JP2015062874A - NOx SELECTIVE REDUCTION CATALYST, METHOD FOR PRODUCING THE SAME AND NOx PURIFICATION METHOD USING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an NOx selective reduction catalyst capable of exhibiting high NOx purification activity at high temperature conditions above 400°C.SOLUTION: There is provided an NOx selective reduction catalyst which is used in reducing a nitrogen oxide (NOx) with a reducing agent and comprises zeolite containing an aluminum (Al) atom, a phosphorus (P) atom and a silicon (Si) atom in the sketon structure, copper (Cu) carried inside and outside of fine pores of the zeolite and at least one added metal (N) selected from the group consisting of nickel (Ni), cobalt (Co), stannum (Sn) and titanium (Ti), where the content of the copper relative to the amount of the silicon atom contained in the zeolite is 0.1 to 0.8 at a Cu/Si molar ratio and the content of the added metal (N) relative to the amount of the copper is 0.05 to 3 at a M/Cu ratio.

Description

The present invention relates to a NOx selective reduction catalyst, a method for producing the same, and a NOx purification method using the same, and more specifically, nitrogen oxide (NOx) is reduced with ammonia (NH ₃ ) or a reducing agent capable of generating ammonia. The present invention relates to a NOx selective reduction catalyst used in the process, a method for producing the catalyst, and a NOx purification method using the catalyst.

Conventionally, ammonia (NH ₃ ) or the like has been used to purify nitrogen oxides (NOx) contained in exhaust gas discharged from internal combustion engines such as diesel engines and lean burn engines with low fuel consumption. NOx selective reduction catalyst (SCR catalyst: Selective Catalytic Reduction catalysis) system, which selectively reduces NOx in exhaust gas with a reducing agent of the above, and decomposes it into harmless N ₂ (nitrogen) and H ₂ O (water), and a lean atmosphere NOx occlusion reduction catalyst that releases and reduces NOx occluded by adsorbing NOx in adsorbent (Ba, K, etc.) on the catalyst and exposing the catalyst to the reducing atmosphere for a short time (intermittently rich atmosphere) (Occlusion reduction type NOx catalyst, NSR catalyst: NOx Storage Reduction catalyst ) System, etc. are developed, have been applied partially to the NOx purification in the exhaust gas from a lean burn engine or the like, the NOx purification rate and the heat resistance can not be said that still sufficient in durability.

  Therefore, in recent years, a NOx selective reduction catalyst containing a zeolite catalyst carrying an active metal as an SCR catalyst has been proposed in exhaust gas treatment of automobiles, particularly diesel vehicles in which it is difficult to purify nitrogen oxides.

Such an SCR catalyst promotes a NOx reduction reaction (exhaust purification reaction). For example, as shown in the following formula, NOx is reduced in the presence of a reducing agent such as ammonia (NH ₃ ) to form nitrogen. It converts to gas and purifies NOx in the exhaust.
2NO + 2NH ₃ + 1 / 2O ₂ → 2N ₂ + 3H ₂ O (1)
NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O (2)
As such a NOx selective reduction catalyst (SCR catalyst), for example, in JP 2012-148272 A (Patent Document 1), a catalyst for purifying nitrogen oxides containing a zeolite supporting a metal such as copper or iron is used. The zeolite contains at least a silicon atom, an aluminum atom, and a phosphorus atom in the framework structure, and the amount of water adsorbed to the catalyst at 25 ° C. and a relative vapor pressure of 0.5 is 0.05 (kg-water / kg-catalyst). Above, 0.2 (kg-water / kg-catalyst) or less nitrogen oxide purification catalyst, and further metal oxide particles such as aluminum, silicon, titanium, cerium, niobium and inorganic binder A nitrogen oxide purifying catalyst characterized in that it is contained is disclosed. However, the conventional exhaust gas purification catalyst as described in Patent Document 1 is difficult to suppress a decrease in NOx purification performance at a high temperature of 400 ° C. or higher, and is not necessarily sufficient in terms of NOx purification activity. It was.

  Moreover, in Japanese translations of PCT publication No. 2010-524677 (patent document 2), it is the method of converting the nitrogen oxide in gas into nitrogen, Comprising: In the presence of the zeolite catalyst containing at least 1 type of transition metal, the said nitrogen oxide In contact with a nitrogen-based reducing agent, wherein the zeolite is a small pore zeolite having a maximum ring size of eight tetrahedral atoms, and the at least one transition metal is Cr, A method selected from the group consisting of Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir, and Pt is disclosed. However, in the conventional method as described in Patent Document 2, it is difficult to suppress a decrease in NOx purification performance at a high temperature of 400 ° C. or higher, and it is not always sufficient in terms of NOx purification activity.

  Further, International Publication No. 2010/084930 (Patent Document 3) discloses a nitrogen oxide purification catalyst in which a metal is supported on a zeolite containing a skeleton structure containing at least aluminum atoms and phosphorus atoms, and a transmission electron microscope. A catalyst for purifying nitrogen oxides is disclosed in which a metal such as Cu or Fe supported in the catalyst is supported as particles having a diameter of 0.5 nm to 20 nm. However, the conventional nitrogen oxide purification catalyst as described in Patent Document 3 is difficult to suppress a decrease in NOx purification performance at a high temperature of 400 ° C. or higher, and is not necessarily sufficient in terms of NOx purification activity. It wasn't.

In addition, in Japanese Translation of PCT International Publication No. 2011-510899 (Patent Document 4), a catalyst containing a non-zeolitic molecular sieve such as Cu-SAPO-34 having a CHA crystal structure and loaded with Cu, wherein the catalyst is 2 Deposited on a honeycomb substrate with a cell density of 400 cpsi at a load of ˜2.5 g / in ³ and tested at a space velocity of 80,000 hr ⁻¹ , where the feed stream provides at least 80% NOx conversion The catalyst uses ammonia in the presence of oxygen in a 200 ° C. exhaust stream when the catalyst contains a mixture of 10% O ₂ , 5% H ₂ O, 500 ppm NO, and 500 ppm NH _3. A catalyst that is efficient for selectively reducing nitrogen oxides and a method for synthesizing the Cu-SAPO-34, comprising a neutral nitrogen-containing organic Mixing a template, an alumina source, a silica source, and a phosphorus source in a gel mixture; heating the gel to less than about 200 ° C. for at least about 12 hours to produce crystalline SAPO-34; Filtering and washing the crystalline SAPO-34; firing the crystalline SAPO-34; ion-exchanging the crystalline SAPO-34 with a copper salt to obtain Cu-SAPO-34; Is disclosed. However, with the conventional ammonia-SCR catalyst as described in Patent Document 4, it is difficult to suppress a decrease in NOx purification performance at a high temperature of 400 ° C. or higher, and it is not always sufficient in terms of NOx purification activity. It was.

  Moreover, in Japanese translations of PCT publication No. 2012-522636 (patent document 5), it is an exhaust treatment system of the exhaust flow of a diesel engine or a lean combustion gasoline engine, Comprising: An ammonia production | generation component and SCR arrange | positioned downstream of the said ammonia production | generation component An SCR catalyst comprising a catalyst and a molecular sieve having a CHA crystal structure such as copper chabazite (CuCHA) or copper SAPO (CuSAPO) is disclosed. However, in the conventional exhaust treatment system as described in Patent Document 5, it is difficult to suppress a decrease in NOx purification performance at a high temperature of 400 ° C. or higher, and it is not always sufficient in terms of NOx purification activity. .

JP 2012-148272 A Special table 2010-524777 International Publication No. 2010/084930 Special table 2011-510899 gazette Special table 2012-522636 gazette

  The present invention has been made in view of the above-described problems of the prior art, and is a NOx selective reduction catalyst capable of exhibiting high NOx purification activity under a high temperature condition of 400 ° C. or higher, its production method, and It aims at providing the used NOx purification method.

  As a result of intensive studies to achieve the above object, the present inventors have found that the pore structure of a specific zeolite containing at least an aluminum (Al) atom, a phosphorus (P) atom, and a silicon (Si) atom in the skeleton structure and The NOx selective reduction catalyst obtained by supporting copper outside the pores and supporting a specific amount of a specific metal outside the pores of the zeolite is high in a high temperature condition of 400 ° C. or higher. The inventors have found that it is possible to exhibit NOx purification activity and have completed the present invention.

  That is, the NOx selective reduction catalyst of the present invention is a NOx selective reduction catalyst used when nitrogen oxide (NOx) is reduced by a reducing agent, and has at least an aluminum (Al) atom and phosphorus (P) in the skeleton structure. Zeolite containing atoms and silicon (Si) atoms, copper (Cu) supported inside and outside the pores of the zeolite, nickel (Ni) and cobalt (Co) supported outside the pores of the zeolite ), At least one additive metal (M) selected from the group consisting of tin (Sn) and titanium (Ti), and the content of the copper with respect to the amount of silicon atoms contained in the zeolite The Cu / Si molar ratio is in the range of 0.1 to 0.8, and the content of the additive metal is in the range of 0.05 to 3 in terms of the M / Cu molar ratio with respect to the amount of copper. Characterized by A.

  In the NOx selective reduction catalyst of the present invention, the zeolite preferably contains SAPO-34.

  Moreover, in the NOx selective reduction catalyst of the present invention, it is preferable that an average particle diameter of the additive metal is 10 nm or less.

  The method for producing a NOx selective reduction catalyst of the present invention is a method for producing a NOx selective reduction catalyst that purifies nitrogen oxides (NOx) in exhaust gas, and includes at least aluminum (Al) atoms and phosphorus (P) atoms in the skeleton structure. And a zeolite containing silicon (Si) atoms, a step of obtaining Cu-zeolite by supporting copper (Cu) inside and outside the pores of the zeolite, and pores of the Cu-zeolite zeolite The NOx selective reduction catalyst of the present invention is supported by at least one additive metal (M) selected from the group consisting of nickel (Ni), cobalt (Co), tin (Sn) and titanium (Ti). And obtaining the method.

The NOx purification method of the present invention purifies nitrogen oxides (NOx) by bringing exhaust gas into contact with the NOx selective reduction catalyst of the present invention in the presence of ammonia (NH ₃ ) or a reducing agent capable of generating ammonia. This is a NOx purification method characterized by this.

In the NOx purification method of the present invention, before contacting the exhaust gas with the NOx selective reduction catalyst, the exhaust gas is brought into contact with the NOx storage reduction catalyst, and the NOx absorbed by the NOx storage reduction catalyst is reduced to NH _3. Then, it is preferable to purify nitrogen oxides (NOx) by bringing the mixture of NH ₃ and untreated NOx in the exhaust gas into contact with the NOx selective reduction catalyst.

  Although the reason why the above object is achieved by the present invention is not necessarily clear, the present inventors infer as follows.

That is, the present inventors first made studies on a silica-aluminophosphate zeolite supporting copper in order to achieve the above object. As a result, the conventional SAPO-34 described in Patent Documents 1 to 5 was used. The SCR catalyst in which Cu is supported on a silica aluminophosphate zeolite carrier such as NO. Has NOx purification performance at low temperatures, but in a high temperature region of 400 ° C. or higher, the microaluminum of a silica aluminophosphate zeolite carrier such as SAPO-34. since the reaction of NH ₃ and O ₂ on CuO species carried on the outside of the hole (formula (3) and (4)) proceeds, and presumed that can not be efficiently supplied to NH ₃ in the pores ing.
NH ₃ + O ₂ → N ₂ + H ₂ O (3)
NH ₃ + O ₂ → NO + H ₂ O (4)
As a result, the selective reduction reaction of NH ₃ and NOx (formulas (1) and (2)) proceeding with Cu species in the pores is hindered, and in particular, sufficient NOx purification activity at a high temperature range of 400 ° C. or higher. Is presumed to be impossible to obtain.
2NO + 2NH ₃ + 1 / 2O ₂ → 2N ₂ + 3H ₂ O (1)
NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O (2)
And based on such consideration results, the present inventors have repeatedly studied, and the present inventors have identified that the skeleton structure contains at least aluminum (Al) atoms, phosphorus (P) atoms, and silicon (Si) atoms. NOx selective reduction catalyst obtained by supporting copper inside and outside the pores of the zeolite with a specific amount of a specific metal outside the pores of the zeolite was obtained at 400 ° C. It has been found that high NOx purification activity can be exhibited under the above high temperature conditions. That is, in the present invention, the additive metal (M) interacts with the CuO species existing outside the pores, thereby suppressing the reaction between NOx and O ₂ on the CuO species existing outside the pores. As a result, it is presumed that NH ₃ can be efficiently supplied to the Cu species in the pores where the selective reduction reaction of NH ₃ and NOx proceeds, and that high NOx purification activity is obtained at a high temperature range of 400 ° C. or higher. ing.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the NOx selective reduction catalyst which can exhibit high NOx purification activity in high temperature conditions of 400 degreeC or more, its manufacturing method, and a NOx purification method using the same. .

2 is a graph showing XRD spectra of catalysts prepared in Examples 1-2, Examples 4-7, and Comparative Example 1. FIG. It is a graph showing the relationship between Examples 1-7 and constant NH ₃ oxidation rate of the catalyst obtained in Comparative Example 1-5 (%) and the additive metal (M) / Cu molar ratio. It is a graph showing the relationship between Examples 1-7 and constant NO _X purification rate of the catalyst obtained in Comparative Example 1-5 (%) and the additive metal (M) / Cu molar ratio. Is a graph showing the relationship between the Examples 1 to 7 and the transient NO _X purification of the catalyst obtained in Comparative Example 1~5 (μmol / g) and the additive metal (M) / Cu molar ratio.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

[NOx selective reduction catalyst]
The NOx selective reduction catalyst of the present invention is a NOx selective reduction catalyst used when nitrogen oxide (NOx) is reduced by a reducing agent, and includes at least an aluminum (Al) atom, a phosphorus (P) atom, and a skeleton structure. Zeolite containing silicon (Si) atoms, copper (Cu) supported inside and outside the pores of the zeolite, nickel (Ni) and cobalt (Co) supported outside the pores of the zeolite, And at least one additive metal (M) selected from the group consisting of tin (Sn) and titanium (Ti), wherein the copper content is Cu / based on the amount of silicon atoms contained in the zeolite. The Si molar ratio is in the range of 0.1 to 0.8, and the content of the additive metal is in the range of 0.05 to 3 in terms of the M / Cu molar ratio with respect to the amount of copper. It is what.

(Zeolite)
The zeolite in the NOx selective reduction catalyst of the present invention includes at least an aluminum (Al) atom, a phosphorus (P) atom, and a silicon (Si) atom in the skeleton structure (hereinafter simply referred to as “zeolite”). There is.)

  As the zeolite in the NOx selective reduction catalyst of the present invention, any zeolite can be used as long as it contains at least aluminum (Al) atom, phosphorus (P) atom and silicon (Si) atom in its skeleton structure. Well, it is not particularly limited, and conventionally known ones can be used. Among such zeolites, SAPO-5, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-37, SAPO-40, SAPO-42, SAPO-43, SAPO-47, and SAPO-56. One or more types of silica aluminophosphate zeolite (also referred to as silicoaluminophosphate, silicoaluminophosphate, etc., hereinafter may be referred to as “SAPO”) are preferred. Among such silica aluminophosphate zeolites, it has excellent thermal stability at high temperatures, especially hydrothermal stability, and when used as a NOx selective reduction catalyst, exhibits high activity and selectivity, and maintains this for a long time. SAPO-34 is more preferable from the viewpoint that it can be produced.

  Such a zeolite of the present invention preferably contains SAPO-34.

In the NOx selective reduction catalyst zeolite according to the present invention, the Si content in the zeolite is preferably 3 to 30 mol%, more preferably 5 to 25 mol%, more preferably 8 to 20 mol%. % Is particularly preferred. If the content of SiO ₂ is less than the lower limit, the amount of Cu ion exchange sites is insufficient, and sufficient activity tends not to be obtained. On the other hand, when the content of the SiO ₂ exceeds the upper limit, the heat resistance of the zeolite becomes insufficient and the activity tends to decrease.

<Constituent atoms>
In the NOx selective reduction catalyst of the present invention, the abundance ratio of aluminum atoms, phosphorus atoms and silicon atoms in the skeleton structure of the zeolite preferably satisfies the following formulas (5), (6) and (7).
0.3 ≦ x ≦ 0.6 (5)
(In the formula, x represents the molar ratio of aluminum atom to the total of aluminum atom, phosphorus atom and silicon atom in the skeleton structure)
0.3 ≦ y ≦ 0.6 (6)
(In the formula, y represents the molar ratio of phosphorus atom to the total of aluminum atom, phosphorus atom and silicon atom in the skeleton structure)
0.03 ≦ z ≦ 0.30 (7)
(In the formula, z represents the molar ratio of silicon atom to the sum of aluminum atom, phosphorus atom and silicon atom in the skeleton structure)
Furthermore, x is preferably 0.35 or more, more preferably 0.40 or more, and preferably 0.55 or less.
Furthermore, y is preferably 0.35 or more, more preferably 0.40 or more, and preferably 0.55 or less.

  Furthermore, z is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.08 or more, particularly preferably 0.09 or more, preferably 0.25 or less, more preferably 0.20. Hereinafter, it is more preferably 0.18 or less.

  In addition, the NOx selective reduction catalyst of the present invention contains an aluminum atom, a phosphorus atom and a silicon atom in the framework structure of the zeolite, and may further contain other atoms other than these atoms. Examples of such other atoms include lithium (Li), magnesium (Mg), calcium (Ca), titanium (Ti), zirconium (Zr), vanadium (V), chromium (Cr), and manganese (Mn). , Iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), zinc (Zr), boron (B), gallium (Ga), germanium (Ge), tin (Sn), arsenic (As) 1 type or 2 types or more of atoms, such as these, Preferably the atom of titanium (Ti), zinc (Zr), germanium (Ge), and tin (Sn) is mentioned. The content of these other atoms is preferably 0.3 or less, more preferably 0.1 or less, in a molar ratio with respect to the total of aluminum atoms, phosphorus atoms and silicon atoms in the framework structure of the zeolite. It is.

  The proportion of atoms in the framework structure of the zeolite is determined by the content (mass%, mmol / mmol) of the silicon, aluminum, and phosphorus atoms in the zeolite framework structure by X-ray Fluorescence Analysis (XRF). g, etc.). In addition, the content (wt%, etc.) of silicon, aluminum and phosphorus atoms in the zeolite skeleton structure can be determined by inductively coupled plasma (ICP) emission spectroscopic analysis after the sample is heated and dissolved in an aqueous hydrochloric acid solution. .

<Zeolite framework structure>
Zeolite is usually crystalline and has a methane type SiO ₄ tetrahedron, AlO ₄ tetrahedron or PO ₄ tetrahedron (hereinafter these are generalized as TO ₄ and atoms other than oxygen contained are referred to as T atoms). It has a regular network structure in which oxygen atoms at each vertex are shared and connected. As T atoms, atoms other than Al, P, and Si are also known. One of the basic units of the network structure is one in which eight TO ₄ tetrahedra are connected in a ring, which is called an 8-membered ring. Similarly, a 6-membered ring, a 10-membered ring, etc. are basic units of the zeolite structure. In addition, the structure of the zeolite in the present invention is determined by an X-ray diffraction method (XRD: X-ray diffraction).

  The zeolite in the NOx selective reduction catalyst of the present invention is a silica aluminophosphate zeolite containing at least an aluminum atom, a phosphorus atom and a silicon atom in the skeleton structure, and a zeolite having a 6-membered ring structure or an 8-membered ring structure. Is preferred.

<Zeolite particle size>
The zeolite particle size in the NOx selective reduction catalyst of the present invention is not particularly limited, but the average particle size is preferably 0.01 to 10 μm, more preferably 0.1 to 1 μm. . If the average particle size of such zeolite is less than the lower limit, hydrothermal stability tends to be insufficient. On the other hand, if it exceeds the upper limit, sufficient strength, wear resistance, etc. are obtained when used as a molded catalyst. It tends to be impossible.

  The average particle size of the zeolite particles in the present invention is determined by observing the zeolite particles by scanning electron micrograph (SEM) observation, measuring the particle size of any 10 or more primary particles of the zeolite particles, It is measured by calculating an average value. When the cross section is not circular, it means the diameter of the minimum circumscribed circle.

(Copper: Cu)
Such a NOx selective reduction catalyst of the present invention includes copper (Cu) supported in the pores of the zeolite and outside the pores of the zeolite.

  The content of copper (Cu) in the NOx selective reduction catalyst of the present invention is in the range of 0.1 to 0.8 in terms of Cu / Si molar ratio with respect to the amount of silicon atoms contained in the zeolite. It is necessary, and it is preferable that it exists in the range of 0.1-0.6, and it is more preferable that it exists in the range of 0.2-0.4. If such content is less than the lower limit, the amount of ion-exchanged Cu is small and sufficient activity tends not to be obtained. On the other hand, if the above upper limit is exceeded, the CuO species outside the zeolite framework will increase more than necessary, and improvement in initial activity cannot be expected, and the heat resistance of the zeolite tends to be adversely affected.

Moreover, it is preferable that the average particle diameter of such copper is 20 nm or less, and it is more preferable that it is 5 nm or less. When the average particle diameter of such copper exceeds the upper limit, the reaction selectivity between NOx and NH ₃ tends to decrease.

  In addition, in this invention, the average particle diameter of copper (Cu) is calculated | required by transmission electron microscope (TEM) observation, the particle diameter of each particle | grain is measured about arbitrary 100 or more particle | grains, and the average value of the particle diameter It is measured by calculating. If the cross section of the particle is not circular, the diameter is the maximum circumscribed circle of the cross section of the particle.

  In such a NOx selective reduction catalyst of the present invention, the copper (Cu) supported in the pores of the zeolite is preferably ionic copper (copper ions). The copper ions include those having a state change (copper chemical species) similar to copper ions in the vicinity of the copper ions. The content of copper (Cu) supported in the pores of the zeolite is in the range of 0.05 to 0.6 in terms of Cu / Si molar ratio with respect to the amount of silicon atoms contained in the zeolite. It is preferable that it is in the range of 0.2 to 0.4. If such content is less than the lower limit, the amount of Cu ions to be contained tends to be insufficient and sufficient activity cannot be obtained. On the other hand, if the upper limit is exceeded, the thermal stability of the zeolite tends to decrease.

  Further, the copper (Cu) supported outside the pores of the zeolite is changed between a metallic copper-like state and a copper (II) -like state due to a change in the copper atmosphere environment (for example, an oxidation-reduction atmosphere change). Copper species (eg, metallic copper, metallic copper-like state, copper (0) state, copper (I) -like state, copper (I) state, copper oxide (I) -like state, copper oxide (II) -like state, oxidation Transition to copper.

The content of copper (Cu) supported outside the pores of the zeolite is preferably 0.6 or less in terms of a Cu / Si molar ratio with respect to the amount of silicon atoms contained in the zeolite, More preferably, it is 0.2 or less. When such content exceeds the upper limit, the reaction selectivity between NOx and NH ₃ tends to decrease.

(Additional metal: M)
In such a NOx selective reduction catalyst of the present invention, at least selected from the group consisting of nickel (Ni), cobalt (Co), tin (Sn) and titanium (Ti) supported outside the pores of the zeolite. A kind of additive metal (M) is included. Such an additive metal may be one of these, or a combination of two or more metals may be supported on the zeolite. The additive metal further supported on such a Cu-zeolite can suppress the catalytic activity of the Cu species supported on the zeolite and supported outside the pores, preferably nickel (Ni) and titanium (Ti ).

  In the present invention, the “metal” is not necessarily limited to the element in the elemental zero-valent state. When the term “metal” is used, the existence state supported in the catalyst, for example, ionic or other species ( Including the existence state as an oxide).

  The content of the additive metal (M) in such a NOx selective reduction catalyst of the present invention needs to be in the range of 0.05 to 3 in terms of M / Cu molar ratio with respect to the amount of copper (Cu). It is preferably in the range of 0.1 to 2, more preferably in the range of 0.3 to 1.5. When such content is less than the lower limit, there is a tendency that the interaction with CuO seeds outside the skeleton cannot be sufficiently performed. On the other hand, if the upper limit is exceeded, the activity tends to decrease because the pores of the zeolite are blocked.

  In addition, as the loading amount of the additive metal (M), the content of the additive metal (M) in the NOx selective reduction catalyst of the present invention is supported in the range of 30 to 100% outside the pores of the zeolite. It is preferable that it exists in the range of 60 to 100%. When the content is less than the lower limit, the activity tends to be reduced by affecting the Cu ion species in the pores.

  Moreover, it is preferable that the average particle diameter of such an additional metal (M) is 10 nm or less, it is more preferable that it is 5 nm or less, and it is especially preferable that it is 2 nm or less. When the average particle diameter of such an additive metal (M) exceeds the upper limit, sufficient interaction with CuO species outside the skeleton cannot be obtained, and the oxidation of NH3 cannot be sufficiently suppressed, and sufficient NOx purification activity is obtained. Tend not to be obtained.

In addition, in this invention, the average particle diameter of the particle | grains of an addition metal (M) is calculated | required by transmission electron microscope (TEM) observation, the particle diameter of each particle | grain is measured about arbitrary 100 or more particles, The particle diameter It is measured by calculating the average value of. If the cross section of the particle is not circular, the diameter is the maximum circumscribed circle of the cross section of the particle.
(NOx selective reduction catalyst)
Further, the form of the NOx selective reduction catalyst of the present invention is not particularly limited, and may be a form of a honeycomb-shaped monolith catalyst, a pellet-shaped pellet catalyst, or the like. A method for producing such a form of the NOx selective reduction catalyst is not particularly limited, and a known method can be appropriately employed. For example, the catalyst is molded into a pellet to obtain a pellet-shaped NOx selective reduction catalyst. A method, a method of obtaining a NOx selective reduction catalyst in a form in which the catalyst base material is coated (fixed) by coating the catalyst base material, and the like may be appropriately employed. Such a catalyst substrate is not particularly limited and is appropriately selected depending on the use of the obtained NOx selective reduction catalyst, and a monolith substrate, a pellet substrate, a plate substrate and the like are preferable. Adopted. The material of such a catalyst substrate is not particularly limited, but a substrate made of a ceramic such as cordierite, silicon carbide, mullite, or a substrate made of a metal such as stainless steel including chromium and aluminum is preferable. Adopted. Furthermore, the NOx selective reduction catalyst of the present invention may be used in combination with other catalysts. Such other catalyst is not particularly limited, and a known catalyst (for example, an oxidation catalyst, a NOx reduction catalyst, a NOx occlusion reduction type (NSR catalyst), etc.) may be used as appropriate.

  Moreover, as a method for producing such a NOx selective reduction catalyst of the present invention, it is preferable to employ a method for producing a NOx selective reduction catalyst of the present invention described later. That is, the NOx selective reduction catalyst of the present invention can be suitably produced by the method for producing the NOx selective reduction catalyst of the present invention described later.

[Method for producing NOx selective reduction catalyst]
The method for producing a NOx selective reduction catalyst of the present invention is a method for producing a NOx selective reduction catalyst that purifies nitrogen oxides (NOx) in exhaust gas, and includes at least aluminum (Al) atoms and phosphorus (P) atoms in the skeleton structure. And a step of obtaining a zeolite containing silicon (Si) atoms (zeolite preparation step), a step of loading Cu (Cu) inside and outside the pores of the zeolite to obtain Cu-zeolite (Cu loading step), And carrying at least one additive metal (M) selected from the group consisting of nickel (Ni), cobalt (Co), tin (Sn) and titanium (Ti) outside the pores of the zeolite of the Cu-zeolite. And a step of obtaining the NOx selective reduction catalyst of the present invention (added metal supporting step).

(Zeolite preparation process)
In such a method for producing a NOx selective reduction catalyst of the present invention, first, a zeolite containing at least an aluminum (Al) atom, a phosphorus (P) atom and a silicon (Si) atom in a skeleton structure is obtained (zeolite preparation step).

  The method for preparing such a zeolite according to the present invention is not particularly limited, and a known method can be appropriately employed. The zeolite according to the present invention is a compound known per se and can be produced according to a commonly used method. For example, JP 2003-183020 A, WO 2010/084930 pamphlet, JP 2013-32268 A, JP 2011-125793 A, JP 4-37007 A, JP 5-21844 A, It can be produced according to the methods described in JP-B-5-51533, US Pat. No. 4,440,871 and the like.

  A method for preparing such a zeolite is not particularly limited, and examples thereof include an aluminum atom raw material, a phosphorus atom raw material, a silicon atom raw material, and, if necessary, a template agent (also referred to as an organic structure directing agent, an organic crystallization agent, etc.). ) Is mixed, and then the zeolite is prepared by hydrothermal synthesis. If necessary, after hydrothermal synthesis, filtration, washing, drying, firing, etc. are performed. In addition, when a template agent is mixed, it is preferable to remove the template agent by baking at 500 to 700 ° C. after hydrothermal synthesis or after supporting copper.

<Aluminum (Al) atomic raw material>
The raw material of the aluminum (Al) atom of the zeolite in the present invention is not particularly limited, and usually, aluminum alkoxide such as boehmite, pseudoboehmite, aluminum isopropoxide, aluminum triethoxide, aluminum hydroxide, alumina sol, sodium aluminate, etc. Can be mentioned. These may be used alone or in combination of two or more. Boehmite or pseudoboehmite is preferable as the aluminum source in terms of easy handling and high reactivity.

<Phosphorus (P) atomic raw material>
The raw material of the phosphorus (P) atom of the zeolite in the present invention is not particularly limited and is usually phosphoric acid, but aluminum phosphate may be used. As the phosphorus atom raw material, one kind may be used alone, or two or more kinds may be mixed and used. Further, the phosphorus atom raw material may be used as a powder or the like, or may be used as a solution containing the raw material such as an aqueous phosphoric acid solution.

<Silicon (Si) atomic raw material>
The raw material for silicon (Si) atoms in the present invention is not particularly limited, and usually includes silica sol, colloidal silica, fumed silica, water glass, ethyl silicate, methyl silicate, and the like. These may be used alone or in combination of two or more. Silica sol and fumed silica are preferable in terms of easy handling and high reactivity.

<Template agent>
In the zeolite preparation step of the method for producing the NOx selective reduction catalyst of the present invention, a template agent (also referred to as an organic structure directing agent, an organic crystallization agent, etc.) can be used as necessary. Such a template agent is not particularly limited, and various commonly used template agents can be used. For example, a quaternary ammonium salt such as TEAH (tetraethylammonium hydroxide) or an organic amine can be used. By using such a templating agent, it is possible to control the Si content in the obtained zeolite, and it is preferable because the Si content and the Si existing state preferable as a NOx selective reduction catalyst can be obtained.

<Preparation of zeolite>
The method for preparing zeolite is not particularly limited, and a known method can be appropriately employed. Specific examples of the method for preparing zeolite include, first, an aluminum atom raw material, a phosphorus atom raw material, a silicon atom raw material, a template agent (also referred to as an organic structure directing agent, an organic crystallizing agent, etc.), and others as necessary. The zeolite raw material composition (liquid, slurry, paste, etc.) is prepared by mixing the additive and water. These raw materials and the like may be in any form, whether in powder form or a solution containing the raw materials. Further, the order of mixing these raw materials is not particularly limited, and may be appropriately selected depending on the materials used, conditions, and the like. Specifically, first, for example, a template agent is mixed with a phosphorus atom raw material solution, an aluminum atomic raw material is added to and mixed with this mixed solution, and a silicon atomic raw material is further added and mixed. As another example, first, a phosphorus atom raw material and an aluminum atomic raw material are mixed in water, and a silicon atom raw material and a template agent are mixed in the mixture. Next, the obtained zeolite raw material composition is hydrothermally treated at a predetermined temperature and time (hydrothermal synthesis). Next, the obtained hydrothermally treated product is filtered, washed, dried and calcined to obtain the zeolite according to the present invention.

  As another specific example of the preparation method of zeolite, first, the silicon atom raw material, the aluminum atom raw material, the phosphorus atom raw material, the template agent and water are mixed to prepare an aqueous gel (zeolite raw material composition). Next, the aqueous gel is hydrothermally synthesized, and then the product is separated by filtration or decantation, and then washed with water, dried, calcined, etc. as necessary to obtain the zeolite according to the present invention. The order of mixing the raw materials and the like is not particularly limited and may be appropriately selected depending on the conditions to be used. For example, first, a phosphorus atom raw material and an aluminum atomic raw material are mixed in water, and a silicon atom raw material and a template agent are mixed in the mixture. To do. In addition, the composition of the zeolite obtained by hydrothermal synthesis has a correlation with the composition of the aqueous gel, and the composition of the aqueous gel is appropriately set in accordance with the composition in order to obtain the target zeolite.

In addition, in the zeolite according to such an invention, the content of Si contained in the zeolite is in the range of 3 to 30 mol% of SiO ₂ with respect to the total amount of zeolite contained in the zeolite in the obtained catalyst. The amount is preferably in the range of 5 to 25 mol%, more preferably in the range of 8 to 20 mol%. If the content of SiO ₂ is less than the lower limit, the amount of Cu ion exchange sites is insufficient, and sufficient activity tends not to be obtained. On the other hand, when the content of the SiO ₂ exceeds the upper limit, the heat resistance of the zeolite becomes insufficient and the activity tends to decrease.

  Further, in the zeolite according to such an invention, silica aluminophosphate zeolite is preferable, and among them, it is excellent in thermal stability at high temperature, particularly hydrothermal stability, and has high activity when used as a NOx selective reduction catalyst. SAPO-34 is more preferable from the viewpoint of showing selectivity and maintaining this for a long time.

  Further, in the hydrothermal synthesis of the zeolite preparation step of the present invention, the hydrothermal synthesis method and conditions are not particularly limited, and known methods and conditions can be appropriately employed. For example, the zeolite raw material composition is pressure resistant. Put in a container and apply a predetermined temperature (for example, 100 to 300 ° C., preferably 150 to 220 ° C.) for a predetermined time (for example, 100 to 300 ° C.) with stirring or standing under self-generated pressure or gas pressurization that does not inhibit crystallization. , 0.5 hours to 30 days, preferably 5 hours to 4 days).

  Further, in the zeolite preparation step of the present invention, the conditions for drying and firing performed as necessary after the hydrothermal synthesis are not particularly limited, and known conditions can be appropriately employed. For example, as drying conditions May employ a condition of heating at 80 to 120 ° C. for about 1 to 50 hours, and a firing condition of 300 to 700 ° C. for about 1 to 10 hours.

(Copper loading process)
In such a method for producing a NOx selective reduction catalyst of the present invention, copper (Cu) is supported in the zeolite pores obtained by the zeolite preparation step and outside the pores of the zeolite to form Cu-zeolite. To obtain (copper loading step).

  The method for supporting copper on the zeolite is not particularly limited as long as it is a method capable of supporting copper on the zeolite, and a known method can be appropriately employed. For example, generally used ion exchange method, impregnation support method, precipitation support method, solid phase ion exchange method, CVD method and the like are used. From the viewpoint of productivity, it is preferable to use an ion exchange method or an impregnation support method.

  The copper raw material (Cu source) to be supported in the present invention is not particularly limited, and a copper salt, a copper complex, a copper simple substance, a copper oxide, or the like can be used. Such a Cu source can be appropriately selected depending on the carrying method and conditions. Specifically, copper salts are used. For example, inorganic acid salts such as nitrates, sulfates and hydrochlorides, or organic acid salts such as acetates can be used. The Cu source may be soluble or insoluble in the dispersion medium.

  As a specific example of the copper loading method, first, an aqueous solution in which a copper salt or the like is dissolved (for example, an aqueous copper acetate solution) is prepared. Next, the zeolite is mixed with the copper source-containing aqueous solution and stirred at a predetermined temperature and time for impregnation with copper. Next, the copper-impregnated zeolite is filtered, washed, dried and calcined to obtain Cu-zeolite (copper-supported zeolite) according to the present invention.

  As another specific example of the method for supporting copper, first, a dispersion of the zeolite powder is prepared. Next, an aqueous solution of a copper compound (for example, cupric nitrate) is prepared and mixed with the zeolite powder dispersion to prepare a mixed dispersion of the zeolite powder and the copper compound. Next, the mixed dispersion is spray-dried, washed, dried and fired to obtain Cu-zeolite (copper-supported zeolite) according to the present invention.

  In addition, the conditions in particular in the case of such drying and baking are not restrict | limited, Well-known conditions can be employ | adopted suitably, for example, as drying conditions, the conditions heated about 80 to 120 degreeC for about 1 to 50 hours, As the firing conditions, conditions of heating at 300 to 700 ° C. for about 1 to 10 hours may be employed.

  The amount of copper (Cu) supported on zeolite is 0.1 to 0.8 in terms of a Cu / Si molar ratio with respect to the amount of silicon (Si) atoms contained in the zeolite in the obtained catalyst. It is necessary to set it as the quantity which becomes the range of 0.1, it is preferable to set it as the quantity which becomes the range of 0.1-0.6, and it is more preferable to set it as the quantity which becomes the range of 0.2-0.4. If such content is less than the lower limit, the amount of ion-exchanged Cu is small and sufficient activity tends not to be obtained. On the other hand, when the above upper limit is exceeded, only the CuO species outside the zeolite skeleton increases, and improvement in initial activity cannot be expected, and the heat resistance of the zeolite tends to be adversely affected.

  In the copper supporting step of the present invention, when supporting copper on the zeolite, the zeolite from which the template agent is removed may be used, or the zeolite containing the template agent may be used. When a zeolite containing a template agent is used, it is preferable to remove the template agent after copper is supported on the template agent-containing zeolite.

  In addition, copper (Cu) can be supported within the zeolite pores and outside the zeolite pores in the hydrothermal synthesis or the like of the above-described step.

(Additional metal loading process)
In such a method for producing a NOx selective reduction catalyst of the present invention, nickel (Ni), cobalt (Co), tin (Sn) and titanium are formed outside the pores of the Cu-zeolite zeolite obtained by the copper supporting step. The NOx selective reduction catalyst of the present invention is obtained by supporting at least one additive metal (M) selected from the group consisting of (Ti) (addition metal supporting step).

<Additive metal M>
In the present invention, the additive metal (M) supported outside the pores of the zeolite of Cu-zeolite is at least selected from the group consisting of nickel (Ni), cobalt (Co), tin (Sn) and titanium (Ti). It is necessary to be a kind of metal, and one kind of these may be used, or two or more kinds of metals may be combined and supported on the zeolite. Such an additional metal further supported on Cu-zeolite can be supported on zeolite and exhibit catalytic activity, and is preferably nickel (Ni) or titanium (Ti).

  In the present invention, the “metal” is not necessarily limited to an element in a zero-valent state, and the term “metal” refers to a state of being supported in the catalyst, for example, ionic or other species. Including the existence state of

<Supported amount>
The amount of the added metal (M) supported must be such that the content of the added metal (M) in the obtained catalyst is in the range of 0.05 to 3 in terms of M / Cu molar ratio. Yes, the amount is preferably in the range of 0.1 to 2, more preferably in the range of 0.3 to 1.5. When such content is less than the lower limit, there is a tendency that the interaction with CuO seeds outside the skeleton cannot be sufficiently performed. On the other hand, if the upper limit is exceeded, the activity tends to decrease because the pores of the zeolite are blocked.

<Metal loading method>
The method for supporting the added metal (M) is not particularly limited as long as it is a method capable of supporting the added metal (M) on the zeolite, and a known method can be appropriately employed. For example, generally used ion exchange method, impregnation support method, precipitation support method, solid phase ion exchange method, CVD method and the like are used. From the viewpoint of productivity, it is preferable to use an ion exchange method or an impregnation support method.

  The raw material (addition metal source) of the additional metal (M) carried in the present invention is not particularly limited, and a metal salt, a metal complex, a single metal, a metal oxide, or the like can be used. Such an additive metal source can be appropriately selected depending on the loading method, conditions, and the like. Specifically, salts of added metals to be supported are used. For example, inorganic acid salts such as nitrates, sulfates, and hydrochlorides, or organic acid salts such as acetates can be used. The additive metal source may be soluble or insoluble in the dispersion medium.

  As a specific example of supporting the added metal (M), first, an aqueous solution (for example, a cobalt acetate solution, a nickel acetate solution, a tin acetate solution, etc.) in which a salt of the added metal is dissolved is prepared. Next, the Cu-zeolite is mixed with the aqueous solution containing the added metal source and stirred at a predetermined temperature and time to impregnate the added metal (M). Next, the additive metal (M) impregnated Cu-zeolite is filtered, washed, dried and calcined to obtain the NOx selective reduction catalyst according to the present invention.

  As another specific example of supporting the additive metal (M), first, a dispersion of the Cu-zeolite powder is prepared. For example, the Cu-zeolite powder is suspended in ion exchange water to obtain a dispersion. Next, an aqueous solution of an additive metal compound (for example, cupric nitrate, etc.) is prepared, mixed with the Cu-zeolite powder dispersion, and a mixed dispersion of the Cu-zeolite powder and the additive metal (M) compound is prepared. Prepare. Next, the mixed dispersion is spray-dried, washed, dried, and calcined to obtain the NOx selective reduction catalyst according to the present invention.

  In addition, the conditions in particular in the case of such drying and baking are not restrict | limited, Well-known conditions can be employ | adopted suitably, for example, as drying conditions, the conditions heated about 80 to 120 degreeC for about 1 to 50 hours, As the firing conditions, conditions of heating at 300 to 700 ° C. for about 1 to 10 hours may be employed.

  In the additive metal supporting step of the present invention, when the additive metal (M) is supported on the Cu-zeolite, Cu-zeolite containing the template agent is used even if Cu-zeolite from which the template agent is removed is used. May be. In addition, when Cu-zeolite containing a template agent is used, it is preferable to remove the template agent after loading the additive metal (M) on the template agent-containing Cu-zeolite.

[NOx purification method]
The NOx purification method of the present invention purifies nitrogen oxides (NOx) by bringing exhaust gas into contact with the NOx selective reduction catalyst of the present invention in the presence of ammonia (NH ₃ ) or a reducing agent capable of generating ammonia. NOx purification method characterized by the above.

  Thus, the present invention is a method of purifying nitrogen oxides (NOx) from exhaust gas from an internal combustion engine or the like using the NOx selective reduction catalyst of the present invention. Here, the internal combustion engine is not particularly limited, and a known internal combustion engine can be used as appropriate. For example, an internal combustion engine of an automobile (diesel engine, lean burn engine, etc.) can be used. Moreover, in this invention, it is preferable to use in oxygen excess atmosphere. In this case, “oxygen-excess atmosphere” means that the air-fuel ratio (mixing ratio of air and fuel: A / F ratio) of the exhaust gas exceeds 14.7, and oxygen is excessive with respect to the fuel contained in the exhaust gas. A state that exists.

  The nitrogen oxide (NOx) to be purified by the present invention includes nitric oxide, nitrogen dioxide, nitrous oxide, and the like. Purifying NOx in the present invention means that NOx is reacted on a NOx selective reduction catalyst and converted into nitrogen, oxygen, or the like.

In such a NOx purification method of the present invention, exhaust gas is brought into contact with the NOx selective reduction catalyst of the present invention in the presence of ammonia (NH ₃ ) or a reducing agent capable of generating ammonia. Such a reducing agent is not particularly limited, and a known reducing agent can be appropriately employed. For example, urea etc. are mentioned.

  Further, a specific method for bringing the exhaust gas from the internal combustion engine or the like into contact with the NOx selective reduction catalyst of the present invention is not particularly limited, and a known method can be appropriately employed. For example, a method of arranging the NOx selective reduction catalyst of the present invention in the gas flow path of exhaust gas from an internal combustion engine or the like and bringing the exhaust gas into contact may be adopted. From the viewpoint of contacting exhaust gas in an oxygen-excess atmosphere, for example, when the exhaust gas from an internal combustion engine or the like is not in an oxygen-excess atmosphere, the air-fuel ratio of the exhaust gas before contacting the NOx selective reduction catalyst (Admixing ratio of air and fuel: A / F ratio) is adjusted to more than 14.7 (more preferably about 15 to 50), and then the exhaust gas in the oxygen excess atmosphere is brought into contact with the NOx selective reduction catalyst. It may be adopted. Such adjustment of the air-fuel ratio can be appropriately performed by a known method. For example, the air-fuel ratio may be adjusted by introducing air into the exhaust gas. If exhaust gas from a diesel engine or lean burn engine can be exhausted without any special adjustment, the exhaust gas from the diesel engine or lean burn engine can be purified. The exhaust gas purification method of the present invention can be carried out by bringing the exhaust gas into contact with the NOx selective reduction catalyst of the present invention. Further, when purifying the exhaust gas, for example, when gas in an oxygen-excess atmosphere is discharged from an internal combustion engine or the like, the exhaust gas path is set so that the exhaust gas contacts the NOx selective reduction catalyst of the present invention. The exhaust gas in an oxygen-excess atmosphere may be brought into contact with the NOx selective reduction catalyst of the present invention by adjusting with a regulating valve or the like, and thereby the NOx purification method of the present invention may be implemented.

In the NOx purification method of the present invention, before contacting the exhaust gas with the NOx selective reduction catalyst, the exhaust gas is treated with an NSR catalyst (NOx Storage Reduction catalyst) or an LNT catalyst (Lean NOx Trap Catalysts: lean NOx trap). catalyst) contacting the NOx occlusion reduction type catalyst, such as by reducing the NH ₃ and NOx absorbed by the NOx storage reduction catalyst, the NOx selective subsequent mixture of untreated NOx with the NH ₃ the flue gas It is preferable to purify nitrogen oxides (NOx) by contacting with the reduction catalyst.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Preparation Example 1)
<Preparation of silica aluminophosphate zeolite>
Phosphoric acid and 35% by mass tetraethylammonium hydroxide (TEAH) are mixed in a predetermined amount of water, and then pseudoboehmite (Al ₂ O ₃ content 75% by mass, manufactured by Nissan Chemical Co., Ltd.) is added for 10 minutes. Stir. To this, silica sol (SiO ₂ concentration 20 mass%, manufactured by Nissan Chemical Co., Ltd.) was added dropwise over 5 minutes to prepare a SAPO-34 synthesis slurry. Al: P: Si: TEAH: H ₂ O was adjusted so as to be a molar ratio of 1: 0.77: 0.18: 2.5: 50.

  Next, 170 mL of the obtained SAPO-34 synthesis slurry was charged into a 200 mL Teflon (registered trademark) autoclave (manufactured by Hosen Co., Ltd.), heated to 190 ° C., and hydrothermally treated at the same temperature for 30 hours. (Hydrothermal synthesis).

  Thereafter, filtration and washing were repeated three times, dried at 110 ° C. for 24 hours, and then calcined in air at 600 ° C. for 5 hours to prepare silica aluminophosphate zeolite (H-SAPO-34).

(Preparation Example 2)
<Preparation of Cu-supported silica aluminophosphate zeolite>
The silica aluminophosphate zeolite (H-SAPO-34) obtained in Preparation Example 1 was suspended in 0.5 L of an aqueous copper acetate solution (0.1 mol / L) and stirred at 60 ° C. for 5 hours. Thereafter, filtration and washing were repeated three times, dried at 110 ° C. for 24 hours, and then calcined in air at 500 ° C. for 5 hours to prepare Cu-supported silica aluminophosphate zeolite (Cu-SAPO-34).

[Analysis of Cu content and zeolite composition]
The composition analysis of the obtained Cu-supported silica aluminophosphate zeolite (Cu-SAPO-34) was performed by X-ray Fluorescence Analysis (XRF). That is, first, the obtained Cu-supported silica aluminophosphate zeolite (Cu-SAPO-34) was compacted at 1000 kgf / cm ² , crushed and sized, and pelletized with a diameter of 0.5 to 1.0 mm. Cu-zeolite was obtained. Next, XRF analysis was performed using 1.0 g of the obtained Cu-zeolite as a sample by a scanning X-ray fluorescence analyzer (product name: ZSX Primus II, manufactured by Rigaku Corporation). As a result, Al was 8.29 mmol / g and P was 6 .24 mmol / g, Si was 1.54 mmol / g, and Cu was 0.46 mmol / g.

Example 1
15 g of the Cu-supported silica aluminophosphate zeolite prepared in Preparation Example 2 was suspended in 0.5 L of a cobalt acetate solution (0.1 mol / L) and stirred at 70 ° C. for 6 hours. Thereafter, it was filtered and washed, dried at 110 ° C. for 24 hours, and then calcined at 550 ° C. for 5 hours to obtain a Co-supported Cu zeolite catalyst.

  The obtained Co-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Preparation Example 2. As a result of XRF analysis, the amount of Co added was 0.17 mmol / g, and the Co / Cu molar ratio was 0.37. The obtained results are shown in Table 1.

(Example 2)
A Ni-supported Cu zeolite catalyst was obtained in the same manner as in Example 1 except that the additive metal-supporting solution was changed to 0.5 L of nickel acetate solution (0.1 mol / L).

  The obtained Ni-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ni added was 0.22 mmol / g, and the Ni / Cu molar ratio was 0.48. The obtained results are shown in Table 1.

(Comparative Example 1)
The Cu-supported silica aluminophosphate zeolite prepared in Preparation Example 2 was used as a comparative Cu zeolite catalyst (Comparative Example 1).

(Comparative Example 2)
A comparative Mn-supported Cu zeolite catalyst (Comparative Example 2) was obtained in the same manner as in Example 1 except that the additive metal-supporting solution was changed to 0.5 L of manganese acetate solution (0.1 mol / L).

  For the obtained comparative Mn-supported Cu zeolite catalyst, fluorescent X-ray analysis was performed in the same manner as in Example 1. As a result of XRF analysis, the amount of Mn added was 0.08 mmol / g, and the Mn / Cu molar ratio was 0.18. The obtained results are shown in Table 1.

(Comparative Example 3)
A comparative Ag-supported Cu zeolite catalyst (Comparative Example 3) was obtained in the same manner as in Example 1 except that the additive metal-supporting solution was changed to 0.5 L of a silver nitrate solution (0.1 mol / L).

  The obtained comparative Ag-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the Ag addition amount was 0.28 mmol / g, and the Ag / Cu molar ratio was 0.62. The obtained results are shown in Table 1.

(Example 3)
10 g of the Cu-supported silica aluminophosphate zeolite prepared in Preparation Example 2 was suspended in 0.2 L of ion-exchanged water, and 0.1 L of nickel acetate solution adjusted so that the Ni / Cu molar ratio was 0.1 was added thereto. In addition, after stirring at 70 ° C. for 3 hours, the solution was evaporated at 100 ° C. Then, after drying at 110 degreeC for 24 hours, it baked at 550 degreeC for 5 hours, and obtained Ni carrying | support Cu zeolite catalyst.

  The obtained Ni-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ni added was 0.0414 mmol / g, and the Ni / Cu molar ratio was 0.09. The obtained results are shown in Table 1.

Example 4
A Ni-supported Cu zeolite catalyst was obtained in the same manner as in Example 3 except that the additive metal-supporting solution was changed to a nickel acetate solution adjusted to have a Ni / Cu molar ratio of 0.5.

  The obtained Ni-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ni added was 0.2254 mmol / g, and the Ni / Cu molar ratio was 0.49. The obtained results are shown in Table 1.

(Example 5)
A Ni-supported Cu zeolite catalyst was obtained in the same manner as in Example 3 except that the additive metal-supporting solution was changed to a nickel acetate solution adjusted to have a Ni / Cu molar ratio of 1.0.

  The obtained Ni-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ni added was 0.4416 mmol / g, and the Ni / Cu molar ratio was 0.96. The obtained results are shown in Table 1.

(Comparative Example 4)
A comparative Ni-supported Cu zeolite catalyst (Comparative Example 4) was prepared in the same manner as in Example 3 except that the additive metal-supporting solution was changed to a nickel acetate solution adjusted to have a Ni / Cu molar ratio of 5.0. Obtained.

  The obtained comparative Ni-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ni added was 2.3046 mmol / g, and the Ni / Cu molar ratio was 5.01. The obtained results are shown in Table 1.

(Example 6)
An Sn-supported Cu zeolite catalyst was obtained in the same manner as in Example 3 except that the additive metal-supporting solution was changed to a tin acetate solution adjusted to have a Sn / Cu molar ratio of 0.5.

  The obtained Sn-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the Sn addition amount was 0.230 mmol / g, and the Sn / Cu molar ratio was 0.50. The obtained results are shown in Table 1.

(Example 7)
A Ti-supported Cu zeolite catalyst was obtained in the same manner as in Example 3, except that the additive metal-supporting solution was changed to a titanyl ammonium oxalate solution adjusted to have a Ti / Cu molar ratio of 0.5.

  The obtained Ti-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ti added was 0.2346 mmol / g, and the Ti / Cu molar ratio was 0.51. The obtained results are shown in Table 1.

(Comparative Example 5)
A comparative Zn-supported Cu zeolite catalyst (Comparative Example 5) was prepared in the same manner as in Example 3, except that the additive metal-supporting solution was changed to a zinc acetate solution adjusted to have a Zn / Cu molar ratio of 0.5. Obtained.

  The obtained comparative Zn-supported Cu zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Zn added was 0.230 mmol / g, and the Ni / Cu molar ratio was 0.50. The obtained results are shown in Table 1.

(Comparative Example 6)
Comparative Co-supported zeolite catalyst (Comparative Example) in the same manner as in Example 1, except that the silica-aluminophosphate zeolite (H-SAPO-34) prepared in Preparation Example 1 was used instead of the Cu-supported silica aluminophosphate zeolite. 6) was obtained.

  The obtained Co-supported zeolite catalyst for comparison was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Co added was 0.54 mmol / g.

(Comparative Example 7)
Comparative Ni-supported zeolite catalyst (Comparative Example) in the same manner as in Example 2 except that the silica-aluminophosphate zeolite (H-SAPO-34) prepared in Preparation Example 1 was used instead of the Cu-supported silica aluminophosphate zeolite. 7) was obtained.

  The obtained comparative Ni-supported zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ni added was 0.28 mmol / g.

(Comparative Example 8)
Comparative Ag-supported zeolite catalyst (Comparative Example) in the same manner as Comparative Example 3 except that the silica-aluminophosphate zeolite (H-SAPO-34) prepared in Preparation Example 1 was used instead of the Cu-supported silica aluminophosphate zeolite. 8) was obtained.

  The obtained comparative Ag-supported zeolite catalyst was subjected to fluorescent X-ray analysis in the same manner as in Example 1. As a result of XRF analysis, the amount of Ag added was 0.27 mmol / g.

[XRD Measurement of Catalysts Obtained in Examples 1-2, Examples 4-7, and Comparative Example 1]
<Measurement of X-ray diffraction (XRD)>
About the NOx selective reduction catalyst obtained in Examples 1-2, Examples 4-7, and Comparative Example 1, as described below, XRD of each catalyst was performed by XRD (X-ray diffraction method). The diffraction pattern was measured.

  That is, first, the catalyst was pulverized and powdered using an agate mortar. Next, about 100 mg of the obtained catalyst was used as a catalyst sample, using a sample holder having the same shape so that the sample amount was constant, and placed in an X-ray diffractometer (manufactured by Rigaku Corporation, Ultimate IV).

<Measurement conditions>
X-ray source: Cu-Kα ray output setting: 40 kV x 50 mA
Optical conditions during measurement:
Divergent slit = 1 °
Scattering slit = 1 °
Receiving slit = 0.2mm
Diffraction peak position: 2θ (diffraction angle)
Measurement range: 2θ = 10 to 70 degrees Scanning speed: 10 degrees / minute Measurement method: Continuous XRD measurement results (XRD spectra) of the catalysts obtained in Examples 1-2, Examples 4-7, and Comparative Example 1 are shown in FIG. It is shown in 1.

<Results of XRD measurement>
As is clear from the results shown in FIG. 1, in the catalysts of the present invention obtained in Examples 1 and 2 and Examples 4 to 7 and Comparative Example 1, both spectra are derived from the SAPO-34 structure which is zeolite. It was confirmed that there was no change in the zeolite structure even when the added metal (M) and Cu were added. Moreover, since no diffraction derived from the supported Cu and the additive metal (M) and their oxides was observed, it was confirmed that Cu and the additive metal (M) were supported on the zeolite in a highly dispersed state. .

[Evaluation of characteristics of NOx selective reduction catalysts obtained in Examples 1 to 7 and Comparative Examples 1 to 8]
<Catalyst activity evaluation test 1: Evaluation of steady NH ₃ oxidation activity>
With respect to the NOx selective reduction catalysts obtained in Examples 1 to 7 and Comparative Examples 1 to 8, the NH ₃ oxidation rate at the steady state was measured as follows, and the steady state NH ₃ oxidation activity of each catalyst was measured. evaluated.

That is, first, the catalyst was compacted at 1000 kgf / cm ² , crushed and sized to form pellets having a diameter of 0.5 to 1.0 mm. Next, 1.0 g of the obtained catalyst was set as a catalyst sample in an atmospheric pressure fixed bed flow type reactor (CATA-5000, manufactured by Best Sokki Co., Ltd.). Next, a model gas composed of NH ₃ (700 ppm), O ₂ (8% by volume), CO ₂ (10% by volume), H ₂ O (8% by volume) and N ₂ (remainder) is added to a gas of 10 liters / minute. It was supplied at a flow rate and adjusted so that the temperature of the gas with catalyst was 500 ° C. Thereafter, the NH ₃ concentration in the steady-state catalyst-containing gas and the catalyst-out gas was measured while maintaining the catalyst-containing gas temperature at 500 ° C. for 15 minutes, and the NH ₃ oxidation rate (%) was calculated from these measured values. . The obtained results are shown in Table 1. Further, a graph showing the relationship between Examples 1-7 and constant NH ₃ oxidation rate of the catalyst obtained in Comparative Example 1-5 (%) and the additive metal (M) / Cu molar ratio in FIG.

<Catalyst activity evaluation test 2: Steady NOx reduction activity evaluation>
For NOx selective reduction catalyst obtained in Examples 1 to 7 and Comparative Examples 1-8, as follows, was measured of the NO _X purification rate at the time of steady respectively, the steady-state NO _X reduction activity of each catalyst evaluated.

That is, first, the catalyst was compacted at 1000 kgf / cm ² , crushed and sized to form pellets having a diameter of 0.5 to 1.0 mm. Next, 1.0 g of the obtained catalyst was set as a catalyst sample in an atmospheric pressure fixed bed flow type reactor (CATA-5000, manufactured by Best Sokki Co., Ltd.). Next, a model gas composed of NO (600 ppm), NH ₃ (700 ppm), O ₂ (8% by volume), CO ₂ (10% by volume), H ₂ O (8% by volume) and N ₂ (remainder) is added 10 The gas was supplied at a gas flow rate of 1 liter / min and adjusted so that the gas temperature with catalyst was 500 ° C. Thereafter, while maintaining the temperature of the gas containing the catalyst at 500 ° C. for 15 minutes, the NO _X concentration in the catalyst-containing gas and the catalyst output gas in the steady state was measured, and the NO _X purification rate (%) was calculated from these measured values. . The obtained results are shown in Table 1. Further, a graph showing the relationship between Examples 1-7 and constant NO _X purification rate of the catalyst obtained in Comparative Example 1-5 (%) and the additive metal (M) / Cu molar ratio in FIG.

<Catalyst activity evaluation test 3: Transient NOx reduction activity evaluation>
For NOx selective reduction catalyst obtained in Examples 1 to 7 and Comparative Examples 1-8, was measured for each amount of NO _X during the transient as follows, to evaluate the transient NO _X reduction activity of each catalyst.

That is, first, the catalyst was compacted at 1000 kgf / cm ² , crushed and sized to form pellets having a diameter of 0.5 to 1.0 mm. Next, 1.0 g of the obtained catalyst was set as a catalyst sample in an atmospheric pressure fixed bed flow type reactor (CATA-5000, manufactured by Best Sokki Co., Ltd.). Next, a model gas composed of NO (150 ppm), O ₂ (8% by volume), CO ₂ (10% by volume), H ₂ O (8% by volume) and N ₂ (remainder) is supplied at a gas flow rate of 10 liters / minute. And the gas temperature with catalyst was adjusted to 500 ° C. Thereafter, the gas temperature containing the catalyst was kept at 500 ° C. for a minute. Thereto, NH ₃ (2000 ppm) was further added for 6 seconds to maintain the model gas conditions and the catalyst-containing gas temperature. From concentration of NO _X output gas of the NO _X concentration and the NH ₃ addition seconds after the NH ₃ addition time of the incoming gas (model gas) was calculated at this time clarified amount of NO _X ([mu] mol / g). The obtained results are shown in Table 1. Further, a graph showing the relationship between the Examples 1 to 7 and the transient NO _X purification of the catalyst obtained in Comparative Example 1~5 (μmol / g) and the additive metal (M) / Cu molar ratio in FIG. 4 .

<Stationary NH ₃ oxidation activity>
As is clear from the results shown in FIG. 2 and Table 1, in the catalyst of the present invention obtained in Examples 1 to 7 and the comparative catalyst obtained in Comparative Examples 2 to 5, the copper-supported zeolite of Comparative Example 1 Compared with the catalyst (Cu-SAPO-34), NH ₃ oxidation activity is suppressed in all cases, and the addition of metal elements suppresses the oxidation reaction of NH ₃ proceeding on CuO seeds existing outside the zeolite framework. Was confirmed.

<Stationary NOx reduction activity and transient NOx reduction activity>
As is apparent from the results shown in FIGS. 3 and 4 and Table 1, the catalysts of the present invention obtained in Examples 1 to 7 are the copper-supported zeolite catalyst (Cu-SAPO—) of Comparative Example 1 containing no additive metal. It was confirmed that all showed high NOx reduction activity compared with 34). On the other hand, it was confirmed that sufficient NOx reduction activity was not obtained in Comparative Example 4 in which the addition amount of the added metal was outside the present invention. In addition, it was confirmed that all of Comparative Examples 6 to 8 containing the added metal but not containing Cu had low NOx reduction activity.

  As described above, according to the present invention, a NOx selective reduction catalyst capable of exhibiting high NOx purification activity under a high temperature condition of 400 ° C. or higher, a method for producing the NOx purification method, and a NOx purification method using the NOx selective reduction catalyst are provided. It becomes possible to do.

  Therefore, the NOx selective reduction catalyst of the present invention, the production method thereof, and the NOx purification method using the NOx purification catalyst can exhibit excellent NOx purification activity under a high temperature condition of 400 ° C. or higher. It is useful for purifying nitrogen oxides (NOx) contained in the exhaust gas discharged from the exhaust gas.

Claims (6)

A NOx selective reduction catalyst used for reducing nitrogen oxide (NOx) with a reducing agent, wherein the skeleton has at least an aluminum (Al) atom, a phosphorus (P) atom, and a silicon (Si) atom; , Copper (Cu) supported inside and outside the pores of the zeolite, and nickel (Ni), cobalt (Co), tin (Sn) and titanium (Ti) supported outside the pores of the zeolite And at least one additive metal (M) selected from the group consisting of:
The copper content is in the range of 0.1 to 0.8 in terms of a Cu / Si molar ratio with respect to the amount of silicon atoms contained in the zeolite, and
The content of the additive metal is in the range of 0.05 to 3 in M / Cu molar ratio with respect to the amount of copper.
The NOx selective reduction catalyst characterized by the above-mentioned.   The NOx selective reduction catalyst according to claim 1, wherein the zeolite contains SAPO-34.   The NOx selective reduction catalyst according to claim 1 or 2, wherein an average particle diameter of the additive metal is 10 nm or less. A method for producing a NOx selective reduction catalyst that purifies nitrogen oxides (NOx) in exhaust gas,
Obtaining a zeolite containing at least an aluminum (Al) atom, a phosphorus (P) atom and a silicon (Si) atom in the skeleton structure;
A step of obtaining Cu-zeolite by supporting copper (Cu) inside and outside the pores of the zeolite;
By supporting at least one additive metal (M) selected from the group consisting of nickel (Ni), cobalt (Co), tin (Sn) and titanium (Ti) outside the pores of the zeolite of the Cu-zeolite. Obtaining the NOx selective reduction catalyst according to any one of claims 1 to 3,
A process for producing a NOx selective reduction catalyst, comprising: In the presence of ammonia (NH ₃ ) or a reducing agent capable of producing ammonia, the NOx selective reduction catalyst according to any one of claims 1 to 3 is brought into contact with exhaust gas to form nitrogen oxides (NOx). A NOx purification method characterized by purifying. Before contacting the exhaust gas with the NOx selective reduction catalyst, the exhaust gas is brought into contact with the NOx occlusion reduction type catalyst to reduce NOx absorbed by the NOx occlusion reduction type catalyst to NH ₃ , and then the NH ₃ and the exhaust gas in the exhaust gas The NOx purification method according to claim 5, wherein nitrogen oxide (NOx) is purified by bringing a mixture of untreated NOx into contact with the NOx selective reduction catalyst.

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