JPH0464736B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a catalyst body that purifies harmful gas components in exhaust gas discharged from various combustion devices. Conventional structure and its problems As a catalyst that simultaneously purifies CO and NO _x , which are the main harmful gas components of exhaust gas emitted from various combustion equipment (gas/oil stoves, boilers, car engines, etc.) It is a perovskite type complex oxide.

[Formula] (Me is one element selected from Fe, Mn, Cr, V, O<x<
1) and SrTiO ₃ have been proposed. The catalyst utilizes the oxygen ion conductivity of the former component to exhibit catalytic activity, but by adding the latter SiTiO ₃ to it, the oxygen ion conductivity is increased and the activity is increased. Improving. This composite catalyst has the advantages of activity comparable to noble metals, excellent heat resistance, and low cost, making it a very distinctive material. When this composite material is used as a practical catalyst, a supported catalyst supported on a carrier is generally used, but when a metal is used as a carrier, the catalyst acts as an oxygen supplier at high temperature and oxidizes the metal. It has the disadvantage of promoting Furthermore, the mixing of the two components is uneven, especially on the surface of the catalyst layer.

In areas where the particles of [Formula] and SiTiO ₃ particles are not in contact, oxygen ion conductivity does not increase, which may impede improvement in catalytic activity or cause variations. OBJECTS OF THE INVENTION In view of the above-mentioned problems, the present invention aims to provide a highly active and highly reliable catalyst. Structure of the invention The present invention includes:

[Formula] (Me is one element selected from Fe, Mn, Cr, V, O<x<
1) A supported catalyst body using a mixed two-component substance consisting of an oxide and SrTiO ₃ represented by 1) as a catalyst, which has a structure in which a layer of SrTiO ₃ is provided between the catalyst layer and the support. In particular, it suppresses the deterioration of the metal-based carrier and realizes a stable improvement in activity. DESCRIPTION OF THE EMBODIMENTS Example 1 The characteristics of the supported catalyst according to the present invention are shown in FIGS. 1 to 3 together with a conventional example. Catalyst components include La _0.35 Sr _0.65 Co _0.7 Fe _0.3 O ₃ 40mol%
A two-component material (200 mesh or less) consisting of 60 mol% SrTiO ₃ was used, and a Fe-Cr heat-resistant wire mesh (equivalent to 40 mesh, 24φmm) was used as the carrier. As an example, SrTiO ₃ was applied to the surface of a wire mesh by hydrogen flame spraying.
(200 mesh or less) was uniformly deposited to a thickness of about 80 μm, and on top of that the catalyst was uniformly deposited to a thickness of about 150 μm by hydrogen flame spraying. The catalyst was directly attached to a wire mesh by hydrogen flame spraying to a thickness of about 150 μm. Five sheets of this catalyst were stacked and placed in a reaction vessel made of quartz glass, the temperature was controlled in an electric furnace, and the activity was measured. For the reaction gas
A homogeneous mixed gas consisting of 150 ppm of CO, 50 ppm of NO ₂ and the remainder of N ₂ was used and was supplied to the catalyst layer at a space velocity of 83000 h ^-1 . Figure 1 shows the CO removal rate, Figure 2 shows the NO production rate, and Figure 3 shows the N ₂ production rate.
Both activities were improved by providing a layer of SrTiO ₃ . The amount of catalyst supported was almost the same, and this improvement in activity is thought to be due to increased oxygen ion conductivity at the catalyst interface between the catalyst layer and the _three SrTiO layers. Example 2 The next example is shown in which it is supported on a ceramic carrier. The same catalyst components as in Example 1 were used. The carrier is an alumina honeycomb molded body (100φ x 10t
mm, 3□mm cells, approximately 500 cells) were used. As an example, the surface of this carrier was coated with hydrogen flame spraying.
SrTiO ₃ is deposited to a thickness of approximately 100 μm, and the catalyst component is deposited to a thickness of approximately 200 μm on top of it by hydrogen flame spraying.As a conventional example, the catalyst component is directly sprayed onto the surface of the carrier by hydrogen flame spraying. Approximately 200μm
The material that was attached to the thickness was used. One of these catalyst bodies was attached to the top of the combustion tube of a commercially available portable kerosene stove, and the CO concentration and NO _x (=NO+NO ₂ ) concentration in the exhaust gas before and after passing through the catalyst body were measured. Exhaust gas temperature is approximately 700℃. The results are shown in the table.

[Table] As is clear from the results, the Examples show excellent activity. Example 3 Next, an example of the durability of the catalyst body will be shown. The same catalyst components as in the previous two examples were used, and the same wire mesh as in Example 1 was used as the carrier. The structure of the catalyst body was the same as in Example 1. However, here, the size of the catalyst body was set to 120φmm. This catalyst body is 4
The sheets were stacked and attached to the top of the combustion tube of a commercially available portable gas stove (exhaust gas temperature approximately 850°C) using a jig, and the cycle of burning for 30 minutes and extinguishing for 10 minutes was repeated 3,000 times to ensure the stability of the catalyst properties. confirmed. Initially and every 1000 times, the CO concentration and NO _x (=NO+
NO ₂ ) concentration is measured, and the CO removal rate is shown in Figure 4, and the CO removal rate is shown in Figure 5.
The figure shows the NO _x removal rates determined for each. At the same time, the appearance of the catalyst was observed to check for any abnormalities. As is clear from the results, the properties of the Examples are very stable, but the properties of the Conventional Examples are slightly inferior to those of the Examples, and a decrease in activity is observed after 2000 cycles. In the examples, no abnormality was observed in the appearance of the catalyst bodies, but in the conventional examples, slight oxidation of the wire gauze occurred, and partial lifting or falling off of the catalyst components was observed. This is reflected in the difference between the presence and absence of characteristic deterioration.
This confirms the effect of interposing _three layers of SrTiO. As described above, the catalyst body of the present invention exhibits excellent properties in terms of catalytic activity and durability. Although thermal spraying is used as a supporting method here, depending on the carrier material and shape, an impregnation method or a coating method may be used, or a combination of these methods may also be used. When the carrier is a metal, the supported amount of SrTiO ₃ may be sufficient to prevent direct contact between the metal surface and the catalyst component, and in the case of other carriers, it may be sufficient to uniformly cover the carrier surface. Furthermore, as a catalyst component
Similar results can be obtained when Me is Mn, Cr, or V. Effects of the Invention By providing a layer of SrTiO ₃ between the catalyst component and the carrier, the catalytic action can be effectively amplified and the life span can be extended, resulting in an excellent catalyst body.

[Brief explanation of the drawing]

Figure 1 is a diagram of the relationship between temperature and CO removal rate, Figure 2 is a diagram of the relationship between temperature and NO production rate, Figure 3 is a diagram of the relationship between temperature and _N2 production rate, and Figure 4 is a diagram of the combustion cycle in the durability test. Figure 5 is a diagram showing the relationship between the CO removal rate and the _combustion cycle in the durability test.

Claims (1)

[Claims] 1 General formula [Formula] (Me is one element selected from Fe, Mn, Cr, and V, O<x<
An exhaust gas purification catalyst body characterized in that the catalyst layer is a substance consisting of a mixed two-component system of the oxide represented by 1) and SrTiO ₃ , and a layer of SrTiO ₃ is provided between the catalyst layer and the carrier. .