CN114797928A - Core-shell ZIFs pyrolysis derived porous carbon material cobalt catalyst and preparation method thereof - Google Patents
Core-shell ZIFs pyrolysis derived porous carbon material cobalt catalyst and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 35
- 238000000197 pyrolysis Methods 0.000 title claims abstract description 29
- 239000013153 zeolitic imidazolate framework Substances 0.000 title claims abstract description 25
- 239000011258 core-shell material Substances 0.000 title claims abstract description 23
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 239000003575 carbonaceous material Substances 0.000 title claims abstract description 13
- 229910017052 cobalt Inorganic materials 0.000 title claims abstract description 10
- 239000010941 cobalt Substances 0.000 title claims abstract description 10
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims abstract description 10
- 239000000463 material Substances 0.000 claims abstract description 32
- 230000001590 oxidative effect Effects 0.000 claims abstract description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 126
- 239000007789 gas Substances 0.000 claims description 30
- 239000013172 zeolitic imidazolate framework-7 Substances 0.000 claims description 26
- 239000000725 suspension Substances 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 21
- 238000003756 stirring Methods 0.000 claims description 20
- 239000011701 zinc Substances 0.000 claims description 19
- 239000013154 zeolitic imidazolate framework-8 Substances 0.000 claims description 12
- MFLKDEMTKSVIBK-UHFFFAOYSA-N zinc;2-methylimidazol-3-ide Chemical compound [Zn+2].CC1=NC=C[N-]1.CC1=NC=C[N-]1 MFLKDEMTKSVIBK-UHFFFAOYSA-N 0.000 claims description 12
- 239000013173 zeolitic imidazolate framework-9 Substances 0.000 claims description 11
- HYZJCKYKOHLVJF-UHFFFAOYSA-N 1H-benzimidazole Chemical compound C1=CC=C2NC=NC2=C1 HYZJCKYKOHLVJF-UHFFFAOYSA-N 0.000 claims description 10
- 239000003446 ligand Substances 0.000 claims description 10
- 229910052725 zinc Inorganic materials 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 9
- 230000001681 protective effect Effects 0.000 claims description 8
- 239000000047 product Substances 0.000 claims description 7
- 150000001868 cobalt Chemical class 0.000 claims description 6
- RAXXELZNTBOGNW-UHFFFAOYSA-N imidazole Natural products C1=CNC=N1 RAXXELZNTBOGNW-UHFFFAOYSA-N 0.000 claims description 6
- 150000003751 zinc Chemical class 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 claims description 4
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 4
- 239000012265 solid product Substances 0.000 claims description 4
- 239000013174 zeolitic imidazolate framework-10 Substances 0.000 claims description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-M Formate Chemical compound [O-]C=O BDAGIHXWWSANSR-UHFFFAOYSA-M 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 239000013078 crystal Substances 0.000 claims description 2
- 238000000227 grinding Methods 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000011148 porous material Substances 0.000 abstract description 23
- 239000006185 dispersion Substances 0.000 abstract description 10
- 239000002243 precursor Substances 0.000 abstract description 4
- 239000002131 composite material Substances 0.000 abstract description 3
- 230000000694 effects Effects 0.000 abstract description 2
- 238000011068 loading method Methods 0.000 abstract description 2
- 239000002245 particle Substances 0.000 abstract 1
- 238000006243 chemical reaction Methods 0.000 description 15
- 238000012512 characterization method Methods 0.000 description 14
- 238000011065 in-situ storage Methods 0.000 description 14
- 238000002156 mixing Methods 0.000 description 13
- 239000007787 solid Substances 0.000 description 9
- 239000002184 metal Substances 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 238000004876 x-ray fluorescence Methods 0.000 description 8
- 238000004364 calculation method Methods 0.000 description 7
- 238000001816 cooling Methods 0.000 description 7
- 238000005984 hydrogenation reaction Methods 0.000 description 7
- 239000002244 precipitate Substances 0.000 description 7
- 239000010453 quartz Substances 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 7
- 238000006555 catalytic reaction Methods 0.000 description 6
- 239000011259 mixed solution Substances 0.000 description 6
- 238000004375 physisorption Methods 0.000 description 6
- 239000012621 metal-organic framework Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- YSWBFLWKAIRHEI-UHFFFAOYSA-N 4,5-dimethyl-1h-imidazole Chemical compound CC=1N=CNC=1C YSWBFLWKAIRHEI-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 239000003426 co-catalyst Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000005622 photoelectricity Effects 0.000 description 2
- 238000000859 sublimation Methods 0.000 description 2
- 230000008022 sublimation Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- BAXOFTOLAUCFNW-UHFFFAOYSA-N 1H-indazole Chemical compound C1=CC=C2C=NNC2=C1 BAXOFTOLAUCFNW-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 239000012018 catalyst precursor Substances 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000007210 heterogeneous catalysis Methods 0.000 description 1
- 238000000703 high-speed centrifugation Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 150000002902 organometallic compounds Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B01J35/394—
-
- B01J35/617—
-
- B01J35/618—
-
- B01J35/635—
-
- B01J35/643—
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
- C01B2203/10—Catalysts for performing the hydrogen forming reactions
- C01B2203/1041—Composition of the catalyst
- C01B2203/1047—Group VIII metal catalysts
- C01B2203/1052—Nickel or cobalt catalysts
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
- C01B2203/10—Catalysts for performing the hydrogen forming reactions
- C01B2203/1041—Composition of the catalyst
- C01B2203/1076—Copper or zinc-based catalysts
Abstract
The invention relates to a porous carbon material cobalt catalyst Zn-CoO derived from core-shell ZIFs pyrolysis x The preparation method comprises the steps of designing and constructing a composite core-shell structure ZIF-X @ ZIF-Y as a precursor template, and preparing the core-shell structure ZIF-X @ ZIF-Y through pyrolysis and oxidizing roasting. The preparation method has the advantages that the distribution and dispersion degree of Co particles are higher through the space confinement effect of the ZIFs material, the cobalt-based catalyst has higher cobalt loading (20-60 wt%), a good pore structure, a higher specific surface area, a larger pore volume and a larger pore diameter, the preparation method is simple, and the catalyst has a wide application prospect in photoelectrocatalysis and thermocatalysis.
Description
Technical Field
The invention relates to a catalyst synthesis technology, and belongs to the field of catalysts. In particular to a carbon material Co catalyst generated by synthesis and pyrolysis of core-shell ZIFs and a preparation method thereof. More particularly, it relates to a porous Zn-CoO using composite ZIFs material as precursor x -CN (CN stands for porous carbon material) catalyst.
Background
Compared with most Metal Organic Frameworks (MOFs), the ZIFs material has higher physical and chemical stability, higher specific surface area and good pore structure. Therefore, ZIFs have become promising materials in various industries, including gas storage, membrane separation, catalysis, and biomedicine. ZIFs can provide tunable coordination space and chemically tailored cavity interior surfaces, and can support nano-metal particles as promising catalyst precursor materials, particularly for heterogeneous catalytic reactions. Due to their high specific surface area, excellent stability and high dispersibility of metal active centers, metal organic compound derivatives have been widely used as active catalysts in heterogeneous catalytic reactions.
The preparation of the core-shell ZIFs precursor can be used for preparing a Co catalyst with high dispersity and high load with a ZIFs special structure through pyrolysis, and has a very high application prospect in heterogeneous catalysis. Compared with a Co-based catalyst directly prepared from MOFs materials, Zn sublimes to promote the pore structure and Co dispersion of the carbon material, the metal utilization rate and the carrier mass transfer efficiency are greatly improved, and the catalyst is not easy to collapse and pulverize in the thermal catalysis process. The preparation process is simple and has a very high industrial utilization prospect.
Disclosure of Invention
The invention aims to prepare a porous carbon material catalyst Zn-CoO derived from core-shell ZIFs pyrolysis x -CN。
The preparation method comprises the following steps:
(1) preparing a core-shell structure of ZIF-X @ ZIF-Y; taking ZIF-X as an inner core, and epitaxially growing ZIF-Y on the inner core ZIF-X (namely the outer surface) to obtain ZIF-X @ ZIF-Y;
ZIF-X: one or more of ZIF-7, ZIF-8 and ZIF-10;
ZIF-Y: one or more of ZIF-67 and ZIF-9;
(2) carrying out pyrolysis on ZIF-X @ ZIF-Y under protective gas, and carrying out pretreatment in oxidizing atmosphere to obtain Zn-CoO x -CN。
The preparation method of the ZIF-X @ ZIF-Y comprises the following steps:
1) preparing ZIF-X: dissolving soluble zinc salt and ligand in methanol, wherein the dosage ratio of the soluble zinc salt to the ligand corresponding to ZIF-X to the methanol is 1-20 g: 1-20 g: 100-; stirring, centrifugally separating, washing a solid product, and drying to obtain a ZIF-X crystal;
2) preparation of ZIF-X @ ZIF-Y: dispersing the dried ZIF-X in methanol, stirring to obtain a ZIF-X suspension, dissolving a soluble cobalt salt and a ligand corresponding to the ZIF-Y in the methanol, and adding the mixture into the ZIF-X suspension, wherein the ratio of the ZIF-X to the soluble cobalt salt to the ligand to the methanol is 1 g: 1-20 g: 1-20 g: 100-1000ml (preferably 5-20 g: 5-20 g: 200-1000 ml); stirring, centrifugally separating, washing a solid product, and drying to obtain ZIF-X @ ZIF-Y;
wherein the ligands are respectively: imidazole (the corresponding product is ZIF-10), benzimidazole (the corresponding product is one or two of ZIF-7 and ZIF-9), 2-methylimidazole (the corresponding product is one or two of ZIF-8 and ZIF-67);
wherein the cobalt salt and zinc salt comprise one or more of formate, acetate, nitrate, chloride, sulfate and citrate of cobalt and/or zinc;
stirring for 5-50h (preferably 10-40h), centrifuging at 12000r/min (preferably 6000 10000r/min) at 5000-.
Zn-CoO of the invention x -CN preparation process is as follows:
grinding the dried ZIF-X @ ZIF-Y into powder, heating the ZIF-X @ ZIF-Y powder, introducing protective gas, and keeping the gas space velocity at 500- -1 (preferably 1000-5000 h) -1 ) Carrying out pyrolysis on ZIF-X @ ZIF-Y for 1-5h at 500-1000 ℃ (preferably 600-1000 ℃); subsequently switching the gas to 1% -20% (preferably 5% -10%) O 2 Protective gas (V/V), oxidizing for 1-5h (preferably 2-4h) at 100- x -a CN material;
wherein the protective gas is one or more than two inert gases of argon, nitrogen or helium; the heating rate from room temperature to the pyrolysis temperature is not more than 5 ℃/min (the preferred range is 1-5 ℃/min).
The invention relates to a porous carbon material catalyst Zn-CoO derived from core-shell ZIFs pyrolysis x CN has good pore structure, higher specific surface area, larger pore volume and pore diameter by physical adsorption; and high Co loading (20-60 wt%) was found by X-ray fluorescence analyzer.
The invention relates to a porous carbon material catalyst Zn-CoO derived from core-shell ZIFs pyrolysis x The preparation method of the-CN is simple and novel, and has a wide application prospect in photoelectricity and thermal catalysis.
The invention has the beneficial effects that: according to the invention, a composite core-shell ZIFs precursor structure is designed and constructed, the core is a ZIFs structure formed by metal zinc, the outer layer is a ZIFs structure formed by metal Co, and metal Zn is easy to sublimate in the high-temperature pyrolysis process; a part of ZIFs structure is reserved through pyrolysis, which is beneficial to the space confinement effect of the catalyst on metal Co, and CN material with good pore structure is generated along with the sublimation of metal zinc and the carbonization of the ZIFs; co coated by the CN material is further exposed by oxidizing roasting, so that the catalytic capability and the adsorption and dissociation capability of the Co to gas and organic substances are improved, and the Co-coated by the CN material has a wide application prospect in photoelectricity and thermal catalysis.
Detailed Description
The invention is further illustrated by the following examples and comparative examples, but the invention is not limited to the examples listed.
Example 1
1. Adding Zn (NO) 3 ) 2 ·6H 2 O (5.95g) and benzimidazole (6.16g) were dissolved in 150mL of methanol, respectively; after mixing and stirring for 24 hours at room temperature, the suspension is centrifuged at high speed (10000r/min) and the solid is washed 3 times by methanol and dried at 60 ℃ to obtain ZIF-7, and the ZIF-7 coordination structure can be observed by a scanning electron microscope.
2. ZIF-7(0.5g) was dispersed in 150mL of methanol to form a ZIF-7 suspension; mixing Co (NO) 3 ) 2 ·6H 2 O (5.82g) and 2-methylimidazole (6.16g) were dissolved in 150mL of methanol, respectively, and added to the ZIF-7 suspension to obtain a mixed solution; after subsequent stirring at room temperature for 24 hours, the precipitate is centrifuged at high speed (10000r/min) solid is washed by methanol for 3 times, and dried at 60 ℃ to obtain ZIF-7@ ZIF-67, and the core-shell structure and the ZIF-67 coordination structure of the catalyst can be observed by characterization of a scanning electron microscope.
3. 2g of ZIF-7@ ZIF-67 is placed in a quartz tube and passes through a tube furnace, and is heated to 600 ℃ from room temperature in He atmosphere at the heating rate of 5 ℃/min for in-situ pyrolysis for 2h, wherein the gas space velocity is 2000h -1 Then naturally cooling to room temperature, switching the atmosphere to 5% O 2 Heating to 300 ℃ at the heating rate of 5 ℃/min and roasting in situ for 2h to obtain Zn-CoO x -CN。
0.05g of Zn-CoO was taken x -the characterization of the CN material by physisorption comprises: specific surface area, pore volume, and pore diameter; 0.8g of Zn-CoO was taken x Detecting the content of Co and Zn in the CN material by an X-ray fluorescence analyzer; 0.1g of Zn-CoO was taken x -CN materials for CO 2 Pulse chemisorption and calculation of dispersion gave the results shown in table 1.
CO is carried out in the catalyst fixed bed reactor 2 The reaction of hydrogenation reverse water gas is carried out under the reaction conditions of 500 ℃ of temperature and 2000h of space velocity -1 Pressure of 3MPa, CO 2 ：H 2 Is 4: 1. the results are shown in Table 2 below.
Example 2
1. Adding Zn (NO) 3 ) 2 ·6H 2 O (5.95g) and benzimidazole (6.16g) were dissolved in 150mL of methanol, respectively; after mixing and stirring for 24 hours at room temperature, the suspension is centrifuged at high speed (10000r/min) and the solid is washed 3 times by methanol and dried at 60 ℃ to obtain ZIF-7, and the ZIF-7 coordination structure can be observed by a scanning electron microscope.
2. ZIF-7(0.6g) was dispersed in 150mL of methanol to form a ZIF-7 suspension; mixing Co (NO) 3 ) 2 ·6H 2 O (5.82g) and 2-methylimidazole (6.16g) were dissolved in 150mL of methanol, respectively, and added to the ZIF-7 suspension to obtain a mixed solution; and then stirring at room temperature for 24 hours, washing the precipitate with methanol for 3 times at a high speed (10000r/min) to obtain ZIF-7@ ZIF-67, and observing the core-shell structure and ZIF-67 coordination structure of the catalyst by scanning electron microscope characterization.
3. 2g of ZIF-7@ ZIF-67 is placed in a quartz tube and passes through a tube furnace, the temperature is raised to 600 ℃ in Ar atmosphere at the temperature rise rate of 5 ℃/min, the in-situ pyrolysis is carried out for 2h, and the gas space velocity is 2000h -1 Then naturally cooling to room temperature, switching the atmosphere to 5% O 2 Heating to 300 ℃ at the heating rate of 5 ℃/min and roasting in situ for 2h to obtain Zn-CoO x -CN。
0.05g of Zn-CoO was taken x -the characterization of the physical adsorption of the CN material comprises: specific surface area, pore volume, and pore diameter; 0.8g of Zn-CoO was taken x Detecting the content of Co and Zn in the CN material by an X-ray fluorescence analyzer; 0.1g of Zn-CoO was taken x -CN materials for CO 2 Pulse chemisorption and calculation of dispersion gave the results shown in table 1.
CO is carried out in the catalyst fixed bed reactor 2 The reaction of hydrogenation reverse water gas is carried out under the reaction conditions of 500 ℃ of temperature and 2000h of space velocity -1 Pressure of 3MPa, CO 2 ：H 2 Is 4: 1. the results are shown in Table 2 below.
Example 3
1. Adding Zn (NO) 3 ) 2 ·6H 2 O (5.95g) and benzimidazole (6.16g) were dissolved in 150mL of methanol, respectively; after mixing and stirring for 24 hours at room temperature, the suspension is centrifuged at high speed (10000r/min) and the solid is washed 3 times by methanol and dried at 60 ℃ to obtain ZIF-7, and the ZIF-7 coordination structure can be observed by a scanning electron microscope.
2. ZIF-7(0.8g) was dispersed in 150mL of methanol to form a ZIF-7 suspension; mixing Co (NO) 3 ) 2 ·6H 2 O (5.82g) and benzimidazole (6.16g) were dissolved in 150mL of methanol, respectively, and added to the ZIF-7 suspension to obtain a mixed solution; and then stirring at room temperature for 24 hours, washing the precipitate with methanol for 3 times at a high speed (10000r/min) to obtain ZIF-7@ ZIF-9, and observing the core-shell structure and ZIF-9 coordination structure of the catalyst by scanning electron microscope characterization.
3. 2g of ZIF-7@ ZIF-9 is placed in a quartz tube and passes through a tube furnace, the temperature is raised to 600 ℃ in Ar atmosphere at the temperature rise rate of 5 ℃/min, the in-situ pyrolysis is carried out for 2h, and the gas space velocity is 2000h -1 Then naturally cooling to room temperature, switching the atmosphere to 5% O 2 Heating to 300 ℃ at the heating rate of 5 ℃/min and roasting in situ for 2h to obtain Zn-CoO x -CN。
0.05g of Zn-CoO was taken x -the characterization of the CN material by physisorption comprises: specific surface area, pore volume, and pore diameter; 0.8g of Zn-CoO was taken x Detecting the content of Co and Zn in the CN material by an X-ray fluorescence analyzer; 0.1g of Zn-CoO was taken x -CN materials for CO 2 Pulse chemisorption and calculation of dispersion gave the results shown in table 1.
CO is carried out in the catalyst fixed bed reactor 2 The reaction of hydrogenation reverse water gas is carried out under the reaction conditions of 500 ℃ of temperature and 2000h of space velocity -1 Pressure of 3MPa, CO 2 ：H 2 Is 4: 1. the results are shown in Table 2 below.
Example 4
1. Adding Zn (NO) 3 ) 2 ·6H 2 O (5.95g) and benzimidazole (6.16g) were dissolved in 150mL of methanol, respectively; after mixing and stirring for 24 hours at room temperature, the suspension is centrifuged at high speed (10000r/min) and the solid is washed 3 times by methanol and dried at 60 ℃ to obtain ZIF-7, and the ZIF-7 coordination structure can be observed by a scanning electron microscope.
2. ZIF-7(0.7g) was dispersed in 150mL of methanol to form a ZIF-7 suspension; mixing Co (NO) 3 ) 2 ·6H 2 O (5.82g) and benzopyrazole (6.16g) were dissolved in 150mL of methanol, respectively, and added to the ZIF-7 suspension to obtain a mixed solution; and then stirring at room temperature for 24 hours, washing the precipitate with methanol for 3 times at a high speed (10000r/min) to obtain ZIF-7@ ZIF-9, and observing the core-shell structure and ZIF-9 coordination structure of the catalyst by scanning electron microscope characterization.
3. 2g of ZIF-7@ ZIF-9 is placed in a quartz tube and passes through a tube furnace, the temperature is raised to 600 ℃ in Ar atmosphere at the temperature rise rate of 5 ℃/min, the in-situ pyrolysis is carried out for 2h, and the gas space velocity is 2000h -1 Then naturally cooling to room temperature, switching the atmosphere to 5% O 2 Heating to 300 ℃ at the heating rate of 5 ℃/min and roasting in situ for 2h to obtain Zn-CoO x -CN。
0.05g of Zn-CoO was taken x -the characterization of the CN material by physisorption comprises: specific surface area, pore volume andthe diameter of the hole; 0.8g of Zn-CoO was taken x Detecting the content of Co and Zn in the CN material by an X-ray fluorescence analyzer; 0.1g of Zn-CoO was taken x -CN materials for CO 2 Pulse chemisorption and calculation of dispersion gave the results shown in table 1.
CO is carried out in the catalyst fixed bed reactor 2 The reaction of hydrogenation reverse water gas is carried out under the reaction conditions of 500 ℃ of temperature and 2000h of space velocity -1 Pressure of 3MPa, CO 2 ：H 2 Is 3: 1. the results are given in Table 2 below.
Example 5
1. Adding Zn (NO) 3 ) 2 ·6H 2 O (5.95g) and dimethylimidazole (6.16g) were dissolved in 150mL of methanol, respectively; after mixing and stirring for 24 hours at room temperature, the suspension is centrifuged at high speed (10000r/min) and the solid is washed 3 times by methanol and dried at 60 ℃ to obtain ZIF-7, and the ZIF-8 coordination structure can be observed by a scanning electron microscope.
2. ZIF-8(0.6g) was dispersed in 150mL of methanol to form a ZIF-8 suspension; mixing Co (NO) 3 ) 2 ·6H 2 O (5.82g) and benzimidazole (6.16g) were dissolved in 150mL of methanol, respectively, and added to the ZIF-8 suspension to obtain a mixed solution; and then stirring at room temperature for 24 hours, washing the precipitate with methanol for 3 times at a high speed (10000r/min) to obtain ZIF-8@ ZIF-9, and observing the core-shell structure and the ZIF-9 coordination structure of the catalyst by characterization of a scanning electron microscope.
3. 2g of ZIF-8@ ZIF-9 is placed in a quartz tube and passes through a tube furnace, the temperature is raised to 600 ℃ in Ar atmosphere at the temperature rise rate of 5 ℃/min, the in-situ pyrolysis is carried out for 2h, and the gas space velocity is 2000h -1 Then naturally cooling to room temperature, switching the atmosphere to 5% O 2 Heating to 300 ℃ at the heating rate of 5 ℃/min and roasting in situ for 2h to obtain Zn-CoO x -CN。
0.05g of Zn-CoO was taken x -the characterization of the CN material by physisorption comprises: specific surface area, pore volume, and pore diameter; 0.8g of Zn-CoO was taken x Detecting the content of Co and Zn in the CN material by an X-ray fluorescence analyzer; 0.1g of Zn-CoO was taken x -CN materials for CO 2 Pulse chemisorption and calculation of dispersion gave the results shown in table 1.
CO is carried out in the catalyst fixed bed reactor 2 The reaction of hydrogenation reverse water gas is carried out under the reaction conditions of 500 ℃ of temperature and 2000h of space velocity -1 Pressure of 3MPa, CO 2 ：H 2 Is 3: 1. the results are shown in Table 2 below.
Example 6
1. Adding Zn (NO) 3 ) 2 ·6H 2 O (5.95g) and dimethylimidazole (6.16g) were dissolved in 150mL of methanol, respectively; after mixing and stirring for 24 hours at room temperature, the suspension is centrifuged at high speed (10000r/min) and the solid is washed 3 times by methanol and dried at 60 ℃ to obtain ZIF-7, and the ZIF-8 coordination structure can be observed by a scanning electron microscope.
2. ZIF-8(0.5g) was dispersed in 150mL of methanol to form a ZIF-8 suspension; mixing Co (NO) 3 ) 2 ·6H 2 O (5.82g) and benzimidazole (6.16g) were dissolved in 150mL of methanol, respectively, and added to the ZIF-8 suspension to obtain a mixed solution; and then stirring at room temperature for 24 hours, washing the precipitate with methanol for 3 times at a high speed (10000r/min) to obtain ZIF-8@ ZIF-9, and observing the core-shell structure and ZIF-9 coordination structure of the catalyst by scanning electron microscope characterization.
3. 2g of ZIF-8@ ZIF-9 was placed in a quartz tube and passed through a tube furnace at N 2 Heating to 600 ℃ at a heating rate of 5 ℃/min in the atmosphere for in-situ pyrolysis for 2h, wherein the gas space velocity is 2000h -1 Then naturally cooling to room temperature, switching the atmosphere to 5% O 2 Heating to 300 ℃ at the heating rate of 5 ℃/min and roasting in situ for 2h to obtain Zn-CoO x -CN。
0.05g of Zn-CoO was taken x -the characterization of the CN material by physisorption comprises: specific surface area, pore volume, and pore diameter; 0.8g of Zn-CoO was taken x Detecting the content of Co and Zn in the CN material by an X-ray fluorescence analyzer; 0.1g of Zn-CoO was taken x -CN materials for CO 2 Pulse chemisorption and calculation of dispersion gave the results shown in table 1.
CO is carried out in the catalyst fixed bed reactor 2 The reaction of hydrogenation reverse water gas is carried out under the reaction conditions of 500 ℃ of temperature and 2000h of space velocity -1 Pressure 3MPa, CO 2 ：H 2 Is 4: 1. the results are shown in Table 2 below.
Comparative example 1
1. Mixing Co (NO) 3 ) 2 ·6H 2 O (5.82g) and benzimidazole (6.16g) are dissolved in 100mL of methanol, mixed and stirred for 24h at room temperature, and then the precipitate is subjected to high-speed centrifugation (12000r/min) to obtain a solid, the solid is washed 4 times with MeOH and dried at 80 ℃ to obtain ZIF-9, and the ZIF-9 coordination structure can be observed by a scanning electron microscope.
2. 2g of ZIF-9 is put in a quartz tube and passes through a tube furnace, the temperature is raised to 700 ℃ in Ar atmosphere at the temperature raising rate of 5 ℃/min, the in-situ pyrolysis is carried out for 2h, and the gas space velocity is 2000h -1 Then naturally cooling to room temperature, switching the atmosphere to 10% O 2 Heating to 400 ℃ at the heating rate of 3 ℃/min and roasting in situ for 2h to obtain CoO x -CN。
0.05g of CoO was taken x -the characterization of the CN material by physisorption comprises: specific surface area, pore volume, and pore diameter; 0.8g of CoO was taken x -detecting the Co content in the CN material by an X-ray fluorescence analyzer; 0.1g of CoO was taken x -CN materials for CO 2 Pulse chemisorption and calculation of dispersion gave the results shown in table 1.
CO is carried out in the catalyst fixed bed reactor 2 The reaction of hydrogenation reverse water gas is carried out under the reaction conditions of 500 ℃ of temperature and 2000h of space velocity -1 Pressure of 3MPa, CO 2 ：H 2 Is 4: 1. the results are shown in Table 2 below.
Table 1 characterization of physical properties of the core-shell ZIFs pyrolysis ZIFs-derived porous carbon material catalyst Co-CN.
Table 2 catalyst reverse water gas shift reaction performance evaluation and product analysis.
From the physicochemical properties and catalytic performance of the catalysts in table 1 it can be seen that: the method can be used for preparing the porous carbon material cobalt catalyst derived from the core-shell ZIFs pyrolysis, Co nanoparticles are difficult to gather and sublimate due to sublimation in the pyrolysis process of metal Zn in the ZIFs framework structure, and the catalyst has good cobalt dispersion degree through partial oxidation of oxygen and has an excellent pore structure. Has wide application prospect in photoelectrocatalysis and thermocatalysis.
Claims (4)
1. A preparation method of a porous carbon material cobalt catalyst derived from core-shell ZIFs pyrolysis is characterized by comprising the following steps:
(1) preparing a core-shell structure of ZIF-X @ ZIF-Y; taking ZIF-X as an inner core, and epitaxially growing ZIF-Y on the inner core ZIF-X (namely the outer surface) to obtain ZIF-X @ ZIF-Y;
ZIF-X: one or more of ZIF-7, ZIF-8 and ZIF-10;
ZIF-Y: one or more of ZIF-67 and ZIF-9;
(2) carrying out pyrolysis on ZIF-X @ ZIF-Y under protective gas, and carrying out pretreatment in oxidizing atmosphere to obtain Zn-CoO x -CN。
2. The process of claim 1, wherein ZIF-X @ ZIF-Y is prepared as follows:
1) preparing ZIF-X: dissolving soluble zinc salt and ligand in methanol, wherein the dosage ratio of the soluble zinc salt to the ligand corresponding to ZIF-X to the methanol is 1-20 g: 1-20 g: 100-; stirring, centrifugally separating, washing a solid product, and drying to obtain a ZIF-X crystal;
2) preparation of ZIF-X @ ZIF-Y: dispersing the dried ZIF-X in methanol, stirring to obtain a ZIF-X suspension, dissolving a soluble cobalt salt and a ligand corresponding to the ZIF-Y in the methanol, and adding the mixture into the ZIF-X suspension, wherein the ratio of the ZIF-X to the soluble cobalt salt to the ligand to the methanol is 1 g: 1-20 g: 1-20 g: 100-; stirring, centrifugally separating, washing a solid product, and drying to obtain ZIF-X @ ZIF-Y;
the ligands are respectively: imidazole (the corresponding product is ZIF-10), benzimidazole (the corresponding product is one or two of ZIF-7 and ZIF-9), 2-methylimidazole (the corresponding product is one or two of ZIF-8 and ZIF-67);
the cobalt salt and the zinc salt comprise one or more of formate, acetate, nitrate, chloride, sulfate and citrate of cobalt and/or zinc;
stirring for 5-50h (preferably 10-40h), centrifuging at 12000r/min (preferably 6000 10000r/min) at 5000-.
3. The production method according to claim 1, wherein Zn-CoO x -CN preparation process is as follows:
grinding the dried ZIF-X @ ZIF-Y into powder, heating the ZIF-X @ ZIF-Y powder, introducing protective gas, and keeping the gas space velocity at 500- -1 (preferably 1000-5000 h) -1 ) Carrying out pyrolysis on ZIF-X @ ZIF-Y for 1-5h at 500-1000 ℃ (preferably 600-1000 ℃); subsequently switching the gas to 1% -20% (preferably 5% -10%) O 2 Protective gas (V/V), oxidizing for 1-5h (preferably 2-4h) at 100- x -a CN material;
the protective gas is one or more than two inert atmosphere gases of argon, nitrogen or helium; the heating rate from room temperature to the pyrolysis temperature is not more than 5 ℃/min (the preferred range is 1-5 ℃/min).
4. Core-shell ZIFs pyrolysis derived porous carbon material catalyst Zn-CoO prepared by the preparation method of any one of claims 1 to 3 x -CN。
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| US20170368535A1 (en) * | 2015-11-11 | 2017-12-28 | Sabic Global Technologies B.V. | Multifunctional and stable nano-architectures containing nanocarbon and nano- or micro structures and a calcined hydrotalcite shell |
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