Porous silica and method for producing same

Abstract

This porous silica comprises mesopores A having a peak diameter of not less than 1 nm but less than 5 nm, mesopores B having a peak diameter of not less than 5 nm but less than 100 nm, and macropores C having a peak diameter of 0.1-0.5 µm. The porous silica according to the present invention exhibits less pressure loss and high flow rate characteristics, and can be suitably used as a filler or the like for use in a chromatography column. The porous silica is also expected for use in applications known for porous silicas, such as a carrier for a gas absorbent.

Description

Porous silica and method for producing same

[0001] The present invention relates to porous silica and a method for producing the same.

[0002] Mesoporous silica has been developed to date, possessing macropores with functionality such as flow and diffusion, and mesopores that are expected to provide a high specific surface area, and is expected to be used as a packing material for chromatography columns.

[0003] Patent Document 1 discloses a method for producing a dual-pore oxide having nanopores and macropores. The invention specifically described in Patent Document 1 makes it possible to form interconnected through-pores (macropores) having a micropore size in the micrometer range by adding a water-soluble polymer, and by simultaneously providing pores having a micropore size in the nanometer range (nanopores), dual-pore silica having a high specific surface area and good fluidity and diffusibility can be obtained.

[0004] Japanese Patent Application Laid-Open No. 2017-222529

[0005] However, the material disclosed in Patent Document 1 may have problems with liquid permeability and breathability, and further improvement is required.

[0006] An object of the present invention is to provide porous silica having excellent liquid permeability and air permeability, and a method for producing the same.

[0007] The present invention relates to the following items [1] to [3]. [1] Porous silica having mesopores A with peak diameters of 1 nm or more and less than 5 nm, mesopores B with peak diameters of 5 nm or more and less than 100 nm, and macropores C with peak diameters of 0.1 μm or more and 0.5 μm or less. [2] A method for producing porous silica according to item [1], comprising the steps of introducing a silica source into a structure-directing agent solution containing an acid to cause a polycondensation reaction, and removing the structure-directing agent from the resulting polycondensation reaction product. [3] The method for producing porous silica according to item [2], further comprising the step of performing a diameter-enlarging treatment using water or water vapor before removing the structure-directing agent.

[0008] According to the present invention, it is possible to provide porous silica having excellent liquid permeability and air permeability, and a method for producing the same.

[0009] FIG. 1 is a pore distribution diagram of the porous silica prepared in Examples 1 to 5 in nitrogen adsorption measurement. FIG. 2 is a pore distribution diagram of the porous silica prepared in Examples 6 to 8 in nitrogen adsorption measurement. FIG. 3 is a pore distribution diagram of the porous silica prepared in Comparative Examples 1 to 4 in nitrogen adsorption measurement. FIG. 4 is a pore distribution diagram of the porous silica prepared in Examples 1 to 5 in mercury porosimetry. FIG. 5 is a pore distribution diagram of the porous silica prepared in Examples 6 to 8 in mercury porosimetry. FIG. 6 is a pore distribution diagram of the porous silica prepared in Comparative Examples 1 to 4 in mercury porosimetry. FIG. 7 is an electron microscope image of the porous silica prepared in Example 1. FIG. 8 is a graph showing the flow rate and column pressure loss of the porous silica prepared in Examples 1 to 5. FIG. 9 is a graph showing the flow rate and column pressure loss of the porous silica prepared in Examples 6 to 8. FIG. 10 is a graph showing the flow rate and column pressure loss of the porous silica prepared in Comparative Examples 1 to 4.

[0010] The porous silica of the present invention has mesopores A having a peak diameter of 1 nm or more and less than 5 nm, mesopores B having a peak diameter of 5 nm or more and less than 100 nm, and macropores C having a peak diameter of 0.1 μm or more and less than 0.5 μm.

[0011] The peak diameter of mesopores A is 1 nm or more and less than 5 nm, preferably 1.5 nm or more and 4 nm or less, more preferably 2 nm or more and 3.5 nm or less, and even more preferably 2 nm or more and 3 nm or less, from the viewpoint of the exclusion limit when used in a chromatography column. The peak diameter of mesopores A herein is measured by the BJH method in nitrogen adsorption measurement. From the viewpoint of obtaining a high specific surface area, the porous silica of the present invention is preferably mesoporous silica in which mesopores A are regularly arranged. The regular arrangement of mesopores A can be confirmed using an electron microscope.

[0012] The peak diameter of mesopores B is 5 nm or more and less than 100 nm, preferably 8 nm or more and less than 80 nm, more preferably 10 nm or more and less than 70 nm, and even more preferably 15 nm or more and less than 70 nm, from the viewpoint of liquid permeability and breathability. Furthermore, from the viewpoint of liquid permeability and breathability, the peak diameter can be 30 nm or more and less than 100 nm, 40 nm or more and less than 100 nm, 50 nm or more and less than 100 nm, 55 nm or more and less than 100 nm, or 60 nm or more and less than 100 nm. The peak diameter of mesopores B herein can be confirmed by the BJH method in nitrogen adsorption measurement.

[0013] From the viewpoint of liquid permeability and air permeability, the peak diameter of the macropores C is 0.1 μm or more and 0.5 μm or less, preferably 0.1 μm or more and 0.4 μm or less, and more preferably 0.1 μm or more and 0.3 μm or less. The peak diameter of the macropores C in this specification can be confirmed by mercury intrusion porosimetry.

[0014] The specific surface area of ​​the porous silica of the present invention is preferably 100 to 900 m from the viewpoint of the adsorption area. ２ / g, more preferably 150 to 850 m ２ / g, more preferably 200 to 800 m ２ / g, more preferably 220 to 750 m ２ / g, more preferably 240 to 720 m ２ The specific surface area is measured by the BET method in nitrogen adsorption measurement.

[0015] The porous silica of the present invention has excellent liquid permeability and air permeability, and can be suitably used as a packing material for use in a chromatography column. Accordingly, the present invention provides a chromatography packing material containing the porous silica of the present invention.

[0016] The method for producing the porous silica of the present invention is not particularly limited, but a preferred production mode will be described below.

[0017] The method for producing porous silica of this embodiment can include a production method comprising the steps of adding a silica source to a structure-directing agent solution containing an acid to carry out polycondensation reaction, and removing the structure-directing agent from the resulting polycondensation reaction product.That is, by mixing and reacting the inorganic raw material that is the silica source with the organic raw material that is used as the structure-directing agent, an organic-inorganic composite is formed in which the structure-directing agent is used as a template around which the inorganic skeleton is formed.Then, after washing with water or hot water, drying is carried out, and the organic structure-directing agent is removed from the resulting composite, thereby obtaining the porous silica of the present invention.

[0018] The production method of this embodiment may further include a step of optionally performing a diameter-enlarging treatment using water or steam after washing or washing and drying the composite and before removing the organic substance serving as the structure-directing agent from the composite. The diameter-enlarging treatment can enlarge the pore diameter, and in particular, can control the pore diameter of the mesopores B.

[0019] As the structure-directing agent in the structure-directing agent solution, an organic raw material can be used, such as a surfactant. The surfactant may be cationic, anionic, or nonionic. Specific examples include chlorides, bromides, iodides, or hydroxides of alkyltrimethylammonium (preferably alkyltrimethylammonium having an alkyl group containing 8 to 22 carbon atoms), alkylammonium, dialkyldimethylammonium, and benzylammonium, as well as fatty acid salts, alkyl sulfonates, alkyl phosphates, polyethylene oxide-based nonionic surfactants, primary alkylamines, triblock copolymer-type polyalkylene oxides, glycerin fatty acid esters, and polyglycerin fatty acid esters. However, alkyltrimethylammonium salts such as dodecyltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, and behenyltrimethylammonium chloride are preferred. These surfactants can be used alone or in combination of two or more.

[0020] The concentration of the structure-directing agent is preferably 0.01 to 0.20 mol / L, more preferably 0.03 to 0.20 mol / L, even more preferably 0.03 to 0.15 mol / L, and still more preferably 0.05 to 0.12 mol / L, relative to the water in the reaction system.

[0021] Examples of the solvent in the structure-directing agent solution include water, a mixture of water and an organic solvent, etc. Examples of the organic solvent that can be used include water-soluble alcohols such as methanol, ethanol, propanol, 2-propanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol, and polyglycerol.

[0022] The structure-directing agent solution contains an acid in addition to the organic raw materials, and examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid and citric acid. The pH of the structure-directing agent solution can be 2 or less, 1.8 or less, or 1.5 or less, but from the viewpoint of forming pores B, it is preferable to adjust the concentration of the acid so that the pH of the structure-directing agent solution during the condensation polymerization reaction, i.e., the pH after the silica source is added, is preferably 2 to 7, more preferably 3 to 7, and even more preferably 3 to 6.

[0023] Examples of silica sources include sodium silicate, kanemite (NaHSi ２ O ５ ・3H ２ Examples of inorganic raw materials include silica, silica, and silica-metal composite oxides. These inorganic raw materials form a silicate skeleton. They can be used alone or in combination of two or more. Among these, sodium silicate is preferably used because it is inexpensive, non-flammable, and does not require explosion-proof equipment.

[0024] The concentration of the silica source relative to the water in the reaction system is preferably 0.1 to 1.0 mol / L, more preferably 0.2 to 0.9 mol / L, even more preferably 0.2 to 0.8 mol / L, and still more preferably 0.2 to 0.7 mol / L.

[0025] The reaction temperature for the polycondensation reaction varies depending on the type and concentration of the organic and inorganic raw materials used, but is preferably 5 to 90°C, more preferably 35 to 85°C, and even more preferably 50 to 80°C.

[0026] The reaction time for the polycondensation reaction is not particularly limited, but is preferably 1 to 24 hours, more preferably 1 to 12 hours, even more preferably 1 to 6 hours, and from the viewpoint of shortening the production time, even more preferably 1 to 4 hours. The polycondensation reaction may be carried out in a static state or in a stirred state, or in a combination thereof.

[0027] The washing method is not particularly limited, but may be carried out by re-dispersing the filtered condensation polymerization reaction product in ion-exchanged water, RO water, or distilled water containing no impurities at a temperature of preferably 5 to 100°C, more preferably 5 to 90°C, and even more preferably 5 to 80°C, and then filtering again, or by continuously passing ion-exchanged water through the condensation polymerization reaction product stacked like a column. These methods may also be combined, and may be repeated.

[0028] The diameter expansion treatment is preferably carried out by adding ion-exchanged water, RO water, or distilled water to the washed polycondensation reaction product and adjusting the temperature to 5 to 90°C, and from the viewpoint of diameter expansion efficiency, adjusting the temperature to 40 to 80°C is more preferable. A drying treatment may be carried out before or after the diameter expansion treatment. The time for the diameter expansion treatment varies depending on the treatment temperature and the desired pore diameter, but examples include treatment for 1 to 10 hours, and from the viewpoint of shortening the production time, treatment for 0.5 to 6 hours.

[0029] The diameter expansion treatment can also be carried out using water vapor, which is gaseous water. The washed condensation polymerization reaction product is preferably exposed to an environment of 10 to 100% RH and 0 to 100°C, more preferably 30 to 100% RH and 15 to 90°C, and even more preferably 50 to 100% RH and 35 to 80°C in terms of temperature and humidity control. Furthermore, when a drying treatment is carried out before the diameter expansion treatment, carrying out the diameter expansion treatment with water vapor allows the diameter of the condensation polymerization reaction product to be expanded without being placed in a liquid, which has the advantage of simplifying the manufacturing process. Furthermore, diameter expansion treatments using water or water vapor can also be used in combination, and these may be carried out multiple times.

[0030] The porous silica of this embodiment can be obtained by removing the organic raw materials from the polycondensation reaction product. The method for removing the organic material from the composite of organic and inorganic materials is not particularly limited, but can be, for example, a method of baking at 250 to 1000°C in an air atmosphere, a method of treating with a solvent such as acid, water, or alcohol, or a combination of these methods.

[0031] Examples and comparative examples are shown below, but the present invention is not limited to these examples. For the porous silica of each example and comparative example, the peak diameter of small mesopores A and the peak diameter of large mesopores B were confirmed by the BJH method of nitrogen adsorption measurement (apparatus: BELSORP mini II manufactured by BEL Japan Co., Ltd.), the peak diameter of macropores C was confirmed by mercury intrusion porosimetry (apparatus: AutoPore V9620 manufactured by Micromeritics Co., Ltd.), and the specific surface area was confirmed by the BET method of nitrogen adsorption measurement, and these results are summarized in Table 1. In addition, Figures 1 to 6 show the pore size distribution of the porous silica of each example and comparative example.

[0032] Preparation of Porous Silica Example 1 8.1 kg of cetyltrimethylammonium chloride and 5.7 kg of ethanol were added to 216 kg of 2.2 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 15.5% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 92 kg of an aqueous solution of 2.09% ethanol (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 5. The resulting polycondensation reaction product was then filtered and dispersed in 2,000 kg of ion-exchanged water. This filtration / dispersion procedure was repeated five times to wash the polycondensation reaction product. The polycondensation reaction product was dried at 70°C, and the dried polycondensation reaction product was exposed to an environment of 70°C and 50% relative humidity for 48 hours to undergo a diameter expansion treatment. The expanded polycondensation reaction product was calcined in air at 700°C for 2 hours to obtain porous silica having multiple mesopores and macropores with different pore diameters. An electron microscope image of the resulting porous silica (Figure 7) confirmed the presence of regularly connected small mesopores A.

[0033] Preparation of Porous Silica Example 2 28.4 kg of cetyltrimethylammonium chloride and 20.3 kg of ethanol were added to 754 kg of 2.2 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 14.9% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 298 kg of an aqueous solution of 2.09% ethanol (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 3.5. The resulting polycondensation reaction product was then filtered and dispersed in 2,000 kg of ion-exchanged water. This filtration and dispersion procedure was repeated five times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was further subjected to a diameter expansion treatment by passing ion-exchanged water at 55°C through it for 6 hours and then dried at 70°C. The dried polycondensation reaction product was exposed to an environment of 70°C and 100% relative humidity for 24 hours to further undergo a diameter expansion treatment. The diameter-expanded polycondensation reaction product was then calcined in air at 700°C for 2 hours to obtain porous silica having multiple mesopores and macropores with different pore diameters. An electron microscope image (not shown) of the resulting porous silica confirmed the presence of regularly connected small mesopores A.

[0034] Preparation of Porous Silica Example 3 28.4 kg of cetyltrimethylammonium chloride and 20.3 kg of ethanol were added to 754 kg of 2.2 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 14.9% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 298 kg of an aqueous solution of 2.09% ammonium hydroxide (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 3.5. The resulting polycondensation reaction product was then filtered, and ion-exchanged water was continuously passed through the filtrate to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was further subjected to a diameter-expansion treatment by passing ion-exchanged water at 55°C through it for 6 hours, and the polycondensation reaction product was then dried at 70°C. The dried polycondensation reaction product was exposed to an environment of 70°C and 100% relative humidity for 48 hours to further undergo a diameter-expansion treatment. The diameter-expansion-treated polycondensation reaction product was calcined in air at 700°C for 2 hours to obtain porous silica having multiple mesopores and macropores with different pore diameters. An electron microscope image (not shown) of the resulting porous silica confirmed the presence of regularly connected small mesopores A.

[0035] Preparation of Porous Silica Example 4 28.4 kg of cetyltrimethylammonium chloride and 19.5 kg of ethanol were added to 681 kg of 2.4 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 25.7% No. 1 sodium silicate (SiO ２ / Na ２ 229 kg of an aqueous solution of 2.09% ethanol (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 4. The resulting polycondensation reaction product was then filtered and dispersed in 2,000 kg of ion-exchanged water. This filtration / dispersion procedure was repeated five times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was further subjected to a diameter-expansion treatment by passing ion-exchanged water at 55°C through it for 6 hours, and the polycondensation reaction product was dried at 70°C. The diameter-expansion-treated polycondensation reaction product was calcined in air at 700°C for 2 hours to obtain porous silica having multiple mesopores and macropores with different pore diameters. An electron microscope image (not shown) of the resulting porous silica confirmed the presence of regularly connected small mesopores A.

[0036] Preparation of Porous Silica Example 5 9.7 kg of cetyltrimethylammonium chloride and 4 kg of ethanol were added to 207 kg of 2.5 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 16.9% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 113 kg of an aqueous solution (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 3.8. The resulting polycondensation reaction product was then filtered and dispersed in 1,000 kg of ion-exchanged water. This filtration / dispersion procedure was repeated five times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was further subjected to a diameter expansion treatment by passing ion-exchanged water at 50°C through it for 3 hours. The polycondensation reaction product that had undergone the diameter expansion treatment was calcined in air at 700°C for 2 hours without drying to obtain porous silica having multiple mesopores and macropores with different pore diameters. An electron microscope image (not shown) of the resulting porous silica confirmed the presence of regularly connected small mesopores A.

[0037] Preparation of Porous Silica Example 6 9.7 kg of cetyltrimethylammonium chloride and 6.8 kg of ethanol were added to 252 kg of 2.2 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 8.4% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 179 kg of an aqueous solution of 1,2-dimethyl-2,4-trimethyl-1,2,4-trimethyl-2,4-trimethyl-1 ...

[0038] Preparation of Porous Silica Example 7 9.7 kg of cetyltrimethylammonium chloride and 6.8 kg of ethanol were added to 253 kg of 2.2 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 9% No. 1 sodium silicate (SiO ２ / Na ２169 kg of an aqueous solution of 1,2-dimethyl-2,4-trimethyl-1,4-dichloro ...

[0039] Preparation of Porous Silica Example 8 9.7 kg of cetyltrimethylammonium chloride and 6.8 kg of ethanol were added to 253 kg of 2.2 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 9% No. 1 sodium silicate (SiO ２ / Na ２ 169 kg of an aqueous solution (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 4.9. The resulting polycondensation reaction product was then filtered and dispersed in 2,500 kg of ion-exchanged water at 40°C. This filtration / dispersion procedure was repeated 12 times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was further subjected to a diameter-expansion treatment by passing ion-exchanged water at 50°C through it for 3 hours. The filtered and washed polycondensation reaction product was dried at 70°C and exposed to an environment of 70°C and 100% relative humidity for 48 hours to further undergo a diameter-expansion treatment. The diameter-expansion-treated polycondensation reaction product was calcined in air at 700°C for 2 hours to obtain porous silica having multiple mesopores and macropores with different pore diameters. An electron microscope image (not shown) of the resulting porous silica confirmed regularly connected small mesopores A.

[0040] Preparation of Porous Silica Comparative Example 1 17.6 kg of cetyltrimethylammonium chloride and 12.3 kg of ethanol were added to 350 kg of 2.7 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 15.3% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 222 kg of an aqueous solution of 2,000 kg of ammonium hydroxide (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 8. The resulting polycondensation reaction product was then filtered and dispersed in 2,000 kg of ion-exchanged water heated to 40°C. This filtration / dispersion procedure was repeated five times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was dried at 70°C and calcined in air at 700°C for 2 hours to obtain porous silica having mesopores and macropores. An electron microscope image (not shown) of the resulting porous silica confirmed the presence of regularly connected small mesopores A.

[0041] Preparation of Porous Silica Comparative Example 2 17.6 kg of cetyltrimethylammonium chloride and 12.3 kg of ethanol were added to 350 kg of 2.7 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 15.3% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 222 kg of an aqueous solution of 2.09% ethanol (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 8. The resulting polycondensation reaction product was then filtered and dispersed in 2,000 kg of ion-exchanged water heated to 40°C. This filtration and dispersion procedure was repeated five times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was further dispersed in 3,000 kg of ion-exchanged water at 50°C, and the dispersion was stirred at 50°C for 3 hours to perform a diameter expansion treatment. The dispersion was filtered, and the polycondensation reaction product was dried at 70°C. The diameter-expanded polycondensation reaction product was calcined in air at 700°C for 2 hours to obtain porous silica having mesopores and macropores. An electron microscope image (not shown) of the resulting porous silica confirmed regularly connected small mesopores A.

[0042] Preparation of Porous Silica Comparative Example 3 6.2% No. 1 Sodium Silicate (SiO ２ / Na ２To 1,076 kg of an aqueous solution of 2.09% cetyltrimethylammonium chloride (O = 2.09), 35.3 kg of cetyltrimethylammonium chloride and 12.4 kg of ethanol were added. While stirring at 70°C, 292 kg of 7.2% hydrochloric acid was added, and the mixture was stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 8.5. The resulting polycondensation reaction product was then filtered and dispersed in 2,000 kg of ion-exchanged water. This filtration / dispersion procedure was repeated five times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was dried at 70°C and calcined in air at 700°C for 2 hours to obtain porous silica with ordered mesopores. An electron microscope image (not shown) of the resulting porous silica confirmed the presence of regularly interconnected small mesopores A.

[0043] Preparation of Porous Silica Comparative Example 4 17.6 kg of cetyltrimethylammonium chloride and 12.3 kg of ethanol were added to 350 kg of 2.7 wt % hydrochloric acid, and the mixture was stirred at 70°C while adding 13.9% No. 1 sodium silicate (SiO ) at 60°C. ２ / Na ２ 202 kg of an aqueous solution of 2,000 kg of ammonium hydroxide (O = 2.09) was added and stirred at 70°C for 3 hours to obtain a polycondensation reaction product. The pH of the resulting solution containing the polycondensation reaction product was 4. The resulting polycondensation reaction product was then filtered and dispersed in 2,000 kg of ion-exchanged water heated to 40°C. This filtration / dispersion procedure was repeated five times to wash the polycondensation reaction product. The filtered and washed polycondensation reaction product was dried at 70°C and calcined in air at 700°C for 2 hours to obtain porous silica having mesopores and macropores. An electron microscope image (not shown) of the resulting porous silica confirmed the presence of regularly connected small mesopores A.

[0044]

[0045] In Table 1, Examples 1 to 8 were able to obtain porous silica having multiple mesopores and macropores with different pore diameters. On the other hand, Comparative Examples 1 to 4 were unable to obtain porous silica having multiple mesopores with different pore diameters. Furthermore, Comparative Examples 1, 2, and 4 were able to obtain porous silica having macropores, but Comparative Example 3 was unable to obtain porous silica having macropores.

[0046] Experimental Example 1 (1) Enzyme Supporting In this experiment, the support of an enzyme in porous silica and the liquid permeability of the enzyme-supported porous silica were confirmed. 0.5 g of the porous silica of Examples 2, 3, and Comparative Example 1 was mixed with 20 mL of 20 mmol / L MES buffer (pH 5.0) containing 3 g / L of lysozyme and stirred at 4°C for 6 hours to prepare a sample. The mixture was then centrifuged at 3,000 rpm for 10 minutes, the supernatant was removed, and the resulting precipitate was resuspended in 20 mL of the same buffer without lysozyme. This was repeated twice, with the precipitate being centrifuged and resuspended in the buffer, to obtain an enzyme support.

[0047] (2) Confirmation of Liquid Permeability The enzyme carriers of Examples 2, 3, and Comparative Example 1 obtained by the above procedure were packed into columns, and 250 ml of the above buffer solution was added from above the carrier. The liquid permeation rate was confirmed by downward flow using an aspirator. The results are summarized in Table 2. As is clear from Table 2, the porous silicas of Examples 2 and 3 exhibited less pressure loss and maintained high flow rate characteristics at the same linear velocity compared to the porous silica of Comparative Example 1.

[0048]

[0049] Experimental Example 2: Confirmation of Gas Diffusion Resistance In this experimental example, the gas diffusion resistance of porous silica was confirmed. 0.5 g of each of the porous silicas of Examples 1 to 8 and Comparative Examples 1 to 4 was packed into a column, and pressure gauges were attached before and after the column. The pressure before and after the column was confirmed when nitrogen gas was passed through it. The gas diffusion resistance can be confirmed by dividing the pressure after passing through the column by the pressure before passing through the column; the closer the value is to 1, the lower the gas diffusion resistance. The results are summarized in Table 3. As is clear from Table 3, Examples 1 to 8 had significantly lower gas diffusion resistance than Comparative Examples 1 to 4, confirming that the presence of mesopores B improves breathability.

[0050]

[0051] Experimental Example 3: Confirmation of Pressure Loss In this experiment, the column pressure loss of porous silica was confirmed. Each of the porous silicas of Examples 1 to 8 and Comparative Examples 1 to 4 was packed into a column (internal diameter: 6.6 mm, length: 250 mm, volume: 8.5 mL), which was then combined with an HPLC system (manufactured by Waters). The pump pressure of the HPLC system was measured when pure water at 25°C was passed through at 0.5 mL / min. The flow rate was then increased in steps of 0.5 mL / min up to the maximum flow rate of the HPLC system, 10 mL / min (linear velocity: 1755 mL / h), and the pump pressure was measured to measure the pressure loss. As a blank, the pressure loss across the column alone, without any porous silica packed inside, was measured, and the pressure loss across the porous silica was calculated using the following formula: Pressure Loss (MPa) = Pressure at Column Inlet (MPa) - Pressure at Column Outlet (MPa) - Pressure Loss Through Column Alone (MPa). The linear velocity was also calculated using the following formula: Linear velocity (cm / h) = flow rate at measurement (ml / h) / column cross-sectional area (cm ２ The results are shown in Figures 8 to 10. As is clear from Figures 8 to 10, the porous silicas of Examples 1 to 8 exhibit less pressure loss and maintain high flow rate characteristics at the same linear velocity compared to the porous silicas of Comparative Examples 1 to 4.

[0052] The porous silica of the present invention has low pressure loss and high flow rate characteristics, making it suitable for use as a packing material for chromatography columns, etc. It is also expected to be used in applications known for porous silica, such as a carrier for gas absorbents.

Claims

1. Porous silica having mesopores A with a peak diameter of 1 nm or more and less than 5 nm, mesopores B with a peak diameter of 5 nm or more and less than 100 nm, and macropores C with a peak diameter of 0.1 μm or more and less than 0.5 μm.

2. A method for producing porous silica according to claim 1, comprising the steps of adding a silica source to a structure-directing agent solution containing an acid to cause a polycondensation reaction, and removing the structure-directing agent from the resulting polycondensation reaction product.

3. The method according to claim 2, further comprising a step of carrying out a diameter expansion treatment using water or steam before removing the structure-directing agent.

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