Diesel selective reduction catalyst and diesel exhaust gas purification device

Abstract

Provided are a selective reduction catalyst for diesel and a diesel exhaust gas purification apparatus, wherein the deterioration of NOx purification performance caused by phosphorus poisoning is unlikely to occur.　This selective reduction catalyst for diesel is disposed in a diesel engine, adsorbs ammonia, and reduces a nitrogen oxide in exhaust gas emitted from the diesel engine by bringing the nitrogen oxide into contact with the ammonia. The selective reduction catalyst for diesel has a catalyst carrier, a catalyst region provided at least on the catalyst carrier, and a phosphorus trap region provided at least on the catalyst region, wherein: the catalyst region includes at least one selected from the group consisting of a zeolite-based catalyst containing at least a zeolite and a transition metal element supported on the zeolite, a W-Ce-Zr composite oxide-based catalyst, and a vanadium-based catalyst; and the phosphorus trap region includes at least one selected from the group consisting of alumina and rare-earth basic oxides.

Description

[Technical field]

[0001] The present invention relates to a diesel selective reduction catalyst and a diesel exhaust gas purification device. [Background technology]

[0002] Emission regulations for nitrogen oxides (hereinafter referred to as "NOx") are becoming stricter every year. In particular, in recent years, as regulations on NOx emissions from diesel engines have become stricter, further improvement of NOx purification performance has become an issue.

[0003] Selective catalytic reduction (hereinafter also referred to as "SCR") systems have traditionally been used as a technology for purifying NOx in exhaust gases emitted from such diesel engines. In SCR systems, a catalyst is used to reduce NOx in exhaust gases to nitrogen, water, etc. For example, urea SCR systems use ammonia (urea) as a reducing agent, and convert NOx into harmless substances such as nitrogen by bringing the nitrogen oxides in the exhaust gases emitted from diesel engines into contact with the ammonia and reducing them. In recent years, there has also been progress in the development of SCR systems that do not use ammonia (urea) as a reducing agent.

[0004] Known catalysts used in SCR systems include SSZ-13, an aluminosilicate with a low Al content, and SAPO-34, a silicoaluminophosphate, and various studies are being conducted to comply with stricter exhaust gas regulations for diesel vehicles. For example, it has been reported that in SSZ-13 containing Cu, the catalytic activity is affected by poisoning with phosphorus and other substances (see, for example, Non-Patent Documents 1 to 3). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Applied Catalysis B: Environmental, Volumes 154-155, July-August 2014, Pages 339-349 [Non-Patent Document 2] Catalysis Today, Volume 297, 15 November 2017, Pages 46-52 [Non-Patent Document 3] Applied Catalysis B: Environmental, Volume 241, February 2019, Pages 205-216 Summary of the Invention [Problem to be solved by the invention]

[0006] In diesel engines, the oxygen concentration in the exhaust gas is high because the air compressed and heated by the piston is ignited by injecting liquid fuel. For this reason, conventional exhaust gas purification systems generally have an oxidation catalyst (hereinafter also referred to as "DOC") that oxidizes HC and CO, and a selective reduction catalyst that reduces NOx behind it. In addition, from the viewpoint of improving the NOx reduction performance, a supply means for a reducing agent such as ammonia is provided upstream of the selective reduction catalyst as necessary.

[0007] However, such conventional exhaust gas purification systems have a problem in that the temperature of the exhaust gas drops before the exhaust gas reaches the selective reduction catalyst. Because the NOx reduction performance of the selective reduction catalyst is strongly temperature dependent, there is a limit to how much the NOx reduction performance can be improved in a configuration in which the selective reduction catalyst is provided behind the oxidation catalyst (DOC).

[0008] Therefore, the placement of a selective reduction catalyst directly below the diesel engine was examined. The results showed that when a selective reduction catalyst is placed directly below the diesel engine, it is expected that the system's NOx purification performance will improve. However, there was concern that performance degradation would be greater than when the catalyst is placed in a conventional position. Further investigation into this issue revealed that this deterioration in catalyst performance is due to catalyst poisoning by phosphorus derived from engine oil, etc. Conventionally, the selective reduction catalyst is placed behind the oxidation catalyst (DOC) or catalyzed soot filter (CSF), and it is thought that the slip of poisoning components downstream is suppressed by the filter catalyst in particular. Therefore, with the conventional catalyst placement, it is thought that the NOx purification performance caused by phosphorus poisoning is reduced. x It is believed that the deterioration of purification performance was not a major issue.

[0009] The present invention has been made in view of the above problems, and its object is to provide a method for preventing NOx from being poisoned by phosphorus. x It is an object of the present invention to provide a diesel selective reduction catalyst and a diesel exhaust gas purification device that are resistant to deterioration of purification performance. Note that, in addition to the object described here, another object of the present invention is to provide an effect that is derived from each configuration shown in the below-mentioned embodiment of the invention and that cannot be obtained by conventional techniques. [Means for solving the problem]

[0010] The inventors have demonstrated that NO x The inventors have conducted extensive research into methods for suppressing the deterioration of the purification performance of the catalyst. As a result, they have found that the above-mentioned problems can be solved by forming a phosphorus trapping region on the catalyst region, and have completed the present invention. That is, the present invention provides various specific embodiments as shown below.

[0011] [1] A diesel selective reduction catalyst that is disposed in a diesel engine, adsorbs ammonia, and reduces nitrogen oxides in exhaust gas discharged from the diesel engine by contacting the ammonia with the ammonia, A catalyst support; At least a catalyst region provided on the catalyst support; and a phosphorus trapping region disposed on the catalyst region, the catalyst region includes one or more selected from the group consisting of a zeolite-based catalyst containing at least a zeolite and a transition metal element supported on the zeolite, a W-containing composite oxide-based catalyst, and a vanadium-based catalyst; The phosphorus trap region contains at least one selected from the group consisting of alumina and rare earth basic oxides. Diesel selective reduction catalyst. [2] The phosphorus trap region is substantially free of platinum group elements; The diesel selective reduction catalyst according to [1]. [3] The loading amount of the phosphorus trapping region is 20 g / L or more per catalyst support. The diesel selective reduction catalyst according to [1] or [2]. [4] The phosphorus trap region has a particle diameter D 90 The particle size is 5.0 μm to 35 μm. The diesel selective reduction catalyst according to any one of [1] to [3]. [5] The transition metal element contains at least one or more selected from the group consisting of Cu, Fe, Ce, Mn, Ni, Co, Ag, Rh, Ru, Pd, Ir and Re. The diesel selective reduction catalyst according to any one of [1] to [4]. [6] The zeolite has a 6-membered oxygen ring structure, a double 6-membered oxygen ring structure, an 8-membered oxygen ring structure, and / or a 12-membered oxygen ring structure. The diesel selective reduction catalyst according to any one of [1] to [5]. [7] The zeolite is at least one selected from the group consisting of CHA, AEI, AFX, KFI, SFW, MFI, and BEA. The diesel selective reduction catalyst according to any one of [1] to [6]. [8] The catalyst support is a flow-through type catalyst support. The diesel selective reduction catalyst according to any one of [1] to [7]. [9] The loading amount of the catalyst region is 100 g / L or more per catalyst support. The diesel selective reduction catalyst according to any one of [1] to [8].

[10] a selective reduction catalyst that adsorbs ammonia and reduces the ammonia by contacting the ammonia with nitrogen oxides in exhaust gas discharged from a diesel engine; and one or more oxidation catalysts that oxidize at least one selected from the group consisting of CO, HC, NO, and NH3 in the exhaust gas discharged from the diesel engine. The selective reduction catalyst is a diesel selective reduction catalyst according to any one of [1] to [9], The selective reduction catalyst is disposed upstream of the oxidation catalyst in an exhaust gas flow path of the exhaust gas such that the exhaust gas contacts the selective reduction catalyst and the oxidation catalyst in that order. Diesel exhaust gas purification equipment. Effect of the Invention

[0012] According to the present invention, NO due to phosphorus poisoning x It is possible to provide a diesel selective reduction catalyst and a diesel exhaust gas purification device in which deterioration of purification performance is resistant. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a diesel exhaust gas purification device 100 equipped with a diesel selective reduction catalyst of the present embodiment. [Diagram 2] 1 is a graph showing the results of a pressure loss test in an example. [Diagram 3]6 is a photograph showing the results of measurement of the catalyst samples of Example 3 and Comparative Example 1 by an electron probe microanalyzer (EPMA). P: phosphorus, CP: composite image DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments of the present invention will be described in detail. The following embodiments are examples (representative examples) of the present invention, and the present invention is not limited to these. Furthermore, the present invention can be modified and implemented as desired without departing from the gist of the invention. In this specification, the positional relationships such as up, down, left, right, etc. are based on the positional relationships shown in the drawings, unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to the ratios shown in the drawings.

[0015] In this specification, when a numerical value or physical property value is enclosed before and after the symbol "~", the values ​​before and after the symbol are included. For example, the expression of a numerical range of "1 to 100" includes both the lower limit "1" and the upper limit "100". The same applies to the expression of other numerical ranges. The same applies to the expression of other numerical ranges.

[0016] Further, in the present specification, "average particle diameter D 50 " refers to the particle diameter when the cumulative value from the smallest particle diameter reaches 50% of the total in the cumulative distribution of particle diameters on a volume basis, which is the so-called median diameter, and refers to the value measured with a laser diffraction particle diameter distribution analyzer (e.g., Shimadzu Corporation's laser diffraction particle diameter distribution analyzer SALD-3100, etc.). "Particle diameter D 90 " refers to the particle size when the integrated value from small particle sizes in the cumulative distribution of volume-based particle sizes reaches 90% of the total.

[0017] The BET specific surface area is a value determined by the BET single point method using a specific surface area / pore distribution measuring device (product name: BELSORP-mini II, manufactured by Microtrack-BEL Co., Ltd.) and analysis software (product name: BEL_Master, manufactured by Microtrack-BEL Co., Ltd.).

[0018] [Exhaust gas purification catalyst] The diesel selective reduction catalyst of this embodiment is a catalyst that is disposed in a diesel engine, adsorbs ammonia, and brings the nitrogen oxides in the exhaust gas discharged from the diesel engine into contact with the ammonia to reduce it. Among these, a selective reduction catalyst disposed immediately downstream of a diesel engine is also called a closed-coupled SCR catalyst (cc-SCR catalyst). Note that "immediately downstream" refers to a catalyst that is downstream of the engine and immediately behind the engine. Therefore, if another catalyst is disposed between the engine and a certain catalyst, the catalyst is not said to be located immediately downstream. Also, if a catalyst is downstream of the engine and immediately behind the engine, it can be said to be a catalyst that is located immediately downstream, even if there is a structure such as a pipe between the engine and the catalyst.

[0019] FIG. 1 is a schematic diagram showing a schematic configuration of a diesel exhaust gas purification device 100 equipped with a diesel selective reduction catalyst (cc-SCR catalyst) of this embodiment. This diesel exhaust gas purification device 100 is equipped with, in order from the engine (EG) side, a diesel selective reduction catalyst (cc-SCR catalyst), an ammonia oxidation catalyst (cc-AMOX) that oxidizes and removes excess ammonia, one or more oxidation catalysts (DOC) that oxidize at least one selected from the group consisting of CO, HC, NO, and NH3 in exhaust gas discharged from a diesel engine, a catalyzed soot filter (CSF) in which a catalyst is supported on a diesel particulate filter (DPF), one or more selective reduction catalysts (SCR catalysts) that adsorb ammonia and reduce it by bringing it into contact with NOx, and an ammonia oxidation catalyst (AMOX). In this embodiment, the "selective reduction catalyst" and the "diesel selective reduction catalyst" are clearly distinguished, and the "diesel selective reduction catalyst" is not abbreviated to "selective reduction catalyst".

[0020] In this embodiment, the diesel selective reduction catalyst, which reduces NOx in exhaust gas using ammonia as a reducing agent, and the oxidation catalyst, which oxidizes CO, HC, NO, NH3, and the like in exhaust gas, are provided in this order from the upstream side to the downstream side of the exhaust gas flow passage. In addition, provided behind the oxidation catalyst are a selective reduction catalyst that adsorbs ammonia and reduces it by bringing the ammonia into contact with nitrogen oxides in exhaust gas discharged from the diesel engine, and an ammonia oxidation catalyst (AMOX, Ammonia oxidation catalyst) that oxidizes and removes excess ammonia. Furthermore, although not shown, a plasma generation device Pl. that performs plasma treatment on exhaust gas, and the like, may be provided.

[0021] Furthermore, the diesel exhaust gas purification device 100 is preferably provided with the reducing agent supply means Red. for supplying a urea component, an ammonia component, and the like, upstream of the diesel selective reduction catalyst or the selective reduction catalyst.

[0022] In this way, by arranging the diesel selective reduction catalyst upstream of the oxidation catalyst in the exhaust gas flow passage so that exhaust gas emitted from the diesel engine comes into contact with the diesel selective reduction catalyst and then the oxidation catalyst, exhaust gas at a relatively high temperature is supplied to the diesel selective reduction catalyst, thereby improving the NOx purification performance of the diesel selective reduction catalyst.

[0023] (Catalyst composition) Hereinafter, the catalyst configuration of the diesel selective reduction catalyst of this embodiment will be described.

[0024] The diesel selective reduction catalyst of the present embodiment includes a catalyst carrier, a catalyst region provided on the catalyst carrier, and a phosphorus trapping region provided on the catalyst region. From the viewpoint of efficiently trapping phosphorus and suppressing phosphorus poisoning of the catalyst region, the phosphorus trapping region is preferably formed as a layer so as to cover the catalyst region.

[0025] (Catalyst Carrier) As an integral structure type catalyst carrier supporting the catalyst region, for example, a honeycomb structure that is widely used in automobile exhaust gas applications is preferably used. Examples of such honeycomb structures include ceramic monolith carriers such as cordierite, silicon carbide, and silicon nitride, metal honeycomb carriers such as stainless steel, wire mesh carriers such as stainless steel, and steel wool-like knit wire carriers. The shape is not particularly limited, and any shape such as a prism, a cylinder, a sphere, a honeycomb, or a sheet can be selected. These can be used alone or in appropriate combination of two or more. In addition, as a honeycomb structure for automobile exhaust gas applications, a flow-through type catalyst carrier in which gas flow paths are connected can be used.

[0026] (Catalyst area) The catalyst region is a region responsible for purifying NOx, and includes one or more selected from the group consisting of a zeolite-based catalyst containing at least a zeolite and a transition metal element supported on the zeolite, a composite oxide-based catalyst containing W, and a vanadium-based catalyst.

[0027] The range of formation of the catalyst region is not particularly limited, but it may be formed over the entire catalyst support in the exhaust gas flow direction, or may be formed in a partial region of the catalyst support in the exhaust gas flow direction. In addition, when the catalyst region is formed in a partial region of the catalyst support in the exhaust gas flow direction, it is preferable that the catalyst region is formed on the downstream side of the exhaust gas flow direction of the catalyst support. In addition, when the catalyst region is formed in a partial region of the catalyst support in the exhaust gas flow direction, other catalyst regions may be provided in the remaining regions of the catalyst support.

[0028] The catalyst region may have one catalyst layer on the catalyst carrier, or two or more different catalyst layers, where different catalyst layers refer to layers that have different metal species or combinations of metal species that form the catalyst.

[0029] Zeolites constituting the zeolite catalyst may be various zeolites that have been used in selective reduction catalysts. The zeolites referred to here include aluminosilicates as well as crystalline metal aluminophosphates having micropores and a layered structure similar to that of zeolites, such as aluminum phosphate (ALPO) and crystalline aluminum silicate phosphate (SAPO). Specific examples of zeolites include so-called aluminophosphates, such as SAPO-34 and SAPO-18, but are not limited to these.

[0030] Specific examples of the zeolite used herein include, but are not limited to, zeolites of Y type, A type, L type, beta type, mordenite type, ZSM-5 type, ferrierite type, mordenite type, CHA type, AEI type, AFX type, KFI type, and SFW type, as well as crystalline metal aluminophosphates such as SAPO and ALPO. These zeolites can be used alone or in any combination and ratio of two or more types.

[0031] The zeolite framework structure is compiled into a database by the International Zeolite Association (hereinafter sometimes abbreviated as "IZA"), and those having a structure defined in the IUPAC structure code (hereinafter also simply referred to as "structure code") can be used without any particular restrictions. These structures can be identified by comparing them with the powder X-ray diffraction (hereinafter referred to as "XRD") patterns described in Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007) or the XRD patterns described in Zeolite Framework Types on the IZA Structure Committee's website http: / / www.iza-struture.org / databases / . Among these, those having heat resistance and various known framework structures can be used.

[0032] Among these, zeolites having a 6-membered oxygen ring structure, a double 6-membered oxygen ring structure, an 8-membered oxygen ring structure, and / or a 12-membered oxygen ring structure are preferred, more preferably a 6-membered oxygen ring structure, a double 6-membered oxygen ring structure, and an 8-membered oxygen ring structure, and even more preferably a 6-membered oxygen ring structure and a double 6-membered oxygen ring structure. Specifically, zeolites having one or more skeletal structures selected from the group consisting of CHA, AEI, AFX, KFI, SFW, MFI, and BEA are more preferred, and zeolites having one or more skeletal structures selected from the group consisting of CHA, AEI, AFX, KFI, and SFW are even more preferred. In addition, the number of acid sites of zeolites varies depending on the Si / Al ratio, and generally, zeolites with a low Si / Al ratio have a large number of acid sites, but the degree of deterioration is large in durability in the presence of water vapor, and conversely, zeolites with a high Si / Al ratio tend to have excellent heat resistance but few acid sites. From these viewpoints, the Si / Al ratio of the zeolite used is preferably 1-500, more preferably 1-100, and even more preferably 1-50.

[0033] Average particle size of zeolite in the catalyst region D50 can be appropriately set according to the desired performance, and is not particularly limited. From the viewpoint of maintaining a large specific surface area and increasing the number of its own catalytic active sites by improving heat resistance, the average particle diameter D of the zeolite is 50 The BET specific surface area of ​​the zeolite can be appropriately set according to the desired performance and is not particularly limited, but from the viewpoint of maintaining a large specific surface area and increasing catalytic activity, the BET specific surface area measured by the BET single point method is preferably 10 to 1000 m. 2 / g is preferable, and 50 to 1000m 2 / g, more preferably 100 to 1000m 2 / g. Zeolites are commercially available in a wide variety of grades from manufacturers both in Japan and overseas.

[0034] Examples of transition metal elements contained in the catalyst region include, but are not limited to, copper (Cu), iron (Fe), cerium (Ce), manganese (Mn), nickel (Ni), cobalt (Co), silver (Ag), ruthenium (Rh), rhodium (Ru), palladium (Pd), iridium (Ir) and rhenium (Re). Among these, copper, iron, manganese, nickel, cobalt and rhenium are preferred, copper, iron, manganese, nickel and cobalt are more preferred, and copper and iron are even more preferred. The transition metal elements may be dispersed and held in the catalyst region, but are preferably supported on the surface of the above-mentioned zeolite. These transition metal elements may be used alone or in any combination and ratio of two or more.

[0035] Generally, zeolite has cations as counter ions at solid acid sites, and the cations are generally ammonium ions or protons. In this embodiment, it is preferable to use the zeolite as a transition metal element ion-exchanged zeolite in which the cationic sites of the zeolite are ion-exchanged with these transition metal elements. Although not particularly limited, the ion-exchange rate of the zeolite is preferably 1 to 100%, more preferably 10 to 95%, and further preferably 30 to 90%. Note that an ion-exchange rate of 100% means that all cationic species in the zeolite are ion-exchanged with transition metal element ions.

[0036] The amount of Cu or Fe added to the zeolite is preferably 0.1 to 10% by weight, more preferably 1 to 10% by weight, and even more preferably 2 to 8% by weight, calculated as oxide (CuO or Fe2O3). The transition metal elements added as ion-exchange species may all be ion-exchanged, or a part of them may be present in the form of oxide such as copper oxide or iron oxide. From the viewpoint of improving exhaust gas purification performance, the content of the transition metal element ion-exchanged zeolite (mass of transition metal element per 1 L of monolithic catalyst carrier) is usually preferably 0.1 to 50 g / L, more preferably 1 to 30 g / L, and even more preferably 2 to 15 g / L, calculated as oxide of the transition metal element.

[0037] As the catalyst region, a monolithic catalyst carrier such as a honeycomb structure is preferably provided with an SCR layer containing ion-exchanged zeolite ion-exchanged with at least one transition metal element selected from the group consisting of nickel, cobalt, copper, iron, and manganese. Among them, Cu ion-exchanged zeolite and Fe ion-exchanged zeolite are particularly preferably used. By providing an SCR layer containing such a zeolite-based catalyst material on the catalyst carrier, it is possible to suppress an increase in pressure loss and achieve high exhaust gas purification performance.

[0038] The W-containing composite oxide catalyst is not particularly limited as long as it is a composite oxide containing tungsten, but a W-Ce-Zr composite oxide containing tungsten, ceria, and zirconia is preferred, and other components such as silica may be included as necessary. Here, tungsten contributes to the adsorption of alkaline components such as urea and ammonia, ceria contributes to the adsorption of NOx and can promote the SCR reaction of NH3 and NOx, and zirconia can contribute as a dispersion-retention material for highly dispersing other components in a thermally stable state.

[0039] The vanadium catalyst includes a catalyst having at least vanadium oxide supported on a carrier, which is not particularly limited, but may be, for example, titanium oxide or zeolite.

[0040] Here, the catalyst region may contain oxygen storage and release materials such as ceria-based oxides and ceria-zirconia-based composite oxides, or other base material particles, as long as they do not excessively impair the effects of the present invention. As the oxygen storage and release materials, inorganic compounds that have been used in this type of exhaust gas purification catalyst can be considered. Specifically, ceria-based oxides and ceria-zirconia-based composite oxides, which not only have excellent oxygen storage capacity but also have relatively excellent heat resistance, are preferably used as the oxygen storage and release materials.

[0041] Examples of other base particles include inorganic compounds known in the art, such as aluminum oxide (alumina: Al2O3) such as γ-alumina, β-alumina, δ-alumina, η-alumina, and θ-alumina, zirconium oxide (zirconia: ZrO2), silicon oxide (silica: SiO2), titanium oxide (titania: TiO2), and composite oxides mainly composed of these oxides, but the types are not particularly limited. These may be composite oxides or solid solutions to which rare earth elements such as lanthanum and yttrium, transition metal elements, and alkaline earth metal elements are added. These oxygen storage and release materials and other base particles may be used alone or in any combination and ratio of two or more types.

[0042] The catalyst region may also contain various other catalyst materials, co-catalysts, and various additives known in the art. For example, the catalyst region may contain various sols such as boehmite, alumina sol, titania sol, silica sol, and zirconia sol; and binders such as soluble salts such as aluminum nitrate, aluminum acetate, titanium nitrate, titanium acetate, zirconium nitrate, and zirconium acetate. The catalyst region may also contain a Ba-containing compound in addition to the above-mentioned components. Furthermore, the catalyst region may contain a dispersion stabilizer such as a nonionic surfactant or an anionic surfactant; a pH adjuster; a viscosity adjuster such as a thickener, and the like. Here, the thickener is not particularly limited, but examples thereof include polysaccharides such as sucrose, polyethylene glycol, carboxymethyl cellulose, and hydroxymethyl cellulose.

[0043] Furthermore, the catalyst region may contain a non-zeolite catalyst material such as a transition metal element-supported ceria-based oxide and / or a ceria-zirconia-based composite oxide, so long as the effect of the present invention is not excessively hindered. When a non-zeolite catalyst material is contained, the content thereof is preferably 0.1 to 300 g / L, more preferably 1 to 200 g / L, and further preferably 5 to 100 g / L.

[0044] The catalyst region may also contain alkaline earth metal elements such as Ca and Mg, and platinum group elements such as rhodium (Rh), ruthenium (Ru), palladium (Pd), and iridium (Ir), and precious metal elements such as gold (Au) and silver (Ag) as catalytically active components. The platinum group elements and precious metal elements may be used alone or in any combination and ratio of two or more. However, it is preferable that the platinum group elements and precious metal elements are substantially free of them because they oxidize ammonia components to generate NOx. From this viewpoint, the content of the platinum group elements in the catalyst region is preferably less than 3 g / L, more preferably less than 1 g / L, and even more preferably less than 0.5 g / L.

[0045] The amount of the catalyst region loaded in the diesel selective reduction catalyst is not particularly limited, but is preferably 50 g / L or more, more preferably 100 g / L or more, and even more preferably 150 g / L or more per 1 L of catalyst carrier from the viewpoint of catalyst performance, etc. The upper limit of the amount of the catalyst region loaded is not particularly limited, but is preferably 500 g / L or less, more preferably 400 g / L or less, and even more preferably 300 g / L or less from the viewpoint of pressure loss, etc.

[0046] The catalyst region may be directly placed on the integral catalyst carrier, or may be provided on the integral catalyst carrier via a binder layer, a base layer, or the like. The binder layer, base layer, or the like may be any known material in the art, and the type is not particularly limited. For example, oxygen storage and release materials (OSCs) such as zeolite, cerium oxide (ceria: CeO2), and ceria-zirconia composite oxide (CZ composite oxide), aluminum oxide (alumina: Al2O3) such as γ-alumina, β-alumina, δ-alumina, η-alumina, and θ-alumina, zirconium oxide (zirconia: ZrO2), silicon oxide (silica: SiO2), and titanium oxide (titania: TiO2), or composite oxides mainly composed of these oxides, may be used. The amount of the binder layer, base layer, or the like applied is not particularly limited, but is preferably 1 to 150 g / L, more preferably 10 to 100 g / L, per 1 L of the integral catalyst carrier.

[0047] (Lintrap area) The phosphorus trapping region is a region that prevents phosphorus contained in exhaust gas from reaching the catalyst region, and contains at least one or more materials selected from the group consisting of alumina and rare earth basic oxides.

[0048] The rare earth element may be one or more selected from the group consisting of praseodymium (Pr), lanthanum (La), cerium (Ce), and neodymium (Nd). These are preferably supported on an inorganic support in the form of an oxide or the like. Among these, from the viewpoint of phosphorus trapping performance, CeO2, Pr6O 11 , La2O3, and Y2O3 are more preferred.

[0049] The inorganic support is not particularly limited, but examples thereof include inorganic oxides such as alumina (Al2O3), titania (TiO2), silica (SiO2), zirconia (ZrO2), and ceria (CeO2).

[0050] The above-mentioned alumina is not particularly limited, but examples thereof include γ-alumina, β-alumina, δ-alumina, η-alumina, θ-alumina, etc. Alumina may be used alone or in any combination and ratio of two or more kinds. Alumina has little effect on catalytic performance and is stable even at high temperatures, so it is suitable for the phosphorus trap region.

[0051] In addition, the phosphorus trap region may contain oxides such as zirconium oxide (zirconia: ZrO2), silicon oxide (silica: SiO2), titanium oxide (titania: TiO2), etc., as well as composite oxides that contain these oxides as main components, as exemplified above as base particles, as necessary.

[0052] The phosphorus trapping region is preferably substantially free of zeolite catalysts, W-containing composite oxide catalysts, vanadium catalysts, and metal elements that may exhibit catalytic activity that is reduced by phosphorus poisoning. Examples of metal elements that may exhibit catalytic activity that is reduced by phosphorus poisoning include platinum group elements. Here, "substantially free" means that the amount of the zeolite catalyst, W-containing composite oxide catalyst, vanadium catalyst, and platinum group element supported in the phosphorus trapping region is preferably 0 to 0.1 g / L, more preferably 0 to 0.05 g / L, and even more preferably 0 to 0.01 g / L, per 1 L of catalyst support. By substantially not including platinum group elements, etc., the phosphorus trapping region tends to suppress the influence on the catalyst region.

[0053] The loading amount of the phosphorus trapping region is preferably 20 g / L or more, more preferably 20 to 70 g / L, and even more preferably 30 to 60 g / L per 1 L of catalyst carrier. When the loading amount of the phosphorus trapping region is 20 g / L or more, phosphorus is less likely to reach the catalyst region, and NOx due to phosphorus poisoning is reduced. x In addition, since the amount of phosphorus carried in the phosphorus trap region is 70 g / L or less, an increase in pressure loss tends to be further suppressed.

[0054] The range of the phosphorus trapping region is not particularly limited, but it may be formed over the entire catalyst support in the exhaust gas flow direction, or may be formed in a partial region of the catalyst support in the exhaust gas flow direction. In addition, when the phosphorus trapping region is formed in a partial region of the catalyst support in the exhaust gas flow direction, it is preferable that the phosphorus trapping region is formed on the upstream side of the exhaust gas flow direction of the catalyst support. Furthermore, it is preferable that the phosphorus trapping region is formed thicker on the upstream side of the exhaust gas flow direction of the catalyst support.

[0055] Average particle diameter D of alumina particles that compose the phosphorus trap area 50 From the viewpoint of preventing peeling and exhaust gas purification performance of the SCR catalyst (layer), the average particle diameter D is preferably 0.1 μm to 100 μm, more preferably 1.0 μm to 30 μm, and further preferably 3.0 μm to 20 μm. 50 By making the diameter 100 μm or less, the specific surface area of ​​the phosphorus trapping region becomes large, making it difficult for phosphorus to reach the catalyst region, and reducing NOx due to phosphorus poisoning. x The deterioration of the purification performance of the ion exchange membrane tends to be suppressed. 50 When the particle size is 1.0 μm or more, the spaces between the alumina particles become wider, and an increase in pressure loss tends to be further suppressed.

[0056] In addition, the particle diameter D of the alumina particles that compose the phosphorus trap region 90From the same viewpoint, the particle diameter D is preferably 5.0 μm to 35 μm, more preferably 8.0 μm to 30 μm, and further preferably 12 μm to 25 μm. 90 By making the diameter 35μm or less, the specific surface area of ​​the phosphorus trap area becomes large, making it difficult for phosphorus to reach the catalyst area, and reducing NOx caused by phosphorus poisoning. x The deterioration of the purification performance of the particle diameter D 90 By making the particle diameter D 5.0 ​​μm or more, the space between the alumina particles becomes wider, and the increase in pressure loss tends to be suppressed. 90 " refers to the particle size when the integrated value from small particle sizes in the cumulative distribution of volume-based particle sizes reaches 90% of the total.

[0057] The phosphorus trapping region may also contain various other catalyst materials, co-catalysts, and various additives known in the art. For example, the phosphorus trapping region may also contain various sols such as boehmite, alumina sol, titania sol, silica sol, and zirconia sol; and binders such as soluble salts such as aluminum nitrate, aluminum acetate, titanium nitrate, titanium acetate, zirconium nitrate, and zirconium acetate. The catalyst region may also contain a Ba-containing compound in addition to the above-mentioned components. The catalyst region may also contain dispersion stabilizers such as nonionic surfactants and anionic surfactants; pH adjusters; and viscosity adjusters such as thickeners.

[0058] Here, the thickener is not particularly limited, but examples thereof include polysaccharides such as sucrose, polyethylene glycol, carboxymethylcellulose, and hydroxymethylcellulose.

[0059] [Diesel exhaust gas purification equipment] The diesel exhaust gas purification device of this embodiment is provided with the diesel selective reduction catalyst on the upstream side and an oxidation catalyst on the downstream side so that exhaust gas comes into contact with the selective reduction catalyst and then the oxidation catalyst.

[0060] An embodiment of a diesel exhaust gas purification device equipped with a diesel selective catalytic reduction catalyst (cc-SCR catalyst) according to the present embodiment is shown in Fig. 1. In Fig. 1, the diesel exhaust gas purification device 100 is further equipped with a diesel selective catalytic reduction catalyst (cc-SCR catalyst) disposed immediately downstream of the diesel engine EG in addition to a conventional purification device configuration equipped with an oxidation catalyst (DOC), a selective catalytic reduction catalyst (SCR catalyst), an ammonia oxidation catalyst (AMOX), and the like.

[0061] (Oxidation catalyst) The oxidation catalyst is a catalyst that oxidizes CO, HC, NO, NH3, etc. in exhaust gas. In this specification, the oxidation catalyst is a concept that includes a lean NOx storage catalyst (LNT, Lean NOx Trap) that stores NOx under lean conditions and releases NOx under rich conditions to oxidize CO and HC to CO2 and H2O and reduce NOx to N2, and a catalyst-coated PF (cPF) in which these are coated on a PF. As the oxidation catalyst of the diesel exhaust gas purification device 100, a composite particle having a base material particle such as a metal oxide such as alumina, zirconia, ceria, or zeolite, and a platinum group element (PGM: Platinum Group Metal) as a catalytically active component supported on the support is generally used. Various types of these are known in the industry, and as the oxidation catalyst, these various oxidation catalysts can be used alone or in any suitable combination.

[0062] The oxidation catalyst preferably has a catalyst layer including inorganic fine particle base particles and a platinum group element-supported catalyst material in which a platinum group element is supported on the base particles, the catalyst layer being provided on a monolithic catalyst carrier such as a honeycomb structure. By using such a platinum group element-supported catalyst material to form an oxidation catalyst, it is possible to suppress an increase in pressure loss and realize high exhaust gas purification performance.

[0063] Here, inorganic fine particles as base particles supporting platinum group elements can be inorganic compounds conventionally used in this type of exhaust gas purification catalyst. For example, oxygen storage and release materials (OSCs) such as zeolite, cerium oxide (ceria: CeO2), and ceria-zirconia composite oxide (CZ composite oxide), aluminum oxide (alumina: Al2O3) such as γ-alumina, β-alumina, δ-alumina, η-alumina, and θ-alumina, zirconium oxide (zirconia: ZrO2), silicon oxide (silica: SiO2), and titanium oxide (titania: TiO2), and composite oxides mainly composed of these oxides, and the types thereof are not particularly limited. In addition, these may be composite oxides or solid solutions to which rare earth elements such as lanthanum and yttrium, transition metal elements, and alkaline earth metal elements are added. These inorganic fine particles can be used alone or in any combination and ratio of two or more kinds. The oxygen storage / release material refers to a material that stores or releases oxygen in response to the external environment.

[0064] Average particle size D of the base material particles of the oxidation catalyst 50 can be appropriately set according to the desired performance, and is not particularly limited. From the viewpoint of maintaining a large specific surface area and increasing the number of catalytic active sites by improving heat resistance, the average particle diameter D 50 The BET specific surface area of ​​the base particles can be appropriately set according to the desired performance and is not particularly limited, but from the viewpoint of maintaining a large specific surface area and enhancing catalytic activity, the BET specific surface area measured by the BET single point method is preferably 10 to 500 m. 2 / g is preferable, and 20 to 300m 2 / g, more preferably 30 to 200m 2 / g. Various grades of various materials that can be used as base particles for oxidation catalysts are commercially available from manufacturers both in Japan and overseas, and various grades of commercially available products can be used as base particles depending on the required performance. They can also be manufactured by methods known in the art.

[0065] Examples of platinum group elements include platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os). The platinum group elements can be used alone or in any combination and ratio of two or more. From the viewpoints of improving exhaust gas purification performance and suppressing the progress of grain growth (sintering) of the platinum group elements on the base particles, the content ratio of the platinum group elements in the oxidation catalyst (mass of platinum group elements per 1 L of monolithic catalyst carrier) is usually preferably 0.1 to 20 g / L, more preferably 0.2 to 15 g / L, and even more preferably 0.3 to 10 g / L.

[0066] The oxidation catalyst may contain various other catalytic materials, co-catalysts, and various additives known in the art. For example, the oxidation catalyst may contain various sols such as boehmite, alumina sol, titania sol, silica sol, and zirconia sol; and binders such as soluble salts such as aluminum nitrate, aluminum acetate, titanium nitrate, titanium acetate, zirconium nitrate, and zirconium acetate. The oxidation catalyst may further contain a Ba-containing compound in addition to the above-mentioned components. By blending the Ba-containing compound, it is expected that the heat resistance can be improved and the catalytic performance can be activated. Examples of Ba-containing compounds include, but are not limited to, sulfates, carbonates, composite oxides, and oxides. More specifically, examples of BaO, Ba(CH3COO)2, BaO2, BaSO4, BaCO3, BaZrO3, and BaAl2O4 may be mentioned. Furthermore, the oxidation catalyst may contain dispersion stabilizers such as nonionic surfactants and anionic surfactants; pH adjusters; viscosity adjusters such as thickeners, and the like.

[0067] As an integral catalyst carrier supporting the oxidation catalyst, a honeycomb structure that is widely used in, for example, automobile exhaust gas applications is preferably used. Specific examples of this honeycomb structure are as explained in the section on oxidation catalysts, and redundant explanations will be omitted here. Note that as a honeycomb structure supporting the second catalyst region, either a flow-through type structure or a wall-flow type structure can be used.

[0068] In the above-mentioned oxidation catalyst, the total coating amount of the above-mentioned catalyst layer is not particularly limited, but from the viewpoint of the balance between catalyst performance and pressure loss, it is preferably 1 to 500 g / L per 1 L of an integral structure type catalyst carrier, more preferably 5 to 450 g / L, and in the case of a wall-flow type catalyst carrier, it is further preferably 5 to 80 g / L, and in the case of a flow-through type catalyst carrier, it is further preferably 200 to 450 g / L.

[0069] The catalytic layer of the oxidation catalyst can be used as a single layer, but can also be used as a laminate of two or more layers depending on the required performance. The catalytic layer of the oxidation catalyst can be directly placed on the catalyst carrier of an integral structure, or can be provided on the catalyst carrier of an integral structure via a binder layer, a base layer, or the like. As the binder layer, base layer, or the like, those known in the art can be used, and the type is not particularly limited. For example, oxygen storage and release materials (OSCs) such as zeolite, cerium oxide (ceria: CeO2), and ceria-zirconia composite oxide (CZ composite oxide), aluminum oxide (alumina: Al2O3) such as γ-alumina, β-alumina, δ-alumina, η-alumina, and θ-alumina, zirconium oxide (zirconia: ZrO2), silicon oxide (silica: SiO2), and titanium oxide (titania: TiO2), and composite oxides mainly composed of these oxides, and the like can be used. The coating amount of the binder layer, undercoat layer, etc. is not particularly limited, but is preferably 1 to 150 g / L, more preferably 10 to 100 g / L, per 1 L of the integral structure type catalyst carrier.

[0070] At least one of the above-mentioned oxidation catalysts may be provided in the exhaust gas passage of the diesel exhaust gas purification device 100 of this embodiment, but multiple (e.g., 2 to 5) may be provided depending on the required performance, etc. Also, a zone-coated oxidation catalyst obtained by zone-coating two types of oxidation catalyst materials on one catalyst carrier can be used. When multiple oxidation catalysts are provided, each oxidation catalyst may be the same type of DOC or different types of DOC.

[0071] When a plurality of oxidation catalysts are provided in the exhaust gas flow passage of the diesel exhaust gas purification device 100 of this embodiment, the oxidation catalysts may be disposed adjacent to each other, or may be disposed apart from each other in the exhaust gas flow passage via a selective reduction catalyst, a reducing agent supply means, a heating device, a plasma generating device, or the like.

[0072] (Selective Reduction Catalyst (SCR Catalyst)) The selective reduction catalyst may be a selective reduction catalyst having the same configuration as the diesel selective reduction catalyst except that it does not have a phosphorus trap region.

[0073] At least one selective reduction catalyst may be provided in the exhaust gas passage of the diesel exhaust gas purification device 100 of this embodiment, but multiple catalysts (for example, 2 to 5 catalysts) may be provided depending on the required performance.

[0074] (Reducing agent supply means Red.) In the diesel exhaust gas purification device 100 of this embodiment, the reducing agent supplying means Red. supplies one or more reducing agents selected from the group consisting of a urea component and an ammonia component into the exhaust gas flow passage. The reducing agent supplying means Red. may be one known in the art, and the type is not particularly limited. Usually, a reducing agent supplying means Red. is used that is composed of a storage tank for the reducing agent, a pipe connected to the tank, and a spray nozzle attached to the tip of the pipe (not shown).

[0075] The position of the spray nozzle of the reducing agent supply means Red. is installed upstream of the selective reduction catalyst described above. When the diesel exhaust gas purification device 100 has a plurality of selective reduction catalysts as shown in Fig. 1, the reducing agent supply means Red. can be provided upstream of the diesel selective reduction catalyst and the selective reduction catalyst, respectively. When other selective reduction catalysts are used in combination and are disposed apart from each other, the spray nozzle of the reducing agent supply means Red. may be provided at a plurality of locations.

[0076] The reducing component is selected from a urea component or an ammonia component. As the urea component, a standardized urea aqueous solution having a concentration of 31.8 to 33.3% by weight, such as Adblue (trade name), can be used. As the ammonia component, ammonia water as well as ammonia gas can be used. Since NH3, which is the reducing component, is itself harmful, such as having an irritating odor, it is preferable to add urea water from the upstream side of the selective reduction catalyst, generate NH3 by thermal decomposition or hydrolysis, and use this as a reducing agent, rather than using NH3 as it is.

[0077] (Heater) In the diesel exhaust gas purification device 100 of this embodiment, an electric heating type heating device Heater (catalyst heating heater) is provided in the exhaust gas flow path downstream of the spray nozzle of the reducing agent supplying means Red. and upstream of the selective reduction catalyst. This heating device is electrically connected to an ECU and an on-board power source (not shown), and the temperature of the heating device Heater, and therefore the exhaust gas temperature in the exhaust gas flow path, can be controlled by controlling the output of these devices. Then, one or more reducing agents selected from the group consisting of a urea component and an ammonia component supplied from the reducing agent supplying means Red. are heated by the heating device Heater in the exhaust gas flow path, and become NH3 by thermal decomposition or hydrolysis, and are adsorbed on the selective reduction catalyst downstream of the heating device Heater. The reactivity of the hydrolysis reaction of urea may vary depending on the concentration, blending composition, pH, etc. of the urea water, but it can be efficiently controlled by controlling the exhaust gas temperature in the exhaust gas flow path. In addition, temperature sensors and NOx sensors electrically connected to the ECU are provided at various points in the exhaust gas flow path, and the NOx concentration of the exhaust gas and the exhaust gas temperature are monitored at any time.

[0078] In this embodiment, the heater is composed of a metal honeycomb, a jacket-type electric heater attached to the outer periphery of the metal honeycomb, and a coil-type electric heater attached so as to be partially embedded in the metal honeycomb body (not shown). This metal honeycomb can be electrically heated by the control of the control unit ECU, and the temperature of the exhaust gas passing through the exhaust gas passage can be controlled by the heat generated by the metal honeycomb. In this embodiment, a heat insulating material is provided on the outer periphery of the exhaust passage over the entire length (not shown). The heat insulating material can be appropriately selected from those known in the art and is not particularly limited, but for example, a material using cellulose fiber or rock wool is preferably used. The heater used here may be, for example, only a jacket-type electric heater, or may be an EHC (Electrically Heated Catalyst) in which an SCR catalyst is supported on the metal honeycomb body. The metal honeycomb can also be heated by passing electricity through the metal honeycomb body to directly heat the metal honeycomb itself. In this case, the metal honeycomb is connected to an on-board power supply and the control unit ECU controls the output, thereby making it possible to control the temperature of the metal honeycomb, and therefore the temperature of the exhaust gas in the exhaust gas flow path.

[0079] (Ammonia oxidation catalyst AMOX) In the diesel exhaust gas purification device 100 of this embodiment, an ammonia oxidation catalyst AMOX that oxidizes and removes excess ammonia is provided downstream of the selective reduction catalyst. As the ammonia oxidation catalyst AMOX, one known in the art can be used, and the type is not particularly limited.

[0080] Usually, in the urea SCR system, when NOx and NH3 cannot be purified to below the regulation value, the ammonia oxidation catalyst AMOX is additionally used. Therefore, the ammonia oxidation catalyst AMOX contains a catalyst component with a function of purifying NOx in addition to a catalyst with a function of oxidizing NH3. As a catalyst with a function of oxidizing NH3, it is preferable that one or more elements selected from platinum, palladium, rhodium, etc. are supported on an inorganic material made of one or more of alumina, silica, titania, zirconia, etc. as a precious metal component. It is also preferable to use an inorganic material with improved heat resistance by adding a promoter such as a rare earth, an alkali metal, an alkaline earth metal, etc. Platinum and palladium as precious metals exhibit excellent oxidation activity. By supporting this on the inorganic material with a high specific surface area and high heat resistance, the precious metal component is less likely to sinter, and by maintaining the specific surface area of ​​the precious metal high, the number of active sites increases, and high activity can be exhibited. On the other hand, as a catalyst having a function of purifying NOx, all of the non-zeolite-based catalyst materials and zeolite-based catalyst materials described in the section on selective reduction catalysts can be used. These two types of catalysts can be mixed uniformly and applied to a honeycomb structure having an integral type, but the catalyst having an NH3 oxidation function may be applied to the lower layer and the catalyst having a NOx purification function may be applied to the upper layer. The capacity (size) of the ammonia oxidation catalyst AMOX and the coating amount of the catalyst material can be appropriately adjusted in consideration of the type and displacement of the engine to which the lean burn engine exhaust gas purification device 100 of this embodiment is applied, and can be appropriately adjusted according to the required amount of catalyst and purification performance, and are not particularly limited.

[0081] The above ammonia oxidation catalyst AMOX may be provided in a plurality (e.g., 2 to 5) according to the required performance. Two kinds of catalyst materials may be zone-coated on one catalyst carrier to be used as zone-coated AMOX (zAMOX). When a plurality of ammonia oxidation catalysts AMOX are provided, the arrangement of the ammonia oxidation catalysts AMOX is not particularly limited. That is, the plurality of ammonia oxidation catalysts AMOX may be disposed adjacent to each other or spaced apart from each other. From the viewpoint of oxidizing and removing excess ammonia, it is preferable that at least one of the plurality of ammonia oxidation catalysts AMOX is disposed downstream of the selective reduction catalyst, and more preferably, it is disposed at the most downstream position in the exhaust gas flow passage including the oxidation catalyst and the selective reduction catalyst. EXAMPLES

[0082] The features of the present invention will be described in more detail below with reference to test examples, examples and comparative examples, but the present invention is not limited by these. That is, the materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. In addition, the values ​​of various manufacturing conditions and evaluation results in the following examples have the meaning of preferred upper limit values ​​or preferred lower limit values ​​in the embodiment of the present invention, and the preferred range may be a range defined by a combination of the above-mentioned upper limit value or lower limit value and the values ​​of the following examples or the values ​​of the examples.

[0083] Example 1 Cu-SSZ-13 (SAR: 18, CuO content 5% by mass), alumina binder, surfactant, and deionized water were mixed and milled using a ball mill to obtain a slurry. This slurry was applied to a honeycomb flow-through type cordierite carrier (300 cpsi / 5 mil, diameter 266.7 mm x length 76.2 mm), which is an integral structure type catalyst carrier, by washcoating. At this time, the amount of catalyst region per 1 L of catalyst carrier was set to 165 g / L. After drying, the mixture was fired at 550 °C for 30 minutes in an air atmosphere to form a catalyst region.

[0084] Next, alumina powder (average particle size D 50 The mixture of 1000g of sintered cellulose (1000g: 60 μm), water, acetic acid, and a thickener was added to a ball mill to obtain a particle size D 90 16~20μm, D 50 The slurry was milled until the particle size was 4.5 to 7.5 μm. The slurry was then applied by washcoat to cover the catalyst region on the catalyst carrier. At this time, the phosphorus trap region per 1 L of catalyst carrier was set to 20 g / L. After drying, the mixture was baked at 550° C. for 30 minutes in an air atmosphere to form a phosphorus trap region on the catalyst region.

[0085] The obtained diesel selective reduction catalyst was packed into a converter, which was then connected to the exhaust port of a diesel engine (displacement: 8 L).

[0086] Example 2 A diesel selective reduction catalyst was obtained by the same procedure as above, except that the phosphorus trap area per 1 L of catalyst carrier was set to 35 g / L.

[0087] Example 3 A diesel selective reduction catalyst was obtained by the same procedure as above, except that the phosphorus trap area per 1 L of catalyst carrier was set to 50 g / L.

[0088] Comparative Example 1 A selective reduction catalyst for diesel was obtained by the same procedure as above, except that the phosphorus trapping region was not formed.

[0089] (Pressure loss measurement) Using an airflow measurement device (SF-1020, SuperFlow), a space velocity of 415,000 h was measured for a diesel selective reduction catalyst. -1 The pressure loss was measured by passing air through the honeycomb structure. The space velocity means the volume of exhaust gas that passed through the honeycomb structure in one hour per volume of the honeycomb structure. The results are shown in Figure 2.

[0090] (Phosphorus poisoning treatment) A diesel selective reduction catalyst was installed directly under the diesel engine, and a phosphorus supplying means for injecting an aqueous solution containing phosphorus was provided in the pipe connecting the diesel engine and the diesel selective reduction catalyst. The diesel engine was then operated at rated speed of 2500 rpm, and an aqueous solution of phosphonic acid amine salt (SN Dispersant 2060, manufactured by San Nopco) was injected in the opposite direction to the gas flow as the aqueous solution containing phosphorus. The amount of phosphorus poisoning the diesel selective reduction catalyst was adjusted by adjusting the injection time.

[0091] (NOx purification performance) As described above, the diesel selective reduction catalyst poisoned with phosphorus for 20 hours was installed directly below the diesel engine, and a urea supplying means for injecting urea was provided in the piping connecting the diesel engine and the diesel selective reduction catalyst. The diesel engine was then operated at rated speed of 2500 rpm to adjust the inlet temperature of the diesel selective reduction catalyst to 200°C. After that, the diesel engine was warmed up, and an equimolar amount of urea was injected with respect to the NOx that reached the inlet of the diesel selective reduction catalyst. Two hours after the start of urea injection, the NOx value supplied to the diesel selective reduction catalyst and the NOx value discharged from the diesel selective reduction catalyst were measured, and the NOx purification rate was calculated.

[0092] In the same manner as above, the same test was performed on a diesel selective reduction catalyst that had been subjected to phosphorus poisoning treatment for 40 hours and a diesel selective reduction catalyst that had not been subjected to phosphorus poisoning, and the NOx purification rate was calculated.

[0093] The NOx purification rate of a diesel selective reduction catalyst that has not been poisoned with phosphorus is set as a reference value of 100, and the NOx purification rates of a diesel selective reduction catalyst that has been poisoned with phosphorus for 20 hours and a diesel selective reduction catalyst that has been poisoned with phosphorus for 40 hours are shown. The decrease from the reference value of 100 can be regarded as the rate of decrease in the NOx purification rate when poisoned. The results are shown below.

[0094] [Table 1]

[0095] [Observation of phosphorus poisoning] The diesel selective reduction catalyst prepared in Example 3 was subjected to phosphorus poisoning treatment for 20 hours, and then a measurement sample (1 cm 2 ) for electron probe microanalysis (EPMA) was taken from the cross section of the partition wall. 3 The measurement samples were embedded in resin and pretreated by carbon deposition. The pretreated measurement samples were observed using an electron probe microanalyzer (manufactured by JEOL Ltd., product name: JXA-8230) to confirm the state of poisoning by phosphorus.

[0096] Similarly, the diesel selective reduction catalyst prepared in Comparative Example 1 was poisoned with phosphorus for 20 hours, and the cross section of the partition wall was observed using an electron probe microanalyzer (manufactured by JEOL Ltd., product name: JXA-8230) to confirm the state of poisoning by phosphorus.

[0097] The results are shown in Figure 3. As shown in Figure 3, it can be seen that in Example 3 having a phosphorus trapping region, phosphorus does not reach the catalyst region, whereas in Comparative Example 1 having no phosphorus trapping region, phosphorus reaches the entire catalyst region. [Industrial Applicability]

[0098] The selective reduction catalyst of the present invention has industrial applicability as a selective reduction catalyst to be disposed in a diesel engine. [Explanation of symbols]

[0099] 100...Exhaust gas purification device for lean burn engines, EG...Engine, cc-SCR catalyst...Selective reduction catalyst for diesel, cc-AMOX, AMOX...Ammonia oxidation catalyst, DOC...Oxidation catalyst (diesel oxidation catalyst), CSF...Catalyzed soot filter, SCR catalyst...Selective reduction catalyst

Claims

1. A diesel selective reduction catalyst that is disposed in a diesel engine, adsorbs ammonia, and reduces nitrogen oxides in exhaust gas discharged from the diesel engine by contacting the ammonia with the nitrogen oxides, A catalyst support; At least a catalyst region provided on the catalyst support; and a phosphorus trapping region disposed on the catalyst region, the catalyst region includes one or more selected from the group consisting of a zeolite-based catalyst containing at least a zeolite and a transition metal element supported on the zeolite, a W-containing composite oxide-based catalyst, and a vanadium-based catalyst; the phosphorus trap region is composed of particles having a particle diameter D 90 of 12 μm to 25 μm, and contains at least one or more selected from the group consisting of alumina and rare earth basic oxides; Diesel selective reduction catalyst.

2. The phosphorus trap region is substantially free of platinum group elements; The diesel selective reduction catalyst according to claim 1.

3. The loading amount of the phosphorus trapping region is 20 g / L or more per catalyst support. The diesel selective reduction catalyst according to claim 1 or 2.

4. The transition metal element contains at least one or more selected from the group consisting of Cu, Fe, Ce, Mn, Ni, Co, Ag, Rh, Ru, Pd, Ir and Re. The diesel selective reduction catalyst according to any one of claims 1 to 3.

5. The zeolite has a 6-membered oxygen ring structure, a double 6-membered oxygen ring structure, an 8-membered oxygen ring structure, and / or a 12-membered oxygen ring structure. The diesel selective reduction catalyst according to any one of claims 1 to 4.

6. The zeolite is at least one selected from the group consisting of CHA, AEI, AFX, KFI, SFW, MFI, and BEA. The diesel selective reduction catalyst according to any one of claims 1 to 5.

7. The catalyst support is a flow-through type catalyst support. The diesel selective reduction catalyst according to any one of claims 1 to 6.

8. The loading amount of the catalyst region is 100 g / L or more per catalyst support. The diesel selective reduction catalyst according to any one of claims 1 to 7.

9. a selective reduction catalyst that adsorbs ammonia and reduces the ammonia by contacting the ammonia with nitrogen oxides in exhaust gas discharged from a diesel engine; CO, HC, NO and NH in the exhaust gas discharged from the diesel engine 3 and one or more oxidation catalysts that oxidize at least one selected from the group consisting of: The selective reduction catalyst is a diesel selective reduction catalyst according to any one of claims 1 to 8, The selective reduction catalyst is disposed upstream of the oxidation catalyst in an exhaust gas flow path of the exhaust gas such that the exhaust gas contacts the selective reduction catalyst and the oxidation catalyst in that order. Diesel exhaust gas purification equipment.

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