JPS61242622A - Oxygen-coexistent exhaust gas purifying apparatus - Google Patents

Abstract

PURPOSE:To enable the removal of NOX without using a special reducing agent and to carry out the reaction even if in the presence of O2 by removing electrochemically O2<-> or O<-> adsorbed onto the catalytic cracking catalyst for NOX. CONSTITUTION:Pd electrodes 2a, 2b hard to adsorb O2 are formed on both upper and lower surfaces of an oxygen ion conductor 1 which are in contact with exhaust gas and air respectively and further a composite oxide 3 which can dissociate and adsorb NOX at an oxygen ion conductor-actuating temperature is supported on the Pd electrode 2a for exhaust gas. NO is dissociated into an N atom and an O atom on the catalyst, which are adsorbed onto the catalyst. The O2<-> and O<-> are removed by vacuum suction into the atmosphere due to the superficial oxygen ion concentration gradient or the outside electric potential gradient of the oxygen ion conductor and the surface of the catalyst is enabled to continuously adsorb NO.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oxygen coexistence purification device, and more particularly to an oxygen coexistence exhaust gas purification device for an internal combustion engine in the coexistence of a large amount of oxygen.

[Conventional branch (11 and problems)] Nitrogen oxides (hereinafter referred to as NO) in exhaust gas discharged from internal combustion engines include, for example, PL and Rh.

The three-way catalyst consisting of the Pd element and the C ('1.
It had been removed. However, when removing NOx from exhaust gas in which oxygen coexists in diesel cars, lean furnaces, burnt gasoline cars, etc., even if the above three-way catalyst is used, the above-mentioned propellant in the exhaust gas will react with oxygen in the atmosphere. This causes a problem in that the original catalytic action is reduced and the purifying activity is hardly exhibited.

In order to remove NO8 from such exhaust gas in the coexistence of oxygen, conventional methods include converting all of the NO to NO□ using an oxidation catalyst and absorbing it into an alkali, or using a reducing agent such as N83 that selectively reacts with NO. Methods of using this method are known.

However, the implementation equipment for these force C removals is very labor intensive and is not effective when installed in a vehicle.

Invention 1: L: N O8 (wa) catalytic cracking catalyst 1 to 7
The reaction rate of the catalytic cracking of 1 ci oxygen, ico (n+': ``*'q 'A conversion'; dual CL ￥, 'r: 4- is C2, so No, is N (1X) The objective is to make the reaction proceed in the same manner as the catalytic reduction and also in the presence of oxygen.

(Means to solve the problem) The problem described in -1- is explained below. In addition, the metal layer which is difficult to absorb oxygen and the nitrogen oxides supported on the surface of the metal layer on one of the two surfaces are dissolved (adsorbed). It is equipped with a flexible metal, and one surface is in contact with the gas and the other surface is in contact with the atmosphere.
This problem is solved by an oxygen coexistence exhaust gas purification device characterized in that the metal layer, which is difficult to adsorb, is made conductive through the oxygen ions.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view for explaining the oxygen/fII gas purification device according to the present invention. According to FIG. Both the upper and lower surfaces of the oxygen ion conductor (solid electrolyte) 1, such as oxidized zirconia, are coated with palladium (P d ) to a thickness of about 0.05 to 0.1 C, which makes it difficult to adsorb oxygen. A porous PD electrode (2a.

2b) is formed. In addition, the exhaust gas I)d electrode 2a)-, the operating temperature of the oxygen ion conductor (e.g. carbon atom oxidation cell), in the case of 400 to 800
Cu, V which can dissociatively adsorb NO8 at temperatures (°C).

14ff of metals such as Mn, Ni, Pr, Pt, Pd, etc.
The composite oxide 3 containing the upper and lower parts is supported.

Hereinafter, using the apparatus according to the present invention, iJ) NOX in air gas
, - As an example, the operating principle for removing No. will be explained based on FIG. 2, which is a schematic representation of FIG. 1.

In the device according to the present invention, the catalyst for dissociating and adsorbing N O is Pd.
Since NO is supported on the electrode layer 2a, NO is adsorbed on the catalyst 1 by decomposition between the oxygen source Y and the nitrogen atom ζ.

The adsorbed nitrogen residue becomes nitrogen molecules and is desorbed by the catalyst, but the oxygen remains in the adsorbed ionic state 02- or O-. Therefore, the catalyst is in an oxidized state. In the coexistence of oxygen, unburned hydrocarbons or CO become reducing agents,
II. The adsorbed oxygen reacts with the catalyst and completes the process.

On the other hand, in the coexistence of oxygen, the catalyst surface is oxidized and the active sites where No can be dissociated and adsorbed are covered with adsorbed oxygen.

Therefore, NO cannot be adsorbed to the active sites, and there is no apparent activity of the catalyst.

In the oxygen coexistence exhaust gas purification device according to the present invention, this adsorbed oxygen is electrochemically removed and the NO of the catalyst itself is removed.
, is intended to bring out the resolution of .

In other words, the 02- or O- adsorbed on the catalyst surface is removed by being drawn into the atmosphere by the oxygen ion concentration gradient on the surface of the oxygen ion conductor (solid electrolyte) or the external potential gradient. A state where NO can be adsorbed continuously! It's sato.

Now consider the electromotive force generated when the two electrodes are opened.

In FIG. 2, NO and 02 exist on the exhaust gas side, and 02 exists on the atmospheric side. In other words, (on the catalyst on the throat gas side, there is a smaller concentration of oxygen due to combustion than on the atmospheric side and a small amount of NO generated by combustion. The adsorption rate of oxygen and NO is determined by the dissociative adsorption capacity of the catalyst. The potential on the exhaust gas side is determined.On the other hand, for example, on the atmospheric side at 1 atm, approximately 0.21 atoms of oxygen exist, but in the device according to the present invention, a metal with a small dissociative adsorption capacity for oxygen is used at the operating temperature. Because it is used, 111 with 4 degrees of oxygen
In other words, the potential is low, that is, the amount of adsorption is small. As shown in FIG. 2, the electromotive force between the two poles is determined by the respective seismic intensities and dissociation/adsorption equilibrium coefficients as shown in FIG. 2.

The electromotive force E0 generated at both poles when no voltage is applied to both poles is: F: Farate constant l A: Gas constant '■゛; Moon temperature PO, - or air Exhaust gas or outside oxygen partial pressure 'N0i
n: N0 partial pressure of exhaust gas γ〉β〉〉α.

However, if N O-·NO8 is used, the multiplier that PNO has is smaller than 1/'2.

Although the electromotive force applied to both poles varies depending on the dissociation adsorption constant (depending on the size of the denominator molecule), FIG. 2 considers the case where the amount of adsorption on the exhaust gas side is larger than on the atmospheric side. When a show 1 is applied between the two electrodes, the potentials between the two electrodes become the same. Most of the adsorbed oxygen ions are on the exhaust gas side, and oxygen and ions flow in the solid electrolyte in the direction of the arrow in the figure, while electrons flow in the shorted conductor. If such a state with a large amount of adsorption on the exhaust gas side continues for a long time, a solid electrolyte that conducts not only oxygen ions, but a mixed conduction system that conducts electrons and oxygen ions equally, will always be used. The removal of NO will proceed. Even if such a state does not continue, apply a potential between the two electrodes (4F) so that the gas side is negative and replenishes electrons to the exhaust gas side.
If so, the removal of NO will continue, and the N
7 Atmospheric side - 0□ is discharged.

3M shows a sectional view perpendicular to the exhaust gas flow of the two-position oxygen coexistence exhaust gas purification according to the present invention. The exhaust gas and the atmosphere in the case 6 are separated by a solid electrolyte 1, with a Pd electrode 2a and a catalyst on the exhaust gas side of the solid electrolyte 1, and a Pd electrode on the atmosphere side.
A d electrode 2b is provided. A potential is applied between the electrodes 2a and 2b in the horn direction to promote the decomposition of NO and I, that is, a negative potential on the JJF air side and a positive potential on the atmospheric side. A heater 4 for heating the solid electrolyte to its operating temperature is attached to the fire side where the solid electrolyte is bent into a U-shape, and supplies battery voltages 12 to 7 through a wire 5. Next, FIG. 4 shows a side view of the exhaust gas flow. The exhaust gas flows through the exhaust pipe] 0 and the cone portion 11 and enters the oxygen coexistence exhaust purification device having the heater 4 (exhaust gas flow 9). So N
Ox is decomposed and adsorbed, N2 gas goes to the exhaust side, and 0□ goes to the atmosphere side.
Gas is emitted.

〔Effect of the invention〕

As explained above, according to the present invention, Ni can be removed even from exhaust gas in which oxygen coexists! NOx can be removed without using a special reducing agent such as No. 2 or an absorbent such as an alkali. In addition, in the absence of oxygen, the catalyst is
Although no activity was shown in the absence of reducing agents such as C and C01H2, N08 can be removed even in the absence of these reducing agents even in the presence of oxygen 1 of the present invention.

(Q)

[Brief explanation of drawings]

FIG. 1 is a partial schematic sectional view of the solid electrolyte electrode part of the oxygen-coexisting υF vaporization device according to the present invention, FIG. 2 is a schematic diagram showing the operating principle of the device, and FIG. Fig. 4 is a cross-sectional view perpendicular to the exhaust gas flow, and Fig. 4 is a view of the above device attached to the trachea. 1... Oxygen ion conductor (solid electrolyte) 2a. 2b... Pd electrode, 3... Sliding oxide, 4... Heater, 5... Riet wire, 6... Case, 9... Exhaust gas flow, lO... IJr gas Pipe, 11... cone part.

Claims (1)

[Claims] an oxygen ion conductor, a metal layer disposed on both upper and lower surfaces of the oxygen ion conductor that is difficult to dissociate and adsorb oxygen; and a metal that easily dissociates and adsorbs oxides,
One surface is in contact with the exhaust gas and the other surface is in contact with the atmosphere, and the metal layer that is difficult to dissociate and adsorb oxygen is electrically connected through the oxygen ion conductor. Coexistence exhaust purification device.