CN112536031B - Catalyst for treating industrial waste gas and preparation method thereof - Google Patents

Catalyst for treating industrial waste gas and preparation method thereof Download PDF

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CN112536031B
CN112536031B CN201910899919.1A CN201910899919A CN112536031B CN 112536031 B CN112536031 B CN 112536031B CN 201910899919 A CN201910899919 A CN 201910899919A CN 112536031 B CN112536031 B CN 112536031B
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catalyst
catalyst layer
molecular sieve
metal
layer
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CN112536031A (en
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杜辰昊
陈航宁
赵相武
顾一丹
许丹丹
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8628—Processes characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8678—Removing components of undefined structure
    • B01D53/8687—Organic components
    • 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
    • B01J27/24—Nitrogen compounds
    • 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
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
    • B01J29/76—Iron group metals or copper
    • B01J29/7615—Zeolite Beta
    • B01J35/23—
    • B01J35/56—
    • 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
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
    • B01D2257/708—Volatile organic compounds V.O.C.'s
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • 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
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
    • 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 discloses a multi-effect catalyst for purifying waste gas, which comprises the following components: a substrate, a first catalyst layer on and/or within the substrate, and a second catalyst layer on the first catalyst layer; the first catalyst includes a support and a noble metal supported on the support; the second catalyst comprises a metal-modified molecular sieve and a palladium catalyst. The catalyst can effectively reduce the content of hydrocarbon and CO in the waste gas at the same time, and reduce NO in the waste gas under the condition of excessive oxygen and NO ammonia reducing agent x The content of (a). It has been found by the present invention that the addition of a Pd-containing light-off catalyst in the top layer of a multilayer catalyst enables the temperature required for the purification of exhaust gases to be reduced without substantially affecting NO x Reduced efficiency and generation of N 2 Selectivity of (2).

Description

Catalyst for treating industrial waste gas and preparation method thereof
Technical Field
The invention relates to a catalyst for treating industrial waste gas, a preparation method thereof and a method for treating industrial waste gas by using the catalyst, belonging to the field of waste gas purification.
Background
The chemical waste gas has the characteristics of wide source and complex components. The discharged waste gas after the purification and absorption of the target product mostly contains relatively harmless nitrogen (N) 2 ) Water vapor (H) 2 O) and carbon dioxide (CO) 2 ). However, the waste gas also contains relatively small amounts of toxic/harmful substances, for example the remainder of the raw materials which are not involved in the synthesis of the target product (common raw materials such as alkanes, alkenes, CO, etc.), N from excessively high combustion temperatures 2 NO produced by oxidation x And so on. In order to reduce the adverse effect of exhaust gas emissions on the atmosphere, specific purification means are required to reduce or eliminate the levels of toxic components.
For the components with toxic hazard such as hydrocarbon, CO and the like, the components are converted into CO by utilizing the catalytic oxidation catalyst at lower reaction temperature 2 And H 2 O is one of the effective methods. For example, CN 106475128a provides a preparation method of an industrial waste gas purification catalyst. The method improves the anti-sintering performance of the catalyst, improves the stability of the catalyst, and shows excellent catalytic activity and stability in the purification process of the benzene series. For NO x The exhaust gas usually contains an excess of O 2 Is not favorable for reducing the nitrogen into N 2 . Therefore, the commonly employed Selective Catalytic Reduction (SCR) technology requires additional addition and NO conversion by means of a nitrogenous reductant (ammonia) x Conversion to N 2 And H 2 And O. The chemical reaction equation for stoichiometric SCR reactions using ammonia is as follows:
4NO+4NH 3 +O 2 →4N 2 +6H 2 O
2NO 2 +4NH 3 +O 2 →3N 2 +6H 2 O
additional NH addition 3 The problems brought byIn the following steps: generally speaking, to achieve NO x Maximization of conversion requires the use of excess NH during the SCR process 3 The escape of excess unreacted ammonia is disadvantageous. This requires that an ammonia oxidation catalyst system be installed downstream of the SCR catalyst in order to reduce ammonia slip.
VOCs (hydrocarbons, alcohols, esters, etc.) present in common industrial waste gases are also components which are considered to have reducing properties. If the VOCs in the waste gas can be directly utilized to directly react NO x Reduction to harmless N 2 And H 2 And O, not only can simplify the process flow of the related technology, but also can reduce the cost for treating the environmental problems.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a catalyst for treating industrial waste gas and a preparation method thereof. The catalyst can effectively reduce the content of hydrocarbon and CO in the waste gas at the same time, and reduce NO in the waste gas under the condition of excessive oxygen and NO ammonia reducing agent x The content of (a). It has been found by the present invention that the addition of a Pd-containing light-off catalyst in the top layer of a multilayer catalyst enables the temperature required for the purification of exhaust gases to be reduced without substantially affecting NO x Reduced efficiency and generation of N 2 Selectivity of (2).
According to an aspect of the present invention, there is provided a multi-effect catalyst for purification of exhaust gas, comprising:
a substrate, a first catalyst and a second catalyst;
the first catalyst includes a support and a noble metal supported on the support;
the second catalyst comprises a metal-modified molecular sieve and a palladium catalyst.
According to a preferred embodiment of the present invention, the first catalyst layer is located on and/or within a substrate and the second catalyst layer is located on the first catalyst layer.
In the invention, the structural characteristics of different components and coating catalysts can bring about particularly good catalytic effect. When the waste gas to be treated passes through the catalyst, the waste gas firstly passes through the first layer of catalyst and then passes through the second layer of catalyst, and the waste gas is ensured to be treated by the first layer of catalyst when finally leaving the catalyst; the structure can regulate and control the intermediate process of catalytic reaction to a certain extent, and influences the catalytic effect. With other combinations of structures, it is difficult to obtain the effects of the present invention.
According to some embodiments of the invention, the support of the first catalyst comprises an oxide support, preferably the oxide comprises at least one of alumina, zirconia, silica, titania, ceria.
According to a preferred embodiment of the present invention, the noble metal of the first catalyst comprises Pt and/or Pd; the weight ratio of the noble metal element to the carrier is preferably (0.05-5): 100.
According to some embodiments of the invention, the metal in the second catalyst comprises Cu and/or Fe, the molecular sieve comprises at least one of a Beta molecular sieve, a MOR molecular sieve, and a Y-type molecular sieve; and/or the weight ratio of the metal element to the molecular sieve is (1-5): 100.
According to a preferred embodiment of the present invention, the palladium catalyst comprises a carrier and palladium supported on the carrier; the carrier comprises a non-metallic carbide and/or a non-metallic nitride, preferably comprising BN and/or SiC.
According to a preferred embodiment of the present invention, the weight ratio of the metal-modified molecular sieve to the palladium catalyst is (70-90): (30-10).
According to some embodiments of the present invention, the ratio of the loading amounts of the first catalyst layer and the second catalyst layer is (1-5): (5-1).
According to a preferred embodiment of the present invention, the loading amount refers to a mass content of the first catalyst layer or the second catalyst layer based on a volume of the substrate.
According to a preferred embodiment of the present invention, the substrate is a honeycomb monolith flow-through substrate; the honeycomb cell density is 100 to 600cpsi.
According to a preferred embodiment of the invention, said first catalyst layer acts for the most part on the inside or on the surface of said base wall; the second catalyst layer acts on the surface of the first catalyst layer, the surface of the substrate wall or inside.
According to another aspect of the present invention, there is provided a method for preparing the above catalyst, comprising the steps of:
s1, preparing first catalyst slurry and second catalyst slurry respectively;
s2, coating the first catalyst slurry on a substrate to form a first catalyst layer;
and S3, coating the second catalyst slurry on the first catalyst layer to form a second catalyst layer.
According to some embodiments of the invention, said step S1 comprises:
1A, loading a noble metal compound on an oxide carrier, and roasting to obtain a first catalyst;
loading metal on the molecular sieve, and roasting to obtain a metal modified molecular sieve;
1C, loading palladium on the non-metal carbide and/or non-metal nitride to obtain a palladium catalyst;
and 1D, mixing the metal modified molecular sieve with a palladium catalyst to obtain a second catalyst.
According to a preferred embodiment of the present invention, the step 1A may be performed as follows: the noble metal compound, the oxide support and water are mixed to obtain a first catalyst slurry.
According to some embodiments of the invention, the noble metal compound comprises a compound of a soluble salt of a noble metal, preferably comprising chloroplatinic acid and/or palladium nitrate.
According to a preferred embodiment of the present invention, the step 1B may be performed as follows: and adding the molecular sieve into the metal compound solution for dipping, drying and roasting to obtain the catalyst.
According to some embodiments of the invention, the metal compound comprises a metal soluble salt compound, preferably comprising iron nitrate and/or copper nitrate.
According to a preferred embodiment of the present invention, the step 1D may be performed as follows: and mixing the metal modified molecular sieve and the palladium catalyst with water and aluminum sol to obtain second catalyst slurry.
According to some embodiments of the invention, said step S2 comprises: and coating the first catalyst slurry on a substrate, drying and roasting to form a first catalyst layer on the substrate.
According to a preferred embodiment of the present invention, the calcination temperature in step S2 is 450 to 650 ℃ and the calcination time is 1 to 10 hours.
According to some embodiments of the invention, said step S3 comprises: and coating the second catalyst slurry on the first catalyst layer, drying and roasting to form a second catalyst layer on the first catalyst layer.
According to a preferred embodiment of the present invention, the calcination temperature in step S3 is 400 to 600 ℃ and the calcination time is 2 to 8 hours.
According to another aspect of the present invention, there is provided a method of treating industrial waste gas, comprising: industrial waste gas is contacted with the catalyst. The exhaust gas VOCs and the nitrogen oxides, wherein the exhaust gas contains hydrocarbons and the nitrogen oxides. After the catalyst treatment, the following effects can be achieved: 1) Part of VOCs is adsorbed on the second catalyst layer and reacts with nitrogen oxide to generate N 2 、CO 2 And H 2 O; 2) Complete oxidation of part of VOCs to CO 2 And H 2 O。
Drawings
Fig. 1 shows a schematic structural view of a plurality of catalysts for treating industrial exhaust gas according to an embodiment of the present invention:
FIG. 2 shows the conversion of non-methane total hydrocarbons and NO, and the production of N, using the catalyst of example 1 of the invention 2 A graph of selectivity results of;
description of reference numerals: 10. a substrate; 20. a second catalyst layer; 30. a first catalyst layer; 201. a palladium catalyst.
Detailed Description
The present invention will be further illustrated by the following examples, but is not limited to these examples.
As shown in fig. 1, the present invention discloses a catalyst for treating industrial exhaust gas, which includes a substrate 10, a first catalyst layer 30 and a second catalyst layer 20.
According to a preferred embodiment of the present invention, the catalyst has a structure shown in fig. 1 (a), in which a first catalyst layer 30 is positioned on a substrate 10, and a second catalyst layer 20 is positioned on the first catalyst layer 30.
According to a preferred embodiment of the present invention, the catalyst has a structure shown in fig. 1 (B), in which a first catalyst layer 30 is positioned on a substrate 10, and a portion of the first catalyst layer 30 penetrates into the substrate 10, and a second catalyst layer 20 is positioned on the first catalyst layer 30.
According to a preferred embodiment of the present invention, the catalyst has a structure shown in fig. 1 (C), in which a first catalyst layer 30 is disposed on the substrate 10, a second catalyst layer 20 is disposed on the first catalyst layer 30, and at least a portion of the palladium catalyst 201 of the second catalyst is in contact with the first catalyst layer.
According to a preferred embodiment of the present invention, the catalyst has a structure shown in fig. 1 (D), wherein a first catalyst layer 30 is disposed on the substrate 10, a second catalyst layer 20 is disposed on the first catalyst layer 30, at least a portion of the palladium catalyst 201 of the second catalyst is in contact with the first catalyst layer, and the second catalyst portion covers the palladium catalyst 201.
According to a preferred embodiment of the present invention, the catalyst has a structure shown in fig. 1 (E), in which a first catalyst layer 30 is positioned on a substrate 10, a second catalyst layer 20 is positioned on the first catalyst layer 30, and a portion of the second catalyst layer is in contact with the substrate 10.
Examples 1 to 4 and comparative examples 1 to 3
Preparing a first layer catalyst: selecting a certain amount of gamma-Al with proper granularity (d 50 in the range of 2-5 mu m) 2 O 3 Adding a certain amount of deionized water and a precursor solution of platinum nitrate and palladium nitrate in a required proportion into the powder and the ball milling tank, wherein the content of noble metal elements accounts for the gamma-Al carrier 2 O 3 1wt% of the mass. The mixture was then ball milled for 2 hours to give a slurry. One end of a honeycomb substrate (rectangular parallelepiped with cell density of 300cpsi, wall thickness of 0.5mm, substrate size of 20mm × 50mm) was circulatedGradually immerging into the slurry in the direction vertical to the liquid level of the slurry until the slurry is totally immerged. Taking out, blowing out the redundant slurry in the pore channel by using compressed air, drying, and roasting for 3 hours at 450 ℃.
Preparing a second layer catalyst: and (3) impregnating the Beta molecular sieve with a copper nitrate solution to obtain the Cu-Beta catalyst with Cu of 2 weight percent. Separately, elemental Pd nanoparticles were generated in situ by a deposition precipitation method using an aqueous palladium nitrate solution as a precursor, and at the same time, the Pd nanoparticles were supported on the BN support in an amount of 0.5wt%, calculated on the BN support.
Deionized water and acidic alumina sol are added into the Cu-Beta catalyst and the Pd/BN catalyst, and slurry is obtained after ball milling. The honeycomb substrate coated with the first catalyst layer was immersed in the slurry, taken out, and excess slurry in the cell channels was blown out with compressed air, dried, and then calcined at 550 ℃ for 4 hours.
The catalyst compositions of examples 1-4 and comparative examples 1-3 are given in table 1.
TABLE 1
Figure BDA0002211504220000051
Figure BDA0002211504220000061
In table 1, the content of Pd is the mass of Pd based on the volume of the substrate, and the content of Pt is the mass of Pt based on the volume of the substrate.
Comparative example 4
(1) Selecting a certain amount of gamma-Al with proper granularity (d 50 in the range of 2-5 mu m) 2 O 3 Adding a certain amount of deionized water and a precursor solution of platinum nitrate and palladium nitrate in a required proportion into the powder and the ball milling tank, wherein the content of noble metal elements accounts for the gamma-Al carrier 2 O 3 1wt% of the mass. The mixture was then ball milled for 2 hours to give a slurry.
(2) And (3) impregnating the Beta molecular sieve with a copper nitrate solution to obtain the Cu-Beta catalyst with Cu of 2 weight percent. Separately, elemental Pd nanoparticles were generated in situ by a deposition precipitation method using an aqueous palladium nitrate solution as a precursor, and at the same time, the Pd nanoparticles were supported on the support BN in an amount of 0.5wt%, calculated on the basis of the BN support. Deionized water and acidic alumina sol are added into the Cu-Beta catalyst and the Pd/BN catalyst, and slurry is obtained after ball milling.
Mixing the slurry obtained in the step (1) and the slurry obtained in the step (2), and then gradually immersing the flow end of a honeycomb substrate (a cuboid with a cell density of 300cpsi, a wall thickness of 0.5mm and a substrate size of 20mm x 50mm) into the slurry in a direction perpendicular to the slurry liquid level until the honeycomb substrate is completely immersed into the slurry. Taking out, blowing out the redundant slurry in the pore channel by using compressed air, drying, and roasting for 4 hours at 450 ℃.
The content of each component in this comparative example is the same as that in example 1, but the coating layer includes the mixed components of the first and second layers in example 1.
Evaluation of catalytic Performance of the catalyst:
the method for testing the catalytic performance of the catalyst comprises the following steps: the catalyst evaluation device consists of a gas distribution system, a gas premixer, a gas preheater, a catalytic fixed bed reactor and a tail gas analysis and detection system. The catalyst adopts a cylindrical honeycomb catalyst with the diameter of phi 20mm and the length of 50mm and the density of holes of 300 meshes. The catalyst was placed in a fixed bed reactor, and the simulated exhaust gas consisted of: CO concentration 500ppm, non-methane Total hydrocarbons 2750mg/m 3 NO concentration 400mg/m 3 Oxygen volume fraction 8%, N 2 The space velocity is 15,000h for balance gas -1 . The activity was evaluated by controlling the reaction temperature at 300 to 500 ℃. The flow of each gas is controlled by a mass flow meter. The mixed gas is premixed and preheated before entering the catalytic reaction bed layer. The outlet non-methane hydrocarbon concentration is analyzed by gas chromatography, NO x The concentration was analyzed by infrared spectroscopy. Data were collected 24h after the catalytic reaction had run steadily.
Catalytic performance of the catalyst from conversion of non-methane hydrocarbons, NO conversion and N 2 The selectivity is reflected by 3 indexes. The conversion of non-methane hydrocarbons is calculated as:
Figure BDA0002211504220000071
wherein, C IN Is the concentration of non-methane alkanes in the feed gas, C OUT Is the concentration of outlet non-methane hydrocarbons.
The formula for calculating the NO conversion is as follows:
Figure BDA0002211504220000072
wherein [ NO ]] in Is the concentration of NO in the feed gas, [ NO ]] out Is the outlet NO concentration.
N 2 The calculation formula of selectivity is:
Figure BDA0002211504220000073
wherein [ NO ]] in Is the concentration of NO in the feed gas, [ NO ]] out [ NO2 ] concentration of Outlet NO] out Is export NO 2 Concentration of [ N2O ]] out Is an outlet N 2 The concentration of O.
FIG. 2 shows the conversion of non-methane total hydrocarbons and NO and the production of N over the catalyst of example 1 2 Of the cell.
Table 2 shows the evaluation effect data of the catalysts of examples 1 to 4 and comparative examples 1 to 4.
TABLE 2
Figure BDA0002211504220000074
Figure BDA0002211504220000081
Any numerical value mentioned in this specification, if there is only a two unit interval between any lowest value and any highest value, includes all values from the lowest value to the highest value incremented by one unit at a time. For example, if it is stated that the amount of a component, or a value of a process variable such as temperature, pressure, time, etc., is 50 to 90, it is meant in this specification that values of 51 to 89, 52 to 88 … … and 69 to 71 and 70 to 71 are specifically enumerated. For non-integer values, units of 0.1, 0.01, 0.001, or 0.0001 may be considered as appropriate. These are only some specifically named examples. In a similar manner, all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be disclosed in this application.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.

Claims (9)

1. A catalyst for treating industrial waste gas, comprising:
a substrate, a first catalyst layer and a second catalyst layer; the first catalyst layer is located on and/or within a substrate and the second catalyst layer is located on the first catalyst layer;
the first catalyst layer includes a carrier and a noble metal supported on the carrier; the noble metal of the first catalyst layer includes Pt and Pd;
the second catalyst layer comprises a metal-modified molecular sieve and a palladium catalyst; the metal element in the metal modified molecular sieve in the second catalyst layer is Cu, the molecular sieve is at least one of a Beta molecular sieve, an MOR molecular sieve and a Y-type molecular sieve, and the weight ratio of the metal element to the molecular sieve is (1-5): 100; the weight ratio of the metal modified molecular sieve to the palladium catalyst is (70-90) to (3-10).
2. The catalyst according to claim 1, wherein the support in the first catalyst layer comprises an oxide support.
3. The catalyst of claim 2, wherein the oxide comprises at least one of alumina, zirconia, silica, titania, and ceria.
4. A catalyst according to any one of claims 1 to 3, characterized in that the weight ratio of the noble metal element to the support is (0.05-5): 100.
5. The catalyst according to any one of claims 1 to 3, wherein the palladium catalyst comprises a carrier and palladium supported on the carrier; the carrier comprises a non-metallic carbide and/or a non-metallic nitride.
6. The catalyst of claim 5, wherein the support comprises BN and/or SiC.
7. The method for preparing the catalyst according to any one of claims 1 to 6, comprising the steps of:
s1, respectively preparing a first catalyst and a second catalyst;
s2, coating a first catalyst on a substrate to form a first catalyst layer;
and S3, coating a second catalyst on the first catalyst layer to form a second catalyst layer.
8. The method according to claim 7, wherein the step S1 includes:
1A, loading a noble metal compound on an oxide carrier, and roasting to obtain a first catalyst;
1B, loading metal on the molecular sieve, and roasting to obtain a metal modified molecular sieve;
1C, loading palladium on the non-metal carbide and/or non-metal nitride to obtain a palladium catalyst;
and 1D, mixing the metal modified molecular sieve with a palladium catalyst to obtain a second catalyst.
9. A method of treating industrial waste gas comprising: contacting a process gas with a catalyst according to any one of claims 1 to 6 or a catalyst prepared by a process according to claim 7 or 8.
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