WO2016195379A1 - Method for preparing metal oxide-silica composite aerogel and metal oxide-silica composite aerogel prepared by means of same - Google Patents

Abstract

The present invention provides a method for preparing metal oxide-silica composite aerogel and metal oxide-silica composite aerogel which is prepared by means of same and has a low tap density and a high specific surface area, the method comprising the steps of: preparing a silicate solution by dissolving water glass so as to have a concentration from 0.125M to 3.0M; adding a metal salt solution, of which the metal ion concentration is from 0.125M to 3.0M, to the silicate solution, mixing same, then adjusting the pH of a mixture obtained as a result thereof to be from 3 to 9, thereby precipitating a metal oxide-silica composite precipitate; and separating the metal oxide-silica composite precipitate and drying same, wherein the metal salt solution comprises magnesium (Mg)-containing metal salts in an amount which enables a magnesium ion content to exceed 50 mol% with respect to the total mol of the metal ions in the metal salt solution.

Description

Method for preparing metal oxide-silica composite airgel and metal oxide-silica composite airgel prepared using the same

Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 2015-0077278 dated June 1, 2015 and Korean Patent Application No. 2016-0067869 dated June 1, 2016. The contents are included as part of this specification.

Technical Field

The present invention provides a method for producing a metal oxide-silica composite airgel having a low tap density and a high specific surface area by a simple manufacturing process without a separate aging, solvent replacement and surface modification step, and to the metal oxide-silica composite airgel prepared using the same. It is about.

Recently, as industrial technologies are advanced, interest in aerogels having excellent thermal insulation properties is increasing. The aerogels developed so far include organic aerogels such as resorcinol-formaldehyde or melamine-formaldehyde aerogel particles, silica (Silica, SiO ₂ ), alumina (Alumina, Al ₂ O ₃ ), titania (Titania, TiO _2). Or inorganic aerogels containing metal oxides such as carbon (C) aerogels.

Among these, silica airgel is a highly porous material, and has high porosity, specific surface area, and low thermal conductivity, and thus can exhibit excellent thermal insulation effect. Therefore, silica aerogel has high porosity, specific surface area, and low thermal conductivity. Applications are expected.

Since silica airgel has a low mechanical strength due to its porous structure, the silica airgel is usually combined with a substrate such as glass fiber, ceramic fiber, or polymer fiber to produce a product such as an airgel blanket or airgel sheet. However, since the silica airgel structurally contains 90% by volume or more of air in the internal pores, the density is too low, there is a severe scattering during processing, difficult to impregnate the substrate. In addition, even if impregnated in part, the difference in density from the substrate is too large and does not mix well, causing problems such as poor appearance and deterioration of physical properties. In addition, it is necessary to mix at least 5% by volume in a volume fraction to effectively block heat transfer to exert an insulating effect by filling, but the powder itself is not easy to process at such a high level of mixing ratio.

Accordingly, a method of mixing an additive with an airgel has been proposed to enhance the processability of the silica airgel, and to enhance the properties of the airgel such as heat insulating property, suction ability, catalytic activity, or to impart additionally required properties. Specifically, the additives are added to the sol before the silica airgel is polymerized, or the prepared silica airgel is contacted with a liquid or gaseous stream containing the additive. The method of introducing the elements to strengthen the structure and increase the density, and the method of forming a composite with the plate-like inorganic material has been proposed.

However, the conventional methods are not easy to control the size, particle size distribution, etc. of the additive materials, and there is a problem such as deformation and reduction of the pore structure in the manufacturing process of the silica airgel.

An object of the present invention is to prepare a metal oxide-silica composite airgel with excellent physical properties such as low tap density and high specific surface area by a simple manufacturing process without additional aging, solvent replacement and surface modification steps. To provide a way.

Still another object of the present invention is to provide a metal oxide-silica composite airgel prepared by the above production method.

In order to solve the above problems, according to an embodiment of the present invention, dissolving a water glass to a concentration of 0.125M to 3.0M to prepare a silicate solution; To the silicate solution, a metal salt solution having a metal ion concentration of 0.125M to 3.0M is added and mixed, and then, an acid catalyst is added to adjust the pH of the resulting mixture to 3 to 9, thereby preparing a metal oxide-silica composite precipitate. Precipitating; And separating and drying the metal oxide-silica composite precipitate, wherein the metal salt solution comprises magnesium (Mg) in an amount such that the content of magnesium ions exceeds 50 mol% with respect to the total moles of metal ions in the metal salt solution. It provides a method for producing a metal oxide-silica composite airgel comprising a metal salt).

According to another embodiment of the present invention, there is provided a metal oxide-silica composite aerogel prepared by the above production method.

The method for preparing a metal oxide-silica composite airgel according to the present invention has excellent physical properties such as low tap density and high specific surface area with excellent pore characteristics through a simple manufacturing process, without a separate aging, solvent replacement and surface modification step. Metal oxide-silica composite aerogels can be prepared. Accordingly, the metal oxide-silica composite aerogel prepared by the above manufacturing method is applicable to various industrial fields such as catalysts or heat insulating materials due to the pore and physical properties described above.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical spirit of the present invention, the present invention is limited to the matters described in such drawings. It should not be construed as limited.

1 is a process chart sequentially showing a manufacturing process of a conventional metal oxide-silica composite airgel.

2 is a process chart sequentially showing a manufacturing process of a metal oxide-silica composite airgel according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

1 is a process chart sequentially showing a manufacturing process of a conventional metal oxide-silica composite airgel. As shown in FIG. 1, in the conventional case, an acid catalyst was added to the silicate solution prepared by mixing water glass with water, followed by solving, and then gelled again, followed by aging, solvent replacement, surface modification, washing, and drying. A metal oxide-silica composite airgel was prepared. As described above, the conventional method for preparing silica airgel has complicated manufacturing processes, generation of a large amount of wastewater due to the use of an organic solvent, and excessive consumption of the surface modifier in the surface modification step.

In the present invention, in the preparation of the metal oxide-silica composite airgel using water glass, a metal salt solution having a controlled magnesium ion content is added to a silicate solution having a controlled concentration of reactants, and together with a silicate solution and a metal salt using an acid catalyst. A simple method of synthesizing a metal oxide-silica composite precipitate by controlling the pH of a mixed solution of a solution and drying it, a metal oxide having a low tap density, high specific surface area and pore volume ratio without aging, solvent replacement, and surface modification steps. Silica aerogels can be prepared.

Specifically, in the method for preparing a metal oxide-silica composite airgel (hereinafter, simply referred to as a 'composite airgel') according to an embodiment of the present invention, preparing a silicate solution by dissolving water glass at a concentration of 0.125M to 3.0M. (Step 1); To the silicate solution, a metal salt solution having a metal ion concentration of 0.125M to 3.0M is added and mixed, and then, an acid catalyst is added to adjust the pH of the resulting mixture to 3 to 9, thereby preparing a metal oxide-silica composite precipitate. Precipitating (step 2); And separating and drying the metal oxide-silica composite precipitate (step 3), wherein the metal salt solution is such that the content of magnesium ions is greater than 50 mol% relative to the total moles of metal ions in the metal salt solution. Metal salts containing magnesium (Mg) in amounts.

2 is a process chart sequentially showing a manufacturing process of the composite airgel according to an embodiment of the present invention. 2 is only an example for describing the present invention and the present invention is not limited thereto. Hereinafter, each step will be described in detail with reference to FIG. 2.

Step 1

In the method of manufacturing a composite airgel according to an embodiment of the present invention, step 1 is a step of preparing a silicate solution containing water glass (Na ₂ SiO ₃ ) at a concentration of 0.125M to 3.0M.

The silicate solution may be prepared by dissolving water glass (Na ₂ SiO ₃ ) in a solvent, specifically water, at a concentration of 0.125M to 3.0M. When using silicate solutions in the above concentration range, the preparation of metal oxide-silica composite aerogels having reduced tap density and increased specific surface area, specifically tap density of 0.41 g / ml or less and specific surface area of 200 m ² / g or more, It is possible. If the concentration of the water glass is less than 0.125M, the silica content in the final composite aerogel is low, and if it exceeds 3.0M, the tap density increases and the specific surface area is increased as the composite airgel is formed in a more compact structure in the reaction solution. There is a fear of reduction. More specifically, considering the tap density further reduced below 0.15 g / ml and the specific surface area further increased above 300 m ² / g, the pore volume increase above 0.5 cm ³ / g and thus the thermal conductivity reduction effect, The silicate solution is more specifically at a concentration of 1.5M to 2.5M, even more specifically at less than 0.1 g / ml tap density and further increased specific surface area and more than 450m ² / g and 0.8 cm ³ / g Considering the above pore volume increase and a significant decrease in thermal conductivity, water glass may be included at a concentration of 2M. At this time, the water glass is not particularly limited, but may contain 28 wt% to 35 wt%, more specifically 28 wt% to 30 wt% silica (SiO ₂ ) based on the total weight of the water glass.

In addition, the silicate solution may include the water glass (Na ₂ SiO ₃ ) in an amount to include 0.04M to 6.0M silica when based on silica (SiO ₂ ) included in the water glass.

Step 2

In the method of manufacturing a composite airgel according to an embodiment of the present invention, step 2 is a step of forming a metal oxide-silica composite precipitate by reacting the silicate solution prepared in step 1 with a metal salt solution.

Specifically, the metal oxide-silica composite precipitate is mixed with the silicate solution prepared in step 1 by adding a metal salt solution having a metal ion concentration of 0.125M to 3.0M, and then acid-catalyzing the pH of the resulting mixture. It can be formed by adjusting to the conditions of 3 to 9 by adding.

The metal salt solution is prepared by dissolving a metal salt, which is a raw material for forming a metal oxide, in a solvent in a composite aerogel to be finally prepared, specifically, a magnesium (Mg) -containing metal salt in total moles of metal ions in the metal salt solution. It is included in an amount such that the content of magnesium ions to more than 50 mol%. If the content of magnesium ions in the metal salt solution is 50 mol% or less, the thermal conductivity may decrease due to an increase in the tap density and a sharp decrease in the specific surface area and the pore volume.

More specifically, the metal salt includes a magnesium-containing metal salt alone, or together with the magnesium-containing metal salt, in the group consisting of alkali metals, alkaline earth metals, lanthanides, actinides, transition metals and metals of Group 13 (IIIA) Any one or two or more selected may be a salt containing a metal, more specifically calcium (Ca), magnesium (Mg), copper (Cu), zinc (Zn), manganese (Mn), cadmium (Cd), Lead (Pb), Nickel (Ni), Chromium (Cr), Silver (Ag), Titanium (Ti), Vanadium (V), Cobalt (Co), Molybdenum (Mo), Tin (Sn), Antimony (Sb) , Halide containing one or two or more metal elements selected from the group consisting of strontium (Sr), barium (Ba), and tungsten (W), more specifically chloride. In addition, among the above metals may be appropriately selected according to the use of the composite aerogel, for example, when considering the application to the application that requires a thermal insulation effect on the composite aerogel, the metal salt includes magnesium, calcium or mixed metals thereof The metal salt may be magnesium chloride alone, considering the reduced tap density, increased specific surface area and pore volume, and thus reduced thermal conductivity of the composite aerogel prepared. Or a mixture of magnesium chloride and calcium chloride.

In addition, when the metal salt includes two metal salts, it is preferable to adjust the concentration ratio of each metal ion so as to satisfy the ratio of the metal element in the metal oxide in the composite aerogel to be finally prepared. In the case of composite airgel it is required for example, to have an excellent heat insulation performance, may include a MgO and CaO as the metal oxide, in which case the metal salt is Mg-containing metal salt under conditions which satisfy the concentration range in the Mg ^{2 +} ion metal salt solution and Ca respectively contained in the content of metal ion ratio of metal salt may include an amount such that the molar ratio of 1: ^{(2 +} Mg: Ca ^{2 +)} is 2.5: 1 to 1.5. When included in such a mixing ratio, it is possible to prepare a metal oxide-silica composite aerogel having a tap density of 0.41 g / ml or less and a specific surface area of 200 m ² / g or more. Furthermore, Mg in metal salt solutions can be considered when the tap density is further reduced below 0.15 g / ml and the specific surface area increased above 300 m ² / g, as well as the pore volume increase above 0.5 cm ³ / g and the resulting thermal conductivity reduction effect. may be included in an amount such that the molar ratio of 1: ^{2 +} ions under the conditions to meet the range of concentrations of the metal salt containing Mg and Ca-containing metal salt Mg ^2+: Ca ²⁺ of 2.1: 1 to 1.95. More specifically, Mg considering the further reduced tap density below 0.1 g / ml and further increased specific surface area above 450 m ² / g and pore volume increase above 0.8 cm ³ / g and consequently a significant reduction in thermal conductivity Containing metal salt, specifically MgCl ₂ and Ca-containing metal salt, specifically CaCl ₂ may be included in an amount such that Mg ^{2 +} : Ca ^{2 +} is in a molar ratio of 2: 1.

In addition, the metal salt may be used in an amount such that the concentration of metal ions derived from the metal salt in the metal salt solution is 0.125M to 3.0M. When using silicate solutions in the above concentration range, the preparation of metal oxide-silica composite aerogels having reduced tap density and increased specific surface area, specifically tap density of 0.41 g / ml or less and specific surface area of 200 m ² / g or more, It is possible. If the concentration of metal ions is less than 0.125M, the amount of metal oxides formed in the composite aerogel is small, and the improvement effect due to the formation of metal oxides is insignificant. There is a possibility that the physical properties of the rather deteriorated. Specifically, considering the tap density further reduced below 0.15 g / ml and the specific surface area further increased above 300 m ² / g, the pore volume of 0.5 cm ³ / g or more and the resulting thermal conductivity reduction effect, the metal salt is The concentration of metal ions in the metal salt solution is 0.4 M to 2.0 M, more specifically even more specifically 0.1 g / ml or less, the tap density is further reduced and the specific surface area more than 450 m ² / g and 0.8 cm ^In consideration of the increase in pore volume of ³ / g or more and a significant decrease in thermal conductivity, it may be used at 0.5M to 0.8M.

In addition, the metal salt may be used in an amount such that the molar ratio of water glass to metal ions is 1: 1 to 5: 1, compared to the concentration of water glass in the silicate solution within the above concentration range. When using silicate solutions in the above concentration range, the preparation of metal oxide-silica composite aerogels having reduced tap density and increased specific surface area, specifically tap density of 0.41 g / ml or less and specific surface area of 200 m ² / g or more, It is possible. If out of the molar ratio range, there is a fear that the tap density of the composite airgel to be produced is increased. More specifically, water glass considering the tap density further reduced below 0.15 g / ml and the specific surface area further increased above 300 m ² / g, as well as the pore volume increase above 0.5 cm ³ / g and the resulting thermal conductivity reduction effect : Molar ratio of metal ions 3: 3 to 5: 1, more specifically 0.1 g / ml or less, further reduced tap density and more specific surface area above 450 m ² / g and pores of 0.8 cm ³ / g or more The volume increase and hence thermal conductivity can also be used in a molar ratio of 3: 1 given the significant reduction effect.

Further, the solvent used for forming the metal salt solution can be used without particular limitation as long as it can dissolve the metal salt. Specific examples thereof include water or a hydrophilic polar organic solvent, and any one or a mixture of two or more thereof may be used. Of these, the hydrophilic polar organic solvent is excellent in miscibility with the above-described silicate solution, and may then be uniformly present in the gel during gelation. As a result, the solvent substitution step may be omitted in the preparation of the composite silica gel.

The hydrophilic polar organic solvent may be specifically an alcohol solvent. In addition, the alcohol solvent is specifically a monohydric alcohol such as methanol, ethanol, isopropanol, butanol and the like; Or polyhydric alcohols such as glycerol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, sorbitol, and the like, and any one or a mixture of two or more thereof may be used. In consideration of the miscibility with water and the uniform dispersibility in silica gel, the alcohol-based compound may be an alcohol having 1 to 8 carbon atoms. In addition to the above effects, when considering the efficiency of the modification reaction on the surface of the silica later, the alcohol-based compound may be a linear alcohol having 1 to 4 carbon atoms, such as methanol, ethanol, propanol, or n-butanol, One kind alone or a mixture of two or more kinds may be used. More specifically, the alcohol-based compound may be methanol, ethanol or a mixture thereof.

Addition and mixing of the metal salt solution to the silicate solution may be performed according to conventional methods.

Thereafter, the pH of the mixture obtained as a result of the mixing process is adjusted to 3 to 9 using an acid catalyst. When the pH of the mixed solution is within the above range, it is possible to prepare a metal oxide-silica composite airgel having a reduced tap density and an increased specific surface area, specifically, a tap density of 0.41 g / ml or less and a specific surface area of 200 m ² / g or more. Do. If the pH of the mixed solution is out of the above range, the tap density may increase, and the specific surface area and pore volume may be greatly reduced. When the pH of the mixture is neutral or basic conditions of 7 or more, condensation may occur during hydrolysis and condensation of silica. When the pH exceeds 9, excessive OH ⁻ concentration in the reduction of metal ions to metal oxides is observed. This results in the formation of metal hydroxides, resulting in condensation of silica and formation of metal hydroxides in addition to the formation of complex aerogels of metal oxide-silica in the particles, resulting in increased non-uniformity in the particles, increased tap density and reduced specific surface area. There is a fear of causing. In addition, if the pH is less than 5, the concentration of OH- required for the reduction of metal ions may be reduced, thereby reducing the reduction reaction. If the pH is less than 3, the concentration of OH ⁻ is too low to inhibit the reduction reaction to form silica. The reaction is generated, the content of the metal oxide, which serves as a structural support of the particles in the structure is reduced and the shrinkage phenomenon during drying is deep, as a result there is a fear that the increase in the tap density and decrease in the specific surface area. As a result, the tap density of the final composite aerogel may increase, and the specific surface area and pore characteristics may decrease.

Balance of tap density, specific surface area and pore characteristics according to pH adjustment In order to obtain a good improvement effect, the pH of the mixed solution can be adjusted to a weakly acidic condition of more than 5 and less than 7, and more specifically, to 5 to 6 by adding an acid catalyst. have.

On the other hand, the acid catalyst serves to increase the production rate of the composite precipitate by promoting the reaction of the silicate solution and the metal salt solution in the formation of the composite precipitate, specifically, an inorganic acid such as hydrochloric acid, sulfuric acid, phosphoric acid or nitric acid ; Or organic acids such as acetic acid or citric acid, and any one or a mixture of two or more thereof may be used. Among these, the acid catalyst may be an inorganic acid, more specifically hydrochloric acid. Hydrochloric acid using, Cl, with H ⁺ ions, mainly involved in the gelling reaction of the ^silica-to occur, wherein the metal salt generated in the ion (Cl ^-) and side reactions due to salt by using an acid catalyst include the same salts as reactants By minimizing this, the physical properties of the composite airgel can be further improved, and wastewater treatment may be advantageous by unifying salt in wastewater after completion of manufacture.

When the acid catalyst is added to the mixture of the silicate solution and the metal salt solution to adjust the pH to 5 or more and less than 7, a metal oxide-silica composite precipitate is formed and precipitated. For example, when MgCl ₂ and CaCl ₂ are used as the metal salt, a composite precipitate of MgO—CaO—SiO ₂ is precipitated by the same reaction as in Scheme 1 below.

Scheme 1

Na ₂ O.nSiO ₂ (I) + 1 / 2Mg ^{2 +} + 1 / 2Ca ^{2 +} -> (Mg, Ca) O.nSiO ₂ (s) + 2Na ⁺

Step 3

In the method of manufacturing a composite airgel according to an embodiment of the present invention, step 3 is a step of preparing a metal oxide-silica composite airgel by separating and drying the metal oxide-silica composite precipitate precipitated in step 2.

In step 3, the separation process of the precipitated metal oxide-silica composite precipitate may be performed according to a conventional method, and specifically, may be performed by separating from a solvent using a vacuum filter or the like.

After separation of the metal oxide-silica composite precipitate, prior to the drying process, unreacted reactants (eg, Si ^{4 +} , Mg ^{2 +} or Ca ^{2 +} ) remaining in the precipitate and additional ions (Na ⁺ or Cl ⁻ May be optionally further performed for removal. In this case, the manufacturing method of the composite airgel according to an embodiment of the present invention may further include a washing step after the formation of the metal oxide-silica composite precipitate.

The washing process may be performed according to a conventional method. However, due to the excellent miscibility with the aqueous phase of the reaction solvent during the washing process, it is easy to penetrate into the pores inside the silica gel particles, and when combined with the subsequent drying process, the drying effect and the possibility of shrinkage and deformation of the pores are low. It may be desirable to use a cleaning solvent. Specifically water; Alcohol compounds such as methanol, ethanol, isopropanol or propanol; Hydrocarbon-based compounds such as hexane, octane, n-decane, n-heptane, n-undodecane, cyclohexane or toluene; Or ketone compounds such as methyl ethyl ketone or acetone, and any one or a mixture of two or more thereof may be used. Among these, alcohol-based compounds, more specifically ethanol, may be used in consideration of better affinity with water and minimizing the shrinkage and deformation of pores during the drying process.

The washing process may be performed once or twice or more, specifically, 3 to 5 times. In addition, when the washing process is performed two or more times, it may be performed using the same washing solvent, it may be carried out using a different heterogeneous washing solvent.

After the separation or washing process of the metal oxide-silica composite precipitate, a drying process is performed.

The drying process may be performed by a method such as heat treatment or hot air injection. In addition, specific temperature conditions during the drying process may be appropriately adjusted according to the washing solvent, specifically, may be carried out at a temperature of 90 ℃ to 200 ℃.

The metal oxide-silica composite airgel finally obtained after the drying process has an average particle diameter (D ₅₀ ) of 7 μm to 15 μm, but when the particle size is excessively large beyond such a range, a pulverizing process to have an appropriate particle size is performed. May optionally be further performed.

The pulverization process may be performed according to a conventional method, and may be performed under conditions such that the average particle diameter (D ₅₀ ) of the metal oxide-silica composite airgel is 7 μm to 15 μm.

In the present invention, the average particle diameter (D ₅₀ ) of the metal oxide-silica composite airgel may be defined as the particle size based on 50% of the particle size distribution, wherein the average particle diameter of the metal oxide-silica composite airgel is laser diffraction method (laser) diffraction method) or as a dry analysis model, a particle size analyzer (Macrotrac Particle Size Analyzer S3500) was used to calculate the average particle diameter (D ₅₀ ) at 50% of the particle size distribution in the measuring device. can do.

Through the control of the concentration and pH of the reactant in the preparation of the composite aerogel by the reaction of the silicate solution and the metal salt solution as described above, the aging, solvent replacement and surface modification step that is essential for the preparation of the conventional metal oxide-silica composite airgel Without performing it, a metal oxide-silica composite aerogel having low tap density, high specific surface area and porosity, and low thermal conductivity as described above can be prepared. Specifically, the metal oxide-silica composite airgel prepared by the above-described manufacturing method has an average particle diameter (D ₅₀ ) of 7 μm to 15 μm, a tap density of 0.41 g / ml or less, and a BET specific surface area of 200 m ² / g or more. More specifically, the average particle diameter (D ₅₀ ) is 7㎛ to 15㎛, the tap density is 0.038g / ml to 0.2g / ml, BET specific surface area is 300m ² / g to 600m ² / g Can be.

The method for preparing the metal oxide-silica composite aerogel according to an embodiment of the present invention, the concentration of water glass in the silicate solution, the concentration of metal ions, the pH range of the mixture, the molar ratio of water glass and metal ions, and magnesium ions in the metal salt By further optimizing the molar ratio of calcium ions, it is possible to exhibit better thermal conductivity by controlling the pore volume along with the tap density and BET specific surface area of the metal oxide-silica composite aerogel to be produced. Specifically, the method for producing a metal oxide-silica composite airgel, the step of preparing a silicate solution by dissolving the water glass in a concentration of 0.125M to 3.0M, more specifically 1.25M to 3.0M; To the silicate solution, a metal salt solution having a metal ion concentration of 0.125M to 3.0M, more specifically 0.4M to 2.0M is added and mixed, and then an acid catalyst is added to adjust the pH of the resulting mixture to 3-9. , More specifically, adjusting to weakly acidic conditions of less than 5 and less than 7 to precipitate the metal oxide-silica composite precipitate; Separating the metal oxide-silica composite precipitate, and then washing and drying the silicate solution, wherein the silicate solution and the metal salt solution include a water glass: metal ion molar ratio of 5: 1 to 1: 1, more specifically 5: 1. MgCl ₂ and CaCl ₂ are used in an amount such that the molar ratio of magnesium to calcium is 2.5: 1 to 1.5: 1, more specifically, 2.1: 1 to 1.95: 1. Including, but the molar ratio of magnesium ions in the total moles of metal ions contained in the metal salt solution may be 50 mol% or more. Tap density further reduced to 0.038 g / ml to 0.15 g / ml, more specifically 0.038 g / ml to 0.1 g / ml when performed by such an optimal combination step, more specifically at least 300 m ² / g, more specifically Metal oxide-silica composite aerogels having a specific surface area which is further increased from 450 m ² / g to 600 m ² / g and pore volume of at least 0.5 cm ³ / g, more specifically from 0.8 cm ³ / g to 1.0 cm ³ / g Can be prepared.

Through the control of the concentration and pH of the reactant in the preparation of the composite aerogel by the reaction of the silicate solution and the metal salt solution as described above, the aging, solvent replacement and surface modification step that is essential for the preparation of the conventional metal oxide-silica composite airgel Without performing it, a metal oxide-silica composite aerogel having low tap density, high specific surface area and porosity, and low thermal conductivity as described above can be prepared.

Accordingly, according to another embodiment of the present invention there is provided a metal oxide-silica composite aerogel prepared by the above-described manufacturing method.

The metal oxide-silica composite airgel is a composite in which a silica airgel and a metal oxide are mixed in the composite airgel structure. The metal oxide-silica composite airgel has a low tap density, a high specific surface area and a porosity, and a low thermal conductivity through controlling conditions in the manufacturing process.

Specifically, the metal oxide-silica composite airgel is 0.41 g / ml or less, or 0.038 g / ml to 0.41 g / ml, more specifically 0.038 g / ml to 0.15 g / ml, even more specifically 0.038 g / ml to It has a tap density of 0.1 g / ml. In this case, the tap density of the metal oxide-silica composite airgel may be measured using a tap density meter (TAP-2S, Logan Instruments co.).

In addition, the metal oxide-silica composite airgel has a BET specific surface area of 200 m ² / g or more, or 200 m ² / g to 600 m ² / g, more specifically 300 m ² / g to 600 m ² / g, may be more specifically 450m ² / g to 600m ² / g. In the present invention, the specific surface area of the metal oxide-silica composite airgel can be measured by the adsorption / desorption amount of nitrogen according to the partial pressure (0.11 <p / p _o <1) using the ASAP 2010 device of Micrometrics.

In addition, the metal oxide-silica composite airgel may have an average particle diameter (D ₅₀ ) of 7 μm to 15 μm, more specifically 8 μm to 15 μm. In the present invention, the average particle diameter (D ₅₀ ) of the metal oxide-silica composite airgel may be defined as the particle size based on 50% of the particle size distribution, wherein the average particle diameter of the metal oxide-silica composite airgel is laser diffraction method (laser) diffraction method) or as a dry analysis model, a particle size analyzer (Macrotrac Particle Size Analyzer S3500) was used to calculate the average particle diameter (D ₅₀ ) at 50% of the particle size distribution in the measuring device. can do.

In addition, the metal oxide-silica composite airgel has a pore volume of 0.4 cm ³ / g to 1.0 cm ³ / g, more specifically 0.5 cm ³ / g to 1.0 cm ³ / g, and more specifically 0.8 cm ³ / g To 1.0 cm ³ / g. At this time, the pore volume in the metal oxide-silica composite airgel can be determined from the amount of mercury intrusion into the pores measured by mercury porosimeter analysis.

In addition, the metal oxide-silica composite airgel may include micropores having a porosity of 80% by volume or more, or 90% by volume to 98% by volume, and an average pore diameter of 20nm or less, or 5nm to 15nm. In this case, the average pore diameter and porosity of the metal oxide-silica composite aerogel can be measured by the adsorption / desorption amount of nitrogen according to the partial pressure (0.11 <p / p _o <1) using an ASAP 2010 device of Micrometrics. .

In addition, within the tap density, specific surface area, particle size, and pore size, the volume occupied by the pores may exhibit low thermal conductivity and improved thermal insulation effect. Specifically, the metal oxide-silica composite airgel may exhibit a thermal conductivity of 30 mW / mK or less. In this case, the thermal conductivity may be measured at 25 using a thermal conductivity meter (NETZSCH, HFM436 Lambda).

On the other hand, in the metal oxide-silica composite airgel, the silica airgel is a particulate porous structure containing a plurality of micropores, the nano-sized primary particles, specifically, the average particle diameter (D ₅₀ ) is 100nm or less, or Primary particles of 1 nm to 50 nm may be combined to include a microstructure, that is, a three-dimensional network structure, to form a network-shaped cluster.

In addition, since the metal oxide is fixed by the silanol groups present on the surface of the silica airgel, in order to increase the immobilization efficiency between the negative charge on the surface of the silica airgel and the positive charge of the metal oxide, It is desirable to control the density appropriately. Specifically, the density of silanol groups present on the surface of the silica may be 10 / nm ² or less, or 5 / nm ² to 7 / nm ² .

Accordingly, the silica airgel has a BET (Brunauer-Emmett-Teller) surface area of 50 m ² / g to 700 m ² / g, an average particle diameter (D ₅₀ ) of 10 μm to 150 μm, and a porosity of 0.5 cm 3 / g to 2.4 Cm 3 / g, and the average pore diameter of pores included in the silica airgel may be 0.5nm to 40nm. If the BET specific surface area, average particle diameter, porosity or average pore diameter of the silica airgel is outside the above-mentioned ranges, for example, if the average pore diameter is less than 0.5 nm, the density of silanol groups is relatively increased and the absolute value of negative charge is greatly increased. As a result, the immobilization efficiency with the positively charged metal oxide is increased, but the hydrophilicity is also increased, thereby reducing the dispersibility of the metal oxide-silica composite aerogel. In addition, when the average pore diameter exceeds 40 nm, the silanol group density is relatively low, so that there is no fear of lowering the dispersibility of the metal oxide-silica composite aerogel, but the absolute value of the negative charge is low, so that the immobilization efficiency may be lowered.

In the metal oxide-silica composite airgel, the metal oxide may be used without particular limitation as long as it is fixed by silanol groups on the surface of the silica airgel and used to form the composite airgel. Specifically, the metal oxide may be an oxide containing any one or two or more metals selected from the group consisting of alkali metals, alkaline earth metals, lanthanides, actinides, transition metals, and metals of Group 13 (IIIA), More specifically, calcium (Ca), magnesium (Mg), copper (Cu), zinc (Zn), manganese (Mn), cadmium (Cd), lead (Pb), nickel (Ni), chromium (Cr), silver (Ag), titanium (Ti), vanadium (V), cobalt (Co), molybdenum (Mo), tin (Sn), antimony (Sb), strontium (Sr), barium (Ba), and tungsten (W) It may be an oxide containing any one or two or more metal elements selected from the group consisting of), and more specifically may be magnesium oxide, calcium oxide or a mixture thereof.

The metal oxides are discontinuously physically immobilized on the surface of the silica by electrical attraction occurring between the negatively charged and relatively positively charged metal oxides resulting from the silanol groups present on the surface of the silica airgel. Accordingly, in order to be easily and efficiently fixed on the silica surface and to exhibit a sufficient effect by the metal oxide, the metal oxide preferably has an appropriate particle size and specific surface area. Specifically, the metal oxide may have a specific surface area of 20 m ² / g to 100 m ² / g and an average particle diameter of 5 nm to 300 nm.

In addition, the metal oxide may be adjusted in the content of the metal oxide contained in the composite airgel according to the use of the metal oxide-silica composite airgel, specifically, the metal oxide is 5 to 80% by weight based on the total weight of the composite airgel May be included as a%. In addition, the metal oxide is a silicon oxide (Si) contained in the metal oxide-silica composite aerogel and a metal (Me) contained in the metal oxide (mole ratio of 1: 1 to 3: 1 (molar ratio of Si / Me)), more specifically May be included in an amount such that 1.5: 1 to 3: 1, and more specifically 3: 1.

More specifically, according to another embodiment of the present invention, the tap density is 0.41 g / ml or less, more specifically, 0.038 g / ml to 0.15 g / ml, and the specific surface area is 200 m ² / g or more, more specifically As a metal oxide-silica composite airgel of 300m ² / g to 600m ² / g is provided.

More specifically, according to another embodiment of the present invention, the concentration of water glass in the silicate solution, the concentration of metal ions, the pH range of the mixture, the mole ratio of water glass and metal ions, and the molar ratio of magnesium and calcium ions in the metal salt Through a manufacturing process configured in a more optimal combination, comprising a silica aerogel and a metal oxide, the metal oxide comprises magnesium oxide and calcium oxide in a content such that the molar ratio of magnesium and calcium is 2.5: 1 to 1.5: 1, The average particle diameter (D ₅₀ ) is 7 μm to 15 μm, the tap density is 0.038 g / ml to 0.1 g / ml, the specific surface area is 450 m ² / g to 600 m ² / g, and the pore volume is 0.8 cm ³ / Provided is a metal oxide-silica composite airgel having a g to 1.0 cm ³ / g.

As described above, the metal oxide-silica composite aerogel prepared by the manufacturing method according to the present invention has excellent physical properties such as low tap density and high specific surface area, and thus, catalysts or industrial furnace pipes or industrial furnaces. Insulation facilities such as thermal insulation, such as aircraft, ships, automobiles, building structures, such as insulation, insulation, or non-combustible materials are useful.

Hereinafter, the present invention will be described in more detail with reference to the following Examples and Experimental Examples. However, the following Examples and Experimental Examples are for illustrating the present invention and the scope of the present invention is not limited by these Examples and Experimental Examples.

Example  1-1

Distilled water was added to the water glass (Na ₂ SiO ₃ ) and mixed to prepare a silicate solution. Separately, MgCl ₂ and CaCl ₂ were dissolved in distilled water to prepare a metal salt solution, which was then added to the silicate solution and mixed. HCl acid catalyst was added to the resulting mixture until the pH of the mixture became as shown in Table 1 below. A white precipitate formed immediately upon reaction of the metal salt solution with the silicate solution. The precipitate was spontaneously precipitated and then the transparent solvent was removed. The precipitate was repeatedly washed three times with deionized water, vacuum filtered, the resulting cake was placed in an oven, and dried at a temperature of 105 ° C. to prepare a metal oxide-silica composite airgel. The amount of each compound was used as described in Table 1 below.

Example  1-2 to 1- 5, and Comparative example  1-1

A metal oxide-silica composite airgel was prepared in the same manner as in Example 1-1, except that each reactant was used in the amount shown in Table 1 below.

Experimental Example  One

Using the composite airgel prepared in Examples 1-1 to 1-5 and Comparative Example 1-1, the tap density change of the metal oxide-silica composite airgel according to the addition of the acid catalyst was measured using a tap density measuring instrument (TAP-2S, Logan Istruments). co.) and measured and evaluated.

In addition, the BET specific surface area was measured by the BET 6 point method by nitrogen gas adsorption | suction distribution method using the porosimetry analyzer (Bell Japan Inc, Belsorp-II mini).

In addition, the pore volume was measured by the mercury porosimeter (Mercury porosimeter) analysis to determine the amount of mercury penetration into the pores, from which pore volume was determined.

The results are shown in Table 1 below.

	Metal salt solution		Silicate solution	Mixed solution pH	Tap Density (g / ml)	Specific surface area (m 2 / g)	Pore volume (cm 3 / g)	Thermal Conductivity (mW / mK)
	MgCl 2 Concentration (M)	CaCl 2 concentration (M)	Na 2 SiO 3 Concentration (M)
Comparative Example 1-1	0.44	0.22	2	9.5	0.175	150	0.31	30.4
Example 1-1	0.44	0.22	2	8.2	0.153	260	0.55	29.4
Example 1-2	0.44	0.22	2	7.1	0.131	330	0.68	28.8
Example 1-3	0.44	0.22	2	5.9	0.098	450	0.88	28.0
Example 1-4	0.44	0.22	2	4.5	0.112	380	0.75	28.4
Example 1-5	0.44	0.22	2	3.0	0.148	280	0.53	29.6

As a result, the composite airgel prepared in the range of pH 3-9 of the mixed solution has a tap density of 0.16 g / ml or less, a specific surface area of 250 m ² / g or more, and a pore volume of 0.5 cm ³ / g or more, and 30 mW / mK or less The thermal conductivity of the composite airgel of Example 1-3, which is prepared in a range of about 5 or more and less than 7, in particular, showed a low tap density of 0.1200 g / ml or less. In contrast, Comparative Example 1-1 having a pH above 9 showed increased thermal conductivity due to higher tap density, lower specific surface area, and pore volume.

In addition, as the pH increased from 3 to 5.9, the tap density of the composite airgel decreased, but as the pH increased above 5.9, the tap density increased. From this it can be seen that there exists a pH optimum range that can minimize the tap density of the composite airgel. Specifically, as determined from Table 1, when the concentration ratio of MgCl ₂ and CaCl _{2 in} the metal salt solution is 2: 1, and the concentration ratio of the metal salt and water glass is 1: 3, lower tap density of 0.15 g / ml or less PH of the mixed solution of the metal salt solution and the silicate solution is 3 to 9 for the production of a composite airgel having a weak acidity of 5 to less than 7 for the preparation of the composite airgel having a lower tap density of 0.100 g / ml or less. It can be seen that the conditions, specifically, the pH is 5-6.

Experimental Example 2

The tap density and specific surface area of the metal oxide-silica composite airgel according to the metal ion concentration ratio were measured and evaluated.

In detail, the metal oxide-silica composite airgel was prepared in the same manner as in Example 1-1, except that the concentration and pH of Table 2 were performed. Tap density was measured in the same manner as in Experimental Example 1 for the prepared composite airgel. In addition, the BET specific surface area of the airgel composite measure the absorption / desorption amount of nitrogen, and therefrom according to the partial pressure _{(0.11 <p / p o <} 1) was measured using a Micrometrics ASAP 2010 equipment. The results are shown in Table 2 below.

	Metal salt solution		Silicate solution	Mixed solution pH	Tap Density (g / ml)	Specific surface area (m 2 / g)	Pore volume (cm 3 / g)	Thermal Conductivity (mW / mK)
	MgCl 2 Concentration (M)	CaCl 2 concentration (M)	Na 2 SiO 3 Concentration (M)
Example 2-1	1.33	0.67	2	6.2	0.113	340	0.55	29.4
Example 2-2	0.44	0.22	2	5.9	0.098	450	0.88	28.0
Comparative Example 2-1	0.22	0.44	2	6.4	0.151	120	0.38	30.1
Example 2-3	0.67	0.00	2	5.8	0.146	440	0.67	29.8
Comparative Example 2-2	0.00	0.67	2	6.1	0.184	30	0.13	30.5
Example 2-4	0.27	0.13	2	6	0.118	360	0.61	29.9

When the tap density, specific surface area, and pore volume of the composite aerogels were determined according to the type and mixing ratio of the metal salts at a pH of 5 to less than 7, the Mg ²⁺ ions in the metal salt was more than 50 mol% based on the total moles of the total metal ions. examples 2-1 to 2-4, Mg ^{2 +} that does not contain the ion Comparative example 2-2, and Mg ^{2 +} ions, including, but further reduced compared with Comparative example 2-1 the content is not more than 50 mole% containing MgCl ₂ and CaCl ₂ under conditions that meet the molar concentration range of Mg ^{2 +} ions, in particular compared to using MgCl ₂ alone, as well as increased tap density, increased specific surface area and pore volume. When used in combination, the effect of improving the tap density, specific surface area and pore volume of the composite airgel was more remarkable.

In addition, as in Example 2-2, when the molar ratio of the metal ion concentration in the metal salt solution and the water glass in the silicate solution satisfies the conditions of 1: 3, the effect is more improved than in the case of 1: 1 or 1: 5. Indicated.

Experimental Example 3

The change in tap density of the metal oxide-silica composite airgel according to the silicate concentration was evaluated.

In detail, the metal oxide-silica composite airgel was prepared in the same manner as in Example 1-1, except that the concentration and pH of Table 3 were performed. The tap density was measured for the prepared composite airgel, and the results are shown in Table 3 below.

	Metal salt solution		Silicate solution	Mixed solution pH	Tap Density (g / ml)	Specific surface area (m 2 / g)	Pore volume (cm 3 / g)	Thermal Conductivity (mW / mK)
	MgCl 2 Concentration (M)	CaCl 2 concentration (M)	Na 2 SiO 3 Concentration (M)
Example 3-1	0.22	0.11	1.00	5.8	0.204	280	0.49	30.9
Example 3-2	0.28	0.14	1.25	5.9	0.168	340	0.54	30.4
Example 3-3	0.33	0.17	1.50	6.2	0.134	390	0.68	29.4
Example 3-4	0.39	0.19	1.75	5.9	0.118	420	0.64	28.8
Example 3-5	0.44	0.22	2.00	6.0	0.098	450	0.88	28.0
Example 3-6	0.56	0.28	2.50	5.7	0.145	410	0.58	29.1
Example 3-7	0.67	0.33	3.00	6.3	0.198	320	0.55	30.0
Comparative Example 3-1	0.22	0.11	1.00	9.3	0.402	90	0.18	34.2
Comparative Example 3-2	0.44	0.22	2.00	9.5	0.175	150	0.31	30.4
Comparative Example 3-3	0.67	0.33	3.00	9.5	0.311	100	0.21	33.4

As in Examples 3-1 to 3-7 in Table 3, using a mixed metal salt of Mg salt and Ca salt in a ratio of 2: 1, the concentration ratio of metal salt and water glass is about 1: 3, the mixed liquid When the composite airgel is prepared at a pH of 5 or more and less than 7, a low tap density of 0.41 g / ml or less and a ratio of 200 m ² / g or more even if the concentration of water glass in the silicate solution varies from 1.0 M to 3.0 M Composite airgels having a surface area and pore volume of about 0.5 cm ³ / g or more were prepared. Above all, when the concentration of water glass contained in the silicate solution is 1.5M to 2.5M, the composite has lower tap density of 0.15g / ml or less, specific surface area of 350m ² / g or more, and pore volume of about 0.5cm ³ / g or more Airgels have been prepared, especially composite airgels having a specific surface area of at least 450 m ² / g and pore volume of at least about 0.8 cm ³ / g, with the lowest tap density of 0.10 g / ml or less, especially when the concentration of water glass is 2.0M Was prepared. From these results, it can be seen that the concentration of the water glass contained in the silicate solution is 1.5M to 2.5M, more specifically 2.0M, for producing a composite airgel having a lower tap density.

Claims (12)

1. Dissolving the water glass at a concentration of 0.125M to 3.0M to prepare a silicate solution;

   To the silicate solution, a metal salt solution having a metal ion concentration of 0.125M to 3.0M is added and mixed, and then, an acid catalyst is added to adjust the pH of the resulting mixture to 3 to 9, thereby preparing a metal oxide-silica composite precipitate. Precipitating; And

   Separating and drying the metal oxide-silica composite precipitate,

   The metal salt solution is a method for producing a metal oxide-silica composite aerogel containing a metal salt containing magnesium (Mg) in an amount such that the content of magnesium ions to more than 50 mol% relative to the total moles of metal ions in the metal salt solution.
2. The method of claim 1,

   Wherein the silicate solution and the metal salt solution are used in an amount such that the molar ratio of water glass to metal ions is 1: 1 to 5: 1.
3. The method of claim 1,

   The pH control method of producing a metal oxide-silica composite aerogel is to be carried out by adding an acid catalyst to adjust the pH of the resulting mixture to more than 5 to less than 7.
4. The method of claim 1,

   The acid catalyst is a method for producing a metal oxide-silica composite airgel is an inorganic acid.
5. The method of claim 4, wherein

   The acid catalyst is a method of producing a metal oxide-silica composite airgel containing hydrochloric acid.
6. The method of claim 1,

   The metal salt is magnesium chloride; Or a mixture of chlorides comprising one or two or more metals selected from the group consisting of magnesium chloride and alkali metals, alkaline earth metals (except magnesium), lanthanides, actinides, transition metals and metals of Group 13 (IIIA) Method for producing a metal oxide-silica composite airgel comprising a.
7. The method of claim 1,

   The metal salt is a method of producing a metal oxide-silica composite airgel containing MgCl ₂ and CaCl ₂ in a content such that the molar ratio of magnesium ions and calcium ions is 2.5: 1 to 1.5: 1.
8. The method of claim 1,

   The drying process is a method for producing a metal oxide-silica composite airgel is carried out at 90 ℃ to 200 ℃.
9. The method of claim 1,

   Dissolving the water glass at a concentration of 0.125M to 3.0M to prepare a silicate solution;

   To the silicate solution, a metal salt solution having a metal ion concentration of 0.125M to 3.0M is added and mixed, and then, an acid catalyst is added to adjust the pH of the resulting mixture to 5 or more and less than 7, thereby preparing a metal oxide-silica composite precipitate. Precipitating; And

   After separating the metal oxide-silica composite precipitate, washing, and drying at 90 ℃ to 200 ℃,

   The silicate solution and the metal salt solution are used in an amount such that the molar ratio of water glass: metal ion is 5: 1 to 1: 1,

   The metal salt comprises a magnesium (Mg) -containing metal salt in an amount such that the content of magnesium ions exceeds 50 mol% with respect to the total moles of metal ions in the metal salt solution, the molar ratio of magnesium ions and calcium ions is 2.5: 1 to Method for producing a metal oxide-silica composite airgel comprising MgCl ₂ and CaCl ₂ in an amount of 1.5: 1.
10. Metal oxide-silica composite airgel prepared by the method of claim 1.
11. The method of claim 10,

    A metal oxide-silica composite airgel having a tap density of 0.41 g / ml or less and a BET specific surface area of 200 m ² / g or more.
12. The method of claim 11,

    A metal oxide-silica composite aerogel having a pore volume of 0.4 cm ³ / g to 1.0 cm ³ / g.

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