CN112516988A - Catalyst with CeZrK/rGO nano solid solution as main component - Google Patents
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- 239000003054 catalyst Substances 0.000 title claims abstract description 172
- 239000006104 solid solution Substances 0.000 title claims abstract description 129
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 66
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 50
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 20
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 20
- 229910052684 Cerium Inorganic materials 0.000 claims abstract description 14
- 239000002105 nanoparticle Substances 0.000 claims abstract description 14
- 229910001414 potassium ion Inorganic materials 0.000 claims abstract description 8
- 239000002245 particle Substances 0.000 claims description 17
- 239000011148 porous material Substances 0.000 claims description 15
- 229910052726 zirconium Inorganic materials 0.000 claims description 7
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims 1
- 230000003197 catalytic effect Effects 0.000 abstract description 42
- 238000006243 chemical reaction Methods 0.000 abstract description 10
- -1 cerium ions Chemical class 0.000 abstract description 9
- 230000015572 biosynthetic process Effects 0.000 abstract description 7
- 230000007547 defect Effects 0.000 abstract description 7
- NPYPAHLBTDXSSS-UHFFFAOYSA-N Potassium ion Chemical compound [K+] NPYPAHLBTDXSSS-UHFFFAOYSA-N 0.000 abstract description 6
- 238000003786 synthesis reaction Methods 0.000 abstract description 5
- GBNDTYKAOXLLID-UHFFFAOYSA-N zirconium(4+) ion Chemical compound [Zr+4] GBNDTYKAOXLLID-UHFFFAOYSA-N 0.000 abstract description 5
- 239000004071 soot Substances 0.000 description 48
- 229910052760 oxygen Inorganic materials 0.000 description 46
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 39
- 239000001301 oxygen Substances 0.000 description 39
- 238000007254 oxidation reaction Methods 0.000 description 33
- 230000003647 oxidation Effects 0.000 description 30
- 229910052799 carbon Inorganic materials 0.000 description 16
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 11
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 10
- 150000002500 ions Chemical class 0.000 description 10
- 238000000034 method Methods 0.000 description 10
- 239000000779 smoke Substances 0.000 description 10
- 238000000634 powder X-ray diffraction Methods 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- 238000001179 sorption measurement Methods 0.000 description 8
- 239000012298 atmosphere Substances 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 7
- 230000009467 reduction Effects 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 5
- 229910000420 cerium oxide Inorganic materials 0.000 description 5
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- 230000000694 effects Effects 0.000 description 5
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- 238000002411 thermogravimetry Methods 0.000 description 5
- 230000004580 weight loss Effects 0.000 description 5
- 230000010718 Oxidation Activity Effects 0.000 description 4
- 238000001354 calcination Methods 0.000 description 4
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 4
- 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 4
- 238000002485 combustion reaction Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- UJVRJBAUJYZFIX-UHFFFAOYSA-N nitric acid;oxozirconium Chemical compound [Zr]=O.O[N+]([O-])=O.O[N+]([O-])=O UJVRJBAUJYZFIX-UHFFFAOYSA-N 0.000 description 4
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 4
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 4
- FGUUSXIOTUKUDN-IBGZPJMESA-N C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 Chemical compound C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 FGUUSXIOTUKUDN-IBGZPJMESA-N 0.000 description 3
- 238000001069 Raman spectroscopy Methods 0.000 description 3
- 238000003917 TEM image Methods 0.000 description 3
- 238000000026 X-ray photoelectron spectrum Methods 0.000 description 3
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 3
- 238000005054 agglomeration Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000009776 industrial production Methods 0.000 description 3
- 238000002329 infrared spectrum Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052700 potassium Inorganic materials 0.000 description 3
- 238000002336 sorption--desorption measurement Methods 0.000 description 3
- 238000004627 transmission electron microscopy Methods 0.000 description 3
- 229910001316 Ag alloy Inorganic materials 0.000 description 2
- 238000004438 BET method Methods 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 238000001237 Raman spectrum Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical group [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000011038 discontinuous diafiltration by volume reduction Methods 0.000 description 2
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 2
- 238000010335 hydrothermal treatment Methods 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- SWELZOZIOHGSPA-UHFFFAOYSA-N palladium silver Chemical compound [Pd].[Ag] SWELZOZIOHGSPA-UHFFFAOYSA-N 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 235000010333 potassium nitrate Nutrition 0.000 description 2
- 239000004323 potassium nitrate Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000007847 structural defect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000009210 therapy by ultrasound Methods 0.000 description 2
- 230000037303 wrinkles Effects 0.000 description 2
- GNFTZDOKVXKIBK-UHFFFAOYSA-N 3-(2-methoxyethoxy)benzohydrazide Chemical compound COCCOC1=CC=CC(C(=O)NN)=C1 GNFTZDOKVXKIBK-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 229910014033 C-OH Inorganic materials 0.000 description 1
- 229910014570 C—OH Inorganic materials 0.000 description 1
- 238000004566 IR spectroscopy Methods 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 230000003698 anagen phase Effects 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- DRVWBEJJZZTIGJ-UHFFFAOYSA-N cerium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ce+3].[Ce+3] DRVWBEJJZZTIGJ-UHFFFAOYSA-N 0.000 description 1
- QQZMWMKOWKGPQY-UHFFFAOYSA-N cerium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QQZMWMKOWKGPQY-UHFFFAOYSA-N 0.000 description 1
- KQJQGYQIHVYKTF-UHFFFAOYSA-N cerium(3+);trinitrate;hydrate Chemical compound O.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O KQJQGYQIHVYKTF-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000004299 exfoliation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000009396 hybridization Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 125000000896 monocarboxylic acid group Chemical group 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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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
- B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
-
- B01J35/61—
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
- F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
The invention provides a catalyst taking CeZrK/rGO nano solid solution as a main component, wherein the active component of the catalyst is the CeZrK/rGO nano solid solution; the CeZrK/rGO nano solid solution is prepared from cerium ions (Ce) taking graphene as a carrier4+) Zirconium ion (Zr)4+) And potassium ion (K)+) The spherical metal oxide nanoparticles of (2). The invention has the characteristics of low reaction temperature, high catalytic activity, easy synthesis, low cost and good thermal stability, and can fill the defects of the catalyst in the prior art.
Description
Technical Field
The invention particularly relates to a catalyst taking CeZrK/rGO nano solid solution as a main component.
Technical Field
Diesel engines are widely used in transportation and various off-road construction machines. However, the exhaust gas discharged therefrom causes serious environmental pollution, in which the discharged soot has a great influence on both the environment and human health due to insufficient combustion. The technology of controlling soot emissions of diesel engines has been the focus of attention by governments and scholars of various countries.
The diesel exhaust temperature is between 150 ℃ and 450 ℃, while the oxidation temperature of soot exceeds 550 ℃. Therefore, to eliminate soot pollution, the exhaust temperature needs to be increased to intensify the soot oxidation reaction, but too high a soot combustion temperature may damage the filter material. So that it is more feasible to doThe method is to reduce the oxidation reaction temperature of soot by using a catalyst. The diesel catalyzed particulate trap does not require an additional heat source and a complex control system, thereby greatly reducing fuel consumption and engine wear. The efficiency of a diesel catalyzed particulate trap is determined by the quality of the catalyst used in the diesel catalyzed particulate trap. Since the catalytic oxidation of soot is O2The reaction between the soot and the catalyst, the contact area of the catalyst and the soot and the intrinsic catalytic activity of the catalyst are two key factors influencing the oxidation efficiency of the soot, and meanwhile, the thermal stability, the economy and the cost of the catalyst can also be influenced factors. Therefore, it is of great significance to design and prepare catalysts with large contact area, high intrinsic catalytic activity, thermal stability and low price.
Chinese patent publication CN108554406B, published japanese 20200424, discloses a supported alloy type carbon smoke oxidation catalyst and its preparation method, wherein the carrier is cerium-zirconium composite oxide and its light rare earth modification system, the alloy type active component is homogeneous palladium-silver alloy, the alloy type active component comprises, by mass, 1% -20% of palladium, 80% -99% of silver, and the total metal loading is 4% -15%. In example 2 of the present invention, the temperature at which the soot oxidation of the loose contact morphology reaches the maximum rate was 416 ℃, the reaction temperature of the soot oxidation was reduced to some extent, and the efficiency was increased.
However, the exhaust temperature of the diesel engine is between 150 ℃ and 450 ℃, the temperature of the invention when the maximum rate of soot oxidation is reached is 416 ℃, although the temperature falls into the exhaust temperature range of the diesel engine, the temperature is in a higher range, and the catalytic activity still has room for improvement. Because the catalyst is a supported alloy type catalyst, the carrier is cerium-zirconium composite oxide and a light rare earth modification system thereof, and the alloy type active component is homogeneous palladium-silver alloy, the cost of the catalyst is still higher.
Therefore, there is a need to invent a new soot oxidation catalyst, which has lower reaction temperature, higher catalytic activity, stronger thermal stability and lower cost.
Disclosure of Invention
The invention provides a catalyst taking CeZrK/rGO nano solid solution as a main component, which has the characteristics of high catalytic activity, easy synthesis, low cost and better thermal stability, thereby filling the defects of the catalyst in the prior art.
The invention relates to a catalyst taking CeZrK/rGO nano solid solution as a main component, wherein the active component of the catalyst is the CeZrK/rGO nano solid solution, and the CeZrK/rGO nano solid solution has the following general formula:
CeAZrBKC/rGO
in the general formula, A, B and C are 5: 1-3.
The CeZrK/rGO nano solid solution is prepared from cerium ions (Ce) taking reduced graphene oxide as a carrier4+) Zirconium ion (Zr)4+) And potassium ion (K)+) The spherical metal oxide nanoparticles of (2).
Further, the reduced graphene oxide (rGO) has mesoporous distribution characteristics, and the CeZrK/rGO nano solid solution has a nano-pore structure, wherein the pore diameter of the CeZrK/rGO nano solid solution is 36.1-36.9 nm.
Further, the specific surface area of the CeZrK/rGO nano solid solution is 117.2-152.4m2/g。
Further, the crystallite size of the CeZrK/rGO nano solid solution is 6.7-8.3 nm.
Further, the average grain diameter of CeAZrBKC/rGO is 7.42-9.65 nm which is smaller than CeZrOxThe average particle diameter of the catalyst (15-20 nm).
The inventors used Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), N2 adsorption-desorption experiments, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman spectroscopy) and H2The method such as TPR characterization (TPR) is used for characteristic evaluation of the structure and morphology of the CeZrK/rGO nano solid solution; and the catalytic performance of the CeZrK/rGO nano solid solution is evaluated by thermogravimetric analysis. The temperature at which the soot oxidation reaches 50% is defined as T in the present invention50The temperature at which the soot oxidation reaches a maximum rate is defined as Tm(ii) a And the evaluation of the catalytic activity of the CeZrK/rGO nano solid solutionAnd (4) evaluating the standard.
Through the above studies, it was found that the base material of graphene in the present invention takes the form of a translucent sheet having wrinkles and folds. The metal oxide particles are uniformly and highly dispersed on the graphene. Using nano-measurement software, Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3The average particle diameter of/rGO is respectively 9.65nm, 7.42nm and 9.39nm, which is less than CeZrOxThe average particle diameter of the catalyst (15-20 nm). This indicates that the graphene inhibits surface migration of the metal oxide nanoparticles and reduces the size of the metal oxide nanoparticles. And elements Ce, Zr, K, C and O are highly dispersed on the catalyst. The well-dispersed metal oxide nanoparticles promote catalytic oxidation of soot.
N2 adsorption-desorption test shows that Ce is in CeZrK/rGO nano solid solution5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3The most probable pore diameters of/rGO are 36.9nm, 36.8nm and 36.1nm, respectively, greater than that of soot: (>20nm) to ensure that the soot can enter the internal pores of the catalyst and fully contact with the active phase.
X-ray powder diffraction (XRD) showed Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3The average grain sizes of/rGO are 8.3nm, 6.9nm and 6.7nm, respectively.
From N based on multipoint BET method2In the adsorption isotherm, the inventors obtained Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3Specific surface area/rGO of 117.2m2/g、151.5m2G and 152.4m2(ii) in terms of/g. The graphene-based catalyst is proved to have a larger specific surface area and a better pore structure, and the high catalytic activity of the CeZrK/rGO nano solid solution is effectively ensured.
X-ray photoelectron spectroscopy (XPS) shows that the CeZrK/rGO nano solid solution shows two kinds of surface oxygen chemisorption oxygen and lattice oxygen, and the CeZrK/rGO nano solid solution has higher chemisorption oxygen concentration.
The inventor carries out H on CeZrK/rGO nano solid solution2The results of the TPR analysis show an increase in oxygen mobility within the CeZrK/rGO lattice and an increase in the reducibility of the CeZrK/rGO. The results indicate that graphene can enhance the redox ability of cerium oxide at low temperatures. All the CeZrK/rGO nano solid solutions show good oxidation-reduction capability, which reflects the improvement of the carbon smoke catalytic oxidation activity of the CeZrK/rGO nano solid solution catalyst.
In the temperature range from room temperature to 650 ℃, the heating rate is 10 ℃ min-1In the case of (2), the inventors have concluded, by thermogravimetric analysis, that a simulated air atmosphere (21% O) in loose contact is present2+79％N2) Middle Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3T of/rGO50390 ℃, 383 ℃ and 432 ℃ respectively, which are far lower than CeO2T of50(523 ℃ C.), T of rGO50(532 ℃ C.) and T without catalyst (604 ℃ C.)50And Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3T of/rGOm347 deg.C, 344 deg.C and 330 deg.C, respectively, far below the T of the other catalystsmAnd the weight loss process of the graphene mainly occurs at 520 ℃, the weight loss rate is 2.3%, and the graphene has good thermal stability.
The analysis can obtain that the catalyst taking the CeZrK/rGO nano solid solution as the main component has the following advantages:
the catalyst has the advantages that metal oxide particles loaded on graphene serving as a carrier of the CeZrK/rGO nano solid solution catalyst are uniform and highly dispersed, and the catalytic oxidation of soot is promoted when the carbon soot is catalyzed and oxidized.
The CeZrK/rGO nano solid solution catalyst has small average grain size, larger specific surface area and better pore structure; effectively ensures the high catalytic activity of the CeZrK/rGO nano solid solution catalyst.
3. The defect sites on the surface of the reduced graphene oxide (rGO) can effectively inhibit the agglomeration of metal oxide nanoparticles, thereby reducing the grain size and improving the dispersion characteristic; thereby improving the catalytic activity of the CeZrK/rGO nano solid solution catalyst.
The CeZrK/rGO nano solid solution catalyst contains more oxygen vacancies, has higher chemisorption oxygen concentration and good redox capability, thereby ensuring high catalytic activity.
5. CeO (CeO) taking graphene as carrier2Middle doped with Zr4+Ions and K+The ions can effectively promote the formation of nano solid solution catalysts. The graphene may enhance the redox ability of the cerium oxide at low temperature. All the CeZrK/rGO nano solid solution catalysts show good oxidation-reduction capability, which reflects the improvement of the carbon smoke catalytic oxidation activity of the CeZrK/rGO nano solid solution catalysts.
6. T of CeZrK/rGO nano solid solution catalyst in loose contact and close contact modes50All the catalysts in the prior art have higher catalytic activity.
The CeZrK/rGO nano solid solution catalyst has the characteristics of easy synthesis and low cost, and is convenient for industrial production and practical application.
The analysis proves that the catalyst taking the CeZrK/rGO nano solid solution as the main component has good carbon smoke oxidation catalytic activity, the reaction temperature of carbon smoke oxidation is greatly reduced, the catalyst has good thermal stability, the catalyst reaches and exceeds various reported carbon smoke oxidation catalysts under the same evaluation condition, and the catalyst is low in cost, easy to operate and suitable for industrial production and practical application.
Drawings
FIG. 1 is a schematic diagram of a preparation process of a CeZrK/rGO nano solid solution catalyst;
FIG. 2 is a Transmission Electron Microscope (TEM) image of the CeZrK/rGO nano solid solution catalyst and a histogram of the average particle size and the ratio of the CeZrK/rGO nano solid solution catalyst according to the TEM image;
FIG. 3 is an X-ray powder diffraction (XRD) pattern of a CeZrK/rGO nano solid solution catalyst;
FIG. 4 is N of CeZrK/rGO nano solid solution catalyst2Adsorption isotherms and pore size distribution line graphs;
FIG. 5 is a Raman spectrum of CeZrK/rGO nano solid solution catalyst and Graphene Oxide (GO);
FIG. 6 is an infrared spectrum of Graphene Oxide (GO) from a CeZrK/rGO nano solid solution catalyst;
FIG. 7 is an X-ray photoelectron Spectroscopy (XPS) of Ce 3d, Zr 3d, O1s and C1s in a CeZrK/rGO nano solid solution catalyst;
FIG. 8 is H of CeZrK/rGO nano solid solution catalyst2-a TPR profile;
FIG. 9 is a graph showing the results obtained in simulated air (21% O)2+79％N2) In the graph, the normalized soot conversion rate of the CeZrK/rGO nano solid solution catalyst changes with the temperature in a close contact mode;
FIG. 10 shows a simulated atmosphere (21% O)2+79％N2) In the graph, the normalized soot conversion rate of the CeZrK/rGO nano solid solution catalyst changes with the temperature in the loose contact mode;
fig. 11 is a graph showing the change of weight loss of graphene under an air atmosphere;
FIG. 12 shows the reaction conditions in pure N2DTG graph of soot combustion in close contact mode of CeZrK/rGO catalyst in atmosphere.
Detailed Description
It should be apparent that the embodiments described below are some, but not all embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Example 1
A catalyst with CeZrK/rGO nano solid solution as a main component comprises an active component of CeZrK/rGO nano solid solution, wherein the CeZrK/rGO nano solid solution catalyst has the following general formula:
CeAZrBKC/rGO
in the general formula, A, B and C are 5: 1-3.
The CeZrK/rGO nano solid solution catalyst is prepared from cerium ions (Ce) taking reduced graphene oxide as a carrier4+) Zirconium ion (Zr)4+) And potassium ion (K)+) The spherical metal oxide nanoparticles of (2).
The reduced graphene oxide (rGO) has mesoporous distribution characteristics, and the CeZrK/rGO nano solid solution catalyst has a nano-pore structure (36.1-36.9 nm).
The specific surface area of the CeZrK/rGO nano solid solution catalyst is 117.2-152.4m2/g。
The crystallite dimension of the CeZrK/rGO nano solid solution catalyst is 6.7-8.3 nm.
The average particle size of CeAZrBKC/rGO is smaller than that of the CeZrOx catalyst (15-20 nm).
As shown in fig. 1, the preparation method of the CeZrK/rGO nano solid solution catalyst is as follows:
a. mixing cerium nitrate hydrate, zirconyl nitrate hydrate and potassium nitrate (KNO)3) Dissolving in deionized water to obtain cerium (Ce) -containing solution4+) Metal ion, zirconium (Zr)4+) Metal ion and potassium (K)+) A salt solution of metal ions;
b. preparing graphene oxide, wherein the mass ratio of the graphene oxide to cerium ions is 5:1, mixing Graphene Oxide (GO) with deionized water, and generating a Graphene Oxide (GO) solution after ultrasonic treatment for 0.5 h;
c. mixing the two solutions prepared in the steps a and b, and then carrying out ultrasonic treatment for 0.5 h;
d. heating the mixed solution in the step c in a water bath for 1 h;
e. adding ammonium hydroxide into the mixed solution obtained in the step d until the pH value of the solution is 10 +/-0.1;
f. carrying out hydrothermal treatment on the solution obtained in the step e for 12 h; generating reduced graphene oxide (rGO);
g. repeatedly centrifugally washing the solution obtained in the step f by using deionized water until the pH value of the solution obtained in the step f is adjusted to be neutral;
h. g, further freeze-drying the solution obtained in the step g in a vacuum freeze dryer for 18 hours to obtain a precursor;
i. and (5) calcining the precursor obtained in the step h in a tubular furnace for 2h under the argon atmosphere to obtain the CeZrK/rGO nano solid solution catalyst.
The general formula of the prepared CeZrK/rGO nano solid solution catalyst is CeAZrBKC/rGO，
In the general formula, A, B and C are 5: 1-3.
Further, in the step a, the molar ratio of cerium ions to zirconium ions to potassium ions in the salt solution is 5: 1-3.
Further, the hydrate of cerium nitrate in the step a is cerium nitrate hexahydrate (Ce (NO)3)3·6H2O), the hydrate of zirconyl nitrate is zirconyl nitrate hexahydrate (ZrO (NO)3)2·6H2O); hydrate of cerium nitrate, hydrate of zirconyl nitrate and potassium nitrate (KNO)3) Dissolved in deionized water by magnetic stirring.
Further, the water bath heating temperature in the step d is 75-85 ℃.
Further, the temperature of the hydrothermal treatment in the step f is 155-165 ℃.
Further, the calcining temperature in the step i is 190-200 ℃. The calcining temperature is far lower than that in the prior art, so that the energy is saved, the environment is protected, the preparation difficulty is reduced, and the preparation is more operable.
Furthermore, all materials in the preparation method are of analytical grade and can be used without purification.
The calcination of the invention can produce CeO2、ZrO2And K2O, reduced graphene oxide (rGO) is used as a catalyst carrier, and CeO is added2、ZrO2And K2O is mixed in a molar ratio of 10:2:1, 5:2:1 and 10:6:3, respectively, to obtain Ce5Zr1K1/rGO、Ce5Zr2K2/rGO, and Ce5Zr3K3Compounds of/rGO.
Example 2
This example describes the morphology and size of the CeZrK/rGO nano solid solution catalyst using Transmission Electron Microscopy (TEM) techniques, as shown in fig. 2. It is known that the base material of graphene takes the form of a translucent sheet having wrinkles and folds. The metal oxide particles supported on the graphene are uniform and highly dispersed. From the TEM image of FIG. 2, it can be found that Ce is present5Zr1K1rGO and Ce5Zr3K3rGO to Ce5Zr2k2The metal oxide particles of/rGO are most uniformly dispersed. Ce can be derived using nano-measurement software5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3The average particle diameter of/rGO is respectively 9.65nm, 7.42nm and 9.39nm, which is less than CeZrOxThe average particle diameter of the catalyst is 15-20 nm. This indicates that the graphene inhibits surface migration of the metal oxide nanoparticles and reduces the size of the metal oxide nanoparticles.
Cerium (Ce), zirconium (Zr), potassium (K), carbon (C) and oxygen (O) are highly dispersed on the catalyst. It can be further verified in TEM images that the reduced graphene oxide (rGO) support supports well-dispersed spherical metal oxide nanoparticles. Catalytic oxidation of soot is a heterogeneous catalytic reaction, so the degree of contact of soot with the catalyst is one of the important factors affecting catalytic activity and efficiency. Thus, well-dispersed metal oxide nanoparticles promote catalytic oxidation of soot.
FIG. 3 shows CeO2And Ce5Zr2K2X-ray powder diffraction (XRD) pattern of/rGO nano solid solution catalyst, CeO was observed where all catalysts showed typical cubic structure2Peak(s). The XRD patterns of the CeZrK/rGO nano solid solution catalyst show a series of typical cubic spinel CeO on 29 degrees (111),33 degrees (200),47 degrees (220),56 degrees (331),59 degrees (222) and 69 degrees (400)2And (4) relevant reflection. Due to cerium ion (Ce)4+) Is coated with zirconium ion (Zr)4+) And potassium ion (K)+) Partially substituted, zirconium ions (Zr)4+) And potassium ion (K)+) The doping of (a) causes the diffraction peaks to shift to lower angle directions, resulting in slight variations in the unit cell parameters and grain size. Diffraction peak ratio CeO of CeZrK/rGO nano solid solution catalyst2The diffraction peak of the catalyst is wide. At the same time, Ce5Zr2K2The half-peak width of/rGO is relatively wider than that of the CeZrK/rGO nano solid solution catalyst, which shows that Ce5Zr2K2Grain size ratio Ce of/rGO5Zr1K1rGO and Ce5Zr3K3The grain size of/rGO is small. The graphene related phase has no characteristic obvious diffraction peak. Complete exfoliation of graphene in hybridization effectively avoids graphene re-stacking.
Example 3
This example uses N2The adsorption-desorption test analyzes the characteristics of the CeZrK/rGO nano solid solution catalyst. FIG. 4 shows N of CeZrK/rGO nano solid solution catalyst2Adsorption isotherms and pore size distribution profiles. As the adsorption and the diffusion are the key processes of the heterogeneous catalytic reaction, the pore structure of the CeZrK/rGO nano solid solution catalyst has great influence on the catalytic performance of the catalyst. In the IUPAC classification, a similar type IV isotherm with a type H3 hysteresis loop indicates that the CeZrK/rGO nano solid solution catalyst has a mesoporous distribution characteristic. As can be seen in b, d and f of FIG. 4, Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3/rGOAre 36.9nm, 36.8nm and 36.1nm, respectively, greater than soot: (>20nm) to ensure that the carbon smoke can enter the internal pores of the CeZrK/rGO nano solid solution catalyst and fully contact with the active phase.
Table 1 shows the average crystallite size and the specific surface area (S) of the catalystBET). The inventors calculated the average grain size by XRD analysis according to Scherrer's formula. Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3The average grain sizes of the/rGO are respectively 8.3nm, 6.9nm and 6.7nm which are all smaller than that of the CeO2Average grain size of 8.9 nm. Because of zirconium ion (Zr)4+) And potassium ion (K)+) The doping-induced lattice distortion of CeO suppresses2Phase crystal growth phase.
Specific surface area (S)BET) Can be derived from N based on the multipoint BET method2Adsorption isotherms. Specific surface area (55-82 m) of cerium (Ce) -based catalyst in the prior art2The ratio of the CeZrK to the rGO to the solid solution catalyst is higher than that of the CeZrK to the rGO. Meanwhile, in the CeZrK/rGO nano solid solution catalyst, Ce5Zr2K2Specific surface area of 151.5 m/rGO2G and Ce5Zr3K3Specific surface area/rGO 152.4m2G is slightly larger than Ce5Zr1K1Specific surface area 117.2 m/rGO2(ii) in terms of/g. The graphene-based catalyst is proved to have a larger specific surface area and a better pore structure, and the high catalytic activity of the CeZrK/rGO nano solid solution catalyst is effectively ensured.
TABLE 1 average grain size and specific surface area of CeZrK/rGO nano solid solution catalysts
Example 4
In this example, the characteristics of the CeZrK/rGO nano solid solution catalyst were studied by raman spectroscopy. Typical of the D-band and G-band, as shown in FIG. 5Raman peaks respectively appear at 1350cm-1And 1594cm-1Left and right. Wherein the D band represents structural defects caused by oxygen-containing functional groups on the carbon group and the G band represents E2gSp in symmetric mode2Hybrid C. The Raman spectrum of the CeZrK/rGO nano solid solution catalyst is 400-500 cm-1Where no band appears to be assigned to CeO2. This shows that CeO2Good dispersion of the particles on the graphene layer.
Intensity ratio of D-band to G-band ID/IGIs the in-plane sp of graphite2Indexes of disorder degree and average size. Ce5Zr1K1/rGO、Ce5Zr2K2/rGO、Ce5Zr3K3I of/rGO and GOD/IG1.10, 1.28, 1.21 and 0.99 respectively. At Ce5Zr2K2Higher I in/rGO nano solid solution catalystsD/IGMeaning that there may be smaller sp2Regions and unrepaired defect sites. The defect sites on the rGO surface can effectively inhibit agglomeration of the metal oxide nanoparticles, thereby reducing the grain size and improving the dispersion characteristics, which is consistent with the above results observed in example 2.
Example 5
This example uses infrared spectroscopy to study the properties of the CeZrK/rGO nano solid solution catalyst.
FIG. 6 shows an infrared spectrum of Graphene Oxide (GO) of a CeZrK/rGO nano solid solution catalyst. The figure shows a number of functional groups containing O, for example O-H in COOH (3423 cm)-1) And C ═ O (1735 cm)-1) Third order C-OH (1384 cm)-1) O-H in (1). Mixing metal ions (Ce) on these oxygen (O) -containing Graphene Oxide (GO) groups during catalyst synthesis4+，Zr4+，k+) First, a negatively charged Graphene Oxide (GO) sheet surface is uniformly adsorbed by electrostatic attraction. Compared with Graphene Oxide (GO), the CeZrK/rGO nano solid solution catalyst has an infrared spectrum of 1735cm-1And 1384cm-1The time is greatly reduced and even disappears. This means that the oxidized stoneGraphene (GO) is deoxygenated and reduced to reduced graphene oxide (rGO).
Example 6
This example illustrates the analysis of X-ray photoelectron spectroscopy (XPS) of Ce 3d, Zr 3d, O1s and C1s in the CeZrK/rGO nano solid solution catalyst.
As shown in fig. 7, the inventors measured the oxidation states of the main elements Ce, Zr, O and C and the estimated atomic ratios in the CeZrK/rGO nano solid solution catalyst using XPS measurement technique. U and v in XPS spectrum of Ce 3d refer to 3d, respectively3/2And 3d5/2The spin orbit component of (a). Since the spikes of u 'and v' are due to Ce3+Ion initiation, so the spikes of u, u 'and v, v' are peaked by Ce4+And (4) ion initiation. Therefore, it can be concluded that the CeZrK/rGO nano solid solution catalyst has Ce4+And Ce3+Two ions.
TABLE 2 atomic surface composition of CeZrK/rGO nano solid solution catalysts
TABLE 3 Ce 3d in CeZrK/rGO nano solid solution catalyst3/2(u”'),Zr 3d5/2、OⅠ1s and OⅡBinding energy of
TABLE 4 Ce in CeZrK/rGO nano solid solution catalyst3+/Ce4+,OⅡ/OⅠAnd the ratio of Ce/Zr
Tables 2 and 3 summarizeAtomic surface concentrations, relative percentages, and binding energies of Ce, Zr, O, and C elements in CeZrK/rGO nano solid solution catalysts. As shown in Table 4, Ce3+The sum of the integrated areas of (u ', v') and Ce4+The ratio of the sum of the integral areas of (u, v, u ', v', u ', v') is the Ce ZrK/rGO nano solid solution catalyst3+/Ce4+The ratio of (a) to (b). Research finds that Ce5Zr2K2/rGO has higher Ce3+Ion concentration, which indicates Ce5Zr2K2the/rGO contains more oxygen vacancies. The XPS spectrum of Zr 3d in b of FIG. 7 shows that there is no difference in the binding energy of Zr element in CeZrK/rGO nano solid solution catalyst. Zr 3d5/2And Zr 3d3/2Has a binding energy of 182.6eV and 185eV, respectively, which can prove that Zr4+Exists in CeZrK/rGO nano solid solution catalyst. The XPS spectrum of O1s in c of fig. 7 shows that two surface oxygens are present in the CeZrK/rGO nano solid solution catalyst. O isI(529.8-530.0eV) is surface lattice oxygen (O) in cerium oxide2-) Is characterized by OII(531.5-531.8eV) shows that the defect is oxygen (O) or oxygen of a hydroxyl group-like group-,O2-,O2 2-) Chemisorbed oxygen is present on the surface. In general, surface adsorption of oxygen from oxygen vacancies of oxide catalysts to gaseous O2The adsorption of (1). It is clear that compared with Ce5Zr1K1rGO and Ce5Zr3K3/rGO，Ce5Zr2K2Higher O for/rGOII/OIPeak area ratio. This effectively increases the concentration of surface adsorbed oxygen. Chemisorption of oxygen (O) compared to lattice oxygenⅡ) Has higher mobility. Thereby chemisorbing oxygen (O)Ⅱ) Plays a more important role in soot oxidation reactions. The deconvolution of the C1s peak in the CeZrK/rGO nano solid solution catalyst is shown in d of FIG. 7. The main peaks are concentrated at 284.5eV-284.6eV, 285.5eV and 288.4eV, which represent graphitic structure, C-O and-O-C ═ O, respectively. The C-O and-O-C ═ O bonds in the graphene indicate that the graphene may be CeO2-ZrO2The directional attachment of the particles provides a rich population of active sites. Furthermore, XPS failed to detect the presence of the K element. This can be stated that K andthe binding energy of C was mainly in the range 291-296eV and 277-295eV, respectively.
This indicates that the CeZrK/rGO nano solid solution catalyst contains more oxygen vacancies, which is beneficial to improving the CeO2And wherein Ce is5Zr2K2the/rGO nano solid solution catalyst has higher chemical adsorption oxygen concentration. The CeZrK/rGO nano solid solution catalyst has good oxidation reduction capability.
Example 7
As shown in FIG. 8, in this example, in order to examine the redox capabilities of graphene oxide GO and the CeZrK/rGO nano solid solution catalyst, H is performed on the GO and the CeZrK/rGO nano solid solution catalyst2TPR characterization analysis.
The result shows that the reduction peak of GO appears at 663 ℃, while the CeZrK/rGO nano solid solution catalyst has no obvious reduction peak at the temperature of 550 ℃ and 650 ℃. This indicates that the oxygen-containing functional groups of the GO surface are deoxygenated during the preparation process, which is consistent with the results shown in fig. 6.
From 250 ℃ to 600 ℃, three obvious reduction peaks are observed on the CeZrK/rGO nano solid solution catalyst. The shoulder peak at 360 deg.C corresponds to the process of adsorbing oxygen, and the reduction peak at 465 deg.C corresponds to Ce4+Outermost layer to Ce3+Reduction of (2). The reduction peak varying from 700 ℃ to 850 ℃ is due to CeO2(Ce4+Inner layer) and volume reduction of lattice oxygen.
Curve b has a higher peak intensity ratio (surface/volume reduction) than the other curves, indicating Ce5Zr2K2Enhanced oxygen mobility within the/rGO lattice. Due to the synergistic effect of Ce and Zr, a shoulder peak is generated at about 301 ℃. In addition, the peak of curve b around 465 ℃ shifts to a low temperature, indicating that Ce5Zr2K2The reducibility of/rGO is enhanced.
Generally, CeO with graphene as carrier2Middle doped with Zr4+Ions and K+The ions can effectively promote the formation of nano solid solution catalysts. The graphene may enhance the redox ability of the cerium oxide at low temperature. All CeZrK/rGO nano solid solutionsThe catalysts all show good oxidation-reduction capability, which reflects the improvement of carbon smoke catalytic oxidation activity of the CeZrK/rGO nano solid solution catalyst.
Meanwhile, the redox capability of the CeZrK/rGO nano solid solution catalyst is influenced by the doping ratio of metals. In the CeZrK/rGO nano solid solution catalyst, in FIG. 7, Ce5Zr2K2the/rGO exhibits the lowest reduction temperature.
Example 8
In this example, we simulated air (21% O)2+79％N2) The catalytic activity of the CeZrK/rGO nano solid solution catalyst on soot oxidation in a close contact mode is evaluated by thermogravimetric analysis. FIG. 9 shows normalized soot conversion as a function of temperature change of the catalyst prepared in the close contact mode. For convenience in comparing catalytic activity, we define the temperature at which soot oxidation reaches 50% as T50The temperature at which the soot oxidation reaches a maximum rate is defined as Tm。
The results show that Ce5Zr1K1/rGO、Ce5Zr2K2/rGO、Ce5Zr3K3rGO and CeO2T of50352 ℃, 339 ℃, 358 ℃ and 419 ℃, respectively. It can be concluded that CeZrK/rGO catalyst ratio CeO2Has higher catalytic activity. T of CeZrK/rGO catalyst due to close contact of soot with the catalyst50The difference is small. Under the condition, the influence of the difference of the structure and the shape of the CeZrK/rGO catalyst on the catalytic activity is small.
Example 9
In this example, the temperature rise rate was 10 ℃ for 2min in the temperature range of room temperature to 650 ℃-1In the case of (2), we simulated air (21% O)2+79％N2) The catalytic activity of the CeZrK/rGO nano solid solution catalyst on soot oxidation in a loose contact mode is evaluated by thermogravimetric analysis.
The loose contact mode is most practical because the process of mixing soot with the CeZrK/rGO nano solid solution catalyst does not have any force effect.Figure 10 shows the normalized soot conversion as a function of temperature for CeZrK/rGO nano solid solution catalysts in loose contact mode. Ce5Zr1K1/rGO、Ce5Zr2K2rGO and Ce5Zr3K3T of/rGO50390 ℃, 383 ℃ and 432 ℃ respectively, which are far lower than CeO2(523 ℃ C.), rGO (532 ℃ C.) and T without catalyst (604 ℃ C.)50。
rGO exhibits catalytic activity for soot oxidation because of its enhanced redox ability due to its residual structural defects. Ce5Zr2K2The higher catalytic activity of/rGO is closely related to the excellent dispersion quality, small particle size, large specific surface area, rich oxygen vacancy and redox capability.
It should be noted that the slope of the curve before 300 ℃ is expressed as Ce5Zr3K3/rGO>Ce5Zr2K2/rGO>Ce5Zr1K1The sequence of/rGO is consistent with the specific surface area sequence in table 1 of example 3 for the three CeZrK/rGO catalysts. The slope of the curve after 300 ℃ is expressed as Ce5Zr2K2/rGO>Ce5Zr1K1/rGO>Ce5Zr3K3Sequential alignment of/rGO, which correlates with oxygen vacancy concentration (Ce)3+/Ce4+) And the concentration of chemisorbed oxygen (O)Ⅱ/OⅠ) Are consistent. This is because the specific surface area has a large influence on the activity of the low-temperature region and the oxygen vacancy concentration has a large influence on the activity of the medium-high temperature region.
In order to avoid the influence of graphene on experimental data, the weight loss condition of modified graphene in an air atmosphere is researched. As shown in fig. 11, the weight loss rate was 2.3 (Wt)% and the process occurred mainly at 520 ℃, which had less effect on the TG experimental data.
Example 10
As shown in FIG. 12, this embodiment is on pure N2In the atmosphere, the temperature rise rate is 10 ℃ for 2min in the temperature range from room temperature to 650 DEG C-1Under the condition of (1), the CeZrK/rGO nano solid solution catalyst is compactedThe carbon smoke combustion in the contact mode adopts a thermogravimetric analysis method to analyze the pure N of the CeZrK/rGO nano solid solution catalyst2The catalytic performance of (1).
Because there is no gaseous O2Soot can only be adsorbed by the activity of the catalyst surface-,O2-) And lattice oxygen (O)2-) And (4) oxidizing. From the DTG spectrum, the CeZrK/rGO catalyst has a valley at 318-322 ℃, which is due to the oxidation of soot by adsorbed oxygen. Ce5Zr2K2rGO and Ce5Zr3K3The valleys of/rGO at 513 ℃ and 521 ℃ respectively correspond to the oxidation of soot by lattice oxygen.
Through the comprehensive comparison of peak intensity and peak temperature, the CeZrK/rGO nano solid solution catalyst has rich active oxygen species and reasonable metal doping concentration, improves the mobility of adsorbed oxygen and lattice oxygen, and has better catalytic performance.
Example 11
In the present example, the temperature rise rate was 10 ℃ for 2min in the air atmosphere at a temperature range of room temperature to 650 DEG C-1Under the condition of (1), the CeZrK/rGO nano solid solution catalyst is subjected to soot oxidation T under the conditions of close contact and loose contact50Compared with other catalysts.
Tables 5 and 6 compare the catalytic performance of various highly catalytically active catalysts for soot oxidation, including perovskite catalysts, noble metal catalysts, and CeZrK/rGO nano solid solution catalysts of the present invention. It is clear that CeZrK/rGO catalysts, in particular Ce, doped with metal oxide particles on graphene5Zr2K2the/rGO has higher catalytic activity than other catalysts.
TABLE 5 soot oxidation T of various catalysts under close and loose contact conditions50
TABLE 6 soot oxidation of various catalysts under close and loose contact conditionsTm
The CeZrK/rGO nano solid solution catalyst obtained by the embodiment has the following characteristics:
the catalyst has the advantages that metal oxide particles loaded on graphene serving as a carrier of the CeZrK/rGO nano solid solution catalyst are uniform and highly dispersed, and the catalytic oxidation of soot is promoted when the carbon soot is catalyzed and oxidized.
The CeZrK/rGO nano solid solution catalyst has small average grain size, larger specific surface area and better pore structure; effectively ensures the high catalytic activity of the CeZrK/rGO nano solid solution catalyst.
3. The defect sites on the surface of the reduced graphene oxide (rGO) can effectively inhibit the agglomeration of metal oxide nanoparticles, thereby reducing the grain size and improving the dispersion characteristic; thereby improving the catalytic activity of the CeZrK/rGO nano solid solution catalyst.
The CeZrK/rGO nano solid solution catalyst contains more oxygen vacancies, has higher chemisorption oxygen concentration and good redox capability, thereby ensuring high catalytic activity.
5. CeO (CeO) taking graphene as carrier2Middle doped with Zr4+Ions and K+The ions can effectively promote the formation of nano solid solution catalysts. The graphene may enhance the redox ability of the cerium oxide at low temperature. All the CeZrK/rGO nano solid solution catalysts show good oxidation-reduction capability, which reflects the improvement of the carbon smoke catalytic oxidation activity of the CeZrK/rGO nano solid solution catalysts.
6. T of CeZrK/rGO nano solid solution catalyst in loose contact and close contact modes50All the catalysts in the prior art have higher catalytic activity.
The CeZrK/rGO nano solid solution catalyst has the characteristics of easy synthesis and low cost, and is convenient for industrial production and practical application.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (6)
1. A catalyst taking CeZrK/rGO nano solid solution as a main component is characterized in that the active component of the catalyst is the CeZrK/rGO nano solid solution; the CeZrK/rGO nano solid solution has the following general formula:
CeAZrBKC/rGO
in the general formula, A, B and C are 5: 1-3.
2. The catalyst as claimed in claim 1, wherein the CeZrK/rGO nano solid solution is composed of spherical metal oxide nanoparticles of cerium, zirconium and potassium ions supported on reduced graphene oxide.
3. The catalyst as claimed in claim 1, wherein the CeZrK/rGO nano solid solution has a nano pore structure with a pore diameter of 36.1-36.9 nm.
4. The catalyst as claimed in claim 1, wherein the CeZrK/rGO nano solid solution has a specific surface area of 117.2-152.4m2/g。
5. The catalyst based on CeZrK/rGO nano solid solution as the claim 1, wherein the crystallite size of the CeZrK/rGO nano solid solution is 6.7-8.3 nm.
6. The catalyst taking CeZrK/rGO nano solid solution as the main component as claimed in claim 1, wherein the average particle size of CeAZrBKC/rGO is 7.42-9.65 nm.
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