (0.9233 g, 0.003605 mol) were dissolved in 15 g of dimethyl sulfoxide. The resulting suspension was sonicated until the mixture was completely clear, then transferred to a 50 mL autogenous pressure reactor lined with polytetrafluoroethylene and placed in a preheated oven at 200 °C for 72 hours. After cooling to room temperature, the white product was centrifuged, washed several times with a mixture of dimethyl sulfoxide and acetone, and dried at 120 °C for 6 hours to obtain UiO-66-NO2 powder.

[0040] The prepared UiO-66-NO2 was pyrolyzed at 600 °C for 3 h under a CO2 atmosphere at a flow rate of 100 ml / min to obtain ZrO2 / C. Then, it was calcined in a muffle furnace at 500 °C for 180 min to obtain ZrO2. 10 wt% Co was then impregnated onto the ZrO2 support using the following steps: a certain amount of cobalt nitrate was dissolved in water, sonicated for 30 min, and then continuously stirred for 24 h. After stirring, sonication was continued for another 30 min, followed by drying to complete the loading and obtain the oxidized catalyst. This catalyst was then reduced at 600 °C for 4 h to obtain the target catalyst Co / ZrO2.

[0041] Example 3

[0042] Citric acid (0.0518 g, 0.00027 mol), zirconium nitrate (0.3058 g, 0.000901 mol), and 2-hydroxyterephthalic acid (0.1189 g, 0.003605 mol) were dissolved in 156 g of diethylformamide. The resulting suspension was sonicated until the mixture was completely clear, then transferred to a 200 mL autogenous pressure reactor lined with polytetrafluoroethylene and placed in a preheated oven at 180 °C for 48 hours. After cooling to room temperature, the white product was centrifuged, washed several times with a mixture of diethylformamide and ethanol, and dried at 120 °C for 6 hours to obtain UiO-66-OH powder.

[0043] The prepared UiO-66-OH (1 g) was pyrolyzed at 800 °C for 2 h under a CO2 atmosphere at a flow rate of 80 ml / min to obtain ZrO2 / C. Then, it was calcined at 800 °C for 180 min in a muffle furnace to obtain ZrO2. 15 wt% Fe active metal was loaded onto the ZrO2 support using an impregnation method. The specific steps were as follows: a certain amount of ferric nitrate was dissolved in water, sonicated for 30 min, and then continuously stirred for 24 h. After stirring, sonication was continued for another 30 min, followed by drying to complete the loading and obtain the oxidized catalyst. Then, it was reduced at 700 °C for 4 h to obtain the target catalyst Fe / ZrO2.

[0044] Example 4

[0045] p-Toluenesulfonic acid (2.2519 g, 0.004708 mol), zirconium oxychloride (0.6642 g, 0.003729 mol), and 2-aminoterephthalic acid (1.0253 g, 0.00566 mol) were dissolved in a mixed solution of 70 g N,N-dimethylformamide and 2 g trichlorobenzene. The resulting suspension was sonicated until the mixed solution was completely clear, and then transferred to a 100 mL autogenous pressure reactor with a polytetrafluoroethylene liner. The reactor was placed in a preheated oven at 100 °C for 24 hours. After cooling to room temperature, the white product was centrifuged, washed several times with ethanol, and dried at 100 °C for 12 hours to obtain UiO-66-NH2 powder.

[0046] The prepared UiO-66-NH2 (1 g by mass) was pyrolyzed at 600 °C for 1 h in a mixed atmosphere of CO2 and CO (volume ratio 1:1) at a flow rate of 40 ml / min to obtain ZrO2 / C. Then, it was calcined at 600 °C for 2 h in a muffle furnace to obtain ZrO2. The ZrO2 support was then loaded with 10 wt% Ni and 5 wt% Co using an impregnation method. The specific steps were as follows: a certain amount of nickel nitrate was dissolved in water, sonicated for 30 min, and then continuously stirred for 24 h. After stirring, sonication was continued for another 30 min, followed by drying to complete the loading and obtain the oxidized catalyst. This was then reduced at 500 °C for 2 h to obtain the target catalyst Ni-Co / ZrO2.

[0047] Example 5

[0048] Lactic acid (6.5147 g, 0.026036 mol), zirconium oxychloride (0.8572 g, 0.004812 mol), terephthalic acid (0.663 g, 0.003991 mol), and trimesic acid (0.0589 g, 0.00028 mol) were dissolved in a mixed solution of 40 g N,N-dimethylformamide and 6 g acetonitrile. The resulting suspension was sonicated until the mixed solution was completely clear, and then transferred to a 100 mL autogenous pressure reactor with a polytetrafluoroethylene liner. The mixture was placed in a preheated oven at 160 °C for 18 hours. After cooling to room temperature, the white product was centrifuged, washed several times with ethanol, and dried at 120 °C for 16 hours to obtain UiO-66-TA powder.

[0049] The prepared UiO-66-TA (1 g) was pyrolyzed at 400 °C for 5 h in a mixed atmosphere of CO2 and CO (volume ratio 2:1) at a flow rate of 30 ml / min to obtain ZrO2 / C. Then, it was calcined at 800 °C for 6 h in a muffle furnace to obtain ZrO2. The ZrO2 support was then loaded with 15 wt% Ni and 0.5 wt% Cu using an impregnation method. The specific steps were as follows: a certain amount of nickel nitrate and ferric nitrate were dissolved in water, sonicated for 30 min, and then continuously stirred for 24 h. After stirring, sonication was continued for another 30 min, followed by drying to complete the loading and obtain the oxidized catalyst. Then, it was reduced at 400 °C for 1 h to obtain the target catalyst Ni-Fe / ZrO2.

[0050] COx-derived catalysts are used in the dry reforming of methane.

[0051] Example 6

[0052] Using the NiO / ZrO2 oxidized catalyst prepared in Example 1 as raw material, 50 mg of catalyst solid particles (40-60 mesh) and 1 g of quartz sand (40-60 mesh) were weighed and mixed evenly. The mixed solid particles were then packed into a quartz tube of a fixed-bed reaction gas system. The reaction gas path was purged with N2 (150 mL / min, 15 min) to remove residual impurities in the tube. The catalyst was then reduced at 500 °C with a 5% H2 / Ar mixed gas flow rate of 60 mL / min for 2 h. After reduction, the temperature was lowered to 200 °C, and nitrogen purging was switched to (150 mL / min, 15 min) until no H2 residue remained in the reaction tube. After purging, the reaction gas was switched to (15 ml CH4: 15 ml CO2: 20 ml N2, space velocity GHSV = 60,000 mLh). -1 gcat -1 After the raw gas was mixed evenly, the system was continuously heated to 600 ℃ at a rate of 10 ℃ / min and maintained for 8 h. Samples were taken 10 min after the reaction started and then every 20 min. It was found that when the active component loading was 5%, the initial conversion rate of methane and carbon dioxide under the action of Ni / ZrO2 catalyst was above 50%. After 8 h of reaction, the methane conversion rate was maintained above 40% and the carbon dioxide conversion rate was maintained at around 45%. The H2 / CO ratio was basically maintained between 0.7 and 0.8.

[0053] Comparative Examples (Non-CO) x Preparation and application of Ni / ZrO2 catalysts derived from (CO2 and / or CO) atmospheres.

[0054] Comparative Example 1: Preparation and Application of Catalysts Using a One-Step Air-Atmosphere Calcination Method

[0055] ZrCl4 (0.1506 g, 0.000646 mol) and BDC-NH2 (0.1174 g, 0.000648 mol) were dissolved separately in 12.5 mL of DMF. The resulting suspensions were sonicated for 30 minutes until complete dissolution, then mixed and sonicated for another 30 minutes. The mixture was then transferred to a 50 mL autoclave and placed in a preheated oven at 120 °C for 24 hours. After cooling to room temperature, the white product was centrifuged, washed several times with a mixture of DMF and methanol, and dried at 100 °C for 12 hours to obtain the MOF precursor.

[0056] The prepared MOF precursor material was pyrolyzed at 700 °C for 180 min in air at a flow rate of 60 mL / min to obtain a ZrO2 support. The ZrO2 support was then impregnated in an appropriate amount of nickel nitrate solution to obtain an oxidized catalyst, NiO / ZrO2. Reduction was then carried out at 500 °C with a 5% H2 / Ar mixed gas flow rate of 60 mL / min for 2 h to obtain the target catalyst, 5% Ni / ZrO2. The catalytic performance of the methane dry reforming reaction was evaluated using a fixed-bed reactor under the process conditions described in Example 6. The initial methane conversion rate of the Ni / ZrO2 catalyst was 25%, the initial carbon dioxide conversion rate was 30%, and the H2 / CO ratio was maintained between 0.7 and 1.0.

[0057] Comparative Example 2: Preparation and Application of Ni / ZrO2 Catalysts Using a Two-Step Strategy of Nitrogen Atmosphere Pyrolysis-Air Calcination

[0058] The prepared conventional MOF precursor material from Comparative Example 1 was pyrolyzed at 700 °C for 180 min under a nitrogen atmosphere at a flow rate of 60 mL / min to obtain ZrO2 / C. 5 wt% Ni active metal was then loaded onto the ZrO2 / C support using an impregnation method. The ZrO2 / C was then calcined at 500 °C for 180 min under an air atmosphere to obtain the oxidized catalyst NiO / ZrO2. Reduction was then performed at 500 °C with a 5% H2 / Ar mixed gas flow rate of 60 mL / min for 2 h to obtain the target catalyst Ni / ZrO2. The catalytic performance of the Ni / ZrO2 catalyst was evaluated using a fixed-bed reactor under the process conditions of Example 6. The initial methane conversion rate was 25%, the initial carbon dioxide conversion rate was 32%, and the H2 / CO ratio remained consistently between 0.7 and 1.0.

[0059] Comparative Example 3: Preparation and Application of Ni / ZrO2 Catalyst via Two-Step Strategy of Hydrogen Atmosphere Pyrolysis and Air Calcination

[0060] The prepared conventional MOF precursor material from Comparative Example 1 was pyrolyzed at 700 °C for 180 min under a hydrogen atmosphere with a flow rate of 60 mL / min to obtain ZrO2 / C. 5 wt% Ni active metal was then loaded onto the ZrO2 / C support using an impregnation method. The ZrO2 / C was then calcined at 500 °C for 180 min under an air atmosphere to obtain the oxidized catalyst NiO / ZrO2. This catalyst was then reduced at 500 °C with a 5% H2 / Ar mixed gas flow rate of 60 mL / min for 2 h to obtain the target catalyst Ni / ZrO2. The catalytic performance of the Ni / ZrO2 catalyst was evaluated using a fixed-bed reactor under the process conditions of Example 6. The initial methane conversion rate was 30%, the initial carbon dioxide conversion rate was 40%, and the H2 / CO ratio remained consistently between 0.7 and 1.0.

[0061] Comparative Example 4: Preparation and Application of Traditional MOF-Derived Ni / ZrO2 Catalysts with Different Loadings

[0062] The prepared conventional MOF precursor material from Comparative Example 1 was pyrolyzed at 700℃ for 3 h under a nitrogen atmosphere to obtain ZrO2 / C. Then, 5wt% Ni active metal was impregnated onto the ZrO2 / C support. Following calcination at 600℃ for 3 h in air atmosphere and reduction at 700℃ in a 5% H2 / Ar mixed gas, a 5% Ni / ZrO2 catalyst was prepared. The catalytic performance of the Ni / ZrO2 catalyst was evaluated using a fixed-bed reactor under the process conditions of Example 6. The initial methane conversion rate was 35%, the carbon dioxide conversion rate was 30%, and the H2 / CO ratio remained between 0.7 and 1.0.

[0063] Comparative Example 5: Preparation and Application of Ni / ZrO2 Catalyst Derived from Conventional UiO-66 Carbon Dioxide Atmosphere Pyrolysis

[0064] Zirconium chloride (ZrCl4, 0.1506 g, 0.000646 mol) and terephthalic acid (TPA, 0.1174 g, 0.000707 mol) were dissolved separately in 12.5 mL of N,N-dimethylformamide (DMF). The resulting suspensions were sonicated for 30 minutes until complete dissolution, then mixed and sonicated for another 30 minutes. The mixture was then transferred to a 50 mL autoclave and placed in a preheated oven at 120°C for 24 hours. After cooling to room temperature, the resulting white product was centrifuged and washed several times with a mixture of DMF and methanol, and then dried at 100°C for 12 hours to obtain conventional UiO-66 powder.

[0065] The prepared conventional UiO-66 powder was pyrolyzed at 700 °C for 180 min under a CO2 atmosphere at a flow rate of 60 mL / min to obtain ZrO2 / C. 5 wt% Ni active metal was loaded onto the ZrO2 / C support using an impregnation method. The specific experimental steps are as follows: A certain amount of nickel nitrate was dissolved in ethanol, and after complete dissolution, it was mixed with the pyrolyzed carbon material. The mixture was ultrasonicated for 30 min and then continuously stirred for 24 h. After stirring, ultrasonication was continued for another 30 min, followed by drying to complete the loading. Then, it was calcined in a muffle furnace at 500 °C for 180 min to obtain the oxidized catalyst NiO / ZrO2. Then, reduction was performed in a fixed bed at 500 °C with a 5% H2 / Ar mixed gas flow rate of 60 mL / min for 2 h to obtain the target catalyst Ni / ZrO2. The catalytic performance of the methane dry reforming reaction was evaluated according to the process conditions of Example 6. The initial methane conversion rate of the Ni / ZrO2 catalyst was 30%, the initial carbon dioxide conversion rate was 30%, and the H2 / CO ratio was basically maintained between 0.7 and 1.0.

Claims

1. A method for preparing a structurally defective Zr-MOF pyrolysis-derived zirconia-supported nano-metal catalyst, characterized in that, The specific steps are as follows: (1) After fully dissolving and mixing the MOF precursor metal salt, organic solvent, carboxyl ligand and defect structure modifier, UiO-66-X with a certain defect structure was prepared by hydrothermal method after cooling, centrifugation, washing and drying. (2) Preparation of M / ZrO2: A two-step strategy is used to pyrolyze the UiO-66-X precursor at high temperature to obtain the derived hierarchical porous ZrO2 support. In the two-step strategy, the precursor is first pyrolyzed in another atmosphere and then calcined in air. The other atmosphere is one or more of carbon dioxide and carbon monoxide. The supported catalyst precursor MO is prepared by impregnation or vapor deposition on the prepared ZrO2 support during the preparation of the ZrO2 support. X / ZrO2; finally, it is reduced by high temperature hydrogen to obtain the high-performance catalyst M / ZrO2 supported on zirconium oxide nano-metal; M is the active material metal component; M is one or more transition metals such as Ni, Co, Fe, Cu and Mn.

2. The method according to claim 1, characterized in that, In step (1), the MOF precursor metal salt zirconium source is one or more of zirconium chloride, zirconium nitrate, and zirconium oxychloride containing Zr. The carboxyl ligand includes one or more of terephthalic acid, aminoterephthalic acid, hydroxyterephthalic acid, trimesic acid, 2,5-dinitroterephthalic acid and their derivatives. The organic solvent includes one or more of N,N-dimethylformamide, acetonitrile, N-methylimidazolium, pyridine, N-methylpyrrolidone, dimethyl sulfoxide, diethylformamide, and trichlorobenzene. The defect structure modifier is a protic acid, including one or more of nitric acid, hydrochloric acid, citric acid, lactic acid, p-toluenesulfonic acid, formic acid, acetic acid, and benzoic acid.

3. The method according to claim 1, characterized in that, In step (1), the molar ratio of the precursor metal salt and the carboxyl ligand is 0.1-80; the molar ratio of the defect structure modifier and the precursor metal salt is 0.1-100; the molar ratio of the organic solvent and the precursor metal salt is 60-2500; the hydrothermal conditions are 80-200℃ and the time is 12-72 h.

4. The method according to claim 1, characterized in that, The molar ratio of the precursor metal salt to the carboxyl ligand is 0.5-1.5; the molar ratio of the defect structure modifier to the precursor metal salt is 0.2-15; and the molar ratio of the organic solvent to the precursor metal salt is 100-2000.

5. The method according to claim 1, characterized in that, Other atmosphere pyrolysis: pyrolysis temperature is 400~800 ℃, pyrolysis time is 0.5~5 h, heating rate is 2~50 ℃ / min, and the carrier gas flow rate per gram of catalyst is 10 ml / min~100 ml / min; calcination in air: calcination temperature is 500~800 ℃, calcination time is 0.5~10 h, heating rate is 2~50 ℃ / min.

6. The method according to claim 1, characterized in that, The content of the active metal component accounts for 0.1~25 wt.% of the total weight of the catalyst. When two active components are used, the molar ratio of the active components is 1:5-5:

1.

7. The method according to claim 6, characterized in that, M is one or two of Ni, Co, and Fe, and its content accounts for 0.1% to 15 wt% of the total weight of the catalyst.

8. The method according to claim 1, characterized in that, Preparation of MO X When using / ZrO2, the metal, metal oxide, and / or metal salt corresponding to the active component is loaded onto the intermediate product after pyrolysis in other atmospheres during the preparation of UiO-66-X, or loaded onto the intermediate product after pyrolysis in other atmospheres during the above two-step pyrolysis strategy; or the metal and metal oxide corresponding to the active component are loaded onto the ZrO2 support obtained by the two-step pyrolysis strategy; the metal salt precursor of the active component is one or more of nitrates, chlorides, acetates, and sulfates.

9. The method according to claim 1, characterized in that, Step (2) High-temperature hydrogen reduction refers to reduction at 300~800 ℃ for 0.1-5 h in a mixed atmosphere of hydrogen, hydrogen and argon, or hydrogen and nitrogen.

10. The method according to claim 9, characterized in that, The reduction temperature is 500~700 ℃, and the reduction time is 1.5h~3.5h.

11. The structural defect MOF pyrolysis-derived zirconia-supported nano-metal catalyst prepared according to any one of claims 1-10 has hierarchical pore characteristics, including micro-mesoporous composite materials with both micropores and mesopores, and hierarchical mesoporous materials with multiple mesopore size distribution ranges; wherein the micropores have a pore size of no more than 2 nm; the mesopores have a pore size of 2~8 nm and 12~25 nm, and a specific surface area greater than 70 m². 2 / g.

12. The application of the structural defect MOF pyrolysis-derived zirconia-supported nano-metal catalyst prepared according to any one of claims 1-10, wherein the catalyst is used in a methane dry reforming reaction; the reaction pressure is atmospheric pressure, the reaction temperature is 400~900 °C, and the reaction space velocity is 6,000~60,000 mLh. -1 gcat -1 The volume ratio of the raw material gas, methane, to carbon dioxide is 1:5 to 5:1.

Images