Catalyst for post-treatment of methanol engine and application of catalyst

Abstract

The invention provides a catalyst for post-treatment of a methanol engine and application of the catalyst, and belongs to the technical field of catalysis. The catalyst comprises a base material and an active coating which are arranged in a laminated manner, the active coating comprises a first active coating and a second active coating, the first active coating comprises a platinum group noble metal loaded on the first carrier, and the second active coating comprises a non-noble metal oxide loaded on the second carrier. The catalyst provided by the invention not only has the effect of oxidizing pollutants such as CO, Cl hydrocarbon, methanol and formaldehyde, but also can reduce NO2 into NO to the greatest extent, so that the emission ratio of NO2 in tail gas of a methanol engine is greatly reduced, and the harm of NO2 toxicity to a human body is greatly weakened. The catalyst is wide in efficiency window and low in manufacturing cost and has application prospects.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysis technology, and particularly relates to a catalyst for post-treatment of a methanol engine and application thereof. BACKGROUND

[0002] The traditional diesel oxidation catalyst (DOC) mainly functions to oxidize and burn the hydrocarbons entering the inside of the DOC, and the heat generated thereby can provide a high-temperature environment for DPF (diesel particulate filter) regeneration; the DOC can also be used to eliminate soluble organic compounds SOF (which are derived from incompletely combusted hydrocarbons or engine oil) in tail gas, thereby reducing part of the particulate matter; and can also serve as a front stage for passive regeneration of the DPF, oxidizing NO emitted by the engine tail gas into NO2 to generate a strong oxidant for oxidation of carbon particles, and enabling active regeneration by opening the post-injection, oxidizing the hydrocarbons and releasing energy to increase the regeneration temperature to the light-off temperature.

[0003] Patent CN1805781A discloses a method for decomposing nitrogen dioxide into nitric oxide in exhaust gas of a lean-burn internal combustion engine, the method comprising adjusting the ratio of Cl hydrocarbon: nitrogen oxide in the exhaust gas to be 0.1 to 2; contacting the gas mixture with a particulate acid-resistant refractory oxide selected from the group consisting of zeolite, titanium dioxide doped with tungsten, silica-titania, zirconia-titania, gamma-alumina, amorphous silica-alumina and a mixture of any two or more thereof; and discharging the exhaust gas into the atmosphere. The particulate refractory oxide is loaded with a metal or a compound thereof, and the metal is selected from the group consisting of rhodium, palladium, iron, copper and a mixture of any two or more thereof. Patent CN101072622A discloses a method for decomposing NO2 in exhaust gas of a lean-burn internal combustion engine into NO, the method comprising the steps of: contacting an acid metal oxide with a gas mixture comprising exhaust gas, the acid metal oxide being selected from the group consisting of zeolite, tungsten-doped titanium oxide, silica-titania, zirconia-titania, gamma-alumina, amorphous silica-alumina and a mixture of any two or more thereof; adjusting the composition of the gas mixture by injecting hydrocarbons thereinto, the rate of injection of the hydrocarbons being varied during the loading cycle so that the ratio of Cl hydrocarbon:nitrogen oxide of the gas mixture in contact with the acid metal oxide during the loading cycle is on average 0.1 to 2.0; and directly passing the exhaust gas to the atmosphere, optionally first contacting the gas mixture with a hydrocarbon oxidation catalyst. The acid metal oxide is loaded with a metal or a compound thereof, and the metal is selected from the group consisting of rhodium, palladium, iron, copper and a mixture of any two or more thereof.

[0004] It can be seen that the traditional DOC focuses on improving the catalyst's ability to oxidize CO, HC and NO. The NO2 concentration in the engine exhaust increases significantly after passing through the DOC. If the traditional DOC is directly used for exhaust treatment of methanol engines (internal combustion engines powered by methanol as the main fuel), it will lead to a high proportion of NO2 in the emissions. Since the toxic effect of NO2 on the human body is 4-5 times that of NO, long-term exposure can easily cause respiratory diseases, cancer, etc., and therefore it is very harmful to the human body and the environment.

[0005] Therefore, there is an urgent need to provide a catalyst for methanol engines that can reduce NO2 emissions and purify pollutants such as CO, Cl hydrocarbons, methanol, and formaldehyde. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention provides a catalyst for methanol engine post-treatment and its application. The catalyst provided by this invention not only oxidizes pollutants such as CO, Cl hydrocarbons, methanol, and formaldehyde, but also reduces NO₂ to NO to the greatest extent possible, significantly reducing the proportion of NO₂ emissions in methanol engine exhaust and significantly reducing the harmful effects of NO₂ toxicity on the human body. The catalyst has a wide efficiency window, low manufacturing cost, and promising application prospects.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a catalyst for post-treatment of a methanol engine, the catalyst comprising a substrate and an active coating layer arranged in layers.

[0009] The active coating comprises a first active coating and a second active coating, wherein the first active coating comprises a platinum group noble metal supported on a first carrier, and the second active coating comprises a non-noble metal oxide supported on a second carrier.

[0010] The catalyst provided by this invention combines a first active coating layer containing a platinum-group noble metal with a second active coating layer containing a non-noble metal oxide. The synergistic effect of these two layers allows the catalyst to oxidize pollutants such as CO, Cl hydrocarbons (hydrocarbon derivatives containing chlorine atoms), methanol, and formaldehyde, while also maximizing the reduction of NO₂ to NO. This significantly reduces the proportion of NO₂ emissions from methanol engine exhaust and significantly mitigates the harmful effects of NO₂ toxicity on the human body. This catalyst has a wide efficiency window, low manufacturing cost, and promising application prospects.

[0011] Preferably, the first active coating and the second active coating are selected from any one of the following combinations:

[0012] Method 1: The first active coating layer and the second active coating layer are stacked in sequence in a direction away from the substrate.

[0013] Mode 2: The first active coating layer and the second active coating layer are arranged side by side, and the first active coating layer and the second active coating layer are arranged laterally along the horizontal direction of the substrate.

[0014] In the present invention, the first method can reduce the space velocity, thereby improving the overall efficiency of the catalyst, and the second method can make the synergistic effect of the first active coating and the second active coating more fully exerted, thereby improving the stability and catalytic efficiency of the catalyst.

[0015] Preferably, the platinum group noble metal includes Pt and / or Pd, preferably a combination of Pt and Pd.

[0016] Preferably, in the combination of Pt and Pd, the mass ratio of Pt to Pd is (10-1):(1-10). Exemplarily, the selection range of Pt "10-1" can be, for example, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1, and the selection range of Pd "1-10" can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc.

[0017] In the present invention, the appropriate mass ratio of Pt and Pd helps to maximize the conversion of NO2 into NO while ensuring the oxidation of CO, Cl hydrocarbons, methanol, and formaldehyde, thereby reducing environmental hazards.

[0018] Preferably, the mass ratio of Pt to Pd is 1: 1. Preferably, the material of the first carrier comprises a metal oxide or a non-noble metal modified mixed oxide thereof.

[0019] Preferably, the metal oxide includes any one of aluminum oxide, cerium oxide and / or cerium-zirconium-aluminum oxide, or a combination of at least two thereof.

[0020] Preferably, the non-noble metal comprises any one of barium, potassium or strontium or a combination of at least two of them. The non-noble metal oxide comprises MoO x1 、CoO x2 or FeO x3 Any one or a combination of at least two of the above, the values ​​of x1, x2 and x3 are independently 2-3, for example, 2, 2.5 or 3.

[0021] Preferably, the material of the second support comprises a metal oxide or a non-noble metal modified mixed oxide thereof.

[0022] Preferably, the metal oxide includes any one or a combination of at least two of titanium oxide, cerium oxide, tungsten oxide, magnesium oxide, aluminum oxide, zirconium oxide, cobalt oxide, nickel oxide, niobium oxide, indium oxide, tin oxide, zinc oxide or copper oxide.

[0023] Preferably, the non-noble metal includes any one or a combination of at least two of nickel, manganese, strontium, titanium, zirconium, niobium, iron, zinc, silver, samarium, europium, lithium, sodium, potassium, cesium, calcium, barium, magnesium, vanadium, chromium, neodymium, praseodymium, yttrium or lanthanum.

[0024] Preferably, in the first active coating, the loading amount of the platinum group noble metal on the first carrier is 20-300 g / L, for example, it can be 20 g / L, 50 g / L, 100 g / L, 150 g / L, 200 g / L, 250 g / L or 300 g / L, etc., preferably 80-150 g / L.

[0025] In the present invention, an appropriate loading amount of platinum group noble metals is combined with non-noble metal oxides, thereby enabling the catalyst to more effectively adsorb reactant molecules and promote chemical reactions while reducing catalyst costs, thereby improving catalytic activity. In the treatment of methanol engine exhaust, harmful gases can be more efficiently converted into harmless substances.

[0026] Preferably, the density of the platinum group noble metal in the first active coating is 2-200 g / ft 3 , for example, it can be 2.5g / ft 3 , 5g / ft 3 , 10g / ft 3 , 50g / ft 3 , 100g / ft 3 、150g / ft 3 or 200g / ft 3 wait.

[0027] Preferably, in the second active coating, the loading amount of the non-precious metal oxide on the second carrier is 20-300 g / L, for example, it can be 20 g / L, 50 g / L, 100 g / L, 150 g / L, 200 g / L, 250 g / L or 300 g / L, etc., preferably 80-150 g / L.

[0028] In this invention, the combination of an appropriate loading of non-precious metal oxides and a suitable loading of platinum-group precious metals can enhance the chemical reaction rates of CO, Cl hydrocarbons, methanol, and NO₂ in methanol engine exhaust, while simultaneously reducing the amount of precious metals used and catalyst costs. Furthermore, it maximizes the conversion of NO₂ to NO, minimizing environmental hazards.

[0029] Preferably, the density of the non-precious metal in the second active coating is 100-2000 g / ft 3 , for example, it can be 100g / ft 3 , 200g / ft 3 、300g / ft 3 , 400g / ft 3, 500g / ft 3 、600g / ft 3 , 700g / ft 3 , 800g / ft 3 , 1000g / ft 3 , 1200g / ft 3 、1400g / ft 3 、1600g / ft 3 、1800g / ft 3 or 2000g / ft 3 etc., preferably 300-1000g / ft 3 .

[0030] Preferably, in the first embodiment, the thickness ratio of the first active coating layer to the second active coating layer is 1:(0.5-1.5), for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.3 or 1:1.5.

[0031] Preferably, in the second embodiment, the lateral length ratio of the first active coating layer to the second active coating layer is 1:(0.8-1.2), for example, it can be 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2.

[0032] Preferably, the substrate is a porous structure.

[0033] It should be noted that the substrate can be composed of materials known in the art, such as ceramics or ceramic-like materials, for example, cordierite, α-alumina, aluminosilicate, cordierite-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconium oxide, mullite, zircon, zircon mullite, zirconium silicate, sillimanite, magnesium silicate, petalite, spodumene, alumina-silica-magnesium oxide or zirconium silicate, etc. In addition, it can also be a metal, such as a heat-resistant metal or a metal alloy, specifically, for example, titanium or stainless steel, etc.

[0034] It should be noted that the substrate may have any possible shape, but must be in contact with the active coating thereon, for example, it may have a circular or square cross-sectional shape.

[0035] Preferably, in the second method, the first active coating is located at the air inlet end of the substrate, and the second active coating is located at the air outlet end of the substrate.

[0036] In the present invention, the purpose of the above design is to increase the local concentration of precious metals, which helps to improve the ignition performance.

[0037] In a second aspect, the present invention provides a method for preparing the catalyst for methanol engine post-treatment as described in the first aspect, the preparation method comprising the following steps:

[0038] The noble metal-containing slurry and the non-noble metal-containing slurry are coated on a substrate respectively, and then calcined and hydrothermally aged to obtain the catalyst for methanol engine post-treatment.

[0039] It should be noted that the present invention does not specifically limit the solvents containing precious metal slurry and non-precious metal slurry. For example, the solvent containing precious metal slurry can be, for example, an acetic acid aqueous solution or water, and the solvent containing non-precious metal slurry can be, for example, an ammonia aqueous solution, an ammonium carbonate aqueous solution or water.

[0040] Preferably, the coating method is method one or method two.

[0041] Method 1: Coating a precious metal slurry and a non-precious metal slurry on the surface of a substrate in sequence.

[0042] Method 2: Coat the precious metal slurry on the air inlet end of the substrate, and coat the non-precious metal slurry on the air outlet end of the substrate.

[0043] Preferably, the calcination atmosphere is air atmosphere or inert atmosphere. Exemplarily, the inert atmosphere may be nitrogen atmosphere.

[0044] Preferably, the calcination temperature is 300-600°C, for example, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or 600°C.

[0045] Preferably, the calcination time is 3-5 hours, for example, 3 hours, 4 hours or 5 hours.

[0046] Preferably, the temperature of the hydrothermal aging is 650-800°C, for example, it can be 650°C, 700°C, 720°C, 740°C, 760°C, 780°C or 800°C.

[0047] Preferably, the hydrothermal aging time is 12-20 h, for example, 12 h, 14 h, 16 h, 18 h or 20 h.

[0048] In a third aspect, the present invention provides a use of the catalyst for methanol engine post-treatment as described in the first aspect, wherein the catalyst is used for exhaust gas treatment of a methanol engine.

[0049] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The catalyst provided by this invention not only oxidizes pollutants such as CO, Cl hydrocarbons, methanol, and formaldehyde, but also reduces NO₂ to NO to the greatest extent possible. This significantly reduces the proportion of NO₂ emissions from methanol engine exhaust and significantly mitigates the harmful effects of NO₂ on the human body. The catalyst has a wide efficiency window, low manufacturing cost, and promising application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic structural diagram of the catalyst provided in Example 1 of the present invention.

[0053] Figure 2 This is a schematic structural diagram of the catalyst provided in Example 4 of the present invention.

[0054] 1 - substrate; 2 - first active coating; 3 - second active coating. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0056] Example 1

[0057] This embodiment provides a catalyst for methanol engine post-treatment, and its structural diagram is shown in FIG. Figure 1 As shown, the catalyst includes a substrate 1 and an active coating layer that are stacked.

[0058] The active coating includes a first active coating 2 and a second active coating 3, which are stacked in sequence along a direction away from the substrate 1; the first active coating 2 includes a platinum group precious metal supported on a first carrier, and the second active coating 3 includes a non-precious metal oxide supported on a second carrier.

[0059] The platinum group noble metals include Pt and Pd in ​​a mass ratio of 1:1; the material of the first carrier is alumina; the non-noble metal oxide is MoO2; the material of the second carrier is magnesium oxide; in the first active coating 2, the loading amount of the platinum group noble metals on the first carrier is 100g / L, and the density of the platinum group noble metals Pt and Pd is 5g / ft 3 In the second active coating 3, the loading amount of the non-precious metal oxide on the second carrier is 100g / L, and the density of the non-precious metal is 500g / ft 3 The thickness ratio of the first active coating 2 and the second active coating 3 is 1:1; the substrate 1 has a porous structure, a circular cross-sectional shape, and is made of cordierite honeycomb ceramic.

[0060] This embodiment also provides a method for preparing the above catalyst, which comprises the following steps:

[0061] (1) coating a slurry of a first carrier loaded with a platinum group noble metal on one side of a cordierite honeycomb ceramic in an amount of 100 g / L to obtain a first active wet membrane; wherein the solvent of the slurry is water.

[0062] (2) coating a slurry of MoO2 loaded on a second carrier on the surface of the first active wet membrane in an amount of 100 g / L to obtain a second active wet membrane; wherein the solvent of the slurry is water.

[0063] (3) The semi-finished product after treatment in step (2) is dried, calcined in an air atmosphere at 500° C. for 3 h, and then hydrothermally aged at 700° C. for 16 h to obtain the catalyst.

[0064] Example 2

[0065] This embodiment provides a catalyst for methanol engine post-treatment, wherein the catalyst includes a substrate and an active coating layer arranged in layers.

[0066] The active coating includes a first active coating and a second active coating, which are stacked in sequence along a direction away from the substrate; the first active coating includes a platinum group noble metal supported on a first carrier, and the second active coating includes a non-noble metal oxide supported on a second carrier.

[0067] The platinum group noble metals include Pt and Pd in ​​a mass ratio of 3:1; the material of the first carrier is alumina; the non-noble metal oxide is MoO3; the material of the second carrier is titanium oxide; in the first active coating, the loading amount of the platinum group noble metals on the first carrier is 50g / L, and the density of the platinum group noble metals Pt and Pd is 8g / ft 3 In the second active coating, the loading amount of the non-precious metal oxide on the second carrier is 50g / L, and the density of the non-precious metal is 800g / ft 3 ; The thickness ratio of the first active coating and the second active coating is 1:1; the substrate has a porous structure, the material is cordierite honeycomb ceramic, and the cross-sectional shape is circular.

[0068] This embodiment also provides a method for preparing the above catalyst, which comprises the following steps:

[0069] (1) Coating a slurry of a first carrier loaded with a platinum group noble metal on one side of a cordierite honeycomb ceramic in a coating amount of 50 g / L to obtain a first active wet membrane; wherein the solvent is water.

[0070] (2) coating a slurry of the second carrier loaded with MoO3 on the surface of the first active wet film, the coating amount being 50 g / L, to obtain a second active wet film; wherein the solvent of the slurry is water.

[0071] (3) drying the semi-finished product after the treatment in step (2), then calcining at 500℃ in an air atmosphere for 3h, and then hydrothermal aging at 700℃ for 20h, to obtain the catalyst.

[0072] Example 3

[0073] The embodiment provides a catalyst for post-treatment of a methanol engine, the catalyst comprising a substrate and an active coating layer which are arranged in a stack.

[0074] The active coating layer comprises a first active coating layer and a second active coating layer, which are arranged in a stack in sequence along a direction away from the substrate; the first active coating layer comprises a platinum group noble metal loaded on a first carrier, and the second active coating layer comprises a non-noble metal oxide loaded on a second carrier.

[0075] The platinum group noble metal comprises Pt and Pd, and the mass ratio is 1:3; the material of the first carrier is cerium oxide; the non-noble metal oxide is composed of MoO2 and MoO3, and the mass ratio is 1:1; the material of the second carrier is zinc oxide; in the first active coating layer, the loading amount of the platinum group noble metal on the first carrier is 200 g / L, and the density of the platinum group noble metal Pt and Pd is 12 g / ft 3 ; in the second active coating layer, the loading amount of the non-noble metal oxide on the second carrier is 200 g / L, and the density of the non-noble metal is 1200 g / ft 3 ; the thickness ratio of the first active coating layer to the second active coating layer is 1:1; the substrate is a porous structure, the material is cordierite honeycomb ceramic, and the cross-sectional shape is circular.

[0076] The embodiment further provides a preparation method of the catalyst, and the preparation method comprises the following steps:

[0077] (1) coating a slurry of the first carrier loaded with the platinum group noble metal on one side surface of the cordierite honeycomb ceramic, the coating amount being 200 g / L, to obtain a first active wet film; wherein the solvent of the slurry is water.

[0078] (2) coating a slurry of the second carrier loaded with the non-noble metal oxide on the surface of the first active wet film, the coating amount being 200 g / L, to obtain a second active wet film; wherein the solvent of the slurry is water.

[0079] (3) The semi-finished product after treatment in step (2) is dried, calcined in an air atmosphere at 500° C. for 3 h, and then hydrothermally aged at 800° C. for 12 h to obtain the catalyst.

[0080] Example 4

[0081] This embodiment provides a catalyst for methanol engine post-treatment, and its structural diagram is shown in FIG. Figure 2 As shown, the catalyst includes a substrate 1 and an active coating layer that are stacked.

[0082] The active coating includes a first active coating 2 and a second active coating 3, which are arranged side by side and laterally arranged along the horizontal direction of the substrate 1, wherein the first active coating 2 is located at the air inlet end of the substrate 1 and the second active coating 3 is located at the air outlet end of the substrate 1; the first active coating 2 includes a platinum group precious metal supported on a first carrier, and the second active coating 3 includes a non-precious metal oxide supported on a second carrier.

[0083] The platinum group noble metals include Pt and Pd in ​​a mass ratio of 1:1; the material of the first carrier is alumina; the non-noble metal oxide is MoO2; the material of the second carrier is magnesium oxide; in the first active coating 2, the loading amount of the platinum group noble metals on the first carrier is 200g / L, and the density of the platinum group noble metals Pt and Pd is 10g / ft 3 In the second active coating 3, the loading amount of the non-precious metal oxide on the second carrier is 200g / L, and the density of the non-precious metal is 1000g / ft 3 The thickness ratio of the first active coating 2 and the second active coating 3 is 1:1; the substrate has a porous structure, a circular cross-sectional shape, and is made of cordierite honeycomb ceramic.

[0084] This embodiment also provides a method for preparing the above catalyst, which comprises the following steps:

[0085] (1) Coating a slurry of a first carrier loaded with a platinum group noble metal on the air inlet end of one side surface of a cordierite honeycomb ceramic with a coating amount of 200 g / L to obtain a first active wet membrane; wherein the solvent of the slurry is water.

[0086] (2) coating a slurry of MoO2 loaded on a second carrier on the gas outlet end of the cordierite honeycomb ceramic on the same side as the first active wet membrane with a coating amount of 200 g / L to obtain a second active wet membrane; wherein the solvent of the slurry is water.

[0087] (3) The semi-finished product after treatment in step (2) is dried, calcined in an air atmosphere at 500° C. for 3 h, and then hydrothermally aged at 750° C. for 16 h to obtain the catalyst.

[0088] Example 5

[0089] The difference between this embodiment and embodiment 1 is that the platinum group noble metal is only Pt.

[0090] The rest of the preparation methods and parameters remained the same as in Example 1.

[0091] Example 6

[0092] The difference between this embodiment and embodiment 1 is that the platinum group noble metal is only Pd.

[0093] The rest of the preparation methods and parameters remained the same as in Example 1.

[0094] Example 7

[0095] The difference between this embodiment and embodiment 1 is that the non-noble metal oxide is tungsten oxide.

[0096] The rest of the preparation methods and parameters remained the same as in Example 1.

[0097] Example 8

[0098] The difference between this embodiment and embodiment 1 is that in the first active coating, the loading amount of the platinum group noble metal on the first carrier is 60 g / L, and the density of the platinum group noble metal is 10 g / ft 3 .

[0099] The rest of the preparation methods and parameters remained the same as in Example 1.

[0100] Example 9

[0101] The difference between this embodiment and embodiment 1 is that in the first active coating, the loading amount of the platinum group noble metal on the first carrier is 350 g / L, and the density of the platinum group noble metal is 2.5 g / ft 3 .

[0102] The rest of the preparation methods and parameters remained the same as in Example 1.

[0103] Example 10

[0104] The difference between this embodiment and embodiment 1 is that in the second active coating, the loading amount of the non-noble metal oxide on the second carrier is 60 g / L, and the density of the non-noble metal oxide is 800 g / ft 3 .

[0105] The rest of the preparation methods and parameters remained the same as in Example 1.

[0106] Example 11

[0107] The difference between this embodiment and embodiment 1 is that in the second active coating, the loading amount of the non-noble metal oxide on the second carrier is 350 g / L, and the density of the non-noble metal oxide is 800 g / ft 3 .

[0108] The rest of the preparation methods and parameters remained the same as in Example 1.

[0109] Example 12

[0110] The difference between this embodiment and embodiment 1 is that the thickness ratio of the first active coating layer to the second active coating layer is 1:0.3.

[0111] The rest of the preparation methods and parameters remained the same as in Example 1.

[0112] Example 13

[0113] The difference between this embodiment and embodiment 1 is that the thickness ratio of the first active coating layer to the second active coating layer is 1:5.

[0114] The rest of the preparation methods and parameters remained the same as in Example 1.

[0115] Comparative Example 1

[0116] The difference between this comparative example and Example 1 is that in the second active coating, the non-noble metal oxide is replaced by Pt.

[0117] The rest of the preparation methods and parameters remained the same as in Example 1.

[0118] Comparative Example 2

[0119] The difference between this comparative example and Example 1 is that no second active coating layer is provided.

[0120] The rest of the preparation methods and parameters remained the same as in Example 1.

[0121] Comparative Example 3

[0122] This comparative example provides a commercial diesel oxidation catalyst, in which the ratio of Pt to Pd is 6:1, the loading amount of the platinum group noble metal on the alumina is 100 g / L, and the density of the platinum group noble metal is 15 g / ft 3 .

[0123] Performance Testing

[0124] The catalytic performance of the catalysts provided in the above examples and comparative examples was tested under the following conditions:

[0125] Methanol engine exhaust (including 10% O2, 6% CO2, 10% H2O, 1000ppm CO, 500ppm NO2, 400ppm C3H6, 2000ppm CH3OH, and the rest N2), space velocity 20000h -1 Starting from room temperature, the temperature was increased to 500°C at a heating rate of 10°C / min, and the T50 and T90 of CO (i.e., the reaction temperature corresponding to 50% or 90% conversion), T50 and T90 of C3H6, T50 and T90 of CH3OH, and the maximum conversion of NO2 were recorded.

[0126] The results are shown in Table 1.

[0127] Table 1

[0128]

[0129] analyze:

[0130] As can be seen from Table 1, the catalyst provided by the present invention can increase the chemical reaction rate of CO, Cl hydrocarbons, methanol and formaldehyde in the exhaust gas of a methanol engine, while converting NO2 into NO to the greatest extent, and also reduces the amount of precious metals used, thereby reducing the catalyst cost.

[0131] From the comparison between Example 1 and Examples 5-6, it can be seen that if the platinum group noble metal is only Pt, the ignition performance of CO will decrease and the NO2 conversion rate will decrease. This is mainly because the oxidation of NO by Pt leads to an increase in the NO2 concentration, which reduces the conversion ability of NO2 to NO; if the platinum group noble metal is only Pd, the ignition performance of CO and Cl hydrocarbons will be improved, and the performance of oxidizing NO is better than pure Pt, but worse than Example 1.

[0132] From the comparison between Example 1 and Example 7, it can be seen that if the non-noble metal oxide is tungsten oxide, it is not conducive to the conversion of NO2 to NO.

[0133] By comparing Example 1 with Examples 8-9, it can be seen that if the loading amount of the platinum group noble metal on the first carrier in the first active coating is small, the oxidizing ability is weak, which is not conducive to the conversion of CO and Cl hydrocarbons; if the loading amount of the platinum group noble metal on the first carrier in the first active coating is too large, the oxidizing ability is too strong, which is not conducive to the conversion of NO2 to NO.

[0134] By comparing Example 1 with Examples 10-11, it can be seen that if the loading amount of the non-precious metal oxide on the second carrier in the second active coating is small, it is not conducive to the conversion of NO2 to NO; if the loading amount of the non-precious metal oxide on the second carrier in the second active coating is too large, the coating is too thick, which is not conducive to gas diffusion and the conversion performance of CO and Cl hydrocarbons decreases.

[0135] It can be seen from the comparison of Example 1 and Examples 12-13 that if the thickness ratio of the first active coating and the second active coating is too small, the conversion of NO2 to NO is not good; if the thickness ratio of the first active coating and the second active coating is too large, the conversion ability of NO2 to NO decreases.

[0136] It can be seen from the comparison of Example 1 and Comparative Example 1 that if the non-noble metal oxide in the second active coating is replaced by Pt, the conversion ability of NO2 to NO decreases.

[0137] It can be seen from the comparison of Example 1 and Comparative Example 2 that if the second active coating is not provided, the conversion ability of NO2 to NO decreases significantly.

[0138] It can be seen from the comparison of Example 1 and Comparative Example 3 that if a commercial diesel oxidation catalyst is used, NO2 is hardly converted.

[0139] It should be noted that the process of the present application is illustrated by the above examples, but the present application is not limited to the above process steps, i.e. it does not mean that the present application must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement of the present application, equivalent replacement of the selected raw materials of the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A catalyst for methanol engine post-treatment, characterized in that: The catalyst comprises a substrate and an active coating layer arranged in layers; The active coating comprises a first active coating and a second active coating, wherein the first active coating comprises a platinum group noble metal supported on a first carrier, and the second active coating comprises a non-noble metal oxide supported on a second carrier.

2. The catalyst according to claim 1, characterized in that The first active coating and the second active coating are selected from any one of the following combinations: Method 1: The first active coating and the second active coating are stacked in sequence in a direction away from the substrate; Mode 2: The first active coating layer and the second active coating layer are arranged side by side, and the first active coating layer and the second active coating layer are arranged laterally along the horizontal direction of the substrate; And / or, the platinum group noble metal includes Pt and / or Pd.

3. The catalyst according to claim 2, characterized in that The platinum group noble metals include a combination of Pt and Pd; In the combination of Pt and Pd, the mass ratio of Pt to Pd is (10-1):(1-10).

4. The catalyst according to claim 1, characterized in that The material of the first carrier includes metal oxide or non-noble metal modified mixed oxide thereof; The metal oxide includes any one of aluminum oxide, cerium oxide or cerium zirconium aluminum oxide or a combination of at least two thereof; The non-noble metal includes any one of barium, potassium or strontium, or a combination of at least two of them.

5. The catalyst according to claim 1, characterized in that The non-noble metal oxide includes MoO x1 、CoO x2 or FeO x3 Any one or a combination of at least two of the following, the values ​​of x1, x2 and x3 are each independently 2-3; And / or, the material of the second carrier includes metal oxide or non-noble metal modified mixed oxide thereof; The metal oxide includes any one or a combination of at least two of titanium oxide, cerium oxide, tungsten oxide, magnesium oxide, aluminum oxide, zirconium oxide, cobalt oxide, nickel oxide, niobium oxide, indium oxide, tin oxide, zinc oxide or copper oxide; The non-noble metal includes any one or a combination of at least two of nickel, manganese, strontium, titanium, zirconium, niobium, iron, zinc, silver, samarium, europium, lithium, sodium, potassium, cesium, calcium, barium, magnesium, vanadium, chromium, neodymium, praseodymium, yttrium or lanthanum.

6. The catalyst according to claim 1, characterized in that In the first active coating, the loading amount of the platinum group noble metal on the first carrier is 20-300 g / L; And / or, in the first active coating, the density of the platinum group noble metal is 2-200 g / ft 3 .

7. The catalyst according to claim 1, characterized in that In the second active coating, the loading amount of the non-noble metal oxide on the second carrier is 20-300 g / L; And / or, in the second active coating, the density of the non-precious metal is 100-2000 g / ft 3 .

8. The catalyst according to claim 2, characterized in that In the first embodiment, the thickness ratio of the first active coating layer to the second active coating layer is 1:(0.5-1.5).

9. The catalyst according to claim 2, characterized in that In the second embodiment, the lateral length ratio of the first active coating layer to the second active coating layer is 1:(0.8-1.2); And / or, the substrate is a porous structure; And / or, in the second method, the first active coating is located at the air inlet end of the substrate, and the second active coating is located at the air outlet end of the substrate.

10. Use of the catalyst for methanol engine post-treatment according to any one of claims 1 to 9, characterized in that: The catalyst is used for treating tail gas from a methanol engine.

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