Catalyst For Removing Nitrogen Oxides and Method For Producing Same

Abstract

The present invention relates to a catalyst for removing nitrogen oxides and a method for manufacturing the same, and more specifically, to an SCR catalyst for removing nitrogen oxides (NOx) contained in exhaust gas by a Selective Catalytic Reduction (SCR) method, characterized in that the titanium dioxide (TiO2) support contains vanadium oxide (V2O5) as an active material and tungsten trioxide (WO3) as a co-catalyst material, but does not contain cerium dioxide (CeO2) and zigkonium dioxide (ZrO2).

Description

Technology Field

[0001] The present invention relates to a catalyst for removing nitrogen oxides and a method for manufacturing the same, and more specifically, to a catalyst for removing nitrogen oxides capable of effectively removing nitrogen oxides contained in exhaust gas over a wide temperature range and a method for manufacturing the same. Background Technology

[0003] Due to global industrialization, the increase in energy consumption is accelerating, and energy consumption in the capital area of ​​Korea surged more than twofold from 18,000 TOE (Ton of Oil Equivalent) in 1990 to 2000.

[0004] These primary energy supplies are concentrated around combined heat and power plants and coal-fired power plants, and since these power plants inject fuel and air together into the combustion chamber to obtain energy, exhaust gases are inevitably generated during this process.

[0005] Meanwhile, exhaust gases emitted from power plants and incinerators generally contain large amounts of harmful substances such as hydrochloric acid, sulfur oxides, nitrogen oxides, and dioxins.

[0006] In particular, nitrogen oxides are gaseous components that cause pollution in large cities and industrial zones, acting as a cause of acid rain as well as causing visibility impairment and the greenhouse effect, and generating various oxidizing agents such as O3, HCHO, and PAN, thereby causing secondary pollution and photochemical smog.

[0007] Selective Catalytic Reduction (SCR) is widely used as a technology to treat NOx contained in such flue gases.

[0008] In selective catalytic reduction, NH3, H2, CO, and even H2S can be used as reducing gases along with a suitable catalyst, and among these, NH3 is the most commonly used.

[0009] Reaction Equation 1) 4NO + 4NH3 + O2 → 4N2 + 6H2O

[0010] Reaction Equation 2) 2NO2 + 4NH3 + O2 → 3N2 + 6H2O

[0011] TiO2, γ-Al2O3, and SiO2 are the most well-known catalyst supports used in selective catalytic reduction reactions. Among these, γ-Al2O3 exhibits the highest catalytic activity, but the catalytic activity decreases significantly in the presence of moisture. Furthermore, the activity decreases significantly due to pore blockage caused by the formation of aluminum sulfate (Al2(SO4)3) on the catalyst by SO2, and the resulting poisoning.

[0012] SiO2 is not widely used because of its low catalytic activity, and currently, TiO2 is the most widely used SCR catalyst. Generally, a mixture of titanium and vanadium oxide as an active material is made into pellets or honeycomb shapes and used.

[0013] Meanwhile, the temperature range of exhaust gases varies depending on the emission source, such as combined heat and power plants, coal-fired power plants, and incinerators; therefore, there is a demand for SCR catalysts capable of effectively removing NO over a wide temperature range. Prior art literature

[0015] Korean Published Patent Application No. 2021-0046786, Korean Published Patent Application No. 2009-0027726, Korean Published Patent Application No. 2022-0003050, Korean Published Patent Application No. 2023-0072484 The problem to be solved

[0016] The present invention aims to solve the problems described above by providing an SCR catalyst capable of effectively removing NO even over a wide temperature range and a method for manufacturing the same. means of solving the problem

[0018] The SCR catalyst according to the present invention for solving the above problems is an SCR catalyst for removing nitrogen oxides (NOx) contained in exhaust gas by a Selective Catalytic Reduction (SCR) method, comprising: a ceramic material support; and a coating material provided on the ceramic material support; wherein the coating material includes vanadium oxide (V2O5) as an active material and tungsten trioxide (WO3) and titanium dioxide (TiO2) as co-catalyst materials, and does not include cerium dioxide (CeO2) and zigkonium dioxide (ZrO2).

[0019] In addition, the SCR catalyst according to the present invention is characterized in that the titanium dioxide (TiO2) is included in an amount of 85 to 95 parts by weight, the vanadium oxide (V2O5) in an amount of 1 to 10 parts by weight, and the tungsten (WO3) in an amount of more than 0 and less than or equal to 9 parts by weight.

[0020] In addition, the SCR catalyst according to the present invention is characterized in that titanium dioxide (TiO2) is included in a ratio of 90 to 93 weight%, vanadium oxide (V2O5) in a ratio of 3 to 9 weight parts, and tungsten (WO3) in a ratio of 1 to 4 weight parts.

[0021] In addition, the SCR catalyst according to the present invention is characterized by including titanium dioxide (TiO2) in a ratio of 93 parts by weight, vanadium oxide (V2O5) in a ratio of 3 parts by weight, and tungsten (WO3) in a ratio of 4 parts by weight.

[0022] In addition, the SCR catalyst according to the present invention is characterized by having a removal rate of nitrogen oxides (NOx) of 80% or more under conditions of a catalyst temperature of 300°C or lower and a contact time with exhaust gas of 0.2 seconds.

[0023] In addition, the SCR catalyst according to the present invention is characterized by having a removal rate of nitrogen oxides (NOx) of 95 to 98% under conditions of a catalyst temperature of 300°C and a contact time with exhaust gas of 0.2 seconds.

[0024] In addition, the SCR catalyst according to the present invention is characterized by having a removal rate of 80 to 85% of nitrogen oxides (NOx) under conditions of a catalyst temperature of 250°C and a contact time with exhaust gas of 0.2 seconds.

[0025] In addition, the SCR catalyst according to the present invention is characterized by having a removal rate of nitrogen oxides (NOx) of 50% or more under conditions of a catalyst temperature of 200°C and a contact time with exhaust gas of 0.2 seconds.

[0026] In addition, the SCR catalyst according to the present invention is characterized by having a removal rate of nitrogen oxides (NOx) of 60% or more under conditions of a catalyst temperature of 200°C and a contact time with exhaust gas of 0.2 seconds.

[0027] In addition, the SCR catalyst according to the present invention is characterized by having a removal rate of nitrogen oxides (NOx) of 70% or more under conditions of a catalyst temperature of 200°C and a contact time with exhaust gas of 0.2 seconds. Effects of the invention

[0029] According to the catalyst for removing nitrogen oxides and the method for manufacturing the same according to the present invention, when vanadium oxide (V2O5), tungsten trioxide (WO3), and titanium dioxide (TiO2) form a coating material, there is an advantage that nitrogen oxides (NOx) can be effectively removed even over a wide temperature range.

[0030] In particular, according to the catalyst for removing nitrogen oxides and the method for manufacturing the same according to the present invention, when a coating material is composed of 93 parts by weight of titanium dioxide (TiO2), 3 parts by weight of vanadium oxide (V2O5), and 4 parts by weight of tungsten trioxide (WO3), it is possible to remove more than 72% of nitrogen oxides (NOx) even at a relatively low temperature of 200℃. Brief explanation of the drawing

[0032] Figure 1 is a photographic result of the catalyst prepared according to the example and comparative example. Figure 2 shows the SEM results of catalysts prepared according to the examples and comparative examples. Figure 3 is a schematic diagram of a test apparatus prepared to verify the effect of the SCR catalyst. Figure 4 shows the NO removal rate results by temperature according to the examples and comparative examples. Specific details for implementing the invention

[0033] In this application, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the features, numbers, steps, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0034] Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0036] The following describes a catalyst for removing nitrogen oxides according to the present invention and a method for manufacturing the same.

[0037] The present invention relates to an SCR catalyst used to reduce nitrogen oxides contained in various exhaust gases, such as those from combined heat and power plants.

[0038] The SCR catalyst of the present invention comprises a support and a coating material supported on the support. First, the support is intended to support the coating material and is made of a ceramic material including Si and Al, and may have a honeycomb structure having a certain surface area.

[0039] Here, a known catalyst support made of ceramic material and having a honeycomb structure may be used.

[0040] The coating material supported on the support may be composed of a catalytic active material and a co-catalytic material, and in this case, it is preferable not to include cerium dioxide (CeO2) and zigkonium dioxide (ZrO2).

[0041] Specifically, vanadium oxide (V2O5) is preferred as the material acting as the catalytic active agent in the SCR reaction temperature range for removing nitrogen oxides, and tungsten trioxide (WO3) and titanium dioxide (TiO2) are preferred as the co-catalyst materials.

[0042] Here, based on the total coating material, it is preferable that titanium dioxide (TiO2) is included in a ratio of 85 to 95 parts by weight, vanadium oxide (V2O5) in a ratio of 1 to 10 parts by weight, and tungsten (WO3) in a ratio greater than 0 and 9 parts by weight; it is more preferable that titanium dioxide (TiO2) is included in a ratio of 90 to 93 parts by weight, vanadium oxide (V2O5) in a ratio of 3 to 9 parts by weight, and tungsten (WO3) in a ratio of 1 to 4 parts by weight; and most preferable that titanium dioxide (TiO2) is included in a ratio of 93 parts by weight, vanadium oxide (V2O5) in a ratio of 3 parts by weight, and tungsten (WO3) in a ratio of 4 parts by weight.

[0043] If the content of vanadium oxide (V2O5), which corresponds to the active material, is less than 1 part by weight, it is difficult to expect sufficient removal efficiency for nitrogen oxides, and conversely, if it exceeds 10 parts by weight, the content of titanium dioxide (TiO2) and tungsten (WO3) becomes relatively low, which may not only reduce the bonding strength with the support but also reduce the reaction rate and thermal durability, so the content of vanadium oxide (V2O5) is preferably within the above range.

[0044] In addition, if the content of titanium dioxide (TiO2), which corresponds to the co-catalyst material, is less than 85 parts by weight, the effect of improving the removal performance of nitrogen oxides is low, and the bonding with the support is weak, so the coating material may separate; conversely, if it exceeds 95 parts by weight, the content of vanadium oxide (V2O5) and tungsten (WO3) becomes relatively low, and the ability to remove nitrogen oxides decreases rapidly, so the content of titanium dioxide (TiO2) is preferably within the above range.

[0045] In addition, if tungsten (WO3), which corresponds to a co-catalyst material, is not included, the reaction rate is very low, making it difficult to expect sufficient removal efficiency for nitrogen oxides and significantly reducing thermal durability; conversely, if it exceeds 9 parts by weight, the content of titanium dioxide (TiO2) and vanadium oxide (V2O5) becomes relatively low, which may reduce the bonding strength with the support and make it difficult to expect sufficient removal efficiency for nitrogen oxides, so the content of tungsten (WO3) is preferably within the above range.

[0046] The SCR catalyst containing the aforementioned materials may have a monolith substrate shape, for example, a honeycomb shape with a certain thickness.

[0047] In addition, SCR catalysts containing the aforementioned materials can be expected to have excellent removal efficiency of nitrogen oxides even at low temperatures.

[0048] For example, when the nitrogen monoxide (NO) content of the exhaust gas is 700 ppm, more than 80% of the nitrogen monoxide (NO) can be removed under conditions where the catalyst temperature is 300°C or lower and the contact time is 0.2 seconds.

[0049] For example, when the nitrogen monoxide (NO) content of the exhaust gas is 700 ppm, 95 to 98% of the nitrogen monoxide (NO) can be removed under conditions where the catalyst temperature is 300°C or lower and the contact time is 0.2 seconds.

[0050] For example, when the nitrogen monoxide (NO) content of the exhaust gas is 700 ppm, 80 to 85% of the nitrogen monoxide (NO) can be removed under conditions where the catalyst temperature is 250°C or lower and the contact time is 0.2 seconds.

[0051] For example, when the nitrogen monoxide (NO) content of the exhaust gas is 700 ppm, more than 50% of the nitrogen monoxide (NO) can be removed under conditions where the catalyst temperature is 200℃ and the contact time is 0.2 seconds.

[0052] For example, when the nitrogen monoxide (NO) content of the exhaust gas is 700 ppm, more than 60% of the nitrogen monoxide (NO) can be removed under conditions where the catalyst temperature is 200℃ and the contact time is 0.2 seconds.

[0053] For example, when the nitrogen monoxide (NO) content of the exhaust gas is 700 ppm, more than 70% of the nitrogen monoxide (NO) can be removed under conditions where the catalyst temperature is 200℃ and the contact time is 0.2 seconds.

[0055] A method for manufacturing an SCR catalyst having the above-described configuration comprises the steps of preparing a support and a coating material, and coating the prepared support with the coating material.

[0056] In the step of preparing the support, ceramic materials such as Si and Al can be used to form a specific shape, for example, a monolith shape. Of course, a known catalyst support having a honeycomb structure may also be used.

[0057] In addition, the step of preparing the coating material involves preparing a mixture in the form of a slurry in which vanadium oxide (V2O5), tungsten trioxide (WO3), and titanium dioxide (TiO2) are mixed.

[0058] Specifically, a coating material can be prepared by mixing vanadium oxide (V2O5) with a certain amount of distilled water and stirring for a certain period of time, and then additionally mixing tungsten trioxide (WO3) and titanium dioxide (TiO2) and stirring again for a certain period of time.

[0059] The step of coating a coating material onto a prepared support involves coating the prepared ceramic carrier with a coating material mixture, for example, by dip coating, to coat the coating material onto the carrier.

[0060] In addition, during the coating step, after dip coating, an additional step of firing under certain conditions can be performed so that the coating material can stably bond with the ceramic carrier.

[0062] Preferred embodiments are presented below to aid in understanding the present invention. However, the following embodiments are provided merely to facilitate a better understanding of the invention and do not limit the scope of the invention.

[0064] Example 1

[0065] First, 3g of vanadium oxide was added to 100mL of distilled water and stirred at 150rpm for about 30 minutes. Then, 4g of tungsten trioxide (WO3) and 93g of titanium dioxide (TiO2) were additionally added and stirred again at 150rpm for about 60 minutes to prepare a coating solution.

[0066] A commercially available honeycomb-shaped support made of ceramic material was used, and a coating material was coated onto the prepared coating solution using a dip coating method.

[0067] Finally, the support coated with the coating material was dried at 120°C for 12 hours, and then calcined at 450°C for 3 hours to prepare the SCR catalyst.

[0069] Example 2

[0070] A catalyst was prepared in the same manner as in Example 1, except that the titanium dioxide (TiO2) content was changed to 92g, vanadium oxide (V2O5) to 5g, and tungsten (WO3) content to 3g.

[0072] Example 3

[0073] A catalyst was prepared in the same manner as in Example 1, except that the titanium dioxide (TiO2) content was changed to 91g, vanadium oxide (V2O5) to 7g, and tungsten (WO3) content to 2g.

[0075] Example 4

[0076] A catalyst was prepared in the same manner as in Example 1, except that the titanium dioxide (TiO2) content was changed to 90g, vanadium oxide (V2O5) to 9g, and tungsten (WO3) content to 1g.

[0078] Comparative Example 1

[0079] A catalyst was prepared in the same manner as in Example 1, except that the titanium dioxide (TiO2) content was changed to 95g and the tungsten (WO3) content was changed to 5g.

[0081] Comparative Example 2

[0082] A catalyst was prepared in the same manner as in Example 1, except that the titanium dioxide (TiO2) content was changed to 83.7g, vanadium oxide (V2O5) to 2.7g, and tungsten (WO3) content to 3.6g, and cerium dioxide (CeO2) to 6.0g and zigkonium dioxide (ZrO2) to 4.0g were added.

[0084] Comparative Example 3

[0085] A catalyst was prepared in the same manner as in Example 1, except that the titanium dioxide (TiO2) content was changed to 82.05g, vanadium oxide (V2O5) to 2.55g, and tungsten (WO3) to 3.4g, and cerium dioxide (CeO2) to 9.0g and zigkonium dioxide (ZrO2) to 3.0g were added.

[0087] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 TiO2 93.0 92.0 91.0 90.0 95.0 83.7 82.05 V2O5 3.0 5.0 7.0 9.0 - 2.7 2.55 WO3 4.0 3.0 2.0 1.0 5.0 3.6 3.4 CeO2 - - - - - 6.0 9.0 ZrO2 - - - - - 4.0 3.0

[0089] Experimental Example 1

[0090] Figure 1 is a photographic result of the catalysts prepared according to Examples 1 to 4 and Comparative Examples 1 to 3.

[0091] SCR catalysts include honeycomb type and plate type catalysts, and in this invention, a honeycomb type catalyst with a large specific surface area is used.

[0093] Experimental Example 2

[0094] Figure 2 is the SEM result of the catalysts prepared according to Examples 1 to 4 and Comparative Examples 1 to 3.

[0096] Experimental Example 3

[0097] The removal effect of nitrogen oxides (NOx) was investigated using catalysts prepared according to Examples 1 to 4 and Comparative Examples 1 to 3.

[0098] As shown in Fig. 3, the device for verifying the effect of the SCR catalyst preheated the mixture to 150°C while supplying N2, O2, NO, and NH3 as a reducing agent in appropriate proportions, taking into account the components of the actual exhaust gas.

[0099] The characteristics of the incoming gas, catalyst volume, contact time, etc. are as shown in Table 2, and the removal rate of NO contained in the discharged gas was measured while varying the furnace temperature to 200℃, 250℃, 300℃, and 350℃, and the results are shown in Table 3 and Figure 4.

[0101] In gas flow(cm 3 / min) NH3 90 N2 1800 O2 150 NO 90 Total 2,130 In gas conc. NH3 700 ppm N2 8 % O2 7.4 % NO 700 ppm Temp.(℃) 0 ~ 350 Catalyst volume 11.25 cm 3 Space velocity 11,360 h -1 Surface area of ​​catalyst 7.2 cm 3 Area velocity 3,530 cm / hr Catalyst contact time 0.2 sec

[0103] First, in the case of the SCR catalysts prepared according to Examples 1 to 4, it was confirmed that the removal rate of NO improved as the reaction temperature increased, and that more than 98% of NO was removed at 350°C.

[0104] However, in Comparative Example 1, which does not contain the active substance V2O5, only 22.65% of NO was removed even at 350°C, so it can be seen that it is not useful as a catalyst.

[0105] Meanwhile, the temperature range of exhaust gas varies depending on the emission source, and therefore, SCR catalysts capable of removing NO over a wide temperature range can be very usefully utilized.

[0106] Even in the case of Comparative Examples 2 and 3, which contain CeO2 and ZrO2 within a certain range, 21-22% of NO was removed at 200°C, and 60.66% and 89.12% were removed at 300°C, respectively.

[0107] However, in the case of Examples 1 to 4, which consist of TiO2, V2O5, and WO3, more than 32% of NO was removed even at a relatively low temperature of 200°C.

[0108] In particular, in the case of Example 1, which consists of 293 wt% TiO2, 53 wt% V2O, and 34 wt% WO, a high removal rate of 72.37% was achieved at 200°C, and 84.65% of NO was removed at 250°C, 97.81% at 300°C, and 98.03% at 350°C, confirming that NO can be efficiently removed from low temperature ranges to high temperature ranges.

[0110] 200 ℃ 250 ℃ 300 ℃ 350 ℃ Example 1 72.37% 84.65% 97.81% 98.03% Example 2 38.33% 41.85% 87.67% 98.24% Example 3 32.51% 72.30% 95.77% 99.56% Example 4 42.84% 57.89% 88.74% 100.00% Example 1 0.59% 2.20% 4.54% 6.15% Comparative Example 2 21.61% 43.96% 60.66% 98.66% Comparative Example 3 22.65% 50.29% 89.12% 97.94%

[0112] The present invention has been described above with reference to its preferred embodiments. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and equivalents thereof should be interpreted as being included in the invention.

Claims

Claim 1 As an SCR catalyst for removing nitrogen oxides (NOx) contained in exhaust gas by the Selective Catalytic Reduction (SCR) method, a ceramic material support; and a coating material provided on the ceramic material support; wherein the coating material comprises 3 to 9 parts by weight of vanadium oxide (V2O5) as an active material, and 1 to 4 parts by weight of tungsten trioxide (WO3) and 90 to 93 parts by weight of titanium dioxide (TiO2) as co-catalyst materials, and does not include cerium dioxide (CeO2) and zirconium dioxide (ZrO2); wherein the removal rate of nitrogen oxides (NOx) is 98.03% or higher under conditions of a catalyst temperature of 350°C and a contact time with exhaust gas of 0.2 seconds, the removal rate of nitrogen oxides (NOx) is 87.67 to 97.81% under conditions of a catalyst temperature of 300°C and a contact time with exhaust gas of 0.2 seconds, the removal rate of nitrogen oxides (NOx) is 41.85 to 84.65% under conditions of a catalyst temperature of 250°C and a contact time with exhaust gas of 0.2 seconds, and the catalyst temperature An SCR catalyst characterized by a nitrogen oxide (NOx) removal rate of 32.51–72.37% under conditions of 200℃ and a contact time with exhaust gas of 0.2 seconds. Claim 2 delete Claim 3 delete Claim 4 An SCR catalyst according to claim 1, characterized in that the titanium dioxide (TiO2) is included in a ratio of 93 parts by weight, vanadium oxide (V2O5) in a ratio of 3 parts by weight, and tungsten trioxide (WO3) in a ratio of 4 parts by weight. Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 A method for manufacturing an SCR catalyst as described in claim 1 or 4, comprising the steps of: adding vanadium oxide (V2O5) to distilled water, stirring at 150 rpm for 30 minutes, adding tungsten trioxide (WO3) and titanium dioxide (TiO2), and stirring again at 150 rpm for 60 minutes to prepare a coating solution; coating a honeycomb-shaped support made of a ceramic material with the prepared coating solution; and drying the support coated with the coating material at 120°C for 12 hours, and then calcining at 450°C for 3 hours.

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