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CN-118831594-B - Preparation method and application of MOF pyrolysis-derived zirconia supported nano metal catalyst with structural defects

CN118831594BCN 118831594 BCN118831594 BCN 118831594BCN-118831594-B

Abstract

A preparation method and application of a structural defect MOF pyrolysis derived zirconia supported nano metal catalyst belong to the technical field of catalytic reforming. The preparation method of the catalyst takes UiO-66-X with structural defect as a precursor, adopts a derivative way of air calcination after CO x and other atmosphere pyrolysis, adopts a hierarchical pore zirconia carrier and loads active nano metal. The preparation method realizes the optimization of the crystal phase, morphology, oxygen-containing defect position and other surface microenvironment of the dry reforming catalyst carrier ZrO 2 by regulating and controlling the defect structure, quantity and pyrolysis atmosphere of the precursor, prepares a supported catalyst, and uses the supported catalyst in methane carbon dioxide reforming to prepare synthesis gas/hydrogen.

Inventors

  • XU BANG
  • HE XINRONG
  • JIA BINGYING
  • ZHANG KEXIN

Assignees

  • 北京工业大学

Dates

Publication Date
20260512
Application Date
20240619

Claims (12)

  1. 1. A preparation method of a structural defect Zr-MOF pyrolysis derived zirconia supported nano metal catalyst is characterized by comprising the following specific steps: (1) Fully dissolving and uniformly mixing MOFs precursor metal salt, an organic solvent, a carboxyl ligand and a defect structure regulator, and preparing UiO-66-X with a certain defect structure by adopting a hydrothermal method through cooling, centrifugal washing and drying; (2) The preparation method comprises the steps of carrying out high-temperature pyrolysis on a UiO-66-X precursor to obtain a derivative hierarchical pore ZrO 2 carrier, carrying out pyrolysis in other atmospheres and then calcining in air in a two-step method, preparing a supported catalyst precursor MO X /ZrO 2 by adopting an impregnation or vapor deposition method in the process of preparing the ZrO 2 carrier or on the prepared ZrO 2 carrier, and finally carrying out high-temperature hydrogen reduction to obtain the zirconia supported nano metal high-performance catalyst M/ZrO 2 , wherein M is an active material metal component, and M is one or more of Ni, co, fe, cu, mn transition metals.
  2. 2. The method of claim 1, wherein the source of zirconium metal salts of the MOFs precursor in step (1) is one or more of zirconium chloride, zirconium nitrate, zirconium oxychloride containing Zr element, the carboxyl ligand comprises one or more of terephthalic acid, amino terephthalic acid, hydroxy terephthalic acid, trimellitic acid, 2, 5-dinitroterephthalic acid, and derivatives thereof, the organic solvent comprises one or more of N, N-dimethylformamide, acetonitrile, N-methylimidazole, pyridine, N-methylpyrrolidone, dimethyl sulfoxide, diethylformamide, trichlorobenzene, and the defect structure modifier is a protonic acid comprising one or more of nitric acid, hydrochloric acid, citric acid, lactic acid, p-toluenesulfonic acid, formic acid, acetic acid, and benzoic acid.
  3. 3. The method of claim 1, wherein the molar ratio of the precursor metal salt to the carboxyl ligand in the step (1) is 0.1-80, the molar ratio of the defect structure modifier to the precursor metal salt is 0.1-100, the molar ratio of the organic solvent to the precursor metal salt is 60-2500, the hydrothermal condition is 80-200 ℃, and the time is 12-72 h.
  4. 4. The method according to claim 1, wherein 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. 5. The method of claim 1, wherein the other atmosphere is subjected to pyrolysis at 400-800 ℃, the pyrolysis time is 0.5-5 h, the heating rate is 2-50 ℃ per minute, the carrier gas flow rate corresponding to each gram of catalyst is 10 ml-100 ml per minute, the calcination in the air is carried out at 500-800 ℃, the calcination time is 0.5-10 h, the heating rate is 2-50 ℃ per minute, and the heating rate is 2-50 ℃ per minute.
  6. 6. The method according to claim 1, wherein the active material metal component content is 0.1-25 wt.% based on the total weight of the catalyst, and the molar ratio of the active components is 1:5-5:1 when two active material components are used.
  7. 7. The method according to claim 6, wherein M is one or two of Ni, co and Fe, and the content of M is 0.1% -15 wt% of the total weight of the catalyst.
  8. 8. The method according to claim 1, wherein when MO X /ZrO 2 is prepared, the metal, metal oxide or/and metal salt substance corresponding to the active component is loaded in the preparation of UiO-66-X or in an intermediate product obtained after pyrolysis in other atmosphere in the pyrolysis of the two-step pyrolysis strategy, or the metal and metal oxide corresponding to the active component are loaded on a ZrO 2 carrier obtained by pyrolysis of the two-step strategy, and the active component metal salt precursor is one or more of nitrate, chloride, acetate and sulfate.
  9. 9. The method of claim 1, wherein the high temperature hydrogen reduction in step (2) is performed at 300-800 ℃ in a mixed atmosphere of hydrogen, hydrogen and argon, and hydrogen and nitrogen, and 0.1-5 h.
  10. 10. The method according to claim 9, wherein the reduction temperature is 500-700 ℃ and the reduction time is 1.5-3.5 h.
  11. 11. The MOF pyrolysis-derived zirconia supported nano metal catalyst with structural defects, which is prepared by the method according to any one of claims 1-10, has a multistage pore characteristic, comprises a micro-mesoporous composite material with micropores and mesopores and a multistage mesoporous material with a plurality of mesoporous pore diameter distribution ranges, wherein the pore diameter of the micropores is not more than 2nm, the pore diameter of the mesopores is 2-8 nm and 12-25 nm, and the specific surface area is more than 70 m 2 /g.
  12. 12. The application of the structural defect MOF pyrolysis derived zirconia supported nano metal catalyst prepared by the method according to any one of claims 1-10, wherein the catalyst is used for methane dry reforming reaction, the reaction pressure is normal pressure, the reaction temperature is 400-900 ℃, the reaction airspeed is 6,000-60,000 mLh -1 gcat -1 , and the volume ratio of raw gas methane to carbon dioxide is 1:5-5:1.

Description

Preparation method and application of MOF pyrolysis-derived zirconia supported nano metal catalyst with structural defects Technical Field The invention belongs to the field of preparation and application of metal oxide carriers and catalysts prepared by pyrolysis and derivatization of MOFs, and particularly relates to a preparation method of a catalyst which takes UiO-66-X with different structural defects as a precursor, adopts a derivatization way of air calcination after CO x atmosphere pyrolysis, and loads active nano metals on a hierarchical pore zirconia carrier. The preparation method realizes the optimization of the crystal phase, morphology, oxygen-containing defect position and other surface microenvironment of the dry reforming catalyst carrier ZrO 2 by regulating and controlling the defect structure, quantity and pyrolysis atmosphere of the precursor, prepares a supported catalyst, and uses the supported catalyst in methane carbon dioxide reforming to prepare synthesis gas/hydrogen. Background With the acceleration of global climate warming process, emission reduction control of carbon dioxide, methane and other room gases has become one of the important issues of global common concern. Methane dry reforming (CH 4 + CO2→ 2CO + 2H2, DRM) can convert two greenhouse gases into syngas at the same time, a typical low carbon process within the framework of carbon capture, utilization and sequestration (CCUS). However, the DRM reaction is a strong endothermic process, and the reaction temperature thereof is generally required to be higher than 700 o C, resulting in huge energy consumption and environmental pollution. Accordingly, there is increasing interest in developing DRM technologies under mild conditions. However, at reaction temperatures below 600 o C, methane cracking reactions with CO disproportionation gases are more likely to occur, resulting in deactivation of the catalyst by carbon deposition. Thus developing high activity, selectivity and stability under mild conditions remains a significant challenge. A great deal of research shows that the transition metal catalyst, especially the nickel-based catalyst, has higher activity and carbon deposit resistance, is low in price, and is considered as the catalyst with the most industrial application prospect. The dissociation and activation performance of the metal Ni in the non-noble metal catalyst for methane is equivalent to that of the noble metal, but the nickel-based catalyst also has the difficult problem of easy carbon deposition or deactivation caused by sintering. The method for improving the carbon deposition resistance of the nickel-based catalyst is mainly carried out from the following three aspects of (1) strengthening the adsorption and activation of CO 2, providing surface active oxygen, inhibiting carbon deposition, such as using an alkaline carrier, an oxygen carrier and the like, such as ZrO 2、CeO2 and the like, (2) modifying the surface of Ni particles, damaging or covering active sites which are easy to generate carbon deposition, such as step positions, edges and corners and the like, and (3) improving the dispersity of Ni active components, reducing the size of Ni particles and the like. ZrO 2 is considered to be an ideal catalyst support for methane dry reforming reactions due to its high thermal stability, good surface properties such as easy generation of oxygen vacancies, high oxygen mobility, lewis acid basicity, and redox properties. The preparation of zirconia carriers is currently researched to be realized in traditional modes such as a coprecipitation method, a sol-gel method, a hydrothermal method and the like, and structural regulation and control of oxygen vacancies, crystalline phases, crystal face exposure, action strength of carriers and active components and the like of the carriers are realized by changing carrier preparation conditions, calcination atmosphere, calcination temperature, reduction temperature, loading modes of active components and the like, and preliminary results show that compared with monoclinic/tetragonal mixed phases and monoclinic phase zirconia, tetragonal phase zirconia has higher oxygen vacancy density, alkaline active sites and stronger metal-carrier interaction, partially reduced Zr species are formed, and better reaction performance and anti-carbon deposition capability are shown. The monoclinic phase zirconia has lower pore volume and specific surface area, so that the dispersity of Ni particles is very low, and the monoclinic phase zirconia is a main reason for low activity of the catalyst for methane dry reforming. Meanwhile, the distribution and the quantity of oxygen vacancies on the surface of the carrier are changed by regulating and controlling the calcining atmosphere, and compared with the nitrogen, oxygen and hydrogen atmospheres, the alkalinity and the oxygen vacancies of the zirconia carrier are maximized, so that the most stable catalyst is prepared, and the remov