JPH11262673A - Production of flue gas denitrification catalyst and flue gas denitrification catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: T produce a catalyst for denitrification of flue gas which has high fine pore volume even with a high opening rate and is high in strength and excels in denitrification performance and cost effectiveness. SOLUTION: In the case of producing an ammonia catalytic reduction catalyst for denitrification of flue gas by forming catalyst paste containing titanium oxide into a honeycomb, granular or plate like structural body and then drying and calcining it, high water absorptive material having water absorption force of >=100 g/g polymer is added to the titanium oxide by 0.1-3 wt.%. This honeycomb catalyst for denitrification of flue gas produced by this method has catalyst sectional opening rate of >=80% and fine pore volume of >=0.35 ml/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a flue gas denitration catalyst and a flue gas denitration catalyst, and more particularly, to a flue gas denitration catalyst suitable for reducing and removing nitrogen oxides in exhaust gas using ammonia. The present invention relates to a production method and a highly active flue gas denitration catalyst which selectively progresses the above reduction reaction.

[0002]

2. Description of the Related Art Conventionally, a method of reducing and removing nitrogen oxides from exhaust gas of a power plant or a chemical plant with ammonia in the presence of a catalyst has been widely used. The catalyst (denitration catalyst) used for this reaction is usually
It contains active components such as vanadium, tungsten, molybdenum, etc. together with the titanium component which is the main component, and after kneading each of these raw materials, it is formed into a honeycomb, granular or plate-like structure, and further dried and fired to produce. You. The catalyst activity (denitration performance) generally increases as the catalyst has the same shape (cell size, sectional opening ratio) and the same component, and has a larger pore volume. JP-B-55-96 describes that a catalyst having a high pore volume can be obtained by adding an organic substance, and this catalyst has excellent denitration performance and a long life.

However, when a large amount (10% by weight or more) of an organic substance is added to the catalyst component, the calorific value increases in the firing step, and as a result, combustion of the active component tends to occur. Since this combustion lowers the activity of the catalyst and causes cracks in the structure, the amount of the organic substance added to the catalyst component is generally set to about 5% by weight or less, and the temperature is gradually increased while promoting heat radiation. A firing method is employed. However, such a method has a problem that the sintering time is long and the production cost is high.

On the other hand, in order to widely use a denitration catalyst, it is necessary to use an inexpensive denitration apparatus which is excellent in denitration performance. It is important to reduce the cost of the catalyst material, reduce the amount of catalyst required, and improve the performance of the catalyst.
In addition, the use of a high-performance catalyst reduces the amount of catalyst waste, which also improves the economics of the entire denitration apparatus. The denitration performance can be improved by increasing the pore volume of the catalyst.
It can be carried out by increasing the water content of the catalyst component (kneading paste) in the production process of the catalyst. However, the amount of water in the catalyst component cannot be increased arbitrarily,
As shown by the chain line (conventional kneading paste) in FIG. 4A, the shape retention force (hardness of the kneading paste) decreases as the water content increases. Therefore, in the case of the honeycomb catalyst, the wall thickness of the cell (grid) becomes thinner as the aperture ratio becomes higher. Therefore, it is necessary to apply a high pressure using a hard kneading paste having a small amount of moisture.

On the other hand, a honeycomb catalyst formed from a low-moisture paste using a die having a high aperture ratio has a high shape-retaining force and can be formed under high pressure. As shown by (conventional catalyst), the pore volume of the catalyst becomes about 0.25 to 0.30 (m ² / g), and the catalyst activity (reaction rate ratio) also decreases. If the water content is increased to increase the pore volume, the shape retention force of the kneading paste is reduced as described above, and the molding pressure during molding is reduced. It is easy to occur. In the case of a honeycomb catalyst, this can be avoided by lowering the aperture ratio, but the area of the catalyst in contact with the exhaust gas is reduced, and the catalyst performance is reduced. It is extremely difficult to obtain a honeycomb catalyst with a high aperture ratio and fine pores, and the present inventors have studied using a die having a different aperture ratio. At a rate of about 0.3
Obtaining a pore volume of ml / g or more proved to be extremely difficult.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, has a high pore volume even at a high opening ratio, and has a high strength, and is excellent in denitration performance and economical efficiency. An object of the present invention is to provide a method for producing a flue gas denitration catalyst and a flue gas denitration catalyst obtained by this method.

[0007]

Means for Solving the Problems The present inventors previously prepared a catalyst by preparing it in advance by a specific method (raw material heat treatment) so that a pore volume of 0.35 (ml / g) or more was obtained. A method for preparing a catalyst that satisfies both high activity and high pressure molding has been proposed (Japanese Patent Application No. Hei 9-134975), but as a result of further research, 0.35 was obtained without pre-preparation (raw material heat treatment). (Ml /
g) The present inventors have found a production method capable of obtaining a catalyst satisfying both high activity and high pressure molding having a pore volume of not less than the above, and have reached the present invention. The invention claimed in the present application is as follows.

(1) A catalyst paste containing titanium oxide is formed into a honeycomb, granular or plate-like structure, and then dried,
When producing the ammonia catalytic reduction flue gas denitration catalyst by calcination, the catalyst paste is mixed with a superabsorbent substance having a water absorbing power of 100 g / g polymer or more in an amount of 0.1% with respect to titanium oxide.
A method for producing a flue gas denitration catalyst, characterized by adding about 3% by weight. (2) A catalyst component containing titanium oxide is kneaded with water to form a paste, and then 0.1 to 3% by weight based on the titanium oxide.
A gel obtained by gelling a water-absorbing substance having a water absorbing power of 100 g / g polymer or more with water is added to the above paste, re-kneaded, and then formed into a honeycomb, granular or plate-like structure. A process for producing an ammonia catalytic reduction flue gas denitration catalyst, comprising drying, drying and calcining. (3) After removing all or a part of the active component from the catalyst component containing titanium oxide and kneading it with water to form a paste, 0.1 to 3% by weight based on the titanium oxide, 100 g / g polymer or more A highly water-absorbing substance having a water-absorbing power and a gelled substance obtained by gelling all or a part of the active ingredient with water are added to the paste and re-kneaded, and then formed into a honeycomb, granular or plate-like structure. A method for producing an ammonia catalytic reduction flue gas denitration catalyst, which comprises forming, drying and calcining.

(4) The superabsorbent substance is at least one selected from a starch / acrylic acid graft polymer, a crosslinked polyacrylate, and a saponified vinyl acetate / acrylate copolymer. ) The method for producing a flue gas denitration catalyst according to any one of (3) to (3). (5) A flue gas denitration catalyst obtained by the production method according to any one of (1) to (4). (6) A flue gas denitration honeycomb catalyst obtained by the production method according to any one of (1) to (5), wherein the catalyst has a sectional opening ratio of 80% or more and a pore volume of 0.35 ml / A flue gas denitration catalyst having a weight of not less than g.

[0010]

Since the superabsorbent used in the present invention can hold a large amount of water in a small amount, it is kneaded with a catalyst component to obtain a solid line in FIG. As shown in (paste), a high-moisture kneading paste can be obtained without lowering the shape retention force. In the multi-moisture kneading paste to which the superabsorbent substance is added, the superabsorbent substance containing water gradually becomes small lumps by kneading, and finally exists in the gap between the titania particles of the catalyst component. Since the high-moisture-kneaded paste containing this superabsorbent material has a high shape-retention force as described above, it is possible to mold a honeycomb-shaped molded body at a high pressure. No buckling occurs. Further, by drying the molded body, the moisture retained in the superabsorbent material evaporates, thereby generating pores supported by titania particles. The superabsorbent material shrinks during drying and remains in the pores, but is burned by the subsequent firing of the molded body and released outside the catalyst.

Such an effect of forming pores can be obtained by using a high-moisture kneading paste in which a superabsorbent substance is added to a catalyst component. The amount can be further increased by adding a gelled product that has been mixed and gelled to an aqueous solution containing a part to a kneading paste in the course of kneading and re-kneading. This is because a gelled product of a predetermined amount of water or an aqueous solution containing an active ingredient and a superabsorbent material has high gel strength and becomes harder, and when this gelled product is mixed with a paste during kneading, moisture is sufficiently retained. This is because the mixture can be kneaded in a state where the paste has been formed, and can be molded under high pressure without lowering the shape retaining force of the paste.

As shown by the solid line in FIG. 4 (c) (catalyst of the present invention), the denitration catalyst obtained by using the multi-moisture kneading paste containing a superabsorbent substance has high activity (high reaction rate ratio). As shown, this is due to the evaporation of water and the burning of the superabsorbent material during drying and firing of the molded body, not the pores having a large pore diameter of 0.3 μm or more but the pores having a pore diameter of 0.1 to 0.3 μm It is considered that the formation of is increased. 0.1 ~
As the pores having a pore diameter of 0.3 μm increase, the strength of the catalyst becomes higher. Even when the sectional opening ratio of the honeycomb catalyst is 80% or more, the pore volume of 0.35 ml / g or more is maintained while maintaining the high strength. It is possible to obtain a catalyst having

When a gel of an aqueous solution containing an active ingredient and a superabsorbent substance is added to a paste in the course of kneading, the pore volume is almost the same as when gelling is performed with water alone. , A more active catalyst can be obtained. This is presumably because the active ingredient can be present in a high concentration in the pores made of the superabsorbent material. In particular, when a vanadium compound having a promoting action of sintering is used as an active ingredient, the vanadium compound becomes more present in the pores made of the superabsorbent material, so that the activity of the increased portion becomes higher, In addition, sintering of the entire catalyst becomes difficult during firing, and the performance of the catalyst is improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the production of a flue gas denitration catalyst of the present invention, a superabsorbent material having a water absorbing power of 100 g / g polymer or more, preferably 100 to 2000 g / g polymer, is added to a catalyst component containing titanium oxide. Is added to the titanium oxide in an amount of 0.1 to 3% by weight, preferably 0.3 to 2% by weight, and kneaded with water.
The amount of water added when producing the paste varies depending on the superabsorbent used, but is adjusted so that a paste having a viscosity suitable for molding is finally obtained.

In the present invention, if the water-absorbing power of the superabsorbent substance is less than 100 g / g polymer, the effect as a pore-forming agent cannot be obtained. When the water absorption exceeds 2000 g / g polymer, the particle size of the superabsorbent becomes larger than that of the catalyst,
The strength of the catalyst may decrease. When the amount of the superabsorbent is less than 0.1% by weight, the ability to retain moisture is low, the molding pressure is reduced, and the shape cannot be maintained.

The superabsorbent substance used in the present invention is not particularly limited, and a known superabsorbent polymer can be used. The superabsorbent substance has a particularly high water-absorbing ability, does not contain a catalyst poisonous substance, and has a high performance. It is preferable to use at least one of a starch-acrylic acid graft polymer, a crosslinked polyacrylate, and a saponified vinyl acetate-acrylate copolymer from the viewpoint of not containing a substance that adversely affects water. In the present invention, a superabsorbent substance having a water absorbing power of 100 g / g polymer or more means a superabsorbent substance that absorbs 100 g or more of water per 1 g of a polymer, that is, has a water absorbing function of 100 times or more its own weight. Say.

The catalyst component containing titanium oxide used in the present invention is not particularly limited. Along with the titanium oxide raw material, vanadium (V), tungsten (W), molybdenum (M
Active ingredients such as o) are used. For example, a titania raw material produced by the sulfuric acid method is added with vanadium 0.5 at an atomic ratio.
-10%, Tungsten 0-10%, Molybdenum 0-1
What is blended in the range of 0% is used. A highly water-absorbing paste obtained by adding a superabsorbent substance to a catalyst component containing titanium oxide and kneading with water is formed into a honeycomb, granular or plate-like structure by a known method, and then a known method. And dried and calcined to obtain a flue gas denitration catalyst. Various additives (inorganic fibers, thickeners, etc.) conventionally used can also be added to the high-moisture kneading paste.

FIG. 1 is a flowchart of a method for manufacturing a flue gas denitration catalyst according to an embodiment of the present invention. In FIG. 1, a titanium oxide raw material (titania), an active ingredient (V compound), a superabsorbent, water and an additive are simultaneously kneaded into a paste, then formed into a honeycomb-shaped structure, dried and fired. To be a honeycomb catalyst. According to such a method, high-pressure molding can be performed without lowering the shape-retaining force of the high-moisture kneading paste, and a large number of pores having a pore diameter of 0.1 to 0.3 μm are formed. Therefore, even when the aperture ratio is 80% or more, the strength is maintained at 0.1% while maintaining high strength.
A catalyst having a pore volume of 35 ml / g or more can be obtained.

FIG. 2 is a flow chart of a method for manufacturing a flue gas denitration catalyst according to another embodiment of the present invention. FIG. 2 is different from FIG. 1 in that first, a titanium oxide raw material, an active ingredient, an additive, and water are kneaded, and a gelled product of a superabsorbent and water is added to the kneaded material, followed by re-kneading. is there. FIG.
FIG. 6 is a flowchart of a method for producing a flue gas denitration catalyst according to still another embodiment of the present invention. 3 is different from FIG. 2 in that a titanium oxide raw material, a part of an active ingredient, an additive, and water are first kneaded, and the kneaded product is mixed with a gel of a superabsorbent, the remaining active ingredient, and water. This is the point of addition and re-kneading.

According to the methods shown in FIGS. 2 and 3, since the decrease in shape retention of the high-moisture kneading paste is further reduced, high-pressure molding is facilitated and a highly active catalyst can be obtained.
In addition, according to the method of FIG. 3, since the active component can be present in the pores at a higher concentration than that of the method of FIG. 2, a catalyst with higher activity can be obtained. In addition, 8
In a method in which a kneaded paste is prepared with a paste water amount capable of being formed with a high opening ratio of 0% or more, and a gel of water and a superabsorbent is added thereto and kneaded, the amount of the superabsorbent substance is 0.5.
A highly active catalyst with developed pores can be obtained in the range of １．５1.5% by weight.

[0021]

Next, the present invention will be described in detail with reference to specific examples, but the present invention is not limited to these examples. Examples 1 to 3 Honeycomb catalysts were produced as described below in accordance with the flowchart of FIG. First, a titania raw material (Ti / W raw material, SO ₄ content 1.5 wt%,
Average particle size 1.0 μm, BET specific surface area 100 m ² / g)
V / compound, inorganic fiber, thickener and water
Kneading so that the / V atomic ratio becomes 90/3/7. During the kneading, 1.5% by weight, 6% by weight, and 15% by weight of water with respect to the titania raw material had a water absorption capacity of 1%.
00 g / g polymer (Example 1), 400 g / g polymer (Example 2) and 1000 g / g polymer (Example 3)
Each of the superabsorbents (starch / acrylic acid graft polymer) was added in an amount of 1% by weight to the titania raw material, and gelled products were added and kneaded again to obtain a kneaded paste. Using these kneaded pastes, a honeycomb (opening ratio: 81%) having a cell pitch of 3.5 mm and a rib thickness of 0.35 mm was extruded. The molding pressures of all Examples and Comparative Examples were almost the same unless otherwise specified.

The obtained molded body was subjected to a temperature of 85 ° C. and a humidity of 70%.
And dried at 500 ° C.
After calcination for a time, a honeycomb catalyst was obtained. When the pore volume of each of the obtained catalysts was measured by a mercury intrusion porosimeter, it was found to be 0.332 ml / g, 0.371 ml / g, 0.41 ml / g.
ml / g. Further, the denitration activity of the obtained catalyst was measured using the supplied gas (NO: 200 ppm, NH ₃ : 240 ppm, O ₂ :
10%, CO ₂ : 6%, H ₂ O: 6% (remaining N ₂ ), temperature 350 ° C., area standard gas flow rate AV 51 m / h (= m ³ / h / m ² )
As a result, the denitration activity (reaction rate constant ratio) of the catalyst was 1.03, 1.08, and 1.11 with the denitration activity of Comparative Example 1 described later as 1 (reference). The crushing strengths of these catalysts in the forming direction (sectional direction) were 38 kg / cm ² , 30 kg / cm ² , and 26 kg / cm ² , respectively. The composition of these catalysts, the amount of water, the shape retention, the amount of the superabsorbent added and its water absorbing ability, the calcination time, the pore volume,
The catalytic activity and crushing strength are summarized in Table 1. In addition, the shape retention force, the firing time, and the denitration activity were described by the ratio based on Comparative Example 1. In addition, the shape retention force was evaluated by the yield pressure of the molded body immediately after molding, and a reference (ratio) of 1 or more was accepted, and a firing time of 1 or less was accepted. The crushing strength was measured with a handy press (manufactured by Toho Hydraulic Equipment Co., Ltd.)
20 kg / cm ² or more was judged to be acceptable.

Example 4 A catalyst was produced in the same manner as in Example 3 except that the catalyst was produced according to the flowchart of FIG. The amount of the V compound in the gelled product was 40% of the total V compound.
% By weight. Table 1 summarizes the characteristics and the like of the obtained catalyst. Example 5 A catalyst was manufactured in the same manner as in Example 3 except that the catalyst was manufactured according to the flowchart of FIG. 1, and the characteristics and the like of the obtained catalyst were summarized in Table 1.

Examples 6 and 7 In Example 2, the water-absorbing ability was 400 g /
g A catalyst was produced in the same manner as in Example 2 except that a saponified polymer of vinyl acetate / acrylate copolymer (Example 6) and a crosslinked polyacrylate (Example 7) were used. Table 1 summarizes the characteristics and the like of the obtained catalysts.

Comparative Example 1 The procedure of Example 1 was repeated except that the gelled product of the superabsorbent and water was added to the paste during kneading and kneading was not performed.
A honeycomb catalyst was manufactured in the same manner as described above, and the characteristics and the like of the catalyst were summarized in Table 1. The water content of the kneading paste at this time was a low water content capable of maintaining the same shape retention force (forming pressure) as in Example 1. Comparative Example 2 A honeycomb catalyst was manufactured in the same manner as in Comparative Example 1, except that the water content of the kneaded paste was changed to a high water content at which the shape retention force (forming pressure) of Comparative Example 1 was reduced by about half. Table 1 summarizes the characteristics and the like of the catalyst.

Comparative Examples 3 and 4 The same procedures as in Example 3 were carried out except that the amount of the superabsorbent was changed to 0.08% by weight (Comparative Example 3) and 3.5% by weight (Comparative Example 4). Similarly, a honeycomb catalyst was manufactured, and the characteristics and the like of the catalyst are summarized in Table 1. The firing time in Comparative Example 4 was 1.6 times that in Comparative Example 1. Comparative Example 5 In the same manner as in Comparative Example 1, except that the kneading paste contained 10.0% by weight of the crystalline cellulose pore-forming agent with respect to the titania raw material and the firing time was extended 2.8 times. A honeycomb catalyst was manufactured, and the characteristics and the like of the catalyst were summarized in Table 1.

Comparative Examples 6 and 7 In Example 1, 0.5% by weight based on the titania raw material
And 10% by weight of a water-absorbing agent (starch, acrylic acid graft polymer) having a water absorption of 50 g / g polymer in 1.0% by weight (Comparative Example 6) and 10.0% by weight with respect to the titania raw material (Comparative Example 7) A honeycomb catalyst was manufactured in the same manner as in Example 1 except that each of the added gelled substances was used, and the characteristics of the catalyst are summarized in Table 1. In addition,
The firing time of Comparative Example 7 was 2.9 times that of Comparative Example 1.

[0028]

[Table 1]

From Table 1, it can be seen that, according to the production method of the present invention (Examples 1 to 7), despite the large amount of water in the kneading paste, the reduction in shape retention is small, so that high pressure formation is possible. This indicates that a honeycomb catalyst having a high pore volume while maintaining high strength and having excellent catalytic activity can be obtained. On the other hand, in Comparative Example 1, since no superabsorbent was used,
A high-moisture kneading paste cannot be obtained, and a highly active catalyst having a high pore volume cannot be obtained. In Comparative Example 2, the high-moisture kneading paste was used, but the shape retention force was low, and deformation or buckling was likely to occur during or immediately after molding. In Comparative Examples 3 and 4, since the amount of the superabsorbent is out of the range of the present invention, the former has a low shape retention force, and the latter requires a long firing time. In Comparative Example 5, since a large amount of crystalline cellulose was used as the pore-forming agent, a high-moisture kneaded paste was obtained, but a long firing time was required, and the crushing strength of the catalyst was low. Further, in Comparative Examples 6 and 7, a high water-absorbing agent having a low water-absorbing power was used, and in the former, a small amount of the water-absorbing agent was not obtained, and a high-moisture kneading paste was not obtained. In the latter case, a long baking time is required because the added amount is too large, and the crushing strength is low.

[0030]

According to the method for producing a flue gas denitration catalyst of the present invention, a high-strength and highly active flue gas denitration catalyst can be produced by a simple production process. Therefore, the same denitration performance can be achieved with a smaller amount of catalyst than conventional products. Further, since the amount of the superabsorbent substance is small, heat generation and cracking do not occur during firing as in the case of firing a conventional molded body to which a large amount of a pore-forming agent is added. Further, despite the small amount of the superabsorbent substance, a hard kneaded paste having a high water content can be obtained, so that a highly active catalyst with fine pores can be obtained even with a high opening ratio. According to the flue gas denitration catalyst obtained by the production method of the present invention, since its strength is high, it is possible to avoid problems such as generation of cracks in the catalyst in handling and unit assembling steps, and complicated processing steps.

[Brief description of the drawings]

FIG. 1 is a flowchart of a method for manufacturing a flue gas denitration catalyst showing an example of the present invention.

FIG. 2 is a flowchart of a method for producing a flue gas denitration catalyst showing another example of the present invention.

FIG. 3 is a flow chart of a method for producing a flue gas denitration catalyst, showing still another example of the present invention.

FIG. 4 is a view showing the relationship between the amount of water and each physical property (shape retention ratio, pore volume, reaction rate ratio) in a conventional kneading paste and catalyst and a kneading paste and catalyst according to an example of the present invention.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tadaaki Mizoguchi 3-36 Takaracho, Kure-shi, Hiroshima Babcock-Hitachi Kure Research Institute

Claims (6)

[Claims] 1. A catalyst paste containing titanium oxide is formed into a honeycomb-shaped, granular or plate-shaped structure, and then dried and fired to produce an ammonia-catalyzed reduction flue gas denitration catalyst. High water-absorbing substance having a water-absorbing power higher than that of polymer is 0.1 to
A method for producing a flue gas denitration catalyst, comprising adding 3% by weight. 2. A kneaded catalyst component containing titanium oxide is mixed with water to form a paste.
３3% by weight of a superabsorbent substance having a water absorption of at least 100 g / g polymer, which is gelled with water, is added to the above paste and kneaded again, and then has a honeycomb, granular or plate-like structure. A method for producing an ammonia catalytic reduction flue gas denitration catalyst, which is formed into a body, dried and calcined. 3. A catalyst component containing titanium oxide, except that all or a part of the active component is removed and kneaded with water to form a paste.
A highly water-absorbing substance having a water-absorbing power of 0 g / g polymer or more and a gelled product obtained by gelling all or a part of the active ingredient with water are added to the paste, and the mixture is kneaded again. A process for producing an ammonia catalytic reduction flue gas denitration catalyst, which is formed into a plate-like structure, dried and calcined. 4. The high water-absorbing substance is at least one of a starch / acrylic acid graft polymer, a crosslinked polyacrylate and a saponified vinyl acetate / acrylate copolymer. 4. The method for producing a flue gas denitration catalyst according to any one of claims 1 to 3. 5. A flue gas denitration catalyst obtained by the production method according to claim 1. 6. A flue gas denitration honeycomb catalyst obtained by the production method according to any one of claims 1 to 4, wherein the catalyst has a sectional opening ratio of 80% or more and a pore volume of 0.35 ml / min. A flue gas denitration catalyst having a weight of more than g