TWI586425B - Denitrification catalyst and method of producing the same - Google Patents

Description

Denitration catalyst and manufacturing method thereof

The present invention relates to a catalyst, and more particularly to a catalyst that combines both denitrification and adsorption.

Exhaust gases from the steel process contain harmful substances such as nitrogen oxides. In order to reduce the environmental hazard of exhaust gas, denitrification catalyst is usually used to remove nitrogen oxides.

The conventional denitrification catalyst mainly uses ammonia (NH ₃ ), carbon or carbon monoxide as a reducing agent to carry out denitration reaction.

When the reducing agent for the denitration reaction is ammonia gas, and the main component of the denitration catalyst is titanium-vanadium-tungsten or titanium-vanadium-molybdenum, and titanium dioxide is used as the support, the denitration catalyst prepared is 300. The denitration efficiency from °C to 400 °C is greater than 80%. However, when ammonia gas is used as the reducing agent, ammonia gas must be additionally introduced into the reaction system, thereby increasing the cost. Secondly, in order not to affect the denitration efficiency, excess ammonia gas often causes NH ₃ slip at the outlet end of the reactor, which increases the harm to the environment and operators. Furthermore, the ammonia gas that is introduced reacts with the sulfur oxides (SO _x ) in the exhaust gas to produce corrosive ammonium hydrogen sulfate [(NH ₄ )HSO ₄ ] or ammonium sulfate [(NH ₄ ) ₂ SO ₄ ], which in turn damages the device.

Further, when ammonia gas is used as the reducing agent, the denitration reaction can also be carried out using a ReACT (Regenerative Activated Coke Technology) process developed by J-POWER EnTech, Inc. However, the ReACT process requires a large amount of activated carbon to increase the reaction cost.

When the reducing agent is carbon, the denitration reaction must be carried out in an environment of high temperature (for example, over 500 ° C). If the concentration of oxygen in the exhaust gas is more than 3%, excessive oxygen may cause combustion. Secondly, the conventional CARBONOX process uses carbon as a reducing agent for denitration, but the lignite coke used in the process participates in the reaction during the reaction. Therefore, the reaction system must be added with lignite coke at any time, thereby increasing the reaction cost.

When the reducing agent is carbon monoxide, the denitration reaction must be carried out at a temperature exceeding 200 °C. Secondly, the denitrification catalyst used must be attached to the activated carbon with copper, cobalt, nickel and iron, and the activated carbon cannot be directly used for the denitration reaction.

In addition, the denitrification catalyst is generally susceptible to poisoning of sulfur oxides in the exhaust gas, which causes the denitration catalyst to lose activity and thus cannot adsorb specific harmful substances in the exhaust gas. The term "poisoning" as used above refers to the combination of the sulfur element in the sulfur oxide and the active substance in the catalyst, so that the active substance is deactivated and cannot be used to remove harmful substances in the exhaust gas.

In view of the above, it is not necessary to provide a method for producing a denitration catalyst and an application thereof to improve the defects of the conventional denitration catalyst manufacturing method and its application.

Accordingly, an aspect of the present invention provides a method for producing a denitration catalyst which uses potassium permanganate (KMnO ₄ ) to prepare a catalyst which can perform a denitration reaction at a low temperature.

Another aspect of the present invention provides a denitration catalyst which is produced by the aforementioned manufacturing method.

According to an aspect of the present invention, a method of manufacturing a denitration catalyst is proposed. This manufacturing method first provides an alkaline aqueous solution containing a basic compound and 0.3 M to 0.6 M potassium permanganate, and the alkaline aqueous solution has a pH of 7 to 10.

Next, an impregnation process is performed. The impregnation process adds the support to an aqueous alkaline solution to form the support into an active support. Wherein, the temperature of the impregnation process does not exceed 50 ° C, and the surface of the active support does not have manganese-containing precipitates.

The total amount of the potassium permanganate and the basic compound used is 100 parts by weight, and the amount of the support is from 400 parts by weight to 600 parts by weight.

After the impregnation process, the above-mentioned active support is subjected to a drying process to obtain a denitrification catalyst.

According to an embodiment of the present invention, the above basic compound may include, but is not limited to, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or any combination of the above compounds.

In accordance with another embodiment of the present invention, the above-described support may include, but is not limited to, lignite coke, activated carbon, alumina, or any combination of the foregoing.

According to still another embodiment of the present invention, the denitration catalyst has a specific surface area greater than 150 square meters per gram (m ² /g), and the denitration catalyst has a pore size of less than 3.5 nm.

According to still another embodiment of the present invention, the denitration catalyst comprises from 2% by weight to 3% by weight of manganese.

According to still another aspect of the present invention, a denitration catalyst is provided. This denitration catalyst is produced by the aforementioned production method. In the environment of 120 ° C without ammonia gas, the denitration catalyst has a denitration efficiency of not less than 58%, and the denitration catalyst contains 2 to 3 weight percent of manganese.

According to an embodiment of the present invention, the carrier of the denitration catalyst is activated carbon, and the denitration catalyst has a denitration efficiency of not less than 76%.

According to another embodiment of the present invention, the carrier of the denitration catalyst is lignite coke, and the denitration catalyst has a denitration efficiency of not less than 58%.

According to another embodiment of the invention, one of the above environments has a concentration of carbon oxide greater than a concentration of nitric oxide.

The method for producing the denitration catalyst of the present invention and the application thereof are characterized in that the potassium permanganate is used to modify the support, and the denitration catalyst can be obtained without performing a calcination process. Therefore, the denitration catalyst produced can be subjected to a denitration reaction in an environment of low temperature (for example, 120 ° C) and without ammonia gas. Further, the denitration reaction can be directly carried out by the above-mentioned modified support.

100‧‧‧ method

110‧‧‧ Provide alkaline aqueous solution

120‧‧‧Add the support to an alkaline aqueous solution and carry out the impregnation process

130‧‧‧Filtering process

140‧‧‧Drying process

150‧‧‧Get denitrification catalyst

Fig. 1 is a view showing a method of manufacturing a denitration catalyst according to an embodiment of the present invention.

The making and using of the embodiments of the invention are discussed in detail below. however, It will be appreciated that the embodiments provide many applicable inventive concepts that can be implemented in a wide variety of specific content. The specific embodiments discussed are illustrative only and are not intended to limit the scope of the invention.

Please refer to FIG. 1 , which illustrates a method of manufacturing a denitration catalyst according to an embodiment of the present invention. In one embodiment, the manufacturing process first provides an aqueous alkaline solution, as shown in step 110. The alkaline aqueous solution contains a basic compound and potassium permanganate of 0.3 M to 0.6 M, and the pH of the alkaline aqueous solution is 7 to 10.

The above basic compound may include, but is not limited to, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or any combination of the above compounds.

If the concentration of potassium permanganate is less than 0.3 M, the amount of potassium permanganate used is too small, and the manganese content of the obtained denitration catalyst is lowered. If the concentration of potassium permanganate is greater than 0.6 M, too much potassium permanganate will precipitate in the aqueous solution. The precipitated potassium permanganate is not easily attached to the surface of the support by impregnation, and the catalytic activity of the obtained denitration catalyst is lowered.

If the pH of the alkaline aqueous solution is less than 7, the acidic aqueous solution corrodes the aforementioned potassium permanganate, and the potassium permanganate is cleaved, thereby deactivating the catalytic activity of the obtained denitrification catalyst. If the pH of the alkaline aqueous solution is greater than 10, the environment with too much alkalinity will reduce the catalytic activity of the denitrification catalyst and reduce the efficiency of the denitrification catalyst.

After performing step 110, an impregnation process is performed, as shown in step 120. This impregnation process adds the support to an aqueous alkaline solution to form the support into an active support. When the impregnation process is carried out, the temperature of the impregnation process is not more than 50 ° C (that is, the temperature of the impregnation process is less than or equal to 50 ° C), and the activity is The surface of the body does not have manganese-containing precipitates.

The foregoing supports may include, but are not limited to, lignite coke, activated carbon, other suitable catalyst supports, or any mixture of the foregoing.

In one embodiment, the other suitable catalyst support may be alumina, ceria or other suitable catalyst support depending on the demand of the denitrification catalyst or the effectiveness of the denitration reaction.

It is additionally noted that one of the features of the present invention is that the lignite coke or activated carbon which is originally used as an adsorbent of oxidized volatile organic compounds (VOCs) is modified into a denitrification catalyst by an impregnation process. It has the dual functions of denitrification and adsorption. In general, when the support is lignite coke, the specific surface area of the lignite coke must be greater than 250 square meters per gram, and the pore size of the lignite catalyst is less than 2 nanometers.

If the specific surface area of the lignite coke is less than or equal to 250 square meters / gram, the excessively small specific surface area will reduce the area of the reaction of the denitrification catalyst, and reduce the efficiency of the denitrification catalyst. If the pore size of the lignite coke is greater than or equal to 2 nm, the excessive pore size reduces the specific surface area of the denitrification catalyst produced and reduces its efficiency.

When the aforementioned support is activated carbon, the specific surface area of the activated carbon is more than 800 m 2 /g, and the pore diameter of the activated carbon is less than 3 nm.

Similarly, if the specific surface area of the activated carbon is less than or equal to 800 square meters / gram, or the pore diameter is greater than or equal to 3 nanometers, the specific surface area of the activated carbon produced is too small, thereby reducing the denitrification touch produced later. The effectiveness of the media.

When the above impregnation process is carried out, if the temperature of the impregnation process is greater than At 50 °C, the impregnation process will cause overheating and reduce the effectiveness of the denitrification catalyst produced. If the surface of the active support has manganese-containing precipitates, the manganese-containing precipitate will reduce the denitration produced. Catalytic activity of the catalyst.

In one embodiment, the temperature of the impregnation process is less than 50 °C.

In the impregnation process, the total amount of the potassium permanganate and the basic compound used is 100 parts by weight, and the amount of the support is from 400 parts by weight to 600 parts by weight.

When the amount of the support is less than 400 parts by weight, excessive potassium permanganate adheres to the support, and the catalytic activity of the denitration catalyst is reduced, thereby reducing the performance of the denitration catalyst. When the amount of the support is more than 600 parts by weight, the manganese content in the denitrification catalyst is relatively reduced, and the catalytic activity of the denitrification coal is reduced, thereby reducing the efficiency of the denitration catalyst.

After the impregnation process described above, a filtration process is performed on the alkaline aqueous solution containing the active support to separate the active support, as shown in step 130. Then, the active support is subjected to a drying process to obtain the denitrification catalyst of the present invention, as shown in steps 140 and 150. Wherein, one of the denitration catalysts may have a specific surface area greater than 150 square meters per gram (m ² /g), and one of the denitration catalysts may have a pore diameter of less than 3.5 nm.

The denitration catalyst may comprise from 2 weight percent to 3 weight percent manganese based on 100 weight percent of the total denitthanation catalyst produced.

If the manganese content of the denitrification catalyst is less than 2% by weight, the manganese content in the denitration catalyst is insufficient, and the catalytic activity of the denitration catalyst is lowered. If the manganese content of the denitrification catalyst is more than 3% by weight, too much manganese will precipitate, and the precipitated manganese will not easily adhere to the surface of the denitrification catalyst, and the denitrification touch will be lowered. The catalyst activity of the medium reduces the effectiveness of the denitrification catalyst.

In one embodiment, when the foregoing system is brown coal coke, the denitrification catalyst has a specific surface area greater than 150 square meters per gram, and the denitration catalyst has a pore diameter of less than 3.5 nanometers.

In another embodiment, when the system is activated carbon, the denitrification catalyst has a specific surface area greater than 500 square meters per gram and a pore diameter of less than 2.5 nanometers.

In a specific example, the denitration catalyst prepared by the foregoing manufacturing method has a denitration efficiency of not less than 58% in a low temperature (for example, 120 ° C) environment without ammonia gas. That is, the denitration efficiency is greater than or equal to 58%), and the denitration catalyst may comprise from 2 weight percent to 3 weight percent manganese.

According to the reaction equation of the denitration catalyst of the present invention [shown in the following formula (I)], the molar ratio of nitrogen monoxide to carbon monoxide is 1:1. Therefore, the concentration of carbon monoxide in the foregoing environment is greater than the concentration of nitric oxide to enhance the denitration efficiency of the aforementioned denitrification catalyst: 2NO+2CO+O ₂ →N ₂ +2CO ₂ (I)

If the concentration of carbon monoxide is less than or equal to the concentration of nitric oxide, since the carbon monoxide content is insufficient as one of the reducing agents, the denitration reaction cannot be completely reacted, thereby reducing the denitration efficiency of the denitrification catalyst.

In one embodiment, when the denitration catalyst acts on the activated carbon of the system, the denitration catalyst has a denitration efficiency of not less than 76% (ie, the denitration catalyst has a denitration efficiency greater than or equal to 76%).

The following examples are used to illustrate the application of the present invention, but it is not In order to limit the invention, it is possible to make various modifications and refinements without departing from the spirit and scope of the invention.

Preparation of denitrification catalyst Example 1

First, an aqueous potassium permanganate solution having a concentration of 0.6 M was prepared in a stirred tank. Then, the prepared aqueous sodium hydroxide solution was added to the above-mentioned potassium permanganate aqueous solution to be stirred to form an alkaline aqueous solution, and the pH of the alkaline aqueous solution was adjusted to be 8.

Next, lignite coke is added in portions to a stirred tank for the impregnation process. Among them, the temperature of the impregnation process is controlled below 50 °C.

After stirring for 1 hour, the stirring was stopped and the impregnated lignite coke was separated by filtration. Thereafter, the lignite catalyst obtained by filtration was placed in an oven at 110 ° C to dry, and the denitrification catalyst of Example 1 was obtained. The specific surface area, pore volume and pore diameter of the obtained denitration catalyst were measured by a conventional method and apparatus, and the measured data are shown in Table 1.

Example 2

First, an aqueous potassium permanganate solution having a concentration of 0.3 M was prepared in a stirred tank. Then, the prepared potassium carbonate aqueous solution was added to the above-mentioned potassium permanganate aqueous solution to be stirred to form an alkaline aqueous solution, and the pH of the alkaline aqueous solution was adjusted to be 9.

Next, the activated carbon is added in portions to the stirring tank to carry out an impregnation process. Among them, the temperature of the impregnation process is controlled below 50 °C.

After stirring for 1 hour, the stirring was stopped and the activity after impregnation was separated by filtration. carbon. Thereafter, the activated carbon obtained by filtration was placed in an oven at 110 ° C to dry, and the denitration catalyst of Example 2 was obtained. The inductively couple plasma optical emission spectrometry (ICP) analysis showed that the manganese concentration of the denitrification catalyst was 2.1%. The specific surface area, pore volume and pore diameter of the denitration catalyst were measured by the same method and apparatus as in Example 1, respectively, and the measured data are shown in Table 1.

Comparative Example 1 and Comparative Example 2

In Comparative Example 1 and Comparative Example 2, the following denitration reactions were carried out using the lignite catalyst and activated carbon similar to those of Example 1 and Example 2, respectively, and the amounts were measured by the same method and apparatus as in Example 1, respectively. The specific surface area, pore volume and pore diameter were measured, and the measured data are shown in Table 1.

Denitrification reaction

First, the granular denitrification catalyst prepared in the foregoing Examples 1 and 2 and Comparative Examples 1 and 2 was uniformly mixed with a glass ball having a size of 6 mm, and the denitration catalyst and the glass sphere were formed. The mixture was separately added to a glass reaction tube having an inner diameter of 30 mm, wherein the lower end of the glass reaction tube was packed with a glass column.

The glass reaction tube is wound with a heating belt, and the reaction temperature of the denitration reaction is controlled by electric heating.

Then, the sintering waste gas was passed into a glass reaction tube at a flow rate of 8 liters/min. The main component of the sintering exhaust gas comprises 120 ppm to 140 ppm of one type of nitrogen oxide, 6000 ppm to 8000 ppm of one carbon oxide, 15% to 15.5% of oxygen, 50 ppm to 80 ppm of sulfur dioxide, and 20% to 25% of carbon dioxide.

Next, the nitric oxide concentration of the exhaust gas passing through the glass reaction tube is measured by a nitric oxide detector, and the respective embodiments are calculated by changing the concentration of nitrogen monoxide after passing through the glass reaction tube and before passing through the glass reaction tube. The denitration efficiency of the denitrification catalyst prepared in the comparative example. The reaction temperature and denitration efficiency of each of the examples and the comparative examples are shown in Table 2.

Stability of denitrification catalyst

The experiment of the stability of the denitrification catalyst was carried out by the same experimental method and apparatus as the aforementioned denitration reaction.

The granular denitrification catalyst prepared in the foregoing Example 1 was filled in a glass reaction tube, the reaction temperature was controlled at 100 ° C, the denitration reaction was repeated three times, and the denitration efficiency of each denitration reaction was measured. . Measured denitration The efficiency is shown in Table 3.

According to the results of Tables 1 to 3, in the environment of low temperature (for example, 120 ° C) and without ammonia gas, the support of the present invention modified by potassium manganate can be used as a reducing agent by carbon monoxide in the exhaust gas. And directly carry out the denitration reaction. The method for producing the denitration catalyst of the present invention can also produce a denitrification catalyst without performing a calcination process.

Secondly, the denitrification catalyst prepared by the present invention has a lower specific surface area and pore volume than the carrier material used. Therefore, depending on the change in specific surface area and pore volume, the potassium permanganate used adheres to the surface of the support and acts as an activation center to cause the denitrification catalyst to be produced in a low temperature (for example, 120 ° C) environment. The denitration reaction can be carried out.

Furthermore, the denitration catalyst of the present invention can be subjected to a denitration reaction by using carbon monoxide as a reducing agent without additional supply of ammonia gas. Since no additional ammonia gas is supplied, the sulfur dioxide in the exhaust gas cannot react to form ammonium hydrogen sulfate [(NH ₄ )HSO ₄ ] or ammonium sulfate [(NH ₄ ) ₂ SO ₄ ], and the catalytic activity in the prior art can be avoided. Reduce defects such as equipment corrosion.

According to the experimental results of the denitration efficiency of Example 2, the denitration efficiency of the denitrification catalyst of Example 2 increased as the reaction temperature increased. When the reaction temperature is 120 ° C, the activated carbon used in Example 2 has a larger specific surface area than that of Example 1, so the denitration efficiency of Example 2 is large. The denitration efficiency of Example 1.

In addition, the denitrification catalyst of the present invention has good denitration efficiency after repeated denitration reactions, and its denitration efficiency does not deteriorate. Accordingly, the denitration catalyst of the present invention has good stability and sulfur resistance.

The present invention has been disclosed in the above embodiments, and is not intended to limit the present invention. Any one of ordinary skill in the art to which the present invention pertains can make various changes without departing from the spirit and scope of the invention. The scope of protection of the present invention is therefore defined by the scope of the appended claims.

100‧‧‧ method

110‧‧‧ Provide alkaline aqueous solution

120‧‧‧Add the support to an alkaline aqueous solution and carry out the impregnation process

130‧‧‧Filtering process

140‧‧‧Drying process

150‧‧‧Get denitrification catalyst

Claims (8)

A method for producing a denitration catalyst, comprising: providing an alkaline aqueous solution, wherein the alkaline aqueous solution comprises a basic compound and 0.3M to 0.6M potassium permanganate, and the pH of the alkaline aqueous solution is 7 to 10: performing an impregnation process, wherein the impregnation process adds a support to the alkaline aqueous solution to form the active support, the temperature of one of the impregnation processes does not exceed 50 ° C, and the activity is a surface of the body does not have a manganese-containing precipitate, wherein the support system is selected from the group consisting of lignite coke, activated carbon, and any combination thereof; and a drying process is performed on the active support to form the a denitration catalyst, wherein the denitration catalyst has a nitrogen oxide removal rate of not less than 58% at 120 ° C, and wherein the total amount of potassium permanganate and one of the basic compounds is 100 parts by weight, One of the supports is used in an amount of from 400 parts by weight to 600 parts by weight. The method for producing a denitration catalyst according to claim 1, wherein the basic compound is selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and any combination thereof. Ethnic group. The method for manufacturing a denitration catalyst according to claim 1, wherein one of the denitration catalysts has a specific surface area greater than 150 m 2 /g (m ² /g), and one of the denitration catalysts The pore size is less than 3.5 nm. The method for producing a denitration catalyst according to claim 1, wherein the denitration catalyst comprises 2 to 3 wt% of manganese. A denitration catalyst produced by the production method according to any one of claims 1 to 4, wherein the denitration catalyst is at one of 120 ° C and does not have an atmosphere of ammonia The nitrate efficiency is not less than 58%, and the denitration catalyst contains 2% by weight to 3% by weight of manganese. The denitration catalyst according to claim 5, wherein one of the denitration catalysts is activated carbon, and the denitration catalyst has a denitration efficiency of not less than 76%. The denitration catalyst according to claim 5, wherein one of the denitration catalysts is lignite coke, and the denitration catalyst has a denitration efficiency of not less than 58%. The denitration catalyst according to claim 5, wherein a concentration of carbon monoxide in the environment is greater than a concentration of nitric oxide.