CN114931962B - Quick ignition catalyst coating and preparation method thereof - Google Patents
Quick ignition catalyst coating and preparation method thereof Download PDFInfo
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- CN114931962B CN114931962B CN202210696468.3A CN202210696468A CN114931962B CN 114931962 B CN114931962 B CN 114931962B CN 202210696468 A CN202210696468 A CN 202210696468A CN 114931962 B CN114931962 B CN 114931962B
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- 238000000576 coating method Methods 0.000 title claims abstract description 100
- 239000011248 coating agent Substances 0.000 title claims abstract description 94
- 239000003054 catalyst Substances 0.000 title claims abstract description 89
- 238000002360 preparation method Methods 0.000 title claims abstract description 24
- 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 42
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 32
- 238000000034 method Methods 0.000 claims abstract description 28
- 239000000919 ceramic Substances 0.000 claims abstract description 24
- 229910021418 black silicon Inorganic materials 0.000 claims abstract description 18
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000000843 powder Substances 0.000 claims description 54
- 229910052782 aluminium Inorganic materials 0.000 claims description 47
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 47
- 238000003756 stirring Methods 0.000 claims description 36
- 238000001035 drying Methods 0.000 claims description 29
- 238000010438 heat treatment Methods 0.000 claims description 28
- 239000011259 mixed solution Substances 0.000 claims description 27
- DLRVVLDZNNYCBX-UHFFFAOYSA-N Polydextrose Polymers OC1C(O)C(O)C(CO)OC1OCC1C(O)C(O)C(O)C(O)O1 DLRVVLDZNNYCBX-UHFFFAOYSA-N 0.000 claims description 22
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 18
- 239000002002 slurry Substances 0.000 claims description 18
- 239000004793 Polystyrene Substances 0.000 claims description 16
- 229920002223 polystyrene Polymers 0.000 claims description 16
- 239000008367 deionised water Substances 0.000 claims description 15
- 229910021641 deionized water Inorganic materials 0.000 claims description 15
- 239000000243 solution Substances 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 229910052878 cordierite Inorganic materials 0.000 claims description 14
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 claims description 14
- BJEPYKJPYRNKOW-UHFFFAOYSA-N malic acid Chemical compound OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 12
- 229920001100 Polydextrose Polymers 0.000 claims description 11
- 239000004005 microsphere Substances 0.000 claims description 11
- 229940035035 polydextrose Drugs 0.000 claims description 11
- 235000013856 polydextrose Nutrition 0.000 claims description 11
- 239000001259 polydextrose Substances 0.000 claims description 11
- ODLHGICHYURWBS-LKONHMLTSA-N trappsol cyclo Chemical compound CC(O)COC[C@H]([C@H]([C@@H]([C@H]1O)O)O[C@H]2O[C@@H]([C@@H](O[C@H]3O[C@H](COCC(C)O)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](COCC(C)O)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](COCC(C)O)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](COCC(C)O)[C@H]([C@@H]([C@H]3O)O)O3)[C@H](O)[C@H]2O)COCC(O)C)O[C@@H]1O[C@H]1[C@H](O)[C@@H](O)[C@@H]3O[C@@H]1COCC(C)O ODLHGICHYURWBS-LKONHMLTSA-N 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 10
- XXJWXESWEXIICW-UHFFFAOYSA-N diethylene glycol monoethyl ether Chemical compound CCOCCOCCO XXJWXESWEXIICW-UHFFFAOYSA-N 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- 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 claims description 8
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 7
- 239000010948 rhodium Substances 0.000 claims description 7
- 239000007864 aqueous solution Substances 0.000 claims description 6
- 239000006255 coating slurry Substances 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 6
- KDXKERNSBIXSRK-UHFFFAOYSA-N lysine Chemical compound NCCCCC(N)C(O)=O KDXKERNSBIXSRK-UHFFFAOYSA-N 0.000 claims description 6
- 235000011090 malic acid Nutrition 0.000 claims 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 claims description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 6
- 229920006395 saturated elastomer Polymers 0.000 claims description 6
- 239000002243 precursor Substances 0.000 claims description 5
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 238000010276 construction Methods 0.000 claims description 2
- 229910052763 palladium Inorganic materials 0.000 claims description 2
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- 229910052703 rhodium Inorganic materials 0.000 claims description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 2
- 230000000630 rising effect Effects 0.000 claims 3
- 238000010304 firing Methods 0.000 claims 1
- 238000012360 testing method Methods 0.000 abstract description 37
- 239000003344 environmental pollutant Substances 0.000 abstract description 25
- 231100000719 pollutant Toxicity 0.000 abstract description 25
- 230000000694 effects Effects 0.000 abstract description 3
- 238000011068 loading method Methods 0.000 abstract description 3
- 230000000977 initiatory effect Effects 0.000 abstract 2
- 239000006185 dispersion Substances 0.000 abstract 1
- 238000003878 thermal aging Methods 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 27
- 230000032683 aging Effects 0.000 description 13
- 239000011148 porous material Substances 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 239000007789 gas Substances 0.000 description 7
- 239000002131 composite material Substances 0.000 description 6
- 239000011232 storage material Substances 0.000 description 6
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical group [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 5
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 5
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 4
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- -1 ethoxy glycol ether Chemical compound 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 1
- 230000003712 anti-aging effect Effects 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 210000002421 cell wall Anatomy 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000003278 mimic effect Effects 0.000 description 1
- QWDUNBOWGVRUCG-UHFFFAOYSA-N n-(4-chloro-2-nitrophenyl)acetamide Chemical compound CC(=O)NC1=CC=C(Cl)C=C1[N+]([O-])=O QWDUNBOWGVRUCG-UHFFFAOYSA-N 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
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- 239000003981 vehicle Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/20—Carbon compounds
- B01J27/22—Carbides
- B01J27/224—Silicon carbide
-
- 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
- B01D53/92—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
-
- B01J35/56—
-
- B01J35/615—
-
- B01J35/635—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/01—Engine exhaust gases
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
The invention belongs to the technical field of catalyst preparation, and particularly relates to a rapid light-off catalyst coating and a preparation method thereof. The rapid light-off catalyst coating comprises a heat conduction layer consisting of black silicon carbide and an active component loaded on the heat conduction layer, wherein the heat conduction layer has high heat conductivity, low heat capacity and high heat stability, can realize rapid conduction of tail gas heat in the coating, achieves the effect of rapid temperature rise, and can also improve the thermal aging resistance of the coating; the active component prepared by combining the modified alumina with the noble metal dispersion loading process can effectively improve the utilization rate of the noble metal and the quick ignition performance of the catalyst. The rapid initiation catalyst coating can be coated on a through-type or wall-flow honeycomb ceramic carrier, and can effectively reduce the initiation temperature and emission of typical gaseous pollutants in the test of national six regulations.
Description
Technical Field
The invention belongs to the technical field of catalyst preparation, and particularly relates to a rapid light-off catalyst coating and a preparation method thereof.
Background
In the six light vehicle exhaust emissions test type I test (WLTC test), HC, CO and NO at low speed stage x The pollutant emissions typically account for over 75%, 60% and 50% of the total emissions of the entire test cycle, respectively. Since the low-velocity phase involves a cold start process, the temperature of the aftertreatment catalyst may gradually rise from ambient temperature to the light-off temperature required by the catalyst, whereas conventional aftertreatment catalysts require at least 300 ℃ to light-off. Before the temperature of the catalyst reaches the light-off temperature, most of the exhaust gas pollutants are directly discharged from the exhaust pipe, so that the pollutant discharge amount of the low-speed stage is obviously increased. Meanwhile, the exhaust control of the national six II type test (actual driving pollutant exhaust test, RDE test) is about to be fully developed in the period of 2023, 7 and 1. Compared with WLTC circulation, the RDE test has more variation factors, the corresponding low-speed stage and cold start working condition are also more severe, and higher control requirements are provided for pollutant emission.
To solve the above-described problems, it is common to employ a method of mounting an aftertreatment catalyst near the outlet of the engine exhaust manifold (close-coupled arrangement) to rapidly warm up the catalyst. However, due to the influence of the catalyst coating material, there is a delay in the temperature conducted to the catalytically active material, which results in the catalytic material failing to reach the light-off temperature for the pollutant conversion in time, resulting in an increase in cold start emissions, and therefore, the realization of rapid light-off by modification of the catalyst coating material is an important research direction for increasing the pollutant conversion during cold start and reducing the emissions of WLTC and RDE tests.
Disclosure of Invention
The invention aims to overcome the defect of low conversion efficiency of gaseous pollutants in a cold start stage in the using process of a post-treatment catalyst coating in the prior art, and provides a rapid ignition catalyst coating and a preparation method thereof. The catalyst coating adopts the black silicon carbide with high thermal conductivity, low heat capacity and high thermal stability as the heat conducting layer, so that the rapid conduction of tail gas heat in the coating can be realized, the effect of rapid temperature rise is achieved, the overall heat aging resistance of the coating can be improved, and meanwhile, the aluminum oxide is modified, and an internal porous system is constructed to reduce the internal diffusion resistance of gas; in addition, the noble metal dispersing and loading process is applied based on an internal porous system, so that the utilization rate of noble metal active components is effectively improved, and the quick ignition performance of the catalyst is further improved.
In order to achieve the technical purpose, the technical scheme adopted by the embodiment of the invention is as follows:
in a first aspect, embodiments of the present invention provide a rapid light-off catalyst coating comprising a thermally conductive layer and an active component supported on the thermally conductive layer, the active component comprising a noble metal-supported modified alumina, the thermally conductive layer comprising black silicon carbide.
Further, the noble metal includes rhodium, and further includes one of palladium and platinum.
In a second aspect, an embodiment of the present invention provides a method for preparing a rapid light-off catalyst coating, including the steps of:
(1) Adding polydextrose, polystyrene and ethoxydiglycol ether into aluminum sol to obtain mixed solution, and uniformly stirring the mixed solution to form aluminum sol mixed solution;
(2) Heating the aluminum gel mixed solution obtained in the step (1) to 80-90 ℃, then transferring the aluminum gel mixed solution into a microwave drying oven for microwave drying, taking out the aluminum gel mixed solution when the drying rate is more than or equal to 90%, and roasting the aluminum gel mixed solution in a muffle furnace at 700-800 ℃ for 2-4 hours to obtain modified aluminum oxide;
(3) Grinding the modified alumina obtained in the step (2) into powder, then placing the powder into a powder stirrer for stirring, adding a saturated aqueous solution of 2, 6-diaminocaproic acid, which is 5-10% of the powder in mass relative to the modified alumina, continuously stirring for 2-4 hours, then dropwise adding a noble metal precursor solution, placing the powder into a 50-60 ℃ oven for drying for 4-8 hours after the dropwise adding is completed, then continuously stirring the powder, adding a 2-hydroxysuccinic acid solution, which is 5-10% of the powder in mass relative to the powder, and placing the obtained powder into a muffle furnace for roasting to prepare the noble metal-loaded modified alumina;
(4) Mixing the noble metal-loaded modified alumina and black silicon carbide according to the mass ratio of 1:3-10, simultaneously adding hydroxypropyl-beta-cyclodextrin, aluminum sol and deionized water to form catalyst coating slurry, and controlling the adding amount of the deionized water to enable the amount of a slurry solidified substance to be 20% -30%;
(5) And (3) coating the catalyst coating slurry prepared in the step (4) on a cordierite honeycomb ceramic carrier, placing the cordierite honeycomb ceramic carrier in a muffle furnace after coating, heating to 200-230 ℃ at a heating rate of 1-2 ℃/min from room temperature, heating to 500-600 ℃ at a heating rate of 5-10 ℃/min, and staying for 1-2 h to finally finish the preparation of the quick-start catalyst coating.
Further, the addition amounts of the polydextrose, the polystyrene and the ethoxy glycol ether in the step (1) are respectively 2% -5%, 5% -10% and 2% -5% of the mass of the aluminum sol solidified substance.
Further, in the step (1), the mass fraction of the aluminum sol is 30% -40%, and the pH is 3-5; the polystyrene is microsphere with a diameter of 1-2 μm.
Further, the modified alumina powder in the step (3) has an average particle diameter of 5 to 8 μm; the solute in the noble metal precursor solution is one of palladium nitrate or platinum nitrate and rhodium nitrate, and the mass fraction is 3% -5%.
Further, the roasting process in the step (3) is as follows: the powder is placed in a muffle furnace to be roasted for 1-2 hours at 300-400 ℃ and 500-600 ℃ respectively, and the heating rate is controlled at 5-10 ℃/min.
Further, the adding amount of the hydroxypropyl-beta-cyclodextrin and the aluminum sol in the step (4) is respectively 10-15% and 5-10% of the mass of the black silicon carbide, and the average particle size of the black silicon carbide is 5-10 mu m; the mass fraction of the aluminum sol is 20% -30%, and the pH value is 3-5.
Further, the cordierite honeycomb ceramic support in step (5) is of a straight-through or wall-flow type structure.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
the catalyst coating adopts the black silicon carbide with high thermal conductivity, low heat capacity and high thermal stability as the heat conducting layer, so that the rapid conduction of tail gas heat in the coating can be realized, the effect of rapid temperature rise is achieved, the overall heat aging resistance of the coating can be improved, and meanwhile, the aluminum oxide is modified, and an internal porous system is constructed to reduce the internal diffusion resistance of gas; in addition, the noble metal dispersing and loading process is applied based on an internal porous system, so that the utilization rate of noble metal active components is effectively improved, and the quick ignition performance of the catalyst is further improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
A rapid light-off catalyst includes a flow-through honeycomb ceramic support and a rapid light-off catalyst coating applied to the support. The carrier specification was phi 118.4X1127 mm, the pore density was 600cpsi, the cell wall thickness was 4mil, and the volume was 1.4L. The coating amount of the coating is 100g/L, the inner coating height is 100%, and the noble metal content is Pd 40g/ft 3 ，Rh：5g/ft 3 。
The preparation method of the rapid light-off catalyst coating comprises the following steps:
(1) Adding polydextrose, polystyrene microsphere and ethoxydiglycol ether into aluminum sol to form a mixed solution, and uniformly stirring the mixed solution to form an aluminum gel mixed solution;
wherein the addition amounts of the polydextrose, the polystyrene microsphere and the ethoxy diglycol ether are respectively 5%, 10% and 5% of the mass of the aluminum sol solidified material; the mass fraction of the aluminum sol is 40%, and the pH value is 3; the diameter of the polystyrene microsphere is 2 mu m;
(2) Heating the aluminum gel mixed solution obtained in the step (1) to 80 ℃, transferring to a microwave drying oven for microwave drying, taking out when the drying rate is more than or equal to 90%, and roasting in a muffle furnace at 700 ℃ for 4 hours to obtain modified alumina;
(3) Grinding the modified alumina obtained in the step (2) into powder with the average particle diameter of 8 mu m, then placing the powder into a powder stirrer for stirring, adding a saturated aqueous solution of 2, 6-diaminocaproic acid with the mass of 10% of the modified alumina powder in the stirring process, continuously stirring for 4 hours, then dropwise adding palladium nitrate and rhodium nitrate with the mass fraction of 5%, placing the mixture into an oven for drying at 50 ℃ for 8 hours after the dropwise adding is completed, then continuously stirring the powder, adding a 2-hydroxysuccinic acid solution with the mass of 10% of the powder, and finally placing the powder into a muffle furnace for sequentially roasting for 2 hours at 300 ℃ and 500 ℃ respectively, wherein the heating rate is controlled at 5 ℃/min, thus preparing the modified alumina loaded with noble metal;
(4) Mixing the noble metal-loaded modified alumina and black silicon carbide with the average particle diameter of 10 mu m according to the mass ratio of 1:10, and simultaneously adding hydroxypropyl-beta-cyclodextrin, aluminum sol and deionized water to form slurry;
wherein the mass fraction of the aluminum sol is 30% and the pH is 3; the addition amounts of the hydroxypropyl-beta-cyclodextrin and the aluminum sol are respectively 15% and 10% of the mass of the black silicon carbide, and the addition amount of deionized water is controlled to make the slurry solidification amount be 30%;
(5) And (3) coating the slurry obtained in the step (4) on a cordierite honeycomb ceramic carrier, placing the cordierite honeycomb ceramic carrier in a muffle furnace after coating, heating to 200 ℃ at a heating rate of 1 ℃/min from room temperature, heating to 500 ℃ at a heating rate of 5 ℃/min, and staying for 2 hours to finally finish the preparation of the rapid light-off catalyst coating.
Comparative example 1
The support dimensions, coating amount, inner coating height and noble metal content used in this example were the same as in example 1.
The difference is that the coating used in the example is a conventional three-way catalyst coating, and the preparation method of the coating adopts a conventional process: mixing commercial aluminum oxide and cerium zirconium oxide composite oxygen storage material powder according to a mass ratio of 1:1, adding deionized water, uniformly stirring, adding palladium nitrate and rhodium nitrate, stirring to form slurry, and coating the slurry on a substrateAnd (3) drying and roasting the through honeycomb ceramic carrier to finish the final preparation process. The composition of the cerium-zirconium composite oxygen storage material is 30 percent CeO 2 +60％ZrO 2 +5％La 2 O 3 +5％Y 2 O 3 The coating is dried at 150 ℃ for 2 hours, and the baking condition is 500 ℃ for 2 hours.
Comparative test of specific surface area and pore volume of coated alumina material:
the modified alumina prepared in step (2) of example 1 and the commercial alumina of comparative example 1 were placed in a specific surface area tester to perform specific surface area and pore volume tests, and the specific surface area and pore volume of the materials were calculated based on BET and BJH model desorption curves, respectively, and the results are shown in table 1:
TABLE 1 specific surface area and pore volume comparison of alumina materials used in the various examples
| Comparison item | Example 1 | Comparative example 1 |
| Specific surface area (m) 2 /g) | 155 | 152 |
| Pore volume (cm) 3 /g) | 0.68 | 0.51 |
As can be seen from Table 1, the modified alumina prepared in example 1 had a pore volume about 33.3% higher than that of comparative example 1 on the basis of the similar specific surface area, indicating that the modified alumina prepared in example 1 had well achieved the construction of an internal porous system, which was conducive to the internal diffusion flow of the reaction gas.
Light-off temperature comparative test:
the catalysts prepared in example 1 and comparative example 1 were packaged and mounted on a 1.5L displacement gasoline engine bench, respectively, and a fresh state light-off temperature test was performed based on the standard requirements of HJ/T331-2006, catalytic converter for gasoline vehicles for environmental protection product technology. And then carrying out standard rack cycle (SBC) aging according to the standard requirements of GB18352.6-2016 (light automobile pollutant emission limit value and measuring method (Chinese sixth stage)), wherein the aging time is 100h. After the aging, the aging state ignition temperature test is carried out according to the method, the ignition temperature test of each scheme is carried out for 3 times, and the average value is taken as a final result. The light-off temperature (T50) is compared to table 2:
TABLE 2 comparison of the light-off T50 of the catalysts prepared in example 1 and comparative example 1
As can be seen from table 2, example 1, to which the rapid light-off catalyst coating provided by the present invention was applied, exhibited more excellent light-off and anti-aging properties, compared to comparative example 1, to which the conventional coating was applied, in which the T50 of the fresh and aged catalysts were reduced by about 45 ℃ and 70 ℃, respectively, on average. At the same time, the exemplary gaseous pollutant light-off T50 of example 1 can be reduced to below 300 ℃ to facilitate pollutant emission control at the low-speed stage of WLTC cycle.
Example 2
A rapid light-off catalyst comprising a flow-through honeycomb ceramic support and a catalyst coating applied to the support, the catalyst coating comprising a rapid light-off catalyst coating and a conventional three-way catalyst coating. The specification of the carrier is phi 132.1X101.6 mm, the pore density is 750cpsi, the wall thickness of the pore canal is 2mil, and the volume is 1.392L; one end of the honeycomb ceramic carrier is an air inlet end in the air inlet and outlet direction, the other end is an air outlet end, and the length ratio of the air inlet end to the air outlet end is 1:1. A rapid light-off catalyst coating is coated on the air inlet end of the carrier, and is coatedThe coating amount is 100g/L, and the noble metal content is Pd 60g/ft 3 ，Rh：5g/ft 3 The method comprises the steps of carrying out a first treatment on the surface of the The conventional three-way catalyst coating is coated on the air outlet end of the carrier, the coating amount is 150g/L, and the noble metal content is Pd:20g/ft 3 ，Rh：5g/ft 3 . The conventional three-way catalyst coating was prepared in the same manner as in comparative example 1.
The preparation method of the rapid light-off catalyst coating comprises the following steps:
(1) Adding polydextrose, polystyrene microsphere and ethoxydiglycol ether into aluminum sol to form a mixed solution, and uniformly stirring the mixed solution to form an aluminum gel mixed solution;
wherein, the addition amounts of the polydextrose, the polystyrene microsphere and the ethoxy glycol ether are respectively 3 percent, 8 percent and 3 percent of the mass of the aluminum sol solidified material; the mass fraction of the aluminum sol is 35%, and the pH value is 4; the diameter of the polystyrene microsphere is 2 mu m;
(2) Heating the aluminum gel mixed solution obtained in the step (1) to 90 ℃, transferring to a microwave drying oven for microwave drying, taking out when the drying rate is more than or equal to 90%, and roasting in a muffle furnace at 800 ℃ for 2 hours to obtain modified alumina;
(3) Grinding the modified alumina obtained in the step (2) into powder with the average particle diameter of 7 mu m, then placing the powder into a powder stirrer for stirring, adding a saturated aqueous solution of 2, 6-diaminocaproic acid accounting for 8% of the mass of the modified alumina powder in the stirring process, continuously stirring for 3 hours, then dropwise adding 4% of palladium nitrate and rhodium nitrate, placing the alumina powder into a baking oven for drying at 60 ℃ for 4 hours after the dropwise adding is completed, then continuously stirring the powder, adding a 2-hydroxysuccinic acid solution accounting for 8% of the mass of the powder, and finally placing the powder into a muffle furnace for sequentially roasting for 2 hours at 350 ℃ and 550 ℃ respectively, wherein the heating rate is controlled at 7 ℃/min, thus preparing the modified alumina loaded with noble metals;
(4) Mixing the noble metal-loaded modified alumina and black silicon carbide with the average particle diameter of 8 mu m according to the mass ratio of 1:8, and simultaneously adding hydroxypropyl-beta-cyclodextrin, aluminum sol and deionized water to form slurry;
wherein the mass fraction of the aluminum sol is 25% and the pH is 4; the addition amounts of the hydroxypropyl-beta-cyclodextrin and the aluminum sol are respectively 12% and 7% of the mass of the black silicon carbide, and the addition amount of deionized water is controlled to ensure that the slurry solidification amount is 25%;
(5) And (3) coating the slurry prepared in the steps on a cordierite honeycomb ceramic carrier, placing the cordierite honeycomb ceramic carrier in a muffle furnace after coating, heating to 230 ℃ at a heating rate of 2 ℃/min from room temperature, heating to 600 ℃ at a heating rate of 10 ℃/min, and staying for 1h to finally finish the preparation of the rapid light-off catalyst coating.
Comparative example 2
The carrier dimensions, inlet and outlet end length ratios, coating application amounts and precious metal content used in this example were the same as in example 2.
The difference is that the coatings used at the air inlet end and the air outlet end of the embodiment are conventional three-way catalyst coatings, and the preparation method of the coatings adopts the conventional process: mixing commercial aluminum oxide and cerium zirconium composite oxygen storage material powder materials according to a mass ratio of 1:1, adding deionized water, uniformly stirring, adding palladium nitrate and rhodium nitrate, stirring to form slurry, coating the slurry on a straight-through honeycomb ceramic carrier, and drying and roasting to finish the final preparation process of the catalyst coating. The composition of the cerium-zirconium composite oxygen storage material is 30 percent CeO 2 +60％ZrO 2 +5％La 2 O 3 +5％Y 2 O 3 The coating is dried at 150 ℃ for 2 hours, and the baking condition is 600 ℃ for 1 hour.
Light-off temperature comparative test:
the catalysts prepared in example 2 and comparative example 2 were packaged and mounted on a 1.5L displacement gasoline engine bench, respectively, and a fresh state light-off temperature test was performed based on HJ/T331-2006 Standard requirement of catalytic converter for gasoline vehicle for environmental protection product technology. And then carrying out standard rack cycle (SBC) aging according to the standard requirements of GB18352.6-2016 (light automobile pollutant emission limit value and measuring method (Chinese sixth stage)), wherein the aging time is 100h. After the aging, the aging state ignition temperature test is carried out according to the method, the ignition temperature test of each scheme is carried out for 3 times, and the average value is taken as a final result. Light-off temperature (T50) versus table 3:
TABLE 3 comparison of the light-off T50 of the catalysts prepared in example 2 and comparative example 2
As can be seen from Table 3, the rapid light-off catalyst coating provided by the invention and the conventional three-way catalyst coating are coated on the same honeycomb ceramic carrier according to the front-back partition, and the catalyst still can show better fresh and aged light-off performance. Therefore, the rapid light-off catalyst coating provided by the invention can be combined with a conventional three-way catalyst coating to ensure three-effect performances such as oxygen storage and oxygen release on the premise of ensuring the light-off performance.
Example 3
A rapid light-off catalyst comprising a wall-flow honeycomb ceramic support and a catalyst coating applied to the support, the catalyst coating comprising a rapid light-off catalyst coating and a conventional three-way catalyst coating. The specification of the carrier is phi 132.1 multiplied by 127mm, the pore density is 300cpsi, the pore channel wall thickness is 8mil, the porosity is 63%, the average pore diameter is 17.5 mu m, the volume is 1.74L, one end of the honeycomb ceramic carrier in the gas inlet and outlet direction is an air inlet end, the other end is an air outlet end, and the length ratio of the air inlet end to the air outlet end is 1:1. The rapid light-off catalyst coating is coated on the air inlet end of the carrier, the coating amount is 100g/L, and the noble metal content is Pt 5g/ft 3 ，Rh：5g/ft 3 . The conventional three-way catalyst coating is coated on the air outlet end of the carrier, the coating amount is 100g/L, and the noble metal content is Pt:5g/ft 3 ，Rh：5g/ft 3 . The preparation method of the conventional three-way catalyst coating is the same as that of comparative example 1;
the preparation method of the quick ignition catalyst coating comprises the following steps:
(1) Adding polydextrose, polystyrene microsphere and ethoxydiglycol ether into aluminum sol to form a mixed solution, and uniformly stirring the mixed solution to form an aluminum gel mixed solution;
wherein the addition amounts of the polydextrose, the polystyrene microsphere and the ethoxy diglycol ether are respectively 2%, 5% and 2% of the mass of the aluminum sol solidified material; the mass fraction of the aluminum sol is 30%, and the pH value is 5; the polystyrene microsphere has a diameter of 1 μm.
(2) Heating the aluminum gel mixed solution obtained in the step (1) to 80 ℃, transferring to a microwave drying oven for microwave drying, taking out when the drying rate is more than or equal to 90%, and roasting in a muffle furnace at 800 ℃ for 2 hours to obtain modified alumina;
(3) Grinding the modified alumina obtained in the step (2) into powder with the average particle diameter of 5 mu m, placing the powder into a powder stirrer for stirring, adding a saturated aqueous solution of 2, 6-diaminocaproic acid, which is 5% of the mass of the modified alumina powder, continuously stirring for 2 hours, dropwise adding platinum nitrate and rhodium nitrate with the mass fraction of 3%, placing the powder into a baking oven for drying at 60 ℃ for 4 hours after dropwise adding, continuously stirring the powder, adding a 2-hydroxysuccinic acid solution with the mass of 5% of the powder, placing the powder into a muffle furnace for sequentially roasting for 1 hour at 400 ℃ and 600 ℃, and controlling the heating rate to be 10 ℃/min to prepare the noble metal-loaded modified alumina;
(4) Mixing the noble metal-loaded modified alumina and black silicon carbide with an average particle size of 5 mu m according to a mass ratio of 1:3, and simultaneously adding hydroxypropyl-beta-cyclodextrin, aluminum sol and deionized water to form slurry;
wherein the mass fraction of the aluminum sol is 20% and the pH is 5; the addition amounts of the hydroxypropyl-beta-cyclodextrin and the aluminum sol are respectively 10 percent and 5 percent of the mass of the black silicon carbide, and the addition amount of deionized water is controlled to ensure that the slurry solidification amount is 20 percent;
(5) And (3) coating the slurry prepared in the step (4) on a cordierite honeycomb ceramic carrier, placing the cordierite honeycomb ceramic carrier in a muffle furnace after coating, heating to 230 ℃ at a heating rate of 2 ℃/min from room temperature, heating to 600 ℃ at a heating rate of 10 ℃/min, and staying for 1h to finally finish the preparation of the rapid light-off catalyst coating.
Comparative example 3
The carrier dimensions, inlet and outlet end length ratios, coating application amounts and precious metal content used in this example were the same as in example 3.
The difference is that the coatings used at the air inlet end and the air outlet end of the embodiment are all conventional three-way catalyst coatings, and the preparation method of the coatings adopts the conventional methodThe technological process comprises the following steps: mixing commercial aluminum oxide and cerium zirconium composite oxygen storage material powder materials according to a mass ratio of 1:1, adding deionized water, uniformly stirring, adding platinum nitrate and rhodium nitrate, stirring to form slurry, coating the slurry on a straight-through honeycomb ceramic carrier, and drying and roasting to finish the final preparation process. The composition of the cerium-zirconium composite oxygen storage material is 30 percent CeO 2 +60％ZrO 2 +5％La 2 O 3 +5％Y 2 O 3 The coating is dried at 150 ℃ for 2 hours, and the baking condition is 600 ℃ for 1 hour.
Emission comparative test:
based on the arrangement form of the typical aftertreatment catalyst in six stages, the catalyst prepared in the embodiment 2+the embodiment 3 and the catalyst prepared in the comparative embodiment 2+the comparative embodiment 3 are respectively combined and packaged into an exhaust assembly structure, and are installed in an exhaust system of a certain 1.5L-displacement six-light gasoline vehicle (a first-class vehicle), and the installation positions are tightly coupled. And then, respectively performing a cold start post-exhaust pollutant emission test (WLTC test) and an actual driving pollutant emission simulation test (hub simulation RDE test based on the combined electron 803 circulation working condition) in a fresh state at normal temperature required by GB18352.6-2016, and comparing the fresh state typical gaseous pollutant emissions of each scheme. The catalysts of the above schemes were then mounted on a gasoline engine bench and subjected to Standard Bench Cycle (SBC) aging according to GB18352.6-2016 for 100 hours. After aging, the catalysts of each scheme are installed in the exhaust system of the six-light gasoline car with 1.5L displacement state, and the aging state WLTC test and the hub-rotating simulation RDE test are conducted for emission comparison. The test for each protocol was performed 3 times and the average was taken as the final result. The WLTC test typical gaseous pollutant emissions and low velocity stage typical gaseous pollutant emissions are shown in tables 4 and 5, respectively, and the simulated RDE test typical gaseous pollutant emissions are shown in table 6.
Table 4 comparison of typical gaseous pollutant emissions from WLTC test
Table 5 comparison of typical gaseous pollutant emissions at low speed stage of WLTC test
From tables 4 and 5, it can be seen that thanks to the rapid light-off catalyst coating provided by the present invention, in the WLTC test typical gaseous pollutant emission test in table 4, the average emissions of the fresh and aged type I test of example 2+ example 3 are about 60% and 68% of the average emissions of comparative example 2+ comparative example 3, and the reduction in emissions is mainly due to the effective control of the pollutant emissions in the low-speed stage, as can be seen in combination with the catalytic layer light-off T50 comparison of example 1 and comparative example 1 (see table 5).
Table 6 comparative exemplary gaseous pollutant emissions from simulated RDE tests
Note that: THC (total hydrocarbons, which refers to the total amount of hydrocarbons contained in the exhaust gas) emissions are not within the RDE investigation range.
As can be seen from Table 6, the CO emissions from the fresh and aged simulated RDEs of the example 2+example 3 protocol were reduced by 43.7% and 26.7% respectively compared to the comparative example 2+comparative example 3; EXAMPLE 2+example 3 fresh and aged states of the protocol mimic the NO of RDE x The emissions were reduced by 41.5% and 35.2% respectively compared to comparative example 2+ comparative example 3, and all were within the national sixth regulation limits. Therefore, the rapid light-off catalyst coating provided by the invention can effectively reduce the emission of gaseous pollutants, and is beneficial to meeting the emission requirements of RDE tests.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and all such modifications and equivalents are intended to be encompassed in the scope of the claims of the present invention.
Claims (8)
1. The rapid light-off catalyst coating is characterized by comprising a heat conducting layer and an active component loaded on the heat conducting layer, wherein the active component comprises modified alumina loaded with noble metal, the heat conducting layer comprises black silicon carbide, the noble metal comprises rhodium and one of palladium and platinum;
the preparation method of the rapid light-off catalyst coating comprises the following steps:
(1) Adding polydextrose, polystyrene and ethoxydiglycol ether into aluminum sol to obtain mixed solution, and uniformly stirring the mixed solution to form aluminum sol mixed solution;
(2) Heating the aluminum gel mixed solution obtained in the step (1) to 80-90 o C, transferring the mixture into a microwave drying oven for microwave drying, taking out the mixture when the drying rate is more than or equal to 90%, and then placing the mixture in a muffle furnace for 700-800% o Roasting for 2-4 hours under the condition of C to obtain modified alumina;
(3) Grinding the modified alumina obtained in the step (2) into powder, then placing the powder into a powder stirrer for stirring, adding a saturated aqueous solution of 2, 6-diaminocaproic acid accounting for 5% -10% of the mass of the modified alumina powder in the stirring process, continuously stirring for 2-4 hours, then dropwise adding a noble metal precursor solution, and placing the mixture in a stirring machine for 50-60 ℃ after the dropwise adding is completed o Drying in a drying oven for 4-8 hours, continuously stirring the powder, adding a 2-hydroxysuccinic acid solution accounting for 5% -10% of the mass of the powder, and placing the obtained powder in a muffle furnace for roasting to prepare the noble metal-loaded modified alumina;
(4) Mixing the noble metal-loaded modified alumina and black silicon carbide according to a mass ratio of 1:3-10, simultaneously adding hydroxypropyl-beta-cyclodextrin, aluminum sol and deionized water to form catalyst coating slurry, and controlling the adding amount of the deionized water to enable the amount of a slurry solidified substance to be 20% -30%;
(5) Coating the catalyst coating slurry prepared in the step (4) on a cordierite honeycomb ceramic carrier, and after the coating is finished, placing the cordierite honeycomb ceramic carrier in a muffle furnace, and starting at room temperature by 1-2 o The temperature rising rate of C/min is increased to 200-230 o C, later, using 5-10 o C/mThe in heating rate is increased to 500-600 o And C, staying for 1-2 h, and finally completing the preparation of the rapid light-off catalyst coating.
2. A method of preparing a rapid light-off catalyst coating as recited in claim 1, comprising the steps of:
(1) Adding polydextrose, polystyrene and ethoxydiglycol ether into aluminum sol to obtain mixed solution, and uniformly stirring the mixed solution to form aluminum sol mixed solution;
(2) Heating the aluminum gel mixed solution obtained in the step (1) to 80-90 o C, transferring the mixture into a microwave drying oven for microwave drying, taking out the mixture when the drying rate is more than or equal to 90%, and then placing the mixture in a muffle furnace for 700-800% o Roasting for 2-4 hours under the condition of C to obtain modified alumina;
(3) Grinding the modified alumina obtained in the step (2) into powder, then placing the powder into a powder stirrer for stirring, adding a saturated aqueous solution of 2, 6-diaminocaproic acid accounting for 5% -10% of the mass of the modified alumina powder in the stirring process, continuously stirring for 2-4 hours, then dropwise adding a noble metal precursor solution, and placing the mixture in a stirring machine for 50-60 ℃ after the dropwise adding is completed o Drying in a drying oven for 4-8 hours, continuously stirring the powder, adding a 2-hydroxysuccinic acid solution accounting for 5% -10% of the mass of the powder, and placing the obtained powder in a muffle furnace for roasting to prepare the noble metal-loaded modified alumina;
(4) Mixing the noble metal-loaded modified alumina and black silicon carbide according to a mass ratio of 1:3-10, simultaneously adding hydroxypropyl-beta-cyclodextrin, aluminum sol and deionized water to form catalyst coating slurry, and controlling the adding amount of the deionized water to enable the amount of a slurry solidified substance to be 20% -30%;
(5) Coating the catalyst coating slurry prepared in the step (4) on a cordierite honeycomb ceramic carrier, and after the coating is finished, placing the cordierite honeycomb ceramic carrier in a muffle furnace, and starting at room temperature by 1-2 o The temperature rising rate of C/min is increased to 200-230 o C, later, using 5-10 o C/min heating rate is increased to 500-600 o And C, staying for 1-2 h, and finally completing the preparation of the rapid light-off catalyst coating.
3. The method for preparing the rapid light-off catalyst coating according to claim 2, wherein the addition amounts of the polydextrose, the polystyrene and the ethoxydiglycol ether in the step (1) are 2% -5%, 5% -10% and 2% -5% of the mass of the aluminum sol cured product respectively.
4. The method for preparing a rapid light-off catalyst coating according to claim 2, wherein in the step (1), the mass fraction of the aluminum sol is 30% -40%, and the pH is 3-5; the polystyrene is microsphere with a diameter of 1-2 μm.
5. The method for preparing a rapid light-off catalyst coating according to claim 2, wherein the modified alumina powder in step (3) has an average particle diameter of 5 to 8 μm; the solute in the noble metal precursor solution is one of palladium nitrate or platinum nitrate and rhodium nitrate, and the mass fraction of the solute is 3% -5%.
6. The method for preparing a rapid light-off catalyst coating according to claim 2, wherein the firing process in step (3) is: placing the powder into a muffle furnace, and sequentially placing the powder into 300-400 parts o C and 500-600 o C is roasted for 1-2 h respectively, and the temperature rising rate is controlled to be 5-10 o C/min。
7. The method for preparing the rapid light-off catalyst coating according to claim 2, wherein the addition amounts of the hydroxypropyl-beta-cyclodextrin and the aluminum sol in the step (4) are respectively 10% -15% and 5% -10% of the mass of black silicon carbide, and the average particle size of the black silicon carbide is 5-10 μm; the mass fraction of the aluminum sol is 20% -30%, and the pH value is 3-5.
8. The method of preparing a rapid light-off catalyst coating according to claim 2, wherein the cordierite honeycomb ceramic support in step (5) is of a straight-through or wall-flow construction.
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