Catalyst and denitrification apparatus equipped with this catalyst

Abstract

The present invention provides a catalyst with improved toxicity resistance to ammonium-based sulfur oxides such as acidic ammonium sulfate, and a denitrification apparatus equipped with this catalyst. [Solution] The catalyst of 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.

Description

Technical Field

[0001] The present disclosure relates to a catalyst and a denitration apparatus including the catalyst.

Background Art

[0002] For example, a selective catalytic reduction apparatus (SCR) is used for the purpose of removing nitrogen oxides (NOx) from combustion exhaust gas discharged from an incinerator (denitration). In the SCR, NOx is reduced by reaction with ammonia. As a catalyst used for such an SCR, for example, a catalyst in which vanadium oxide is supported as an active component on a titanium oxide carrier is used. Since a catalyst supporting only vanadium oxide exhibits high activity at a high temperature exceeding 200°C, it is necessary to heat the combustion exhaust gas flowing out from a dust collector (for example, a bag filter) to a temperature exceeding 200°C and supply it to the denitration apparatus. In the case of low-temperature exhaust gas at 200°C or lower, the need to heat the combustion exhaust gas to such a high temperature has been a factor increasing the denitration cost.

[0003] In order to reduce the denitration cost, a catalyst that exhibits high activity even at a low temperature of 200°C or lower is required, and catalysts of various compositions and forms have been developed. For example, in Patent Document 1, it has been verified that a catalyst containing 50% by mass or more of vanadium oxide in terms of vanadium pentoxide (V2O5) exhibits high activity even at a low temperature of 200°C or lower.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when sulfur compounds are present in the combustion exhaust gas, it is known that ammonium-based sulfur oxides such as acidic ammonium sulfate (NH4HSO4), which are produced by the reaction of sulfur oxides with ammonia, accumulate in the catalyst pores and on the catalyst surface, thereby degrading the catalyst's performance over time. For this reason, there is concern that the catalyst's performance will deteriorate over time if denitrification is performed at low temperatures below 200°C 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. [Means for solving the problem]

[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. [Effects of the Invention]

[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. [Brief explanation of the drawing]

[0009] [Figure 1] This is a conceptual diagram showing a part of the configuration of a denitrification apparatus equipped with the catalyst of this disclosure. [Figure 2] This is a schematic diagram of a specific example of a denitrification apparatus equipped with the catalyst of this disclosure. [Figure 3] This is a schematic diagram of another specific example of a denitrification apparatus equipped with the catalyst of this disclosure. [Figure 4]This is a schematic diagram of yet another specific example of a denitrification apparatus equipped with the catalyst of the present disclosure. [Figure 5] This graph shows the denitrification evaluation results for the catalysts of Examples 1-22 and Comparative Examples 1-3. [Figure 6] This graph shows the results of X-ray photoelectron spectroscopy analysis of the catalysts in Example 11 and Comparative Example 4. [Figure 7] This graph shows the relationship between K1 / K0 and the amount of acidic ammonium sulfate produced for the catalysts of Examples 12 and 13 and Comparative Example 3. [Modes for carrying out the invention]

[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] <Configuration of the catalyst in this disclosure> The catalyst of 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 of 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 such 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 in particular. When denitrification is performed using the catalyst of this disclosure, the catalyst of this disclosure is a denitrification catalyst, and the addition of a NOx reducing agent such as ammonia to the denitrification catalyst is necessary.

[0012] <Configuration of the denitrification apparatus in this disclosure> As shown in Figure 1, a denitrification device 3 can be constructed by attaching a catalyst 1 to a component 2 of any configuration. For example, as shown in Figure 2, such a component 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 device 3 with 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 entire filter 5). Furthermore, 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] The member 2 may be a mesh 8 made of metal or ceramic shown in FIG. 3. When using a mesh 8 made of metal or ceramic as the member 2, the catalyst 1 may be formed only around the aggregate of the mesh 8, or may be formed so as to fill all the meshes of the mesh 8 or cover the entire mesh 8. Further, the member 2 may be a honeycomb structure 9 shown in FIG. 4. FIG. 4 exemplarily shows a honeycomb structure 9 having the form of a diesel particulate filter (DPF), but is not limited to the form of DPF, and may also be a honeycomb structure such as a corrugated shape or a shape formed by laminating plates. The honeycomb structure 9 is such that a plurality of spaces, i.e., flow paths 9b, extending longitudinally between one end face 9a1 and the other end face 9a2 of a base material 9a of an arbitrary shape, for example, a cylindrical shape or a polygonal prism shape, are formed inside. For example, the catalyst 1 may be attached to the inner peripheral surface 9b1 of the flow path 9b. The honeycomb structure 9 may be in a form in which all the flow paths 9b are open at each of the both end faces 9a1, 9a2, or may be a configuration in which the flow paths 9b include both a flow path that is open at one end face 9a1 and blocked at the other end face 9a2 and a flow path that is blocked at one end face 9a1 and open at the other end face 9a2. In the latter case, it is necessary to form the base material 9a with a porous material through which the gas flowing through the flow path 9b can pass. By installing the mesh 8 to which the catalyst 1 is attached or the honeycomb structure 9 to which the catalyst 1 is attached in a pipe through which a gas containing NOx (for example, combustion gas, etc.) flows, the gas containing NOx can be denitrified.

Example

[0014] <Preparation of Catalysts of Examples 1 to 22 and Comparative Examples 1 to 3> For each of Examples 1 to 22 and Comparative Examples 1 to 3, ammonium metavanadate, ammonium molybdate, manganese nitrate hexahydrate, titanium oxide, oxalic acid, and water were each weighed in the amounts shown in Table 1 below.

[0015]

Table 1

[0016] For each of Examples 1 to 22 and Comparative Examples 1 to 3, each substance in the amounts described in Table 1 was 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. In Table 2, each composition is shown as the content converted as the oxide of each element described in Table 2.

[0017] [Table 2]

[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 K1 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 K2 was calculated.

[0019] Figure 5 shows the relationship between the ratio of the mass of manganese oxide (converted to dimangas trioxide) to the mass of vanadium (converted to divanadium pentoxide) and K2 / K1 in the catalysts of Examples 1-22 and Comparative Examples 1-3. In Figure 5, the experimental data for Examples 1-22 are shown as circular plots, and the experimental results for Comparative Examples 1-3 are shown as triangular plots. According to the results in Figure 5, the catalysts of Examples 1-22, which contain manganese oxide, have a larger K2 / K1 value than the catalysts of Comparative Examples 1-3, which do not contain manganese oxide. In other words, the decrease in reaction rate after poisoning with sulfur compounds is smaller compared to before poisoning with sulfur compounds. As a result, it was confirmed that the latter catalysts have higher toxicity resistance to ammonium sulfur oxides such as acidic ammonium sulfate than the former catalysts. 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 effects of manganese> Comparative Example 4 catalyst was prepared using 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 decrease in manganese). The electronic states of the elements constituting the catalysts of Example 11 and Comparative Example 4 were evaluated using a fully automated scanning X-ray photoelectron spectroscopy analyzer (Quantera, ULVAC-PHIE, Inc.) 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 thought to indicate that the electronic state of vanadium in the catalyst of Example 11 was modulated by the presence of manganese, and that the vanadium was in a relatively more oxidized state.

[0021] For the catalysts of Examples 12 and 13, the amount of sulfate ions and ammonium ions attached to each catalyst after the above experiment, in which the K2 / K1 ratio was 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 relationship between K2 / K1 and the amount of acidic ammonium sulfate produced for the catalysts of Examples 12 and 13 and Comparative Example 3. This result indicates that the greater the amount of acidic ammonium sulfate produced, the smaller the K2 / K1 value, i.e., the greater the decrease in reaction rate. Therefore, according to Figures 6 and 7, it is considered that 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, thereby suppressing the production of acidic ammonium sulfate and thus reducing catalyst degradation.

[0022] Furthermore, the composition of the catalysts in Example 11 and Comparative Example 4 are the same in terms of 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-based 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 converted to dimanganese trioxide to vanadium oxide converted to 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] A catalyst relating to one embodiment is A catalyst containing vanadium and manganese, The mass ratio of manganese oxide (converted to dimanadium trioxide) to vanadium oxide (converted to divanadium pentoxide) is between 0.179 and 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], Vanadium and manganese are supported on a carrier, The vanadium oxide content, converted to divanadium pentoxide, ranges from 1.9% to 4.5% by mass, and the manganese oxide content, converted to dimanganese trioxide, ranges from 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], Vanadium and manganese are mixed with substances other than vanadium and manganese. The vanadium oxide content, converted to divanadium pentoxide, ranges from 1.9% to 4.5% by mass, and the manganese oxide content, converted to dimanganese trioxide, ranges from 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 catalyst according to yet another embodiment is the catalyst of [1], It also contains molybdenum, The mass ratio of molybdenum oxide (converted to molybdenum trioxide) to vanadium oxide (converted to vanadium pentoxide) is between 1.33 and 11.8.

[0031] 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.

[0032] [5] A further embodiment of the catalyst is the catalyst of [4], Vanadium, manganese, and molybdenum are supported on a carrier. The vanadium oxide content, converted to divanadium pentoxide, ranges from 1.9% to 4.5% by mass; the manganese oxide content, converted to dimanganese trioxide, ranges from 0.5% to 4.1% by mass; and the molybdenum oxide content, converted to molybdenum trioxide, ranges from 6.0% to 22.5% by mass.

[0033] 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.

[0034] [6] A further embodiment of the catalyst is the catalyst of [4], Vanadium, manganese, and molybdenum are mixed with substances other than vanadium, manganese, and molybdenum. The vanadium oxide content, converted to divanadium pentoxide, ranges from 1.9% to 4.5% by mass; the manganese oxide content, converted to dimanganese trioxide, ranges from 0.5% to 4.1% by mass; and the molybdenum oxide content, converted to molybdenum trioxide, ranges from 6.0% to 22.5% by mass.

[0035] 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.

[0036] [7] A denitrification apparatus according to one embodiment is: The present invention includes a member (2) to which one of the catalysts (1) from [1] to [6] is attached.

[0037] With this configuration, it is possible to construct a denitrification device that has improved toxicity resistance to ammonium-based sulfur oxides such as acidic ammonium sulfate.

[0038] [8] Another denitrification apparatus is the denitrification apparatus of [7], The aforementioned member (2) is a filter (5) provided in a filter-type dust collector (4).

[0039] With this configuration, a filter-type dust collector with a denitrification function can be constructed.

[0040] [9] Another denitrification apparatus is the denitrification apparatus of [7], The aforementioned member (2) is a metal or ceramic mesh (8).

[0041] With this configuration, the gas can be denitrified by installing a mesh with a catalyst attached inside a pipe through which a gas containing NOx flows.

[0042]

[10] Another denitrification apparatus is the denitrification apparatus of [7], The aforementioned member (2) is a honeycomb structure (9).

[0043] With this configuration, by installing a honeycomb structure with a catalyst attached inside a pipe through which NOx-containing gas flows, the gas can be denitrified. [Explanation of symbols]

[0044] 1. Catalyst 2 components 3 Denitration equipment 4. Filter-type dust collector 5 Filters 8 mesh 9 Honeycomb structure

Claims

1. A catalyst containing vanadium and manganese, A catalyst having a mass ratio of manganese oxide (converted to dimangas trioxide) to vanadium oxide (converted to divanadium pentoxide) of 0.179 to 1.

52.

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

3. Vanadium and manganese are mixed with substances other than vanadium and manganese. The catalyst according to claim 1, wherein the vanadium oxide content, converted to vanadium pentoxide, is 1.9% to 4.5% by mass, and the manganese oxide content, converted to manganese trioxide, is 0.5% to 4.1% by mass.

4. It also contains molybdenum, The catalyst according to claim 1, wherein the mass ratio of molybdenum oxide (converted to molybdenum trioxide) to vanadium oxide (converted to vanadium pentoxide) is 1.33 to 11.

8.

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

6. Vanadium, manganese, and molybdenum are mixed with substances other than vanadium, manganese, and molybdenum. The catalyst according to claim 4, wherein the vanadium oxide content, converted to vanadium pentoxide, is 1.9% to 4.5% by mass, the manganese oxide content, converted to manganese trioxide, is 0.5% to 4.1% by mass, and the molybdenum oxide content, converted to molybdenum trioxide, is 6.0% to 22.5% by mass.

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

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

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

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

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