Deodorizing catalyst

Abstract

[Problem] The purpose of the present invention is to provide a deodorizing catalyst which is capable of decomposing an odorous substance even at low temperatures of 100°C or less. [Solution] A deodorizing catalyst which decomposes an odorous substance and is characterized by containing a manganese oxide that satisfies formula (1) and formula (2), while having a peak of maximum intensity at a diffraction angle (2θ) of 37 ± 1° in the X-ray diffraction pattern thereof.　(1): 0 < A ≤ 0.90 (2): 0 < B ≤ 250 In formula (1), A represents the content ratio of manganese having an oxidation number of 3 (Mn3+) relative to manganese having an oxidation number of 4 (Mn4+), namely (Mn3+ / Mn4+) in the manganese oxide. In formula (2), B represents the specific surface area (m2 / g) of the manganese oxide.

Description

Technical Field

[0001] The present invention relates to a deodorizing catalyst capable of decomposing malodorous substances such as ammonia, amines, and sulfur compounds.

Background Art

[0002] When natural organic substances such as seafood and fruits and vegetables decay, various malodorous substances are generated. Also, a bad smell of human urine is generated from human urine. As malodorous substances, nitrogen compounds such as ammonia and trimethylamine, hydrogen sulfide generated from sulfur-containing amino acids, sulfur compounds such as methyl mercaptan, and organic compounds such as formic acid, butyric acid, and acetic acid are known. At places where there is a risk of generating malodorous substances such as waste treatment facilities and toilets, various means are being taken to remove them.

[0003] As a method for removing malodorous substances, adsorption to an adsorbent such as activated carbon, decomposition and removal methods using radicals generated by a plasma generator, and active species such as ozone are widely used. However, in the adsorption treatment using an adsorbent, there is an upper limit to the adsorption amount, and it is necessary to periodically replace the adsorbent. Also, decomposition by plasma or the like is a complicated method that requires a generator and the power to operate the generator.

[0004] In addition to the method of oxidizing and decomposing with physically generated active species such as the above-mentioned plasma method, methods of promoting an oxidation reaction using various catalysts and decomposing have been studied. For example, a catalyst containing a platinum group element and a metal oxide having an acid strength of -5.6 or more (Patent Document 1) has been studied.

[0005] Among the catalysts that promote the oxidation reaction, manganese compounds have attracted attention as inexpensive catalysts. For example, in Patent Document 2, an ammonia decomposition catalyst in which zeolite having a molar ratio of SiO2 / Al2O3 of 10 or more and manganese oxide are mixed has been studied.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-254981 [Patent Document 2] Japanese Patent Publication No. 2007-216082 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Reactions to decompose malodorous substances should ideally proceed at low temperatures below 100°C. For example, to decompose malodorous substances generated from food, the catalyst needs to decompose the substances at a temperature below the food's storage temperature, i.e., room temperature.

[0008] Here, the catalyst in Patent Document 1 contains platinum group elements, which makes it expensive to manufacture and limits its applications. The catalyst in Patent Document 2 oxidizes (decomposes) ammonia at a very high temperature of 350°C, and no consideration has been given to the decomposition of ammonia at low temperatures.

[0009] The present invention aims to provide a deodorizing catalyst that can decompose malodorous substances even at low temperatures of 100°C or below. [Means for solving the problem]

[0010] The inventors have discovered that manganese oxide meeting specific conditions can decompose malodorous substances such as ammonia, amines, and sulfur compounds, particularly ammonia and amines, even at low temperatures below 100°C, and have completed the present invention.

[0011] The gist of this invention is as follows: [1] A deodorizing catalyst for decomposing malodorous substances, characterized in that it contains manganese oxide that satisfies the following equations (1) and (2), and the diffraction angle (2θ) of the peak of maximum intensity in the X-ray diffraction pattern is 37±1°. 0 <A≦0.90 ···(1) 0 <B≦250 ···(2) Here, in equation (1) above, A is manganese (Mn) with an oxidation state of 4 in the manganese oxide. 4+ Manganese (Mn) with an oxidation state of 3 relative to ) 3+ ) content ratio (Mn 3+ / Mn 4+ ) represents the specific surface area (m²) of the manganese oxide in equation (2) above, where B is the specific surface area (m²) of the manganese oxide. 2 / g) represents [2] The deodorizing catalyst according to [1], characterized in that the deodorizing catalyst further satisfies the following formula (3). 0 <A·B≦200 ···(3) Here, in equation (3) above, A and B are the same as described above. [3] The deodorizing catalyst according to [1] or [2], characterized in that the manganese oxide contains an alkali metal element cation. [4] The deodorizing catalyst according to any one of [1] to [3], characterized in that metal particles are supported on the manganese oxide, and the metal components contained in the metal particles are one or more selected from the group consisting of gold, platinum, silver, copper, palladium, rhodium, iridium, ruthenium, osmium, and rhenium. [5] The deodorizing catalyst according to any one of [1] to [4], characterized in that the malodorous substance is one or more substances selected from the group consisting of ammonia, amines and sulfur compounds. A deodorizing body characterized by containing a deodorizing catalyst and an adsorbent as described in any one of [6], [1] to [5]. A deodorization method characterized by bringing one of the deodorizing catalysts from [7] [1] to [5] into contact with a fluid to be treated containing malodorous substances in the presence of oxygen at a temperature of 20°C to 100°C. [8] The deodorization method according to [7], characterized in that the deodorizing catalyst and the fluid to be treated are brought into contact in an environment with a relative humidity of 50% or more. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a deodorizing catalyst that can decompose malodorous substances even at low temperatures of 100°C or below. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described in detail below.

[0014] The odor-deodorizing catalyst of this embodiment can decompose odor-causing substances in a treated gas or liquid (hereinafter also referred to as the "treated fluid") containing odor-causing substances by bringing it into contact with the decomposition catalyst in the presence of oxygen. Here, the decomposition reaction of odor-causing substances by the decomposition catalyst of this embodiment is, for example, an oxidative decomposition reaction that decomposes odor-causing substances by oxidation.

[0015] The malodorous substances that are decomposed are substances that have an unpleasant odor, and include volatile organic compounds, nitrogen compounds, and sulfur compounds. Examples of volatile organic compounds include alcohols such as butanol, aldehydes such as acetaldehyde, and fatty acids such as valeric acid. Examples of nitrogen compounds include ammonia and amines such as trimethylamine, and examples of sulfur compounds include hydrogen sulfide and thiols such as methanethiol. The deodorizing catalyst of this embodiment is particularly effective in the oxidative decomposition of sulfur compounds, ammonia, and amines.

[0016] Normally, when ammonia or amines undergo oxidative decomposition, the nitrogen contained in ammonia or amines is oxidized and decomposed into nitrogen gas or nitrogen oxides. Therefore, a deodorizing catalyst must not only decompose malodorous substances but also be able to promote oxidation reactions to safe substances without producing harmful by-products such as carbon monoxide or nitrogen oxides. In addition to the nitrogen oxides mentioned above, harmful substances include carbon monoxide, which can be produced as a by-product when fatty acids are decomposed, and hydrogen sulfide, which can be produced as a by-product when sulfur compounds are decomposed.

[0017] The deodorizing catalyst of this embodiment can decompose malodorous substances even at low temperatures below 100°C, and also tends to generate fewer harmful substances when decomposing malodorous substances. In particular, when the deodorizing catalyst of this embodiment satisfies equation (4), in addition to equations (1) and (2) described later, the nitrogen elements contained in ammonia and amines are easily converted into nitrogen gas during the decomposition process of ammonia and amines, making it less likely for harmful substances such as nitrogen oxides to be generated. In other words, one form of the deodorizing catalyst of this embodiment also has the characteristic of high nitrogen selectivity.

[0018] In this specification, nitrogen selectivity is defined as the proportion of nitrogen (N) contained in ammonia or amines decomposed by the deodorizing catalyst that has been converted into substances other than nitric oxide, nitrogen dioxide, and dinitrogen monoxide. The specific calculation formula is shown in equation (5) below. Nitrogen selectivity (%) = [{(CAa-CAb)-(CN1b+CN2b+C2Nb)} / (CAa-CAb)]*100 ···(5) CAa: Amount of nitrogen (mol / L) of ammonia and / or amines contained in the gas to be treated before being supplied to the deodorizing catalyst. CAb: Amount of nitrogen (mol / L) of ammonia and / or amines contained in the treated gas after it has been supplied to the deodorizing catalyst. CN1b: Amount of nitric oxide (mol / L) contained in the treated gas after it has been supplied to the deodorizing catalyst. CN2b: Amount of nitrogen dioxide (mol / L) contained in the treated gas after it has been supplied to the deodorizing catalyst. C2Nb: Amount of nitrous oxide (mol / L) contained in the treated gas after it has been supplied to the deodorizing catalyst.

[0019] The deodorizing catalyst of this embodiment contains manganese oxide that satisfies the following equations (1) and (2), and has a diffraction angle (2θ) of 37±1° at the peak of maximum intensity in the X-ray diffraction pattern. 0 <A≦0.90 ···(1) 0 <B≦250 ···(2) Here, in equation (1) above, A is manganese (Mn) with an oxidation state of 4 in the manganese oxide.4+ ) the content ratio (Mn 3+ ) of manganese (Mn) with an oxidation number of 3 to 3+ / Mn 4+ ) is represented. In the above formula (2), B represents the specific surface area (m 2 / g) of the manganese oxide.

[0020] As described above, when the manganese oxide contained in the deodorizing catalyst is subjected to X-ray diffraction measurement, the diffraction angle (2θ) of the peak with the maximum intensity in the X-ray diffraction pattern is 37 ± 1°. Here, the peak with the maximum intensity in the X-ray diffraction pattern refers to the peak with the highest intensity in the X-ray diffraction pattern obtained by performing X-ray diffraction measurement under the conditions described in the examples below. Also, the diffraction angle (2θ) of the peak with the maximum intensity being 37 ± 1° means that the peak top of the above-mentioned peak with the maximum intensity appears in the range of the diffraction angle (2θ) of 37 ± 1°.

[0021] Note that the manganese oxide contained in the deodorizing catalyst does not have to be a single crystal as long as the diffraction angle (2θ) of the peak with the maximum intensity is 37 ± 1°, and an amorphous part may be mixed.

[0022] The existence of manganese oxide in the states of manganese with oxidation numbers of 2 (+2), 3 (+3), 4 (+4), 6 (+6), and 7 (+7) is known. Manganese oxide is known not only when it is composed of a single oxidation number, but also when manganese with a plurality of oxidation numbers coexists. However, in the manganese oxide according to the present embodiment, the content ratio (hereinafter simply referred to as "Mn 4+ ") of manganese (hereinafter simply referred to as "Mn 3+ ") with an oxidation number of 3 to manganese (hereinafter simply referred to as "Mn 3+ / Mn 4+ ") is greater than 0 and not more than 0.90 (that is, satisfies the above formula (1)).

[0023] The reason why the deodorizing catalyst of the present embodiment can decompose malodorous substances even at a low temperature of 100°C or lower is not well understood, but Mn 3+ and Mn 4+When manganese is mixed, it is considered that local strain occurs in the crystal structure compared to manganese oxide composed of manganese with a single oxidation number, and that is the active site as a catalyst. Therefore, when satisfying the above formula (1), when Mn 3+ / Mn 4+ is 0 (A = 0), or compared with the case where Mn 3+ / Mn 4+ is greater than 0.9 (0.90 < A), it is inferred that active sites are more likely to occur. From the viewpoint that malodorous substances are more easily decomposed, Mn 3+ / Mn 4+ is preferably 0.20 or more and 0.90 or less (0.20 ≦ A ≦ 0.90), and more preferably 0.30 or more and 0.90 or less (0.30 ≦ A ≦ 0.90).

[0024] The manganese oxide contained in the deodorizing catalyst satisfies the condition (the above formula (1)) that A representing Mn 3+ / Mn 4+ is greater than 0 and not more than 0.90, and further satisfies the condition (the above formula (2)) that B representing the specific surface area (m 2 / g) of manganese oxide is greater than 0 and not more than 250. Although the relationship between satisfying the above formula (2) and the tendency of hardly by-producing harmful substances is not well understood, it is inferred that the density of the above active sites does not become excessive, and it becomes difficult for excessive oxidation of malodorous substances (for example, ammonia) to proceed, and harmful substances are less likely to be by-produced (for example, the nitrogen selectivity increases). From the viewpoint of making malodorous substances more easily decomposed or making harmful substances less likely to be by-produced (further increasing the nitrogen selectivity), the specific surface area (B) of manganese oxide is preferably 30 m 2 / g or more and 250 m 2 / g or less, and more preferably 40 m 2 / g or more and 250 m 2 / g or less. When metal particles described later are supported on manganese oxide, the specific surface area (B) of manganese oxide refers to the specific surface area of manganese oxide containing metal particles (specific surface area considering the surface area of metal particles).

[0025] Furthermore, the manganese oxide contained in the deodorizing catalyst is not particularly limited, but in addition to satisfying equations (1) and (2) above, it is preferable that it also satisfies equation (3) below, and more preferably that it satisfies equation (4) below. If equation (3) below is satisfied, malodorous substances become more easily decomposed even at low temperatures, and if equation (4) below is satisfied, in addition to making it easier to decompose malodorous substances, harmful substances are less likely to be produced as by-products (nitrogen selectivity is further increased), which is desirable. 0 <A·B≦200 ···(3) 0 <A·B≦100 ···(4) Here, in equations (3) and (4) above, A and B are the same as described above.

[0026] Note: Mn 4+ Mn 3+ The ratio (Mn 3+ / Mn 4+ The specific surface area of ​​manganese oxide can be calculated using the X-ray photoelectron spectroscopy method described in the examples below, and the specific surface area of ​​manganese oxide can be calculated using an automated specific surface area measuring device based on the BET method by performing nitrogen adsorption measurements at liquid nitrogen temperature (-196°C).

[0027] In the deodorizing catalyst of this embodiment, the manganese oxide may further contain cations of metal elements other than manganese. The types of metal elements other than manganese that can be contained in the manganese oxide are not particularly limited, but examples include alkali metal elements such as Li, Na, and K, and transition metal elements such as Mg, Ca, St, Ba, Zn, Cu, Ni, Co, and Fe, which are desirable because they increase the stability of the deodorizing catalyst. The content of metal elements other than manganese (cations) is not particularly limited, but it is desirable to have an content of 0.01% by mass or more and 20% by mass or less per 100% by mass of the deodorizing catalyst.

[0028] Next, the method for producing the deodorizing catalyst of this embodiment will be described. In the following description, manganese oxide that satisfies equations (1) and (2) above, and whose diffraction angle (2θ) of the peak of maximum intensity in the X-ray diffraction pattern is 37±1° will be referred to as "manganese oxide that satisfies the predetermined conditions".

[0029] The method for producing the deodorizing catalyst of this embodiment includes an acquisition step for obtaining manganese oxide and a calcination step for calcining the manganese oxide obtained in the acquisition step. Various methods are known for obtaining manganese oxide, such as the solid-phase method, the molten salt flux method, and the redox precipitation method, but it is preferable to use the redox precipitation method in the acquisition step described above. The redox precipitation method is desirable because the reaction conditions are mild and it does not require complex manufacturing equipment.

[0030] When using the redox precipitation method, manganese oxide is obtained as a precipitate by reacting a reducing agent with a manganese compound with an oxidation number greater than 4 dissolved in an aqueous solution, or by reacting an oxidizing agent with a manganese compound with an oxidation number less than 3 dissolved in an aqueous solution. In the redox precipitation method described above, it is preferable that the oxidizing agent and reducing agent be manganese compounds. It is preferable that manganese compounds are used as oxidizing agents and reducing agents because they yield manganese oxide of this embodiment with fewer impurities (substances other than manganese and oxygen). In particular, it is preferable to react a manganese compound with an oxidation number of 2 (hereinafter also referred to as a "divalent manganese compound") with a manganese compound with an oxidation number of 7 (hereinafter also referred to as a "heptavalent manganese compound"), so that the heptavalent manganese compound is reduced by the divalent manganese compound and the divalent manganese compound is oxidized by the heptavalent manganese compound. When using a redox precipitation method that reacts a divalent manganese compound with a heptavalent manganese compound, it is particularly preferable because it makes it easier to obtain manganese oxide with a diffraction angle (2θ) of 37±1° at the peak of maximum intensity in the X-ray diffraction pattern, compared to redox precipitation methods that react other substances.

[0031] As a heptavalent manganese compound, for example, potassium permanganate (KMnO4) can be used, and as a divalent manganese compound, for example, manganese(II) sulfate (MnSO4) can be used. Other permanganates besides KMnO4 can also be used as heptavalent manganese compounds, such as NaMnO4·3H2O, AgMnO4, Zn(MnO4)2·6H2O, Mg(MnO4)2, Ca(MnO4)2, and Ba(MnO4)2. Other manganese salts with an oxidation state of 2 besides MnSO4 (hereinafter also referred to as "divalent manganese salts") can also be used as divalent manganese compounds, such as manganese chloride, manganese carbonate, and manganese nitrate.

[0032] When using a redox precipitation method to react a divalent manganese compound with a heptavalent manganese compound, the following reaction conditions are used as an example. Manganese oxide obtained under these reaction conditions can be subjected to the calcination treatment described later to obtain manganese oxide that satisfies the specified conditions. The heptavalent manganese compound (permanganate) and the divalent manganese compound (divalent manganese salt) are reacted in an aqueous solution at a reaction temperature of 20-200°C for 0.5 to 36 hours, using a pressure vessel if necessary. The ratio of the heptavalent manganese compound (permanganate) to the divalent manganese compound (manganese salt) is 0.05 to 10 in molar ratio, but it is preferable to use a ratio of 0.5 to 10 to increase the yield. Furthermore, it is desirable to carry out the reaction of the divalent manganese compound and the heptavalent manganese compound in an acidic aqueous solution, as this makes it easier to obtain manganese oxide with a diffraction angle (2θ) of 37±1° at the peak of maximum intensity in the X-ray diffraction pattern. In the method for preparing manganese oxide described above, an acidic aqueous solution is usually obtained. However, if necessary, an acid may be added separately to adjust the acidity before the reaction. There are no particular restrictions on the type of acid to be added, but inorganic strong acids such as hydrochloric acid, nitric acid, and sulfuric acid are preferred because they allow for a smaller amount of acid to be added.

[0033] The reaction conditions in the redox precipitation method, such as the reaction temperature, are related to the Mn of the manganese oxide obtained. 3+ / Mn 4+Although it affects (A in equation (1) above), specific surface area (B in equation (2) above), and X-ray diffraction pattern, it is difficult to obtain manganese oxide that satisfies the predetermined conditions simply by changing the reaction conditions. In other words, the manganese oxide obtained by the acquisition process is Mn 3+ / Mn 4+ If the value exceeds 0.90 (i.e., equation (1) above is not satisfied), or if the specific surface area of ​​manganese oxide is 250 (m²), 2 The amount exceeds ( / g) (i.e., it does not satisfy equation (2) above). Therefore, the manganese oxide obtained by the acquisition process is calcined to obtain manganese oxide that satisfies the predetermined conditions.

[0034] When the manganese oxide obtained in the acquisition process is subjected to calcination, the Mn 3+ / Mn 4+ This can be made even smaller. Furthermore, if the manganese oxide obtained in the acquisition process is subjected to calcination, the specific surface area of ​​the manganese oxide can be made even smaller compared to the manganese oxide obtained in the acquisition process (manganese oxide before calcination).

[0035] In the firing process, the firing temperature is determined by the amount of manganese oxide (Mn) before firing. 3+ / Mn 4+ The temperature range varies depending on the specific surface area, but for example, it can be between 100°C and 700°C. Also, the firing time depends on the manganese oxide (Mn) being fired. 3+ / Mn 4+ The firing time varies depending on the specific surface area, but for example, it can be 1 to 24 hours. Note that increasing the firing temperature tends to decrease the specific surface area of ​​manganese oxide, and increasing the firing time increases the specific surface area of ​​Mn 3+ / Mn 4+ The value of tends to decrease. Therefore, taking these trends into consideration, the firing temperature and firing time should be adjusted to satisfy equations (1) and (2) above.

[0036] The manganese oxide obtained by the calcination process described above can be used as a deodorizing catalyst in this embodiment. In addition to the acquisition and calcination processes described above, the method for producing the deodorizing catalyst may also include a filtration process to filter out the manganese oxide produced in the reaction during the acquisition process, a washing process to wash the filtered manganese oxide with water, and a drying process to dry the washed manganese oxide. The conditions for filtration, washing, and drying can be known conditions and are not particularly limited.

[0037] The form of manganese oxide (the form of the deodorizing catalyst) is not particularly limited, but for example, it can be in the form of a powder. Furthermore, the manganese oxide (deodorizing catalyst) may be fixed to a substrate, or molded into a filter or pellet form, depending on the intended use. The manganese oxide (deodorizing catalyst) may also be in the form of a powder with pores.

[0038] When manganese oxide (deodorizing catalyst) is in powder form, its particle size can be, for example, 0.005 to 100 μm in average particle diameter, and even 0.1 to 10 μm. The particle size can be adjusted by grinding the manganese oxide using a ball mill or other grinding method known to those skilled in the art.

[0039] The deodorizing catalyst of this embodiment may also be used as a deodorizer in a composition with an adsorbent. Compared to conventional deodorizing catalysts, the deodorizing catalyst of this embodiment can be used at low temperatures (below 100°C), but the deodorizing effect can be further enhanced by using it in combination with an adsorbent. Even if the adsorption sites of the adsorbent become saturated with the adsorption of malodorous substances, the deodorizer can be regenerated by heating it and reused repeatedly. When heated, malodorous substances are released from the adsorbent, but they are decomposed by the manganese oxide present in the deodorizer.

[0040] The adsorbent is not particularly limited, but substances known to those skilled in the art, such as activated carbon, silica gel, zeolite, and alumina, can be used.

[0041] Furthermore, in order to make the catalyst less susceptible to the effects of moisture, the catalyst may be hydrophobized or a hygroscopic material or desiccant may be added using known methods.

[0042] In the deodorizing catalyst of this embodiment, metal particles may be further supported on the manganese oxide. The presence of metal particles makes it easier to decompose malodorous substances and reduces the generation of harmful by-products. In addition, the presence of metal particles further lowers the minimum decomposition temperature for malodorous substances. The metal components contained in the metal particles may be in zero-valent elemental form (i.e., metallic state), oxide form, or a state in which elemental and oxide forms coexist. Furthermore, two or more metal elements may be used as the metal component, in which case the two or more metal elements may exist as an alloy or as a mixture of metals.

[0043] Examples of metallic components that can be included in metal particles include gold, platinum, silver, copper, palladium, rhodium, iridium, ruthenium, osmium, and rhenium. However, silver and copper are preferred because they are inexpensive and easy to handle in manufacturing.

[0044] The method for supporting the metal particles is not particularly limited, but it can be done by methods known to those skilled in the art, such as dispersing (immersing) manganese oxide in a metal salt solution to adsorb the metal salt onto the surface of the manganese oxide, and then calcining it in the presence of a reducing agent if necessary. Note that the specific surface area (B) of manganese oxide tends to increase when metal particles are supported, so if the specific surface area (B) is 250 m² 2 The specific surface area (B) may be adjusted by a firing process to support the metal particles so as not to exceed / g. As mentioned above, increasing the firing temperature tends to decrease the specific surface area of ​​manganese oxide, and increasing the firing time tends to decrease the specific surface area of ​​Mn 3+ / Mn 4+ Since the value of tends to decrease, the firing process performed to support the metal particles can be carried out under conditions that take these tendencies into account, such that the manganese oxide with metal particles supported obtained after firing satisfies equations (1) and (2) above.

[0045] The particle size of the metal particles is preferably such that the average particle diameter is 10 nm or less, and particularly preferably between 0.1 and 10 nm, in order to further enhance catalytic activity.

[0046] In this specification, particle size refers to the diameter of a particle that can be measured from a transmission electron microscope (TEM) image, and average particle diameter refers to the average value obtained by adding up the diameters of the target particles. If the number of target particles exceeds 200, the average value is obtained by adding up the diameters of at least 200 particles.

[0047] To further enhance catalytic activity, the amount of metal particles supported according to this embodiment is preferably 0.1 to 15.0% by mass, and more preferably 0.5 to 12.0% by mass, relative to 100% by mass of manganese oxide (manganese oxide without supported metal particles).

[0048] Next, a method for decomposing malodorous substances using the deodorizing catalyst of this embodiment will be described. As described above, the deodorizing catalyst of this embodiment can decompose malodorous substances in a fluid to be treated by bringing the fluid to be treated, which contains malodorous substances, into contact with the deodorizing catalyst in the presence of oxygen.

[0049] The concentration of malodorous substances in the fluid to be treated is not particularly limited, but from the viewpoint of achieving a high decomposition rate, it is preferable that the concentration be 5 ppm or more and 50% or less by volume for gases, and 5 ppm or more and 50% or less by weight for liquids. In addition to malodorous substances (and oxygen, if necessary), the fluid to be treated may contain other components.

[0050] The method and conditions for bringing the fluid to be treated into contact with the deodorizing catalyst are not particularly limited, but from the viewpoint of reducing the generation of harmful substances as by-products (increasing nitrogen selectivity), the fluid to be treated is brought into contact with 1,000 mlh -1 g-cat -1 The total is 7,000,000 mlh. -1 g-cat -1It is preferable to contact the deodorizing catalyst at the following space velocity. Space velocity is defined as the rate by which the volume of the fluid to be treated, relative to the volume or weight of the deodorizing catalyst, comes into contact with (passes through) the deodorizing catalyst per unit time. It is calculated by dividing the flow rate (volume) of the fluid to be treated per unit time by the volume or weight of the deodorizing catalyst. Furthermore, contact between the fluid to be treated and the deodorizing catalyst may be carried out under atmospheric pressure, or under a reduced pressure atmosphere or a pressurized atmosphere.

[0051] Methods for contacting the fluid to be treated with a deodorizing catalyst in the presence of oxygen include contacting the oxygen-containing fluid to be treated with the deodorizing catalyst, or contacting the fluid to be treated with an oxygen-containing gas with the deodorizing catalyst. The oxygen concentration is not particularly limited and can be the same as that of the atmosphere as an oxygen-containing gas. However, from the viewpoint of increasing the decomposition rate of malodorous substances, it is preferable that the oxygen concentration be at least 1.0 times the volume of the malodorous substances contained in the fluid to be treated (e.g., ammonia, amines, and sulfur compounds such as hydrogen sulfide).

[0052] The temperature at which the fluid to be treated and the deodorizing catalyst come into contact is not particularly limited, but is preferably between 20°C and 100°C, and more preferably between 50°C and 100°C. Conventional decomposition methods have problems in that, unless the fluid to be treated and the catalyst are brought into contact at a temperature exceeding 100°C, malodorous substances are difficult to decompose, and nitrogen oxides are easily generated due to the high temperature. However, in the decomposition method of this embodiment, malodorous substances can be decomposed even if the fluid to be treated and the catalyst are brought into contact at a low temperature of 100°C or less. Furthermore, there is a tendency to suppress the generation of harmful substances such as nitrogen oxides (i.e., there is a tendency for high nitrogen selectivity). Note that contact between the fluid to be treated and the deodorizing catalyst may be carried out at a temperature exceeding 100°C, and when contact is carried out at a temperature exceeding 100°C, malodorous substances are more easily decomposed compared to when contact is carried out at 100°C or below.

[0053] The temperature at which the fluid to be treated comes into contact with the deodorizing catalyst can be adjusted by heating and cooling the deodorizing catalyst, or by heating and cooling the fluid to be treated. Alternatively, the temperature can be adjusted by heating and cooling both the deodorizing catalyst and the fluid to be treated. For example, by setting the temperature of the deodorizing catalyst to between 20°C and 100°C, or the temperature of the fluid to be treated to between 20°C and 100°C, contact between the fluid to be treated and the deodorizing catalyst can be performed at a temperature between 20°C and 100°C.

[0054] The humidity environment in which the deodorizing catalyst of this embodiment is used is not particularly limited, but it can be suitably used even in high humidity environments with a relative humidity of 50% or higher. Conventional deodorizing catalysts are difficult to use in high humidity environments because their catalytic activity rapidly decreases in high humidity environments, and require prior drying of the gas to be treated. However, with the deodorizing catalyst of this embodiment, malodorous substances in high humidity environments can be decomposed without such prior drying. In addition, with conventional deodorizing catalysts, catalytic activity may decrease due to water generated in the oxidation reaction adhering to the catalyst, but as described above, the deodorizing catalyst of this embodiment has high resistance to humidity, so it is presumed that the decomposition of malodorous substances can be promoted even at low temperatures.

[0055] The deodorizing catalyst of this embodiment can be used in components or gas purification devices that have the action or function of removing ammonia or sulfur compounds such as amines or hydrogen sulfide, and can be used by contacting the gas to be treated, which contains ammonia or amines, in the presence of oxygen. Examples of such components and devices include air conditioners, refrigerators, deodorizing devices installed in warehouses and showcases, deodorizers for livestock farms, air purifiers installed in offices, smoking rooms, toilets, hospitals, nursing homes, etc., or exhaust gas purification devices for internal combustion engines, etc. The components and devices may be equipped with functions that allow for setting an operating environment in which the deodorizing catalyst operates suitably, such as a heating mechanism for the deodorizing catalyst or a blowing mechanism for supplying the gas to be treated to the catalyst. Furthermore, the deodorizing catalyst of this embodiment can also be used as an odor suppressant to suppress malodorous odors. The odor suppressant is not particularly limited in dosage form, as long as it can contact the gas to be treated, which contains malodorous substances, with the catalyst in the presence of oxygen, and may contain other components other than the deodorizing catalyst. [Examples]

[0056] Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

[0057] "Example 1" 5.85 g (37 mmol) of KMnO4 was dissolved in 100 mL of pure water. 8.8 g (5.2 mmol) of MnSO4·H2O was dissolved in 30 mL of pure water. 3 mL of nitric acid was then added. The two solutions were mixed and refluxed at 100°C for 24 hours. The resulting solid was filtered off, washed several times with pure water, and then calcined at 120°C for 6 hours to obtain the deodorizing catalyst (manganese oxide) of Example 1.

[0058] Example 2 1.25 g (7.9 mmol) of KMnO4 was dissolved in 40 mL of pure water. 0.525 g (3.1 mmol) of MnSO4·H2O was dissolved in 20 mL of pure water. The two solutions were mixed and stirred at room temperature (25°C) for 30 minutes. The resulting solid was filtered off, washed several times with pure water, and dried at 60°C. The mixture was then calcined at 150°C for 6 hours to obtain the deodorizing catalyst (manganese oxide) of Example 2.

[0059] "Example 3" The same procedure as in Example 1 was followed, except that the reflux reaction conditions were changed to 80°C for 30 minutes, to obtain the deodorizing catalyst (manganese oxide) of Example 3.

[0060] "Example 4" 75 mL of pure water was mixed with MnSO4·H2O at a concentration of 0.196 mol / L and KMnO4 at a concentration of 0.14 mol / L. The mixture was stirred at room temperature (25°C) for 30 minutes, then transferred to a pressure vessel and heated at 160°C for 24 hours. The resulting solid was filtered off, washed several times with pure water, dried at 120°C, and then calcined at 500°C for 6 hours to obtain manganese oxide, which was then subjected to the following silver loading process.

[0061] An ammoniacal silver nitrate aqueous solution was prepared by dropwise adding an ammoniacal silver nitrate aqueous solution to an ammoniacal silver nitrate aqueous solution. Manganese oxide was added to pure water and stirred for 30 minutes while cooling with ice. The ammoniacal silver nitrate aqueous solution and hydrogen peroxide solution were then added dropwise and stirred for a further 3 hours. After that, the solids were collected by filtration. The solids were washed several times with pure water, dried at 80°C, and then calcined at 400°C for 6 hours to obtain the deodorizing catalyst (silver-supported manganese oxide) of Example 4. The silver content was calculated from the mass difference of manganese oxide before and after the silver-supporting process, and was 10% by mass relative to 100% by mass of manganese oxide. The average particle size was 2.7 nm as observed by TEM.

[0062] Example 5 A 2.2 wt% potassium permanganate aqueous solution was prepared by dissolving 2.2 g (13.9 mmol) of KMnO4 in 97.8 g of pure water. A 33.3 wt% manganese sulfate aqueous solution was prepared by dissolving 33.3 g MnSO4·H2O (197 mmol) in 66.7 g of pure water. The liquid temperature was adjusted to 20°C, and the two solutions were mixed and stirred while the reaction was carried out at 20°C for 4 hours. The resulting solid was filtered off and washed several times with pure water, then the temperature was raised to 300°C at a rate of 5°C per minute, and calcination was carried out at 300°C for 6 hours to obtain the deodorizing catalyst (manganese oxide) of Example 5.

[0063] "Example 6" The deodorizing catalyst for Example 6 was obtained by following the same procedure as in Example 5, except that the firing conditions were changed to 400°C for 6 hours.

[0064] Example 7 The manganese oxide obtained in Example 4 (manganese oxide before the silver loading process) was subjected to the following copper loading process. The manganese oxide was added to an 8.3 mM CuCl2 aqueous solution and stirred at room temperature for 15 minutes. Then, the pH of the reaction solution was adjusted to 12 using a 1.0 M NaOH aqueous solution and stirred at room temperature for 24 hours. The solid components were filtered off and recovered from the reaction solution, washed several times with a large amount of pure water, and then calcined at 150°C for 12 hours to obtain the deodorizing catalyst (copper-supported manganese oxide) of Example 7. The copper content was calculated from the mass difference of manganese oxide before and after the copper loading process, and was 5% by mass relative to 100% by mass of manganese oxide, and the average particle size was 8.0 nm as observed by TEM.

[0065] "Comparative Example 1" A commercially available manganese oxide (CMD-200, manufactured by Shin-Nippon Denko Co., Ltd.) was used as the deodorizing catalyst in Comparative Example 1.

[0066] "Comparative Example 2" A commercially available manganese oxide (AMD-200, manufactured by Nippon Heavy Chemical Industries Co., Ltd.) was used as the deodorizing catalyst in Comparative Example 2.

[0067] "Comparative Example 3" A commercially available manganese oxide (AMD-250, manufactured by Nippon Heavy Chemical Industries Co., Ltd.) was used as the deodorizing catalyst in Comparative Example 3.

[0068] "Comparative Example 4" Solution 1 was prepared by dissolving 2.0 g of potassium permanganate (KMnO4) and 0.8 g of 95% sulfuric acid in 100 mL of pure water. Solution 2 was prepared by diluting 2 mL of 30% hydrogen peroxide solution in 100 mL of pure water. Solution 2 was then added dropwise to Solution 1 while stirring at room temperature, and after stirring for another 30 minutes, the mixture was allowed to stand for 12 hours. The reaction mixture was then filtered by suction, washed with pure water, and the resulting precipitate was collected. The precipitate was heated at 110°C for 12 hours and calcined at 400°C for 2 hours to obtain the deodorizing catalyst (manganese oxide) of Comparative Example 4.

[0069] "Comparative Example 5" A 2.2 wt% potassium permanganate aqueous solution was prepared by dissolving 2.2 g of KMnO4 in 97.8 g of pure water. A 33.3 wt% manganese sulfate aqueous solution was prepared by dissolving 33.3 g of MnSO4·H2O in 66.7 g of pure water. The liquid temperature was adjusted to 80°C, and the two solutions were mixed and stirred while reacting at 80°C for 4 hours. The product was filtered off, washed several times with water, and dried at 40°C for 48 hours to obtain the deodorizing catalyst (manganese oxide) of Comparative Example 5. The deodorizing catalyst of Comparative Example 5 was a sticky solid and difficult to handle. Furthermore, the stickiness of the deodorizing catalyst of Comparative Example 5 was not eliminated even after drying it further at 40°C for 72 hours.

[0070] (Mn 3+ / Mn 4+ (Measurement) From the XPS spectrum obtained using an X-ray photoelectron spectrometer (XPS, JEOL Ltd.: JPS-9010MX), Mn 3+ The peak that shows this (hereinafter referred to as "Mn 3+ (Peak) and Mn 4+ The peak that shows this (hereinafter referred to as "Mn 4+ The peaks (called "peaks") are separated by waveform, and from the ratio of the peak intensity (area ratio) of each peak, the manganese oxide of each example and comparative example is determined as follows: Mn 3+ / Mn 4+ The value was calculated. The results are shown in Table 1.

[0071] The XPS measurements were performed under the following conditions. Measurement temperature: room temperature Excitation source: MgKα (12kV, 50mA) Sample holder installation angle: 0°

[0072] Furthermore, the peaks in the spectrum acquired by XPS were corrected for charge at 284.8 eV using the C1s peak, and background correction was performed using the Shirley method. Curve fitting (waveform separation) was performed using the Gauss-Lorentz method, and Mn 3+ Peak (641.4±0.5eV) and Mn 4+ The peak (642.6 ± 0.6 eV) was fitted. In the region corresponding to Mn 2p3 / 2 (636-650 eV), the Mn obtained by curve fitting was... 3+ Peak and Mn 4+ Find the area of ​​the peak, Mn 4+ Mn as a function of peak area 3+ The ratio of peak areas is Mn 3+ / Mn 4+ It was calculated as the value of [this value].

[0073] In this curve fitting, the energy values, full width at half maximum, and intensity were adjusted to approximate the measured spectrum, and waveform separation was performed. However, the value of the sum of squared residuals in the least squares method shown in equation (a) below was kept to 2 or less. TIFF0007870037000001.tif13149x 2 : Residual sum of squares N: Fitting points I0: Measured spectral intensity If: Strength of fitting calculation result

[0074] (Measurement of specific surface area) Using a high-precision gas adsorption measurement device (Microtrac-Bel), nitrogen adsorption isotherms were measured at liquid nitrogen temperature (-196°C), and the specific surface area of ​​manganese oxide for each example and comparative example was calculated based on the BET method. The results are shown in Table 1.

[0075] (X-ray diffraction pattern measurement) X-ray diffraction measurements were performed on the catalysts of each example and comparative example using an X-ray diffractometer, and the diffraction angle of the peak with the maximum intensity (hereinafter also referred to as the "diffraction angle of the maximum peak") was detected. The results are shown in Table 1. The measurements were performed using a Rigaku SmartLab with the following measurement conditions: X-ray source: Cu-Kα, X-ray output: 40kV, 30mA, scan speed: 2.0deg / min, step size: 0.02deg, scan axis: 2θ / θ, scan range: 5.0~90.0deg.

[0076] (Ammonia decomposition evaluation) A mixed gas containing 100 ppm ammonia, consisting of Ar gas, O2 gas, and Ar gas in a volume ratio of 50:20:30, was used as the gas to be treated. This mixed gas was supplied at a flow rate of 100 mL / min to 0.15 g of the deodorizing catalysts of each example and comparative example, which were filled into the reaction vessel, while being controlled by a flow controller (space velocity 40,000 mlh). -1 g-cat -1 The temperature of both the deodorizing catalyst and the treated gas was adjusted to 80°C. The concentrations of ammonia, nitrous oxide, nitric oxide, and nitrogen dioxide in the treated gas before and after supplying it to the deodorizing catalyst were measured using an infrared spectrophotometer (FTIR-6000, manufactured by JASCO Corporation). The nitrogen selectivity was calculated based on equation (6) below, and the ammonia decomposition rate was calculated based on equation (7) below. Measurements were carried out continuously for a maximum of 10 hours, and the values ​​reached were taken as the respective measured values. CAa, CAb, CN1b, CN2b, and C2Nb shown in equation (6) below were calculated from the measured values ​​mentioned above.

[0077] Nitrogen selectivity (%) = [{(CAa-CAb)-(CN1b+CN2b+C2Nb)} / (CAa-CAb)]*100 ···(6) CAa: Amount of nitrogen (mol / L) of ammonia contained in the gas to be treated before being supplied to the catalyst. CAb: Amount of nitrogen (mol / L) of ammonia contained in the treated gas after it has been supplied to the catalyst. CN1b: Amount of nitric oxide (mol / L) contained in the treated gas after it has been supplied to the catalyst. CN2b: Amount of nitrogen dioxide (mol / L) contained in the treated gas after it has been supplied to the catalyst. C2Nb: Amount of nitrous oxide (mol / L) contained in the treated gas after it has been supplied to the catalyst.

[0078] Ammonia decomposition rate (%) = {(Ca-Cb) / Ca} * 100 ... (7) Ca: Ammonia concentration (ppm) in the gas to be treated before being supplied to the catalyst. Cb: Ammonia concentration (ppm) in the treated gas after it has been supplied to the catalyst.

[0079] [Table 1]

[0080] As shown in Table 1, the deodorizing catalysts of Examples 1 to 7 all showed higher ammonia decomposition rates compared to the deodorizing catalysts of Comparative Examples 1 to 5. From this result, it was understood that the deodorizing catalysts of Examples 1 to 7 are able to decompose malodorous substances even at low temperatures below 100°C. Furthermore, as shown in Table 1, the deodorizing catalysts of Examples 1, 2, 4, and 7 that satisfy equation (4) all showed higher nitrogen selectivity compared to Examples 3, 5, and 6 that do not satisfy equation (4). From this result, it was understood that the deodorizing catalysts of Examples 1, 2, 4, and 7 that satisfy equation (4) can decompose malodorous substances even at low temperatures below 100°C, and that they do not generate nitrogen oxides (harmful substances) when decomposing ammonia.

[0081] (Evaluation of hydrogen sulfide decomposition) A mixed gas containing 8 ppm hydrogen sulfide, 20% O2, and 80% N2 was used as the gas to be treated. This mixture was supplied at a flow rate of 1.0 L / min, controlled by a flow controller, to 0.01 g of the deodorizing catalysts of Examples 4 and 7, respectively, which were filled into the reaction vessel (space velocity 6,000,000 mlh). -1g). The temperature of both the deodorizing catalyst and the gas to be treated was adjusted to 25°C. The gas to be treated was supplied continuously, and after a certain period of time, starting from the point when the gas to be treated was supplied, a sample of the gas that had permeated the deodorizing catalyst was taken, and the hydrogen sulfide concentration in the sample was measured using a detector tube (Gastec Co., Ltd. No. 4LB). The relative humidity of the gas to be treated was adjusted to 50%, and the hydrogen sulfide removal rate was calculated based on the following formula (8). Hydrogen sulfide decomposition rate (%) = {(Da - Db) / Da} * 100 ... (8) Da: Hydrogen sulfide concentration (ppm) in the gas to be treated before being supplied to the deodorizing catalyst. Db: Hydrogen sulfide concentration (ppm) in the treated gas after being supplied to the deodorizing catalyst.

[0082] The hydrogen sulfide decomposition rate for the deodorizing catalyst in Example 4 was 60% after 8 minutes, 50% after 29 minutes, and 30% after 139 minutes, after which it stabilized at approximately 30%. For the deodorizing catalyst in Example 7, the hydrogen sulfide removal rate was 56% after 15 minutes, 43% after 65 minutes, and 30% after 145 minutes, after which it stabilized at approximately 30%. As described above, it was confirmed that the deodorizing catalysts in Examples 4 and 7 can decompose hydrogen sulfide at room temperature (25°C).

Claims

1. A deodorizing catalyst for decomposing ammonia or amines, A deodorizing catalyst characterized by containing manganese oxide that satisfies the following equations (1) and (2), and whose diffraction angle (2θ) of the peak of maximum intensity in the X-ray diffraction pattern is 37 ± 1°. 0 < A ≤ 0.9 ... (1) 0 < B ≤ 250 ... (2) Here, in equation (1) above, A is manganese (Mn) with an oxidation state of 4 in the manganese oxide. ４＋ Manganese (Mn) with an oxidation state of 3 relative to ) ３＋ ) Content ratio (Mn ３＋ / Mn ４＋ ) represents the specific surface area (m²) of the manganese oxide in equation (2) above, where B is the specific surface area (m²) of the manganese oxide. ２ It represents / g).

2. The deodorizing catalyst according to claim 1, characterized in that the manganese oxide further satisfies the following formula (3). 0<A・B≦200...(3) Here, in equation (3) above, A and B are the same as described above.

3. The deodorizing catalyst according to claim 1 or 2, characterized in that alkali metal element cations are adsorbed onto the manganese oxide.

4. Metal particles are supported on the manganese oxide, The deodorizing catalyst according to any one of claims 1 to 3, characterized in that the metal component contained in the metal particles is one or more selected from the group consisting of gold, platinum, silver, copper, palladium, rhodium, iridium, ruthenium, osmium, and rhenium.

5. A deodorizing body characterized by comprising a deodorizing catalyst and an adsorbent according to any one of claims 1 to 4.

6. A deodorizing method characterized by bringing a deodorizing catalyst, which can be one of claims 1 to 4, into contact with a fluid to be treated containing ammonia or amines in the presence of oxygen at a temperature of 20°C to 100°C.

7. The deodorization method according to claim 6, characterized in that the deodorizing catalyst and the fluid to be treated are brought into contact in an environment with a relative humidity of 50% or higher.

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