KR100979031B1 - Nitrogen oxide removal catalyst and its manufacturing method - Google Patents

Abstract

The present invention relates to a catalyst for removing nitrogen oxide and a method for preparing the same, which can effectively remove nitrogen oxide using urea as a reducing agent. To develop and provide new catalysts with improved durability,

A catalyst used in a process for converting nitrogen and water by reacting with ammonia, a reducing agent, on a catalyst for removing nitrogen oxides contained in a diesel engine or combustion gas, wherein the catalyst is a bentonite solution or a tin filler solution in a mixed solution of bentonite and activated carbon. And a titania filler solution are added / stirred, the pH is maintained at 9 by ammonia water, and then a carrier is formed by filtration, washing, drying, and calcination, and the powdered carrier is placed in a solution in which the active substance is dissolved. A catalyst for removing nitrogen oxides having a meso and macro (50 to 150 kPa) area under the micro area (<30 kPa) of surface area increase and pore distribution by stirring, drying / firing and supporting the active substance, and a method of manufacturing the same In providing.

SCR, NOx, PILC, Clay, Bentonite

Description

Catalyst for nitrogen oxide removal and its manufacturing method {Catalyst for Nitrogen Oxide Removal and method for Manufacturing the same}

1 is BET measurement data of Ti-PLIC

2 is BET measurement data of Sn-Ti-PILC

3 is BET measurement data of Sn-Ti-activated carbon 30% by weight-PILC

4 is BET measurement data of 10 wt% -PILC of Sn-Ti-activated carbon;

The present invention relates to a catalyst for removing nitrogen oxides capable of effectively removing nitrogen oxides using urea as a reducing agent, and a method of manufacturing the same. The present invention relates to a carrier made of tin-filled Ti-PLIC, such as vaniadia, tungsten, and molybdenum. The present invention relates to a catalyst supporting an active substance and a method of preparing the same.

Nitrogen oxides are mainly produced in power plants, internal combustion engines, and nitric acid plants. Seven kinds of nitrogen oxides are known: nitrogen monoxide, nitrogen dioxide, nitrogen trioxide, dinitrogen monoxide, dinitrogen trioxide, dinitrogen tetraoxide, and dinitrogen pentoxide. Most of them are dinitrogen monoxide, nitrogen monoxide and nitrogen dioxide. In general, nitrogen oxides (NOx) refer to nitrogen monoxide and nitrogen dioxide. Since most nitrogen oxides generated in power plants or automobiles are in the form of nitrogen monoxide, it is important to develop a technology for reducing them.

Until now, various techniques for removing nitrogen oxides generated when using fossil fuels in power plants have been studied. Among them, Selective Catalytic Reduction (SCR) technology has been studied to remove nitrogen oxides from fixed sources. Among the technologies presented, it is a technology that can satisfy all economic, legal and technical aspects. In this technology, the proportion of the nitrogen oxide removal catalyst contained in the exhaust gas using the catalyst is very large in the overall investment and operating cost of the SCR process.

Since the 1970s, many studies and patents on nitrogen oxide reduction catalyst processes using ammonia as a reducing agent have been published. In US Pat. No. 4,048,112 (1976), Matsushita et al. Proposed a catalyst supporting vanadia in Titania, and since then, many studies have been conducted on catalysts based on vanadia-titania. In addition, in US Pat. No. 4,085,193 (1978), Nakajima et al. Described molybdenum (Mo), tungsten (W), iron (Fe), vanadium (V), nickel (Ni), and cobalt (Co) based on titania. Catalysts to which various metal oxides, such as chromium (Cr) and uranium (U), are added, have been proposed. Recently, many attempts have been made to improve the performance of catalysts by imparting various functions to the catalysts to improve the performance of existing catalysts. In particular, in the selective catalytic reduction process of nitrogen monoxide using ammonia as a reducing agent, the durability of the catalytic poison of sulfur compounds such as sulfur dioxide (SO2) is the most important factor, and many studies have been conducted to improve this. The development of a new carrier including the properties of vanadia-titania or titania, which is widely used as an SCR catalyst, has been carried out in terms of research. Prior to the present invention, US Patent No. 6,475,944 (2002) has registered and patented an excellent V2O5 / Ti-PILC catalyst which converts nitrogen oxides into nitrogen and water by reacting nitrogen oxides with a reducing agent on a catalyst even in a combustion gas containing sulfides.

The selective reduction of nitrogen oxides using catalysts has applications of very different catalysts depending on the installation location. However, the conventional catalysts and the vanadia-titania catalysts commonly used as commercial catalysts have relatively high durability against sulfur compounds. Branches are weak in mechanical strength, and have problems due to catalyst poisons such as alkali or alkaline earth metals.

In addition, the catalysts of the present invention tend to occupy most of the pores in the macro region in terms of their specific surface area, but the degradation of durability due to pore blockage, which has been a problem in the durability of nitrogen oxide removal catalysts, has been raised. There was a problem.

The present invention has been made in consideration of the above problems, and an object thereof is to develop a new catalyst having improved durability against various factors of deterioration of catalyst activity as well as excellent nitrogen oxide removal activity. In other words, the present invention provides a more excellent mechanical strength of the catalyst based on titania as a support, and improves the specific surface area, thereby providing a space in which the reaction between the nitrogen oxide in the exhaust gas and the ammonia as the reducing agent can be performed. It is to provide a catalyst for removing nitrogen oxide and a method for producing the same that can secure the efficiency.

Another object of the present invention is to change the structural characteristics of the catalyst to have meso and macro (50 to 150 Å) pores rather than micro (<30 Å) pores in terms of pore distribution, thereby prolonging the life of the catalyst, thereby causing concern when using the catalyst. This is to prevent the catalyst pore clogging caused by the soot or secondary synthetic material in the exhaust gas as much as possible.

It is another object of the present invention to provide a catalyst for removing nitrogen oxide and a method for producing the same, which can increase the durability of catalyst poisons such as alkali or alkaline earth metals as well as sulfur compounds and extend the range of nitrogen oxide removal activity to a low temperature region. It is.

According to the present invention, ammonia, which is a thermal decomposition product of urea injected into a nitrogen oxide and a reducing agent contained in exhaust gas of a power plant, a diesel engine, an incinerator, etc., in which excess oxygen exists, is supported on Sn-Ti-PILC and Sn-Ti-activated carbon-PILC. Catalyst for the catalytic reaction of reacting on the catalyst such as vanadium, tungsten, molybdenum and the like and converted to nitrogen and water, and a catalyst for removing nitrogen oxide capable of controlling the internal structure of the catalyst so that the removal reaction can be efficiently performed The catalyst developed in the present invention relates to a carrier made by filling tin (Sn) or tin and active carbon (Ti) with Ti-PILC prepared by a general known technique, such as vaniadia, tungsten, molybdenum, and the like. It is intended to support the active substance of. That is, the present invention 0.5 in the active material such as vanadium (V2O5), tungsten (WO3), molybdenum (MoO3) in Sn-Ti-PILC prepared by filling tin oxide (SnO ₂ ) and titania (TiO2) in bentonite It is supposed to carry 20 wt%.

The bentonite is a clay composed of extremely fine particles, and refers to one composed of smectite-type minerals, and the main constituent mineral is montmorillonite. Montmorillonite is a silicate mineral that has different properties depending on the chemical composition of the substitutable base (Ca, K, Na, Mg). When the replaceable cation is sodium (Na), it is swellable bentonite having the property of expanding up to 15 times in volume by absorbing moisture, and non-swellable bentonite when the replaceable cation is calcium (Ca). Since the filler phenomenon is based on reversible expansion phenomenon, bentonite used in the present invention is bentonite which is mostly sodium or ion exchanged with sodium as a substitutional cation.

In addition, when the active material is supported 20wt% or more, the adverse effect of blocking the path to the gas diffusion will appear, so only the active material supported on the surface will participate in the reaction, 0.5 to 20 wt% It is preferable to carry it within the range.

In addition, the tin and titanium are filler based on 1 to 100 millimoles per gram of bentonite in order to increase the specific surface area. When the amount of the tin and titanium implanted is 100 millimolar or more, there is no further increase in specific surface area, so that further implantation becomes meaningless in terms of economic and specific surface area improvement.

In addition, the present invention is mixed with bentonite and activated carbon, and the tin oxide (SnO ₂ ) and titania (TiO ₂ ) to be filler to prepare Sn-Ti-activated carbon-PILC, vanadium (V 2 O 5), tungsten oxide ( WO 3) and molybdenum oxide (MoO 3) may be supported.

The activated carbon is an aggregate of well-developed amorphous carbon made of carbonaceous materials such as palm shell, wood, lignite, anthracite, bituminous coal, and the like, and micropores of molecular size are formed through an activation process. It is an adsorbent having a large internal surface area. Activated carbon has a large internal surface area of 1000 m 2 or more per g, and the functional group of carbon atoms present on the inner surface attracts molecules of adsorbate by attracting the surrounding liquid or gas.

In addition, the tin and titanium are filler based on 1 to 100 millimoles each gram of bentonite and activated carbon mixture to increase the specific surface area. When the amount of the tin and titanium implanted is 100 millimolar or more, there is no further increase in specific surface area, so that further implantation is meaningless in terms of economic and specific surface area improvement.

A catalyst supporting vanadium (V 2 O 5), tungsten oxide (WO 3) and molybdenum oxide (MoO 3) in Sn-Ti / PILC prepared by such a filler, and vanadia (V 2 O 5) in Sn-Ti-activated carbon / PILC , A catalyst supporting tungsten oxide (WO 3) and molybdenum oxide (MoO 3) has a surface area of 150 to 300 m 2 / g.

The catalyst of the present invention forms a carrier by adding / stirring a tin filler solution and a titania filler solution to a suspension solution of clay and maintaining a pH of 9 with ammonia water and then forming a carrier by filtration, washing, drying and calcining. And the active material carrying step of supporting the active material by stirring the dried powder carrier in a solution in which the active material is dissolved, and drying / firing.

In the carrier forming step, bentonite is added to distilled water and stirred to form a bentonite suspension solution or a mixed solution of bentonite and activated carbon, a tin filler solution and a titania solution are aged and aged at room temperature, and then the bentonite suspension or bentonite and activated carbon The tin filler solution and the titania filler solution were added to the mixed solution in this order, and adjusted to maintain pH 9 by adding ammonia water thereto, followed by filtration, washing, drying and firing.

In addition, the active material supporting step is to dissolve the active material precursor in distilled water and adjust the pH to 2 ~ 3.0 using oxalic acid, and to put the powder carrier in the stirring and evaporate the water, and then to dry / fire have.

The final shape of the catalyst prepared as described above is, firstly, when the entire amount of the catalyst material is kneaded in the form of honeycomb, plate, etc. in the extruder, and when the kneaded catalyst is made into granules (or pallets) of a constant size, third, There is a method of coating the catalyst material on the substrate (carrier), such as metal, ceramic, etc., to which the catalyst may be attached, by wash coating or dipping. Sol, silica sol, etc.) to prepare a mixed slurry, and then, the honeycomb cordialite is coated with a catalyst material using wash coating or dipping. Then, the prepared honeycomb catalyst is dried at 110 ° C. and 350 ° C. It was calcined for 5 hours at, and the active material was prepared by preparing a predetermined amount of active material (V, W, Mo) precursor in solution and prepared the above-described substrates of Sn-Ti-PILC and Sn-Ti-Bow. The honeycomb cordial coated with Na-PILC was used to complete the catalyst with the final activity by dipping.

FIG. 3 shows BET measurement data of Sn-Ti-activated carbon 30 wt% -PILC, which has a specific surface area of 240 m 3 / g, and a pore distribution mainly formed in the micro and macro region. 4 shows BET measurement data of 10 wt% -PILC of Sn-Ti-activated carbon, showing a BET measurement result having a specific surface area of 148 m 3 / g and pore distribution mainly formed in the micro and macro regions.

In general, up to 20 ms are classified into micro-pore areas, 20-100 ms to meso pore regions, and more than 100 ms are classified as macro regions. The graphs of FIGS. 1 to 4 show pore volume per gram of catalyst displayed on the Y axis for each pore diameter of the X axis. FIGS. 1 and 2 show that the micro area (<20-30 μs) is 0.17 0.325 cm 3 / g pore volume is mainly developed. However, the graphs of FIGS. 3 and 4 show the results of pore volume development up to 100 mm pore diameter, which is a meso pore, by adding activated carbon.

As such, the present invention used a mixture of bentonite, bentonite and activated carbon in the filler to adjust the pore structure distribution and size, the mixture of activated carbon is 1 to 50% per gram of bentonite, more preferably at 20% or more It is effective to manufacture. Other components include tartaric acid, cellulose, surfactants, and the like.

Since Sn-Ti-PILC used in the present invention exhibits different characteristics according to manufacturing conditions and processes, the present invention uses titanium tetrachloride as a titania precursor, and stenic tetrachloride and steners bichloride as precursors of tin. It was used to obtain an effective filler effect.

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

Example 1

-Preparation of Sn-Ti-PILC carrier is as follows.                     

Filling of titania in the present invention is generally prepared according to known methods. As the clay material underlying PILC, activated sodium bentonite provided by Vol Clay is used as bentonite mainly composed of montmorillonite structure. In a specific manufacturing method, first, about 10 g of bentonite is put in 1.5 L of distilled water and stirred for 5 hours or more so as to be well dispersed. Then, 9.2 g of stenus chloride as a precursor is dissolved in 0.25 L distilled water to prepare tin filler. In addition, titanium tetrachloride is added to a solution of 2M hydrochloric acid (HCl) to fill titanium, and distilled water is slowly added to the mixture to form a filler solution of 0.1-1.0M titanium and 0.1-1.0M hydrochloric acid. Each solution was aged at room temperature for 12 hours, and then the tin filler solution was slowly added to the clay suspension solution, followed by the titania filler solution. The suspension is then stirred vigorously for about 12 hours. And 0.018 L of ammonia water was added here and pH was set to 9. Next, the resultant was filtered and sufficiently washed, followed by drying in an atmosphere of 110 ° C., and the dried sample was slowly heated to 350 ° C. at a temperature rising rate of 2 ° C./min, and then fired at 350 ° C. for 5 hours.

Example 2

Preparation of vanadia, tungsten and molybdenum catalysts supported on Sn-Ti-PILC is as follows.                     

In the present invention, the vanadium, tungsten, and molybdenum catalyst supported on Sn-Ti-PILC were prepared by a supporting method, which is generally known to Sn-Ti-PILC carrier prepared by the same method as Example 1, wherein vanadia Ammonium meta vanadate (NH 4 VO 3) was used as a precursor. As a precursor of tungsten, ammonium metatungstate hydrate [(NH 4) 6 W 12 O 39 .H 2 O] was used. As the precursor of molybdenum, ammonium molybdate [(NH 4) 6 Mo 7 O 24. 4H 2 O] was used. In the manufacturing process, first, the precursor of vanadia is weighed by a calculated amount and dissolved in distilled water, and then oxalic acid (COOHCOOH) is used to make Sn-Ti-PILC, which is a carrier, according to pH = 2-3.0. After stirring well, water is evaporated using a rotary evaporator. And after drying for 12 hours at 110 ℃ was prepared by firing at 450 ℃ for 5 hours. In the case of tungsten and molybdenum, each of the required amounts of basis weight was prepared by stirring in distilled water. The amount of vanadium, tungsten, molybdenum on the catalyst was prepared to include 8% by weight, 5% by weight, 5% by weight.

Example 3

-Preparation of Sn-Ti-activated carbon-PILC carrier is as follows.

The activated carbon used for the filler in the present invention used powdered activated carbon provided by Samchully. In a specific manufacturing method, first, a mixture of about 10 g of bentonite and about 2 g of activated carbon in 1.5 L of distilled water is stirred for 5 hours or more so as to be well dispersed. Filling of tin and titania of the Sn-Ti-activated carbon-PILC carrier was prepared in the same manner as in Example 1.

Example 4

Preparation of vanadia, tungsten and molybdenum catalysts supported on Sn-Ti-activated carbon-PILC is as follows.

In the present invention, the vanadium, tungsten, and molybdenum catalysts supported on Sn-Ti-activated carbon-PILC were prepared by the same method as in Example 2. Sn-Ti-activated carbon-PILC carrier used was prepared in the same manner as in Example 3.

In the present invention, the catalysts prepared according to Examples 1-4 were examined for the selective catalytic reduction reaction of nitrogen monoxide in nitrogen oxide in a nitrogen atmosphere containing 5% oxygen. The results are shown in Table 1 below. In addition, in the present invention, a fixed bed reactor system was used to test nitrogen oxide removal performance of the prepared catalyst, and the fixed bed reactor system includes a gas injection part, a reactor part, and an analysis part to make a desired exhaust gas composition.

In addition, unless otherwise specified, the present invention consists of nitrogen containing 1,000 ppm of nitrogen monoxide and 5% oxygen of ammonia, and the reaction conditions were performed at a reactor space velocity of 10,000 / hr and a range of 200-500 ° C. Selective catalytic reduction (SCR) technology for removing nitrogen oxides, the reaction temperature range is different depending on the catalyst, in the present invention can be operated in the range of 200 ~ 500 ℃, preferably better nitrogen oxide removal at 300 ~ 450 ℃ Results.

TABLE 1

catalyst % Removal activity
Reaction temperature (℃) 250 300 350 400 V ₂ O ₅ -WO ₃ -MoO ₃ / Ti-PILC 88 95 96 95 V ₂ O ₅ -WO ₃ -MoO ₃ / Sn-Ti-PILC 93 98 98 97 V ₂ O ₅ -WO ₃ -MoO ₃ // Sn-Ti-Activated Carbon-PILC 91 96 95 95

The results shown in the above table compare the activity of the catalyst (V ₂ O ₅ -WO ₃ -MoO ₃ / Ti-PILC) mentioned in the US patent registration (US 6,475,944) with the nitrogen oxide removal activity of the catalyst prepared in the present invention. It is.

In addition, in the present invention, the specific surface area and pore distribution were measured by using a BET device (ASAP2000 device) in order to determine the structure and physical properties of the prepared catalyst, and the results of the investigation are shown in Table 2.

TABLE 2

Catalyst type Clay mixing composition Aver. BET
(㎡ / g) Max. PA
(PV)
Diameter
(A) Sn + Ti / PILC 4 ^_a)  Clay 240 32 Sn + Ti + Activated Carbon / PILC 1 ^_b)  Clay + Activated Carbon 2.5g [10 wt%] 196 (70) Sn + Ti + Activated Carbon / PILC 2 ^c)  Clay + Activated Carbon 5g [20 wt%] 148.8 25 (90) Sn + Ti + Activated Carbon / PILC 3 ^_d)  Clay + activated carbon 8.5g [30 wt%] 240 (10-100) TiO _{2 ^e)} - 72.5 74 Sn / PILC 4 ^f)  Clay 141 20 Sn / PILC 5 ^g) Clay + TiO ₂ Powder + CeO ₂ Powder 154 20 (102) Ti / PILC 4 ^h)  Clay 150 30

a) Catalyst with Sn and Ti fillerd in clay

b-d) Sn and Ti fillers on clay and activated carbon

e) reagent grade commercial TiO2

f) Sn only filler

g) Catalyst prepared after Sn filler by mixing reagent grade commercial TiO2 in Clay

As described above, while the specific surface area and average pore distribution of the Ti / PILC catalyst are distributed in the micro region, the catalyst (a) prepared in the present invention has a significant increase in the specific surface area. In addition, it can be seen that the catalyst (bd) prepared in the present invention improved the average value of the pore distribution in the micro region to the macro region while significantly increasing the specific surface area of the existing Ti / PILC catalyst.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

Thus, in the case of the V, W, Mo / Sn-Ti-PILC catalyst and V, W, Mo / Sn-Ti-activated carbon-PILC catalyst developed in the present invention, the conventional commercial catalyst and V, W, Mo / Ti- Compared to the PILC catalyst, the specific surface area is improved, and the structure of the macropores, which helps to improve the durability, is increased and the efficiency is also excellent.

That is, the durability of the catalyst poison and the sulfur compound can be controlled by the structural variables of the material used as the carrier in the catalyst, and by controlling the pore size distribution by the structural variable of the carrier, that is, macropores and omstrongs having a pore diameter in microns. The catalyst poison problem can be solved by designing the catalyst such that the micropores having the unit have a pore distribution at the same time. Catalytic poisons having a low diffusivity are mainly deposited in the macropores and thus can improve the durability to the catalyst poison by making the macropores act as a filter for filtering the catalyst poisons. In addition, by increasing the pore size, it is possible to reduce the clogging of the pores of the catalyst, such as ammonium sulfate, which is known as a deactivation factor, and thus has many effects such as excellent life and durability.

Claims (15)

In the catalyst used in the process of converting nitrogen and water by reacting with ammonia, a reducing agent, on a catalyst for removing nitrogen oxide contained in a diesel engine or combustion gas, The catalyst is supported by 0.5 to 20wt% of an active material on a carrier in which tin oxide (SnO 2) and titania (TiO 2) are filled in bentonite. The active material is a nitrogen oxide removal catalyst, characterized in that at least one selected from the group consisting of vanadium (V2O5), tungsten (WO3), molybdenum (MoO3). The method of claim 1; Catalyst for removing nitrogen oxides, characterized in that activated carbon is further added to the carrier. The method of claim 2; The activated carbon is a nitrogen oxide removal catalyst, characterized in that mixed in the range of 1 to 50wt% per gram of bentonite. The method of any one of claims 1 to 3; Per gram of bentonite, tin and titanium per gram of bentonite and activated carbon mixture are added in an amount of 1 to 100 millimoles, respectively. delete The method of any one of claims 1 to 3; The catalyst for removing nitrogen oxides, characterized in that having a surface area of 150 ~ 300 m 2 / g. The method of claim 1; The catalyst for removing nitrogen oxides, characterized in that used for the nitrogen monoxide reduction reaction by ammonia and urea to remove the nitrogen oxides. The method of claim 7; Nitrogen oxide removal catalyst, characterized in that the temperature in the nitrogen monoxide reduction reaction for nitrogen oxide removal is 200-500 ℃. The method of claim 7 or 8; The catalyst is used for coating on the cordialite honeycomb carrier, or a catalyst for removing nitrogen oxides, characterized in that formed in the form of a pallet. In the method for producing a catalyst used in the process of converting nitrogen and water by reacting with ammonia as a reducing agent on a catalyst for removing nitrogen oxide contained in a diesel engine or combustion gas, The catalyst is a carrier forming step of forming a carrier by filtration, washing, drying and calcining after adding / stirring a tin filler solution and a titania filler solution to a suspension solution of clay and maintaining the pH at 9 with ammonia water; Wherein the carrier in the powder form formed in the active material is dissolved in the solution and stirred, dried / fired to carry out the active material carrying step of supporting the active material, The active material is a method for producing a catalyst for removing nitrogen oxides, characterized in that at least one selected from the group consisting of vanadia (V2O5), tungsten (WO3), molybdenum (MoO3). The method of claim 10; The carrier forming step includes the steps of adding bentonite to distilled water to form a suspension of clay; Dissolving stenus chloride in distilled water to form a tin filler solution; Adding titanium tetrachloride to the hydrochloric acid solution and distilled water to the mixture to form a solution for filling titanium; Aging the respective solutions at room temperature; Adding a tin filler solution to the suspension of clay, adding a titania filler solution in order, and then stirring the suspension; Adjusting to maintain pH 9 by adding ammonia water to the stirred suspension; The method for preparing a catalyst for removing nitrogen oxides, characterized in that the carrier is prepared by filtration / washing the pH-adjusted solution, drying and calcining the solution. 12. The method of claim 10 or 11; Activated carbon is further added to the suspension of clay, the method for producing a catalyst for removing nitrogen oxides, characterized in that. The method of claim 10; The active material supporting step may be performed by dissolving the active material precursor in distilled water and adjusting the pH to 2 to 3.0 using oxalic acid; The method of preparing a catalyst for removing nitrogen oxides, characterized in that the active material solution is put into a powder carrier and stirred, followed by evaporating water and drying / firing it. delete The method of claim 10; The precursor of vanadia is ammonium meta vanadate, the precursor of tungsten is ammonium metatungstate hydrate, the precursor of molybdenum is ammonium molybdate, the method for producing a catalyst for removing nitrogen oxides.

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