JPH06142456A - Method for removing nox in exhaust gas - Google Patents

Abstract

PURPOSE:To improve the durability and life of a specific catalyst by using the specific catalyst and using DE lubricating oil having a specific ratio or below of the contents of an alkaline metal and alkaline earth metal and low- sulfurized DE fuel oil. CONSTITUTION:NOx is removed by bringing at least one of the catalysts among metal oxides consisting of alumina, titania, zirconia and zinc oxide or proton type zeolite or the catalysts formed by incorporating elements belonging to group VIIB, VIII, IB of periodic table therein or the catalysts formed by incorporating the perovskite type crystal structures of cobalt lanthanum trioxide and iron lanthanum trioxide therein or metallosilicate contg. B, P, Ga, Ti, Fe, Cu, Zn, Mo, La in zeolite aggregate lattice into contact with DE exhaust gases. The DE lubricating oil contg. <=0.1wt.% >=1 kinds among the alkaline metals and alkaline earth metals is used and the DE fuel oil contg. <=0.2wt.% sulfur content is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing nitrogen oxides in exhaust gas of a diesel engine by using a specific catalyst, and more particularly to the content of alkali metal or alkaline earth metal in diesel engine lubricating oil. The present invention relates to a method for removing nitrogen oxides in diesel exhaust gas by specifying the sulfur content in diesel engine fuel oil to improve the durability and life of the specified catalyst.

[0002]

2. Description of the Related Art Nitrogen oxides in various exhaust gases (hereinafter referred to as
Since "NOx") is harmful to the human body and may cause photochemical smog and acid rain, it is desired to develop an effective removal means.

Conventionally, as a method of removing NOx, several methods of reducing it by using a catalyst have already been put into practical use. For example, (a) a three-way catalyst method in a gasoline automobile, and (b) a selective catalytic reduction method using ammonia for exhaust gas from a large facility emission source such as a boiler. Also, as another proposed method,
(C) As a method for removing NOx in exhaust gas using hydrocarbons, a method of contacting with a gas containing NOx in the presence of hydrocarbons using a metal oxide such as alumina supporting a metal such as copper as a catalyst (Japanese Patent Laid-Open No. Sho 63-63). (Gazette of No. 100919)
There is.

[0004]

The method (a) above is
Hydrocarbon components and carbon monoxide contained in automobile flue gas are made into water and carbon dioxide by a catalyst, and at the same time NOx
Is reduced to nitrogen, but combustion is adjusted so that the amount of oxygen contained in NOx and the amount of oxygen required to oxidize hydrocarbon components and carbon monoxide are stoichiometrically equal. There is a serious problem that it cannot be applied in principle, especially in a system in which excess oxygen exists such as a diesel engine.

Further, in the method (b), since ammonia, which is extremely toxic and must be handled as a high-pressure gas in many cases, is used, it is not easy to handle.
Moreover, the equipment becomes huge, and it is technically extremely difficult to apply it to a small-sized exhaust gas source, especially a mobile source, and it is not economical.

On the other hand, the method (c) is mainly applied to gasoline automobiles, and is difficult to apply under exhaust gas conditions of a diesel engine due to catalyst poisoning by sulfur oxides. N in
It is not suitable for removing Ox and has not yet been put to practical use.

The inventors of the present invention have made extensive studies to solve various problems existing in (a) to (c) above, and as a result,
It was found that proton type zeolite and metal oxides such as alumina, titania and zirconia have high catalytic performance for reduction and removal of NOx by hydrocarbons in an oxygen excess atmosphere, and it has already been proposed (Japanese Patent Laid-Open No. 4-9082).
No. 5, Japanese Patent Application Laid-Open No. 4-118030, etc.-hereinafter, these are referred to as "previous proposals").

By the way, the catalysts represented by these prior proposals exhibit epoch-making performance and are relatively stable in terms of the ability to reduce and remove NOx in the exhaust gas of a diesel engine under an oxygen excess atmosphere. Although the performance is maintained, it is said that the deterioration of the activity due to the deterioration of the catalyst cannot be avoided in the evaluation of the actual exhaust gas for an extremely long period.

As one of the causes of the decrease in the activity of this catalyst,
Since a diesel engine fuel containing sulfur oxides is used, it is presumed that sulfur oxides are discharged as one of the components in the exhaust gas, which affects the catalytic performance. However, depending on the catalyst species, it has been reported that sulfur oxides accelerate the reaction (Chemistry).
Letters, p. 2179, 1991), the effect of sulfur oxides on the catalyst is not clarified.

In consideration of the above points, the present invention provides a method for reducing and removing NOx by contacting a diesel engine exhaust gas with a specific catalyst in the presence of hydrocarbons or oxygen-containing compounds. An object of the present invention is to propose a method capable of performing stable NOx removal for a long period of time without lowering the removal activity, in other words, improving the durability and life of the specific catalyst.

[0011]

Means and Actions for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the diesel engine lubricating oil contains alkali metal or alkaline earth metal in a specific amount or less. It has been found that the durability and life of a specific type of catalyst can be greatly improved by using those which are not preferably contained or by using a low-sulfur diesel engine fuel oil together with the diesel engine lubricating oil. The present invention has been completed.

That is, the present invention provides (1) a metal oxide or a composite oxide comprising at least one of alumina, titania, zirconia and zinc oxide, (2) a proton type zeolite, (3) a metal oxide of (1). Compound or complex oxide, or the proton type zeolite of (2), to the periodic table VIIB,
VIII, containing one or more elements belonging to Group IB, (4) zeolite, or metal oxide or composite oxide of (1), cobalt lanthanum trioxide, lanthanum trioxide, strontium cobalt trioxide Containing at least one of the perovskite-type crystal structures of (5) B, P, Ga, Ti,
A method for removing nitrogen oxides by contacting at least one catalyst selected from the group consisting of metallosilicates containing one or more of Fe, Cu, Zn, Mo, and La with diesel engine exhaust gas containing nitrogen oxides. And (i) the content of at least one of alkali metal and alkaline earth metal is 0.1 w
Use a diesel engine lubricating oil of t% or less, or (ii) use a diesel engine lubricating oil containing 0.1 wt% or less of at least one kind of alkali metal or alkaline earth metal and sulfur content Is 0.2 wt%
The summary is a method for removing nitrogen oxides in exhaust gas, which is characterized by using the following diesel engine fuel oil.

In the present invention, the fact that the content of at least one alkali metal or alkaline earth metal is 0.1 wt% or less is used as the diesel engine lubricating oil is based on the following facts and consideration. During operation of the diesel engine, a part of the diesel engine lubricating oil scatters and mixes into the exhaust gas, and accumulates in the catalyst layer as ash containing alkali metal or alkaline earth metal as a main component. It is considered that the accumulated ash not only deteriorates the catalyst performance but also promotes the adsorption of the sulfur oxides coexisting in the exhaust gas onto the catalyst surface, which is the main cause of deterioration of the catalyst. On the other hand, if this ash does not exist, or if the content of alkali metal or alkaline earth metal is 0.1 wt% or less even if it exists, the adsorption of sulfur oxide is not promoted on the catalyst surface,
It is considered that the durability and life of the catalyst are greatly improved.

In the present invention, the content of at least one of the above-mentioned alkali metals and alkaline earth metals is 0.1 wt.
The use of diesel engine lubricating oil of less than 1% and the use of low-sulfurized diesel engine fuel oil is based on the following facts and considerations. When sulfur oxides coexist in the exhaust gas of a diesel engine, the degree of deterioration of a specific catalyst depends on the concentration of the sulfur oxides (derived from the sulfur compounds in the fuel) coexisting in the exhaust gas and the lubricating oil at this time. It depends on the content of alkali metal or alkaline earth metal in the metal. Explaining the phenomenon in detail, the sulfur oxides in the exhaust gas deteriorate the catalyst and cause NOx.
The removal performance is reduced to a certain range (steady state). The concentration of sulfur oxides at this time has an influence on the rate of decrease in NOx removal performance, but is largely unrelated to the performance itself at the time when the steady state is reached. In other words, even if the concentration of sulfur oxide is about 10 ppm,
Even at about 100 ppm, there is almost no difference in catalyst performance at the time when the steady state is reached. However, the content of alkali metal or alkaline earth metal in the lubricating oil makes a great difference in the NOx removal performance in this steady state. That is, when the content of alkali metal or alkaline earth metal is large, a large amount of ash is scattered in the exhaust gas and a large amount is accumulated in the catalyst layer. As a result, the adsorption of sulfur oxides on the catalyst is promoted, and the catalyst performance when the steady state is reached is significantly reduced. On the other hand, when the content of the alkali metal or the alkaline earth metal is small, the above-mentioned phenomenon does not occur, or even if it does occur, the catalyst performance in the steady state can be maintained. On the other hand, they have also found the fact that when ash is present on the catalyst, the influence of sulfur oxides in the exhaust gas on the catalyst performance also changes. That is, the concentration of sulfur oxides is not only related to the rate of decrease in catalyst performance, but also affects the NOx removal performance itself when ash is present on the catalyst. Although the details are unknown, it is considered that the behavior such as the above-described adsorption of sulfur oxide is involved. From the above, the present invention relates to the NOx removal performance of a specific catalyst,
The result of newly finding the relationship between the sulfur oxide and the alkali metal or the alkali metal on the catalyst has been completed, and it can be said to be extremely epoch-making in the technical field.

The details of the present invention will be described below together with the operation. In the present invention, the following five kinds of catalysts can be used. (1) 1 of alumina, titania, zirconia, zinc oxide
Metal oxides consisting of more than one species, or 2 of these
(2) Proton-type zeolite; (3) Metal oxide or complex oxide of (1), or Proton-type zeolite of (2), Periodic Table VIIB,
VIII, containing one or more elements belonging to Group IB; (4) Zeolite, or metal oxide or composite oxide of (1), cobalt lanthanum trioxide, lanthanum iron trioxide, cobalt strontium trioxide Containing at least one of the perovskite-type crystal structure of (5) B, P, Ga, Ti,
A metallosilicate containing at least one of Fe, Cu, Zn, Mo and La;

All of these five types of catalysts have been conventionally known as NOx reduction and removal catalysts (for example, in addition to the above-mentioned prior proposals, Japanese Examined Patent Publication Nos. 3-217218 and 3-13).
5437, Japanese Patent Application Nos. 4-20304 and 3-41.
359, etc.), and thus can be produced by these conventionally known methods. In addition, these five types of catalysts are conventionally used in the form of powder, granules, pellets,
It can be used in a honeycomb shape or any other shape, and its shape and structure are not particularly limited. Further, when the catalyst is used after being molded, a binder that is usually used at the time of molding, that is, silica sol, polyvinyl alcohol, or the like, or a lubricant, that is, graphite, wax, fatty acid salt, carbon wax, or the like can be used.

In order to improve the durability and life of the above-mentioned five kinds of catalysts, in the present invention, the content of at least one kind of alkali metal and alkaline earth metal in the diesel engine lubricating oil is about 0.1 wt% or less. Use one. That is,
In the present invention, instead of a diesel engine lubricating oil to which a metal detergent that has been widely used in the past has been added, a metal detergent-free type, or an alkali metal, or an alkaline earth metal content of 1 or more A so-called ashless type diesel engine lubricating oil having a small amount of about 0.1 wt% or less can be used as a typical one.

Conventionally used diesel engine lubricating oils are prepared by adding various additives to paraffinic mineral oils. An example of this additive is, for example, a bis type succinimide as an ashless type dispersant,
As a metal type detergent, an alkaline earth metal sulfonate or an alkaline earth metal phenate (the ashless type dispersant and the metal type detergent are collectively referred to as a detergent dispersant),
Zinc dialkyldithiophosphate (Zn-
DTP), and defoaming agent such as dimethyl silicone.

The diesel engine lubricating oil used in the present invention is limited to the above additives to which no metallic detergent has been added at all or whose addition amount is extremely small. As described above, the extremely small amount of addition is an amount in which the content of one or more kinds of alkali metals and alkaline earth metals in the diesel engine lubricating oil is about 0.1 wt% or less, and the lower limit is particularly No limit, optimally 0w
The amount is t%.

In the present invention, the above alkali metal,
The content of one or more alkaline earth metals is about 0.1 wt%
Using the following diesel engine lubricants alone,
It is possible to improve the durability and life of the above-mentioned five types of catalysts, but in order to further improve the durability and life, in addition to this diesel engine lubricating oil, diesel with a sulfur content of about 0.2 wt% or less is used. It is desirable to use engine fuel oil.

As the diesel engine fuel oil,
As described above, the sulfur content is about 0.2 wt% or less,
Preferably about 0.06 wt% or less, optimally almost 0
Up to, low-sulfur heavy oil, light oil, kerosene, etc. can be mentioned. The density, viscosity, distillation range, aromatic content, etc. of these diesel engine fuel oils are not particularly limited as long as they have general properties.

Examples of the diesel engine exhaust gas to be treated in the present invention include NOx-containing exhaust gas exhausted from diesel automobiles, stationary diesel engines, and various other diesel engines. You may have.

The removal of NOx from these exhaust gases is carried out by contacting the exhaust gases with the above-mentioned five catalysts in the presence of hydrocarbons or oxygen-containing compounds in an oxidizing atmosphere using the above-mentioned five catalysts. By.

Here, the oxidizing atmosphere means carbon monoxide, hydrogen and hydrocarbons contained in the exhaust gas, and a reducing substance of hydrocarbons or oxygen-containing compounds added as necessary in the present invention, An atmosphere that contains an excess of oxygen in excess of the amount of oxygen required to completely oxidize and convert it into water and carbon dioxide.For example, in the case of exhaust gas emitted from an internal combustion engine of a diesel automobile, it is empty. The atmosphere has a large fuel ratio (lean region), and the excess oxidation rate is usually about 20% to 200%. In this oxidizing atmosphere, the above-mentioned five kinds of catalysts preferentially promote the reaction between the hydrocarbons or the oxygen-containing compound and NOx over the reaction between the hydrocarbons or the oxygen-containing compound and oxygen.
x is reduced and removed.

The above-mentioned five kinds of catalysts work well in an oxidizing atmosphere, but the reducing decomposition activity against NOx decreases in a reducing atmosphere, so it is preferable to carry out the reaction in an oxidizing atmosphere.

As the reducing substance for reducing and decomposing hydrocarbons or oxygen-containing compounds, that is, NOx, to be present, particulates which are incomplete combustion products such as hydrocarbons and fuel remaining in the exhaust gas may be used. If the amount is insufficient to accelerate the above reaction, it is necessary to add hydrocarbons or oxygen-containing compounds from the outside.

The amount of hydrocarbons or oxygen-containing compounds to be present is not particularly limited, and when the required NOx removal rate is low, for example, it may be smaller than the theoretical amount required for reductive decomposition of NOx. . However, since the reduction reaction proceeds more when the amount exceeds the required theoretical amount, it is generally preferable to add the amount excessively. Usually, the amount of hydrocarbons or oxygenates is about 20% to 2000% excess of the stoichiometric amount required for reductive decomposition of NOx, preferably about 30% to 15%.
Present in a 00% excess.

Here, the necessary theoretical amount of hydrocarbons or oxygen-containing compounds means that oxygen exists in the reaction system.
In the present invention, it is defined as hydrocarbons or oxygen-containing compounds necessary for reductive decomposition of nitrogen dioxide (NO2). For example, 1000 ppm of nitric oxide (NO) using propane as the hydrocarbons. The theoretical amount of propane when reductively decomposing benzene in the presence of oxygen is 200 ppm. Generally, depending on the amount of NOx in the exhaust gas, the amount of hydrocarbons or oxygen-containing compounds to be present is about 50 to 10,000 ppm in terms of methane.

By the above-mentioned five kinds of catalysts in the present invention, N
As a reducing substance for reducing Ox, any substance is effective as long as it is a carbon-containing substance such as a flammable organic compound. However, from the practical viewpoint, compounds such as nitrogen, sulfur and halogen are priced and expensive. There are many problems such as subsequent generation of organic substances or damage to the catalyst.In addition, solid substances such as carbon black and petroleum are generally unfavorable from the viewpoints of supply to the catalyst layer and contact with the catalyst, and hydrocarbons. Alternatively, an oxygen-containing compound is preferable. From the viewpoint of supply to the catalyst layer, a gas or liquid is particularly preferable, and from the viewpoint of reaction, those which vaporize at the reaction temperature are particularly preferable.

Specific examples of the hydrocarbons in the present invention include gaseous ones such as methane, ethane, ethylene,
Hydrocarbon gas such as propane, propylene, butane, butylene, etc. as liquid form, pentane, hexane,
Heptane, octane, octene, benzene, toluene,
Examples include single hydrocarbons such as xylene, and mineral oil-based hydrocarbon oils such as gasoline, kerosene, light oil, and heavy oil.

The oxygen-containing compound means an oxygen-containing organic compound and includes alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol and octyl alcohol, ethers such as dimethyl ether, ethyl ether and propyl ether, methyl acetate and acetic acid. Examples thereof include esters such as ethyl and fats and oils, and oxygen-containing organic compounds such as ketones such as acetone and methyl ethyl ketone.

These hydrocarbons or oxygen-containing compounds may be used alone or in combination of two or more.

It should be noted that unburned or incompletely burned products such as fuel existing in the exhaust gas, that is, hydrocarbons and particulates are also effective as reducing agents, and these are also hydrocarbons and oxygen-containing substances in the present invention. Included in compounds. From this, the above five kinds of catalysts in the present invention are
It can be said that it also has a function as a catalyst for reducing / removing hydrocarbons, oxygen-containing compounds, particulates, etc. in exhaust gas.

The reaction is carried out by preparing a reactor in which at least one of the above-mentioned five catalysts is arranged, allowing hydrocarbons or oxygen-containing compounds to exist in an oxidizing atmosphere, and passing the diesel engine exhaust gas therethrough. To do. The reaction temperature at this time varies depending on the type of the catalyst and the hydrocarbons or oxygen-containing compounds, but a temperature close to the temperature of the exhaust gas is preferable because heating equipment for the exhaust gas is not required, and generally, about 100 to 800 ° C. Particularly, the range of about 200 to 600 ° C. is preferable. The reaction pressure is not particularly limited, and the reaction proceeds under pressure or reduced pressure, but it is convenient to introduce the exhaust gas into the catalyst layer at a normal exhaust pressure to proceed the reaction. The space velocity is determined by the type of catalyst, other reaction conditions, the required NOx removal rate, etc. and cannot be specified unconditionally, but is generally about 500 to 100,000 Hr ⁻¹ , preferably about 1000.
The range is up to 70,000 Hr ⁻¹ . In the present invention, when treating the exhaust gas from the internal combustion engine, the catalyst is preferably arranged downstream of the exhaust manifold.

[0035]

【Example】

Example 1 (Preparation of Ashless Type Diesel Engine Lubricating Oil) A bis type succinimide, zinc dialkyldithiophosphate and dimethyl silicon are added to paraffinic mineral oil to add a metal type detergent-free diesel engine. A lubricating oil was prepared. The contents of alkali metals (Li, Na, K) and alkaline earth metals (Mg, Ca, Sr, Ba) of this diesel engine lubricating oil were all 0.1 wt% or less.

(Catalyst used) Alumina (Neobead GB, manufactured by Mizusawa Chemical Co., Ltd.) was used as a catalyst. The surface area of this catalyst was about 190 m ² · g ⁻¹ . This catalyst was subjected to reaction after being calcined at 600 ° C. for 3 hours in an air stream.

(Used diesel engine fuel oil) As a diesel engine fuel oil, the sulfur content is 0.35w
t%, density 0.8440 kg / l (15 ° C), viscosity 3.11 cSt (37.8 ° C), aromatic content 34.5v
Light oil of ol% (FIA) was used.

(NOx removal experiment) A diesel engine lubricating oil prepared as described above was used as a water-cooled 4-cycle in-line 4-cylinder diesel engine (direct injection type, 27
71CC) and the exhaust gas when the diesel engine fuel oil was used for operation was subjected to the experiment. The engine operating conditions were 1300 rpm and a load of 10 kg · m. The average composition of the exhaust gas at this time was about 500 NOx.
ppm, CO about 350 ppm, CO ₂ about 4%, THC
(Total Hydro Carbon) About 500p
pm, SOx about 80 ppm, and O ₂ about 16%. A part of this exhaust gas was split, and after removing particulates with a SUS filter, it was introduced into a catalyst layer filled with the above-mentioned alumina catalyst to conduct an experiment. The amount of methanol introduced as a reducing agent was 2000 ppm. As a general rule, the space velocity is 10,000 Hr ⁻¹ and the reaction temperature is 40.
It was set to 0 ° C. Evaluation of catalytic performance, the front and rear of the exhaust gas in the catalyst layer, in total exhaust gas analyzer, NOx, CO, _CO 2, T
It was measured by measuring HC, SOx and the like. In this way
The results of the NOx removal experiment conducted for about 250 hours are shown in Table 1.

[0039]

[Table 1]

As is clear from Table 1, 0.35 wt%
Even if it is an exhaust gas containing about 80 ppm of sulfur oxides as the fuel oil and the diesel oil containing the sulfur content of the above is used when the lubricating oil with the content of the alkali metal or the alkaline earth metal as described above is used. It can be seen that no significant decrease in the NOx removal performance of the alumina catalyst is observed and the durability is improved.

Example 2 (Preparation of Co-Supported Alumina Catalyst) 200 g of alumina (Neobead GB manufactured by Mizusawa Chemical Co., Ltd.) was impregnated with an aqueous solution of 16.95 g of cobalt acetate tetrahydrate dissolved in 110 g of water for 3 hours. I left it. This is dried at 100 ° C for a whole day and night, then fired at 600 ° C for 3 hours in an air stream to obtain 2 wt.
% Co-supported alumina catalyst was obtained. The surface area of this catalyst is
It was about 185 m ² · g ⁻¹ .

(NOx removal experiment) A NOx removal experiment was conducted for about 250 hours in the same manner as in Example 1 except that the 2 wt% Co-supported alumina catalyst prepared as described above was used. It was shown to.

[0043]

[Table 2]

As is clear from Table 2, even in the Co-supported alumina catalyst, when the lubricating oil having the alkali metal and alkaline earth metal contents as in Example 1 was used, the sulfur oxidation was about 80 ppm. It can be seen that even with exhaust gas containing substances, the NOx removal performance of the Co-supported alumina catalyst is not significantly reduced, and the durability is improved.

Example 3 (Preparation of pentasil-type zeolite) Water 16 g was added to an aqueous solution prepared by dissolving 957 g of sodium silicate in 1200 g of water.
3 g of an aqueous solution prepared by dissolving 41 g of aluminum sulfate, 80 g of concentrated sulfuric acid, and 360 g of sodium chloride in 00 g were prepared.
The mixture was gradually added with stirring at 0 minutes and mixed. Furthermore, 120 g of tetrapropylammonium bromide was added to adjust the pH to 10
Was prepared. Charge this mixture into an autoclave, and
When stirred at 65 ° C. for 16 hours, a crystalline compound was produced. The product was separated, washed with water and dried to obtain a pentasil-type ZSM-5 zeolite with SiO ₂ / Al ₂ O ₃ = 62.7 as a base material.

(Preparation of Proton-Type Pentacyl-Type Zeolite) 500 ml of 1 mol / l ammonium nitrate solution
2 g of the above-mentioned pentasil-type zeolite was added to the above, and the mixture was refluxed with stirring for 24 hours and then centrifuged. This was washed 5 times with pure water, dried at 110 ° C. overnight, and air-baked at 500 ° C. for 3 hours to prepare a proton type ZSM-5 zeolite which is a proton type pentasil type zeolite.

(Preparation of proton type ZSM-5 washcoat catalyst) 1 g of silica sol (trade name "Snowtex 0" 20 wt% SiO ₂ manufactured by Nissan Chemical Industries, Ltd.) was added to 100 g of water.
0 g, and then the above-mentioned proton type ZSM-5 was mixed with 20 g.
g and mixed well. This suspension is cordierite honeycomb (product name "Monolith 7R" manufactured by Nippon Denso Co., Ltd. 50 m
mφ × 80 mm, 200 mesh / inch ² ), and dried at 110 ° C. for 1 hour. By repeating this operation three times, a honeycomb catalyst wash-coated with the proton type ZSM-5 was obtained. In addition, proton type ZS
The coat amount of M-5 was about 14 g.

(NOx removal experiment) A NOx removal experiment was performed in the same manner as in Example 1 except that the proton type ZSM-5 honeycomb prepared as described above was used as a catalyst.
The results obtained after 50 hours are shown in Table 3.

[0049]

[Table 3]

As is clear from Table 3, the proton type ZS
Also in the M-5 zeolite catalyst, when the lubricating oil having the alkali metal and alkaline earth metal contents as in Example 1 is used, even if the exhaust gas contains about 80 ppm of sulfur oxides, It can be seen that the NOx removal performance of the proton type ZSM-5 zeolite does not change significantly and the durability is improved.

Example 4 (Preparation of copper-supported zeolite) 0.05 m of commercially available copper nitrate
An ol / l aqueous solution was prepared, and the base material ZSM-5 prepared in the same manner as in Example 3 was added thereto, and the mixture was stirred at room temperature for 24 hours, refluxed, and then centrifuged. This operation was repeated 3 times, and finally, washed with pure water 5 times and dried overnight at 110 ° C. to prepare a copper-supported zeolite. The obtained copper-supported zeolite was wash-coated on the honeycomb in the same manner as in Example 3 to prepare a copper-supported ZSM-5 honeycomb catalyst. The coated amount of copper-supported ZSM-5 was about 17 g.

(NOx removal experiment) Similar to Example 1 except that the copper-supported ZSM-5 honeycomb prepared as described above was used as a catalyst and about 1000 ppm of propylene was used as the reducing agent instead of methanol. Table 4 shows the results of the NOx removal experiment conducted for about 250 hours.

[0053]

[Table 4]

As is clear from Table 4, ZSM-supported on copper
In the case of using the lubricating oil having the content of alkali metal or alkaline earth metal as in Example 1, the 5 zeolite catalyst depends on the elapsed time even if the exhaust gas contains about 80 ppm of sulfur oxide. It can be seen that the catalyst activity is almost decreased and the durability is improved.

Comparative Example 1 (Preparation of Diesel Engine Lubricating Oil Containing Ash) Parasitic mineral oil was mixed with bis type succinimide and Ca.
A metal detergent-added type diesel engine lubricating oil was prepared by adding sulfonate, zinc dialkyldithiophosphate and dimethyl silicone. No alkali metal was detected in this diesel engine lubricating oil, but 0.4 wt% of Ca was contained as an alkaline earth metal.

(NOx removal experiment) Table 5 shows the results of the NOx removal experiment carried out for about 250 hours in the same manner as in Example 1 except that the diesel engine lubricating oil prepared as described above was used. It was

[0057]

[Table 5]

As is clear from Table 5, when the ash-containing lubricating oil was used, a remarkable initial performance deterioration was observed, and the NOx removal rate at the time of stability was higher than that when the ashless type lubricating oil was used. It turns out that it becomes low.

Examples 5 to 8 (Diesel engine fuel oil used) As diesel fuel oil, sulfur content 0.04 wt%, density 0.8075 k
g / 1 (15 ° C.), viscosity 2.23 cSt (37.8)
C.), a low-sulfurized gas oil having an aromatic content of 16.0 vol% (FIA) was used.

(NOx removal experiment) The NOx removal rate was examined in the same manner as in Examples 1 to 4 except that the above-mentioned low-sulfurized light oil was used as the diesel engine fuel oil. The results are shown in Table 6 as Examples 5-8.

[0061]

[Table 6]

As is clear from Table 6, alkali metal,
When the diesel engine lubricating oil having the alkaline earth metal content as in Example 1 is used and the low sulfur light oil having the sulfur content as described above is used as the diesel engine fuel oil, It can be seen that the NOx removal performance of each catalyst does not change more than in 1 to 4, and the durability of each catalyst is improved.

Further, in order to make it easier to understand the change in the NOx removal performance due to the difference between the fuel and the lubricating oil, the results obtained in the above Example 1, Comparative Example 1 and Example 5 (Table 1,
Example 5) of Tables 5 and 6 is graphed and shown in FIG.

[0064]

As described in detail above, according to the present invention,
The content of alkali metal or alkaline earth metal in the lubricating oil, which is considered to act to promote the adsorption of sulfur oxides in the exhaust gas to the catalyst, and which is derived from the components of the diesel engine lubricating oil, is the specified amount or less. By this, the adsorption / accumulation of sulfur oxides on the catalyst can be effectively suppressed. As a result, the NOx removing activity of the catalyst of the specific type can be favorably maintained for a long time, and NOx can be effectively removed.

Further, in the present invention, when a low-sulfurized diesel engine fuel oil is used together with the above diesel engine lubricating oil, the adsorption and accumulation of the above sulfur oxide on the catalyst of a specific species is further promoted. Therefore, the NOx removal activity of the specific type of catalyst can be better maintained, and NOx can be removed more effectively.

[Brief description of drawings]

FIG. 1 is a graph showing the results obtained in an example of the present invention, showing a change in NOx removal performance due to a difference between a fuel used and a lubricating oil.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location B01J 29/06 ZAB A 9343-4G 29/34 ZAB A 9343-4G (71) Applicant 000001144 Industrial technology Director 1-3-1, Kasumigaseki, Chiyoda-ku, Tokyo (74) One of the above-mentioned sub-agent, Chika Kubota (2 outside) Attorney Mitsunori Tabata 1134-2 (72) Gongendo, Satte City, Saitama Prefecture Inventor Hiroshi Tsuchida 2-24-6-408 Kyomachi, Kawasaki-ku, Kanagawa Prefecture 2-24-6-408 (72) Katsumi Miyamoto 1-11-17 Sagimiya, Sagimiya-cho, Kitakatsushika-gun, Saitama Prefecture Inventor Akihiro Kitazume, Sugito-cho, Kitakatsuka-gun, Saitama Prefecture 2-15-36 Sugito (72) Masaaki Kawatsuki, Masaaki Kawatsuki 2856-1, Osawa, Koshigaya, Saitama Century Condominium No. 103 Saga (72) Inventor Tadao Nakatsuji 5-chome, Enoshimacho, Sakai, Osaka Central Institute of Chemical Industry Co., Ltd. (72) Hiromitsu Shimizu 5-1, Ebishima-cho, Sakai City, Osaka Prefecture Central Laboratory, Sakai Chemical Co., Ltd. (72) Ritsu Yasukawa 5-1-1, Ebisu-cho, Sakai City, Osaka Prefecture Sakai Chemical Industry Co., Ltd. Central Research Institute (72) Inventor Hideaki Hamada 1-1 Higashi, Tsukuba, Ibaraki Prefecture Industrial Technology Institute, Institute of Chemical Technology (72) Inventor Takehiko Ito 1-1, East Tsukuba City, Ibaraki Institute of Industrial Technology In the laboratory

Claims (1)

[Claims] 1. A metal oxide or composite oxide comprising at least one of alumina, titania, zirconia and zinc oxide, (2) a proton type zeolite, (3) a metal oxide or composite oxide of (1). Or the proton type zeolite of (2), the periodic table VIIB,
VIII, containing one or more elements belonging to Group IB, (4) zeolite, or metal oxide or composite oxide of (1), cobalt lanthanum trioxide, lanthanum trioxide, strontium cobalt trioxide Containing at least one of the perovskite-type crystal structures of (5) B, P, Ga, Ti,
A method for removing nitrogen oxides by contacting at least one catalyst selected from the group consisting of metallosilicates containing one or more of Fe, Cu, Zn, Mo, and La with diesel engine exhaust gas containing nitrogen oxides. And (i) the content of at least one of alkali metal and alkaline earth metal is 0.1 w
Use a diesel engine lubricating oil of t% or less, or (ii) use a diesel engine lubricating oil containing 0.1 wt% or less of at least one kind of alkali metal or alkaline earth metal and sulfur content Is 0.2 wt%
A method for removing nitrogen oxides in exhaust gas, comprising using the following diesel engine fuel oil.