Catalyst for post-treatment of methanol engine as well as preparation method and application of catalyst

Abstract

The invention relates to a catalyst for post-treatment of a methanol engine and a preparation method and application thereof.The catalyst comprises a substrate, a first active layer and a second active layer, the first active layer is arranged at the gas inlet end of the first surface of the substrate, and the second active layer is arranged at the gas outlet end of the first surface of the substrate; the first active layer comprises a first carrier and a first active component loaded on the first carrier, and the first active component comprises non-noble metal; the second active layer comprises a second carrier and a second active component loaded on the second carrier, and the second active component comprises MoS2, Mo2C or MoOx. According to the catalyst, through the synergistic effect of the non-noble metal and the specific second active component and the design of combining the position relation of the non-noble metal and the specific second active component, the control requirement can be simplified, the cost can be reduced, and meanwhile reduction of NO2 emission and purification of pollutants such as CO, HC, methanol and formaldehyde are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a catalyst for methanol engine post-treatment, a preparation method thereof, and an application thereof. Background Art

[0002] Engine exhaust purification of pollutants such as CO, HC, methanol, and formaldehyde requires the use of oxidation catalysts. The use of traditional diesel oxidation catalysts (DOCs) can oxidize and burn the above pollutants, but it cannot reduce the proportion of NO2 in the exhaust. DOCs will oxidize NO into NO2, increasing environmental hazards.

[0003] Industrial, such as boilers, incinerators and power plants and other stationary sources as well as motor vehicle exhaust treatment NO x It is necessary to use the selective catalytic reduction (NH3-SCR) process, using ammonia as a reducing agent to reduce NO in the exhaust gas under the action of the catalyst. x Ammonia is a gas with a strong pungent odor and is not easy to use directly. Usually, the ammonia required for the reaction is provided by injecting urea aqueous solution into the exhaust pipe.

[0004] In the existing technology, the article "Research on After-treatment Schemes for Nitrogen Dioxide Emissions from Methanol-Diesel Dual-Fuel Engines" (10.13949 / j.cnki.nrjgc.2019.04.011) introduces the possibility of reducing NO2 emissions in principle. DOC restores the NO2 ratio to the diesel engine emission level and significantly reduces methanol emissions, but the purification effect on formaldehyde is not ideal. The SCR+DOC scheme completely eliminates formaldehyde and methanol emissions from dual-fuel engines while maintaining the NO2 ratio at the normal level of diesel engines.

[0005] However, traditional DOCs focus on enhancing the catalyst's ability to oxidize CO, HC, and NO. This significantly increases NO2 concentration in engine exhaust after passing through the DOC. Directly using traditional DOCs for methanol engine exhaust treatment results in a high proportion of NO2 in the emissions, posing significant risks to the environment and health. Traditional NH3-SCRs require a urea injection system, placing high demands on engine control and requiring the addition of a DOC to treat pollutants such as CO, HC, methanol, and formaldehyde in methanol engine exhaust.

[0006] Therefore, there is an urgent need to develop a catalyst for methanol engines that is simple to control, low in cost, and can simultaneously reduce NO2 emissions and purify pollutants such as CO, HC, methanol, and formaldehyde. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention aims to provide a catalyst for methanol engine post-treatment and its preparation method and application. The catalyst for methanol engine post-treatment provided by the present invention is provided with a first active layer containing non-precious metal active components at the inlet end of the substrate, and a first active layer containing MoS2, Mo2C or MoO2 at the outlet end. x The second active layer of the active component, through the synergistic effect of the two active components at the intake and outlet ends, and the design combining the positional relationship between the two, can simplify the engine control process and reduce costs, while achieving the reduction of NO2 emissions and the purification of pollutants such as CO, HC, methanol, and formaldehyde.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a catalyst for methanol engine post-treatment, the catalyst comprising a substrate, a first active layer and a second active layer, the first active layer being arranged on an air inlet end of a first surface of the substrate, and the second active layer being arranged on an air outlet end of the first surface of the substrate;

[0010] The first active layer includes a first carrier and a first active component supported on the first carrier, wherein the first active component includes a non-noble metal;

[0011] The second active layer includes a second carrier and a second active component supported on the second carrier, wherein the second active component includes MoS2, Mo2C or MoO x Any one or a combination of at least two of .

[0012] In the present invention, the "inlet end of the first surface of the substrate" refers to the inlet area where the reactants first contact the catalyst during the post-treatment process of the methanol engine, that is, the end that enters the catalyst; the "outlet end of the first surface of the substrate" refers to the outlet area where the reaction products leave the catalyst during the post-treatment process of the methanol engine.

[0013] The catalyst for methanol engine post-treatment provided by the present invention is provided with an active layer of non-precious metal active components on the air inlet end of the substrate, and MoS2, Mo2C or MoO2 is provided on the air outlet end of the substrate. xThe active layer of active components, the two active components at the inlet and outlet ends, work together, and combined with the design of the positional relationship of the active components on the substrate, can effectively oxidize pollutants such as CO, HC, methanol, and formaldehyde, achieving purification of pollutants in methanol exhaust treatment. It can also reduce NO2 to NO, reducing the proportion of NO2 emissions in methanol engine exhaust without adding a urea injection system, significantly reducing the toxicity of NO2 to the environment and human health, and lowering the control requirements for methanol engines. Furthermore, the present invention uses non-precious metals as active components, while ensuring catalytic performance, and can effectively reduce the cost of the catalyst.

[0014] Preferably, the first carrier comprises any one of magnesium aluminum spinel, cobalt aluminum spinel, cobalt iron spinel, hydroxyapatite or hydroxyvanadium wollastonite.

[0015] Preferably, the non-noble metal in the first active component includes any one of Mn, Fe or Co, or a combination of at least two of them.

[0016] Preferably, in the catalyst, the loading amount of the first active layer is 20-500 g / L, for example, 20 g / L, 50 g / L, 100 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L or 500 g / L, etc., preferably 50-300 g / L.

[0017] In the present invention, the "loading amount" refers to the ratio of the total mass of the active layer to the volume of the substrate in the catalyst.

[0018] Preferably, in the catalyst, the concentration of the first active component in the first active layer is 100-2000 g / cft, for example, 100 g / cft, 150 g / cft, 200 g / cft, 300 g / cft, 400 g / cft, 500 g / cft, 600 g / cft, 700 g / cft, 800 g / cft, 900 g / cft, 1000 g / cft, 1100 g / cft, 1200 g / cft, 1300 g / cft, 1400 g / cft, 1500 g / cft, 1600 g / cft, 1700 g / cft, 1800 g / cft, 1900 g / cft or 2000 g / cft, etc., preferably 150-500 g / cft.

[0019] In the present invention, the "concentration of the first active component" refers to the ratio of the mass of the first active component to the volume of the substrate in the catalyst.

[0020] Preferably, in the catalyst, the loading amount of the second active layer is 20-300 g / L, such as 20 g / L, 50 g / L, 100 g / L, 150 g / L, 200 g / L, 250 g / L or 300 g / L, etc., preferably 100-200 g / L.

[0021] Preferably, in the catalyst, the concentration of the second active component in the second active layer is 5-200 g / cft, for example, 5 g / cft, 10 g / cft, 20 g / cft, 40 g / cft, 60 g / cft, 80 g / cft, 100 g / cft, 120 g / cft, 140 g / cft, 160 g / cft, 180 g / cft or 200 g / cft, etc., preferably 50-150 g / cft.

[0022] In the present invention, the “concentration of the second active component” refers to the ratio of the mass of the second active component to the volume of the substrate in the second active layer.

[0023] Preferably, the MoO x where x is 2 or 3.

[0024] Preferably, the second support comprises a metal oxide or a modified metal oxide.

[0025] Preferably, the modified metal oxide adopts a modifier including any one of non-metal or metal.

[0026] Preferably, in the second carrier, the non-metal includes any one or a combination of at least two of B, C, N, F, P, Se, Te, Cl, Br, I or Si.

[0027] Preferably, in the second carrier, the metal includes any one or a combination of at least two of Na, K, Mg, Ca, Sr, Ba, Rb, Cs, Cr, Mn, Co, Fe, Ni, Cu, Zn, W, Bi, In, Sn, Sb, La, Y, Zr, Nd or Pr.

[0028] The present invention modifies the metal oxide in the second carrier by using a specific non-metal or metal. The non-metal or metal used for carrier modification and doping can reduce the precipitation of the molybdenum compound loaded on the second carrier and increase the firmness of the molybdenum compound loaded on the second carrier.

[0029] Preferably, in the second carrier, the metal oxide includes any one of aluminum oxide, cerium oxide, zirconium oxide, cerium zirconium oxide, cerium zirconium aluminum oxide, titanium oxide, tungsten oxide, magnesium oxide, cobalt oxide, nickel oxide, niobium oxide, indium oxide, tin oxide, zinc oxide or copper oxide, or a combination of at least two thereof.

[0030] Preferably, in the modified metal oxide of the second carrier, the mass percentage of the non-metal to the metal oxide is 0.1-10%, for example, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5% or 10.0%, etc., preferably 0.5-5%.

[0031] Preferably, in the modified metal oxide of the second carrier, the mass percentage of the metal in the metal oxide is 0.5-30%, for example, 0.5%, 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, 29% or 30%, etc., preferably 0.5-15%.

[0032] Preferably, a direction parallel to the first surface of the substrate is a horizontal direction, and in the horizontal direction, the first active layer and the second active layer are in contact with each other and arranged side by side.

[0033] Preferably, with the direction parallel to the first surface of the substrate as the horizontal direction, the area ratio of the first active layer to the second active layer in the horizontal direction is 1:(0.5-1.5), for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, etc.

[0034] Preferably, with the direction perpendicular to the first surface of the substrate as the vertical direction, the thickness ratio of the first active layer and the second active layer in the vertical direction is (1-5):1, for example, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1 or 5.0:1, etc.

[0035] Preferably, the direction perpendicular to the first surface of the substrate is taken as the vertical direction, and in the vertical direction, the thickness ratio of the first active layer to the substrate is 1:(0.5-1.5), for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, etc.

[0036] Preferably, the substrate comprises any one of cordierite, silicon carbide or metal.

[0037] Preferably, the structure of the substrate comprises a honeycomb structure.

[0038] Preferably, the cross-sectional shape of the substrate includes any one of a circle and a square.

[0039] In a second aspect, the present invention provides a method for preparing the catalyst according to the first aspect, the preparation method comprising the following steps:

[0040] The first slurry and the second slurry are respectively placed on the air inlet end and the air outlet end of the first surface of the substrate, and after drying, calcination and hydrothermal aging, a first active layer and a second active layer are formed on the first surface of the substrate to obtain the catalyst;

[0041] The first slurry includes a first active component and a first carrier, wherein the first active component includes a non-noble metal;

[0042] The second slurry includes a second active component and a second carrier, wherein the second active component includes MoS2, Mo2C or MoO x Any one or a combination of at least two of .

[0043] The present invention coats a slurry containing a first active component and a first carrier on the air inlet end of the substrate, and coats a slurry containing a second active component and a second carrier on the air outlet end of the substrate, and then combines drying, baking and hydrothermal aging processes to form a first active layer and a second active layer on the air inlet end and the air outlet end of the substrate, respectively. The non-precious metal in the first active layer and the MoS2, Mo2C or MoO in the second active layer are x By working together, they can simplify the control requirements of methanol engines, reduce preparation costs, and at the same time reduce the proportion of NO2 emissions in methanol engine exhaust, significantly reduce the harm of NO2 toxicity to the environment and human body, and purify pollutants such as CO, HC, methanol, and formaldehyde.

[0044] Preferably, the first slurry further includes a first solvent, a first binder and a first thickener.

[0045] Preferably, the first solvent comprises water.

[0046] Preferably, the first binder includes any one of silica sol, pseudo-boehmite, aluminum sol or titanium sol.

[0047] Preferably, the first thickener includes any one of methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose or sodium carboxymethyl cellulose.

[0048] Preferably, in the first slurry, the mass of the first solvent accounts for 50-80wt% of the total mass of the first slurry, for example, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt% or 80wt%.

[0049] Preferably, in the first slurry, the mass of the first binder accounts for 2-20wt% of the total mass of the first slurry, for example, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt% or 20wt%, etc.

[0050] Preferably, in the first slurry, the mass of the first thickener accounts for 0.2-1wt% of the first slurry, for example, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt% or 1.0wt%, etc.

[0051] It should be noted that, in the present invention, the coating amount of the first slurry and the amount of the first active component added to the first slurry are determined according to the loading amount of the first active layer and the concentration of the first active component of the first active layer in the catalyst.

[0052] Preferably, the second slurry further includes a second solvent, a second binder and a second thickener.

[0053] Preferably, the second solvent comprises water.

[0054] Preferably, the second binder includes any one of silica sol, pseudo-boehmite, aluminum sol or titanium sol.

[0055] Preferably, the second thickener includes any one of hydroxyethyl cellulose or hydroxypropyl methyl cellulose.

[0056] Preferably, in the second slurry, the mass of the second solvent accounts for 50-80wt% of the total mass of the second slurry, such as 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt% or 80wt%.

[0057] Preferably, in the second slurry, the mass of the second binder accounts for 5-20wt% of the total mass of the second slurry, for example, 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt% or 20wt%, etc.

[0058] Preferably, in the second slurry, the mass of the second thickener accounts for 0.2-1wt% of the total mass of the second slurry, for example, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt% or 1.0wt%, etc.

[0059] It should be noted that, in the present invention, the coating amount of the second slurry and the amount of the second active component added to the second slurry are determined according to the loading amount of the second active layer and the concentration of the second active component of the second active layer in the catalyst.

[0060] Preferably, the calcination temperature is 300-400°C, for example, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C or 400°C.

[0061] Preferably, the calcination time is 3-5 h, for example, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, 4.0 h, 4.2 h, 4.4 h, 4.6 h, 4.8 h or 5.0 h.

[0062] Preferably, the calcination atmosphere is air atmosphere, nitrogen atmosphere or inert atmosphere.

[0063] Illustratively, the inert atmosphere includes an argon atmosphere, a helium atmosphere, or a neon atmosphere.

[0064] Preferably, the temperature of the hydrothermal aging is 500-800°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C.

[0065] Preferably, the hydrothermal aging time is 12-24 h, for example, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h or 24 h.

[0066] In a third aspect, the present invention provides an application of the catalyst according to the first aspect, wherein the catalyst is applied to exhaust gas treatment of a methanol engine.

[0067] Compared with the prior art, the present invention has at least the following beneficial effects:

[0068] The catalyst for methanol engine post-treatment provided by the present invention is provided with an active layer of non-precious metal active components on the air inlet end of the substrate, and MoS2, Mo2C or MoO2 is provided on the air outlet end of the substrate. x The active layer of active components, the two active components at the inlet and outlet ends, work together, and combined with the design of the positional relationship of the active components on the substrate, can effectively oxidize pollutants such as CO, HC, methanol, and formaldehyde, achieving purification of pollutants in methanol exhaust treatment. It can also reduce NO2 to NO, reducing the proportion of NO2 emissions in methanol engine exhaust without adding a urea injection system, significantly reducing the toxicity of NO2 to the environment and human health, and lowering the control requirements for methanol engines. Furthermore, the present invention uses non-precious metals as active components, while ensuring catalytic performance, and can effectively reduce the cost of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is a structural schematic diagram of the catalyst provided in Embodiment 1 of the present application.

[0070] wherein 1 is a substrate; 2 is a first active layer; and 3 is a second active layer. DETAILED DESCRIPTION

[0071] The technical solutions of the present application will be further described below in combination with the drawings and through specific embodiments. However, the following examples are only simple examples of the present application and do not represent or limit the protection scope of the present application, and the protection scope of the present application is subject to the claims.

[0072] Embodiment 1

[0073] The present embodiment provides a catalyst, a structural schematic diagram of which is shown in Figure 1 which includes a substrate 1 and a first active layer 2 and a second active layer 3 arranged on a first surface of the substrate 1, the first active layer 2 is arranged at an air inlet end on the first surface of the substrate 1, and the second active layer 3 is arranged at an air outlet end on the first surface of the substrate 1, the direction parallel to the first surface of the substrate 1 is the horizontal direction, the first active layer 2 and the second active layer 3 are arranged in contact with and side by side in the horizontal direction, the area ratio of the first active layer 2 and the second active layer 3 in the horizontal direction is 1:1, the direction perpendicular to the first surface of the substrate 1 is the vertical direction, and the thickness ratio of the first active layer 2 and the second active layer 3 in the vertical direction is 2:1.

[0074] The first active layer 2 includes a first carrier and a first active component loaded on the first carrier, the first active component is Mn, and the first carrier is magnesium-aluminum spinel. In the catalyst, the concentration of Mn in the first active layer 2 is 200 g / cft, and the upper loading amount of the first active layer 2 in the catalyst is 300 g / L.

[0075] The second active layer 3 includes a second carrier and a second active component loaded on the second carrier, the second carrier is B-doped modified cerium-zirconium oxide (the molar ratio of cerium to zirconium is 1:1), and in the second carrier, B accounts for 3% of the mass percentage of the cerium-zirconium oxide. The second active component is Mo2C. In the catalyst, the concentration of Mo2C in the second active layer 3 is 100 g / cft, and the upper loading amount of the second active layer 3 in the catalyst is 200 g / L.

[0076] The substrate 1 includes cordierite honeycomb ceramic, the cross-sectional shape of the substrate 1 is circular, and the thickness ratio of the substrate 1 and the first active layer 2 in the vertical direction is 1:1.

[0077] The present embodiment provides a preparation method of the above-mentioned catalyst, which includes the following steps:

[0078] (1) Mixing the formulated amounts of Mn and magnesium aluminum spinel with water, aluminum sol and hydroxyethyl cellulose to obtain a first slurry, wherein the amount of water added accounts for 70wt% of the total mass of the first slurry, the mass of the aluminum sol accounts for 5wt% of the total mass of the first slurry, and the mass of the hydroxyethyl cellulose accounts for 0.5wt% of the total mass of the first slurry.

[0079] The Mo2C and B-doped modified cerium zirconium oxide are mixed with water, pseudo-boehmite, hydroxyethyl cellulose, etc. to obtain a second slurry, wherein the amount of water added accounts for 70wt% of the total mass of the second slurry, the mass of the pseudo-boehmite accounts for 8wt% of the total mass of the second slurry, and the mass of the hydroxyethyl cellulose accounts for 0.2wt% of the total mass of the second slurry.

[0080] (2) The first slurry and the second slurry obtained in step (1) are respectively coated on the air inlet end and the air outlet end of the first surface of the cordierite honeycomb ceramic, the coating amount of Mn and magnesium aluminum spinel in the first slurry is 300 g / L, and the coating amount of Mo2C and B-doped cerium zirconium oxide in the second slurry is 200 g / L to obtain a semi-finished product.

[0081] (3) The semi-finished product obtained in step (2) is dried, and then the dried product is calcined at 350° C. for 4 h in an air atmosphere, followed by hydrothermal aging at 600° C. for 16 h to obtain a catalyst.

[0082] Example 2

[0083] This embodiment provides a catalyst, including a substrate and a first active layer and a second active layer arranged on a first surface of the substrate, the first active layer being arranged at an air inlet end on the first surface of the substrate, and the second active layer being arranged at an air outlet end on the first surface of the substrate, with the direction parallel to the first surface of the substrate being the horizontal direction, the first active layer and the second active layer being in contact with each other and arranged side by side in the horizontal direction, the area ratio of the first active layer and the second active layer in the horizontal direction being 1:0.5, and the thickness ratio of the first active layer and the second active layer in the vertical direction being 1:1 with the direction perpendicular to the first surface of the substrate being the vertical direction.

[0084] The first active layer includes a first carrier and a first active component loaded on the first carrier, the first active component is Fe, the first carrier is cobalt aluminum spinel, the Fe concentration of the first active layer in the catalyst is 150 g / cft, and the loading amount of the first active layer in the catalyst is 150 g / L.

[0085] The second active layer comprises a second carrier and a second active component supported on the second carrier, the second carrier is N-doped alumina, in the second carrier, N accounts for 0.5% of the mass percentage of alumina, the second active component is MoS2, in the catalyst, the concentration of MoS2 in the second active layer is 50 g / cft, and the loading of the second active layer in the catalyst is 100 g / L.

[0086] The substrate comprises a silicon carbide honeycomb ceramic, the cross-sectional shape of the substrate is square, and the thickness ratio of the substrate to the first active layer is 0.5:1 in the vertical direction.

[0087] The embodiment provides a preparation method of the above catalyst, comprising the following steps:

[0088] (1) A formula amount of Fe and cobalt aluminum spinel is mixed with water, aluminum sol and hydroxyethyl cellulose to obtain a first slurry, wherein the addition amount of water accounts for 60wt% of the total mass of the first slurry, the mass of the aluminum sol accounts for 20wt% of the total mass of the first slurry, and the mass of the hydroxyethyl cellulose accounts for 0.3wt% of the total mass of the first slurry.

[0089] A formula amount of MoS2 and N-doped alumina is mixed with water, aluminum sol and hydroxyethyl cellulose to obtain a second slurry, wherein the addition amount of water accounts for 60wt% of the total mass of the second slurry, the mass of the aluminum sol accounts for 20wt% of the total mass of the second slurry, and the mass of the hydroxyethyl cellulose accounts for 0.2wt% of the total mass of the second slurry.

[0090] (2) The first slurry and the second slurry obtained in step (1) are respectively coated on the gas inlet end and the gas outlet end of the first surface of the silicon carbide honeycomb ceramic, the coating amount of Fe and cobalt aluminum spinel in the first slurry is 150 g / L, and the coating amount of MoS2 and N-doped alumina in the second slurry is 100 g / L, to obtain a semi-finished product.

[0091] (3) The semi-finished product obtained in step (2) is dried, and then the dried product is placed in an air atmosphere at 300℃ for 5h, and then hydrothermally aged at 800℃ for 12h to obtain a catalyst.

[0092] Example 3

[0093] The embodiment provides a catalyst, which comprises a substrate and a first active layer and a second active layer arranged on a first surface of the substrate, the first active layer is arranged at an air inlet end on the first surface of the substrate, the second active layer is arranged at an air outlet end on the first surface of the substrate, a direction parallel to the first surface of the substrate is a horizontal direction, the first active layer and the second active layer are arranged in contact with each other and in parallel in the horizontal direction, an area ratio of the first active layer to the second active layer in the horizontal direction is 1:1, a direction perpendicular to the first surface of the substrate is a vertical direction, a thickness ratio of the first active layer to the second active layer in the vertical direction is 4:1.

[0094] The first active layer comprises a first carrier and a first active component supported on the first carrier, the first active component is Co, and the first carrier is cobalt-iron spinel, in the catalyst, the concentration of Co in the first active layer is 500 g / cft, and the loading of the first active layer in the catalyst is 300 g / L.

[0095] The second active layer comprises a second carrier and a second active component supported on the second carrier, the second carrier is C-doped cerium-zirconium oxide (the molar ratio of cerium to zirconium is 1:1), in the second carrier, the mass percentage of C in the cerium-zirconium oxide is 0.8%, and the second active component is MoO2, in the catalyst, the concentration of MoO2 in the second active layer is 150 g / cft, and the loading of the second active layer in the catalyst is 125 g / L.

[0096] The substrate comprises a silicon carbide honeycomb ceramic, the cross-sectional shape of the substrate is square, and the thickness ratio of the substrate to the first active layer in the vertical direction is 0.75:1.

[0097] The embodiment provides a preparation method of the catalyst, which comprises the following steps:

[0098] (1) a formula amount of Co and cobalt-iron spinel is mixed with water, titanium sol and hydroxyethyl cellulose to obtain a first slurry, wherein the addition amount of water accounts for 80 wt% of the total mass of the first slurry, the mass of the titanium sol accounts for 10 wt% of the first slurry, and the mass of the hydroxyethyl cellulose accounts for 0.5 wt% of the total mass of the first slurry.

[0099] A formula amount of MoO2 and C-doped cerium-zirconium oxide is mixed with water, silicon sol and hydroxypropyl methyl cellulose to obtain a second slurry, wherein the addition amount of water accounts for 80 wt% of the total mass of the second slurry, the mass of the silicon sol accounts for 10 wt% of the total mass of the second slurry, and the mass of the hydroxypropyl methyl cellulose accounts for 1 wt% of the total mass of the second slurry.

[0100] (2) The first slurry and the second slurry obtained in step (1) are respectively coated on the air inlet end and the air outlet end of the first surface of the silicon carbide honeycomb ceramic, the coating amount of Co and cobalt iron spinel in the first slurry is 300 g / L, and the coating amount of MoO2 and C-doped cerium zirconium oxide in the second slurry is 125 g / L, to obtain a semi-finished product.

[0101] (3) The semi-finished product obtained in step (2) is dried, and then the dried product is calcined at 400° C. for 3 h in an argon atmosphere, followed by hydrothermal aging at 500° C. for 24 h to obtain a catalyst.

[0102] Example 4

[0103] The only difference between this embodiment and embodiment 1 is that the catalyst provided in this embodiment omits the B doping in the B-doped cerium-zirconium oxide and only uses the second carrier of cerium-zirconium oxide. The rest of the contents are the same as those in embodiment 1.

[0104] Example 5

[0105] The only difference between this embodiment and embodiment 1 is that in the second carrier, the mass percentage of B in the cerium-zirconium oxide is 0.05%. The rest of the contents are the same as those in embodiment 1.

[0106] Example 6

[0107] The only difference between this embodiment and embodiment 1 is that in the second carrier, the mass percentage of B in the cerium-zirconium oxide is 12%. The rest of the contents are the same as those in embodiment 1.

[0108] Example 7

[0109] The only difference between this embodiment and embodiment 1 is that the loading amount of the first active layer in the catalyst is 20 g / L. The rest of the contents are the same as those in embodiment 1.

[0110] Example 8

[0111] The only difference between this embodiment and embodiment 1 is that the loading amount of the first active layer in the catalyst is 500 g / L. The rest of the contents are the same as those in embodiment 1.

[0112] Example 9

[0113] The only difference between this embodiment and embodiment 1 is that the loading amount of the second active layer in the catalyst is 50 g / L. The rest of the contents are the same as those in embodiment 1.

[0114] Example 10

[0115] The only difference between this embodiment and embodiment 1 is that the loading amount of the second active layer in the catalyst is 300 g / L. The rest of the contents are the same as those in embodiment 1.

[0116] Comparative Example 1

[0117] The only difference between this comparative example and Example 1 is that the positions of the first active layer and the second active layer are swapped. That is, the first active layer is disposed on the first surface of the substrate at the outlet end, and the second active layer is disposed on the first surface of the substrate at the inlet end. All other details are the same as in Example 1.

[0118] Comparative Example 2

[0119] The only difference between this comparative example and Example 1 is that the first active layer is omitted. The rest of the contents are the same as Example 1.

[0120] Comparative Example 3

[0121] The only difference between this comparative example and Example 1 is that the second active layer is omitted. The rest of the contents are the same as Example 1.

[0122] Comparative Example 4

[0123] This comparative example uses commercial DOC as a catalyst. The catalyst has platinum group noble metals as active components and alumina as a carrier. The mass ratio of Pt:Pd is 6:1, the loading amount of platinum group noble metals on alumina is 100 g / L, and the concentration of platinum group noble metals in the DOC catalyst is 15 g / cft.

[0124] Performance Testing

[0125] The catalytic performance of the catalysts provided in the above examples and comparative examples was tested under the following conditions:

[0126] Methanol engine exhaust (including 10% O2, 6% CO2, 10% H2O, 1000ppm CO, 500ppm NO2, 400ppm C3H6, 10000ppm CH3OH, and the rest N2), space velocity 80000h -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.

[0127] The test results are shown in Table 1.

[0128] Table 1

[0129]

[0130] The test results show that:

[0131] (1) It can be seen from Examples 1 to 3 that the catalyst for methanol engine post-treatment provided by the present invention has a first active layer containing a non-precious metal active component at the air inlet end of the substrate, and a first active layer containing MoS2, Mo2C or MoO3 at the air outlet end. x The second active layer of active components is made of non-noble metals and MoS2, Mo2C or MoO x The synergistic effect of the two active components and the design of their positional relationship can simplify the engine control process and reduce costs, while also reducing NO2 emissions and purifying pollutants such as CO, HC, methanol, and formaldehyde.

[0132] (2) By comparing Example 1 with Example 4, it can be seen that omitting the doping of B in the second carrier in the present invention will result in the Mo2C in the second active layer being loosely loaded in the second carrier, resulting in precipitation, which affects the catalytic performance of the catalyst.

[0133] (3) By comparing Example 1 with Examples 5-6, it can be seen that if the mass ratio of B to cerium zirconium oxide in the second carrier of the present invention is too low, and the amount of B modified doping added is relatively too low, it will lead to insufficient modification of the second carrier, thereby still causing the active components loaded on the second carrier to be weak, precipitation occurs, and the catalytic performance of the catalyst is affected; if the mass ratio of B to cerium zirconium oxide is too high, and the amount of B modified doping added is relatively too high, it will lead to excessively high B content in local areas, covering the cerium zirconium oxide and reducing its specific surface area, which is not conducive to the dispersion of the second active component and thus affects the catalyst performance.

[0134] (4) By comparing Example 1 with Examples 7-8, it can be seen that if the loading amount of the first active layer in the catalyst of the present invention is too low, the catalytic performance of the first active layer will be reduced, and the purification effect of pollutants such as CO, HC, methanol, and formaldehyde in the post-treatment of methanol engines will be worse; if the loading amount of the active components in the first layer is too high, the gas diffusion will be slowed down, and the catalyst efficiency will be reduced.

[0135] (5) By comparing Example 1 with Examples 9-10, it can be seen that if the loading amount of the second active layer in the catalyst of the present invention is too low, it is insufficient to reduce NO2 to NO, thereby increasing the proportion of NO2 emissions and endangering the environment and human body; if the loading amount of the active component in the second active layer is too high, it will cause gas diffusion to slow down and reduce the efficiency of the catalyst.

[0136] (6) By comparing Example 1 with Comparative Example 1, it can be seen that if the first active layer containing non-precious metals is arranged at the outlet end of the substrate and the second active layer containing Mo2C is arranged at the inlet end of the substrate, the purification effect of pollutants such as CO, HC, methanol, and formaldehyde in the post-treatment of the methanol engine will be deteriorated.

[0137] (7) By comparing Example 1 with Comparative Examples 2-3, it can be seen that if the first active layer is omitted in the present invention, the purification effect of pollutants such as CO, HC, methanol, and formaldehyde in the methanol engine post-treatment will be deteriorated; if the second active layer is omitted, the catalyst's ability to treat NO2 will be significantly reduced.

[0138] (8) By comparing Example 1 with Comparative Example 4, it can be seen that compared with commercial DOC catalysts, the catalyst provided by the present invention can significantly reduce the proportion of NO2 emissions in engine exhaust, and can effectively oxidize pollutants such as CO, HC, methanol, and formaldehyde, thereby achieving purification of pollutants in methanol exhaust treatment.

[0139] In summary, the catalyst for methanol engine post-treatment provided by the present invention is provided with an active layer of non-precious metal active components on the air inlet end of the substrate, and MoS2, Mo2C or MoO2 is provided on the air outlet end of the substrate. x The active layer of active components, the two active components at the inlet and outlet ends, work together, and combined with the design of the positional relationship of the active components on the substrate, can effectively oxidize pollutants such as CO, HC, methanol, and formaldehyde, achieving purification of pollutants in methanol exhaust treatment. It can also reduce NO2 to NO, reducing the proportion of NO2 emissions in methanol engine exhaust without adding a urea injection system, significantly reducing the toxicity of NO2 to the environment and human health, and lowering the control requirements for methanol engines. Furthermore, the present invention uses non-precious metals as active components, while ensuring catalytic performance, and can effectively reduce the cost of the catalyst.

[0140] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A catalyst for methanol engine post-treatment, characterized in that: The catalyst comprises a substrate, a first active layer and a second active layer, wherein the first active layer is arranged on an air inlet end of a first surface of the substrate, and the second active layer is arranged on an air outlet end of the first surface of the substrate; The first active layer includes a first carrier and a first active component supported on the first carrier, wherein the first active component includes a non-noble metal; The second active layer includes a second carrier and a second active component supported on the second carrier, wherein the second active component includes MoS2, Mo2C or MoO x Any one or a combination of at least two of .

2. The catalyst according to claim 1, characterized in that The first carrier comprises any one of magnesium aluminum spinel, cobalt aluminum spinel, cobalt iron spinel, hydroxyapatite or hydroxyvanadium wollastonite; Preferably, the non-noble metal in the first active component includes any one of Mn, Fe or Co or a combination of at least two thereof; Preferably, in the catalyst, the loading amount of the first active layer is 20-500 g / L, preferably 50-300 g / L; Preferably, in the catalyst, the concentration of the first active component in the first active layer is 100-2000 g / cft, preferably 150-500 g / cft.

3. The catalyst according to claim 1 or 2, characterized in that In the catalyst, the loading amount of the second active layer is 20-300 g / L, preferably 100-200 g / L; Preferably, in the catalyst, the concentration of the second active component in the second active layer is 5-200 g / cft, preferably 50-150 g / cft; Preferably, the MoO x where x is 2 or 3; Preferably, the second support comprises any one of a metal oxide or a modified metal oxide; Preferably, the modified metal oxide adopts a modifier including any one of non-metal or metal.

4. The catalyst according to claim 3, characterized in that In the second carrier, the non-metal includes any one or a combination of at least two of B, C, N, F, P, Se, Te, Cl, Br, I or Si; Preferably, in the second carrier, the metal includes any one or a combination of at least two of Na, K, Mg, Ca, Sr, Ba, Rb, Cs, Cr, Mn, Co, Fe, Ni, Cu, Zn, W, Bi, In, Sn, Sb, La, Y, Zr, Nd or Pr; Preferably, in the second carrier, the metal oxide includes any one or a combination of at least two of aluminum oxide, cerium oxide, zirconium oxide, cerium zirconium oxide, cerium zirconium aluminum oxide, titanium oxide, tungsten oxide, magnesium oxide, cobalt oxide, nickel oxide, niobium oxide, indium oxide, tin oxide, zinc oxide or copper oxide; Preferably, in the modified metal oxide of the second carrier, the mass percentage of the non-metal to the metal oxide is 0.1-10%, preferably 0.5-5%; Preferably, in the modified metal oxide of the second carrier, the mass percentage of the metal in the metal oxide is 0.5-30%, preferably 0.5-15%.

5. The catalyst according to any one of claims 1 to 4, characterized in that Taking a direction parallel to the first surface of the substrate as a horizontal direction, in the horizontal direction, the first active layer and the second active layer are in contact with each other and arranged side by side; Preferably, with the direction parallel to the first surface of the substrate as the horizontal direction, the area ratio of the first active layer to the second active layer in the horizontal direction is 1:(0.5-1.5); Preferably, with the direction perpendicular to the first surface of the substrate as the vertical direction, the thickness ratio of the first active layer to the second active layer in the vertical direction is (1-5):1; Preferably, a direction perpendicular to the first surface of the substrate is taken as a vertical direction, and in the vertical direction, a thickness ratio of the first active layer to the substrate is 1:(0.5-1.5).

6. The catalyst according to any one of claims 1 to 5, characterized in that The substrate comprises any one of cordierite, silicon carbide or metal; Preferably, the structure of the substrate comprises a honeycomb structure; Preferably, the cross-sectional shape of the substrate includes any one of a circle and a square.

7. A method for preparing the catalyst according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: The first slurry and the second slurry are respectively placed on the air inlet end and the air outlet end of the first surface of the substrate, and after drying, calcination and hydrothermal aging, a first active layer and a second active layer are formed on the first surface of the substrate to obtain the catalyst; The first slurry includes a first active component and a first carrier, wherein the first active component includes a non-noble metal; The second slurry includes a second active component and a second carrier, wherein the second active component includes MoS2, Mo2C or MoO x Any one or a combination of at least two of .

8. The preparation method according to claim 7, characterized in that The first slurry further includes a first solvent, a first binder and a first thickener; Preferably, in the first slurry, the mass of the first solvent accounts for 50-80 wt% of the total mass of the first slurry; Preferably, in the first slurry, the mass of the first binder accounts for 2-20wt% of the total mass of the first slurry; Preferably, in the first slurry, the mass of the first thickener accounts for 0.2-1 wt% of the first slurry.

9. The preparation method according to claim 7 or 8, characterized in that The second slurry further includes a second solvent, a second binder and a second thickener; Preferably, in the second slurry, the mass of the second solvent accounts for 50-80 wt% of the total mass of the second slurry; Preferably, in the second slurry, the mass of the second binder accounts for 5-20wt% of the total mass of the second slurry; Preferably, in the second slurry, the mass of the second thickener accounts for 0.2-1 wt% of the total mass of the second slurry; Preferably, the calcination temperature is 300-400°C; Preferably, the temperature of the hydrothermal aging is 500-800°C.

10. Use of the catalyst 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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