JPS63171643A - Catalyst for removing nitrogen oxide - Google Patents

Abstract

PURPOSE:To improve an anti-poisoning property to arsenic, by allowing a tita nium oxide to support a compd. of at least one element among V, Cr, Mn, Mo, etc., adding with a substance having high specific surface area such as activated carbon and forming a catalyst. CONSTITUTION:The titanium oxide support is allowed to support the compd. of at least one element selected among a group consisting of V, Cr, Mn, W, Mo, Fe, Co, Cu and etc. Then the catalyst for removing nitrogen oxide is obtained by adding and mixing the material having high specific surface area selected among a group consisting of acti activated carbon, zeolite, silica and silica-alumina to the titanium oxide support. The content of the additional material having high specific surface area is preferable to be under 50wt.% of the total amt. of the catalyst and the material having high specific surface area preferably has the specific surface area of >=200m<2>/g. Then, the amt. of the active component such as V, W or Mo supported with the catalyst support is suitable to be 1-6wt.% of the total amt.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a ninth catalyst for removing nitrogen oxides contained in combustion exhaust gas such as boiler exhaust gas.

[Prior Art] Conventionally known methods for removing nitrogen oxides from combustion exhaust gas include a wet absorption method in which nitrogen oxides are absorbed using an alkaline aqueous solution or a sulfite aqueous solution, and a dry catalytic reduction method using a catalyst.

Among them, the catalytic reduction method using ammonia using a catalyst is most often applied industrially. This method involves reacting nitrogen oxides and ammonia in exhaust gas in the presence of a catalyst to reduce them to harmless water and nitrogen. Tungsten oxide, vanadium oxide, molybdenum oxide, iron oxide, etc. are used as catalysts. Catalyst supported on titanium oxide (Special Publication No. 57-3
6012) and a catalyst in which cerium oxide is supported on titanium oxide (Japanese Patent Publication No. 53-13339) are known.

In addition to catalysts using titanium oxide as a carrier, we developed a nine-catalyst catalyst using vanadium oxide supported on aluminum oxide, which has a high specific surface area.
6-44778), but in order to treat exhaust gases containing sulfur oxides such as heavy oil and coal combustion exhaust gases, the following catalysts with titanium oxide as a carrier are better from the viewpoint of adhesion resistance against sulfur oxides. It is excellent.

[Problem that the invention seeks to solve]

Is a catalyst made of titanium oxide supporting a transition metal compound such as vanadium, tungsten, or molybdenum a sulfur oxide for the above reasons? It is widely used as a catalyst for the treatment of heavy oil-fired or coal-fired exhaust gas, but depending on the type of fuel used, arsenic compounds may exist as gaseous substances in the exhaust gas, and this may cause adsorption or oxidation of the catalyst. Because it is captured and accumulated in the catalyst by action, it causes blockage of catalyst pores and compounds with active ingredients? This has the disadvantage that the catalyst activity rapidly decreases.

[Object of the Invention] The present invention provides a catalyst with improved poisoning resistance against gaseous arsenic compounds in exhaust gas.

[Ninth way to solve the problem]

The present invention is based on vanadium 9m, chromium%ingan, ri/guste/
, at least one compound selected from the group consisting of molybdenum, iron, cobalt, and copper is supported on titanium oxide, and this is further loaded with activated carbon, zeolite, silica, and silica-alumina. This is a catalyst for removing nitrogen oxides, characterized in that it is formed by adding and mixing a specific surface area substance.

The catalyst of the present invention uses titanium oxide as a carrier, and the active component is (L
1 to 40 vtl, preferably α5 to 30 wt%, is further added with activated carbon, zeolite, silica, or silica-alumina with a large specific surface area of 200 m''/ Arsenic compounds present in the exhaust gas are selectively collected in the many micropores present in the surface area material, thereby suppressing the poisoning of the titanium oxide-based material that maintains the catalytic activity.

The specific surface area of conventional catalysts using titanium oxide as a carrier is about 50 to 12 G-/f, but that of activated carbon, zeolite, silica + silica/alumina has a surface area of more than 200 m/f, as mentioned above. (Especially activated carbon is 1
000 to 3000 m"/iF), and has many microscopic pores compared to conventional catalysts. The adsorption of gaseous arsenic substances is achieved through the capillary condensation action of activated carbon, zeolite, and silica. has a higher adsorption rate on high specific surface area materials such as silica and alumina,
Conventional catalysts with small specific surface areas do not accumulate arsenic.

The activated carbon may be prepared from any carbonaceous raw material such as wood, coconut shell, lignin charcoal, or coal.

Zeolite as a high specific surface area substance to be added is of type X and Y type.
type, mordenite, 28M-5, silicalite, etc. can be used. Mu-type zeolite is not preferred because its pore diameter is smaller than that of arsenic vapor molecules (mugao@), and arsenic compounds cannot enter the zeolite pores.

Since the high specific surface area substance itself does not have any activity for removing nitrogen oxides, it is not preferable to add too much of it, and the amount added is preferably in the range of 10 to 4 sovtl based on the entire catalyst.

Hereinafter, in order to prove the effect of the catalyst of the present invention, further explanation will be given using Examples.

[Example 1] 80 parts of anatase-type titanium oxide, 11 parts of vanadium oxide
A catalyst consisting of part S, 7 parts of tungsten oxide, and 12.5 parts of a binder component (this is designated as comparative catalyst-1.N!
Activated carbon with a specific surface area of 100Ω-z/y was mixed with 10wt%, 2GWt, and !5of%, respectively, and extruded into a honeycomb mold. The prepared catalysts were designated as Catalyst-1 to Catalyst-3, respectively.

Comparative catalyst-1 and catalyst-1 to catalyst-3 were prepared with an inner diameter of 24-
Fill it into a small reactor and conduct a denitrification activity test under the following conditions. In addition, 25 ppm Mueg for each catalyst
o@OR with steam; 5%, 801: 1000 p
PM's N! Pace gas at 350℃, 8V: 4500
hr-' for 10 hours, and the catalyst activity after the treatment was measured under the same conditions.

The results are summarized in Table 1.

(Denitrification activity measurement conditions) No.: 100p10 0pp: 100 ppm 1301: 800 ppm 0 spirits 4%Co,:
12 Person in charge H! 0: ρ1% N! : Residual temperature: 350C 8'V: 16300hr-' Table 1 [Example 2] Comparative catalyst-1 of Example 1 was mixed with each substance shown in Table 2 below, and the mixture was prepared in the same manner as shown in Example 1. Extrusion molded. The prepared catalysts are referred to as catalysts 4 to 9, respectively.

Table 2 Catalysts-4 to Catalyst-9i A denitrification activity test was conducted under the same conditions as those shown in Example 1, and the results are summarized in Table 3.

Table 3 [Implementation row 3] 85 parts of anatase titanium oxide, 5 parts of copper oxide.

A catalyst consisting of 10 parts of a binder component (this catalyst is referred to as Comparative Catalyst-2).The specific surface area measured by the N1 adsorption method is 60
m''/f) were mixed with each substance shown in Table 4 below and extruded into a honeycomb shape to form Catalyst-10 to Catalyst-13, respectively.

Table 4 Comparative Catalyst 2 and Catalyst-10 to Catalyst-13 were used in row 1
A denitrification activity test was conducted under the same conditions as shown in Table 5, and the results are summarized in Table 5.

Table 5 [Example 4] Catalyst consisting of 85 parts of anatase-type titanium oxide, 5 parts of iron oxide, and 10 parts of a binder component (this is designated as Comparative Catalyst-3.N, specific surface area measured by adsorption method is 55 m”
/ t), the same additives as in Example 3 were added to the following No. 6
They were mixed as shown in the table and extruded into a honeycomb mold to form catalysts 14 to 17, respectively.

Table 6 Comparative Catalyst 3 and Catalyst-14 to Catalyst-17 in Example 1
Conduct a denitrification activity test under the same conditions as shown in Table 7 and summarize the results in Table 7.

Table 7 [Example-5] Catalyst consisting of 80 parts of anatase-type titanium oxide, 10 parts of molybdenum oxide, and 10 parts of a binder component (this catalyst is referred to as Comparative Catalyst-4. N! Specific surface area by adsorption method: 60 m"
/t) were mixed with the same additives as in Example 3 as shown in Table 8 and extruded into a honeycomb shape to form catalysts 18 to 21, respectively.

Table 8 Comparative Catalyst 4 and Catalyst-18 to Catalyst-21 in Example 1
A denitrification activation test was conducted under the same conditions as shown in Table 9, and the results are summarized in Table 9.

Table 9 [Example-6] Anatase type titanium oxide 85 parts, manganese dioxide 5 parts,
Catalyst consisting of 10 parts of binder component (this is referred to as Comparative Catalyst-5. M, specific surface area by adsorption method is 60 m
"/t) were mixed with the same additives as in Example 3 as shown in Table 10 and extruded into a honeycomb mold, and each catalyst was mixed with catalyst 2.
2 to Catalyst-25.

Table 10 Comparative Catalyst 5 and Catalyst-22 to Catalyst-25 in Example 1
A denitrification activation test was conducted under the same conditions as shown in Table 11, and the results are summarized in Table 11.

Table 11 [Example 8iIl-7] A catalyst consisting of 87 parts of anatase titanium oxide, 3 parts of cobalt oxide, and 10 parts of a binder component (this was used as a comparison catalyst -
Set it to 6. M! The specific surface area by adsorption method is 65 m”/
f) were mixed with the same additives as in Example-3 as shown in Table 12 and extruded into a honeycomb shape, and each catalyst was mixed with catalyst-26.
~Catalyst-29.

Table 12 Comparative Catalyst 6 and Catalyst-26 to Catalyst-29 in Example 1
A denitrification activation test was conducted under the same conditions as shown in Table 13, and the results are summarized in Table 13.

Table 13 [Example-8] 86 parts of anatase titanium oxide, 1 part of vanadium oxide,
The same additives as in Example 3 were added to a catalyst consisting of 3 parts of chromium oxide and 10 parts of a binder component (this is designated as Comparative Catalyst-7. The specific surface area by the Ml adsorption method is b 5 m"/f) as shown in Table 14. Mix as shown and extrude into a honeycomb mold.
Catalyst-30 to Catalyst-33, respectively.

Table 14 Comparative Catalyst-7 and Catalyst-30 to Catalyst-33 shown in Example 1 were subjected to a denitrification activation test under the same conditions as in Example 9, and the results are summarized in Table 15.

Table 15 [Effects of the Invention] As is clear from the examples above, the catalyst of the present invention maintains high denitrification activity after arsenic gas treatment and is an excellent catalyst compared to the conventional comparative catalyst. .

Claims (2)

[Claims] (1) Vanadium, chromium, manganese, tungsten,
At least one compound selected from the group consisting of molybdenum, iron, cobalt and copper is supported on titanium oxide,
Furthermore, a catalyst for removing nitrogen oxides is prepared by adding and mixing a high specific surface area substance selected from the group consisting of activated carbon, zeolite, silica, and silica/alumina. (2) The content of the high specific surface area substance to be added is 5% of the total catalyst.
The catalyst for removing nitrogen oxides according to claim (1), which has a content of 0 wt% or less.