CN113304745A - Pt-Pd-Rh ternary catalyst and preparation method thereof - Google Patents
Pt-Pd-Rh ternary catalyst and preparation method thereof Download PDFInfo
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- CN113304745A CN113304745A CN202110623692.5A CN202110623692A CN113304745A CN 113304745 A CN113304745 A CN 113304745A CN 202110623692 A CN202110623692 A CN 202110623692A CN 113304745 A CN113304745 A CN 113304745A
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- cerium
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- oxygen storage
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- 239000003054 catalyst Substances 0.000 title claims abstract description 130
- 238000002360 preparation method Methods 0.000 title claims abstract description 29
- 239000011248 coating agent Substances 0.000 claims abstract description 56
- 238000000576 coating method Methods 0.000 claims abstract description 56
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 55
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 55
- 239000001301 oxygen Substances 0.000 claims abstract description 55
- 239000011232 storage material Substances 0.000 claims abstract description 52
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 50
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 50
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims abstract description 44
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 33
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910018967 Pt—Rh Inorganic materials 0.000 claims abstract description 25
- WLLURKMCNUGIRG-UHFFFAOYSA-N alumane;cerium Chemical compound [AlH3].[Ce] WLLURKMCNUGIRG-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000002131 composite material Substances 0.000 claims abstract description 22
- 239000000853 adhesive Substances 0.000 claims abstract description 15
- 230000001070 adhesive effect Effects 0.000 claims abstract description 15
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 9
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000000843 powder Substances 0.000 claims description 58
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 56
- 238000001035 drying Methods 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 27
- 239000002002 slurry Substances 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- 239000012266 salt solution Substances 0.000 claims description 24
- 229910001868 water Inorganic materials 0.000 claims description 21
- 238000005470 impregnation Methods 0.000 claims description 19
- 238000002156 mixing Methods 0.000 claims description 19
- 238000005303 weighing Methods 0.000 claims description 19
- 239000000463 material Substances 0.000 claims description 17
- 239000006104 solid solution Substances 0.000 claims description 16
- 238000003756 stirring Methods 0.000 claims description 16
- 238000000498 ball milling Methods 0.000 claims description 15
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 claims description 13
- 238000005507 spraying Methods 0.000 claims description 12
- -1 neodymium modified cerium-zirconium Chemical class 0.000 claims description 11
- 239000010970 precious metal Substances 0.000 claims description 11
- 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 claims description 8
- 229910052684 Cerium Inorganic materials 0.000 claims description 4
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052703 rhodium Inorganic materials 0.000 claims description 3
- 150000000703 Cerium Chemical class 0.000 claims description 2
- 229910052779 Neodymium Inorganic materials 0.000 claims description 2
- 239000007767 bonding agent Substances 0.000 claims description 2
- 229910000420 cerium oxide Inorganic materials 0.000 claims description 2
- 238000007654 immersion Methods 0.000 claims description 2
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 23
- 230000000694 effects Effects 0.000 abstract description 18
- 238000006243 chemical reaction Methods 0.000 abstract description 11
- 239000003345 natural gas Substances 0.000 abstract description 11
- 239000007789 gas Substances 0.000 abstract description 9
- 239000000446 fuel Substances 0.000 abstract description 7
- 239000003344 environmental pollutant Substances 0.000 abstract description 6
- 231100000719 pollutant Toxicity 0.000 abstract description 6
- 229910052593 corundum Inorganic materials 0.000 abstract description 5
- 230000007547 defect Effects 0.000 abstract description 5
- 229910001845 yogo sapphire Inorganic materials 0.000 abstract description 5
- 238000011068 loading method Methods 0.000 abstract description 3
- 239000011230 binding agent Substances 0.000 abstract description 2
- 230000008859 change Effects 0.000 abstract description 2
- 239000010948 rhodium Substances 0.000 description 59
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 52
- 239000000243 solution Substances 0.000 description 29
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 18
- 239000010410 layer Substances 0.000 description 14
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 9
- 229910002091 carbon monoxide Inorganic materials 0.000 description 9
- 150000002430 hydrocarbons Chemical class 0.000 description 9
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 description 9
- 238000004537 pulping Methods 0.000 description 9
- 229930195733 hydrocarbon Natural products 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 230000032683 aging Effects 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 6
- 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 5
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
- 238000004090 dissolution Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 238000001354 calcination Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- WRWKMJCISLXRMU-UHFFFAOYSA-N [Zr].[Ce].[Y].[La] Chemical class [Zr].[Ce].[Y].[La] WRWKMJCISLXRMU-UHFFFAOYSA-N 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- GSHDNSHZGPBFAC-UHFFFAOYSA-N cerium lanthanum neodymium zirconium Chemical compound [Ce][Zr][La][Nd] GSHDNSHZGPBFAC-UHFFFAOYSA-N 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical class N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- FLALLKCVDYLTMT-UHFFFAOYSA-N [Zr].[Ce].[Pr].[La] Chemical compound [Zr].[Ce].[Pr].[La] FLALLKCVDYLTMT-UHFFFAOYSA-N 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
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- 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
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/42—Platinum
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- 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
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
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- 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
- B01D53/864—Removing carbon monoxide or hydrocarbons
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
- B01D53/9413—Processes characterised by a specific catalyst
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D—SEPARATION
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
- B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
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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
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
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- B01J23/44—Palladium
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- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/46—Ruthenium, rhodium, osmium or iridium
- B01J23/464—Rhodium
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
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- B01J23/63—Platinum group metals with rare earths or actinides
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0215—Coating
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- 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
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/20—Capture or disposal of greenhouse gases of methane
Abstract
The invention discloses a Pt-Pd-Rh three-way catalyst and a preparation method thereof. The catalyst comprises a carrier and an active coating, wherein the active coating is of a double-coating structure, the bottom layer is a Pd coating, and the upper layer is a Pt-Rh coating; the Pd coating is made of lanthanum modified alumina (La) supporting noble metal Pd2O3‑Al2O3) And a binder; the Pt-Rh coating is formed by loading noble metal Pt cerium dioxide modified first rare earth oxygen storage material, Rh-loaded second rare earth oxygen storage material, Rh-loaded cerium-aluminum composite oxide (Ce-Al)2O3) And an adhesive. The catalyst overcomes the defects of poor thermal stability and durability of a Pt catalyst, improves the conversion performance of the catalyst on pollutants under high airspeed and high air-fuel ratio fluctuation, has good conversion effect on CO, HC and NOx, is particularly applied to tail gas treatment of natural gas vehicles with large air-fuel ratio fluctuation and large airspeed change, and can be used for treating CO, CH4NMHC and NOx have good conversion effect, and the catalyst is used for CH4Low ignition temperature and good durability.
Description
Technical Field
The invention relates to a noble metal catalyst and a preparation method thereof, belongs to the technical field of automobile exhaust purification catalysts and preparation thereof, and relates to a high-activity high-stability Pt-Pd-Rh ternary catalyst and a preparation method thereof.
Background
With the development of economy and improvement of life of the nation, the quantity of automobile reserves in China increases year by year, the pollution of motor vehicle exhaust becomes one of the important reasons of urban air pollution, and China puts forward higher requirements on the emission control of the motor vehicle exhaust in order to protect the environment. The natural gas vehicle starts to implement the national emission standard six from 7/1/2019, the emission limit value is greatly reduced on the basis of national five, and the requirement of cold start of the engine is increased. The main pollutants of natural gas vehicle tail gas are carbon monoxide (CO), Hydrocarbons (HC) and Nitrogen Oxides (NO)x). The natural gas engine in the fifth stage of China adopts a lean-burn technical route, and the oxidation catalyst adopted by the aftertreatment catalyst is mainly used for purifying CO and HC and cannot treat NOx. In the sixth stage of China, the technology of the natural gas engine adopting the theoretical air-fuel ratio for combustionIn the route, the aftertreatment catalyst needs to be matched with a three-way catalyst and can purify three pollutants of CO, HC and NOx at the same time.
The three-way catalyst is widely applied to gasoline vehicles. However, the tail gas components of the natural gas vehicle and the tail gas components of the gasoline vehicle are different, and pollutants to be purified are also different, so that the traditional three-way catalyst for the gasoline vehicle is difficult to meet the requirements of tail gas purification of the natural gas vehicle. This is mainly because HC in the tail gas of natural gas vehicles is mainly CH4，CH4Is the hydrocarbon compound having the most stable chemical structure, and the purification difficulty is greater than that of HC in the conventional gasoline car, so that a catalyst having higher activity is required.
Three-way catalysts are generally composed of two parts: a honeycomb ceramic or metal substrate, and a catalyst coating adhered to the honeycomb substrate. The catalyst coating is usually made of an inorganic oxide material (e.g., γ -Al) having a large specific surface area2O3And cerium-zirconium solid solution, etc.) and an active component (usually one or more of Pt (platinum), Pd (palladium), Rh (rhodium). However, the catalyst using Pt as an active component has the defects of poor thermal stability, poor durability and the like, and is used in the early stage of the catalyst of the gasoline car because the gasoline product is poor (high in sulfur content) and the requirement on the durability of the catalyst is not high at that time. With the continuous upgrading of gasoline products and the continuous improvement of the requirement on the durability of the catalyst, Pt is gradually replaced by Pd, and the current gasoline car catalyst mainly adopts a bimetallic catalyst taking Pd-Rh as activity.
Disclosure of Invention
The invention aims to overcome the defect that the Pt catalyst is easy to agglomerate at high temperature so as to cause the reduction of the activity of the catalyst, and provides a Pt-Pd-Rh three-way catalyst with high activity and high stability.
The invention is realized by the following technical scheme:
a Pt-Pd-Rh three-way catalyst is composed of a carrier and an active coating coated on the surface of the carrier, and is characterized in that: the active coating is of a double-coating structure, the bottom layer is a Pd coating, and the upper layer is a Pt-Rh coating;
the Pd coating is made of lanthanum modified alumina (La) supporting noble metal Pd2O3-Al2O3) And a binder;
the Pt-Rh coating is made of a first rare earth oxygen storage material modified by cerium dioxide loaded with noble metal Pt, a second rare earth oxygen storage material loaded with Rh, a cerium-aluminum composite oxide loaded with Rh and a bonding agent; the first rare earth oxygen storage material is cerium-zirconium solid solution with high cerium content or cerium dioxide with large specific surface area, wherein the cerium dioxide content is 80-99.9 wt%.
The ceria-modified first rare earth oxygen storage material is a first rare earth oxygen storage material prepared by mixing a rare earth oxygen storage material with a soluble cerium salt.
The content of cerium dioxide in the second rare earth oxygen storage material loaded with Rh is 10-30 wt%.
The cerium oxide content in the Rh-loaded cerium-aluminum composite oxide is 1-15 wt%.
The preparation method of the Pt-Pd-Rh three-way catalyst comprises the following steps:
(1) preparing a bottom layer catalyst: weighing a noble metal Pd salt solution A, weighing a lanthanum modified alumina material, uniformly spraying the diluted Pd salt solution A onto the lanthanum modified alumina material by adopting an isometric immersion method, uniformly stirring, pre-drying for 4-6 h at 80-120 ℃, roasting for 2h at 500 ℃ to obtain Pd-containing catalyst powder A1, adding the obtained Pd-containing catalyst powder into a ball milling tank, adding an adhesive and pure water, ball-milling to obtain noble metal Pd-containing slurry, coating the slurry on a carrier, and drying and roasting to obtain a Pd-containing active layer catalyst;
(2) preparing upper-layer catalyst powder:
the first rare earth oxygen storage material is modified by cerium dioxide, and the specific preparation method comprises the following steps: weighing cerium nitrate, adding pure water to dissolve the cerium nitrate, then adding a first rare earth oxygen storage material, stirring and mixing uniformly, standing for 8-12 h, drying at 80-120 ℃ for 4-6 h, and then roasting at 500-600 ℃ for 4h to obtain a cerium dioxide modified first rare earth oxygen storage material;
weighing a precious metal Pt salt solution B, weighing the cerium dioxide modified first rare earth oxygen storage material, uniformly stirring the diluted Pt salt solution B and the cerium dioxide modified first rare earth oxygen storage material by adopting an isovolumetric impregnation method, standing for 1h, pre-drying for 4-6 h at the temperature of 80-120 ℃, and roasting for 1-4 h at the temperature of 500 ℃ to obtain Pt-containing catalyst powder B1;
weighing an Rh salt solution C and a second rare earth oxygen storage material, uniformly mixing the diluted Rh salt solution C and the second rare earth oxygen storage material by an isometric impregnation method, impregnating for 1 hour, pre-drying for 4-6 hours at 80-120 ℃, and roasting for 2 hours at 500 ℃ to obtain Rh-containing catalyst powder C1;
weighing Rh salt solution D and a cerium-aluminum composite oxide, uniformly mixing the diluted Rh salt solution D and the cerium-aluminum composite oxide by adopting an isometric impregnation method, pre-drying for 4-6 h at 80-120 ℃ after impregnating for 1h, and roasting for 2h at 500 ℃ to obtain Rh-containing catalyst powder D1;
(3) preparing an upper layer catalyst: mixing and ball-milling the catalyst powder B1, the catalyst powder C1, the catalyst powder D1, the adhesive and pure water prepared in the step (2) to obtain uniform upper-layer slurry; and (3) coating the upper layer slurry on the catalyst obtained in the step (1), and drying and roasting to obtain the Pt-Pd-Rh double-coating catalyst.
In the steps (1) and (2), the noble metal Pd salt solution A, Pt salt solution B, Rh salt solution C is a soluble salt solution, more specifically nitrate, hydrochloride, ammonia salt or the like; preferably a nitrate.
The first rare earth oxygen storage material in the step (2) is cerium-zirconium solid solution, or lanthanum-yttrium-praseodymium-modified cerium-zirconium solid solution, or cerium dioxide with large specific surface area; the second rare earth oxygen storage material is cerium-zirconium solid solution or lanthanum, yttrium and neodymium modified cerium-zirconium solid solution.
In the step (3), the mass ratio of the first rare earth oxygen storage material for dispersing the noble metal Pt to the second rare earth oxygen storage material for dispersing the Rh is 2: 1-1: 2; the mass ratio of the second rare earth oxygen storage material for dispersing Rh to the cerium-aluminum composite oxide is 2: 1-1: 1.
The Pd consumption in the step (1) is 10-100 g/ft3(ii) a The amount of Pt used in the step (3) is 10-50 g/ft3The amount of Rh used is 1-10 g/ft3。
The catalyst overcomes the defects of poor thermal stability and durability of a Pt catalyst, has good conversion effect on CO, HC and NOx, is particularly applied to tail gas treatment of natural gas vehicles, and can be used for treating CO and CH4NMHC and NOx have good conversion effect, and the catalyst is used for CH4The ignition temperature is low, so that the emission of the natural gas vehicle can reach the national emission standard of six.
Compared with the prior art, the catalyst has the advantages that: by selecting high CeO2The rare earth oxygen storage material with the content is firstly processed by CeO2After modification, the surface and the bulk phase of the material are rich in CeO2. Then, when the modified material is used for loading noble metal Pt, a stable chemical bond of Pt-O-Ce is formed on the surface of the material, so that the dispersibility and stability of Pt on the material are obviously improved. The catalyst of the invention can realize the redispersion of Pt under partial use conditions, thereby improving the activity and durability of the catalyst. In addition, the oxygen storage material with high cerium content also has larger oxygen storage amount, and has obvious advantages in dealing with engines with larger air-fuel ratio fluctuation. Rh is loaded on the second rare earth oxygen storage material and the cerium-aluminum composite oxide respectively, and is especially loaded on a lanthanum-yttrium-neodymium modified cerium-zirconium solid solution with low cerium content, so that Rh can easily form a stable chemical bond of Rh-O-Nd, and the activity and stability of Rh can be improved. Because the specific surface area, pore volume and pore diameter of the oxygen storage material are usually small, the prepared catalyst is limited by certain mass transfer under high-flow-rate gas, part of Rh is loaded on the cerium-aluminum composite oxide material with large pores and high specific surface area, the cerium-aluminum composite oxide has large specific surface area and high pore volume and also has certain oxygen storage performance, the mass transfer performance, the activity and the oxygen storage performance of the catalyst coating can be simultaneously improved, and the conversion performance of the catalyst to pollutants under the fluctuation of high airspeed and high air-fuel ratio can be further improved.
The catalyst overcomes the defects of poor thermal stability and durability of the Pt catalyst, improves the conversion performance of the catalyst on pollutants under high airspeed and high air-fuel ratio fluctuation, has good conversion effect on CO, HC and NOx, and is particularly applied to the catalyst with large air-fuel ratio fluctuation,For treating tail gas of natural gas vehicle with great change of space velocity, CO and CH are treated4NMHC and NOx have good conversion effect, and the catalyst is used for CH4Low ignition temperature and good durability.
Detailed Description
The present invention is further described below in conjunction with the following detailed description, which is intended to further illustrate the principles of the invention and is not intended to limit the invention in any way, but is equivalent or analogous to the present invention without departing from its scope.
Comparative example 1: preparing double-coating Pt-Pd-Rh catalyst (bottom Pd and upper Pt-Rh) by adopting an isovolumetric impregnation method
The first step is as follows: preparation of bottom Pd coating
A palladium nitrate solution (containing Pd: 2.1g) was weighed, 100g of deionized water was added, and the mixture was stirred uniformly. Uniformly spraying the palladium nitrate solution to 97.9g of La by adopting a spraying mode2O3-Al2O3And spraying the powder while stirring, and continuously stirring for 1 hour after spraying. Then dried at 100 ℃ for 5 hours and calcined at 500 ℃ for 2 hours to obtain noble metal powder A1 with the Pd content of 2.1 percent. And performing ball milling pulping on the obtained Pd powder according to 95 wt% of A1, 5 wt% of adhesive and pure water to obtain Pd slurry. Coating the Pd slurry on a honeycomb ceramic carrier with the diameter of 1 inch, the length of 1 inch and the mesh number of 400 meshes according to 106.21g/L, drying and roasting to obtain the Pd content of 60g/ft3The catalyst of (1).
The second step is that: preparation of upper Pt-Rh coating
Platinum nitrate solution (containing Pt:2g) was weighed, 60g of deionized water was added, and the mixture was stirred uniformly. 98g of a cerium zirconium solid solution (in which CeO is present) was weighed2Content 40%), mixing the diluted platinum nitrate solution with the above cerium-zirconium solid solution, standing for 1h, drying at 100 deg.C for 5h, and calcining at 500 deg.C for 2h to obtain noble metal powder B1 with Pt content of 2%.
A rhodium nitrate solution (containing Rh:0.5886g) was weighed, 60g of deionized water was added, and the mixture was stirred well. 99.41g of a cerium zirconium solid solution (in which CeO is present) was weighed2Content 20%), and mixing the diluted rhodium nitrate solution with the CeO by an equal volume impregnation method2In an amount ofThe cerium-zirconium solid solution with 20 percent is mixed and stirred evenly, is dried for 5 hours at 100 ℃ after being kept stand for 1 hour, and is calcined for 2 hours at 500 ℃ to obtain the noble metal powder C1 with the Rh content of 0.5886 percent. And adding water into the obtained noble metal powder B1 and C1 according to the weight percentages of 44.55 percent B1, 50.45 percent C1 and 5 percent of adhesive for ball milling and pulping to obtain Pt-Rh slurry. Coating the Pt-Rh slurry on the Pd catalyst obtained in the first step according to 118.92g/L, and drying and roasting to obtain the final Pt-Pd-Rh double-coating catalyst, wherein the Pd content is 60g/ft3Pt content of 30g/ft3Rh content of 10g/ft3. Designated comparative catalyst 1.
Example 1:
the first step is as follows: preparation of bottom Pd coating
A palladium nitrate solution (containing Pd: 2.1g) was weighed, 100g of deionized water was added, and the mixture was stirred uniformly. Uniformly spraying the palladium nitrate solution to 97.9g of La by adopting a spraying mode2O3-Al2O3And spraying the powder while stirring, and continuously stirring for 1 hour after spraying. Then dried at 100 ℃ for 5 hours and calcined at 500 ℃ for 2 hours to obtain noble metal powder A1 with the Pd content of 2.1 percent. 5 wt% of adhesive is added into the obtained Pd powder A1, and ball milling and pulping are carried out by pure water, thus obtaining Pd slurry. Coating the Pd slurry on a 400-mesh honeycomb ceramic carrier with the diameter of 1 inch and the length of 1 inch according to 106.21g/L, drying and roasting to obtain the Pd content of 60g/ft3The catalyst of (1).
The second step is that: preparation of powder for upper layer
Weighing 50.46g of cerous nitrate hexahydrate, adding pure water for dissolution, and then adding 180g of first rare earth oxygen storage material (cerium-zirconium-lanthanum-praseodymium complex, CeO)2Content 80%), stirring, standing for 12 hr, drying at 120 deg.C for 4 hr, and calcining at 600 deg.C for 4 hr to obtain 10% CeO2Modified cerium zirconium lanthanum yttrium complex (10% CeO)2/CeZrLaYO)。
Platinum nitrate solution (containing Pt:2g) was weighed, and 98g of the above 10% CeO was weighed2CeZrLaYO by soaking in an equal volume of 10% CeO2The CeZrLaYO material is evenly stirred, is pre-dried for 5 hours at the temperature of 100 ℃ after being kept stand for 1 hour, and is roasted for 2 hours at the temperature of 500 DEG CThus, a noble metal powder B2 containing Pt was obtained.
Weighing rhodium nitrate solution (containing Rh: 0.2943g) and 49.71g of second rare earth oxygen storage material (cerium-zirconium-lanthanum-yttrium compound, CeO)2Content 20%), adopting an isometric impregnation method to uniformly mix the diluted rhodium nitrate and the cerium-zirconium-lanthanum-yttrium compound, impregnating for 1h, drying for 5h at 100 ℃, and roasting for 2h at 500 ℃ to obtain the precious metal powder C2 containing Rh.
A rhodium nitrate solution (containing Rh: 0.2943g) and 49.71g of a cerium-aluminum composite oxide (CeO) were weighed2Content of 8%), uniformly mixing the diluted rhodium nitrate solution with the cerium-aluminum composite oxide by an isometric impregnation method, impregnating for 1h, drying at 100 ℃ for 5h, and roasting at 500 ℃ for 2h to obtain the Rh-containing precious metal powder D2.
The third step: preparation of upper Pt-Rh coating
And ball milling and pulping the noble metal powder B2, C2 and D2 obtained in the step of respectively adding water into 44.55 wt% of B2, 25.225 wt% of C2 and 25.225 wt% of D2 and 5% of adhesive to obtain Pt-Rh slurry. Coating the Pt-Rh slurry on the Pd catalyst obtained in the first step according to 118.92g/L, and drying and roasting to obtain the final Pt-Pd-Rh double-coating catalyst, wherein the Pd content is 60g/ft3Pt content of 30g/ft3Rh content of 10g/ft3. Designated catalyst 1.
Example 2:
the first step is as follows: preparation of bottom Pd coating layer the same as in example 1
The second step is that: preparation of powder for upper layer
151.38g of cerous nitrate hexahydrate is weighed, pure water is added for dissolution, and 140g of first rare earth oxygen storage material (cerium-zirconium-lanthanum-yttrium compound, CeO) is added2Content 85%), stirring, standing for 12 hr, drying at 120 deg.C for 4 hr, and calcining at 600 deg.C for 4 hr to obtain 30% CeO2Modified cerium zirconium lanthanum yttrium complex (30% CeO)2/CeZrLaYO)。
Platinum nitrate solution (containing Pt:2g) was weighed, and 98g of the above 30% CeO was weighed2CeZrLaYO by soaking in an equal volume of 30% CeO2The CeZrLaYO material is evenly stirred and standsAfter 1 hour, predrying for 5 hours at 100 ℃, and roasting for 2 hours at 500 ℃ to obtain Pt-containing noble metal powder B3.
Weighing rhodium nitrate solution (containing Rh: 0.2943g) and 49.71g of second rare earth oxygen storage material (cerium-zirconium-lanthanum-neodymium compound, CeO)2Content of 20%), uniformly mixing the diluted rhodium nitrate with the cerium-zirconium-lanthanum-neodymium compound by an isometric impregnation method, impregnating for 1h, drying for 5h at 100 ℃, and roasting for 2h at 500 ℃ to obtain the precious metal powder C3 containing Rh.
A rhodium nitrate solution (containing Rh: 0.2943g) and 49.71g of a cerium-aluminum composite oxide (CeO) were weighed2Content 10%), uniformly mixing the diluted rhodium nitrate solution with the cerium-aluminum composite oxide by an isometric impregnation method, impregnating for 1h, drying at 100 ℃ for 5h, and roasting at 500 ℃ for 2h to obtain the Rh-containing precious metal powder D3.
The third step: preparation of upper Pt-Rh coating
And ball milling and pulping the noble metal powder B3, C3 and D3 obtained in the step of respectively adding water into 44.55 wt% of B3, 33.63 wt% of C3, 16.82 wt% of D3 and 5% of adhesive to obtain Pt-Rh slurry. Coating the Pt-Rh slurry on the Pd catalyst obtained in the first step according to 118.92g/L, and drying and roasting to obtain the final Pt-Pd-Rh double-coating catalyst 2, wherein the Pd content is 60g/ft3Pt content of 30g/ft3Rh content of 10g/ft3。
Example 3:
the first step is as follows: the preparation method of the bottom layer Pd coating is the same as that of the example 1.
The second step is that: preparation of powder for upper layer
50.46g of cerous nitrate hexahydrate is weighed, pure water is added for dissolution, and then 180g of a first rare earth oxygen storage material (CeO) is added2The content is more than 99.5 percent), evenly stirred and mixed, kept stand for 12 hours, dried for 4 hours at the temperature of 120 ℃, and then roasted for 4 hours at the temperature of 600 ℃ to obtain 10 percent CeO2 modified cerium dioxide (10 percent CeO)2/CeO2)。
Platinum nitrate solution (containing Pt:2g) was weighed, and 98g of the above 10% CeO was weighed2/CeO2Adopting an equal-volume impregnation method to mix the diluted Pt salt solution with 10% CeO2/CeO2Material stirring deviceUniformly stirring, standing for 1h, pre-drying for 5h at 100 ℃, and roasting for 2h at 500 ℃ to obtain the Pt-containing noble metal powder B4.
Weighing rhodium nitrate solution (containing Rh: 0.2943g) and 49.71g of second rare earth oxygen storage material (cerium-zirconium-lanthanum-yttrium compound, CeO)230 percent of content), uniformly mixing the diluted rhodium nitrate and the cerium-zirconium-lanthanum-yttrium compound by adopting an isometric impregnation method, drying for 5 hours at 100 ℃ after impregnating for 1 hour, and roasting for 2 hours at 500 ℃ to obtain the precious metal powder C3 containing Rh.
A rhodium nitrate solution (containing Rh: 0.2943g) and 49.71g of a cerium-aluminum composite oxide (CeO) were weighed2Content of 12%), uniformly mixing the diluted rhodium nitrate solution with the cerium-aluminum composite oxide by an isometric impregnation method, impregnating for 1h, drying at 100 ℃ for 5h, and roasting at 500 ℃ for 2h to obtain the Rh-containing precious metal powder D3.
The third step: preparation of upper Pt-Rh coating
And ball milling and pulping the noble metal powder B4, C3 and D3 obtained in the step of adding water into 44.55 wt% of B4, 33.63 wt% of C3, 16.82 wt% of D3 and 5 wt% of adhesive respectively to obtain Pt-Rh slurry. Coating the Pt-Rh slurry on the Pd catalyst obtained in the first step according to 118.92g/L, and drying and roasting to obtain the final Pt-Pd-Rh double-coating catalyst 3, wherein the Pd content is 60g/ft3Pt content of 30g/ft3Rh content of 10g/ft3。
Example 4:
the first step is as follows: preparation of bottom Pd coating
The palladium nitrate solution (containing 1.47g Pd) was weighed, 100g deionized water was added, and the mixture was stirred well. The palladium nitrate solution is evenly sprayed to 98.53g of La by adopting a spraying mode2O3-Al2O3Adding the materials while stirring, and continuously stirring for 1 hour after spraying. Then dried at 100 ℃ for 5 hours and calcined at 500 ℃ for 2 hours to obtain a noble metal powder A2 containing 1.47 percent of Pd. And adding an adhesive into the obtained Pd powder A2, and performing ball milling and pulping by using pure water to obtain Pd slurry. Coating the Pd slurry on a 400-mesh honeycomb ceramic carrier with the diameter of 1 inch and the length of 1 inch according to 106.21g/L, drying and roasting to obtain the Pd content of 42g/ft3The catalyst of (1).
The second step is that: preparation of powder for upper layer
50.46g of cerous nitrate hexahydrate is weighed, pure water is added for dissolution, and then 180g of first rare earth oxygen storage material (large specific surface area CeO) is added2(specific surface area 140 m)2/g)，CeO2The content is more than 99.5 percent), evenly stirred and mixed, kept stand for 12 hours, dried for 4 hours at the temperature of 120 ℃, and then roasted for 4 hours at the temperature of 600 ℃ to obtain 10 percent CeO2Modified CeO with large specific surface area2(10％CeO2/CeO2)。
A platinum nitrate solution (containing Pt: 1.3332g) was weighed, and 98.67g of the above 10% CeO was weighed2/CeO2Adopting an equal-volume impregnation method to mix the diluted platinum nitrate solution with 10 percent CeO2/CeO2The material is stirred uniformly, is kept stand for 1h, is pre-dried for 5h at the temperature of 100 ℃, and is roasted for 2h at the temperature of 500 ℃ to obtain the Pt-containing noble metal powder B5. The preparation of Rh-containing noble metal powder was carried out in the same manner as in example 3.
The third step: preparation of upper Pt-Rh coating
And ball milling and pulping the noble metal powder B5, C3 and D3 obtained in the step of adding water into 44.55 wt% of B4, 33.63 wt% of C3, 16.82 wt% of D3 and 5 wt% of adhesive respectively to obtain Pt-Rh slurry. Coating the Pt-Rh slurry on the Pd catalyst obtained in the first step according to 118.92g/L, and drying and roasting to obtain the final Pt-Pd-Rh double-coating catalyst 4, wherein the Pd content is 42g/ft3Pt content of 20g/ft3Rh content of 10g/ft3。
Example 5:
the first step is as follows: preparation of bottom Pd coating layer same as example 4
The second step is that: preparation of powder for upper layer
50.46g of cerous nitrate hexahydrate is weighed, pure water is added for dissolution, and then 180g of first rare earth oxygen storage material (large specific surface area CeO) is added2(specific surface area 140 m)2/g)，CeO2The content is more than 99.5 percent), evenly stirred and mixed, kept stand for 12 hours, dried for 4 hours at the temperature of 120 ℃, and then roasted for 4 hours at the temperature of 600 ℃ to obtain 10 percent CeO2Modified high specific surface area ceria (10% CeO)2/CeO2)。
A platinum nitrate solution (containing Pt: 2.3544g) was weighed, and 97.65g of the above 10% CeO was weighed2/CeO2Adopting an equal-volume impregnation method to mix the diluted platinum nitrate solution with 10 percent CeO2/CeO2The material is stirred uniformly, is kept stand for 1h, is pre-dried for 5h at the temperature of 100 ℃, and is roasted for 2h at the temperature of 500 ℃ to obtain the Pt-containing noble metal powder B6.
Weighing rhodium nitrate solution (containing Rh: 0.3924g) and 99.61g of second rare earth oxygen storage material (cerium-zirconium-lanthanum-yttrium compound, CeO)230 percent of content), uniformly mixing the diluted rhodium nitrate and the cerium-zirconium-lanthanum-yttrium compound by adopting an isometric impregnation method, drying for 5 hours at 100 ℃ after impregnating for 1 hour, and roasting for 2 hours at 500 ℃ to obtain the precious metal powder C4 containing Rh.
A rhodium nitrate solution (containing Rh: 0.1962g) and 49.80g of a cerium-aluminum composite oxide (CeO) were weighed2Content of 12%), uniformly mixing the diluted rhodium nitrate solution with the cerium-aluminum composite oxide by an isometric impregnation method, impregnating for 1h, drying at 100 ℃ for 5h, and roasting at 500 ℃ for 2h to obtain the Rh-containing precious metal powder D4.
The third step: preparation of upper Pt-Rh coating
And (3) adding water into 23.75 wt%, 47.5 wt%, 23.75 wt% and 5 wt% of adhesive to perform ball milling pulping on the obtained catalyst powder B6, C4 and D4 respectively to obtain the Pt-Rh slurry. Coating the Pt-Rh slurry on the Pd catalyst obtained in the first step according to 126.32g/L, and drying and roasting to obtain the final Pt-Pd-Rh double-coating catalyst 4 (with the Pd content of 42 g/ft) 3 with the precious metal content of 72g/ft3Pt content 20g/ft3Rh content 10g/ft3)。
The Pt-containing catalyst powders of comparative example 1 and examples 1 to 4 were subjected to Pt dispersion tests after fresh and aged. The test results are shown in table 1 below.
TABLE 1 summary of the dispersion of Pt in the fresh and aged state for different Pt-containing catalyst powders
The aging conditions of the Pt-containing catalyst powder are 800 ℃, 20H and 10% H2And O, performing hydrothermal aging.
As can be seen from Table 1, the Pt-containing catalyst powder prepared by the method of the present invention is more stable after aging, and the Pt dispersion degree deterioration rate is lower. Particularly, the catalyst powder materials B5 and B6 prepared in examples 4 and 5 with low Pt loading amount have redispersion of Pt after aging, and the dispersity of Pt is improved more than that of the Pt which is fresh.
The catalysts prepared in comparative example 1 and examples 1 to 5 were subjected to fresh and aged catalyst activity evaluation on a simulated atmosphere evaluation system. Evaluation atmosphere: 10000ppm CO, 1000ppm NO, 3000ppm CH4，3000ppmH2，8％CO2，10％H2O, adjustment of O2The concentrations were such that the lambda values were equal to 0.97, 1.00 and 1.03 and the dynamic light-off test was carried out at a conversion frequency of 5 s/time. The aging conditions of the catalyst are 850 ℃, 50H and 10% H2And O, performing hydrothermal aging. The test results are shown in tables 2 and 3 below.
TABLE 2 comparison of the fresh state activities of different catalysts
| Name of catalyst | CH4-T50(℃) | CH4-T90(℃) | NO-T50(℃) | NO-T90(℃) |
| Comparative catalyst 1 | 341 | 362 | 351 | 360 |
| Catalyst 1 | 320 | 341 | 316 | 334 |
| Catalyst 2 | 270 | 290 | 275 | 288 |
| Catalyst 3 | 295 | 310 | 296 | 308 |
| Catalyst 4 | 280 | 298 | 282 | 292 |
| Catalyst 5 | 285 | 300 | 285 | 296 |
TABLE 3 comparison of the activity of different catalysts in the aged state
| Name of catalyst | CH4-T50(℃) | CH4-T90(℃) | NO-T50(℃) | NO-T90(℃) |
| Comparative catalyst 1 | 454 | 472 | 451 | 470 |
| Catalyst 1 | 390 | 406 | 394 | 406 |
| Catalyst 2 | 326 | 346 | 328 | 341 |
| Catalyst 3 | 355 | 369 | 354 | 365 |
| CatalysisAgent 4 | 346 | 365 | 349 | 363 |
| Catalyst 5 | 350 | 375 | 352 | 365 |
As can be seen from the above results of the catalyst activity test, the catalyst prepared by the process of this patent is on CH4And NO have very low light-off temperatures, especially for CH after aging4And NO has a lower light-off temperature and a complete conversion temperature, catalyst 2 can be more than 120 ℃ lower than comparative catalyst 1.
Claims (9)
1. A Pt-Pd-Rh three-way catalyst is composed of a carrier and an active coating coated on the surface of the carrier, and is characterized in that: the active coating is of a double-coating structure, the bottom layer is a Pd coating, and the upper layer is a Pt-Rh coating;
the Pd coating is made of lanthanum modified alumina loaded with noble metal Pd and an adhesive;
the Pt-Rh coating is made of a first rare earth oxygen storage material modified by cerium dioxide loaded with noble metal Pt, a second rare earth oxygen storage material loaded with Rh, a cerium-aluminum composite oxide loaded with Rh and a bonding agent; the first rare earth oxygen storage material is cerium-zirconium solid solution with high cerium content or cerium dioxide with large specific surface area, wherein the cerium dioxide content is 80-99.9 wt%.
2. The Pt-Pd-Rh three-way catalyst according to claim 1, characterized in that: the first rare earth oxygen storage material modified by the cerium dioxide loaded with the noble metal Pt is prepared by mixing a rare earth oxygen storage material with soluble cerium salt.
3. The Pt-Pd-Rh three-way catalyst according to claim 1, characterized in that: the content of cerium dioxide in the second rare earth oxygen storage material loaded with Rh is 10-30 wt%.
4. The Pt-Pd-Rh three-way catalyst according to claim 1, characterized in that: the cerium oxide content in the Rh-loaded cerium-aluminum composite oxide is 1-15 wt%.
5. A preparation method of a Pt-Pd-Rh three-way catalyst is characterized by comprising the following steps: the catalyst is as claimed in any one of claims 1 to 4, and the preparation method comprises the following steps:
(1) preparing a bottom layer catalyst: weighing a noble metal Pd salt solution A, weighing a lanthanum modified alumina material, uniformly spraying the diluted Pd salt solution A onto the lanthanum modified alumina material by adopting an isometric immersion method, uniformly stirring, pre-drying for 4-6 h at 80-120 ℃, roasting for 2h at 500 ℃ to obtain Pd-containing catalyst powder A1, adding the obtained Pd-containing catalyst powder into a ball milling tank, adding an adhesive and pure water, ball-milling to obtain noble metal Pd-containing slurry, coating the slurry on a carrier, and drying and roasting to obtain a Pd-containing active layer catalyst;
(2) preparing upper-layer catalyst powder:
the first rare earth oxygen storage material is modified by cerium dioxide, and the specific preparation method comprises the following steps: weighing cerium nitrate, adding pure water to dissolve the cerium nitrate, then adding a first rare earth oxygen storage material, stirring and mixing uniformly, standing for 8-12 h, drying at 80-120 ℃ for 4-6 h, and then roasting at 500-600 ℃ for 4h to obtain a cerium dioxide modified first rare earth oxygen storage material;
weighing a precious metal Pt salt solution B, weighing the cerium dioxide modified first rare earth oxygen storage material, uniformly stirring the diluted Pt salt solution B and the cerium dioxide modified first rare earth oxygen storage material by adopting an isovolumetric impregnation method, standing for 1h, pre-drying for 4-6 h at the temperature of 80-120 ℃, and roasting for 1-4 h at the temperature of 500 ℃ to obtain Pt-containing catalyst powder B1;
weighing an Rh salt solution C and a second rare earth oxygen storage material, uniformly mixing the diluted Rh salt solution C and the second rare earth oxygen storage material by an isometric impregnation method, impregnating for 1 hour, pre-drying for 4-6 hours at 80-120 ℃, and roasting for 2 hours at 500 ℃ to obtain Rh-containing catalyst powder C1;
weighing Rh salt solution D and a cerium-aluminum composite oxide, uniformly mixing the diluted Rh salt solution D and the cerium-aluminum composite oxide by adopting an isometric impregnation method, pre-drying for 4-6 h at 80-120 ℃ after impregnating for 1h, and roasting for 2h at 500 ℃ to obtain Rh-containing catalyst powder D1;
(3) preparing an upper layer catalyst: mixing and ball-milling the catalyst powder B1, the catalyst powder C1, the catalyst powder D1, the adhesive and pure water prepared in the step (2) to obtain uniform upper-layer slurry; and (3) coating the upper layer slurry on the catalyst obtained in the step (1), and drying and roasting to obtain the Pt-Pd-Rh double-coating catalyst.
6. The method for preparing a Pt-Pd-Rh three-way catalyst according to claim 4, characterized in that: the salt solution B, Rh C of the noble metal Pd salt solution A, Pt in the steps (1) and (2) is a soluble salt solution.
7. The method for preparing a Pt-Pd-Rh three-way catalyst according to claim 4, characterized in that: the first rare earth oxygen storage material in the step (2) is cerium-zirconium solid solution, or lanthanum-yttrium-praseodymium-modified cerium-zirconium solid solution, or cerium dioxide with large specific surface area; the second rare earth oxygen storage material is cerium-zirconium solid solution or lanthanum, yttrium and neodymium modified cerium-zirconium solid solution.
8. The method for preparing a Pt-Pd-Rh three-way catalyst according to claim 4, characterized in that: in the step (3), the mass ratio of the first rare earth oxygen storage material for dispersing the noble metal Pt to the second rare earth oxygen storage material for dispersing the Rh is 2: 1-1: 2; the mass ratio of the second rare earth oxygen storage material for dispersing Rh to the cerium-aluminum composite oxide is 2: 1-1: 1.
9. The method for preparing a Pt-Pd-Rh three-way catalyst according to claim 4, characterized in that: the Pd consumption in the step (1) is 10-100 g/ft3(ii) a The amount of Pt used in the step (3) is 10-50 g/ft3The amount of Rh used is 1-10 g/ft3。
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| CN114700085A (en) * | 2022-05-07 | 2022-07-05 | 中自环保科技股份有限公司 | High-stability three-way catalyst and preparation method thereof |
| CN114700085B (en) * | 2022-05-07 | 2023-08-18 | 中自环保科技股份有限公司 | High-stability three-way catalyst and preparation method thereof |
| CN114950423A (en) * | 2022-06-08 | 2022-08-30 | 重庆大学 | Indoor low-concentration formaldehyde purification catalyst product and preparation method thereof |
| CN114950423B (en) * | 2022-06-08 | 2023-06-09 | 重庆大学 | Indoor low-concentration formaldehyde purification catalyst product and preparation method thereof |
| CN114931962A (en) * | 2022-06-20 | 2022-08-23 | 无锡威孚环保催化剂有限公司 | Quick ignition catalyst coating and preparation method thereof |
| CN114931962B (en) * | 2022-06-20 | 2023-07-18 | 无锡威孚环保催化剂有限公司 | Quick ignition catalyst coating and preparation method thereof |
| CN115254103A (en) * | 2022-07-28 | 2022-11-01 | 湖北航特科技有限责任公司 | Tail gas purification catalyst and preparation method thereof |
| CN115254103B (en) * | 2022-07-28 | 2024-02-02 | 湖北航特科技有限责任公司 | Tail gas purifying catalyst and preparation method thereof |
| CN115382540A (en) * | 2022-07-29 | 2022-11-25 | 凯龙蓝烽新材料科技有限公司 | Preparation method of modified alumina carrier supported noble metal catalyst for lean burn CNG |
| CN117414821A (en) * | 2023-12-08 | 2024-01-19 | 中自环保科技股份有限公司 | High-temperature-resistant sintering Pt-based three-way catalyst and preparation method thereof |
| CN117414821B (en) * | 2023-12-08 | 2024-03-15 | 中自环保科技股份有限公司 | High-temperature-resistant sintering Pt-based three-way catalyst and preparation method thereof |
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