JPH09287435A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine wherein methanol is produced from carbon dioxide and water in exhaust gas from the engine using a photo-catalyzer and nitrogen oxide in the exhaust gas is reduced using the produced methanol as a reducing agent. SOLUTION: On a pass 32 for exhaust gas from an internal combustion engine 30, a photo-catalyzer 34 and a reducing catalyzer 36 are disposed in turn from the upper stream. Using carbon dioxide and water in the exhaust gas, methanol is produced, thereafter this methanol is applied to a reducing catalyzer 36 as a reducing agent, allowing nitrogen oxide in the exhaust gas to rarefy.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to exhaust gas from an internal combustion engine.
Regarding purification device, carbon dioxide in exhaust gas from the internal combustion engine
Elementary (CO_Two) And water (H_TwoO) and a photocatalyst
Knoll (CH_ThreeOH) is generated, and the
Nitrogen oxides (NO) using tanol as a reducing agent _X)
The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine.

[0002]

As it is known, currently diesel engine, and directed to removal of exhaust gas or the like of a lean burn engine such as a gasoline engine of lean-burn, oxygen and nitrogen oxides in the exhaust gas containing excess (NO _X) Various catalysts have been proposed, but all of them have problems in the removal rate of nitrogen oxides and durability, and it is considered that it will take some time before they are put into practical use.

[0003] Further, above the excess oxygen exhaust gas containing, it can not be used a three-way catalyst shows purification performance only delicate balance of oxygen and NO _X and HC. On the other hand, there is a catalyst capable of removing some of the above nitrogen oxides by injecting light oil into the exhaust gas, but a problem with the catalyst to which this light oil is added is that the purification rate is low.

The above light oil is composed of various types of hydrocarbons, but few of them effectively act as the most effective hydrocarbons, and there is no catalyst for converting them into effective reducing agents. Further, the catalyst to which light oil is added has a drawback that fuel efficiency is reduced because the light oil is injected to the catalyst.

In the exhaust gas containing the above-mentioned excess oxygen,
Even if a reducing agent is added, the added reducing agent will be directly oxidized.
NO or NO_TwoCannot be reduced
Nitrogen oxides are not reduced. (Reduction of nitrogen oxides) NO_X+ HC → N_Two+ H_TwoO + CO_X (Under oxygen excess) HC + O_Two→ H_TwoO + CO_X  Also, means for converting HC in the exhaust gas into an effective reducing agent
Is not established, and if a certain amount of HC is added,
Since it can be activated a little, the nitrogen oxides can be purified to some extent.
However, the above HC (reducing agent) is added.
A tank for storing the HC for
It is necessary to replace the fuel and replenish the HC (reducing agent).
There is a point, and still effective HC (reducing agent) is applied to the above engine.
It has not been installed yet.

Under the current circumstances as described above, a method for reducing and removing nitrogen oxides in exhaust gas containing excess oxygen such as exhaust gas of lean burn engines such as diesel engines has been proposed. 6-19813
No. 2 publication is available. The technique described in the publication reduces the nitrogen oxides by contacting an alumina catalyst containing tin and an exhaust gas containing nitrogen oxides in the presence of methanol in an oxidizing atmosphere containing excess oxygen. This is to remove the methanol itself, which is stored and held in a special tank.

Further, as another conventional example, a proposal using a photocatalyst as an exhaust gas purifying apparatus for an automobile has been proposed, for example, Japanese Utility Model Laid-Open No. 4-76924. The technology described in the publication is applied to a three-way catalyst 2 for medium and high use for purifying medium and high temperature exhaust gas, a photocatalyst 4 for purifying exhaust gas by irradiation of ultraviolet rays, and a photocatalyst 4 for exhaust gas as shown in FIG. The on-off valve 5 for opening and closing the flow path of the exhaust gas, the ultraviolet irradiation lamp 3 for irradiating the photocatalyst 4 with ultraviolet rays, and the temperature sensor 9 detect the exhaust gas temperature. A control unit 7 is provided which opens the low temperature exhaust gas to the photocatalyst 4 and turns on the ultraviolet irradiation lamp 3 to irradiate the photocatalyst 4 with ultraviolet rays.

In the technique described in Japanese Utility Model Laid-Open No. 4-76924, the temperature sensor 9 detects the temperature of the exhaust gas, and if the exhaust gas temperature is less than 300 degrees Celsius, the control unit 7 causes the solenoid valve 1 to operate.
The ON signal is output to 0, the intake pressure P is applied to the diaphragm 8 to open the opening / closing valve 5, the exhaust gas is guided to the photocatalyst 4, and the ultraviolet lamp 3 is turned on to irradiate the ultraviolet rays.

Therefore, in the above, first, the medium and high temperature catalysts 2 are used to purify HC, CO, and NO _x to some extent. Since the purification here is still insufficient, the exhaust gas is further converted by the photocatalyst 4 into the ultraviolet irradiation lamp 3. HC, CO, NO by irradiation
Purify _X to purify exhaust gas at low temperature. If the temperature sensor 9 detects medium or high temperature exhaust gas of 300 degrees Celsius or more, the control unit 7 outputs an OFF signal to the solenoid valve 10,
The supply of intake pressure P is stopped, the on-off valve 5 is closed, and the exhaust pipe 1
And the communication with the upstream bypass pipe 11 is closed, and the ultraviolet irradiation lamp 3 is turned off.

The exhaust gas is not guided to the photocatalyst 4 but is guided to the medium / high temperature catalyst 2 to purify HC, CO and NO _x NO. Therefore, in the above device, ultraviolet rays are radiated only for a short time immediately after the start of the engine, and when the exhaust gas becomes medium or high temperature, its harmful components are purified by the medium or high temperature catalyst 2. Is not restricted.

As described above, the technique described in Japanese Utility Model Publication No. 4-76924 removes the above nitrogen oxides by the action of the photocatalyst 4 when the exhaust gas is at a low temperature. It is formed of a composition having a function of removing nitrogen oxides.
In addition to the above, it is also known to produce chemicals as industrial products by directly producing methanol from the photocatalyst itself.

Further, in order to reduce the global warming caused by carbon dioxide emitted from a boiler or the like, a useful substance in which carbon dioxide is produced and immobilized as methanol is produced,
Some are trying to reuse.

[0013]

However, in the conventional technique described in the above-mentioned Japanese Patent Laid-Open No. 6-198132, since the methanol is directly injected into the exhaust gas, a tank for storing the methanol is special. In particular, in the case of an automobile, the total weight increases, which leads to deterioration of fuel efficiency and maintenance costs for the methanol tank and its supply, resulting in an increase in cost.

The technique described in Japanese Utility Model Laid-Open No. 4-76924 described above removes the nitrogen oxides by the action of the photocatalyst 4 when the exhaust gas is at a low temperature. Formed from a composition having the action of removing the exhaust gas, and is used only when the temperature of the exhaust gas is low immediately after the engine is started, and is effectively utilized in consideration of the exhaust gas purifying apparatus as a whole. Instead, the cost will increase.

Further, the other conventional example is a method for producing methanol as a mere chemical,
Further, in order to reduce global warming, carbon dioxide is produced as methanol and immobilized, and a useful substance is manufactured and reused. Therefore, in any of the above-mentioned conventional techniques, such as an exhaust gas purifying apparatus for an engine mounted on an automobile, a lightweight, compact and technical idea of manufacturing the above-mentioned device at low cost is not suggested, Moreover, there is no description of anything.

Further, it is contained in the exhaust gas in the exhaust gas passage.
To produce methanol from the
A reducing agent is used as a reducing agent, and is installed downstream of the exhaust gas passage.
The NO in the exhaust gas._X
Manufacturing the above device based on the technical idea of removing
There is no suggestion that can be made. The present invention is this
It was created in consideration of such problems, and
Carbon dioxide (CO_Two) And water (H_TwoO) and light touch
Methanol (CH _ThreeOH) is generated and
Nitrogen oxide (N
O_X) To provide an exhaust gas purifying device for an internal combustion engine
The purpose is to:

[0017]

Therefore, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention as defined in claim 1, a photocatalyst and a reducing catalyst are arranged in this order from the upstream side in the exhaust gas passage of the internal combustion engine. From the above exhaust gas to methanol (CH
₃ OH) to generate a, it is characterized in that it is configured to remove the NO _X using the generated methanol by the reduction catalyst as a reducing agent.

According to a second aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect, wherein the exhaust gas passage portion downstream of the exhaust gas passage portion in which the reduction catalyst is disposed is oxidized. It is characterized in that a catalyst is provided. An exhaust gas purifying apparatus for an internal combustion engine according to a third aspect of the present invention is arranged such that a photocatalyst and a reducing catalyst are sequentially arranged from an upstream side in an exhaust gas passage of the internal combustion engine, and an exhaust gas passage portion in which the photocatalyst is arranged is disposed. And a nitrogen oxide concentration detecting means for detecting the nitrogen oxide concentration in the exhaust gas in the exhaust gas passage portion on the downstream side, a light source for irradiating the photocatalyst with light, and the nitrogen oxide concentration detecting means on the downstream side of the photocatalyst. A control means for controlling the amount of light to the photocatalyst in the light source based on the detected detection result, wherein the photocatalyst produces methanol (CH ₃ OH) from the exhaust gas, and the produced methanol is produced as described above. It is characterized in that the NO _x can be removed by using it as a reducing agent of a reduction catalyst.

According to a fourth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, wherein an exhaust gas passage of the internal combustion engine is sequentially arranged from an upstream side.
A photocatalyst and a reducing catalyst are provided, and a nitrogen oxide concentration detecting means for detecting the nitrogen oxide concentration in the exhaust gas in the exhaust gas passage portion on the downstream side of the exhaust gas passage portion in which the photocatalyst is provided, Hydrocarbon concentration detecting means in the exhaust gas in the exhaust gas passage portion downstream of the exhaust gas passage portion where the photocatalyst is disposed, a light source for irradiating the photocatalyst with light, and the nitrogen oxide concentration downstream of the photocatalyst Based on the detection result detected by the detection means and the hydrocarbon concentration detection means, a control means for controlling the amount of light to the photocatalyst in the light source, and methanol (CH ₃ OH) from the exhaust gas in the photocatalyst. generated, the generated methanol and characterized by being constituted such that the NO _X can be removed by using as a reducing agent for the reduction catalyst There.

According to a fifth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the first or third aspect, wherein the photocatalyst is a titanium dioxide-based catalyst, and The reduction catalyst is characterized by being composed of silver-based and alumina-based catalysts.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 schematically shows a case where the exhaust gas purifying apparatus for an internal combustion engine of the present invention is applied to a diesel engine. 2 is an explanatory view showing the structure of the photocatalyst of FIG. 1, (A) is a schematic explanatory view showing a cross section of the photocatalyst of FIG. 1, and (B) is a line 2B-2B of FIG. 2 (A). FIG. 1 is a sectional view taken along the line of FIG.
And FIG. 4 is an explanatory diagram showing a state similar to FIG. 3 showing another application example of the embodiment of the present invention.

As shown in FIG. 1, a photocatalyst 34 formed of a titanium dioxide (TiO ₂ ) based material is connected to the exhaust gas passage 32 of the diesel engine 30, and an exhaust pipe 32 is provided downstream of the photocatalyst 34. A reduction catalyst 36 made of an alumina-based material, a silver (Ag) -based material, or the like is connected. Further, in the exhaust gas passage 32 downstream of the reduction catalyst 36, the nitrogen oxide concentration detecting means 38 and the hydrocarbon concentration detecting means 4 are provided.
0 is provided and is connected to the control means 45, and the irradiation amount of the light source 44 of the photocatalyst 34 is controlled by these detected output signals.

Further, the control means 45 outputs to the photocatalyst 34 the output signal of the detection result detected by at least the nitrogen oxide concentration detecting means 38 among the nitrogen oxide concentration detecting means 38 and the hydrocarbon concentration detecting means 40. It has a built-in CPU, etc. that controls the amount of light. Further, the purification rate of nitrogen oxides and the hydrocarbon concentration are calculated by the ratio of the nitrogen oxide concentration and the hydrocarbon concentration detected by the nitrogen oxide concentration detecting means 38 and the hydrocarbon concentration detecting means 40. The output signal corresponding to the value is controlled by the control means 45, and the light amount from the light source is adjusted.

Next, the structure of the photocatalyst 34 will be described with reference to FIG. The photocatalyst 34 includes a catalyst chamber 54a and a light source chamber 54b.
And a photocatalyst body 50 disposed in the catalyst chamber 54a, and a light source 44 disposed in the light source chamber 54b. Then, the wire mesh type gasket 52 obtained by compression-molding the both ends of the photocatalyst main body 50 with a wire mesh containing a heat insulating material such as asbestos is used as the casing 5
The photocatalyst 50 is arranged between the supporting portions 54c and 54d inside the photocatalyst 4 in a compressed state.

At the boundary between the catalyst chamber 54a and the light source chamber 54b, a light transmitting member 58 having heat resistance, vibration resistance and impact resistance, such as quartz glass or a concave lens for diverging light rays, is used.
Are attached to the outer periphery of the catalyst chamber 54a. Therefore, as shown in FIGS. 2 (A) and 2 (B), the exhaust gas is photocatalyst 3
The gap 54e surrounded by the light transmitting member 58 and the catalyst 50 is closed by the mesh type gasket 52 even after passing through 4, so that the exhaust gas does not enter, and the light source 44 is provided. It does not interfere with the transmission of light from.

Further, since the wire mesh type gasket 52 has heat resistance, elasticity, airtightness, etc., heat resistance, vibration resistance,
The photocatalyst body 50 is supported so as to be protected from impact resistance and prevent the exhaust gas from entering the gap 54e. Further, the wire mesh type gasket 52 is not limited to the above-mentioned one, but may be a fixing member having heat resistance, elasticity, airtightness, vibration resistance, impact resistance, etc. and capable of carrying the photocatalyst body 50. Good.

Further, a light source chamber 54b is provided so as to surround the outer periphery of the catalyst chamber 54a, an opening 54f is provided so as to correspond to the light transmitting member 58, and the opening 5f is provided.
The light is transferred to the photocatalyst body 5 via the 4 f and the light transmitting member 58.
The light source 44 is provided in the light source chamber 54b so as to reach 0. In addition, the light source 4 is provided for
When 4 is particularly small, if a concave lens for diverging light rays is used as the light transmitting member 58, smaller light can be diverged to the concave lens 58 and the light can be irradiated to the large photocatalyst main body 50 as a whole. .

Further, the photocatalyst body 50 is not in a cylindrical shape,
If it is formed in an elliptic cylindrical shape, it can be formed in a thin shape, so that the photocatalyst 34 having a small light transmittance can be obtained. Although not shown in detail, a light source having excellent heat resistance is provided in the photocatalyst body 50 as shown in FIG. 2, whereby activation of the photocatalyst 50 can be promoted. The light source 44 may be a commonly used lamp, a fluorescent lamp, or the like, and an optical fiber is provided along the outer periphery of the photocatalyst body 50 to form a light source chamber 54b.
Alternatively, the light may be transmitted from a light source provided at a remote location, and the energy of a battery power source or sunlight can be used.

Since the present embodiment is configured as described above, when the exhaust gas from the engine 30 enters the photocatalyst 34 through the exhaust gas passage 32, it receives the light from the light source 44 and the titanium dioxide ( TiO ₂ ) and CO ₂ and H ₂ O in the exhaust gas act to produce methanol (CH ₃ OH) as shown in the following chemical formula. CO ₂ + H ₂ O → CH ₃ OH This generated methanol (CH ₃ OH) flows as a reduction catalyst agent to the downstream reduction catalyst 36 formed of alumina-based, silver-based (Ag-based) or the like, and is contained in the exhaust gas. As shown in the following chemical formula by reacting with NO _x , NO _x can be removed with high efficiency.

NO _x + CH ₃ OH → N ₂ + H ₂ O + CO _{x Further} , after passing through the photocatalyst 50, the nitrogen oxide concentration detecting means 3
8. The concentration of NO _x and HC in the exhaust gas detected by the hydrocarbon concentration detecting means 40, and the NO _x purification rate and H
Since the amount of C is calculated by the control means 45 and an output signal corresponding to the value is output and the amount of light is adjusted, the energy of the light source 44 can be suppressed to the minimum.

Further, in the above, the nitrogen oxide concentration detecting means 3 is used.
8, by using the detection signal from the hydrocarbon concentration detector 40, has been determined a control amount of the light source 44 is not limited to this, for purifying the amount of NO _X by the nitrogen oxide concentration detection means 38 Even when the required amount of methanol is calculated by the control means 45 and the operation time of the light source 44 is controlled, the same effect as the above can be obtained.

[0032] HC to the downstream side of the reduction catalyst 36 in the above embodiment, NO _X in the nitrogen oxide concentration detection means 38 is provided with the hydrocarbon concentration detector 40, the above-mentioned photocatalyst 5
Even if it is provided between 0 and the reduction catalyst 36, the same effects as the above can be obtained. Next, an application example of the above-described embodiment of the present invention will be described with reference to FIG. 3, and substantially the same parts as those in the above-described embodiment will be denoted by the same reference numerals.

Since the basic principle of the one shown in FIG. 3 is the same as that shown in FIG. 1, the nitrogen oxide concentration detecting means 38 and the hydrocarbon concentration detecting means 40 are not described, but the above-mentioned embodiment is carried out. It is needless to say that the same operational effect can be obtained by arranging in the same manner as the form. Therefore, to explain the difference from the above embodiment, the present application example has an oxidation catalyst 60 which oxidizes the methanol via the exhaust gas passage 32 on the downstream side of the nitrogen oxide concentration detecting means 38 in the embodiment. It was set up.

Since this application example is configured as described above, the exhaust gas from the engine 30 is converted to methanol by the photocatalyst 50 by CO ₂ and H ₂ O in the exhaust gas as described above with reference to FIG. (CH ₃ OH) is produced, and the produced methanol is caused to flow into the reduction catalyst 36 as a reducing agent, and the produced methanol is used to produce N in the exhaust gas.
O _x is reduced to NO _x + CH ₃ OH → N ₂ + H ₂ O +
It removes NO _x like CO _x .

Further, although the exhaust gas from which NO _X has been removed by the reduction catalyst 36 has excess methanol, the oxidation catalyst 60 disposed on the downstream side of the reduction catalyst 36 has the following chemical formula: CH ₃ OH + O ₂ → CO ₂ + H ₂ O is oxidized to form harmless CO ₂ . Therefore, in the application example of the present embodiment, when methanol (CH ₃ OH) generated from components in the exhaust gas of the engine is used as the reducing agent, high NO in the above-mentioned silver-based, alumina-based reducing catalyst and the like.
The purification rate of _x can be obtained, and the operation cost can be reduced without the need to add light oil, HC and the like.

Also, when the oxidation catalyst 60 is disposed downstream of the reduction catalyst 36 of the embodiment of the present invention shown in FIG. 1 described above and in the case of the above application example, the electric heater 62 is attached to the oxidation catalyst 60. By disposing the temperature detecting means 64 in the vicinity of the oxidation catalyst 60 when the exhaust gas temperature is low and the amount of NO _x and CO ₂ is small and the amount of HC is large when the engine 30 is started. The electric heater 62 is provided at a part to detect the temperature, and an output signal corresponding to the temperature is transmitted to the control means 45 shown in FIG.
As a result, it is possible to accelerate the oxidation of HC in the exhaust gas passing through the oxidation catalyst 60 at low temperature, and it is possible to effectively remove HC at low temperature.

When it is desired to remove the soot in the exhaust gas,
In either of the above-described embodiments and application examples of the present invention, a trap filter 70 for removing the soot may be arranged between the engine 30 and the photocatalyst 34 as shown in FIG. Therefore, the present invention is capable of purifying the exhaust gas from a low temperature to a medium / high temperature of the exhaust gas of the engine.

Like the above-mentioned conventional apparatus, a device for injecting light oil, HC, CH ₃ OH, which is specially provided, into the exhaust gas is required, or the above light oil, HC, CH ₃ O is used.
In the case of the H storage tank or the above diesel oil, it is not necessary to increase the diesel oil tank for fuel unless the above-mentioned special diesel oil tank is provided. Therefore, the cost is low and the daily maintenance and management of them is completely unnecessary. do not need.

Moreover, the present invention is directed to the formation in the exhaust gas of the engine.
Methanol (CH _ThreeOH) as a reducing agent
Therefore, high NO in silver-based and alumina-based catalysts, etc.
_xA purification rate is obtained, and as described above, addition of light oil, HC, etc.
It is possible to reduce the operating cost without the need to add.
Also, depending on the operating conditions, NO_xAnd HC concentration in exhaust gas
The nitrogen oxide concentration detecting means 38 and the hide are different in degree.
The photocatalyst 3 detects the concentration with the carbon concentration detector 40.
Necessary for reaction by adjusting the energy given to 4
Proper amount of CH_ThreeSince OH can be generated,
It is possible to save Rugi and surplus CH_ThreeOH is outside the exhaust system
Emissions can be reduced.

Further, in the present invention, since H ₂ O is decomposed,
The adverse effect of H ₂ O on the reduction catalyst 36 is small. Further, since high concentrations of CO ₂ and H ₂ O exist in the exhaust gas, a sufficient amount as a reducing agent can be expected even if the conversion rate in the photocatalyst 50 is somewhat low. And the conventional engine 3
0 or the vehicle can be used as it is, and its action and effect cannot be obtained by the conventional engine.

[0041]

As described above in detail, according to the exhaust gas purifying apparatus for an internal combustion engine of the present invention as set forth in claim 1, the photocatalyst and the reducing catalyst are arranged in the exhaust gas passage of the internal combustion engine in order from the upstream side, Methanol (C
H ₃ OH) generates, since the generated methanol is configured to remove the NO _X was used as the reducing agent in the reducing catalyst, the methanol produced (CH ₃
OH) flows as a reduction catalyst to the reduction catalyst on the downstream side,
By reacting with NO _X in the exhaust gas, it is capable of removing NOx at a high efficiency.

According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention as set forth in claim 2, in the structure as set forth in claim 1, the exhaust gas passage portion on the downstream side of the exhaust gas passage portion in which the reduction catalyst is disposed. , Because the oxidation catalyst is installed,
When there is excess methanol in the exhaust gas from which NO _X has been removed by the reduction catalyst, it can be oxidized by an oxygen catalyst arranged downstream of the reduction catalyst to produce harmless CO _2. .

Exhaust gas from the internal combustion engine of the present invention according to claim 3
According to the purifying device, the exhaust gas passage of the internal combustion engine from the upstream side
The photocatalyst and the reduction catalyst are arranged in this order, and
Exhaust gas on the downstream side of the exhaust gas passage where the medium is placed
The concentration of nitrogen oxides in the exhaust gas in the exhaust passage is detected.
And means for irradiating the photocatalyst with light.
Light source and means for detecting the concentration of nitrogen oxides downstream of the photocatalyst
The light in the light source based on the detection result detected in
And a control means for controlling the amount of light to the catalyst,
From the above exhaust gas to methanol (CH_ThreeOH) is generated
The produced methanol is used as a reducing agent for the reduction catalyst.
By using as NO_XConfigured to remove
Therefore, the photocatalyst is used to
(CH _ThreeOH) is produced, and this produced methanol
(CH_ThreeOH) as the reduction catalyst, and the reduction catalyst on the downstream side
To NO in the exhaust gas_XReact with NOx
Can be removed with high efficiency.

Further, the necessary amount of methanol for purifying the NO _x amount detected by the nitrogen oxide concentration detecting means is calculated by the controlling means, and the operating time of the light source is controlled, so that the light source is controlled. Can minimize the energy of. According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention as set forth in claim 4, a photocatalyst and a reduction catalyst are arranged in this order from the upstream side in the exhaust gas passage of the internal combustion engine, and the exhaust gas passage in which the photocatalyst is arranged. Nitrogen oxide concentration detecting means for detecting the nitrogen oxide concentration in the exhaust gas in the exhaust gas passage portion downstream of the portion, and the exhaust gas in the exhaust gas passage portion downstream of the exhaust gas passage portion where the photocatalyst is arranged The hydrocarbon concentration detecting means, a light source for irradiating the photocatalyst with light, and the light source based on the detection results detected by the nitrogen oxide concentration detecting means and the hydrocarbon concentration detecting means on the downstream side of the photocatalyst. and control means for controlling the amount of light to the photocatalyst in, generates methanol (CH ₃ OH) from the flue gas in the photocatalyst, the generated methanol Since serial The NO _X by using as a reducing agent for the reduction catalyst is configured to be removed, methanol from the flue gas in the photocatalyst (CH ₃ OH) is yielding, this product methanol (CH ₃ OH) As a reduction catalyst flows to the reduction catalyst on the downstream side, reacts with NO _X in the exhaust gas, and NO
x can be removed with high efficiency.

Further, after passing through the photocatalyst, the NO _x purification rate and the amount of HC are controlled by the ratio of the concentrations of NO _x and HC in the exhaust gas detected by the nitrogen oxide concentration detecting means and the hydrocarbon concentration detecting means. Since the output signal corresponding to the calculated value is output and the light amount is adjusted, the energy of the light source can be minimized. According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention as set forth in claim 5, in the configuration of claims 1, 3 and 4, the photocatalyst is configured as a titanium dioxide-based catalyst and the reduction catalyst is a silver-based catalyst. , Since it is configured as an alumina-based catalyst, when exhaust gas from the engine enters the photocatalyst through the exhaust gas passage, it receives light from a light source, and the titanium dioxide (TiO 2) of the photocatalyst is received.
₂ ) and CO ₂ and H ₂ O in the exhaust gas act to generate methanol (CH ₃ OH).

The produced methanol (CH ₃ OH) flows as a reduction catalyst into the downstream silver-based and alumina-based reducing catalyst and reacts with NO _x in the exhaust gas to remove NO x with high efficiency. Is what you can do.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view schematically showing an embodiment of the present invention.

2 is a schematic explanatory view schematically showing the structure of the photocatalyst of FIG. 1, (A) is a schematic explanatory view showing a cross section of the photocatalyst of FIG. 1, (B) is 2B- of FIG. 2 (A). It is a schematic sectional drawing which follows the 2B line, and shows only a left half.

FIG. 3 is a schematic diagram showing an application example of an embodiment of the present invention.
It is explanatory drawing which shows the state similar to.

FIG. 4 is a schematic explanatory view showing a state similar to FIG. 3 schematically showing another application example of the embodiment of the present invention.

FIG. 5 is an explanatory view showing a conventional exhaust gas purifying apparatus for automobiles.

[Explanation of symbols]

 30 engine 32 exhaust gas passage 34 photocatalyst 36 reduction catalyst 38 nitrogen oxide concentration detection means 40 hydrocarbon concentration detection means 44 light source 45 control means 50 photocatalyst body 52 wire mesh type gasket 54 casing 54a catalyst chamber 54b light source chamber 54c support portion 54d support portion 54e Gap 54f Opening 60 Oxidation catalyst 58 Light transmission member 60 Oxidation catalyst 62 Electric heater 64 Temperature detection means 70 Trap filter

Claims (5)

[Claims] 1. A photocatalyst and a reduction catalyst are arranged in this order from the upstream side in an exhaust gas passage of an internal combustion engine, and the photocatalyst produces methanol (CH ₃ OH) from the exhaust gas, and the produced methanol is reduced by the reduction. An exhaust gas purifying apparatus for an internal combustion engine, characterized by being used as a reducing agent for a catalyst and capable of removing the NO _X. 2. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein an oxidation catalyst is provided in an exhaust gas passage portion downstream of the exhaust gas passage portion in which the reduction catalyst is provided. apparatus. 3. A photocatalyst and a reducing catalyst are arranged in this order from the upstream side in the exhaust gas passage of the internal combustion engine, and the exhaust gas in the exhaust gas passage portion downstream of the exhaust gas passage portion in which the photocatalyst is arranged. A nitrogen oxide concentration detecting means for detecting the nitrogen oxide concentration, a light source for irradiating the photocatalyst with light, and the light source based on the detection result detected by the nitrogen oxide concentration detecting means on the downstream side of the photocatalyst. and control means for controlling the amount of light to the photocatalyst in methanol from the flue gas in the photocatalyst (CH ₃ O
H) is produced, and the produced methanol is used as a reducing agent for the reduction catalyst to remove the NO _x , and an exhaust gas purifying apparatus for an internal combustion engine. 4. A photocatalyst and a reduction catalyst are arranged in this order from the upstream side in the exhaust gas passage of the internal combustion engine, and the exhaust gas in the exhaust gas passage portion downstream of the exhaust gas passage portion in which the photocatalyst is arranged. A nitrogen oxide concentration detecting means for detecting the nitrogen oxide concentration, a hydrocarbon concentration detecting means in the exhaust gas in the exhaust gas passage portion downstream of the exhaust gas passage portion where the photocatalyst is arranged, and a light for the photocatalyst. A light source for irradiating, and a control means for controlling the amount of light to the photocatalyst in the light source based on the detection result detected by the nitrogen oxide concentration detecting means and the hydrocarbon concentration detecting means on the downstream side of the photocatalyst. The exhaust gas is mixed with methanol (CH ₃ O 2) by the photocatalyst.
H) is produced, and the produced methanol is used as a reducing agent for the reduction catalyst to remove the NO _x , and an exhaust gas purifying apparatus for an internal combustion engine. 5. The photocatalyst is configured as a titanium dioxide-based catalyst, and the reduction catalyst is configured as a silver-based or alumina-based catalyst.
The exhaust gas purifying apparatus for an internal combustion engine according to any one of 3 and 4.