JPH02184344A - Catalyst for removal of nitrogen oxide - Google Patents

Abstract

PURPOSE:To obtain a catalyst maintaining NOx removing performance and having low ability to oxidize SO2 to SO3 by incorporating phosphate ore and titanium oxide in a specified ratio and further incorporating the oxide of V, W, etc. CONSTITUTION:This catalyst for removal of NOx in exhaust gas after combus tion contains phosphate ore (A) and titanium oxide (B) in 0.05-0.3 weight ratio of B/(A+B) and further contains one or more among vanadium oxide, tungsten oxide and molybdenum oxide. This catalyst has slightly inferior denitrifying performance but is very effective in reducing the rate of oxidation of SO2 and has superior practicality.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a nitrogen oxide removal method that removes nitrogen oxides from combustion exhaust gas discharged from boilers, internal combustion engines such as gas turbines or diesel engines, and various combustion devices. related to commercial catalysts.

[Conventional technology]

Currently, the mainstream method for removing nitrogen oxides from exhaust gas is to add ammonia to the exhaust gas, catalytically reduce the nitrogen oxides on a catalyst, and decompose them into nitrogen and water. Catalysts used to remove nitrogen oxides from exhaust gas are known to have titanium oxide as the main component and contain vanadium, tungsten, molybdenum, etc. as active metal components. It is also known to have an excellent object removal effect.

In order to prevent clogging due to dust components in the exhaust gas and to reduce the pressure loss of the exhaust gas, this catalyst is extruded into a catalyst molded body in the form of a lattice-like honeycomb or plate-like structures arranged in parallel. There is.

However, when forming this titanium oxide-based catalyst into a honeycomb, in order to maintain a good shape and obtain high strength, it is necessary to carefully dry it after extrusion for a sufficient amount of time without causing cracks. It was cheap to do and manufacturing was not always easy. Although the entire catalyst is still made of titanium oxide, which is a relatively expensive material, and other active ingredients, the portion of the catalyst molded body that contributes to the denitrification reaction, according to the inventors' study, This is the surface layer within 100μ from the surface, and expensive materials are not used effectively.

In view of these problems, catalysts using gypsum as a carrier have recently been proposed (for example, Japanese Patent Publication No. 53-730).
No. 6 and Japanese Patent Publication No. 6m-12902), the inventors have also proposed a catalyst using ■-type anhydrite (
(See Japanese Patent Application No. 62-304770).

[Problem to be solved by the invention]

The performance required of a denitration catalyst is, of course, that it has excellent ability to remove nitrogen oxides, but another requirement is that it has the ability to oxidize SO2 to S03 when sulfur oxides are included in the exhaust gas. It is required to be as small as possible. This is because the oxidation of SO2 to SO3 is undesirable because it causes corrosion and blockage of the downstream equipment of the denitrification equipment.

A catalyst using gypsum that the inventors had proposed earlier (patent application 1986)
2-504770) was found to have a drawback in that it had a greater ability to oxidize 802 to 803 than conventional catalysts containing titanium oxide as a main component.

[Failure to solve the problem]

The present invention aims to improve the shortcomings listed in -1- (this was discovered after repeated studies), and the catalyst of the present invention is based on the type 1 anhydrite of the inventors' earlier application (Japanese Patent Application No. 1983-304770). is replaced with phosphate rock or silicic anhydride powder, thereby retaining the characteristics of the lead shaft catalyst and making it a catalyst with a small ability to oxidize SO2 to SO3.

That is, the present invention provides (]) a weight ratio of B, /(A+B') of component A consisting of phosphate rock and component B consisting of titanium oxide from 0.05 to 0.
3 and further contains one or more oxides of vanadium, tungsten, and molybdenum (2) A catalyst consisting of component A consisting of silicic anhydride and component B consisting of titanium oxide. The catalyst for removing nitrogen oxides is characterized in that the weight ratio of /(A+B) is 0.05 to 06 and further contains one or more oxides of vanadium, tungsten and molybdenum.

The ratio of phosphate rock or silicic anhydride to titanium oxide in the present invention is preferably 005 to 03 in terms of titanium oxide/titanium oxide weight (phosphate rock or silicic anhydride). As with the previous application, this is because when the weight ratio of titanium oxide/titanium oxide + (phosphate rock or silicic acid anhydride) is less than 005, the activity decreases rapidly, and when it is more than 06, the extruded product may crack during drying. It depends on how easy it is.

The reason why the oxidation of SO2 to S03 is suppressed by using phosphate rock or anhydrous silicic acid is not clear, but one factor is that the phosphate rock (Oa5 F (PO2) 3) used in the present invention and the anhydrous oxidation of SO2 are suppressed. Silicic acid raw materials hardly dissolve in water, and the solubility in water is very low compared to gypsum (for example, phosphate rock is about 1/100 of that of gypsum), so it is a component that dissolves when kneaded with water during catalyst production. This is thought to be because the influence of (particularly Ca ions) has almost disappeared.

Note that as the silicic anhydride raw material in the present invention, natural amorphous silicic acid, silica sand, diatomaceous earth, white clay, pearlite, permiculite, white carbon, silica gel, etc. can be used.

Example 1 Titanium oxide powder was impregnated with a 10-functional methylamine aqueous solution of ammonium metavanadate and ammonium paratungstate, dried, and then calcined at 450°C for 5 hours to form V2O5.
Titanium oxide powder containing 3 weight ratio and WO 38 weight ratio was obtained. After mixing 2 parts by weight of this titanium oxide powder A with 63 parts by weight of phosphate rock powder, 4 parts by weight of kaolin, and 2 parts by weight of glass fiber, 16 parts by weight of water and 6.8 parts by weight of an organic binder component.
After adding parts by weight and kneading with a kneader, 6 kakuφX 5 ran
It was extruded into a cylindrical shape of size L, air-dried overnight, and then fired at 550°C for 3 hours in an electric furnace.

Example 2 In fruit 2tl'lJ1, using ammonium molybdate in place of ammonium paratungstate,
A catalyst was obtained using the same procedure except that a titanium oxide powder containing 2056 parts by weight and 38 parts by weight of MoO was obtained.

Example 3 66 parts by weight of phosphate rock powder, 73 parts by weight of titanium oxide powder,
After thoroughly mixing 4 parts by weight of kaolin and 2 parts by weight of glass fiber, a 10th scale methylamine aqueous solution of ammonium paratungstate containing 0.7 parts by weight of WO3 and ammonium metavanadate containing 0.25 parts by weight of V205 were added.
A 0% methylamine aqueous solution and 10 parts by weight of water were added and kneaded in a kneading machine, then extrusion molded into a cylindrical shape of 3 dia.

Example 4 In Example s, instead of using an aqueous solution of ammonium paratungstate in 104 methylamine, an aqueous solution of ammonium paratungstate in 1091 containing 08 parts by weight of MoO3 was used.
A catalyst was obtained in the same manner using + methylamine aqueous solution.

Comparative Examples 1 to 4 In each of Examples 1 to 4, catalysts were prepared using ■ type Suiseki noble powder instead of phosphate rock, and Comparative Examples 1 to 4 were prepared, respectively.
Toshida.

Test Example 1 Catalysts from Examples 1 to 4 and Comparative Examples 1 to 4
Regarding the catalyst, the denitrification rate and SO2 oxidation rate were measured under the following conditions, and the results shown in Table 1 were obtained.

Conditions Catalyst i: 20 ml EI02: 4
00 ppm5 V:5000Hr' 0
2:54 Temperature: 380℃ H2O: 10c
I) NO: 150 ppm remaining 2N2Nu
3: 150 ppm Inlet No. (ppm) - Outlet No. (ppm) Inlet No.
(ppm) × 100 NOx removal rate width) Table 1 Denitration rate and SO2 oxidation rate measurement results Catalyst denitration rate (%) SO2 oxidation rate (regret) Example 1 Example 2 Example 4 Comparative example 1 Comparative example 2 Comparison Example 6 Comparative Example 4 92.0 91.0 89.0 9 & 5 Example 5 Titanium oxide powder was impregnated with a 10th ratio methylamine aqueous solution of ammonium metavanadate and ammonium paratungstate, dried and then fired at 450°C for 5 hours. ■20.3
By weight, WO38038 parts by weight titanium oxide powder was obtained.

After mixing 8.2 parts by weight of this titanium oxide powder, 63 parts by weight of silica sand powder, 4 parts by weight of kaolin, and 2 parts by weight of glass fiber, 16 parts by weight of water and 6.8 parts by weight of an organic binder component were added. After kneading with a kneading machine, extrusion molding into a cylindrical shape of 3 mm φ x 5 mm L, air drying at -i night, and heating at 550°C in an electric furnace.
, filter time calcined 1, Example 6 Actual Mli In Example 5, using ammonium molybdate instead of ammonium paratungstate, VB
A catalyst was obtained using the same procedure except that titanium oxide powder having a weight width of 0.053 and containing 38 parts by weight of MoO was obtained.

Example 7 After thoroughly mixing 63 parts by weight of silica sand powder, 73 parts by weight of titanium oxide powder, 4 parts by weight of kaolin, 2 parts by weight of glass fiber, and 68 parts by weight of an organic binder component, paratungstic acid containing 0.65 parts by weight of WO3 was prepared. Add 10% methylamine aqueous solution of ammonium metavanadate containing 0.2 parts by weight of 205 to 10 parts by weight of water and mix with a kneader. Extruded into a cylindrical shape, air-dried on a stormy night, then heated in an electric furnace at 550°C.
It was baked for 3 hours.

Example 8 In Example 7, instead of using a 10-group methylamine aqueous solution of ammonium paratungstate, a 10-group solution of ammonium paratungstate containing 0.65 parts by weight of MoC2 was used.
A catalyst was obtained in the same manner using an aqueous methylamine solution.

Example 9 A catalyst was obtained in the same manner as in Example 7 using silica gel (manufactured by Fuji Davison Chemical, trade name: Siloid) instead of using silica sand.

Comparative Examples 5 to 8 In each of Examples 5 to 8, catalysts were prepared using ■-type anhydrite powder instead of silica sand, and Comparative Examples 5 to 8 were prepared, respectively.

Test Example 2 From Example 5 to Example? Catalysts and Comparative Examples 5 to 8
Regarding the catalyst, the denitrification rate and S
When the O2 oxidation rate was measured, the results shown in Table 2 were obtained.

Table 2 Denitration rate and SO2 oxidation rate measurement results Catalytic denitration rate (related) SO2 oxidation rate (壬) Example 5 Example 6 Example 7 Example 8 Example 9 Comparative example 5 Comparative example 6 Comparative example 7 Comparative example 8 91 .0 90.5 91.0 95.0 93.5 [Effects of the Invention] As is clear from Tables 1 and 2, the catalyst of the present invention has slightly inferior denitrification performance compared to the catalyst whose main component is gypsum. However, it has a remarkable effect of reducing the sO□ oxidation rate, and is a practically excellent catalyst.

Claims (2)

[Claims] (1) Component A consisting of phosphate rock and B consisting of titanium oxide
A catalyst for removing nitrogen oxides, which has a weight ratio of components B/(A+B) of 0.05 to 0.3, and further contains one or more oxides of vanadium, tungsten, and molybdenum. (2) The weight ratio of B/(A+B) of component A consisting of silicic anhydride and component B consisting of titanium oxide is 0.05 to 0.3, and one or more oxides of vanadium, tungsten, and molybdenum are further added. A catalyst for removing nitrogen oxides, comprising: