KR20070094312A - Nano-porous silica beads with uniform pore size and their manufacturing process - Google Patents

Abstract

A method for preparing silica beads is provided to obtain porous silica beads having a millimeter scaled-size and containing nanosized pores distributed uniformly therein while preventing emission of contaminants. A method for preparing millimeter scaled-size silica beads containing nanosized pores distributed uniformly therein comprises the steps of: mixing a silica sol in which nanoparticles are well dispersed with alkali metal silicate salts including sodium silicate, potassium silicate or ammonium silicate; adding sodium alginate thereto to form slurry; passing the slurry through a nozzle or spinneret and reacting it immediately with a calcium chloride solution to perform curing of beads; and baking the beads at 600-1000 deg.C to form nanopores therein.

Description

Nano-Porous Silica Beads Containing Porous Size and Their Manufacturing Process {Nano-Porous Silica Beads with Uniform Pore Size and Their Manufacturing Process}

The present invention relates to millimeter-sized silica beads (Silica Beads) in which nano-sized pores are uniformly distributed and a method for producing the beads. Beads with nano-sized pores range in size from 0.5 mm to 10 mm and the pore size ranges from 10 nanometers (nm = 10 ^-9 m) to 1000 nanometers, and the beads are fired at a constant temperature. It has high thermal insulation and nano-sized pores and is used as a filter material for air purification or water purification through catalyst coating.

In the conventional process for producing spherical silica containing nano-sized pores, ammonium salt is used in the oil phase and gelation process, and the millimeter-sized beads are prepared using a large amount of oil vapor solvent. The manufacturing process is slow and takes a long time to separate and use the used oil solvent, and the used oil and ammonium salt have the disadvantage of causing enormous environmental pollution.

   In order to solve the problem of long manufacturing process as described above and causing enormous environmental pollution, there is provided a spherical silica manufacturing process containing nano-sized pores, which has a simple manufacturing process and reduces pollutant emissions by almost 100%. There is a purpose.

    The present invention relates to millimeter-sized silica beads (Silica Beads) in which nano-sized pores are uniformly distributed and a method for producing the beads.

Beads with nano-sized pores range in size from 0.5 mm to 10 mm with pore sizes ranging from 10 nanometers (nm = 10 ^-9 m) to 1000 nanometers, with very small pore size distributions. And it does not deviate significantly from the average pore size. This uniform pore distribution is characterized in that the beads are prepared by drying the entire beads in the form of a zero gel by colloidal silica in which nanometer-sized silica particles are dispersed in a stable state.

These nano-sized pores have a small amount of alkali metals and have excellent thermal insulation properties that can withstand temperatures above 1000 ° C. Most of the millimeter-sized silica beads produced in the present invention are characterized in that their size can be freely adjusted without exceeding the average particle size.

This manufacturing process is simple, uniform and reproducible in size and shape control compared to other common ceramic manufacturing processes such as slip casting, powder processing and spray drying. It has a big advantage. In addition, while the sol-gel process has a problem in that cracks, etc., occur during the manufacture and drying of the bead-type gel, the manufacturing process of the present invention has uniform pores. Millimeter-sized beads can be cured or gelled on the fly without using expensive gelling medium, so that millimeter-sized beads can be easily automated and manufactured in bulk at low cost. In addition, the millimeter beads can be easily separated and dried without cracking while being cured or gelled without sticking to each other, thereby producing silica beads containing nano-sized pores of excellent properties. There is this.

The method for producing silica beads containing nano-sized pores according to the present invention for achieving the above object will be described in the following examples.

<Example 1>

Put _3-4 drops of NH ₄ OH solution in 30 g of water. After stirring sufficiently, 1 g of Fumed Silica is mixed in the mixer for 3 minutes. 35 g of gallium silicate (Potassuim Silicate) solution is mixed with the silica sol (Sol) thus made, and 1 g of alginic acid powder is slowly added while stirring with a stirrer. This mixed solution is dropped into a container with a pre-made gallium chloride solution through a 10-hole nozzle with a diameter of 3 mm. At this time, when droplets of mixed solution come into contact with the calcium chloride solution, the millimeter-sized beads are immediately cured or gelled into the stirred calcium chloride solution. At this time, beads that are cured or gelled are accumulated as they are stacked until at least half the volume of the calcium chloride solution in the container is produced, without contacting each other in the solution. Continuously stir and filter out beads made by filtration after 10 to 30 minutes, made of steel with about 1 mm holes drilled. The filtered beads are naturally dried or dried at room temperature in the range of about 80 ° C., and then the alkali metal is filtered out while maintaining a solution of 1 mol (mm) of ammonium nitrate (NH ₄ NO ₃ ) at 90 ° C. After washing three times or more with distilled water and dried again in an oven at 80 ℃. The dried beads were raised to 1000 ° C. at a rate of 5 ° C. per minute and then calcined by holding at 1000 ° C. for 1 hour.

The beads prepared after firing had an average size of 2.0 mm and a pore size of 40 nm on average.

<Example 2>

While stirring 28 g of alginic acid powder with stirrer, add to 980 g of potassium silicate solution, mix, and stir slowly for 10 minutes in 420 g of colloidal silica sol. Mix while giving. The mixed solution was dropped into a membrane and dropwise through a 10-mm nozzle with a 3 mm hole in a pre-prepared container of calcium chloride (1 liter of water / 25 g CaCl ₂ · 2H ₂ O). Drop. At this time, when the droplets of the mixed solution come into contact with the calcium chloride solution, the millimeter-sized beads are immediately cured or gelled into the calcium chloride solution. At this time, all the beads which are cured or quenched are prepared by stacking in the calcium chloride solution contained in the container without any contact with each other even if they are in contact with each other in solution.

The beads thus produced are filtered separately from the calcium chloride solution as in Example 1. Thereafter, the drying step and the firing step are the same as in Example 1. The beads produced had an average size of 2.0 mm and a pore size of 90 nm on average.

<Example 3>

Add 25 drops of ammonia (NH ₄ OH) solution to 25 g of water, adjust the pH (pH) to about 14, and add 5 g of fumed silica to mix in a blender. 35 g of potassium silicate solution is mixed with the silica sol thus prepared (mixture A).

Add 2-3 drops of ammonia (NH ₄ OH) solution to 20 g of water, adjust pH to 13-14, add 30 g of fumed silica, and mix in blender. All. (Mixture B)

Mixed solution B is mixed with mixed solution A, and then 1 g of alginic acid is added. The final mixed solution thus prepared is dropwise introduced into the calcium chloride solution through a nozzle or a spinnerret as in <Example 1> to prepare beads having a millimeter size.

Thereafter, the drying process and the firing process are the same as in <Example 1>. The size of the beads produced was 2.0 mm on average and the pore size was 500 nm on average.

According to the present invention, it is an environmentally friendly process because it completely excludes the use of an oil solvent used in the manufacturing process of the silica beads containing the nano-sized pores. In addition, because the manufacturing process is simple, mass production is possible and the manufacturing process time can be greatly reduced, thereby minimizing the manufacturing cost.

In addition, it is possible to produce beads of good quality having a very small size and distribution of pores.

Claims (9)

Sodium Silicate, an alkali metal silicate, in a stabilized silica sol in which nano particles are well dispersed in millimeter-sized silica beads with a uniform distribution of nano-sized pores, and a method of preparing the beads. ), Potassium silicate, lithium polysilicate, ammonium silicate, etc. After the slurry passes through a nozzle or a spinneret, the slurry reacts with the calcium chloride liquid and immediately cures to form beads having a millimeter size. The beads thus prepared are calcined at 600 ° C. to 1000 ° C. so that the nano pores are formed by the nano particles uniformly distributed in the beads. Beads) and a method for producing the beads. The method of claim 1, wherein the size of the nano pores uniformly distributed in the prepared silica beads is in the range of 10 nm to 1000 nm, the size of the beads having nano-sized pores is in the range of 0.5 mm to 10 mm. The method of claim 1, wherein the particles that control the nanopores are silica nanoparticles dispersed in a silica sol, the size of the nanoparticles is 2 nm to 500 nm. 2. The content of soda alginate added to the mixture of silica sol and alkali metal silicate is in the range of 5 to 20% of the solid solution in the slurry by weight. The mixed liquid of the silica sol and the alkali metal silicate is in the range of 8-15. The mixture of silica sol and alkali metal silicate to which the alginic acid soda salt is added has a viscosity in the range of 10 to 500 poise. The method of claim 1, wherein the calcium chloride solid solution in the calcium chloride solution is in the range of 1 to 10% weight ratio. The temperature for drying the cured silica beads is in the range of 25 ° C to 100 ° C. The method of claim 1, wherein the firing temperature of the dried beads range from 600 ℃ to 1000 ℃.