JPS59179157A - Catalyst for treating waste gas - Google Patents

Abstract

PURPOSE:To suppress poisoning of a catalyst activator and to extend its life by coating a solid acidic material consisting of 10-90wt% SiO2 and 10-90wt% Al2O3 or 10-90wt% SiO2 and 10-90wt% ZrO2 on the surface of a catalyst. CONSTITUTION:A solid acidic material consisting of 10-90wt% SiO2 and 10- 90wt% Al2O3 or 10-90wt% SiO2 and 10-90wt% ZrO2 is coated on the surface of a catalyst formed by depositing a catalytic compsn. on a carrier, thereby obtaining a catalyst which reduces the NOx in waste gas contg. NOx and makes the gas pollution-free by adding ammonia to said gas. The coating thickness of said solid acidic material is preferably 10-50mu and if <10mu, the intended effect is not thoroughly obtd. If the thickness exceeds 50mu, the decrease in the initial activity of the catalyst increases and is undesirable. The catalyst obtd. in the above-mentioned way is capable of maintaining active power for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst for treating waste gas containing nitrogen oxides.

More specifically, nitrogen oxides (hereinafter referred to as NOx)
This invention relates to a catalyst that reduces and removes NOx by adding ammonia to waste gas containing NOx, and which has a longer lifespan.

Air pollution caused by NOx contained in waste gas from combustion furnaces such as large power boilers and private boilers, incinerators, chemical plants, etc. has become a social problem, and various acid sludge denitrification devices have been developed as a preventive measure. As a result of progress, selective catalytic reduction methods using 7-ammoni-7 as a reducing agent in the presence of a catalyst are now mainstream.

The catalyst used in this denitrification equipment is required not only to have high activity but also to be able to maintain its performance stably for a long period of time.

The inventors of the present invention have discovered through analysis of sludge catalysts and various laboratory tests that the performance of denitrification catalysts deteriorates due to the accumulation of Na and K, which are alkali metal components contained in waste scum dust, and the life of the catalyst is shortened. (I found out that.

The present invention was achieved as a result of various studies in order to reduce the degree of deterioration in catalyst performance due to the accumulation of alkali metal components. The coating layer is coated with an acidic substance, and the coating layer collects the alkali metals in the exhaust gas dust using the ion exchange ability of the solid acidic substance, suppressing the attack on the catalyst active body and extending the life of the catalyst. This invention relates to a catalyst for waste gas treatment.

In the catalyst of the present invention, the solid acidic substance to be coated has a chemical composition of 5 in, 210 to 90 wt, % and A/20.
Consisting of 10-90 wt% or 510210-9
0 wt% and 10 to 90 wt% of ZrO2 is used. If the thickness of the coating is too thin, it will not be effective, so it should be more than 10 μm, and if it is too thick, the initial activity of the catalyst will drop significantly (which is not desirable, or it will reduce the NOx caused by the catalyst that is currently in practical use. The reaction of NH3 is extremely fast (
・As long as the thickness is about 50 μm, there is no practical problem in reducing the initial activity.

Examples of the catalyst of the present invention will be explained below.

[Example 1] Tio (1 wt% V2O5,8 in Anacuse type)
50 wt% 8102-50 was added to the catalyst supporting wt% W03 at a thickness of 5, 10, 20゜30.50.70μ, respectively.
The initial activity and life test results of the catalyst coated with a single acidic substance consisting of wt% Z r O2 are shown in FIG. 1 in comparison with the results of the coated/treated catalyst.

From Figure 1, 5 Q wt%5iO2-50wt%zr
It can be seen that the O2 coating has a significant effect on increasing the catalyst life.

[Example 2] 90 wt% Sln210wt was added to the same catalyst as in Example 1.
%AI! 5, i of a solid acidic substance consisting of 205,
o.

For catalysts coated to a thickness of 20.30, 50.70μ (
・The results of the initial activity and life test are shown in Figure 2 in comparison with the results of the uncoated catalyst.

From Figure 2, 90 wt%5107-10wt%k12
It is clear that the 0° coat increases catalyst life.

[Example 3] The same catalyst as in Example 1 was added with a chemical composition of 90 wt%5in.
2-10 Comparing the initial activity and life test results of catalysts coated with a solid acidic substance consisting of ZrO2 to a thickness of 5, 10, 30, and 50.70μ with the results of uncoated catalysts. It is shown in Figure 6.

From Figure 6, 90wt%5102-10wt%Z r
The O2 coating clearly increases the catalyst life (・
Ru.

[Example 4] The same catalyst as in Example 1 was added with a chemical composition of 50 wt% Sj,
The initial activity and life test results of catalysts coated with a solid acidic substance consisting of O-50vvt%Aj'205 to a thickness of 5, 10, 30, and 50.70μ, respectively, were compared with the results of uncoated catalysts. This is shown in Figure 4.

As is clear from FIG. 4, as with the other examples, when the coating thickness is in the range of about 1D to 50μ, it is effective in increasing the front part without significantly impairing the initial activity.

[Example 5] The same catalyst as in Example 1 was added with a chemical composition of 10 wt% SiO-
A solid acidic substance consisting of 90 wt% Z r O2 was
, 10, 30, and 50. The initial activity and life test results of the coated catalysts with a thickness of 70 μm are shown in FIG. 5 in comparison with the results of the uncoated catalyst.

As is clear from FIG. 5, the catalyst coated with the above-mentioned solid acidic substance has a longer catalyst life than the uncoated catalyst.

[Example 6] The same catalyst as in Example 1 was added with a chemical composition of 1 Qwt% 5102
-90 wt% A/205 solid acidic catalyst coated with a thickness of 5, 10, 30, 50, and 70 μm (・) The initial activity and life test results were compared to the uncoated catalyst. The results are shown in Figure 6 for comparison.

As is clear from FIG. 6, it can be seen that the coating with the solid acidic substance described above is effective in increasing the lifespan, as in the above embodiments.

[Brief explanation of the drawing]

1 to 6 are graphs showing the relationship between the initial activity and life of the catalyst of the present invention (expressed as relative values to the uncoated catalyst) and the coating thickness thereof. Figure 1 50 is %5LO250wt%Zr0z : ] hlJ
FF and (p) FIG. (μ) Fig. 4 50u+t%SL, 02 50u+t% AJL203 coating layer thickness) Fig. 5 10wt% 5LO290u+t% ZrO2 coating layer thickness) l) Fig. 6

Claims (1)

[Claims] Adding 7mmoni7 to the waste gas containing nitrogen oxides,
In the catalyst that reduces nitrogen oxides in the gas and makes them harmless, the catalyst surface has a chemical composition of 510210 to 90 wt%.
and A/203, consisting of 10 to 90 wt%, or 510
A catalyst for waste gas treatment characterized by being coated with a solid acidic substance consisting of 210 to 90 wt% of ZrO and 210 to 90 wt% of ZrO.