JPS62121646A - Preparation of denitration catalyst - Google Patents

Abstract

PURPOSE:To enhance catalytic activity in spite of a small support amount of palladium, by forming a denitration catalyst by a method wherein a vanadium compound is contacted wit a carrier composed of oxide of a metal selected from the Group III and the Group IV in a gaseous phase to be supported by said carrier. CONSTITUTION:A vanadium compound is contacted and reacted with a carrier composed of oxide of a metal selected from the Group III and the Group IV in a gaseous phase pref. at 150-800 deg.C and vanadium is supported by the carrier from the gaseous phase to form a denitration catalyst. As Group III metal oxide, there are aluminum oxide, indium oxide, tallium oxide, etc. and, as Group IV metal oxide, there are titanium oxide and zirconium oxide etc. As the vanadium compound, there are VOCl3, VCl4, etc. each being a liquid substance at ambient temp. The support amount of vanadium by the carrier is 0.05-20wt%, pref. 0.2-10wt%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a catalyst applied to the removal of NoX from waste gas from combustion furnaces such as large power boilers and private boilers, incinerators, and chemical plants. Regarding the manufacturing method.

[Conventional technology]

As catalysts for exhaust gas denitrification, catalysts in which active metals such as vanadium, tungsten, molybdenum, iron, and copper are supported on titanium oxide, alumina, or zeolite as carriers are known. However, most of these catalysts have conventionally been produced by a method in which a carrier is impregnated with or kneaded with an aqueous solution of various active metal salts or a solution dissolved in an organic solvent.

Catalysts prepared in this way have a certain level of performance and are widely used in practical use, but they do not necessarily have sufficient performance in terms of reducing the amount of catalyst and reducing pressure loss in the reactor. It cannot be said that it has

Improving the performance per unit weight (or volume) of the catalyst means making the processing equipment more compact, reducing pressure loss,
There is no doubt that it is useful from the point of view of saving resources and energy as it leads to the saving of expensive catalyst raw material resources.

[Problem that the invention seeks to solve]

The inventors investigated the activity expression of catalysts prepared by conventional techniques and found that the proportion of active metal supported by the impregnation method or cross-fertilization method that contributes to the activity expression is the total supported amount. I found that there was a slight difference in contrast. −
For example, in a 3 wt% V2O5/TiO2 catalyst, only 15% of v20s acts as an active site.
The remaining 85 points are not active points. This indicates that v2011 is not uniformly dispersed on the carrier, and in the preparation by the conventional impregnation and kneading method, the active metal is supported in a wasteful manner from the standpoint of catalytic activity. I found out that there is.

The present invention aims to provide a method for producing a denitrification catalyst that does not have the drawbacks of the conventional methods for producing a denitrification catalyst as described above.

[Means for solving problems]

The inventors discovered that, as an alternative to conventional catalyst preparation, when a gaseous vanadium compound is applied to a carrier, vanadium metal is uniformly supported on the carrier surface, and a catalyst with higher activity than conventional catalysts can be obtained. This discovery led to the completion of the present invention.

That is, the present invention involves contacting a metal oxide consisting of Group Ⅰ or Group Ⅰ with a vanadium compound in a vapor phase,
This is a method for producing a denitrification catalyst characterized by supporting vanadium from a gas phase on a metal oxide carrier.

The following are preferred embodiments of the present invention.

(1) The group III metal oxide is aluminum, indium, thallium, the group II metal oxide is titanium, zirconium,
Must be selected from hafnium, thorium, silicon, germanium, and tin.

(2) The vanadium compound has voct3. VOBr3
.

Must be vct4.

(3) The temperature at which the vanadium compound is brought into contact with the metal oxide support of group (1) or group (2) is 150 to 800°C, preferably 200 to 600°C.

[Effect]

Compared to conventional impregnated catalysts, the vanadium-supported catalyst of the present invention has better dispersibility on the surface of the carrier, forms a uniform molecular layer, and has high denitrification performance with a small amount of support. shows.

In the catalyst preparation method of the present invention, the amount of supported ① is 0.05 to 20% by weight, preferably 0.2% by weight based on the carrier.
It is preferable that the amount is between 10% and 10% by weight.

The carrier used is a metal oxide of group III or group III, and can be used with a metal oxide containing at least one of reed, titanium, aluminum, silicon, zirconium, thallium, hafnium, thorium, soot, potassium, indium, and germanium. .

The vanadium compound carried in the gas phase is VOCl2. which is a liquid substance at room temperature. V C4, VOBr3, and solid state (r) VCl3, VCl2, VOCl2,
VBr3, etc., are brought into contact with a metal oxide carrier in a gas phase to obtain a catalyst.

The metal oxide support is preferably reacted with a vapor phase vanadium compound at a temperature in the range of 150°C to 800°C, preferably 200°C to 600°C, to carry out vanadium loading.

[Example 1] 6ooy of titanium tetrachloride (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 900y of pure water, and an appropriate amount of ammonia was added to adjust the pH to 10.
A precipitate formed. This precipitate was aged for a day and night, filtered, washed and dried to obtain 180F white precipitate of TI(OH)4. This white precipitate was calcined at 500°C for S hr, and the generated TiO2 (anatase type) 20y was heated in a reactor at a constant temperature of 400°C to voa, which is a liquid vanadium compound.
At t3, at room temperature, add N2 carrier gas to 40 m//
The VOct3 vapor produced by blowing in at min was passed through the furnace for 2 hours.

Next, voct3 was replaced with water, and steam was passed into the furnace under the same conditions. Further, the catalyst was taken out from the reactor and calcined in air at 500°C for 5 hours, and this was designated as Catalyst A. The amount of V supported in this product was 0.72 wt.

〔Example? ]

A catalyst was prepared in the same manner as in Example 1, except that VOBr3 was used as the V raw material, and Catalyst B was obtained.

The supported amount of (2) was 0.15 wt%.

[Example 3] (1) A catalyst was prepared in the same manner as in Example 1, except that VO64 was used as the raw material, and Catalyst C was obtained.

The supported amount of (2) was 0.61 wt%.

[Example 4] Using vocz3 as the V raw material, voct shown in Example 1
3 Steam treatment and steam treatment were repeated 2 times, 3 times, and 5 times to obtain catalysts E and F, respectively. The supported amount of each of these V is 1
．． They were 5 wt%, 2.3 wt%, and 4.1 wt%.

In addition, as in this example, if the voats steam treatment is followed by the steam treatment and then the voct3 steam treatment, the amount of V supported on the carrier can be increased as shown in the model below. 1I OOO [Comparative Example 1] Implementation TiO2 prepared in the same manner as in Example 1 was used as a carrier.
Impregnated with ammonium metavanadate aqueous solution, dried 500
By baking at ℃ for 3 hours, the amount of v supported was 0.2
wt%, 0.6 wt%, 1.5 wt%, 3. Owt
%, 5. Owt% catalyst was obtained. Catalysts a, b, c respectively
, d, and e.

[Example 5] Catalysts A, B, O, D, obtained in Examples 1 to 3
E.

A denitrification performance test was conducted on catalysts a, b, c, d, and e obtained in Comparative Example 1 and F under the conditions shown in Table 1. The test results are shown in Table 2.

[Example 6] Aluminum isopropoxide (manufactured by Wako Tsumugi Co., Ltd.) 700
Dissolve y in 1,000 ml of pure water, adjust the pH, age,
Filter and dry the At(OH)3 white powder to 21
I got 0y. This powder was fired at 500° C. for 3 hr, and voct3 vapor and water vapor were alternately passed through the produced At203 under the same conditions as in Example 1, so that 10 wt% of V was supported on the Az2o3 support.

This catalyst will be referred to as catalyst G.

Furthermore, ammonium metavanadate aqueous solution was added to At20
3 was impregnated to prepare a catalyst f having the same composition as the above catalyst. The denitrification performance test conducted in Example 5 was conducted on these catalysts. The performance test results are also shown in Table 2.

[Example 7] ■Using VCl2 as a raw material, heating to 100°C,
The solid phase vct3 is sublimed. A catalyst was prepared in the same manner as in Example 1, except that this VCl3 vapor was sent by N2 carrier gas, and a catalyst with a V loading of 0.70 wt% was obtained. This catalyst will be referred to as catalyst (2).

This catalyst was subjected to the same denitrification performance test as in Example 5, and the results are also shown in Table 2.

Table 1 Table 2 Denitrification performance test results [Effects of the invention] As is clear from the results in Table 2, the gas-phase supported catalyst (Catalyst A
, B, O, D, E, IP, G, and H) are catalysts (catalysts a, b, c, d, e.

Compared to (f), the activity is clearly superior even with a small amount of V supported, and it is clear that by using the catalyst prepared by the preparation method of the present invention, the p1 denitrification equipment can be made more compact and the amount of catalyst can be reduced. It is.

Sub-agent: 1) Akira Sub-agent Ryo Hagi Hara - Sub-agent Atsuo Yasunishi

Claims (1)

[Claims] (1) A method for producing a denitrification catalyst, which comprises bringing a group III or group IV metal oxide into contact with a vanadium compound in a gas phase, and supporting vanadium from the gas phase on a metal oxide carrier.