阅读说明：本技术 高纯拟薄水铝石的生产方法及生产的高纯拟薄水铝石 (Production method of high-purity pseudo-boehmite and produced high-purity pseudo-boehmite ) 是由 魏际伦 魏存弟 蒋引珊 于 2019-04-10 设计创作，主要内容包括：本发明公开了一种高纯拟薄水铝石的生产方法,包括：a.取金属铝,与金属催化剂进行熔炼,所得合金铝与水反应,制取氢气,其中,所述金属铝的纯度不小于99.9wt％；b.铝水反应后对料浆进行分离,将分离得到的悬浮料浆进行干燥,获得拟薄水铝石,任选地拟薄水铝石经过煅烧得到氧化铝；c.对分离料浆后的铝水反应残渣进行处理以便回收使用；本发明还公开了获得的拟薄水铝石；本发明工艺简单,流程短、氢气制备条件易于实现；合金中催化剂镓、铟用量少,原料成本低且容易回收重复使用；本发明既可实现氢气生产的安全、环保、低成本、高效率,又能得到拟薄水铝石的高附加值产品,经济效益显著。(The invention discloses a production method of high-purity pseudo-boehmite, which comprises the following steps: a. taking metal aluminum, smelting the metal aluminum and a metal catalyst, and reacting the obtained alloy aluminum with water to prepare hydrogen, wherein the purity of the metal aluminum is not less than 99.9 wt%; b. separating slurry after the reaction of aluminum water, drying the separated suspension slurry to obtain pseudo-boehmite, and optionally calcining the pseudo-boehmite to obtain alumina; c. treating the aluminum water reaction residue after slurry separation so as to be recycled; the invention also discloses the obtained pseudoboehmite; the method has the advantages of simple process, short flow and easy realization of hydrogen preparation conditions; the consumption of the catalysts gallium and indium in the alloy is low, the cost of the raw materials is low, and the raw materials are easy to recover and reuse; the method can realize the safety, environmental protection, low cost and high efficiency of hydrogen production, can also obtain the high value-added product of pseudo-boehmite, and has obvious economic benefit.)

1. A production method of high-purity pseudoboehmite is characterized by comprising the following steps:

a. smelting metal aluminum and a metal catalyst, wherein the metal catalyst is a metal mixture containing metal gallium and metal indium, the sum of the contents of the metal gallium and the metal indium in the metal mixture is not less than 85 wt%, and performing hydrolysis reaction on the alloy aluminum obtained after smelting the mixed gallium indium catalyst and water to prepare hydrogen; wherein the purity of the metallic aluminum is not less than 99.9 wt%;

b. separating the slurry after the hydrolysis reaction to separate residual metal to obtain suspended slurry, and drying the suspended slurry to obtain pseudo-boehmite;

c. optionally, the separated residual metal is treated to recover the metal catalyst therein for reuse.

2. The production method according to claim 1, wherein the metal Ga to In mass ratio In the metal catalyst is 74-84: 16-26, preferably 76-82: 18-24, and the sum of the contents of metal gallium and metal indium In the metal catalyst is preferably not less than 90 wt%, preferably not less than 95 wt%.

3. The production method according to claim 1 or 2, wherein, when the alloy aluminum is prepared by smelting, the sum of the amount of the gallium and the indium is 1.5-0.01 wt% of the amount of the aluminum.

4. A production method according to any one of claims 1 to 3, wherein the temperature of water at the time of hydrolysis is not lower than 85 ℃, preferably not lower than 90 ℃, further preferably not lower than 95 ℃.

5. The production method according to any one of claims 1 to 4, wherein in the step b, residual metals in the slurry after the reaction are separated by means of cyclone separation to obtain suspended slurry.

6. The production method according to any one of claims 1 to 5, wherein in the step b, the separated suspension slurry is dried by means of spray drying to obtain pseudo-boehmite powder; preferably, the spray drying temperature is 170 ℃ to 240 ℃.

7. The production method according to any one of claims 1 to 6, wherein in the step b, the solid content of the suspension slurry obtained after separation is adjusted to 20 to 30%.

8. The production method according to any one of claims 1 to 7, wherein in the step a, before the hydrolysis reaction, the alloy aluminum obtained by smelting is divided to obtain refined alloy aluminum fragments so as to carry out the hydrolysis reaction.

9. A production method according to any one of claims 1 to 8, characterized in that the hydrolysis reaction is carried out under pressure.

10. Pseudo-boehmite product prepared according to the production method according to any one of claims 1-9.

Technical Field

The invention relates to a preparation process of high-purity pseudo-boehmite, which is realized by hydrolysis reaction of high-purity aluminum and produces hydrogen as a byproduct.

Background

Pseudo-boehmite (gamma-AlOOH. nH)₂0.08 to 0.62% O, n) is also called colloidal thin waterThe crystal phase structure of the aluminum or pseudo boehmite is similar to that of boehmite, but the crystallization is incomplete. The pseudo-boehmite has the characteristics of large pore volume, high specific surface area, good peptization performance and the like, can be used as a catalyst carrier, a catalyst, a ceramic base material and the like to be widely applied to the petrochemical industry, and also can be used for preparing gamma-Al₂O₃And an important precursor of a series of products, namely alumina. Pseudoboehmite as a catalyst support generally needs to have a large pore volume, a large specific surface area, a low sodium content, and a suitable pore size distribution.

The existing production methods of pseudo-boehmite can be roughly divided into two types, namely an organic aluminum alkoxide method and an acid-base neutralization method. The organic aluminum alkoxide method uses metal aluminum, hydrogen, ethylene or alcohol as raw materials, firstly synthesizes triethyl aluminum or alcohol-based aluminum, and then hydrolyzes to prepare the pseudo-boehmite. The product obtained by the method has high purity and good quality, but has the problems of complex production process, easy explosion of organic solvent and the like. The acid-base neutralization method is also called a precipitation method, and can be classified into an alkaline method and an acid method. The alkali method is to neutralize alkali with acid, namely to inject carbon dioxide (or add hydrochloric acid, nitric acid, ammonium bicarbonate, sodium bicarbonate and other acids) into the sodium aluminate solution prepared by Bayer process or sintering process, and react under proper conditions. The alkaline process is mature, but the sodium aluminate solution contains high sodium ions, the specific surface area of the pseudo-boehmite is large and porous, so that the sodium content in the product is high, the washing process is complex, the washing water amount is large, the washing water amount per ton of the pseudo-boehmite can reach 100 tons, the sodium content in the washing mother solution is low, and the recycling is difficult. Meanwhile, the heterophases such as the Bayer stone, the nauterite, the gibbsite and the like are often generated in the preparation process and are difficult to remove, so that the pseudoboehmite with high crystalline phase purity is difficult to obtain. The acid process is a process of neutralizing an aluminate (e.g., aluminum sulfate, aluminum nitrate) solution with a base to precipitate hydrated alumina. Compared with the alkaline method, the acid method has the advantages of low material consumption and cost, no sodium ions, and simplified washing process. However, since metal ions such as iron are very soluble in acid, the acid process introduces high levels of iron impurities. In addition, the pseudo-boehmite prepared by the acid method has the defect of low crystallinity. In recent years, for example, patent 201110021780 discloses "a method for preparing high-purity pseudo-boehmite", which adopts metal aluminum with the purity of more than 99.5%, C5-C8 and n-butanol to prepare alkyl aluminum, and then hydrolyzes to prepare pseudo-boehmite. The method adopts more carbon organic solvents as the preparation raw materials of the alkyl aluminum, has high production cost and is easy to generate pollution. Some adopt the reaction hydrolysis of high-purity metal aluminum and water to prepare high-purity pseudo-boehmite, but in order to solve the problem of oxidation of metal aluminum, a certain amount of low-melting point metal, such as one or more of gallium, indium and tin, must be added. For example, the application number 201510937351.X provides a preparation technology of nano aluminum oxyhydroxide powder, introduces the preparation technology of ball-milling aluminum powder, gallium, indium and tin powder under the protection of argon, adding inorganic salt to obtain an aluminum-based material, reacting in 70 ℃ water for 24 hours to obtain hydrogen and AlOOH microspheres, and then carrying out subsequent treatment on the microspheres to obtain the nano aluminum oxyhydroxide. In the method, the dosage of the low-melting-point alloy reaches 4 wt%, and the dosage of the sodium chloride exceeds 5 wt%. In the preparation process of the AlOOH microspheres, gallium, indium and tin cannot be effectively recovered and are mixed into products, so that the product cost is high, and meanwhile, the products also contain a large amount of impurities. The similar researches have the problems of high cost, large consumption of low-melting-point alloy, difficult recovery, complex preparation process of the pseudo-boehmite and the like, so that the industrialization is difficult.

Therefore, the invention aims to solve the problems of greatly reducing the consumption of low-melting-point metal, adjusting the reaction condition of aluminum water, preparing a high-purity pseudo-boehmite product with a single crystal phase and simultaneously producing hydrogen as a byproduct.

Disclosure of Invention

The invention aims to provide a simpler, lower-cost and high-purity pseudo-boehmite production method, a produced high-purity pseudo-boehmite and a method for producing hydrogen.

In order to achieve one aspect of the above object, the present invention adopts the following technical solution,

a production method of high-purity pseudoboehmite comprises the following steps:

a. smelting metal aluminum and a metal catalyst, wherein the metal catalyst is a metal mixture containing metal gallium and metal indium, the sum of the contents of the metal gallium and the metal indium in the metal mixture is not less than 85 wt%, and performing hydrolysis reaction on alloy aluminum obtained after smelting the mixed gallium indium catalyst and water to prepare hydrogen; wherein the purity of the metallic aluminum is not less than 99.9 wt%;

b. separating the slurry after the hydrolysis reaction to separate out residual metal to obtain suspended slurry, and drying the suspended slurry to obtain pseudo-boehmite;

c. optionally, the separated metal is treated to recover the metal catalyst for reuse.

In step a of the present invention, the metallic aluminum is high-purity metallic aluminum (e.g., 3N, 4N or 5N aluminum), for example, having a purity of not less than 99.9 wt% or 99.99 wt%; the metal catalyst has a metal ratio of Ga to In of 74-84: 16-26, for example 76-82: 18-24 or 78-80: 20-22, for example, gallium to indium is 78.9: 21.1.

When the alloy aluminum is prepared by smelting, the aluminum ingot can be prepared by mixing the metallic aluminum and the metallic catalyst (the catalyst can be added as a whole or the components can be added separately) under the condition of fully stirring by adopting the vacuum smelting or inert gas protection smelting technology of the metal, and the technology is well known in the art and is not described again. The gallium and indium content of the obtained alloy aluminum (or aluminum ingot) is 1.5-0.01 wt%, such as 1.0 wt%, 0.5 wt%, 0.2 wt% or 0.1 wt% of the aluminum content. Although those skilled in the art will appreciate that higher purity of the starting material is more beneficial to the high purity of the subsequent product, those skilled in the art will appreciate that the starting material purity may not be as critical as the maximum amount of aluminum metal used because the overall amount of metal catalyst used in the present invention is lower.

In the present invention, the sum of the contents of metal gallium and metal indium in the metal catalyst is preferably not less than 90 wt%, not less than 95 wt%, not less than 99 wt%, or the metal catalyst is an alloy catalyst composed of gallium and indium.

Cutting an aluminum ingot obtained by smelting, and then carrying out hydrolysis reaction with water, for example, cutting particles with the particle size of below 1cm, such as 0.2-1cm, preparing hydrogen, and collecting, wherein the water can be deionized water, which is beneficial to improving the purity of the subsequently obtained pseudo-boehmite; the temperature of water in the hydrolysis reaction may be not less than 85 ℃ and not less than 90 ℃, for example, 92 ℃, 95 ℃, 97 ℃ or 99 ℃, 100 ℃ and the water may be nearly boiling or boiling in the reaction, or the pressure of the reaction system may be appropriately increased to increase the reaction temperature. Because the hydrolysis temperature is higher, close to or at the boiling point, the hydrogen generated by the reaction is mixed with the water vapor and coexists, and then the water can be recovered by a condensation separation mode and recycled, so that the pure hydrogen is obtained.

In one embodiment, the hydrolysis reaction is carried out under pressure, for example, at a pressure of not less than 0.2MPa, 0.5MPa, 1MPa, 2MPa or higher, since the hydrolysis reaction can be carried out at a higher temperature, for example, not less than 100 ℃, 120 ℃, 150 ℃, 200 ℃ or 250 ℃ or higher, the speed of the hydrolysis reaction is increased, which is beneficial to obtaining high-quality steam for recovering heat, reducing the amount of metal catalyst, and improving the purity of the pseudo-boehmite product.

In the step b of the present invention, in the reaction system obtained after the reaction of the aluminum water is completed, the aluminum hydroxide generated by the hydrolysis reaction of the present invention has low density and fine particles in a suspension state, and the residual metal (a small amount of residual metal aluminum and unreacted gallium-indium alloy catalyst) is easily gathered at the bottom of the reaction system because of significantly large relative specific gravity, so that the separation of the aluminum hydroxide and the residual metal can be smoothly realized, and the temperature of the system can be properly reduced to be lower than 70 ℃ after the reaction is completed, for example, or the system is directly sent to the separation step without arranging a special temperature reduction step. The specific separation method may be to directly extract the reaction system suspended slurry to facilitate the separation of the metal (residue) at the bottom or to separate the suspended slurry at the middle upper part by using the overflow principle to make the metal at the bottom remain in the reaction system, or preferably may be cyclone separation, for example, cyclone separation under stirring condition to separate the residual metal with high specific gravity, which will not be described in detail herein.

Drying the separated pseudo-boehmite slurry, for example, spray drying to obtain pseudo-boehmite powder, for example, spray drying at 170-240 ℃ under normal pressure, such as 180, 200, 210 or 220 ℃, or spray drying at a suitably reduced temperature under reduced pressure, can obtain substantially pure pseudo-boehmite powder, although a person skilled in the art can also think of increasing the pressure appropriately, and at the same time, the person skilled in the art can understand that the higher the purity of the raw material aluminum is, the higher the purity of the obtained aluminum hydrolysate is, and the pseudo-boehmite is low in sodium, low in iron and low in sulfur, and can be used as a high-quality catalyst carrier.

In one embodiment, after separation and before spray drying, the suspended slurry is adjusted to have a solid content of 20-30 wt%, such as 22 wt%, 24 wt%, 26 wt% or 28 wt%, for example, the obtained suspended slurry can be filtered to obtain a filter cake, and then the filter cake is added with water for pulping, so that not only can the solid content be adjusted and controlled to better perform spray drying to obtain pseudo-boehmite powder, but also the filtering is beneficial to filtering out part of possible impurities, such as soluble impurities, and improving the purity of the pseudo-boehmite powder.

In the step c, the gallium-indium alloy and the residual aluminum which do not participate in the hydrolysis reaction are recovered and reused, a small amount of aluminum hydrolysate coated on the surface is washed and separated by ultrasonic and other modes, and the residual aluminum metal and the gallium-indium alloy are recovered, tested for content and reused.

In order to achieve another aspect of the above object, the present invention further provides a pseudo-boehmite product prepared according to the above method.

The invention adopts high-purity aluminum (such as 4N or 5N aluminum) as a raw material, is matched with gallium-indium alloy with lower dosage as a catalyst, and prepares hydrogen under the reaction condition of boiling water and obtains the pseudo-boehmite at the same time. Research finds that the limiting factor of hydrogen production through the aluminum water reaction is the reaction inhibition of an aluminum oxide film, the aluminum alloy containing low-melting-point metal has the low-melting-point metal in the grain interior or in the grain boundary, when the aluminum alloy reaches the molten-state temperature of the low-melting-point metal or above, the molten-state metal has strong permeability, particularly the gallium has small surface tension, can be spread on the surface of the aluminum metal and melted and permeated in the grain boundary, and interferes with the formation of aluminum oxide, cracks or cavities are easy to occur even if the aluminum oxide film is generated, and compared with a structure without the low-melting-point metal, the aluminum water reaction hydrogen production method has obvious local embrittlement and atomic arrangement disordered regions, and provides favorable conditions for the aluminum water reaction. On the other hand, because water is polar molecules, the water exists in an aggregation state of weak intermolecular force combination at normal temperature, the binding force is weakened along with the increase of the water temperature, the kinetic energy of small molecular water is increased, particularly when the water reaches a boiling point, the mass transfer capacity is enhanced, the reaction induction period of the aluminum water can be obviously shortened, the hydrogen generated on the surface of metal aluminum is promoted to be rapidly diffused, and the reaction rate is greatly improved. In fact, the low-melting-point alloy formed by gallium and indium can be molten at a low temperature at and near the eutectic composition, the viscosity of the melt is reduced and the surface tension is reduced along with the increase of the temperature, and the low-melting-point alloy is also more favorable for wetting the aluminum crystal boundary and surface and preventing the aluminum from being oxidized due to element migration. Therefore, the invention uses a small amount of low melting point gallium-indium alloy as the catalyst, and realizes the rapid and continuous aluminum-water reaction by increasing the reaction temperature (reaching the boiling point of water), thereby greatly reducing the cost of raw materials and the difficulty of recovery. The reaction product of aluminum and boiling water except hydrogen is hydrolyzed to produce pseudoboehmite phase. Previous studies have confirmed that aluminum reacts with water at temperatures below 60 ℃ in the form of a mixed crystal of bayer and pseudoboehmite, with the pseudoboehmite phase being predominant at temperatures above 60 ℃. The reaction conditions of the invention just meet the formation of the pseudo-boehmite structure of the aluminum hydrolysis product.

In conclusion, the invention prepares the high-purity pseudo-boehmite by the metal aluminum hydrolysis method, and the dosage of the low-melting-point alloy element added in the raw material aluminum in the aluminum water reaction process is obviously reduced compared with the reported (the minimum dosage is 3wt percent) and is only 0.01wt percent to 1.5wt percent, so that the cost of the method is greatly reduced. Meanwhile, because the low-melting-point alloy gallium-indium is less in use amount, the residual gallium and indium impurities in the pseudo-boehmite are less. In the process of preparing the pseudo-boehmite by the alumina-water reaction, the acid-base condition of a reaction system does not need to be regulated, dangerous organic reagents are not used, the reaction condition is easy to control, the process is pollution-free, and waste gas and waste water are not generated; the pseudo-boehmite product obtained by the process has single crystal phase, uniform particles and stable performance; because no other impurities are introduced in the hydrolysis process, the prepared pseudo-boehmite product has low sodium, low iron and low content of sodium,Low sulfur content and very low impurity content, thus having high value. The specific surface area is more than 310m in production²The high-purity pseudo-boehmite product with the pore volume of more than 0.31ml/g can also obtain a high-purity hydrogen byproduct, and has obvious economic benefit.

Drawings

FIG. 1 is an XRD pattern of pseudoboehmite for various examples;

FIGS. 2 and 3 are SEM images of pseudoboehmite of example 1.

Detailed Description

The present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

The following examples are given below for the determination of the parameters/conditions, all according to the methods customary in the art, unless otherwise specified:

specific surface area, pore volume, pore diameter: see national standard GB/T19587-2017 determination of specific surface area of solid substance by gas adsorption BET method;

XRD: using a DX-2700 x-ray diffractometer; wavelength:target material: Cu-Kalpha radiation; tube voltage: 40 kV; pipe flow: 30 mA.