JPS61283349A - Catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To widen an active temp. region by enhancing catalytic activity, by using perovskite type oxide comprising a specific two-component system material as a catalyst for purifying exhaust gas. CONSTITUTION:A catalyst is formed as a mixture consisting of oxide represented by general formula (wherein Ae is Nd or Ho, Be is at least one element selected from Fe, Mn, Cr and V, 0<=x<=1 and 0<=z<=1) and oxide represented by formula II (wherein A is Ca or Sr, B is one element selected from Ti, Zr and Hf and 0<=y<=1) or a mixed sintered body thereof. As mentioned above, for example, if a HoSrCoO3 or NdSrCoO3 system material is used, CO-oxidizing and NO2-reducing catalytic activities are enhanced and lower limit temp. capable of keeping catalytic activity can be widened up to 400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a catalyst that purifies harmful gas components in exhaust gas discharged from various combustion devices.

Conventional technology Perovskite-type catalysts have been used as catalysts to simultaneously purify GO and NOx, which are the main harmful gas components of exhaust gas emitted from various combustion equipment (gas/oil stoves, boilers, automobile engines, etc.). 1) and SrMe05
A two-component material consisting of (Me=one type of element selected from Ti, Zr, and Hf) has been proposed.

Problems to be Solved by the Invention The above-mentioned catalysts have low catalytic activity at temperatures below 500°C, and the applicable temperature is limited to 600°C or above.

The present invention was made in view of these problems, and an object of the present invention is to provide an exhaust gas purification catalyst whose active temperature range as a catalyst is expanded to 400°C.

Means for Solving the Problems The present invention is a general ceremony person +5. -2Sr2Co, -xBex
O, (Ae=Nd or Ho; Be=Fe, Mn,
Or, at least one element selected from V, 0≦X≦1
．． 0≦z≦1) and AB, mul y
Os (A = Ca i or Sr; B = Ti, Zr
, Hf, and a mixture or mixed sintered body with an oxide represented by 0≦y≦1).

Function The catalytic active sites for the oxidation reaction of co in perovskite-type oxides are located in the co produced by Sr injection.

In the crystal field, the 3d electron orbital splits into two electron orbitals, tzg and 6g. In trivalent cobalt, there are 6 electrons in this 3d orbital, and the arrangement in the split orbital is (tzg6.,,O) and (tzg,6
There are two ways of entering (g), the former is called a low spin state and the latter is a high spin state, and are represented by the symbols Go and Go, respectively. And this Go is Sr
The ratio increases as more is injected. And the C of Go
When the lone electron group existing in Go is adsorbed on the catalyst surface, Go
enters one of the electron orbits, dz. At that time, the electron that was in the t 2 g orbit of co at the same time is the π of CO.
enters the main orbit, and as a result, CO is in an electron-deficient state (co
)2+, and the other bond in Go -0-Go is
It separates into Co-Go and male-, and this 02- becomes (c
o) It reacts with 2+ to form C02. The activity of Tsumashi as a CO oxidation catalyst increases as Go increases, and SrNd is more active than the SrLaCoMeO3 system.
CoMeO3-based and SrHaCoMeO3-based materials have a larger amount of Go and have higher catalytic activity, and as a result, the lower temperature limit at which they can maintain catalytic activity has been extended to 400''C.

Practical row <Practical row 1> FIGS. 1 and 2 show the characteristics of the supported catalyst according to the present invention together with the conventional row. HOQ, 5SrO, 5GO0,
7Feo, 50 mol% of 505,! : CaH
A two-component material consisting of 50 m01% of fa, aAlo, and 205 was powdered to 200 mesh or less, and a Fe-Or heat-resistant wire mesh (equivalent to 40 mesh, φ2) was prepared as a carrier.
411nII) by hydrogen spraying to a thickness of about 100 μm.

On the other hand, in the conventional column, Sr O,65La O,5
5” 0.7Feo, 30540mo1% and SrTiO
A material consisting of 360 mo1% was used.

Five sheets of this catalyst were stacked and placed in a reaction vessel made of quartz glass, and the temperature was controlled in an electric furnace to measure the activity. The reaction gas contains 00150pp11・, No250ppm,
, a uniform mixture consisting of the remainder of N2 is obtained using , and the space velocity is 83
000h was supplied to the catalyst layer. FIG. 1 shows the GO removal rate, and FIG. 3 shows the NO and NO2 production rates. As can be seen from the figure, the activity of this example is higher than that of the conventional example, and it can be said that it has the ability to purify exhaust gas from a lower temperature range. Note that in this example, AS, -2SrzGo1-
Although a mixture of xBexO3 and B1-yM(lyOs) and fired material was used as the material, almost the same results were obtained when a mixture of the two was used.

<Example 2> Next, an example of the case where it is supported on a ceramic carrier will be shown. The catalyst components are 1'iao, 5sro, 5Coo, sl'e
o, sos and 5rZro, 5mlo, 50s and mo/I
/ ratio o, es: 0.35 was used. The carrier is an alumina honeycomb molded body (φ110MNX
t 10gM, 3MM mouth 7k.

Approximately 500 cells) were used. In both the example and the conventional example, a hydrogen flame sprayed catalyst was applied to the surface of this carrier to a thickness of about 200 μm.
The material that was attached to the thickness was used.

One of these catalyst bodies was attached to the upper part of the combustion tube of a commercially available vortaple oil stove, and the GO concentration and NOx (==NO-1-No2) concentration in the exhaust gas after passing through the catalyst body was measured. The exhaust gas temperature is approximately 700'C. The results are shown in the table. However, in the conventional example, Sr, 65La
0j5co o, 71'ej C40540m01%
and SrTiOs60rnol were used.

Table Effects of the Invention As mentioned above, conventional Sr L as a catalyst component
a Co O3-based material! 1lHoSrC005 series and N
It is better to use d5rCoO3-based materials because Go oxidation and NO3
Catalytic activity for reduction becomes higher.

[Brief explanation of the drawing]

FIG. 1 is a relationship diagram between the temperature and CO removal rate of an exhaust gas purification catalyst according to an embodiment of the present invention, FIG. 2 is a relationship diagram between temperature and CO removal rate of an exhaust gas purification catalyst of a conventional example, and FIG. The figure is a relationship diagram of the No production rate+N2 production rate with respect to the temperature of the exhaust gas purification catalyst of the present invention and the conventional example. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4! -Ryoaki HoO, 55+0. ! ;Coo, 7FeO, 30atC
a, Hfo, δ/Jlo, lO, 32σθ 4θ
Fu 〃σ # in 5Z & C
'CのFig.2 Solitary t''J Sr o, uLao, Js coa, 7Fe o, sO
a t5prro3 layer y: ja, L ("C) Figure 3 washing L ("S

Claims (1)

[Claims] General formula Ae_1_-_zSr_zCo_1_-_xBe
_xO_3(Ae=Nd or Ho; Be=Fe, Mn
, Cr, at least one element selected from V, 0≦x≦1
, 0≦z≦1) and AB_1_-_
yAl_yO_3 (A=Ca or Sr; B=Ti, Z
An exhaust gas purification catalyst comprising a mixture or a mixed sintered body of one element selected from r, Hf and an oxide represented by 0≦y≦1.