CN114247450A

CN114247450A - Catalytic composition, catalyst layer, catalytic device and gas treatment system

Info

Publication number: CN114247450A
Application number: CN202111608402.6A
Authority: CN
Inventors: 唐杨; 赵峰; 刘中清
Original assignee: China Chemical Technology Research Institute
Current assignee: China Chemical Environmental Protection Catalyst Co ltd
Priority date: 2020-12-28
Filing date: 2021-12-24
Publication date: 2022-03-29
Anticipated expiration: 2041-12-24
Also published as: CN114247450B

Abstract

The invention relates to a catalytic composition, a catalyst layer, a catalytic device and a gas treatment system. The catalytic composition has improved ammoxidation catalytic activity.

Description

Catalytic composition, catalyst layer, catalytic device and gas treatment system

Technical Field

The invention relates to the field of catalysts, in particular to a catalytic composition, a catalyst layer, a catalytic device and a gas treatment system.

Background

In the exhaust gas purification system of a diesel engine, ammonia (NH) is used₃) As reducing agent to Nitrogen Oxides (NO)_x) Selective Catalytic Reduction (SCR) is performed. In order to maximize NOx conversion, excess ammonia is typically employed. This results in excess NH being present in the products after the SCR reaction₃。

Related art an Ammonia Slip Catalyst (ASC Catalyst) is disposed downstream of a Selective Catalytic Reduction (SCR) Catalyst to remove unreacted NH passing through the SCR Catalyst₃. NH over ASC catalyst₃Oxidizing and forming N as selectively as possible₂And H₂And O. The relevant reaction equation is as follows:

4NH₃+3O₂＝2N₂+6H₂O

2NH₃+2O₂＝N₂O+3H₂O

4NH₃+5O₂＝4NO+6H₂O

4NH₃+7O₂＝4NO₂+6H₂O

in the related technology, carriers such as titanium dioxide, aluminum oxide, silicon dioxide, zirconium oxide and the like are used for supporting noble metals (such as platinum, palladium or rhodium) to serve as ammonia slip catalysts.

Disclosure of Invention

The present disclosure provides a novel catalytic composition that exhibits significantly improved performance for use as an ammonia slip catalyst.

In some aspects, the present disclosure provides a catalytic composition comprising

(i) Tungsten oxide;

(ii) a zirconium oxide;

(iii) an M oxide comprising manganese oxide, cerium oxide, copper oxide, iron oxide, or combinations thereof.

In some embodiments, the molar ratio of the metal element in the tungsten oxide to the metal element in the zirconium oxide is 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1) to 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1);

in some embodiments, the molar ratio of the metal elements in the tungsten oxide to the total metal elements in the M oxide is 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1) to 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1).

In some embodiments, the M oxide comprises manganese oxide.

In some embodiments, the molar ratio of the metal element in the tungsten oxide to the metal element in the manganese oxide is 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1) to 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1);

in some embodiments, the M oxide comprises cerium oxide.

In some embodiments, the molar ratio of the metal elements in the tungsten oxide to the total metal elements in the cerium oxide is 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1) to 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2, or 1.9 to 2.1).

In some embodiments, the catalytic composition comprises tungsten oxide, zirconium oxide, manganese oxide, and cerium oxide.

In some embodiments, the catalytic composition comprises tungsten oxide, zirconium oxide, manganese oxide, and cerium oxide, the tungsten oxide, zirconium oxide, manganese oxide, and cerium oxide having the following proportions, in terms of moles of the metal elements each comprising: tungsten element: zirconium element: manganese element: the cerium element is 0.5 to 2.5 (e.g., 0.5 to 1, 1 to 1.5, 1.5 to 2, 2 to 2.5, 0.8 to 1.2, 0.9 to 1.1, 1.8 to 2.2 or 1.9 to 2.1) or 0.5 to 2.5 (e.g., 0.5 to 1, 1.5 to 2, 1.5 to 2, 1.2, 1.2.2, 0.9 to 1.1.1, 1.8 to 2.1, or 1.1).

In some embodiments, the catalytic composition comprises tungsten oxide, zirconium oxide, manganese oxide, and cerium oxide, the tungsten oxide, zirconium oxide, manganese oxide, and cerium oxide having the following proportions, in terms of moles of the metal elements each comprising: tungsten element: zirconium element: manganese element: the cerium element is 0.8 to 1.2 (e.g., 0.9 to 1.1):0.8 to 1.2 (e.g., 0.9 to 1.1).

In some embodiments, the catalytic composition comprises tungsten oxide, zirconium oxide, manganese oxide, and cerium oxide, the tungsten oxide, zirconium oxide, manganese oxide, and cerium oxide having the following proportions, in terms of moles of the metal elements each comprising: tungsten element: zirconium element: manganese element: cerium element 1:1:1: 1.

In some embodiments, the catalytic composition does not contain a platinum group metal element.

In some embodiments, the platinum group metal refers to platinum (Pt), palladium (Pd), osmium (Os), iridium (Ir), ruthenium (Ru), rhodium (Rh).

In some embodiments, the tungsten oxide is WO₃。

In some embodiments, the zirconium oxide is ZrO₂。

In some embodiments, the oxides of manganese include MnO, MnO₂、MnO₃、Mn₂O₃、Mn₂O₅、Mn₂O₇And Mn₃O₄One or more of (a).

In some embodiments, the cerium oxide comprises CeO₂、Ce₂O₃。

In some embodiments, the copper oxide comprises Cu₂O, CuO, respectively.

In some embodiments, the iron oxide comprises FeO, Fe₂O₃、Fe₃O₄One or more of (a).

In some embodiments, the catalytic composition is a powder.

In some embodiments, the powder of the catalytic composition has a D90 value of 1 to 100 μm, such as 1 to 50 μm, such as 1 to 20 μm, such as 1 to 10 μm.

In some aspects, the present disclosure provides the use of the above-described catalytic composition as an ammonia slip catalyst.

In some embodiments, the ammonia slip catalyst described above is used to catalyze the oxidation of ammonia gas by oxygen to form nitrogen and water.

In some embodiments, the above-described ammonia slip catalyst is used to catalyze the following reaction:

4NH₃+3O₂＝2N₂+6H₂O。

in some aspects, the present disclosure provides a method of catalyzing a composition as described above, comprising:

(1) providing a solution containing a corresponding proportion of metal ions (e.g., a salt solution of metal ions) based on the molar proportions of each metal element in the catalytic composition;

(2) adding alkali into the solution in the previous step to precipitate metal ions;

(3) carrying out solid-liquid separation on the product obtained in the last step, and collecting solids;

(4) roasting the solid in the last step;

optionally, the method further comprises:

(5) and (4) crushing the product in the last step.

In some embodiments, the solution of step (1) contains ammonium metatungstate (NH)₄)₆H₂W₁₂O₄₀。

In some embodiments, the solution of step (1) contains manganese acetate Mn (CH)₃COO)₂。

In some embodiments, the solution of step (1) contains cerium nitrate Ce (NO)₃)₃。

In some embodiments, the solution of step (1) contains zirconyl nitrate ZrO (NO)₃)₂。

In some embodiments, the base in step (2) comprises ammonia at a concentration of 10 to 30 wt% (e.g., 20 wt%).

In some embodiments, the solution is heated to 60-80 ℃ (e.g., 70 ℃) prior to the addition of the base in step (2).

In some embodiments, step (2) adds a base to a solution having a pH of 7.5 to 9 (e.g., 8).

In some embodiments, the solid-liquid separation in step (3) is filtration or centrifugation.

In some embodiments, step (3) further comprises the step of drying the collected solids at 100 to 150 ℃ (e.g., 120 ℃).

In some embodiments, the firing in step (4) is performed at 700 to 1000 ℃ (e.g., 800 to 900 ℃).

In some embodiments, the calcination in step (4) is for a time of 0.5 to 5 hours (e.g., 0.5 to 1.5 hours, e.g., 1 hour).

In some aspects, the present disclosure provides an ammonia slip catalyst comprising the catalytic composition of any of the above.

In some embodiments, the ammonia slip catalyst further comprises a binder.

In some embodiments, NH of the ammonia slip catalyst₃The conversion rate is 70-100% (e.g., 70-100%, 80-100%, 90-100%, e.g., 95-100%).

In some embodiments, N of the ammonia slip catalyst₂The selectivity is 50-100% (e.g., 60-100%, 70-100%, 80-100%, 90-100%, e.g., 95-100%).

In some aspects, the present disclosure provides a catalyst layer comprising

A first layer containing a selective catalytic reduction catalyst;

a second layer containing the ammonia slip catalyst;

wherein the second layer is located deeper in the catalyst layer than the first layer.

In some embodiments, in the first layer, the weight of the selective catalytic reduction catalyst > the weight of the ammonia slip catalyst ≧ 0;

in some embodiments, the weight of the ammonia slip catalyst > the weight of the selective catalytic reduction catalyst ≧ 0 in the second layer.

In some embodiments, a Selective Catalytic Reduction (SCR) catalyst is a catalyst that catalyzes a Selective Catalytic Reduction (SCR) process.

In an exemplary SCR process, NH₃Selectively and NO in the presence of oxygen_xReaction to produce N₂And H₂O。NO_xThe reduction process may involve one or more of the following chemical reactions:

1)4NH₃+4NO+O₂＝4N₂+6H₂o (Standard SCR reaction)

2)4NH₃+2NO+2NO₂＝4N₂+6H₂O (Rapid SCR reaction)

3)4NH₃+3NO₂＝3.5N₂+6H₂O (Slow SCR reaction)

In some embodiments, the selective catalytic reduction catalyst is a transition metal supported molecular sieve, for example a transition metal supported zeolite molecular sieve, for example a transition metal supported small pore zeolite molecular sieve. Transition metals include, for example, copper, iron, manganese, and cerium.

In some aspects, the present disclosure provides a catalytic device comprising a substrate and the ammonia slip catalyst described above coated on at least a portion of a surface of the substrate.

In some embodiments, the substrate has a porous structure.

In some embodiments, a catalytic device comprises a catalyst layer as described above overlying at least a portion of a surface of the substrate.

In some aspects, the present disclosure provides a gas treatment system comprising:

a first catalytic zone containing a selective catalytic reduction catalyst;

a second catalytic zone containing an ammonia slip catalyst;

wherein the first catalytic zone is located upstream of the second catalytic zone with respect to the gas stream to be treated passing through the system;

in some embodiments, in the first catalytic zone, the weight of the selective catalytic reduction catalyst > the weight of the ammonia slip catalyst ≧ 0;

in some embodiments, the weight of the ammonia slip catalyst > the weight of the selective catalytic reduction catalyst ≧ 0 in the second catalytic zone.

In some embodiments, the first catalytic zone and the second catalytic zone are each a porous ceramic support loaded with a catalyst.

In some embodiments, the catalytic composition is present at 0.5 to 5g/inch³(e.g., 0.5 to 1 g/inch)³、1～2g/inch³、2～3g/inch³、3～4g/inch³、4～5g/inch³、2～2.6g/inch³Or 2.5g/inch³) Deposited on a honeycomb ceramic support having a cell density of 400cpsi (cells per square inch) and a wall thickness of 6 mils, a diameter of 1 inch, and a length of 3 inches, at 100,000hr^-1At a space velocity of (a) in the feed stream comprising 500ppmNO, 550ppmNH₃、10％O₂、5％H₂O, in N₂The catalyst is effective to provide an average NO conversion of 70% to 100% (e.g., 70-100%, 80-100%, 90-100%, e.g., 95-100%) when tested at 150 ℃ -600 ℃ (e.g., 200 ℃, 550 ℃) in the presence of an equilibrium gas.

In some embodiments, the catalytic composition is present at 0.5 to 5g/inch³(e.g., 0.5 to 1 g/inch)³、1～2g/inch³、2～3g/inch³、3～4g/inch³、4～5g/inch³、2～2.6g/inch³Or 2.5g/inch³) Deposited on a honeycomb ceramic support having a cell density of 400cpsi (cells per square inch) and a wall thickness of 6 mils, a diameter of 1 inch and a length of 2 inches, and a duration of 100,000hr^-1At a space velocity of 500ppmNO, 550ppmNH in the feed stream₃、10％O₂、5％H₂O, in N₂The catalyst is effective in providing a catalyst when tested at 350 ℃ in the case of an equilibrium gas<Ammonia slip concentration of 10 ppm.

In some embodiments, the catalytic composition is at 10% H₂The retention rate of the NO conversion rate is 50-100% (such as 60-100%, 70-100%, 80-100%, 90-100%, such as 95-100%) after hydrothermal aging for 50 hours at 700 ℃ in the presence of O.

In some embodiments, the catalytic composition/catalyst layer/catalytic device/gas treatment system may be performed on gas from a combustion process, such as from an internal combustion engine (whether mobile or stationary), a gas turbine, and a coal-, oil-, or natural gas-fired plant or engine. The process may also be used to treat gases from industrial processes such as refineries, from refinery furnaces and boilers, smelters, chemical processing industries, coke ovens, municipal waste treatment and incinerators, coffee roasting plants, and the like. In one embodiment, the catalytic composition/catalyst layer/catalytic device/gas treatment system of the present invention is used to treat exhaust gas from a vehicular internal combustion engine, such as a gasoline engine, under rich conditions, or from a stationary engine powered by liquid petroleum gas or natural gas.

Description of terms:

as used herein, the term "catalyst" refers to a material that promotes a reaction.

The term "catalytic composition" refers to a combination of two or more catalysts, for example a combination of two different materials that promote a reaction. The catalytic composition may be in the form of a washcoat.

The term nitrogen oxides NOx denotes nitrogen oxides, in particular nitrous oxide (N)₂O), Nitric Oxide (NO), dinitrogen trioxide (N)₂O₃) Nitrogen dioxide (NO)₂) Dinitrogen tetroxide (N)₂O₄) Dinitrogen pentoxide (N)₂O₅) Nitrogen peroxide (NO)₃)。

"comprising", "including" and "containing" may mean a content greater than zero, such as 1% or more, such as 10% or more, such as 20% or more, such as 30% or more, such as 40% or more, such as 50% or more, such as 60% or more, such as 70% or more, such as 80% or more, such as 90% or more, such as 100%. The meaning of "comprising", "including" and "containing" corresponds to "consisting of …" when the content is 100%.

The Ammonia Oxidation Catalyst (AMOX Catalyst), Ammonia Slip Catalyst (ASC), and Ammonia Slip Catalyst (ASC) have the same meaning in the present invention

Advantageous effects

One or more technical schemes of the present disclosure have one or more of the following beneficial effects:

(1) the catalytic composition has improved ammoxidation catalytic activity;

(2) catalytic compositions having improved N₂Selectivity;

(3) the catalytic composition has improved resistance to hydrothermal aging;

(4) the catalytic composition has simple preparation method and low cost, and is suitable for large-scale application.

Drawings

FIG. 1 shows a schematic catalyst layout for a catalytic device;

fig. 2 shows a schematic catalyst layout for yet another catalyst layer.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The medicines or instruments used are not indicated by manufacturers, and are all conventional products which can be obtained commercially.

Example 1.1 [ WMnCeZrO_xPowder (C)

Composite oxide (WMnCeZrO)_x) Preparation of powder:

ammonium metatungstate (NH)₄)₆H₂W₁₂O₄₀Manganese acetate Mn (CH)₃COO)₂Cerium nitrate Ce (NO)₃)₃Zirconium oxynitrate ZrO (NO)₃)₂Mixing and dissolving the components in deionized water according to the molar ratio of W to Mn to Ce to Zr of 1:1:1:1, uniformly stirring, heating to 70 ℃, then slowly dropwise adding 20% ammonia water to generate a precipitate until the pH value is adjusted to 8, keeping stirring at 70 ℃ for 20min, then carrying out suction filtration, drying the obtained filter cake at 120 ℃ for 2h, then roasting at 850 ℃ for 1h, and finally grinding the roasted solid into powder.

The above-described composite oxide powder is subsequently used as an ammonia slip catalyst powder.

Example 1.2 [ WMnCeZrO_xSlurry

Composite oxide (WMnCeZrO)_x) Preparation of slurry:

WMnCeZrO prepared in example 1.1 was added to deionized water_xPowdering and adding a certain amount of surfactant, grinding the slurry to a particle size D90 of 6-9 μm, adjusting the slurry to pH 8-9 with ammonia water, and finally adjusting the slurry concentration to 40 wt% solids content.

The above-described composite oxide slurry was used as an ammonia slip catalyst slurry (ASC catalyst slurry) in the subsequent example.

Example 2.1 [ WMnCeZrO_xCatalytic device

Preparation of the ammonia slip catalytic device:

a honeycomb ceramic support having a cell density of 400cpsi (cells per square inch) and a wall thickness of 6 mils, a diameter of 1 inch, and a length of 3 inches was provided. The composite oxide slurry prepared in example 1.2 was coated on a honeycomb ceramic support. The coated carrier was dried at 120 ℃ for 1h and calcined at 450 ℃ for 30 minutes to obtain the catalytic device of the present example. The total dry weight of the catalyst coating was 2.5g/inch³。

Example 2.2 [ SCR + WMnCeZrO_xLayered catalytic apparatus ]

Fig. 1 shows a schematic catalyst layout of a catalytic device comprising an upstream zone 11 and a downstream zone 12, as shown, with respect to the flow direction of the gas stream 6 to be treated passing through the catalytic device. The upstream zone 11 contains an SCR catalyst and the downstream zone 12 contains an ASC catalyst.

The preparation method of the catalytic device comprises the following steps:

a honeycomb ceramic support having a cell density of 400cpsi (cells per square inch) and a wall thickness of 6 mils, a diameter of 1 inch, and a length of 3 inches was provided.

Provided is a selective catalytic reduction catalyst slurry (SCR catalyst slurry), which is prepared by the following steps: a quantity of copper acetate and molecular sieve was added to deionized water and stirred for 30 minutes, with stirring, dilute acetic acid and zirconium acetate binder (containing 30% ZrO)₂) Adding the copper-containing composite into the slurry, adding a certain amount of surfactant to adjust the property of the slurry, grinding, and finally adjusting the concentration of the slurry to 40% of solid content, wherein the copper loading in the slurry is 4 wt%, and the copper loading is calculated as the weight percentage of CuO/(CuO + molecular sieve).

The honeycomb ceramic support is divided into an upstream coating region and a downstream coating region along the length direction of the honeycomb ceramic support, and the length ratio of the upstream coating region to the downstream coating region is 2: 1. The SCR catalyst slurry was coated on the upstream zone of the carrier, the ASC catalyst slurry prepared in the above example 1.2 was coated on the downstream zone of the carrier, and the coated carrier was dried at 120 ℃ for 1h and calcined at 450 ℃ for 30 minutes to obtain the catalytic device of example 2.1. The total dry weight of the catalyst coating was 2.5g/inch³The dry weight ratio of the coating in the upstream and downstream regions was 2: 1.

Example 2.3 [ SCR + WMnCeZrO_xLayered catalytic apparatus ]

Fig. 2 shows a schematic catalyst layout of yet another catalytic device, which, as shown, includes a catalyst layer 2, the catalyst layer 2 including a first layer 21, the first layer 21 containing a first layer of molecular sieves containing elemental copper at a loading of 4.5%; and a second layer 22, wherein the second layer 22 contains a second molecular sieve, and the second molecular sieve contains 4.8% of copper element. The second layer is located deeper in the catalyst layer than the first layer, i.e. the second layer 22 is located further from the gas flow 6 to be treated than the first layer 21.

A honeycomb ceramic support having a cell density of 400cpsi (cells per square inch) and a wall thickness of 6 mils, a diameter of 1 inch, and a length of 2 inches was provided.

The ASC catalyst slurry prepared in example 1.2 was coated on the above-mentioned carrier, and dried at 120 ℃ for 1h after coating to be used as an undercoat layer. Then the SCR catalyst slurry (same as example 2.2) was coated on the lower coat and dried at 120 ℃ for 1h to form the upper coat. The coated support was calcined at 450 ℃ for 30 minutes to obtain the catalytic device of example 2.2. The total coating dry weight of the catalytic device was 2.5g/inch³The dry weight ratio of the upper coating to the lower coating was 4: 1.

Comparative example 1.1 [ MnCeZrO ]_xCatalytic unit comparative example 1.1 differs from example 2.1 in the composition of the ASC catalyst slurry. In this comparative example, the preparation of the ASC catalyst slurry was as follows:

(1) composite oxide (MnCeZrO)_x) Preparation of powder: mixing manganese acetate Mn (CH)₃COO)₂Cerium nitrate Ce (NO)₃)₃Zirconium oxynitrate ZrO (NO)₃)₂Mixing and dissolving the components in deionized water according to the molar ratio of W to Mn to Ce to Zr of 1:1:1:1, uniformly stirring, heating to 70 ℃, then slowly dropwise adding 20% ammonia water to generate a precipitate until the pH value is adjusted to 8, keeping stirring at 70 ℃ for 20min, then carrying out suction filtration, drying the obtained filter cake at 120 ℃ for 2h, then roasting at 850 ℃ for 1h, and finally grinding the roasted solid into powder.

(2) Adding the prepared MnCeZrO into deionized water_xPowdering and adding a certain amount of surfactant, grinding the slurry to a particle size D90 of 6-9 μm, adjusting the slurry to pH 8-9 with ammonia water, and finally adjusting the slurry concentration to 40 wt% solids content.

In addition to the differences described above, the other process parameters were kept in accordance with example 2.1, obtaining a catalytic device according to this comparative example.

Comparative example 1.2 [ SCR + MnCeZrO ]_xZoned catalytic device

Comparative example 1.2 differs from example 2.2 in the composition of the ASC catalyst slurry.

The preparation method of the ASC catalyst slurry of this example is as follows:

In addition to the differences described above, the other process parameters were kept in accordance with example 2.2, and the catalytic device of this comparative example was obtained.

Comparative example 1.3 [ SCR + MnCeZrO ]_xLayered catalytic apparatus ]

Comparative example 1.3 differs from example 2.3 in the composition of the ASC catalyst slurry.

(1) composite oxide (MnCeZrO)_x) Preparation of powder: mixing manganese acetate Mn (CH)₃COO)₂Cerium nitrate Ce (NO)₃)₃Zirconium oxynitrate ZrO (NO)₃)₂Mixing and dissolving the components in deionized water according to the molar ratio of W to Mn to Ce to Zr of 1:1:1:1, uniformly stirring, heating to 70 ℃, then slowly dropwise adding 20% ammonia water to generate a precipitate until the pH value is adjusted to 8, keeping stirring at 70 ℃ for 20min, then performing suction filtration, and drying the obtained filter cake at 120 DEG CDrying for 2h, then roasting for 1h at 850 ℃, and finally grinding the roasted solid into powder.

In addition to the above differences, the other process parameters were kept in accordance with example 2.3, and the catalytic device of this comparative example was obtained.

Comparative example 2.1 [ SCR + Pt layered catalytic device ]

The difference from example 2.1 is the composition of the ASC catalyst slurry. In this comparative example, the preparation of the ASC catalyst slurry was as follows:

soaking a certain amount of platinum nitrate solution in 5% SiO in the same volume₂/Al₂O₃Adding the powder impregnated with the noble metal into deionized water, stirring, adding a certain amount of surfactant to adjust the property of the slurry, grinding, and finally adjusting the concentration of the slurry to 40% of solid content.

In addition to the differences described above, the other process parameters were kept in accordance with example 2.2, and the catalytic device of this comparative example was obtained. The coating dry weight of the honeycomb porous catalytic device was 2.5g/inch³Platinum (Pt) loading of 2g/ft³。

Analysis and detection 1: test for catalytic reaction

Providing a reactor containing the catalysts of the above examples and comparative examples, and introducing a gas to be catalyzed into the reactor, wherein the gas comprises the following components: 500ppmNO, 550ppmNH₃、10％O₂、5％H₂O, in N₂Is the balance gas. At the temperature of 150-600 ℃ for 100,000h^-1The space velocity of (3) for catalytic oxidation treatment. Analyzing ammonia, NO and NO in gas before and after catalysis by Fourier Transform Infrared (FTIR) detector₂And N₂The amount of O. The NO conversion and NH were calculated by the following formulas₃Leakage amount (ppm):

wherein (1) represents the mass content of each corresponding component in the gas before the catalytic oxidation treatment, and (2) represents the mass content of each corresponding component in the gas after the catalytic oxidation treatment.

And (3) analysis and detection 2: hydrothermal stability test:

and carrying out hydrothermal aging treatment on the freshly prepared catalytic device. The hydrothermal aging treatment conditions were as follows: at 10% H₂The mixture was left at 700 ℃ for 50 hours in an atmosphere containing O. Then carrying out catalytic reaction test on the catalytic device after hydrothermal aging treatment, and testing the NO conversion rate and N of the catalytic device₂And (4) selectivity.

Low and high temperature NOx conversion and ammonia slip tests were performed as in example 2.3 and comparative example 2.1 and the results are shown in the table below.

As can be seen from the results in the table, the NOx conversion and NH of the examples which do not contain noble metals₃The leakage amount can be close to or equal to that of a comparative example containing precious metal, and the preparation cost of the catalyst can be obviously reduced by using nonmetal to replace the traditional precious metal catalyst, such as a platinum metal catalyst, so that the potential of a non-precious metal formula is shown.

While specific embodiments of the invention have been described in detail, those skilled in the art will understand that: various modifications may be made in the details within the teachings of the disclosure, and these variations are within the scope of the invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

Claims

1. A catalytic composition comprising

(i) Tungsten oxide;

(ii) a zirconium oxide;

(iii) an M oxide comprising manganese oxide, cerium oxide, copper oxide, iron oxide, or a combination thereof;

preferably, the catalytic composition does not contain platinum group metal elements.

2. The catalytic composition of claim 1, having one or more of the following characteristics:

-the molar ratio of the metal element in the tungsten oxide to the metal element in the zirconium oxide is 0.5-2.5: 0.5-2.5;

-the molar ratio of the metal elements in the tungsten oxide to the total metal elements in the M oxide is 0.5-2.5: 0.5-2.5;

the M oxide comprises manganese oxide, preferably, the molar ratio of the metal element in the tungsten oxide to the metal element in the manganese oxide is 0.5-2.5: 0.5-2.5;

the M oxide comprises cerium oxide, and preferably, the molar ratio of the metal elements in the tungsten oxide to the total metal elements in the cerium oxide is 0.5-2.5: 0.5-2.5.

3. The catalytic composition of claim 1, having one or more of the following characteristics:

-said tungsten oxide is WO₃；

-the zirconium oxide is ZrO₂；

-said oxides of manganese comprise MnO, MnO₂、MnO₃、Mn₂O₃、Mn₂O₅、Mn₂O₇And Mn₃O₄One or more of;

-said cerium oxide comprises CeO₂、Ce₂O₃；

-said copper oxide comprises Cu₂O, CuO;

-said iron oxide comprises FeO, Fe₂O₃、Fe₃O₄One or more of (a).

4. Use of a catalytic composition according to any one of claims 1 to 3 as an ammonia slip catalyst;

preferably, the ammonia slip catalyst is used to catalyze the following reaction:

4NH₃+3O₂＝2N₂+6H₂O。

5. a process for preparing the catalytic composition of any of claims 1 to 3, comprising:

(1) providing a solution containing metal ions in a corresponding ratio (e.g., a salt solution of the metal ions) based on the molar ratio of each metal element in the catalytic composition;

(4) roasting the solid in the last step;

optionally, the method further comprises:

(5) and (4) crushing the product in the last step.

6. The method of claim 5, having one or more of the following features;

-the solution of step (1) contains ammonium metatungstate (NH)₄)₆H₂W₁₂O₄₀；

Manganese acetate Mn (CH) in the solution of step (1)₃COO)₂；

The solution of step (1) contains cerium nitrate Ce (NO)₃)₃；

The solution of step (1) contains zirconium oxynitrate ZrO (NO)₃)₂；

-the base in step (2) comprises ammonia at a concentration of 10% to 30% by weight;

-heating the solution to 60-80 ℃ before adding the base in step (2);

adding alkali in the step (2) until the pH value of the solution is 7.5-9;

-step (3) further comprises the step of drying the collected solid at a temperature of 100 ℃ to 150 ℃;

-the calcination in step (4) is carried out at a temperature of 700 ℃ to 1000 ℃;

the calcination time in step (4) is between 0.5 and 5 hours.

7. An ammonia slip catalyst comprising the catalytic composition of any one of claims 1 to 3;

preferably, NH of the ammonia slip catalyst₃The conversion rate is 70% -100% (e.g. 70% -100%, 80% -100%, 90% -100%, e.g. 95% -100%);

preferably, N of the ammonia slip catalyst₂The selectivity is 50% -100% (e.g. 60% -100%, 70% -100%, 80% -100%, 90% -100%, e.g. 95% -100%).

8. A catalyst layer comprising

A first layer containing a selective catalytic reduction catalyst;

a second layer containing the ammonia slip catalyst of claim 7;

wherein the second layer is located deeper in the catalyst layer than the first layer;

preferably, in the first layer, the weight of the selective catalytic reduction catalyst is more than or equal to 0;

preferably, in the second layer, the weight of the ammonia slip catalyst > the weight of the selective catalytic reduction catalyst ≧ 0.

9. A catalytic device comprising a substrate and the ammonia slip catalyst of claim 7 coated on at least a portion of a surface of the substrate;

preferably, the substrate has a porous structure;

preferably, the catalytic device comprises the catalyst layer of claim 9 overlying at least a portion of a surface of the substrate.

10. A gas treatment system, comprising:

a first catalytic zone containing a selective catalytic reduction catalyst;

a second catalytic zone containing the ammonia slip catalyst of claim 7;

preferably, in the first catalytic zone, the weight of the selective catalytic reduction reaction catalyst is more than or equal to 0;

preferably, in the second catalytic zone, the weight of the ammonia slip catalyst > the weight of the selective catalytic reduction catalyst ≧ 0.