CN112973758A - ZIFs-based high-dispersion Co-based bimetallic catalyst and preparation method thereof - Google Patents
ZIFs-based high-dispersion Co-based bimetallic catalyst and preparation method thereof Download PDFInfo
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- 239000013153 zeolitic imidazolate framework Substances 0.000 title claims abstract description 127
- 239000003054 catalyst Substances 0.000 title claims abstract description 87
- 239000006185 dispersion Substances 0.000 title claims abstract description 43
- 238000002360 preparation method Methods 0.000 title claims abstract description 28
- 229910052751 metal Inorganic materials 0.000 claims abstract description 82
- 239000002184 metal Substances 0.000 claims abstract description 78
- 150000003839 salts Chemical class 0.000 claims abstract description 48
- 239000002904 solvent Substances 0.000 claims abstract description 41
- 238000000034 method Methods 0.000 claims abstract description 26
- 239000011148 porous material Substances 0.000 claims abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 11
- 238000006243 chemical reaction Methods 0.000 claims abstract description 10
- 238000003837 high-temperature calcination Methods 0.000 claims abstract description 9
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 153
- 239000002243 precursor Substances 0.000 claims description 63
- 239000000243 solution Substances 0.000 claims description 45
- 238000001354 calcination Methods 0.000 claims description 33
- 238000001035 drying Methods 0.000 claims description 24
- 239000011701 zinc Substances 0.000 claims description 23
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 claims description 20
- 239000011259 mixed solution Substances 0.000 claims description 17
- 239000012535 impurity Substances 0.000 claims description 16
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 14
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 14
- 239000012266 salt solution Substances 0.000 claims description 14
- 230000002209 hydrophobic effect Effects 0.000 claims description 13
- 238000005406 washing Methods 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical group CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 11
- 238000007872 degassing Methods 0.000 claims description 11
- 239000002244 precipitate Substances 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 11
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 7
- 150000001868 cobalt Chemical class 0.000 claims description 7
- 150000003751 zinc Chemical class 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 239000011261 inert gas Substances 0.000 claims description 5
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 4
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical group Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 4
- SONJTKJMTWTJCT-UHFFFAOYSA-K rhodium(iii) chloride Chemical group [Cl-].[Cl-].[Cl-].[Rh+3] SONJTKJMTWTJCT-UHFFFAOYSA-K 0.000 claims description 4
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical group [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 claims description 4
- 229910002621 H2PtCl6 Inorganic materials 0.000 claims description 3
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 claims description 3
- 229910019891 RuCl3 Inorganic materials 0.000 claims description 3
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 claims description 3
- RFLFDJSIZCCYIP-UHFFFAOYSA-L palladium(2+);sulfate Chemical compound [Pd+2].[O-]S([O-])(=O)=O RFLFDJSIZCCYIP-UHFFFAOYSA-L 0.000 claims description 3
- 229910000364 palladium(II) sulfate Inorganic materials 0.000 claims description 3
- 229910021604 Rhodium(III) chloride Inorganic materials 0.000 claims description 2
- 238000001179 sorption measurement Methods 0.000 claims description 2
- 230000000536 complexating effect Effects 0.000 claims 1
- 239000002923 metal particle Substances 0.000 abstract description 9
- 230000008569 process Effects 0.000 abstract description 8
- 238000005984 hydrogenation reaction Methods 0.000 abstract description 6
- 230000000737 periodic effect Effects 0.000 abstract description 5
- 230000015572 biosynthetic process Effects 0.000 abstract description 4
- 238000011065 in-situ storage Methods 0.000 abstract description 4
- 150000002739 metals Chemical class 0.000 abstract description 4
- 239000011943 nanocatalyst Substances 0.000 abstract description 4
- 238000003786 synthesis reaction Methods 0.000 abstract description 4
- 239000002086 nanomaterial Substances 0.000 abstract description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 abstract description 2
- 239000000203 mixture Substances 0.000 abstract description 2
- 230000003647 oxidation Effects 0.000 abstract description 2
- 238000007254 oxidation reaction Methods 0.000 abstract description 2
- 238000009210 therapy by ultrasound Methods 0.000 description 36
- 238000010438 heat treatment Methods 0.000 description 30
- SLCITEBLLYNBTQ-UHFFFAOYSA-N CO.CC=1NC=CN1 Chemical compound CO.CC=1NC=CN1 SLCITEBLLYNBTQ-UHFFFAOYSA-N 0.000 description 18
- 238000011068 loading method Methods 0.000 description 18
- 238000009849 vacuum degassing Methods 0.000 description 18
- 238000001291 vacuum drying Methods 0.000 description 18
- 229910002441 CoNi Inorganic materials 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 238000003917 TEM image Methods 0.000 description 10
- 239000007864 aqueous solution Substances 0.000 description 10
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 238000006555 catalytic reaction Methods 0.000 description 8
- 239000010948 rhodium Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 239000013154 zeolitic imidazolate framework-8 Substances 0.000 description 7
- 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 description 7
- 230000000694 effects Effects 0.000 description 6
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 6
- 229910003321 CoFe Inorganic materials 0.000 description 4
- 229910018936 CoPd Inorganic materials 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 230000004075 alteration Effects 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000000731 high angular annular dark-field scanning transmission electron microscopy Methods 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 229910052703 rhodium Inorganic materials 0.000 description 4
- 238000002604 ultrasonography Methods 0.000 description 4
- 230000002779 inactivation Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910018979 CoPt Inorganic materials 0.000 description 2
- 229910017061 Fe Co Inorganic materials 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 239000012621 metal-organic framework Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- LQNUZADURLCDLV-UHFFFAOYSA-N nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1 LQNUZADURLCDLV-UHFFFAOYSA-N 0.000 description 2
- 239000013110 organic ligand Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- -1 Co appeared Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000010000 carbonizing Methods 0.000 description 1
- 239000012018 catalyst precursor Substances 0.000 description 1
- 238000004517 catalytic hydrocracking Methods 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 150000004696 coordination complex Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000002283 diesel fuel Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 125000002883 imidazolyl group Chemical group 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
Images
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
-
- B01J35/23—
-
- B01J35/399—
-
- B01J35/635—
-
- 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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/082—Decomposition and pyrolysis
- B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention discloses a ZIFs-based high-dispersion Co-based bimetallic catalyst and a preparation method thereof, belonging to the technical field of synthesis of nano materials and catalysts, and the method skillfully utilizes the characteristics of high dispersion of metal nodes and periodic pore channel structure in ZnCo-ZIFs, and firstly utilizes a double-solvent method to introduce a second active metal salt into a ZIFs pore channel; and then in the high-temperature calcination process, the low-boiling-point metal Zn volatilizes to play a fence role, the distance between the active metals is increased, and the Co node and the second active metal are reduced in situ to obtain the high-dispersion Co-based bimetallic catalyst loaded on the nitrogen-doped carbon carrier. The method has simple process and convenient operation, the composition of the obtained high-dispersion Co-based bimetallic catalyst is flexible and adjustable, the metal particles are distributed in a high-dispersion form, and the high-dispersion Co-based bimetallic catalyst has better stability and is expected to be applied to reactions such as hydrogenation reaction, synthesis gas conversion, alcohol selective oxidation and the like.
Description
Technical Field
The invention belongs to the technical field of synthesis of nano materials and catalysts, and relates to a ZIFs-based high-dispersion Co-based bimetallic catalyst and a preparation method thereof.
Background
Zeolite-imidazolate framework (ZIFs) materials, which are a subclass of Metal-organic framework (MOFs) materials, are made of Metal ions with a tetrahedrally coordinated configuration (e.g., Zn)2+、Co2+) Coordinated with imidazolyl organic ligands, including Zn-based ZIF-8, Co-based ZIF-67, etc. The ZIFs material has a typical zeolite-like periodic topological structure, has the characteristics of large specific surface area, high thermal stability and easiness in preparation, and has wide application in the fields of gas storage and separation, sensing, catalysis, membrane science and the like.
The Chinese invention patent with the application number of 201510168261.9 discloses a ZIF-8-based hydrogenation catalyst and a synthesis method thereof, which comprises the steps of firstly taking ZIF-8 as a carrier, introducing active metal by an impregnation method, and then carrying out high-temperature roasting reduction treatment to obtain the hydrogenation catalyst, wherein the catalytic efficiency of the catalyst in the diesel oil hydrocracking reaction is improved by dozens of times compared with that of the traditional alumina catalyst, but the active metal particles in the catalyst are in a nanometer scale, and the metal utilization rate is not high. The Chinese patent with the application number of 201510891468.9 discloses a preparation method of a catalyst of a ZIF-8 material loaded CoB, which utilizes Zn2+And Co2+The catalyst can be coordinated with 2-methylimidazole simultaneously, a ZIF-8/ZIF-67 mixed material is prepared by taking cobalt salt, zinc salt and 2-methylimidazole as raw materials, and the ZIF-8 loaded CoB catalyst is obtained after reduction of sodium borohydride liquid phase.
With the continuous progress of nanotechnology and characterization technology, the research dimension of nanomaterials is gradually reduced, and high-dispersion supported metal catalysts, including nanoclusters (<2nm), sub-nanometers (<1nm) and monatomic catalysts, gradually attract people's attention.
When the size of the metal particles is reduced, the utilization rate of the metal can be improved, the preparation cost of the catalyst is reduced, and the electronic and geometric structures of the catalyst can also be obviously changed, such as a large amount of unsaturated coordination environments, metal-carrier interaction, uniform active sites and the like, so that the high-dispersion metal catalyst has excellent performance different from that of a common nano catalyst. For example, the queen iron peak team uses a ZIF-8/ZIF-67 mixed material as a catalyst precursor, and the catalyst is calcined at high temperature by inert gas to obtain a Co monatomic catalyst, the hydrogenation activity of the catalyst in the nitrobenzene hydrogenation reaction is 5.4 times of that of a Co nano catalyst with the same load, and the catalyst has better stability, [ ACS appl.Mater.Interfaces,2020,12,34021-34031 ]. Compared with a single metal catalyst, the bimetallic catalyst has better catalytic performance due to unique electronic effect and geometric effect. Currently, the focus on ZIFs-based bimetallic catalysts is mostly on the nanoscale. For example, the Chinese patent application No. 201911417367.2 discloses a preparation method of a supported Fe-Co/ZIF-67 bimetallic catalyst, which takes ZIF-67 as a template, iron and cobalt are supported on the ZIF-67 in a coprecipitation mode, and the magnetic Fe-Co/ZIF-67 bimetallic catalyst is obtained by calcining, wherein the mass fractions of Fe and Co are between 5 and 15 percent, metal particles are in a nanometer scale, and the problem of low metal utilization rate exists.
In view of the above, it is highly desirable to develop a highly dispersed bimetallic catalyst based on ZIFs to solve the above problems.
Disclosure of Invention
The invention aims to overcome the defect of low metal utilization rate in the bimetallic catalyst in the prior art, and provides a ZIFs-based high-dispersion Co-based bimetallic catalyst and a preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a high-dispersion Co-based bimetallic catalyst based on ZIFs, wherein Co is loaded on a nitrogen-doped carbon carrier in a form of nano-cluster or single atom.
A preparation method of a ZIFs-based high-dispersion Co-based bimetallic catalyst comprises the following steps:
step 1) mixing soluble zinc salt and soluble cobalt salt to prepare a metal salt solution with the mass concentration of 1-10%, and preparing a 2-methylimidazole solution with the mass concentration of 1-22%; the method comprises the following steps of (1) mixing a 2-methylimidazole solution and a metal salt solution according to a molar ratio (4-8): 1, mixing to obtain a first mixed solution, placing the mixed solution at 30-50 ℃ for a complex reaction, and centrifuging, washing and drying once after the reaction to obtain a ZnCo-ZIFs precursor;
step 2) degassing and removing impurities of the ZnCo-ZIFs precursor;
and 3) dispersing the degassed and impurity-removed ZnCo-ZIFs precursor in the step 2) in a hydrophobic solvent to obtain a second mixed solution with the mass concentration of 0.6-0.8%, mixing the second mixed solution with a second active metal salt solution of 0-150 mg/mL, stirring for 6-12 h, and drying to obtain the metal salt @ ZnCo-ZIFs.
And 4) calcining the metal salt @ ZnCo-ZIFs in the step 3) at high temperature in inert gas, wherein the calcining temperature is 900-1000 ℃, and air cooling is performed after the calcining is finished, so that the ZIFs-based high-dispersion Co-based bimetallic catalyst is obtained.
Preferably, in the metal salt solution in the step 1), the molar ratio of the soluble zinc salt to the soluble cobalt salt is (24-100): 1.
preferably, the zinc salt in step 1) is Zn (NO)3)2·6H2O or Zn (OAc)2·2H2O; the cobalt salt is Co (NO)3)2·6H2O or Co (OAc)2·4H2O。
Preferably, the time of the coordination reaction in the step 1) is 6-12 h; drying in the step 1) is to dry the centrifuged precipitate at 40-60 ℃ for 8-12 h; the high-temperature calcination time in the step 4) is 3-6 h.
Preferably, the metal salt solution and the 2-methylimidazole solution in the step 1) are both prepared by taking methanol as a solvent; the washing was carried out with methanol.
Preferably, the ZnCo-ZIFs precursor subjected to degassing and impurity removal in the step 2) is of a porous structure, and the pore volume of the ZnCo-ZIFs precursor is 0.57cm measured by physical adsorption3(ii)/g; in the step 3), the volume of the second active metal salt solution is less than or equal to the pore volume of the degassed and purified ZnCo-ZIFs precursor in the step 2).
Preferably, the inert gas in step 4) is argon or nitrogen.
Preferably, the second active metal salt in step 3) is any one of a water-soluble Ni salt, a water-soluble Rh salt, a water-soluble Fe salt, a water-soluble Ru salt, a water-soluble Pd salt and a water-soluble Pt salt; the hydrophobic solvent is n-hexane or chloroform.
Further preferably, the water-soluble Ni salt is Ni (NO)3)2·6H2O or NiCl2·6H2O; the water-soluble Rh salt is RhCl3·3H2O; the water-soluble Fe salt is FeCl3·6H2O or Fe (NO)3)3·9H2O; the water-soluble Ru salt is RuCl3·3H2O; the water-soluble Pd salt is Pd (NO)3)2·2H2O or PdSO4·2H2O; the water-soluble Pt salt is H2PtCl6·6H2O。
Preferably, the degassing and impurity removing in the step 2) are carried out in vacuum, the degassing temperature is 80-150 ℃, and the degassing time is 8-10 h.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a ZIFs-based high-dispersion Co-based bimetallic catalyst, wherein metal particles are in a nano-cluster or monoatomic scale, so that the improvement of the metal utilization rate is facilitated, and the preparation cost of the catalyst is reduced. Because the high-dispersion bimetallic catalyst has size effect and electronic effect and the synergy exists between the bimetallic catalysts, compared with the corresponding single metal catalyst, the Co-based bimetallic catalyst can embody excellent catalytic performances such as high activity, high selectivity and the like in the catalytic reaction, and the Co-based bimetallic catalyst is calcined at high temperature in the preparation processThe catalyst has high thermal stability, and is not easy to generate the phenomena of metal particle clustering and inactivation in the application process of catalytic reaction. Such Co-based bimetallic catalysts have the advantage of flexible and tunable active metal composition and loading due to Zn2+And Co2+The metal can be coordinated with 2-methylimidazole to form a zeolite-like periodic topological structure, and the ratio of two metal nodes is flexible and adjustable, so that the loading capacity of Co can be flexibly adjusted by changing the Zn/Co ratio; in addition, when the second active metal is introduced by the two-solvent method, the kind and the loading amount of the second active metal can be flexibly adjusted by using different kinds or concentrations of metal salt aqueous solutions.
The invention also discloses a preparation method of the high-dispersion Co-based bimetallic catalyst based on ZIFs, which makes full use of Zn2+And Co2+The metal complex can be coordinated with 2-methylimidazole to form a zeolite-like periodic topological structure at the same time, and the ratio of two metal nodes is flexible and adjustable to form a ZnCo-ZIFs precursor; by utilizing the channel structure and the hydrophilic characteristic of the ZnCo-ZIFs precursor and introducing other active metals into the channel structure of the precursor by utilizing a double-solvent method, the metal salt @ ZnCo-ZIFs is obtained. Further in the high temperature calcination process, Zn2+Node evaporation plays a role of a fence for active metal, and active metal particles are prevented from being agglomerated; in-situ carbonizing the organic ligand to form a nitrogen-doped carbon carrier; and the Co node and the introduced second active metal are reduced in situ, so that the nitrogen-doped carbon carrier-supported high-dispersion Co-based bimetallic catalyst is obtained.
The method skillfully utilizes the characteristics of high dispersion of metal nodes and periodic pore channel structure in ZnCo-ZIFs, and firstly introduces a second active metal salt into the ZIFs pore channel by utilizing a double-solvent method; and then in the high-temperature calcination process, the low-boiling-point metal Zn volatilizes to play a fence role, the distance between the active metals is increased, and the Co node and the second active metal are reduced in situ to obtain the high-dispersion Co-based bimetallic catalyst loaded on the nitrogen-doped carbon carrier. In the catalyst, the active components are flexible and adjustable, the active bimetal is fixed on the nitrogen-doped carbon carrier in a highly dispersed form, the metal utilization rate is greatly improved, high-temperature calcination is carried out in the preparation process, the thermal stability is higher, and the phenomena of metal particle clustering and inactivation are not easy to occur in the catalytic reaction application process.
The high-dispersion Co-based bimetallic catalyst prepared by the invention can be applied to catalytic reaction processes such as hydrogenation catalysis, synthesis gas conversion, alcohol selective oxidation and the like.
Further, the metal salt solution and the 2-methylimidazole solution are prepared by using methanol as a solvent, and are mixed with other solvents (such as NH)4OH and DMF), the ZnCo-ZIFs crystal grain prepared by using methanol as a solvent has concentrated distribution, smaller average grain diameter, larger specific surface area and more acid-base sites.
Further, the ZnCo-ZIFs precursor subjected to degassing and impurity removal in the step 2) is of a porous structure, and the volume of pores is 0.57cm3(ii)/g; in the step 3), the volume of the second active metal salt solution is less than or equal to the pore volume of the degassed and purified ZnCo-ZIFs precursor in the step 2). So as to ensure that metal ions are all introduced into the ZIFs material pore canal under the action of capillary, and avoid the metal loading on the outer surface of the ZIFs precursor.
Drawings
FIG. 1 is the XRD pattern of the CoNi/NC catalyst synthesized in example 1.
FIG. 2 is a TEM image of CoNi/NC catalyst synthesized in example 1, and (a) and (b) are TEM images at different magnifications; (c) HAADF-STEM map for spherical aberration correction;
fig. 3 is a TEM image (a) of the CoNi/NC catalyst synthesized in example 1 and its corresponding element scans ((b) to (f)), where (b) is a C element, (C) is an N element, (d) is a Ni element, (e) is a Co element, and (f) is a Zn element.
FIG. 4 is the XRD pattern of the CoRh/NC catalyst synthesized in example 2.
FIG. 5 is a TEM image of a CoRh/NC catalyst synthesized in example 2, with (a) and (b) being TEM images at different magnifications; (c) HAADF-STEM map for spherical aberration correction;
fig. 6 is a TEM image (a) of the CoRh/NC catalyst synthesized in example 2 and its corresponding element scans ((b) to (f)), where (b) is a C element, (C) is an N element, (d) is a Co element, (e) is an Rh element, and (f) is a Zn element.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
example 1:
a preparation method of a ZIFs-based high-dispersion CoNi bimetallic catalyst specifically comprises the following steps:
step 1) 5.357g (297.49g/mol, 18mmol) Zn (NO)3)2·6H2O and 0.218g (291.03g/mol, 0.75mmol) Co (NO)3)2·6H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; 6.160g (82.1g/mol, 75mmol) of 2-methylimidazole is dissolved in 150mL of methanol and is subjected to ultrasonic treatment for 10min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 10min, and standing in a constant temperature box at 35 ℃ for 12 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 60 ℃ for 8 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating from room temperature to 100 deg.C at a heating rate of 10 deg.C/min, maintaining for 10min, heating to 150 deg.C at 10 deg.C/min, maintaining for 8h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the ZnCo-ZIFs precursor degassed in the step 2), and loading nickel nitrate into the ZnCo-ZIFs pore channel. Dispersing 200mg of degassed ZnCo-ZIFs in 40mL of hydrophobic solvent n-hexane by ultrasonic, and dropwise adding 100 mu L of 100mg/mL Ni (NO)3)2·6H2An aqueous solution of O; and (3) after ultrasonic treatment is carried out for 20min, stirring is carried out for 12h at room temperature, and after the solvent is volatilized, drying is carried out for 8h in a vacuum drying oven at the temperature of 60 ℃ to obtain the nickel salt @ ZnCo-ZIFs.
And 4) calcining the nickel salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in argon, wherein the gas flow is 0.6L/min, the high-temperature calcination temperature is 900 ℃, the temperature rise rate is 5 ℃/min, and the high-dispersion catalyst CoNi/NC is obtained after calcining for 6 hours.
The highly dispersed catalyst CoNi/NC was obtained according to the above procedure, wherein the loading of Co was 1.52 wt% and the loading of Ni was 1.50 wt%.
As shown in figure 1, no metal Co or Ni characteristic peak appears in the XRD pattern of the catalyst CoNi/NC, only the characteristic peak of C (PDF #41-1487), the characteristic peak of C (002) appears at 26.381 degrees, and the characteristic peak of C (101) appears at 44.391 degrees, which indicates that Co and Ni are loaded on the nitrogen-doped carbon carrier in a highly dispersed form.
As shown in fig. 2, no significant nanoparticles were observed in the TEM image of the catalyst CoNi/NC at different magnifications, and the isolated bright spots in the spherical aberration correction HAADF-STEM image of fig. 2(c) are metal elements present in the form of a single atom, which indicates that the metal elements are present in a highly dispersed form.
As shown in fig. 3, in the TEM image and the corresponding elemental scan image of the catalyst CoNi/NC, signals of metals Ni, Co appeared, and Ni and Co were uniformly dispersed on the nitrogen-doped carbon support; in addition, a signal for Zn was also present, indicating that Zn remained partially after 900 ℃ calcination.
Example 2:
a ZIFs-based high-dispersion CoRh bimetallic catalyst and a preparation method thereof specifically comprise the following steps:
step 1) 5.357g (297.49g/mol, 18mmol) Zn (NO)3)2·6H2O and 0.218g (291.03g/mol, 0.75mmol) Co (NO)3)2·6H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; 6.160g (82.1g/mol, 75mmol) of 2-methylimidazole is dissolved in 150mL of methanol and is subjected to ultrasonic treatment for 10min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 10min, and standing in a thermostat at 50 ℃ for 6 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 40 ℃ for 12 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating to 80 deg.C at a heating rate of 10 deg.C/min from room temperature, maintaining for 10min, heating to 100 deg.C at 10 deg.C/min, maintaining for 10h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the ZnCo-ZIFs precursor degassed in the step 2), and loading rhodium chloride into the ZnCo-ZIFs pore channel. Dispersing 200mg of degassed ZnCo-ZIFs in 40mL of hydrophobic solvent chloroform by ultrasonic, and dropwise adding 100 mu L of 5.16mg/mL rhodium chloride aqueous solution; and (3) after ultrasonic treatment is carried out for 30min, stirring is carried out for 8h at room temperature, and after the solvent is volatilized, drying is carried out for 12h in a vacuum drying oven at the temperature of 60 ℃ to obtain the rhodium salt @ ZnCo-ZIFs.
And 4) calcining the rhodium salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in argon, wherein the gas flow is 0.5L/min, the calcining temperature is 900 ℃, the heating rate is 2 ℃/min, and the high-dispersion catalyst CoRh/NC is obtained after calcining for 5 h.
The highly dispersed catalyst CoRh/NC was obtained according to the above procedure, in which the loading of Co was 1.50 wt% and the loading of Rh was 0.15 wt%.
As shown in fig. 4, in the XRD pattern of the catalyst CoRh/NC, no characteristic peak of metal Co or Rh appears, only the characteristic peak of C (PDF #41-1487), the characteristic peak of C (002) appears at 26.381 °, and the characteristic peak of C (101) appears at 44.391 °, indicating that Co and Rh are supported on the nitrogen-doped carbon support in a highly dispersed form.
As shown in fig. 5, no significant nanoparticles were observed in the TEM image of the catalyst costh/NC at different magnifications, and the isolated bright point and the bright point cluster in the spherical aberration correction HAADF-STEM image of fig. 5(c) are metal elements present in the form of monoatomic atoms and nanoclusters, respectively, which indicates that the metal elements are present in a highly dispersed form.
As shown in fig. 6, in the TEM image and the corresponding elemental scan image of the catalyst CoRh/NC, signals of Co and Rh appeared, and Co and Rh were uniformly dispersed on the nitrogen-doped carbon support; in addition, a signal for Zn was also present, indicating that Zn remained partially after 900 ℃ calcination.
Example 3
A ZIFs-based high-dispersion CoFe bimetallic catalyst and a preparation method thereof specifically comprise the following steps:
step 1) 7.902g (219.51g/mol, 36mmol) Zn (OAc)2·2H2O and 0.187g (249.08g/mol, 0.75mmol) Co (OAc)2·4H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; 12.315g (82.1g/mol, 150mmol) of 2-methylimidazole is dissolved in 150mL of methanol, and the solution is subjected to ultrasonic treatment for 15min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 15min, and standing in a 30-DEG C thermostat for 12 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 50 ℃ for 10 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating from room temperature to 100 deg.C at a rate of 5 deg.C/min, maintaining for 10min, heating to 150 deg.C at a rate of 10 deg.C/min, maintaining for 8h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the degassed ZnCo-ZIFs precursor in the step 2), and loading ferric nitrate into the ZnCo-ZIFs pore channel. Dispersing 200mg of degassed ZnCo-ZIFs in 40mL of hydrophobic solvent n-hexane by ultrasonic, and dropwise adding 100 mu L of 143.24 mg/mL Fe (NO)3)3·9H2An aqueous solution of O; and (3) after ultrasonic treatment is carried out for 15min, stirring at room temperature for 10h, and after the solvent is volatilized, drying in a vacuum drying oven at 60 ℃ for 8h to obtain iron salt @ ZnCo-ZIFs.
And 4) calcining the iron salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in nitrogen, wherein the gas flow is 0.4L/min, the calcining temperature is 950 ℃, the heating rate is 3 ℃/min, and the high-dispersion catalyst CoFe/NC is obtained after calcining for 4 h.
Example 4
A ZIFs-based high-dispersion CoRu bimetallic catalyst and a preparation method thereof specifically comprise the following steps:
step 1) 5.357g (297.49g/mol, 18mmol) Zn (NO)3)2·6H2O and 0.218g (291.03g/mol, 0.75mmol) Co (NO)3)2·6H2Dissolving O in 150mL of methanol, and forming metal after ultrasonic treatment for 10minA salt methanol solution; dissolving 12.32g (82.1g/mol, 150mmol) of 2-methylimidazole in 150mL of methanol, and carrying out ultrasonic treatment for 10min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 10min, and standing in a thermostat at 50 ℃ for 6 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 50 ℃ for 12 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating to 80 deg.C at a heating rate of 10 deg.C/min from room temperature, maintaining for 10min, heating to 120 deg.C at 10 deg.C/min, maintaining for 8h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the ZnCo-ZIFs precursor degassed in the step 2), and loading ruthenium chloride into the ZnCo-ZIFs pore channel. Dispersing 200mg of degassed ZnCo-ZIFs in 40mL of hydrophobic solvent chloroform by ultrasound, and dropwise adding 100 mu L of 40.64mg/mL RuCl3·3H2An aqueous solution of O; and (3) after ultrasonic treatment is carried out for 30min, stirring is carried out for 8h at room temperature, and after the solvent is volatilized, drying is carried out for 12h in a vacuum drying oven at the temperature of 60 ℃ to obtain ruthenium salt @ ZnCo-ZIFs.
And 4) calcining the ruthenium salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in argon, wherein the gas flow is 0.5L/min, the calcining temperature is 950 ℃, the heating rate is 2 ℃/min, and the high-dispersion catalyst CoRu/NC is obtained after calcining for 5 h.
Example 5
A high-dispersion CoPd bimetallic catalyst based on ZIFs and a preparation method thereof specifically comprise the following steps:
step 1) 5.357g (297.49g/mol, 18mmol) Zn (NO)3)2·6H2O and 0.218g (291.03g/mol, 0.75mmol) Co (NO)3)2·6H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; 6.160g (82.1g/mol, 75mmol) of 2-methylimidazole is dissolved in 150mL of methanol and is subjected to ultrasonic treatment for 10min to form a 2-methylimidazole methanol solution; quickly pouring the metal salt methanol solution into the 2-methylimidazole methanol solutionCarrying out ultrasonic treatment for 10min, and standing in a constant temperature oven at 40 ℃ for 12 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 60 ℃ for 12 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating to 80 deg.C at a heating rate of 10 deg.C/min from room temperature, maintaining for 10min, heating to 120 deg.C at 10 deg.C/min, maintaining for 12h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the ZnCo-ZIFs precursor degassed in the step 2), and loading palladium sulfate into the ZnCo-ZIFs pore channel. Dispersing 200mg of degassed ZnCo-ZIFs in 40mL of hydrophobic solvent chloroform by ultrasound, and dropwise adding 100 mu L of 37.67 mg/mL PdSO4·2H2An aqueous solution of O; and (3) after ultrasonic treatment is carried out for 30min, stirring is carried out for 8h at room temperature, and after the solvent is volatilized, drying is carried out for 10h in a vacuum drying oven at the temperature of 40 ℃ to obtain the palladium salt @ ZnCo-ZIFs.
And 4) calcining the palladium salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in nitrogen, wherein the gas flow is 0.6L/min, the high-temperature calcination temperature is 1000 ℃, the temperature rise rate is 5 ℃/min, and the high-dispersion catalyst CoPd/NC is obtained after calcining for 4 hours.
Example 6
A ZIFs-based high-dispersion CoPt bimetallic catalyst and a preparation method thereof specifically comprise the following steps:
step 1) 5.357g (297.49g/mol, 18mmol) Zn (NO)3)2·6H2O and 0.218g (291.03g/mol, 0.75mmol) Co (NO)3)2·6H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; dissolving 12.32g (82.1g/mol, 150mmol) of 2-methylimidazole in 150mL of methanol, and carrying out ultrasonic treatment for 10min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 10min, and standing in a thermostat at 50 ℃ for 6 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 40 ℃ for 12 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating to 80 deg.C at a heating rate of 10 deg.C/min from room temperature, maintaining for 10min, heating to 120 deg.C at 10 deg.C/min, maintaining for 10h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the ZnCo-ZIFs precursor degassed in the step 2), and loading chloroplatinic acid into the ZnCo-ZIFs pore channel. Dispersing 200mg of degassed ZnCo-ZIFs in 40mL of hydrophobic solvent chloroform by ultrasound, and dropwise adding 100 mu L of 52.57 mg/mL H2PtCl6·6H2An aqueous solution of O; and (3) after ultrasonic treatment is carried out for 30min, stirring is carried out for 8h at room temperature, and after the solvent is volatilized, drying is carried out for 12h in a vacuum drying oven at the temperature of 60 ℃ to obtain platinum salt @ ZnCo-ZIFs.
And 4) calcining the platinum salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in argon, wherein the gas flow is 0.5L/min, the calcining temperature is 900 ℃, the heating rate is 2 ℃/min, and the high-dispersion catalyst CoPt/NC is obtained after calcining for 5 h.
Example 7
A high-dispersion CoPd bimetallic catalyst based on ZIFs and a preparation method thereof specifically comprise the following steps:
step 1) 3.951g (219.51g/mol, 18mmol) Zn (OAc)2·2H2O and 0.062g (249.08g/mol, 0.25mmol) Co (OAc)2·4H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; 6.158g (82.1g/mol, 75mmol) of 2-methylimidazole is dissolved in 150mL of methanol and is subjected to ultrasonic treatment for 15min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 10min, and standing in a 30-DEG C thermostat for 12 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 60 ℃ for 8 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating to 80 deg.C at a rate of 5 deg.C/min from room temperature, maintaining for 10min, heating to 150 deg.C at a rate of 10 deg.C/min, maintaining for 8h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the ZnCo-ZIFs precursor degassed in the step 2), and loading palladium nitrate into the ZnCo-ZIFs pore channel. 200mg of degassed ZnCo-ZIFs is ultrasonically dispersed in 40mL of hydrophobic solvent n-hexane, and 100 mu L of 49.58 mg/mL Pd (NO) is dropwise added3)2·2H2An aqueous solution of O; and (3) after ultrasonic treatment is carried out for 20min, stirring is carried out for 12h at room temperature, and after the solvent is volatilized, drying is carried out for 8h in a vacuum drying oven at the temperature of 60 ℃ to obtain palladium salt @ ZnCo-ZIFs.
And 4) calcining the palladium salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in nitrogen, wherein the gas flow is 0.4L/min, the calcining temperature is 900 ℃, the heating rate is 3 ℃/min, and the high-dispersion catalyst CoPd/NC is obtained after calcining for 4 h.
Example 8
A ZIFs-based high-dispersion CoFe bimetallic catalyst and a preparation method thereof specifically comprise the following steps:
step 1) 3.951g (219.51g/mol, 18mmol) Zn (OAc)2·2H2O and 0.187g (249.08g/mol, 0.75mmol) Co (OAc)2·4H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; 12.315g (82.1g/mol, 150mmol) of 2-methylimidazole is dissolved in 150mL of methanol, and the solution is subjected to ultrasonic treatment for 15min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 15min, and standing in a 30-DEG C thermostat for 12 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 50 ℃ for 10 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating to 80 deg.C at a rate of 5 deg.C/min from room temperature, maintaining for 10min, heating to 100 deg.C at a rate of 10 deg.C/min, maintaining for 8h, cooling to room temperature, and taking out.
Step 3) to step 2) of removingAnd carrying out double-solvent treatment on the gasified ZnCo-ZIFs precursor, and loading ferric chloride into the ZnCo-ZIFs pore channel. Dispersing 200mg of degassed ZnCo-ZIFs in 40mL of hydrophobic solvent n-hexane by ultrasound, and dropwise adding 100 mu L of 95.8 mg/mL FeCl3·6H2An aqueous solution of O; and (3) after ultrasonic treatment is carried out for 15min, stirring at room temperature for 10h, and after the solvent is volatilized, drying in a vacuum drying oven at 60 ℃ for 8h to obtain iron salt @ ZnCo-ZIFs.
And 4) calcining the iron salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in nitrogen, wherein the gas flow is 0.4L/min, the calcining temperature is 900 ℃, the heating rate is 3 ℃/min, and the high-dispersion catalyst CoFe/NC is obtained after calcining for 4 h.
Example 9
A ZIFs-based high-dispersion CoNi bimetallic catalyst and a preparation method thereof specifically comprise the following steps:
step 1) 3.951g (219.51g/mol, 18mmol) Zn (OAc)2·2H2O and 0.062g (249.08g/mol, 0.25mmol) Co (OAc)2·4H2Dissolving O in 150mL of methanol, and performing ultrasonic treatment for 10min to form a metal salt methanol solution; 6.158g (82.1g/mol, 75mmol) of 2-methylimidazole is dissolved in 150mL of methanol and is subjected to ultrasonic treatment for 15min to form a 2-methylimidazole methanol solution; quickly pouring a metal salt methanol solution into a 2-methylimidazole methanol solution, carrying out ultrasonic treatment for 10min, and standing in a 30-DEG C thermostat for 12 h; and centrifuging the mixed solution, washing the precipitate for 3 times by using methanol, and drying in a vacuum drying oven at 60 ℃ for 8 hours to obtain the ZnCo-ZIFs precursor.
And 2) carrying out vacuum degassing treatment on the ZnCo-ZIFs precursor obtained in the step 1) to remove impurities in the precursor. Firstly, putting a ZnCo-ZIFs precursor into a U-shaped tube, then installing the U-shaped tube on vacuum degassing equipment, and setting a temperature rise program as follows: heating to 80 deg.C at a rate of 5 deg.C/min from room temperature, maintaining for 10min, heating to 150 deg.C at a rate of 10 deg.C/min, maintaining for 8h, cooling to room temperature, and taking out.
And 3) carrying out double-solvent treatment on the ZnCo-ZIFs precursor degassed in the step 2), and loading nickel chloride into the ZnCo-ZIFs pore channel. 200mg of degassed ZnCo-ZIFs is ultrasonically dispersed in 40mL of hydrophobic solvent chloroform, and 100 mu L of 1.88 mg/mL NiCl is dropwise added2·6H2O waterA solution; and (3) after ultrasonic treatment is carried out for 20min, stirring is carried out for 12h at room temperature, and after the solvent is volatilized, drying is carried out for 8h in a vacuum drying oven at the temperature of 60 ℃ to obtain the nickel salt @ ZnCo-ZIFs.
And 4) calcining the nickel salt @ ZnCo-ZIFs obtained in the step 3) at high temperature in argon, wherein the gas flow is 0.4L/min, the calcining temperature is 900 ℃, the heating rate is 3 ℃/min, and the high-dispersion catalyst CoNi/NC is obtained after calcining for 4 h.
In conclusion, compared with the corresponding single metal catalyst, the high-dispersion Co-based bimetallic catalyst based on ZIFs prepared by the method disclosed by the invention can show excellent catalytic performance, such as high activity and high selectivity, in a catalytic reaction. After high-temperature calcination, the catalyst has high thermal stability, and is not easy to have the phenomena of metal particle clustering and inactivation in the application process of catalytic reaction. When the second active metal is introduced by the two-solvent method, the type and the loading amount of the second active metal can be flexibly adjusted by using different types or concentrations of metal salt aqueous solutions.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (10)
1. A ZIFs-based highly-dispersed Co-based bimetallic catalyst is characterized in that Co is loaded on a nitrogen-doped carbon carrier in a form of nanoclusters or single atoms.
2. A preparation method of a ZIFs-based high-dispersion Co-based bimetallic catalyst is characterized by comprising the following steps:
step 1) mixing soluble zinc salt and soluble cobalt salt to prepare a metal salt solution with the mass concentration of 1-10%, and preparing a 2-methylimidazole solution with the mass concentration of 1-22%; the method comprises the following steps of (1) mixing a 2-methylimidazole solution and a metal salt solution according to a molar ratio (4-8): 1, mixing to obtain a first mixed solution, placing the mixed solution at 30-50 ℃ for a complex reaction, and centrifuging, washing and drying once after the reaction to obtain a ZnCo-ZIFs precursor;
step 2) degassing and removing impurities of the ZnCo-ZIFs precursor;
step 3) dispersing the degassed and impurity-removed ZnCo-ZIFs precursor in the step 2) in a hydrophobic solvent to obtain a second mixed solution with the mass concentration of 0.6% -0.8%, mixing the second mixed solution with a second active metal salt solution of 0-150 mg/mL, stirring for 6-12 h, and drying to obtain metal salt @ ZnCo-ZIFs;
and 4) calcining the metal salt @ ZnCo-ZIFs in the step 3) at the high temperature of 900-1000 ℃ in inert gas, and air-cooling after the calcination is finished to obtain the ZIFs-based high-dispersion Co-based bimetallic catalyst.
3. The preparation method according to claim 2, wherein in the metal salt solution in the step 1), the molar ratio of the soluble zinc salt to the soluble cobalt salt is (24-100): 1.
4. the method according to claim 2, wherein the zinc salt in step 1) is Zn (NO)3)2·6H2O or Zn (OAc)2·2H2O; the cobalt salt is Co (NO)3)2·6H2O or Co (OAc)2·4H2O。
5. The preparation method according to claim 2, wherein the time of the complexing reaction in step 1) is 6-12 h; drying in the step 1) is to dry the centrifuged precipitate at 40-60 ℃ for 8-12 h; the inert gas in the step 4) is argon or nitrogen; the high-temperature calcination time in the step 4) is 3-6 h.
6. The method according to claim 2, wherein the metal salt solution and the 2-methylimidazole solution in step 1) are prepared using methanol as a solvent; the washing was carried out with methanol.
7. The article of claim 2The preparation method is characterized in that the ZnCo-ZIFs precursor subjected to degassing and impurity removal in the step 2) is of a porous structure, and the pore volume of the ZnCo-ZIFs precursor is 0.57cm measured by physical adsorption3(ii)/g; in the step 3), the volume of the second active metal salt solution is less than or equal to the pore volume of the degassed and purified ZnCo-ZIFs precursor in the step 2).
8. The method according to claim 2, wherein the second active metal salt in step 3) is any one of a water-soluble Ni salt, a water-soluble Rh salt, a water-soluble Fe salt, a water-soluble Ru salt, a water-soluble Pd salt, and a water-soluble Pt salt; the hydrophobic solvent is n-hexane or chloroform.
9. The method according to claim 8, wherein the water-soluble Ni salt is Ni (NO)3)2·6H2O or NiCl2·6H2O; the water-soluble Rh salt is RhCl3·3H2O; the water-soluble Fe salt is FeCl3·6H2O or Fe (NO)3)3·9H2O; the water-soluble Ru salt is RuCl3·3H2O; the water-soluble Pd salt is Pd (NO)3)2·2H2O or PdSO4·2H2O; the water-soluble Pt salt is H2PtCl6·6H2O。
10. The preparation method of claim 2, wherein the degassing and impurity removal in the step 2) are carried out under vacuum, the degassing temperature is 80-150 ℃, and the degassing time is 8-10 h.
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