CN116768283A - Sub-nanometer thickness porous cobaltosic oxide sheet exposing specific crystal face and preparation method and application thereof - Google Patents
Sub-nanometer thickness porous cobaltosic oxide sheet exposing specific crystal face and preparation method and application thereof Download PDFInfo
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- UBEWDCMIDFGDOO-UHFFFAOYSA-N cobalt(2+);cobalt(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[Co+2].[Co+3].[Co+3] UBEWDCMIDFGDOO-UHFFFAOYSA-N 0.000 title claims abstract description 50
- 239000013078 crystal Substances 0.000 title claims abstract description 43
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 10
- 239000010941 cobalt Substances 0.000 claims abstract description 10
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000003756 stirring Methods 0.000 claims abstract description 9
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 3
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 18
- 239000001294 propane Substances 0.000 claims description 18
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 9
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 8
- GPKIXZRJUHCCKX-UHFFFAOYSA-N 2-[(5-methyl-2-propan-2-ylphenoxy)methyl]oxirane Chemical compound CC(C)C1=CC=C(C)C=C1OCC1OC1 GPKIXZRJUHCCKX-UHFFFAOYSA-N 0.000 claims description 7
- GEMHFKXPOCTAIP-UHFFFAOYSA-N n,n-dimethyl-n'-phenylcarbamimidoyl chloride Chemical compound CN(C)C(Cl)=NC1=CC=CC=C1 GEMHFKXPOCTAIP-UHFFFAOYSA-N 0.000 claims description 4
- CHMRTILFZHXKDS-UHFFFAOYSA-N B([O-])[O-].[Co+2] Chemical compound B([O-])[O-].[Co+2] CHMRTILFZHXKDS-UHFFFAOYSA-N 0.000 claims description 3
- 238000006555 catalytic reaction Methods 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 2
- JFCQEDHGNNZCLN-UHFFFAOYSA-N glutaric acid Chemical compound OC(=O)CCCC(O)=O JFCQEDHGNNZCLN-UHFFFAOYSA-N 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 23
- 230000003197 catalytic effect Effects 0.000 abstract description 22
- 230000003647 oxidation Effects 0.000 abstract description 12
- 238000007254 oxidation reaction Methods 0.000 abstract description 12
- 230000000694 effects Effects 0.000 abstract description 9
- 239000002135 nanosheet Substances 0.000 abstract description 8
- 230000007547 defect Effects 0.000 abstract description 3
- 230000009881 electrostatic interaction Effects 0.000 abstract description 3
- 239000001257 hydrogen Substances 0.000 abstract description 3
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 3
- 230000003993 interaction Effects 0.000 abstract description 3
- 239000003054 catalyst Substances 0.000 description 38
- 229910020599 Co 3 O 4 Inorganic materials 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 12
- 239000002244 precipitate Substances 0.000 description 11
- 238000012360 testing method Methods 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 7
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 238000001291 vacuum drying Methods 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 238000004817 gas chromatography Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- CUJRVFIICFDLGR-UHFFFAOYSA-N acetylacetonate Chemical compound CC(=O)[CH-]C(C)=O CUJRVFIICFDLGR-UHFFFAOYSA-N 0.000 description 2
- 150000001335 aliphatic alkanes Chemical class 0.000 description 2
- 229920000180 alkyd Polymers 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000001493 electron microscopy Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 239000002064 nanoplatelet Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 231100000572 poisoning Toxicity 0.000 description 2
- 230000000607 poisoning effect Effects 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 239000012855 volatile organic compound Substances 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- WRSVIZQEENMKOC-UHFFFAOYSA-N [B].[Co].[Co].[Co] Chemical compound [B].[Co].[Co].[Co] WRSVIZQEENMKOC-UHFFFAOYSA-N 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 238000000089 atomic force micrograph Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- FJDJVBXSSLDNJB-LNTINUHCSA-N cobalt;(z)-4-hydroxypent-3-en-2-one Chemical compound [Co].C\C(O)=C\C(C)=O.C\C(O)=C\C(C)=O.C\C(O)=C\C(C)=O FJDJVBXSSLDNJB-LNTINUHCSA-N 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- -1 polytetrafluoroethylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G51/00—Compounds of cobalt
- C01G51/04—Oxides; Hydroxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8668—Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
-
- 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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/74—Iron group metals
- B01J23/75—Cobalt
-
- 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
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
- B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
-
- 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
- B01J37/10—Heat treatment in the presence of water, e.g. steam
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Environmental & Geological Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Inorganic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Catalysts (AREA)
Abstract
The invention discloses a porous cobaltosic oxide sheet with a sub-nanometer thickness exposing a specific crystal face, a preparation method and application thereof, wherein a cobalt source is added into an alcohol solution, and after uniform stirring, the cobalt source is subjected to hydrothermal reaction for 48-96 hours at 190-220 ℃ to obtain an ultrathin CoO sheet exposing (111) crystal face; and (3) heating the ultrathin CoO sheet with the exposed (111) crystal face. Due to HOCH 2 COO ‑ Hydrogen bonding and van der waals interactions between species, coO nuclei can create directional short range attractive forces between the CoO nuclei. The CoO core is self-assembled into a two-dimensional CoO nano-sheet with a sub-nanometer thickness and an exposed (111) crystal face under the drive of directional short-range attraction and electrostatic interaction. The porous cobaltosic oxide flake with the sub-nanometer thickness prepared by the method has a large number of low-coordination Co atoms, defect sites and larger reaction area, so that the activity of low-temperature catalytic oxidation of the cobaltosic oxide flake is improved.
Description
Technical Field
The invention belongs to the field of air pollution control and technology, and in particular relates to a sub-nanometer thickness porous cobaltosic oxide sheet exposing a specific crystal face, a preparation method and application thereof.
Background
As the lower alkane in VOCs, the alkane molecule is very stable and difficult to break because of the large C-H bond energy. Noble metal catalysts are highly active but are expensive and susceptible to sintering and poisoning deactivation, limiting their industrial use. The transition metal oxide catalyst has the advantages of good catalytic performance, low cost, strong poisoning resistance and the like, and is considered as a catalyst with great application prospect.
Chinese patent 201410207035.2 discloses a 'cobaltosic oxide propane complete catalytic oxidation agent, a preparation method and application thereof', wherein the catalyst is prepared from Co 3 O 4 Is prepared with the transformation temperature still higher, T 90 The low-temperature activity of the metal oxide is poor at 219 ℃.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention aims to provide a sub-nanometer thickness porous cobaltosic oxide sheet with a specific crystal face exposed, a preparation method and application thereof, and the porous cobaltosic oxide sheet has the characteristics of economy, low cost, simple preparation material, high low-temperature reaction activity, good high-temperature stability, good water resistance and the like.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the preparation method of the porous cobaltosic oxide flake with the sub-nanometer thickness exposing the specific crystal face comprises the following steps:
adding a cobalt source into the alcohol solution, uniformly stirring, performing hydrothermal reaction at 190-220 ℃ for 48-96 hours, washing, and drying to obtain an exposed (111) crystal face ultrathin CoO sheet;
and heating the ultrathin CoO sheet with the exposed (111) crystal face to obtain the porous cobaltosic oxide sheet with the subnanometer thickness with the specific crystal face exposed.
Further, the alcohol solution is prepared by adding alcohol or water, wherein the volume ratio of the alcohol to the water is 50-200mL:28-40.
Further, the alcohol is ethylene glycol, propylene glycol or isopropanol.
Further, the dosage ratio of the alcohol to the cobalt source is 50-200mL:200-1000mg.
Further, the cobalt source is cobalt 2, 4-glutarate, cobalt naphthenate or cobalt boronate.
Further, the stirring time is 60-120min.
Further, the drying temperature is 60-100 ℃ and the drying time is 12-24 hours.
Further, the heating temperature is 300-400 ℃ and the heating time is 30-60min.
A porous tricobalt tetraoxide sheet of sub-nanometer thickness exposing specific crystal planes prepared according to the method described above.
Use of a porous tricobalt tetraoxide flake of sub-nanometer thickness exposing specific crystal planes as defined in the claims for low temperature catalysis of propane.
Compared with the prior art, the invention has the beneficial results that:
in the present invention, ethylene glycol (HOCH) is used at 190-220 DEG C 2 CH 2 OH) can be partially oxidized to alkyd (HOCH) 2 COOH) while CoO nucleates, its surface energy can be increased by adsorbing HOCH on its surface 2 COO - To decrease. HOCH2COO due to ionization of carboxyl group - The presence of (c) can cause the CoO core to generate a net negative charge. In addition, due to HOCH 2 COO - Hydrogen bonding and van der waals interactions between species, coO nuclei can create directional short range attractive forces between the CoO nuclei. The CoO core is self-assembled into a two-dimensional CoO nano-sheet with a sub-nanometer thickness and an exposed (111) crystal face under the drive of directional short-range attraction and electrostatic interaction. The porous cobaltosic oxide flake with the sub-nanometer thickness prepared by the method has a large number of low-coordination Co atoms, defect sites and larger reaction area, so that the activity of low-temperature catalytic oxidation of the cobaltosic oxide flake is improved. The raw materials of the invention have low cost and low cost.
At 20000h -1 Is introduced with balance gas N under the airspeed condition 2 21% O 2 And 2500ppm of C 3 H 8 . At a reaction temperature of only 165 ℃, propane can be completely oxidized. Co prepared by the invention 3 O 4 The catalyst has good catalytic oxidation performance on propane at low temperature, the degradation rate of propane at 165 ℃ reaches 100%, and the performance is superior to other types of Co reported at present 3 O 4 A catalyst. Thus using the Co thus prepared 3 O 4 The catalyst is used for catalyzing and oxidizing low-carbon alkane, and has a certain practical value.
Drawings
FIG. 1 is Co 3 O 4 -electron microscopy of SPS. Wherein, (A) is a field emission scanning electron microscope image, and (B) is a field emission scanning electron microscope image.
FIG. 2 is Co 3 O 4 -high power projection electron microscopy of SPS. Wherein, (A) is a high-power projection electron microscope image, and (B) is a simulated crystal face atomic arrangement image.
FIG. 3 is Co 3 O 4 -SPS sheet thickness map. Wherein, (a) is an atomic force microscope image, (b) is a thickness image of the corresponding section S1, (c) is a thickness image of the corresponding section S2, and (d) is a thickness image of the corresponding section S3.
FIG. 4 is Co 3 O 4 TS and Co 3 O 4 -field emission scanning electron microscopy of C. Wherein (A) is Co 3 O 4 -field emission scanning electron microscopy of TS, (B) Co 3 O 4 -field emission scanning electron microscopy of C.
FIG. 5 is Co 3 O 4 Catalyst at C 3 H 8 Concentration is 2500ppm, space velocity is 20000h -1 Graph of catalytic oxidation performance of propane under test conditions.
FIG. 6 is Co 3 O 4 Catalyst at C 3 H 8 Concentration is 2500ppm, space velocity is 20000h -1 Catalytic oxidation of CO of propane under test conditions 2 Selectivity map.
FIG. 7 is Co 3 O 4 SPS catalyst at a temperature of 165℃C 3 H 8 The concentration is 2500ppm, emptyThe speed is 20000h -1 Long-term stability profile of catalytic oxidation of propane under test conditions.
FIG. 8 is Co 3 O 4 SPS catalyst at C 3 H 8 Concentration is 2500ppm, space velocity is 20000h -1 Water resistance profile of catalytic oxidation of propane under test conditions.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
The invention discloses a preparation method of a porous cobaltosic oxide sheet with a sub-nanometer thickness and a specific crystal face exposed, which comprises the following steps:
firstly, 50-200mL of ethylene glycol (or propylene glycol or isopropanol) is dissolved in 28-40mL of deionized water, then 200-1000mg of Co (acac) 3 (cobalt naphthenate or cobalt boronate) is added, and stirring is carried out for 60-120min. The solution was then transferred to a polytetrafluoroethylene-lined autoclave and heated at 190-220 c for 48-96 hours. At 190-220 ℃, ethylene glycol (HOCH 2 CH 2 OH) can be partially oxidized to alkyd (HOCH) 2 COOH) while CoO nucleates, its surface energy can be increased by adsorbing HOCH on its surface 2 COO - To decrease. HOCH2COO due to ionization of carboxyl group - The presence of (c) can cause the CoO core to generate a net negative charge. In addition, due to HOCH 2 COO - Hydrogen bonding and van der waals interactions between species, coO nuclei can create directional short range attractive forces between the CoO nuclei. The CoO core is self-assembled into a two-dimensional CoO nano-sheet with a sub-nanometer thickness and an exposed (111) crystal face under the drive of directional short-range attraction and electrostatic interaction. And after the high-pressure reaction kettle is naturally cooled, centrifugally collecting the precipitate after the reaction. The ratio of water and ethanol for the collected precipitate was 1:9-1:20, and then placing the mixture in a vacuum drying oven at 60-100 ℃ for drying for 12-24 hours. Then the obtained ultrathin CoO sheet with the exposed (111) crystal face is heated in the air at 300-400 ℃ for 30-60min, and the ultrathin CoO sheet with the exposed (111) crystal face is subjected to topological transformation to obtain porous Co with the sub-nanometer thickness of the exposed (111) crystal face 3 O 4 A nano-sheet.
The invention examines Co with sub-nanometer thickness 3 O 4 Nanoplatelets and traditional bulk Co 3 O 4 The low temperature catalytic activity of the two catalysts and the influence of oxygen on the catalytic activity.
The method for using the catalyst comprises the following steps: at 20000h -1 Co at sub-nanometer thickness under airspeed conditions 3 O 4 The nanosheets are catalysts for catalytic oxidation of propane in volatile organic compounds, the catalytic reaction temperature is 25-500 ℃, the concentration of propane is 2500ppm, and the volume concentration of oxygen is 21%.
Example 1
160mL of ethylene glycol was first dissolved in 30mL of deionized water, and 700mg of Co (acac) was then added 3 Stirring for 100min. And transferring the solution into a polytetrafluoroethylene-lined high-pressure reaction kettle, heating at 200 ℃ for 60 hours, and centrifugally collecting the precipitate after the reaction after the high-pressure reaction kettle is naturally cooled. The ratio of water and ethanol for the collected precipitate was 1:9-1:20 is washed for 4-8 times and then is dried in a vacuum drying oven at 70 ℃ for 20h. Then the obtained ultrathin CoO sheet with the exposed (111) crystal face is heated for 40min in the air at 350 ℃ to obtain porous Co with sub-nanometer thickness 3 O 4 The nano-sheet is crushed and sieved by a tablet for 40-60 meshes to obtain a porous cobaltosic oxide sheet with a subnanometer thickness exposing a specific crystal face, which is marked as Co 3 O 4 -SPS catalyst.
As can be seen from FIGS. 1A and B, FIGS. 2A and B, and FIGS. 3 (a) - (d), the catalyst prepared in example 1 is porous Co with sub-nanometer thickness exposing the (111) crystal face 3 O 4 A nanoplatelet structure.
Example 2
50mL of propylene glycol was first dissolved in 28mL of deionized water, then 200mg of cobalt naphthenate was added and stirred for 60min. And transferring the solution into a polytetrafluoroethylene-lined high-pressure reaction kettle, heating at 220 ℃ for 48 hours, and centrifugally collecting the precipitate after the reaction after the high-pressure reaction kettle is naturally cooled. The ratio of water and ethanol for the collected precipitate was 1:9-1:20, and then placing the mixture in a vacuum drying oven at 60 ℃ for drying for 24 hours. Then the obtained ultrathin CoO sheet with the exposed (111) crystal face is heated for 30min in the air at 400 ℃ to obtain porous Co with sub-nanometer thickness 3 O 4 NanosheetsAnd (3) crushing and sieving the powder through a tablet to obtain porous cobaltosic oxide flakes with a subnanometer thickness exposing a specific crystal face.
Example 3
First 100mL of isopropanol was dissolved in 40mL of deionized water, then 1000mg of cobalt boride was added and stirred for 80min. Then transferring the solution into a polytetrafluoroethylene-lined high-pressure reaction kettle, heating at 210 ℃ for 80 hours, and centrifugally collecting the precipitate after the reaction after the high-pressure reaction kettle is naturally cooled. The ratio of water and ethanol for the collected precipitate was 1:9-1:20, and then placing the mixture in a vacuum drying oven at 80 ℃ for drying for 17 hours. Then the obtained ultrathin CoO sheet with the exposed (111) crystal face is heated for 60min in the air at 3000 ℃ to obtain porous Co with sub-nanometer thickness 3 O 4 The nano-sheet is crushed and sieved by a tabletting sieve of 40-60 meshes to obtain the porous cobaltosic oxide sheet with the subnanometer thickness and the specific crystal face exposed.
Example 4
200mL of propylene glycol was first dissolved in 35mL of deionized water, and 500mg of Co (acac) was then added 3 Stirring for 120min. And transferring the solution into a polytetrafluoroethylene-lined high-pressure reaction kettle, heating at 190 ℃ for 96 hours, and centrifugally collecting the precipitate after the reaction after the high-pressure reaction kettle is naturally cooled. The ratio of water and ethanol for the collected precipitate was 1:9-1:20, and then placing the mixture in a vacuum drying oven at 100 ℃ for drying for 12 hours. Then the obtained ultrathin CoO sheet with the exposed (111) crystal face is heated in the air at 320 ℃ for 50min to obtain porous Co with sub-nanometer thickness 3 O 4 The nano-sheet is crushed and sieved by a tabletting sieve of 40-60 meshes to obtain the porous cobaltosic oxide sheet with the subnanometer thickness and the specific crystal face exposed.
Comparative example 1
6mmol Co (OAc) was stirred magnetically 2 Dissolving in 30mL deionized water, stirring for 15min, adding 60mL 1gL -1 The carboxymethyl cellulose solution was stirred for a further 30min. 60mL of dilute ammonia (ammonia/water=1/9) was then added dropwise to the stirred solution. Subsequently, the solution was transferred to a 250mL polytetrafluoroethylene lined autoclave, sealed and heated at 80 ℃ for 12h. Centrifugal collection heightThe precipitate at the bottom of the autoclave was washed several times with distilled water and ethanol and dried in an oven at 100 ℃. Heating the obtained powder directly in air at 300 deg.C for 30min, and cooling to room temperature to obtain tablet Co 3 O 4 . Pulverizing, sieving with 40-60 mesh sieve, and recording as Co 3 O 4 -a TS catalyst.
As can be seen from FIG. 4A, the catalyst prepared in comparative example 1 is Co in the form of a plate 3 O 4 。
Comparative example 2
Co (NO) 3 ) 2 ·6H 2 O was heated in a muffle furnace at 900℃for 18h and cooled to room temperature. Collecting the obtained powder, denoted as Co 3 O 4 -C。
As can be seen from FIG. 4B, the catalyst prepared in comparative example 2 was bulk Co 3 O 4 。
Test of the activity of the catalysts in example 1, comparative example 1 and comparative example 2: the catalysts obtained in example 1, comparative example 1 and comparative example 2 were placed in a fixed bed reactor for catalytic activity evaluation under the following experimental conditions: 2500ppm C 3 H 8 ，21％ O 2 ，N 2 For balancing the gas, the reaction space velocity is 20000h -1 . The propane concentration was measured by gas chromatography. The results of the catalytic performance are shown in FIG. 5, and it can be seen from FIG. 5 that Co 3 O 4 The SPS catalyst is capable of completely oxidizing propane at 165℃and at a temperature much lower than the other two catalysts.
Example 1, catalysts in comparative example 1 and comparative example 2 catalyze the oxidation of propane CO 2 Selectivity test: the catalysts obtained in example 1, comparative example 1 and comparative example 2 were placed in a fixed bed reactor for catalytic activity evaluation under the following experimental conditions: 2500ppm C 3 H 8 ，21％ O 2 ，N 2 For balancing the gas, the reaction space velocity is 20000h -1 。CO 2 Detection was performed by gas chromatography. Catalyst CO 2 The selectivity results are shown in FIG. 6, and it can be seen from FIG. 6 that Co 3 O 4 SPS catalyst can completely oxidize propane into CO at 175 DEG C 2 The temperature is much lower than the other two catalysts.
Example 1 long-term temperature stability test of catalyst: the catalytic activity evaluation was carried out by placing 0.15g of the catalyst of example 1 in a fixed bed reactor under the following experimental conditions: 2500ppm C 3 H 8 ，21％ O 2 ，N 2 For balancing the gas, the reaction space velocity is 20000h -1 . The temperature was controlled at 165℃for 40 hours to test activity. The propane concentration was measured by gas chromatography. The results of the catalytic high temperature stability are shown in FIG. 7, and it can be seen from FIG. 7 that Co 3 O 4 The SPS catalyst is maintained at 160 ℃ for 40 hours, the activity of the SPS catalyst is basically unchanged, and the SPS catalyst has excellent thermal stability.
Example 1 test of water resistance of catalyst: the catalytic activity evaluation was carried out by placing 0.15g of the catalyst of example 1 in a fixed bed reactor under the following experimental conditions: 2500ppm C 3 H 8 ，21％ O 2 ，N 2 For balancing the gas, the reaction space velocity is 20000h -1 . The temperature was controlled at 165℃and 160℃respectively and maintained for 40 hours for activity testing. During this period, 5% and 10% water was added to the reactor for ten hours, and then the water addition was stopped. The propane concentration was measured by gas chromatography. The catalyst water resistance results are shown in FIG. 8, and it can be seen from FIG. 8 that Co 3 O 4 SPS catalyst can keep better catalytic activity when 5% and 10% of water are added, and has excellent water resistance.
The low coordination metal atoms of the catalyst in the catalytic oxidation can be used as high active sites, which is important for catalytic activity, and the prepared porous cobaltosic oxide flake with sub-nanometer thickness has a large number of low coordination Co atoms, defect sites and larger reaction area, so that the activity of the low-temperature catalytic oxidation is improved.
Claims (10)
1. The preparation method of the porous cobaltosic oxide flake with the sub-nanometer thickness, which exposes a specific crystal face, is characterized by comprising the following steps:
adding a cobalt source into the alcohol solution, uniformly stirring, performing hydrothermal reaction at 190-220 ℃ for 48-96 hours, washing, and drying to obtain an exposed (111) crystal face ultrathin CoO sheet;
and heating the ultrathin CoO sheet with the exposed (111) crystal face to obtain the porous cobaltosic oxide sheet with the subnanometer thickness with the specific crystal face exposed.
2. The method for preparing the porous cobaltosic oxide flake with the subnanometer thickness exposing the specific crystal face according to claim 1, wherein the alcohol solution is prepared by adding alcohol or water, wherein the volume ratio of the alcohol to the water is 50-200mL:28-40.
3. The method for preparing a porous tricobalt tetraoxide sheet with a sub-nanometer thickness exposing a specific crystal face according to claim 2, wherein the alcohol is ethylene glycol, propylene glycol or isopropanol.
4. The method for preparing the porous cobaltosic oxide flake with the sub-nanometer thickness exposing the specific crystal face according to the claim 1, wherein the dosage ratio of the alcohol to the cobalt source is 50-200mL:200-1000mg.
5. The method for preparing the porous cobaltosic oxide flake with the sub-nanometer thickness exposing the specific crystal face according to claim 1, wherein the cobalt source is 2, 4-cobalt glutarate, cobalt naphthenate or cobalt boronate.
6. The method for preparing the porous cobaltosic oxide flake with the sub-nanometer thickness exposing the specific crystal face according to claim 1, wherein the stirring time is 60-120min.
7. The method for preparing a porous tricobalt tetraoxide sheet with a sub-nanometer thickness exposing a specific crystal face according to claim 1, wherein the drying temperature is 60-100 ℃ and the time is 12-24h.
8. The method for preparing a porous tricobalt tetraoxide sheet with a sub-nanometer thickness exposing a specific crystal face according to claim 1, wherein the heating temperature is 300-400 ℃ for 30-60min.
9. A sub-nanometer thickness porous tricobalt tetraoxide flake exposing specific crystal planes prepared according to the method of any one of claims 1-8.
10. Use of a porous tricobalt tetraoxide flake of sub-nanometer thickness exposing specific crystal planes according to claim 9 for low temperature catalysis of propane.
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