A selective reduction catalyst and NO-containing X Gas treatment systems and methods

Abstract

This invention relates to a selective reduction catalyst and a system and method for treating NOx-containing gases. The catalyst comprises at least a first catalytic region and a second catalytic region; the first catalytic region includes at least a first SCR coating, and the second catalytic region includes at least a second SCR coating; the first and second SCR coatings each contain a second molecular sieve containing copper oxide, wherein the copper oxide loading of the first molecular sieve is lower than that of the second molecular sieve; the framework structure of the first molecular sieve is selected from one or more combinations of AEI, BEA, MFI, and CHA; the framework structure of the second molecular sieve is selected from AEI and / or CHA. The DeNOx catalytic activity of this catalyst is significantly improved in both low and high temperature ranges.

Description

Technical Field

[0001] This invention relates to a selective reduction catalyst and a treatment system and method for NOx-containing gases, belonging to the field of catalysis technology. Background Technology

[0002] NO in diesel exhaust x The removal of urea is mainly achieved through selective reduction catalysis (SCR). In the SCR process, an aqueous urea solution is injected into the engine exhaust gas through a urea injector. At temperatures above 180°C, NH3 is generated through hydrolysis and pyrolysis. Then, under the action of the SCR catalyst and in oxygen-rich conditions, NH3 reacts with NO. x A reaction occurs, selectively producing N2 and H2O. NO x The reduction process can be illustrated by the following chemical reactions:

[0003] 1) 4NH3 + 4NO + O2 = 4N2 + 6H2O (Standard SCR reaction, main reaction)

[0004] 2) 4NH3 + 2NO + 2NO2 = 4N2 + 6H2O (Fast SCR reaction)

[0005] 3) 4NH3 + 3NO2 = 3.5N2 + 6H2O (slow SCR reaction)

[0006] Molecular sieves are a hot research topic in SCR catalyst composition. The size and shape of molecular sieves partially influence their catalytic activity because they exert steric effects on reactants, controlling their entry and exit. For example, small molecules such as NOx can typically enter or leave the unit cell or diffuse through the channels of small pores, while larger molecules such as long-chain hydrocarbons cannot. Molecular sieves with small-pore frameworks, i.e., molecular sieves with a maximum ring size of 8, have been found suitable for SCR applications. Small-pore molecular sieves have catalyst configurations such as CHA, AEI, LEV, and ERI.

[0007] Typically, the SCR catalytic performance of molecular sieves can be improved through cation exchange in a specific environment. During cation exchange, some ions present on the surface or framework are replaced by metal cations; that is, the catalytic performance of the molecular sieve can be improved by loosely retaining one or more metal ions on the molecular sieve framework. The most common metal cations exchanged are copper or iron ions (Cu). 2+ or Fe 3+ This forms copper-based or iron-based molecular sieve SCR catalysts.

[0008] SCR catalysts aim for a wide operating window, exhibiting high catalytic activity at both low and high temperatures. While high metal loading on the molecular sieve can lead to higher SCR activity at low operating temperatures, high metal loading often compromises high-temperature stability, thus affecting high-temperature catalytic activity. Therefore, in SCR catalyst formulation design, single-metal-based molecular sieve formulations often struggle to meet the requirement of high DeNOx performance across all temperature ranges.

[0009] To improve DeNOx performance, the following technical solutions have been disclosed in the prior art:

[0010] In US2011 / 0305613, a mixture of two molecular sieve structures, MFI and BEA, with iron ion exchange was used in the SCR catalyst. MFI, with its smaller silica-alumina ratio, had a higher Fe loading. In the DeNOx activity test, the NOx emission of the MFI and BEA mixture was significantly lower than that of the BEA-only mixture.

[0011] In CN101568368A, a mixture of molecular sieves appears in applications for adsorbing hydrocarbons from cold-start engine exhaust gases, specifically a mixture of small-pore and medium-pore molecular sieves. The small-pore molecular sieve is also described in an embodiment where AEI (SSZ-39) and CHA (SSZ-13) are mixed. In the examples, the small-pore molecular sieve (SSZ-13) and the medium-pore molecular sieve (such as SSZ-33) are mixed at a weight ratio of 3:1 or 1:1, resulting in a significantly higher ethane absorption rate at 30°C compared to that of each molecular sieve alone.

[0012] CN104736243A discloses a scheme for the selective reduction of catalytic nitrogen oxides in the presence of a reducing agent using a mixture of two molecular sieves. The mixture includes a copper-promoted first 8-ring microporous molecular sieve and an iron-promoted first 8-ring microporous molecular sieve, with the molecular sieve structures selected from AEI, CHA, AFT, AFX, etc. In the examples, the copper-promoted molecular sieves (Cu-CHA) and iron-promoted molecular sieves (Fe-CHA) exhibit higher NOx conversion rates than Cu-CHA alone under very low NH3 leakage conditions.

[0013] Besides uniform mixing, existing technologies also include methods for dividing different formulations into sections before and after mixing, as shown in the following examples:

[0014] CN10714939A mentions two SCR regions, with the upstream first SCR catalyst region comprising vanadium supported on a metal oxide selected from TiO2, ZrO2, SiO2, CeO2, and Al2O3. The downstream second SCR catalyst region comprises a copper-supported microporous molecular sieve. The first SCR catalyst region has a higher support coating loading and a higher overall copper oxide loading than the second SCR catalyst region.

[0015] CN106714940B mentions different designs for the upstream and downstream SCR regions. The upstream first SCR catalyst region contains a mesoporous or macroporous molecular sieve with iron supported and a BEA framework, which has a first ammonia storage capacity. The downstream second SCR catalyst region contains a microporous molecular sieve with copper supported and a framework selected from CHA, AEI, AFX and AFT, which has a second ammonia storage capacity (the first SCR catalyst region does not contain copper and the second catalyst region does not contain iron).

[0016] In the front and rear partitioned coatings mentioned in CN106457147A, the upstream first SCR region contains a first copper oxide-supported CHA structure molecular sieve, and the downstream second SCR region contains a second copper oxide-supported CHA structure molecular sieve. The upstream and downstream regions are different CHA structure molecular sieves with different SARs.

[0017] Existing technologies also include methods of dividing different formulations into upper and lower layers. For example, CN10714939A mentions placing the first SCR catalyst region on the top layer and the second SCR catalyst region on the bottom layer, while CN106457147A also mentions placing the second SCR catalyst on the top layer.

[0018] CN105026038B also mentions different formulations with upper and lower layer partitioning. The first SCR catalyst composition is located on the top layer, containing vanadium oxide / titanium oxide, while the second SCR catalyst composition is located on the bottom layer, containing metal-exchanged 8-ring microporous molecular sieves. It further states that the first SCR catalyst layer promotes higher N2 selectivity and lower N2O formation compared to the second SCR catalyst layer.

[0019] In the presence of nitrogen oxides (NO) x During the purification and treatment of waste gas, NO present in the waste gas x While numerous solutions have been proposed to improve DeNOx performance through selective catalytic reduction (SCR) to convert nitrogen into harmless gas, they still fall short of increasingly stringent emission standards. Furthermore, with engine exhaust temperatures decreasing, there is a growing demand in industry for further improvements in DeNOx activity up to 200°C. Summary of the Invention

[0020] To address the aforementioned technical problems, the present invention aims to provide a selective reduction catalyst that significantly improves the performance of copper-exchanged molecular sieve SCR while maintaining DeNOx activity at both high and low temperatures by controlling the distribution of the active coating and the loading of the active components.

[0021] To achieve the above objectives, the present invention first provides a selective reduction catalyst, wherein the selective reduction catalyst comprises at least: a first catalytic region and a second catalytic region; wherein:

[0022] The first catalytic region includes at least a first SCR coating, and the second catalytic region includes at least a second SCR coating;

[0023] Wherein, the first SCR coating contains a first molecular sieve containing copper oxide, the second SCR coating contains a second molecular sieve containing copper oxide, and the copper oxide loading of the first molecular sieve is lower than the copper oxide loading of the second molecular sieve.

[0024] The framework structure of the first molecular sieve is selected from one or more combinations of AEI, BEA, MFI, and CHA.

[0025] The framework structure of the second molecular sieve is selected from AEI and / or CHA;

[0026] The copper oxide loading of the first molecular sieve is 2.0 wt%-5.5 wt%, and the copper oxide loading of the second molecular sieve is 3.5 wt%-8.0 wt%.

[0027] The coating loading of the first SCR coating is 2.0-5.0 g / in. 3 The coating loading of the second SCR coating is 1.5-4.0 g / in. 3 .

[0028] According to some specific embodiments of the present invention, the copper oxide loading of the first molecular sieve can be 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, or 5.5 wt%, and the copper oxide loading of the second molecular sieve can be 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, 6.0 wt%, 6.5 wt%, 7.0 wt%, 7.5 wt%, or 8.0 wt%.

[0029] According to some specific embodiments of the present invention, preferably, the copper oxide loading of the first molecular sieve is 3.0wt%-4.5wt%.

[0030] According to some specific embodiments of the present invention, preferably, the copper oxide loading of the second molecular sieve is 4.0 wt%-7.0 wt%.

[0031] According to some specific embodiments of the present invention, the coating loading of the first SCR coating can specifically be 2.0 g / in. 3 2.5g / in 3 3.0g / in 3 3.5g / in 3 4.0g / in 3 4.5g / in 3 5.0g / in 3 The loading capacity of the second SCR coating can be specifically 1.5 g / in. 3 2.0g / in 3 2.5g / in 3 3.0g / in 3 3.5g / in 3 4.0g / in 3 .

[0032] According to some specific embodiments of the present invention, preferably, the coating loading of the first SCR coating is 2.5-4.5 g / in. 3 .

[0033] According to some specific embodiments of the present invention, preferably, the coating loading of the second SCR coating is 2.0-3.5 g / in. 3 .

[0034] According to some specific embodiments of the present invention, preferably, the silicon-to-aluminum atomic ratio of the first molecular sieve is 10-30, more preferably 15-25.

[0035] According to some specific embodiments of the present invention, preferably, the silicon-to-aluminum atomic ratio of the second molecular sieve is 10-30, more preferably 15-25.

[0036] According to some specific embodiments of the present invention, preferably, the second catalytic region further comprises an ASC coating located at the rear end of the second catalytic region. The ASC coating is an ammonia oxidation coating, typically containing noble metals. By combining the SCR coating and the ASC coating, the functions of oxidizing excess ammonia and reducing nitrogen oxides can be simultaneously achieved. The specific composition of the ASC coating used in this invention can be a composition of ASC coatings commonly used in the art.

[0037] According to some specific embodiments of the present invention, preferably, the ASC coating is covered by a second SCR coating or the second SCR coating is partially mixed with the ASC coating. Wherein, the second SCR coating is partially mixed with the ASC coating means that the slurry for preparing the second SCR coating is mixed with a portion of the slurry for preparing the ASC coating to form a coating with a certain ammonia oxidation function, which then covers the pure ASC coating formed by the other portion of the slurry for preparing the ASC coating.

[0038] According to some specific embodiments of the present invention, preferably, the first catalytic region further includes a second SCR coating.

[0039] According to some specific embodiments of the present invention, preferably, when the first catalytic region further includes a second SCR coating, the first SCR coating and the second SCR coating in the first catalytic region can be configured as follows:

[0040] The first SCR coating and the second SCR coating are arranged side by side, and the second SCR coating is located at the rear end of the first catalytic region;

[0041] Alternatively, the first SCR coating may cover part or all of the second SCR coating;

[0042] Alternatively, in the first catalytic region, the second SCR coating covers a portion of the first SCR coating.

[0043] According to some specific embodiments of the present invention, preferably, when the first catalytic region further includes a second SCR coating, the length of the second SCR coating in the first catalytic region accounts for 20%-80% of the length of the first catalytic region, more preferably 30%-70%, for example 30%, 40%, 50%, 60%, 70%.

[0044] According to some specific embodiments of the present invention, preferably, the second catalytic region further includes a first SCR coating.

[0045] According to some specific embodiments of the present invention, preferably, when the second catalytic region also includes a first SCR coating, the first SCR coating and the second SCR coating in the second catalytic region can be configured as follows:

[0046] The first SCR coating and the second SCR coating are arranged side by side, and the first SCR coating is located at the front end of the second catalytic region;

[0047] Alternatively, in the second catalytic region, the first SCR coating covers a portion of the second SCR coating;

[0048] Alternatively, in the second catalytic region, the second SCR coating covers part or all of the first SCR coating.

[0049] According to some specific embodiments of the present invention, preferably, when the second catalytic region also includes the first SCR coating, the length of the second SCR coating in the second catalytic region accounts for 20%-80% of the length of the first catalytic region, more preferably 30%-70%, for example 30%, 40%, 50%, 60%, 70%.

[0050] According to some specific embodiments of the present invention, preferably, the selective reduction catalyst further includes at least one catalytic region disposed between the first catalytic region and the second catalytic region, and the catalytic region is provided with a first SCR coating and / or a second SCR coating.

[0051] According to some specific embodiments of the present invention, preferably, the first molecular sieve and the second molecular sieve have the same framework structure.

[0052] According to some specific embodiments of the present invention, preferably, the first molecular sieve and the second molecular sieve have different framework structures.

[0053] According to some specific embodiments of the present invention, preferably, the first molecular sieve is AEI, and the second molecular sieve is AEI or CHA.

[0054] According to some specific embodiments of the present invention, preferably, the first catalytic region, the second catalytic region, and the further included catalytic region each comprise a substrate, and the SCR coating (the first SCR coating and / or the second SCR coating) at least covers a portion of the surface of the substrate.

[0055] According to some specific embodiments of the present invention, preferably, the substrate has a porous structure, such as a honeycomb porous structure.

[0056] According to some specific embodiments of the present invention, preferably, the substrate is a ceramic honeycomb carrier.

[0057] The present invention also provides a NO-containing x A gas processing system comprising the selective reduction catalyst provided by the present invention, wherein the first catalytic region is located in a region that contacts the NO-containing gas before the second catalytic region. x The position of the gas.

[0058] The present invention also provides a NO-containing x The method for treating the NO-containing gas involves using the selective reduction catalyst provided by this invention, wherein the first catalytic region contacts the NO-containing gas before the second catalytic region. x The gas.

[0059] According to some specific embodiments of the present invention, the first SCR coating of the selective reduction catalyst of the present invention can still have DeNOx activity in a temperature range below 200°C, and the second SCR coating can still have DeNOx activity in a temperature range above 500°C. That is, the reaction temperature on the first SCR coating is below 200°C, preferably 175°C-200°C, and the reaction temperature on the second SCR coating is above 500°C, preferably 500°C-600°C.

[0060] According to some specific embodiments of the present invention, preferably, the NO-containing x The gases include exhaust gases produced by diesel combustion, such as the exhaust fumes from diesel vehicles.

[0061] The technical solution of this invention, through an optimized zoning layout and the optimization of a series of influencing factors, including the copper loading in specific regions, the silica-alumina ratio of the molecular sieve, the coating loading in specific regions, and the layout of specific regions, can not only be used to complement the strengths and weaknesses of different molecular sieve combinations, but also tap the potential of molecular sieves. This results in a significant improvement in the DeNOx catalytic activity of the catalyst in both the low-temperature (<200℃) and high-temperature (>550℃) ranges. For example, after hydrothermal aging at 700℃ for 50 hours in the presence of 10% H2O, the NOx conversion rate at both 200℃ and 600℃ reaches over 80%. Compared to catalysts using a single copper oxide loading, the catalyst of this invention achieves a high NOx conversion rate at 600℃ while simultaneously reducing the N2O formation concentration by approximately 20%-25% at 600℃. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the first embodiment of the present invention.

[0063] Figure 2 This is a schematic diagram of the second embodiment of the present invention.

[0064] Figure 3 This is a schematic diagram of the third embodiment of the present invention.

[0065] Figure 4a and Figure 4b This is a schematic diagram of the fourth embodiment of the present invention.

[0066] Figure 5 This is a schematic diagram of the fifth embodiment of the present invention.

[0067] Explanation of icon numbers:

[0068] First SCR coating 1; Second SCR coating 2; ASC coating 3; Airflow direction 4; First catalytic region 5; Second catalytic region 6; Third catalytic region 7 Detailed Implementation

[0069] In this invention, "front end" and "back end" are defined by the order in which they come into contact with the gas to be treated. The end that comes into contact with the gas to be treated first is the front end, and the end that comes into contact with the gas to be treated later is the back end.

[0070] In this invention, "upstream" and "downstream" are defined by the flow direction of the gas to be treated, which flows from upstream to downstream.

[0071] In this invention, the copper oxide loading is expressed as a weight percentage of CuO / (CuO + molecular sieve).

[0072] In this invention, the copper oxide loading of the first molecular sieve is lower than that of the second molecular sieve. When selecting the copper oxide loading of the first and second molecular sieves, this requirement should be met. For example, when the copper oxide loading of the second molecular sieve is 4.0 wt%, the first molecular sieve should be selected with a copper oxide loading of less than 4.0 wt%.

[0073] In this invention, the coating loading is measured by the dry weight of the coating per unit volume of catalyst.

[0074] The selective reduction catalyst provided by this invention can be implemented in various ways:

[0075] Figure 1 This is a schematic diagram of the first embodiment of the present invention. Figure 1 As shown, the selective reduction catalyst includes a first catalytic region 5 and a second catalytic region 6;

[0076] The first catalytic region 5 is located upstream of the second catalytic region 6 (i.e., upstream of the airflow direction 4); wherein:

[0077] The first catalytic region 5 includes a honeycomb support and a first SCR coating 1 disposed on the surface of the support;

[0078] The second catalytic region 6 includes a honeycomb support, a second SCR coating 2 disposed on the surface of the support, and an ASC coating 3 disposed at the end of the support, wherein the ASC coating 3 is covered by the second SCR coating 2.

[0079] The first SCR coating 1 is a molecular sieve loaded with copper oxide, and has a low copper oxide loading, which ranges from 2.0 wt% to 5.5 wt%, preferably from 3.0 wt% to 4.5 wt%.

[0080] The second SCR coating 2 is a molecular sieve loaded with copper oxide, and has a high copper oxide loading, which ranges from 3.5 wt% to 8.0 wt%, preferably from 4.0 wt% to 7.0 wt%.

[0081] The copper oxide loading of the first SCR coating 1 is lower than that of the second SCR coating 2;

[0082] The molecular sieve framework structure of the first SCR coating 1 is preferably AEI; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0083] The molecular sieve framework structure of the second SCR coating 2 is preferably AEI or CHA; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0084] The coating loading in the first catalytic region 5 ranges from 2.0 to 5.0 g / in. 3 Preferably, it is 2.5-4.5 g / in. 3 ;

[0085] The coating loading in the second catalytic region 6 ranges from 1.5 to 4.0 g / in. 3 Preferred concentration: 2.0-3.5 g / in 3 .

[0086] Figure 2 This is a schematic diagram illustrating a second embodiment of the present invention. (As shown) Figure 2 As shown, the selective reduction catalyst includes a first catalytic region 5 and a second catalytic region 6;

[0087] The first catalytic region 5 is located upstream of the second catalytic region 6; wherein:

[0088] The first catalytic region 5 includes a honeycomb support, a first SCR coating 1 and a second SCR coating 2 disposed on the surface of the support, that is, the first catalytic region 5 includes the first SCR coating 1 and the second SCR coating 2 arranged side by side, and the first SCR coating 1 is located upstream of the second SCR coating 2; in the first catalytic region 5, the length of the second SCR coating 2 accounts for 20%-80% of the overall length of the first catalytic region 5, preferably 30%-70%.

[0089] The second catalytic region 6 includes a honeycomb support, a second SCR coating 2 disposed on the surface of the support, and an ASC coating 3 disposed at the end of the support, wherein the ASC coating 3 is covered by the second SCR coating 2.

[0090] The second SCR coating 2 on the first catalytic region 5 can be considered as an extension of the second SCR coating 2 on the second catalytic region 6;

[0091] The first SCR coating 1 is a molecular sieve loaded with copper oxide, and has a low copper oxide loading, which ranges from 2.0 wt% to 5.5 wt%, preferably from 3.0 wt% to 4.5 wt%.

[0092] The second SCR coating 2 is a molecular sieve loaded with copper oxide, and has a high copper oxide loading, which ranges from 3.5 wt% to 8.0 wt%, preferably from 4.0 wt% to 7.0 wt%.

[0093] The copper oxide loading of the first SCR coating 1 is lower than that of the second SCR coating 2;

[0094] The molecular sieve framework structure of the first SCR coating 1 is preferably AEI; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0095] The molecular sieve framework structure of the second SCR coating 2 is preferably AEI or CHA; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0096] The coating loading in the first catalytic region 5 ranges from 2.0 to 5.0 g / in. 3 Preferably, it is 2.5-4.5 g / in. 3 ;

[0097] The coating loading in the second catalytic region 6 ranges from 1.5 to 4.0 g / in. 3 Preferably 2.0-3.5 g / in 3 .

[0098] Figure 3 This is a schematic diagram of the third embodiment of the present invention. (As shown) Figure 3 As shown, the selective reduction catalyst includes a first catalytic region 5 and a second catalytic region 6;

[0099] The first catalytic region 5 is located upstream of the second catalytic region 6; wherein:

[0100] The first catalytic region 5 includes a honeycomb support and a first SCR coating 1 disposed on the surface of the support;

[0101] The second catalytic region 6 includes a honeycomb support, a first SCR coating 1 and a second SCR coating 2 disposed on the surface of the support, and an ASC coating 3 disposed at the end of the support. That is, the second catalytic region 6 includes the first SCR coating 1 and the second SCR coating 2 arranged side by side, and the first SCR coating 1 is located upstream of the second SCR coating 2. In the second catalytic region 6, the length of the second SCR coating 2 accounts for 20%-80% of the overall length of the second catalytic region 6, preferably 30%-70%. The ASC coating 3 is covered by the second SCR coating 2.

[0102] The first SCR coating 1 on the second catalytic region 6 can be considered as an extension of the first SCR coating 1 on the first catalytic region 5.

[0103] The first SCR coating 1 is a molecular sieve loaded with copper oxide, and has a low copper oxide loading, which ranges from 2.0 wt% to 5.5 wt%, preferably from 3.0 wt% to 4.5 wt%.

[0104] The second SCR coating 2 is a molecular sieve loaded with copper oxide, and has a high copper oxide loading, which ranges from 3.5 wt% to 8.0 wt%, preferably from 4.0 wt% to 7.0 wt%.

[0105] The copper oxide loading of the first SCR coating 1 is lower than that of the second SCR coating 2;

[0106] The molecular sieve framework structure of the first SCR coating 1 is preferably AEI; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0107] The molecular sieve framework structure of the second SCR coating 2 is preferably AEI or CHA; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0108] The coating loading in the first catalytic region 5 ranges from 2.0 to 5.0 g / in. 3 Preferably, it is 2.5-4.5 g / in. 3 ;

[0109] The coating loading in the second catalytic region 6 ranges from 1.5 to 4.0 g / in. 3 Preferably 2.0-3.5 g / in 3 .

[0110] Figure 4a and Figure 4b This is a schematic diagram illustrating the fourth embodiment of the present invention. (As shown) Figure 4a and Figure 4bAs shown, the selective reduction catalyst includes a first catalytic region 5 and a second catalytic region 6;

[0111] The first catalytic region 5 is located upstream of the second catalytic region 6; wherein:

[0112] The first catalytic region 5 includes a honeycomb support, a first SCR coating 1 and a second SCR coating 2 disposed on the surface of the support, wherein the second SCR coating 2 is located at the rear end of the first catalytic region 5 and is covered by the first SCR coating 1 (e.g., Figure 4a (as shown) or covering a portion of the first SCR coating 1 (such as...) Figure 4b (as shown); in the first catalytic region 6, the length of the second SCR coating 2 accounts for 20%-80% of the total length of the first catalytic region 5, preferably 30%-70%;

[0113] The second catalytic region 6 includes a honeycomb support, a second SCR coating 2 disposed on the surface of the support, and an ASC coating 3 disposed at the end of the support, wherein the ASC coating 3 is covered by the second SCR coating 2.

[0114] The first SCR coating 1 is a molecular sieve loaded with copper oxide, and has a low copper oxide loading, which ranges from 2.0 wt% to 5.5 wt%, preferably from 3.0 wt% to 4.5 wt%.

[0115] The second SCR coating 2 is a molecular sieve loaded with copper oxide, and has a high copper oxide loading, which ranges from 3.5 wt% to 8.0 wt%, preferably from 4.0 wt% to 7.0 wt%.

[0116] The copper oxide loading of the first SCR coating 1 is lower than that of the second SCR coating 2;

[0117] The molecular sieve framework structure of the first SCR coating 1 is preferably AEI; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0118] The molecular sieve framework structure of the second SCR coating 2 is preferably AEI or CHA; the silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 10-30, preferably 15-25;

[0119] The coating loading in the first catalytic region 5 ranges from 2.0 to 5.0 g / in. 3 Preferably, it is 2.5-4.5 g / in. 3 ;

[0120] The coating loading in the second catalytic region 6 ranges from 1.5 to 4.0 g / in. 3 Preferably 2.0-3.5 g / in3 .

[0121] Figure 5 This is a schematic diagram illustrating the fifth embodiment of the present invention. (As shown) Figure 5 As shown, the selective reduction catalyst includes a first catalytic region 5, a second catalytic region 6, and a plurality of third catalytic regions 7 disposed between the first catalytic region 5 and the second catalytic region 6;

[0122] The first catalytic region 5 and the second catalytic region 6 can be configured with reference to any one of the first to fourth embodiments described above.

[0123] The third catalytic region 7 is provided with a first SCR coating and / or a second SCR coating, and the first SCR coating and the second SCR coating of the third catalytic region 7 are identical in material, structure, molecular sieve (framework structure and silicon-to-aluminum ratio), and copper oxide loading to the SCR coatings of the upstream and downstream adjacent catalytic regions, for example:

[0124] When the third catalytic region 7 includes both the first SCR coating located upstream and the second SCR coating located downstream, the upstream catalytic region should contain the first SCR coating and the downstream catalytic region should contain the second SCR coating; the coating loading of the third catalytic region 7 can be set with reference to either the first catalytic region 5 or the second catalytic region 6.

[0125] When the first catalytic region 5 and the second catalytic region 6 are configured according to the second embodiment, all third catalytic regions 7 contain the second SCR coating; the coating loading of the third catalytic region 7 is set with reference to the second catalytic region 6.

[0126] When the first catalytic region 5 and the second catalytic region 6 are configured according to the third embodiment, all third catalytic regions 7 contain the first SCR coating; the coating loading of the third catalytic region 7 is set with reference to the first catalytic region 5.

[0127] When the first catalytic region 5 and the second catalytic region 6 are configured according to the fourth embodiment, all third catalytic regions 7 contain the second SCR coating; the coating loading of the third catalytic region 7 is configured with reference to the second catalytic region 6.

[0128] The fifth embodiment can further enhance the DeNOx performance of the catalyst at low or high temperatures.

[0129] To further illustrate specific embodiments of the present invention, the following specific examples are provided:

[0130] Example 1

[0131] This embodiment provides a catalytic reduction catalyst, the preparation method of which includes:

[0132] Preparation of slurry and coating of ASC coating containing precious metals: A certain amount of precious metal salt solution (such as Pt or Pd precious metal salt) is impregnated on an alumina (including but not limited to alumina) support, and then deionized water and an appropriate amount of surfactant are added to prepare a slurry. The slurry is then applied to the end position of the second catalytic region, ensuring that the content of precious metal in the coating is 1.0-5.0 g / ft. 3 The coating loading is 0.3-1.0 g / in. 3 .

[0133] Preparation of copper molecular sieve slurry: Add an appropriate amount of copper ion exchanged molecular sieve to deionized water and stir for 30 minutes. While stirring, add a certain amount of acid and binder to the slurry, then add an appropriate amount of surfactant to adjust the properties of the slurry, and grind it to finally obtain a slurry with a solid content of about 40%.

[0134] Two copper-containing molecular sieve slurries were prepared according to the above steps. Both molecular sieves had an AEI structure with a silica-alumina ratio (SAR) of 15-25. One slurry (J1) had a relatively low copper oxide loading, ranging from 3.0 wt% to 4.5 wt%, while the other slurry (J2) had a relatively high copper oxide loading, ranging from 4.0 wt% to 7.0 wt%. The copper oxide loading of slurry (J2) was higher than that of slurry (J1).

[0135] The coating scheme is a single-layer, zoned coating (i.e.) Figure 1 As shown, two slurries were applied to a 1-inch diameter porous ceramic support with a pore density of 400 cpsi (pores per square inch) and a wall thickness of 6 mils, respectively: the slurry containing a low copper oxide loading was applied to a 1-inch diameter, 1.5-inch length support as the first catalytic region (upstream SCR1 region), with a coating loading of 2.5-4.5 g / in. 3 A slurry containing a high copper oxide loading was coated onto a support with a diameter of 1 inch and a length of 1.5 inches as the second catalytic region (downstream SCR2 region), with a coating loading of 2.0-3.5 g / in. 3 .

[0136] The coated carrier was dried at 120°C for 1 hour and then calcined at 450°C for 30 minutes to obtain a catalyst sample.

[0137] Example 2

[0138] Two copper-containing molecular sieve slurries were prepared according to the preparation steps of the copper molecular sieve slurry in Example 1. The two slurries with low copper oxide loading and high copper oxide loading were the same as those in Example 1.

[0139] The parameters of the carrier, as well as the slurry coating, drying, and calcination processes and parameters, are the same as in Example 1 (such as the pore density of the carrier, the wall thickness of the carrier, the size of the carrier in the first catalytic region and the second catalytic region, the drying temperature and time, the calcination temperature and time, etc.), and the coating scheme of the second catalytic region is the same as in Example 1.

[0140] Unlike Example 1, the first catalytic region, which is 1.5 inches long, is subjected to a partitioned coating with low and high copper oxide loadings (i.e., Figure 2 As shown, a slurry containing a low copper oxide loading is applied to the front section of the first catalytic region, with a coating loading of 2.5-4.5 g / in. 3 A slurry with a high copper oxide loading was applied to the rear section of the first catalytic region, with a coating loading of 2.0-3.5 g / in. 3 The latter part of the first catalytic region accounts for 30%-70% of the total length of the first catalytic region.

[0141] Example 3

[0142] Two copper-containing molecular sieve slurries were prepared according to the preparation steps of the copper molecular sieve slurry in Example 1, wherein the two slurries with low copper oxide loading and high copper oxide loading were the same as those in Example 1.

[0143] The parameters of the carrier, as well as the slurry coating, drying, and calcination processes and parameters, are the same as in Example 1 (such as the pore density of the carrier, the wall thickness of the carrier, the size of the carrier in the first catalytic region and the second catalytic region, the drying temperature and time, the calcination temperature and time, etc.), and the coating scheme of the first catalytic region is the same as in Example 1.

[0144] Unlike Example 1, the 1.5-inch-long second catalytic region was subjected to partitioned coating with low and high copper oxide loadings. A slurry containing low copper oxide loading was applied to the front section of the second catalytic region, with a coating loading of 2.5-4.5 g / in. 3 A slurry with a high copper oxide loading was applied to the latter part of the second catalytic region, with a coating loading of 2.0-3.5 g / in. 3 The latter part of the second catalytic region accounts for 30%-70% of the total length of the second catalytic region.

[0145] Example 4

[0146] Two copper-containing molecular sieve slurries were prepared according to the preparation steps of the copper molecular sieve slurry in Example 1, wherein the two slurries with low copper oxide loading and high copper oxide loading were the same as those in Example 1.

[0147] The parameters of the carrier, as well as the slurry coating, drying, and calcination processes and parameters, are the same as in Example 1 (such as the pore density of the carrier, the wall thickness of the carrier, the size of the carrier in the first catalytic region and the second catalytic region, the drying temperature and time, the calcination temperature and time, etc.). The coating scheme of the second catalytic region is the same as in Example 1.

[0148] Unlike Example 1, the first catalytic region is coated in two layers (e.g., ...). Figure 4a and Figure 4b As shown), the coating loading in the first catalytic region ranges from 2.5 to 4.5 g / in. 3 (Total dry weight including low copper oxide loading coating and high copper oxide loading coating). In the first catalytic region, the high copper oxide loading coating accounts for 30%-70% of the total coating length in the first catalytic region.

[0149] Comparative Example 1

[0150] A copper molecular sieve-containing slurry was prepared according to the preparation steps of the copper molecular sieve slurry in Example 1.

[0151] Unlike Example 1, both the first catalytic region and the second catalytic region adopt a uniform coating design with the same copper oxide loading. The total copper oxide loading of the first catalytic region and the second catalytic region is consistent with the total copper oxide loading of the partitioned coating in Example 1.

[0152] The parameters of the carrier, as well as the slurry coating, drying, and calcination processes and parameters, are the same as in Example 1 (such as the pore density of the carrier, the wall thickness of the carrier, the size of the carrier in the first catalytic region and the second catalytic region, the drying temperature and time, the calcination temperature and time, etc.).

[0153] Test example: Catalytic reaction test

[0154] The catalytic performance testing method of the present invention is as follows: by adding a feed gas mixture of 500ppm NO, 500ppm NH3, 10% O2, 5% H2O, and N2 as the balance gas to a reactor containing 1”D×3”L of catalyst, the conversion rate of nitrogen oxides (NOx) selective catalytic reduction (SCR) and N2 selectivity of the fresh catalyst are tested.

[0155] The reaction was carried out at a temperature range of 150℃-600℃ for 60,000 hours. -1The space velocity was determined. The catalyst was hydrothermally aged at 700°C for 50 hours in the presence of 10% H2O, and then the conversion rate and N2 selectivity of nitrogen oxide (NOx) selective catalytic reduction (SCR) were tested using the same method as for testing fresh catalyst.

[0156] A certain amount of copper ion-exchanged molecular sieves were added to deionized water and stirred for 30 minutes. While stirring, a certain amount of acid and binder were added to the slurry, and a certain amount of surfactant was added to adjust the properties of the slurry. The slurry was then ground to obtain a slurry with a solid content of about 40%. The slurry was then coated onto a carrier to prepare catalysts with copper molecular sieve coatings of the AEI, BEA, MFI, CHA, and ACO types, respectively. The silica-alumina ratio of the molecular sieves was 10-20.

[0157] For the various copper-containing molecular sieves mentioned above, the copper loading content in each structural type of copper-containing molecular sieve was adjusted, and they were coated onto the carrier with different loading amounts, and DeNOx performance tests were conducted. The test results are shown in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] As can be seen from the test results recorded in Table 1, the performance of ACO, AFT and DUR is relatively good under both high and low temperature conditions. Under high temperature conditions, AEI has the best performance, while under low temperature conditions, AEI and CHA have the best performance.

[0162] Catalysts were prepared using different combinations of molecular sieve structures, silicon-to-aluminum ratios, and coating methods. For specific preparation methods, please refer to Examples 1-2, and their DeNOx performance was tested, as shown in Table 2.

[0163] In this study, the molecular sieve structure combinations were adjusted using the molecular sieve structure and copper loading in two catalyst regions as variables, and the silicon-to-aluminum ratio and coating method were adjusted for each combination. It should be noted that "single-layer partitioning" in the coating method refers to... Figures 1-2 The proportions indicated in parentheses for the molecular sieve coating structures refer to the length ratio of the first SCR coating to the second SCR coating within the first and second catalytic regions.

[0164] Table 2

[0165]

[0166]

[0167] Among them, single-layer partitioning (30:70) is adopted. Figure 2 As shown, the high-load coating occupies 70% of the sum of the lengths of the first and second catalytic regions;

[0168] Single-level partitioning (30:70) is adopted Figure 2 As shown, the high-load coating accounts for 30% of the sum of the lengths of the first and second catalytic regions;

[0169] Single-level partitioning (50:50) is adopted Figure 2 As shown, the high-load coating occupies 50% of the sum of the lengths of the first and second catalytic regions;

[0170] The partial overlap of the technical solution in serial number 11 is achieved by adopting Figure 4a As shown, the overlapping portion accounts for 30% of the length of the first catalytic region;

[0171] The partial overlap of the technical solution in serial number 24 is achieved by adopting Figure 4b As shown, the overlapping portion accounts for 30% of the length of the first catalytic region.

[0172] The test results recorded in Table 2 show that:

[0173] Technical solution No. 13 (comparative solution): The copper oxide loading in the first catalytic region is higher than that in the second catalytic region, and its DeNOx is relatively poor.

[0174] Technical solutions 14-16 (comparative solutions): The molecular sieves used in the first catalytic region have framework structures of ACO, AFT, and DUR, respectively. Their DeNOx is relatively poor, significantly lower than that of molecular sieves with a framework structure of AEI, such as technical solutions 17-18.

[0175] Technical solutions 22, 25, and 26 (comparative solutions): The molecular sieves used in the second catalytic region have framework structures of ACO and DUR, respectively, and their DeNOx is relatively poor, significantly lower than that of molecular sieves with a framework structure of CHA, such as technical solutions 17-18.

[0176] In summary, the technical solution of this invention, through an optimized partitioned layout and by optimizing a series of influencing factors, including controlling the loading of copper oxide, the silicon-to-aluminum ratio of the molecular sieve, and the coating loading in specific areas within a suitable range, and in conjunction with a specific layout, can not only be used to complement the strengths of different molecular sieve combinations, but also tap the potential of molecular sieves, resulting in a significant improvement in the DeNOx catalytic activity of the catalyst in both the low-temperature (<200℃) and high-temperature (>550℃) ranges.

Claims

1. A NO-containing x The method for treating the gas involves using a selective reduction catalyst, which comprises at least: First catalytic region and second catalytic region; wherein: The first catalytic region includes at least a first SCR coating, and the second catalytic region includes at least a second SCR coating; Wherein, the first SCR coating contains a first molecular sieve containing copper oxide, the second SCR coating contains a second molecular sieve containing copper oxide, and the copper oxide loading of the first molecular sieve is lower than the copper oxide loading of the second molecular sieve. The framework structure of the first molecular sieve is AEI; The framework structure of the second molecular sieve is CHA; The first molecular sieve has a copper oxide loading of 3.0 wt% - 4.5 wt%, and the second molecular sieve has a copper oxide loading of 4.0 wt% - 7.0 wt%. The reaction temperature on the first SCR coating is 175℃-200℃ and the coating loading is 2.5-4.5 g / in. 3 The reaction temperature on the second SCR coating is 500℃-600℃ and the coating loading is 2.0-3.5 g / in. 3 ; The silicon-to-aluminum atomic ratio of the first molecular sieve is 15-25; the silicon-to-aluminum atomic ratio of the second molecular sieve is 15-25. The first catalytic region contacts the NO-containing material before the second catalytic region. x The gas.

2. The processing method according to claim 1, wherein, The second catalytic region also contains an ASC coating, which is located at the rear end of the second catalytic region.

3. The processing method according to claim 2, wherein, The ASC coating is covered by a second SCR coating.

4. The processing method according to claim 1, wherein, The first catalytic region also includes a second SCR coating.

5. The processing method according to claim 4, wherein, In the first catalytic region, the first SCR coating and the second SCR coating are arranged side by side, and the second SCR coating is located at the rear end of the first catalytic region; Alternatively, the first SCR coating may cover part or all of the second SCR coating; Alternatively, the second SCR coating may cover a portion of the first SCR coating.

6. The processing method according to claim 4 or 5, wherein, In the first catalytic region, the length of the second SCR coating accounts for 20%-80% of the length of the first catalytic region.

7. The processing method according to claim 6, wherein, In the first catalytic region, the length of the second SCR coating accounts for 30%-70% of the length of the first catalytic region.

8. The processing method according to claim 1, wherein, The second catalytic region also includes a first SCR coating.

9. The processing method according to claim 8, wherein, In the second catalytic region, the first SCR coating and the second SCR coating are arranged side by side, and the first SCR coating is located at the front end of the second catalytic region; Alternatively, the first SCR coating may cover a portion of the second SCR coating; Alternatively, the second SCR coating may cover part or all of the first SCR coating.

10. The processing method according to claim 8 or 9, wherein, In the second catalytic region, the length of the second SCR coating accounts for 20%-80% of the length of the second catalytic region.

11. The processing method according to claim 10, wherein, In the second catalytic region, the length of the second SCR coating accounts for 30%-70% of the length of the second catalytic region.

12. The processing method according to claim 1, wherein, The selective reduction catalyst further includes at least one catalytic region disposed between the first catalytic region and the second catalytic region, and the catalytic region is provided with a first SCR coating and / or a second SCR coating.

13. The processing method according to claim 1, wherein, The NO-containing x The gases include exhaust gases produced by diesel combustion.

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