阅读说明：本技术 一种制备高纯平行六面体状勃姆石的方法及高纯平行六面体状勃姆石 (Method for preparing high-purity parallelepipedal boehmite and high-purity parallelepipedal boehmite ) 是由 梁武洋 刘中清 邓兆敬 赵峰 于 2021-11-05 设计创作，主要内容包括：本发明提供一种制备高纯平行六面体状勃姆石的方法及高纯平行六面体状勃姆石,制备方法包括以下步骤：S1.将铝源、洗涤助剂、水混合,制成浆料,然后采用氨水调节pH为8-12,铝源为氢氧化铝、拟薄水铝石、快脱粉、γ-氧化铝中的一种或几种的混合；洗涤助剂为铵盐；S2.将步骤S1得到的浆料于高压釜中升温至140-180℃,反应1-4小时,然后升温至200-250℃,反应4-24h,得到高纯平行六面体状勃姆石。该制备方法采用廉价的工业产品作原料,使用铵盐作为洗涤助剂,氨水作pH调节剂,经水热即可制备高纯平行六面体状勃姆石；制备得到的平行六面体状勃姆石具有杂质含量低、形状规整、结晶度高、粒度可调、粒度分布窄的优势。(The invention provides a method for preparing high-purity parallelepipedal boehmite and the high-purity parallelepipedal boehmite, the preparation method comprises the following steps: s1, mixing an aluminum source, a washing assistant and water to prepare slurry, and then adjusting the pH to 8-12 by adopting ammonia water, wherein the aluminum source is one or a mixture of aluminum hydroxide, pseudo-boehmite, quick-release powder and gamma-alumina; the washing auxiliary agent is ammonium salt; s2, heating the slurry obtained in the step S1 to 140-180 ℃ in an autoclave for reaction for 1-4 hours, then heating to 200-250 ℃ for reaction for 4-24 hours to obtain the high-purity parallelepipedal boehmite. The preparation method adopts cheap industrial products as raw materials, ammonium salt as a washing assistant and ammonia water as a pH regulator, and high-purity parallelepipedal boehmite can be prepared by hydrothermal reaction; the prepared parallelepipedal boehmite has the advantages of low impurity content, regular shape, high crystallinity, adjustable particle size and narrow particle size distribution.)

1. A process for the preparation of high purity parallelepipedal boehmite comprising the steps of:

s1, mixing an aluminum source, a washing assistant and water to prepare slurry, and then adjusting the pH to 8-12 by adopting ammonia water, wherein the aluminum source is one or a mixture of aluminum hydroxide, pseudo-boehmite, quick-release powder and gamma-alumina; the washing auxiliary agent is ammonium salt;

s2, heating the slurry obtained in the step S1 to 140-180 ℃ in an autoclave for reaction for 1-4 hours, then heating to 200-250 ℃ for reaction for 4-24 hours to obtain the high-purity parallelepipedal boehmite.

2. The process for preparing high purity parallelepiped boehmite according to claim 1, characterized in that:

in step S1, the molar ratio of water to aluminum element is (7.5-50): 1; the molar ratio of ammonium ions to aluminum elements of the ammonium salt is (0.002-0.15): 1.

3. the process for preparing high purity parallelepiped boehmite according to claim 1, characterized in that:

the washing auxiliary agent is one or a mixture of more of ammonium chloride and hydrate thereof, ammonium sulfate and hydrate thereof, ammonium acetate and hydrate thereof, ammonium oxalate and hydrate thereof, and ammonium citrate and hydrate thereof.

4. The process for preparing high purity parallelepiped boehmite according to claim 1, characterized in that:

the aluminum source is the mixture of aluminum hydroxide and gamma-alumina.

5. The process for preparing high purity parallelepiped boehmite according to claim 4, characterized in that:

the mass ratio of the aluminum hydroxide to the gamma-alumina is 1: (0.01-0.4).

6. The process for preparing high purity parallelepiped boehmite according to claim 4, characterized in that:

the particle size of the aluminum hydroxide is 0.5-20 μm.

7. The process for preparing high purity parallelepiped boehmite according to claim 1, characterized in that:

in step S2, the temperature rise rate is 1-6 deg.C/min.

8. The process for preparing high purity parallelepiped boehmite according to claim 1, characterized in that:

step S2 further includes separating, washing, and drying after the reaction is completed.

9. The process for preparing high purity parallelepiped boehmite according to claim 8, characterized in that:

the drying temperature is 100-150 ℃.

10. Highly pure parallelepipedal boehmite prepared by the process for preparing highly pure parallelepipedal boehmite according to any one of claims 1-9.

Technical Field

The invention belongs to the technical field of new materials, and particularly relates to a method for preparing high-purity parallelepipedal boehmite and the high-purity parallelepipedal boehmite.

Background

Boehmite (γ -AlOOH), also known as boehmite, is a partially dehydrated aluminum hydroxide. Boehmite is fine white crystal in appearance, belongs to an orthorhombic system and has a layered structure; within the single structural layer, oxygen ions (O)^2-) Aluminum ions (Al) arranged at the vertices of octahedron in cubic close packing³⁺) In the center of the octahedron, hydroxyl (OH)^-) Is positioned on the surface of the laminated structure, and the layers are connected by hydrogen bonds. In addition, boehmite has high thermal conductivity, good thermal stability and low bulk density, and water vapor is released by thermal decomposition to absorb a large amount of heat, so that Al generated by decomposition₂O₃Covering the surface of the substrate, the flame retardant can delay the burning rate and achieve the flame retardant effect. Due to its good microstructure and thermal stability, boehmite is widely used in the fields of ceramic materials, semiconductor materials, coating materials, flame retardant materials, catalysts, carriers, and the like; particularly, due to the fact that boehmite has the characteristics of low density, soft texture, good thermal conductivity, good organic matter compatibility and the like, the safety performance and the energy density of the lithium battery can be actively improved by coating the lithium battery diaphragm with high-purity boehmite, and therefore boehmite gradually replaces the traditional Al₂O₃And TiO₂The proportion of the coating materials of the lithium battery diaphragm in the new energy battery cell diaphragm and the pole piece coating materials is continuously improved.

The characteristics of boehmite often change with the difference of particle size and morphology, different boehmites have different requirements in application, and the preparation of high-purity boehmite has been the research focus of the industry. For example, CN111453751A discloses a method for preparing high-purity boehmite, in which the reaction progress is controlled by controlling the reaction ratio and gas flow rate of high-temperature water vapor and aluminum alkoxide to prepare high-purity nano-bulk boehmite; the boehmite prepared by the method has narrow particle size distribution, good dispersibility and high purity; however, the operation is complicated, and the aluminum alkoxide with high price is used as the aluminum source, which is not beneficial to industrial scale-up. CN110078104A discloses a method for producing a low-cost industrial raw materialMethod for producing boehmite by using gamma-Al₂O₃As an aluminum source, boehmite is prepared by a one-step hydrothermal method without using an additive and a pH regulator; although the method uses low-cost industrial raw materials, the prepared boehmite primary particles have no regular appearance, are nested with each other and are extremely seriously agglomerated, and the boehmite primary particles which are dispersed independently hardly exist.

In the prior art, most of the methods for preparing high-purity high-end boehmite pass through additives, and other ions or substances are inevitably introduced into the additives, so that the purity of the boehmite is inevitably reduced, and the high-end requirements cannot be met, therefore, the development of a preparation process of the high-purity boehmite is urgent.

Disclosure of Invention

The invention provides a method for preparing high-purity parallelepipedal boehmite and the high-purity parallelepipedal boehmite, wherein the high-purity parallelepipedal boehmite can be prepared by one-step hydrothermal method by using cheap industrial products as raw materials, using ammonium salt as a washing assistant and using ammonia water as a pH regulator; the prepared parallelepipedal boehmite has the advantages of low impurity content, regular shape, high crystallinity, adjustable particle size and narrow particle size distribution.

In order to solve the above problems, an aspect of the present invention provides a method for producing high-purity parallelepiped boehmite, comprising the steps of:

s1, mixing an aluminum source, a washing assistant and water to prepare slurry, and then adjusting the pH to 8-12 by adopting ammonia water, wherein the aluminum source is one or the mixture of aluminum hydroxide, pseudo-boehmite, quick-release powder and gamma-alumina; the washing auxiliary agent is ammonium salt;

s2, heating the slurry obtained in the step S1 to 140-180 ℃ in an autoclave for reaction for 1-4 hours, then heating to 200-250 ℃ for reaction for 4-24 hours to obtain the high-purity parallelepipedal boehmite.

The method for preparing the high-purity parallelepipedal boehmite adopts aluminum hydroxide, quick-release powder, pseudoboehmite and gamma-alumina as raw materials, adds a washing assistant which is beneficial to converting sodium in the raw materials into soluble sodium salt and is easy to wash and remove, adjusts the pH value of a reaction system by using ammonia water, and prepares the high-purity parallelepipedal boehmite by a hydrothermal method. The preparation raw materials adopted by the method are cheap industrial products, and the production cost is low; compared with the prior art that metal salt is used as the washing assistant, the ammonium ions can replace other impurity cations in the raw materials, and can be decomposed and removed in the heating and drying process, and the ammonium salt is used as the washing assistant, so that no additional impurity cations are introduced, and the impurity content in the product can be further reduced; the pH value is adjusted by using the ammonia water, on one hand, the ammonia water does not introduce impurity ions, and the ammonia can be completely removed from the product in the washing and drying processes to reduce the impurity content in the product, and on the other hand, the relative ratio change of the ammonia water and the ammonium salt can influence the dissociation of the washing assistant ammonium salt, so that the content of anions in a reaction system is changed, and the particle size of boehmite can be deeply regulated and controlled.

Preferably, in step S1, the molar ratio of water to aluminum element is (7.5-50): 1; the molar ratio of ammonium ions to aluminum elements in the ammonium salt is (0.002-0.15): 1.

further preferably, in step S1, the molar ratio of water to aluminum element is (15-35): 1; the molar ratio of ammonium ions to aluminum elements in the ammonium salt is (0.005-0.05): 1.

preferably, the washing assistant is one or a mixture of more of ammonium chloride and hydrate thereof, ammonium sulfate and hydrate thereof, ammonium acetate and hydrate thereof, ammonium oxalate and hydrate thereof, and ammonium citrate and hydrate thereof.

Further preferably, the washing assistant is one or a mixture of ammonium oxalate and hydrate thereof, ammonium citrate and hydrate thereof.

Wherein the ammonia water is an aqueous solution of ammonia with any concentration.

Preferably, the aluminum source is a mixture of aluminum hydroxide and gamma-alumina.

Preferably, the mass ratio of aluminum hydroxide to gamma-alumina is 1: (0.01-0.4).

Further preferably, the mass ratio of aluminum hydroxide to gamma-alumina is 1: (0.04-0.15).

Preferably, the particle size of the aluminum hydroxide is 0.5 to 20 μm.

Wherein the water is one or more of deionized water, distilled water, high purity water and reverse osmosis water.

Further preferably, the particle size of the aluminum hydroxide is 0.5 to 5 μm.

Preferably, in step S2, the temperature increase rate is 1-6 deg.C/min.

Further preferably, in step S2, the temperature increase rate is 2-4 deg.C/min.

Preferably, step S2 further includes separating, washing, and drying after the reaction is completed.

Preferably, the temperature of the drying is 100-150 ℃.

Another aspect of the present invention provides a high purity parallelepiped boehmite prepared by the above method for preparing a high purity parallelepiped boehmite.

Compared with the prior art, the invention has the following beneficial effects:

1. the method for preparing the high-purity parallelepipedal boehmite adopts cheap industrial raw materials and has low production cost; compared with the prior art that metal salt is adopted as the washing assistant, the ammonium ions can replace other impurity cations in the raw materials, and can be decomposed and removed in the heating and drying process, and the ammonium salt is adopted as the washing assistant, so that no additional impurity cation is introduced, and the impurity content in the product can be further reduced; the pH value is adjusted by using ammonia water, on one hand, different from other inorganic bases and organic bases, impurity ions cannot be introduced into the ammonia water, the ammonia can be completely removed from a product in the washing and drying processes, and on the other hand, the dissociation of a washing assistant ammonium salt can be influenced by the change of the relative proportion of the ammonia water/the ammonium salt, so that the content of anions in a reaction system is changed, and the particle size of the boehmite can be further regulated and controlled;

2. the method for preparing the high-purity parallelepipedal boehmite uses a two-step heating temperature control method, firstly reacts for 1-4h within a temperature range of 140-; the method comprises the steps of pre-reacting raw materials at a low temperature to fully adjust the morphological structure of the raw materials, carrying out crystal transformation to stable flaky boehmite crystal cells to avoid clustering caused by too fast crystal transformation and influence on crystal growth, reacting at a high temperature to promote uniform growth of crystals, and facilitating the obtainment of boehmite with narrow particle size distribution;

3. the method of the present invention for producing high purity parallelepipedal boehmite, wherein the boehmite produced is parallelepipedal, the side length of the boehmite is 0.5 to 2.0 mu m, and the crystallinity of the boehmite is>99% boehmite purity>99.9％，Na⁺The content is lower than 300ppm, the pH value can be further adjusted through ammonia water, the particle size can be deeply regulated, and the method has the advantages of low impurity content, regular shape, high crystallinity, adjustable particle size, narrow particle size distribution and the like;

4. the method for preparing the high-purity parallelepipedal boehmite has the advantages of simple process, low cost, small equipment corrosivity and less washing wastewater, and is suitable for large-scale industrial production.

Drawings

FIG. 1 is an XRD pattern of high purity parallelepiped boehmite obtained in example 1;

FIG. 2 is an SEM photograph of high-purity parallelepipedal boehmite obtained in example 1;

FIG. 3 is an SEM photograph of high-purity parallelepipedal boehmite obtained in example 2;

FIG. 4 is an SEM photograph of high-purity parallelepipedal boehmite obtained in example 3;

FIG. 5 is an SEM photograph of high-purity parallelepipedal boehmite obtained in example 4;

FIG. 6 is an SEM image of boehmite obtained in example 5;

FIG. 7 is an SEM photograph of boehmite obtained in example 6;

FIG. 8 is an SEM photograph of high-purity parallelepipedal boehmite obtained in example 7;

FIG. 9 is an SEM photograph of high-purity parallelepipedal boehmite obtained in example 8;

fig. 10 is an SEM image of boehmite obtained in example 9.

Detailed Description

The technical solutions of the present invention will be described clearly and completely below with reference to embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

A method for producing high purity parallelepiped boehmite according to this example, comprising the steps of:

s1, mixing 90g of aluminum hydroxide with the particle size of 5 mu m, 10g of gamma-alumina, 2.5g of ammonium citrate and 600g of water, stirring, pulping and uniformly mixing, and then adjusting the pH to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 150 ℃ at a speed of 4 ℃/min, preserving heat for 4h, heating to 240 ℃ at a speed of 4 ℃/min, preserving heat for reacting for 8h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at 120 ℃ to obtain the high-purity parallelepipedal boehmite.

FIG. 1 shows an XRD pattern of high purity parallelepiped boehmite obtained in this example; FIG. 2 is an SEM photograph of high-purity parallelepiped boehmite obtained in this example.

Example 2

A method for producing high purity parallelepiped boehmite according to this example, comprising the steps of:

s1, mixing 100g of aluminum hydroxide with the particle size of 5 mu m, 2.5g of ammonium citrate and 600g of water, stirring, pulping and uniformly mixing, and then adjusting the pH value to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 150 ℃ at a speed of 4 ℃/min, preserving heat for 4h, heating to 220 ℃ at a speed of 4 ℃/min, preserving heat for reacting for 8h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at 120 ℃ to obtain the high-purity parallelepipedal boehmite.

The preparation steps were the same as in example 1 except that in step S1, 100g of aluminum hydroxide having a particle size of 5 μm was used as the starting material. FIG. 3 shows an SEM photograph of high purity parallelepipedal boehmite obtained according to this example.

Example 3

A method for producing high purity parallelepiped boehmite according to this example, comprising the steps of:

s1, mixing 90g of aluminum hydroxide with the particle size of 5 mu m, 10g of quick-release powder, 2.5g of ammonium citrate and 600g of water, stirring, pulping and uniformly mixing, and then adjusting the pH to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 150 ℃ at a speed of 4 ℃/min, preserving heat for 4h, heating to 240 ℃ at a speed of 4 ℃/min, preserving heat for reacting for 8h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at 120 ℃ to obtain the high-purity parallelepipedal boehmite.

The preparation steps were the same as in example 1 except that in step S1, 90g of aluminum hydroxide having a particle size of 5 μm and 10g of quick-release powder were used as the starting material. FIG. 4 is an SEM photograph of high-purity parallelepipedal boehmite obtained in this example.

Example 4

A method for producing high purity parallelepiped boehmite according to this example, comprising the steps of:

s1, mixing 90g of aluminum hydroxide with the particle size of 5 mu m, 10g of pseudo-boehmite, 2.5g of ammonium citrate and 600g of water, stirring, pulping and uniformly mixing, and then adjusting the pH to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 160 ℃ at a speed of 4 ℃/min, preserving heat for 4h, heating to 240 ℃ at a speed of 4 ℃/min, preserving heat for reacting for 8h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at 120 ℃ to obtain the high-purity parallelepipedal boehmite.

The preparation steps were the same as in example 1 except that in step S1, 90g of aluminum hydroxide having a particle size of 5 μm and 10g of pseudoboehmite were used as raw materials. FIG. 5 is an SEM photograph of high-purity parallelepipedal boehmite obtained according to this example.

Example 5

A method of making boehmite according to this example, comprising the steps of:

s1, mixing 75g of aluminum hydroxide with the particle size of 5 mu m, 25g of gamma-alumina, 2.5g of ammonium citrate and 600g of water, stirring, pulping and uniformly mixing, and then adjusting the pH value to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 150 ℃ at a speed of 4 ℃/min, preserving heat for 4h, heating to 240 ℃ at a speed of 4 ℃/min, preserving heat for reacting for 8h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at 120 ℃ to obtain the high-purity parallelepipedal boehmite.

The preparation steps were the same as in example 1 except that in step S1, 75g of aluminum hydroxide having a particle size of 5 μm and 25g of γ -alumina were used as raw materials. Fig. 6 and 7 show SEM images of boehmite obtained in this example.

Example 6

A method for producing high purity parallelepiped boehmite according to this example, comprising the steps of:

s1, mixing 100g of aluminum hydroxide with the particle size of 5 mu m, 3.0g of ammonium oxalate and 600g of water, stirring, slurrying and uniformly mixing, and then adjusting the pH value to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 170 ℃ at the speed of 5 ℃/min, preserving heat for 2h, heating to 220 ℃ at the speed of 5 ℃/min, preserving heat for reaction for 12h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at the temperature of 130 ℃ to obtain the high-purity parallelepipedal boehmite.

FIG. 8 is an SEM photograph of high-purity parallelepiped boehmite obtained in this example.

Example 7

A method for producing high purity parallelepiped boehmite according to this example, comprising the steps of:

s1, mixing 100g of aluminum hydroxide with the particle size of 10 mu m, 1.5g of ammonium oxalate, 2.5g of ammonium citrate and 600g of water, stirring, pulping and uniformly mixing, and then adjusting the pH to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 180 ℃ at the speed of 6 ℃/min, preserving heat for 1.5h, heating to 210 ℃ at the speed of 6 ℃/min, preserving heat for reaction for 18h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at the temperature of 150 ℃ to obtain the high-purity parallelepipedal boehmite.

Fig. 9 is an SEM image of high-purity parallelepiped boehmite obtained in this example.

Example 8

A method of making boehmite according to this example, comprising the steps of:

s1, 225g of aluminum hydroxide with the particle size of 5 mu m, 25g of gamma-alumina, 0.95g of ammonium citrate and 450g of water are mixed, stirred, slurried and uniformly mixed, and then 25 wt% of ammonia water is adopted to adjust the pH value to 10;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 180 ℃ at the speed of 4 ℃/min, preserving heat for 4h, heating to 200 ℃ at the speed of 4 ℃/min, preserving heat for reacting for 8h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at 120 ℃ to obtain the high-purity parallelepipedal boehmite.

The dry process for preparing high purity boehmite according to this example comprises the same steps as those of example 1 except that in step S1, the raw materials include 225g of aluminum hydroxide having a particle size of 5 μm, 25g of γ -alumina, 0.95g of ammonium citrate, and 450g of water; due to the low water content and the viscous slurry, a large amount of white solids accumulated on the upper part of the reaction kettle after the reaction. FIG. 10 shows an SEM image of Boehm's stone obtained in this example.

Example 9

A method of making boehmite according to this example, comprising the steps of:

s1, mixing 54g of aluminum hydroxide with the particle size of 5 mu m, 6g of gamma-alumina, 5.0g of ammonium citrate and 600g of water, stirring, pulping and uniformly mixing, and then adjusting the pH value to 10 by adopting 25 wt% of ammonia water;

s2, filling the slurry obtained in the step S1 into a high-pressure kettle, heating to 150 ℃ at a speed of 4 ℃/min, preserving heat for 4h, heating to 220 ℃ at a speed of 4 ℃/min, preserving heat for reacting for 8h, cooling after the reaction is finished, filtering, separating, washing with deionized water, and drying in an oven at 120 ℃ to obtain the high-purity parallelepipedal boehmite.

The dry process for preparing high purity boehmite according to this example was identical to example 1 except that 54g of aluminum hydroxide having a particle size of 5 μm, 6g of γ -alumina, 5.0g of ammonium citrate, and 600g of water were used in step S1.

Comparative example 1

The method of this comparative example for producing high-purity parallelepiped boehmite has the same production steps as those of example 1 except that 2.5g of ammonium citrate was replaced with 5.37g of potassium sulfate in step S1. This comparative example gives a cubic boehmite.

Comparative example 2

The method of this comparative example for producing high-purity parallelepipedic boehmite has the same production steps as in example 1 except that in step S1, 2.5g of ammonium citrate was replaced with 1.85g of magnesium sulfate. This comparative example yielded rhombohedral flaky boehmite.

Comparative example 3

The method of this comparative example for producing high-purity parallelepiped boehmite has the same production steps as those of example 1 except that 2.5g of ammonium citrate was replaced with 2.48g of zinc sulfate in step S1. This comparative example gives cubic boehmite.

Comparative example 4

The method of this comparative example for producing high-purity parallelepipedic boehmite has the same production steps as in example 4, except that in step S1, 2.5g of ammonium sulfate was replaced with 1.85g of magnesium sulfate, and 1.5g of ammonium oxalate was replaced with 1.15g of magnesium chloride. This comparative example gives parallelepipedal boehmite.

The side length, crystallinity, purity, and impurity ion content of boehmite obtained in each of the above examples and comparative examples are shown in table 1 below. In contrast to examples 1-4, which differ only by the aluminum source, the aluminum hydroxide of example 1, when mixed with gamma-alumina as the aluminum source, yields boehmite of the highest purity and the lowest level of hetero-ions; in comparison with examples 1, 8 and 9, which differ only in the molar ratio of water to aluminum and the molar ratio of ammonium ions to aluminum, the values obtained in example 1 give boehmite with the highest purity and the lowest content of hetero-ions; in contrast to examples 1 and 5, which differ only in the mass ratio of aluminum hydroxide to gamma-alumina, the boehmerite obtained in example 1 has the highest purity and the lowest content of hetero ions, with the mass ratio being in the preferred range.

TABLE 1

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.