JPS5867343A - Catalytic body for purification of gas - Google Patents

Abstract

PURPOSE:To reduce oxidative gases and reducing gases simultaneously and efficiently by means of the titled catalytic body obtd. by consisting the same of a perovskite type composite oxide contg. rare earth elements, alkaline earth metals, Co and specific transition metals. CONSTITUTION:This catalyst for purification of gases consists of the perovskite type composite oxide expressed by the formula (A is 1 kind of element selected among rare earth elements, A' is 1 kind of element selected along alkaline earth metals, B is Co, B' is 1 kind of element selected among V, Cr, Mn, Fe and Ni, O is oxygen. 0<=x<=1, 0<=y<=1). This catalytic body converts oxidative gases, for example, NOx to N2 by exhibiting electron donative characteristic thereto and incorporates oxygen into the lattice. The catalytic body donates oxygen ions to reducing gases, for example, CO, and converts the same to CO2. The oxygen pulled from the lattice is replenished by the oxidative gases or from the atmospheric air.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst for gas purification, and provides a catalyst that simultaneously and efficiently processes and reduces oxidizing gas and reducing gas.

Gases emitted from factories, automobiles, household combustion appliances, etc. contain reducing gases such as CO and oxidizing gases such as NOx, which cause environmental pollution including effects on the human body. . Conventionally, as means for treating these exhaust gases, combustion catalysts have been used for reducing gases, and wet methods have been used for oxidizing gases that cannot be treated with these methods. has been used.

Recently, a three-way catalyst system using precious metals has been partially put into practical use for automobile exhaust gas treatment, but this system has the drawback that oxidizing gas and reducing gas must be present in equivalent amounts. However, it is necessary to control the combustion mixture in advance so that it has an equivalent composition, and there are performance problems such as high-temperature deterioration and cost problems.
There are gaps in its spread.

The gas purifying catalyst of the present invention is made of a perovskite-type composite oxide represented by the following general formula.

Ai -y, "x 5t-y B'A03 However, humans are an element selected from rare earth elements, A' is an element selected from alkaline earth metals, B is GO1B' is V, Or , an element selected from the group consisting of Mn, Fe, and Ni, 0 represents oxygen, O≦X≦1.○≦y
≦1.

This perovskite type composite oxide VL1 is the metal constituting this oxide.q1. 1: When baking mixtures such as acid salts, oxalates, oxalates, d-nitrates, etc.! However, it is advantageous to impregnate an alumina-containing support, such as a porous tube or pereno, with a mixed solution of the above-mentioned salts [7], and to impregnate these supports by calcining.

In addition, it is advantageous to configure the catalyst body as a catalyst tube supported on a carrier having the shape C: of the above-mentioned cylindrical body. You can improve efficiency.

The perovsky) type composite oxide described in ``-'' is characterized by being a mixed conductor of electrons and oxygen ions and exhibiting a catalytic action against both oxidizing gases and reducing gases. That is, oxidation ('l gas, for example, NOx, exhibits electron donating property and converts it to N2, and oxygen is incorporated into the lattice.';
On the contrary, it provides oxygen ions! J, let it be CO2. Pull it out of the grid! 1. /ζOxygen V11, supplied from oxidizing gas or alternatively from atmospheric air. Therefore, in a system in which amphoteric gases coexist, gases other than the equivalent amount react quickly through electron and oxygen ion exchange reactions, and both have the characteristic of being able to treat excess gases.

The present invention will be explained in detail below.

The drawing shows an exhaust gas purification device using the catalyst of the present invention. The catalyst tube 1 is filled with catalyst pellets 2, and the catalyst tube 1 is filled with catalyst pellets 2.
The outside is exposed to the atmosphere. Exhaust gas inlet 3
Exhaust gas that enters is treated and reduced by the catalyst tube 1 and the catalyst pellets 2, and is discharged to the outside from the outlet 4. The purpose of filling the catalyst pellets is to allow equivalent amounts of oxidizing gas and reducing gas to react in the pellets, and to react the remainder in the catalyst tube, and also to prevent the inflow gas from creating a turbulent flow as it passes through the pellet bed. It also has the purpose of ensuring sufficient contact with the catalyst.

Next, we will describe the implemented configuration and effects. The catalyst composition is La
o, 38 r o, 7COo, 7 F f3
o, s O3 was selected, and a mixed solution of a predetermined amount of the acetate of this constituent metal dissolved in distilled water was vacuum impregnated into an alumina tube with an apparent porosity of about 15 degrees, an inner diameter of 3 om, an outer diameter of 40 mm, and a length of 300 layers. and then thermally decomposed at about 400°C/After this, 1
A catalyst tube was obtained by firing at 100"C for 3 hours. 1.
The same catalyst was similarly supported on an alumina sphere with an apparent porosity of about 60% and a diameter of 3 rrrm! An exhaust gas purification device was constructed by filling 111 tubes with l(pellets and j~/ζ0 and 10017 catalyst pellets:!fQ.Furthermore, as a comparative example, 1 g+('4i: Quartz tubes with the same inner diameter as the one in which the sample was loaded were prepared and used in appropriate combinations.

The reaction gases were GO 1% (volume ratio) and N.

A mixed gas of 0.5% and the balance N2 was flowed into the catalyst tube for 60 minutes, and the CO and NO levels in the outflow gas were measured when the steady state was reached at 300'C and 600''C. The results are shown in the table below.The data is expressed as the average value of n=5.

As is clear from the results, the effectiveness of the exhaust gas purification KW using the catalyst of the present invention is significant. Catalyst tubes and catalyst pellets can be composed of sintered composite oxides, but in actual use, only the layer near the surface of the catalyst is used, so it is not efficient to support them thinly on a carrier. In fact, there is no difference in purification ability. Moreover, the effect in terms of material cost and manufacturing cost is also large. In addition, in the examples, catalyst pellets were produced by an impregnation method, but in addition, 7.
- It is also possible to use means such as sputtering and thermal spraying.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is a partial cross-sectional sketch showing the main parts of a JIJI gas purification apparatus using the catalyst of the present invention. 1...Catalyst tube, 2...Catalyst pellet, 3
......(IJI gas inlet, 4...Purified gas outflow 11.. Name of agent: Patent attorney Toshio Nakao and 1 other person 1)
the law of nature

Claims (1)

[Claims] General formula A1-X "X"1-7B'703 (However, A' is an element selected from rare earth elements, A' is an element selected from alkaline earth metals, B is C01B' is V , Or
. An element selected from the group consisting of Ml, Fe, and Ni, where 0 represents oxygen, and 0≦X≦1. ○≦y≦1. ) A catalyst body for gas purification consisting of a perovskite-type composite oxide.