CN115340113A - Preparation method of vapor phase method nano alumina - Google Patents

Abstract

A preparation method of vapor phase method nanometer alumina relates to the technical field of nanometer material preparation. Firstly, pretreating the alumina sol to obtain high-purity alumina sol, then carrying out instantaneous reaction by using a high-temperature plasma reactor, finally cooling by using a quenching system, and obtaining the vapor-phase nano alumina by using a grading collection system. The invention realizes the preparation of the high-purity alumina nano powder, has the advantages of simple and convenient process, low cost, high product purity and the like, and can be used for large-scale production. The prepared alumina is in the form of spherical particles, the diameter of the alumina is 10-50 nm, no aggregation exists, and the alumina is in a monodisperse form. The invention abandons the defects of the traditional powder material feeding, puts forward that the alumina sol enters the reaction chamber in a spraying mode for the first time, can realize uniform reaction, can realize effective control of the particle size by controlling the feeding flow, and is beneficial to preparing the monodisperse form of the alumina nano powder.

Description

A kind of preparation method of gas-phase method nano-alumina

technical field

The invention relates to the technical field of nano powder material preparation, in particular to a method for preparing alumina, in particular to a method for preparing nano alumina by gas phase method.

Background technique

Alumina has a high melting point, high hardness, and high chemical stability, and is widely used in coatings, plastics, paper, printing inks, chemical fibers, rubber, cosmetics and other industries. At present, the preparation methods of alumina mainly include: firstly prepare hydrated alumina, and then further process it into activated alumina. Hydrated alumina often uses sodium metaaluminate, aluminum hydroxide, aluminum sulfate, aluminum chloride, aluminum isopropoxide, and aluminum amalgam obtained from bauxite processing as raw materials, and then uses aluminum alcohol method, aluminum amalgam, etc. Method, alkali method (or acid precipitation method), acid method (or alkali precipitation method) preparation.

With the continuous development of plasma technology, the application of plasma technology to the production of alumina also exists in some literature or patent reports. Chinese patent application CN 112723399 A discloses a plasma arc flame combustion reaction system and a method for preparing high-purity γ-Al ₂ O ₃ by using it. The novelly designed plasma arc flame combustion reaction system can realize high-purity γ-Al ₂ Rapid preparation of O ₃ nano-powder, through one-step ion arc combustion to quickly synthesize nano-γ-Al ₂ O ₃ with high purity and large specific surface area of powder. This method mainly uses high-purity pseudo-boehmite coarse powder (purity generally reaches 99.9% level) and uses dispersion grinding equipment to obtain high-purity pseudo-boehmite fine powder, which is more conducive to the plasma arc flame combustion reaction. The prepared high-purity γ-Al ₂ O ₃ nanopowder can obtain uniform fineness nanopowder without re-grinding.

However, this reaction system mainly uses the carrier gas to carry high-purity pseudo-boehmite fine powder into the plasma arc flame combustion chamber, and the delivery flow rate of the powder material is difficult to control. Compared with powder materials, the colloidal sol is easier to be injected into the combustion chamber, and the feed flow rate is controllable, which can realize the preparation of alumina materials with uniform morphology.

Contents of the invention

In view of the above-mentioned technical defects in the preparation of alumina powder, the present invention provides a method for preparing nano-alumina by gas phase method. First, the aluminum sol is pretreated to obtain high-purity aluminum sol, and then the high-temperature plasma reactor is used to react instantaneously. , and finally cooled by a quenching system, and using a graded collection system to obtain gas-phase nano-alumina.

In order to achieve the above object, the technical solution adopted in the present invention is: a preparation method of gas-phase method nano-alumina, the steps are as follows:

①. Purification of crude aluminum sol to prepare high-purity aluminum sol;

②. Use high-pressure spraying method to spray into high-temperature plasma reactor for instantaneous reaction to prepare nano-alumina;

③, quenching system cooling;

④. Classified collection system to prepare nano-alumina by gas phase method.

As a preferred technical solution of the present invention, the step of preparing high-purity aluminum sol by using the crude product of aluminum sol in step ① is:

(1) Evaporate the crude aluminum sol slurry under vacuum heating until the water content reaches 15-30%, then cool to room temperature;

(2) Add absolute ethanol to the slurry, ultrasonically disperse evenly, then add silane coupling agent KH550, heat up to 50-60°C and stir for 1-3 hours; the weight ratio of slurry, absolute ethanol, and silane coupling agent KH550 1: 1.5～2.5: 0.3～0.6;

(3) Evaporate again under vacuum heating until the water-ethanol content reaches 5-10%, then cool to room temperature to obtain high-purity aluminum sol.

As a preferred technical solution of the present invention, the concrete steps in step 2. are:

Using the high-pressure injection method, the high-purity aluminum sol is sprayed into the reaction chamber of the high-temperature plasma reactor by using a pump. The plasma excitation gas of the high-temperature plasma reactor is nitrogen or argon, and the aluminum sol is instantly vaporized and cracked when exposed to high temperature. , depolymerization, and polymerization into nano-alumina particles.

Further preferably, the injection flow rate of the high-purity aluminum sol in the high-temperature plasma reactor is 300-500 g/min.

As a preferred technical solution of the present invention, the specific steps in steps 3. and 4. are:

The nano-alumina particles generated in the reaction chamber of the high-temperature plasma reactor fall rapidly, and are cooled by a quenching system to avoid the aggregation of nanoparticles and reduce agglomeration. Finally, the gas-phase method nano-alumina is prepared through a graded collection system.

Preferably, the plasma flame temperature in the high-temperature plasma reactor is adjustable from 1500 to 2500° C., the reaction time is less than 1 s, and the power of the high-temperature plasma reactor is adjustable from 50 to 85 kW.

Preferably, the flow rate of the plasma excitation gas in the high temperature plasma reactor is 100-200 sccm.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1) The present invention realizes the preparation of high-purity alumina nanopowder, which has the advantages of simple process, low cost, high product purity, etc., can be used in large-scale production, and can significantly reduce reaction temperature and production energy consumption.

2) In the plasma reaction system, the reaction is completed instantaneously and can reach the millisecond level, and the particle size of the prepared product is small and there is no hard agglomeration, which has a crucial impact on the formation of low particle size nanopowders.

3) The alumina prepared in the present invention is in the form of spherical particles with a diameter of 10-50 nm, without aggregation, and in a monodisperse form.

4), the present invention abandons the disadvantages of traditional powder material feeding, and for the first time proposes to use a pump to spray aluminum sol into the reaction chamber, so that the reaction can be carried out uniformly, and the particle size can be realized by controlling the feed flow rate. The effective control and help to prepare the monodisperse morphology of alumina nanopowder.

Description of drawings

Figure 1 is the SEM images of crude aluminum sol (a) and high-purity aluminum sol (b).

Fig. 2 is the XRD pattern of the product prepared in Example 1.

Fig. 3 is the SEM image of the product prepared in Example 1.

Figure 4 is a SEM image of the product prepared in the comparative example (a corresponds to the injection flow rate of 100g/min, b corresponds to the injection flow rate of 1500g/min).

Detailed ways

The present invention proposes a method for preparing nano-alumina by a vapor phase method, and the method of the present invention will be further described in detail below with examples and accompanying drawings.

Example 1

A method for preparing nano-alumina by gas phase method, the steps are as follows:

①. Purify the crude aluminum sol to prepare high-purity aluminum sol.

(1) Evaporate the crude aluminum sol slurry under vacuum heating until the water content reaches 25%, and then cool to room temperature.

(2) Add absolute ethanol to the slurry, ultrasonically disperse evenly, then add silane coupling agent KH550, heat up to 55°C and stir for 2 hours. The weight ratio of slurry, absolute ethanol and silane coupling agent KH550 is 1:2:0.5.

(3) Evaporate again under vacuum heating until the water-ethanol content reaches 10%, then cool to room temperature to obtain high-purity aluminum sol.

It can be seen from Figure 1 that the crude aluminum sol is in the form of cotton wool-like aggregates, and the distribution of morphology is uneven. However, the high-purity aluminum sol prepared by purification treatment is obviously more uniform in distribution and has a high degree of uniformity in morphology.

②. Use high-pressure spraying method to spray into high-temperature plasma reactor for instantaneous reaction to prepare nano-alumina.

Using the high-pressure injection method, the high-purity aluminum sol is sprayed into the reaction chamber of the high-temperature plasma reactor by using a pump. The plasma excitation gas of the high-temperature plasma reactor is nitrogen or argon, and the aluminum sol is instantly vaporized and cracked when exposed to high temperature. , depolymerization, and polymerization into nano-alumina particles.

Among them, the plasma flame temperature in the high-temperature plasma reactor is 2000°C, the reaction time is less than 1s, and the jet flow rate of the high-purity aluminum sol is 400g/min.

③, quenching system cooling, classification collection system collection

The nano-alumina particles generated in the reaction chamber of the high-temperature plasma reactor fall rapidly, and are cooled by a quenching system to avoid the aggregation of nanoparticles and reduce agglomeration. Finally, the gas-phase method nano-alumina is prepared through a graded collection system.

Fig. 2 is the SEM image of the product prepared in Example 1, and Fig. 3 is the SEM image of the product prepared in Example 1. It can be seen from the figure that the prepared alumina is in the form of dispersed nearly spherical particles with a diameter of 20-50 nm, which is nearly spherical and has no hard agglomeration. Comparing the XRD pattern shown in Figure 2 with the standard PDF card (46-1131), it can be found that the prepared product is alumina. After testing, the prepared nano-alumina powder has a purity of over 99.9%.

comparative example

The steps of the preparation method are the same as those in Example 1, except that the injection flow rate of the high-purity aluminum sol is adjusted to 100 g/min and 1500 g/min respectively.

It can be seen from Figure 4 that with the change of the injection flow rate, the morphology of the prepared product is greatly affected, especially as shown in Figure 4b, when the injection flow rate is too high, the agglomeration of the prepared product is more serious, and it is impossible to prepare Alumina in monodisperse form.

Example 2

A method for preparing nano-alumina by gas phase method, the steps are as follows:

①. Purify the crude aluminum sol to prepare high-purity aluminum sol.

(1) Evaporate the crude aluminum sol slurry under vacuum heating until the water content reaches 30%, and then cool to room temperature.

(2) Add absolute ethanol to the slurry, ultrasonically disperse evenly, then add silane coupling agent KH550, heat up to 55°C and stir for 3 hours. The weight ratio of slurry, absolute ethanol, and silane coupling agent KH550 is 1:2.5:0.4.

(3) Evaporate again under vacuum heating until the water-ethanol content reaches 8%, then cool to room temperature to obtain high-purity aluminum sol.

②. Use high-pressure spraying method to spray into high-temperature plasma reactor for instantaneous reaction to prepare nano-alumina.

Using the high-pressure injection method, the high-purity aluminum sol is sprayed into the reaction chamber of the high-temperature plasma reactor by using a pump. The plasma excitation gas of the high-temperature plasma reactor is nitrogen or argon, and the aluminum sol is instantly vaporized and cracked when exposed to high temperature. , depolymerization, and polymerization into nano-alumina particles.

Among them, the plasma flame temperature in the high-temperature plasma reactor is 1800°C, the reaction time is less than 1s, and the jet flow rate of the high-purity aluminum sol is 350g/min.

③, quenching system cooling, classification collection system collection

The nano-alumina particles generated in the reaction chamber of the high-temperature plasma reactor fall rapidly, and are cooled by a quenching system to avoid the aggregation of nanoparticles and reduce agglomeration. Finally, the gas-phase method nano-alumina is prepared through a graded collection system.

Example 3

A method for preparing nano-alumina by gas phase method, the steps are as follows:

①. Purify the crude aluminum sol to prepare high-purity aluminum sol.

(1) Evaporate the crude aluminum sol slurry under vacuum heating until the water content reaches 20%, and then cool to room temperature.

(2) Add absolute ethanol to the slurry, ultrasonically disperse evenly, then add silane coupling agent KH550, heat up to 60°C and stir for 2 hours. The weight ratio of slurry, absolute ethanol, and silane coupling agent KH550 is 1:2:0.6.

(3) Evaporate again under vacuum heating until the water-ethanol content reaches 5%, then cool to room temperature to obtain high-purity aluminum sol.

②. Use high-pressure spraying method to spray into high-temperature plasma reactor for instantaneous reaction to prepare nano-alumina.

Using the high-pressure injection method, the high-purity aluminum sol is sprayed into the reaction chamber of the high-temperature plasma reactor by using a pump. The plasma excitation gas of the high-temperature plasma reactor is nitrogen or argon, and the aluminum sol is instantly vaporized and cracked when exposed to high temperature. , depolymerization, and polymerization into nano-alumina particles.

Among them, the plasma flame temperature in the high-temperature plasma reactor is adjustable at 2200°C, the reaction time is less than 1s, and the jet flow rate of high-purity aluminum sol is 450g/min.

③, quenching system cooling, classification collection system collection

The nano-alumina particles generated in the reaction chamber of the high-temperature plasma reactor fall rapidly, and are cooled by a quenching system to avoid the aggregation of nanoparticles and reduce agglomeration. Finally, the gas-phase method nano-alumina is prepared through a graded collection system.

The above content is only an example and description of the concept of the present invention. Those skilled in the art make various modifications or supplements to the described specific embodiments or replace them in similar ways, as long as they do not deviate from the concept of the invention Or beyond the scope defined in the claims, all should belong to the protection scope of the present invention.

Claims (8)

1. a preparation method of gas-phase method nano-alumina, is characterized in that, step is as follows: ①. Purification of crude aluminum sol to prepare high-purity aluminum sol; ②. Use high-pressure spraying method to spray into high-temperature plasma reactor for instantaneous reaction to prepare nano-alumina; ③, quenching system cooling; ④. Classified collection system to prepare nano-alumina by gas phase method. 2. preparation method as claimed in claim 1 is characterized in that, the step of utilizing aluminum sol crude product to prepare high-purity aluminum sol in step 1. is: (1) Evaporate the crude aluminum sol slurry under vacuum heating until the water content reaches 15-30%, then cool to room temperature; (2) Add absolute ethanol to the slurry, ultrasonically disperse evenly, then add silane coupling agent KH550, heat up to 50-60°C and stir for 1-3 hours; the weight ratio of slurry, absolute ethanol, and silane coupling agent KH550 1: 1.5～2.5: 0.3～0.6; (3) Evaporate again under vacuum heating until the water-ethanol content reaches 5-10%, then cool to room temperature to obtain high-purity aluminum sol. 3. preparation method as claimed in claim 1, is characterized in that, step 2. in concrete steps are: Using the high-pressure injection method, the high-purity aluminum sol is sprayed into the reaction chamber of the high-temperature plasma reactor by using a pump. The plasma excitation gas of the high-temperature plasma reactor is nitrogen or argon, and the aluminum sol is instantly vaporized and cracked when exposed to high temperature. , depolymerization, and polymerization into monodisperse nano-alumina particles. 4. The preparation method according to claim 3, characterized in that the jet flow rate of the high-purity aluminum sol in the high-temperature plasma reactor is 300-500 g/min. 5. preparation method as claimed in claim 1 is characterized in that, step 3. and 4. concrete steps are: The monodisperse nano-alumina particles generated in the reaction chamber of the high-temperature plasma reactor fall rapidly, and are cooled by a quenching system to avoid aggregation of nanoparticles and reduce agglomeration. Finally, the gas-phase method nano-alumina is prepared through a graded collection system. 6. The preparation method according to claim 1, wherein the temperature of the plasma flame in the high-temperature plasma reactor is adjustable from 1500 to 2500° C., the reaction time is lower than 1 s, and the power of the high-temperature plasma reactor is 50 ~120kW adjustable. 7. The preparation method according to claim 1, characterized in that the flow rate of the plasma excitation gas in the high temperature plasma reactor is 100-200 sccm. 8. The gas-phase nano-alumina prepared by the method according to any one of claims 1-7 is characterized in that it is in the form of spherical particles with a diameter of 10-50 nm, without aggregation, and in a monodisperse form.

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