KR930004501B1 - Catalyst for removing nitrogen dioxide and nitric oxide - Google Patents

Abstract

A catalyst comprises copper supported on the zeolite carrier and is available to remove nitrogen oxides in the combustion exhaust gas layer which contains surfurous acid gas, using ammonia as a reducing agent. The zeolite used is a natural zeolite containing mordenite type having the weight ratio of silicon to aluminum, 4-5. The above copper from copper sulfate, copper nitrate and copper acetate is supported on natural zeolite by ion exchange reactions, the amount of supporting being 0.75-2.25 wt.% against the overall weight of the catalyst.

Description

Nitrogen oxide removal catalyst

1 is a graph showing the nitrogen monoxide removal rate of the natural zeolite catalyst having a copper loading according to the present invention.

The present invention relates to a copper ion-exchanged natural zeolite catalyst composition which is used to remove nitrogen oxide contained in flue gas discharged from a fixed source such as a power plant, a chemical plant, or a steel mill by decomposing it into water and nitrogen using ammonia as a reducing agent. will be. Nitrogen oxides are mainly produced by the oxidation of nitrogen compounds in fuels or the reaction of nitrogen and oxygen in the air which is supplied excessively in high-temperature combustion facilities, and are released into the atmosphere to be a cause of photochemical smog and the main cause of acid rain. Much effort is being put into individual removal techniques. Nitrogen oxide is a material that is produced during the combustion process is known to suppress its generation by improving combustion conditions, such as low oxygen combustion, two-stage combustion, exhaust gas circulation technology for its original removal. However, flue gas denitrification has been proposed as a more aggressive nitrogen oxide treatment technology, although the efficiency is more than 60%, although it varies depending on the object or technology.

The thermal denitrification technology is roughly classified into a wet method for removing nitrogen oxides using a solution in an oxidation, absorption, and reduction process, and a dry method without using a solution such as adsorption, catalytic decomposition, and catalytic reduction. The wet method is economical and technically disadvantageous compared to the dry method due to the secondary wastewater treatment problem in addition to the disadvantage that the investment cost and operation cost is higher than the dry method. Currently, the most widely used nitrogen oxide removal technology is a selective catalytic reduction technology that decomposes and removes nitrogen oxides into water and nitrogen that are harmless to the human body by using ammonia as a reducing agent in the presence of a catalyst. In general, however, it was so easy to bring about deactivation of the catalyst, and the durable catalyst for SO ₂ required NOx that the combustion gas contains sulfur dioxide (hereinafter, SO ₂ hereinafter) containing co-exist, which poison the catalyst .

Catalysts currently in use include titanium dioxide (TiO ₂ ) as a carrier, as suggested in Japanese Patent Application Nos. 50-51966 and 52-12293, and include vanadium (V), tungsten (W), and molybdenum (Mo). Metal oxide catalysts carrying oxides such as the < RTI ID = 0.0 >) and synthetic zeolite catalysts < / RTI >

An object of the present invention is excellent denitrification rate by the ion exchange of copper (Cu) in a natural zeolite having a weight ratio (Si / Al) of silicon (Si) and aluminum (Al) of 4 to 5 to the sulfur dioxide (SO ₂ ) An object of the present invention is to provide a catalyst for removing nitrogen oxide having excellent durability.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention is a catalyst used to remove nitrogen oxides in combustion flue gas containing sulfurous acid gas with ammonia as a reducing agent, wherein the weight ratio (Si / Al) of silicon (Si) to aluminum (Al) is 4 to 5 ( 7.71-9.64 molar ratio of SiO ₂ / Al ₂ O ₃ and 0.75-2.25% by weight of copper (0.02-0.008 atoms relative to Si atom) in natural zeolite containing zeolite in the form of mordenite The present invention relates to a catalyst for removing nitrogen oxide supported by ion exchange.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. Normally, zeolite includes: fauzasite having a Si / Al weight ratio of about 1-2; Mordenite having a Si / Al weight ratio of about 5-6; And Si / Al weight ratio of about 20-30 can be roughly divided into ZSM-5. Since the zeolite used as a carrier in the present invention has a Si / Al ratio of 4-5, mordenite is the main component and spores are contained therein. It is. Converting the Si / Al ratio of the carrier to the SiO ₂ / Al ₂ O ₃ molar ratio, SiO ₂ / Al ₂ O ₃ molar ratio of the carrier to be used in the present invention is a 7.71 to 9.64.

In the present invention, copper is ion-exchanged in the natural zeolite catalyst (CuNZA) copper is supported by the natural zeolite to form a new active point to increase the adsorption amount of the reactants to remove nitrogen oxides than the natural zeolite (NZA) is not copper exchanged It will increase the activity of. Copper acetate (Cu (NO ₃ ) ₂ ), copper sulfate (CuSO ₄ ), copper chloride (CuCl ₂ ) and the like may be used as a raw material of the active ingredient copper.

In general, the higher the amount of copper supported, the higher the activity at a relatively low temperature. However, the present invention can be applied at a temperature of 250 ° C. to 300 ° C. or higher and the space velocity, which is one of the reaction conditions in the embodiment, is sufficiently large. The amount of copper supported on the lower surface is 0.75 to 2.25 wt%, so that a sufficiently high nitrogen oxide removal activity can be obtained.

When the supported amount of copper is 0.75% by weight or less, it shows a low denitrification rate of 50% or less due to the lack of catalyst content applied to the active point, and because the supported amount shows a sufficiently high denitrification rate that reaches almost 100% at 2.25% by weight. The above copper addition is unnecessary. Therefore, the content range is preferably 0.75-2.25% by weight.

When the supported amount of copper is converted to the Si atom, the supported copper amount of the present invention becomes 0.02-0.008 atom relative to the Si atom.

In general, SO ₂ which poisons the catalyst by reacting with the active material of the catalyst or the carrier does not poison the catalyst by reacting with copper, which is the active point of the catalyst, or natural zeolite, which is the carrier of the catalyst, and reacts with ammonium sulfate (( NH ₄ ) ₂ SO ₄ ) is produced to modify the structure of the catalyst to cause a decrease in catalytic activity. However, the catalyst for removing nitrogen oxides according to the present invention has excellent durability in the SO ₂ coexisting in the flue gas containing nitrogen oxides, and is thus a combustion flue gas which is discharged by containing a relatively large amount of SO ₂ in power plants, chemical plants, and steel mills. It can be usefully used without removing the catalyst for a long time when removing the nitrogen oxides.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1

Crush the natural zeolite ore in Yeongil, Gyeongsangbuk-do, Korea, with weight ratio of 4 to 5 in 20-30 mesh and 200 grams of crushed natural zeolite into 800cc of 1 normal-hydrochloric acid (HCl) solution at 80 ℃ for about 4 hours. The mixture was stirred with stirring to remove impurities and dried at 100 ° C. for 24 hours.

The dried sample was placed in 1-2 normal copper nitrate (Cu (NO ₃ ) ₂ ) solution and ion exchanged at 90 ° C. for 8 hours, dried at 100 ° C. for 12 hours, and calcined at 500 ° C. for 8 hours in an air atmosphere. . At this time, the supported amount of copper was increased by repetition of the ion exchange process to prepare catalysts each having 0.75, 1.08, and 2.25 wt% copper.

1 g of the natural zeolite catalyst, in which the copper is not exchanged, of the natural zeolite catalyst having the copper exchanged as described above was charged to the center of the reactor of the fixed bed atmospheric pressure reactor, and a reaction gas having a gas composition of Table 1 was added thereto.

[Table 1]

Experiment to measure the activity of the nitrogen monoxide (NO) removal reaction under the reaction conditions of Table 1 and the results are shown in FIG.

According to FIG. 1, it can be seen that the catalyst according to the present invention supported by ion exchange of 0.75-2.25 wt% of copper on natural zeolite is much superior to the conversion rate of NO, compared to natural zeolite (NZA).

Example 2-6

One gram of a catalyst having a weight of 2.25% by weight, prepared by the method of Example 1, was packed in the center of a fixed bed atmospheric reactor, and in addition to the gas composition of Table 1 of Example 1, SO ₂ was mixed at 500-20,000 ppm. The experiment was carried out to measure the activity of the nitrogen monoxide (NO) removal reaction was added to the reaction conditions of Table 2.

[Table 2]

As described above, the measurement result of the initial activity after the experiment of the nitrogen monoxide (NO) removal reaction and the activity measurement after the reaction time elapsed as shown in Table 3 by adding the SO ₂ mixed gas are shown in Table 3 below. .

[Table 3]

As shown in Table 3, the copper-supported catalyst according to the present invention can be seen to have excellent durability against sulfurous acid gas.

As described above, the nitrogen oxide removal catalyst prepared according to the present invention has an excellent denitrification rate because of excellent durability against sulfur dioxide.

Claims (1)

In a catalyst composed of copper supported on a zeolite serving as a carrier for use in removing nitrogen oxides in a combustion flue gas layer containing sulfurous acid gas with ammonia as a reducing agent, the zeolite has an increase ratio of silicon to aluminum (Si / Al). ) Is 4 to 5 and is a natural zeolite containing a zeolite in the form of mordenite, and the copper is supported on the natural zeolite by ion exchange, the loading amount is 0.75-2.25% by weight based on the weight of the catalyst Catalyst for oxide removal.