Catalyst and denitration device provided with said catalyst

Abstract

A catalyst of the present disclosure contains vanadium and manganese, wherein the mass ratio of manganese oxide calculated in terms of dimanganese trioxide to vanadium oxide calculated in terms of divanadium pentoxide is 0.179-1.52.

Description

Catalyst and denitrification apparatus equipped with this catalyst

[0001] This disclosure relates to a catalyst and a denitrification apparatus equipped with the catalyst. This application claims priority under Japanese Patent Application No. 2024-203696, filed with the Japan Patent Office on November 22, 2024, the contents of which are incorporated herein by reference.

[0002] For example, selective catalytic reduction (SCR) systems are used to remove nitrogen oxides (NOx) from combustion exhaust gases discharged from incinerators (denitrification). In SCRs, NOx is reduced by a reaction with ammonia. As a catalyst used in such SCRs, for example, a catalyst in which vanadium oxide is supported as the active component on a titanium oxide support is used. Since catalysts supported solely on vanadium oxide exhibit high activity at high temperatures exceeding 200°C, it is necessary to heat the combustion exhaust gas flowing out of the dust collector (e.g., a bag filter) to a temperature exceeding 200°C before supplying it to the denitrification system. In the case of low-temperature exhaust gases below 200°C, the need to heat the combustion exhaust gas to such high temperatures has been a factor in increasing denitrification costs.

[0003] To reduce denitrification costs, catalysts that exhibit high activity even at low temperatures below 200°C are needed, and catalysts of various compositions and forms are being developed. For example, Patent Document 1 describes a catalyst for denitrification of vanadium oxide to divanadium pentoxide (V ２ O ５ It has been verified that by using a catalyst containing 50% or more by mass (calculated as ), the catalyst exhibits high activity even at low temperatures below 200°C.

[0004] Patent No. 7445925

[0005] However, if the combustion exhaust gas contains sulfur compounds, acidic ammonium sulfate (NH₃) is produced by the reaction of sulfur oxides with ammonia. ４ HSO ４ It is known that ammonium sulfur oxides such as ) accumulate in the catalyst pores and on the catalyst surface, causing the catalyst performance to deteriorate over time. Therefore, there is a concern that the catalyst performance will deteriorate over time if denitrification is performed at a low temperature of 200°C or less using the catalyst described in Patent Document 1.

[0006] In view of the circumstances described above, at least one embodiment of this disclosure aims to provide a catalyst with improved toxicity resistance to ammonium sulfur oxides such as acidic ammonium sulfate, and a denitrification apparatus equipped with this catalyst.

[0007] To achieve the above objective, the catalyst relating to this disclosure is a catalyst containing vanadium and manganese, wherein the mass ratio of manganese oxide converted to dimanganese trioxide to vanadium oxide converted to divanadium pentoxide is 0.179 to 1.52.

[0008] According to the catalyst of this disclosure, the action of the manganese compound modulates the electronic state of the vanadium compound, causing the vanadium compound to become more oxidized. This change in the state of the vanadium compound makes it less likely for reactions to occur on the catalyst surface that generate ammonium sulfur oxides such as acidic ammonium sulfate, thus improving toxicity resistance to ammonium sulfur oxides such as acidic ammonium sulfate.

[0009] This is a conceptual diagram showing a part of the configuration of a denitrification apparatus equipped with the catalyst of this disclosure. This is a schematic diagram of a specific example of a denitrification apparatus equipped with the catalyst of this disclosure. This is a schematic diagram of another specific example of a denitrification apparatus equipped with the catalyst of this disclosure. This is a schematic diagram of yet another specific example of a denitrification apparatus equipped with the catalyst of this disclosure. This is a graph showing the denitrification evaluation results of the catalysts of Examples 1 to 22 and Comparative Examples 1 to 3. This is a graph showing the results of X-ray photoelectron spectroscopy analysis of the catalysts of Example 11 and Comparative Example 4. K for the catalysts of Examples 12 and 13 and Comparative Example 3 １ / K ０ This graph shows the relationship between the amount of acidic ammonium sulfate produced and the amount of acidic ammonium sulfate produced.

[0010] The catalysts according to embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below represent one aspect of this disclosure and are not limiting, and can be modified at will within the scope of the technical idea of ​​this disclosure.

[0011] <Composition of the Catalyst in This Disclosure> The catalyst in this disclosure is a catalyst containing vanadium and manganese, wherein the mass ratio of manganese oxide (calculated as dimanganese trioxide) to vanadium oxide (calculated as divanadium pentoxide) is 0.179 to 1.52. The catalyst in this disclosure may further contain molybdenum, wherein the mass ratio of molybdenum oxide (calculated as molybdenum trioxide) to vanadium oxide (calculated as divanadium pentoxide) is 1.33 to 11.8. Vanadium and manganese may be supported on a carrier or mixed with a substance other than vanadium and manganese. When vanadium and manganese are supported on a carrier or mixed with a substance, the content of vanadium oxide (calculated as divanadium pentoxide) is 1.9% to 4.5% by mass, the content of manganese oxide (calculated as dimanganese trioxide) is 0.5% to 4.1% by mass, and the remainder is the carrier or the substance and unavoidable impurities. If the catalyst of this disclosure further contains molybdenum, the molybdenum may also be supported on the carrier, or may be mixed with substances other than vanadium, manganese, and molybdenum. When vanadium, manganese, and molybdenum are supported on the carrier or mixed with such substances, the content of molybdenum oxide, calculated as molybdenum trioxide, is 6.0% to 22.5% by mass. When vanadium, manganese, and molybdenum are supported on the carrier or mixed with such substances, they are, for example, supported on the carrier as oxides or mixed with such substances. As the carrier, for example, one or more of titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, tungsten oxide, calcium oxide, and zeolite can be selected from oxides or composite oxides, and good results are likely to be obtained by selecting a carrier with excellent acid resistance and high thermal stability, and even better results are likely to be obtained by selecting titanium oxide. When denitrification is performed using the catalyst of this disclosure, the catalyst of this disclosure is a denitrification catalyst, and it is necessary to add a NOx reducing agent such as ammonia to the denitrification catalyst.

[0012] <Configuration of the Denitrification Apparatus of the Disclosure> As shown in Figure 1, the denitrification apparatus 3 can be configured by attaching the catalyst 1 to a member 2 of any configuration. For example, as shown in Figure 2, such a member 2 may be a filter 5 provided in a filter-type dust collector 4. By attaching the catalyst 1 to the filter 5, the filter-type dust collector 4 can also function as a denitrification apparatus 3 having a denitrification function. The form in which the catalyst 1 is attached to the filter 5 may be by attaching the catalyst 1 to the surface of the filter 5, by attaching the catalyst 1 to the inside of the filter 5, or by attaching the catalyst 1 to both the surface and the inside of the filter 5 (i.e., the whole). In addition, a protective layer 6 made of a reaction aid may be provided upstream of the surface 5a of the filter 5 to which the catalyst 1 is attached (the surface of the filter 5 to which the gas G processed by the filter-type dust collector 4 first hits the filter 5), or a further layer 7 made of slaked lime and activated carbon may be provided upstream of the protective layer 6. By providing the protective layer 6, clogging of the filter 5 and deterioration due to acidic gases (gases including hydrogen chloride and sulfur oxides) can be suppressed, and by providing the layer 7, acidic gases, mercury, dioxins, hydrocarbons, etc. can be adsorbed and removed.

[0013] Component 2 may be a metal or ceramic mesh 8 as shown in Figure 3. When a metal or ceramic mesh 8 is used as component 2, the catalyst 1 may be formed only around the aggregate of the mesh 8, or it may be formed to fill all the holes of the mesh 8 or to cover the entire mesh 8. Alternatively, component 2 may be a honeycomb structure 9 as shown in Figure 4. Figure 4 shows an exemplary honeycomb structure 9 in the form of a diesel particulate filter (DPF), but it is not limited to the form of a DPF, and can also be a honeycomb structure in the form of a corrugated shape or a shape of stacked plates. The honeycomb structure 9 has a base material 9a of any shape, for example, a cylindrical or polygonal prism shape, in which multiple elongated spaces, i.e., flow channels 9b, are formed between one end face 9a1 and the other end face 9a2 of the base material 9a. For example, the catalyst 1 may be attached to the inner circumferential surface 9b1 of the flow channels 9b. The honeycomb structure 9 may be configured such that all the flow paths 9b are open at both end faces 9a1 and 9a2, or the flow paths 9b may include both a flow path that is open at one end face 9a1 and closed at the other end face 9a2, and a flow path that is closed at one end face 9a1 and open at the other end face 9a2. In the latter case, the base material 9a must be formed from a porous material that allows the gas flowing through the flow paths 9b to pass through. By installing a mesh 8 with the catalyst 1 attached or a honeycomb structure 9 with the catalyst 1 attached in a pipe through which a gas containing NOx (e.g., combustion gas) flows, the gas containing NOx can be denitrified.

[0014] <Preparation of catalysts for Examples 1-22 and Comparative Examples 1-3> For each of Examples 1-22 and Comparative Examples 1-3, ammonium metavanadate, ammonium molybdate, manganese nitrate hexahydrate, titanium dioxide, oxalic acid, and water were weighed in the amounts listed in Table 1 below.

[0015]

[0016] For each of Examples 1 to 22 and Comparative Examples 1 to 3, the respective substances in the amounts described in Table 1 were placed in a mortar and kneaded with a pestle. The paste obtained by kneading was formed into pellets. The formed pellets were dried at a temperature of 110°C for 3 hours. The dried pellets were fired at a temperature of 500°C for 2 hours. The fired pellets were placed in a mortar and pulverized with a pestle to form powders. The compositions of the respective catalysts thus obtained are shown in Table 2 below. Note that each composition in Table 2 is shown as the content converted as the oxide of each element described in Table 2.

[0017]

[0018] <Method for Denitration Experiment Using Catalysts of Examples 1 to 22 and Comparative Examples 1 to 3> In the denitration experiment, experimental gas A under conditions without poisoning by sulfur compounds was supplied to each catalyst to cause a denitration reaction, and the denitration reaction rate K １ of NOx per unit catalyst surface area was calculated. Then, experimental gas B under conditions with poisoning by sulfur compounds was passed through each catalyst, and then, again, experimental gas A was supplied to each catalyst to cause a denitration reaction, and the reaction rate K ２ was calculated.

[0019] The relationship between the ratio of the mass of manganese oxide converted as manganese sesquioxide to the mass of vanadium converted as vanadium pentoxide in each of the catalysts of Examples 1 to 22 and Comparative Examples 1 to 3 and K ２ / K １ is shown in Fig. 5. In Fig. 5, the experimental data of Examples 1 to 22 are shown as round plots, and the data of the experimental results of Comparative Examples 1 to 3 are shown as triangular plots. According to the results of Fig. 5, the catalysts of Examples 1 to 22 containing manganese oxide have a higher K ２ / K １A large value indicates that the decrease in reaction rate after poisoning with sulfur compounds is smaller compared to before poisoning. As a result, it was confirmed that the latter catalyst has higher toxicity resistance to ammonium sulfur oxides such as acidic ammonium sulfate compared to the former catalyst. Furthermore, from these results, it can be said that if the mass ratio of manganese oxide (converted to dimangas trioxide) to vanadium oxide (converted to divanadium pentoxide) is in the range of 0.179 to 1.52, an effect of improved toxicity resistance to acidic ammonium sulfate can be obtained.

[0020] <Verification of the effect of manganese> Comparative Example 4 catalyst was prepared with a composition that did not contain manganese compared to the catalyst of Example 11 (a composition in which the amount of titanium oxide increased by an amount equivalent to the amount of manganese decreased). Using a fully automated scanning X-ray photoelectron spectroscopy analyzer (Quantera, ULVAC-PHIE, Inc.), the electronic states of the elements constituting the catalysts of Example 11 and Comparative Example 4 were evaluated under conditions of an energy step of 0.1 eV and a pass energy of 112 eV. The results are shown in Figure 6. The V2p peak of the catalyst of Example 11 was shifted to the higher energy side (left side of the horizontal axis) compared to the V2p peak of the catalyst of Comparative Example 4. This is considered to indicate that the electronic state of vanadium in the catalyst of Example 11 is modulated by the presence of manganese, and that the vanadium is in a relatively more oxidized state.

[0021] Regarding the catalysts of Examples 12 and 13, K ２ / K １ The amount of sulfate ions and ammonium ions attached to each catalyst after the above experiment, in which the above values ​​were calculated, was analyzed by ion chromatography to measure the amount of ammonium sulfur oxides (such as acidic ammonium sulfate) produced. For the ion chromatography method (JIS K 0127), an ICS-1100 ion chromatograph system manufactured by Thermo Fisher Scientific Corporation (Massachusetts, USA) was used. Figure 7 shows the results for the catalysts of Examples 12 and 13 and Comparative Example 3. ２ / K １ This shows the relationship between the amount of acidic ammonium sulfate produced and K ２ / K １A small value indicates a significant decrease in the reaction rate. Therefore, according to Figures 6 and 7, the inclusion of manganese in the catalyst of this disclosure modulates the electronic state of vanadium, resulting in a relatively more oxidized state of vanadium. This suppresses the formation of acidic ammonium sulfate, thereby reducing catalyst degradation.

[0022] Furthermore, the compositions of the catalysts in Example 11 and Comparative Example 4 are the same in terms of their vanadium and molybdenum oxide content, except that the former contains manganese while the latter does not. Therefore, it is thought that the effect of suppressing the formation of ammonium sulfur oxides such as acidic ammonium sulfate is mainly due to the presence of manganese, and the effect of molybdenum is small. Thus, in the catalyst of this disclosure, molybdenum is an optional component, and it can be said that the essential constituent element of the catalyst of this disclosure is that it contains vanadium and manganese, and the mass ratio of manganese oxide (calculated as dimanganese trioxide) to vanadium oxide (calculated as divanadium pentoxide) is 0.179 to 1.52.

[0023] The contents described in each of the above embodiments can be understood, for example, as follows:

[0024] [1] The catalyst according to one embodiment is a catalyst containing vanadium and manganese, wherein the mass ratio of manganese oxide converted to dimanganese trioxide to vanadium oxide converted to divanadium pentoxide is 0.179 to 1.52.

[0025] According to the catalyst of this disclosure, the action of the manganese compound modulates the electronic state of the vanadium compound, causing the vanadium compound to become more oxidized. This change in the state of the vanadium compound makes it less likely for reactions to occur on the catalyst surface that generate ammonium sulfur oxides such as acidic ammonium sulfate, thus improving toxicity resistance to ammonium sulfur oxides such as acidic ammonium sulfate.

[0026] [2] A catalyst according to another embodiment is the catalyst of [1], wherein vanadium and manganese are supported on a carrier, the vanadium oxide content, calculated as divanadium pentoxide, is 1.9% to 4.5% by mass, and the manganese oxide content, calculated as dimanganese trioxide, is 0.5% to 4.1% by mass.

[0027] With this configuration, the manganese compound modulates the electronic state of the vanadium compound, causing it to become more oxidized. This change in the state of the vanadium compound makes it less likely for reactions to occur on the catalyst surface that generate ammonium sulfur oxides such as acidic ammonium sulfate, thus improving toxicity resistance to ammonium sulfur oxides such as acidic ammonium sulfate.

[0028] [3] A further embodiment of the catalyst is the catalyst of [1], wherein vanadium and manganese are mixed with a substance other than vanadium and manganese, and the vanadium oxide content, calculated as divanadium pentoxide, is 1.9% to 4.5% by mass, and the manganese oxide content, calculated as dimanganese trioxide, is 0.5% to 4.1% by mass.

[0029] With this configuration, the manganese compound modulates the electronic state of the vanadium compound, causing it to become more oxidized. This change in the state of the vanadium compound makes it less likely for reactions to occur on the catalyst surface that generate ammonium sulfur oxides such as acidic ammonium sulfate, thus improving toxicity resistance to ammonium sulfur oxides such as acidic ammonium sulfate.

[0030] [4] A further embodiment of the catalyst is the catalyst of [1], further containing molybdenum, wherein the mass ratio of molybdenum oxide converted to molybdenum trioxide to vanadium oxide converted to vanadium pentoxide is 1.33 to 11.8.

[0031] According to such a configuration, the action of the manganese compound modulates the electronic state of the vanadium compound, causing the vanadium compound to be in a more oxidized state. Such a change in the state of the vanadium compound makes it difficult for a reaction to occur on the surface of the catalyst to generate ammonium-based sulfur oxides such as acidic ammonium sulfate. Therefore, the poisoning resistance against ammonium-based sulfur oxides such as acidic ammonium sulfate is improved.

[0032] [5] The catalyst according to still another aspect is the catalyst of [4], wherein vanadium, manganese, and molybdenum are supported on a carrier, the content of vanadium oxide in terms of vanadium pentoxide is 1.9% by mass to 4.5% by mass, the content of manganese oxide in terms of manganese sesquioxide is 0.5% by mass to 4.1% by mass, and the content of molybdenum oxide in terms of molybdenum trioxide is 6.0% by mass to 22.5% by mass.

[0033] According to such a configuration, the action of the manganese compound modulates the electronic state of the vanadium compound, causing the vanadium compound to be in a more oxidized state. Such a change in the state of the vanadium compound makes it difficult for a reaction to occur on the surface of the catalyst to generate ammonium-based sulfur oxides such as acidic ammonium sulfate. Therefore, the poisoning resistance against ammonium-based sulfur oxides such as acidic ammonium sulfate is improved.

[0034] [6] The catalyst according to still another aspect is the catalyst of [4], wherein vanadium, manganese, and molybdenum are mixed with a substance different from vanadium, manganese, and molybdenum, the content of vanadium oxide in terms of vanadium pentoxide is 1.9% by mass to 4.5% by mass, the content of manganese oxide in terms of manganese sesquioxide is 0.5% by mass to 4.1% by mass, and the content of molybdenum oxide in terms of molybdenum trioxide is 6.0% by mass to 22.5% by mass.

[0035] According to such a configuration, the action of the manganese compound modulates the electronic state of the vanadium compound, causing the vanadium compound to be in a more oxidized state. Such a change in the state of the vanadium compound makes it difficult for a reaction to occur on the surface of the catalyst to generate ammonium-based sulfur oxides such as acidic ammonium sulfate. Therefore, the poisoning resistance against ammonium-based sulfur oxides such as acidic ammonium sulfate is improved.

[0036] [7] The denitration device according to one aspect includes a member (2) to which the catalyst (1) according to any one of [1] to [6] is attached.

[0037] According to such a configuration, a denitration device with improved poisoning resistance against ammonium-based sulfur oxides such as ammonium sulfate can be configured.

[0038] [8] The denitration device according to another aspect is the denitration device of [7], wherein the member (2) is a filter (5) provided in a filter type dust collector (4).

[0039] According to such a configuration, a filter type dust collector having a denitration function can be configured.

[0040] [9] The denitration device according to another aspect is the denitration device of [7], wherein the member (2) is a mesh (8) made of metal or ceramic.

[0041] According to such a configuration, by installing a mesh to which a catalyst is attached in a pipe through which a gas containing NOx flows, the gas can be denitrified.

[0042]

[10] The denitration device according to another aspect is the denitration device of [7], wherein the member (2) is a honeycomb structure (9).

[0043] According to such a configuration, by installing a honeycomb structure to which a catalyst is attached in a pipe through which a gas containing NOx flows, the gas can be denitrified.

[0044] 1 Catalyst 2 Member 3 Denitration device 4 Filter type dust collector 5 Filter 8 Mesh 9 Honeycomb structure

Claims

1. A catalyst containing vanadium and manganese, wherein the mass ratio of manganese oxide (calculated as dimanganese trioxide) to vanadium oxide (calculated as divanadium pentoxide) is 0.179 to 1.

52.

2. The catalyst according to claim 1, wherein vanadium and manganese are supported on a carrier, the vanadium oxide content, calculated as divanadium pentoxide, is 1.9% to 4.5% by mass, and the manganese oxide content, calculated as dimanganese trioxide, is 0.5% to 4.1% by mass.

3. The catalyst according to claim 1, wherein vanadium and manganese are mixed with a substance other than vanadium and manganese, and the vanadium oxide content, calculated as divanadium pentoxide, is 1.9% to 4.5% by mass, and the manganese oxide content, calculated as dimanganese trioxide, is 0.5% to 4.1% by mass.

4. The catalyst according to claim 1, further comprising molybdenum, wherein the mass ratio of molybdenum oxide to vanadium oxide converted to vanadium pentoxide converted to molybdenum trioxide is 1.33 to 11.

8.

5. The catalyst according to claim 4, wherein vanadium, manganese, and molybdenum are supported on a carrier, and the vanadium oxide content, calculated as divanadium pentoxide, is 1.9% to 4.5% by mass, the manganese oxide content, calculated as dimanganese trioxide, is 0.5% to 4.1% by mass, and the molybdenum oxide content, calculated as molybdenum trioxide, is 6.0% to 22.5% by mass.

6. The catalyst according to claim 4, wherein vanadium, manganese, and molybdenum are mixed with a substance other than vanadium, manganese, and molybdenum, and the vanadium oxide content, calculated as divanadium pentoxide, is 1.9% to 4.5% by mass, the manganese oxide content, calculated as dimanganese trioxide, is 0.5% to 4.1% by mass, and the molybdenum oxide content, calculated as molybdenum trioxide, is 6.0% to 22.5% by mass.

7. A denitrification apparatus comprising a member to which the catalyst described in any one of claims 1 to 6 is attached.

8. The denitrification apparatus according to claim 7, wherein the member is a filter provided in a filter-type dust collector.

9. The denitrification apparatus according to claim 7, wherein the member is a metal or ceramic mesh.

10. The denitrification apparatus according to claim 7, wherein the member is a honeycomb structure.

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