JP3110921B2 - Exhaust gas purification catalyst and exhaust gas purification method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an exhaust gas for decomposing nitrogen oxides emitted from various internal furnaces such as mobile internal combustion engines such as gasoline vehicles and diesel vehicles, stationary internal combustion engines such as cogeneration, boilers and the like into harmless gases. Purification catalyst
And a method for purifying exhaust gas using the same .

[0002]

BACKGROUND ART Generally, exhaust gas from automobiles, stationary internal combustion engines and various industrial furnaces contains a large amount of nitrogen oxides (NO _X ) represented by NO and NO _2. ing. It is said that these NO _Xs not only cause photochemical smog, but also cause respiratory disorders for the human body. For information on how to reduce these NO _X, as gasoline vehicles, if a small amount of oxygen in the exhaust gas, carbon monoxide, NO _X with a reducing agent such as hydrocarbon
A so-called three-way catalyst type exhaust gas treatment for reducing and removing carbon dioxide has been established.

On the other hand, when a large amount of oxygen is contained in the gas, such as a large stationary discharge source such as a boiler, a selective NO _X reduction method for reducing the amount of NO _X by adding ammonia from the outside operates. And has a certain effect. However, the former method can be applied only to exhaust gas from gasoline engines with extremely low oxygen concentration, and the latter method uses ammonia, so it should not be used for small stationary or mobile sources. Above, difficult.

Therefore, as a reducing agent other than ammonia,
Various methods using hydrogen, carbon monoxide or various hydrocarbons have been studied, but most of them are non-selective contacting methods that can remove nitrogen oxides only after oxygen in exhaust gas is completely consumed. It has the disadvantage of being a reduction method.
Conventionally, the following methods have been proposed as a novel selective catalytic reduction method (a method for selectively reducing and removing nitrogen oxides even in the presence of oxygen) which can solve such difficulties. However, satisfactory results have not been obtained.

That is, according to JP-A-2-149317,
Using a catalyst composed of hydrogen-type mordenite or clinoptilolite, or a catalyst composed of hydrogen-type mordenite or clinoptilolite supporting metals such as Cu, Cr, Mn, Fe, and Ni, and burning various fuels A method has been proposed in which flue gas containing oxygen generated when the flue gas is contacted with these catalysts in the presence of an organic compound to remove nitrogen oxides in the flue gas. According to this method, a denitration rate of 30 to 60% is obtained under the conditions of a reaction temperature of 300 to 600 ° C. and a gas hourly space velocity (GHSV) of 1200 h ^-1 . The denitration effect is unknown. Further, there is no description about the change over time of the catalyst activity, and the life of the catalyst is unknown. Furthermore, since the evaluated catalyst in a pseudo-gas containing no SO _X, it is unclear resistant SO _X of the catalyst.

According to Japanese Patent Application Laid-Open No. 1-130735, a catalyst is used in which a zeolite ion-exchanged with a transition metal (Cu, Co, Ni, Fe, Mg, Mn, etc.) is supported on a refractory carrier. ,
A method capable of purifying nitrogen oxides even in an oxidizing atmosphere has been proposed. This method purifies exhaust gas from a gasoline engine with high efficiency even when the air-fuel ratio is lean, and the oxygen concentration in the exhaust gas is at most about 3%. Therefore, it is unclear whether nitrogen oxides can be selectively reduced and denitrated even in a gasoline engine under lean conditions with a higher air-fuel ratio or with an oxygen concentration of 5 to 10% like exhaust gas from a diesel engine. is there. Also in Example, with increasing oxygen concentration, No _X removal rate shows a tendency to decrease significantly. Also, the durability is unknown.

According to JP-A-63-283727, SiO ₂ / Al
Cu, V, Mn, Fe, C are added to hydrophobic zeolite with ₂ O ₃ ratio of 15 or more.
Using a catalyst supporting a metal such as r, carbon monoxide and 1
Methods have been proposed for reducing nitrogen oxides in the oxygen-containing exhaust gas of internal combustion engines in the presence of one or more hydrocarbons. In this method, when a zeolite catalyst supporting a metal other than copper is used, the denitration rate is as low as 4 to 26%. On the other hand, when a copper zeolite catalyst is used, a relatively high activity is obtained, but the durability is unknown. The oxygen concentration in the exhaust gas of the embodiment is 1.6%. For example, even when the oxygen concentration is high, such as in the case of a gasoline engine under lean conditions with a high air-fuel ratio or in the exhaust gas of a diesel engine, nitrogen oxidation is similarly performed. It is unclear whether the product can be selectively reductively denitrated.

According to Japanese Patent Application Laid-Open No. 63-100919, a catalyst comprising copper supported on a porous carrier such as alumina, silica, zeolite or the like is used, and nitrogen oxides in an exhaust gas containing oxygen in the presence of hydrocarbons are used. Methods for removing objects have been proposed. In this method, the denitration rate is 10 to 25%, and high denitration activity cannot be obtained. Further, the oxygen concentration in the exhaust gas of the example is 2.1
%, And it is unclear whether nitrogen oxides can be selectively reductively denitrated even when the oxygen concentration is higher. Further, the durability is unknown. JP-A-4-404
According to JP-A-5, an exhaust gas treatment catalyst in which copper and a specific metal coexist in a crystalline silicate having a specific X-ray diffraction pattern and a specific chemical formula is proposed.

In this catalyst, the coexisting specific metal is 27
Very diverse with species, but the differences in the effects of these metals,
That is, the superiority is unknown. Moreover, the preferred range of the content is 100 parts by weight of the carrier, and in the case of copper, 0.2 to 8
Parts by weight and 0.1 to 6 parts by weight in the case of other metals are all uniform and wide, and the specific optimum content of each of the 27 specific metals is unknown. In addition, the amount of the specific metal to coexist is considered to depend on the amount of supported copper,
In this catalyst, although the preferred amount of copper is described, the optimum amount of the specific metal relative to the amount of copper [specific metal / copper (molar ratio)]
Is unknown. Therefore, the present invention provides a highly efficient exhaust gas purifying catalyst which can purify nitrogen oxides into harmless gas with high efficiency even when oxygen in the exhaust gas has a high concentration.
An object of the present invention is to provide a method for purifying used exhaust gas .

[0010]

SUMMARY and effects of the Invention The exhaust gas purifying catalyst according to the present invention, nitrogen oxides (NO _X) in an oxidizing atmosphere in the exhaust gas, a catalyst for reducing removed in the presence of hydrocarbons, catalyst support comprising a pentasil-type crystalline aluminosilicate is configured by supporting copper component and the phosphorus component, the supported amount of the phosphorus component is 0.1 ~ 5.0 wt% in terms _of P ₂ O _5,
The amount of the copper component carried is 0.8 to 30.0 wt% in terms of CuO . Further, the exhaust gas purifying catalyst according to the present invention is provided.
The medium converts nitrogen oxides (NOx) in the exhaust gas into an oxidizing atmosphere,
A catalyst for reducing and removing in the presence of a hydrocarbon,
The catalyst support containing the sil-type crystalline aluminosilicate is copper
Component and a phosphorus component, and the phosphorus, copper and
That the ratio [P / Cu (molar ratio)] is 0.0037 to 7.0.
Features . The oxidizing atmosphere is defined as H ₂ O and C by completely oxidizing carbon monoxide, hydrogen, hydrocarbons contained in the exhaust gas and reducing substances of hydrocarbons added as required in the present treatment.
This is a state in which an excess amount of oxygen is included in the oxygen required for conversion to O ₂ .

As the copper component, for example, when the copper component is supported by an ion exchange method or an impregnation method, or when the zeolite is synthesized by using a copper component, a soluble salt can be used. Examples of such substances include nitrates, halogen compounds, carbonates, organic acid salts, and copper ammine complexes. When a copper component is contained in the catalyst by a physical mixing method, an oxide or a hydroxide may be used in addition to the soluble salt. And the content of this copper component with respect to the entire catalyst is
0.8 to 30.0 wt%, preferably 2.0 to 15.0 wt% in terms of CuO. The phosphorus component is a simple substance of phosphorus and a phosphorus compound. Examples of the phosphorus simple substance include yellow phosphorus and red phosphorus.

Examples of the phosphorus compound include (a) an inorganic phosphoric acid having a low oxidation number such as orthophosphoric acid, hypophosphoric acid, phosphorous acid, and hypophosphorous acid, and alkali metal salts and ammonium salts thereof; Acid, tripolyphosphoric acid, condensed phosphoric acid typified by polyphosphoric acid such as tripolyphosphoric acid and trimetaphosphoric acid, tetrametaphosphoric acid, metaphosphoric acid such as hexametaphosphoric acid, and alkali metal salts and ammonium salts thereof, (c)
Phosphorus chalcogenide, (d) organophosphorus, (e) organophosphoric acid, (f)
Organic phosphates and the like can be mentioned, and one or more of these can be used in combination. Among these, a catalyst excellent in heat resistance can be obtained by using an alkali metal salt such as a lithium salt and a sodium salt, and a phosphate such as an ammonium salt.

Such a phosphorus component is supported by a reaction such as an impregnation method, a liquid phase reaction method, a vapor phase deposition method, an ion exchange method, or is contained when a zeolite is synthesized. The phosphorus content is calculated as P ₂ O _{5 based} on the whole catalyst.
And 0.1 to 5.0 wt%, but preferably 0.1 ~4.0wt%, more preferably between 0.1 2.0 wt%. If the content is less than 0.1 wt%, high purification activity and durability cannot be obtained due to the phosphorus component contained in the present invention, and if it exceeds 5.0 wt%, the exhaust gas purification performance will be reduced and the durability will be improved. I can't see it either. The ratio of phosphorus in the phosphorus component to copper in the copper component [P
/ Cu (molar ratio)] is 0.0037 to 7.0 , but 0.0037 to 7.0
0.3 is preferable, and 0.0037 to 0.2 is more preferable. P
When / Cu exceeds 7.0 , the exhaust gas purification performance is lowered and the durability is not improved.

The pentasil-type crystalline aluminosilicate is a zeolite whose basic unit is a 5-membered oxygen ring. For example, ferrierite, mordenite, ZSM-5, ZSM-11, etc. are applicable. Since zeolites other than pentasil-type crystalline aluminosilicate have relatively low hydrothermal resistance, the durability of the catalyst after supporting the phosphorus component may be reduced. Among such pentasil-type crystalline aluminosilicates, SiO ₂ / Al ₂ O ₃ (molar ratio)
Is preferably 10 or more.

If the ratio of SiO ₂ / Al ₂ O ₃ is less than 10, the durability after supporting the phosphorus component may be reduced because the hydrothermal resistance is relatively low. Further, among the pentasil-type crystalline aluminosilicates, those having an MFI structure are preferable. The MFI structure refers to a structure that is the same as or similar to ZSM-5. In addition to ZSM-5, for example, ZSM-
8, ZSM-11, zeta 1, zeta 3, Nu-4, N
Structures such as u-5, TZ-1, and TPZ-1 correspond. Further, among the pentasil-type crystalline aluminosilicate,
In powder X-ray diffraction, those having the lattice spacing (d) shown in Table 2 below are most preferred.

[0016]

[Table 2 ]

The pentasil-type crystalline aluminosilicate is preferably synthesized using mordenite as a seed crystal. Such a mordenite may be a natural product or a synthetic product, but preferably has a lattice spacing (d) shown in Table 3 below in powder X-ray diffraction. Further, mordenite having a length in the major axis direction of the holes of 2 μm or more is preferable.

[0018]

[Table 3 ]

The catalyst may have any shape, for example, a pellet, a plate, a column, or a lattice. The catalyst may be coated on a grid-like carrier such as cordierite, mullite or alumina and a base material such as a wire mesh. The catalyst according to the present invention can be prepared by supporting a copper component and a phosphorus component on a pentasil-type crystalline aluminosilicate by, for example, an ion exchange method, an impregnation method, a physical mixing method, or a vapor deposition method.

Alternatively, it can be prepared by incorporating a copper component and a phosphorus component into the gel when synthesizing the zeolite. During the preparation of the catalyst, the copper component and the phosphorus component
They may be added at one time, or may be added sequentially at a later time. Thus, the catalyst of the present invention can be prepared by various methods.

The method for purifying exhaust gas using the exhaust gas purifying catalyst according to the present invention, in an oxidizing atmosphere, THC concentration / NO _X
Concentration in the presence of hydrocarbons 0.5-200, the exhaust gas is contacted with the catalyst to reduce and remove nitrogen oxides in the exhaust gas into N ₂ and H ₂ O. The THC (total hydrocarbon) concentration is:
This is the concentration when hydrocarbons are converted to methane.

[0022] Specific reaction conditions, with respect to the concentration of hydrocarbons, when expressed in THC concentration / NO _X concentration, and 0.5 to 200, preferably 1 to 100. For example, NO _X concentration 100p
In the case of pm, the THC concentration is between 50 and 20,000 ppm. When the amount of hydrocarbons is lower than the lower limit, the denitration performance is not exhibited, and when the amount is higher than the upper limit, the denitration rate increases, but the economic efficiency of the entire system decreases and the heat of combustion of hydrocarbons decreases. This is not preferable because of abnormal heat generation of the catalyst layer due to the above.

The hydrocarbon may be a hydrocarbon remaining in the exhaust gas. However, when the amount of the hydrocarbon is less than that required for causing a denitration reaction, or when the exhaust gas contains no hydrocarbon, It is preferable to add a hydrocarbon from outside. The type of hydrocarbon added for this purpose is not particularly limited, and examples thereof include methane, LPG, gasoline, light oil, kerosene, and heavy oil A.

The catalyst reaction temperature is set to 200 to 800 ° C, preferably 300 to 600 ° C. Normally, the higher the temperature, the higher the denitration rate. However, if the temperature exceeds 800 ° C., the catalyst deteriorates, which is not preferable. If the temperature is lower than 200 ° C., the denitration rate decreases. Gas space velocities (GHSV) are typically between 2,000 and 200,0
00h ⁻¹ , preferably 5,000 to 100,000 h ⁻¹ . GHSV,
When it is slower than 2,000 h ⁻¹ , the denitration rate is high, but the amount of catalyst used increases, and when it is faster than 200,000 h ⁻¹ , the denitration rate decreases.

The exhaust gas purifying catalyst is an object of the present invention is a gas containing NO _X and oxygen, for example, lean-burn type gasoline automobile, the mobile internal combustion engine such as a diesel automobile, cogeneration, etc. Exhaust gas discharged from stationary internal combustion engines, boilers, various industrial furnaces, and the like.

[0026]

【Example】 Example 1 First, 337.5 g of aluminum sulfate, 362.5% of sulfuric acid (97%)
g, a solution consisting of 8250 g of water (hereinafter referred to as solution I), water glass
(SiO_Two28.4%, Na_TwoO 9.5%) than 5275g, 5000g of water
Solution (hereinafter referred to as solution II) and 987.5 g of sodium chloride,
A solution consisting of 2300 g of water (hereinafter referred to as solution III) was prepared.
Next, the solutions I and II should not be gradually dropped simultaneously into the solution III.
Mixed. Adjust the reaction mixture to pH 9.5 with sulfuric acid
Mordenite (SiO 2)_Two/ Al_TwoO_Three= 20
(Molar ratio)] 12.5 g was added.

Next, the reaction mixture was placed in an autoclave having a capacity of 25 liters, and allowed to stand for 20 hours while stirring at 300 ° C. and 170 ° C. under self-pressure. After cooling, the reaction mixture was filtered, and the precipitate was sufficiently washed with excess pure water. Thereafter, by drying at 120 ° C. for 20 hours, ZSM-5 is obtained.
An aluminosilicate zeolite having a structure (MFI structure) was synthesized. This aluminosilicate zeolite powder X
Table 4 shows the measurement results by the line diffraction.

[0028]

[Table 4 ]

Next, this zeolite was placed in an air stream at 550 ° C.
For 6 hours. The SiO ₂ / Al ₂ O ₃ (molar ratio) of the aluminosilicate zeolite thus obtained was 32. Next, an aluminosilicate zeolite catalyst supporting diphosphorus pentoxide and copper was synthesized using an aqueous solution of copper acetate and diphosphorus pentoxide on this aluminosilicate zeolite. The content of the phosphorus component in this catalyst is calculated as P ₂ O ₅
1.0 wt%, the content of the copper component was 4.8 wt% in terms of CuO, and P / Cu (molar ratio) was 0.233. Next, this catalyst was evaluated for initial activity and activity after steaming (hydrothermal) treatment as described below.

That is, regarding the evaluation of the initial activity, first,
After filling 2 cc of this catalyst into a stainless steel reaction tube, a model gas was used as a processing gas, and GHSV = 80,000 h was introduced into the reaction tube.
Introduced at ^-1 . The composition of this model gas is NO _X : 500ppm,
O ₂ : 4.5%, LPG: 833ppm (THC concentration is about 2500pp
m). Thus, THC concentration / NO _X concentration is 5.
Then, by introducing a gas from the outlet of the reaction tube chemiluminescence analyzer to determine the NO _X concentration. The NO _X removal rate of the model gas after the catalytic reaction was calculated by comparing the NO _X concentration of the model gas before and after introduction into the reaction tube. This is the reaction tube
The tests were performed for cases where the temperature was maintained at 350 ° C and 400 ° C, respectively. The results are shown in Table 5 below.

For the evaluation of the activity after the steaming treatment, first, as the steaming treatment, the catalyst prepared in this example was treated with 10% water, 4.5% oxygen, GHSV = 80,000h ^-1 ,
The temperature was kept at 650 ° C. for 8 hours. Then, cold catalyst in the same manner as in the evaluation of the initial activity, after filling into a stainless steel reaction tube, the model gas was introduced into the reaction tube as the process gas, then the similar to the NO _X removal rate Calculated. This was performed for the case where the reaction tube was maintained at 350 ° C. and 400 ° C., respectively. The results are shown in the table below.
It is shown in FIG.

Examples 2 to 9 In each of the examples, the catalyst was prepared in the same manner as in Example 1, except that the supported amounts of the phosphorus component and the copper component were changed as follows. That is, the content of the phosphorus component in the catalyst according to Example 2 was 0.9 wt% in terms of P ₂ O ₅ , and the content of the copper component was in terms of CuO.
4.9 wt% and P / Cu (molar ratio) was 0.203. The content of the phosphorus component in the catalyst according to Example 3 was calculated as P ₂ O ₅ .
1.0 wt%, the content of the copper component was 4.8 wt% in terms of CuO, and P / Cu (molar ratio) was 0.233.

The content of the phosphorus component in the catalyst according to Example 4 was 0.9% by weight in terms of P ₂ O ₅ , and the content of the copper component was in terms of CuO.
4.6 wt% and P / Cu (molar ratio) was 0.219. The content of the phosphorus component in the catalyst according to Example 5 was calculated as P ₂ O ₅ .
0.9 wt%, the content of the copper component was 4.0 wt% in terms of CuO, and the P / Cu (molar ratio) was 0.252. The content of the phosphorus component in the catalyst according to Example 6 was 0.7 wt% in terms of P ₂ O ₅ , the content of the copper component was 3.4 wt% in terms of CuO, and the P / Cu (molar ratio) was 0.231. Met. The content of the phosphorus component in the catalyst according to Example 7 was 1.4 wt% in terms of P ₂ O ₅ , the content of the copper component was 4.6 wt% in terms of CuO, and the P / Cu (molar ratio) was 0.34%.
Was one.

The content of the phosphorus component in the catalyst according to Example 8 was 0.7 wt% in terms of P ₂ O ₅ , and the content of the copper component was in terms of CuO.
4.3 wt% and P / Cu (molar ratio) was 0.182. The content of the phosphorus component in the catalyst according to Example 9 was calculated as P ₂ O ₅ .
1.4 wt%, the content of the copper component was 4.1 wt% in terms of CuO, and the P / Cu (molar ratio) was 0.383. Next, with respect to the catalysts of Examples 2 to 9, the initial activity and the activity after the steaming treatment were evaluated under the same conditions as in Example 1. The results are shown in Table 5 below. In addition, such evaluation of the activity was similarly performed on the catalysts of Examples 10 to 20 described below.

Examples 10 and 11 In Examples 10 and 11, catalysts according to Examples were prepared in the same manner as in Example 1 except that orthophosphoric acid was used instead of diphosphorus pentoxide. That is, the content of the phosphorus component in the catalyst according to Example 10 was 0.8 wt% in terms of P ₂ O ₅ , the content of the copper component was 3.8 wt% in terms of CuO, and the P / Cu (molar ratio) was Was 0.236. The content of the phosphorus component in the catalyst according to Example 11 was 0.6 wt% in terms of P ₂ O ₅ , the content of the copper component was 3.5 wt% in terms of CuO, and P / Cu (molar ratio) was 0.19%.
Was 2. Example 12 In Example 1, the introduced model gas was changed to a gas having a higher oxygen concentration than in Example 1, and the initial activity and the activity after the steaming treatment were evaluated. That is, the composition of the introduced model _{gas, NO X: 500ppm, O 2} : 10%, LPG: a 833 ppm.

Example 13 A catalyst according to this example was obtained in the same manner as in Example 1 except that sodium pyrophosphate was used instead of diphosphorus pentoxide. The content of the phosphorus component in this catalyst is
0.8 wt% in terms of P ₂ O ₅ , copper content is 5.
4 wt% and P / Cu (molar ratio) were 0.165. Example 14 A catalyst according to this example was obtained in the same manner as in Example 1 except that sodium hexametaphosphate was used instead of diphosphorus pentoxide. The content of the phosphorus component in this catalyst was 0.9 wt% in terms of P ₂ O ₅ , the content of the copper component was 4.8 wt% in terms of CuO, and the P / Cu (molar ratio) was 0.210.

Examples 15, 16, and 17 In Examples 15, 16, and 17, the same procedures as in Example 1 were carried out except that sodium tripolyphosphate was used instead of diphosphorus pentoxide. A catalyst was obtained. That is, the content of the phosphorus component in the catalyst according to Example 15 was calculated as P ₂ O ₅ .
0.2 wt%, the content of the copper component was 3.8 wt% in terms of CuO, and the P / Cu (molar ratio) was 0.060. The content of the phosphorus component in the catalyst according to Example 16 was 0.5% by weight in terms of P ₂ O ₅ , the content of the copper component was 4.7% by weight in terms of CuO, and the P / Cu (molar ratio) was 0.119%. Met. The content of the phosphorus component in the catalyst according to Example 17 was 3.2 wt% in terms of P ₂ O ₅ , the content of the copper component was 9.6 wt% in terms of CuO, and P / Cu (molar ratio) was 0.37%.
Was 3.

Examples 18 and 19 In Examples 18 and 19, the catalysts of Examples 1 and 2 were prepared in the same manner as in Example 1 except that sodium metaphosphate was used instead of diphosphorus pentoxide. . That is, Example 18
The content of the phosphorus component in the catalyst according to the, 0.5 wt in terms _of P ₂ O ₅
%, Copper content is 4.9wt% in CuO conversion, and P / Cu
(Molar ratio) was 0.115. The content of the phosphorus component in the catalyst according to Example 19 was 3.3 wt% in terms of P ₂ O ₅ , the content of the copper component was 9.1 wt% in terms of CuO, and P / Cu (molar ratio).
Was 0.403. Example 20 A catalyst according to this example was obtained in the same manner as in Example 1 except that sodium phosphate was used instead of diphosphorus pentoxide. The content of the phosphorus component in this catalyst is P ₂ O ₅
0.4wt% in conversion, content of copper component is 4.2wt in CuO conversion
%, And P / Cu (molar ratio) was 0.102.

Comparative Example 1 In Example 1, the step of impregnating with an aqueous solution of diphosphorus pentoxide was omitted, and the other conditions were the same as in Example 1 to obtain a catalyst supporting only copper according to this comparative example. The content of the copper component in this catalyst was 4.0 wt% in terms of CuO. With respect to the catalyst of this comparative example, the initial activity and the activity after the steaming treatment were evaluated under the same conditions as in Example 1. The results are shown in Table 6 below. Further, such evaluation of the activity was similarly performed on the catalysts of Comparative Examples 2 to 4 described below. Comparative Example 2 In Comparative Example 1, a copper nitrate aqueous solution was used, and the other conditions were adjusted in the same manner as in Comparative Example 1 to obtain a catalyst supporting only the copper component according to this comparative example. The content of the copper component in this catalyst is CuO
It was 4.7 wt% in conversion.

Comparative Examples 3 and 4 In Comparative Examples 3 and 4, the amount of P ₂ O ₅ supported was 6 wt% or more, and P / Cu
The catalyst was prepared so that (molar ratio) was 0.7 or more. Comparative Example 3 was prepared using an aqueous solution of copper nitrate and diphosphorus pentoxide. The content of the phosphorus component in this catalyst is calculated as P ₂ O ₅
7.9 wt%, the content of the copper component was 4.5 wt% in terms of CuO, and the P / Cu (molar ratio) was 1.97. In Comparative Example 4, an aqueous solution of cupric chloride and orthophosphoric acid was used, and an aluminosilicate zeolite was co-impregnated to contain 1 mmol / g of copper and phosphorus, respectively, to obtain a catalyst according to this comparative example. The content of the phosphorus component in this catalyst is calculated as P ₂ O ₅
The content of copper component was 8.0 wt% in terms of CuO, and the P / Cu (molar ratio) was 0.99.

[0041]

[Table 5 ]

[0042]

[Table 6 ]

Discussion of Examples and Comparative Examples From Table 5 , according to Examples 1 to 20, according to Examples 1 to 20, a catalyst support containing a pentasil-type crystalline aluminosilicate is configured to support a copper component and a phosphorus component. P ₂ O ₅
0.1 to 5.0 wt% in conversion, and the ratio of phosphorus to copper [P / Cu
Since the (molar ratio)] is the use of a catalyst is 0.0037 to 7.0, after steaming, the reaction temperature is 350 ° C.
Even in this case, it can be seen that the decrease in the catalytic activity is not as large as that of the catalyst of the comparative example. Also, when the reaction temperature rises to 400 ° C,
It can be seen that the catalyst activity is remarkably improved as compared with the case of 350 ° C. Therefore, the catalyst according to this example has high catalytic activity and excellent durability even after long-time use.

On the other hand, Table 6 shows that the catalysts of Comparative Examples 1 and 2 only support the copper component,
Since the phosphorous component is not supported, the initial activity is close to that of the example, but the activity after the steaming treatment is as follows.
It can be seen that at 0 ° C., the temperature was significantly lower than that of the example. Also, it can be seen that even when the reaction temperature is increased to 400 ° C., the catalytic activity is not improved as much as in the example.

According to the catalysts according to Comparative Examples 3 and 4, the catalyst support containing a pentasil-type crystalline aluminosilicate is configured to support a copper component and a phosphorus component.
Since a catalyst having a phosphorus content exceeding 5.0 wt% in terms of P ₂ O ₅ and a P / Cu (molar ratio) exceeding 7.0 was used, the initial activity was as high as that of Comparative Examples 1 and 2. The activity after the steaming treatment is lower than that of the catalyst supporting only the copper component, and is equal to or less than that of the catalyst according to Comparative Examples 1 and 2 at any of the reaction temperatures of 350 ° C. and 400 ° C., and the improvement is improved. It turns out that it is not seen. Therefore, the catalyst according to the comparative example has a remarkable decrease in catalytic activity due to use, and is inferior in durability.

[0046]

According to the exhaust gas purifying catalyst of the present invention, nitrogen oxides can be purified into harmless gas with high efficiency even when oxygen in the exhaust gas is high in concentration, and the catalytic activity is high even at low temperatures. It is durable and has a long life.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Hayasaka 1280 Kamiizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd. (72) Inventor Hiroshi Akama 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. 56) References JP-A-6-277522 (JP, A) JP-A-4-4238 (JP, A) JP-A-4-4045 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) B01J 21/00-37/36 B01D 53/86

Claims (8)

(57) [Claims] 1. A catalyst for reducing and removing nitrogen oxides (NO _X ) in an exhaust gas in an oxidizing atmosphere in the presence of a hydrocarbon, wherein the catalyst support containing a pentasil-type crystalline aluminosilicate comprises a copper component and is constituted by carrying a phosphorus component, the supported amount of the phosphorus component is 0.1 to 5.0% by terms _of P ₂ O _5, before
Exhaust gas purifying catalyst loading of kidou component and wherein this <br/> and a 0.8～30.0Wt% in terms of CuO. 2. An oxidizing atmosphere for removing nitrogen oxides (NOx) in exhaust gas.
It is a catalyst that reduces and removes in the presence of hydrocarbons in an atmosphere.
Comprising a pentasil-type crystalline aluminosilicate
The carrier is configured to support a copper component and a phosphorus component,
When the ratio of phosphorus to copper [P / Cu (molar ratio)] is 0.0037 to 7.0
An exhaust gas purifying catalyst, comprising: Crystalline aluminosilicates according to claim 3, wherein the pentasil type, the SiO ₂ / Al ₂ O ₃ (molar ratio) of claim 1 or 2, wherein the exhaust gas purifying catalyst is characterized in that 10 or more. 4. The pentasil-type crystalline aluminosilicate has an MFI structure.
An exhaust gas purifying catalyst according to any one of claims 1 to 3 . 5. The crystalline aluminosilicate of the pentasil type, according to any one of claims 1 to 4, characterized in that in a powder X-ray diffraction with the lattice spacing shown in Table 1 (d) Exhaust gas purification catalyst. [Table 1] 6. The crystalline aluminosilicate of the pentasil type, exhaust gas-purifying catalyst according to any one of claims 1 to 5, characterized in that is synthesized mordenite as the seed crystal. 7. THC concentration / NO in an oxidizing atmosphere _X Concentration
Exhaust gas in the presence of 0.5 to 200 hydrocarbons.
The exhaust gas is brought into contact with the catalyst according to any one of
Exhaust gas characterized by reducing and removing nitrogen oxides in air
Purification method. 8. A reaction temperature of 200 to 800 ° C. and a THC concentration /
NO _X Nitrogen oxidation in exhaust gas in the presence of hydrocarbons with concentrations of 1-100
8. The exhaust gas according to claim 7, wherein the material is reduced and removed.
Cleaning method.