CN114931962A - Quick ignition catalyst coating and preparation method thereof - Google Patents
Quick ignition catalyst coating and preparation method thereof Download PDFInfo
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- 238000000576 coating method Methods 0.000 title claims abstract description 98
- 239000011248 coating agent Substances 0.000 title claims abstract description 92
- 239000003054 catalyst Substances 0.000 title claims abstract description 88
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- 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 67
- 238000000034 method Methods 0.000 claims abstract description 25
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 25
- 239000000919 ceramic Substances 0.000 claims abstract description 24
- 229910021418 black silicon Inorganic materials 0.000 claims abstract description 17
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000000843 powder Substances 0.000 claims description 45
- 239000011259 mixed solution Substances 0.000 claims description 31
- 238000003756 stirring Methods 0.000 claims description 31
- 238000001035 drying Methods 0.000 claims description 29
- 238000010438 heat treatment Methods 0.000 claims description 28
- 229910052782 aluminium Inorganic materials 0.000 claims description 21
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 21
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 20
- 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 20
- 239000002002 slurry Substances 0.000 claims description 17
- 239000004793 Polystyrene Substances 0.000 claims description 15
- 229920002223 polystyrene Polymers 0.000 claims description 15
- 239000000243 solution Substances 0.000 claims description 14
- 239000008367 deionised water Substances 0.000 claims description 13
- 229910021641 deionized water Inorganic materials 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 229910052878 cordierite Inorganic materials 0.000 claims description 12
- 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 12
- 229920001100 Polydextrose Polymers 0.000 claims description 10
- XXJWXESWEXIICW-UHFFFAOYSA-N diethylene glycol monoethyl ether Chemical compound CCOCCOCCO XXJWXESWEXIICW-UHFFFAOYSA-N 0.000 claims description 10
- BJEPYKJPYRNKOW-UHFFFAOYSA-N malic acid Chemical compound OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 10
- 229940035035 polydextrose Drugs 0.000 claims description 10
- 235000013856 polydextrose Nutrition 0.000 claims description 10
- 239000001259 polydextrose Substances 0.000 claims description 10
- 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 10
- 238000002156 mixing Methods 0.000 claims description 8
- 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
- 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
- 239000007864 aqueous solution Substances 0.000 claims description 5
- 238000000227 grinding Methods 0.000 claims description 5
- KDXKERNSBIXSRK-UHFFFAOYSA-N lysine Chemical compound NCCCCC(N)C(O)=O KDXKERNSBIXSRK-UHFFFAOYSA-N 0.000 claims description 5
- 235000011090 malic acid Nutrition 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 229920006395 saturated elastomer Polymers 0.000 claims description 5
- 239000006255 coating slurry Substances 0.000 claims description 4
- 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
- 239000010970 precious metal Substances 0.000 claims description 4
- 239000012694 precious metal precursor Substances 0.000 claims description 3
- 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
- 238000001354 calcination Methods 0.000 claims 1
- 239000003292 glue Substances 0.000 claims 1
- 239000007788 liquid Substances 0.000 claims 1
- 239000002243 precursor Substances 0.000 claims 1
- 239000000758 substrate Substances 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
- 230000032683 aging Effects 0.000 abstract description 16
- 230000000694 effects Effects 0.000 abstract description 4
- 239000006185 dispersion Substances 0.000 abstract description 3
- 238000011068 loading method Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 27
- 239000004005 microsphere Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 7
- 239000001301 oxygen Substances 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 6
- 239000002131 composite material Substances 0.000 description 6
- 239000011148 porous material Substances 0.000 description 6
- 239000011232 storage material Substances 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 4
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 4
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 239000003981 vehicle Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 210000002421 cell wall Anatomy 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 238000003795 desorption Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
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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 quick ignition catalyst coating and a preparation method thereof. The quick ignition 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 quick conduction of tail gas heat in the coating, achieves the effect of quick temperature rise, and can improve the heat aging resistance of the coating; the active component prepared by combining the modified alumina and the noble metal dispersion loading process can effectively improve the utilization rate of the noble metal and improve the quick ignition performance of the catalyst. The fast ignition catalyst coating can be coated on a straight-through or wall-flow honeycomb ceramic carrier, and can effectively reduce the ignition temperature and the emission of typical gaseous pollutants in the national six-regulation test.
Description
Technical Field
The invention belongs to the technical field of catalyst preparation, and particularly relates to a quick ignition catalyst coating and a preparation method thereof.
Background
In the type I test (WLTC test) of the emission test of national six light vehicle tail gases, HC, CO and NO at low speed stage x Pollutant emissions typically account for over 75%, 60%, and 50% of the total emissions over the test cycle, respectively. Since the low speed stage comprises a cold start process, during which the temperature of the aftertreatment catalyst gradually rises from ambient to the desired light-off temperature of the catalyst, conventional aftertreatment catalysts require a temperature of at least 300 ℃ to light off. Before the temperature of the catalyst reaches the light-off temperature, most of the exhaust pollutants are directly discharged from the exhaust pipe, so that the pollutant discharge amount ratio in the low-speed stage is remarkably increased. Meanwhile, the emission control of the national type II test (actual driving pollutant emission test, RDE test) is about to be comprehensively carried out in 2023, 7 months and 1 day. Compared with WLTC circulation, the RDE test has more variation factors, the corresponding low-speed stage and the cold start working condition are worse, and higher pollutant emission is providedAnd (5) controlling the requirements.
In order to solve the above-described problems, a method (close-coupled arrangement) of installing an aftertreatment catalyst near the outlet of the exhaust manifold of the engine is generally adopted to rapidly warm up the catalyst. However, due to the influence of the catalyst coating material, the temperature conducted to the catalytically active material is delayed, so that the catalytic material cannot reach the ignition temperature of pollutant conversion in time, and cold start emission is increased, so that rapid ignition is realized by improving the catalyst coating material, and the method is an important research direction for improving the pollutant conversion in the cold start stage and reducing WLTC and RDE test emission.
Disclosure of Invention
The invention aims to overcome the defect that the conversion efficiency of gaseous pollutants is low in a cold start stage in the using process of a post-treatment catalyst coating in the prior art, and provides a quick ignition catalyst coating and a preparation method thereof. The catalyst coating adopts black silicon carbide with high thermal conductivity, low heat capacity and high thermal stability as a heat conduction layer, can realize the rapid conduction of tail gas heat in the coating, achieves the effect of rapid temperature rise, and can improve the overall heat aging resistance of the coating; in addition, a noble metal dispersion loading process is applied based on an internal porous system, so that the utilization rate of the active component of the noble metal is effectively improved, and the quick ignition performance of the catalyst is further improved.
In order to achieve the technical purpose, the embodiment of the invention adopts the technical scheme that:
in a first aspect, embodiments of the present invention provide a rapid light-off catalyst coating, the catalyst coating includes a heat conducting layer and an active component supported on the heat conducting layer, the active component includes modified alumina supporting a noble metal, and the heat conducting layer includes black silicon carbide.
Further, the noble metal comprises rhodium and one of palladium and platinum.
In a second aspect, embodiments of the present invention provide a method for preparing a fast light-off catalyst coating, including the following steps:
(1) adding polydextrose, polystyrene and ethoxy diglycol ether into the alumina sol to obtain a mixed solution, and then uniformly stirring the mixed solution to form an alumina sol mixed solution;
(2) heating the alumina gel mixed solution obtained in the step (1) to 80-90 ℃, then transferring the alumina gel mixed solution to a microwave drying oven for microwave drying, taking out the alumina gel mixed solution when the drying rate is more than or equal to 90%, and then roasting the alumina gel mixed solution in a muffle furnace at 700-800 ℃ for 2-4 h 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 2, 6-diaminocaproic acid saturated aqueous solution accounting for 5-10% of the mass of the modified alumina powder during stirring, continuously stirring for 2-4 h, then dropwise adding a precious metal precursor solution, placing the powder in a 50-60 ℃ drying oven for drying for 4-8 h after dropwise adding is completed, then continuing 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 obtain the precious metal-loaded modified alumina;
(4) mixing noble metal-loaded modified alumina and black silicon carbide according to the mass ratio of 1: 3-10, simultaneously adding hydroxypropyl-beta-cyclodextrin, alumina sol and deionized water to form catalyst coating slurry, and controlling the addition of the deionized water to enable the content of solidified slurry 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 ℃ from room temperature at a heating rate of 1-2 ℃/min, then heating to 500-600 ℃ at a heating rate of 5-10 ℃/min, and staying for 1-2 hours to finally complete the preparation of the fast ignition catalyst coating.
Further, the adding amount of the polydextrose, the polystyrene and the ethoxy diglycol ether in the step (1) is respectively 2-5%, 5-10% and 2-5% of the mass of the alumina sol condensate.
Further, the mass fraction of the aluminum sol in the step (1) is 30-40%, and the pH value is 3-5; the polystyrene is microspherical and has a diameter of 1-2 μm.
Further, the average particle size of the modified alumina powder in the step (3) is 5-8 μm; the solute in the precious 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: and placing the powder into a muffle furnace, and sequentially roasting at 300-400 ℃ and 500-600 ℃ for 1-2 hours respectively, wherein 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 10-15% and 5-10% of the mass of the black silicon carbide respectively, 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.
Further, the cordierite honeycomb ceramic carrier in the step (5) is of a flow-through or wall-flow structure.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
the catalyst coating adopts black silicon carbide with high heat conductivity, low heat capacity and high thermal stability as a heat conduction layer, can realize the quick conduction of the heat of tail gas in the coating, achieves the effect of quick temperature rise, can improve the integral heat aging resistance of the coating, and simultaneously carries out modification treatment on alumina to construct an internal porous system so as to reduce the internal diffusion resistance of gas; in addition, a noble metal dispersion loading process is applied based on an internal porous system, so that the utilization rate of the active components of the noble metal is effectively improved, and the rapid 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 is further described in detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A quick ignition catalyst is composed of a straight-through honeycomb ceramic carrier and a quick ignition catalyst coated on said carrierA fast light-off catalyst coating. The carrier specification was Φ 118.4 × 127mm, cell density 600cpsi, cell wall thickness 4mil, and volume 1.4L. The coating amount of the coating is 100g/L, the inner coating height is 100 percent, and the content of noble metal is Pd:40g/ft 3 ，Rh：5g/ft 3 。
The preparation method of the quick ignition catalyst coating comprises the following steps:
(1) adding polydextrose, polystyrene microspheres and ethoxy diglycol ether into the alumina sol to form a mixed solution, and then uniformly stirring the mixed solution to form an alumina sol mixed solution;
wherein the addition amounts of the polydextrose, the polystyrene microspheres and the ethoxy diglycol ether are respectively 5 percent, 10 percent and 5 percent of the mass of the cured aluminum sol; the mass fraction of the aluminum sol is 40 percent, and the pH value is 3; the diameter of the polystyrene microsphere is 2 mu m;
(2) heating the alumina gel mixed solution obtained in the step (1) to 80 ℃, then transferring the alumina gel mixed solution to a microwave drying oven for microwave drying, taking out the alumina gel mixed solution when the drying rate is more than or equal to 90%, and then roasting the alumina gel mixed solution 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 size of 8 microns, 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 obtained mixture into a drying oven for drying at 50 ℃ for 8 hours after the dropwise adding is completed, then continuing to stir the powder, adding a 2-hydroxysuccinic acid solution with the mass of 10% of the powder, finally placing the obtained mixture into a muffle furnace for respectively roasting at 300 ℃ and 500 ℃ for 2 hours in sequence, and controlling the heating rate at 5 ℃/min to prepare the modified alumina loaded with noble metal;
(4) mixing noble metal-loaded modified alumina and black silicon carbide with the average particle size 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 percent, and the pH value 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 the deionized water is controlled to ensure that the solidified mass of the slurry is 30%;
(5) and (4) 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 ℃ from room temperature at a heating rate of 1 ℃/min, then heating to 500 ℃ at a heating rate of 5 ℃/min, and staying for 2h to finally finish the preparation of the rapid light-off catalyst coating.
Comparative example 1
The support dimensions, coating application, internal coating height and noble metal content used in this example were the same as in example 1.
Except 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: the method comprises the steps of mixing commercial aluminum oxide powder and cerium-zirconium composite oxygen storage material powder according to the 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 complete the final preparation process. The cerium-zirconium composite oxygen storage material comprises 30 percent of CeO 2 +60％ZrO 2 +5％La 2 O 3 +5％Y 2 O 3 The drying condition of the coating is 150 ℃ for 2h, and the roasting condition is 500 ℃ for 2 h.
Comparative test of specific surface area and pore volume of coated aluminum oxide material:
the modified alumina prepared in step (2) of example 1 and the commercial alumina of comparative example 1 were subjected to specific surface area and pore volume tests in a specific surface area tester, and the specific surface area and pore volume of the material were calculated based on BET and BJH model desorption curves, respectively, and the results are shown in table 1:
TABLE 1 comparison of specific surface area and pore volume of alumina materials used in different examples
| Comparing items | Example 1 | Comparative example 1 |
| Specific surface area (m) 2 /g) | 155 | 152 |
| Pore volume (cm) 3 /g) | 0.68 | 0.51 |
As shown in Table 1, the modified alumina prepared in example 1 has a pore volume about 33.3% higher than that of comparative example 1 based on the similar specific surface area, which indicates that the modified alumina prepared in example 1 has a good effect of constructing an internal porous system and contributes to the internal diffusion flow of the reaction gas.
Ignition temperature comparative test:
the catalysts prepared in example 1 and comparative example 1 are respectively packaged and installed on a 1.5L displacement gasoline engine bench, and a fresh-state ignition temperature test is carried out based on the standard requirements of HJ/T331-2006 catalytic converter for gasoline vehicles for technical requirements of environmental protection products. And then carrying out standard rack cycle (SBC) aging according to GB18352.6-2016 limit value of emission of pollutants for light automobiles and the standard requirement of a measurement method (sixth stage of China), wherein the aging time is 100 h. And after the aging is finished, carrying out an aging state ignition temperature test according to the method, carrying out 3 times of ignition temperature tests of each scheme, and taking an average value as a final result. Light-off temperature (T50) is compared as in table 2:
TABLE 2 catalyst light-off T50 comparison of example 1 and comparative example 1
As can be seen from table 2, example 1 using the fast light-off catalyst coating provided by the present invention shows an average decrease in T50 of about 45 ℃ and 70 ℃ compared to the fresh and aged catalysts of comparative example 1 using the conventional coating, respectively, and shows superior light-off and aging resistance. Meanwhile, the typical gaseous pollutant ignition T50 of the embodiment 1 can be reduced to below 300 ℃, and is beneficial to pollutant emission control in a low-speed stage of a WLTC cycle.
Example 2
A fast ignition catalyst comprises a straight-through honeycomb ceramic carrier and a catalyst coating coated on the carrier, wherein the catalyst coating comprises a fast ignition catalyst coating and a conventional three-way catalyst coating. The specification of the carrier is phi 132.1 multiplied by 101.6mm, the density of the holes is 750cpsi, the wall thickness of the hole channel is 2mil, and the volume is 1.392L; one end of the honeycomb ceramic carrier is an air inlet end and the other end of the honeycomb ceramic carrier is an air outlet end in the air inlet and outlet direction, and the length ratio of the air inlet end to the air outlet end is 1: 1. The fast ignition catalyst coating is coated on the air inlet end of the carrier, the coating amount is 100g/L, and the content of the noble metal is Pd:60g/ft 3 ，Rh：5g/ft 3 (ii) a The conventional three-way catalyst coating is coated on the air outlet end of the carrier, the coating amount is 150g/L, and the content of noble metal is Pd: 20g/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 microspheres and ethoxy diglycol ether into the alumina sol to form a mixed solution, and then uniformly stirring the mixed solution to form an alumina sol mixed solution;
wherein the addition amounts of the polydextrose, the polystyrene microspheres and the ethoxy diglycol ether are respectively 3 percent, 8 percent and 3 percent of the mass of the cured alumina sol; the mass fraction of the aluminum sol is 35 percent, and the pH value is 4; the diameter of the polystyrene microsphere is 2 μm;
(2) heating the alumina gel mixed solution obtained in the step (1) to 90 ℃, then transferring the alumina gel mixed solution to a microwave drying oven for microwave drying, taking out the alumina gel mixed solution when the drying rate is more than or equal to 90%, and then roasting the alumina gel mixed solution 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 size of 7 microns, then placing the powder into a powder stirrer for stirring, adding 8% by mass of 2, 6-diaminocaproic acid saturated aqueous solution relative to the modified alumina powder during stirring, continuously stirring for 3 hours, then dropwise adding 4% by mass of palladium nitrate and rhodium nitrate, placing the alumina powder in a drying oven for drying at 60 ℃ for 4 hours after dropwise adding is completed, then continuing to stir the powder, adding 8% by mass of 2-hydroxysuccinic acid solution relative to the powder, finally placing the powder in a muffle furnace for roasting at 350 ℃ and 550 ℃ for 2 hours respectively, and controlling the heating rate at 7 ℃/min to prepare the modified alumina loaded with noble metal;
(4) mixing noble metal-loaded modified alumina and black silicon carbide with the average particle size 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 percent, and the pH value is 4; the adding amount of the hydroxypropyl-beta-cyclodextrin and the aluminum sol is 12 percent and 7 percent of the mass of the black silicon carbide respectively, and the adding amount of the deionized water is controlled to ensure that the solidified mass of the slurry is 25 percent;
(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 ℃ from room temperature at a heating rate of 2 ℃/min, then heating to 600 ℃ at a heating rate of 10 ℃/min, and staying for 1h to finally finish the preparation of the quick ignition catalyst coating.
Comparative example 2
The support dimensions, inlet end to outlet end length ratios, coating application and precious metal content used in this example were the same as in example 2.
Except that the coatings used at the air inlet end and the air outlet end of the embodiment are both conventional three-way catalyst coatings, and the preparation method of the coatings adopts a conventional process: the method comprises the steps of mixing commercial aluminum oxide and cerium-zirconium composite oxygen storage material powder materials according to the 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 complete the final preparation process of the catalyst coating. The cerium-zirconium composite oxygen storage material comprises 30 percent of CeO 2 +60％ZrO 2 +5％La 2 O 3 +5％Y 2 O 3 The drying condition of the coating is 150 ℃ for 2h, and the roasting condition is 600 ℃ for 1 h.
Ignition temperature comparative test:
the catalysts prepared in the example 2 and the comparative example 2 are respectively packaged and installed on a 1.5L displacement gasoline engine bench, and a fresh ignition temperature test is carried out based on the standard requirements of HJ/T331-2006 catalytic converter for gasoline vehicles for technical requirements of environmental protection products. And then carrying out standard rack cycle (SBC) aging according to GB18352.6-2016 limit value of emission of pollutants for light automobiles and the standard requirement of a measurement method (sixth stage of China), wherein the aging time is 100 h. And after the aging is finished, carrying out an aging state ignition temperature test according to the method, carrying out 3 times of ignition temperature tests of each scheme, and taking an average value as a final result. Light-off temperature (T50) versus, for example, table 3:
TABLE 3 light-off of catalyst prepared in example 2 and comparative example 2T 50 comparative
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 front and rear subareas, and the catalyst still can show better fresh and aged light-off performance. Therefore, the rapid ignition catalyst coating provided by the invention can be combined with a conventional three-way catalyst coating for use, and the three-way performance of oxygen storage and release can be ensured on the premise of ensuring the ignition performance.
Example 3
A rapid light-off catalyst comprises a wall-flow honeycomb ceramic carrier and a catalyst coating coated on the carrier, wherein the catalyst coating comprises 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 hole density is 300cpsi, the wall thickness of the hole channel is 8mil, the porosity is 63 percent, the average hole diameter is 17.5 mu m, the volume is 1.74L, one end of the honeycomb ceramic carrier is an air inlet end and the other end is an air outlet end according to the air inlet and outlet directions, and the air inlet end is connected with the honeycomb ceramic carrier in seriesThe length ratio of the end to the air outlet end is 1: 1. The fast ignition catalyst coating is coated on the air inlet end of the carrier, the coating amount is 100g/L, and the content of noble metal is 5g/ft of Pt 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 content of noble metal 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 the comparative example 1;
the preparation method of the fast ignition catalyst coating comprises the following steps:
(1) adding polydextrose, polystyrene microspheres and ethoxy diglycol ether into the alumina sol to form a mixed solution, and then uniformly stirring the mixed solution to form an alumina sol mixed solution;
wherein the addition amounts of the polydextrose, the polystyrene microspheres and the ethoxy diglycol ether are respectively 2 percent, 5 percent and 2 percent of the mass of the cured aluminum sol; the mass fraction of the aluminum sol is 30 percent, and the pH value is 5; the polystyrene microspheres had a diameter of 1 μm.
(2) Heating the alumina gel mixed solution obtained in the step (1) to 80 ℃, then transferring the alumina gel mixed solution to a microwave drying oven for microwave drying, taking out the alumina gel mixed solution when the drying rate is more than or equal to 90%, and then roasting the alumina gel mixed solution 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 size of 5 microns, then placing the powder into a powder stirrer for stirring, adding a saturated aqueous solution of 2, 6-diaminocaproic acid accounting for 5% of the mass of the modified alumina powder during stirring, continuously stirring for 2 hours, dropwise adding platinum nitrate and rhodium nitrate with the mass fraction of 3%, placing the powder into an oven for drying at 60 ℃ for 4 hours after dropwise adding, then continuing to stir the powder, adding a 2-hydroxysuccinic acid solution accounting for 5% of the mass of the powder, finally placing the powder into a muffle furnace for roasting at 400 ℃ and 600 ℃ for 1 hour respectively in sequence, and controlling the heating rate at 10 ℃/min to prepare the modified alumina loaded with noble metal;
(4) mixing noble metal-loaded modified alumina and black silicon carbide with the average particle size of 5 mu m according to the 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 percent, and the pH value is 5; the addition amounts of the hydroxypropyl-beta-cyclodextrin and the aluminum sol are respectively 10% and 5% of the mass of the black silicon carbide, and the addition amount of the deionized water is controlled to enable the solidified mass of the slurry to be 20%;
(5) and (4) 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 ℃ from room temperature at a heating rate of 2 ℃/min, then heating to 600 ℃ at a heating rate of 10 ℃/min, and staying for 1h to finally finish the preparation of the rapid ignition catalyst coating.
Comparative example 3
The support dimensions, inlet end to outlet end length ratios, coating application and precious metal content used in this example were the same as in example 3.
Except that the coatings used at the air inlet end and the air outlet end of the embodiment are both conventional three-way catalyst coatings, and the preparation method of the coatings adopts a conventional process: the method comprises the steps of mixing commercial aluminum oxide and cerium-zirconium composite oxygen storage material powder materials according to the 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 complete the final preparation process. The cerium-zirconium composite oxygen storage material comprises 30 percent of CeO 2 +60％ZrO 2 +5％La 2 O 3 +5％Y 2 O 3 The drying condition of the coating is 150 ℃ for 2h, and the roasting condition is 600 ℃ for 1 h.
Emission comparative test:
based on the arrangement form of the national six-stage typical post-treatment catalyst, the catalyst prepared in the embodiment 2+ the embodiment 3 and the catalyst prepared in the comparative example 2+ the comparative example 3 are respectively combined and packaged into an exhaust assembly structure, and the exhaust assembly structure is installed in an exhaust system of a certain 1.5L displacement national six light gasoline vehicle (first type vehicle), and the installation positions are tightly coupled. And then respectively carrying out a fresh-state cold start exhaust pollutant emission test (WLTC test) and a simulated actual driving pollutant emission test (hub simulation RDE test based on the circulation condition of the combined electronics 803) required by GB18352.6-2016 (standard test for emissions of fresh-state typical gaseous pollutants) in each case. And then, the catalyst in the scheme is arranged on a gasoline engine bench, and Standard Bench Cycle (SBC) aging is carried out according to the GB18352.6-2016 requirement, wherein the aging time is 100 h. After the aging is finished, the catalyst of each scheme is installed in the exhaust system of the national six-light gasoline vehicle with the 1.5L displacement, and the emission comparison of an aging state WLTC test and a hub rotation simulation RDE test is carried out. The experiments for each protocol were performed 3 times and the average was taken as the final result. The results of comparison of typical gaseous pollutant emission in WLTC test and low-speed stage are shown in tables 4 and 5, respectively, and the results of comparison of typical gaseous pollutant emission in simulated RDE test 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 the low-speed stage of WLTC testing
From tables 4 and 5, it can be seen that, thanks to the fast 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 type I test fresh and aged typical gaseous pollutants of example 2+ example 3 are about 60% and 68% of the average emissions of comparative example 2+ comparative example 3, and in combination with the catalytic layer light-off T50 comparison of example 1 and comparative example 1, it can be seen that the reduction in emissions is mainly due to the effective control of pollutant emissions in the low-speed stage (see table 5).
Table 6 comparison of typical gaseous pollutant emissions from simulated RDE tests
Note: THC (total hydrocarbons, which refers to the total amount of hydrocarbons contained in the emitted gas) emissions are not within the RDE range.
As can be seen from Table 6, the fresh and aged simulated RDEs of example 2+ example 3 had a 43.7% and 26.7% reduction in CO emissions, respectively, over comparative example 2+ comparative example 3; example 2+ fresh and aged state of the protocol of example 3 simulating the NO of the RDE x The emission is reduced by 41.5 percent and 35.2 percent respectively compared with the comparative example 2 and the comparative example 3, and the emission is within the limit of the national six-regulation. Therefore, the rapid ignition catalyst coating provided by the invention can effectively reduce the emission of gaseous pollutants, and is beneficial to meeting the emission requirement of an RDE test.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, 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 or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (9)
1. The quick ignition catalyst coating is characterized by comprising a heat conduction layer and an active component loaded on the heat conduction layer, wherein the active component contains modified aluminum oxide loaded with noble metal, and the heat conduction layer comprises black silicon carbide.
2. The fast light-off catalyst coating of claim 1 wherein the precious metal comprises rhodium and further comprises one of palladium and platinum.
3. The method of preparing a fast light-off catalyst coating as recited in claim 1, comprising the steps of:
(1) adding polydextrose, polystyrene and ethoxy diglycol ether into the alumina sol to obtain a mixed solution, and then uniformly stirring the mixed solution to form an alumina sol mixed solution;
(2) heating the aluminum glue mixed liquid obtained in the step (1) to 80-90 DEG o C, then transferring the mixture to a microwave drying box for microwave drying, taking the mixture out when the drying rate is more than or equal to 90%, and then putting the mixture into a muffle furnace for 700-800% o Roasting for 2-4 h under C to obtain the modifiedAlumina;
(3) grinding the modified alumina obtained in the step (2) into powder, placing the powder into a powder stirrer for stirring, adding a 2, 6-diaminocaproic acid saturated aqueous solution accounting for 5-10% of the mass of the modified alumina powder in the stirring process, continuously stirring for 2-4 h, dropwise adding a noble metal precursor solution, and placing the solution into a stirrer for 50-60 h after dropwise adding o Drying in an oven for 4-8 h, then continuously stirring the powder, adding a 2-hydroxysuccinic acid solution with the mass being 5-10% of that of the powder, and roasting the obtained powder in a muffle furnace to prepare modified alumina loaded with noble metal;
(4) mixing noble metal-loaded modified alumina and black silicon carbide according to the mass ratio of 1: 3-10, simultaneously adding hydroxypropyl-beta-cyclodextrin, alumina sol and deionized water to form catalyst coating slurry, and controlling the addition of the deionized water to enable the solidified mass of the slurry to be 20% -30%;
(5) 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, and starting from room temperature by 1-2 o The temperature rises to 200-230 ℃ at a temperature rise rate of C/min o C, then 5 to 10 o Heating to 500-600 ℃ at a C/min heating rate o And C, staying for 1-2 hours, and finally completing the preparation of the fast ignition catalyst coating.
4. The method for preparing the fast light-off catalyst coating according to claim 3, wherein the polydextrose, the polystyrene and the ethoxydiglycol ether are added in the step (1) in an amount of 2% to 5%, 5% to 10% and 2% to 5% by mass, respectively, based on the mass of the cured alumina sol.
5. The preparation method of the fast light-off catalyst coating according to claim 3, wherein the mass fraction of the aluminum sol in the step (1) is 30-40%, and the pH is 3-5; the polystyrene is microspherical and has a diameter of 1-2 μm.
6. The method for preparing the rapid light-off catalyst coating according to claim 3, wherein the average particle size of the modified alumina powder in the step (3) is 5 to 8 μm; the solute in the precious metal precursor solution is one of palladium nitrate or platinum nitrate and rhodium nitrate, and the mass fraction of the solute is 3% -5%.
7. The method for preparing a rapid light-off catalyst coating according to claim 3, wherein the calcination process in the step (3) is: placing the powder into a muffle furnace in sequence at 300-400 DEG o C and 500-600 o Roasting C for 1-2 hours respectively, and controlling the heating rate to be 5-10 o C/min。
8. The preparation method of the fast light-off catalyst coating according to claim 3, wherein the addition amount of the hydroxypropyl-beta-cyclodextrin and the aluminum sol in the step (4) is 10% -15% and 5% -10% of the mass of the black silicon carbide respectively, 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.
9. The method of producing a rapid light-off catalyst coating according to claim 3, wherein the cordierite honeycomb ceramic substrate in the step (5) has a flow-through or wall-flow structure.
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