Platinum group element-supporting silica

Abstract

The purpose of the present invention is to provide an ethylene degrading agent that is not easily charged, has good handleability, and has excellent ethylene degrading ability. The present invention provides a platinum group element-supporting silica in which the number of surface silanol groups per unit surface area is more than 1.3 groups / nm2.

Description

Platinum group element-supported silica

[0001] The present invention relates to silica on which a platinum group element is supported, that is, platinum group element-supported silica.

[0002] Agricultural products such as vegetables, fruits, and flowers are delivered to consumers after a certain period of time has passed since they were harvested, and their freshness can decrease depending on the storage and handling environment during that time. This is thought to be because the ethylene gas produced and released by the produce itself causes the produce to ripen, resulting in spoilage.

[0003] Therefore, in order to prevent the production of ethylene, storage methods that suppress the respiration of agricultural products, adsorption removal using adsorbents such as activated carbon, and decomposition removal using ozone have been considered. However, with respiration suppression methods, ethylene is released before the atmosphere is controlled, making it often difficult to maintain freshness sufficiently.

[0004] In addition, since the adsorbent needs to be replaced once it reaches saturation, it is not suitable for long-term storage or transportation when transporting overseas, etc. Furthermore, because high concentrations of ozone can have an adverse effect on the human body, when using an ozone generator, care must be taken to manage the ozone concentration in warehouses, containers, and other work sites.

[0005] Therefore, Patent Document 1 studies the decomposition of ethylene into carbon dioxide and water in an atmosphere of −1° C. to −40° C. using an ethylene decomposition agent comprising porous silica carrying platinum or a platinum-containing compound.

[0006] It is also known that porous silica carrying particles containing platinum group elements can be used as an antibacterial / antifungal porous material (Patent Documents 2 and 3), and it has been confirmed that when each material was added to a bacterial solution and stored, it exhibited a high antibacterial / antifungal effect against Escherichia coli, Staphylococcus aureus, and Penicillium.

[0007] JP 2017-23889 A JP 2019-136655 A JP 2019-137637 A

[0008] However, conventional platinum group element-supported silica is prone to charging, making it difficult to handle. Therefore, an object of the present invention is to provide a platinum group element-supported silica that is resistant to charging, easy to handle, and has excellent ethylene decomposition ability. Another object of the present invention is to provide a platinum group element-supported silica that is resistant to charging, easy to handle, and quickly develops antibacterial effects.

[0009] As a result of extensive research, the present inventors have found that the number of surface silanol groups per unit surface area of ​​platinum group element-supported silica is 1.3 / nm ２ It has been found that the above-mentioned problems can be solved by making the number of surface silanol groups per unit surface area greater than 1.3 / nm. ２ (2) The platinum group element-supported silica of (1), wherein the platinum group element-supported silica is a platinum group element-supported silica gel. (3) The platinum group element-supported silica of (1) or (2), which contains chlorine at a concentration of 150 ppm or less. (4) The platinum group element-supported silica of any of (1) to (3), wherein the ratio of the platinum group element to the platinum group element-supported silica is 0.1 mass % or more and 5 mass % or less. (5) The platinum group element-supported silica of any of (1) to (4), wherein the platinum group element is platinum. (6) The platinum group element-supported silica of any of (1) to (5), wherein the pore volume is 0.3 to 1.6 mL / g. (7) The platinum group element-supported silica of any of (1) to (5), wherein the specific surface area is 200 to 1000 m ２ (8) The platinum group element-supported silica according to any one of (1) to (6), wherein the mode diameter of pores (D ｍａｘ ) is less than 20 nm, and D ｍａｘ(1) A platinum group element-supported silica according to any one of (1) to (7), wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores. (9) Amorphous platinum group element-supported silica according to any one of (1) to (8). (10) A platinum group element-supported silica according to any one of (1) to (9), which is a catalyst for decomposing hydrocarbons and / or aldehydes. (11) A platinum group element-supported silica according to any one of (1) to (10), which is a freshness-preserving agent. (12) An ethylene decomposition agent for decomposing ethylene in the co-presence of alcohol, comprising the platinum group element-supported silica according to any one of (1) to (11). (13) A method for decomposing ethylene using an ethylene decomposition agent comprising the platinum group element-supported silica according to any one of (1) to (11). (14) A method for decomposing ethylene according to (13), in which ethylene is decomposed in the co-presence of alcohol. (15) An antibacterial agent comprising any one of platinum group element-supported silicas (1) to (11). (16) An antibacterial method using an antibacterial agent comprising any one of platinum group element-supported silicas (1) to (11). (17) A method for producing platinum group element-supported silica, comprising supporting a platinum group element on silica and then heating the resulting silica in water at 80°C or higher for 30 minutes or more or calcining the resulting silica at a temperature of 550°C or higher for 1 hour or more. (18) The method for producing platinum group element-supported silica according to any one of (1) to (11), which is the method for producing platinum group element-supported silica according to (17).

[0010] In another aspect, the present invention is summarized as follows: [1] The number of surface silanol groups per unit surface area is 1.5 / nm 2 or more. [2] A platinum group element-supported silica gel that satisfies the following formula (1): B / (A+B)×100≧5% ... formula (1) (In formula (1), A represents the number of platinum group elements supported on the silica gel in a metallic state, and B represents the number of platinum group elements supported on the silica gel in a hydroxide state.) [3] A platinum group element-supported silica gel according to [1] or [2], wherein the proportion of platinum group elements per 100 parts by mass of the platinum group element-supported silica gel is 0.1 to 5 parts by mass. [4] A platinum group element-supported silica gel according to any of [1] to [3], wherein the platinum group element is elemental platinum. [5] A platinum group element-supported silica gel according to any of [1] to [4], wherein the pore volume is 0.3 to 1.6 mL / g. [6] A platinum group element-supported silica gel having a specific surface area of ​​200 to 1000 m２ [7] The platinum group element-supported silica gel according to any one of [1] to [5], wherein the mode diameter of the pores (D ｍａｘ ) is less than 20 nm, D ｍａｘ

[10] The platinum group element-supported silica gel according to any one of [1] to [9], wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores.

[11] The platinum group element-supported silica gel according to any one of [1] to [9], wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores.

[12] The platinum group element-supported silica gel according to any one of [1] to [9], wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores.

[13] The platinum group element-supported silica gel according to any one of [1] to

[10] , wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores.

[14] The platinum group element-supported silica gel according to any one of [1] to

[10] , wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores.

[15] The platinum group element-supported silica gel according to any one of [1] to

[10] , wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores.

[16] The platinum group element-supported silica gel according to any one of [1] to

[10] , wherein the total volume of pores within ±20% of the total volume of all pores is 40% or more of the total volume of all pores.

[17] The platinum group element-supported silica gel according to any one of [1] to

[10] , wherein the total volume of pores within ±20% of the total volume of all pores is 4

[0011] This specification includes the contents of the specification and the like of Japanese Patent Application No. 2024-087008, filed on May 29, 2024, which is the priority document of this application. All publications, patents, and patent applications cited in this specification are hereby incorporated by reference in their entirety.

[0012] The platinum group metal-supported silica of the present invention is suitable as an ethylene decomposition agent because it is resistant to charging, easy to handle, and has excellent ethylene decomposition ability.

[0013] Furthermore, the platinum group-supported silica of the present invention is suitable as an antibacterial agent (also called an antifungal agent) because it is difficult to become charged, is easy to handle, and can quickly exhibit antibacterial effects.

[0014] The present invention will be described in detail below based on embodiments, but the present invention is not limited to the following embodiments as long as the effects of the present invention are achieved.

[0015] The platinum group element-supported silica according to this embodiment has a surface silanol group number per unit surface area of ​​1.3 / nm 2 More than 1.4 particles / nm, preferably 1.4 particles / nm 2 More preferably, 1.5 / nm 2 That's all.

[0016] In the present invention, the term "silica carrying a platinum group element" refers to silica carrying a platinum group element in the form of a metal and / or a compound. The platinum group element may be supported on the surface of the silica in the form of particles, or may be partially permeated into the pore walls of the silica.

[0017] Furthermore, at least a portion of the platinum group elements may be bonded to silicon atoms of silica directly or via other elements, or may be present in a form bound to other elements or compounds.

[0018] In the present invention, the silica is preferably porous silica, and mesoporous silica is particularly preferred. Preferably, in the present invention, the silica is silica gel, and the platinum group element-supported silica is preferably silica gel on which the platinum group element is supported in the form of a metal and / or a compound. More preferably, in the present invention, the silica is porous silica gel, and mesoporous silica gel is particularly preferred, and the platinum group element-supported silica is preferably porous silica gel on which the platinum group element is supported in the form of a metal and / or a compound, and mesoporous silica gel is particularly preferred.

[0019] Platinum group elements are elements located in groups 8 to 10 of periods 5 and 6 in the periodic table, i.e., platinum, palladium, rhodium, iridium, ruthenium, and osmium.

[0020] The platinum group element-supported silica may support one or more platinum group elements, but it is preferred that the platinum group element supported by silica is elemental platinum.

[0021] The number of surface silanol groups per unit surface area of ​​the platinum group element-supported silica is 1.3 / nm 2 More than 1.4 particles / nm, preferably 1.4 particles / nm 2 More preferably, 1.5 / nm ２ or more, and 1.6 particles / nm ２ More preferably, it is 1.8 particles / nm or more. ２ On the other hand, there is no upper limit, but it is usually 8 particles / nm ２ The following is the result.

[0022] The number of surface silanol groups per unit surface is 1.3 / nm 2 More than 1.4 particles / nm, preferably 1.4 particles / nm 2 More preferably, 1.5 / nm ２ If the thickness is more than this, the toner is less likely to be charged, and therefore the toner is easy to handle.

[0023] Platinum group element-supported silica tends to aggregate when charged, but the number of surface silanol groups per unit surface is 1.3 / nm 2 More than 1.4 particles / nm, preferably 1.4 particles / nm 2 More preferably, 1.5 / nm ２ If the particle size is above 1.3, the powder is less likely to be charged and therefore less likely to aggregate. The powder's surface area can be maintained by being less likely to aggregate, allowing for efficient decomposition of ethylene and / or efficient contact with alcohol, thereby promoting rapid development of antibacterial effects. Furthermore, the number of surface silanol groups per unit surface area is set to 1.3 / nm. 2 More than 1.4 particles / nm, preferably 1.4 particles / nm 2 More preferably, 1.5 / nm ２ By adjusting the surface area to the above value, it is possible to enhance hydrophilicity, increase the contact efficiency with alcohol, and promote the rapid development of antibacterial effects. The number of surface silanol groups per unit surface area can be measured by the method described in the Examples below.

[0024] The proportion of platinum group element in 100% by mass of platinum group element-supported silica is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of improving ethylene decomposition or improving contact efficiency with alcohol for exhibiting antibacterial effect, while from the viewpoint of durability, it is preferably 5% by mass or less, more preferably 4% by mass or less.

[0025] The average particle size of the platinum group element-supported silica is not particularly limited, but in order to suppress particle aggregation, it is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. On the other hand, in order to maintain a certain degree of particle surface area, it is preferably 1,000 μm or less, more preferably 800 μm or less, and even more preferably 600 μm or less. The average particle size of the platinum group element-supported silica can be measured using a laser diffraction particle size distribution analyzer.

[0026] The pore volume of the platinum group element-supported silica is not particularly limited, but from the viewpoint of improving the contact efficiency with ethylene or alcohol, it is preferably 0.3 mL / g or more, more preferably 0.4 mL / g or more, and even more preferably 0.5 mL / g or more, while from the viewpoint of ease of production, it is preferably 1.6 mL / g or less, more preferably 1.5 mL / g or less, and even more preferably 1.3 mL / g or less.

[0027] The specific surface area of ​​the platinum group element-supported silica is not particularly limited, but is preferably 200 m ２ On the other hand, it is preferable that the viscosity is 1000m / g or more. ２ / g or less, and ２ / g or less is more preferable, and 700m ２ The pore volume and specific surface area can be measured by the BET method using nitrogen gas adsorption and desorption.

[0028] The platinum group element-supported silica according to this embodiment is a pore distribution curve calculated from an isothermal desorption curve measured by a nitrogen gas adsorption / desorption method by the BJH method described in EP Barrett, LG Joyner, PH Haklenda, J. Amer. Chem. Soc., vol. 73, 373 (1951), that is, the most frequent diameter (D) on a graph plotting the differential nitrogen gas adsorption amount (ΔV / Δ(log d); V is the nitrogen gas adsorption volume) against the pore diameter d (nm). ｍａｘ ) is preferably less than 20 nm, and although there is no particular lower limit, it is preferably 2 nm or more.

[0029] The platinum group element-supported silica according to this embodiment has the above-mentioned mode diameter (D ｍａｘ The total volume of pores within ±20% of the value of the mode diameter (D) is preferably 40% or more, more preferably 50% or more, of the total volume of all pores. ｍａｘ The total volume of pores within a range of ±20% from the value of (1) is preferably 90% or less of the total volume of all pores.

[0030] This means that the diameter of the pores of the platinum group element-supported silica of the present invention is the mode diameter (D ｍａｘ ) means that the pores are aligned in the vicinity of each other.

[0031] The platinum group element-supported silica according to this embodiment has a modal diameter (D ｍａｘ ) is preferably 2 to 20 mL / g, more preferably 3 to 12 mL / g (where d is the pore diameter (nm) and V is the nitrogen gas adsorption volume).

[0032] The differential pore volume ΔV / Δ(log d) falls within the above range. ｍａｘ ) is an extremely large absolute amount of pores aligned in the vicinity of

[0033] The platinum group element-supported silica according to this embodiment preferably has a chlorine concentration of 150 ppm or less, more preferably 100 ppm or less, even more preferably 50 ppm or less, and particularly preferably 45 ppm or less. The lower limit of the chlorine concentration is not particularly limited, but is preferably 10 ppm or more. Since chlorine inhibits contact between alcohol and platinum group element-supported silica, it is preferable to set the chlorine concentration contained in the platinum group element-supported silica within the above range to increase the efficiency of the contact and promote the rapid development of the antibacterial effect. On the other hand, the inclusion of chlorine is preferable because it can provide the antibacterial effect of chlorine and compensate for the antibacterial performance until the antibacterial effect based on contact with alcohol is developed.

[0034] The chlorine concentration contained in the platinum group element-supported silica can be adjusted by appropriately selecting the amount and type of platinum group element-containing compound containing chlorine as a raw material in the production of the platinum group element-supported silica, or by subjecting the platinum group element-supported silica to a heat treatment as described below.The chlorine concentration contained in the platinum group element-supported silica can be measured by the method described in the examples below.

[0035] Furthermore, in addition to the above-mentioned pore structure characteristics, the platinum group element-supported silica according to this embodiment is preferably amorphous, i.e., no crystalline structure is observed in its three-dimensional structure. This means that when the foreign element-supported silica of the present invention is analyzed by X-ray diffraction, substantially no crystalline peaks are observed. In the case of crystalline porous materials, it is more difficult to form large pores than in amorphous materials, and the pores tend to be small. Small pores slow the diffusion of alcohol, making it difficult for the reaction to proceed. In this specification, amorphous silica is significantly more productive than crystalline silica.

[0036] <Method for producing platinum group element-supported silica> There are no particular limitations on the method for producing platinum group element-supported silica, but it can be preferably obtained by reducing a mixture of silica and a platinum group element raw material such as a platinum-containing compound or an organic complex containing a platinum group element. For example, platinum group element-supported silica can be obtained by preparing an aqueous solution containing a platinum group element raw material, impregnating silica with the aqueous solution, drying the aqueous solution, and then performing a reduction treatment.

[0037] The obtained platinum group element-supported silica is preferably subjected to a heat treatment by heating in water at 80°C or higher for 30 minutes or more, preferably boiling for 1 hour or more, or by calcining at a temperature of 550°C or higher, preferably 600°C or higher, for 1 hour or more, preferably 4 hours or more. By subjecting the platinum group element-supported silica to this heat treatment, the chlorine concentration can be reduced, and platinum group element-supported silica that quickly develops its antibacterial effect can be obtained.

[0038] As the platinum group element-containing compound, hydrochlorides of platinum group elements are preferred because they are readily available and relatively inexpensive.

[0039] The platinum group element-supported silica according to this embodiment supports a specific amount of platinum group element-containing hydroxide, and the amount of hydroxide can be adjusted by the amount of silanol groups inside the silica that supports the platinum group element. That is, to increase the amount of platinum group element-containing hydroxide supported on the resulting platinum group element-supported silica, silica with a large amount of internal silanol groups can be used. On the other hand, to decrease the amount of platinum group element-containing hydroxide supported on the resulting platinum group element-supported silica, silica with a small amount of internal silanol groups can be used.

[0040] There are no particular limitations on the specific surface area, pore volume, and particle size of the silica before loading it with a platinum group element, and these may be appropriately selected so as to obtain the desired platinum group element-loaded silica. Therefore, the preferred ranges for these are the same as those given above for the platinum group element-loaded silica.

[0041] <Method for Producing Silica> There are no particular limitations on the method for producing silica. For example, silica can be produced by applying a method in which a silica hydrogel obtained by hydrolyzing an alkali silicate or a silica hydrogel obtained by hydrolyzing a silicon alkoxide is subjected to hydrothermal treatment without aging. A method in which silicon alkoxide is hydrolyzed is preferred.

[0042] Examples of silicon alkoxides include tri- or tetraalkoxysilanes having a lower alkyl group having 1 to 4 carbon atoms, such as trimethoxysilane, tetramethoxysilane, triethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, and oligomers thereof, with tetramethoxysilane, tetraethoxysilane, and oligomers thereof being preferred.

[0043] The above silicon alkoxides can be easily purified by distillation, making them suitable as raw materials for high-purity silica. The total content of metal impurities in the silicon alkoxide is usually preferably 100 ppm or less, more preferably 10 ppm or less. The content of metal impurities can be measured using the same method as that for measuring impurities in silica.

[0044] The hydrolysis of silicon alkoxide is carried out using 2 to 20 moles, preferably 3 to 10 moles, more preferably 4 to 8 moles of water per mole of silicon alkoxide, to produce silica hydrogel and alcohol.

[0045] This hydrolysis reaction is usually carried out at room temperature to about 100°C, but it can also be carried out at higher temperatures by maintaining the liquid phase under pressure. The reaction time depends on the reaction solution composition (type of silicon alkoxide and molar ratio with water) and reaction temperature, and the time until gelation varies, so it cannot be generally defined. The reaction time is the time during which the breaking stress of the hydrogel does not exceed 6 MPa.

[0046] The hydrolysis can be accelerated by adding a catalyst such as an acid, alkali, or salt to the reaction system. However, as will be described later, the use of such additives can cause aging of the produced hydrogel, and therefore it is preferable not to use such additives in the production of silica.

[0047] In the hydrolysis reaction of silicon alkoxide, silicon alkoxide is hydrolyzed to produce silicate, which is then condensed, increasing the viscosity of the reaction solution and finally gelling to form silica hydrogel. In order to produce silica, it is preferable to immediately carry out hydrothermal treatment without substantial aging, so as not to increase the hardness of the silica hydrogel produced by the hydrolysis.

[0048] The above-mentioned hydrothermal treatment of the silica hydrogel formed by hydrolysis immediately without substantially aging means that the silica hydrogel is subjected to the subsequent hydrothermal treatment while maintaining the soft state it has immediately after formation.

[0049] Adding acids, alkalis, salts, etc. to the hydrolysis reaction system of silicon alkoxide, or setting the temperature of the hydrolysis reaction too high, is not preferred because it accelerates the aging of the hydrogel. Furthermore, it is preferable not to use excessively high temperatures or time for post-treatments such as washing with water, drying, and leaving after hydrolysis.

[0050] The hydrothermal treatment may be carried out under conditions in which the water is either liquid or gaseous, and may be diluted with a solvent or other gas, but liquid water is preferably used. The silica hydrogel is usually added with 0.1 to 10 times, preferably 0.5 to 5 times, and more preferably 1 to 3 times the weight of water to form a slurry, and the treatment is carried out at a temperature of usually 40 to 250°C, preferably 50 to 200°C, for usually 0.1 to 100 hours, preferably 1 to 10 hours.

[0051] The water used for the hydrothermal treatment may contain lower alcohols, methanol, ethanol, propanol, etc. This hydrothermal treatment method is also applicable to materials in which silica is formed in the form of a film or layer on a substrate such as particles, a substrate, or a tube for the purpose of producing a membrane reactor, etc.

[0052] Under the above hydrothermal treatment conditions, increasing the temperature tends to increase the pore size and pore volume of the resulting silica. Furthermore, the specific surface area of ​​the resulting silica tends to reach a maximum and then gradually decrease with the treatment time.

[0053] In consideration of the above-mentioned trends, it is necessary to select the conditions appropriately depending on the desired physical property values. However, since the hydrothermal treatment is performed to change the physical properties of silica, it is usually preferable to use higher temperature conditions than the reaction conditions for the hydrolysis described above.

[0054] If the temperature and time of the hydrothermal treatment are set outside the above ranges, it will be difficult to obtain the silica of the present invention.For example, if the temperature of the hydrothermal treatment is too high, the pore size and pore volume of the silica will be too large, and the pore distribution will also be broad.On the other hand, if the temperature of the hydrothermal treatment is too low, the silica produced will tend to have a low degree of crosslinking and poor thermal stability.

[0055] When hydrothermal treatment is performed in ammonia water, the same effect can be obtained at a lower temperature than when it is performed in pure water. Furthermore, when hydrothermal treatment is performed in ammonia water, the final silica generally becomes more hydrophobic than when it is treated in pure water, but the hydrophobicity is particularly enhanced when hydrothermal treatment is performed at a relatively high temperature, usually 30 to 250°C, preferably 40 to 200°C.

[0056] The ammonia concentration of the ammonia water is preferably 0.001 to 10%, more preferably 0.005 to 5%.

[0057] The hydrothermally treated silica hydrogel is typically dried at 40 to 200°C, preferably 60 to 120°C. The drying method is not particularly limited, and either a batch or continuous method may be used, and drying can be performed under normal pressure or reduced pressure. If carbon derived from the silicon alkoxide raw material is present, it can be removed by firing typically at 400 to 600°C. To control the surface condition, firing may also be performed at a maximum temperature of 900°C. Furthermore, pulverization and classification may be performed as necessary.

[0058] Silica with a crystalline structure tends to have poor thermal stability in water, and when silicon alkoxide is hydrolyzed in the presence of a template such as a surfactant used to form pores in the gel, the gel easily becomes crystalline. Furthermore, high-temperature calcination is required to remove the template after the reaction step, which reduces the amount of internal silanol groups, and therefore tends to reduce the proportion of platinum group element-containing hydroxide in the resulting platinum group element-supported silica.

[0059] Therefore, in the present invention, it is preferable to carry out hydrolysis in the absence of a template such as a surfactant, that is, under conditions where such a template is not present in an amount sufficient to function as a template.

[0060] The platinum group element-supported silica according to this embodiment can be suitably used as a catalyst for decomposing hydrocarbons and / or aldehydes. Examples of hydrocarbons include ethylene, propylene, and isobutene. Aldehydes are not particularly limited as long as they are compounds having an aldehyde group, and examples thereof include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, crotonaldehyde, hexanal, and nonenal.

[0061] In particular, the platinum group element-supported silica according to this embodiment can be effectively used as a catalyst for ethylene decomposition (ethylene decomposition agent), and can be used in an ethylene decomposition method. Specifically, agricultural products such as vegetables, fruits, and flowers generate and release ethylene themselves, which causes spoilage during storage and transportation, making it difficult to maintain their freshness. Therefore, it is effective to use the platinum group element-supported silica gel according to this embodiment as a freshness-preserving agent during the transportation and storage of agricultural products, etc.

[0062] When the platinum group element-supported silica according to this embodiment is used as a freshness-preserving agent, it may be provided in articles used for storage and transportation, such as bags, containers, refrigerators, and refrigerated containers.

[0063] Furthermore, when using the platinum group element-supported silica according to this embodiment as a freshness-preserving agent, ethylene decomposition may be carried out in the presence of alcohol. The coexistence of alcohol is preferable because it can provide the antibacterial effect described below. Furthermore, the coexistence of platinum group element-supported silica and alcohol can suppress a decrease in the catalytic activity of the platinum group element-supported silica even in the presence of moisture. This is thought to be because, when water is present near the catalytic active sites of the platinum group element-supported silica, the miscibility of the water and alcohol increases the hydrophobicity near the catalytic active sites, facilitating the arrival of ethylene.

[0064] The platinum group element-supported silica according to this embodiment can also be particularly effectively used as an antibacterial agent (also called an antifungal agent) and can be used in an antibacterial method. In the present invention, "antibacterial" means at least suppressing or preventing the growth of bacteria. Examples of "bacteria" include bacteria and fungi, such as Escherichia coli, yeast, and fungi (mold), but are not limited to these. The "antibacterial" effect in the present invention is an antibacterial effect brought about by contact of the platinum group element-supported silica with alcohol. It is believed that this antibacterial effect occurs when the platinum group element in the platinum group element-supported silica acts as a catalyst to oxidize gaseous alcohol to generate an antibacterial component, which suppresses or prevents the growth of bacteria.

[0065] In the present invention, "alcohol" refers to an organic compound having a hydroxyl group, and may be a monoalcohol, a diol, or a polyhydric alcohol. Among these, ethanol, which is commonly used as a food or food additive, is particularly preferred as the "alcohol" in the present invention, from the viewpoint of use in the vicinity of food. When ethanol is used as the alcohol in the present invention, the ethanol is oxidized to produce acetaldehyde upon contact with the platinum group element-supported silica, and carboxylic acid (acetic acid) is generated from the acetaldehyde via peracetic acid. Any one or more selected from the group consisting of aldehyde, carboxylic acid, and peracetic acid acts as an antibacterial component, and peracetic acid in particular has a high antibacterial effect.

[0066] When the platinum group element-supported silica according to this embodiment is used as an antibacterial agent, it may be provided in the presence of alcohol in articles used for storage and transportation, such as bags, containers, refrigerators, and refrigerated containers.

[0067] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0068] (Production of Silica Gel A) 1,000 g of pure water was charged into a 5 L separable glass flask (jacketed) equipped with an air-open water-cooled condenser at the top. While stirring at 80 rpm, 1,400 g of tetramethoxysilane was charged over 3 minutes. The molar ratio of water to tetramethoxysilane was approximately 6. Hot water at 50°C was passed through the jacket of the separable flask. Stirring was continued until the contents reached the boiling point, at which point the stirring was stopped. Hot water at 50°C was then passed through the jacket for approximately 0.5 hours to gel the resulting sol.

[0069] The gel was then quickly removed and crushed through a nylon mesh with 600 micron openings to obtain a powdery wet gel (silica hydrogel). 450 g of this hydrogel and 450 g of pure water were placed in a 1 L glass autoclave and subjected to hydrothermal treatment at 130°C for 3 hours.

[0070] After the hydrothermal treatment for a predetermined time, the mixture was filtered through No. 5A filter paper, and the filter cake was dried under reduced pressure at 100°C without washing with water until it reached a constant weight, thereby obtaining silica gel A.

[0071] (Preparation of Platinum-Supported Silica Gel A) 1 g of silica gel A was suspended in 50 mL of water, and a platinum compound (H ２ PtCl ６ The resulting solution was stirred at room temperature for 12 hours. The solvent was removed using an evaporator heated to 50°C, and the resulting powder was dried in vacuum at 60°C for 16 to 18 hours.

[0072] The dried powder was treated at 150° C. for 2 hours while flowing hydrogen gas at a rate of 30 mL / min, to obtain platinum-supported silica gel A.

[0073] (Preparation of Platinum-Supported Silica Gel B) Platinum-supported silica gel B was prepared in the same manner as in the preparation of Platinum-supported Silica Gel A described above, except that Silica Gel B (CARiACT G-6 manufactured by Fuji Silysia Chemical Ltd.) was used instead of Silica Gel A.

[0074] <Production Example I> (Production of Platinum-Supported Silica Gel I: Boiling Treatment After Platinum Support) Approximately 50 g of platinum-supported silica gel A was placed in a commercially available pot with approximately 1 L of demineralized water, brought to a boil, and heated for 1 hour. The filtrate was discarded, and washed and filtered twice with 500 mL of hot water. The platinum-supported silica gel A was returned to the pot, and heating for 1 hour and filtration were repeated twice as described above. The platinum-supported silica gel A after filtration was dehydrated with a nonwoven towel and then dried in a hot air dryer at 120°C for 2.5 hours to obtain platinum-supported silica gel I.

[0075] The number of surface silanol groups per unit surface area of ​​the obtained platinum-supported silica gel, the proportion of platinum group elements supported on the porous silica in the form of hydroxides, the adhesion state of the powder to the funnel, the chlorine concentration, the time until acetic acid is generated, the pore volume, the specific surface area, and the mode diameter (D ｍａｘ The results are shown in Table 1.

[0076] <Preparation Example II> (Platinum-supported Silica Gel II) Platinum-supported Silica Gel B was evaluated in the same manner as platinum-supported silica gel I. The results are shown in Table 1.

[0077] <Production Example III> (Production of Platinum-Supported Silica Gel III: Platinum Supported Silica Gel, Then Calcined at 650°C for 4 Hours) Approximately 50 g of platinum-supported silica gel A was heated to a set temperature of 665°C over 1 hour, maintained at that temperature for 4 hours, and then cooled to room temperature to obtain platinum-supported silica gel III. Instrument air was circulated at a rate of approximately 0.4 L / min. The obtained platinum-supported silica gel III was evaluated in the same manner as platinum-supported silica gel I. The results are shown in Table 1.

[0078] <Production Example IV> (Production of Platinum-Supported Silica Gel IV: Water Washing After Platinum Support) Approximately 50 g of platinum-supported silica gel A was placed in a wire mesh sieve lined with nonwoven fabric and washed by pouring demineralized water over it. The mixture was washed with approximately 1 L of demineralized water. The mixture was dried at room temperature and then dried in a hot air dryer at 120°C for approximately 5 hours to obtain platinum-supported silica gel IV. The resulting platinum-supported silica gel IV was evaluated in the same manner as platinum-supported silica gel I. The results are shown in Table 1.

[0079] (Number of surface silanol groups per unit surface area) 0.05 g of sample was placed in a glass container, to which an organic solvent, a base catalyst, and a fluorine-based silane treatment agent (3,3,3-trifluoropropyl)chlorodimethylsilane were added, then the container was sealed and heated. After heating, the sample was washed with an organic solvent and dried.

[0080] To determine the fluorine content in the dried product after silane treatment, total fluorine analysis was performed using combustion tube decomposition and ion chromatography. The amount of reactive silanol groups on the sample surface was calculated from the results of the total fluorine analysis.

[0081] The amount of reactive silanol groups on the sample surface was divided by the specific surface area determined by the BET method using nitrogen gas adsorption and desorption to obtain the number of surface silanol groups per unit surface area.

[0082] <Combustion and absorption conditions> System: AQF-2100H, GA-210 (Mitsubishi Chemical Corporation) Electric furnace temperature: Inlet 1000°C, Outlet 1100°C Gas: Ar / O ２ , 200mL / min :O ２, 400 mL / min Absorption liquid: H ２ O ２ 90 μg / mL, internal standard Br 4 μg / mL Absorption solution volume: 20 mL

[0083] <Conditions for ion chromatography and anion analysis> System: ICS-1600 (DIONEX) Mobile phase: 2.7 mmol / L Na ２ CO ３ / 0.3 mmol / L NaHCO ３ Flow rate: 1.5 mL / min Detector: Electrical conductivity detector Injection volume: 20 μL

[0084] (Status of powder adhesion to funnel) Approximately 6 g of sample was transferred to a container using a Teflon funnel (entrance diameter φ75 mm, leg diameter φ12 mm), and after transfer, it was checked whether powder adhered to the funnel. The same procedure was repeated three times. ◯: Almost no adhesion △: Adhesion ×: Adhesion and deposition

[0085] (Method for analyzing chlorine concentration) The sample was pulverized using a tungsten carbide mill to prepare the analysis sample. 60 mg of combustion improver (tungstic acid) was weighed into a magnetic boat, and approximately 30 mg of the sample was weighed and roughly mixed therein. The mixture was then combusted using an automatic sample combustion apparatus (AQF-2100H), and the combustion gas was absorbed into the absorption solution. The ions in the absorption solution were measured using ion chromatography under the following conditions. Automatic sample combustion apparatus: AQF-2100H manufactured by Nitto Seiko Analytech Co., Ltd. Ion chromatography: ICS-5000+ manufactured by ThermoScientific Column: IonPac AS22-Fast Eluent: 4.5 mM Na2CO3 / 1.4 mM NaHCO3 mixed aqueous solution

[0086] (Method for analyzing acetic acid generation) A quartz tube was filled with 0.6 g of sample, and the catalyst temperature was set to 70°C. After water adsorption by flowing 85% RH water vapor, the total flow rate of gas flowing into the quartz tube was 10 mL / min, and ethanol was bubbled to 12,000 vol ppm and oxygen to 20%. SV was set to 300. The generated gas was analyzed by GC (TCD) under the following conditions: GC System: GL Science GC3210 Column: Gaskuropack-54 2 m Oven Temp Profile: 140°C Front Detector: 140°C Column Flow Rate: 40 mL / min (He)

[0087] (pore volume, specific surface area, mode diameter (D ｍａｘ Nitrogen adsorption isotherms were measured using a BELSORP MINIX manufactured by Microtrac-Bell Corporation, and the pore volume and specific surface area were determined using the BET method. The mode diameter (D ｍａｘ ) was sought.

[0088] FT-eco catalyst (manufactured by Furuya Metal Co., Ltd.) was also evaluated in the same manner as platinum-supported silica gel I. The results are shown in Table 1.

[0089]

[0090] The number of surface silanol groups per unit surface area is 1.3 / nm ２ For the FT-eco catalyst, the number of surface silanol groups per unit surface area is 1.3 / nm ２ It was confirmed that almost no adhesion to the funnel occurred in Examples 1 to 4, where the number of surface silanol groups per unit surface area of ​​the platinum-supported silica gel was 1.3 / nm ２ It was found that by making the powder ultra-high, the charging of the powder can be suppressed and adhesion to the funnel can be prevented.

[0091] Furthermore, in Examples 1 and 3, in which the chlorine concentration was reduced to a relatively low value by the heat treatment of boiling and baking, it was confirmed that the time until acetic acid was generated upon contact with ethanol was shortened. Since it is believed that peracetic acid, which has a strong antibacterial effect, was generated during the process of generating acetic acid, it was confirmed that by lowering the chlorine concentration in the platinum-supported silica gel (for example, to 150 ppm or less), the antibacterial effect can be rapidly exerted in the presence of alcohol.

Claims

1. The number of surface silanol groups per unit surface area is 1.3 / nm ２ Super platinum group element supported silica.

2. The platinum group element-supported silica according to claim 1, wherein the platinum group element-supported silica is a platinum group element-supported silica gel.

3. The platinum group element-supported silica according to claim 1 or 2, which contains chlorine at a concentration of 150 ppm or less.

4. The platinum group element-supported silica according to claim 1 or 2, wherein the ratio of the platinum group element to the platinum group element-supported silica is 0.1% by mass or more and 5% by mass or less.

5. The platinum group element-supported silica according to claim 1 or 2, wherein the platinum group element is platinum.

6. The platinum group element-supported silica according to claim 1 or 2, having a pore volume of 0.3 to 1.6 mL / g.

7. Specific surface area is 200 to 1000 m ２ 3. The platinum group element-supported silica according to claim 1, wherein the PGM / PGM content is 1 / g.

8. Mode diameter of pores (D ｍａｘ ) is less than 20 nm, and D ｍａｘ 3. The platinum group element-supported silica according to claim 1, wherein the total volume of pores falling within a range of ±20% of said total volume of pores is 40% or more of the total volume of all pores.

9. The platinum group element-supported silica according to claim 1 or 2, which is amorphous.

10. The platinum group element-supported silica according to claim 1 or 2, which is a catalyst for decomposing hydrocarbons and / or aldehydes.

11. The platinum group element-supported silica according to claim 1 or 2, which is a freshness-preserving agent.

12. An ethylene decomposition agent, which comprises the platinum group element-supported silica according to claim 1 and is used for decomposing ethylene in the presence of alcohol.

13. A method for decomposing ethylene using an ethylene decomposition agent containing the platinum group element-supported silica according to claim 1.

14. The method for decomposing ethylene according to claim 13, wherein the decomposition of ethylene is carried out in the coexistence of an alcohol.

15. An antibacterial agent comprising the platinum group element-supported silica according to claim 1.

16. An antibacterial method using an antibacterial agent containing the platinum group element-supported silica of claim 1.

17. A method for producing platinum group element-supported silica, comprising supporting a platinum group element on silica and then heating the resulting product in water at 80°C or higher for 30 minutes or more or calcining the resulting product at 550°C or higher for 1 hour or more.

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