CN113477240B - CeO (CeO)2Nanoparticles, and preparation method and application thereof - Google Patents
CeO (CeO)2Nanoparticles, and preparation method and application thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 33
- 239000003054 catalyst Substances 0.000 claims abstract description 102
- 239000002105 nanoparticle Substances 0.000 claims abstract description 75
- 239000002904 solvent Substances 0.000 claims abstract description 47
- 239000002202 Polyethylene glycol Substances 0.000 claims abstract description 46
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims abstract description 46
- 229920001223 polyethylene glycol Polymers 0.000 claims abstract description 46
- 238000003756 stirring Methods 0.000 claims abstract description 43
- 150000000703 Cerium Chemical class 0.000 claims abstract description 39
- 238000002156 mixing Methods 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000001035 drying Methods 0.000 claims abstract description 21
- 238000001354 calcination Methods 0.000 claims abstract description 19
- 229910001868 water Inorganic materials 0.000 claims abstract description 16
- 238000001914 filtration Methods 0.000 claims abstract description 10
- 238000007598 dipping method Methods 0.000 claims abstract description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 48
- 238000010438 heat treatment Methods 0.000 claims description 30
- 239000004094 surface-active agent Substances 0.000 claims description 21
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 18
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims description 18
- 239000004926 polymethyl methacrylate Substances 0.000 claims description 18
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims description 16
- 238000006116 polymerization reaction Methods 0.000 claims description 11
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 9
- 238000005406 washing Methods 0.000 claims description 9
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 claims description 6
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical group [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 6
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 claims description 5
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 claims description 5
- 239000012046 mixed solvent Substances 0.000 claims description 4
- 239000002957 persistent organic pollutant Substances 0.000 claims description 2
- 238000005119 centrifugation Methods 0.000 claims 1
- 230000003197 catalytic effect Effects 0.000 abstract description 29
- 239000012855 volatile organic compound Substances 0.000 abstract description 16
- 238000007254 oxidation reaction Methods 0.000 abstract description 15
- 230000003647 oxidation Effects 0.000 abstract description 14
- 239000002243 precursor Substances 0.000 description 49
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 47
- 239000000243 solution Substances 0.000 description 31
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 29
- 239000002245 particle Substances 0.000 description 18
- 230000000694 effects Effects 0.000 description 15
- 238000006243 chemical reaction Methods 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000001816 cooling Methods 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 239000008367 deionised water Substances 0.000 description 7
- 229910021641 deionized water Inorganic materials 0.000 description 7
- 238000002791 soaking Methods 0.000 description 6
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 description 4
- 125000003827 glycol group Chemical group 0.000 description 4
- 239000011259 mixed solution Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 239000010815 organic waste Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 229910052723 transition metal Inorganic materials 0.000 description 4
- 150000003624 transition metals Chemical class 0.000 description 4
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- OZECDDHOAMNMQI-UHFFFAOYSA-H cerium(3+);trisulfate Chemical compound [Ce+3].[Ce+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O OZECDDHOAMNMQI-UHFFFAOYSA-H 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000005587 bubbling Effects 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- VGBWDOLBWVJTRZ-UHFFFAOYSA-K cerium(3+);triacetate Chemical compound [Ce+3].CC([O-])=O.CC([O-])=O.CC([O-])=O VGBWDOLBWVJTRZ-UHFFFAOYSA-K 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000004626 scanning electron microscopy Methods 0.000 description 2
- 239000006004 Quartz sand Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000010436 fluorite Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 230000002779 inactivation Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Images
Classifications
-
- 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
- B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
-
- 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
- B01D53/8678—Removing components of undefined structure
- B01D53/8687—Organic components
-
- B01J35/40—
-
- B01J35/61—
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
- C01F17/224—Oxides or hydroxides of lanthanides
- C01F17/235—Cerium oxides or hydroxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
- B01D2257/708—Volatile organic compounds V.O.C.'s
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
The invention discloses CeO2The preparation method of the nano-particle catalyst comprises the following steps: mixing cerium salt, a solvent and polyethylene glycol, and stirring and mixing uniformly to obtain a transparent solution; adding a template, dipping, filtering, drying and calcining to obtain CeO2A nanoparticle catalyst; wherein the mass ratio of the cerium salt, the solvent and the polyethylene glycol is 1-10: 1-4: 1. in the invention, CeO is optimized2The structure of the nano-particle catalyst improves CeO2Low temperature catalytic activity of the nano-particle catalyst. By optimizing the preparation conditions of the catalyst, CeO is realized2The nano-particle catalyst is used for removing VOCs by high-efficiency catalytic oxidation at a lower temperature. CeO in the invention2The nano-particle catalyst has good catalytic performance and water resistance, and the stability reaches more than 72 h.
Description
Technical Field
The invention belongs to the fields of air pollution control technology and catalyst preparation, and relates to a preparation method of a transition metal catalyst and application of the catalyst in removing volatile organic pollutants.
Background
The catalyst is used as the core of the catalytic oxidation technology and has an important function in the aspect of removing Volatile Organic Compounds (VOCs) by catalytic oxidation. At present, in the oxidation process of VOCs, the catalysts used mainly include noble metal-based catalysts and transition metal-based catalysts. However, the noble metal-based catalyst has problems of high price, poor sintering resistance, poor water resistance, and the like. The transition metal-based catalyst has good stability, strong water resistance and toxicity resistance, but has the problems of high reaction temperature, low activity and the like. Under the background, the development of a novel low-temperature high-activity transition metal-based catalytic oxidation technology has important significance for effectively controlling the pollution of VOCs.
CeO2As a transition metal oxide, the oxide has the advantages of low price, stable performance and good oxygen storage-release function. Research reports that a material (3 DOM) with a three-dimensional ordered macroporous structure can be prepared by using a template method, but the three-dimensional macroporous structure material has the phenomena of not good enough activity and poor stability.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: provides CeO with high catalytic activity and good stability2A nano-particle catalyst, a preparation method and application thereof.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
CeO (CeO)2The preparation method of the nanoparticle catalyst comprises the following steps:
mixing cerium salt, a solvent and polyethylene glycol, and stirring and mixing uniformly to obtain a transparent solution; adding a template, dipping, filtering, drying and calcining to obtain CeO2A nanoparticle catalyst; wherein the mass ratio of the cerium salt, the solvent and the polyethylene glycol is 1-10: 1-4: 1.
preferably, the preparation method of the template comprises the following steps: dissolving methyl methacrylate or styrene, a surfactant and persulfate in water, heating and stirring to obtain a milky liquid; and centrifuging, washing and drying to obtain the PMMA or PS template.
Preferably, the mass ratio of the methyl methacrylate or the styrene to the surfactant is 100-600: 1, the persulfate is potassium persulfate or sodium persulfate, and the addition amount of the persulfate is 1-10% of the mass of the surfactant.
Preferably, the mass ratio of the methyl methacrylate or the styrene to the surfactant is 500: 3.
The quality of the template prepared at this ratio is the best.
Preferably, the heating temperature is 30-90 ℃; the heating time is 1-8 h.
The temperature range is moderate, and the heating time is more appropriate.
Further preferably, the heating temperature is 60-80 ℃; the heating time is 3-4 h.
The preparation time under the temperature condition is short, the heating temperature is moderate, the prepared template is uniform, the size is proper, and the activity of the subsequently prepared catalyst is optimal.
Preferably, the particle size of the template is 200-500 nm, and preferably, the particle size is 250-350 nm.
The template has moderate particle size range, and is beneficial to the entering of precursor solution in the preparation process.
Preferably, the stirring speed is 80-700 rpm, and the stirring time is 1-24 h.
More preferably, the stirring speed is 700rpm, and the stirring time is 4 h.
The stirring speed is moderate, the energy consumption is low, the time consumption is short, and the uniform mixing of the precursor solution is facilitated.
Preferably, the mass ratio of the cerium salt to the solvent to the polyethylene glycol is 2-3: 1-4: 1.
proper amount of cerium salt and solvent has obvious influence on the homogeneity and size of catalyst grains, and the homogeneity and size of catalyst grains in the range can meet the requirement of subsequent catalytic activity.
Preferably, the polymerization degree of the polyethylene glycol is one or more of 400-11000.
The precursor solution prepared in the polymerization degree range is stable and is not easy to agglomerate in the subsequent calcining process.
Preferably, the polymerization degree of the polyethylene glycol is 11000.
Preferably, the cerium salt is one or more of cerium chloride, cerium sulfate, cerium nitrate or cerium acetate.
The cerium salt has wide selection range, low price and high use safety.
Preferably, the cerium salt, the solvent and the polyethylene glycol are mixed in the following order: firstly adding cerium salt and a solvent, and then adding polyethylene glycol; or adding cerium salt and polyethylene glycol, and then adding a solvent; or firstly adding polyethylene glycol and a solvent, and then adding cerium salt; or the cerium salt, the solvent and the polyethylene glycol are added simultaneously.
Further preferred are cerium salts, solvents and poly(s)The mixing sequence of the ethylene glycol is as follows: first polyethylene glycol and solvent are added, then cerium salt is added. This sequence of addition will directly affect the subsequent CeO2Quality and yield of nanoparticle product. The order of addition is different and may form three-dimensional mesoporous particles, nanoparticles, or even mixed particles. However, the inventors of the present invention have conducted extensive studies to find that the activity of the nanoparticles prepared in this preparation method is optimal.
Preferably, the solvent is one or more of water, methanol or ethanol.
The solvent has wide source, easy obtaining and low price.
Preferably, the solvent is a mixed solvent of methanol and ethanol.
Further preferably, the mass ratio of methanol to ethanol in the mixed solvent is 4-6: 5.
The choice of solvent has a significant effect on the solubility and yield of the catalyst particles.
Preferably, the mass ratio of the adding amount of the template (one or more of PMMA or PS) to the cerium salt solution is 1:1 to 6.
CeO is obtained in this ratio range2The quality of the nanoparticle product is optimal.
Preferably, the dipping temperature is 10-100 ℃, and the dipping time is 1-24 h; the drying temperature is 20-180 ℃, and the drying time is 2-72 h.
Preferably, the specific calcination process is as follows: raising the temperature to 300-700 ℃ in the air atmosphere, keeping the temperature for 1-9 h, and then naturally cooling to room temperature.
The quality and yield of the product obtained by this calcining temperature range and time range are optimal. The calcination temperature is too low, the template cannot be completely calcined, the temperature is too high, the forming rate of particles is low, and the yield is too low.
More preferably, the calcination temperature is 450-550 ℃, and the calcination is kept for 2-4 h.
Preferably, the CeO2The size of the nanoparticle catalyst is 5-200 nm.
The invention also claims the application of the catalyst in degrading organic waste gas, which comprises the following specific steps: placing the above-mentioned catalyst inThe organic waste gas is catalyzed in a fixed bed reactor to carry out degradation reaction, the reaction temperature is 100 ℃ and 300 ℃, and the space velocity is 15000-80000 h < -1 >; the total gas amount is 50-150 mL/min, organic waste gas steam is carried out by a bubbling method through high-purity nitrogen as carrier gas, the concentration of the organic waste gas at the inlet of the fixed bed reactor is 1000ppm, and O is2=21%, nitrogen as the balance gas.
The invention is further explained below:
in the present invention, the catalyst is prepared as nanoparticles due to the difference in the addition amounts and the order of the cerium salt, the solvent and the polyethylene glycol, and in addition, the nanoparticles have a large surface area to expose more active sites, so that CeO2The activity of the nano-particle catalyst is superior to that of CeO2Activity of three-dimensional structure.
Compared with the prior art, the invention has the advantages that:
1. CeO in the invention2The preparation method of the nano-particle catalyst is simple and easy to prepare, the specific surface area of the catalyst and the particle size of the catalyst can be controlled and adjusted by the size and the adding amount of a template (one or two of PMMA and PS), and the prepared CeO2The nano-particle catalyst has the characteristics of uniform nano-size particle size, high specific surface area and the like, and can provide sufficient reaction active sites for the whole catalytic oxidation reaction process of VOCs. Sufficient contact of the VOCs with the catalyst is achieved. Avoid the metal CeO2Insufficient utilization or local agglomeration, etc. CeO (CeO)2As a material for storing and releasing oxygen, sufficient active oxygen can be provided for the reaction. Meanwhile, the specific surface area is increased, more active sites can be exposed, and the performance of the catalyst for removing VOCs is improved. In addition, the raw materials in the invention have wide and various sources (one or more of cerium chloride, cerium sulfate, cerium nitrate and cerium acetate) and low cost.
2. In the invention, CeO is optimized2The structure of the nano-particle catalyst improves CeO2Low temperature catalytic activity of the nano-particle catalyst. By optimizing the preparation conditions of the catalyst, CeO is realized2Nanoparticle catalysts with high VOCs at lower temperaturesAnd (4) removing by effective catalytic oxidation. The heat supply in the reaction process can be greatly reduced, and the operation treatment cost is saved.
3. CeO in the invention2The nano-particle catalyst has no strict requirement on the water content in the environment, can normally work under the premise of keeping higher catalytic efficiency under the condition of higher water content, has good water resistance and obvious effect, can greatly reduce the inactivation of the catalyst, prolongs the service life cycle of the catalyst, and has the stability of more than 72 hours.
4. CeO in the invention2The nano-particle catalyst can realize long-time stable and efficient work, has good reusability, and still has high catalytic efficiency after repeated use (X)>99%), and multiple tests prove that the catalyst of the invention has high activity after being reused for 10 times.
Drawings
FIG. 1 is a schematic representation of CeO prepared from groups A-E in example 1 of the present invention2XRD pattern of nanoparticle catalyst;
FIG. 2 shows CeO prepared from group A of example 1 of the present invention2The activity curve of the nanoparticle catalyst for the catalytic oxidation of toluene;
FIG. 3 shows CeO prepared in example 3 of the present invention2Scanning electron micrographs of the nanoparticle catalyst;
FIG. 4 shows CeO prepared in example 4 of the present invention2The activity curve of the nanoparticle catalyst for the catalytic oxidation of toluene;
FIG. 5 shows CeO prepared in example 6 of the present invention2Scanning electron micrographs of the nanoparticle catalyst;
FIG. 6 shows CeO prepared in example 7 of the present invention2Stability profile of nanoparticle catalysts for catalytic oxidation of toluene.
Detailed Description
In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
study on mass ratio of cerium nitrate to solvent to polyethylene glycol
CeO (CeO)2The preparation method of the nanoparticle catalyst comprises the following steps:
(1) preparing a PMMA template: mixing Methyl Methacrylate (MMA) and a surfactant according to a mass ratio of 200: 1 dissolving in deionized water, introducing N after ultrasonic action2Protecting, maintaining for 4h under the stirring condition of 300rpm, adding 1% of potassium persulfate (relative to the mass of the surfactant), continuously stirring for 8h at 20 ℃ to obtain milky liquid, and centrifuging, washing and drying to obtain a PMMA template;
(2) preparation of a cerium salt precursor solution: firstly adding polyethylene glycol (400) and a solvent, mixing and stirring for 1h, and then adding cerium nitrate. Subsequently, the mixture was maintained for 1 hour under stirring at 700rpm, to obtain a precursor solution. Wherein, the mass ratio of the cerous nitrate to the solvent to the polyethylene glycol is set as A-E group,
the mass ratio of the group A cerium nitrate to the solvent to the polyethylene glycol is 1: 1: 1;
the mass ratio of the cerium nitrate in the group B to the solvent to the polyethylene glycol is 1: 4: 1;
the mass ratio of the group C cerium nitrate to the solvent to the polyethylene glycol is 10: 1: 1;
the mass ratio of the cerium nitrate in the group D to the solvent to the polyethylene glycol is 2: 3: 1;
the mass ratio of the group E cerium nitrate to the solvent to the polyethylene glycol is 10: 4: 1;
（3）CeO2preparing a precursor: adding a certain amount of PMMA (1) into the group A-E cerium salt precursor solution (the mass ratio is 1: 1) in the step (2), dipping for 24 hours at the temperature of 10 ℃, filtering, drying for 2 hours at the temperature of 180 ℃ to obtain white blocky CeO2Precursor body。
(4) White massive CeO obtained in the step (3)2Placing the precursor in air atmosphere, heating to 200 ℃, keeping for 9h, and then naturally cooling to room temperature to obtain CeO2A nanoparticle catalyst.
FIG. 1 shows CeO prepared in groups A to E of this example2XRD pattern of nanoparticle catalyst, from the following figure, CeO prepared in this example2Nanoparticle catalysts are typically fluorite in structure. But the peak areas of XRD of D and E are more prominent, with D being optimal. Indicating that crystal formation was most complete for group D.
5 groups of CeO to be prepared with toluene as a typical representative contaminant of VOCs2The nano particles are used as a catalyst for removing toluene by catalytic oxidation, and all show excellent catalytic activity, but the result of the group D is optimal.
FIG. 2 shows CeO prepared in group D2The activity curve of the nano-particle catalyst for the catalytic oxidation of toluene can be seen from FIG. 2, the CeO prepared by group D2The nano-particle catalyst is used for the catalytic oxidation treatment of toluene, shows excellent catalytic activity and can completely oxidize 1000ppm of toluene into CO at 200 DEG C2And H2O。
Example 2:
investigation of solvent selection
CeO (CeO)2The preparation method of the nanoparticle catalyst comprises the following steps:
(1) preparation of a PS template: mixing styrene and a surfactant according to a mass ratio of 600: 1 dissolving in deionized water, introducing N after ultrasonic action2Protecting, maintaining for 5h under the stirring condition of 300rpm, adding 10% of sodium persulfate (relative to the mass of the surfactant), continuously stirring for 8h at 20 ℃ to obtain milky liquid, and centrifuging, washing and drying to obtain a PS template;
(2) preparation of a cerium salt precursor solution: firstly adding polyethylene glycol (11000) and a solvent, mixing and stirring for 1h, and then adding cerium chloride. And then maintaining the stirring condition at 500rpm for 4 hours to obtain a precursor solution, wherein the mass ratio of the precursor solution to the solvent is 1: 1: 1;
wherein the desired solvent may be provided in groups (1) to (6),
(1) selecting water as a solvent;
(2) selecting methanol as a solvent;
(3) ethanol is selected as a solvent;
(4) the mixed solution of methanol and water in the same amount is used as a solvent;
(5) the mixed solution of ethanol and water in equal amount is used as a solvent;
(6) the mixed solution of methanol and ethanol with equal amount is used as a solvent;
（3）CeO2preparing a precursor: adding a certain amount of PS (1) into a cerium salt precursor solution (2) (the mass ratio is 1: 1), soaking for 24h at 10 ℃, filtering, and drying for 72h at 20 ℃ to obtain white blocky CeO2And (3) precursor.
(4) White massive CeO obtained in the step (3)2Placing the precursor in air atmosphere, heating to 700 ℃, keeping for 1h, and then naturally cooling to room temperature to obtain CeO2The yield of the nano-particle catalyst is measured, and the result is as follows:
(1) obtained CeO2The yield of the nanoparticle catalyst was 53%;
(2) obtained CeO2The yield of the nanoparticle catalyst was 75%;
(3) obtained CeO2The yield of the nanoparticle catalyst was 71%;
(4) obtained CeO2The yield of the nanoparticle catalyst was 67%;
(5) obtained CeO2The yield of the nanoparticle catalyst was 64%;
(6) obtained CeO2The yield of the nanoparticle catalyst was 78%.
It can be seen that the yield of the obtained catalyst is the highest by using the mixed solution of methanol and ethanol as a solvent, and the methanol solution is the next step.
Example 3:
research on heating temperature and heating time in template preparation process
CeO (CeO)2Nanoparticle catalystThe preparation method of the reagent comprises the following steps:
(1) preparing a template: mixing Methyl Methacrylate (MMA) and a surfactant according to a mass ratio of 300: 1 dissolving in deionized water, introducing N after ultrasonic action2Protecting, maintaining for 3 hours under the stirring condition of 500rpm, adding 3 percent of potassium persulfate (relative to the mass of the surfactant), stirring at a certain temperature to obtain milky liquid, and centrifuging, washing and drying to obtain a PMMA template; wherein, the relationship between the heating temperature and the heating time is set in I-V groups,
the heating temperature of the group I is 30 ℃, and the heating time is 1 h.
The heating temperature of the group II is 30 ℃, and the heating time is 8 h.
Group III heating temperature is 70 deg.C, heating time is 3 h.
And the heating temperature of the group IV is 90 ℃, and the heating time is 1 h.
Group V heating temperature is 90 deg.C, and heating time is 8 h.
Scanning electron microscopy is performed on the prepared template, and the appearance of the template are respectively shown in fig. 3. The result is that the template arrangement of the I group, the IV group and the V group is disordered and uneven, the II group is not neat, and only the template of the III group is uniform and neat, and the gap is uniform. The integrity of the template formation is closely related to the performance of the subsequent catalyst.
(2) Preparation of a cerium salt precursor solution: firstly adding polyethylene glycol (8000) and solvent, mixing and stirring for 1h, and then adding cerium sulfate. Subsequently, the solution was maintained for 6 hours under stirring at 500rpm, to obtain a precursor solution. Wherein the adding mass ratio is 1: 4: 1;
（3）CeO2preparing a precursor: adding a certain amount of PMMA (1) into a cerium salt precursor solution (2) (the mass ratio is 1: 2), soaking for 18h at the temperature of 40 ℃, filtering, and drying for 18h at the temperature of 140 ℃ to obtain white blocky CeO2And (3) precursor.
(4) White massive CeO obtained in the step (3)2Placing the precursor in air atmosphere, heating to 300 ℃, keeping for 7h, and then naturally cooling to room temperature to obtain CeO2A nanoparticle catalyst.
For prepared CeO2The catalytic activity of the nanoparticle catalyst is compared, and the catalyst activity of the group III is obviously superior to that of the other four groups.
Example 4:
study of addition sequence of cerium salt, solvent and polyethylene glycol
CeO (CeO)2The preparation method of the nano-particle catalyst and the application of the nano-particle catalyst in the aspect of VOC removal comprise the following steps:
(1) preparing a PMMA template: mixing Methyl Methacrylate (MMA) and a surfactant according to a mass ratio of 500: 1 dissolving in deionized water, introducing N after ultrasonic action2Protecting, maintaining for 2h under the stirring condition of 500rpm, adding 7% of potassium persulfate (relative to the mass of the surfactant), continuing stirring for 2h at 80 ℃ to obtain milky liquid, and centrifuging, washing and drying to obtain a PMMA template;
(2) preparation of a cerium salt precursor solution: cerium salt, a solvent and polyethylene glycol (400) are mixed according to a mass ratio of 1: 1:1, mixing and stirring to obtain a precursor solution. Wherein, the addition sequence of the cerium salt, the solvent and the polyethylene glycol is set as (i) - (iii):
mixing and stirring cerium nitrate and methanol for 2 hours, adding polyethylene glycol (400), and continuously stirring for 4 hours to obtain a precursor solution;
secondly, mixing and stirring cerium nitrate and polyethylene glycol (400) for 2 hours, adding methanol, and continuously stirring for 4 hours to obtain a precursor solution;
thirdly, mixing and stirring polyethylene glycol (400) and methanol for 2 hours, adding cerium nitrate, and continuously stirring for 4 hours to obtain a precursor solution;
（3）CeO2preparing a precursor: adding a certain amount of template (PMMA: PS =1:1, mass ratio) into the cerium salt precursor solution (2) (mass ratio 1: 4), soaking for 6h at 80 ℃, filtering, and drying for 48h at 60 ℃ to obtain white blocky CeO2And (3) precursor.
(4) White massive CeO obtained in the step (3)2Placing the precursor in air atmosphere, heating to 500 ℃, keeping for 3h, and then naturally cooling to room temperature to obtain CeO2A particulate catalyst.
The CeO prepared by the group (i) to (iii) of the present example was used as a representative contaminant of VOCs2The particles were used as catalyst for the catalytic oxidative removal of toluene, and the results are shown in fig. 4. (III) CeO prepared by group2The particles all show better catalytic activity, wherein the third group has the best activity, and 1000ppm of toluene can be completely oxidized into CO at 180 DEG C2And H2O。
CeO prepared from the group of (1) - (III)2The particles are further characterized, and are found to be superior to the difference of the adding sequence, the shapes of the particles are very obviously different, wherein the group III is nano particles with the uniform size of about 50nm, and the group I is CeO2Three-dimensional porous structure of CeO with non-uniform particle size2The particle size of part of the particles is obviously larger than that of the group III. But obviously, the catalytic activity of the nano particles is superior to that of the three-dimensional mesoporous particles. Probably because of the large surface area of the nanoparticles, more active sites may be exposed, and thus, CeO2The activity of the nano-particle catalyst is superior to that of CeO2Activity of three-dimensional structure.
Example 5:
investigation of polymerization degree of polyethylene glycol
CeO (CeO)2The preparation method of the nano-particle catalyst and the application of the nano-particle catalyst in the aspect of VOC removal comprise the following steps:
(1) preparing a PMMA template: mixing Methyl Methacrylate (MMA) and a surfactant according to a mass ratio of 400: 1 dissolving in deionized water, introducing N after ultrasonic action2Protecting, maintaining for 3h under the stirring condition of 400rpm, adding 10% of potassium persulfate (relative to the mass of the surfactant), continuously stirring for 1h at 90 ℃ to obtain milky liquid, and centrifuging, washing and drying to obtain a PMMA template;
(2) preparation of a cerium salt precursor solution: mixing and stirring polyethylene glycol and methanol for 2 hours, adding cerium nitrate, and continuously stirring for 4 hours, wherein the mass ratio is 4: 4: and maintaining the stirring condition at 1,400 rpm for 4 hours to obtain a precursor solution. Wherein the polymerization degrees of the polyethylene glycol are respectively 400, 8000 and 11000;
（3）CeO2preparing a precursor: adding a certain amount of PMMA (1) into a cerium salt precursor solution (2) (the mass ratio is 1: 6), soaking for 1h at 100 ℃, filtering, and drying for 72h at 20 ℃ to obtain white blocky CeO2And (3) precursor.
(4) White massive CeO obtained in the step (3)2Placing the precursor in air atmosphere, heating to 700 ℃, keeping for 1h, and then naturally cooling to room temperature to obtain CeO2The yield of the nano-particle catalyst is measured, and CeO obtained by polyethylene glycol group with polymerization degree of 400 is found2The yield of the nanoparticle catalyst was 64%; CeO obtained from polyethylene glycol group with polymerization degree of 80002The yield of the nanoparticle catalyst was 80%; CeO obtained from polyethylene glycol group with degree of polymerization of 110002The yield of the nanoparticle catalyst was 85%. The yield is optimal with the polyethylene glycol group with the polymerization degree of 11000.
Example 6:
study on calcination temperature and calcination time
CeO (CeO)2The preparation method of the nano-particle catalyst and the application of the nano-particle catalyst in the aspect of VOC removal comprise the following steps:
(1) preparation of a PS template: mixing styrene and a surfactant according to a mass ratio of 300: 1 dissolving in deionized water, introducing N after ultrasonic action2Protecting, maintaining for 5h under the stirring condition of 300rpm, adding 3% of sodium persulfate (relative to the mass of the surfactant), continuously stirring for 2h at 80 ℃ to obtain milky liquid, and centrifuging, washing and drying to obtain a PS template;
(2) preparation of a cerium salt precursor solution: mixing and stirring polyethylene glycol (400) and methanol for 2h, adding cerium chloride, and maintaining for 6h under the stirring condition of 500rpm to obtain a precursor solution. Wherein the adding mass ratio is 2: 3: 1;
（3）CeO2preparing a precursor: adding a certain amount of PS (1) into a cerium salt precursor solution (2) (the mass ratio is 1: 4), soaking for 6h at 80 ℃, filtering, and drying for 18h at 140 ℃ to obtain white blocky CeO2And (3) precursor.
(4) White massive CeO obtained in the step (3)2Placing the precursor in an air atmosphere for calcining, wherein the calcining temperature and the calcining time are set to be E-I groups;
the group E is calcined at the temperature of 300 ℃ for 1 hour, and then naturally cooled to the room temperature;
the calcination temperature of the group F is 300 ℃, the calcination temperature is maintained for 9 hours, and then the group F is naturally cooled to the room temperature;
the G group is calcined at 500 ℃ for 3 hours, and then naturally cooled to room temperature;
the calcination temperature of the H group is 700 ℃, the H group is maintained for 1 hour, and then the H group is naturally cooled to the room temperature;
group I was calcined at 700 ℃ for 9 hours, followed by natural cooling to room temperature.
The appearance of the prepared catalyst was tested, and the results of the scanning electron microscopy are shown in fig. 5. CeO from groups E and F2The catalyst contains a large amount of templates (incomplete template removal); CeO obtained from group F2The catalyst contains a small amount of template (incomplete template removal); the CeO2 catalyst obtained from the group G is uniformly dispersed nano particles, and the template is completely removed; CeO obtained from groups H and I2The template in the nano-particle catalyst is completely removed, but the particle arrangement is disordered, the forming rate is low, and the yield of the catalyst is obviously lower than that of the G group.
Example 7:
CeO (CeO)2The preparation method of the nano-particle catalyst and the application of the nano-particle catalyst in the aspect of VOC removal comprise the following steps:
(1) preparing a PMMA template: mixing styrene and a surfactant according to a mass ratio of 500: 1 dissolving in deionized water, introducing N after ultrasonic action2Protecting, maintaining for 2h under the stirring condition of 500rpm, adding 1% of sodium persulfate (relative to the mass of the surfactant), continuously stirring for 1h at 90 ℃ to obtain milky liquid, and centrifuging, washing and drying to obtain a PMMA template;
(2) preparation of a cerium salt precursor solution: cerium nitrate and methanol are mixed and stirred for 1h, then polyethylene glycol (11000) is added, and then the mixture is maintained for 1h under the stirring condition of 700rpm, so as to obtain a precursor solution. Wherein the adding mass ratio is 10: 4: 1;
（3）CeO2preparing a precursor: adding a certain amount of PMMA (1) into a cerium salt precursor solution (2) (the mass ratio is 1: 6), soaking for 18h at the temperature of 40 ℃, filtering, and drying for 2h at the temperature of 180 ℃ to obtain white blocky CeO2And (3) precursor.
(4) White massive CeO obtained in the step (3)2Placing the precursor in air atmosphere, heating to 500 ℃, keeping for 4h, and naturally cooling to room temperature to obtain CeO2A nanoparticle catalyst.
(5) Toluene is taken as a typical pollution representative of VOCs, and catalytic oxidation removal is carried out on the pollution representative. Accurately weighing 0.1g of CeO2Mixing the nano-particle catalyst and 0.4g of quartz sand uniformly, and placing the mixture in a fixed bed reactor (the reaction temperature is 100 ℃ C. and 300 ℃ C.), wherein the total gas quantity in the reaction process is 100 mL/min, and the space velocity is 60000 mL ∙ g-1∙h-1Toluene vapor is carried out by a bubbling method through high-purity nitrogen as carrier gas, the concentration of toluene at the inlet of the fixed bed reactor is 1000ppm, and O is2=21%, the concentration of toluene in the simulated atmosphere was measured by gas chromatography (Shimadzu GC-2014, Japan) using nitrogen as the equilibrium gas. CeO prepared in this example2The nano-particle catalyst is used for the catalytic oxidation treatment of toluene, and the experimental result of FIG. 6 shows that CeO2The nano-particle catalyst still shows excellent stability (X) after 72 hours of continuous toluene catalytic removal reaction at 210 DEG C>99%). The stability tests were also performed on the better catalysts of examples 1-5, and it was found that the stability was stable for over 72 hours. Meanwhile, 5-10g of water is added into the reaction system, the catalytic performance of the catalyst is not changed greatly and can be stabilized for more than 72 hours. Indicating that the catalyst of the present invention is excellent in water resistance.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.
Claims (4)
1. CeO (CeO)2The preparation method of the nanoparticle catalyst is characterized by comprising the following steps:
mixing cerium salt, a solvent and polyethylene glycol, and stirring and mixing uniformly to obtain a transparent solution; adding a template, dipping, filtering, drying and calcining to obtain CeO2A nanoparticle catalyst; wherein the mass ratio of the cerium salt, the solvent and the polyethylene glycol is 1-10: 1-4: 1;
the preparation method of the template comprises the following steps: dissolving methyl methacrylate or styrene, a surfactant and persulfate in water, heating and stirring to obtain a milky liquid; obtaining a PMMA or PS template through centrifugation, washing and drying; the mass ratio of the methyl methacrylate or the styrene to the surfactant is 100-600: 1, the persulfate is potassium persulfate or sodium persulfate, and the addition amount of the persulfate is 1-10% of the mass of the surfactant;
the heating temperature is 70 ℃; the heating time is 3-4 h;
the polymerization degree of the polyethylene glycol is one or more of 400-11000;
the mixing sequence of the cerium salt, the solvent and the polyethylene glycol is as follows: firstly, adding polyethylene glycol and a solvent, and then adding cerium salt;
the solvent is a mixed solvent of methanol and ethanol; in the mixed solvent, the mass ratio of methanol to ethanol is 1-6: 5;
the calcination temperature is 450-550 ℃, and the calcination is kept for 2-4 h.
2. The CeO of claim 12The nano-particle catalyst is characterized in that the mass ratio of cerium salt to solvent to polyethylene glycol is (2-3): 1-4: 1.
3. the CeO of claim 12The nanoparticle catalyst is characterized in that the polymerization degree of the polyethylene glycol is 11000.
4. The CeO according to any one of claims 1 to 32The application of the nano-particle catalyst in removing volatile organic pollutants.
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| CN111601691A (en) * | 2017-09-11 | 2020-08-28 | 哈佛大学 | Microspheres comprising polydisperse polymeric nanospheres and porous metal oxide microspheres |
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| CN101982414A (en) * | 2010-10-19 | 2011-03-02 | 北京航空航天大学 | Method for preparing doped nano ceria powder by utilizing solvent-thermal method |
| CN103495418A (en) * | 2013-09-26 | 2014-01-08 | 中国石油大学(北京) | Macroporous-mesoporous cerium-zirconium solid solution silver-loaded catalyst and preparation method and application thereof |
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