KR20100054036A - Continuous preparation of surface-modified nanoparticles using supercritical fluids and surface-modified nanoparticles prepared thereby - Google Patents

Abstract

PURPOSE: A method for sequentially manufacturing a nanoparticle of which surface is modified is provided to massively produce nanoparticles by performing nanoparticle generation and surface modification. CONSTITUTION: A method for sequentially manufacturing a nanoparticle of which surface is modified comprises: a dissolving particle precursor and surface modifying agent in alcohol to produce a particle precursor solution and surface modifying solution; a step of continuously introducing the particle precursor solution, surface modifying solution, and alcohol in a reactor of high temperature and pressure under critical condition to obtain surface-modified nanopaticles; and a step of cooling the nanopaticles.

Description

CONTINUOUS PREPARATION OF SURFACE-MODIFIED NANOPARTICLES USING SUPERCRITICAL FLUIDS AND SURFACE-MODIFIED NANOPARTICLES PREPARED THEREBY}

The present invention relates to a method of continuously producing nanoparticles having excellent dispersibility in a heat transfer fluid at a high speed and to surface modified nanoparticles prepared by the above method.

Heat exchangers include distillation towers used for the decomposition of crude oil in petroleum refining plants, processes for heating or cooling equipment when manufacturing products in general plants, waste liquid recovery processes, reactor reactor cooling, automotive cooling, electronic device cooling, air conditioners and refrigerators. It is a device that is used as a core device in almost all industrial fields such as household electric appliances. Although these devices consume a lot of energy, research on improving the efficiency of heat exchangers has not made much progress due to the fundamental problem of low thermal conductivity of water and ethylene glycol used as heat exchange fluids of heat exchangers. to be.

Nanofluid refers to a fluid in which thermal conductivity is significantly improved compared to a conventional heat exchange fluid by dispersing nano-sized metals, metal oxides, and carbon nanotubes in existing heat exchange fluids such as water and ethylene glycol. Nanoparticles currently used in the manufacture of nanofluids include metal particles such as copper (Cu), silver (Ag), aluminum (Al), copper oxide (CuO), alumina (Al ₂ O ₃ ), and iron oxide (Fe ₂ O _3). Metal oxide particles, such as a), and carbon nanotube particle | grains are mentioned.

As a method of preparing a nanofluid, a one-step method of preparing a nanofluid by preparing nanoparticles and condensing it in a fluid, a step of preparing nanoparticles, and a method of manufacturing the nanoparticles There is a two-step method consisting of dispersing within. U. S. Patent No. 6,221, 275 discloses a method for producing nanofluid by the one step method. The patent document describes a technique for vaporizing a substance to be dispersed in a fluid in a high vacuum chamber and directly condensing the vaporized material in a low vapor pressure fluid spinning in the high vacuum chamber to produce nanoparticles and to disperse it in a fluid. It is. Although the nanofluid produced by this method has excellent dispersibility of particles, the types of nanoparticles that can be produced are extremely limited, the production time of the nanofluid is very long, the nanoparticles are prepared batchwise, and the inside of the chamber is in a high vacuum state. The method is inadequate for mass production and commercialization of nanofluids, in that it must be maintained at and the entire high vacuum chamber must be rotated. In the two-stage method, first, nanoparticles are produced using a commercially available nanoparticle manufacturing method, such as gas phase method, and nanoparticles produced using methods such as pH control of fluid, sonication, physical dispersion stabilizer, and chemical surface modification. There is a method of improving the dispersibility of the fluid in the fluid and then dispersing it in the fluid. In spite of various efforts to improve dispersibility, the two-step method has a problem of coagulation and precipitation when the nanoparticles are dispersed in a fluid due to the inherent properties of the nanoparticles. Proceeding batchwise has the disadvantage that the manufacturing time is long and uneconomical.

Conventional dual processes of first producing the nanoparticles and then modifying the surface of the nanoparticles in a separate process include a gas phase method, a liquid phase method, and a mechanical chemistry method. Among them, the gas phase method using a fluidized bed and a fixed bed reactor is not efficient due to the cohesiveness of particles of 100 nm or less. In the case of the liquid phase method, in order to advance the reaction in the highly dispersed state of the nanoparticles, since a small amount of the nanoparticles are dispersed in an excess of an organic solvent to perform surface modification, productivity is low, and it is easy to secure uniformity of the surface modification as a batch reaction. It does not take a long time, and there is a disadvantage in that a high cost is required when the used organic solvent is post-treated. In addition, in the case of the mechanical chemistry method, there is a disadvantage in that a high possibility of incorporation of impurities during ball milling, it is difficult to obtain uniform surface modification, and is inefficient due to a long time reaction.

It is an object of the present invention to continuously introduce a particle precursor and a surface modifier into a reaction apparatus using a supercritical fluid, thereby simultaneously performing the generation of the nanoparticles and the surface modification of the produced nanoparticles, thereby producing a conventional nanoparticle generation step and surface modification. A single process of a dual process consisting of steps and a continuous process of the production of nanoparticles, thereby providing a method for continuous production of surface-modified nanoparticles that are easy to mass produce and have high productivity, and the surface-modified nanoparticles prepared by the above method. will be.

Accordingly, the present inventors have tried to solve the problems of the prior art as described above, and as a result, the dual process consisting of the existing nanoparticle generation step and the surface modification step is simplified into a single process, and a continuous process using a supercritical fluid, The present invention was completed by developing a method for preparing surface-modified nanoparticles capable of mass production of nanoparticles having excellent dispersibility within a high speed.

In the present invention, the method for producing surface-modified nanoparticles

(a) dissolving the particle precursor and the surface modifier in alcohol to produce a particle precursor solution and a surface modifier solution;

(b) continuously introducing the particle precursor solution, the surface modifier solution and the alcohol into the high temperature and high pressure reactor under supercritical conditions, respectively, to produce surface modified nanoparticles;

(c) cooling the solution of the surface modified nanoparticles,

(d) separating and recovering the surface-modified nanoparticles from the cooled solution using a filter

.

The present invention also relates to surface modified nanoparticles prepared by the above method.

As described above, according to the present invention, the supercritical fluid is used to continuously introduce the particle precursor and the surface modifier into the high temperature and high pressure reaction apparatus to generate nano-sized particles, and simultaneously chemically modify the surface of the nanoparticles. The nanoparticles which are excellent in dispersibility inside can be manufactured. The method for producing the surface-modified nanoparticles of the present invention simplifies the dual process of the production step and the surface modification step of the existing nanoparticles in a single process, thereby lowering the equipment cost and operation cost, and easy to mass-produce because it uses a continuous manufacturing method. In addition, since the nanoparticles are manufactured at a high speed, they are economical and have an advantage of generating various kinds of nanoparticles. In addition, the nanoparticles prepared according to the method of the present invention have a good surface dispersibility and excellent dispersibility in the heat transfer fluid.

Continuous production method of surface-modified nanoparticles using a supercritical fluid according to the present invention,

(a) dissolving the particle precursor and the surface modifier in alcohol to produce a particle precursor solution and a surface modifier solution;

(b) continuously introducing the particle precursor solution, the surface modifier solution and the alcohol into the high temperature and high pressure reactor under supercritical conditions, respectively, to produce surface modified nanoparticles;

(c) cooling the solution of the surface modified nanoparticles,

(d) separating and recovering the surface-modified nanoparticles from the cooled solution using a filter

.

The method according to the present invention constitutes a continuous reaction apparatus using a supercritical fluid, and continuously introduces a particle precursor and a surface modifier into the reaction apparatus to produce nanoparticles having a diameter of 1 to 500 nm and at the same time the surface of the nanoparticles. Chemical modification. In particular, when manufacturing the surface-modified nanoparticles according to the present invention, it is possible to produce nanoparticles with excellent dispersibility in ethylene glycol used as a heat transfer fluid.

In the step (a), the particle precursor and the surface modifier may be dissolved in alcohol, respectively, to separately prepare the particle precursor solution and the surface modifier solution, or the particle precursor and the surface modifier may be dissolved together in alcohol to prepare a mixed solution. have.

The particle precursor is, for example, magnesium (Mg), aluminum (Al), titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), zinc (Zn), zirconium (Zr), ruthenium (Ru) , Compounds of metals selected from the group consisting of rhodium (Rh), silver (Ag), palladium (Pd), platinum (Pt) and cerium (Ce), salts thereof, and mixtures thereof. Although it is not limited to this, What is necessary is just a precursor which melt | dissolves in alcohol. Specific examples of such particle precursor compounds include cerium nitrate (Ce (NO ₃ ) ₃ ), zinc nitrate (Zn (NO ₃ ) ₂ ), aluminum nitrate (Al (NO ₃ ) ₃ ), magnesium nitrate (Mg (NO ₃ ) ₂ ), Titanium sulfate (Ti (SO ₄ ) ₂ ), manganese nitrate (Mn (NO ₃ ) ₂ ), iron nitrate (Fe (NO ₃ ) ₃ ), iron sulfate (Fe (SO ₄ ) ₃ ), cobalt nitrate (Co (NO ₃ ) ₂ ), zirconium nitrate (Zr (NO ₃ ) ₄ ), ruthenium chloride (RuCl ₃ ), rhodium chloride (RhCl ₃ ), silver nitrate (AgNO ₃ ), palladium nitrate (Pd (NO ₃ ) ₂ ), nitrate Platinum (Pt (NO ₃ ) ₂ ), and the like.

The alcohol may be selected from, for example, methanol, ethanol, propanol, butanol, pentanol, and mixtures thereof, but is not limited thereto. Alcohols having a carbon number range from 1 to 5 are particularly preferred. If an alcohol having 6 or more carbon atoms in the above range is used, the solubility of the particle precursor may be significantly reduced.

The surface modifier is not particularly limited as long as it is an organic substance which is dissolved in alcohol and can react with hydroxyl groups on the surface of the nanoparticles, and preferably includes carboxylic acid, aldehyde, amine, and the like. Specific examples of surface modifiers include hexanoic acid (CH ₃ (CH ₂ ) ₄ COOH), octanoic acid (CH ₃ (CH ₂ ) ₆ COOH), decanoic acid, CH ₃ (CH ₂ ) ₈ COOH), dodecanoic acid (CH ₃ (CH ₂ ) ₁₀ COOH), tetradecanoic acid (CH ₃ (CH ₂ ) ₁₂ COOH), heptadecanoic acid (CH ₃ (CH ₂ ) ₁₄ COOH), octadecanoic acid (CH ₃ (CH ₂ ) ₁₆ COOH), oleic acid, CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOH), linoleic acid, CH ₃ (CH ₂ ) ₄ CH = CHCH ₂ CH = CH (CH ₂ ) ₇ COOH), hexylamine, CH ₃ (CH ₂ ) ₅ NH ₂ ), octylamine, CH ₃ (CH ₂ ) ₇ NH ₂ ), decylamine, CH ₃ (CH ₂ ) ₉ NH ₂ ), dodecylamine, CH ₃ (CH ₂ ) ₁₁ NH ₂ ), tetratradecaamine, CH ₃ (CH ₂ ) ₁₃ NH ₂ ), hexaaldehyde (hexaldehyde, CH ₃ (CH ₂ ) ₄ CHO), octaaldehyde (octaldehyde, CH ₃ (CH ₂ ) ₆ CHO), decaaldehyde (decaldehyde, CH ₃ (CH ₂ ) ₈ CHO), dodecaal Dodecaldehyde, CH ₃ (CH ₂ ) ₁₀ CHO, tetradecaaldehyde (tetradecaldehyde, CH ₃ (CH ₂ ) ₁₂ CHO) and mixtures thereof, but are not limited thereto.

In the present invention, the concentration of the particle precursor in the alcohol is not particularly limited, but may be preferably 0.001 mol / l to 1 mol / l, more preferably 0.01 mol / l to 0.5 mol / l. If the concentration of the particle precursor is less than 0.001 mol / l out of the above range, the concentration is too thin, resulting in low productivity due to low productivity, and if the concentration of the particle precursor exceeds 1 mol / l, the concentration is too high to give viscosity. Higher, adversely affecting continuous flow and as a result, the quality of the particles produced can be degraded.

In the present invention, the concentration of the surface modifier in the alcohol is not particularly limited, but may preferably be from 0.001 / L mol to 5 mol / L, more preferably from 0.01 mol / L to 1 mol / L. If the concentration of the surface modifier is outside the above range and less than 0.001 mol / l, the concentration is too thin to carry out effective surface modification. If the concentration of the surface modifier exceeds 5 mol / l, the concentration is too thick to increase the viscosity. It may adversely affect the continuous flow and as a result degrade the quality of the particles produced.

In the present invention, in order to maintain the supercritical fluid state, the reaction temperature is 200 ℃ to 600 ℃, preferably 250 ℃ to 400 ℃, the reaction pressure is 20 bar to 500 bar, preferably 50 bar to 500 bar Particle generation and surface modification reactions can be carried out in a phosphorus reactor. If the reaction temperature is less than 200 ℃, the reaction pressure is less than 20 bar has a problem that the size of the nanoparticles to be prepared, the particle size distribution is widened and the crystallinity is reduced, the reaction temperature is more than 600 ℃, the reaction pressure is more than 500 bar In this case, economics are reduced because high temperature and high pressure must be maintained.

In the present invention, a general method such as a heat exchanger can be used for the cooling step of (c), and methods such as filtration and centrifugal separation can be used for the separation and recovery step of (d).

In the present invention, the step of washing and drying the surface-modified nanoparticles after the step (d) can be further performed. General methods, such as washing an organic solvent, can be used for a washing process, and methods, such as vacuum drying, oven drying, and freeze drying, can be used for a drying process. As the organic solvent, an organic solvent for dissolving surface modifiers such as methanol, ethanol and tetrahydrofuran can be used.

In the present invention, the diameter of the surface-modified nanoparticles is 1 nm to 500 nm, preferably 2 nm to 250 nm, more preferably 5 nm to 100 nm. When the diameter of the particles exceeds 500 nm, the nano-sized particulate properties are greatly reduced and the dispersibility is lowered. When the diameter of the particles is less than 1 nm, the dispersibility is not only difficult to handle, but also due to the increase of cohesion between particles. This can be degraded.

Therefore, the surface-modified nanoparticles according to the present invention prepared by the above-described method is a surface modified with at least one surface modifier selected from carboxylic acids, aldehydes, amines and mixtures thereof, cerium having a diameter of 1 to 500 nm, At least one nanoparticle selected from zinc, aluminum, magnesium, titanium, manganese, iron, cobalt, zirconium, ruthenium, rhodium, silver, palladium or platinum, mixtures thereof.

1 illustrates an example of an apparatus for continuously producing surface modified nanoparticles using a supercritical fluid in accordance with the present invention. Continuous production apparatus for surface-modified nanoparticles according to the present invention is a high pressure reactor ( 10 ), high pressure pump ( 70 , 71 ), heater ( 30 ), preheater ( 31 ), filter ( 50 ), rear pressure regulator ( 60 ), And a particle precursor solution and a surface modifier solution storage container 80 , an alcohol storage container 81 . Hereinafter, a method of continuously preparing surface-modified nanoparticles using a supercritical fluid is shown in FIG. 1 . It demonstrates concretely with reference.

First, the particle precursor and the surface modifier are dissolved in alcohol, and then introduced into the particle precursor solution and the surface modifier solution storage container 80 . Alcohol in the alcohol storage container 81 is transferred into the high pressure reactor 10 using the high pressure pump 71 . At this time, the temperature of the alcohol introduced into the high pressure reactor is controlled by using a preheater ( 20 ), the temperature of the high pressure reactor is controlled by using a heater ( 30 ), the pressure of the high pressure reactor using a rear pressure regulator ( 60 ). Control to keep the alcohol introduced into the high pressure reactor in a supercritical fluid state. Surface-modified nanoparticles are prepared by continuously transferring a particle precursor solution and a surface modifier solution into a high pressure reactor at a predetermined temperature and pressure to react with the supercritical fluid alcohol. The temperature of the resulting solution of surface-modified nanoparticles is lowered using a cooler 40 , and then the filter 50 is used to separate and recover the surface-modified nanoparticles from the cooled solution.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for describing the present invention in detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples.

Examples and Comparative example

Characterization of Surface Modified Nanoparticles

In order to confirm the surface modification of the nanoparticles prepared by the manufacturing method of the present invention, DuPont's thermogravimetric analysis (hereinafter referred to as 'TGA') and Fourier transform infrared spectrometer manufactured by Thermo Electron (Fourier transform infrared spectroscopy, hereinafter referred to as 'FT-IR'), and transmission electron microscopy (EFI's, called 'TEM') was used to analyze particle morphology. .

Example 1

Methanol was introduced into a 1000 ml glass vessel, whereby cerium nitrate (Ce (NO ₃ ) ₃ ) was introduced as a particle precursor to adjust the concentration to 0.05 mol / l and decanoic acid as a surface modifier to introduce a concentration of 0.3 It was adjusted to mol / l. The mixed solution was pressurized to 300 bar by pumping at a rate of 2 ml / min using a high pressure pump. Methanol was introduced into another 1000 ml glass vessel and pumped at a rate of 6 ml / min using a high pressure pump to pressurize to 300 bar and transferred to the preheater. The pressurized mixed solution and methanol were mixed in a mixer maintained at 400 ° C., and then the mixture was transferred to a high pressure reactor maintained at 400 ° C. for 40 seconds. The resulting solution of surface modified nanoparticles was cooled using a cooler, and then the surface modified nanoparticles were separated and recovered using a filter. Unreacted decanoic acid was separated from the surface-modified nanoparticles recovered using a centrifuge and then washed with methanol. After washing, the surface-modified nanoparticles were dried in a vacuum oven at 60 ° C. for one day to remove methanol. 2 shows a TEM image of nanoparticles surface modified with decanoic acid after washing. 3 shows FT-IR results of nanoparticles surface modified with decanoic acid after washing. 4 shows the TGA results of nanoparticles surface modified with decanoic acid after washing. 5 shows the dispersion in water and ethylene glycol of nanoparticles surface modified with decanoic acid.

Comparative Example 1

Nanoparticles were prepared in the same manner as in Example 1, except that no decanoic acid was introduced. The prepared nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in FIGS. 2 , 3 , 4 , and 5 .

Comparative Example 2

Nanoparticles were prepared in the supercritical water in the same manner as in Example 1 except that no decanoic acid was used and water was used instead of alcohol. The prepared nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in FIGS. 2 , 3 , 4 , and 5 . The comparative example is a general method for preparing a conventional nanoparticles, an experiment for comparing with the surface-modified nanoparticles of the present invention.

As shown in FIG . 2 , the diameter of the ceria nanoparticles prepared using methanol and decanoic acid in Example 1 (a) is 2 to 3 nm. On the other hand, the diameter of the ceria nanoparticles prepared using only methanol without using decanoic acid in Comparative Example 1 (b) was 40-80 nm, and only water was used without using decanoic acid in Comparative Example 2 (c). Ceria nanoparticles prepared by the diameter of 20 ~ 60 nm. Therefore, it can be seen that decanoic acid is the cause of reducing the size of the nanoparticles. On the other hand, as shown in Figure 3, on the surface of the ceria nanoparticles prepared using water in Comparative Example 2 -OH group (3000 ~ 3750 cm ^-1 ) is present, while in Comparative Example 1 using methanol On the surface of one ceria nanoparticle, -CO- group (1050 cm ^-1 ), -CH ₃ group (1330 cm ^-1 ), -OH group (3000-3750 cm ^-1 ) were detected. Therefore, it was confirmed that the surface of the ceria nanoparticles prepared using methanol was surface modified with CH ₃ O-. In Example 1, in the surface of ceria nanoparticles prepared by using methanol and acid C = O groups _{^{(1780 cm -1), -CH 2}} - group (2850 cm ^-1), -CH ₃ group (2920 cm ^{- 1} ), -OH group (3000-3750 cm ^-1 ) was detected. Therefore, unlike Comparative Example 1 and Comparative Example 2 in Example 1 it can be seen that the ceria nanoparticles are surface-modified by decanoic acid.

As shown in FIG . 4, in the case of ceria manufactured by using water in Comparative Example 2 (c), since there was no organic substance on the surface, there was almost no change in weight even when heated to 800 ° C., Example 1 (a When the nanoparticles prepared in) were heated to 800 ° C., the weight was reduced to 88%. From this, it can be seen that the surface of the nanoparticles of Example 1 was modified with an organic material. As shown in Figure 5 , it can be seen that the surface-modified ceria nanoparticles prepared in Example 1 is very excellent in dispersibility in ethylene glycol. This is believed to be due to the very small particle diameter of 2-3 nm and the surface modified with decanoic acid. On the other hand, ceria nanoparticles prepared using methanol and water in Comparative Examples 1 and 2, respectively, were agglomerated in ethylene glycol, and it was confirmed that they precipitated at the bottom. From this, it was found that the dispersibility of these particles was poor.

Example 2

Ceria nanoparticles were surface-modified in the same manner as in Example 1, using hexanoic acid instead of decanoic acid. The prepared ceria nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Example 3

Ceria nanoparticles were surface-modified in the same manner as in Example 1, using decylamine instead of decanoic acid. The prepared ceria nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Example 4

Hexaaldehyde was used instead of the decanoic acid to prepare ceria nanoparticles surface-modified in the same manner as in Example 1. The prepared ceria nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Example 5

Ceria nanoparticles were surface-modified in the same manner as in Example 1, using ethanol instead of methanol. The prepared ceria nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Example 6

Surface-modified ceria nanoparticles were prepared in the same manner as in Example 1, using propanol instead of methanol. The prepared ceria nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Example 7

Using butanol instead of methanol, ceria nanoparticles were surface-modified in the same manner as in Example 1. The prepared ceria nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Example 8

The cerium nitrate (Ce (NO _{3) 3)} was prepared in place of zinc nitrate (Zn (NO _{3) 3)} carried out the surface-modified zinc oxide nanoparticles by the acid in the same manner as in Example 1 using. The prepared zinc oxide nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Example 9

The cerium nitrate (Ce (NO _{3) 3)} was prepared in place of the surface-modified alumina nanoparticles by acid in the same manner as in Example 1 by using aluminum nitrate _{(Al (NO 3) 3)} . The prepared alumina nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Comparative Example 3

Zinc oxide nanoparticles were prepared in the same manner as in Example 8, except that the decanoic acid was not used. The prepared zinc oxide nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Comparative Example 4

Zinc oxide nanoparticles were prepared in a supercritical water in the same manner as in Example 8, except that decanoic acid was not used and water was used instead of methanol. The prepared nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

Comparative Example 5

Alumina nanoparticles were prepared in the same manner as in Example 9, except that the decanoic acid was not used. The prepared alumina nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 below.

Comparative Example 6

Alumina nanoparticles were prepared in supercritical water in the same manner as in Example 9, except that decanoic acid was not used and water was used instead of methanol. The prepared alumina nanoparticles were analyzed in the same manner as in Example 1, and the results are shown in Table 1 .

division Manufactured Nanoparticles Alcohol Particle diameter (nm) Surface modifier Dispersion in ethylene glycol after one month Example 1 Ceria Methanol 2 ~ 3 Decanoic acid Dispersion Example 2 Ceria Methanol 2 ~ 4 Hexanoic acid Dispersion Example 3 Ceria Methanol 3 ~ 10 Decylamine Dispersion Example 4 Ceria Methanol 3 ~ 10 Hexaaldehyde Dispersion Example 5 Ceria ethanol 3 ~ 8 Decanoic acid Dispersion Example 6 Ceria Propanol 3 ~ 8 Decanoic acid Dispersion Example 7 Ceria Butanol 4-10 Decanoic acid Dispersion Example 8 Zinc oxide Methanol 5 to 10 Decanoic acid Dispersion Example 9 Alumina Methanol 30-50 Decanoic acid Dispersion Comparative Example 3 Zinc oxide Methanol 300-500 none Flocculation and sedimentation Comparative Example 4 Zinc oxide water 500-1,000 none Flocculation and sedimentation Comparative Example 5 Alumina Methanol 300-800 none Flocculation and sedimentation Comparative Example 6 Alumina water 300-800 none Flocculation and sedimentation

As shown in Table 1, in Examples 1 and 2, even in the case of using hexanoic acid having 6 carbon atoms instead of decanoic acid having 10 carbon atoms, surface modification of the particles was successfully performed, resulting in excellent ceria dispersibility in ethylene glycol. It was confirmed that the nanoparticles were prepared. Meanwhile, in Examples 1, 3, and 4, even when decylamine and hexaaldehyde were used instead of decanoic acid, surface modification of the particles was successfully performed to confirm that ceria nanoparticles having excellent dispersibility in ethylene glycol were produced. Therefore, it was confirmed that organic materials having functional groups such as carboxyl groups, amine groups and aldehyde groups that can react with hydroxyl groups on the surface of nanoparticles can be used as surface modifiers. On the other hand, in Examples 5 to 7, even when producing nanoparticles surface-modified with decanoic acid using ethanol, propanol and butanol instead of methanol is very small with a diameter of 3 ~ 10 nm and excellent dispersibility in ethylene glycol It was confirmed that was prepared.

As shown in Table 1, in Examples 8 and 9, even when producing surface-modified zinc oxide and alumina instead of surface-modified ceria, the particle diameter was 5-10 nm for zinc oxide, 30 for alumina Very small at ˜50 nm, surface modification was successfully performed to confirm that nanoparticles having excellent dispersibility in ethylene glycol were formed. On the other hand, when the surface modifier is not used in Comparative Examples 3 to 6, the diameter of the particles is very large, 300 to 1,000 nm for zinc oxide and 300 to 800 nm for alumina, and after one month when these particles are dispersed in ethylene glycol. It was confirmed that aggregation and precipitation resulted in poor dispersibility.

1 shows a supercritical fluid testing apparatus used for the production of surface modified nanoparticles of the present invention.

In FIG. 2, photograph (a) shows a TEM image of surface-modified nanoparticles prepared using methanol and decanoic acid in Example 1, and photograph (b) is prepared using methanol in Comparative Example 1 The TEM image of the nanoparticles is shown, and the photograph (c) shows the TEM image of the nanoparticles prepared using water in Comparative Example 2.

In Figure 3, curve (a) shows the results of the FT-IR analysis of the surface-modified nanoparticles prepared using methanol and decanoic acid in Example 1, curve (b) using methanol in Comparative Example 1 The FT-IR analysis results of the nanoparticles prepared by the above, and the curve (c) shows the FT-IR analysis results of the nanoparticles prepared using water in Comparative Example 2.

In Figure 4, curve (a) shows the results of TGA analysis of the surface-modified nanoparticles prepared using methanol and decanoic acid in Example 1, curve (b) is prepared using methanol in Comparative Example 1 TGA analysis results of one nanoparticle are shown, and curve (c) shows TGA analysis results of nanoparticles prepared using water in Comparative Example 2.

In FIG. 5, photograph (a) shows a photograph after one month after dispersing the surface-modified nanoparticles prepared using methanol and decanoic acid in Example 1 in ethylene glycol, and photograph (b) shows comparative example 1 1 minute after dispersing the nanoparticles prepared by using methanol in ethylene glycol, and the picture (c) is 1 month after dispersing the nanoparticles prepared using water in Comparative Example 2 in ethylene glycol The picture is shown.

* Description of symbols for the main devices in the drawings

10: high pressure reactor 20: preheater

30, 31: heater 40: cooler

50 filter 60 rear pressure regulator

70, 71 high pressure pump 80 particle precursor solution / surface modifier solution storage container

81: Alcohol Storage Container

Claims (14)

(a) dissolving the particle precursor and the surface modifier in alcohol to produce a particle precursor solution and a surface modifier solution; (b) continuously introducing the particle precursor solution, the surface modifier solution, and the alcohol into a high temperature and high pressure reactor under critical conditions, respectively, to produce surface modified nanoparticles; (c) cooling the solution of the surface modified nanoparticles, (d) separating and recovering the surface-modified nanoparticles from the cooled solution using a filter Continuous production method of surface-modified nanoparticles comprising a. The method of claim 1, further comprising washing and drying the surface-modified nanoparticles after the step (d). The process according to claim 1 or 2, wherein the step (a) separately prepares the particle precursor solution and the surface modifier solution by dissolving the particle precursor and the surface modifier in alcohol, respectively. The process according to claim 1 or 2, wherein the step (a) dissolves the particle precursor and the surface modifier together in alcohol to prepare a mixed solution. The method of claim 1 or 2, wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, and mixtures thereof. The method of claim 1 or 2, wherein the particle precursor is magnesium (Mg), aluminum (Al), titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), zinc (Zn), zirconium Compounds of metals selected from the group consisting of (Zr), ruthenium (Ru), rhodium (Rh), silver (Ag), palladium (Pd), platinum (Pt) and cerium (Ce), salts thereof, and their Characterized in that it is selected from the group consisting of mixtures. 3. The surface modifier of claim 1 or 2, wherein the surface modifier is hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, heptadecanoic acid, octadecanoic acid, oleic acid, linoleic acid, hexylamine, octylamine, decylamine , Dodecylamine, tetradecaamine, hexaaldehyde, octaaldehyde, decaaldehyde, dodecaaldehyde, tetradecaaldehyde and mixtures thereof. The method according to claim 1 or 2, wherein the concentration of the particle precursor solution in the step (a) is 0.001 mol / l to 1 mol / l. The method of claim 1 or 2, wherein the concentration of the surface modifier solution in the step (a) is 0.001 mol / l to 5 mol / l. The method of claim 1 or 2, wherein the reaction temperature in the step (b) is 200 ℃ to 600 ℃, the reaction pressure is characterized in that 20 bar to 500 bar. The method of claim 1 or 2, wherein the diameter of the surface-modified nanoparticles is 1 nm to 500 nm. The method of claim 2, wherein the washing process is performed using an organic solvent selected from methanol, ethanol, tetrahydrofuran and mixtures thereof. 3. The method of claim 2, wherein the drying step is carried out using one or more methods of vacuum drying, oven drying, and freeze drying. Cerium, zinc, aluminum having a surface modified and having a diameter of 1 to 500 nm with at least one surface modifier selected from carboxylic acids, aldehydes, amines and mixtures thereof prepared by the process according to claim 1. At least one nanoparticle selected from magnesium, titanium, manganese, iron, cobalt, zirconium, ruthenium, rhodium, silver, palladium or platinum, and mixtures thereof.

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