CN114160142B - Preparation method of microwave-assisted hydrogen peroxide modified sepiolite group mineral loaded Co monoatomic catalyst - Google Patents
Preparation method of microwave-assisted hydrogen peroxide modified sepiolite group mineral loaded Co monoatomic catalyst Download PDFInfo
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- 239000004113 Sepiolite Substances 0.000 title claims abstract description 68
- 229910052624 sepiolite Inorganic materials 0.000 title claims abstract description 68
- 235000019355 sepiolite Nutrition 0.000 title claims abstract description 68
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 title claims abstract description 60
- 229910052500 inorganic mineral Inorganic materials 0.000 title claims abstract description 57
- 239000011707 mineral Substances 0.000 title claims abstract description 57
- 239000003054 catalyst Substances 0.000 title claims abstract description 33
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000000034 method Methods 0.000 claims abstract description 25
- 238000004108 freeze drying Methods 0.000 claims abstract description 7
- 239000000843 powder Substances 0.000 claims description 11
- 239000002243 precursor Substances 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 7
- 239000000243 solution Substances 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 5
- 239000011259 mixed solution Substances 0.000 claims description 5
- 239000000047 product Substances 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- 239000012266 salt solution Substances 0.000 claims description 4
- 150000003839 salts Chemical class 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 239000006228 supernatant Substances 0.000 claims description 4
- 238000009210 therapy by ultrasound Methods 0.000 claims description 4
- 230000032683 aging Effects 0.000 claims description 3
- QOSATHPSBFQAML-UHFFFAOYSA-N hydrogen peroxide;hydrate Chemical compound O.OO QOSATHPSBFQAML-UHFFFAOYSA-N 0.000 claims description 3
- 239000004570 mortar (masonry) Substances 0.000 claims description 3
- 238000012216 screening Methods 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- 239000007864 aqueous solution Substances 0.000 claims description 2
- GFHNAMRJFCEERV-UHFFFAOYSA-L cobalt chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Co+2] GFHNAMRJFCEERV-UHFFFAOYSA-L 0.000 claims description 2
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 claims description 2
- ZBYYWKJVSFHYJL-UHFFFAOYSA-L cobalt(2+);diacetate;tetrahydrate Chemical compound O.O.O.O.[Co+2].CC([O-])=O.CC([O-])=O ZBYYWKJVSFHYJL-UHFFFAOYSA-L 0.000 claims description 2
- 238000005342 ion exchange Methods 0.000 abstract description 18
- 150000002500 ions Chemical class 0.000 abstract description 16
- 239000011148 porous material Substances 0.000 abstract description 16
- 238000011946 reduction process Methods 0.000 abstract description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 3
- 230000007547 defect Effects 0.000 abstract description 3
- 238000005516 engineering process Methods 0.000 abstract description 3
- 230000006911 nucleation Effects 0.000 abstract description 3
- 238000010899 nucleation Methods 0.000 abstract description 3
- 229910052760 oxygen Inorganic materials 0.000 abstract description 3
- 239000001301 oxygen Substances 0.000 abstract description 3
- 238000012545 processing Methods 0.000 abstract description 3
- 239000003426 co-catalyst Substances 0.000 abstract description 2
- 238000000354 decomposition reaction Methods 0.000 abstract description 2
- 125000004429 atom Chemical group 0.000 description 9
- 239000002121 nanofiber Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 6
- 229910000510 noble metal Inorganic materials 0.000 description 5
- 229910052625 palygorskite Inorganic materials 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 4
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 4
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000000969 carrier Substances 0.000 description 3
- 229910021389 graphene Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 239000011777 magnesium Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- 239000002074 nanoribbon Substances 0.000 description 3
- 230000035484 reaction time Effects 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- HYBBIBNJHNGZAN-UHFFFAOYSA-N furfural Chemical compound O=CC1=CC=CO1 HYBBIBNJHNGZAN-UHFFFAOYSA-N 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000005476 size effect Effects 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 239000011787 zinc oxide Substances 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical group [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- -1 cyanamide compound Chemical class 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 1
- 239000000391 magnesium silicate Substances 0.000 description 1
- 229910052919 magnesium silicate Inorganic materials 0.000 description 1
- 235000019792 magnesium silicate Nutrition 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002055 nanoplate Substances 0.000 description 1
- 239000002077 nanosphere Substances 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 238000002256 photodeposition Methods 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000036647 reaction Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000004627 transmission electron microscopy 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
- 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
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/78—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with alkali- or alkaline earth metals
-
- 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
- B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
- B01J37/341—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation
- B01J37/344—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of electromagnetic wave energy
- B01J37/346—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of electromagnetic wave energy of microwave energy
Abstract
The invention relates to a preparation method of a microwave-assisted hydrogen peroxide modified sepiolite group mineral loaded Co monoatomic catalyst. The method comprises the steps of firstly treating minerals by a microwave-assisted hydrogen peroxide method, further unbeaming the sepiolite group minerals by utilizing a large amount of oxygen generated by hydrogen peroxide decomposition in a microwave field, and increasing the number of exposed ion exchange sites, so that the ion exchange efficiency of Co ions and the sepiolite group minerals is improved, the Co ions are easier to enter pore channels of the sepiolite group minerals through ion exchange, nucleation of the Co ions in the sepiolite group minerals is limited by means of freeze drying, and the size of the pore channels controls the growth size of the Co ions exchanged in the reduction process, so that Co exists stably in a single atom form. The invention overcomes the defects of low atom utilization rate, poor selectivity and stability of the traditional Co catalyst, complex preparation and processing technology of the single-atom catalyst carrier and high cost.
Description
Technical Field
The technical scheme of the invention relates to the field of catalyst synthesis, in particular to a preparation method of a sepiolite group mineral loaded Co monoatomic catalyst.
Background
Co is used as one of the representatives of non-noble metals, compared with noble metal catalysts, the noble metal catalyst has the advantages of abundant storage capacity, low price, and the unique anti-carbon property and the like, so that Co becomes one of the most promising substitutes of noble metals and one of research hot spots in the current catalysis field. Co-based catalysts are now widely used in environmental and energy fields such as electrocatalytic hydrogen evolution, fischer-Tropsch synthesis, carbon dioxide reduction, and the like.
To further increase the atomic utilization of Co and thus the catalytic activity, researchers have continuously reduced the particle size of Co in various ways, yet their atomic utilization is still well below 100%. For Co monoatomic catalysts, the atom utilization efficiency can reach 100% theoretically, and the single active site and the strong action force between the single active site and the carrier also lead to good selectivity and stability. In conclusion, the Co single-atom catalyst greatly improves the utilization efficiency of Co atoms, improves the catalytic activity, and simultaneously has better selectivity and stability due to single active site and strong interaction with a carrier. Therefore, the method for searching the simple and low-cost preparation of the single-atom Co-based catalyst has important significance.
CN111020625a relates to a graphene nanoribbon supported monoatomic catalyst, which adopts freeze drying and heat treatment to disperse Co in the form of monoatomic atoms in the graphene nanoribbon, but the preparation and processing of the graphene nanoribbon require a large amount of chemical, and the treatment process is complex and the cost is high. CN110961134a provides a method for preparing a stable monoatomic catalyst by a sacrificial template method, which takes polystyrene nanospheres as a sacrificial template, fully reacts a cyanamide compound, furfural and a metal source to obtain a high polymer, and then cracks the high polymer at high temperature to form a nitrogen-doped carbon nano-plate and stabilize noble metal monoatoms, but the cracking process needs high temperature and consumes a large amount of energy. CN107537481B discloses a method for preparing a catalyst by anchoring a single atom by utilizing nano zinc oxide O vacancy, which adopts an impregnation method to prepare a metal precursor and then reduces the metal precursor in hydrogen at a low temperature, but hydrogen also reduces part of the carrier zinc oxide in the reduction process, so that the carrier is lost. CN107008290B provides a preparation method of a hydrotalcite-like structured dispersion monoatomic catalyst, which comprises the steps of preparing semiconductor hydrotalcite-like compound by a double-drop method and reducing palladium atoms by a photo-deposition method, and although cheap minerals are used as carriers, a large amount of chemical reagents are used for carrier treatment, and the preparation process of the catalyst is complex and is not beneficial to actual production.
The sepiolite group mineral is an ideal environment material, has rich reserves, low price, small influence on ecological environment, high regeneration and recycling rate and excellent usability and environment harmony. It mainly comprises sepiolite and palygorskite, and has rich pore canal structure (theoretical pore diameter: sepiolite isPalygorskite is->). Sepiolite is taken as an example, and is an aqueous magnesium silicate clay mineral, the main chemical components are silicon and magnesium, and the chemical structural general formula is Mg 8 [Si 12 O 30 ](OH) 4 (OH 2 ) 4 ·8H 2 O. The crystal structure unit is composed of two layers of silicon oxygen tetrahedron and one layer of octahedron interposed therebetween, and has +.>Is a porous structure of (a). The pore structure in sepiolite nanofiber contains Mg and Al ions which can be exchanged with Co ions, and +.>The open cell structure of (a) can limit the size of Co so that Co is present in the sepiolite as a monoatomic form. Similarly, mg and Al ions in the palygorskite pore structure can be exchanged with Co ions, which is +.> The pore size of (2) also ensures that Co is dispersed in the palygorskite as a single atom. However, sepiolite group minerals have large specific surface energy, and are easily agglomerated into fiber bundles and even micrometer-sized blocky shapes in a natural state, so that a large number of ion exchange sites cannot be exposed, the ion exchange efficiency is low, and therefore dispersion and unbinding are required, and the number of exposed ion exchange sites is increased.
Disclosure of Invention
The invention aims at overcoming the defects of the prior art and provides a preparation method of a microwave-assisted hydrogen peroxide modified sepiolite group mineral loaded Co monoatomic catalyst.The method comprisesThe method comprises grinding primarily dispersed sepiolite group mineral, treating the mineral with microwave-assisted hydrogen peroxide method, and further unbinding the sepiolite group mineral by using a large amount of oxygen generated by decomposing hydrogen peroxide in microwave field to expose ion exchange sitesThe number is increased, so that the ion exchange efficiency of Co ions and sepiolite group minerals is improved, the Co ions are easier to enter pore channels of the sepiolite group minerals through ion exchange, nucleation of the Co ions inside the sepiolite group minerals is limited by means of freeze drying, and the size of the pore channels controls the growth size of the exchanged Co ions in the reduction process, so that Co exists stably in a single atom form. The invention overcomes the defects of low atom utilization rate, poor selectivity and stability of the traditional Co catalyst, complex preparation and processing technology of the single-atom catalyst carrier and high cost.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the preparation method of the microwave-assisted hydrogen peroxide modified sepiolite group mineral loaded Co monoatomic catalyst comprises the following steps:
(1) Fully grinding sepiolite family minerals in a mortar, screening by using a 200-400 mesh screen, and collecting undersize;
(2) Immersing the mineral powder obtained in the step (1) into hydrogen peroxide water solution, stirring for 1-3 h, and then carrying out ultrasonic treatment for 0.5-2 h;
(3) Centrifuging the mixed solution obtained in the step (2), discarding supernatant, placing the centrifuged solid in a microwave reactor for reaction, cooling to room temperature with microwave emission power of 300-700W, placing the mixture in an oven for full drying at 60-100 ℃, and obtaining the sepiolite family mineral powder modified by the microwave-assisted hydrogen peroxide;
(4) Adding the microwave-assisted H obtained in the step (3) into the Co salt solution 2 O 2 Modified sepiolite group mineral powder, stirring and ultrasonic aging for 1-12 h at room temperature; washing and centrifuging the product, and putting the centrifuged product into a freeze dryer for drying to obtain a Co precursor;
wherein, the freeze drying temperature is between 70 ℃ below zero and 20 ℃ below zero, and the drying time is between 12 and 72 hours;
(5) Placing the precursor obtained in the step (4) in a tubular atmosphere furnace, and introducing H 2 /N 2 Reducing the mixed gas at 200-400 ℃ for 1-4 h to obtain the microwave-assisted hydrogen peroxide modified sea foamStone-like minerals support Co monoatomic catalysts.
The mass fraction of hydrogen peroxide in the hydrogen peroxide aqueous solution in the step (2) is between 10% and 40%.
The microwave irradiation time of the step (3) is 8-15 min.
The Co salt in the step (3) is cobalt chloride hexahydrate, cobalt nitrate hexahydrate or cobalt acetate tetrahydrate; the concentration of the Co salt solution is 0.1-2 mmol/L.
The mass ratio of the Co salt in the step (3) to the sepiolite mineral modified by the microwave-assisted hydrogen peroxide is 1:25-1:300.
The preparation method of the microwave-assisted hydrogen peroxide modified sepiolite group mineral loaded Co monoatomic catalyst is characterized in that other raw materials, reagents and equipment except for the sepiolite group mineral are obtained through known methods, and the operation process can be mastered by a person skilled in the art.
The invention has the substantial characteristics that:
according to the method, firstly, the sepiolite group mineral is primarily dispersed through grinding, then the mineral is treated through a microwave-assisted hydrogen peroxide method, the sepiolite group mineral is further unbeamed by utilizing a large amount of oxygen generated by decomposing hydrogen peroxide in a microwave field, so that the number of exposed ion exchange sites is increased, the ion exchange efficiency of Co ions and the sepiolite group mineral is improved, the Co ions are easier to enter pore channels of the sepiolite group mineral through ion exchange, then the nucleation of the Co ions inside the sepiolite group mineral is limited by means of freeze drying, and the growth size of the Co ions exchanged in the reduction process is controlled by the pore channel size, so that Co exists stably in a single atom form.
The beneficial effects of the invention are as follows: compared with the prior art, the invention has the following outstanding substantial characteristics and remarkable progress:
(1) The size of Co is limited by utilizing the pore canal size effect of the sepiolite mineral, so that Co is uniformly distributed in the sepiolite mineral in a single-atom form, the atom utilization rate of Co is improved, and the use amount of Co is reduced.
(2) Compared with CN111020625A, the invention takes sepiolite group minerals as carriers, has abundant reserves in the nature and low price, and does not need to consume a large amount of chemical in the treatment process.
(3) Compared with CN110961134A, the invention is treated at low temperature, does not need high-temperature cracking and has less energy consumption.
(4) In contrast to CN107537481B, the present invention does not lose carrier during the preparation process.
(5) Compared with CN107008290B, the method has simple treatment process and preparation process for sepiolite family minerals.
(6) The Co monoatoms can form stable coordination with O in sepiolite group minerals, so that electrons of Co d orbitals are transferred to O atoms coordinated with the Co monoatoms, the electron saturation of Co 3d orbitals is reduced, the adsorption and dissociation of Co on reactant molecules are facilitated, and the reaction rate is improved.
(7) The sepiolite mineral has the advantages of low price, abundant resources and the like as the natural mineral, utilizes the natural mineral as the natural resource, saves the cost, and can be widely applied to Fischer-Tropsch synthesis, carbon dioxide reduction and NO in the fields of energy, environmental protection and the like x Low temperature water gas shift reaction and novel fuel cell reactions.
Drawings
FIG. 1 is a high-resolution transmission electron microscope image of spherical aberration corrected high-angle dark field image of the monoatomic Co/sepiolite nanofiber catalyst prepared in example 1;
FIG. 2 is a high angle dark field image transmission electron microscopy image of spherical aberration correction of Co/sepiolite nanofiber catalyst prepared in comparative example 1;
Detailed Description
The present invention will be described with reference to specific examples, but the scope of the present invention is not limited to these examples.
The sepiolite group mineral is a known material, and is specifically sepiolite or palygorskite. Sepiolite was used in the examples below. But is not limited thereto.
Example 1
Sepiolite nanofiber powder (100 mesh) was placed in a mortar for full grinding, followed by screening using 300 mesh screen, leaving passing through the screenPowder of the mesh; weighing 700mg of sieved powder, immersing the powder into 100ml of 30wt.% hydrogen peroxide water solution, stirring at 700rpm/min for 2 hours, performing ultrasonic treatment for 1 hour, fully centrifuging the mixed solution, and discarding the supernatant; placing the centrifuged solid into a microwave reactor, setting the power to be 500W and the reaction time to be 13min; cooling to room temperature, and then placing in an oven at 80 ℃ for drying for 12 hours to obtain the sepiolite nanofiber powder modified by the hydrogen peroxide assisted by microwaves; weighing 99ml of deionized water, placing into a beaker, adding 1ml of 0.025mmol/ml cobalt nitrate solution, stirring for 15min, adding 500mg of treated sepiolite nanofiber powder, continuously stirring for 1h, performing ultrasonic treatment for 1h, aging for 2h at room temperature, washing and centrifuging the mixed solution, removing supernatant, placing the centrifuged solid into a refrigerator for freezing for 24h, and performing freeze drying at-70 ℃ for 48h in a freeze dryer to obtain the precursor. Placing the precursor into a quartz boat, placing into a tubular atmosphere furnace, and introducing 5%H 2 +95％N 2 And (3) mixing the gases at a heating rate of 5 ℃/min to 400 ℃, preserving heat for 1h, and naturally cooling to room temperature to finish the preparation of the catalyst.
FIG. 1 is a spherical aberration-corrected high-angle dark-field image high-resolution transmission electron microscope of the prepared monoatomic Co/sepiolite nanofiber catalyst obtained in this example, and the area marked by circles in the figure is Co monoatomic signal (bright spot), so that it can be explained that Co in the catalyst exists stably in monoatomic form.
Example 2
The other steps were the same as in example 1 except that "1 ml of 0.025mmol/ml of cobalt nitrate solution was added" was replaced with "1 ml of 0.1mmol/ml of cobalt nitrate solution was added".
The higher loading monoatomic Co/sepiolite nanofiber catalyst is obtained, which shows that the sepiolite pore canal has good domain-limiting effect, and proper increase of the concentration of the cobalt nitrate solution does not cause Co to grow into Co particles.
Comparative example 1
Other steps are the same as in example 1 except that "submerge it in 30wt.% aqueous hydrogen peroxide" is replaced by submerging it in 5wt.% aqueous hydrogen peroxide.
In comparative example 1, the concentration of 5wt.% hydrogen peroxide in water was too low, making the sepiolite beam-splitting effect in the microwave reaction inferior, resulting in fewer exposed ion exchange sites and low ion exchange efficiency. It can be seen from fig. 2 that Co is not easily entered into sepiolite channels when the sepiolite ion exchange efficiency is low, and the non-porous method limits the size of Co, which grows into nanoparticles.
Comparative example 2
The other steps are the same as in example 1 except that "set power at 500W, reaction time at 13min" is replaced with "set power at 500W, reaction time at 30min".
The resulting Co/sepiolite composite material was substantially free of Co monoatomic signals, and a small amount of Co nanoparticles were present on the surface of the sepiolite, because in comparative example 2, after the decomposition of hydrogen peroxide was completed, the unbeamed sepiolite was re-agglomerated under the high temperature of the microwave field, the number of exposed ion exchange sites was decreased, the ion exchange efficiency was decreased, which resulted in Co being difficult to enter the pore channels by ion exchange, and the non-pore size limited Co growth to nanoparticles.
As can be seen from the above examples and comparative examples, the present invention prepares a sepiolite group mineral supported Co monoatomic catalyst by a simple impregnation method on the basis of modifying a sepiolite group mineral, and limits the size of Co by using the pore size effect of the sepiolite group mineral, so that Co is uniformly distributed in the sepiolite group mineral in a monoatomic form. The invention has simple preparation process, adopts natural minerals with abundant reserves as carriers and has low price.
The foregoing has shown and described the basic principles and main features of the present invention and the advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
The invention is not a matter of the known technology.
Claims (3)
1. The preparation method of the microwave-assisted hydrogen peroxide modified sepiolite group mineral loaded Co monoatomic catalyst is characterized by comprising the following steps of:
(1) Fully grinding sepiolite family minerals in a mortar, screening by using a 200-400 mesh screen, and collecting undersize products;
(2) Immersing the mineral powder obtained in the step (1) in a hydrogen peroxide water solution, stirring for 1-3 h, and then performing ultrasonic treatment for 0.5-2 h;
(3) Centrifuging the mixed solution obtained in the step (2), discarding supernatant, placing the centrifuged solid in a microwave reactor for reaction, cooling to room temperature with microwave emission power of 300-700W, placing the cooled mixed solution in an oven, and fully drying at 60-100 ℃ to obtain sepiolite family mineral powder modified by microwave-assisted hydrogen peroxide;
(4) Adding the microwave-assisted H obtained in the step (3) into the Co salt solution 2 O 2 Modified sepiolite group mineral powder, stirring and ultrasonic aging at room temperature for 1-12 h; washing and centrifuging the product, and putting the centrifuged product into a freeze dryer for drying to obtain a Co precursor;
wherein the freeze drying temperature is-70 ℃ to-20 ℃ and the drying time is 12-72 hours; the mass ratio of Co salt to the microwave-assisted hydrogen peroxide modified sepiolite family mineral is 1:25-1:300;
(5) Placing the precursor obtained in the step (4) in a tubular atmosphere furnace, and introducing H 2 /N 2 Reducing the mixed gas at 200-400 ℃ to 1-4 h to obtain the microwave-assisted hydrogen peroxide modified sepiolite family mineral-loaded Co monoatomic catalyst;
the mass fraction of hydrogen peroxide in the hydrogen peroxide aqueous solution in the step (2) is 10% -40%;
and (3) the microwave irradiation time of the step (3) is 8-15 min.
2. The method for preparing a microwave-assisted hydrogen peroxide modified sepiolite family mineral supported Co monoatomic catalyst according to claim 1, wherein the Co salt in the step (3) is cobalt chloride hexahydrate, cobalt nitrate hexahydrate or cobalt acetate tetrahydrate.
3. The method for preparing the microwave-assisted hydrogen peroxide modified sepiolite family mineral supported Co single-atom catalyst according to claim 1, wherein the concentration of the Co salt solution in the step (4) is 0.1-2 mmol/L.
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