KR20010096628A - Method for preparing porous silica, porous silica based molding material, and nano-sized silica particle derived from rice husk - Google Patents

Abstract

PURPOSE: Provided is a preparation method of porous silica with nano-sized(less than 10nm) canals and pores from rice hulls or rice straws, silica formings using porous silica as a raw material, and homogeneous nano-sized silica particles(50-500nm) by separating porous silica. CONSTITUTION: The method for preparing porous silica is as follows: acid-treating rice hulls or rice straws; carbonizing by heating at 100-900deg.C for 1-6hrs. in anaerobic atmosphere; oxidizing by heating at 100-900deg.C for 1-6hrs. in aerobic atmosphere. The porous silica formings is obtained by pressing the prepared silica containing 5-100mol(based on 100mol of silicon) of at least one additive selected from oxides, chlorides and nitrides of Al, Mg, Zr, Co and Mo; heating at 500-1500deg.C in vacuum, inert(He, N2 and Ar) or reactive(H2, O2 and HF) atmosphere. The nano-sized silica particles are obtained by breaking canals in silica through a physical method., that is, mixing the prepared silica with solvent, followed by ultrasonic treating or freezing and thawing.

Description

Method for producing porous silica, porous silica molded body and nano-sized silica particles produced from rice husks

The present invention relates to a porous silica obtained from chaff or rice straw, in particular a method for producing a porous silica having a canal or pores of less than 10 nm from chaff or rice straw, nano-sized bone or pores using the porous silica It relates to a method for producing a silica molded body (molding plate) having a, and a method for producing nano-sized silica particles by separating the porous silica.

The presence of silica in plants has been known for a relatively long time. In particular, rice contains about 10% by weight of silica in rice hulls or rice straw, and has a high purity silicon raw material (JA Amick, J. Electrochem. Soc. 129, 864 (1982); LP Hunt, et.r, J Electrochem.Soc. 131, 1683 (1984)), raw materials of silicon carbide (RV Krishnarao, et.r, J. Am. Chem. Soc. 74, 2869 (1991)), cement additives (Jose James, et.r. , J. Sci. Ind. Res. 51, 383 (1992)). This silica is one of the potential resources in the Asia region where rice is grown.

Such silica is treated with chaff or rice straw with acid (Germany Patent Publication No. 276,671, Chinese Patent Publication No. 1,062,315, Chinese Patent Publication No. 1,039,000, Chinese Patent Publication No. 1,039,568, Soviet Patent No. 1,699,918). After treatment at a high temperature can be obtained silica. These patents focus on the silica component rather than the structure of the silica obtained.

In addition, after treating the rice husk or rice straw with an enzyme and heating at high temperature, silica can be obtained (Korean Patent Publication No. 1995--18466). Although it is mentioned here that the obtained silica will have pores of several nm, the amount of pores, the size of the pores, the form of the pores, and the origin of the pores of the silica prepared from rice straw or rice husk can be used. It is not studied if there is any.

In view of the problems of the prior art, the present invention provides a method for producing a porous silica having a bone or pores of 10 nm or less from chaff or rice straw, a method for producing a molded article containing the porous silica as a main raw material, and obtained by breaking down the pores. It is an object to provide a method for producing fine silica particles.

1 is an electron micrograph of porous silica obtained from rice husks.

2 is a pore distribution graph of porous silica obtained from rice husks.

Figure 3 is an electron micrograph obtained after the ultrasonic wave to the porous silica obtained from the chaff.

Figure 4 is a pore distribution graph obtained after the ultrasonic wave to the porous silica obtained from the chaff.

5 is an electron micrograph obtained after compressing the porous silica obtained from the chaff and heating to a temperature of 700 ℃.

6 is an electron micrograph obtained after compressing the porous silica obtained from the chaff and heating to a temperature of 750 ℃.

7 is an electron micrograph obtained after compressing the porous silica obtained from the chaff and heating to a temperature of 800 ℃.

8 is an electron micrograph obtained after compressing the porous silica obtained from the chaff and heating to a temperature of 850 ℃.

In order to achieve the above object, the present invention provides a method for producing a porous silica having a bone or pores of 10 nm or less,

Chaff or rice straw is carbonized in an acid-treated and anoxic atmosphere and then oxidized in an aerobic atmosphere

It provides a method for producing a porous silica comprising a.

In addition, the present invention is a method for producing a porous silica molded article,

a) chaff or rice straw is acidified and carbonized in an anaerobic atmosphere, followed by aerobic

Oxidizing in an atmosphere to produce porous silica;

b) pressure molding the porous silica of step a); And

c) the molding of step b) is vacuum, inert gas, or reactive gas atmosphere.

Heat treatment to a temperature of 500 to 1500 ° C. under

It provides a method for producing a porous silica formed body comprising a.

In addition, the present invention provides a method for producing nano-sized silica particles,

a) chaff or rice straw is acidified and carbonized in an anaerobic atmosphere, followed by aerobic

Oxidizing in an atmosphere to produce porous silica;

b) an average particle diameter of 50 by physically treating the porous silica of step a)

Separating into silica particles having from 500 nm to 500 nm

It provides a method for producing nano-sized silica particles comprising a.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for easily producing a porous silica having a bone or pores of 10 nm or less from rice husks or rice straws, a method for producing a silica molded body that can use the bones or pores of the porous silica, and the porous silica rice husks or rice straws. It is to provide a method of obtaining uniform silica particles having an average particle diameter of 50 to 500 nm by disrupting the valleys of the obtained porous silica.

First, a method for producing porous silica from rice husk or rice straw will be described.

Method for producing porous silica having a bone or pore size of 10 nm or less of the present invention is treated with chaff or rice straw with an acid such as hydrochloric acid, nitric acid, sulfuric acid, etc., in an oxygen-free atmosphere at a temperature of 100 ℃ to 900 ℃ for 1 hour to 6 Carbonized by heating for a time, and then oxidized by heating for 1 to 6 hours at a temperature of 100 ℃ to 900 ℃ in an aerobic (or air) atmosphere to prepare a porous silica. The porous silica prepared in this way has a micron size, and maintains a bone of 10 nm or less inherent in the silica contained in the rice hull or rice straw. If each heat treatment temperature exceeds 900 ℃ it is difficult to maintain the bone or pores contained in chaff.

The acid treatment serves to decompose and dissolve organic matter contained in rice husk or rice straw and to dissolve metal ions present in rice straw or rice husk, and heat treatment in an oxygen-free atmosphere is to carbonize rice husk or rice straw, Heat treatment in an aerobic atmosphere is the final oxidation of the carbonized rice husk or rice straw.

Therefore, such acid treatment and heat treatment can be largely carried out in two ways.

In the first method, the rice hull or rice straw is acid-treated as it is with acid such as hydrochloric acid, nitric acid, sulfuric acid, etc., and the acid treated product is subjected to an acid free atmosphere (vacuum or inert gas atmosphere) at a temperature of 100 to 900 ° C. for 1 hour to 6 After the heat treatment for a time, the heat treatment for 1 to 6 hours at a temperature of 100 ℃ to 900 ℃ again in an aerobic atmosphere.

Another second method is heat treatment of chaff or rice straw as it is in an oxygen-free atmosphere at a temperature of 100 ℃ to 900 ℃ for 1 hour to 6 hours, the acid treatment of the heat treated with acid such as hydrochloric acid, nitric acid, sulfuric acid In addition, heat treatment is performed for 1 hour to 6 hours at a temperature of 100 ° C to 900 ° C in an aerobic (or air) atmosphere.

The first method is to perform carbonization after the acid treatment and oxidize it, and to perform the acid treatment after the carbonization treatment of the second method and to oxidize it. In particular, since the second method is subjected to acid treatment after carbonization, it is easy to remove residual organic matter and metal contained in rice hull or rice straw, and thus, there is an advantage of obtaining a higher purity porous silica.

Porous silica prepared by this method has a large surface area of 300 m ² / g or more, it is possible to produce a high-purity porous silica more easily than conventional methods from rice straw or chaff. Porous silica prepared by the manufacturing method of the present invention has a large surface area and high purity, so that it can be used in various applications such as gas adsorbents, fillers for liquid or gas chromatography using bone, coating materials for thin layer chromatography, and ink bleeding inhibitors for paper. Can be used.

Next, the manufacturing method of the silica molded body which uses the said porous silica as a main raw material is demonstrated.

The silica molded body is manufactured by using a porous silica having a bone of 10 nm or less obtained from the chaff and rice straw described above as it is, or as a main raw material, by press molding by a method such as compression, mold press molding, or the like, and heating at a high temperature. Such a silica molded body retains the valley of 10 nm or less of silica obtained from chaff and rice straw. In this case, the silica molded body has various physical properties depending on the heat treatment temperature and time or the type or amount of the material added to the silica, and from this, various types of silica structures having a valley of 10 nm or less can be manufactured.

Additives of metal compounds selected from the group consisting of oxides, nitrates, chlorides, and sulfur oxides of aluminum, magnesium, titanium, zirconium, chromium, iron, cobalt, nickel, molybdenum and tungsten when compression molding the porous silica Press molding may be further added, and the use of such an additive is preferably added in an amount corresponding to 5 to 100 mole parts by weight of the metal component in the oxide or compound with respect to 100 mole parts by weight of silicon of the silica. The addition of these additives can change the molding temperature and control the molding's mechanical strength, adsorption capacity, affinity for molecules and chemical properties.

The silica molded product to be press-molded above is heat-treated at a temperature of 500 to 1500 ° C. under a vacuum, inert gas, or reactive gas atmosphere to produce a final silica molded body. The heating time varies depending on the type, size, and thickness of the molding, and is not particularly limited, but heat treatment can be performed evenly in most cases of 10 minutes or more.

The inert gas is preferably helium, nitrogen, argon or the like, and the reactive gas is preferably hydrogen, oxygen, hydrogen fluoride or the like. At this time, as the heat treatment temperature increases, the strength of the molded body increases and the overall porosity of the molded body changes according to the type of the reaction gas.

The silica molded body thus produced can be purified and filtered in a chemical process; Ultrapure water production and clean room in semiconductor processes; Isolation of micro organisms or viruses in the biological industry; Protection against biochemical attack using bacteria or viruses; Clean room that requires the removal of allergens or pathogens; Catalyst carriers; Optical instrument components; And the purification of gases.

Next, the manufacturing method of a nano size silica particle is demonstrated.

Method for producing nano-sized silica particles of the present invention is to prepare a nano-sized silica particles by disintegrating the bone by physically treating porous silica having a bone of 10 nm or less obtained from the chaff or rice straw described above by a physical method.

This physical treatment separates porous silica, which was macroscopically larger than microns into 50 to 500 nm size silica particles, which has the advantage of being able to mass produce very small size silica particles of constant size. The physical treatment may be a treatment method such as ultrasonic irradiation, freeze thawing, etc., and is distinguished from mechanical treatment by a strong force such as grinding.

Silica particles prepared as described above have a very small and uniform particle diameter, and thus may be used as various materials such as optical fiber materials, wear resistant materials, abrasives, tool materials, particle dispersion, high temperature strength materials, optical lenses, and the like.

The present invention will be described in more detail with reference to the following examples. However, an Example is for illustrating this invention and is not limited only to these.

EXAMPLE

Example 1

The washed rice husks were acid treated with 1 mol hydrochloric acid for 6 to 10 hours, filtered and dried, and then heated to a temperature of 200 ° C. for 6 hours while flowing nitrogen. The heat-treated chaff was further heated in air at 600 ° C. for 1 hour to obtain silica.

This silica has a surface area of 327 m 2 / g measured by nitrogen adsorption, shows a broad peak at 22 ° of double diffraction angle in X-ray diffraction, and a sharp peak of -111 ppm at silicon solid nuclear magnetic resonance with atomic weight 29 Indicates. The resulting silica contains 508 ppm aluminum, 498 ppm potassium, 177 ppm calcium, 100 ppm sodium, 95 ppm iron, 81 ppm magnesium, 24 ppm titanium, and the purity of silica is 99.8% by weight or more. to be.

1 is an electron micrograph of the obtained silica, and it can be observed that uniform spherical silica having a diameter of about 50 nm is accumulated.

Figure 2 shows the pore distribution according to the nitrogen adsorption of the silica, there is a pore of 4 nm size, the pore volume is 0.24 ml / g. Comparing the pore distribution by nitrogen adsorption of FIG. 2 with the electron micrograph of FIG. 1, it is understood that the valleys between the silica particles have a width of about 4 nm, and the valleys serve as pores.

It is understood that these silica particles present in rice and the valleys between them (4 nm wide) play a role in passing water and air while protecting rice grains from the microorganisms surrounding the rice habitat when the rice is ripe.

Example 2

The washed rice husks were dried and heated at a temperature of 200 ° C. for 1 hour while flowing nitrogen. The heat-treated rice husk was treated with 1 mol hydrochloric acid for 6 to 10 hours, filtered and dried, and then heated in air at 600 DEG C for 6 hours to obtain silica.

The surface area measured by nitrogen adsorption of this silica, twice the diffraction angle of X-ray diffraction, silica purity, electron microscope structure, pore distribution, pore volume, and the like were the same as those of the silica obtained in Example 1.

Examples 3 and 4

Each of the porous silicas obtained in Examples 1 and 2 was placed in a beaker with water and the ultrasonic wave was spun for 2 hours with a 100 watt ultrasonic cleaner at 25 ° C., followed by drying to obtain silica having an average particle diameter of 50 nm.

3 is an electron microscope to observe the dried sample after the ultrasound. Compared with FIG. 1, the valleys between the silica particles are widened or a plurality of silica particles are formed in agglomerates. The surface area measured by nitrogen adsorption of ultrasonically treated silica was reduced to 205 m 2 / g than before, while the pore volume was increased to 0.29 ml / g than before.

4 is a pore distribution of silica treated with ultrasonic waves, and it can be seen that the pore distribution is widened after ultrasonication as compared with the pore distribution graph of the silica before the treatment (FIG. 2). These results indicate that some of the silica particles may be entangled by sonication, but the width of the bones in between may be increased, and the silica particles may be completely separated.

Example 5

After dispersing the silica prepared in Example 1 in water, completely frozen in a freezer at -10 ℃, it was put in a thermostat at 50 ℃ again and rapidly melted, dried in a dispersed state to obtain silica particles.

The fused silica has a wider valley between the silicas or a plurality of silica particles in the same way as the silica treated with ultrasonic waves of Examples 3 and 4. The surface area measured by nitrogen adsorption of the lysed silica was 205 m 2 / g, which was lower than before treatment, while the pore volume was increased to 0.29 ml / g than before treatment.

Example 6

Press-molding (molding) the silica prepared in Example 1 to prepare a disk-shaped molded product, and the molded product was heated at 700 ° C., 750 ° C., 800 ° C., and 850 ° C. for 12 hours, respectively. The silica molded body in which the bone was preserve | saved as it was produced.

5, 6, 7, and 8 are electron micrographs obtained by compressing the silica obtained from the chaff and heating it at 700 ° C., 750 ° C., 800 ° C., and 850 ° C. for 12 hours. It can be seen that the microstructure becomes denser as the heating temperature increases.

Table 1 shows the silica obtained from the rice hulls in a disk shape, and after heating for 12 hours at temperatures of 700 ° C., 750 ° C., 800 ° C., and 850 ° C., respectively, the permeability to air is measured and the same area, It shows the relative size in terms of the same thickness, the surface area measured by the nitrogen adsorption method, and the total pore volume. As the treatment temperature increased, the air permeability, surface area, and total volume of pores to the molecules decreased.

division Heat treatment temperature (℃) 700 750 800 850 Air permeability 3.36 2.70 2.24 0.80 Surface area (㎡ / g) 161 157 128 59 Total pore volume (ml / g) 0.27 0.26 0.24 0.15

5, 6, 7, 8 and Table 1 it can be seen that according to the heating temperature and the heating time of the compression-molded chaff silica structure, the density of the structure and the permeability to any molecules, particles, microorganisms can be adjusted. .

The method for preparing porous silica of the present invention can easily prepare high-purity silica having a size of 10 microns or more from rice hulls or rice straws, and the method for preparing silica molded bodies is characterized by the processing temperature of silicas obtained from rice hulls or rice straws. Depending on the time or the type or amount of the material added to the silica can be produced a molded structure having a bone of 10 nm or less as the main component of any type of silica having a variety of properties, the method of producing nano-size silica particles It is possible to mass produce very small silica particles of size. The porous silica particles, silica molded bodies, and silica particles prepared as described above can be easily used in various fields.

Claims (15)

In the method of producing a porous silica having a bone or pores of 10 nm size or less, Chaff or rice straw is subjected to acid treatment and carbonization in an oxygen-free atmosphere, followed by oxidation in an aerobic atmosphere. Method for producing a porous silica comprising a. The method of claim 1, Iii) acidifying the rice bran or rice straw; Ii) the acid treated product at a temperature of 100 ° C. to 900 ° C. under an oxygen-free atmosphere. Heat treatment for 1 to 6 hours; And Iii) the heat treated product at a temperature of 100 ° C. to 900 ° C. under an aerobic atmosphere. Heat treatment for 1 to 6 hours Method for producing a porous silica comprising a. The method of claim 1, Iii) the rice husk or rice straw at the temperature of 100 ℃ to 900 ℃ under an oxygen-free atmosphere Heat treatment for 1 to 6 hours; Ii) acid treating the heat treated product; And Iii) the acid treated product at a temperature of 100 ° C. to 900 ° C. under an aerobic atmosphere. Heat treatment for 1 to 6 hours Method for producing a porous silica comprising a. In the method for producing a porous silica compact, a) after chaff or rice straw is acidified and carbonized in an oxygen-free atmosphere, Oxidizing in an aerobic atmosphere to produce porous silica; b) pressure molding the porous silica of step a); And c) the molding of step b) is vacuum, inert gas, or reactive gas atmosphere. Heat treatment to a temperature of 500 to 1500 ° C. under Method for producing a porous silica molded body comprising a. The method of claim 4, wherein The porous silica of step a) Iii) acidifying the rice bran or rice straw; Ii) the acid treated product at a temperature of 100 ° C. to 900 ° C. under an oxygen-free atmosphere. Heat treatment for 1 to 6 hours; And Iii) the heat treated product at a temperature of 100 ° C. to 900 ° C. under an aerobic atmosphere. Heat treatment for 1 to 6 hours Method for producing a porous silica molded body produced by the method comprising a. The method of claim 4, wherein The porous silica of step a) Iii) the rice husk or rice straw at the temperature of 100 ℃ to 900 ℃ under an oxygen-free atmosphere Heat treatment for 1 to 6 hours; Ii) acid treating the heat treated product; And Iii) the acid treated product at a temperature of 100 ° C. to 900 ° C. under an aerobic atmosphere. Heat treatment for 1 to 6 hours Method for producing a porous silica molded body produced by the method comprising a. The method of claim 4, wherein The compression molding of step b) is a method for producing a porous silica formed by further adding an additive of a metal compound to silica. The method of claim 7, wherein Method for producing a porous silica molded body wherein the additive is at least one selected from the group consisting of oxides, chlorides, nitrates, and sulfur oxides of aluminum, magnesium, titanium, zirconium, chromium, iron, cobalt, nickel, molybdenum, and tungsten. . The method of claim 7, wherein The additive is a method for producing a porous silica molded body is added in an amount corresponding to 5 to 100 moles of the metal component in the additive with respect to 100 moles of silicon of the silica. The method of claim 4, wherein The method of preparing a porous silica formed body is selected from the group consisting of helium, nitrogen, and argon, and the reactive gas is selected from the group consisting of hydrogen, oxygen, and hydrogen fluoride. In the method for producing nano-sized silica particles, a) after chaff or rice straw is acidified and carbonized in an oxygen-free atmosphere, Oxidizing in an aerobic atmosphere to produce porous silica; And b) an average particle diameter of 50 by physically treating the porous silica of step a) Separating into silica particles having from 500 nm to 500 nm Method for producing nano-sized silica particles comprising a. The method of claim 11, The porous silica of step a) Iii) acidifying the rice bran or rice straw; Ii) the acid treated product at a temperature of 100 ° C. to 900 ° C. under an oxygen-free atmosphere. Heat treatment for 1 to 6 hours; And Iii) the heat treated product at a temperature of 100 ° C. to 900 ° C. under an aerobic atmosphere. Heat treatment for 1 to 6 hours Method for producing nano-sized silica particles produced by a method comprising a. The method of claim 11, The porous silica of step a) Iii) the rice husk or rice straw at the temperature of 100 ℃ to 900 ℃ under an oxygen-free atmosphere Heat treatment for 1 to 6 hours; Ii) acid treating the heat treated product; And Iii) the acid treated product at a temperature of 100 ° C. to 900 ° C. under an aerobic atmosphere. Heat treatment for 1 to 6 hours Method for producing nano-sized silica particles produced by a method comprising a. The method of claim 11, The physical treatment of step b) is a method for producing nano-sized silica particles that is subjected to ultrasonic treatment after mixing the silica with the solvent. The method of claim 11, The physical treatment of step b) is a method for producing nano-sized silica particles that is freeze melting after mixing the silica in the solvent.