CN1752006A - Preparation method of ultrafine aluminium hydroxide - Google Patents

Preparation method of ultrafine aluminium hydroxide Download PDF

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CN1752006A
CN1752006A CN 200510032296 CN200510032296A CN1752006A CN 1752006 A CN1752006 A CN 1752006A CN 200510032296 CN200510032296 CN 200510032296 CN 200510032296 A CN200510032296 A CN 200510032296A CN 1752006 A CN1752006 A CN 1752006A
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aluminum hydroxide
reactor
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crystal forms
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CN100462303C (en
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周继承
李友凤
廖立民
谢放华
赵虹
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Xiangtan University
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Abstract

A process for preparing superfine aluminium hydroxide includes such steps as carbonifying reaction between NaAlO2 solution and the gas containing CO2 in gravitation condition to obtain aluminium hydroxide gel, preparing superfine aluminium hydroxide, filtering, washing, and drying. The product (nanofibers or nanoparticles of aluminium hydroxide) can be used as inorganic flame-retarding agent or for preparing catalyst.

Description

Preparation method of superfine aluminum hydroxide
Technical Field
The invention relates to a preparation method of aluminum hydroxide, in particular to a method for preparing superfine aluminum hydroxide with different crystal forms by using a sodium aluminate solution under the condition of a hypergravity carbonization reaction.
Background
Aluminum hydroxide is the most used inorganic flame retardant in the world at present, and is widely applied to various industries such as plastics, building materials, high polymer materials, electronics and the like due to the characteristics of no toxicity, no halogen and low smoke. The nanometer active aluminum hydroxide fire retardant is one of halogen-free fire retardants of synthetic materials, has three functions of fire retardation, smoke abatement and filling, has no secondary pollution during combustion, has larger specific surface area, higher surface energy and better fire retardation effect, does not influence the mechanical property and the processing characteristic of the material when being used as an additive, and has compensation performance. The superfine aluminum hydroxide, the development of high-performance synergist and the development of high-efficiency surface treating agent are the development directions of aluminum hydroxide flame retardants.
Pseudo boehmite (fibrous aluminum hydroxide) is one of the series products of aluminum hydroxide, is derived from boehmite, is a colloidal, insufficiently crystallized pseudo boehmite, and contains alumina crystals of a crystal water molecule. The product is non-toxic, odorless and tasteless, is white colloid (wet product) or powder (dry product), has high crystalline phase purity and good forming performance, and has the characteristic of thixotropic gel. The product is mainly used as a forming adhesive for producing catalyst carriers, active alumina raw materials or molecular sieves and the like, and is widely applied to the fields of catalysis, precision ceramics, refractory materials and the like.
At present, the industrial aluminum hydroxide is mainly prepared by a process route of reprecipitating by ammonia water or other alkali after being dissolved by acid in China. The method has complex production process, needs anti-corrosion equipment and consumes expensive chemical raw materials. The cost of the hydrolysis preparation of the byproduct organic aluminum compound produced by other industries in foreign countries is much lower. Since the price of the pseudo-boehmite produced at home cannot compete with that of other countries, research and development of cheap preparation routes and methods are very valuable. Chinese patent application publication No. CN85100161A carbonic acid method (CO)2Method) for producing pseudoboehmite ", using intermediate-industrial sodium aluminate solutionUsing high-concentration CO as raw material2The gas is used as precipitant, and the pseudoboehmite is obtained by quick carbonation and gelatinization under low temperature and low concentration, the carbonation and gelatinization process can be carried out discontinuously and continuously, and the obtained product has high purity and good peptization. But long carbon separation time, raw material liquid Al2O3When the content is about 40 g, CO is introduced when the colloid is formed by adopting discontinuous carbonation2Gas velocity 2-8 g CO2Per gram of Al2O3.H, the time is 10-30 minutes; when the continuous carbonation is adopted for forming the gel, CO is introduced2Gas velocity of 1-6 g CO2Per gram of Al2O3.The carbonation process time is 30-90 minutes. For another example, chinese patent publication No. CN1116185A discloses a method for directly preparing ultrafine aluminum hydroxide by a one-step method under the condition of a rotary packed bed high gravitational field, and ultrafine aluminum hydroxide with a particle size of about 30-100 nm can be obtained. However, the aluminum hydroxide particles obtained by the method have no fixed crystal form, the particle size distribution is not uniform, and the particles with the average particle size of less than 30nm are difficult to obtain. Also, Chinese patent publication No. CN1092145C discloses a method for preparing ultra-fine aluminum hydroxideThe method for preparing the superfine aluminum hydroxide by two working procedures of carbon decomposition and hydrothermal treatment under the condition of force comprises the step of carrying out carbon decomposition reaction in a porous packing layer of a rotating bed to obtain fibrous aluminum hydroxide particles with the average particle size of 1-5 nm and the length-diameter ratio of 5-100. However, the special feature of the ultra-fine particle system causes the RPB device to be easily clogged.
Some international researches on high-purity ultrafine nano powder are in the leading position, and researches in some countries are in progress and achieve a series of results. In recent years, China also carries out some research works in this aspect, but many of the research works are in experimental research stages. The demand of China for high-purity superfine alumina is rising year by year, and according to latest statistics, the import of China alumina reaches 457 ten thousand tons in 2002, and the year-by-year increase is 36.6%, and at present, China is theworld with the largest import of aluminum hydroxide and aluminum oxide.
Disclosure of Invention
In view of the above situation, the present invention aims to provide a method for preparing superfine aluminum hydroxide with different crystal forms, which has the advantages of low cost, easy industrial production, simple and reliable production process, no blockage, no pollution and excellent product performance.
In order to achieve the purpose, the preparation method of the superfine aluminum hydroxide comprises the steps of mixing sodium aluminate NaAlO2The solution contacts with gas containing carbon dioxide, pseudo-boehmite gel is prepared in a carbonization reaction mode under the condition of supergravity, and then superfine aluminum hydroxide with different crystal forms is obtained, wherein the method mainly comprises the steps of carbonization, filtration, washing and drying, and comprises the following steps:
1) control of sodium aluminate NaAlO2The concentration of the solution is 0.05-2 mol/L;
2) in sodium aluminate NaAlO2Adding 1-2% by mass of an organic polymer dispersant into the solution;
3) adding the mixture into a reactor, starting the reactor, introducing CO with concentration into the reactor after the liquid flow in the reactor is stable2Controlling the rotating speed of the reactor to be 200-3000 rpm, the gas-liquid ratio to be 0.5-20, controlling the carbonization reaction temperature to be 0-100 ℃, recording the temperature and the pH value at regular time, and stopping introducing CO when the pH value reaches 9-122Gas, reducing the rotating speed of the reactor and recycling for a period of time to obtain an aluminum hydroxide precursor;
4) continuing to further process the product in different crystal forms, such as aging; the reactor is a rotating bed hypergravity reactor, which mainly comprises a rotor, a distributor arranged in the center of the rotor, a liquid inlet, an air inlet, an exhaust gas outlet and a discharge hole.
In order to achieve the best effect, the further measures are as follows:
the rotary bed hypergravity reactor is a spiral channel type RBHC reactor, which is provided with a spiral linear channel without filling materials.
The organic polymer dispersant is polyethylene glycol or Tween 80 or sodium dodecyl benzene sulfonate.
And the further treatment of different crystal forms comprises the steps of carrying out solid-liquid separation on an aluminum hydroxide precursor, then adding a proper amount of distilled water into a filter cake, keeping ageing for 2-6 hours at 75-100 ℃, filtering, washing and adding isobutanol into a product, and drying at 80-100 ℃ to obtain the fibrous superfine aluminum hydroxide with the crystal form.
The further treatment of the different crystal forms is to control sodium aluminate NaAlO2The concentration of the solution is 0.05-1.2 mol/L, and CO is introduced into the reactor2The gas content is not lower than 90%, the gas-liquid ratio is 1-20, the pH value is 10-11, and the carbonization reaction temperature is controlled at 15-50 ℃.
The further treatment of different crystal forms is to carry out solid-liquid separation on the aluminum hydroxide precursor, and then the product is filtered, washed and dried to obtain the granular ultrafine aluminum hydroxide.
The further treatment of the different crystal forms is to control sodium aluminate NaAlO2The concentration of the solution is 0.1-2 mol/L, and CO is introduced into the reactor2The gas content is not higher than 30%, the rotating speed of the reactor is controlled to be 400-2000 rpm, the gas-liquid ratio is 0.5-10, the pH value is 11-12, and the carbonization reaction temperature is controlled to be 50-80 ℃.
The invention utilizes intermediate product NaAlO2Solution and CO2The method for preparing nano-scale superfine aluminum hydroxide by using waste gas as a reaction raw material and adopting spiral channel type rotating bed RBHC as a supergravity carbonization reaction as a main process mainly overcomes the defect that equipment is easy to block in the process of the supergravity carbonization reaction of a rotating packed bed RPB, can respectively prepare nano-fibrous aluminum hydroxide and nano-scale superfine granular aluminum hydroxide with different crystal forms, refreshes new records of pore volume, specific surface and average pore diameter of products prepared in the field, and opens up a brand new way for the production of superfine aluminum hydroxide and aluminum oxide in China. It is suitable for preparing various superfine aluminium hydroxide by using carbon method and hydrothermal treatment and applying supergravity device.
Compared with the existing method for preparing the superfine aluminum hydroxide, the method also comprises the following steps:
1. NaAlO using RBHC hypergravity reactor2-CO2CarbonizingThe reaction preparation method can reasonably adjust and control the technological parameters and prepare the fibrous pseudo-boehmite with low content of alumina trihydrate mixed crystals, average grain diameter of 5-10nm and length of hundreds of nanometers.
2. The solution concentration, the terminal pH value and the aging process condition in the carbonization reaction process which influences the pseudoboehmite form and the particlesize can be controlled through the supergravity carbonization reaction operating condition and the aging process.
3. The spiral channel type rotating bed RBHC can not only prepare nano fibrous pseudo-boehmite with uniform particle size and good quality, but also greatly improve CO compared with the traditional stirred tank reactor2The gas absorption rate is reduced, the carbonization time is shortened by more than 50%, and the production efficiency is higher. 4. The prepared nano fibrous pseudo-boehmite has large specific surface area (up to 351.6 m)2The catalyst has the characteristics of large average pore diameter (up to 28.4nm) and large pore volume (2.41ml/g), and the nano fibrous pseudo-boehmite with the characteristics can be used for preparing a hydrogenation catalyst with better performance and treating heavy oil and residual oil; new reforming catalysts may also be developed.
5. The method has the advantages of wide raw material source, low cost, simple production process, no pollution, good product performance, small equipment volume, low operation strength, large volume mass transfer coefficient and difficult blockage.
6. The invention can respectively prepare nano fibrous superfine pseudo-boehmite and nano granular superfine aluminium hydroxide with different crystal forms, and the nano fibrous gamma-Al is prepared by calcining the fibrous pseudo-boehmite at a certain temperature2O3And has wide application prospect in the field of catalysis. The nanometer superfine aluminum hydroxide is a good inorganic flame retardant, and can be well applied to the aspects of fire prevention and flame retardance.
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Drawings
FIG. 1 is a flow chart of a process for preparing aluminum hydroxide with different crystal forms by the ultragravity carbonization reaction of sodium metaaluminate RBHC.
FIG. 2 is a schematic diagram of the structure of a rotary bed hypergravity reactor RBHC for carbonization reaction of the present invention.
FIG. 3 is a schematic view of a helical channel rotor of an RBHC hypergravity reactor for carbonization reaction according to the present invention.
FIG. 4 is an electron microscope TEM photograph of the fibrous ultrafine aluminum hydroxide of the present invention.
FIG. 5 is an electron microscope TEM photograph of the granular ultrafine aluminum hydroxide of the present invention.
Detailed Description
Referring to the attached drawings, the preparation method of the superfine aluminum hydroxide of the invention is to prepare sodium aluminate NaAlO2The solution contacts with gas containing carbon dioxide, aluminum hydroxide gel is prepared in a carbonization reaction mode under the condition of supergravity, and then superfine aluminum hydroxide with different crystal forms is obtained, wherein the superfine aluminum hydroxide mainly comprises the steps of carbonization, filtration, washing and drying, and is divided into fibrous products and granular products with two different crystal forms.
As shown in attached figures 1, 2 and 3, the invention comprises post-treatment processes such as carbonization reaction, solid-liquid separation of products and the like, and adopts a spiral channel type rotating bed RBHC hypergravity reactor 4 to replace a traditional stirring tank as a reactor for the carbonization reaction. Introducing CO2Gas and sodium aluminate solution are respectively introduced into the rotating bed through the gas inlets 3 and 9 and the liquid inlet pipe orifice 8, gas-liquid-solid multiphase mass transfer-reaction process, namely carbonization reaction, is carried out in the spiral channel of the rotating bed, and emulsion after reaction is discharged from the discharge ports 14 and 16 at the bottom of the rotating bed. Returning the emulsion discharged from the bottom discharge ports 14 and 16 from the liquid feed port through the circulating tank 13 to the rotating bed for continuous carbonization reaction until the pH value of the emulsion is 9-12, indicating that the carbonization reaction is complete, and performing aging hydrothermal treatment or post-treatment procedures such as filtering and drying on the slurry to obtain the nano-scale superfine aluminum hydroxide.
1. The preparation of fibrous superfine aluminium hydroxide, i.e. pseudo-boehmite, mainly comprises the procedures of carbon decomposition under the condition of supergravity of spiral channel type rotating bed and hydrothermal treatment, and it is made up by using the processes ofThe method comprises the following specific steps: setting the rotating speed of a spiral channel type rotating bed reactor to be 200-3000 rpm, the gas-liquid ratio to be 1-20, and enabling the content of CO with the concentration not less than 90%2Gas and NaAlO with the concentration of 0.05-1.2 mol/L2Introducing the solution into a rotor of a reactor through an air inlet and a liquid inlet pipe respectively, adding 1-2% by mass of an organic polymer dispersant, and performing gas-liquid-solid multiphase mass transfer reaction, namely carbonization reaction, in a spiral channel of the rotor of the reactor, controlling the temperature of the carbonization reaction to be 0-50 ℃, recording the temperature and the pH value at regular time, and stopping introducing CO when the pH value reaches 10-112Gas, reducing the rotating speed of the reactor 4 and recycling for a period of time to obtain an aluminum hydroxide precursor; the further treatment of the product which is suitable for fibrous crystal form is to carry out solid-liquid separation on the aluminum hydroxide precursor, and the separated emulsion is discharged from the discharge ports 14 and 16 at the bottom of the rotating bed; and then adding a proper amount of distilled water into the separated filter cake, keeping aging at 75-100 ℃ for 2-6 h, filtering and washing the product, adding isobutanol, and drying at 80-100 ℃ to obtain the fibrous superfine aluminum hydroxide with the crystal form. The sodium hydroxide solution can be recovered by separating mother liquor and partial washing liquid.
The gelling mechanism is as follows:
introducing CO into sodium aluminate solution2Gas, first CO2The gas reacts with excess sodium hydroxide, i.e. Leading to a decrease in the caustic ratio of the solution and thus to destabilization of the solution, sodium aluminate solution with CO2The gas is neutralized to form aluminum hydroxide precipitate, i.e. 。The optimal process parameters of the preparation method are as follows: the carbonization reaction temperature is 15-50 ℃, the rotor rotating speed is 400-2000 rpm, and CO is2The concentration is more than 95%, the gas-liquid ratio is 1-10, and the concentration of the sodium aluminate solution is less than 1 mol/L. 1.5 percent of organic high molecular polymer can be added as a dispersing agent in the carbon decomposition process, and isobutanol azeotropic solvent is added into a filter cake to carry out azeotropic distillation and drying, so that the particles are dispersed and refined without agglomeration and are uniformly distributed.
The superfine high-purity aluminum hydroxide prepared by the method has the average particle size of about 5nm, the length of 200-300 nm, fibrous shape and uniform particle size distribution, and the content of the aluminum hydroxide trihydrate is within 3 percent as shown in figure 4.
2. The preparation of granular superfine aluminium hydroxide product is mainly completed by one-step direct method under the condition of supergravity of spiral channel type rotating bed, and its concrete steps are as follows: setting the rotating speed of a spiral channel type rotating bed reactor to be 200-3000 rpm, the gas (calculated by the clean carbon dioxide in a standard state) to liquid ratio to be 1-20, and enabling the CO content to be not higher than 30%2Gas and NaAlO with the concentration of 0.05-2 mol/L2Introducing the solution into a rotor of a reactor through an air inlet and a liquid inlet pipe respectively, adding 1-2% by mass of an organic polymer dispersant, performing gas-liquid-solid multiphase mass transfer reaction, namely carbonization reaction, in a spiral channel of the rotor of the reactor, controlling the temperature of the carbonization reaction to be 0-100 ℃, recording the temperature and the pH value at regular time, and stopping introducing CO when the pH value reaches 11-122Gas, reducing the rotating speed of the reactor 4 and recycling for a period of time to obtain an aluminum hydroxide precursor; the further treatment of the product in the form of crystal suitable for grains is to separate the solid from the liquid of the aluminum hydroxide precursor, and then to filter, wash and dry the product to obtain the superfine aluminum hydroxide with grain crystal.
The gelling mechanism of the aluminum hydroxide is as follows:
the essence of carbonation decomposition is that carbon dioxide is introduced into sodium metaaluminate solution, and the carbon dioxide and caustic alkali in the solution are subjected to neutralization reaction:
therefore, the stability of the sodium metaaluminate solution is destroyed along with the sharp reduction of the caustic ratio of the solution in the reaction process, and the solution is subjected to the following hydrolysis reaction to separate out aluminum hydroxide precipitate:
the optimal process parameters of the preparation method are as follows: the carbonization reaction temperature is 50-80 ℃, the rotating speed of a rotor of the rotating bed is 400-2000 rpm, the content of carbon dioxide is less than 30%, and the gas (calculated by the pure carbon dioxide in a standard state) liquid ratio is 0.5-5. The dispersant is added in the carbon decomposition process, and the effect of various dispersants is the same.
The granular superfine aluminum hydroxide with the average grain diameter of about 10nm is prepared by the method, and the grain size distribution is uniform and is shown in figure 5.
Example 1: the technological process of the invention is as shown in figure 1, sodium aluminate solution with certain volume is extracted, filtered and purified, diluted to 0.4mol/L and placed in a circulating tank 13, and the sodium aluminate solution enters a spiral channel of a rotor 5 from a liquid inlet 8 of a spiral channel type rotating bed through a water pump 12, a valve 11 and a fluid flowmeter 10 and then passes through a distributor 15; high concentration of CO2After the gas is decompressed from a gas source of a steel cylinder, the gas is introduced into a spiral channel of a rotor 5 of a rotary bed RBHC from gas inlets 3 and 9 to the outer side of the spiral channel through a gas valve 1 and a gas flowmeter 2, the gas-liquid volume flow ratio is 3, and CO is2The gas and the sodium aluminate solution are in reverse contact in a rotating spiral channel to carry out carbonization reaction, 1-2% by mass of organic polymer dispersant is added in the carbonization reaction process to generate nano-scale aluminum hydroxide ultrafine particles, and the residual gas is discharged from the center of the spiral channel to a waste gas discharge port 7 through a valve 6; control rotor 5The rotating speed is 1200rpm, the liquid which is not completely reacted is discharged from the discharge ports 14 and 16 at the bottom of the rotating bed and then enters the circulating tank 13 again, and is continuously circulated by a pump and CO2The reaction is carried out in a rotating bed, the whole reaction temperature is controlled to be 20-30 ℃, when the pH value of the gel is 10.5, the carbon content is completely decomposed, the gel is filtered and washed, then deionized water is added, the gel is placed in a water area at 97 ℃ for heating and aging for 0.5h, after being filtered, washed and dried by adding isobutanol at 100 ℃, a sample is taken for transmission electron microscope analysis, and from a TEM picture, fibrous superfine aluminum hydroxide with the average particle size of about 5nm and the length of 200-300 nm can be seen, and the figure is 4.
Example 2: example 2 the same as example 1 except that it was changed from example 1: the concentration of the sodium aluminate solution is 0.2mol/L, and high-concentration CO is introduced2The rotation speed of the rotor 5 is 1000rpm, after the carbonization reaction is completed, the gel is filtered and washed, then deionized water is added, the gel is placed in a water area with the temperature of 97 ℃ for heating and aging for 6h, and after the filtration, the washing and the drying by adding isobutanol at the temperature of 100 ℃, thefibrous superfine aluminum hydroxide is obtained.
Example 3: example 3 the same as example 1 except that it was changed from example 1: sodium aluminate solution is 0.2mol/L, and CO with high concentration is introduced2And (2) controlling the rotation speed of a rotor (5) to be 1000rpm, controlling the gas-liquid volume flow ratio to be 3, filtering and washing gel after complete carbonization reaction, adding deionized water, placing the gel in a water area at 97 ℃, heating and aging for 4 hours, filtering, washing, adding isobutanol, and drying at 80 ℃ to obtain the fibrous superfine aluminum hydroxide with the particle size of 5-10nm and the length of 200-300 nm.
Example 4: example 4 the same as example 1 except that it was changed from example 1: preparing 1.2mol/L sodium aluminate solution, and introducing 30% CO2And 70% of air, controlling the volume flow ratio of gas to liquid to be 2, controlling the whole carbonization temperature to be 50-60 ℃, and controlling the pH value at the end point of the carbon decomposition reaction to be 11-12. The obtained gel does not need hydrothermal aging treatment, and superfine aluminum hydroxide with the average particle size of about 10nm can be finally obtained after filtration, washing and drying, and the figure 5 shows.
Example 5: example 5 the same as example 1 except that it was changed from example 1: preparing 0.8mol/L sodium aluminate solution, and introducing 20% CO2And 80% of air, wherein the volume flow ratio of gas to liquid is controlled to be 2, the rotating speed of the rotor 5 is 800rpm, the whole carbonization temperature is 50-60 ℃, and the pH value at the end point of the carbon decomposition reaction is 11-12. The obtained gel is filtered, washed and dried to finally obtain the superfine aluminum hydroxide with the average particle size of about 10 nm.
Example 6: example6 the same as example 1 except that it was changed from example 1: preparing 0.6mol/L sodium aluminate solution, and introducing 10% CO2And 90% of air, controlling the volume flow ratio of gas to liquid to be 5, not adding a surfactant, controlling the whole carbonization temperature to be 60-70 ℃, and controlling the pH value at the end point of the carbon decomposition reaction to be 11-12. The obtained gel is filtered, washed and dried to finally obtain the superfine aluminum hydroxide with the average particle size of about 30 nm.
The above is only a preferred embodiment of the present invention, and various modifications and changes can be made thereto by those skilled in the art based on the above-described concept of the present invention. For example, adjustments in process parameters, changes in reactor operating conditions, adjustment changes in aging processes, and the like. However, such similar changes and modifications are also within the spirit of the present invention.

Claims (7)

1. A method for preparing superfine aluminum hydroxide comprises preparing sodium aluminate NaAlO2The solution contacts with gas containing carbon dioxide, pseudo-boehmite gel is prepared in a carbonization reaction mode under the condition of supergravity, and then superfine aluminum hydroxide with different crystal forms is obtained, and the method mainly comprises the steps of carbonization, filtration, washing and drying, and is characterized in that:
1) control of sodium aluminate NaAlO2The concentration of the solution is 0.05-2 mol/L;
2) in sodium aluminate NaAlO2Adding 1-2% by mass of an organic polymer dispersant into the solution;
3) the mixture is put into the reactor (4), the reactor (4) is startedto operate, and CO with concentration is introduced into the reactor (4) after the liquid flow in the reactor (4) is stable2Controlling the rotating speed of the reactor (4) to be 200-3000 rpm, the gas-liquid ratio to be 0.5-20, controlling the carbonization reaction temperature to be 0-100 ℃, recording the temperature and the pH value at regular time, and stopping introducing CO when the pH value reaches 9-122Gas, the rotating speed of the reactor (4) is reduced and the gas is recycled for a period of time to obtain an aluminum hydroxide precursor;
4) continuing to further process the product in different crystal forms, such as aging; the reactor (4) is a rotating bed hypergravity reactor (4) and mainly comprises a rotor (5), a distributor (15) arranged in the center of the rotor (5), a liquid inlet (8), air inlets (3, 9), an exhaust gas outlet (7) and discharge outlets (14, 16).
2. The method for preparing ultra-fine aluminum hydroxide as claimed in claim 1, wherein the rotating bed hypergravity reactor (4) is a spiral channel type RBHC reactor, which is provided with a spiral linear channel without packing.
3. The method for preparing the ultrafine aluminum hydroxide according to claim 1, wherein the organic polymeric dispersant is polyethylene glycol or Tween 80 or sodium dodecylbenzene sulfonate.
4. The method for preparing the superfine aluminum hydroxide according to claim 1, wherein the further treatment of different crystal forms comprises the steps of performing solid-liquid separation on an aluminum hydroxide precursor, adding a proper amount of distilled water into a filter cake, aging at 75-100 ℃ for 2-6 h, filtering, washing and adding isobutanol into the product, and drying at 80-100 ℃ to obtain thefibrous superfine aluminum hydroxide with the crystal form.
5. The method for preparing ultrafine aluminum hydroxide according to claim 1 or 4, wherein the further treatment of the different crystal forms is sodium aluminate NaAlO2The solution concentration is 0.05-1.2 mol/L, and CO is introduced into the reactor (4)2The gas content is not lower than 90%, the gas-liquid ratio is 1-20, the pH value is 10-11, and the carbonization reaction temperature is controlled at 15-50 ℃.
6. The method for preparing ultrafine aluminum hydroxide according to claim 1, wherein the further treatment of different crystal forms comprises the steps of performing solid-liquid separation on an aluminum hydroxide precursor, and then filtering, washing and drying the product to obtain ultrafine aluminum hydroxide with granular crystal forms.
7. The method for preparing ultrafine aluminum hydroxide according to claim 1 or 6, wherein the further treatment of the different crystal forms is sodium aluminate NaAlO2The solution concentration is 0.1-2 mol/L, and CO is introduced into the reactor (4)2The gas content is not higher than 30%, the rotating speed of the reactor (4) is controlled to be 400-2000 rpm, the gas-liquid ratio is 0.5-10, the pH value is 11-12, and the carbonization reaction temperature is controlled to be 50-80 ℃.
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