WO2016186455A1 - Method and apparatus for purifying nanodiamond using medium fluidized bed - Google Patents

Abstract

The present invention relates to a method and apparatus for purifying nanodiamond, wherein a raw nanodiamond aggregate formed by an explosion method is fluidized to selectively remove a graphite (amorphous carbon) layer. The method and apparatus of the present invention use a fluidized bed reactor, thereby ensuring a uniform oxidation temperature and increasing the contact efficiency between oxidized gas and the raw nanodiamond aggregate. Furthermore, the present invention can increase the mixing and contact efficiencies using a fluidized medium, such as diamond, thereby removing impurities, such as the graphite layer, more rapidly.

Description

Nanodiamond purification method and apparatus using a medium fluidized bed

The present invention relates to a nanodiamond purification method and apparatus using a medium fluidized bed. More specifically, the present invention relates to a nanodiamond purification method and apparatus for selectively removing a graphite layer by fluidizing raw nanodiamond aggregates formed by an explosion method.

Detonation Nano Diamond (DND) by explosion reaction is used for other carbon nanotube particles such as fullerenes, single wall (SWCNT), double wall (DWCNT), and multiwall carbon nanotubes (MWCNT). It was found relatively early in the Soviet Union in the 1960s compared to other carbon nanoparticles such as fibers. Initially, DND was considered a military technology in the former Soviet Union and was not well known until 1990, but began to attract attention after two groundbreaking papers were published in the international journal.

The production of nanodiamonds by an explosion reaction takes place in a closed metal alloyed chamber under a gas atmosphere, for example under carbon dioxide (CO2) or water (H2O) or other liquid reducing agent conditions. Obtained by explosion reaction with, 4,6-trinitrotoluene (TNT) / 1,3,5-trinitrotriazacyclohexane (also known as hexogen or RDX).

In other words, DND occurs instantaneously when an explosive substance reacts with a mixture of explosive trinitrotoluene (TNT) and white crystalline non-aqueous explosive (RDX), at a certain ratio, for example, in the tens percent by weight. In the high temperature and high pressure atmosphere, the carbon component of the composition generates nuclei (carbon SP3 structure) of diamond crystal phase, and the nucleus grows to a certain size. There are functional groups of. Representative functional groups thereof are known to have a large number of COOH, -C = O, -NH2, -CHO, -OH, -NO2, -C-O-C- and the like.

Several studies have shown that DND has little toxicity in vivo and is biocompatible due to the stability of the structure, and has a very small particle diameter of several nm in size and a specific surface area of 250 m 2 / g to 450 m 2 / g, which is usually about tens of times higher than that of diamond. It is known to exhibit unique electrical, chemical and optical characteristics, such as being several hundred times larger and including a large number of hydrophilic functional groups on its surface. In particular, recently, researches for attaching a functional group to a surface to have a biomedical function or to attach a useful substance having an anti-biomedical function have been in the spotlight as a drug delivery material. For this purpose, high purity and uniform nanodiamonds are essential.

Nevertheless, DND has a very short explosion process and contraction occurs at the same time, which makes it difficult to separate single or several particle clusters due to the strong aggregation of single diamond particles. Impurities contained in were also difficult to purify.

The raw nanodiamond obtained by the explosion reaction in the reaction chamber contains not only diamond particles but also metals, metal oxides and other impurities. In general, chemicals are used to remove impurities by the wet method, but the wet method is not environmentally friendly and requires a high processing cost.

U.S. Patent No. 8,940,267 discloses a method for purifying raw nanodiamonds in a liquid phase, and Japanese Patent Application JP 2006-273704 uses a mechanical method.

Recently, in order to solve the problem of purifying nanodiamonds by a wet method, US Patent Publication No. US2010 / 0028675 uses a method of heating nanodiamonds at 375 to 630 ° C. under the presence of oxygen gas. However, the method disclosed in the U.S. Patent Application has a problem that it is difficult to purify a large amount of nanodiamonds with a uniform quality because it is simply heated in air.

The present invention is to provide a method for securing a uniform oxidation temperature to purify the nanodiamonds to a uniform quality.

The present invention provides a method for selectively removing amorphous carbon and other impurities including graphite layers present on the surface of nanodiamond aggregates.

The present invention is to provide a method for reducing the purification time and temperature of the raw nanodiamond aggregates.

One aspect of the present invention

Supplying oxidizing gas and nanodiamond aggregates to a fluidized bed reactor;

Flowing media particles and the nanodiamond aggregates into the oxidizing gas in a fluidized bed reactor;

 It relates to a nanodiamond purification method using a medium fluidized bed comprising separating and recovering the gas discharged to the top of the fluidized bed reactor and the nanodiamond aggregates.

In another aspect the invention

Oxidizing gas supply;

A fluidized bed reactor formed on the oxidizing gas and flowing media particles and raw material nanodiamond aggregates to the oxidizing gas introduced from the oxidizing gas supply unit;

A raw material supply unit supplying raw nanodiamond aggregates to the fluidized bed reactor; And

It relates to a nanodiamond purification device including a separation unit for separating the gas and the nanodiamond aggregates are connected to the fluidized bed reactor upper side.

Since the method and apparatus of the present invention use a fluidized bed reactor, it is possible to ensure a uniform oxidation temperature and to improve the contact efficiency between the oxidizing gas and the raw material nanodiamond aggregates. In addition, the present invention can increase the mixing and contact efficiency by using a fluid medium such as diamond, it is possible to remove impurities such as graphite layer more quickly.

1 illustrates the structure of raw material nanodiamond aggregates.

Figure 2 shows a nanodiamond purification apparatus using a medium fluidized bed according to an embodiment of the present invention.

3 shows a nanodiamond purification apparatus using a fluidized bed according to another embodiment of the present invention.

4 shows a nanodiamond purification apparatus using a medium fluidized bed according to another embodiment of the present invention.

The present invention can all be achieved by the following description. The following description is to be understood as describing preferred embodiments of the invention, but the invention is not necessarily limited thereto.

The present invention relates to a nanodiamond purification method and apparatus using a medium fluidized bed.

1 shows the structure of nanodiamond aggregates formed by explosion. Figure 2 shows a nanodiamond purification apparatus using a medium fluidized bed according to an embodiment of the present invention. Referring to FIG. 1, in the nanodiamond aggregate 100, several to several hundred nanodiamonds are aggregated, and a graphite layer (sp2 structure) 20 forms a shell along the surface thereof. In addition, the nanodiamond of the single particle shape 10 is typically formed by including a core 1 having a diamond crystal structure (SP3) and a graphite layer (sp2 structure, 2) surrounding it, the size of the core is 4 ~ 7nm The graphite layer is about 1 nm.

Meanwhile, the nanodiamond aggregate 100 includes a portion of amorphous carbon such as carbon, soot, coke, and graphene in addition to the graphite layer 20 on the surface. For the sake of convenience, the present invention describes only the graphite layer, which occupies most of the amorphous carbon formed on the surface of the nanodiamond aggregate, and does not remove carbon, soot, coke and other amorphous carbons and graphene by the method of the present invention. It is not impossible. That is, in the present invention, "graphite removal" is used to encompass that amorphous carbons and graphene that may be formed on the nanodiamond surface may also be removed.

Nanodiamond purification method and apparatus of the present invention is a method and apparatus for separating and removing the graphite layer 20 surrounding the nanodiamond aggregate (100).

More specifically, the present invention oxidizes the graphite layer 20 by fluidizing the nanodiamond aggregates 100.

The nanodiamond purification method of the present invention includes a feeding step, a fluidization step and a separation recovery step. The nanodiamond purification method of the present invention can use the apparatus of FIG. 2 comprising a fluidized bed reactor. Referring to FIG. 2, the nanodiamond purification apparatus of the present invention includes an oxidizing gas supply unit 10, a fluidized bed reactor 20, a raw material supply unit 30, and a separation unit 40.

The feeding step is to inject the oxidizing gas and the raw material nanodiamond aggregates 31 into the fluidized bed reactor 20.

The oxidizing gas may be supplied to the oxidizing gas supply unit 10 and the raw material nanodiamond aggregates 31 through the raw material supply unit 30.

As the oxidizing gas, air, oxygen, water vapor, or the like may be used.

The fluidization step is a step of flowing the media particles and the nanodiamond aggregates into the oxidizing gas in the fluidized bed reactor (20). The fluidization step is an oxidation reaction between the oxidizing gas and the graphite layer surrounding the nanodiamond aggregates.

The oxidation reaction in the fluidized bed reactor takes place as follows.

C + O2 → CO2

Carbon monoxide (CO) may also be generated in the oxidation reaction.

The flow rate of the oxidizing gas in the fluidized bed, the reaction temperature, etc. may be appropriately adjusted according to the size, content, and the like of the nanodiamond injected.

For example, the oxidation reaction can be carried out in the range of 200 ~ 650 ℃, the flow rate of the oxidizing gas can be varied depending on the size and processing speed of the media particles.

The surface of the nanodiamond aggregate is a carbon material having a graphite (sp2) structure.

In the present invention, the nanodiamond aggregates are fluidized to efficiently perform oxidation reaction between the graphite layer and the oxidizing gas. That is, fluidization using a fluidized bed reactor rapidly mixes the nanodiamond aggregated particles so that a uniform temperature can be applied to the entirety of the reactor and consequently the surface of the nanodiamond aggregates flowing in the reactor. Since the contact efficiency with the oxidizing gas is improved, the reaction rate between the oxidizing gas and the graphite layer can also be increased. In addition, the use of a fluidization reactor allows large-scale oxidation reactions that can be mass produced.

The present invention can more efficiently perform the oxidation reaction of the nanodiamond aggregates using the media particles 60 in the fluidization step.

The media particles may correspond to Geldart A or B particles and may be particles which are no longer oxidized in the above temperature range. The media particles may be any material that does not have a chemical reaction at high temperatures such as diamond, SiO 2, TiO 2, zirconia, steel balls, and the like and has good wear resistance.

The size of the media particles may be larger than the size of the raw material nanodiamond aggregates.

Referring to FIG. 2, the fluidized bed reactor 20 is composed of a medium fluidized bed 21 in which most of the media particles flow and a lean layer 22 in which the media solid is present in a very small amount.

In the medium fluidized bed 21, media particles and the nanodiamond aggregates are suspended by the oxidizing gas flow rate to form a fluidized bed. In particular, the present invention uses media particles larger in size than the nanodiamond aggregates, wherein the media particles and the nanoparticles are bonded to each other by van der Waals forces and flow together. Referring to FIG. 1, it is conceptually shown that the nanodiamond aggregate 31 is wrapped around the media particle 60.

The fluidization step may be mainly carried out in the medium fluidized bed 21 of the fluidized bed reactor 20. The flow rate of the oxidizing gas in the medium fluidized bed, the reaction temperature, etc. may be appropriately adjusted according to the size, content, etc. of the raw nanodiamond and the medium particles to be injected.

The present invention improves heat transfer and mass transfer between the media particles in the fluidized bed and aggregates including nanodiamonds, thereby effectively oxidizing the graphite layer and graphene attached to the surface of the nanodiamonds to be removed in the gas phase with carbon dioxide or carbon monoxide.

The separation recovery step is a step of separating and recovering the nanodiamond aggregates from which gas and graphite discharged to the fluidized bed reactor are removed.

Separation recovery step may use the cyclone 40 as the separation unit 40, and may further use a water trap (70). Cyclones can be used to capture unreacted nanodiamond aggregates or media particles, and purified nanodiamond aggregates can also be collected according to particle size.

The water trap 70 is capable of separating from the gas the purified nanodiamond aggregates having a particle size of 100 nm or less in sun nano. That is, when the gas containing the nanodiamond aggregates passes through the water trap, the nanodiamond aggregates may be dispersed in the water, and the gas may be discharged upward.

The method may increase the fluidity of the medium and the nanodiamond aggregates by vibrating the fluidized bed reactor. By vibrating, the fluidity of the media particles having a relatively large particle size may be further increased, and thus the fluidity of the nanodiamond aggregates may be increased. In more detail, when the vibration is periodically applied to the entire fluidized bed, even when the size of the medium particles is large, the minimum fluidization rate of the particles can be lowered.

The method may vibrate the fluidized bed reactor by adding a vibrator 80 to the bottom outer surface of the fluidized bed reactor. The vibrator 80 is shown in FIG. 3.

The intensity of the vibration applied to the vibrator 80 may be appropriately controlled according to the size of the refining apparatus or the size, density of particles to be injected. For example, the vibration unit may apply a vibration of 0.01 ~ 100 Hz to the purification apparatus.

The method may increase the fluidity of the medium by additionally supplying air to the bottom of the fluidized bed reactor periodically (pulsed-air). Further supply of air may use the air supply unit 90, as shown in FIG.

When a very small amount of oxidizing gas is supplied to secure the residence time required to remove the graphite layer in the fluidized bed reactor, abnormal operations such as channeling or defluidization occur in the media particle layer. Accordingly, the method of the present invention can periodically inject air into the medium fluidized bed 21 in a pulsed manner to eliminate channeling phenomenon and the like. Like the pulse-pulverizing air method, the fluidity of the media particles can be increased, and the amount of oxidizing gas per unit time can be reduced. Therefore, supplying air in pulses improves the fluidity of the media particles and effectively purifies the nanodiamonds from the fluidized bed.

In another aspect, the present invention provides a nanodiamond purification device. Referring to FIG. 1, the purification apparatus of the present invention includes an oxidizing gas supply unit 10, a fluidized bed reactor 20, a raw material supply unit 30, and a separation unit 40.

The oxidizing gas supply unit 10 supplies the oxidizing gas into the purification apparatus.

The fluidized bed reactor 20 is formed on the oxidizing gas and flows media particles and raw nanodiamond aggregates to the oxidizing gas introduced from the oxidizing gas supply unit.

The purification apparatus includes a dispersion plate 50 located between the oxidizing gas supply unit 10 and the fluidized bed reactor 20. The oxidizing gas is supplied from an external source and provided at a constant flow rate to the fluidized bed reactor 20 through the dispersion plate 50. The dispersion plate may be a bubble cap type dispersion plate.

The raw material supply unit 30 supplies the raw material nanodiamond aggregates to the fluidized bed reactor.

The separation unit is connected to the fluidized bed reactor upper side to separate the discharged gas and the nanodiamond aggregates.

The separator may use a cyclone 40 and may additionally use a water trap 70. For example, cyclones can be used to capture unreacted nanodiamond aggregates or media particles, and purified nanodiamond aggregates can also be collected according to particle size.

The cyclone 40 and the water trap 70 may be referred to the above description.

The fluidized bed reactor 20 may be an oxidation reactor in which the oxidizing gas and the graphite layer surrounding the nanodiamond aggregates react.

Oxidation reaction in the fluidized bed reactor can be referred to the above-described details.

The apparatus of the present invention can more efficiently perform the oxidation reaction of the nanodiamond aggregates by flowing the media particles inside the fluidized bed reactor.

The above-mentioned contents may also be referred to the media particles and the media fluidized layer.

FIG. 2 is a device in which a vibrator 80 is added to the device of FIG. 1. Referring to FIG. 2, the apparatus of the present invention may further include a vibrator 80 at the bottom or the side of the oxidizing gas supply part of FIG. 1.

The vibrator 80 may increase fluidity of media particles having a relatively large particle size.

The intensity of the vibration applied to the vibrator 80 may be appropriately controlled according to the size of the refining apparatus or the size, density of particles to be injected. For example, the vibration unit may apply a vibration of 0.01 ~ 100 Hz to the purification apparatus.

3 is a device in which an air supply unit 90 is added to the device of FIG. 1. Referring to FIG. 3, the apparatus of the present invention may further include an air supply unit 80 that may periodically supply air to the oxidizing gas supply unit of FIG. 1.

Purification apparatus of the present invention can prevent the occurrence of abnormal operation by periodically injecting air into the medium fluidized bed 21 through the air supply unit (90).

For the vibrator 80 and the air supply unit 90 may be referred to the above-described content.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

The present invention can be used as a drug carrier by purifying the explosive nanodiamond.

Claims (16)

1. Supplying oxidizing gas and nanodiamond aggregates to a fluidized bed reactor;

   Fluidizing the media particles and the nanodiamond aggregates into the oxidizing gas in a fluidized bed reactor;

   The nanodiamond purification method using a medium fluidized bed comprising the step of separating and recovering the gas discharged to the top of the fluidized bed reactor and the nanodiamond aggregates.
2. The method of claim 1, wherein the fluidizing step comprises oxidizing the oxidizing gas and the graphite layer surrounding the nanodiamond aggregates.
3. The method of claim 1, wherein the size of the media particles is larger than that of the nanodiamond aggregates.
4. The method of claim 1, wherein the fluidizing step comprises attaching the nanodiamond aggregates to a surface of the media particles to flow the nanodiamond aggregates.
5. The method of claim 1, wherein the method controls the temperature inside the fluidized bed reactor at 200 to 650 ° C. 2.
6. The method of claim 1, wherein the medium particles correspond to Geldart A or B particles and are particles that are no longer oxidized.
7. The method of claim 1, wherein the fluidized bed reactor vibrates to increase fluidity of the medium.
8. 8. The method of claim 7, wherein the method comprises applying a vibrator to an outer surface of the bottom of the fluidized bed reactor to vibrate the fluidized bed reactor.
9. The method of claim 1, wherein the method further comprises supplying air to the bottom of the fluidized bed reactor (pulsed-air) to increase fluidity of the medium.
10. Oxidizing gas supply;

    A fluidized bed reactor formed on the oxidizing gas and flowing media particles and raw material nanodiamond aggregates to the oxidizing gas introduced from the oxidizing gas supply unit;

    A raw material supply unit supplying raw nanodiamond aggregates to the fluidized bed reactor; And

    Nanodiamond purification apparatus comprising a separation unit for separating the nanodiamond aggregates and the gas discharged connected to the fluidized bed reactor upper side.
11. The apparatus of claim 10, wherein the fluidized bed reactor is an oxidation reactor in which the oxidizing gas and the graphite layer surrounding the nanodiamond aggregates react.
12. The nanodiamond purification apparatus of claim 10, wherein the fluidized bed reactor has a temperature of 200 ° C. to 650 ° C. 12.
13. 11. The nanodiamond refining apparatus according to claim 10, wherein a size of the media particles is larger than that of the raw nanodiamond aggregates.
14. 11. The nanodiamond purification apparatus of claim 10, wherein the media particles correspond to Geldart A or B particles and are no longer oxidized in the temperature range.
15. The nanodiamond purification apparatus according to claim 10, wherein the apparatus further comprises a vibrator at the bottom or the side of the oxidizing gas supply unit.
16. The nanodiamond refining apparatus of claim 10, wherein the apparatus includes an air supply unit configured to periodically supply air to the oxidizing gas supply unit.

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