JPH0256245A - Catalyst for removing nitrogen oxide - Google Patents

Abstract

PURPOSE:To obtain the catalyst having excellent heat resistance by incorporating FeTiO3 having an ilmenite structure or the FeTiO3 and a transition metal compd. into the catalyst. CONSTITUTION:An ilmenite ore which is the raw material of titanium oxide or the synthetic ilmenite ore is used for the ilmenite or the ilmenite may be partly substd. with TiO2, ZrO2, Al2O3, etc., within an about 50wt.% range. V2O5, MoO3, WO3, Fe2O3, etc., are used within an about 0.01-20wt.% range as the oxide of the transition metal and clay, inorg. fibers, org. binder, etc., are used as a carrier material. These materials are kneaded or impregnated and calcined. This catalyst is higher in activity per specific surface area than the conventional catalyst essentially consisting of the titanium oxide and exhibits an excellent effect in heat resistance as well.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel catalyst for catalytic reduction of ammonia for efficiently removing nitrogen oxides contained in exhaust gas.

Speed-following m Various catalysts for catalytic reduction of NOx using ammonia have been proposed.

Among them, titanium oxide and transition metal oxides (e.g. V
z OS, W O3, M 603, F e2
Q.

A composite catalyst containing Cu, O, etc.) had high initial performance and excellent durability.

However, although titanium oxide has excellent acid resistance, it has the disadvantage of poor heat resistance.

Therefore, the catalyst has a problem in that its specific surface area gradually decreases during use (crystals grow at 500° C.), resulting in a decrease in activity.

The present invention has been made to solve the above-mentioned problems, and has superior heat resistance ( The object of the present invention is to provide a catalyst that is heated to at least 700°C.

for The catalyst according to the invention has the following composition.

(1) Fe Ti Oz with ilmenite structure
Catalyst for catalytic reduction of nitrogen oxides with ammonia containing.

(2) F e T i O having an ilmenite structure,
A catalyst for the catalytic reduction of nitrogen oxides with ammonia containing at least one type of transition metal oxide.

FeTi0. with ilmenite structure. (hereinafter referred to as ilmenite) is a natural product.

Any synthetic material is fine.

Ilmenite ore, which is a raw material for producing titanium oxide, is known as a natural mineral, and is more suitable because it is available at a lower price than synthetic minerals.

In addition, a part of ilmenite is TiO2゜ZrO2, Al
One or more known carrier materials such as 2O, 5in2, etc. may be substituted.

The amount of substitution is up to 50% by weight of the total amount of ilmenite.

Examples of transition metal oxides include Vz Os = MQ 03- W○, , Fe, 03.
CuO.

Cr, 03s Mn O2? L a OX t
CeOx yNb20. etc.

(1) The content of ilmenite in the catalyst containing ilmenite is 50% to 100% by weight, and if ilmenite alone does not reach 100% by weight, molding of known carrier materials, clay, etc., which are often used in catalysts. Auxiliary agent.

Inorganic fibers, organic binders, etc., which are reinforcing agents for the molded body, may be contained.

(2) In a catalyst containing ilmenite and a transition metal oxide, the respective contents are ilmenite 50% by weight or more, transition metal 0.01% to 20% by weight, and other components as described in (1) above. be.

The method for producing the catalyst according to the present invention is not particularly limited, and any known method may be used as appropriate, but a preferred method is as follows.

(1) Kneading method A method in which solid components such as ilmenite and carrier materials and liquid components such as water and organic binder liquid are kneaded in a kneader or the like, and the mixed material is extruded or granulated into spherical shapes.

(2) Impregnation method Solid components such as ilmenite and carrier material, water, and organic binder liquid are simultaneously fed into a spherical granulator (pan-type granulator, etc.) to form a spherical shape, and after firing, the solid components are immersed in a transition metal solution. Method of preparing supported catalysts.

The catalyst of the present invention has superior heat resistance compared to conventional catalysts whose main component is titanium oxide, and can be heated to as low as 700°C, depending on the preparation method. is 9
It can be used up to about 50°C without losing its activity.

Further, the specific surface area of the catalyst is 3 to 1 ord/g.

Conventional catalysts had low activity at this level of specific surface area and were not practical, but the catalyst of the present invention has high activity per specific surface area (in other words, high reaction rate per specific surface area).
Therefore, it is quite practical.

It also has excellent acid resistance and is suitable as a catalyst for the catalytic reduction of NOx by NH.

This will be explained in detail below using examples.

Example 1 Malayan ilmenite having the chemical composition shown in Table 1 was ground in a dry ball mill.

The specific surface area of the obtained ilmenite powder is 3.9rd/
The g average particle size was 35μ.・20kg of this ilmenite powder, 1kg of clay with an average particle size of 2μ, ceramic fiber made by Nichias (Fine Seal #1)
300), 2 kg of polyvinyl alcohol aqueous solution (2 kg),
0% solution) 6Q was roughly mixed in advance with a mixer, and this was thoroughly mixed with a mixer, so that the wall thickness was 1.4 on and the pitch was 7.4 m.
A honeycomb structured die was attached to a vacuum extruder, and extrusion was performed at an extrusion pressure of 50 kg/-.

After drying the extrudate, it was calcined at 500° C. for 3 hours to obtain a catalyst. The specific surface area of the obtained catalyst was 4.2 I/g.

Example 2 A catalyst was obtained in the same manner as in Example 1, except that 15 kg of ilmenite was prepared in the same manner as in Example 1, 5 kg of anatase-type acidic titanium having a specific surface area of 80 rrll/g, and 8Q of polyvinyl alcohol aqueous solution. The specific surface area of the obtained catalyst was 21.6 i/g.

Example 3 The catalyst obtained in Example 2 was further impregnated with an aqueous solution of vanadyl oxalate to obtain a catalyst supporting 2% of V2O. The specific surface area of the obtained catalyst was 20.9 m/g.

Example 4 The catalyst obtained in Example 2 was further immersed in an aqueous solution of vanadyl oxalate and ammonium metatungstate.
．． A catalyst was obtained in which 0.5% of W○ was supported and 5% of W was supported. The specific surface area of the obtained catalyst was 23.2 rri'/g.

Example 5 50 kg of ferric nitrate and 10 kg of titanium tetrachloride (T i 0 ) were added to 100 Q of water and thoroughly stirred to obtain a homogeneous solution. While stirring, ammonia gas was added until pl+ reached 7.0 to form a precipitate, which was filtered, thoroughly washed with water, dried, and then calcined at 800° C. for 3 hours.

The specific surface area of the fired product was 8.9 m/g. In addition, when X-ray diffraction was performed, d indicated that it was ilmenite.
=2.74A A broad peak was obtained at 1.72A.

When pulverized in the same manner as in Example 1, the average particle size was 28μ. Thereafter, a catalyst was obtained in the same manner as in Example 1. The specific surface area of the obtained catalyst was 9.2rn'/g.

Example 6 The catalyst obtained in Example 5 was further impregnated in an ammonium molybdate solution to obtain a catalyst containing 5% MoO. The specific surface area of the obtained catalyst was 10.1 i/g.

Example 7 15 kg of ilmenite prepared in the same manner as in Example 5
, 10 alumina with a specific surface area of 210 ni'/g
A catalyst was obtained in the same manner as in Example 1 except that the polyvinyl alcohol aqueous solution was changed to 9Q.6 This was further impregnated with a copper nitrate aqueous solution to obtain a catalyst containing 2.5% Cu 2 O. The specific surface area of the obtained catalyst was 39.7 rri'/g.

Reference Example 1 A catalyst was obtained in the same manner as in Example 1 except that 20 kg of anatase-type titanium oxide (average particle size 2 μ) having a specific surface area of 95.0 m/g was used as polyvinyl alcohol aqueous solution 1 (H2).

In addition, V2O was added in the same manner as in Example 3.

A catalyst containing 2% of was obtained. The specific surface area of the obtained catalyst was 78.2 rri'/g.

Example 8 The catalysts obtained in Examples 1 to 7 and Reference Example 1 were placed in 3 cells x
It was cut into 3 cells x 15offlIIIQ and filled into a catalytic reaction bed to perform a catalytic reaction.

The reaction conditions at this time were a reaction temperature of 300'C.

400°C, 500°C S V = 10675H-'' The gas composition was as follows.

(AV=25) N　O200ppm N H3200ppm 02 2% SO2500ppm 820 10% The test results are shown in Table 2.

Example 9 Example 1. The catalyst obtained in Reference Example 1 was cut into 3 cells x 3 cells x 150as+jll.

This was filled into a heat resistance tester set at 500° C. through which air was circulated, and a heat resistance test was conducted for 1000 hours.

After the heat resistance test, the samples were taken out and subjected to an activity test in the same manner as in Example 8, and compared with the initial activity. ) The test results are shown in Table 3.

Claims (1)

[Claims] 1. A catalyst for catalytic reduction of nitrogen oxides with ammonia containing FeTiO_3 having an ilmenite structure. 2. Catalyst for catalytic reduction of nitrogen oxides using FeTiO_3 having an ilmenite structure and ammonia containing one or more transition metal oxides.