CN115069261A - Cobalt chromate with core-shell structure, preparation method and application thereof - Google Patents
Cobalt chromate with core-shell structure, preparation method and application thereof Download PDFInfo
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- XTUHPOUJWWTMNC-UHFFFAOYSA-N cobalt(2+);dioxido(dioxo)chromium Chemical compound [Co+2].[O-][Cr]([O-])(=O)=O XTUHPOUJWWTMNC-UHFFFAOYSA-N 0.000 title claims abstract description 75
- 239000011258 core-shell material Substances 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 239000003054 catalyst Substances 0.000 claims abstract description 37
- 239000011259 mixed solution Substances 0.000 claims abstract description 16
- 150000001868 cobalt Chemical class 0.000 claims abstract description 15
- 238000006243 chemical reaction Methods 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 13
- PHFQLYPOURZARY-UHFFFAOYSA-N chromium trinitrate Chemical compound [Cr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O PHFQLYPOURZARY-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000002243 precursor Substances 0.000 claims abstract description 12
- 239000004094 surface-active agent Substances 0.000 claims abstract description 11
- 238000001354 calcination Methods 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 10
- 230000003197 catalytic effect Effects 0.000 claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000008367 deionised water Substances 0.000 claims abstract description 8
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 8
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000004202 carbamide Substances 0.000 claims abstract description 7
- 230000015556 catabolic process Effects 0.000 claims abstract description 7
- 238000006731 degradation reaction Methods 0.000 claims abstract description 7
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims abstract description 5
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 5
- 238000005406 washing Methods 0.000 claims abstract description 5
- 238000001914 filtration Methods 0.000 claims abstract description 4
- 239000000843 powder Substances 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 3
- 238000001291 vacuum drying Methods 0.000 claims description 3
- 239000012855 volatile organic compound Substances 0.000 claims description 3
- 229910000684 Cobalt-chrome Inorganic materials 0.000 claims description 2
- 229940011182 cobalt acetate Drugs 0.000 claims description 2
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 claims description 2
- 229910001981 cobalt nitrate Inorganic materials 0.000 claims description 2
- QAHREYKOYSIQPH-UHFFFAOYSA-L cobalt(II) acetate Chemical compound [Co+2].CC([O-])=O.CC([O-])=O QAHREYKOYSIQPH-UHFFFAOYSA-L 0.000 claims description 2
- 239000010952 cobalt-chrome Substances 0.000 claims description 2
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 abstract description 75
- 230000009286 beneficial effect Effects 0.000 abstract description 5
- 238000009792 diffusion process Methods 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 5
- 239000000463 material Substances 0.000 abstract description 4
- 239000000376 reactant Substances 0.000 abstract description 4
- 238000001035 drying Methods 0.000 abstract 1
- 239000002105 nanoparticle Substances 0.000 description 10
- 239000007787 solid Substances 0.000 description 8
- 238000002441 X-ray diffraction Methods 0.000 description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- 238000001179 sorption measurement Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000012065 filter cake Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910052596 spinel Inorganic materials 0.000 description 3
- 239000011029 spinel Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000010718 Oxidation Activity Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- GVHCUJZTWMCYJM-UHFFFAOYSA-N chromium(3+);trinitrate;nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Cr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GVHCUJZTWMCYJM-UHFFFAOYSA-N 0.000 description 2
- 229910017052 cobalt Inorganic materials 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- RJNPRNCPYHCHHV-UHFFFAOYSA-N cobalt(2+) dinitrate tetrahydrate Chemical compound O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O RJNPRNCPYHCHHV-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 230000002195 synergetic effect Effects 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000010170 biological method Methods 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000007084 catalytic combustion reaction Methods 0.000 description 1
- 238000009903 catalytic hydrogenation reaction Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 210000000653 nervous system Anatomy 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 235000011837 pasties Nutrition 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000241 respiratory effect Effects 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- 210000002345 respiratory system Anatomy 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
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- 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
- B01J23/84—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 arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/85—Chromium, molybdenum or tungsten
- B01J23/86—Chromium
- B01J23/864—Cobalt and chromium
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- 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
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
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- 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
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Abstract
The invention discloses cobalt chromate with a core-shell structure, a preparation method and application thereof, and particularly relates to the field of preparation of catalyst materials. The method comprises the steps of firstly dissolving a certain proportion of cobalt salt, hydrated chromium nitrate and urea in deionized water, fully stirring until the cobalt salt, the hydrated chromium nitrate and the urea are completely dissolved, and then adding a proper amount of surfactant cetyl trimethyl ammonium bromide to prepare a mixed solution. And then placing the mixed solution in a high-pressure reaction kettle for hydrothermal reaction for a period of time to obtain a cobalt chromate precursor, filtering, washing, drying, and calcining in an air atmosphere to finally obtain the cobalt chromate catalyst with the core-shell structure. The middle hollow-out layer with the core-shell structure of the cobalt chromate is beneficial to the diffusion of reactants, promotes the low-temperature activity of formaldehyde catalytic degradation, and has better application prospect.
Description
Technical Field
The invention belongs to the field of catalyst material preparation, and particularly relates to a preparation method and application of a cobalt chromate catalyst with a core-shell structure.
Background
Formaldehyde is a typical volatile organic pollutant, and the continuous exposure to a relatively low concentration (<0.5ppm) of formaldehyde can also cause serious damage to the respiratory and nervous systems of the human body. Indoor decoration materials, building materials, fabrics, furniture and the like can release formaldehyde with certain concentration, and the development of novel materials capable of efficiently controlling formaldehyde pollution is of great significance.
Compared with adsorption method, absorption method, biological method and other technologies, the catalytic oxidation method can completely convert formaldehyde into CO 2 And H 2 O, has significant advantages and has received much attention so far. The high-efficiency catalyst developed at present mostly takes noble metal as a main active component, and the strong oxidizing property of the noble metal is utilized to realize the complete degradation of formaldehyde at the condition of near room temperature. However, the relatively expensive price of noble metals limits their large-scale use. Therefore, much research is currently being conducted on transition metal oxide catalysts as well. The chromium-based oxide and the cobalt-based oxide both have certain formaldehyde degradation performance, but the low-temperature activity of the chromium-based oxide and the cobalt-based oxide is still to be further improved. The chromium atom and the cobalt atom form a solid solution or the synergistic effect of the chromium atom and the cobalt atom can be effectively utilized to promote the oxidation activity of formaldehyde to be improved. The spinel type oxides have a special spatial structure and are generally represented by the formula AB 2 O 4 Due to the synergistic effect between different metals and A 2+ And B 3+ The spinel oxide has good catalytic activity and stability due to the electron transfer effect among ions. By controlling chromiumThe relative proportions of salt to cobalt salt allow the synthesis of spinel type solid solutions of cobalt chromate. Compared with the common nanoparticle catalyst, the catalyst with the core-shell structure has larger specific surface area and higher porosity, and is more beneficial to the diffusion of reactant molecules to react. The core-shell structure catalyst generally comprises an inner core, an outer shell and a middle hollow layer, but a preparation method of cobalt chromate with a core-shell structure and catalytic performance of the cobalt chromate for formaldehyde degradation are not reported so far.
Disclosure of Invention
The invention aims to: firstly, a preparation method of cobalt chromate with a core-shell structure, which has simple steps, is provided: secondly, the special space structure of the cobalt chromate with the core-shell structure is utilized to promote the adsorption and diffusion of formaldehyde molecules in the reaction, so that the catalytic activity of the cobalt chromate under the low-temperature condition is improved.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
cobalt chromate with core-shell structure, chemical formula of which is CoCr 2 O 4 。
A preparation method of a cobalt chromate catalyst with a core-shell structure comprises the following steps:
dissolving cobalt salt, hydrated chromium nitrate and urea in deionized water according to a certain proportion, and stirring until all components are fully dissolved to obtain a mixed solution 1;
adding a proper amount of surfactant into the mixed solution 1, and stirring until the surfactant is fully dissolved to obtain a mixed solution 2;
transferring the mixed solution 2 to a high-pressure reaction kettle, and carrying out hydrothermal reaction at the temperature of 120-150 ℃ for 6-12h to generate a cobalt chromate precursor;
washing and filtering the cobalt chromate precursor for several times, and putting the cobalt chromate precursor in a vacuum drying oven until the cobalt chromate precursor is completely dried to obtain first powder;
and (3) placing the first powder in a tubular furnace, and calcining for 2-4h at the temperature of 600-900 ℃ in the air atmosphere to obtain the cobalt chromate catalyst with the core-shell structure.
Further, the cobalt salt is hydrated cobalt nitrate or hydrated cobalt acetate.
Further, the molar ratio of the cobalt salt to the hydrated chromium nitrate is 1: 2.
Further, the molar ratio of the urea to the cobalt salt is 3-5: 1.
Further, the surfactant is cetyl trimethyl ammonium bromide.
Further, the molar ratio of the surfactant to the cobalt salt is 1-2: 1.
Further, the addition amount of the deionized water is as follows: the concentration of the cobalt salt in the mixed solution 1 is 0.05-0.2 mol/L.
Further, the temperature rise rate during the calcination is 3-5 ℃/min.
The application of the cobalt chromate catalyst prepared by the preparation method of the cobalt chromate catalyst is characterized in that the cobalt chromate catalyst can be applied to the catalytic degradation of volatile organic compounds, such as the degradation of formaldehyde.
The surface active agent cetyl trimethyl ammonium bromide is a key reagent which needs to be added, and the surface active agent is wrapped in the cobalt chromate of the nuclear layer and then calcined at high temperature to form a hollow nuclear shell structure; the calcination temperature and the heating rate are key parameters to be controlled, and both too low or too high calcination temperature can cause the formation of an intermediate hollow layer to be difficult, because too low temperature can cause poor crystallization of cobalt chromate, and too high temperature can cause the sintering of the catalyst to cause the collapse of gaps between the core and the shell. In addition, core-shell structure collapse can be caused by too fast temperature rise rate, and the catalyst preparation efficiency is not high when the temperature rise rate is too slow. The cobalt chromate catalyst with the core-shell structure prepared by the preparation method can be applied to but not limited to VOCs catalytic combustion, selective catalytic reduction denitration, CO 2 Catalytic hydrogenation and the like.
The invention has the beneficial effects that:
the core-shell structure cobalt chromate disclosed by the invention is prepared by adopting a hydrothermal reaction, and has the advantages of readily available raw materials and simple preparation process. The obtained cobalt chromate with the core-shell structure is novel in structure, and the unique hollow structure is more beneficial to diffusion and adsorption of reactant molecules than common nano-particle cobalt chromate, so that the catalytic oxidation activity of formaldehyde in a low-temperature area is remarkably improved, the formaldehyde purification efficiency is close to that of a catalyst containing a noble metal active component, and good durability is demonstrated.
Drawings
FIG. 1(a) is a TEM (transmission electron microscope) image of the cobalt chromate with core-shell structure in the present invention at 8000 times magnification;
FIG. 1(b) is a TEM (transmission electron microscope) image of the core-shell structure of cobalt chromate at 50000 times magnification in the present invention;
FIG. 2 is an XRD (X-ray diffraction) diagram of a cobalt chromate catalyst with a core-shell structure and a solid nanoparticle cobalt chromate catalyst in the invention;
FIG. 3 is a diagram of the formaldehyde purification efficiency of the cobalt chromate core-shell structure and solid nanoparticle cobalt chromate catalyst of the present invention;
FIG. 4 is a test chart of durability of the core-shell structure cobalt chromate catalyst of the present invention.
Detailed Description
The features and characteristics of the present invention will be described in further detail below with reference to the accompanying drawings and examples.
Example 1
The core-shell structure cobalt chromate of the present example was prepared by the following steps:
(1) dissolving 1mmol of cobalt nitrate tetrahydrate, 2mmol of chromium nitrate nonahydrate and 3mmol of urea in 10mL of deionized water, and stirring until all components are fully dissolved;
(2) adding 1mmol of hexadecyl trimethyl ammonium bromide into the mixed solution in the step (1), and magnetically stirring for 3 hours to obtain a viscous pasty mixed solution;
(3) transferring the solution in the step (2) to a 25mL hydrothermal reaction kettle, and reacting in a 120 ℃ oven for 6h to obtain a cobalt chromate precursor;
(4) washing the product obtained in the step (3) with deionized water for 2 times, washing with ethanol for 2 times, filtering to obtain a filter cake, and putting the filter cake in a vacuum drying oven at 90 ℃ until the filter cake is completely dried to obtain first powder;
(5) and (3) placing the first powder in a tubular furnace, calcining for 3h at 800 ℃, heating up at the rate of 3 ℃/min, and calcining for 3h in air atmosphere to obtain second powder, namely a cobalt chromate final product with a core-shell structure. FIG. 1 is a TEM image of cobalt chromate with a core-shell structure, and FIG. 2 is an XRD image of cobalt chromate with a core-shell structure.
Comparative example 1:
the comparative example provides a solid nanoparticle cobalt chromate, and the preparation method comprises the following steps:
(1) dissolving 1mmol of cobalt nitrate tetrahydrate and 2mmol of chromium nitrate nonahydrate in 10mL of deionized water, and stirring until all components are fully dissolved;
(2) adding 3.6mmol of citric acid into the mixed solution obtained in the step (1), and magnetically stirring for 3 hours to obtain a mixed solution;
(3) transferring the solution obtained in the step (2) to a 50mL beaker, and stirring in a water bath kettle at 90 ℃ until viscous sol is formed, so as to obtain a cobalt chromate precursor;
(4) and (3) placing the cobalt chromate precursor in a tubular furnace, calcining for 3h at 500 ℃ in the air atmosphere, and heating at the rate of 5 ℃/min to obtain the solid nano-particle cobalt chromate final product. Figure 2 is an XRD pattern of solid nanoparticle cobalt chromate.
And (3) activity test: carrying out formaldehyde catalytic reaction in a fixed bed reactor, taking 0.3g of catalyst, tabletting and screening to 40-60 meshes for evaluating catalytic activity;
example 1: core-shell structure cobalt chromate
Comparative example 1: solid nanoparticle cobalt chromate
The concentration of formaldehyde gas is controlled at 300ppm, and the carrier gas is N with the concentration of 80 percent 2 With 20% of O 2 The reaction space velocity is 30000 mL.h -1 ·g -1 And recording data after each temperature point is stabilized for 1h, and carrying out online analysis on the concentration of formaldehyde at an inlet and an outlet by using gas chromatography. As shown in fig. 3, the conversion rate of formaldehyde of the cobalt chromate with the core-shell structure is significantly improved compared with that of the cobalt chromate with the solid nanoparticles, the conversion rate of formaldehyde of the cobalt chromate with the core-shell structure reaches 50% at 72 ℃, and the reaction temperature of the cobalt chromate with the solid nanoparticles needs to reach 122 ℃. In addition, the former can realize 100% conversion rate of formaldehyde at 182 ℃, and the latter needs to reach 213 ℃.
And (3) testing the stability:
the catalyst stability test was performed at 175 ℃ (99% formaldehyde conversion) and the other reaction conditions were consistent with the activity test conditions. As can be seen in FIG. 4, the cobalt chromate with the core-shell structure shows good stability, and the formaldehyde conversion rate does not decrease continuously for 24 h.
In summary, XRD characterization results are shown at 18 ° 、30 ° 、36 ° 、37 ° 、43 ° 、54 ° 、57 ° 、63 ° 、71 ° 、74 ° Diffraction peaks (JCPDS 78-0711 of powder diffraction standard association) belonging to cobalt chromate exist nearby, and no diffraction peaks of other substances appear, which indicates that the cobalt chromate with the core-shell structure synthesized by the method has good crystallinity and high purity. TEM photograph results show that the cobalt chromate synthesized by the method has an obvious core-shell structure and the particle size is about 100 nm. Experimental results show that the cobalt chromate with the unique core-shell structure is more beneficial to diffusion and adsorption of reactant molecules, so that the cobalt chromate has better formaldehyde oxidation performance in a low-temperature range. At a space velocity of 30000 mL. h -1 ·g -1 Under the condition of (3), the conversion rate of formaldehyde is 100% at 182 ℃, and good stability is kept at 175 ℃, thereby showing good application prospect.
Claims (10)
1. A preparation method of a cobalt chromate catalyst with a core-shell structure is characterized by comprising the following steps:
dissolving cobalt salt, hydrated chromium nitrate and urea in deionized water according to a certain proportion, and stirring until all components are fully dissolved to obtain a mixed solution 1;
adding a proper amount of surfactant into the mixed solution 1, and stirring until the surfactant is fully dissolved to obtain a mixed solution 2;
transferring the mixed solution 2 to a high-pressure reaction kettle, and carrying out hydrothermal reaction at the temperature of 120-150 ℃ for 6-12h to generate a cobalt chromate precursor;
washing and filtering the cobalt chromate precursor for several times, and putting the cobalt chromate precursor in a vacuum drying oven until the cobalt chromate precursor is completely dried to obtain first powder;
and (3) placing the first powder in a tubular furnace, and calcining for 2-4h at the temperature of 600-900 ℃ in the air atmosphere to obtain the cobalt chromate catalyst with the core-shell structure.
2. The method of preparing a cobalt chromate catalyst as set forth in claim 1, wherein the cobalt salt is hydrated cobalt nitrate or hydrated cobalt acetate.
3. The method of preparing a cobalt chromate catalyst as set forth in claim 1 wherein the cobalt salt to hydrated chromium nitrate is present in a molar ratio of 1: 2.
4. The method for preparing a cobalt chromate catalyst as claimed in claim 1, wherein the molar ratio of urea to cobalt salt is 3-5: 1.
5. The method of claim 1, wherein the surfactant is cetyltrimethylammonium bromide.
6. The method for preparing a cobalt chromate catalyst as claimed in claim 1, wherein the molar ratio of the surfactant to the cobalt salt is 1-2: 1.
7. The method for preparing a cobalt chromate catalyst as claimed in claim 1, wherein the deionized water is added in an amount of: the concentration of the cobalt salt in the mixed solution 1 is 0.05-0.2 mol/L.
8. The method of claim 1, wherein the temperature increase rate during calcination is 3-5 ℃/min.
9. A cobalt chromate catalyst with a core-shell structure, which is characterized by being prepared by the preparation method of the cobalt chromate catalyst as claimed in any one of claims 1 to 8, and the chemical formula of the cobalt chromate catalyst is CoCr 2 O 4 。
10. The application of the cobalt chromate catalyst prepared by the preparation method of the cobalt chromate catalyst as claimed in any one of claims 1 to 8, wherein the cobalt chromate catalyst can be applied to catalytic degradation of volatile organic compounds.
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