CN113578307B - Efficient vehicle natural gas catalyst and preparation method thereof - Google Patents

Efficient vehicle natural gas catalyst and preparation method thereof Download PDF

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CN113578307B
CN113578307B CN202110913708.6A CN202110913708A CN113578307B CN 113578307 B CN113578307 B CN 113578307B CN 202110913708 A CN202110913708 A CN 202110913708A CN 113578307 B CN113578307 B CN 113578307B
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coating
catalyst
slurry
stirring
composite oxide
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CN113578307A (en
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承晓华
王卫东
孙亮
李小明
王德冰
薛大为
许刚
李晨鼎
潘其建
王俊
邱祎源
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Wuxi Weifu Environmental Protection Catalyst Co Ltd
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Wuxi Weifu Environmental Protection Catalyst Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0244—Coatings comprising several layers
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to a high-efficiency natural gas catalyst for a vehicle and a preparation method thereof. The invention relates to a high-efficiency natural gas catalyst for a vehicle, which comprises a carrier and a coating material coated on the carrier, wherein the coating material comprises alumina and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, noble metal Ir and one or more of Pt, pd and Rh are loaded in the coating material, a diluted Ir-containing solution is impregnated on an active alumina material in an equal volume, and the Ir-containing solution is fixed in a roasting manner, so that the ageing resistance of Ir in the catalyst is greatly improved, the problem that the ageing performance is poor is effectively solved, the treatment capacity of the ageing catalyst for nitrogen oxides is remarkably improved, the catalytic capacity of the catalyst for methane is partially improved, and the preparation cost of the catalyst can be greatly reduced by partially replacing noble metal Rh with noble metal Ir.

Description

Efficient vehicle natural gas catalyst and preparation method thereof
Technical Field
The invention belongs to the technical field of catalyst preparation, and particularly relates to a high-efficiency natural gas catalyst for a vehicle and a preparation method thereof.
Background
Along with the continuous development of global science and technology, the use of fossil fuel has been related to the aspects of human life, people in ancient times travel by riding on horses, and people now travel by riding on cars, boats and planes, so that the real one-day thousand-life is achieved, and pollution caused by fossil fuel is an unavoidable environmental problem while enjoying the convenience.
The catalytic cleaner device capable of carrying out catalytic purification on exhaust pollutants is additionally arranged at the exhaust outlet of the motor vehicle, so that the content of pollutant gas discharged in tail gas of the motor vehicle can be effectively reduced, and the air can be effectively purified and the environment can be protected.
Compared with gasoline and diesel engines, the pollutant gas generated by gas engines, namely natural gas engines, mainly comprises methane, nitrogen oxides and carbon monoxide, but the total emission amount of harmful substances is far lower than that of gasoline engines and diesel engines. At present, with the continuous tightening of national regulations, the limit value of pollutants is continuously reduced, the requirements on the catalyst are also higher and higher, and under the same cost, how to realize that the catalyst has higher pollutant treatment capability is already the direction of continuous progress of various catalyst manufacturers.
Since 2018, the cost price of noble metals Pd and Rh has increased to different degrees, wherein the price fluctuation of noble metals Rh has exceeded 1000%, which brings great cost pressure to various manufacturers. Ir, as a transition metal, also has a high conversion efficiency for nitrogen oxides, but the properties after aging are greatly reduced.
Disclosure of Invention
Aiming at the problem that the performance of the noble metal Ir is obviously reduced after aging, the noble metal Ir is fixed first and then conventional pulping and coating are carried out, so that the aging resistance of the Ir-containing catalyst can be effectively improved; in addition, the noble metal Ir with relatively low price is introduced into the upper coating of the catalyst, so that the noble metal Rh can be partially replaced, and the preparation cost of the catalyst is greatly reduced.
In order to solve the defects in the prior art, the invention adopts the following technical scheme: the high-efficiency natural gas catalyst for the vehicle comprises a carrier and a coating material coated on the carrier, wherein the coating material comprises aluminum oxide and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, and noble metal Ir and one or more of Pt, pd and Rh are loaded in the coating material.
Further, the coating material comprises an upper coating layer and a lower coating layer, the coating amount of the lower coating layer is 50-200 g/L, and the coating amount of the upper coating layer is 30-150 g/L.
Further, the coating material comprises an upper layer, a middle layer and a lower layer, the coating amount of the lower coating is 50-150 g/L, the coating amount of the middle coating is 10-100 g/L, and the coating amount of the upper coating is 20-100 g/L.
Further, the Rh and Ir are distributed on the upper coating; the Pd is distributed in the lower coating and/or the middle coating; the Pt is distributed on the middle coating and/or the upper coating, wherein the total loading amount of Rh and Ir is 0.02-1 g/L, and the mass ratio of Rh to Ir is 1:9-9:1; pd loading is 0.2-5 g/L; the loading of Pt is 0-3.5 g/L.
Further, the carrier is a cordierite honeycomb ceramic carrier, the mesh number is 300-600 mesh, and the wall thickness is 3-6 mils.
Further, the preparation method of the efficient natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: preparing primary slurry of alumina and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, placing the primary slurry in a specified container, stirring, adding soluble solution containing noble metal Pd, stirring for 0.5-2 h, tackifying, continuing stirring for 6-20 h to obtain lower coating slurry of the catalyst, coating the lower coating slurry on a catalyst carrier, and drying and roasting to obtain a semi-finished catalyst;
(2) And (3) coating an upper coating: measuring the water absorption value of aluminum oxide per unit mass, recording the water absorption value as a g/g, weighing b g active aluminum oxide material, diluting Ir-containing soluble solution with deionized water to a mass of a. b g, immersing the diluted Ir-containing soluble solution in the active aluminum oxide material in an equal volume, drying and roasting, uniformly mixing with Ce-Zr composite oxide again, preparing into slurry, adding rhodium nitrate or rhodium nitrate and platinum nitrate solution into the slurry to prepare the catalyst upper coating slurry, coating the upper coating slurry on the semi-finished catalyst prepared in the step (1), and drying and roasting to finally obtain the finished catalyst.
Further, the preparation method of the efficient natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: preparing primary slurry of alumina and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, placing the primary slurry in a designated container, stirring, adding soluble solution containing noble metal Pd, stirring for 0.5-2 h, tackifying, continuing stirring for 6-20 h to obtain catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, and drying and roasting to obtain a first semi-finished catalyst;
(2) And (3) intermediate coating: preparing primary slurry of alumina and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, placing the primary slurry in a designated container, stirring, adding soluble solution containing noble metal Pd and/or noble metal Pt, stirring for 0.5-2 h, tackifying and continuing stirring for 6-20 h to obtain catalyst intermediate coating slurry, coating the catalyst intermediate coating slurry on the first semi-finished catalyst prepared in the step (1), and drying and roasting to obtain a second semi-finished catalyst;
(3) And (3) coating an upper coating: measuring the water absorption value of the active alumina component per unit mass, recording the water absorption value as a g/g, weighing b g active alumina material, diluting the Ir-containing soluble solution with deionized water to a mass of a x b g, immersing the diluted Ir-containing soluble solution in the active alumina material in an equal volume, drying and roasting, uniformly mixing with Ce-Zr composite oxide again to prepare slurry, adding rhodium nitrate or rhodium nitrate and platinum nitrate solution to prepare coating slurry of the upper coating of the catalyst, coating the coating slurry on the second semi-finished catalyst prepared in the step (2), and drying and roasting to finally obtain the finished catalyst.
Further, the alumina is gamma-alumina with specific surface area of 150-180 m 2 /g。
Further, the Ce-Zr composite oxide is a cerium-zirconium solid solution, wherein the Ce-Zr composite oxide comprises 20-60% of cerium oxide by mass.
Further, when the coating is carried out, a negative pressure type coating special machine is adopted to coat the catalyst carrier, the air pressure of the negative pressure type coating special machine is-20 to-80 kPa, and each layer of coating is dried and roasted after finishing; the conditions of drying and roasting are as follows: drying at 150-180 deg.c for 3-4 hr and roasting at 500-650 deg.c for 2-3 hr.
Compared with the prior art, the invention has the following advantages:
according to the invention, the noble metal Ir with relatively low price is introduced into the upper coating of the catalyst, so that the noble metal Rh can be partially replaced, and the preparation cost of the catalyst is greatly reduced; in addition, a novel noble metal Ir loading mode is adopted in the preparation of the catalyst, the noble metal Ir is impregnated on the active alumina carrier in an equal volume mode, and is fixed in a roasting mode, so that the ageing resistance of the Ir in the catalyst is greatly improved, and the problem of poor ageing performance of the catalyst is effectively solved.
Detailed Description
The technical scheme of the invention will be further described with reference to specific examples.
Comparative example 1
The preparation method of the natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: 2000g of Ce-Zr composite oxide containing 3% Pr and 4% La and Al with the solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide andAl 2 O 3 placing the catalyst into a beaker with the mass ratio of 1:1, stirring, slowly dripping a palladium nitrate solution into the slurry, stirring for 1h, tackifying and stirring for 10h to obtain a catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, baking at 150 ℃ for 3h and baking at 550 ℃ for 2h to obtain a semi-finished catalyst;
(2) And (3) coating an upper coating: 2000g of Ce-Zr composite oxide containing 2% of Nd and 3% of Y element and Al with a solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 1:1, stirring, sequentially and slowly dropwise adding iridium nitrate and rhodium nitrate solution into the slurry, stirring for 1h, tackifying and stirring for 10h to obtain a catalyst upper coating slurry, coating the catalyst upper coating slurry on the semi-finished catalyst prepared in the step (1), drying at 150 ℃ for 3h, and roasting at 550 ℃ for 2h to obtain a finished catalyst; wherein Al is 2 O 3 Is gamma-alumina with specific surface area of 150-180 m 2 /g。
In the prepared catalyst, the coating amount of the lower coating layer is 100g/L, the coating amount of the upper coating layer is 100g/L, and the noble metal loading is: the Pd of the lower coating is 1g/L, the Rh of the upper coating is 0.1g/L, and Ir is 0.14g/L.
Example 1
The preparation method of the efficient vehicle natural gas catalyst comprises the following steps:
(1) And (2) coating the following coating: a catalyst lower coating slurry was prepared in the same manner as in comparative example 1, and a corresponding semi-finished catalyst was obtained;
(2) And (3) coating an upper coating: the same mass of Al as that of the upper slurry in comparative example 1 was weighed separately 2 O 3 And Ce-Zr composite oxide containing Nd and Y elements, and separately placing, diluting iridium nitrate solution to Al 2 O 3 Water absorption rate of Al 2 O 3 Corresponding value of mass and equal volume of impregnated with Al 2 O 3 Drying at 150deg.C for 3h, calcining at 550deg.C for 2h, mixing with Ce-Zr composite oxide uniformly and preparing into slurry, slowly dripping rhodium nitrate solution, stirring for 1h, tackifying and stirring for 10h to obtain coating slurry of catalyst upper coating, and coating it on the catalyst upper coating layer (1)) And (3) drying the prepared semi-finished catalyst at 150 ℃ for 3h, and roasting at 550 ℃ for 2h to obtain the finished catalyst.
In the prepared catalyst, the coating parameters of the upper and lower coating layers and the loading parameters of the noble metal were kept consistent with comparative example 1.
Comparative example 2
The preparation method of the natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: 2000g of Ce-Zr composite oxide containing 2% Ti and 3% La and Al with a solid content of 40% were weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 2:1, stirring, slowly dripping a palladium nitrate solution into the slurry, stirring for 0.5h, tackifying and stirring for 12h to obtain a catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, drying at 160 ℃ for 3.2h, and roasting at 550 ℃ for 2.2h to obtain a semi-finished catalyst;
(2) And (3) coating an upper coating: 2000g of Ce-Zr composite oxide containing 3% La and 5% Y elements and Al with a solid content of 40% were weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 2:1, stirring, sequentially and slowly dropwise adding iridium nitrate, rhodium nitrate and platinum nitrate solution into the slurry, stirring for 0.5h, tackifying and stirring for 12h to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the semi-finished catalyst in the step (1), drying at 160 ℃ for 3.2h, and roasting at 550 ℃ for 2.2h to obtain a finished catalyst; wherein Al is 2 O 3 Is gamma-alumina with specific surface area of 150-180 m 2 /g。
In the prepared catalyst, the coating amount of the lower coating layer is 50g/L, the coating amount of the upper coating layer is 30g/L, and the noble metal loading is as follows: the Pd of the lower coating is 0.2g/L, the Rh of the upper coating is 0.03g/L, ir is 0.06g/L, and Pt is 0.07g/L.
Example 2
The preparation method of the efficient vehicle natural gas catalyst comprises the following steps:
(1) And (2) coating the following coating: a catalyst lower coating slurry was prepared in the same manner as in comparative example 2, and a corresponding semi-finished catalyst was obtained;
(2) And (3) coating an upper coating: the same mass of Al as in the coating slip of comparative example 2 was weighed separately 2 O 3 And Ce-Zr composite oxide containing La and Y elements, and separately placing, diluting iridium nitrate solution to Al 2 O 3 Water absorption rate Al 2 O 3 Corresponding value of mass and equal volume of impregnated with Al 2 O 3 Drying at 160 ℃ for 3.2 hours, roasting at 550 ℃ for 2.2 hours, uniformly mixing with Ce-Zr composite oxide, preparing slurry, slowly dripping rhodium nitrate and platinum nitrate solution, stirring for 0.5 hour, tackifying and stirring for 12 hours to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the semi-finished catalyst prepared in the step (1), drying at 160 ℃ for 3.2 hours, and roasting at 550 ℃ for 2.2 hours to obtain the finished catalyst.
In the prepared catalyst, the coating parameters of the upper and lower coating layers and the loading parameters of the noble metal were kept identical to comparative example 2.
Comparative example 3
The preparation method of the natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: 2000g of Ce-Zr composite oxide containing 5% of Ba and 3% of La and Al with the solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 1:2, stirring, slowly dropwise adding palladium nitrate solution into the slurry, stirring for 1.5h, tackifying and stirring for 15h to obtain catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, drying at 155 ℃ for 3.1h, and roasting at 555 ℃ for 2.1h to obtain a first semi-finished catalyst;
(2) And (2) coating an intermediate coating: 2000g of Ce-Zr composite oxide containing 5% of Ba and 3% of La and Al with the solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the mixture in a beaker with the mass ratio of 1:2, stirring, slowly dripping a platinum nitrate solution into the slurry, stirring for 1.5h, tackifying and stirring for 15h to obtain a catalyst intermediate coating slurry, coating the catalyst intermediate coating slurry on the first semi-finished catalyst prepared in the step (1),drying at 155 ℃ for 3.1h, and roasting at 555 ℃ for 2.1h to obtain a second semi-finished catalyst;
(3) And (3) coating an upper coating: 2000g of Ce-Zr composite oxide containing 4% of Ba and 2% of Pr elements and Al with the solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 1:2, stirring, sequentially and slowly dropwise adding iridium nitrate and rhodium nitrate solution into the slurry, stirring for 1.5h, tackifying and stirring for 15h to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), drying at 155 ℃ for 3.1h, and roasting at 555 ℃ for 2.1h to obtain a finished catalyst; wherein Al is 2 O 3 Is gamma-alumina with specific surface area of 150-180 m 2 /g。
In the prepared catalyst, the coating amount of the lower coating layer is 120g/L, the coating amount of the middle coating layer is 50g/L, the coating amount of the upper coating layer is 100g/L, and the noble metal loading is: and (3) coating: pd is 2.58g/L, intermediate coating: pt was 0.39g/L, top coat: rh was 0.03g/L and Ir was 0.27g/L.
Example 3
The preparation method of the efficient vehicle natural gas catalyst comprises the following steps:
(1) Coating of the under coating and the intermediate coating: catalyst lower coating and middle coating slurries were prepared in the same manner as in comparative example 3, and corresponding semi-finished catalysts were obtained;
(2) And (3) coating an upper coating: the same mass of Al as that of the coating paste in comparative example 3 was weighed separately 2 O 3 And Ce-Zr composite oxide containing Ce and Pr elements, placing separately, diluting iridium nitrate solution to Al 2 O 3 Water absorption rate Al 2 O 3 Corresponding value of mass, and is impregnated to Al by equal volume 2 O 3 Drying the material at 155 ℃ for 3.1h, roasting at 555 ℃ for 2.1h, uniformly mixing the material with Ce-Zr composite oxide, preparing slurry, slowly dripping rhodium nitrate solution, stirring for 1.5h, tackifying and stirring for 15h to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (1), drying at 155 ℃ for 3.1h, roasting at 555 ℃ for 2.1h to obtain the catalystAnd (3) preparing the catalyst.
The coating parameters of the upper, middle and lower coating layers and the loading parameters of the noble metals in the prepared catalyst were consistent with comparative example 3.
Comparative example 4
The preparation method of the natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: 2000g of Ce-Zr composite oxide containing 6% of Ba, 2% of Nd and 1%Y elements and Al with the solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 2:3, stirring, slowly dripping a palladium nitrate solution into the slurry, stirring for 2 hours, tackifying and stirring for 20 hours to obtain a catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, drying at 170 ℃ for 3.3 hours, and roasting at 570 ℃ for 2.3 hours to obtain a first semi-finished catalyst;
(2) And (3) intermediate coating: 2000g of Ce-Zr composite oxide containing 6% of Ba, 2% of Nd and 1%Y elements and Al with the solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the mixture in a beaker with the mass ratio of 2:3, stirring, sequentially and slowly dropwise adding palladium nitrate and platinum nitrate solution into the slurry, stirring for 2 hours, tackifying and stirring for 20 hours to obtain catalyst intermediate coating slurry, coating the catalyst intermediate coating slurry on the first semi-finished catalyst prepared in the step (1), drying at 170 ℃ for 3.3 hours, and roasting at 570 ℃ for 2.3 hours to obtain a second semi-finished catalyst;
(3) And (3) coating an upper coating: 2000g of Ce-Zr composite oxide containing 4% Ti, 3% Pr and 2% La and Al with a solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 2:3, stirring, sequentially and slowly dropwise adding iridium nitrate, rhodium nitrate and platinum nitrate solution into the slurry, stirring for 2 hours, tackifying and stirring for 20 hours to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), drying at 170 ℃ for 3.3 hours, and roasting at 570 ℃ for 2.3 hours to obtain a finished catalyst; wherein Al is 2 O 3 Is gamma-alumina with specific surface area of150～180m 2 /g。
In the prepared catalyst, the coating amount of the lower coating layer is 90g/L, the coating amount of the middle coating layer is 30g/L, the coating amount of the upper coating layer is 50g/L, and the noble metal loading is: and (3) coating: pd is 0.4g/L, the intermediate coating: pd is 0.3g/L, pt is 0.3g/L; and (3) coating: pt is 0.4g/L, ir is 0.02g/L, rh is 0.19g/L.
Example 4
The preparation method of the efficient vehicle natural gas catalyst comprises the following steps:
(1) And (3) coating a lower coating and an intermediate coating: catalyst lower coating and middle coating slurries were prepared in the same manner as in comparative example 4, and corresponding semi-finished catalysts were obtained;
(2) And (3) coating an upper coating: the same mass of Al as in the upper coating paste in comparative example 4 was weighed separately 2 O 3 And Ce-Zr composite oxide containing Zr, pr and La elements, and separately placing, diluting iridium nitrate solution to Al 2 O 3 Water absorption rate Al 2 O 3 Corresponding value of mass, and is impregnated to Al by equal volume 2 O 3 And (3) drying at 170 ℃ for 3.3 hours, roasting at 570 ℃ for 2.3 hours, uniformly mixing with Ce-Zr composite oxide, preparing slurry, sequentially and slowly dripping rhodium nitrate and platinum nitrate solution, stirring for 2 hours, tackifying and stirring for 20 hours to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), drying at 170 ℃ for 3.3 hours, and roasting at 570 ℃ for 2.3 hours to obtain the finished catalyst.
The coating parameters of the upper, middle and lower coating layers and the loading parameters of the noble metals in the prepared catalyst were consistent with comparative example 4.
Comparative example 5
The preparation method of the natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: 2000g of Ce-Zr composite oxide containing 5% of Ba, 3% of Ti and 1% of Pr and Al with a solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Is placed in a 5L beaker, stirred and the palladium nitrate solution is slowly added into the slurry in a dropwise mannerStirring for 1.8h, tackifying and stirring for 18h to obtain catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, drying at 180 ℃ for 3.4h, and roasting at 580 ℃ for 2.4h to obtain a first semi-finished catalyst;
(2) And (3) intermediate coating: 2000g of Ce-Zr composite oxide containing 5% of Ba, 3% of Ti and 1% of Pr and Al with a solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the mixture in a beaker with the mass ratio of 4:3, stirring, sequentially and slowly dropwise adding palladium nitrate and platinum nitrate solution into the slurry, stirring for 1.8h, tackifying and stirring for 18h to obtain catalyst intermediate coating slurry, coating the catalyst intermediate coating slurry on the first semi-finished catalyst prepared in the step (1), drying at 180 ℃ for 3.4h, and roasting at 580 ℃ for 2.4h to obtain a second semi-finished catalyst;
(3) And (3) coating an upper coating: 2000g of Ce-Zr composite oxide containing 4% Ba, 3% Pr and 3% Y elements and Al with a solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 4:3, stirring, sequentially and slowly dropwise adding iridium nitrate and rhodium nitrate solution into the slurry, stirring for 1.8h, tackifying and stirring for 18h to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), drying at 180 ℃ for 3.4h, and roasting at 580 ℃ for 2.4h to obtain a finished catalyst; wherein Al is 2 O 3 Is gamma-alumina with specific surface area of 150-180 m 2 /g。
In the prepared catalyst, the coating amount of the lower coating layer is 60g/L, the coating amount of the middle coating layer is 40g/L, the coating amount of the upper coating layer is 80g/L, and the noble metal loading is: and (3) coating: pd is 1.0g/L; and (3) intermediate coating: pd is 0.59g/L, pt is 0.78g/L; and (3) coating: rh was 0.05g/L and Ir was 0.05g/L.
Example 5
The preparation method of the efficient vehicle natural gas catalyst comprises the following steps:
(1) And (3) coating a lower coating and an intermediate coating: catalyst washcoat and washcoat slurries were prepared in the same manner as in comparative example 5, and corresponding first and second semi-finished catalysts were obtained;
(2) And (3) coating an upper coating: the same mass of Al as that of the coating paste in comparative example 5 was weighed separately 2 O 3 And Ce-Zr composite oxide containing Ce, pr and Y elements, and separately placing, diluting iridium nitrate solution to Al 2 O 3 Water absorption rate Al 2 O 3 Corresponding value of mass, and is impregnated to Al by equal volume 2 O 3 And (3) drying the material at 180 ℃ for 3.4 hours, roasting at 580 ℃ for 2.4 hours, uniformly mixing with Ce-Zr composite oxide, preparing slurry, sequentially and slowly dripping rhodium nitrate solution, stirring for 1.8 hours, tackifying and stirring for 18 hours to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), drying at 180 ℃ for 3.4 hours, and roasting at 580 ℃ for 2.4 hours to obtain the finished catalyst.
The coating parameters of the upper, middle and lower coating layers and the loading parameters of the noble metals in the prepared catalyst were consistent with comparative example 5.
Comparative example 6
The preparation method of the natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: 2000g of Ce-Zr composite oxide containing 3% Ti, 4% Pr and 2% Nd with a solid content of 40% and Al are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 3:1, stirring, slowly dropwise adding palladium nitrate solution into the slurry, stirring for 1.7h, tackifying and stirring for 17h to obtain catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, drying at 175 ℃ for 3.6h, and roasting at 590 ℃ for 2.6h to obtain a first semi-finished catalyst;
(2) And (3) intermediate coating: 2000g of Ce-Zr composite oxide containing 3% Ti, 4% Pr and 2% Nd with a solid content of 40% and Al are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the mixture in a beaker with the mass ratio of 3:1, stirring, slowly dripping palladium nitrate solution into the slurry, stirring for 1.7h, tackifying and stirring for 17h to obtain catalyst intermediate coating slurry, and coating the catalyst intermediate coating slurry on the first semi-finished catalyst prepared in the step (1)Drying at 175 ℃ for 3.6h, and roasting at 590 ℃ for 2.6h to obtain a second semi-finished catalyst;
(3) And (3) coating an upper coating: 2000g of Ce-Zr composite oxide containing 2% Ti, 3% Pr, 1% La and 1%Y elements with solid content of 40% and Al are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 3:1, stirring, sequentially and slowly dropwise adding iridium nitrate, rhodium nitrate and platinum nitrate solution into the slurry, stirring for 1.7h, tackifying and stirring for 17h to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), drying at 175 ℃ for 3.6h, and roasting at 590 ℃ for 2.6h to obtain a finished catalyst; wherein Al is 2 O 3 Is gamma-alumina with specific surface area of 150-180 m 2 /g。
In the prepared catalyst, the coating amount of the lower coating layer is 150g/L, the coating amount of the middle coating layer is 100g/L, the coating amount of the upper coating layer is 100g/L, and the noble metal loading is: the Pd in the lower coating layer is 2.0g/L, the Pd in the middle layer is 1.0g/L, the Rh in the upper coating layer is 0.14g/L, the Ir is 0.21g/L, and the Pt is 0.88g/L.
Example 6
The preparation method of the efficient vehicle natural gas catalyst comprises the following steps:
(1) And (3) coating a lower coating and an intermediate coating: catalyst washcoat and washcoat slurries were prepared in the same manner as in comparative example 6, and corresponding first and second semi-finished catalysts were obtained;
(2) And (3) coating an upper coating: the same mass of Al as that of the coating paste in comparative example 6 was weighed separately 2 O 3 And Ce-Zr composite oxide containing Zr, pr, la, Y element, separately placing, diluting iridium nitrate solution to Al 2 O 3 Water absorption rate Al 2 O 3 Corresponding value of mass, and is impregnated to Al by equal volume 2 O 3 Drying the material at 175 ℃ for 3.6 hours, roasting at 590 ℃ for 2.6 hours, uniformly mixing the material with Ce-Zr composite oxide, preparing slurry, slowly dripping rhodium nitrate and platinum nitrate solution in sequence, stirring for 1.7 hours, tackifying and stirring for 17 hours to obtain coating slurry of the upper coating of the catalyst, and coating the coating slurry on the second prepared in the step (1)And (3) drying the semi-finished catalyst at 175 ℃ for 3.6h, and roasting at 590 ℃ for 2.6h to obtain the finished catalyst.
The coating parameters of the upper, middle and lower coating layers and the loading parameters of the noble metals in the prepared catalyst were consistent with comparative example 6.
Comparative example 7
The preparation method of the natural gas catalyst for the vehicle comprises the following steps:
(1) And (2) coating the following coating: 2000g of Ce-Zr composite oxide containing 3% Ti, 2% Pr, 1% Nd and 3% Y element with a solid content of 40% and Al are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the catalyst into a beaker with the mass ratio of 1:3, stirring, slowly dropwise adding palladium nitrate solution into the slurry, stirring for 0.9h, tackifying and stirring for 9h to obtain catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, drying at 150 ℃ for 3.9h, and roasting at 650 ℃ for 2.9h to obtain a first semi-finished catalyst;
(2) And (3) intermediate coating: 2000g of Ce-Zr composite oxide containing 3% Ti, 2% Pr, 1% Nd and 3% Y element with a solid content of 40% and Al are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the mixture in a beaker with the mass ratio of 1:3, stirring, slowly dripping a platinum nitrate solution into the slurry, stirring for 0.9h, tackifying and stirring for 9h to obtain a catalyst intermediate coating slurry, coating the catalyst intermediate coating slurry on the first semi-finished catalyst prepared in the step (1), drying at 150 ℃ for 3.9h, and roasting at 650 ℃ for 2.9h to obtain a second semi-finished catalyst;
(3) And (3) coating an upper coating: 2000g of Ce-Zr composite oxide containing 4% Pr, 2% La, 1% Nd and 1%Y element and Al with solid content of 40% are weighed 2 O 3 Is a primary slurry of Ce-Zr composite oxide and Al 2 O 3 Placing the mixture in a beaker with the mass ratio of 1:3, stirring, sequentially and slowly dropwise adding iridium nitrate, rhodium nitrate and platinum nitrate solution into the slurry, stirring for 0.9h, tackifying and stirring for 9h to obtain a catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), drying at 150 ℃ for 3.9h, and roasting at 650 ℃ for 2.9h to obtain the catalyst upper coating slurryA finished catalyst; wherein Al is 2 O 3 Is gamma-alumina with specific surface area of 150-180 m 2 /g。
In the prepared catalyst, the coating amount of the lower coating layer is 100g/L, the coating amount of the middle coating layer is 90g/L, the coating amount of the upper coating layer is 40g/L, and the noble metal loading is: the Pd of the lower coating layer is 1.06g/L, the Pt of the middle coating layer is 0.23g/L, the Pt of the upper coating layer is 0.3g/L, the Rh of the upper coating layer is 0.11g/L, and the Ir of the upper coating layer is 0.07g/L.
Example 7
The preparation method of the efficient vehicle natural gas catalyst comprises the following steps:
(1) And (3) coating a lower coating and an intermediate coating: catalyst washcoat and washcoat slurries were prepared in the same manner as in comparative example 7, and corresponding first and second semi-finished catalysts were obtained;
(2) And (3) coating an upper coating: the same mass of Al as in the coating slip of comparative example 7 was weighed separately 2 O 3 And Ce-Zr composite oxide containing Zr, pr, la, Y element, separately placing, diluting iridium nitrate solution to Al 2 O 3 Water absorption rate Al 2 O 3 Corresponding value of mass, and is impregnated to Al by equal volume 2 O 3 Drying at 175 ℃ for 3.6 hours, roasting at 590 ℃ for 2.6 hours, uniformly mixing with Ce-Zr composite oxide, preparing slurry, slowly dripping rhodium nitrate and platinum nitrate solution in sequence, stirring for 1.7 hours, tackifying and stirring for 17 hours to obtain catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (1), drying at 175 ℃ for 3.6 hours, and roasting at 590 ℃ for 2.6 hours to obtain the finished catalyst.
The coating parameters of the upper, middle and lower coating layers and the loading parameters of the noble metals in the prepared catalyst were consistent with comparative example 7.
Comparison of catalytic performances was performed on the catalyst patches prepared in comparative examples 1 to 7 and examples 1 to 7, and comparison was performed between comparative example 1 and example 1, and between comparative example 2 and example 2. . . Comparative example 7 is compared with example 7.
The fresh catalyst and the aged catalyst were tested for the pollutant light-off temperature (T50) under the same experimental conditions, respectively, whereinThe catalyst in the ageing state is 10% H at 850 DEG C 2 Aging in an aging oven for O for 25 hours gave a lower T50 indicating a higher catalyst pollutant conversion capacity. The test experiment is carried out on a Fourier infrared tester, the reaction gas is uniformly mixed in a gas mixing tank in advance, and the components in the reaction gas comprise 0.75% CO and 0.24% H according to the volume fraction 2 、5％H 2 O、8％CO 2 1400ppm NO and 1500ppm CH 4 N is used in the reaction tube 2 To balance the gas, then O is introduced into the reaction tube 2 The lambda was adjusted to stabilize lambda at 0.994 in the experiment. Where λ refers to the excess air ratio, i.e., the ratio of the amount of air actually supplied to the fuel combustion to the theoretical amount of air. When λ=1, the fuel is just completely burned; when lambda is less than 1, the fuel cannot be fully combusted; lambda > 1, air is excessive.
TABLE 1 comparison of pollutant light-off temperatures for example 1 and comparative example 1
Comparison item CH 4 -T 50 -Fresh/℃ NOx-T 50 -Fresh/℃ CH 4 -T 50 -Aged/℃ NOx-T 50 -Aged/℃
Example 1 386 211 442 221
Comparative example 1 391 215 452 251
Table 2 comparison of pollutant light-off temperatures for example 2 and comparative example 2
Comparison item CH 4 -T 50 -Fresh/℃ NOx-T 50 -Fresh/℃ CH 4 -T 50 -Aged/℃ NOx-T 50 -Aged/℃
Example 2 425 247 459 243
Comparative example 2 429 250 468 275
TABLE 3 comparison of pollutant light-off temperatures for example 3 and comparative example 3
Comparison item CH 4 -T 50 -Fresh/℃ NOx-T 50 -Fresh/℃ CH 4 -T 50 -Aged/℃ NOx-T 50 -Aged/℃
Example 3 368 176 397 192
Comparative example 3 370 178 411 233
TABLE 4 comparison of pollutant light-off temperatures for example 4 and comparative example 4
TABLE 5 comparison of pollutant light-off temperatures for example 5 and comparative example 5
TABLE 6 comparison of pollutant light-off temperatures for example 6 and comparative example 6
Comparison item CH 4 -T 50 -Fresh/℃ NOx-T 50 -Fresh/℃ CH 4 -T 50 -Aged/℃ NOx-T 50 -Aged/℃
Example 6 357 162 383 193
Comparative example 6 363 165 391 218
TABLE 7 comparison of pollutant light-off temperatures for example 7 and comparative example 7
Comparison item CH 4 -T 50 -Fresh/℃ NOx-T 50 -Fresh/℃ CH 4 -T 50 -Aged/℃ NOx-T 50 -Aged/℃
Example 7 377 197 425 213
Comparative example 7 380 200 431 236
From the results of comparing the pollutant light-off temperatures in examples 1-7 and comparative examples 1-7 in tables 1-7, it can be seen that:
CH of fresh catalyst in example 1 4 And NOx light-off temperatures, 5℃and 4℃lower than comparative example 1, respectively, and 10℃and 30℃lower than the oven aged。
CH of fresh catalyst in example 2 4 And NOx light-off temperatures, 4℃and 3℃lower than comparative example 2, respectively, and 9℃and 32℃lower than the oven aged.
CH of fresh catalyst in example 3 4 And NOx light-off temperatures, 2℃and 2℃lower than comparative example 3, respectively, and 14℃and 41℃lower than the oven aged.
CH of fresh catalyst in example 4 4 And NOx light-off temperatures, 2℃and 2℃lower than comparative example 4, respectively, and 2℃and 13℃lower than the oven aged.
CH of fresh catalyst in example 5 4 And NOx light-off temperatures, 5℃and 2℃lower than comparative example 5, respectively, and 6℃and 24℃lower than after oven aging, respectively.
CH of fresh catalyst in example 6 4 And NOx light-off temperatures, 6℃and 3℃lower than comparative example 6, respectively, and 8℃and 25℃lower than the oven aged.
CH of fresh catalyst in example 7 4 And NOx light-off temperatures, 3℃and 3℃lower than comparative example 7, respectively, and 6℃and 23℃lower than the oven aged.
As can be seen from the comparison of the above data, in the comparison of the data of examples 1 to 7 and comparative examples 1 to 7, the catalysts prepared by using Ir as a fixed noble metal in examples 1 to 7 were compared with the catalysts prepared by ordinary mechanical mixing of examples 1 to 7, and CH after fresh state and furnace aging 4 And the NOx ignition temperature is low, and meanwhile, the higher the proportion of the fixed noble metal Ir content to the total noble metal amount is, the more the corresponding NOx ignition temperature is reduced after aging. The catalyst is prepared by immersing noble metal Ir in equal volume on an active alumina carrier and fixing the noble metal Ir in a roasting mode, so that the ageing resistance of the Ir in the catalyst is greatly improved, and the problem of poor ageing performance of the catalyst is effectively solved.
In addition, the noble metal Ir with relatively low price is introduced into the upper coating of the catalyst, so that the noble metal Rh can be partially replaced, and the preparation cost of the catalyst can be greatly reduced.
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 (7)

1. The natural gas catalyst for the vehicle comprises a carrier and a coating material coated on the carrier, and is characterized in that the coating material comprises aluminum oxide and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, and noble metals Ir, pt, pd and Rh are loaded in the coating material;
the coating material comprises an upper coating layer and a lower coating layer, wherein the coating amount of the lower coating layer is 50-200 g/L, and the coating amount of the upper coating layer is 30-150 g/L;
or the coating material comprises an upper layer, a middle layer and a lower layer, wherein the coating amount of the lower coating is 50-150 g/L, the coating amount of the middle coating is 10-100 g/L, and the coating amount of the upper coating is 20-100 g/L;
the Rh and Ir are distributed on the upper coating; the Pd is distributed in the lower coating and/or the middle coating; the Pt is distributed on the middle coating and/or the upper coating, wherein the total loading amount of Rh and Ir is 0.02-1 g/L, and the mass ratio of Rh to Ir is 1:9-9:1; pd is loaded in an amount of 0.2-5 g/L; the loading amount of Pt is 0-3.5 g/L;
when the upper coating is prepared, the diluted Ir-containing soluble solution is immersed on the active alumina material in an equal volume, and is dried and roasted, and then the diluted Ir-containing soluble solution is uniformly mixed with Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y to prepare slurry, and rhodium nitrate solution or rhodium nitrate and platinum nitrate solution is added into the slurry to prepare the coating slurry of the upper coating of the catalyst.
2. The automotive natural gas catalyst of claim 1, wherein the support is a cordierite honeycomb ceramic support having a mesh size of 300-600 mesh and a wall thickness of 3-6 mils.
3. The method for preparing the natural gas catalyst for the vehicle as claimed in claim 1, comprising the following steps:
(1) And (2) coating the following coating: preparing primary slurry of alumina and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, placing the primary slurry in a specified container, stirring, adding a soluble solution containing noble metal Pd, stirring for 0.5-2 h, tackifying, continuing stirring for 6-20 h to obtain lower coating slurry of the catalyst, coating the lower coating slurry on a catalyst carrier, and drying and roasting to obtain a semi-finished catalyst;
(2) And (3) coating an upper coating: measuring the water absorption value of aluminum oxide per unit mass, recording the water absorption value as a g/g, weighing b g active aluminum oxide material, diluting Ir-containing soluble solution with deionized water to a mass of a. b g, immersing the diluted Ir-containing soluble solution in an equal volume on the active aluminum oxide material, drying and roasting, uniformly mixing with Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y again to prepare slurry, adding rhodium nitrate solution or rhodium nitrate and platinum nitrate solution into the slurry to prepare catalyst upper coating slurry, coating the upper coating slurry on the semi-finished catalyst prepared in the step (1), and drying and roasting to finally obtain the finished catalyst.
4. The method for preparing the natural gas catalyst for the vehicle as claimed in claim 1, comprising the following steps:
(1) And (2) coating the following coating: preparing primary slurry of alumina and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, placing the primary slurry in a specified container, stirring, adding a soluble solution containing noble metal Pd, stirring for 0.5-2 h, tackifying, continuing stirring for 6-20 h to obtain a catalyst lower coating slurry, coating the catalyst lower coating slurry on a catalyst carrier, and drying and roasting to obtain a first semi-finished catalyst;
(2) And (3) intermediate coating: preparing primary slurry of aluminum oxide and Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y, placing the primary slurry in a specified container, stirring, adding a soluble solution containing noble metal Pd and/or noble metal Pt, stirring for 0.5-2 h, tackifying, continuing stirring for 6-20 h to obtain a catalyst intermediate coating slurry, coating the catalyst intermediate coating slurry on the first semi-finished catalyst prepared in the step (1), and drying and roasting to obtain a second semi-finished catalyst;
(3) And (3) coating an upper coating: measuring the water absorption value of the active alumina component per unit mass, recording the water absorption value as a g/g, weighing b g active alumina material, diluting the Ir-containing soluble solution with deionized water to a mass of a x b g, immersing the diluted Ir-containing soluble solution in an equal volume on the active alumina material, drying and roasting, uniformly mixing with Ce-Zr composite oxide containing one or more modified oxides of Ba, ti, pr, la, nd and Y again to prepare slurry, adding rhodium nitrate solution or rhodium nitrate and platinum nitrate solution to prepare catalyst upper coating slurry, coating the catalyst upper coating slurry on the second semi-finished catalyst prepared in the step (2), and drying and roasting to finally obtain the finished catalyst.
5. The method for preparing a natural gas catalyst for vehicles according to claim 3 or 4, wherein the alumina is gamma-alumina having a specific surface area of 150 to 180m 2 /g。
6. The method for preparing a natural gas catalyst for vehicles according to claim 3 or 4, wherein the Ce-Zr composite oxide is a cerium-zirconium solid solution, and comprises 20 to 60 mass% of cerium oxide.
7. The method for preparing the natural gas catalyst for the vehicle according to claim 3 or 4, wherein the catalyst carrier is coated by a negative pressure type coating machine, the air pressure of the negative pressure type coating machine is-20 to-80 kPa, and each layer of the catalyst carrier is baked after the coating is completed; the conditions of drying and roasting are as follows: drying at 150-180 ℃ for 3-4 h, and roasting at 500-650 ℃ for 2-3 h.
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