Porous silica, method for producing porous silica, metal honeycomb flow body, method for producing a metal honeycomb flow body

Abstract

The objectives are to provide a porous silica capable of achieving highly efficient dynamic absorption and concentration performance of heavy VOCs consisting of high-boiling-point polar organic solvents of 150°C or higher, and purification performance during VOC desorption, or to provide a heavy VOC absorbent comprising a metal catalyst in the porous silica, and to provide a metal honeycomb flow body coated with the heavy VOC absorbent. [Solution] The micropores are identified by the IUPAC absorption isotherm classification, and the micropore volume is 0.35 cm³. 3 Porous silica characterized by having a density of 1 / g or more and an average micropore diameter of 0.80 nm to 1.15 nm.

Description

[Technical Field]

[0001] This invention provides an effective technology for porous silica that enables the large-scale absorption and concentration of heavy VOCs consisting of high-boiling-point solvents of 150°C or higher. Furthermore, it provides a metal honeycomb flow body coated with the porous silica of the present invention, which allows for the efficient absorption and concentration of the heavy VOCs, followed by heating, purification, regeneration, and repeated cooling cycles. [Background technology]

[0002] Among VOCs (volatile organic compounds), high-boiling-point solvents with a boiling point of 150°C or higher have a slow evaporation rate, strong dissolving power, and high compatibility with solutes such as resins, preventing precipitation. As a retarder for paint solvents, they can improve the smoothness of painted surfaces, prevent whitening, and provide gloss.

[0003] In recent years, there has been a growing demand for high-capacity, miniaturized electronic components for fifth-generation smartphones, laptops, and autonomous and connected vehicles.

[0004] In particular, capacitors are electronic components that have the function of temporarily storing electricity. They are used in various ways in electronic circuits to handle electricity and radio waves, such as removing noise contained in the current, extracting only the necessary signals, and blocking DC while allowing only AC to pass through. Approximately 800 capacitors are installed in a smartphone, about 900 in a laptop, and about 1,000 in a car.

[0005] Traditionally, capacitors have used other materials such as tantalum and aluminum electrolytic capacitors, but today, multilayer ceramics made of dielectrics have become mainstream due to their miniaturization, low profile, high capacitance, high reliability, low loss, and environmental friendliness. The number of ceramic capacitors used worldwide each year has reached approximately 2 trillion units.

[0006] Increasing the capacitance of multilayer ceramic capacitors requires multilayering, and both the dielectric ceramic layer and the electrode layer must be precisely multilayered using 0.8 μm thin films, ensuring there are no stacking misalignments or structural defects.

[0007] Multilayer ceramic capacitors are constructed by applying a conductive paste consisting of a binder resin (methacrylic resin), a polar organic solvent, and metal powder (Ni, Al, Ag, Cu, Pd, Cr, Fe, and Co, or alloys selected from these) onto a ceramic green sheet using screen printing or the like, and then layering them.

[0008] One example of an application in which heavy VOCs consisting of high-boiling-point solvents with a boiling point of 150°C or higher are used in the manufacturing process is the polar organic solvent contained in the conductive paste, where the difference in solubility parameters with the binder resin is 0-3 (J / cm²). 3 High-boiling point solvents such as hexyl acetate and terpineol are used because they provide a smooth coating film.

[0009] Therefore, VOC separation by absorption inevitably involves a step of separating VOCs from air, requiring the use of absorbents in the presence of oxygen. However, activated carbon and molecular sieving carbon (MSC), which have high absorption performance, can absorb more VOCs than inorganic oxides such as silica, alumina, silica-alumina, and zeolites, but because they are flammable, their use in the presence of oxygen is undesirable from a safety standpoint. Rather, from a safety perspective, non-flammable inorganic oxide absorbents, such as silica, alumina, zeolites, and silica-alumina, are preferable. Furthermore, the necessity of using inorganic oxide absorbents with lower VOC absorption capacity compared to activated carbon and MSCs is one of the bottlenecks in the development of VOC processes. Consequently, in order to recover VOCs by absorption, a novel absorbent with a high dynamic absorption capacity is needed, which is a non-flammable inorganic oxide absorbent, particularly suitable for heavy VOCs consisting of high-boiling point solvents with a boiling point of 150°C or higher, but such an absorbent has not yet been established.

[0010] Porous silica is expected to have applications as an absorbent for removing harmful volatile organic compounds (VOCs). In typical applications such as exhaust gas treatment, strong absorbency is required because the target components must be absorbed from the flowing gas. For this purpose, it is preferable that the absorbent has a pore diameter of 1 to 1.2 times or less the dynamic molecular diameter of the VOC. While the dynamic molecular diameter of intermediate VOCs, such as toluene and methylcyclohexane, which are medium-boiling point solvents below 150°C, is about 0.62 nm, many heavy VOCs, which are high-boiling point solvents above 150°C, have a large dynamic molecular diameter of 0.8 nm to 1 nm. Therefore, it is preferable that the absorbent has many micropores with a diameter of about 0.8 to 1.15 nm, and a thin pore wall thickness and large micropore volume contribute to the absorption capacity.

[0011] Cationic surfactants composed of quaternary ammonium salts are highly toxic and have a high environmental impact. Therefore, from a safety standpoint, triblock copolymers containing polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide (PEO) are preferred. In order to achieve an average micropore diameter of approximately 0.8 to 1.15 nm, it is necessary to synthesize porous silica with many micropores by controlling the diameter of the associated micelles to 0.8 nm to 1 nm.

[0012] Since the absorption separation and catalytic activity of porous materials largely depends on the chemical surface properties of the pores, their shape, size, and uniformity, porous materials are classified by IUPAC according to the size of their pores (pore diameter).

[0013] [Table 1]

[0014] Patent Document 1 proposes a method for producing porous silica by mixing an alkoxysilane and a low molecular weight cationic surfactant without using an alcohol-based solvent, and then adding water as a reactant to adjust the pH, thereby gelling the resulting precursor solution to form silica.

[0015] According to Patent Document 1, as the cationic surfactant, octadecyltrimethylammonium chloride with 18 to 14 carbon atoms, hexadecyltrimethylammonium chloride, and tetradecyltrimethylammonium bromide have the presence of mesopores confirmed, and dodecyltrimethylammonium bromide, decyltrimethylammonium bromide, octyltrimethylammonium bromide, hexyltrimethylammonium bromide, and butyltrimethylammonium chloride with 12 or fewer carbon atoms have the presence of micropores confirmed.

[0016] Furthermore, it has been shown that the porous silica having micropores obtained using the cationic surfactant with 12 or fewer carbon atoms has improved toluene absorption performance. Among them, hexyltrimethylammonium bromide with 6 carbon atoms has the highest toluene absorption performance, and it is also described that adding an organic silane increases the toluene absorption performance.

[0017] However, in the example having the presence of the micropores in Patent Document 1, the example with 6 carbon atoms has a micropore average diameter of 1.12 nm, and in the range of 0.80 nm to 1.15 nm, the total pore volume is 0.32 cm 3 / g, which is the maximum. Naturally, since the micropore volume is a part of the total pore volume, it is less than 0.32 cm 3 / g.

[0018] On the other hand, in the example with 8 carbon atoms to which an organic silane was added, the micropore average diameter is 0.99 nm, and in the range of 0.80 nm to 1.15 nm, the total pore volume of 0.25 cm 3 / g is the maximum.

[0019] In Patent Document 1, although porous silica mainly having micropores is obtained by using the cationic surfactant having 12 or less carbon atoms, in the range where the average pore diameter of the micropores optimal for heavy VOCs is 0.80 nm to 1.15 nm, the micropore volume is not shown. However, since the total pore volume consisting of the sum of the micropore volume and the mesopore volume is small, it is suggested from the examples that the micropore volume optimal for heavy VOCs has not been obtained.

[0020] Next, a mixed solution containing an acidic aqueous solution, a nonionic surfactant, a silicate ester, and water is mixed in the presence of a metal salt, stirred at 30°C or higher and lower than 50°C for 30 minutes to 2 hours, and the resulting reaction suspension is aged at 30 to 100°C for 30 minutes to 10 hours. Then, the obtained fibrous silica precursor is filtered off, and then the nonionic surfactant in the precursor is removed, thereby obtaining fibrous porous silica particles having a micropore volume of 0.10 to 0.25 cm 3 / g and having a uniform length and high monodispersity. A method for producing fibrous porous silica particles is proposed in Patent Document 2.

[0021] According to this Patent Document 2, in the nonionic surfactant, particularly in the triblock copolymer (PEO-PPO-PEO), it is desirable that the weight average molecular weight is about 4000 to about 8000. In the examples, only Pluronic P123 having a weight average molecular weight of 5800 and 30% of PEO in the total molecular weight is suggested.

[0022] It is described that the larger the micropore volume, the higher the absorption ability. However, looking at the examples, for a total pore volume of 0.70 to 0.90 cm 3 / g, the micropore volume is 0.10 to 0.17 cm 3 / g and the proportion of micropores is small, and the pore diameter is 6.07 to 7.22 nm, which is porous silica mainly composed of mesopores.

[0023] Regarding porous silica mainly having micropores, nothing is suggested by using the triblock copolymer (PEO-PPO-PEO).

[0024] Patent Document 3 discloses spherical microporous silica porous particles having micropores with a pore diameter of 2 nm or less and a pore volume of 0.25 cm 3 / g or more, a BET specific surface area of 600 m 2 / g or more, a C constant by the BET analysis method of 450 or more, and consisting of spherical particles with a particle size of 20 to 500 μm.

[0025] According to the above Patent Document 3, an aqueous alkali silicate solution and a mineral acid are mixed and stirred in the presence of a nonionic surfactant, and the reaction is carried out at a temperature of 5°C to 35°C. A method for producing spherical microporous silica porous particles by removing the nonionic surfactant from the generated spherical particles, wherein the mineral acid is used in an amount corresponding to 3.5 to 10 moles per mole of the alkali silicate in terms of SiO2, and the nonionic surfactant is a triblock copolymer of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) or polyethylene oxide-polybutylene oxide-polyethylene oxide (PEO-PBO-PEO), having a molecular weight of 4,500 to 16,000 and a proportion of the hydrophilic part (PEO) in the total molecular weight of 75% or more.

[0026] Looking at the examples, the micropore volume is 0.328 cm 3 / g to 0.367 cm 3 / g, and their average micropore diameter is 0.66 nm to 0.76 nm. The average micropore diameter is small, and the porous silica with insufficient average micropore diameter for the dynamic absorption of heavy VOCs in the present invention.

[0027] Patent Document 4 proposes a component that absorbs intermediate VOCs consisting of medium-boiling point organic solvents such as toluene and xylene, which have a boiling point between 100°C and 150°C, and then purifies them by an oxidation catalyst during the desorption and regeneration of those intermediate VOCs. The component is suggested to consist of an absorbent material on which silver and palladium are supported using beta-type zeolite or mordenite-type zeolite as a support, and an oxidation catalyst containing palladium, which are supported on the surface of a paper honeycomb.

[0028] The maximum pore size of beta-type zeolite is 0.73 × 0.71 nm, while that of mordenite-type zeolite is 0.70 × 0.65 nm. Although these are suitable for the aforementioned medium-grade VOCs, the pore size is too small and the absorption capacity is insufficient for the heavy VOCs with boiling points of 150°C or higher according to the present invention.

[0029] Due to the problems described above, the industrial applications of heavy VOCs in dynamic absorption and concentration have been very limited. [Prior art documents] [Patent Documents]

[0030] [Patent Document 1] Patent No. 5647669 [Patent Document 2] Patent No. 5051512 [Patent Document 3] Patent No. 4484193 [Patent Document 4] Japanese Patent Publication No. 2007-21363 [Overview of the Initiative] [Problems that the invention aims to solve]

[0031] The object of the present invention is to provide a porous silica that can efficiently achieve dynamic absorption and concentration performance of heavy VOCs consisting of high-boiling-point polar organic solvents of 150°C or higher, and purification performance during VOC desorption, or a heavy VOC absorbent comprising a metal catalyst in the porous silica.

[0032] The objective is to provide a metal honeycomb flow body coated with the aforementioned heavy VOC absorbent. [Means for solving the problem]

[0033] To solve the above problems, the porous silica of the present invention has micropores identified by the IUPAC absorption isotherm classification, and the micropore volume is 0.35 cm³. 3 / g or more 0.55cm 3 It is characterized by having a concentration of less than or equal to / g, and an average micropore diameter of 0.80nm to 1.15nm.

[0034] The average diameter of the micropores may be between 0.88 nm and 1.12 nm.

[0035] The micropore volume (B) as a percentage of the total pore volume (A) of the porous silica may be 90% or more.

[0036] The porous silica may comprise at least one of the precious metals selected from platinum, palladium, and rhodium.

[0037] The content of the aforementioned precious metal may be 0.5 to 1.5% by mass.

[0038] Furthermore, in order to solve the above problems, the present invention provides a method for producing porous silica, the present invention, which is a method for producing porous silica from a nonionic surfactant and an alkoxysilane without using a cationic surfactant consisting of a quaternary ammonium salt, and comprises: (A1) adding the nonionic surfactant, an acidic catalyst, a metal salt, and the alkoxysilane to water as a solvent, forming associated micelles of the nonionic surfactant at 50°C to 60°C, and simultaneously carrying out a hydrolysis reaction with the alkoxysilane to produce a silica sol; (B1) after the hydrolysis reaction, a maturation step of holding the silica sol at 80°C to 100°C for 2 to 5 hours to mature the silica sol and obtain a gel substance; and (C1) solid-liquid separation by filtration. The process includes a post-treatment step in which, after separating the gel substance, the gel substance is washed with water and dried, and then the gel substance is calcined at 500-600°C, wherein the nonionic surfactant is a triblock copolymer containing polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide (PEO), the weight-average molecular weight of the triblock copolymer is greater than 1500 and less than 3000, and the polypropylene oxide (PEO) is contained in the total molecular weight of the triblock copolymer from more than 10% by mass to less than 50% by mass, and in step (A1), the mixed molar ratio of the starting materials is the alkoxysilane:the nonionic surfactant:the acidic catalyst:the water:the metal salt = 1:0.02-0.05:2-3:10-40:0.5-0.8.

[0039] Furthermore, in order to solve the above problems, the metal honeycomb flow material of the present invention is formed by coating the surface of a metal honeycomb having a specific heat of 500 (J / kg·℃) or less and a thermal conductivity of 15 (W / m·℃) or less with the porous silica of the present invention.

[0040] The material composition of the metal honeycomb may be 73-80% by mass of Fe, 17-21% by mass of Cr, and 3-6% by mass of Al.

[0041] Furthermore, in order to solve the above problems, the present invention provides a method for manufacturing a metal honeycomb flow body, which is a method for manufacturing a metal honeycomb flow body comprising coating the surface of a metal honeycomb with porous silica, and includes: (A2) a step of preparing a slurry consisting of the porous silica, an inorganic sol liquid and water; (B2) a step of adjusting the average particle size of the porous silica in the slurry to an average particle size of 1 to 10 μm using a wet pulverizer; (C2) a step of coating the cell surface of the metal honeycomb with the slurry after step (B2); and (D2) a step of drying and firing the metal honeycomb after coating with the slurry.

[0042] Furthermore, in order to solve the above problems, the present invention provides a method for manufacturing a metal honeycomb flow body, which is a method for manufacturing a metal honeycomb flow body comprising coating the surface of a metal honeycomb with porous silica containing a noble metal catalyst, and includes the steps of: (A3) preparing a slurry consisting of the porous silica, an inorganic sol liquid, and water; (B3) adjusting the average particle size of the porous silica in the slurry to 1 to 10 μm using a wet pulverizer; (C3) coating the cell surface of the metal honeycomb with the slurry after step (B3); (D3) drying and calcining the metal honeycomb after coating with the slurry to obtain a metal honeycomb flow body; (E3) preparing a noble metal liquid consisting of a noble metal salt solution and water; (F3) immersing the metal honeycomb flow body in the noble metal liquid; and (G3) drying and calcining the metal honeycomb flow body after immersion in the noble metal liquid.

[0043] Furthermore, in order to solve the above problems, the present invention provides a method for manufacturing a metal honeycomb flow body, which is a method for manufacturing a metal honeycomb flow body comprising coating the surface of a metal honeycomb with porous silica containing a noble metal catalyst, and includes: (A4) a step of preparing a slurry consisting of the porous silica, an inorganic sol liquid, a noble metal salt solution and water; (B4) a step of adjusting the average particle size of the porous silica in the slurry to 1 to 10 μm using a wet pulverizer; (C4) a step of coating the cell surface of the metal honeycomb with the slurry after step (B4); and (D4) a step of drying and firing the metal honeycomb after coating with the slurry.

[0044] Furthermore, the heavy VOCs consisting of high-boiling point solvents with a boiling point of 150°C or higher include ester-based VOCs such as hexyl acetate, heptyl acetate, octyl acetate, dodecyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, benzyl acetate, butyl butyrate, butyl benzoate, benzyl benzoate, and dihydroterpineol acetate; ether-based VOCs such as anisole, phenethole, benzyl ethyl ether, diphenyl ether, dibenzyl ether, and ethylene glycol diethyl ether; and alcohol-based VOCs such as n-octanol, n-decanol, n-dodecanol, α-terpionel, and dihydroterpineol. The metal honeycomb flow body of the present invention is characterized by absorbing and concentrating at least one of the heavy VOCs with the porous silica, and purifying and regenerating the porous silica that has absorbed and concentrated the heavy VOCs. [Effects of the Invention]

[0045] The porous silica and porous silica containing precious metals of the present invention, a metal honeycomb flow body coated therewith, and an apparatus comprising them can achieve more than double the dynamic absorption of heavy VOCs consisting of high-boiling-point polar organic solvents of 150°C or higher compared to the conventional technology. Furthermore, it enables a reduction in the purification performance during heavy VOC desorption to a temperature of approximately 30°C, thereby providing a technology with high cycle efficiency for absorption, purification, regeneration, and cooling. [Brief explanation of the drawing]

[0046] [Figure 1] An example of the VOC absorption and purification material of the present invention is shown in the SEM image (100x magnification) of Example 2. [Figure 2] An example of the VOC absorption and purification material of the present invention is shown in the SEM image (500x magnification) of Example 2. [Figure 3] This is the IUPAC classification of nitrogen absorption isotherms. [Figure 4] This shows the relationship between the proportion of hydrophilic portion in the total molecule of the surfactant in the examples and its weight-average molecular weight. [Figure 5] This shows the relationship between the proportion of hydrophilic parts and the molecular weight of hydrophobic parts in the total molecule of the surfactant in the examples. [Figure 6] This is an example of a comparison of nitrogen absorption isotherms between the present invention and the prior art [I]. [Figure 7] This is an example of a comparison of nitrogen absorption isotherms between the present invention and the prior art [II]. [Figure 8] This is an example of a comparison of the micropore diameter distribution in the examples [I]. [Figure 9] This is an example of a comparison of the micropore diameter distribution in the examples [II]. [Figure 10] This shows the relationship between the average diameter and pore volume in the micropores of the example. [Figure 11] This describes the performance test method for dynamic absorption and purification / regeneration in the examples. [Figure 12] This shows the results of the VOC absorption, VOC purification and regeneration, and cooling cycle test of Example 2M. [Figure 13] This shows the results of a cycle test of VOC absorption, VOC purification and regeneration, and cooling for Example 7PM. [Figure 14] This shows the results of a cycle test of VOC absorption, VOC purification and regeneration, and cooling for Example 8 PPM. [Figure 15] This shows the results of a cycle test of VOC absorption, VOC purification and regeneration, and cooling for Comparative Example 15M. [Figure 16]This is a comparison of the heat generated by the purification and regeneration of metal honeycomb flow bodies coated with VOC absorbers in Examples 2M, 7PM, and 8PPM. [Figure 17] This is a comparison of the hexyl acetate decomposition and purification performance of Example 2M, Example 7PM, and Example 8PPM. [Modes for carrying out the invention]

[0047] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0048] The inventors diligently researched porous silica that can efficiently achieve dynamic absorption performance of heavy VOCs consisting of high-boiling-point polar organic solvents of 150°C or higher, and purification performance during VOC desorption. As a result, they found that porous silica mainly consists of micropores, with a micropore volume of 0.35 cm³. 3 We found an absorbent material with a concentration of 0.80 nm to 1.15 nm and a micro-average pore diameter of 0.80 nm or more.

[0049] The heavy VOCs consisting of high-boiling point solvents of 150°C or higher that are the subject of this invention include hexyl acetate and α-terpionelle, and have a dynamic molecular diameter of 0.8 nm to 1 nm.

[0050] On the other hand, intermediate VOCs consisting of medium-boiling point solvents between 100°C and 150°C that are not covered by the present invention include toluene and methylcyclohexane, which have a dynamic molecular diameter of approximately 0.62 nm.

[0051] The former of the present invention has a larger dynamic molecular diameter compared to the latter, and therefore, it is preferable that the absorbent has a pore diameter 1.0 to 1.2 times the dynamic molecular diameter of the VOC.

[0052] The absorbent material of the present invention is made of porous silica, and has many micropores with a diameter of approximately 0.8 nm to 1.15 nm, and a micropore volume of 0.35 cm³. 3 This porous silica is characterized by its large weight of 1 / g or more.

[0053] The means for solving the problems of the present invention are described below in detail.

[0054] (Molecular weight of nonionic surfactants) The heavy VOC absorbent of the present invention is a porous silica having micropores, synthesized from a nonionic surfactant and an alkoxysilane, without using a cationic surfactant consisting of a quaternary ammonium salt, and is characterized in that the nonionic surfactant has a weight-average molecular weight of more than 1,500 and less than 3,000.

[0055] (PEO content ratio of nonionic surfactants) The heavy VOC absorbent of the present invention is characterized in that the nonionic surfactant is a triblock copolymer containing polyethylene oxide (PPEO)-polypropylene oxide (PPO)-polyethylene oxide (PPEO), wherein the polypropylene oxide (PPEO) is present in an amount of more than 10% to less than 50% of the total molecule.

[0056] (Average micropore diameter and micropore volume) The material for absorbing, concentrating, and purifying heavy VOCs according to the present invention is a porous silica synthesized from the nonionic surfactant and alkoxysilane, wherein the porous silica has micropores identified by the IUPAC absorption isotherm classification, and the micropore volume is 0.35 cm³. 3 It is characterized by having a concentration of 1 / g or more, and a micro-average pore diameter of 0.80 nm to 1.15 nm.

[0057] (Precious metal catalyst) The material for absorbing, concentrating, and purifying heavy VOCs according to the present invention is characterized in that the porous silica contains at least one precious metal selected from the group consisting of platinum, palladium, and rhodium.

[0058] (Precious metal catalyst content) The material for absorbing, concentrating, and purifying heavy VOCs according to the present invention is characterized by containing 0.5 to 1.5% by mass of the aforementioned precious metal.

[0059] (Porous silica manufacturing method) A method for producing porous silica from a nonionic surfactant which is a triblock copolymer containing polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide (PEO), having a weight-average molecular weight of more than 1,500 to less than 3,000 and containing more than 10% to less than 50% of the total molecule of polypropylene oxide (PEO), and an alkoxysilane, comprising the following steps (A1) to (C1).

[0060] (A1) The process involves adding the nonionic surfactant, acidic catalyst, metal salt, and alkoxysilane to a water solvent, raising the bath temperature to 50°C to 60°C, then slowly cooling to 35°C to 40°C to form aggregate micelles of the nonionic surfactant and simultaneously allowing the hydrolysis reaction of the alkoxysilane to occur. In step (A), the mixed molar ratio of the starting materials is: alkoxysilane:nonionic surfactant:acidic catalyst:water:metal salt = 1:0.02~0.05:2~3:10~40:0.5~0.8.

[0061] (B1) A maturation process in which the above hydrolysis reaction is carried out, followed by maturation at 80°C to 100°C for 2 to 5 hours.

[0062] (C1) Post-treatment process involving filtration, washing with water and drying, followed by calcination at 500-600°C.

[0063] (Physical properties of metal honeycomb material) The metal honeycomb flow material of the present invention is characterized by having a specific heat of 500 (J / kg·℃) or less and a thermal conductivity of 15 (W / m·℃) or less.

[0064] (Composition of metal honeycomb material) The metal honeycomb flow material of the present invention is characterized by comprising 73-80% by mass of Fe, 17-21% by mass of Cr, and 3-6% by mass of Al.

[0065] (Absorbent coating method for heavy VOCs) The metal honeycomb flow body coated with the heavy VOC absorbent of the present invention is characterized by being manufactured by the following steps (A2) to (D2).

[0066] (A2) A process for preparing a slurry consisting of a material for absorbing, concentrating, and purifying the heavy VOCs, an inorganic sol, and water. (B2) A step of adjusting the slurry to an average particle size of 1 to 10 μm using a wet grinder. (C2) A step of coating the cell surface of the metal honeycomb with the slurry. (D2) After coating the slurry, drying and firing the slurry.

[0067] (Absorbent coating method for heavy VOCs, including precious metal catalysts) The metal honeycomb flow body of the present invention, which is coated with a heavy VOC absorbent including a precious metal catalyst, is characterized by being manufactured from the following steps (A3) to (G3).

[0068] (A3) A process for preparing a slurry consisting of a material for absorbing, concentrating, and purifying the heavy VOCs, an inorganic sol, and water. (B3) A step of adjusting the slurry to an average particle size of 1 to 10 μm using a wet grinder. (C3) A step of coating the cell surface of the metal honeycomb with the slurry. (D3) After coating the slurry, drying and firing the slurry. (E3) Steps to prepare a noble metal solution consisting of a noble metal salt solution and water. (F3) A process of immersing a metal honeycomb flow body coated with the heavy VOC absorbent in the precious metal liquid. (G3) After immersion in the precious metal solution, drying and firing are performed.

[0069] (Absorbent coating method for heavy VOCs, including precious metal catalysts) The metal honeycomb flow body of the present invention, which is coated with a heavy VOC absorbent including a precious metal catalyst, is characterized by being manufactured by the following steps (A4) to (D4). (A4) A process for preparing a slurry consisting of a material for absorbing, concentrating, and purifying the heavy VOCs, an inorganic sol solution, a noble metal salt solution, and water. (B4) A step of adjusting the slurry to an average particle size of 1 to 10 μm using a wet grinder. (C4) A step of coating the cell surface of the metal honeycomb with the slurry. (D4) After coating the slurry, drying and firing the slurry.

[0070] (Target heavy VOCs) The metal honeycomb flow medium of the present invention is characterized by absorbing, concentrating, and purifying heavy VOCs consisting of ester-based, ether-based, and alcohol-based high-boiling point solvents as shown below.

[0071] (Ester compounds) Hexyl acetate, heptyl acetate, octyl acetate, dodecyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, benzyl acetate, butyl butyrate, butyl benzoate, benzyl benzoate, dihydroterpineol acetate (Ether-based) Anisole, phenethole, benzyl ethyl ether, diphenyl ether, dibenzyl ether, ethylene glycol diethyl ether (Alcohol-based) n-octanol, n-decanol, n-dodecanol, α-terpionol, dihydroterpineol

[0072] (Embodiment 1) Porous silica In this invention, an alkoxysilane, a metal salt and a mineral acid are used as the silica source, and a block polymer consisting of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO), a non-toxic, low-tolerance-load, and inexpensive nonionic surfactant, with a weight-average molecular weight of 1500 to 3000 and a hydrophilic PEO content of more than 10% to less than 50% of the total molecule, is used as the organic structure-directing agent (OSDA).

[0073] We found that the higher the PPO content (lower the PEO content) of the nonionic surfactant in total molecules, the lower the critical micelle concentration (cmc) and critical micelle temperature (cmt), making it easier to form micelles. Furthermore, we discovered that raising the reaction bath temperature to 50°C to 60°C increases hydrophobicity, significantly reducing the size of associated micelles and leading to the formation of intermolecular aggregates.

[0074] The aforementioned nonionic surfactant, coupled with its low weight-average molecular weight of 1500-3000, allows for extremely small micelle size and uniform control of the micelle structure, resulting in an average micropore diameter of 0.8 nm to 1.15 nm and a micropore volume of 0.35 cm³. 3 This invention represents a remarkable advancement in enabling the production of porous silica with an unparalleled large pore volume of over / g.

[0075] The porous silica particles of the present invention do not need to be fibrous in shape, and have an average micropore diameter of 0.8 nm to 1.15 nm and a micropore volume of 0.35 cm³. 3 It must be at least / g and have an irregular shape as shown in Figures 1 and 2.

[0076] The following describes specific embodiments of the porous silica particles of the present invention.

[0077] (Porous silica manufacturing method) A method for producing porous silica from a nonionic surfactant which is a triblock copolymer containing polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide (PEO), having a weight-average molecular weight of more than 1,500 to less than 3,000 and containing more than 10% to less than 50% of the total molecule of polypropylene oxide (PEO), and an alkoxysilane, comprising the following steps (A5) to (C5).

[0078] (A5) The process includes a step of preparing a precursor (sol) in which the nonionic surfactant, acidic catalyst, metal salt, and alkoxysilane are added in this order to a water solvent, and an associated micelle of the nonionic surfactant is formed at 50°C to 60°C while the hydrolysis reaction of the alkoxysilane is carried out. In step (A5), the mixed molar ratio of the starting materials is: alkoxysilane:nonionic surfactant:acidic catalyst:water:metal salt = 1:0.02~0.05:2~3:10~40:0.5~0.8. (B5) After the hydrolysis reaction described above, a maturation (dehydration condensation gelation) process is carried out at 80°C to 100°C for 2 to 5 hours. (C5) Post-treatment process: After filtration, washing, and drying, the material is calcined at 500-600°C.

[0079] (Nonionic surfactant) The nonionic surfactant of the present invention is preferably a block polymer having a weight-average molecular weight of 1500 to 3000 and a hydrophilic PEO content of more than 10% to less than 50% of the total molecule, and more preferably a block polymer having a weight-average molecular weight of 1500 to 2000 and a hydrophilic PEO content of 20% or more to 40% or less.

[0080] When the weight-average molecular weight exceeds 3000, the average micropore diameter becomes larger than 1.15 nm, reducing the number of micropores and increasing the number of mesopores. As a result, heavy VOCs are less likely to condense and be absorbed as single molecules within the pores, leading to a decrease in dynamic absorption capacity. On the other hand, when the weight-average molecular weight is less than 1500, the average micropore diameter becomes less than 0.8 nm, which is equal to or less than the dynamic molecular diameter of heavy VOCs, resulting in a decrease in condensation and single-molecule absorption within the pores.

[0081] In the present invention, if the proportion of hydrophilic PEO in the total molecule of the nonionic surfactant is 10% or less, the hydrophobicity is excessive, the associated micelle structure becomes too large, and the average micropore diameter becomes larger than 1.15 nm, which is undesirable. On the other hand, if the proportion of hydrophilic PEO in the total molecule is 50% or more, the hydrophobicity is insufficient, making it difficult to form an associated micelle structure, resulting in an average micropore diameter of less than 0.8 nm, which is undesirable.

[0082] In the precursor preparation step (A5) of the present invention, in which association micelles of the nonionic surfactant are formed and the hydrolysis reaction of alkoxysilane is carried out, the temperature of the reaction bath is raised to 50°C to 60°C, then slowly cooled and maintained at 35°C to 40°C. This increases the hydrophobicity and changes the association micelles into a compact form, with an average micropore diameter of 0.8 nm to 1.15 nm and a micropore volume of 0.35 cm³. 3 To produce porous silica of the present invention at a concentration of 1 / g or more, it is preferable to raise the temperature of the reaction bath to 50°C to 60°C, then slowly cool it and maintain continuous stirring at 35°C to 40°C for 2 to 20 hours, and more preferably raise the bath temperature to 50°C to 55°C, then slowly cool it and maintain continuous stirring at 35°C to 40°C for 3 to 18 hours.

[0083] If the temperature of the reaction bath rises to less than 50°C, the hydrophobicity does not increase, micelle association formation is low, and the average micropore diameter becomes less than 0.8 nm, which is undesirable. On the other hand, if the temperature of the reaction bath rises to more than 70°C, not only hydrolysis but also dehydration condensation reactions proceed, forming siloxanes and resulting in a non-uniform pore distribution, which is undesirable.

[0084] In the precursor preparation (A5) step, it is important that the reaction bath is stirred uniformly so that the precursor (sol) solution is uniformly stirred throughout so that the alkoxysilane is hydrolyzed and absorbed around the associated micelles. The stirring method is not particularly limited as long as the precursor (sol) solution is uniformly stirred throughout, but it is preferable that the baffle plates or rods and stirring blades occupy 40% or more of the diameter of the reaction vessel, with a baffle plate or rod accounting for 10-20% of the diameter.

[0085] Subsequently, in the maturation (B5) step, it is preferable to mature the mixture at a bath temperature of 80°C to 100°C for 2 to 5 hours. Furthermore, it is even more preferable to mature it at 90°C to 98°C for 3 to 4 hours. During maturation, stirring may or may not be performed, but if stirring is performed, it is preferable to perform uniform stirring in the same manner as in the precursor preparation (A) step described above.

[0086] The post-processing step (C5) involves filtration, washing with water, and drying, followed by calcination at 500-600°C, although this is influenced by the quantity of the sample and the calcination time. In particular, calcination at 550-600°C is preferred.

[0087] As acidic catalysts, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, as well as organic acids such as acetic acid, can be used. Inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid are preferred, and among these, hydrochloric acid is preferred from the viewpoint of catalytic properties and the fact that it does not easily remain as a residue, such as nitrate roots, sulfate roots, and phosphoric acid roots.

[0088] The alkoxysilane used in this invention can be tetramethoxysilane, tetraethoxysilane, tetraisopropylsilane, etc. However, tetraethoxysilane (hereinafter abbreviated as TEOS) is preferred because of the toxicity caused by methanol production when using tetramethoxysilane and the slow reaction rate when using tetraisopropylsilane.

[0089] The mixed molar ratio of the starting materials is as follows: alkoxysilane:nonionic surfactant:acidic catalyst:water:metal salt = 1:0.02~0.05:2~3:10~40:0.5~0.8.

[0090] The metal species in the metal salt of the present invention are preferably Na, K, Li, and Cs, and among these, Na and K are preferred because as the concentration increases, the cmc and cmt of the nonionic surfactant decrease, and associated micelles grow. As the metal salt, chlorides, sulfates, nitrates, etc. can be used as starting materials. Chlorides are preferred from the viewpoint of being less likely to remain as residual salts of nitrates and sulfates.

[0091] (Embodiment 2) Metal honeycomb distribution body The metal honeycomb flow body of the present invention is made of ferritic stainless steel and, compared to conventionally used glass fiber honeycomb flow bodies, has a lower specific heat (Table 5). This allows VOCs absorbed in the VOC absorption and concentration zone to be purified and regenerated in a short time by circulating heated air in the VOC purification and regeneration zone, and then cooled in a short time by blown air in the cooling process. This is preferable because it increases the cycle efficiency of absorption and concentration, purification and regeneration, and cooling, allowing for the processing of a large amount of VOC per unit time.

[0092] On the other hand, the metal honeycomb flow body of the present invention is made of ferritic stainless steel, and compared to general-purpose stainless steels such as austenitic stainless steel (e.g., SUS304) and martensitic stainless steel (e.g., SUS410), it has the characteristic of having a low thermal conductivity (Table 5). As a result, heat from the heated air in the VOC purification and regeneration zone is less likely to be transferred to the VOC absorption and concentration zone and the cooling zone, which is preferable because it has less impact on the amount of VOC absorbed and concentrated and the cooling efficiency.

[0093] (Physical properties of metal honeycomb material) The metal honeycomb flow body of the present invention is preferably made of ferritic stainless steel Fe-20Cr-5Al (JFE20-5USR, manufactured by JFE Steel Corporation) or ferritic stainless steel Fe-18Cr-3Al (JFE18-3USR, manufactured by JFE Steel Corporation), which has a specific heat of 500 (J / kg·℃) or less and a thermal conductivity of 15 (W / m·℃) or less. (Table 5)

[0094] (Composition of metal honeycomb material) The metal honeycomb flow material of the present invention uses ferritic stainless steel Fe-20Cr-5Al (JFE20-5USR, manufactured by JFE Steel Corporation) or ferritic stainless steel Fe-18Cr-3Al (JFE18-3USR, manufactured by JFE Steel Corporation), which consists of 73-80% by mass of Fe, 17-21% by mass of Cr, and 3-6% by mass of Al. (Table 6)

[0095] The metal honeycomb flow body of the present invention is manufactured by forming a roll having a honeycomb of triangular cells by overlapping and winding a pleated sheet and a flat sheet of foil (thickness 20 μm to 40 μm) of ferritic stainless steel Fe-20Cr-5Al (JFE20-5USR, manufactured by JFE Steel Corporation) or ferritic stainless steel Fe-18Cr-3Al (JFE18-3USR, manufactured by JFE Steel Corporation), with a brazing material sandwiched or applied between the two sheets. Subsequently, the brazing material is melted in a heating furnace to bond the components. The outer circumference of the honeycomb roll is not particularly limited, but is an outer cylinder made of stainless steel (thickness 1 mm to 3 mm), which is bonded to the honeycomb roll by heating with brazing material in the same way as the honeycomb.

[0096] The metal honeycomb flow medium of the present invention has a cell count of 200 cells / inch, from the viewpoint of VOC absorption and pressure loss. 2 ~400 cells / inch 2 Preferably, 250 cells / inch 2 ~350 cells / inch 2 It is preferable.

[0097] [Table 2]

[0098] [Table 3]

[0099] [Table 4]

[0100] (Embodiment 3) Coating of porous silica The porous silica of the present invention is obtained by mixing an inorganic binder with water, adjusting the particle size using a ball mill or the like to form a slurry, coating it onto the metal honeycomb, and then drying and firing it.

[0101] The inorganic binder is preferably made of a material with a similar coefficient of thermal expansion to the porous silica and metal honeycomb of the present invention, so that they can maintain continuous adhesion during the heating and cooling cycles of purification and regeneration. In this respect, alumina sol is preferred.

[0102] The mixture of materials in the slurry is preferably such that the mass ratio, calculated on a solid content basis (excluding water), is porous silica:alumina sol:water = 1:0.1~0.2:2~4 according to the present invention.

[0103] The porous silica of the present invention in the slurry has an average particle size D 50 From the viewpoint of adhesion with the metal honeycomb flow body, the average particle size D is preferably 1 μm to 10 μm, and particularly preferably 2 μm to 5 μm. 50 If the average particle size is less than 1 μm, the viscosity of the slurry increases, the inner surface of the cells in the metal honeycomb flow body becomes clogged, reducing the VOC absorption and concentration performance and / or increasing the pressure loss, which is undesirable. On the other hand, the average particle size D 50 If the particle size exceeds 10 μm, the adhesion between the porous silica particles of the present invention and between the layers with the metal honeycomb flow body decreases, leading to a decrease in VOC absorption and the generation of dust, which is undesirable.

[0104] The porous silica of the present invention is preferably coated on the inner surface of the metal honeycomb cells at a concentration of 80 g / L to 150 g / L per volume (L) of the metal honeycomb, and particularly preferably at a concentration of 90 g / L to 140 g / L. If the coating amount is less than 80 g / L, the coating amount is insufficient, and the VOC absorption and concentration performance decreases, which is undesirable. If the coating amount exceeds 150 g / L, the inner surface of the cells of the metal honeycomb flow body becomes clogged, reducing the VOC absorption and concentration performance and / or increasing the pressure loss, which is undesirable.

[0105] (Embodiment 4) Precious metal catalyst The material for absorbing, concentrating, and purifying heavy VOCs according to the present invention is characterized by comprising the porous silica of the present invention and at least one precious metal selected from the group consisting of platinum, palladium, and rhodium.

[0106] When porous silica and precious metals are supported on the inner surface of the cells of a metal honeycomb fluid, purification begins at around 170°C when heated air is blown in for regeneration, and the metal honeycomb outlet gas temperature rises to over 300°C due to the exothermic oxidation reaction of heavy VOCs. On the other hand, in the case of porous silica alone, purification begins at around 200°C when blown in for metal honeycomb, and the metal honeycomb outlet gas temperature only rises to 220°C. (Figure 11)

[0107] When porous silica and a precious metal are supported on the inner surface of the cell, the purification start temperature is shifted to a lower temperature of approximately 30°C compared to when only porous silica is supported on the inner surface of the cell. This shortens the purification and regeneration cycle time and contributes to energy saving of heated air.

[0108] The inventors found that, as precious metals, platinum exhibits high oxidation activity in the low-temperature range of 150°C to 250°C, while palladium and rhodium exhibit high oxidation activity in the higher-temperature range of 250°C and above.

[0109] It is more preferable to load platinum at a concentration of 0.5 g / L to 1.0 g / L and palladium and / or rhodium at a concentration of 0.25 g / L to 0.5 g / L in total on the inner surface of the cell.

[0110] (Precious metal catalyst content) The material for absorbing, concentrating, and purifying heavy VOCs according to the present invention is characterized in that the noble metal contains 0.5 g / L to 1.5 g / L per volume (L) of the metal honeycomb.

[0111] From the viewpoint of the amount of purification by oxidative decomposition of heavy VOCs, reduction of regeneration time, and cost, it is preferable that the aforementioned precious metal is contained in an amount of 0.7 g / L to 1.2 g / L. Below 0.5 g / L, the amount of purification by oxidative decomposition of heavy VOCs and the reduction of regeneration time are insufficient and therefore undesirable. On the other hand, above 1.5 g / L, the cost is high and therefore undesirable. [Examples]

[0112] The embodiments of the present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. The obtained porous silica was evaluated using the following apparatus.

[0113] (Observation using an electron microscope) Analysis equipment: A scanning electron microscope, JSM-6610LA, manufactured by JEOL Ltd., was used. The sample was directly fixed to the sample stage with double-sided carbon tape at an acceleration voltage of 15kV, and images were observed in low vacuum mode.

[0114] (Specific surface area, total pore volume, micropore volume, micro-average pore diameter) The samples were pre-treated at 200°C for 3 hours under vacuum. The IUPAC classification and BET specific surface area were determined from nitrogen absorption isotherms measured at liquid nitrogen temperature (-196°C) using a BELSORP-max from Microtrac-Bel Corporation. The total pore volume was determined as the sum of the mesopore volume and micropore volume from the maximum absorption amount at relative pressure (P / P0 = 0.980). The micropore volume and average micropore diameter were determined using the t-plot method, with the micropore volume obtained from the intercept of the second line and the average micropore diameter (2t) from the inflection point. The micropore distribution was then shown using the MP method, which differentiates the curvature near the inflection point of the t-plot.

[0115] (Example 1) L-64 In Example 1, porous silica was synthesized using a nonionic surfactant consisting of a triblock copolymer containing polyethylene oxide (PEO)-polypropylene oxide (PEO)-polyethylene oxide (PEO), with a weight-average molecular weight of 2900 and 40% ethylene oxide (PEO) in the total molecule. The resulting porous silica was used to synthesize porous silica.

[0116] Specifically, 245g of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 40% of total molecules) and 1540g of deionized water were added to a glass container (5L) while stirring. Next, 130g of sodium chloride (99% or more) and 290g of concentrated hydrochloric acid (37%) were added. Then, stirring was continued at 35-40°C for 4 hours to fully dissolve the ADEKA® Pluronic L-64 and form associative micelles.

[0117] To the aforementioned solution, 711 g of tetraethoxysilane (TEOS) was added as an alkoxysilane, and the bath temperature was raised to 50-55°C. After that, it was slowly cooled and the bath temperature was maintained at 35-40°C while stirring was continued to hydrolyze the alkoxysilane. This solution was used as the precursor solution.

[0118] Subsequently, the precursor solution was heated to 90-100°C and held for 3-4 hours to mature, completing the gelation process, and the entire solution became a colorless, gel-like solid visible to the naked eye.

[0119] Next, the gel-like solid was filtered and washed repeatedly until the washing water reached a pH of 5-6. Then, it was transferred to a refractory container, dried, and then fired at 550°C for 3 hours to obtain porous silica.

[0120] (Example 2) L-34 In Example 2, porous silica was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-34 (weight-average molecular weight 1700, ethylene oxide (PEO) 40% of the total molecule) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 40% of the total molecule) which was a nonionic surfactant in Example 1.

[0121] (Example 3) L-72 In Example 3, porous silica was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-72 (weight-average molecular weight 2750, total molecular weight 20% ethylene oxide (PEO)) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, total molecular weight 40% ethylene oxide (PEO)) which was a nonionic surfactant in Example 1.

[0122] (Example 4) L-62 In Example 4, porous silica was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-62 (weight-average molecular weight 2500, total molecular weight 20% ethylene oxide (PEO)) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, total molecular weight 40% ethylene oxide (PEO)) which was a nonionic surfactant in Example 1.

[0123] (Example 5) L-42 In Example 5, porous silica was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-42 (weight-average molecular weight 1630, total molecular weight 20% ethylene oxide (PEO)) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, total molecular weight 40% ethylene oxide (PEO)) which was a nonionic surfactant in Example 1.

[0124] (Example 6) L-44 In Example 6, porous silica was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-44 (weight-average molecular weight 2200, ethylene oxide (PEO) 40% of total molecules) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 39.7% of total molecules) which was a nonionic surfactant in Example 1.

[0125] (Comparative example 1) P-123 Comparative Example 1 involved stirring a nonionic surfactant, triblock copolymer PEO-PPO-PEO (Pluronic P-123, weight-average molecular weight 5800, manufactured by BASF), with hydrochloric acid at 45°C at approximately 550 rpm. After 10 minutes, sodium chloride was added, and after another 10 minutes, a mixture of TPEOS and water was added. In this example, the amount of sodium chloride added was varied, and the molar ratio of the mixed solution was set to TPEOS:P123:HCl:H2O:NaCl = 1:0.017:5.85:199:1.495. After stirring this mixed solution for another hour, stirring was stopped, and the solution was transferred to a constant temperature water bath preheated to 80°C and aged for 3 hours. The solid product was filtered from the reaction suspension, thoroughly dried at 60°C, and then heated at 600°C for 1 hour to remove organic components and obtain fibrous mesoporous silica particles. Comparative Examples 1 to 5 correspond to Examples 1 to 5 of Patent Document 2.

[0126] (Comparative example 2) P-103 Comparative Example 2 was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 40% of the total molecule) was replaced with ADEKA® Pluronic P-103 (weight-average molecular weight 4900, ethylene oxide (PEO) 30% of the total molecule) as the nonionic surfactant used in Example 1.

[0127] (Comparative example 3) L-61 Comparative Example 3 was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-61 (weight-average molecular weight 2000, ethylene oxide (PEO) 10% of total molecules) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 39.7% of total molecules), which is a nonionic surfactant used in Example 1.

[0128] (Comparative example 4) P-65 Comparative Example 4 was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 40% of total molecules) was used instead of the nonionic surfactant ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 40% of total molecules) used in Example 1.

[0129] (Comparative example 5) L-31 Comparative Example 5 was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-31 (weight-average molecular weight 1100, total molecular weight 10% ethylene oxide (PEO)) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, total molecular weight 40% ethylene oxide (PEO)) which was a nonionic surfactant in Example 1.

[0130] (Comparative example 6) L-35 Comparative Example 6 was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-35 (weight-average molecular weight 1900, total molecular weight 50% ethylene oxide (PEO)) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, total molecular weight 40% ethylene oxide (PEO)) which was a nonionic surfactant in Example 1.

[0131] (Comparative Example 7) L-23 Comparative Example 7 was synthesized in the same manner as in Example 1, except that ADEKA® Pluronic L-23 (weight-average molecular weight 1055, ethylene oxide (PEO) 30% of the total molecule) was used instead of ADEKA® Pluronic L-64 (weight-average molecular weight 2900, ethylene oxide (PEO) 40% of the total molecule), which was a nonionic surfactant in Example 1.

[0132] (Comparative Example 8) A solution of Pluronic F88 (weight-average molecular weight 11400, hydrophilic PEO content 80%, manufactured by BASF), consisting of the triblock copolymer PEO-PPO-PEO, dissolved in 2N hydrochloric acid, was to which an aqueous sodium silicate solution, diluted with water using commercially available JIS No. 3 sodium silicate, was added while stirring at 600 rpm. The molar ratio of the mixed solution was SiO2:Pluronic F88:Na2O:HCl:H2O = 1:0.0064:0.312:3.93:152. Note that H2O includes water derived from all raw materials. The reaction temperature was 25°C to 27°C, and after stirring for 2 hours, the solid product was filtered off, washed with 60°C hot water, and thoroughly dried at 50°C. Finally, the organic components were removed by calcination in an electric furnace at 600°C for 1 hour to obtain perfectly spherical, shaped porous silica particles. Comparative Example 8 corresponds to Example 8 of Patent Document 3.

[0133] (Comparative Example 9) 8 g (0.038 mol; 1 eq) of tetraethoxysilane (TEOS) was placed in a polypropylene container as a silica source, followed by the dispersion of a cationic surfactant at a concentration of 0.2 to 1.2 eq (0.038 mol × 0.2 to 0.038 mol × 1.2), and the mixture was stirred. At this point, the TEOS and the surfactant did not mix; that is, a homogeneous mixture was not formed. Dodecyltrimethylammonium bromide was used as the cationic surfactant to synthesize porous silica.

[0134] Next, 2 to 4 eq (0.038 mol × 2 to 0.038 mol × 4) of water, whose pH was adjusted to approximately 0 to 2 using hydrochloric acid, was added to the above mixture and stirred at room temperature. After stirring for about an hour, hydrolysis of TEOS proceeded, and a nearly homogeneous solution was obtained. This solution (precursor solution) was kept at room temperature or 60°C and continuously stirred or allowed to stand. Gelation was completed in 12 hours to several days, and the entire solution became a colorless, transparent gel visible to the naked eye. This gel was dried at 60°C and calcined at 600°C for 3 hours to remove the surfactant. As a result, a colorless, transparent, monolithic porous silica was obtained.

[0135] (Comparative Example 10) Comparative Example 10 yielded porous silica in the same manner as Comparative Example 9, except that decyltrimethylammonium bromide was used instead of dodecyltrimethylammonium bromide, the cationic surfactant used in Comparative Example 9.

[0136] (Comparative Example 11) Comparative Example 11 was obtained in the same manner as in Comparative Example 9, except that decyltrimethylammonium bromide was used instead of dodecyltrimethylammonium bromide, the cationic surfactant used in Comparative Example 9.

[0137] (Comparative Example 12) Comparative Example 12 obtained porous silica in the same manner as in Comparative Example 9, except that hexyltrimethylammonium bromide was used instead of dodecyltrimethylammonium bromide, the cationic surfactant used in Comparative Example 9.

[0138] (Comparative Example 13) Comparative Example 13 obtained porous silica in the same manner as in Comparative Example 9, except that butyltrimethylammonium chloride was used instead of dodecyltrimethylammonium bromide, the cationic surfactant used in Comparative Example 9.

[0139] (Comparative Example 14) [Pore size control by adding organic silanes] Comparative Example 14 was obtained in the same manner as Comparative Example 9, except that triethoxyvinylsilane was added to the precursor solution of Comparative Example 11.

[0140] Specifically, 8 g (0.038 mol; 1 eq) of tetraethoxysilane (TEOS) and 8 g × 5% (0.038 mol × 5%) of triethoxyvinylsilane (TEVS) were mixed in a polypropylene container as a silica source. Subsequently, 0.2 to 1.2 equivalents of a surfactant were added and the mixture was stirred. To this mixture, 2 to 4 equivalents of water adjusted to pH 0 to 2 using hydrochloric acid were added and the mixture was stirred at room temperature. After about 1 hour of stirring, hydrolysis of TEOS proceeded, and a nearly homogeneous solution was obtained. Furthermore, this solution (precursor solution) was maintained at room temperature or 60°C and continuously stirred or allowed to stand. Gelation was completed in 12 hours to several days, and the entire solution became a colorless, transparent gel visible to the naked eye. This gel was dried at 60°C and calcined at 600°C for 3 hours to remove the surfactant. The surfactant used was a cationic surfactant consisting of octyltrimethylammonium bromide.

[0141] (Comparative Example 15) Comparative Example 15 was obtained in the same manner as Comparative Example 14, except that hexyltrimethylammonium bromide was used instead of octyltrimethylammonium bromide, the cationic surfactant used in Comparative Example 14.

[0142] (Comparative Example 16) Comparative Example 16 was obtained in the same manner as Comparative Example 14, except that butyltrimethylammonium chloride was used instead of octyltrimethylammonium bromide, the cationic surfactant used in Comparative Example 14.

[0143] Tables 5-7 show the types of raw materials, blending ratios, and synthesis conditions for the porous silica in Examples 1-6 and Comparative Examples 1-16. Furthermore, Figure 4 shows the relationship between the proportion of hydrophilic parts in the total molecule and the weight-average molecular weight, and Figure 5 shows the relationship between the proportion of hydrophilic parts in the total molecule and the molecular weight of the hydrophobic parts.

[0144] Table 8 shows the pore analysis results for porous silica in Examples 1-6 and Comparative Examples 1-16, including the IUPAC classification of absorption isotherms, BET specific surface area, total pore volume (A), average micropore diameter, micropore volume (B), and the percentage of micropore volume (B) to total pore volume (A).

[0145] (Nitrogen absorption isotherms) Figure 6 shows the nitrogen absorption isotherms of porous silica for Examples 1 and 2 as an example of the present invention, and Comparative Examples 2, 4, 5, and 7 as an example of the prior art. Similarly, Figure 7 shows the nitrogen absorption isotherms of porous silica for Examples 1 and 2 as an example of the present invention, and Examples 12 and 15 as examples of the prior art.

[0146] (Micropore size distribution) Figure 8 shows the micropore size distribution of porous silica in Examples 1 and 2 as an example of the present invention, and Comparative Examples 4 and 7 as an example of the prior art. Similarly, Figure 9 shows the micropore size distribution of porous silica in Examples 1 and 2 as an example of the present invention, and Comparative Examples 12 and 15 as examples of the prior art.

[0147] (Relationship between average micropore diameter and pore volume) Figure 10 shows the relationship between the average diameter of the micropores and the pore volume in porous silica of Examples 1-6 and Comparative Examples 1-16.

[0148] [Table 5]

[0149] [Table 6]

[0150] [Table 7]

[0151] [Table 8]

[0152] (Embodiment 2) Fabrication of a metal honeycomb flowing body The metal honeycomb flow system of the present invention uses metal foil made of ferritic stainless steel Fe-20Cr-5Al (JFE20-5USR, manufactured by JFE Steel Corporation, 30 μm thick, 120 mm wide). A corrugated foil and a flat foil without corrugation are arranged in a wave-like shape, with a brazing material inserted between them and on the top surface of the flat foil. The winding tension is kept constant, resulting in a wave-like cell shape of 300 cells / inch. 2 A metal honeycomb section was fabricated by winding it onto a roll with a diameter of 122 mm.

[0153] For the outer cylinder, a sheet of stainless steel (SUS304, 1.5 mm thick, 140 mm wide) was prepared in advance. This sheet was then cut to a length that resulted in an inner diameter of 122 mm when rolled into a cylinder, and the outer cylinder was processed into a curved shape using a roll bending machine.

[0154] Next, the metal honeycomb section was enclosed in a curved outer cylinder, a brazing material was inserted between them, the ends of the outer cylinder were welded together, and then the brazing material was heated and fused in a vacuum heating furnace to produce a metal honeycomb flow body (honeycomb section diameter 122 mm x width 120 mm, volume 1.4 L).

[0155] (Embodiment 3) Method for coating porous silica First, 200g of the sample was mixed with 800g of deionized water and 200g of alumina sol AS200 (alumina component 10wt%, manufactured by Nissan Chemical Corporation), and a slurry was made using a ball mill. Next, a metal honeycomb (honeycomb section diameter 122mm, length 120mm, volume 1.40L, cell count 300 / inch) was used. 2 The sample was applied to a metal honeycomb (manufactured by ACR Corporation), dried, and fired at 500°C to adjust the loading amount of each sample to 100±15 g / L, thereby producing porous silica-coated metal honeycomb flow bodies (hereinafter referred to as Examples 1M to 6M and Comparative Examples 1M to 16M).

[0156] (Embodiment 4) Method for coating porous silica containing a precious metal catalyst (Example 7PM) Example 7PM is an example of a metal honeycomb flow body that absorbs, concentrates, purifies, and regenerates heavy VOCs, made of porous silica containing the platinum catalyst of the present invention. First, 16.0 g of a platinum salt solution (dinitrodiamine Pt(II) nitrate solution, 8.368% as Pt, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was mixed with 2,000 g of deionized water to prepare a platinum-supported solution. Next, a metal honeycomb flow body coated with 92 g / L of porous silica from Example 2M was immersed in the platinum-supported solution for 12 hours so that the entire honeycomb portion was submerged. After that, it was dried and calcined at 500°C for 2 hours to prepare the metal honeycomb flow body of Example 7M, which was coated with porous silica containing 0.75 g / L of platinum.

[0157] (Example 8 PPM) Example 8 PPM is an example of a metal honeycomb flow body that absorbs, concentrates, purifies, and regenerates heavy VOCs, consisting of porous silica containing the platinum and palladium catalysts of the present invention. In this example, 4.0 g of palladium salt solution (palladium(II) nitrate solution, 8.300% as Pd, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was mixed with 500 g of deionized water to prepare a palladium-supported solution.

[0158] The metal honeycomb flow body of Example 7PM was immersed in a palladium-supported solution for 12 hours, with the immersion reaching 30 mm from the end of the honeycomb portion. Subsequently, it was dried and calcined at 500°C for 2 hours to produce the metal honeycomb flow body of Example 8PPM, which was coated with porous silica containing 0.25 g / L of palladium.

[0159] (Embodiment 5) Cyclic testing of heavy VOCs Cycle tests of absorption and concentration, purification and regeneration, and cooling processes were performed for Examples 1M-6M, 7PM, 8PPM, and Comparative Examples 1M-16M. Hexyl acetate (boiling point: 169.2°C, Chapman (2009)) was used as the heavy VOC.

[0160] (Adjustment of the concentration of volatile gas produced by heating hexyl acetate) In a volatilization device, hexyl acetate is heated to 150°C to volatilize it and mixed with air. The resulting 150 ppm hexyl acetate volatilized gas is then passed through the metal honeycomb flow chamber at a volume of 1.4 L and a space velocity of 30,000 h. -1 The inlet gas temperature of the meta-honeycomb flow chamber was adjusted to 60°C.

[0161] (Hexyl acetate absorption and concentration process) Furthermore, the endpoint of absorption concentration was defined as the point when the leak concentration of xyl acetate as hydrocarbons reached 30 ppm at the metal honeycomb flow outlet.

[0162] (Hexyl acetate purification and regeneration process) Immediately after the end point of the absorption and concentration process, a superheater is used to heat the air to a space velocity of 22,000 h⁻¹. -1 The metal honeycomb flow chamber was then flowed in so that the inlet gas temperature reached 200°C, and hexyl acetate was desorbed and purified for 15 minutes.

[0163] (Cooling process for metal honeycomb flow system) Immediately after 15 minutes have elapsed since the hexyl acetate desorption and purification, ambient air is introduced into the metal honeycomb flow medium at a spatial velocity of 22,000 h⁻¹. -1 The mixture was then poured in, and the metal honeycomb flowing body was cooled.

[0164] (Repeating cycle) The three steps of hexyl acetate absorption and concentration, purification and regeneration, and cooling were repeated again.

[0165] The test setup is shown in Figure 11. The inlet and outlet gas concentration detectors for the metal honeycomb flow chamber were Horiba, Ltd.'s MOTOR EXHAUST GAS ANALYZER MEXA-7100DEGR, and the hydrocarbon concentration was measured. Furthermore, at the outlet, the concentration of the purified and decomposed gas components was measured using DATABIRD's FT-IR MOTOR EXHAUST GAS ANALYZER FAST-2100.

[0166] Figures 12 to 14 show an example of the cycle test results, and Table 9 shows the dynamic absorption amount of hexyl acetate.

[0167] (Purification and regeneration effect of hexyl acetate by precious metal catalysts) Figure 16 shows a comparison of the inlet and outlet temperatures of the metal honeycomb flow bodies in Examples 2M, 7PM, and 8PPM during the purification and regeneration of hexyl acetate by heating at 200°C.

[0168] In Example 2M, the metal honeycomb flow material reached an outlet temperature of approximately 220°C when the inlet temperature reached 200°C, shifting to a higher temperature of approximately 20°C due to an exothermic reaction caused by the oxidative decomposition of hexyl acetate. On the other hand, in Example 7PM, the metal honeycomb flow material reached an outlet temperature of approximately 330°C when the inlet temperature was around 180°C, shifting to a higher temperature of approximately 150°C due to an exothermic reaction caused by the oxidative decomposition of hexyl acetate. Furthermore, in Example 8PPM, the metal honeycomb flow material reached an outlet temperature of approximately 340°C when the inlet temperature was around 170°C, shifting to a higher temperature of approximately 160°C due to an exothermic reaction caused by the oxidative decomposition of hexyl acetate.

[0169] Tables 10 to 12 show the gas composition detected by FT-IR analysis at the outlet of the metal honeycomb flow chamber when the inlet temperature of the metal honeycomb flow chamber reaches 170-200°C. Example 8 PPM can be purified to the largest amount of H2O and CO2 by oxidative decomposition of hexyl acetate (Equation 1).

[0170]

number

[0171] Figure 17 shows the change in hydrocarbon (HC) concentration during the purification and regeneration time at 200°C. Example 8 PPM showed the shortest time to purify and regenerate hydrocarbons (HC).

[0172] Example 7PM, which contains platinum, shows improved purification and regeneration performance compared to Example 2M due to the effect of the oxidation catalyst. This reduces the thermal energy required for heating, shortens the regeneration time, and enables highly efficient heavy VOC treatment. Furthermore, Example 8PPM, which contains platinum and palladium, shows even better purification and regeneration performance than Example 7PM due to the effect of the oxidation catalyst. This further reduces the thermal energy required for heating, shortens the regeneration time, and enables highly efficient heavy VOC treatment.

[0173] [Table 9]

[0174] [Table 10]

[0175] [Table 11]

[0176] [Table 12] [Industrial applicability]

[0177] The present invention relates to a triblock copolymer containing polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide (PEO) as a safe and environmentally friendly nonionic surfactant, which has a weight-average molecular weight of more than 1,500 to less than 3,000 and a hydrophilic portion of more than 10% to less than 50% of the total molecule, and is used as a template with a micropore volume of 0.35 cm³. 3Having discovered porous silica with a large concentration of over / g and an average micropore diameter of 0.8nm to 1.15nm, it can absorb more than twice the amount of heavy VOCs compared to conventional technologies. Furthermore, by using the metal honeycomb and / or oxidation catalyst of the present invention, it is possible to process large amounts of heavy VOCs in short cycles for purification and regeneration, making it particularly effective for industrial applications such as finely stacked electronic components.

Claims

[Claim 1] It has micropores that can be identified by the IUPAC adsorption isotherm classification, The average diameter of the micropores is 0.94 nm to 1.15 nm. Micropore volume is 0.45 cm³ ３ / g ~ 0.55cm ３ Porous silica characterized by having a density of / g.

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